Userguide

User Guide

Version 10.2

Aspen Pinch 10.2 February 2000 Copyright (c) 1984-2000 by Aspen Technology, Inc. All rights reserved. Aspen Plus®, Aspen Properties®, Aspen Engineering Suite, AspenTech®, ModelManager, Aspen Pinch, the aspen leaf logo and Plantelligence are trademarks or registered trademarks of Aspen Technology, Inc., Cambridge, MA. BATCHFRAC and RATEFRAC are trademarks of Koch Engineering Company, Inc. All other brand and product names are trademarks or registered trademarks of their respective companies. This manual is intended as a guide to using AspenTech's software. This documentation contains AspenTech proprietary and confidential information and may not be disclosed, used, or copied without the prior consent of AspenTech or as set forth in the applicable license agreement. Users are solely responsible for the proper use of the software and the application of the results obtained. Although AspenTech has tested the software and reviewed the documentation, the sole warranty for the software may be found in the applicable license agreement between AspenTech and the user. ASPENTECH MAKES NO WARRANTY OR REPRESENTATION, EITHER EXPRESSED OR IMPLIED, WITH RESPECT TO THIS DOCUMENTATION, ITS QUALITY, PERFORMANCE, MERCHANTABILITY, OR FITNESS FOR A PARTICULAR PURPOSE.

Corporate Aspen Technology, Inc. Ten Canal Park Cambridge, MA 02141-2201 USA Phone: (617) 949-1000 Fax: (617) 949-0130 URL: http://www.aspentech.com

Division Design, Simulation and Optimization Systems Aspen Technology, Inc. Ten Canal Park Cambridge, MA 02141-2201 USA Phone: (617) 949-1000 Fax:(617) 949-1030

Contents 1

Getting Started with Aspen Pinch A Typical Heat Integration Study ................................................................................ 1-1 Understanding Projects and Cases .............................................................................. 1-4 Case Trees and Inherited Data.............................................................................. 1-5 Working with the Aspen Pinch Interface .................................................................... 1-5 Starting Aspen Pinch.............................................................................................. 1-5 Understanding the Aspen Pinch Interface............................................................ 1-6 The Help System ........................................................................................................... 1-8 Starting Help .......................................................................................................... 1-8 Online Help ............................................................................................................. 1-8 User Guide .............................................................................................................. 1-9 Context-Sensitive Help........................................................................................... 1-9 Quitting Aspen Pinch.................................................................................................... 1-9

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Working with Projects, Cases, and Data Creating a New Project................................................................................................. 2-1 Switching on the Case Manager Toolbar .............................................................. 2-2 Setting a New Base Directory................................................................................ 2-2 Creating a Case....................................................................................................... 2-4 Designating Units................................................................................................... 2-4 Stream, Utility and DTmin Data........................................................................... 2-9 Economic and Cost Data ...................................................................................... 2-28 Shell Targeting Data ............................................................................................ 2-30 Data Tools ............................................................................................................. 2-31 Working with an Existing Project .............................................................................. 2-34 Selecting the Base Directory................................................................................ 2-34 Selecting an Existing Case................................................................................... 2-36 Editing Existing Data........................................................................................... 2-37 Moving Cases and Case Data............................................................................... 2-37 Copying Cases and Case Data ............................................................................. 2-38 Renaming Cases.................................................................................................... 2-39 Deleting Cases ...................................................................................................... 2-39 Using Data from Older Versions of Aspen Pinch or ADVENT................................. 2-40 Moving UNIX Data............................................................................................... 2-40 Checking Whether Data Files Need To Be Updated .......................................... 2-41 Updating Data Files Within Aspen Pinch........................................................... 2-43

3

Targeting for a New Process Working with Composite Curves.................................................................................. 3-1 Activating Targeting Functions ............................................................................. 3-2

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Switching on the Targeting Toolbar ......................................................................3-2 Viewing Composite Curves.....................................................................................3-3 Viewing, Adding, and Deleting Pinches ................................................................3-4 Obtaining Exergy Composite Curves ....................................................................3-5 Using Plot Tools.............................................................................................................3-6 Updating Plot Views ...............................................................................................3-7 Identifying Streams in Plots ..................................................................................3-7 Identifying Coordinate Values in Plots .................................................................3-7 Working with Text Within Plots ............................................................................3-8 Viewing Plots with or Without Markers................................................................3-8 Zooming into and Out of Plots................................................................................3-8 Taking a Plot Snapshot ..........................................................................................3-9 Setting Plot Grid Lines.........................................................................................3-10 Setting Background Color in a Plot .....................................................................3-10 Viewing/Printing in Color or Black and White ...................................................3-10 Setting the Limits on Plot Axes ...........................................................................3-11 Printing a Plot.......................................................................................................3-11 Obtaining a Targeting Report ....................................................................................3-12 Report Tools ..........................................................................................................3-13 Obtaining the Grand Composite Curve .....................................................................3-17 Obtaining the Exergy Grand Composite Curve ........................................................3-18 Placing Utilities ...........................................................................................................3-19 Removing Utilities ................................................................................................3-19 Automatically Placing All Utilities ......................................................................3-19 Placing Utilities One at a Time............................................................................3-20 Changing the Utility Duty ...................................................................................3-21 Optimizing Utilities.....................................................................................................3-22 Optimizing DTmin/Utility Loads for Two Utilities.............................................3-22 Setting the Optimization Range ..........................................................................3-25 Optimizing Utility Loads for Multiple Utilities ..................................................3-25 4

Importing and Segmenting Data Introduction ...................................................................................................................4-1 Importing Aspen Plus and Pro/II Simulation Results ................................................4-2 Before You Start......................................................................................................4-2 Selecting the Aspen Plus Simulation.....................................................................4-3 Setting Data Extraction Options ...........................................................................4-5 Segmenting Streams .....................................................................................................4-9 Auto Segmentation ...............................................................................................4-10 Interactive Segmentation .....................................................................................4-11 Changing Auto Segmentation Accuracy..............................................................4-14 Importing Files from SuperTarget .............................................................................4-15

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Retrofit Targeting What You Need for Retrofit Targets ............................................................................5-1 Starting Retrofit Targeting...........................................................................................5-1 Toolbars ...................................................................................................................5-3

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Adding New Alpha Values............................................................................................ 5-3 Specifying Constant Alpha Values ........................................................................ 5-4 Specifying Incremental Alpha Values ................................................................... 5-4 Switching Between Constant and Incremental Alpha ......................................... 5-5 Switching Between Units and Shell Targets............................................................... 5-5 Creating Retrofit Plots.................................................................................................. 5-5 Energy Savings Plot ............................................................................................... 5-6 Creating Reports ........................................................................................................... 5-7 Specific Payback Report ......................................................................................... 5-7 Retrofit Targeting Report....................................................................................... 5-8 Redesigning the Heat Exchanger Network ................................................................. 5-9 6

Total Site Targeting Starting Total Site Targeting ....................................................................................... 6-1 Identifying Total Site Cases ......................................................................................... 6-2 Entering Case Information .................................................................................... 6-2 Total Site Existing Utilities ................................................................................... 6-3 Displaying Source Sink Profiles ............................................................................ 6-4 Enabling the Total Site Toolbars ........................................................................... 6-5 Placing Utilities............................................................................................................. 6-6 Modifying Targeting Data ............................................................................................ 6-7 Targeting for One Case ................................................................................................. 6-7 Obtaining a Total Site Report ...................................................................................... 6-8 Customizing Your Total Site Report ..................................................................... 6-8

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Network Design Starting Network Design.............................................................................................. 7-2 Switching on the Network Design Toolbars.......................................................... 7-3 Changing the Appearance of the Design Grid ...................................................... 7-4 Obtaining More Stream Information .................................................................... 7-5 Placing and Specifying Heat Exchangers .................................................................... 7-7 Placing a Heat Exchanger...................................................................................... 7-7 Specifying a B-JAC Hetran Model......................................................................... 7-8 Calculating B-JAC Hetran Matches.................................................................... 7-16 Specifying Exchanger Conditions ........................................................................ 7-17 Editing and Deleting Exchangers........................................................................ 7-20 Undoing Network Changes .................................................................................. 7-21 Restarting Your Design ........................................................................................ 7-21 Reinitialising Your Design ................................................................................... 7-21 Obtaining Exchanger Information ...................................................................... 7-22 Plot Tools in the Design Grid............................................................................... 7-25 Splitting and Mixing Streams .................................................................................... 7-25 Splitting a Stream ................................................................................................ 7-25 Specifying Split Flows .......................................................................................... 7-26 Mixing a Stream ................................................................................................... 7-27 Deleting Stream Splits and Mixers ..................................................................... 7-27 Placing and Specifying Multi-Stream Exchangers ................................................... 7-27

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Placing a Multi-Stream Exchanger .....................................................................7-28 Specifying Multi-Stream Exchanger Conditions ................................................7-29 Plate-Fin Heat Exchangers ..................................................................................7-30 Specifying New or Existing Exchangers ....................................................................7-32 Design Tools.................................................................................................................7-32 CP Table ................................................................................................................7-33 Driving Force Plots ...............................................................................................7-33 Exchanger Heating/Cooling Profile .....................................................................7-36 Automatic Design..................................................................................................7-37 Working with Network Loops and Paths ...................................................................7-38 Network Loops ......................................................................................................7-38 Network Paths ......................................................................................................7-40 Setting Loop/Path Parameters ...................................................................................7-43 Ordering By Exchanger Number Or Duty ..........................................................7-43 Required and Excluded Exchangers....................................................................7-44 Setting Network Design Parameters .........................................................................7-46 Match Data Temperatures ...................................................................................7-46 CP Table ................................................................................................................7-47 Heat Exchanger Profiles.......................................................................................7-47 Heat Exchanger Defaults .....................................................................................7-47 Heat Exchanger Style ...........................................................................................7-48 Setting Autosave ...................................................................................................7-48 Producing Reports .......................................................................................................7-49 Heat Exchanger Network Report.........................................................................7-49 Heat Exchanger Report ........................................................................................7-50 Cross-Pinch Heat Transfer Report ......................................................................7-50 Customizing Reports.............................................................................................7-51 Printing Networks, Plots, and Reports................................................................7-52 8

Retrofit Design Using Network Pinch Introduction ...................................................................................................................8-1 Before You Start ............................................................................................................8-2 Retrofit Design Data .....................................................................................................8-3 Exchanger Temperature Approach Limits............................................................8-4 Exchanger Duty Bounds.........................................................................................8-5 Match Constraints ..................................................................................................8-6 Solver Options .........................................................................................................8-7 Retrofit Design Toolbars ...............................................................................................8-8 Locate Network Pinch ...................................................................................................8-8 Execute Retrofit Design ................................................................................................8-9 Resequence Modifications ....................................................................................8-10 Repipe Modifications ............................................................................................8-12 New Exchanger Modifications .............................................................................8-13 Stream Split Modifications...................................................................................8-14 Solver Control ..............................................................................................................8-16 Optimizing Network Modifications ............................................................................8-17 Infeasible Results ........................................................................................................8-17

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Heat and Power Models Furnace .......................................................................................................................... 9-2 Modeling a Simple Furnace ................................................................................... 9-3 What Data Do You Need?....................................................................................... 9-4 Saving Your Furnace Model................................................................................. 9-12 Deleting your Furnace Model .............................................................................. 9-13 Running the Furnace Model Standalone ............................................................ 9-13 Running the Furnace Model in Targeting .......................................................... 9-14 Customizing Your Furnace Report ...................................................................... 9-17 Gas Turbine ................................................................................................................. 9-18 Modeling a Simple Gas Turbine .......................................................................... 9-19 What Data Do You Need?..................................................................................... 9-20 Saving your Gas Turbine Model .......................................................................... 9-31 Deleting your Gas Turbine Model ....................................................................... 9-31 Running the Gas Turbine Model Standalone ..................................................... 9-32 Running the Gas Turbine Model in Targeting ................................................... 9-33 Customizing Your Gas Turbine Report ............................................................... 9-34 Steam Turbine ............................................................................................................. 9-35 Modeling a Simple Steam Turbine ...................................................................... 9-36 What Data Do You Need?..................................................................................... 9-37 Saving Your Steam Turbine Model ..................................................................... 9-46 Deleting Your Steam Turbine Model................................................................... 9-46 Running the Steam Turbine Model Standalone ................................................. 9-46 Running the Steam Turbine Model in Targeting ............................................... 9-47 Customizing Your Steam Turbine Report........................................................... 9-48 Adding a Fired Heater to Your Steam System ................................................... 9-48 Adding Extra Stages to your Turbine Model ...................................................... 9-50 Additional Turbine Feeds and By-Passes ........................................................... 9-50 Refrigeration................................................................................................................ 9-52 Modeling a Simple Refrigeration System............................................................ 9-54 What Data Do You Need?..................................................................................... 9-55 Saving your Refrigeration Model......................................................................... 9-64 Deleting Refrigeration Systems and Cycles........................................................ 9-65 Running the Refrigeration Model Standalone .................................................... 9-65 Running the Refrigeration System Model in Targeting..................................... 9-67 Customizing Your Refrigeration System Report ................................................ 9-67 Adding More Heat Discharge Exchangers to your Model .................................. 9-68 Adding More Refrigeration Levels to your Model .............................................. 9-68

10 Heat Exchanger Network Simulation and Optimization Data Files Used in Simulation/ Optimization ........................................................... 10-3 Stream Information .............................................................................................. 10-4 Network Information............................................................................................ 10-6 Cost Information................................................................................................... 10-7 Simple HEN Simulation ............................................................................................. 10-8 Before You Start a Simple HEN Simulation....................................................... 10-8 Performing a Simple Simulation ......................................................................... 10-9

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Omitting Exchangers from the Simulation .......................................................10-13 Data Files Used in Simple Simulation ..............................................................10-14 The Simulation Report .......................................................................................10-22 Simulation Report Tools .....................................................................................10-23 Detailed HEN Simulation .........................................................................................10-26 Before You Start a Detailed HEN Simulation ..................................................10-27 Detailed Physical Property Data .......................................................................10-36 Detailed Block Data ............................................................................................10-39 Detailed HEN Simulation: Rating .....................................................................10-51 Detailed HEN Simulation: Design.....................................................................10-53 Simple HEN Optimization ........................................................................................10-54 Before You Start a Simple HEN Optimization .................................................10-55 Optimization Variables and Specifications .......................................................10-56 Performing a Simple Optimization ....................................................................10-59 Detailed HEN Optimization .....................................................................................10-63 Simulation to Meet a Design Specification ..............................................................10-64 Performing Simulation, Optimization and Design Runs for a Single Network ....10-65 Errors and Diagnostics..............................................................................................10-66 Setting Diagnostic Levels ...................................................................................10-67 Index

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Chapter 1

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Getting Started with Aspen Pinch This chapter provides an overview of a typical heat integration study. It shows the steps in such a study, and how Aspen Pinch should be applied at each stage. It also introduces Aspen Pinch and its interface, and shows you how to start and quit from Aspen Pinch.

A Typical Heat Integration Study The following figure shows the major steps in a heat integration study, together with the corresponding Aspen Pinch feature. Although the figure implies that a heat integration study is a once-through procedure, in fact there are several iterations required to ensure overall optimum results.

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Obtain Data (Stream, Utilities, Cost): Heat & Material Balance Aspen Plus

Aspen Pinch FEATURE

Aspen Plus INTERFACE TARGETING DATA ENTRY STREAM SEGMENTATION

Step in Heat Integration Study

Heat Exchanger Table TARGETING HEAT & POWER MODELING New Design Targets: Energy & Cost, Simulate Heat & Power System

Total Cost Optimization

TARGETING MULTIPLE UTILITIES OPTIMIZATION HEAT & POWER MODELING

RETROFIT TARGETING

Retrofit Target: Energy & Cost, TOTAL SITE TARGETING HEAT & POWER MODELS Total Site Targets: Energy & Cost, Simulate Heat and Power System

TARGETING COMPOSITE CURVES Evaluate Process Modifications

Design Heat Exchanger Network (HEN)

Evolve HEN Design to Reduce Overall Cost

Simulate/ Optimize/ Rate your HEN Design

GRID DIAGRAM HEAT EXCHANGER NETWORK DESIGN TOOLS RETROFIT DESIGN DESIGN EVOLUTION

NETWORK SIMULATION NETWORK OPTIMIZATION NETWORK RATING B-JAC INTERFACE NETWORK FLEXIBILITY

Evaluate the Flexibility of your HEN Design

Figure 1-1. Steps in a Heat Integration Study, and the Various Features of Aspen Pinch

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A heat integration study consists of the following steps: 1. Obtain data from your process. 2. Establish performance targets for utility consumption, energy costs, and capital costs. 3. Develop a heat exchanger network design. 4. Check the performance of your heat exchanger network design. The following section describes these steps. Obtain data from your process A heat integration study starts by obtaining data from your process. The data required for a heat integration study are temperature and duty information for each process stream. For each utility, temperature and cost information are required. If you want to include a cost analysis, heat exchanger cost data are also required.

Stream data can be taken directly from a heat and material balance of the process. Alternatively, the data can be imported from an Aspen Plus simulation or some other software program. To enter stream data, use Aspen Pinch’s data entry, the interface to Aspen Plus, and stream segmentation features. Establish performance targets The next step in a study is to establish performance targets for utility consumption, energy costs, and capital costs. For a new heat exchanger network design, use Aspen Pinch’s targeting feature. It includes the ability to optimize for multiple utilities. For a heat exchanger network retrofit, use Aspen Pinch’s retrofit targeting feature. For a total site, where heat can be recovered within and between different process units, use Aspen Pinch’s total site targeting feature.

When evaluating utility usage and costs, you may want to consider the performance of any utility system in detail. Aspen Pinch has heat and power models that simulate utility system performance and enable you to accurately predict utility system size and cost. Up to this point, the heat integration study will have predicted the best performance and cost of the process, using base case operating conditions. You should also investigate how changes to operating conditions of the process(es) change the overall heat exchanger network performance. It may be that a change in operating conditions leads to an improvement in overall cost. You should use Aspen Pinch’s targeting features—for example, composite curves—to evaluate process changes. Develop a heat exchanger network design The next step in a heat integration

study is to move from targeting to design. You will develop a new or revamped heat exchanger network design. Use Aspen Pinch’s grid diagram and heat exchanger network design tools to complete your design.

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The network design may contain some small heat exchangers that you will probably want to remove. Use Aspen Pinch’s network evolution tools, within network design, to remove any such small heat exchangers, and so reduce overall cost. If you are retrofitting a heat exchanger network, use Aspen Pinch's powerful retrofit design feature, which uses the latest “network pinch” techniques. Check the performance of your network design Finally, you should check the

performance of your heat exchanger network design. Use Aspen Pinch’s detailed simulation/optimization/rating features to check the geometric details of the heat exchangers. You can use such Aspen Pinch features to select tube lengths, tube pitch, baffle cut, and so on. If you want to check the flexibility of the network—for example, to check the effects of changes to stream supply temperatures, or to overall heat transfer coefficient (due to fouling)—use Aspen Pinch’s flexibility feature.

Understanding Projects and Cases Each Aspen Pinch study for a different process or site is referred to as an Aspen Pinch project. Each project will likely cover several different operating cases, and these are referred to as Aspen Pinch cases. For a study that covers several process units on one site, each process will be referred to as a case. When you start Aspen Pinch on a new project, you should select a new directory or folder on disk, where you will store all project and case information. The following figure shows a typical Aspen Pinch study, and the relationship between a project and cases: Base directory for the project

Subdirectories for individual cases

CRUDE

FEED1

- Stream data - Utility data - DTmin

SUMMER - Stream data

WINTER - Stream data

FEED2

- Stream data - Utility data - DTmin

MAXGAS - Stream data

Figure 1-2. Relationship Between Project and Cases for a Crude Unit

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As Figure 1-2 shows, all operating cases are collected under the base directory CRUDE. Subdirectories FEED1 and FEED2 represent different feedstock cases. FEED1 itself has two operating cases, represented by the subdirectories SUMMER and WINTER. FEED2 has a single operating case, represented by MAXGAS.

Case Trees and Inherited Data Within an Aspen Pinch project, cases are arranged as parent and child cases. If data is required by Aspen Pinch, and the data is not in a given case, Aspen Pinch looks for the data in the parent case. (The search starts at the case directory and ends at the base directory.) This minimizes the amount of data that is stored for a project. For example, in the earlier Figure 1-2, FEED1 and FEED2 are parent cases, while SUMMER, WINTER, and MAXGAS are child cases. Stream, utility, and DTmin data are specified within case FEED1. The child case SUMMER has its own stream data, but it inherits its utility and DTmin data from the parent case FEED1. Data inheritance warning You should exercise caution when editing data that is inherited by a child case. Any changes you make will be inherited. Aspen Pinch warns you if your data edits are likely to affect a child case.

Working with the Aspen Pinch Interface Before you begin working with Aspen Pinch, you should understand the Aspen Pinch interface and how that interface presents study data.

Starting Aspen Pinch To start Aspen Pinch, double-click the Aspen Pinch icon in the Advent window:

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The Aspen Pinch startup screen appears.

Understanding the Aspen Pinch Interface Most of your work in Aspen Pinch is carried out within the Aspen Pinch window and, within that, the Case Manager window.

The Main Aspen Pinch Window When Aspen Pinch starts, you see an Aspen Pinch window surrounding a smaller Case Manager window: Base directory

Aspen Pinch cases

Menu bar Tool bar

Case Manager window

Data tables

The Aspen Pinch window displays context-sensitive menu bars and toolbars. Many of the commands on the menu bar have equivalent toolbar buttons. You can use either, depending on your preference.

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The Case Manager Window The Case Manager window displays the arrangement of Aspen Pinch data. For each Aspen Pinch project, the Case Manager shows the base directory and the directories representing each case within that directory. The base directory contains all cases for a particular project. For any case selected in the left pane of the Case Manager window, corresponding data files for the case are shown in the right pane. For details on how to create and edit cases and data, refer to Chapter 3.

Directories and Cases The Case Manager shows the relationship between parent and child cases. If child cases exist and are not shown in the left pane of the Case Manager window, the parent case name is flagged with a plus sign ( ). When you click the plus sign, the child cases are revealed and the plus sign changes to a minus sign ( ). To hide the child case names, click the minus sign. Any case you are working in assumes an open-folder icon:

.

If data has changed within a case but is not yet saved, the folder icon for that cases changes from to . You can save or discard any changes to the data in a case at any time, by rightclicking the mouse on that case. Select Save Case or Discard Changes to case from the resulting popup menu.

Case Data When you click on a case in the left pane of the Case Manager window, the right pane displays Aspen Pinch data files for that case. Both input and calculated data files are shown. All inherited files are displayed when the Show Inherited Files box is checked. Each data file is marked with one of the following symbols: Text file Empty file Inherited file Inherited and empty file Note

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For more information about Case Manager and the organization of your data, see Chapter 3.

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The Help System Aspen Pinch has an extensive Help system, which enables you to get information by: • Browsing topics by category • Searching index entries • Looking up keywords and phrases Context-sensitive Help is also available within Aspen Pinch.

Starting Help To start the Aspen Pinch Help system, select Help from the menu bar. You see four options: • Aspen Pinch Help Topics Select this if you want to browse through Help topics, either in the Online Help system or in the User Guide. • Aspen Pinch Online User Guide Select this if you want to browse through Help topics only in the User Guide. • Using Help Select this if you want more information on how to use the Help system. • About Aspen Pinch Select this if you want to check on the version number of your copy of Aspen Pinch. If you selected Aspen Pinch Help Topics, the Help Topics dialog box appears. By clicking on the Contents tab sheet, you can access Aspen Pinch On-Line Help and the Aspen Pinch User Guide.

Online Help You can view Aspen Pinch online Help by selecting the Contents tab in the Help Topics dialog box and clicking the Aspen Pinch Online Help book. Online Help is a summary of all Aspen Pinch Help topics. These entries have many hypertext links to associated topics and provide a very useful way for you to learn about a specific subject. Hypertext links are displayed as green, underlined words. By clicking a hypertext link, you can jump to Help on the indicated subject.

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User Guide You can view the online version of this Aspen Pinch User Guide by selecting the Contents tab in the Help Topics dialog box and clicking the Aspen Pinch User Guide book.

Context-Sensitive Help Context-sensitive Help is available throughout Aspen Pinch. To access it, press Function key F1 at any time.

Quitting Aspen Pinch To quit Aspen Pinch, click Exit from the File menu. For each unsaved data file, Aspen Pinch asks whether you want to save the data. As you exit Aspen Pinch, a Save/Discard Cases Worked On window appears:

If you want to save all the updates you have made during your Aspen Pinch session, select Save All. If you want to discard all changes, select Discard All. Optionally, to save or discard changes to an individual case, select the case and click Save or Discard, as appropriate. After the save or discard operation, exit Aspen Pinch.

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Working with Projects, Cases, and Data This chapter shows you how to organize your study data into projects and cases using Aspen Pinch’s Case Manager. It describes how to: • Create a new project and work with an existing project • Create a new case and work with existing cases • Set your working units • Enter your targeting data See Chapter 2 for information about how to organize your study data. You should save each study as a separate project. If you look at several cases within one project, you should save these with separate case names

Creating a New Project To create a new project, you must: • Set a base directory • Create a case • Designate units • Enter target data Each Aspen Pinch project requires its own base directory on disk. Each case within an Aspen Pinch project is stored in the base directory. If a suitable base directory does not already exist, you must create it.

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Switching on the Case Manager Toolbar Aspen Pinch has a dedicated toolbar for use with projects, cases, and data. To switch on the Case Manager toolbar, from the menu bar select View, then Toolbars. A Toolbars window appears:

If you want the Case Manager Toolbar displayed, check the Case Mgr Toolbar box, then OK. The toolbar appears:

Setting a New Base Directory When you start a new Aspen Pinch project, you need to designate the base directory that will be used to store all project data.

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To designate the base directory: 1. Within the Aspen Pinch window, select File from the menu bar, then New, then Base Directory. Alternatively, click the New Base Directory button on the Case Manager toolbar: The Choose Base Directory window appears:

2. Click the Create New Base Directory button, then OK.. A Create Base Directory window appears:

3. Complete the Name box or select the path to the new base directory in the Directory box, then click OK. If you want to create a base directory on a network, click the network button to connect to a network drive. You are now ready to start specifying an Aspen Pinch Case to work in, as well as your operating units and your project data.

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Creating a Case Each project is likely to require the study of different operating cases—for example, a summer case and winter case. Each case should be given a unique name. To create a new case: 1. From the Aspen Pinch menu bar, select File, then New, then Case. Alternatively, click on the base directory name in the Case Manager window, click the right mouse button, and select New from the pop-up menu. The New Case window appears:

2. If you are creating a child case, the Parent Case field should display the name of the parent case. Otherwise, the Parent Case box should be left blank. For a detailed explanation of child and parent cases, refer to Chapter 2. 3. Type a name for the new case in the New Case Name field, then click OK. The Aspen Pinch Case Manager window displays the base directory with the new case name below it.

Designating Units You can either use units that already exist within Aspen Pinch or create your own units. This section describes how to: • Set project units • Select a unit set for your project • View units used in a pre-defined set • Change default unit sets

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Setting Project Units To set the units required for your project, click the Units button on the common toolbar in the Aspen Pinch window: Alternatively, select Data from the Aspen Pinch menu bar, then Units . The Unit Settings window appears:

The Unit Settings window contains four tabs: Use this tab

To

Set Current Units

Select a unit set from among predefined or user-defined sets

Short Unit List

View and edit units for the most important entities of a unit set

All Units

View and edit a full list of entities and units in a set

Add Units

Create your own units

Selecting a Units Set Aspen Pinch is delivered with the following standard units sets predefined: Standard Units Set

Units

US-ENG

°F, MMBtu/hr, ft 2 , psia

METRIC

°C, MMkcal/h, m2 , kg cm2

SI SI BASED

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K, W, m2 , Pa °C, KW , m2 , bar

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You can create your own units sets to add to this list. To select a units set: 1. Click the Set Current Units tab in the Unit Settings window. 2. In the Current Unit Set field, select the units you want by clicking the arrow to display a default set of units. The units set appears in the window’s Sample box. 3. In the Unit Settings field, specify how to apply the units set: Choose

To apply the units set to

Global

All Aspen Pinch projects on your computer

Case Specific

Current case only

4. Click OK.

Viewing Your Units You can view either a summary list of your selected units or a comprehensive list of all units selected. To view the summary units list, click the Short Unit List tab in the Unit Settings window:

Use the scroll bars to fully examine all the units.

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To view the comprehensive units list: 1. Click the All Units tab in the Unit Settings window:

Use the scroll bars to fully examine all the units. 2. To view other units sets, click Previous or Next. If the units are displayed in record format, only one units set appears in the window. 3. To view all units sets together in table format, click the Table button. Use the scroll bars to view all units.

Customizing Your Units To customize units in your selected units set: 1. Select the All Units tab in the Unit Settings window. The Unit Settings window appears. It displays units for each Aspen Pinch default units set. 2. Double-click the units to change. A units list appears. 3. Click the units you require. 4. Repeat Steps 2 and 3 for all the units that you want to change. 5. Be certain to enter a units Set Name. This name will appear in the Set Current Units list. 6. Click Save to save the units in the default units set.

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Creating New Units You can create your own units for use in your project. However, first you must know the relationship between the units you want to create and their corresponding SI units. This relationship should obey the form of the following equation: New Unit = C0 + C1 * (SI Unit) + C2 * (SI Unit)2 Where C0, C1 and C2 are constants To create a new unit: 1. In the Unit Settings window, click the Add Units tab. 2. Click Table to view all units in table format. 3. Use the scroll bar to move to the bottom of the completed fields, to the first empty row. 4. To view a list of valid entries for a field, click the field and then click the right mouse button. From the shortcut menu, select Edit. Complete each field. 5. Click Verify to confirm that you have entered all required parameters. 6. Click Save. The new units are available for use. The following figure illustrates the data required to set up temperature units of F, shown in Record format:

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Stream, Utility and DTmin Data Aspen Pinch enables you to estimate the minimum energy usage for any process. This minimum energy usage is referred to as the energy target. This section describes how to enter the data required to calculate such an energy target for your process. This basic data includes: • Stream data — Temperature and duty information for the process streams • Utility data — Temperature/cost data for the utilities • DTmin — The minimum approach temperature at which heat may be exchanged within the process This section describes how to: • Select a data filter • Create new data • Edit data • Enter or edit a case description, stream data, utility data, DTmin, heat exchanger cost data, economic data, and heat exchanger shells data

Selecting a Data Filter You can display all Aspen Pinch data in the Case Manager window. Or you can display only the data used by a particular feature of Aspen Pinch, such as targeting or network design. To filter Aspen Pinch data: 1. From the menu bar, select Options and Data Filter. Alternatively, click the Data Filter button on the Case Manager toolbar: The Choose Data Filter dialog box appears:

2. Use the Data Group Filter list box to select the type of data you are interested in. 3. Click OK. The right pane of the Case Manager displays the data in that group.

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Creating New Data To create commonly used data, such as DTmin, Streams, Utilities, Economic data, Case Description or Title, select Data from the menu bar. From the list that appears, select the name of the data you want to create. Alternatively, to view the full list of possible data files required in Aspen Pinch and then create data from this list, use the following procedure: 1. Click the Create Data button on the Case Manager toolbar: The Create New Data dialog box appears:

2. Use the Choose the Type of Data list box to select the type of data you want to create. 3. Click OK. An Editing Data window appears. 4. Use the window to enter your data. The following sections explain how to enter each type of targeting data. Field Help For each data entry field in each editing data window, online Help is

available. To activate online Help, click in the field and press function key F1.

Editing Data You may already have existing data in Aspen Pinch that you want to edit. To edit existing data: 1. Find and double-click on the name of the data you want to edit, in the Case Manager window. 2. Use the window to edit your data. The following sections explain how to enter each type of targeting data.

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Case Description It is important to have a description of each case, especially if you are working with several different cases. To create a case description: 1. From the menu bar, select Data, then Case Description. Alternatively, click the Create Data button on the Case Manager toolbar: The Create New Data dialog box appears. From the list box within this window, select Case Description. Then click OK. 2. Type the description of your case in freeform format, as shown:

Stream Data The minimum stream data required for a given case are stream supply and target temperatures, stream heat duties, and stream names. You can also create stream data easily by using the Heat Exchanger Table. To create stream data: 1. From the menu bar, select Data, then Streams. Alternatively, click the Create Data button on the Case Manager toolbar: 2. The Create New Data dialog box appears. From the list box within this window, select Stream Data. Then click OK. A Stream Data window appears.

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3. In this window enter the data for your streams, by completing the fields as shown:

A stream name must be entered before stream data can be input. The form then requires that at least Tsupp, Ttarg and Duty are supplied for each segment. When the first segment of a stream has been entered, it is then only necessary to enter a Tout value in the next row and the editor will assume that this row represents the next segment in the same stream. The Tsupp for this segment will therefore automatically become the Ttarg of the previous segment.

The stream name is only written once. So, any segments which do not have a stream name belong to the stream above. Any time a temperature is changed, and there is an associated Ttarg or Tsupp value on another segment, that segment will be updated accordingly. A value for MCP is calculated automatically, when there is Ttarg, Tsupp and Duty data available. Alternatively, Duty will be calculated if MCP is provided. Individual segments can be switched on or off using the ON checkbox in each row. Segments which are switched off are greyed out. The Type column shows whether the stream is hot or cold. This is automatically determined from the Ttarg and Tsupp and cannot be input.

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The form performs certain checks on the completeness of the data. If it finds an error, the row(s) containing the error(s) will be highlighted in yellow. When a cell on a row containing an error is selected the status bar at the bottom of the form gives an explanation of the error (see the previous example). You can get help for each field by pressing F1 when the field is selected. 4. An example set of completed stream data is:

To determine energy targets for your process, the minimum stream data required for each stream are temperatures and duty. To ensure that Aspen Pinch can calculate the duty of a segment (stream), you must enter one of the following: • Segment Heat Duty • Segment MCP (mass * specific heat)

Toolbar

The toolbar has tool-tips that show you what each button does. Hold the mouse pointer motionless over a button to see a tool-tip. From left to right the buttons represent: Save Saves any changes made to the data. Export Allows the data to be saved to a variety of formats, including Excel. Print Prints the current visible sheet

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Copy Copies the selected cells to the clipboard Paste Pastes text from the clipboard into the editor Insert Row Inserts a new row above the one currently selected Delete Row Deletes the row (or rows) currently selected View Columns Brings up the following form:

This form allows the customisation of the stream data editor. The width of each column and the column name can be changed, as well as the number formatting for each column - the no. of figures to the right of the decimal point and the total no. of displayed characters. Columns can also be hidden.

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Column Order Allows the ordering of columns, using the following form:

Options Brings up the following form:

As new rows of data are input, numbers for the IDs of Streams and stream Segments are automatically generated. These two options, when activated, will keep the numbers allocated to stream IDs and segments IDs sequential. If these are switched off you have control and can use any numbers for stream and segment IDs. Find The Find drop down box brings up a list of all stream names which have been defined, and selecting one will move the focus to that stream.

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Optional Stream Data If you want to calculate heat transfer area targets and cost targets, you must enter additional optional stream data, such as: • Hfilm — Segment film heat transfer coefficient • Contrib — Segment’s contribution to minimum temperature difference, sometimes called a delta-T contribution (this is not required for area and cost targets) • Cost Law — Stream-specific heat exchanger capital cost law identifier. This identifier should correspond to one of the identifiers in your heat exchanger cost data (see Heat Exchanger Cost Data on page 2-28 for more information).

Streams and Segments For streams where specific heat changes significantly with temperature, the heating/cooling curve may be broken down into several segments, each with a different specific heat capacity. This allows the actual heating/cooling curve to be closely modeled. To enter several segments for a particular stream into Aspen Pinch, enter each segment as you would a separate stream. The name and stream number for each segment must be the same. Each segment ID will be different.

Utility Data To create utility data: 1. From the menu bar, select Data, then Utilities, then General Data. Alternatively, click the Create Data button on the Case Manager toolbar: 2. The Create New Data dialog box appears. From the list box within this window, select Utility Data. Then click OK. An Editing Utility Data window appears:

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3. In the Editing Utility Data window, enter the data for your first utility, by completing the fields as shown in the preceding figure. A more detailed description of each data field is given on the following pages. 4. To enter data for other utilities, and also to verify that all utility data has been entered and is acceptable to Aspen Pinch, refer to Data Tools on page 231.

Utility Stream Type Several types of utilities can be modeled in Aspen Pinch. Specify the utility type in the Type field of the Editing Utility Data window. To view the different utility types available: 1. Click the field that requires a type. 2. Click the right mouse button. 3. Select List from the shortcut menu. A Select window appears:

Use this window to scroll through the alphabetic list of utility types, and select the utility type you require.

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The utility types available in Aspen Pinch are:

Note

Utility Type

Utility ID

Air preheat (for furnace model)

AIR

Steam generation boiler feed water preheat

BFWP

Coal for fired heater

COAL

Cold stream generated by heat and power model

COLDSTRM

Refrigeration economizer

ECON

Electricity

ELEC

Furnace flue gas

FFLUE

Gas for fired heater

GAS

Gas turbine flue gas

GTFLUE

Steam for heating

HEATST

Hot stream generated by heat and power model

HOTSTRM

Hot water

HOTWATER

Oil for fired heater

OIL

Refrigerant

REFRIG

Steam generation vaporization

SGEN

Steam generation superheat

SUPER

Steam condensate flashed and used as vapor

VAPCOND

Cooling water

WATER

Steam for driving turbine

WORKST

You can also double-click in the Type field of the Editing Utility Data window to display this list.

Optional Utility Data If you want to calculate heat transfer area targets and cost targets, you may want to enter additional utility data, such as: • Hfilm—Utility film heat transfer coefficient • Contrib—Utility’s contribution to minimum temperature difference, sometimes called a delta-T contribution • Cost Law—Utility-specific heat exchanger capital cost law identifier. This identifier should correspond to one of the identifiers in your Heat Exchanger Cost Data (see Heat Exchanger Cost Data for more information).

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Utilities Connected to Each Other Some of Aspen Pinch’s utilities can be connected, as follows: • Boiler feed water preheat (BFWP), steam vaporization (SGEN), and steam superheating (SUPER). If the utility data file contains BFWP, SGEN, and SUPER utilities, and the supply and target temperatures of these utilities are monotonic (for example, the target temperature of the BFWP equals the supply temperature of SGEN), Aspen Pinch assumes these utilities are connected to each other. When Aspen Pinch places steam generation in targeting, it will determine a steam flow and steam generation profile based on boiler feed water preheat, vaporization, and superheat, using in-built steam tables. • Steam generation (SGEN/SUPER) and steam use (HEATST). If you want to use the same mass flow of steam that you have generated either at the same or lower pressure, connect SGEN or SUPER utilities to a HEATST utility, using the Connect field. The following Editing Utility Data window shows steam generation SGEN connected to boiler feed water BFW:

•

•

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This is particularly useful in total site analyses (see Chapter 7). Steam for heating (HEATST) and flashed condensate vapor (VAPCOND). Once steam has condensed against the process, you may want to flash the condensate and generate some flash steam at a lower pressure. This steam can then be used to further heat the process. Aspen Pinch’s built-in steam tables calculate the amount of lower-pressure flash steam generated per mass of higher-pressure saturated condensate. Only the flash vapor (and not the flash liquid) is then used to heat the process. To connect such utilities, set the Connect field of the HEATST utility in the Editing Utility Data window to be the name of the VAPCOND utility. Flashed condensate vapor (VAPCOND) with a lower-pressure flashed condensate vapor (VAPCOND). Once the higher-pressure flash vapor has condensed against the process, it can be flashed to a lower pressure to get a cooler flash steam. To connect such utilities together, set the Connect field of the higher pressure VAPCOND utility, in the Editing Utility Data window, to be the name of the lower pressure VAPCOND utility.

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•

•

• •

Hot water (HOTWATER) and a flashed condensate vapor (VAPCOND). Once the hot water has cooled, it can be flashed to a lower pressure and the resulting flash steam used to heat the process. To connect such utilities together, set the Connect field of the HOTWATER utility, in the Editing Utility Data window, to be the name of the VAPCOND utility. Steam used for heating (HEATST) with hot water (HOTWATER). Once steam has condensed against the process, the condensate can be further used to heat the process, as hot water. To connect such utilities together, set the Connect field of the HEATST utility, in the Editing Utility Data window, to be the name of the HOTWATER utility. Flashed condensate vapor (VAPCOND) with hot water (HOTWATER) Hot water (HOTWATER) with hot water (HOTWATER)

Note

More than one utility can be connected to any one VAPCOND or HOTWATER utility. All feed utilities are mixed and flashed to the pressure of the VAPCOND/HOTWATER utility. The pressure is set by the supply temperature of the utility. This feature can be used to model desuperheaters, where superheated steam is mixed with water to reduce its temperature. To see a list of utilities that can be connected to a VAPCOND or HOTWATER utility, select the Connect field of the utility in question, then click the right mouse button and select List from the popup menu.

Utilities Connected to Heat and Power Models Several utilities can be used only if they are connected to heat and power models—for example, AIR, COAL, COLDSTRM, ELEC, GAS, HOTSTRM, OIL, and WORKST. Other utilities, such as BFWP, ECON, FFLUE, GTFLUE, HEATST, REFRIG, SGEN, and SUPER can be used either alone or as part of a heat and power model. For more information on heat and power models, see Chapter 10.

Fixed Flow Rate Utilities If a utility has a fixed mass flow rate, enter its flow in the Editing Utility Data window. Targeting will then give this utility a constant (fixed) heat duty.

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DTmin The minimum temperature difference for heat exchange is referred to as DTmin. To create a DTmin data file: 1. From the menu bar, select Data and DTmin. Alternatively, click the Create Data button on the Case Manager toolbar: 2. The Create New Data dialog box appears. From the list box within this window, select DTmin. Then click OK. An Editing DTmin window appears:

3. Enter the value for DTmin in the window. 4. Click OK to save your DTmin value and return to Aspen Pinch’s Case Manager window. In Targeting, you have a different way to set DTmin:

In You can enter a DTmin directly or you can specify the hot or cold utility target and have the program calculate DTmin. Click the Set DTmin button to set DTmin.

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Heat Exchanger Table The Heat Exchanger Table is used to quicky create stream data, utility data, the heat exchanger network, and Total Site Existing Utilities (utility summary information that can be used in Total Site Analysis – see Chapter 7). The stream data is approximate – in most cases with segments created around each heat exchanger on the stream. The Heat Exchanger Table is usually used to quickly screen the energy saving potential of a process. To create the Heat Exchanger Table: 1. From the menu bar, select Data, then Heat Exchanger Table. Alternatively, click the Create Data button on the Case Manager toolbar: 2. The Create New Data dialog box appears. From the list box within this window, select Heat Exchanger Table . Then click OK. A Heat Exchanger Table window appears. 3. In this window enter the heat exchangers in your process, by completing the fields as shown:

This table contains columns which hold information about names of heat exchangers, names of the streams connecting the heat exchangers, input and output temperatures, duty and further details about the individual heat exchangers. There are two sheets for data input. The sheet shown above is the heat exchanger-centric view. There is also a stream-centric view where heat exchanger information is entered stream-by-stream. Each view lets you view the data grouped by stream or heat exchanger. There is also a Utility Summary sheet which summarizes the utility information that you enter in the other two sheets. Data can cannot be input in this view. To change between the views click on the tabs at the bottom of the window.

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When entering new data, either a stream name or a heat exchanger name (depending on the view) must be input first. You then enter the remaining data about the streams and the heat exchangers. When starting a new row of data, always use the topmost empty row – do not have empty rows between rows of data or the data may be lost. You only need to enter names of streams or heat exchangers one time. When you click in one of these name fields, a drop down list appears with all streams or heat exchanger entered so far. You can either select one of these or type in a new name.

The checkbox on the UT column should be checked for rows which specify a utility stream. In the previous example, STEAM is a utility stream so UT is checked. Utility streams are greyed out to distinguish them from process streams. The Upstream column is used to define the topology (connections) of the network. Here you enter the name(s) of heat exchanger(s) which are upstream of the heat exchanger being input. You can have more than one upstream heat exchanger, this is how you indicate a mixer. For example, if you have an arrangement such as:

Exchangers E2 and E3 both have E1 as upstream exchangers – indicating a stream split. Exchanger E4 has E2 and E3 upstream – indicating a mixer. When there is more than one upstream heat exchanger, the names are separated by a semi-colon. When you click in the Upstream cell, a list appears containing all heat exchangers entered. Selecting an exchanger that is not in the Upstream cell appends it to the end; selecting an exchanger that is already in the Upstream cell removes it.

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The form performs certain checks on the completeness of the data. For example, that temperature in and out, and duty values have been entered for all heat exchangers, streams do not contain hot and cold segments, etc. If it finds an error, the row(s) containing the error(s) will be highlighted in yellow. When a cell on a row containing an error is selected the status bar at the bottom of the form gives an explanation of the error (see the previous example). Temperature values entered will automatically be copied to respective inputs or ouputs of other stream segments where the topology has been defined. You can get help for each field by pressing F1 when the field is selected. If required, segmented stream data can be input for a heat exchanger. Just specify the same names, or alternatively, after a row of data has been entered, you need only enter a Tout value in the following blank row and it will assume the same heat exchanger and stream (similar to the Stream Data editor):

As mentioned, data can be entered and viewed in either the stream-centric view or heat-exchanger-centric view. Although they both essentially contain the same data, the stream-centric view can also be used to enter segmented stream data for streams which are not connected to any heat exchanger. This data will not be displayed in the heat-exchanger-centric view:

Rows containing no heat exchanger names will have that column highlighted.

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The utility summary shows total heat duties for all process – process heat exchangers and for each utility stream:

4. An example set of a completed Heat Exchanger table is:

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Generating Stream Data You can generate stream, utility, and heat exchanger network data in two ways: When you click the Save button you are asked whether you want to generate Stream data. Click yes to generate stream data. Use the File-Import menu item:

Note that in both cases any existing Stream data, heat exchanger network data (Network Design Hxers, Splitters, Mixers, Multi-stream Hxers), and Utility data will be replaced.

Toolbar

The toolbar is the same as described for the stream data editor (see Toolbar on page 2-13. The toolbar has tool-tips that show you what each button does. Hold the mouse pointer motionless over a button to see a tool-tip.

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View Columns Brings up the following form:

This form allows the customisation of the Heat Exchanger Table editor. The width of each column and the column name can be changed, as well as the number formatting for each column - the no. of figures to the right of the decimal point and the total no. of displayed characters. Columns can also be hidden. Column Order Allows the ordering of columns, using the following form:

To change the order of columns, drag and drop the column name.

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Economic and Cost Data This section describes how to enter economic and cost data for your project. This data includes: • Heat exchanger cost data — an equation for exchanger cost as a function of heat exchange area • Economic data — operating time each year, lifetime; interest rate on borrowed capital Each type is explained in the following section.

Heat Exchanger Cost Data In order to enter or edit your heat exchanger cost data, you should have your heat exchanger cost equation in one of the following forms: Actual Cost = Mobiliz + RefCost * (Size) Exponent

– Or – (Actual Cost) / RefCost = (Size / Refsize) Exponent

To create a heat exchanger cost data file: 1. From the menu bar, select Data, then Economic, then User Heat Exchanger Cost. Alternatively, click the Create Data button on the Case Manager toolbar: 2. The Create New Data dialog box appears. From the list box within this window, select User Heat Exchanger Cost. Then click OK. An Editing Heat Exchanger Cost Data window appears:

3. Enter the data for your first heat exchanger cost law, as shown in the preceding figure. Specify DEFAULT for the first CostID. This will be the cost law used for your case.

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4. If you have other heat exchanger cost equations you want to use, enter these as separate records. The additional heat exchanger cost equations can be applied to different streams in targeting (see page 2-11) or to different heat exchangers in network design (see Chapter 8).

Economic Data Aspen Pinch uses economic data to annualize capital costs and utility costs. To create an Economy data file: 1. From the menu bar, select Data, then Economic, then General Data. Alternatively, click the Create Data button on the Case Manager toolbar: 2. The Create New Data dialog box appears. From the list box within this window, select Economic Data. Then click OK. An Editing Economic Data window appears:

3. Fill out the boxes in this window with the operating time per year and the lifetime of your equipment, as shown. For information on Economic Method, refer to the following section.

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Capital Cost Annualization (Economic Method) Three economic methods are available to annualize capital costs. To view these methods: 1. In the Editing Economic Data window, click in the Economic Method box. 2. Click the List button in the Editing Economic Data window. A Select box appears, showing the equations that are used with each method:

3. Select the economic method you want to use, and click OK.

Shell Targeting Data Aspen Pinch determines area and cost targets using either units (pure counter current) or heat exchanger shells (non-counter-current heat exchange). Aspen Pinch calculates such targets based on shells only if shells targeting data is supplied. To create a Shell Targeting Data file: 1. From the menu bar, select Data, then Shell Targets. Alternatively, click the Create Data button on the Case Manager toolbar: 2. The Create New Data dialog box appears. From the list box within this window, select Shell Targeting Data. Then click OK.

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An Editing Shell Targeting Data window appears:

3. Fill out the boxes in the window as follows: • Shell Targets—If you want Aspen Pinch to calculate targets using shells, enter YES. Otherwise, enter NO. If you enter YES, fill out the FTmin or X fields. • FTmin or X—Enter either the minimum temperature difference correction factor for heat exchangers FT min, or a value for the parameter X. The X parameter defines the fraction of the maximum allowable temperature overlap in multi-pass heat exchangers. A typical value of X is 0.9, which corresponds to an FT factor of 0.75 for a 1-2 shell-tube heat exchanger with heat capacity flow ratio (R) of 1.0.

Data Tools Once you have clicked the Create Data or Edit Data buttons on the Case Manager toolbar, the Edit toolbar appears:

This toolbar is designed to help you enter and edit your data. The various features of the toolbar, together with some additional tips, are explained in the sections that follow. Note

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Most items on this toolbar are also available from a popup menu, activated by clicking the right mouse button in the Editing Data window.

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Switching Between Record and Table Format In Aspen Pinch data can be represented in record or table format. In record format, only one record is shown in the data window. In table format, all streams are shown in the data window. To view data in record format, click the Record button: To view data in table format, click the Table button:

Moving Between Records To move between records in Record format, click the Next Record or Prev (previous) Record button: Next Record Previous Record

Inserting and Deleting Records To insert a record in either Table or Record format: 1. Use the mouse to select the record after the insertion point. 2. Click the Insert Rec button: To delete a record in either Table or Record format: 1. Use the mouse to select the record to be deleted. 2. Click the Delete Rec button:

Cutting, Copying, and Pasting Records To cut, copy, or paste records in Table format: 1. Highlight the row or cells to be cut, copied, or pasted into. 2. With the mouse positioned over the active row, click the right mouse button. A shortcut menu appears. The menu includes Cut, Copy, and Paste commands. 3. Click the command you want to execute.

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Verifying Your Data Once you have entered your data, you can check it for consistency using Aspen Pinch’s data checker. To do this, click the Verify button: This check will tell you whether there are errors in your input data.

Searching Through Your Data To search for a specific record or field in your data: 1. Click the Find button: A Find window appears:

2. In the Find What box of the Find window, click either Record or Field. 3. Use the menu in the Find Field box to specify the variable to be found.

Creating a Data Report To create a report of the data being edited or input, click either the Report Table or Report Record button: Report Table Report Record

The Report Table button generates a report of input data in table format (all streams on one page). The Report Record button generates a report of all input data in record format (separate stream to a page).

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Printing a Data Report To print a data report, with the report window highlighted on screen, select File, then Print from the Aspen Pinch menu bar. If you want to view the report on screen before printing, select File, then Print Preview from the Aspen Pinch menu bar.

Customizing a Printed Data Report To customize a printed data report, with the report window highlighted on screen, select File, then Page Setup from the Aspen Pinch menu bar. A Report Page Setup window appears, where you can edit the headers and footers of your reports, the thickness of lines, page borders, and margin sizes.

Working with an Existing Project To work in an existing project directory, where some data files have been previously created, you must: • Select a base directory • Select a case You may also want to: • Edit data within a case • Move or copy data between cases • Rename and delete cases Each activity is discussed in the following sections.

Selecting the Base Directory To open an existing base directory: 1. Start Aspen Pinch by clicking on the Aspen Pinch icon on your computer screen. When Aspen Pinch starts, the Case Manager window appears. The base directory will be the directory opened the last time Aspen Pinch was used.

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2. You may select a different base directory. From the menu bar, select File, then New, then Base Directory. Alternatively, click the New Base Directory button: A Choose Base Directory window appears. 3. In this window, click on the Set Base Directory button. A window appears titled Set Base Directory:

This window shows directories and files. 3. Use the mouse to select the new base directory, then click OK. Aspen Pinch is now set to work in the new base directory.

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Selecting an Existing Case In most projects you will want to study several operating cases. You may want to continue working with an existing Aspen Pinch case. To select an existing case: 1. In Aspen Pinch’s Case Manager window, make sure all cases are listed beneath the base directory name. If they are not, double-click on the base directory name: Base directory

Aspen Pinch cases

Menu bar Tool bar

Case Manager window

Data tables

2. Using the mouse, click the required case in the left pane of Aspen Pinch’s Case Manager window (see Chapter 2). The folder adjacent to the case name opens, indicating that the case is active. You have now set up your working case and are ready to continue.

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Editing Existing Data To edit an existing data file: 1. Select the existing case where you want to work, as explained in the previous section. All data files associated with the selected case should be listed in the right pane of Aspen Pinch’s Case Manager window. 2. Double-click on the name of the data you want to edit. An Editing Data window appears. 3. Edit the data in this window. 4. When you have finished editing, close the window. Aspen Pinch prompts you to save the data.

Moving Cases and Case Data You may want to move a case and all its associated data files to another branch in your directory tree. Alternatively, you may want to move data files between cases. To move a case: 1. In the left pane of the Case Manager window, click the case to be moved. 2. Using the mouse, drag the case icon onto the case’s new parent directory. All files within that case are also moved. Note

Inherited data files are not moved.

To move data files between cases: 1. In the right pane of the Case Manager window, click the file to be moved. If more than one file is to be moved, use the mouse to click on each file while holding down CTRL. 2. Drag the file(s) to the new directory.

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Copying Cases and Case Data Aspen Pinch allows you to copy a case and all its associated files to a new parent case. It also allows you to copy selected files from one case to another. Copying a Case To copy a case and all its associated data files:

1. In the left pane of the Case Manager window, click the case to be copied. 2. Click the right mouse button to reveal a shortcut menu. 3. Select Copy from this menu. A Select Copy Options window appears:

If only one case is to be copied, without any child cases, check the Copy One Case box. If Inherited files are to be copied, check the Copy Inherited Files Also box. 4. In the left pane of the Case Manager window, click the case that is to receive the copy. 5. Click the right mouse button and, from the resulting shortcut menu, select Paste. A confirmation message appears. 6. Click OK, and your case will be copied. Note

To avoid duplication, the case name is automatically modified by Aspen Pinch. This can be changed later, as described in Renaming Cases, page 2-39.

Copying Case Data

To copy individual data files between cases: 1. In the right panel of the Case Manager window, click the file to be copied. If more than one file is to be copied, use the mouse to click on each file while holding down the CTRL key.

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2. Click the right mouse button and, from the resulting shortcut menu, select Copy. 3. Click the case to which the files are to be copied. 4. Click the right mouse button and, from the resulting shortcut menu, select Paste. The files are copied. If files with the same name already exist in that case, you are asked whether you want to overwrite the existing files.

Renaming Cases To rename a case: 1. In the left pane of the Case Manager window, click the case name. 2. Click the right mouse button. 3. From the resulting shortcut menu, select Rename. A Rename window appears:

4. Type the new case name in the To box, then click OK. The case name in Aspen Pinch’s Case Manager is automatically updated.

Deleting Cases To delete a case and all its child cases: 1. Click the case in the left pane of the Case Manager window. 2. Click the right mouse button and, from the resulting shortcut menu, select Delete Subtree. To delete a single case: 1. Click the case in the left pane of the Case Manager window. 2. Click the right mouse button and, from the resulting shortcut menu, select Delete This Case.

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Using Data from Older Versions of Aspen Pinch or ADVENT If you have data that you created using an older version of Aspen Pinch or ADVENT, you may need to convert that data before your latest version of Aspen Pinch is able to read it. This applies to data that was created in either the older UNIX version of ADVENT, in earlier Windows versions of ADVENT, or in an earlier Windows version of Aspen Pinch. If the data was created in UNIX, it must first be moved to the computer where your Windows version of Aspen Pinch is running. After the older Aspen Pinch data is on your Windows computer, you can, if necessary, update it for use with your new version of Aspen Pinch.

Moving UNIX Data Before working with Aspen Pinch or ADVENT data from a UNIX machine, you first need to move the data to the Windows computer. An efficient way to do this is to use a tar file. A single tar file contains all the UNIX data files used by Aspen Pinch.

Creating a tar File on Your UNIX Computer To create a tar file of the Aspen Pinch or ADVENT data on your UNIX computer: 1. On your UNIX computer, move to the base directory that contains all your Aspen Pinch or ADVENT data. 2. Create a tar file by typing: tar -cvf tarfilename . It is recommended that you use a descriptive file name with the extension .tar — for example, workshop.tar. The period (.) at the end of the tar command places all the files and subdirectories in your base directory into the tar file. To include only certain subdirectories, replace the period with a list of subdirectories you want included.

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For example, to include only subdirectories SD1 and SD2 in your tar file, you might type: tar -cvf tarfilename ./SD1 ./SD2 Transfer the tar file to the base directory of the Windows computer where you are running the new version of Aspen Pinch.

Extracting Data from the tar File After you copy the tar file from your UNIX computer to the base (working) directory on your Windows computer, you can begin to extract your data from the file. There are several ways you can do this, depending on the software you already have. Some Windows file compression programs have the ability to extract data from tar files. If you do not have any Windows software that can handle tar files, use the tar program provided with Aspen Pinch. To use the tar program supplied by AspenTech: 1. Open a DOS window, and move to your new base directory. This is the directory in which your tar file should currently reside. 2. In the DOS window, type: C:\advent\admin\tar -xvf tarfilename Note

If you installed Aspen Pinch in a directory other than C:\advent, you need to specify the appropriate path to the tar program.

3. The tar program opens the tar file and reassigns all constituent files into your new base directory. You will see several messages in the DOS window as the tar command acts on your tar file. After the tar command has been executed, you can close the DOS window.

Checking Whether Data Files Need To Be Updated If your data files were created in either the UNIX version or a previous Windows version of ADVENT or Aspen Pinch, they may require updating for use in the latest version of Aspen Pinch.

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To check whether your files need to be updated for use in the latest version of Aspen Pinch: 1. From within Aspen Pinch, select either the base directory where your files are stored, or select a single case that you want checked. 2. From the menu bar, select Manager, then Check Data. A Check Data window appears:

3. In the Check Data window, select the checking mode you desire — either the whole tree or just the selected case. Then click OK. The program checks to see if your data must be converted, before being used in the new version of Aspen Pinch. After the check has been done, you can view the data check report. Double click on the Check Data Report icon in the right side of the Case Manager window. A file check window appears:

The file check window will tell you if files need to be converted. If files need to be updated, follow the update procedure described in the following section.

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Updating Data Files Within Aspen Pinch If some of your data files require updating for use by your new version of Aspen Pinch, follow these steps: 1. From the menu bar, select Manager and Convert Data. A Convert Data window appears:

2. Select the conversion mode you require: either the entire tree or just the case you selected in Case Manager. Then click OK. 3. Aspen Pinch converts the data files. If you want to look at exactly what has been converted, double click on the Check Data Report icon in the right side of the Case Manager window. A file check window appears, indicating what data was converted:

Your data files are now ready for use in your new version of Aspen Pinch.

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Targeting for a New Process This chapter describes how to: • Target the energy consumption for your process • Select any number of utilities to heat and cool your process • Optimize utility targets The chapter assumes that you are working in the appropriate Aspen Pinch case, and that you have entered all your targeting data, as described in Chapter 3.

Working with Composite Curves Composite curves are used to determine the optimal heat exchange in a process. They show composite heating and cooling profiles for all process streams, and are the basic tool used in energy targeting. This section explains how to: • View composite curves • Obtain balanced composite curves • Use two composite curve tools • View, add, and delete pinches • Obtain exergy composite curves

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Activating Targeting Functions To work with composite curves, you need to activate targeting functionality in Aspen Pinch. Select Tools and Targeting from the menu bar . Alternatively, click the Targeting button on the Aspen Pinch common toolbar:

Switching on the Targeting Toolbar Aspen Pinch has several dedicated toolbars for use with targeting. To switch on the targeting toolbars, select View and Toolbars from the menu bar. A Toolbars window appears:

Check the boxes against the toolbars you want, then click OK. Depending on your selection, the toolbars will appear in the Aspen Pinch window as follows: Targeting Common Toolbar — Used to print, zoom, and plot utilities Targeting Operations Toolbar — Used to switch between Composite and Grand Composite Curve views, to view reports, and to update results Common Data Toolbar — Used to quickly edit streams, utilities or minimum approach temperature

Targeting Information Toolbar — Used to determine streams and coordinates of streams in Aspen Pinch’s targeting plots, and to add labels to the plots Targeting View Toolbar — Used to include utilities, show shifted temperature plots and exergy curves User Pinch Toolbar — Used to view, add, and delete pinches

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Viewing Composite Curves To view composite curves, click the Targeting button on the Targeting Operations Toolbar: Alternatively, select Targets and Composite Curves from the menu bar. The Targeting-Composite Curves window appears:

The window shows the composite curves for your process, and the value used for DTmin.

Balanced Composite Curves If utilities have been placed, you can view the balanced composite curves, including utilities. For information on placing utilities, see Placing Utilities on page 3-19. To view balanced composite curves, from the menu bar select Options and Balanced Composites. Alternatively, click the Show Utils button on the Targeting View Toolbar: When this button is clicked, the composite curves in the Targeting - Composite Curve window are redrawn to include any utilities that have been selected.

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Shifted Temperature Composite Curves To view the composite curves in shifted temperature coordinates, from the menu bar, select Options and Shifted Composites. Alternatively, click the shifted temperatures button of the Targeting View toolbar: When this button is clicked, the composite curves in the Targeting - Composite Curve window are redrawn in shifted temperature against enthalpy axes.

Viewing, Adding, and Deleting Pinches You can view, add, or delete pinches in composite curves. This is particularly important when you optimize utilities.

Viewing Pinches To view pinches, select Options, Pinches and Display from the menu bar. Alternatively, click the Display Pinches button:

Adding Pinches To add pinches: 1. From the menu bar, select Options, then Pinches, then Add. Alternatively, click the Add Pinches button: Note

If either Add or the Add Pinches button are greyed, you should first display the pinches before adding new ones.

2. The cursor changes to a pinch with a ‘+’ sign. Move the cursor to the new pinch point, and click on the composite curve. If more than one stream causes the pinch, a message window appears, listing the possible pinch-causing streams. Select the appropriate stream from the list displayed in the window.

Deleting All Pinches To delete all pinches that have been added, from the menu bar select Options from the menu bar, then Pinches, then Delete All. Alternatively, click the Delete All Pinches button:

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Deleting User Pinches To delete a user pinch: 1. From the menu bar, select Options, then Pinches, then Delete. Alternatively, click the Delete Pinches button: 2. The cursor changes to a pinch with a ‘-’ sign. Move the cursor to the pinch to be deleted, and click on the pinch..

Obtaining Exergy Composite Curves To obtain the exergy composite curves: 1. From the menu bar, select Targets, then Properties, then Exergy On . This starts exergy calculations in Aspen Pinch. 2. Obtain the Exergy Composite curves, by selecting Options from the menu bar, then Exergy Composites. Alternatively, click the Exergy Composites button on the Targeting View toolbar: 3. If you have not already specified an ambient temperature, the Editing Ambient Temperature window appears:

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4. Enter the ambient temperature, and the exergetic efficiencies of your power systems below and above ambient temperature, in the appropriate boxes. Then click OK. The exergy composite curves appear, showing the exergy loss:

To obtain the exergy target report, select Targets from the menu bar, then Report, then View. Alternatively, click the Report button on the Targeting Operations toolbar:

Using Plot Tools Aspen Pinch has many tools to help you understand and manipulate plots. You can: • Update plot views • Identify streams and coordinate values • Add comments to plots • Set markers at each calculated point in a plot • Zoom in to one section of a plot • Take a snapshot of a plot • Set grid lines and a background color • View/print in color or black and white • Set the limits on plot axes • Print a plot The following sections describe how to perform these tasks.

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Updating Plot Views Aspen Pinch will automatically update all plots and results. This automatic update occurs only if you have selected Targets from the pull-down menus, then Properties, and Enable Automatic Update is checked. If Enable Automatic Update is not checked and you want to update your plots after you have modified and saved your data, click the Update All Views button on the Targeting Operations toolbar:

Identifying Streams in Plots To identify the streams that exist at a particular point in the composite curves: 1. From the menu bar, select Options, then Identify Streams. Alternatively, click the Identify Streams button on the Targeting Information toolbar: 2. The cursor changes to an ID shape. Click any point on the curves in your plot. The names of the streams passing through the selected point appear next to that point. To switch off the Identify Streams feature, double click on any point in your plot.

Identifying Coordinate Values in Plots To identify coordinate values in plots: 1. From the menu bar, select Options and X,Y Values. Alternatively, click the X,Y Values button on the Targeting Information toolbar: 2. The cursor changes to a cross. Click any point on the curves in your plot. The coordinates of the touched point appear next to that point. To switch off the X,Y Values feature, double click on any point in your plot.

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Working with Text Within Plots To add text to plots: 1. From the menu bar, select Options and Text. Alternatively, click the Text button on the Targeting Information toolbar: 2. Use the mouse to select a point in the plot window, then type your text. The text will appear in the plot at your selected point. To switch off the Text feature, double click on any point in your plot. To reposition text that you have previously added to a plot: 1. Click on the text, which then becomes highlighted. 2. With the pointer positioned over the highlighted text, keep the left mouse button pressed, and move the pointer to the new text location. The text moves with the pointer.

Viewing Plots with or Without Markers Aspen Pinch can display your plot with a marker at each calculated point. To display markers, from the menu bar select Options and ensure that Markers On is checked. Alternatively, click the Markers On button in the Targeting Common toolbar: To remove markers, click the Markers On button again.

Zooming into and Out of Plots To zoom in on one section of your plot: 1. Click in the plot window. 2. While pressing the left mouse button, drag the cursor to mark a rectangular area for enlargement. 3. From the menu bar, select View, Zoom and Zoom In. Alternatively, click the Zoom In button:

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You can maintain the same degree of enlargement while viewing a different part of your plot. To do this: 1. Zoom in on one section of your plot, as described in the last procedure. 2. From the menu bar, select View, then Zoom, then Pan. Alternatively, click the Pan button in the Targeting Common toolbar: 3. Your plot appears unmagnified, but with a box showing the area to be enlarged:

4. Click the box and drag it until it covers the area you want enlarged. Release the mouse button. The plot inside the box appears enlarged. You can also change the degree of enlargement by dragging the corners of the box. To reset the zoom, select View from the menu bar, then Zoom, then Zoom Full. Alternatively, click the Zoom Full button in the Targeting Common toolbar:

Taking a Plot Snapshot You can take a snapshot of a plot, perhaps for reference later in your study. Once you have taken a snapshot, the snapshot remains in a separate Snapshot window within the main Aspen Pinch working window. It remains there until you close the Snapshot window or you shut down Aspen Pinch. Once removed, the snapshot cannot be retrieved.

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To take a snapshot: 1. Click the plot window of the plot you want to snapshot. 2. From the menu bar, select View and Snapshot. Alternatively, click the Snapshot button in the Targeting Common toolbar: A new Snapshot window is created containing a copy of your plot. This snapshot remains in the main Aspen Pinch working window until either you close it or shut down Aspen Pinch.

Setting Plot Grid Lines To add major grid lines to a plot, from the menu bar select Options, then Grid Lines, then Major Lines. Alternatively, click the Major Lines button in the Targeting Common toolbar: To add major and minor grid lines to a plot, select Options from the menu bar, then Grid Lines, then Major and Minor Lines . Alternatively, click the Major and Minor Lines button in the Targeting Common toolbar: To remove all grid lines from your plot, select Options from the menu bar, then Grid Lines, then No Grid Lines from the menu bar. Alternatively, click the No Grid Lines button in the Targeting Common toolbar:

Setting Background Color in a Plot To set a white background color for your plot, from the menu bar select Options, then Background, then White. Alternatively, click the White Background button in the Targeting Common toolbar: To set a black background color for your plot, from the menu bar select Options, then Background, then Black. Alternatively, click the Black Background button in the Targeting Common toolbar:

Viewing/Printing in Color or Black and White To toggle between color and black and white views/printouts for your plots, from the menu bar select Options, then Monochrome Mode.

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Setting the Limits on Plot Axes To change the limits on a particular Aspen Pinch plot: 1. With a plot window active, select View from the menu bar, then Zoom, then Set Min Max. A Set Graph Limits window appears:

2. To enter your own limits for the axes, check the first box for Enter axes mnima and maxima in the Set Graph Limits window. 3. If you want tick marks on your axes, check the second box for Enter major and minor tick marks. Then complete the window according to your preference.

Printing a Plot To print a plot: 1. Make the plot window active by clicking it. 2. From the menu bar, select File then Print Preview. Alternatively, click the Print Preview button on the Targeting Common toolbar:

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3. If the print preview plot appears the way you want it, click the Print button within the preview window. If the plot does not appear the way you want it in the preview: • Close the print preview window. • Select File from the menu bar, then Page Setup . • Change the print parameters and preview the plot again. You can change headers and footers, set a page border, alter line thickness, and change margin sizes. • When the print preview shows the plot you want, select Print. 4. After your printing preferences are set, you can make additional prints by selecting File and Print from the menu bar. Alternatively, click the Print button from the main toolbar:

Obtaining a Targeting Report To obtain a Targeting report, from the menu bar select Targets, then Report, then View. Alternatively, click the Report button in the Targeting Operations toolbar: The report appears in a Targeting Report window:

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Report Tools Aspen Pinch has several tools to help you quickly review and move within your report. The tools can be used with any Aspen Pinch report. The tools can be activated from the menu bar, or from the Report toolbar. To view the Report toolbar: 1. With the report window active, select View from the menu bar, then Toolbars. A Toolbars window appears:

2. Check the Report toolbar box, then click on OK. The Report toolbar should then be displayed.

Find Text To find text in your report: 1. From the menu bar, select Edit, then Find. Alternatively, click the Find button on the Report toolbar: A Find window appears:

2. Enter the text you want to find in the box provided within the window.

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Qualify your find operation by checking either the Up or the Down button in the Direction box, and by checking the Match Case box. If you want to search using the wildcard character (*), check the Use Pattern Matching box. 3. Click Find Next. If Aspen Pinch finds the text, the cursor position in the Report window moves to that text.

Set Bookmarks To easily move within your report, Aspen Pinch allows you to set bookmarks. For example, you could set a bookmark called Results at the beginning of the targeting results. To set bookmarks in your report: 1. Move the cursor to the position in your report where you want to place the bookmark. 2. From the menu bar, select Edit and Bookmark. Alternatively, click the Bookmark button on the Report toolbar. A Bookmark window appears:

3. Enter the name you want to give the bookmark, then click Add. If you have several bookmarks, each will be listed. This helps you pick a unique bookmark name. 4. To delete or go to other bookmarks, highlight the bookmark name you want to delete or go to, then click either the Delete or Go To box. Multiple bookmarks in the Bookmark window can be listed in alphabetical or positional order. Select your preference by clicking either Name or Position.

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Go To Aspen Pinch allows you to quickly move within a report, using line numbers or bookmarks. To use the Go To facility: 1. From the menu bar, select Edit and Go To. Alternatively, click the Go To button on the Report toolbar: A Go To window appears:

2. To move to a given line using a line number, click Line in the Go To What box, then enter the line number in the Line Number field, as shown in the window above. 3. Click Go To. The cursor moves in the Report window to the beginning of your specified line. 4. To move to a given bookmark, select the bookmark you want from the Bookmark listbox:

5. Click Go To. The cursor moves in the Report window to the bookmark position you specified.

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Snapshot Aspen Pinch lets you take a snapshot of your report, perhaps for comparison with another report later in your analysis. To take a snapshot of the report, from the menu bar select View, then Snapshot. Alternatively, click the Snapshot button in the Report toolbar: A new window is created, titled Snapshot of Targeting Report, and containing a copy of your report.

Refresh Report If you want to refresh your report view, select View from the menu bar, then Refresh. Alternatively, click the Refresh button in the Report toolbar:

Split Report Aspen Pinch allows you to split your report view in up to four separate windows. This is useful if you want to compare different parts of the same report. To split your Report window into several windows: 1. From the menu bar, select Window, then Split. Alternatively, click the Split button in the Report toolbar: The cursor appears over the Report window, dividing it into four regions. 2. Move the cursor to set the size of the windows you want, then click the left mouse button. The window splits.

Formatting Several buttons on the Report toolbar and items in the menu bar allow you to edit your report format: Select All — Selects the whole report. From the menu bar select Edit, then Select All. Alternatively, click the Select All button:

Set Tab Spacing for This Window — Lets you set the number of character columns between tabs. From the menu bar select View, then Set Tab Stops. Alternatively, click the Set Tab Spacing button:

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Select Font — Lets you change the fonts used in the report. Use this button if you want to change the font, font style, and/or text size. From the menu bar select View, then Font. Alternatively, click the Change Font button:

Printing To print your report, select File from the menu bar, then Print . Alternatively, click Print on the Report toolbar: To preview your Report print, select File from the menu bar, then Print Preview. Alternatively, click the Print Preview button in the Report toolbar: If you want to change the appearance of your printed report: 1. Close the Print Preview window. 2. From the menu bar, select File, then Print Setup. 3. Change the print parameters and preview the report again. 4. When the preview shows the report in the format you want, click Print from within Print Preview.

Obtaining the Grand Composite Curve Composite curves are used to set overall energy targets for a process. However, to determine the minimum duty on individual utilities, you should use the grand composite curve. The grand composite curve represents the heating and cooling that has to be done after all process-process heat exchange is accounted for. To obtain the grand composite curve, you should be working in Targeting. (The main Aspen Pinch window will be labeled Targeting.) From the menu bar, select Targets, then Grand Composite Curve. Alternatively, click the Grand Composite Curve button in the Targeting Operations toolbar:

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The Targeting - Grand Composite Curve window appears:

To modify and print the grand composite curve, see Using Plot Tools.

Obtaining the Exergy Grand Composite Curve The exergy grand composite curve is used to estimate the exergy loss in a heat exchanger network. To obtain the exergy grand composite curve: 1. Make sure the exergy feature is enabled by selecting Targets from the menu bar, then Properties, then Exergy On. 2. Select Targets from the menu bar, then Grand Composite Curve. Alternatively, click the Grand Composite Curve button in the Targeting toolbar: 3. From the menu bar, select Options, then Exergy Grand Composite. Alternatively, click the Exergy Grand Composite button in the Targeting View toolbar:

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Placing Utilities When you obtain a grand composite curve, if you have switched the toolbar on, the Targeting Place Utility toolbar appears:

Use either the menu bar or this toolbar to set the minimum usage of each utility. Minimum utility usage is calculated using the grand composite curve.

Removing Utilities If some utilities have already been placed against the grand composite curve, you can remove them by selecting Targets from the menu bar, then Utility Placement, then Remove All. Or click the Remove All Utils button on the Place Utility Toolbar:

Automatically Placing All Utilities To automatically place all utilities against the grand composite curve, on the menu bar select Targets, then Utility Placement, then Auto Place, then At DTmin. Alternatively, click the Auto Place at DTmin button on the Place Utility toolbar:

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Aspen Pinch places the active utilities against the Grand Composite Curve, as illustrated in the figure below:

Placing Utilities One at a Time To place one utility at a time or to edit an individual utility: 1. From the menu bar, select Targets, then Utility Placement, then Select Utility. Alternatively, click the Select Utility button on the Place Utilities toolbar: The Select Utility window appears:

2. Click the utility you want to place in the grand composite curve, then click Apply. Aspen Pinch places the utility against the grand composite curve. 3. Repeat Step 2 for each utility, until all utilities have been placed. After all utilities have been placed and the process’ heating and cooling requirements have been satisfied exactly, the grand composite curve has the label Heat Balance.

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Changing the Utility Duty Select a single utility by clicking on that utility in the grand composite curve. Once the utility is selected, you can change the utility duty in a number of ways. One way is to click the right mouse button over the plot, and select one of the various utility and plot options in the pop-up menu that appears. Alternatively, you can use the menu bar or the buttons in the Place Utility Toolbar: To set the duty of a utility you have placed 1. Make sure the utility is highlighted in the grand composite curve. 2. From the menu bar, select Targets, then Utility Placement, then Heat Duty. Alternatively, click the Heat Duty button: A dialog box appears:

3. In the dialog box, double-click the Utility Heat Load field, and enter the new duty. 4. Click OK. Aspen Pinch updates the utility duty in the grand composite curve. To maximize the utility duty to fit the grand composite curve Select

Targets, then Utility Placement, then Complete. Alternatively, click the Complete Utility button: To force the utility into a pocket in the grand composite curve Select Targets, then Utility Placement, then Into Pocket. Alternatively, click the Utility Into Pocket button: To remove the utility from the grand composite curve Select Targets, then Utility Placement, then Remove. Alternatively, click the Remove Utility button:

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Optimizing Utilities You use the menu bar or the Targeting Optimization toolbar to optimize the targeted utilities. This toolbar appears when you click the Targeting button and the grand composite curve window is active. Targeting Optimization Toolbar

Optimizing DTmin/Utility Loads for Two Utilities To optimize DTmin/Utility loads for two utilities: 1. Make sure you are in Targeting. (The main Aspen Pinch window is labeled Aspen Pinch - Targeting.) 2. Make sure the grand composite curve window is active. 3. From the menu bar, select Targets, then Optimize, then Select Utilities. Alternatively, click the Optimization Utilities button: The Select Optimization Utilities dialog box appears:

The left panel lists the utilities that will not be optimized. The right panel lists the utilities to be optimized. 4. Select two utilities for optimization. Use the Add, Remove, and Clear buttons to move utilities between the two panels, then click OK. 5. Click the Optimization Type/Run button:

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The Optimization Type window appears:

You can optimize utility load, Dtmin, or utility level. Utility load is recommended, because Aspen Pinch does not then need to verify that all temperature differences are greater than DTmin. 6. Select an Optimization type. Utility-level optimization is available only for refrigerant (REFRIG) and refrigeration economizer (ECON) type utilities . 7. Click OK to run the optimization . An optimization message appears in the bottom left of the Aspen Pinch window, indicating the type of optimization selected and the progress of the optimization. 8. Once the optimization is completed, select Targets, then Optimize, then Plots. Alternatively, click the Define Optimization Plots button to select the optimization plots you want to view:

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The Define Optimization Variable window appears:

You can select one X axis variable and any number of Y axis variables from the list. 9. Click the variables you want from the Define Optimization Variable window, then click OK. A window containing the required plot appears:

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If you want to view multiple plots, repeat Steps 8 and 9. You can define optimization plots at any time.

Setting the Optimization Range By default, Aspen Pinch optimizes utility loads over a full range. To control the optimization range, click the Range button in the Optimization Type dialog box. The Optimization Range window appears:

If you used optimization type: • Load, the Optimization Range window, enables you to specify the range of utility duty to be studied during optimization, given as a fraction of the full load range, as shown in the previous figure. • DTmin, the Optimization Range, window enables you to set the DTmin values to be used in the optimization.

Optimizing Utility Loads for Multiple Utilities Aspen Pinch can optimize capital and energy costs for more than two multiple utilities. To do that: 1. Place all your utilities at the smallest acceptable value for DTmin, DTmin = 1° C. A simple way to do this is to select Targets from the menu bar, then Utility Placement, then Auto Place, then At 1 deg C. 2. With the grand composite curve active, select Targets from the menu bar, then Optimize, then Auto Optimization Utilities.

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The Editing Auto-Optimization Utils window appears:

3. Use the Include column to select the utilities to be included in the optimization. YES indicates inclusion, NO indicates omission. 4. Click OK to accept your choices. 5. To optimize, select Targets from the menu bar, then Optimize, then Auto Optimize . Aspen Pinch optimizes the utilities. You can observe the progress of optimization in the bottom left corner of the main Aspen Pinch window. Once optimization is completed, the grand composite curve is still active. Although the original value of DTmin is shown, the utility loads will have changed, due to the optimization.

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To view the results of automatic optimization Select Targets from the main menu bar, then Optimize, then Auto Optimization Report. The Auto Optimization Report window appears:

The Auto Optimization Report window shows the results of each step of the optimization, and the overall results.

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4

Importing and Segmenting Data This chapter explains how to: 



•

Import Aspen Plus or Pro/II simulation results into Aspen Pinch

• •

Segment streams to accurately represent stream heating/cooling curves Import data from other programs such as SuperTarget™

Introduction Aspen Technology has provided a powerful interface between Aspen Pinch and its steady-state simulation tool, Aspen Plus. This interface saves time, increases accuracy, and minimizes or eradicates transcription errors. Once an Aspen Plus simulation has been completed, you can easily run Aspen Pinch and import the simulation results, automatically creating stream and heat exchanger network data. Aspen Pinch can retrieve from Aspen Plus: • Simple stream data • Detailed heating and cooling curve information • Physical and transport properties for process streams • Heat exchanger network information

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It is important to be able to retrieve heating and cooling curves for process streams because, in many cases, stream-specific heats change significantly with stream temperature. For such streams, you should use several segments to describe the heating or cooling profile. Each segment has a different specific heat. The use of segments ensures that the stream data used by Aspen Pinch closely matches actual data. This is especially important when small errors in a stream’s heating/cooling curve could affect the heat recovery system design, such as in low-temperature systems in which small temperature differences are used.

Importing Aspen Plus and Pro/II Simulation Results This section describes: • What you need to do before importing simulation results from either Aspen   Plus or Pro/II into Aspen Pinch • •

How to select a simulation for data extraction How to select data extraction options

Before You Start The description here uses Aspen Plus as the simulator. Unless otherwise noted, the description also applies to importing a Pro/II 5.x simulation. Before beginning to import results from an Aspen Plus simulation, make sure: • The simulation has converged. • Simulation results are saved as a backup (.bkp) file, or as an Aspen Plus document file (.apw). In the case of Pro/II make sure the results are saved with extension .pr1, .pr2, or .pr3 (not the compressed database with a .prz extension) and that they all are saved in the same folder. You do not have to open Aspen Plus on your PC. Once Aspen Pinch starts to read the data, it will start Aspen Plus as needed. The following example shows how data is extracted from Aspen Plus in a process to hydrogenate benzene to cyclohexane. The Aspen Plus backup file (.bkp) for this example is in the Sample Problems directory supplied with Aspen Pinch.

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H2RCY

BFW

R-COOL

V-FLOW

RX-COOL STEAM1

H2IN

FEED-MIX

VAP

PURGE

FEED-HTR RXIN

FEEDMIX BZIN

RXOUT REACT

HP-SEP LTENDS

Q STEAM2

BFWOUT AVAILH CHRCY

LIQ

L-FLOW

COLUMN COLFD

PRODUCT

Figure 4-1. Example Flowsheet, Hydrogenation of Benzene to Cyclohexane

Selecting the Aspen Plus Simulation To select the Aspen Plus simulation to be imported into Aspen Pinch: 1. Select an existing Aspen Pinch case, or create a new case in which you will work and store your data files. For more information, see the chapter Working with Projects, Cases and Data. 2. Choose the File-Import option in Aspen Pinch and select the simulator of interest:

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3. In the Aspen Pinch main window, select from the menu bar File, Import and Aspen Plus. The Open ASPEN PLUS Simulation window appears:

In the case of Pro/II simulations:

4. Select the location and name of the file that contains your converged simulation. Click the Open button to start the import procedure into Aspen Pinch. Aspen Plus is automatically started in a separate window. The Pro/II simulator is not started. You might see the Server Busy dialog box as Aspen Plus is starting. You can click either the Switch To… or Retry button, or simply wait for this message box to go away. After Aspen Plus has started, you will be ready to set the data extraction parameters within Aspen Pinch. These are described in the next section.

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Setting Data Extraction Options After you have performed the steps in the previous section, the Data Extraction Options dialog box will display, as follows:

The following sections describe the checkboxes in this dialog box.

Apply Data Extraction Rules Select this option if you want Aspen Pinch to apply in-built data extraction rules when retrieving data. This option can reduce the amount of effort you have to put in selecting appropriate data. Leaving this option unchecked usually results in stream data that more closely matches your Aspen Plus simulation. For more information on data extraction, see the Pinch Technology Training Course Using Aspen Pinch.

Ignore Pseudostreams Pseudostreams can exist in any Aspen Plus simulation. These streams usually are internal flows within a simulation block, for example distillation column internal flows. In most cases, pseudostreams do not represent streams between units, and hence are not likely to be relevant for heat integration. You should still review such streams to make sure they do not represent real process streams that could take part in heat exchange. If you do not want Aspen Pinch to read pseudostreams, select this option (default). This option us disabled with Pro/II.

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Review Extracted Streams Before Saving If you select this option in the Data Extraction Options dialog box, Aspen Pinch will create a provisional list of the stream data that can be extracted from the simulation file. It will then present this list for you to review and change. For example:

The list comprises the streams in the simulation. The stream names Aspen Pinch creates are derived from the Aspen Plus block names. The stream name could just be the Aspen Plus name (for heaters/coolers). The letters FD or PR might be added to the end, depending on whether the stream is a feed or a product. If heat is associated with the Aspen Plus block, the word HEAT might be added. Distillation columns use the Aspen Plus column name, with COND and REB added for the condenser and reboiler respectively. If you want to replace the stream name, use the Editing Data Extraction Information dialog box shown above. In the Editing Data Extraction Information dialog box, enter Y in the Save? column next to the names of the streams you want to extract and pass into Aspen Pinch. Enter N next to the streams you don't want to extract. You may also change stream information here, such as stream names, temperatures, pressures, flows and duties. Click OK to save and close the window. Aspen Pinch extracts only your selected streams, incorporating any changes you made.

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Apply Changes Made in Previous Data Extraction Suppose that, during a process improvement study of a process flowsheet, you extracted streams from an Aspen Plus simulation once, and modified the simulation conditions, perhaps following recommendations from your Aspen Pinch results. If you want to extract the streams from the revised simulation into Aspen Pinch again, select the Apply changes made in previous data extraction option in the Data Extraction Options dialog box. Any changes made to data in the previous data import will be incorporated into the new data import. For example, this includes stream names, temperatures, pressures, flows, and even the addition of new streams. This is a very useful option. The first time data is extracted from the Aspen Plus flowsheet, make sure the data is correctly extracted in the right form for Aspen Pinch. After you have verified the data extraction once, subsequent data imports are easy and automatic.

Single Step You can use the Single Step option in the Data Extraction Options dialog box to review the temperatures and conditions of each stream as it is extracted. You can change temperatures and pressures, and obtain additional information about any data extraction rule followed to obtain the data for a stream. When you select this option, the Extracted Pinch Stream dialog box appears during the data extraction.

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If you want to extract the stream, check the Include Stream box and perform the following procedure. Otherwise, leave the Include Stream box blank. 1. If required, change the stream name in the Name box. 2. If you want to extract density, viscosity, thermal conductivity or surface tension data, in addition to enthalpy data, then click on the Properties button. Such data is required if performing a detailed simulation of the heat exchanger network. A Select Physical Properties window appears:

After selecting the options, click OK to save and close the window. 3. Use the Supply and Target panes in the Extracted Pinch Stream window to change the stream supply or target information. Here, you can change the stream conditions. To restore the conditions from the flowsheet, click the appropriate Get From Simulation button. If you change any values, the simulation results are overridden and you may get a different heat and material balance in your Aspen Pinch study. If you selected the Apply changes made in previous data extraction box in the Data Extraction Options dialog box, the values you enter will be used in subsequent data extractions. If you click the Get From Simulation button, subsequent data extractions will revert to retrieving values from the simulation. 4. To save and close the Extracted Pinch Stream dialog box, click OK to move to the next stream, or Finish to extract all the remaining streams from the simulation. If you selected the Review Extracted Streams Before Saving option in the Data Extraction Options dialog box, you will still be able to review stream data before importing them into Aspen Pinch.

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Heating/Cooling Curves Aspen Pinch enables you to extract detailed heating and cooling curve data for streams in the Aspen Pinch simulation. This is very important if you want to accurately model heat exchange systems, especially for low temperature systems where small differences in temperature can lead to large discrepancies in energy and area targets. By clicking on the Properties button, you can also set Aspen Pinch to extract density, viscosity, thermal conductivity or surface tension data, in addition to enthalpy data, at each point in your heating/cooling curve. Aspen Pinch requires this data if you want to do detailed simulation/optimization of the heat exchanger network.

Heat Exchanger Network If you check the Heat Exchanger Network box, Aspen Pinch will also extract the heat exchanger network contained within your Aspen Plus simulation. The data extraction retrieves two stream and multistream heat exchangers in the simulation, as well as blocks connected by heat streams. If you have Aspen BJAC Hetran heat exchangers in your simulation, these are extracted as Hetran models in Aspen Pinch and Network Design/Simulation will run Aspen B-JAC during calculations. This can save a large amount of work later in your heat integration study.

Flowsheet This shows the Aspen Plus file from which stream data is being extracted. This can be changed by clicking on the Browse button.

Segmenting Streams Pinch technology requires all streams to be represented by a straight-line heating or cooling profile. Sometimes, such a simple representation is not accurate enough, and so the stream must be represented by several smaller straight line segments. Aspen Pinch automatically segments all streams that are extracted from Aspen Plus.

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Auto Segmentation If you are importing data directly from Aspen Plus, Aspen Pinch automatically segments the stream data. You may want to either: • Resegment this data subject to different accuracy criteria • Segment heating and cooling curve data that you have entered manually into Aspen Pinch yourself To automatically segment any streams: 1. From the main Aspen Pinch menu bar, select Tools and Auto Segmentation. As an alternative, click the Auto Segmentation button of the common toolbar: 2. The Editing Streams to Segment dialog box appears:

The dialog box lists all the streams that Aspen Pinch can segment in the current case. 3. If there are streams that you do not want segmented, enter N in the Y/N column next to the stream name. You can also change the stream name using the NewName column if required. 4. Once you have made your selection and edited any stream names, click OK. Aspen Pinch calculates segments for each stream that you selected by keeping the temperature difference between the actual stream heating/cooling profile and the segmented stream heating/cooling profile within a certain limit. For information on how to view and change this limit, see Changing Auto Segmentation Accuracy on page 4-14.

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After segmentation has finished, you can examine the stream data to see the segments that Aspen Pinch has calculated. You can also run interactive segmentation, as described in the following section, and review the results of segmentation graphically.

Interactive Segmentation If you are importing data directly from Aspen Plus, Aspen Pinch automatically segments the stream data. If you want to review or resegment this data, or if you want to segment heating and cooling curve data that you have entered manually into Aspen Pinch yourself, you can use Interactive Segmentation. To run Aspen Pinch’s interactive stream segmentation feature: 1. From the menu bar, select Tools and Segmentation. As an alternative, click the Segmentation button of the common toolbar: The Segment Streams dialog box appears, listing all the streams that can be interactively segmented:

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2. Click the stream to be segmented, then click OK. The Segmenting stream window appears:

The original heating/cooling curve data from Aspen Plus is shown by the curve labeled DATA. The linear segments saved in Aspen Pinch are represented by the curve labeled SEG1. With the Segmenting stream window active, a Segmentation toolbar also appears:

If you do not see this toolbar, activate it by selecting from the menu bar, View and Toolbars, and selecting the Segmentation box. This toolbar allows you to save the segments, add segments, remove segments, interactively add or remove segments, automatically, and select another stream to segment.

Automatically Segmenting a Single Stream To automatically segment a single stream, from the menu bar select Segment and Auto Segment. As an alternative, click the Auto Segment button: Aspen Pinch automatically calculates the linear segments for the stream in the active Segmenting window and displays the new segments in the window as the SEG1 curve.

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Deleting All Segments To delete all segments of a single stream, from the menu bar select Segment and Remove All Segments. As an alternative, click the Remove All Segments button: A single stream segment remains and assumes a constant specific heat for the stream, starting at its supply temperature and ending at its target temperature.

Adding Segments To add segments to a single stream: 1. From the menu bar, select Segment and Add Segments. As an alternative, click the Add Segments button: The cursor changes shape to include a '+' sign. 2. In the Segmenting window, click the location where you want one stream segment to finish and another to start. Aspen Pinch redraws the stream’s segmented heating/cooling curve, including the new segment. Additional segments can be added in the same way.

Deleting a Segment To delete individual stream segments: 1. From the menu bar, select Segment and Remove Segments. As an alternative, click the Remove Segments button: The cursor changes shape to include a '-' sign. 2. Click the points in the stream’s segmented heating/cooling curve to be deleted. Aspen Pinch redraws the stream’s segmented heating/cooling curve.

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Saving Segmented Data After you have segmented your stream interactively, you should save your segmented stream data. From the menu bar, select File and Save stream name segments. As an alternative, click the Save button: The Editing Temp File (SEGMENT) dialog box appears:

This dialog box shows the numerical values associated with the segments you selected interactively in the Segmenting window. If the values are acceptable, click OK. You can still edit the data in the window before clicking OK. Aspen Pinch saves the stream segments in the stream data file.

Changing Auto Segmentation Accuracy By default, Aspen Pinch automatically segments streams within a temperature of three degrees of the actual heating/cooling profile. The actual values are those stored in Aspen Pinch's total enthalpy table. For more information on the total enthalpy table, see Chapter 11.

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To change the accuracy of auto segmentation: 1. While in Segmentation, with the Segmenting stream window active, from the menu bar select Settings and Auto Segment. The Editing Auto-segment Accuracy dialog box appears:

2. In the Accuracy of Linearization box, enter the maximum temperature difference you want between the actual heating/cooling curve data and the segmented heating/cooling curves. Click OK to save this parameter.

Importing Files from SuperTarget You can also import text-based data files from SuperTarget, including stream and utility data, together with network design and cost data. 1. Create a new case or select an existing case in which to import your data. Any existing data files will be overwritten by the import routine. 2. From the file menu, select File, Import and SuperTarget. The Select SuperTarget Input File dialog box appears. 3. Enter the name of the SuperTarget file you want to import, then click OPEN to start the import process.

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4. The following window appears:

Check the box according to the data you wish to save, either design or simulation data. Click OK to save and close the window. Aspen Pinch imports any SuperTarget targeting and network design data. Note

4-16

After importing SuperTarget data into Aspen Pinch, you should check the type classification of each utility.

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5

Retrofit Targeting This section explains how to perform retrofit targeting in Aspen Pinch. For a given existing heat exchanger network design, retrofit targeting is used to estimate the energy savings possible over a range of different capital investments. If you have a certain amount of capital to invest in new heat exchangers, retrofit targeting will tell you the associated energy cost savings you can expect. If your retrofit projects have to meet certain payback criteria, retrofit targeting will tell you what investment and energy savings will meet such criteria.

What You Need for Retrofit Targets Before you begin calculating retrofit targets, your working case needs: • A heat exchanger network design, with all heat exchanger areas calculated and all heat exchangers defined as existing (for more information, see the chapter New Network Design) • Stream, utility, economic, and heat exchanger cost data

Starting Retrofit Targeting To start retrofit targeting, select from the menu bar Tools and Retrofit. As an alternative, you can click the Retrofit Targeting button on the common toolbar:

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A plot of area target against heat duty appears:

This is the starting point for performing retrofit targets. The lower (red) curve on the plot is the area-energy curve for your data, based on a new design. The upper (green) curve is the area-energy curve at the calculated alpha-value for your process, including some area inefficiency. The area efficiency value, alpha, is defined as the targeted heat exchange area divided by the actual heat exchange area for a process at a given energy consumption. The value of alpha is always less than 1.0. The labels above the plot show the existing energy consumption, the 1-1 (pure counter-current) and 1-2 (shell-and-tube) area requirement of your design, and the calculated value of area efficiency, alpha.

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Toolbars When the 1-1 area target window is active, you can display the retrofit toolbars. From the menu bar, select View and Toolbars. The Toolbars dialog box appears:

Select the toolbars you want to display, then click OK. The selected toolbars are displayed. The Retrofit Targeting Common toolbar contains buttons to edit the appearance of and print your plots:

The Retrofit Targeting Views toolbar contains the Define plots button (left) and the Report button:

The Retrofit Targeting Info toolbar contains buttons for identifying X-axis and Y-axis values of any point in the retrofit target plot, identifying alpha, adding text to the retrofit plots, and specifying the desired payback:

Adding New Alpha Values Aspen Pinch automatically calculates the alpha value (heat transfer area efficiency) based on your heat exchanger network, stream, and utility data. You may want to add your own values for constant alpha and incremental alpha. The following sections describe how to specify these values.

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Specifying Constant Alpha Values To specify your own constant alpha values, from the menu bar select Options and Add Alpha Curves. The Add Constant Alpha Curves dialog box appears:

You can specify up to 10 separate values of constant alpha to be used in the AreaEnergy plot.

Specifying Incremental Alpha Values To specify your own incremental alpha values, from the menu bar select Options and Add Inc Alpha Curves. The Add Incremental Alpha Curves dialog box appears:

You can specify up to 10 separate values of incremental alpha to be used in the Area-Energy plot. After you specify new values for alpha, the Area-Energy plot is redrawn to incorporate the new values.

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Switching Between Constant and Incremental Alpha You may want to switch between retrofit targets using constant or incremental alpha. Under certain circumstances, incremental alpha gives more accurate area targets and retrofit design initialization. For more information, see the Aspen Pinch Training Course. To switch between constant and incremental alpha retrofit targets, from the menu bar select Retrofit, Properties, and Use Incremental Alpha. When this menu item is checked, incremental alpha is used. Otherwise, constant alpha is used.

Switching Between Units and Shell Targets You may want to switch between retrofit targets using units (pure countercurrent heat exchangers) or shells (shell-and-tube heat exchangers). If you use units, all heat exchange is assumed to occur in a purely countercurrent manner. If you use shells, heat exchange is assumed to occur in multi-pass heat exchangers. These exchangers combine pure countercurrent heat exchange with a small amount of cocurrent heat exchange. In most industrial studies, shells should be used. To switch between units or shell targets, from the menu bar select Retrofit, Properties, and Shell Target. When this menu item is checked, shell targets are used. Otherwise, units targets are used.

Creating Retrofit Plots Many plots are available in retrofit targeting. To view a listing of the plots, from the menu bar select Retrofit and Plots. As an alternative, click the Define Plots button on the Retrofit Targeting Views toolbar: The Define Retrofit Targeting Variables dialog box appears:

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You can select a single X-axis variable and any number of Y-axis variables.

Energy Savings Plot A popular retrofit targeting plot is energy savings against investment. If you select this plot, you can add a payback line to the plot. To do this, from the menu bar select Options and Add Payback Lines. The Add Payback Lines dialog box displays, which you can use to specify up to 10 payback periods:

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After you complete this dialog box, the energy savings against investment plot will be updated to include the payback lines you added:

Creating Reports You can create two types of retrofit targeting reports: • Specific Payback Report • Retrofit Targeting Report

Specific Payback Report The Payback Report gives all results for a given payback. To create a Payback Report: 1. From the menu bar, select Retrofit and Calculate Payback. As an alternative, click the Specify Payback button on the Retrofit Targeting Info toolbar: The Specify Payback dialog box is displayed:

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2. Choose a payback range within the range limits given. 3. Click OK. After you specify a payback, Aspen Pinch displays a Payback Report window, which shows a full summary of the savings and investment you can expect from a retrofit project that satisfies your payback criteria:

.

Retrofit Targeting Report A Retrofit Targeting report contains all calculated values, including minimum approach temperature, energy savings, required investment and payback. To create a full retrofit targeting report, select Retrofit, Report, and View from the menu bar. As an alternative, click the Report button on the Retrofit Targeting Views toolbar:

Customizing the Retrofit Targeting Report You may customize your retrofit targeting report and change the report options: 1. From the menu bar select Retrofit, Report, and Settings. The Customize Retrofit Targeting Report dialog box is displayed:

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2. To view the default report settings, click the Defaults button. 3. To customize the report settings, check the boxes for each report option. 4. Click OK to close the window.

Printing Retrofit Targeting Reports Before printing any retrofit targeting reports, make sure that you can see the report to be printed on your screen and that the window containing the report is active. You can make the window active by clicking anywhere inside it. In the active window, click the Print button on the Report toolbar: As alternative, right-click the mouse within the report window, and select Print from the resulting popup menu.

Redesigning the Heat Exchanger Network While performing the retrofit targeting steps, you established an acceptable investment, energy savings, and payback. You also established the initial value of minimum approach temperature to use for your retrofit design. Next, you need to redesign your heat exchanger network, using this initial value of minimum approach temperature. Go to the network design tool in Aspen Pinch, and view the network with this new value for minimum approach temperature. You should then redesign the network, minimizing cross-pinch heat exchange. You may also want to proceed to re-design the heat exchanger network using "network pinch" techniques. For more information, see the chapter Retrofit Design Using Network Pinch.

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6

Total Site Targeting This section describes how to perform total site targeting in Aspen Pinch. Total site targeting allows you to estimate the heat exchange that is possible both within and between process units, and the utility system requirements for a whole manufacturing site. It is particularly important when site layout prevents full heat integration between different units. Total site targeting provides a powerful analysis tool for the utility system. For example, you can set steam system pressures and flows that make best use of the heating and cooling requirements of the whole site, as opposed to a single unit.

Starting Total Site Targeting Preparation Your total site will consist of several different process units and a

utility system. Before you can begin total site targeting, you need to create a separate Aspen Pinch case for each process unit. Into each case, enter stream data, utility data, DTmin data, and so on, as you would for a usual pinch study on several individual processes. Alternatively, you may want to include only the utility usage information for a process rather than the process data itself. In this case, complete the Total Site Existing Utilities table. Performing Total Site Targeting Once the data for each process is in a separate

case, you will create a new case in which you will perform total site targeting. In this new case, you will complete a Total Site Cases input form, which will tell Aspen Pinch where to get the data for each process in the site being studied. This approach is flexible, as it allows you to look at both the total site heat integration possibilities, and the heat integration possibilities within each individual process.

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To start total site targeting: 1. Create a new case or select an existing case in which you want to perform total site targeting. 2. From the menu bar, select Tools and Total Site, As an alternative, click the Total Site Analysis button in the common toolbar:

Identifying Total Site Cases The first time you initiate total site targeting for a particular case, the Editing Total Site Analysis Cases window appears:

If you do not see this window when you click the Total Site Analysis button, double-click on Total Site Analysis Cases in the Case Manager window. The window then appears. Use this window to tell Aspen Pinch where to find the data for all the processes that make up the site. Each process should have been saved in a separate Aspen Pinch case (see Starting Total Site Targeting). If you plan on using the Total Site Existing Utilities table for any case, ProcUtil must be selected to be UTILITY.

Entering Case Information Enter case information by completing the Editing Total Site Analysis Cases window: 1. In the TSiteCas column, enter the name of each Aspen Pinch case containing data for a process on the site that you want to include in your total site study. (To display a list of available cases, click the right mouse button and select List from the popup menu.)

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2. In the DfltCas column, enter Yes if you want a case to be the default. Otherwise enter No. Only one case can be the default. Note

The economic and heat exchanger cost data for the total site are taken from the default case.

3. In the InclPock column, enter Yes if you want to include pockets from each process grand composite curve. Otherwise enter No. 4. Optionally, in the Case DTmin column, enter the DTmin you want to use for each case to generate the site source-sink profiles. If you want to use the DTmin already stored in your case data, leave the fields blank. 5. Verify that all your input is correct by clicking the Verify button on the Edit toolbar: As an alternative, you can select Edit and Verify from the menu bar. If errors exist, correct them in the Editing Total Site Analysis Cases window. Otherwise, close the window.

Total Site Existing Utilities As mentioned earlier, you may want to include only the utility usage information for a process rather than the process data itself, treating the process as a "black box". You do this with the Total Site Existing Utilities table:

UtilID is the utility ID and is required. HxerID is the identifier of the heat exchanger using the utility and is optional. Duty is the heat duty the utility provides and is required.

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The next five fields control which temperatures will be displayed in the SourceSink profile. If you select ProcUtil to be PROCESS, the process stream temperatures are used and are required (ProcTin and ProcTout). If you select ProcUtil to be UTILITY, the utility temperatures are used and are required (Tin and Tout). When utility temperatures are used, they are inverted so that they will represent the process requirements. In the example above, a hot stream going from 25 degrees C to 20 degrees C would be used in the Source-Sink profile to represent the CW requirements. You create as many records as required by the utility usage of the process. When a UtilID is present in more than one record, the heat duties are summed up. Note: To use the Total Site Existing Utilities table in a case, ProcUtil must be selected to be UTILITY in the Total Site Analysis Cases table as shown here:

Displaying Source Sink Profiles After you close the Editing Total Site Analysis Cases window, Aspen Pinch automatically generates the Total Site - Source Sink Profile:

This profile shows the overall heating and cooling requirements of the site, based on the processes you included in the Editing Total Site Analysis Cases window.

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The red curve (left) is the source profile. It shows the total heat available in the site, which is the heat to be removed, most likely by utilities. The blue curve (right) is the sink profile. It represents the total heating required by the site. This heat will again most likely be supplied by utilities.

Enabling the Total Site Toolbars Aspen Pinch has several toolbars dedicated for use with total site targeting. To enable these toolbars, from the menu bar select View and Toolbars. The Toolbars dialog box appears:

Select the toolbars you want. To customize your toolbars, click the Customize button. After selecting OK and depending on your selection, the toolbars will appear in the Aspen Pinch window as follows: Total Site Source Sink Profiles Toolbar — Used to view targeting results for individual processes that make up the total site data, view reports, and switch between the site source and site sink profiles Total Site Common Data Toolbar — Used to edit stream, utility and DTmin data

Total Site View Toolbar — Used to include utilities in the source-sink profiles and toggle the view of the curves between actual and shifted temperatures Total Site Place Utility Toolbar — Used to place utilities against the Source-Sink profiles

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Placing Utilities Now that you have the source sink profiles for the site, you will probably want to determine the operating conditions of the corresponding utility system. You can use Aspen Pinch to determine which utilities are needed, and what the level and duty requirement is for each utility. When you create a total site case, Aspen Pinch takes utility data from all the cases used to construct the total site curves and creates a new utility data file. To place utilities in the total site source sink profile: 1. From the menu bar, select Options and Show Utilities. As an alternative, click the Show Utils button on the Total Site View toolbar: The site source sink profile in the Total Site-Source Sink Profile window is redrawn to include any utilities that had previously been placed against the profiles. The profile also displays an additional label — either Sink Active or Source Active. 2. To activate either the sink profile or source profile, select from the menu bar Site and either Sink Active or Source Active. As an alternative, click the Sink Active or Source Active button: Sink Active Source Active

Sink and Source cannot both be active at the same time. With either the source or sink active, you can now place utilities. Use the Total Site Place Utility toolbar in the same way as the Targeting Place Utility toolbar, described in the chapter Targeting for a New Process. As an alternative, from the menu bar select Site and Utility Placement to reveal a menu of utility placement options.

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Modifying Targeting Data If you want to quickly modify the stream, utility, or DTmin data for any case used in your site source sink profiles, first click on the case to be edited in the Case Manager window. Then click the Edit Streams, Edit Utilities, or Edit DTmin button, as appropriate: Edit Streams Edit Utilities Edit DTmin

As an alternative, from the menu bar, select Data and then the appropriate data menu item. An editing stream, utility, or DTmin window appears. You can use the window to edit the data.

Targeting for One Case The total site source sink profiles may consist of data from several different cases. To view the composite curves for a total site case, from the menu bar select Site and Target Case. The Select the case for Targeting dialog box appears:

Select the case you want to target, then click OK. The composite curves for your selected case will appear.

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Obtaining a Total Site Report To obtain a total site targeting report, either select Site Report and View from the menu bar, or click the Report button: Aspen Pinch displays the Total Site Report, which contains all the data and results of your total site analysis:

Customizing Your Total Site Report You can customize total site targeting reports to print only the information you want. For example, you can customize the report to contain a brief summary of the results. Or you may want a very detailed breakdown of the results, including all input data. To customize your total site targeting report: 1. From the menu bar select Site, Report and Settings: Total Site. The Editing Targeting Report Options dialog box appears:

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2. Select the categories of data and results to be reported, then click OK. 3. From the menu bar select Site, Report and Settings: Heat Power. The Editing Heat & Power Report Opt dialog box appears:

Select the categories of heat and power system data and results to be reported, then click OK.

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Network Design This chapter explains how to design a new (grassroots) heat exchanger network. It also shows how you can alter your heat exchanger network design to reduce the number of heat exchangers and help to reduce network cost. Before starting to develop a new design, you should have completed the targeting and selected utilities and utility loads to be used for your design. For more information on these activities, see Chapter 4.

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Starting Network Design To start Aspen Pinch’s network design feature, click the Network Design button on the main toolbar: A Network Design Grid window appears, showing all process and utility streams:

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Switching on the Network Design Toolbars Aspen Pinch has several dedicated toolbars for use with network design. To switch on the network design toolbars, from the menu bar select View and Toolbars. A Toolbars window appears:

Check the boxes against the toolbars you want. After selecting OK and depending on your selection, the toolbars will appear in the Aspen Pinch window as follows: Network Design View Toolbar — Used to obtain design information Network Information Toolbar — Used to obtain exchanger/stream information Network Identify Toolbar — Used to obtain exchanger information Design Toolbar — Used to place heat exchangers (matches) and stream splits Design Evolution Toolbar — Used to evolve the network design

The buttons on these toolbars are discussed later in the chapter.

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Changing the Appearance of the Design Grid You can change the appearance of your design grid—for example, by controlling which streams are displayed. This is useful if you have many streams and want to view or design only one part of the network at a time. To change the appearance of the design grid: 1. From the menu bar select View and Show. The Show window appears:

2. If you want utility streams shown, leave the Utilities box checked. 3. If you want to view only some of the process or utility streams and hide others, clear the All streams box. If you leave the All streams box blank and then click OK, the Editing Temp File (GRIDSTR) window appears, listing all the streams and utilities in your process:

To indicate whether the stream should or should not be included in your view of the design grid, select either IN or OUT in the In/Out field next to each stream name. Then click OK.

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The design grid is redrawn to include only the streams and utilities you chose. Another way to hide process or utility streams is: 1. Select the stream or utility to be hidden, by clicking on it in the Network Design Grid window. 2. Right-click the mouse. The following network popup menu appears:

3. From this menu, select Hide. The network will be redrawn in the window, without the selected stream.

Obtaining More Stream Information Aspen Pinch allows you to retrieve more stream information, which will be useful as you develop your heat exchanger network design.

Adding Information to the Design Grid To obtain more information for the process and utility streams, such as MCPs (heat capacity flow rates), remaining stream duties, and temperatures: To do that: 1. Click a stream in the Network Design Grid. If more information is required for several streams, select each stream while pressing the CTRL key on your computer keyboard. All selected streams turn from red or blue to green. Right-click the mouse and a popup menu appears. From this menu, select More Information, then either Temperature, Duty, or MCP.

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An alternative approach to using the popup menu is, with the streams highlighted, click either the Temperature button, the Pinch Region Remaining Duty button, or the Stream MCP button on the Network Information toolbar: Temperature Pinch Region Remaining Duty

Stream MCP

Corresponding values appear next to the selected stream(s).

Viewing Stream Data Table To view a table of stream information, including stream name, temperatures, heat capacity flow rate, and duty: 1. In the Network Design Grid, click the stream or streams for which you require more information. Select several streams by pressing CTRL while clicking on the streams. 2. Click the Stream Duty/MCP button: Alternatively, right-click the mouse and from the popup menu that appears, select Show Duty/MCP Report. A Stream Duty/MCP window appears containing the summary stream information:

Note

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Placing and Specifying Heat Exchangers Having obtained the design grid and additional stream information, you can now develop your heat exchanger network design.

Placing a Heat Exchanger A heat exchanger exchanges heat between one hot utility or hot process stream and one cold utility or cold process stream. In pinch technology, a heat exchanger is often referred to as a match. The default heat exchanger model in Network Design is a shortcut model. If your stream data was generated by the Aspen Plus interface, you have the option of specifiying an Aspen B-JAC Hetran model for any process/process match. Both streams in the match must have originated in Aspen Plus. B-JAC Hetran can be used in either simulation mode (exchanger geometry specified) or in design mode (exchanger geometry calculated). To place a match (heat exchanger): 1. With the Network Design Grid window open, right-click the mouse on any stream, and from the resulting pop-up menu, select Heat Exchanger. Alternatively, click the Make Match button on the Design toolbar: The cursor is now shown with a heat exchanger symbol added. 2. In the Network Design Grid window, select a hot stream and a cold stream at the position where the new heat exchanger is required, as illustrated in the following figure:

You should now specify conditions for the heat exchanger, as described in the following section.

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Specifying a B-JAC Hetran Model After you place a heat exchanger, the next, optional step, is to specify the exchanger model – shortcut or B-JAC Hetran. By default, all newly placed matches use shortcut models. If both streams in the match originated in Aspen Plus, you have the option of specifiying an Aspen B-JAC Hetran. To do this click on the desire match and select Design-Heat Exchanger Type:

When you select one of the options the data entry form is displayed. For Aspen Hetran this is:

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B-JAC Process Conditions Many of the fields in this form are the same as those in Aspen B-JAC. Here, the Calculation Mode in the lower left is set to simulation and some of the tabs in the form are disabled. You can get pop-up help in for any field by pressing F1. You can rename the match by entering a new name in the Heat Exchanger Id: field at the top of the form.

Simulation Mode In simulation mode, the hot and cold inlet temperatures and the exchanger geometry are always the specifications. However, you are free to change either inlet temperature. In simulation mode, the exchanger geometry is specified in the Aspen B-JAC program. In simulation mode, you can also specify the hot and cold side fouling factor and whether the hot/cold stream is on the shell or tube side.

Design Mode In design mode, the hot and cold inlet temperatures are always specifications. You must make one specification to set the desired thermal performance of the exchanger:

In design mode, check boxes appear to the left of the outlet temperatures and the heat duty. You must specify one of these three parameters; when one is specified, the other two check boxes become diabled.

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B-JAC File Tab Use the B-JAC file tab to set the B-JAC input/results file name and to control the data that is written to the B-JAC file:

The Aspen B-JAC file name must be given. If you are using simulation mode this file must exist. You can control how the B-JAC file is updated at then end of the calculation by using the options in the Update B-JAC file frame. You can save the hot or cold stream parameters (conditions and cooling/heating curves), the results of the heat exchanger design, or all of the data. When the button in the upper right of this tab is enabled, clicking it will start Aspen B-JAC with the current exchanger opened. Press F1 or click the

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B-JAC Application Tab The Application tab is enabled only in design mode. Use this tab to set the hot and cold side application type (e.g., single or two phase) and, if two phase, the condenser and vaporizer type.

You normally do not need to change anything here. The program will automatically dtermine the hot and cold side application type (e.g., single phase, two phase), and the condenser and vaporizer type. You are free to override any of these. Press F1 or click the

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B-JAC Shell Tab The Shell tab is enabled only in design mode. Use this tab to set shell design preferences:

If you leave any setting Program, B-JAC Hetran will automatically determine the value. Press F1 or click the

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B-JAC Bundle Tab The Bundle tab is enabled only in design mode. Use this tab to set tube design preferences:

If you leave any setting Program, B-JAC Hetran will automatically determine the value. Press F1 or click the

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B-JAC Constraints Tab The Constraints tab is enabled only in design mode. Use this tab to set design constraints such as maximum allowable pressure drop, minimum and maximum shell diameter and tube length, etc.:

If you leave any field blank, B-JAC Hetran will automatically determine the value. Press F1 or click the

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B-JAC Options Tab Use the Options tab to set options for simulation and design modes such as film coefficients, multipliers, etc.:

If you leave any field blank, B-JAC Hetran will automatically determine the value. Press F1 or click the

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Calculating B-JAC Hetran Matches Be sure that you have Aspen B-JAC version 10.2 installed before using this interface. Some modifications were made to Aspen B-JAC after version 10.1 to enable the Aspen Pinch interface. After you specify the B-JAC Hetran input, you execute Aspen B-JAC by selecting Network-Simulate:

Use this option for any B-JAC calculation – simulation or design mode. This option actually starts the Network Simulator to do the calculation.With the Network Simulator, if you have more than one match selected, the selected matches are calculated; if you have nothing selected, the entire network is simulated. Therefore, you can have any combination of shortcut heat exchangers and B-JAC Hetran exchnagers and the Hetran exchangers can be in either simulation or design mode. To view the results, select Network-Reports-Simulation:

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Sample B-JAC results A sample B-JAC Hetran report section is:

The results show the outlet temperatures calculated by B-JAC and those used by Aspen Pinch. Aspen Pinch re-calculates the outlet temperatures from the heat duty that Aspen B-JAC determines. There will typically be small differences (as seen here) due to the linearized heating/cooling curves used in Aspen Pinch and the isobaric calculations done by Aspen B-JAC. Two-phase streams will typically show a larger difference.

Specifying Exchanger Conditions After you place a heat exchanger, the next step is to specify exchanger conditions, such as temperatures and duty. Aspen B-JAC exchangers were described in the previous section. For shortcut heat exchangers, this is done by using the Tick Off or Match Data methods.

Tick Off Tick off is the phrase used to set the duty on a heat exchanger. The exchanger duty is maximized, so that it satisfies the remaining heating/cooling requirements of one stream in the exchanger. As the heating/cooling requirements of that stream are satisfied, there is no need to consider it further, and it can be “ticked off”.

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To tick off the match and satisfy the remaining heating/cooling requirements of one stream in the match: 1. Right-click the mouse on the exchanger, and from the resulting popup menu, select Tick Off. Alternatively, with the match selected, click the Tick Off button on the Design toolbar: The Enter Match Data window appears:

The Enter Match Data window contains the tick-off exchanger temperatures and duty, as calculated by Aspen Pinch. It also includes the names of the streams making the match, and shows the U-value and shells design information. Another tab sheet within the lower half of the window, labeled Cost, shows the cost data used for the exchanger. You can change such data at any time. 2.

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If the exchanger conditions and design values are acceptable, click OK to save. If the exchanger conditions are not acceptable, change the conditions, as described in the following discussion.

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Match Data If you do not want to tick off either stream in the match, but want to enter your own temperatures and/or duty values, follow these steps: 1. Right-click the mouse on the exchanger, and from the resulting popup menu, select Match Data. Alternatively, with the match selected, click the Enter Match Data button on the Design toolbar: The Enter Match Data window appears as described in Tick Off on page 717.) 2. Supply values for three of: • Thot In • Thot Out • Tcold In • Tcold Out • Duty For each field where you supply a value, make sure you select the accompanying check box. 3. Click on the Calculate button. Aspen Pinch calculates all other design values associated with the match. If you want to calculate the conditions on either the hot or cold stream alone, perhaps as you vary the exchanger duty, you can click on the calculator icon in the Enter Match Data window, next to the appropriate stream: 4. Optionally, in the Enter Match Data window, use the HX Id box to edit the exchanger identifier. 5. Optionally, on the Shells tab sheet, specify whether the exchanger is singlepass (a pure counter-current heat exchanger), co-current or multipass (for example, a shell-and-tube heat exchanger with one shell pass and two tube passes). Select the type using the menu in the Type list box. If you specify a multipass heat exchanger, Aspen Pinch calculates the number of 1-2 shell-tube heat exchangers needed to satisfy the temperatures in the match. The number of 1-2 exchangers is also dependent on the minimum allowable temperature difference correction factor FTmin, and on the maximum area per shell you specify in the Enter Match Data window. 6. If you have earlier supplied a cost law for heat exchangers, click on the Cost tab sheet within the Enter Match Data window to see the exchanger cost. 7. Once you have completed all exchanger entries, click OK to close the window and save your exchanger design details.

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The following figure illustrates a multipass heat exchanger for which duty as well as the output temperature of the hot stream and the input temperature of the cold stream have been specified:

Editing and Deleting Exchangers As you develop your design, you may want to edit the duties and temperatures associated with a match (heat exchanger), or even delete the match altogether.

Editing a Match To edit a match: 1. Right-click the mouse on the exchanger, and from the resulting popup menu, select Match Data. Alternatively, with the match selected, click the Enter Match Data button on the Design toolbar: The Enter Match Data window appears, as explained in Tick Off on page 717. 2. Edit the match data in this window. Ensure that the check boxes for your input values for temperatures and (if applicable) duty are selected, and that the check boxes are cleared for fields in which you are not specifying values.

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3. Click Calculate to determine the new match conditions. 4. Click OK to save your exchanger design details and close the Enter Match Data window.

Deleting a Match To delete a match: 1. Right-click the mouse on the exchanger, and from the resulting popup menu, select Delete. Alternatively, with the match selected, press the Delete key on the computer keyboard. 2. The match is deleted and the network redrawn. To undo a deletion, see the following section.

Undoing Network Changes Aspen Pinch allows you to undo any changes you have made to your design since it was last saved. To undo any changes made since your last save, select Edit and Undo from the menu bar.

Restarting Your Design If you decide you want to start your network design again, discarding the design you already have in your working case, select Design and Start Over from the menu bar. Alternatively, click the Start Over button on the Network Design toolbar:

Reinitialising Your Design Occasionally your network design may contain small rounding errors, which cause small discrepancies in energy balances or temperatures between exchangers. This may happen if you perform several edits of a heat exchanger network. If small discrepancies occur, you should recalculate the conditions in your network by reinitializing it. From the menu bar, select Design and Reinitialize Design. Aspen Pinch will ask if you want to save the network. Reply yes and then continue. The reinitialization should remove any minor inconsistencies in your design.

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Obtaining Exchanger Information You can display information about heat exchangers in the design grid.

Displaying Exchanger Information on the Design Grid For each exchanger in your network, you can display information such as duty, heat transfer area, and identifier. To do that: 1. In the Network Design Grid window, click the exchanger for which you want to display information. If more information is required for several exchangers, select the exchangers while pressing CTRL. All selected exchangers turn from orange to green. 2. Click the Duty button on the Network Information toolbar, or the Match Area or Identify buttons on the Network Identify toolbar: Duty Match Area Identify

As soon as one of these buttons is clicked, corresponding values for duty, area, or identifier appear in the design grid, next to the selected exchanger(s). Alternatively, having selected a single heat exchanger, click the right mouse button to display a heat exchanger popup menu:

From the popup menu, select More Information, and the item of interest to you. Note

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From the exchanger popup menu, you can view information about the exchanger and also change the specification of the exchanger.

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Identify Information Options In the default installation of Aspen Pinch, when you select ID as described in the previous section, only the stream or exchanger identifier is displayed. However, you can customize this so that more information is displayed-- for example, stream MCP or exchanger area. To customize the variables displayed: 1. From the menu bar, select Options and Identify Options. Alternatively, rightclick the mouse in the design grid, and from the popup menu that appears, select Identify Options. A Set Identify Information window appears:

2. Select the stream and exchanger information to be displayed. Then click on OK to save your selection.

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Heat Exchanger Representation Aspen Pinch uses a specific convention to represent heat exchangers in the design grid. Heat exchangers are shown as solid or dashed lines, depending on whether the heat exchangers: • Have been fully or under-specified • Exchange heat at a temperature difference below the minimum, or across the pinch The following diagram shows a network design grid with four heat exchangers, A to D:

Each exchanger is represented in a slightly different way: • Exchanger A (long-dashed line) — An exchanger that has not been completely specified. For example, temperatures, duty, or heat transfer coefficients have not been given. • Exchanger B (solid line) — A fully specified exchanger. • Exchanger C (short-dashed line) — A fully specified exchanger that transfers heat at temperature differences less than DTmin. • Exchanger D (solid line with cross-pinch indication) — A fully specified heat exchanger that transfers heat across the pinch, as indicated by the attached horizontal dashed line across the pinch. If you do not want cross-pinch heat transfer lines included in your design, you can remove them by selecting, from the main menu bar, View and Show. In the Show window that appears, clear the Xpinch Match Lines box.

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Plot Tools in the Design Grid Many of the plot tools used in Targeting are applicable in network design. For example, working with text, zooming in and out, snapshots, background color, viewing/printing in color or black and white and printing. For more information on these topics, refer to the plot tools section in Chapter 4.

Splitting and Mixing Streams Sometimes it is necessary to split or mix streams to achieve stream target temperatures.

Splitting a Stream Follow these steps to split a stream: 1. Right-click the mouse on the stream where you want the stream split to start, and from the resulting pop-up menu, select Split Stream. The network design grid will be redrawn with the stream split incorporated and the new branch located above the main stream. 2. Alternatively, click the Split Stream button of the Design toolbar: The cursor changes to a splitting stream icon. In the Network Design Grid window, click the stream to be split at the point where you want the split and then click either above or below the stream to show the position of the new branch.

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Specifying Split Flows To enter the flows in a stream split:: 1. Right-click the mouse on a stream split and from the pop-up menu, select Enter MCP. Alternatively, with the stream split selected, click on the Enter MCP button on the Network Design toolbar: The Enter MCP window appears:

2. Click either Use Flow Fraction or Use MCP. It is preferable to use flow fractions to specify the flows in each branch of the split. If you use flow fractions, the fractions are shown in the data boxes in the Enter MCP window. The flow fractions on the branches must add up to the flow fraction given for the whole stream. If you specify Use MCP, the boxes show the MCP values for the whole stream and each branch, together with the associated units. Note

The flow fractions are relative to the whole stream, and not to each other. Hence, if a stream is split twice, the flow fraction of the stream entering the second split will be less than 1, and will show up in the Enter MCP window as having a flow fraction less than 1.

3. Specify values for two of the three flow fraction/MCP fields, and make sure that the corresponding check boxes are selected. 4. Click on the Calculate button. Aspen Pinch calculates the flow fraction or MCP value for the other branch.

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5. Click on OK to save and close the window.

Mixing a Stream Aspen Pinch allows two branches of the same stream to be mixed. It does not allow two different streams to be mixed. To mix two branches of the same stream: 1. Right-click the mouse on one of the stream branches to be mixed and from the pop-up menu that appears, select Mix Stream. Alternatively, click the Mix Streams button of the Network Design toolbar: 2. The cursor changes to a mixing stream icon. In the Network Design Grid window, click on the branches to be mixed at the position of the mixing point. The design grid is redrawn with the mix in place.

Deleting Stream Splits and Mixers To delete either a stream split or mix: 1. Click on the stream split or mix to be deleted. 2. Right-click the mouse and from the pop-up menu that appears, select Delete. Alternatively, click the Delete key on your keyboard. The design grid will be redrawn with the split or mix deleted.

Placing and Specifying Multi-Stream Exchangers Some heat exchangers can have more than two streams exchanging heat, for example, plate-fin exchangers in low-temperature processes. You can place and specify such heat exchangers in Aspen Pinch.

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Placing a Multi-Stream Exchanger To place a multi-stream exchanger: 1. With the Network Design Grid window highlighted, right-click the mouse on any network stream and from the pop-up menu that appears, select Multistream Heat Exchanger. Alternatively, click the Multi-stream Hxer button on the Design toolbar: The cursor changes shape to a multi-stream heat exchanger icon. 2. In the Network Design Grid window, click each of the streams that are to exchange heat in your multi-stream exchanger. 3. Once you have selected all streams that will pass through the multi-stream exchanger, click again on the Multi-stream Hxer button, or again from the right-mouse button pop-up menu, select Multi-stream Heat Exchanger. 4. You may need to remove some construction lines in the Network Design Grid window. Do this by refreshing the view window by selecting View and Refresh from the menu bar. You then see a design grid that shows the new multi-stream heat exchanger:

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Specifying Multi-Stream Exchanger Conditions Having placed a multi-stream heat exchanger, you should specify the conditions of the exchanger, such as temperatures in and out or duty, as follows: 1. Right-click the mouse on the multi-stream exchanger and from the pop-up menu that appears, select Match Data. Alternatively, with the multi-stream exchanger highlighted click the Enter Match Data button on the Network Design toolbar: The Editing Temp File window appears, showing some of the data associated with the multi-stream heat exchanger:

2. Edit the multi-stream exchanger data in this window. You must enter enough data for Aspen Pinch to be able to calculate all temperatures and duty. For example, in the exchanger illustrated by the preceding figure, you could specify only the hot outlet temperature for the cold stream. Aspen Pinch would then calculate the exchanger duty, and the hot outlet temperatures. Unless otherwise input in the window, Aspen Pinch would assume that the outlet temperatures were equal. Alternatively, you could specify the two hot outlet temperatures. Aspen Pinch would then be able to calculate the exchanger duty, and the cold outlet temperature.

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3. After you have entered some data, click the Verify button within the window. Aspen Pinch indicates whether you have under- or over-specified the exchanger. If you receive no warning message, then the exchanger is successfully specified. An example of the exchanger data, once Aspen Pinch has established temperatures and duties, follows. Note

The area of the exchanger is also calculated.

4. Once you are satisfied with the exchanger conditions, click OK to save the results and close the window. Aspen Pinch returns to the design grid window, where you can add another heat exchanger.

Plate-Fin Heat Exchangers In many low-temperature processes, several multi-stream heat exchangers may be physically connected in a single plate-fin heat exchanger. It is more accurate to cost all plate-fin exchangers in one exchanger core as one exchanger, rather than several individual multi-stream exchangers.

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Defining a Plate-Fin Exchanger To define a plate-fin exchanger: 1. Make sure that no exchangers are highlighted in the Network Design Grid window. To achieve this, you can click on the window background. 2. From the menu bar, select Design and Plate-fin Hxer. Alternatively, click the Define Plate-Fin Hxer button on the Network Design toolbar: The cursor changes to a plate-fin exchanger icon. 3. In the Network Design Grid window, click each multi-stream exchanger to be included in the plate-fin exchanger. Once you have finished selecting heat exchangers, switch off the selection tool: either select Design and Plate-fin Hxer from the menu bar again, or click the Define Plate-Fin Hxer button on the Network Design toolbar again. The network is redrawn to include a box, representing the plate-fin exchanger, surrounding the selected multi-stream exchangers.

Naming a Plate-Fin Exchanger To name a plate-fin exchanger: 1. Right-click the plate-fin exchanger, and from the popup menu that appears, select ID Plate Fin. Alternatively, with the plate-fin exchanger highlighted, from the menu bar select Design and Plate-Fin ID. 2. In the message window that appears, enter the ID. Click OK to save the ID and close the message window.

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Specifying New or Existing Exchangers If you are developing a retrofit heat exchanger network design, you may want to specify which exchangers are new and which are existing. To specify a heat exchanger as new or existing: 1. In the Network Design Grid window, click the exchanger to be specified as new or existing. 2. From the menu bar, select Design and Define as Existing. Alternatively, click the Define As Existing button on the design toolbar: 3. The exchanger changes in appearance. If the exchanger is new, the circles in the exchanger icon are filled. If the exchanger already exists, the circles in the exchanger icon are not filled. If you want to change this convention for the representation of existing and new exchangers, refer to the section Heat Exchanger Style on page 7-48. To switch an exchanger between new and existing, repeat Steps 1 and 2. You can also define an exchanger as new or existing while entering or editing match data, by clearing or checking the Define as Existing box in the Enter Match Data window.

Design Tools Aspen Pinch has several design tools to enable you to generate efficient, low-cost network designs. They include: • CP table • Driving force plots • Heating/cooling profiles • Automatic design

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CP Table When developing a network design, you should start one pinch and design away, by placing heat exchangers to satisfy the heating and cooling requirements of your process streams. To meet the energy targets in your design, each heat exchanger placed next to the pinch has to obey the following equation: CPStream entering the pinch ≤ CPStream leaving the pinch

Where CP is the stream heat capacity flowrate ( = mass * specific heat) To quickly view the CP values of each stream entering and leaving a pinch, you can obtain the CP table for that pinch. To obtain the CP table: 1. In the Network Design Grid window, click the pinch you are designing near. 2. Click the CP Table button on the Network Design View toolbar: Alternatively, right-click the mouse and select CP Table from the popup menu that appears. The cursor changes shape to a pinch icon with ?s on each side. 3. Click either to the left or to the right of the pinch, depending on whether you want the CP table values for above or below the pinch. A CP Table window appears, showing the streams, heat capacity flowrates, and duties for hot and cold streams at the pinch:

Driving Force Plots Driving force plots show how temperature differences in a heat exchanger compare to the temperature differences available in the process, as indicated by the composite curves.

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Obtaining Driving Force Plots To obtain a driving force plot for an exchanger: 1. In the Network Design Grid window, click the heat exchanger where driving forces are to be studied. 2. To select the driving force plot you want, either: Right-click the mouse to get the following popup menu:

From this menu, select Driving Force Profiles and the plot you want. Alternatively, click the Driving Force Plots button on the Network Design View toolbar: The Select Driving Force Plots window appears:

Check the box next to the name of each plot you want to view, then click OK.

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3. Aspen Pinch draws the plots you want, with the selected exchanger highlighted. One example of a driving force plot:

Identifying Streams in the Plots To identify the streams in a particular heat exchanger or in a particular section of a driving force plot: 1. Right-click the mouse in the driving force plot, and from the popup menu that appears, select Identify Stream:

Alternatively, click the Identify Stream button on the Identify toolbar: 2. The cursor changes shape to a cross with an ID label. Click the point of interest. The stream identifier(s) appear(s) next to the point selected.

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Identifying Exchangers in the Plots To identify the exchangers presented in the driving force plot: 1. Right-click the mouse in the driving force plot, and from the popup menu that appears, select Identify Hxer. Alternatively, click the Identify Hxer button of the identify toolbar: 2. The cursor changes shape to a cross with an ID label. Click the exchanger driving force plot of interest. The heat exchanger identifier appears in the driving force plot, next to the heat exchanger selected.

Exchanger Heating/Cooling Profile To view heating/cooling profiles of streams in an exchanger: 1. In the Network Design Grid window, click the exchanger to be viewed. 2. Right-click the mouse, and from the popup menu that appears, select Heat Exchanger T,Q Profile. Alternatively, click the T,Q Profile button on the Network Design View toolbar: Aspen Pinch draws the heating and cooling curve of the streams in that exchanger:

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Automatic Design Aspen Pinch has an automatic design feature that can generate maximum energy recovery network designs for you. The automatic design tool is intended for simpler networks. The tool can be used in two modes: New Design - where Aspen Pinch designs the whole network Finish Design - applied after the user has placed the important pinch matches. Aspen Pinch adds the remaining minor exchangers, heaters and coolers. Note

It is recommended that Aspen Pinch be used in the Finish Design mode.

To use Aspen Pinch's automatic design tool: 1. With the Network Design window active, from the menu bar select Design, Automatic Design and either New Design or Finish Design. An Editing Temp File window appears:

2. In the Editing Temp File window, enter the case names for the cases that will contain the network designs without and with splits. These cases will become child cases under the current case. Once you have entered the case names for the without and with splits designs, click on OK. 3. Aspen Pinch calculates the networks for the two cases. A successful completion of the calculations is marked by a message window. 4. To view the network results, change case to one of the case names specified, and view the network in network design.

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Working with Network Loops and Paths Aspen Pinch enables you to work with the heat exchanger loops and paths, perhaps to reduce the number of heat exchangers and total network cost.

Network Loops Most heat exchanger networks that meet their energy targets contain loops. A loop is a closed path traced from any single point in the network, through heat exchangers and along streams, back to the same point without retracing. It is often possible to move heat around a loop, to remove a small heat exchanger. Aspen Pinch automatically finds loops in your heat exchanger network.

Identifying Loops To identify loops in your network: 1. With the Network Design Grid window active, right-click the mouse on any heat exchanger, and from the popup menu that appears, select Loop/Path and Find Loops. Alternatively, click the Find Loops button in the Design Evolution toolbar: If loops exist within your network, one loop will be highlighted in green and purple. The purple exchanger is the one with the smallest duty in the loop. This is the exchanger you will probably try to remove, if you move energy around this loop. 2. To find another loop in your network, click one of the following buttons in the Design Evolution toolbar: Next Loop/Path Previous Loop/Path

Alternatively, right-click the mouse on any heat exchanger, and from the popup menu that appears, select Loop/Path and Next or Previous.

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Displaying Only Loop Streams You may want your network design grid to show only the streams that make up loops. To do this: 1. With a loop highlighted in the Network Design Grid window, select View and Show from the menu bar. The Show window appears:

2. In the Show window, check Loop/Path Streams. 3. Click OK to save and close the window.

Breaking a Loop You can break a loop by moving heat around the loop until the load on one exchanger is reduced to zero. That heat exchanger can then be removed. To break a loop: 1. Identify the loop in the Network Design Grid window, using the procedure described in Identifying Loops on page 7-38. 2. With the loop highlighted, click the exchanger you want to remove. 3. Right-click the mouse, and from the popup menu that appears, select Loop/Path and Break. Alternatively, click the Break button on the Design Evolution toolbar: Aspen Pinch moves duty around the highlighted loop, until the exchanger that you selected has zero duty. The exchanger is then removed. After the exchanger is removed, Aspen Pinch recalculates all temperatures in between the exchangers, and recalculates all exchanger surface areas. Note

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Controlling a Loop’s Shifted Duty If a network loop is broken, an amount of heat is moved around the loop, until the duty on one of the exchangers reduces to zero. That exchanger can then be removed. Aspen Pinch automatically decides how much heat is to be moved around the loop, and recalculates all network conditions. However, you can specify how much heat should be moved around a loop. To do that: 1. With a network loop highlighted in the Network Design Grid window, rightclick the mouse over an exchanger in the loop. From the popup menu that appears, select Loop/Path and Shift Duty. Alternatively, click the Specify Shift button on the Design Evolution toolbar: The Load Shift window appears:

The Load Shift window shows the lower and upper limits of duty that can be shifted around the loop. 2. Enter a duty value in the Heat Duty box between the two limits, then click OK. Aspen Pinch shifts your specified duty and recalculate all conditions in the network.

Network Paths Most heat exchanger networks contain paths. A path can be traced from a heater, through heat exchanges and along streams, to a cooler. It is often possible to move heat along a path, to remove a small heat exchanger. You may also want to move heat along a path to increase the temperature differences in individual heat exchangers. Aspen Pinch automatically finds paths in your heat exchangers network.

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Identifying Paths To identify paths in your network: 1. With the Network Design Grid window active, right-click the mouse on any network exchanger. From the popup menu that appears, select Loop/Path and Find Paths. Alternatively, click the Find Paths button on the Design Evolution toolbar: If paths exist within your network, one path will be highlighted in green and purple. The purple exchanger is the exchanger with the smallest duty in the path. 2. To find another path in your network, click one of the following buttons on the Design Evolution toolbar: Next Loop/Path Previous Loop/Path

Alternatively, right-click the mouse on any heat exchanger, and from the popup menu that appears, select Loop/Path and Next or Previous.

Displaying Only Path Streams You may want your network design grid to show only the streams that make up paths. To display only path streams: 1. With a path highlighted in the Network Design Grid window, select View and Show from the main menu bar. The show window appears:

2. Check Loop/Path Streams in the Show window. 3. Click OK to save and close the window.

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Controlling a Path’s Shifted Duty To specify how much heat should be moved along a network path: 1. With a network path highlighted in the Network Design Grid window, rightclick the mouse over an exchanger in the path, and from the popup menu that appears, select Loop/Path and Shift Duty. Alternatively, click the Specify Shift button on the Design Evolution toolbar: The Load Shift window appears:

The load shift window shows the lower and upper limits of duty that can be shifted along the path. 2. Enter a duty value in the Heat Duty box between the two limits, then click OK. Aspen Pinch shifts your specified duty and recalculates all conditions in the network.

Specifying Stream Temperature to Control a Path’s Shifted Duty You may want to move heat along a path solely for the purposes of increasing the temperature differences in your network. Aspen Pinch allows you to specify a desired temperature at any point along an identified path. It then automatically calculates the amount of heat that must be shifted along the path to meet your temperature specification. Finally, Aspen Pinch automatically recalculates all network conditions. To achieve a desired temperature on a path: 1. In the Network Design Grid window, identify the point on a stream where you want to change the temperature. 2. Identify a path that passes through this point, using Aspen Pinch’s Find Paths and Next/Previous Loop/Path features.

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3. Either: Right-click the mouse on the stream point where you want to set the temperature. From the popup menu that appears, select Specify temperature. Or Left-click the mouse on the stream point where you want to set the temperature. Click the Specify Temperature button on the Design Evolution toolbar: 4. The Specify Temperature window appears:

The window shows what the lower and upper temperature limits are at the point you want to specify. 5. Enter your required temperature in the box provided, then click OK. Aspen Pinch automatically calculates the heat that has to be shifted along the path and then recalculates all network conditions.

Setting Loop/Path Parameters Aspen Pinch allows you to sort through loops and paths, in order of number of exchangers or minimum exchanger duty. It also allows you to include or exclude loops and paths from consideration that contain certain heat exchangers. Such features are very useful when dealing with large and complex heat exchanger networks that contain very many loops and paths.

Ordering By Exchanger Number Or Duty It was described in an earlier section that when scrolling through the different loops and paths in your network, you should use the following buttons:

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Next Loop/Path Previous Loop/Path

Alternatively, right-click the mouse on any heat exchanger, and from the popup menu that appears, select Loop/Path and Next or Previous. Aspen Pinch will show the loops and paths in order, based either on the minimum number of exchangers, or the minimum exchanger heat duty. To set the sort order, from the menu bar select Design, Loop/Path and Ordering. Alternatively, right-click the mouse on any network exchanger, and from the popup menu that appears, select Loop/Path and Ordering. A Loop/Path ordering window appears:

Select either duty or length, to order the loops and paths by minimum exchanger duty or by minimum number of exchangers, respectively.

Required and Excluded Exchangers You may want to work only with loops or paths that include certain heat exchangers. Alternatively, you may want to work with loops and paths that exclude certain heat exchangers.

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Required Exchangers To enable Aspen Pinch to only consider loops and paths that contain a particular heat exchanger: 1. With the Network Design Grid window active, and the loops or paths highlighted, click on the exchanger that must be included in all loops and paths. If several heat exchangers are required, click on each while holding down the CNTRL key. 2. With the cursor located over a network exchanger, right-click your mouse, and from the popup menu that appears, select Loop/Path and Required Units. Only the loops and paths that include your specified exchangers will then be displayed.

Excluded Exchangers To enable Aspen Pinch to only consider loops and paths that exclude a particular heat exchanger: 1. With the Network Design Grid window active, and the loops or paths highlighted, click the exchanger that must be excluded in all loops and paths. If several heat exchangers are to be excluded, click each while holding down the CNTRL key. 2. With the cursor located over a network exchanger, right-click your mouse and from the popup menu that appears, select Loop/Path and Excluded Units. Only the loops and paths that include your specified exchangers will then be displayed.

Reset Required/Excluded Preferences You can reset the required/excluded preferences so that all loops and paths are considered. With the Network Design Grid window active, and the loops or paths highlighted, and with the cursor located over the network loop or path, right-click your mouse. From the popup menu that appears, select Loop/Path and Remove Constraints. All loops and paths will then be considered by Aspen Pinch.

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Setting Network Design Parameters To set some design parameters, according to your own preferences: 1. From the main menu bar, select Design, Properties and Design Parameters. The Set Network Design Parameters window appears:

The window consists of a number of tabbed sheets, each of which controls some aspect of network design. Each is explained in the following discussions.

Match Data Temperatures This tab controls which temperatures are displayed when entering match data for a newly placed heat exchanger. To set the display: 1. Select the Match Data Temperatures tab in the Set Network Design Parameters window. 2. Check the button of the temperature locations you want. Aspen Pinch allows only one choice. The most common setting is to show pinch temperatures.

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CP Table The CP Table can show data either solely for pinch streams or for all streams. It can show the pinch segment MCP or stream-average MCP for all streams at the pinch. To set CP Table parameters: 1. Select the CP Table tab in the Set Network Design Parameters window. 2. Check the boxes for the stream and MCP defaults you want included in your CP table. The most common setting is to show only pinch streams, and segment MCP's at the pinch.

Heat Exchanger Profiles To set Aspen Pinch to show either all heat exchanger profiles or only selected heat exchanger profiles: 1. Select the Heat Exchanger Profiles tab in the Set Network Design Parameters window. 2. Check the boxes for the exchanger defaults you want. The default setting is to show all heat exchangers.

Heat Exchanger Defaults You can set Aspen Pinch’s heat exchanger defaults, such as exchanger type (single pass, multi-pass, co-current), minimum allowable temperature difference correction factor FTmin, maximum allowable area per shell and heat exchanger name format. To set these defaults: 1. Select the Heat Exchanger Defaults tab in the Set Network Design Parameters window. 2. Check the boxes for the exchanger defaults you want. For most industrial studies, you should select multi-pass heat exchangers. Typical values for 2 FTmin and Maximum area per shell are 0.85 and 500 m respectively.

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Heat Exchanger Style You can set Aspen Pinch to represent new heat exchangers with either filled or empty stream connections, as illustrated in the following figure:

To set this parameter: 1. Select the Heat Exchanger Style tab in the Set Network Design Parameters window. 2. Check the boxes for the exchanger defaults you want.

Setting Autosave You can set the time interval for Aspen Pinch’s automatic data-saving feature. To set autosave parameters or disable autosaving: 1. Select the Autosave tab in the Set Network Design Parameters window. 2. Enter the interval in between autosaves in minutes. Enter zero if you do not want Aspen Pinch to do any autosaving.

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Producing Reports Aspen Pinch enables you to obtain the following types of reports: • Heat Exchanger Network • Heat Exchanger • Cross-Pinch Heat Transfer You can also customize the network design report.

Heat Exchanger Network Report To obtain a report for your heat exchanger network, from the menu bar select Network, Reports and Main. Alternatively, click the Main Report button of the Network Information toolbar: A Network Design Report window appears, containing the report:

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Heat Exchanger Report To obtain a report for an individual heat exchanger: 1. In the Network Design Grid window, click the exchanger to be reported. 2. Right-click the mouse, and from the pop-up menu that appears, select Heat Exchanger Report. Alternatively, click the Hxer Report button on the Network Design View toolbar: The Heat Exchanger Report window appears:

Cross-Pinch Heat Transfer Report A report on all the exchangers transferring heat across each pinch is very useful, particularly in a retrofit project. To obtain a cross-pinch heat transfer report for all heat exchangers, from the menu bar, select Network, Reports and Cross Pinch. Alternatively, click the Cross-pinch heat report button on the Network Design View toolbar:

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A Cross Pinch Heat Table window appears, containing the cross-pinch heat transfer of each exchanger at each pinch:

Customizing Reports Aspen Pinch enables you to customize the network design report. To do that: 1. With the Network Design Grid window active, from the menu bar select Network, Reports, Main Options and Custom. The Network Design Report Selections window appears:

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2. Check the boxes next to the report sections you want. 3. If you want to format the actual numbers in your report—for example, number of reported decimal places—select Network, Reports, Main Options and Format. The Editing Report Formatting window appears, in which you can set the formats for your report:

Printing Networks, Plots, and Reports Aspen Pinch enables you to print a network, plot, or report.

Print a Network or Plot To print a network or a plot: 1. Make sure the network or plot window is active. 2. Preview the print, using the Print Preview button from the main toolbar: Alternatively, from the menu bar select File and Print Preview. 3. If the print preview: • Displays what you want, click Print in the print preview window. • Does not display what you want, close the print preview window and, from the menu bar, select File and Print Setup. 4. Change the print parameters and click the Print Preview button again. When the print preview shows the plot you want, select Print in the print preview window.

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Print a Report To print a report: 1. Make sure the report window is active. 2. Click the print button on the main toolbar: Alternatively, from the menu bar select File and Print.

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8

Retrofit Design Using Network Pinch This chapter describes how to use Aspen Pinch to develop retrofit designs for heat exchanger networks. Aspen Pinch uses Network Pinch, a powerful new technology which significantly improves your ability to find minimum cost retrofits for complex networks.

Introduction Retrofit design has always been a challenge, especially for complex heat exchanger networks. However, a powerful new technology is now available which greatly simplifies retrofit design. This new technology relies upon identifying the network pinch, and it has now been incorporated into Aspen Pinch. The network pinch approach recognizes that the network structure — not the composite curves — cause the pinch, thus limiting heat recovery. The network pinch approach recognizes that the best way to improve heat recovery is to introduce a structural change to the network, and thus remove the bottleneck to heat recovery. Aspen Pinch not only identifies the bottlenecks to heat recovery, but also suggests ways in which you can change the structure to remove the bottleneck. Hence, retrofit design by the network pinch approach combines powerful mathematical programming techniques, but still leaves you in control of the design. Nothing is changed without your authority. The types of structural change that Aspen Pinch looks for are intended to move heat from below the pinch to above the pinch. They are: • Resequencing existing exchangers • Repiping existing exchangers

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• •

Inserting new exchangers Splitting streams

Aspen Pinch identifies simple modifications, involving only one or two heat exchangers. Such modifications tend to be easier to implement, and generally yield short paybacks.

Before You Start Before starting retrofit design, you should be working in a case containing an existing heat exchanger network, designed and saved using Aspen Pinch's network design tool. The network could have been imported from Aspen Plus or another program. It is recommended that you also simulate your network prior to starting retrofit design. This will make it easier to recalculate network conditions incorporating retrofit design modifications. For more information on network simulation, see the chapter Heat Exchanger Network Simulation and Optimization. You should also have heat exchange cost data, utility cost data and economic data. Use the network design tool to access the full features of Aspen Pinch's retrofit design tool.

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Retrofit Design Data Before launching Aspen Pinch's retrofit design algorithms, you should set up the retrofit design parameters that Aspen Pinch will use to determine retrofit modifications. With the network design window active, from the menu bar select Data and Retrofit Design. The following menus appear:

The following sections explain each menu item.

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Exchanger Temperature Approach Limits Aspen Pinch uses exchanger approach temperatures to establish the limits of possible heat recovery within the heat exchanger network. To set Exchanger Temperature approach limits, from the menu bar select Data, Retrofit Design and Exchanger DT Limits. The Set Approach Temperatures dialog box appears:

Use this dialog box to set the required approach temperatures for each heat exchanger. There are four tab sheets, where you can set temperature approaches for existing heat exchangers, new process heat exchangers, new heaters and new coolers. On the tab sheets for new exchangers, enter the temperature approach for each combination of streams. Click on any temperature approach to change its value and enter your required value. To set all values of approach temperature on the tab sheet to the same value, enter the required value in the Default Value box, then click the Set all to default button. Note

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Do not set temperature approaches too large, as you could lose good retrofit design options. In subambient heat exchange systems, small temperature differences can be essential for feasibility. In such systems, if temperature approaches are too large, Aspen Pinch may not be able to determine feasible retrofit design options.

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Exchanger Duty Bounds During the retrofit design calculations, Aspen Pinch will vary the duty of heat exchangers to attempt to get the best retrofit design options. You can set minimum and maximum values of heat duty for the existing heat exchangers, which Aspen Pinch will use in its calculations. To set duty bounds on existing heat exchangers, from the menu bar select Data, Retrofit Design and Exchanger Duty Bounds. The Exchanger Duty Bounds dialog box appears:

For each exchanger, the default minimum duty values are zero. The default maximum duty values are the maximum total stream duty of the either stream passing through the exchanger. To change a value, click on the value, then type in your own value. Click OK to save and close the dialog box.

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Match Constraints Aspen Pinch can determine retrofit design options even when match constraints are present. For example, a match constraint might forbid heat exchange between two streams because of a safety or operability risk. To set match constraints between streams, from the menu bar select Data, Retrofit Design and Match Constraints. The Set New Match Constraints dialog box appears:

Hot streams appear along the top of the grid, and cold streams to the left of the grid. ALLOWED indicates that heat exchange between a hot and cold stream is allowed. BANNED indicates that heat exchange between a hot and cold stream is not allowed. To switch between ALLOWED and BANNED for a particular stream match, left-click on the constraint box between the two streams, then right-click to change the constraint label. To commit the constraints to the calculation algorithms, click the Update button.

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Solver Options You might want to review the solver options before calculating the retrofit design modifications. To check your solver options: 1. With the network design window active, from the menu bar select Data, Retrofit Design and Solver Options. The Solver Options dialog box appears:

2. If you want Aspen Pinch to write a log file listing the iteration steps that the solver takes, select the Output Iteration log box. A text file called Iteration.log will be written to the current case. Review this log by double-clicking on it in the Case manager window. 3. By default, Aspen Pinch applies linear programming using the simplex algorithm to search retrofit design modification options. For large, complex heat exchanger networks where streams are segmented, the simplex algorithm may take some time to search the full range of modification options. In this situation, you may want to use the alternative, faster interior point algorithm. Although this algorithm will work faster, it may run into convergence problems under certain conditions. To use the interior point algorithm in place of the simplex algorithm, select the Use Interior Point Solver box. 4. By default, Aspen Pinch searches all retrofit design modifications. Because the search is exhaustive, some modifications may actually result in greater energy use. Although such results may of interest, you will probably want to consider only retrofit modifications that reduce energy usage. You can set Aspen Pinch to list but not calculate such modifications. As they are not calculated, they will be listed in the modification options as being infeasible. To list only the modifications which reduce energy consumption and report all other modifications as infeasible, select the Cut off worse than current option box.

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5. It is recommended to place dummy heaters and coolers on cold and hot streams respectively, to ensure design feasibility after a modification is established. To ensure feasibility, select the Use dummy heaters and coolers box. 6. It is recommended that you leave the Infeasibility tolerance given in the Solver Options window at the default value of 1.0 E-06. If you have problems establishing network feasibility or feasibility with the retrofit design modifications, you may increase the Infeasibility tolerance. 7. Click the OK button.

Retrofit Design Toolbars With the network design grid window open, several retrofit design toolbars are available: Solver Control Toolbar — Used to pause, restart and terminate the retrofit design modifications solver Retrofit Design Toolbar — Used to identify the heat recovery pinch, and find resequence, repipe, new exchanger and stream split modifications

If you do not see these toolbars even with the network design grid window open, you can display them by selecting from the menu bar View and Toolbars. In the Toolbars window, select Retrofit Design and Solver Control. The following sections describe the features activated by the toolbar buttons and menu options.

Locate Network Pinch When identifying retrofit design modifications within an existing heat exchanger network, the structure of the network limits the heat recovery that can be achieved. Aspen Pinch can identify the exchangers that limit heat recovery at the so-called network pinch. Only when these exchangers are identified can suitable retrofit design modifications be established.

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To identify the exchangers at the network pinch, with the Network Design Grid window open, from the menu bar select Retrofit Design and Locate Network Pinch. As an alternative, click the Locate Network Pinch button of the Retrofit Design toolbar: The network pinch report appears:

This report shows the heat exchangers at the network pinch. It also indicates the minimum heat demand of the network, which assumes that area can be added to existing exchangers and that the network structure does not change. Aspen Pinch has added two dummy heat exchangers to ensure network design feasibility.

Execute Retrofit Design Now that the parameters for retrofit design modifications are established, Aspen Pinch can search for structural changes in the network to reduce energy consumption. Aspen Pinch uses mathematical routines to search for potential beneficial modifications. It then lists these modifications in reducing order of heat recovery. You choose the modification you want Aspen Pinch to incorporate into the network. From a thermal viewpoint, you will probably choose the first modification on the list, as this represents the largest energy savings. As a general rule, this modification also minimizes the overall area requirement.

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Aspen Pinch can search for the following structural changes that in the network: Resequence - change the sequence of exchangers on a stream without changing the streams that flow through exchangers

Repipe - change the streams that flow through exchangers

Add new exchanger

Split stream - this is generally considered when adjacent pinching matches occur at the process pinch when the network and process pinches coincide

When searching for retrofit design options, first look for resequence options. Such modifications tend to be easier to implement, and have less capital cost implications. Next, you should consider repipe options, then new exchangers. Consider stream splits when adjacent pinching matches occur at the process pinch.

Resequence Modifications To generate a list of resequence modifications and select one to incorporate into the retrofit design:

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1. With the network design grid window active, from the menu bar select Retrofit Design and Resequence. As an alternative, click the Resequence button on the retrofit design toolbar: The Resequence Modification List dialog box appears, showing the results of the resequence modification search. Aspen Pinch indicates when all calculations have been completed.

Use the scroll bar to view the full list. The list comprises:

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Units

The modification identifier

Calculation ON or OFF

Depends on the constraints set up in the Match Constraints section of the retrofit design parameters. Toggle between ON and OFF by double-clicking the entry. After changing the calculation mode, you can restart the solver calculations.

Exchanger Name

The name of the exchanger to be resequenced

Hot Stream and Location

Indicates where the exchanger should be moved to on the hot stream, in terms of the adjacent exchanger and the stream name. If the exchanger will not to be moved, it will have the label 'current'. If it will be moved, it will have the label 'new'.

Cold Stream and Location

Indicates where the exchanger should be moved to on the cold stream, in terms of the adjacent exchanger and the stream name. If the exchanger will not to be moved, it will have the label 'current'. If it will be moved, it will have the label 'new'.

Minimum Heat Demand

Is the smallest possible energy consumption for the network with the modification included. It is determined by assuming that area can be added to any heat exchanger, but that the network structure remains unchanged. It indicates the energy consumption that can be expected once the network modification is incorporated.

Heat Demand Reduction

Is the energy reduction that can be achieved by implementing the retrofit design modification. If this value is positive, then energy savings are achievable. IIf value is negative, the modification is not beneficial.

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You can change the listing order of the resequence modifications. The default order is by increasing minimum heat demand, which also gives a list by reducing heat demand reduction. To sort alphabetically or by increasing value, double-click the label of the column you want to sort by. For example, to view the resequence results alphabetically by exchanger name, double-click the column label Exchanger Name. This feature applies to all retrofit modification list views. 2. The Modification List window presents the full results of the search. To commit a modification to the design, click on it and then click the Implement Selection button. The Select Resequence Options dialog box appears, in which you can review the position of the resequenced exchanger. Click OK to commit the retrofit modification to the design. 3. The network in the design grid window is redrawn to incorporate the selected retrofit design modification. There will likely be some heat imbalance due to the resequencing. 4. You can either: • Correct the heat imbalance and establish the new network cost by simulating your network. With the network design grid active, from the menu bar select Network and Run Simulation. You will see the simulation proceed, with each heat exchange in the design grid being highlighted as its conditions are calculated. Once you have simulated your retrofitted network including the new modification, you can either stop, optimize the network or proceed to find more retrofit design modifications. • Search for more retrofit design modifications without correcting the heat imbalance. Even though the network in the design grid may not be in heat balance, Aspen Pinch can still find retrofit design modifications because of its advanced search algorithms. Once you have implemented one retrofit design modification, you can continue to search for more. You can either search for more resequence modifications by repeating the preceding steps, or you can search for repiping, new exchanger and stream split opportunities.

Repipe Modifications To generate a list of repipe modifications and select one to incorporate into the retrofit design: 1. With the network design grid window active, from the menu bar select Retrofit Design and Repipe. As an alternative, click the Repipe button on the retrofit design toolbar:

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The Repiping Modification List dialog box appears, showing the results of the repiping modification search. Aspen Pinch indicates when all calculations have been completed.

This dialog box looks very much like the Resequence Modifications dialog box described in the previous section. Again, you can sort the rows alphabetically or by increasing value by double-clicking on the label of the column you want to sort by. To commit a repiping modification to the design, follow the procedure outlined in the previous section, using the Implement Selection button.

New Exchanger Modifications To generate a list of new process exchanger modifications and select a new exchanger to incorporate into the retrofit design: 1. With the network design grid window active, from the menu bar select Retrofit Design and Add Process Exchanger. As an alternative, click the Add Process Exchanger button on the retrofit design toolbar: The New Exchanger Options list dialog box appears, showing the results of the repiping modification search. Aspen Pinch indicates when all calculations have been completed.

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This dialog box looks very much like the Resequence Modifications dialog box described in the section Resequence Modifications on page 8-10. You can sort the rows alphabetically or by increasing value by double-clicking on the label of the column you want to sort by. To commit a new exchanger modification to the design, follow the procedure outlined in this previous section, using the Implement Selection button.

Stream Split Modifications To generate a list of stream split modifications and select a stream split to incorporate into the retrofit design: 1. With the network design grid window active, from the menu bar select Retrofit Design and Split Stream. As an alternative, click the Split Stream button on the retrofit design toolbar: The Stream Splitting Options list dialog box appears, showing the results of the stream split modification search. Aspen Pinch indicates when all calculations have been completed.

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This dialog box presents the full results of the search and looks very much like the Resequence Modifications dialog box described in the section Resequence Modifications on page 8-10. 2. To commit a modification to the design, click on it and then click the Implement Selection button. The Insert Stream Split dialog box appears:

3. In this window, you can review the name and position of the stream split. You cannot edit the data. Click OK to commit the retrofit modification to the design. Aspen Pinch redraws the network in the design grid window to incorporate the selected stream split. As a result, some heat imbalance will probably occur. 4. You can either: • Correct the heat imbalance and establish the new network cost by simulating your network.

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•

With the network design grid active, from the menu bar select Network and Run Simulation. You will see the simulation proceed, with each heat exchange in the design grid being highlighted as its conditions are calculated. Once you have simulated your retrofitted network including the new modification, you can either stop or proceed to find more retrofit design modifications. Search for more retrofit design modifications without correcting the heat imbalance. Even though the network in the design grid may not be in heat balance, Aspen Pinch can still find retrofit design modifications because of its advanced search algorithms.

Solver Control The solver control toolbar and menu bar allow you to pause, restart and terminate solver calculations. You may want to pause calculations if: • They are taking a long time to process. • An attractive retrofit modification has already been identified. • You see that a particular match constraint is preventing acceptable heat recovery, so that you can remove the match constraint. To pause solver calculations, either select from the menu bar Retrofit Design and Pause Solve, or click the Pause Solve button of the solver control toolbar: Once you have paused and/or changed any retrofit design parameters, you can restart the solver calculations by either selecting from the menu bar Retrofit Design and Restart Solve or by clicking the Restart Solve button of the solver control toolbar: You can terminate the solver calculations at any time by either selecting from the menu bar Retrofit Design and Terminate Solve or by clicking the Terminate Solve button of the solver control toolbar:

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Optimizing Network Modifications After each retrofit modification is incorporated into the network, some heat imbalances will be identified in the network in Aspen Pinch's design grid window. You can still proceed to identify the next retrofit design modification. Aspen Pinch's advanced search and solver routines do not require this heat balance to be resolved in order to find new, valid retrofit design modifications. The main reason for resolving heat imbalances would be if you wanted to review the costs of the network exchangers. The easiest way to do this is to simulate the network. From the menu bar, select Network and Run Simulation. Once you have incorporated all retrofit design modifications, you can also optimize the network. For more information, see the chapter Heat Exchanger Network Simulation and Optimization.

Infeasible Results On rare occasions, Aspen Pinch may have difficulty in overcoming an infeasibility, caused either by a fault in the solver formulation, or by convergence tolerance. If you experience difficulty in overcoming an infeasibility, you should: 1. Make sure the solver includes dummy heaters and coolers on process streams. With the network design grid window active, from the menu bar select Data, Retrofit Design and Solver Options. Make sure the Use dummy heaters and coolers to ensure feasibility box is selected. Restart the solver calculations. 2. Review your approach temperatures and duty bounds. If these are set too high, it may not be possible to find a feasible retrofit modification. For example, this might happen if large exchanger temperature differences are specified in a subambient heat exchange system, where traditionally temperature differences have to be small. 3. Review the Iteration.Log file. Double-click on this file in the Case Manager window. Review its contents to establish the causes for the infeasibility and then take corrective action. 4. Increase the iteration tolerance value. With the network design grid window active, from the menu bar select Data, Retrofit Design and Solver Options. In the Solver Options window that appears, reduce the value in the Infeasibility Tolerance box and restart the solver calculations.

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9

Heat and Power Models Aspen Pinch has heat and power models that enable the user to simulate utility systems. The models currently available are furnaces, gas turbines, steam turbines and refrigeration systems. The advantage of using heat and power models is that they give the user a more accurate value for energy consumption, energy costs, and utility system size and cost. For example, if a process requires steam at different levels and the requirement at each level is known, the user can use the steam turbine models to calculate how much high-pressure steam is required, how much fuel is required, and the investment cost of turbines and boilers. Heat and power models can be run standalone with flows or duties supplied by the user. They can also be run while connected to targeting or optimization. In such a situation, the targeted utility loads are used by the simulation models to determine conditions in the utility system. This chapter shows you how to specify Aspen Pinch heat and power models for use in targeting and optimization.

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Furnace The furnace model in Aspen Pinch is represented by the following figure: Flue Gas TLow

Tlow or Tpinch

MCpExhaust or ExhaustFlow

FurnacID

Q1

Duty, Qex

Q2

Q3

Flame Temperature, TTFT Pressure

Air

Fuel

Tair Qairpreheat AirFlow

Fexcess Air composition: O2comp N2comp CO2comp H2Ocomp Tair,ambient

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Fuel ID MWfuel Heat of combustion, DHcomb Reference, Temp., Tref C atoms H atoms

FuelFlow

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Air with a user-supplied composition is fed to a furnace, perhaps after some preheat. A known fuel is also supplied to the furnace. The air and fuel burn, and the resulting flue gas, cools down from a theoretical flame temperature TTFT to a low temperature TLow or the pinch temperature. As it cools, the flue gas heats the process.

Modeling a Simple Furnace The following diagram shows specifications for a simple furnace system example. This will be used here to explain the inputs required by Aspen Pinch. Stack Temperature = 150°C

FURNACE ID = HEATER Lifetime = 10 yrs. Operates 8000 hr/yr Mobilization Cost = $100,000 Reference Purchased Cost = $400,000 Reference Size = 300 kW Cost Exponent = 0.8 Installed Cost/Purchased Cost = 4

AIR Ambient Temperature = 25°C Air Temperature After Preheat = 125°C 15% excess air

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Process Heat Duty = 747 kW

FUEL ID = FUEL GAS MW = 16.043 LVH = 50,010 kJ/kg Cost = $0.01/kWhr Number Carbon Atoms = 1 Number Hydrogen Atoms = 4

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What Data Do You Need? To model a furnace, you need to specify data for: • Furnace model • Fuel • Inlet Air • Process Heat Duty • Flue Gas • Combustion • Utility • Economics Note

You can have several furnaces.

To enter data for your furnace into Aspen Pinch: 1. From the menu bar, select Data, then Heat and Power and Furnace Model. A Furnace window appears.

2. In the Furnace ID box, select New if the furnace is new, or use the drop down list to select the name of a furnace that you have previously created. Click on the OK button to proceed. 3. A Furnace Model window appears, where you see a representation of a furnace, as in the following figure. You can move the pointer on the scale at the top of the window to the left or right, to reduce or increase magnification of the diagram.

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Move the cursor over any data group in the diagram to highlight it. To edit the data in any data group, highlight that group and double-click your mouse. Or click on the group and choose Edit from the popup menu. If sufficient data is given to Aspen Pinch in one data group for calculations to be made, that group is marked with a blue tick mark ([). If data in a data group is under-specified, Aspen Pinch will not be able to calculate conditions for the whole model. In such a situation, the data group is marked with a red cross. For the heat/power model conditions to be calculated, all data groups must be marked with a blue tick mark ([).

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Furnace Model Data To enter Furnace Model Data (name, calculation basis, type, cost basis): 1. In the Furnace window, double-click on the Furnace Model data group (labeled Furnace ID). An Overall Furnace Parameters window appears:

2. Enter a unique Furnace ID. 3. Select the calculation basis: Excess Air

Excess air is supplied, and flame temperature is calculated

Flame Temperature

Flame Temperature is supplied, and excess air is calculated

4. Click on the Cost button in the Overall Furnace Parameters window to enter cost data. A Furnace Cost window appears:

Note

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You can go to this Furnace Cost window directly from the Furnace Model window. Right-click on the Furnace ID data group, and select Cost from the popup menu that appears.

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5. Aspen Pinch has built-in cost models for a pyrolysis furnace, a process heater, and a reformer (without catalyst). If you specify any of these heater types, you can also select the material of construction. Available materials are carbon steel, chrome/molybdenum and stainless steel. If you select such cost laws and materials in the Furnace Cost window, Aspen Pinch will use its own built-in cost equations to cost the furnace. As an alternative to the built-in furnace cost equations, you can supply your own cost equation. In the Furnace Cost Model box of the Furnace Cost window, select User Supplied Power Law Constants. The User Power Law pane in the Furnace Cost window then becomes active. If you have a furnace cost law in a furnace cost data file, check the Cost Law button and enter the unique identifier of the cost law to be used in the Cost Law box. Alternatively, to supply a cost equation for the furnace directly into the furnace model, check the Cost equation button in the Furnace Cost window, and click on the Cost Data button. A Furnace Cost window appears:

6. Enter your cost data, then click OK to save. All furnace model data is now saved.

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Fuel Data To enter fuel data: 1. In the Furnace Model window, double-click on the fuel data group. A Fuel window appears:

Enter your fuel data, as shown. The unique Fuel ID must correspond to a fuel utility of the same ID in the utility data file. If you already have fuel utilities in your utility data file, you can view these and select one, by using the list button. If you do not already have such utilities in your utility data file, enter a new fuel ID in the Fuel ID box. At the same time, it is recommended that you click on the Case Manager window and create or edit your utility data file to include the new fuel utility. You must enter a fuel molecular weight, fuel stoichiometry, heat of combustion, and reference temperature values. You can enter fuel stoichiometry either as the number of carbon to hydrogen atoms in a fuel molecule, or as a molar ratio requirement of oxygen to fuel. The reference temperature corresponds to the heat of combustion.

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Inlet Air Data To enter inlet air data: 1. In the Furnace Model window, double-click on the inlet air data group. An Inlet Air window appears:

2. In the Inlet Air window, enter air temperature, flow (optional), fraction excess air, and composition details. If air preheat is to be considered, check the Preheat Air box, and fill in either duty or temperature values associated with air preheat.

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Process Heat Duty Data To enter duty data: 1. In the Furnace Model window, double-click on the duty data group. A Process Heat Duty window appears:

2. Enter the process duty, then click OK. Note

If the furnace is connected to targeting, this value will be overridden by the targeted furnace duty.

Flue Gas Data To enter flue gas data: 1. In the Furnace Model window, double-click on the flue gas data group. A Flue Gas window appears:

2. Enter either the stack temperature, flue gas flow, or heat capacity flowrate (MCP) required. Click OK to save and close the window.

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Combustion Data To enter combustion data: 1. In the Furnace Model window, double-click the combustion data group. A Combustion Conditions window appears:

Note

The theoretical flame temperature value may not be used by Aspen Pinch, depending on the calculation method you specified earlier in your Furnace Model Data.

Utility Data To perform furnace calculations, the associated utility data file must include a fuel. If you want to run the furnace model in targeting, the utility data file must also contain a flue gas. Create utility data as explained in Chapter 3. The utility data file for the sample furnace looks as follows (the 19 columns in the file are captured in three separate figures):

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Economic Data In order to calculate annual utility and capital costs, you should supply economic data for Aspen Pinch. Create economic data as explained in Chapter 3. The economic data file for the sample furnace looks as follows:

Saving Your Furnace Model To save your heat and power system model at any time, with the Furnace Model window open, from the menu bar select File, then Save Model.

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Deleting your Furnace Model To delete a furnace model: 1. From the main menu bar of Aspen Pinch, select Data, then Heat and Power, then Furnace Model. A Furnace window appears:

2. In the Furnace ID box, use the list button to select the furnace to be deleted, and click the Delete button.

Running the Furnace Model Standalone Once you have created furnace data, utility data, and economic data, you can run your furnace model. To run the furnace model standalone, not as part of targeting: 1. If you have not already done so, click the Heat & Power button of the common toolbar: An empty Heat and Power window appears. 2. If you have only one furnace, go to Step 3. If you have several furnaces, you need to select the furnace you want to run: • From the menu bar, select Heat/Power, then Select, then Furnace. An Editing Furnace Model Selection window appears:

•

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In the Furnace Block to be Used box, enter the name of the furnace you want to run.

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• •

By clicking the List button, you can view and select from all the furnaces you have supplied data for. Enter a name for the furnace report. Click on OK to save and close the window.

3. From the main menu bar, with the Heat and Power window active, select Heat/Power, then Run Furnace. Aspen Pinch calculates the furnace conditions and then writes them into the Heat and Power window. If errors occur during the calculation of furnace conditions, Aspen Pinch indicates what these errors are. You see a new window containing all errors. Errors flagged with ERROR LABEL: 1 are warning messages and usually minor. Such errors may arise if Aspen Pinch tries to extrapolate some thermodynamic relationship beyond its bounds. However, an error flagged with ERROR LABEL: 4 is a terminal error and must be corrected. The error will have a description to help you sort out the problem.

Running the Furnace Model in Targeting When you have checked that your furnace runs without errors in standalone mode, you can connect the furnace to targeting. To run the furnace in targeting: 1. Modify your utility data so that the flue gas utility has the following additional parameters: • Tin: Enter the revised theoretical flame temperature to match that calculated when you ran the furnace model standalone. Note At this point you may not want to consider any air preheat. If not, make sure that your standalone furnace run does not include air preheat. •

•

Modact: This is the model activity, which should have the value 1. This indicates that the flue gas duty calculated during targeting should be used in detailed furnace model calculations. ModelID: This is the identifier for the furnace that is to supply the flue gas. In the preceding example, ModelID = HEATER.

2. Run targeting and place your flue gas and other utilities, as described in Chapter 4. 3. Check the targeting report.

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You should see a section towards the end of this report titled, Furnace Calculation Results. This section contains all the calculated conditions for the furnace that supplies the targeted duty.

Varying Flue Gas Stack Temperature Any flue gas heating of process streams below a process or utility pinch may not be necessary. In fact, by using flue gas in such a way, you may be increasing the use of cold utility. To avoid this, you may want to increase the furnace stack temperature. To do this, in the utility data file, increase the Tout value for your furnace flue gas, and then retarget. In some situations, Aspen Pinch automatically changes the stack temperature. For example, this occurs if a utility pinch is formed when the furnace is placed in the grand composite curve. In such a situation, the flue gas line crosses the temperature axis at a temperature higher than the target temperature supplied. Aspen Pinch automatically increases the stack temperature to the temperature at which the flue gas line crosses the temperature axis. This is seen in the following figure:

In this example, the target temperature for flue gas was originally set to be 100°C. However, when the furnace was placed against the grand composite curve as shown, the flue gas had only to cool to 138°C (equal to 113°C interval temperature).

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Air Preheat Aspen Pinch also enables you to account for the effects of air preheat in targeting. To be able to consider the opportunities for air preheat in your process/utility system: 1. Add an Air Preheat utility to your utility data, and modify your flue gas data, as shown in the following figures. In particular: • Leave the Tin value of flue gas equal to the theoretical flame temperature assuming no air preheat. • Ensure that the Modact values for both air preheat and flue gas are 1 (they are both connected to the furnace model and are active). • Ensure that the ModelID values for both air preheat and flue gas equal the identifier of your furnace. • Ensure that the Connect values for your flue gas and air preheat are cross-referenced (that is, the Connect value for the flue gas is the name of the air preheat utility, and the Connect value for air preheat is the name of the flue gas utility). This is important, as Aspen Pinch will use the calculated air preheat information to determine flue gas conditions. Use the following utility data figures as examples:

2. Retarget your furnace conditions by placing air preheat and flue gas (and any other utilities) against the grand composite curve, as described in Chapter 4. 3. Look at the targeting report to check that furnace conditions have been calculated.

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You will see that the furnace model has recalculated the theoretical flame temperature of the flue gas, based on the temperature of air after preheat. 4. After studying the utilities placed against the grand composite curve, you may want to change the temperature of the air after preheat. Do this by changing the Tout value of air in the utility data file, then retarget. The flue gas theoretical flame temperature will be recalculated each time air preheat temperature is changed.

Customizing Your Furnace Report You can customize your furnace report: 1. With a targeting window active, from the menu bar select Targets, then Report, then Settings: Heat Power. Alternatively, with a Heat and Power window active, from the menu bar select Heat/Power, then Reports, then Report Section Settings. An Editing Heat & Power Report Opt window appears:

2. Use the option boxes to customize your heat and power report and, in particular, your furnace report. Use the scroll bar on the right side of this window to view the full range of customization options.

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Gas Turbine The gas turbine model in Aspen Pinch is represented by the following figure:

Regener = NO Tex Qex ExhastFl O2comp N2comp CO2comp H2Ocomp Tair Press

4 DPcomb 2

1

3

Tadiab

AirFl

Wnet

CreditID

ComprID Pratio Ceff Cmeff

TurbID Teff Tmeff

FuelID MWfuel DHcomb Tref Catom Hatom or Stoic Air Fuel Fl

Qex = MCP ex * ("Tex-T-low")

Regener = YES Tex Qex ExhastFl

DPhxGas

6 O2comp N2comp CO2comp H2Ocomp Tair Press

4 Uvalue

1

2

Tappr

DPcomb 5

Tadiab 3

DphxAir

AirFl Wnet CreditID

ComprID Pratio Ceff Cmeff

FuelID MWfuel DHcomb Tref Catom Hatom or Stoic Air Fuel Fl

TurbID Teff Tmeff

Qex = MCP ex * ("Tex-T-low")

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Air is compressed before entering a combustion chamber, where it is burned with fuel. The resulting high-pressure hot gases are expanded to lower pressure. During the expansion, power is produced. Some of the power is used to compress the air, and excess power can be used to drive other machinery or a generator. The hot exhaust is then available to heat the process. A regenerator may be included to recover some of the exhaust heat into the compressed air before it enters the combustion chamber.

Modeling a Simple Gas Turbine The following diagram shows specifications for a simple gas turbine system example. This example will be used to explain the inputs required by Aspen Pinch. Stack Temperature = 150 °C

GAS TURBINE ID = GTURB1

COMPRESSOR ID = COMP1

TURBINE ID = TURB1

NET POWER POWER CREDIT ID = PWRCRED

Process Heating Duty =46830 kW 3 % pressure drop

1100 °C 5% pressure drop

REGENERATOR Exhaust T=400°C 4% pressure drop Lifetime = 3 yrs Operates 8000 hr/yr Cost = $250/kW

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T Appr = 40 °C U = 0.085174 kW/m ap pr

2 °

FUEL ID = METHANE MW = 16.043 LVH = 50,014 kJ/kg Number Carbon Atoms = 1 Number Hydrogen Atoms = 4

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What Data Do You Need? To model a gas turbine, you need to specify: • Gas turbine model data • Combustion fuel data • Inlet Air data • Process Heating data • Compressor data • Turbine data • Regenerator Data • Utility data • Economic data Note that you can have several gas turbines. To enter data for your gas turbine into Aspen Pinch: 1. From the menu bar, select Data, then Heat and Power, then Gas Turbine. A Gas Turbine window appears.

2. In the Gas Turbine ID box, select New if the turbine is new, or use the drop down list to select the name of a turbine that you have previously created. Click on the OK button to proceed. 3. A Gas Turbine Model window appears, where you see a representation of a gas turbine, as in the following figure. The pointer on the scale at the top of the window can be moved to the left or right to reduce or increase magnification of the diagram.

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Move the cursor over each data group in the diagram. The data group will become highlighted. To edit the data in any data group, move the cursor over that group and double-click your mouse. If sufficient data is given to Aspen Pinch in one data group for calculations to be made, that group is marked with a blue tick mark ([). If data in a data group is under-specified, Aspen Pinch will not be able to calculate conditions for the whole model. In such a situation, the data group is marked with a red cross. For the heat/power model conditions to be calculated, all data groups must be marked with a blue tick.

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Gas Turbine Model Data To enter Gas Turbine Model Data (name, calculation basis, type, cost basis): 1. In the Gas Turbine Model window, double-click on the Gas Turbine ID data group. An Overall Gas Turbine Parameters window appears:

2. Enter a unique Gas Turbine ID. 3. Select the calculation basis as either: Exhaust Temperature

Exhaust temperature is supplied, and compression ratio is calculated

Compression Ratio

Compression ratio is supplied, and exhaust temperature is calculated

The gas turbine produces power. Any cost credit that results from this power is costed using an electricity utility. In the Utility power credit ID box, enter a power credit ID. This ID must correspond to a unique electricity utility ID in the Utility data file. If you already have electricity utilities in your utility data file, you can view these and select one by using the list button. If you do not already have such utilities in your utility data file, enter a new electricity ID in the Utility Power Credit ID box. At the same time, it is recommended that you click on the Case Manager window and create or edit your utility data file to include the new electricity utility.

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4. Click on the Cost button to enter cost data. A Gas Turbine Cost window appears:

Note that you can go to this Gas Turbine Cost window directly from the Gas Turbine Model window by right-clicking on the Gas Turbine ID data group and selecting Cost from the pop up menu that appears. In the Gas Turbine Cost window, you can supply your own cost equation. Enter the parameters of your turbine cost equation into the fields in the window, then click OK to save and close.

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Combustion Fuel Data To enter combustion fuel data: 1. In the Gas Turbine Model window, double-click the combustion fuel data group. A Combustion Fuel window appears:

Enter your fuel and combustion data, as shown. The unique Fuel ID must correspond to a fuel utility of the same name in the utility data file. If you already have fuel utilities in your utility data file, you can view these and select one by using the list button. If you do not already have such utilities in your utility data file, enter a new fuel ID in the Fuel ID box. At the same time, it is recommended that you click on the Case Manager window and create or edit your utility data file to include the new fuel utility. Fuel stoichiometry can be entered either as the number of carbon to hydrogen atoms in a fuel molecule, or as a molar ratio requirement of oxygen to fuel. Heat of combustion relates to the fuel, measured at the reference temperature. The adiabatic flame temperature is the temperature that exists at the outlet of the combustion chamber, entering the expander turbine.

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Inlet Air Data To enter inlet air data: 1. In the Gas Turbine Model window, double-click on the inlet air data group. An Inlet Air window appears:

2. In the Inlet Air window, enter air temperature, pressure, flow (if allowed), and composition. Click on OK to save and close the window.

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Process Heating Data To enter process heating data: 1. In the Gas Turbine Model window, double-click the process heating data group. A Process Heating window appears:

2. Enter the process duty and other exhaust parameters, then click OK.

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Compressor Data The gas turbine is made up of a compressor and an expander (also called a turbine). To enter compressor data: 1. In the Gas Turbine Model window, double-click the compressor data group. A Compressor window appears:

2. Enter a unique compressor ID. The compressor can of type polytropic or isentropic. The calculation method can be either using an equation of state, using a supplied K-value (next box) or a K-value calculated based on the ideal gas law. An equation of state calculation method is recommended.

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Turbine Data The gas turbine is made up of a compressor and an expander (also called a turbine). To enter turbine data: 1. In the Gas Turbine Model window, double-click the turbine data group. A Turbine window appears:

2. Enter a unique turbine ID. The turbine can of type polytropic or isentropic. The calculation method can be either using an equation of state, using a supplied K-value (next box) or a K-value calculated based on the ideal gas law. An equation of state calculation method is recommended.

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Regenerator Data The regenerator is used to improve the efficiency of the gas turbine cycle. To specify regenerator conditions: 1. In the Gas Turbine Model window, double-click the regenerator data group. A Regenerator window appears:

2. If the regenerator is to be used, check the Use regenerator box and complete the details in the other boxes in the window.

Utility Data The utility data file that allows you to run the gas turbine model should include fuel and electricity. The fuel is burned in the gas turbine, thereby incurring a cost. However, electricity is produced by the turbine, so there will be some cost credit when the gas turbine runs. If you are going to run the gas turbine model in targeting, you also need to specify a flue gas utility. To enter utility data into Aspen Pinch: 3. From the menu bar, select Data, then Utilities, then General Data. Alternatively, click the Create Data button on the Case manager toolbar: 4. A Create New Data window appears. From the menu within this window, select Utility Data. An Editing Utility Data window appears. Enter your utility data in this window.

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The utility data file used for our sample gas turbine looks as follows:

Economic Data To calculate annual utility and capital costs, enter economic data into Aspen Pinch. To do that: 5. From the menu bar, select Data, Economic and General Data. Alternatively, click the Create Data button on the Case Manager toolbar: A Create New Data window appears. 6. From the menu within this window, select Economic Data. An Editing Economic Data window appears. 7. Enter your economic data in this window.

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The economic data file used for our sample gas turbine looks as follows:

Saving your Gas Turbine Model To save your heat and power system model at any time, with the Gas Turbine Model window open, from the menu bar select File and Save Model.

Deleting your Gas Turbine Model To delete a gas turbine model: 1. From the main menu bar of Aspen Pinch, select Data, Heat and Power and Gas Turbine. A Gas Turbine window appears:

2. In the Gas Turbine ID box, use the list button to select the gas turbine to be deleted, and click the Delete button.

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Running the Gas Turbine Model Standalone After you have created gas turbine model data, combustion fuel data, inlet Air data, process Heating data, compressor data, turbine data, regenerator Data, utility data and economic data, you can run the gas turbine model. To run the gas turbine model standalone, not as part of targeting: 1. Click the Heat Power button of the common toolbar: An empty Heat and Power window appears. 2. If you have only one gas turbine, go to Step 3. If you have several gas turbines: • From the menu bar, select Heat/Power, Select and Gas Turbine. The Editing Gas Turb Model Selection window appears:

•

• •

In the Gas Turbine Block to be Used box, enter the name of the gas turbine you want to run. By clicking the List button, you can view and select from all the gas turbines you have supplied data for. Enter a name for the gas turbine report. Click OK to save and close the window.

3. From the menu bar, select Heat/Power and Run Gas Turbine. Aspen Pinch calculates the gas turbine conditions, and then writes them into the Heat and Power window. If errors occur during the calculation of gas turbine conditions, Aspen Pinch indicates what these errors are. You see a new window containing all errors. Errors flagged with ERROR LABEL: 1 are warning messages and are usually minor. Such errors may arise if Aspen Pinch tries to extrapolate some thermodynamic relationship beyond its bounds. However, an error flagged with ERROR LABEL: 4 is a terminal error and must be corrected. The error will have a description to help you sort out the problem.

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Running the Gas Turbine Model in Targeting Having checked that your gas turbine runs without errors in a standalone way, you can now connect the gas turbine to targeting. To do that: 1. Modify your utility data, so that you have a flue gas with the following parameters: • Tin: Enter the gas turbine exhaust temperature. • Modact: This is the model activity, which should have the value 1. This indicates that the flue gas duty calculated during targeting should be used in the detailed gas turbine model calculations. • ModelID: This is the identifier for the gas turbine that is to supply the flue gas. In the preceding example, ModelID is GTURB1. 2. Run targeting and place your flue gas and other utilities, as described in Chapter 4. 3. Check the targeting report. You should see a section towards the end of the targeting report, titled Gas Turbine or Gas Turbine Calculation Results. This section contains all the calculated conditions for the gas turbine that supplies the targeted duty. Any gas turbine exhaust heating below a process or utility pinch may not be necessary. In fact, by using exhaust in such a way, you may be increasing the use of cold utility. To avoid this, you should increase the gas turbine exhaust stack temperature. To do this, in the utility data file, increase the Tout value for your flue gas, and retarget. In some situations Aspen Pinch automatically changes the stack temperature. For example, if a utility pinch is formed when the gas turbine is placed in the grand composite curve, the flue gas line crosses the temperature axis at a temperature higher than the target temperature supplied. Aspen Pinch automatically increases the stack temperature to the temperature at which the flue gas line crosses the temperature axis. An example of this is shown for a furnace on page 9-15.

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Customizing Your Gas Turbine Report To customize your gas turbine report: 1. With a targeting window active, from the menu bar select Targets, Report and Settings Heat and Power. Alternatively, with a heat and power window active, from the menu bar select Heat/Power, Reports and Report Section Settings. An Editing Heat & Power Report Opt window appears. 2. Use the option boxes to customize your heat and power report and, in particular, your gas turbine report. Use the scroll bar on the right side of this window to view the full range of customization options.

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Steam Turbine The steam turbine model in Aspen Pinch is represented by the following figure:

SteamID

Tin, Pin

FurnEff

StageNam StageEff

Water/Steam

StageNam StageEff

Tin, Pin Quality FuelID

Power

StageID

Condensing Stage

Tout or Pout Tdesupr

Duty Flow Tdesupr

Tin or Pin

Tout or Pout

Tout or Pout

Tdesupr Tdesupr

Duty

flow

STMTUR (one steam turbine and one stage ID)

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Superheated steam is either generated in a boiler or supplied from an external source. The steam enters a turbine and is let down in pressure, for use either to supply process steam or supply steam for heating purposes. Several steam levels can be considered. The steam used for heating purposes can be desuperheated. Steam can also be reheated before it is put into another steam turbine stage.

Modeling a Simple Steam Turbine The following diagram shows specifications for a simple steam turbine system. We will refer to this example when explaining data entry and modeling. 80 bar.a 500°C

TURBINE

DESUPERHEAT WATER 100 C

GENERATED POWER

STEAM LEVEL = ‘MP’ 30 bar 5 kg/s Saturated

STEAM TURBINE Mobilization Cost = $20,000 Reference Purchased Cost = $80,000 Reference Size = 100 kW Cost Law Exponent = 0.8 Installed Cost/Purchased Costs = 4 Equipment Life = 5 yrs Operating Time = 8000 hrs/yr

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What Data Do You Need? To model a simple steam turbine, you must specify: • Steam turbine model data • Steam turbine cost data • Inlet steam data • Steam level data • Extraction steam data • Desuperheating water data • Utility data • Economic data Note

You can have several steam turbines.

To enter data for your steam turbine into Aspen Pinch: 1. From the menu bar, select Data, Heat and Power and Steam Turbine Model. A Steam Turbine window appears.

2. In the Steam Turbine ID box, select New if the turbine is new, or use the drop down list to select the name of a turbine that you have previously created. Click on the OK button to proceed. 3. A Steam Turbine Model window appears. If you are creating new turbine data, you will see a representation of a single-stage steam turbine. You can move the pointer on the scale at the top of the window to the left or right, to reduce or increase magnification of the diagram.

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Move the cursor over each data group in the diagram. The data group will become highlighted. To edit the data in any data group, move the cursor over that group and double-click your mouse. If sufficient data is given to Aspen Pinch in one data group for calculations to be made, that group is marked with a blue tick mark ([). If data in a data group is under-specified, Aspen Pinch will not be able to calculate conditions for the whole model. In such a situation, the data group is marked with a red cross. For the heat/power model conditions to be calculated, all data groups must be marked with a blue tick.

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Steam Turbine Model Data To enter Steam Turbine Model Data (name, efficiency, output, cost basis): 1. In the Steam Turbine Model window, double-click the Steam Turbine ID data group. An Overall Steam Turbine Parameters window appears:

2. Enter a unique Steam Turbine ID and efficiency. 3. The steam turbine produces power. Any cost credit that results from this power is costed, using an electricity utility. In the Utility power credit ID box, enter a power credit ID. This ID must correspond to a unique electricity utility ID in the Utility data file. If you already have electricity utilities in your utility data file, you can view and select from these, using the list button in this box. If you do not already have such utilities in your utility data file, enter a new electricity ID in the Utility Power Credit ID box. At the same time, it is recommended that you click on the Case Manager window and create or edit your utility data file to include the new electricity utility. 4. If the turbine is to generate a given amount of power, complete the power load in the Power output required box. 5. If you want to enter cost data for the turbine, click on the Cost button and refer to the next section. Otherwise, close the Overall Steam Turbine Parameters window, by clicking the OK button.

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Cost Data To enter cost data for the turbine: 1. Click the Cost button in the Overall Steam Turbine Parameters window, as shown in the previous section. Alternatively, right click the mouse over the Steam Turbine ID data group, and from the popup menu, click Cost. A Steam Turbine Cost window appears:

If you have a steam turbine cost law in a steam turbine cost data file, check the Cost Law button and enter the unique identifier of the cost law to be used in the Cost Law box. Alternatively, to supply a cost equation for the steam turbine directly into the steam turbine model, check the Cost equation button in the Steam Turbine Cost window and click the Cost Data button. A Steam Turbine Cost Data window appears:

Enter your cost data into this window, as shown. To save and close the window, click OK.

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Inlet Steam Data To enter inlet steam data: 1. In the Steam Turbine Model window, double-click on the inlet steam data group. A Default Inlet Steam window appears:

2. Enter the conditions of the steam feeding the steam turbine system in the boxes provided. If the steam is saturated, you can enter either the temperature or pressure together with the steam quality. Steam quality is the vapor fraction, which has a value between 0 and 1. 3. The work steam ID is used to determine the cost of the steam, and must correspond to a unique work-steam ID in the utility data file. If you already have appropriate work-steam utilities in your utility data file, use the list button to view these and select one. Otherwise, enter a new work-steam ID in the box. At the same time, it is recommended that you click the Case Manager window and create or edit your utility data file to include the new work-steam utility. 4. Click OK to save and close the Default Inlet Steam window.

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Steam Level Data To enter steam level data: 1. In the Steam Turbine Model window, double-click the turbine. A Steam Level window appears:

2. Enter an identifier for the steam level in the Level ID box, and an efficiency for the turbine stage in the Efficiency box. 3. Enter the temperature and pressure of the steam feeding the turbine. Note

These may be the same as or different from the conditions of the steam entered in the Inlet Steam Data. If the temperature you enter is higher than the temperature entered in the Inlet Steam Data, Aspen Pinch assumes that a fired heater provides the temperature lift. If you then close the Steam Level window, the steam turbine system diagram will be redrawn, to include a fired heater. For more information, refer to Adding a Fired Heater to Your Steam System on page 9-48.

4. In the Outlet Conditions pane of the Steam Level window, enter the pressure or saturation temperature of the outlet steam. 5. Click OK to save and close the window.

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Extraction Steam Data To set the conditions of steam leaving the turbine stage: 1. In the Steam Turbine Model window, double-click the extracted steam data group. An Extracted Steam window appears:

2. Extracted steam is the steam flow that exists in addition to any steam flow determined later due to targeting. This steam will not play a part in any process heating for the streams in your stream data, but will be used for fixed process users such as steam strippers, steam tracing, etc. In the Steam Extraction pane of the Extracted Steam window, enter either the duty required of the extracted steam, or its flowrate. Note

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These values must correspond to the requirements of the ultimate steam user. The actual steam flow leaving the turbine may be different, perhaps due to the addition of desuperheating water (see Step 3).

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3. In the Extracted Steam Conditions box, three options are available: Saturated - if steam leaves the stage superheated, desuperheating water will be added to the extracted steam to ensure it is delivered in a saturated state. In such a situation, less steam will be extracted from the turbine than is required by the user, because the delivered steam includes the desuperheating water. If the steam leaving the stage is two-phase (liquid and vapor), only the vapor part of the steam will be considered as being used. In such a situation, more steam will be extracted from the turbine than is required by the user. Superheated - if this option is selected, the Superheated Conditions pane of the Extracted Steam window will become active, and the steam will be heated, either to the superheat temperature or by the degrees of superheat you enter in this pane. If you close the Extracted Steam window (click OK) and save the steam model (from the menu bar, select File and Save Model), the steam system diagram will be redrawn without the desuperheating water. The superheat will be provided either by the inlet steam, or by steam with conditions that you specify in the Superheating Steam pane of the Extracted Steam window. Outlet Conditions - the conditions at the outlet of the steam turbine stage are not altered by the addition of water or by superheating, but are as calculated by the steam turbine model. Select one of these three options in the Extracted Stream Conditions box, and complete the additional required data. 4. Save and close the window by clicking OK. You return to the Steam Turbine Model window.

Desuperheating Water Data If your extracted steam is to be saturated, you must specify the temperature of desuperheating water. Click the desuperheating water data group. A Desuperheating Water window appears:

Enter the water temperature, then click OK to save and close the window.

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Utility Data The utility data file that allows you to run the steam turbine model should include data for the feed steam, as well as electricity. The electricity produced by the steam turbine will likely give some cost credit when the turbine runs. If you are ultimately going to connect the steam turbine to targeting, you will also want to add in the exhaust steam as a utility into the utility data file, as shown in the following figure. For more information on entering utility data, refer to Chapter 3.

Economic Data To calculate annual utility and capital costs, enter economic data into Aspen Pinch as follows. For more information on entering economic data, refer to Chapter 3.

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Saving Your Steam Turbine Model To save your heat and power system model at any time, with the Steam Turbine Model window open, from the menu bar select File and Save Model.

Deleting Your Steam Turbine Model To delete a steam turbine model: 1. From the main menu bar of Aspen Pinch, select Data, Heat and Power and Steam Turbine Model. A Steam Turbine window appears:

2. In the Steam Turbine ID box, use the list button to select the steam turbine to be deleted, and click the Delete button.

Running the Steam Turbine Model Standalone After you have created the steam turbine data described in the preceding section, you can run the steam turbine model.

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To run the steam turbine model standalone, not as part of targeting: 1. Click the Heat Power button of the common toolbar. An empty Heat and Power window appears. 2. If you have only one steam turbine, go to Step 3. If you have several steam turbines: • From the menu bar, select Heat/Power, Select and Steam turbine. The Editing Steam Turb Model Selection window appears:

•

• •

In the Steam Turbine Block to be Used box, enter the name of the steam turbine you want to run. By clicking on the List button, you can view and select from all the steam turbines you have supplied data for. Enter a name for the steam turbine report. Click OK to save and close the window.

3. From the menu bar, select Heat/Power and Run Steam Turbine. Aspen Pinch calculates the steam turbine conditions and then writes these into the Heat and Power window. If errors occur during the calculation of steam turbine conditions, Aspen Pinch indicates what these errors are. You see a new window containing all errors. Errors flagged with ERROR LABEL: 1 are warning messages and are usually minor. Such errors may arise if Aspen Pinch tries to extrapolate some thermodynamic relationship beyond its bounds. However, an error flagged with ERROR LABEL: 4 is terminal and must be corrected. The error will have a description to help you sort out the problem.

Running the Steam Turbine Model in Targeting When you have checked that your steam turbine runs without errors standalone, you can connect the steam turbine to targeting.

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To run the steam turbine in targeting: 1. Make sure that all steam levels in the utility file that are connected to the steam turbine model have the following parameters: • Modact: This is the model activity, which should have the value 1. This indicates that the steam flow calculated during targeting should be used in the detailed steam turbine model calculations. • ModelID: This is the identifier for the steam turbine that is to supply steam for process heating. In the preceding example, ModelID is TURBINE. 2. Run targeting and place your flue gas and other utilities, as described in Chapter 4. 3. Check the targeting report. You should see a section titled, Steam Turbine or Steam Turbine Calculation Results, which contains all the calculated conditions for the steam turbine supplying the targeted duty. If only a short report is seen, and you want to look at the detailed steam turbine model results, from the menu bar select Targets, Report and Settings: Target. In the Report Options window that appears, make sure that Steam Turbine Model Report = YES.

Customizing Your Steam Turbine Report To customize your steam turbine report: 1. With a targeting window active, from the menu bar select Targets, Report and Settings: Heat and Power. Alternatively, with a heat and power window active, from the menu bar select Heat/Power, Reports and Report Section Settings. An Editing Heat & Power Report Opt window appears. 2. Use the available option boxes to customize your heat and power report and, in particular, your steam turbine report. Use the scroll bar on the right side of this window to view the full range of customization options.

Adding a Fired Heater to Your Steam System Aspen Pinch lets you incorporate a boiler or fired heater into your steam system model. It will automatically place a boiler in the system, if the temperature of the steam entering the first steam turbine stage is higher than the temperature of the feed steam-- in the previous example, the feed steam to the system would be at 500°C.

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By editing the steam level data group and setting the steam temperature into the first turbine stage at 550°C, Aspen Pinch will redraw the steam system diagram to include a fired heater:

You must enter fuel and efficiency data for the furnace. To do this: 1. In the Steam Turbine Model window, double-click the furnace data group. A Furnace window appears:

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2. Enter a unique fuel identifier in the Fuel ID box. The unique Fuel ID must correspond to a fuel utility of the same name in the utility data file. If you already have fuel utilities in your utility data file, you can view these and select one, by using the list button. If you do not already have such utilities in your utility data file, enter a new fuel ID in the Fuel ID box. At the same time, it is recommended that you click the Case Manager window and create or edit your utility data file to include the new fuel utility. 3. Close the furnace window by clicking OK. With the Steam Turbine Model window active, save your steam system model by selecting File and Save Model from the menu bar. You are now ready to run your steam system model with the furnace included.

Adding Extra Stages to your Turbine Model Aspen Pinch allows you to have many different steam turbine stages. To create an additional turbine stage: 1. In the Steam Turbine Model window, right click the mouse over a steam turbine icon to reveal the following popup menu:

2. To add a turbine stage after the selected stage, choose Insert After. To add a turbine stage before the selected stage, choose Insert Before. Note

If the selected stage includes a furnace, the turbine will be added before the furnace.

3. Complete the data input by clicking on the various data groups in the Steam Turbine Model window, as explained earlier in this chapter.

Additional Turbine Feeds and By-Passes Aspen Pinch allows you to add extra steam feeds to each stage of your steam turbine model. It also allows you to by-pass some of the steam feed around the turbine.

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Adding a New Steam Feed To add an additional steam feed to a particular turbine stage: 1. In the Steam Turbine Model window, right click the mouse over the steam turbine stage icon. From the resulting popup menu, select Add Feed. The Steam Turbine Model window is redrawn to include an additional steam feed. 2. Double-click the data group of the new steam feed. A Feed window appears:

3. Enter a unique Feed Steam ID, together with the temperature, pressure and flowrate of that feed. 4. Click OK to save and close the Feed window.

Adding a Turbine By-Pass Aspen Pinch allows you to set up a turbine by-pass. Steam will be removed from the turbine feed and fed into the turbine exhaust. To enter a turbine by-pass, follow the steps outlined in the previous section. In the By-Pass Flowrate box of the Feed window, enter the desired by-pass flowrate.

Deleting a Steam Feed To delete a steam feed, right-click the mouse over the feed data group in the Steam Turbine Model window, and from the popup menu that appears, select Delete. The feed will be deleted from the Steam Turbine Model window.

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Refrigeration The refrigeration model in Aspen Pinch is represented by the following figure:

ComprID UtilID

EconDuty EconDp

CW

EconDuty EconDp EconDuty EconDp

HxerID Tout Duty

Tsat or Psat Phigh or Thigh

Tsat or Psat

Tsat or Psat

Duty

ComprID UtilID

EconDuty EconDp EconDuty EconDp

EconDuty EconDp

Tsat or Psat HxerID Tout

Tsat or Psat Duty

Tsat or Psat

CW

Phigh or Thigh

Duty

Duty Optional )

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Using a refrigeration system model, you can calculate refrigerant flows, power requirements, equipment sizes and equipment costs with a high level of accuracy. The refrigeration systems that Aspen Pinch models can comprise up to three refrigeration cycles. These can be connected, so that the heat from one cycle can be discharged into another cycle (sometimes called cascaded). Each cycle can have multiple refrigeration levels. Refrigerant flows are calculated by Aspen Pinch, based on user-supplied values for saturated temperature or pressure and refrigeration duty at each level. Economizers can also be considered in the model. The refrigeration models can be connected to targeting, and the refrigeration or economizer duties obtained from the targets. Aspen Pinch has built-in property models for a range of different refrigerants, to maximize the accuracy of the model.

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Modeling a Simple Refrigeration System The following diagram shows a simple propylene refrigeration system. The example will be used to explain the basics of refrigeration system modeling in Aspen Pinch.

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What Data Do You Need? To model a refrigeration system, you need to specify: • Refrigeration system data • Refrigeration cycle data • Compressor data • Refrigeration level data • Economizer data • Heat discharge data • Refrigerant condensing data • Utility data • Economic data To enter data for your refrigeration system into Aspen Pinch: 1. From the menu bar, select Data, Heat and Power and Refrigeration. A Refrigeration System window appears.

2. For Refrigeration System ID, select New if you are entering data for a new system, or pick from an existing system using the list button. For a new system, enter the name of the system in the System ID box. Each system can have up to three refrigeration cycles, for example ethylene and propylene. Select Cycle 1, 2 or 3 in the Cycle box, then click OK to save and close the window.

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3. A Refrigeration Model window appears, in which you see a representation of a refrigeration cycle. You can move the pointer on the scale at the top of the window to the left or right, to reduce or increase magnification of the diagram.

Move the cursor over each data group in the diagram. The data group will become highlighted. To edit the data in any data group, move the cursor over that group and double-click your mouse. If sufficient data is given to Aspen Pinch in one data group for calculations to be made, that group is marked with a blue tick mark ([). If data in a data group is under-specified, Aspen Pinch will not be able to calculate conditions for the whole model. In such a situation, the data group is marked with a red cross. For the heat/power model conditions to be calculated, all data groups must be marked with a blue tick.

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Refrigeration Cycle Data To enter refrigeration cycle data (name, refrigerant): 1. In the Refrigeration Model window, double-click the Cycle ID data group. An Overall Refrigeration Cycle window appears:

2. Enter a unique cycle ID and select a refrigerant for the cycle, using the list box. Aspen Pinch has built in property models to accurately model the following refrigerants: NH3 (Ammonia) C2H6 (Ethane) C2H4 (Ethylene) CH4 (Methane) C3H8 (Propane) C3H6 (Propylene) R22 (Refrigerant 22) 3. Click OK to save and close the window.

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Compressor Data To enter compressor data: 1. In the Refrigeration Model window, double-click the compressor data group. A Compressor window appears:

2. Enter a unique identifier for the compressor. 3. Select the compressor type, using the list box. Available types are Isentropic and Polytropic. 4. Enter the drive type, using the list box. Available types are Electric Motor, Gas Turbine, and Steam Turbine. These do not invoke the gas or steam turbine heat and power models, but are used by Aspen Pinch to select the appropriate driver cost correlation. 5. In the Utility Stream ID box, enter the identifier of an electricity utility used to power the compressor. This ID must correspond to a unique electricity utility ID in the Utility data file. If you already have electricity utilities in your utility data file, you can view and select from these, using the list button in this box. If you do not already have such utilities in your utility data file, enter a new electricity ID in the Utility Power Credit ID box. At the same time, it is recommended that you click the Case Manager window and create or edit your utility data file to include the new electricity utility. 6. Enter the calculation method, using the list box. Available methods are Equation of state, specified K-value, and calculated K-value, using the ideal gas law. An equation of state method is recommended. If you enter Specified K-value, you must also enter a value into the Compressor K-value box in the window. 7. Complete the efficiency data boxes.

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8. Enter the cost correlation by clicking the Cost button in the Compressor window. A Compressor Cost window appears:

Note

You can go directly to this Compressor Cost window, by rightclicking the mouse over the compressor icon in the Refrigeration Model window, and selecting Cost from the popup menu.

9. In the Compressor cost model box, enter a cost model. You can use the list box to select from: User supplied power law, Centrifugal cost law and Reciprocating cost law. If you specify User supplied power law, the Compressor User Power Law pane in the window becomes active, and you should use this to enter your compressor cost equation. 10. In the Driver cost model box, enter a cost model. You can use the list box to select from User supplied power law or Built-in correlation. If you specify User supplied power law, the Driver User Power Law pane in the window becomes active, and you should use this to enter your driver cost equation. 11. Once you have entered your compressor and driver cost data, click OK to save and close the Compressor Cost window. You will return either to the Compressor window or directly to the Refrigeration Model window.

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Refrigeration Level Data To enter Refrigeration Level Data: 1. In the Refrigeration Model window, double-click the Refrigeration Level data group. A Refrigeration Level window appears:

2. In the Level ID box, enter a unique refrigeration level ID. This ID must correspond to a unique refrigerant ID in the Utility data file. If you do not already have such utilities in your utility data file, enter a new refrigerant ID in the Level ID box. At the same time, it is recommended that you click the Case Manager window and create or edit your utility data file, to include the new refrigerant utility. 3. In the Heat Duty box, enter a duty for this refrigeration level. Note

This is a fixed duty. If you later connect this refrigeration level to targeting, the model will use the process refrigeration duty, plus this fixed duty, as the total requirement for refrigeration at this level.

4. Enter the saturation conditions for the refrigerant, either as temperature or pressure. 5. Click OK to save and close the window.

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Economizer Data To enter Economizer Data: 1. In the Refrigeration Model window, double-click the Economizer data group. An Economizer window appears:

2. Specify the duty and pressure drop within the economizer. Then click OK to save and close the Economizer window.

Heat Discharge Data Heat from the refrigeration cycle can discharge either into another refrigeration cycle, or into one of the utilities listed in your utility data file. To enter Heat Discharge Data for the refrigeration cycle: 1. In the Refrigeration Model window, double-click the Heat Discharge data group. An Exchanger window appears:

This Exchanger window shows that the heat from the refrigeration cycle is discharged into cooling water utility CW in exchanger C3CW. The heat could also have been discharged into another refrigeration cycle-- for example, as in cascaded cycles. 2. In the Exchanger ID box, enter a unique exchanger ID.

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3. Click on the Cost button to select the cost law that Aspen Pinch should use for the exchanger. A wide range of built-in exchanger types and materials of construction are available. If preferred, you can also supply your own cost law here. 4. In the Heat Sink pane, enter either the utility or cycle and level that receives the heat discharged. This ID must correspond to a unique cold utility ID in the Utility data file. If you do not already have such a utility in your utility data file, enter a new utility ID in the To Utility box. At the same time, it is recommended that you click the Case Manager window and create or edit your utility data file to include the new utility. 5. Complete the Exchanger Operating Data pane, then click OK to save and close the window.

Refrigerant Condensing Data To specify the temperature or pressure at which the refrigerant condenses at high pressure: 1. In the Refrigeration Model window, double-click the T-high data group. A Refrigerant Condensing Conditions window appears:

2. Enter either the temperature or pressure at which you want the refrigerant to condense. 3. Click OK to save and close the window.

Utility Data Utility data are required to model a refrigeration system. To input utility data into Aspen Pinch, follow the steps described in Chapter 3.

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The following figure shows a portion of the utility data file that corresponds to the refrigeration system described in the last figure. The electricity used by the refrigeration system has a cost and is included in the utility data file. So also is cooling water, which is used on the compressor discharge streams.

For more information on utility data entries, see Chapter 3.

Economic Data Economic data are also required for a refrigeration system. To input such data into Aspen Pinch, follow the steps described in Chapter 3.

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The following figure provides an illustration of the economic data required:

Saving your Refrigeration Model To save your heat and power system model at any time, with the Refrigeration Model window open, from the menu bar select File and Save Model.

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Deleting Refrigeration Systems and Cycles To delete either a refrigeration system or cycle: 1. From the main menu bar of Aspen Pinch, select Data, Heat and Power and Refrigeration. A Refrigeration System window appears:

2. To delete the refrigeration system and/or cycle, click the Delete System or Delete Cycle buttons. Then click OK to save and close the window.

Running the Refrigeration Model Standalone After you have created all the refrigeration system data files described previously, you can run the refrigeration system model. To run the refrigeration system model standalone, not as part of targeting: 1. Click the Heat & Power button of the common toolbar: An empty Heat and Power window appears. 2. If you have only one refrigeration system, go to Step 3. If you have several refrigeration systems: • From the menu bar, select Heat/Power, Select and Refrigeration.

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The Editing Refrig Model Selection window appears:

•

• •

In the Refrigeration System Block to Be Used box, enter the identifier of the refrigeration system you want to run. By clicking the List button, you can view and select from all the refrigeration systems you have supplied data for. Enter a name for the refrigeration system report. Click OK to save and close the window.

3. From the menu bar, select Heat/Power and Run Refrigeration. Aspen Pinch calculates the refrigeration system conditions and writes these into the Heat and Power window. If errors occur during the calculation of refrigeration system conditions, Aspen Pinch indicates what these errors are. You see a new window containing all errors. Errors flagged with ERROR LABEL: 1 are warning messages and are usually minor. Such errors may arise if Aspen Pinch tries to extrapolate some thermodynamic relationship beyond its bounds. However, an error flagged with ERROR LABEL: 4 is terminal and must be corrected. The error will have a description to help you sort out the problem.

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Running the Refrigeration System Model in Targeting When you have checked that your refrigeration system runs without errors in a standalone way, you can connect the refrigeration system to targeting: 1. Make sure that each utility associated with the refrigeration systems in your utility data has the following parameters: • Modact — This is the model activity, which should have the value 1. This indicates that the refrigeration level or economizer level duty calculated during targeting should be used in the detailed refrigeration system model calculations. • ModelID — This is the identifier for the refrigeration system which is to supply the refrigeration levels. In the previous example, ModelID is OLEFINS. 2. Run targeting and place your refrigeration levels and other utilities, as described in Chapter 4. 3. Check the targeting report. You should see a section titled Refrigeration, which contains all the calculated conditions for the refrigeration system supplying the targeted refrigeration duties. If only a short report is seen, and you want to look at the detailed refrigeration model results, from the menu bar select Targets, Report and Settings: Target. In the Report Options window that appears, make sure that Refrigeration Model Report = YES.

Customizing Your Refrigeration System Report To customize your refrigeration system report: 1. With a targeting window active, select Settings, Report and Heat and Power Report from the main menu bar. An Editing Heat & Power Report Opt window appears. 2. Use the option boxes to customize your heat and power report, and in particular, your refrigeration system report. Use the scroll bar on the right side of this window to view the full range of customization options.

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Adding More Heat Discharge Exchangers to your Model You can add more heat discharge exchangers to your refrigeration cycle. To create an additional heat discharge exchanger to one of your refrigeration cycles: 1. In the Refrigeration Model window with your refrigeration cycle showing, right-click the mouse over the heat discharge exchanger to reveal the following popup menu:

2. To insert a new heat discharge exchanger before the existing one, click Insert Before. To insert a new heat discharge exchanger after the existing one, click Insert After. The refrigeration system in the Refrigeration Model window will be redrawn to include the new exchanger. 3. Double-click the new exchanger to complete the exchanger details, as described in Heat Discharge Data, on page 9-61.

Adding More Refrigeration Levels to your Model You can add more refrigeration levels to your refrigeration cycle. To create an additional refrigeration level to one of your refrigeration cycles: 1. In the Refrigeration Model window with your refrigeration cycle showing, right-click the mouse over the Refrigeration Level data group. From the popup menu that appears, select either Insert Before to add a lowertemperature refrigeration stage, or select Insert After to add a higher temperature refrigeration level. The refrigeration Model window will be redrawn to include the new refrigeration level. 2. Complete the details for this new refrigeration level, as explained earlier in this chapter.

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Heat Exchanger Network Simulation and Optimization This chapter describes how Aspen Pinch is used to simulate or optimize a heat exchanger network (HEN). Simulation and optimization can be performed in either rating mode or design mode. Use this mode

To determine the

Rating

Operating conditions of the HEN, given the detailed geometrical details of each heat exchanger in the HEN and stream physical properties.

Design

Size and geometry of new heat exchangers. Optimization is used to minimize the total annualized cost of your HEN, considering both capital and energy costs. Or Aspen Pinch’s optimization can minimize only capital costs.

Before simulating or optimizing a HEN, you should already have identified a HEN design. This design should either exist on paper or have been designed within Aspen Pinch, as described in the chapter Working with Projects, Cases and Data. Aspen Pinch's simulation and optimization features allow you to establish the design parameters of the heat exchangers in your HEN design. Ultimately in your design, pressure drop, exchanger geometries and layout become important. Aspen Pinch’s HEN simulation/optimization feature helps you add more detail to your design. It gives you the opportunity to identify variables and gain more insight into the final design. It also enables you to obtain a more accurate cost estimate for your network.

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In addition, Aspen B-JAC Hetran models can be used in Network Simulation/Optimization. The prerequisites to using Aspen B-JAC and the input forms are described in Chapter 8. If you intend to simulate a network that has only splitters, mixers, and B-JAC Hetran unit operations (no pumps, valves, etc.), you will find it much simpler to use Network Design. This chapter explains simulation and optimization beginning with the simplest feature (simple simulation). As the chapter develops, so the level of complexity is increased. The main sections in this chapter are: • Simple simulation — Simple refers to a simulation in which heat exchanger models are described by surface areas, user-supplied heat transfer coefficients, temperatures and duty. Process streams are described by temperatures and duty. No detailed heat exchanger design information or detailed stream physical property information is required. • Detailed simulation — Detailed refers to a simulation in which detailed heat exchanger models are used. These detailed models include the geometrical features of the exchangers, such as tube diameters and baffle spacings. Detailed stream physical property information is also required, including physical properties such as viscosity and density over the full temperature range of the stream. • Simple optimization — This involves simple heat exchangers, with no physical property information. • Detailed optimization — This involves detailed heat exchangers, where exchanger geometry is considered and stream physical property values are required. An important principle in this chapter, to be followed as you simulate/optimize your network, is to start with a simple system and progress to the detailed system. Always make sure your simulation works in a simple form before progressing to the detailed analysis.

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Data Files Used in Simulation/ Optimization Aspen Pinch uses many data files to simulate and optimize a heat exchanger network. An overview of the files required is given in Figure 10-1.

Stream Data temperatures, pressures, physical properties (either as tables or equations)

Utility Data temperatures, pressures, physical properties (either as tables or equations) Economic Data operating time per year, equipment lifetime

HEN SIMULATION/ OPTIMIZATION Network Data (Block Data) equipment types, connectivity, equipment design details

Cost Data for each equipment type in network Variable/ Convergence Data tolerance, number of iterations

Figure 10-1. Data Required for Simulation/Optimization The following sections describe each category of data in detail.

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Stream Information In detailed simulation, many data files are required for process streams, in part because all stream physical properties have to be specified. Figure 10-2 outlines the data files that are required for the process streams within a network. Stream Data Single file which lists for each stream: stream name, temperatures, duty estimate, HTC estimate, simulation stream ID

Simulation Stream Data File Single file which lists for each simulation stream: simulation stream ID, pressure, either Physical Property Set IDor refinery stream characteristics (UOPK, API), flow

Property Tables - separate table (file) for each property, each table includes tabular data of that property for all streams

If data in Tabular form

Enthalpy Table Heat Transfer Coeffic. Table

Physical Property Sets File Single file which for each Physical Property Set ID lists a Property Table ID or Property Equation IDwhich describes each physical property: enthalpy, HTC, vapor fraction, viscosity, If Data in Equation Form density, thermal conductivity, surface tension, API gravity. (separate filename for each property).

Vapor Fraction Table Viscosity Table Density Table Thermal Conductivity Table Surface Tension Table API gravity Table API Table ID 1, Temp 1, Press 1, value 1 API Table ID 1,Temp 2, Press 2, value 2 API Table ID 1, Temp 3, Press 3, value 3 etc API Table ID 2, Temp 1, Press 1, value 1 API Table ID 2,Temp 2, Press 2, value 2 API Table ID 2,Temp 3, Press 3, value 3 etc etc (API gravity data for all streams stored in this file)

Property Equations separate table (file) for each property

Enthalpy Equation Heat Transfer Coeffic. Equation Vapor Fraction Equation Viscosity Equation Density Equation Thermal Conductivity Equation Surface Tension Equation API gravity Table API equation ID 1, Equation constants 1 to 5 API equation ID 2, Equation constants 1 to 5 API equation ID 3, Equation constants 1 to 5 etc (API gravity equation for all streams stored in this file)

Figure 10-2. Stream Information Required by Simulation/Optimization

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The temperature and duty information are stored in the Stream Data. This data is primarily used in targeting. For simulation/optimization, each process stream also has a simulation stream ID. This ID relates the stream to more detailed stream information which is stored in the Simulation Stream Data file. Hence, each simulation stream has its own ID that identifies it with a unique stream in the stream data. If your simulation stream is a refinery stream, you can specify an API gravity and UOP characterization factor for that stream within the simulation stream data. From these values, Aspen Pinch automatically calculates stream physical properties. If the streams are not refinery streams, you must enter physical property data directly into physical property tables. Each simulation stream has a Physical Property Set ID, which tells Aspen Pinch where to look for the stream's physical property data. The Physical Property Sets file tells Aspen Pinch whether values for a given physical property are in table form or are calculated from a user-supplied equation. It points Aspen Pinch to the appropriate file where either tabular or equation data are stored. Figure 10-2 shows the physical property data required for a detailed HEN simulation/ optimization. Note

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If you import data from Aspen Plus, you can choose to import stream data, network data and all the physical property information required for simulation/optimization. See the chapter Importing and Segmenting Data.

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Network Information Your network might contain several types of unit operation blocks. Figure 10-3 describes the block types available in Aspen Pinch. A simple network will comprise simple heat exchangers and perhaps flow splitters and stream mixers. Component Splitter Decanter/Desalter Flash Valve Stream Relation Compressor Pump Air Cooler Furnace Fired Heater Stream Mixer Flow Splitter Simple Heat Exchanger Detailed Heat Exchanger Exchanger ID, stream in and out ID's, New/Old exchanger, Tubeside calculation method, geometry (No. tubes, tube diameters, tube pitch, shell diameter, etc),

Figure 10-3. Heat Exchanger Network Information Required by Simulation/Optimization

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Cost Information One significant advantage of simulating your network in detail is that you will gain a high degree of accuracy in equipment design details. You can use this information to improve cost estimates for equipment. To help achieve accurate cost estimates, Aspen Pinch has different cost files to describe the costs of each different block type. Each file allows you to enter a reference cost, reference size, and cost law exponent. This allows Aspen Pinch to determine equipment costs based on relative size. Additional factors can be placed for the effects of pressure, temperature, and materials. Figure 10-4 shows the cost files used by Aspen Pinch for a range of different equipment-types, to determine accurate investment costs. Heat Exchanger Fired Heater Furnace Air Cooler Pump Compressor Motor Steam Turbine Cost ID, Ref Size, Ref Cost, Cost Law Exponent, Installation factor, etc.

Figure 10-4. Cost Information Required by Simulation/Optimization

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Simple HEN Simulation This section describes simple simulation, in which Aspen Pinch calculates the conditions in a network, based on user inputs. Simple simulation does not consider the detailed geometry of heat exchangers. It simply calculates network performance, based on temperatures, duties, heat transfer coefficients, and surface area of heat exchangers. You may specify some temperatures, some exchanger areas and some exchanger duties. Aspen Pinch will use the stream data and network information to determine network conditions. In simple simulation, only enthalpy is used. No other physical properties are considered.

Before You Start a Simple HEN Simulation To perform a simple HEN simulation, you need the following information. If you have an Aspen Plus simulation of your process and heat exchanger network, you can import stream data, network data and all the physical property information required for simulation/optimization. For more information, see the chapter Importing and Segmenting Data.

Specify Stream Data You should already have entered your stream data, as described in the chapter Working with Projects, Cases and Data. This data should comprise stream temperatures, duties and heat transfer coefficients.

Specify Network Data Before you can simulate a heat exchanger network, you must have a HEN design already completed, either operating or designed. The easiest way to enter your HEN design into Aspen Pinch is using the Network Design option. For instructions on how to do this, see the chapter New Network Design. When developing your HEN design, make sure to completely specify each heat exchanger, not only entering duties and temperatures but also including stream heat transfer coefficients. Aspen Pinch can then calculate heat transfer area requirements for each heat exchanger.

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Specify Utility Data Enter utility data in the same way as described in the chapter Working with Projects, Cases and Data. The utilities used in simulation cannot be connected to heat and power models. Also, unlike targeting, it is not necessary to have at least one hot and one cold utility.

Specify Cost Data Enter your heat exchanger cost data in the same way as described in the chapter Working with Projects, Cases and Data.

Specify Economic Data Enter your economic data in the same way as described in the chapter Working with Projects, Cases and Data.

Performing a Simple Simulation In a simple HEN simulation, Aspen Pinch calculates the thermal performance of each heat exchanger in the network. The performance is based on simple heat exchanger specifications such as area, temperatures, and duty. A simple simulation does not account for the geometry of any heat exchanger. Before starting a simple simulation, you should have entered your network in grid diagram form in Aspen Pinch’s Network Design tool, or imported a network from Aspen Plus. You can perform a simple simulation either from within Network Design, or by directly activating Aspen Pinch's Simulation feature, as described in the following sections.

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Simple Simulation from Within Network Design To perform a simple simulation from within Network Design, the Network Design Grid window should be open and the network completed and saved, as follows:

To perform a simple simulation of your network: 1. With the Network Design Grid window active, from the menu bar, select Network and Simulate. Aspen Pinch creates the data files required, and calculates the performance of each exchanger within the network. As the conditions of each exchanger are calculated, the exchangers in the Network Design Grid window are each highlighted in turn. The progress of the simulation is also shown in the footer of the main Aspen Pinch window. Once the simulation is complete, you can view the simulation results. 2. From the menu bar, select Network, Reports and Simulation.

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The Simulation Report window appears:

Use the scroll bars to scroll through the report. The report for the simple simulation shows the calculated conditions in each heat exchanger in the network. The operating conditions are determined based on the variables that were set in network design, such as area, temperatures and duty. For more details about the report, see The Simulation Report on page 10-22.

Simple Simulation Using the Simulation Feature Although you can perform simple simulation from within Aspen Pinch's Network Design feature, you should access the full capabilities of simulation and optimization through Aspen Pinch's Simulation feature. Before starting a simple simulation, you should have entered your network in grid diagram form in Aspen Pinch’s Network Design tool. To start Aspen Pinch’s simulation feature, click the Simulation button on the common toolbar: As an alternative, from the menu bar select Tools and Simulation. A blank Simulation window appears:

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To perform a simple simulation of your network: 1. Start the simulation, as described above. 2. Transfer your network data into a form suitable for Aspen Pinch's simulation tool. With the Simulation window active, select Data and Transfer Design to Simulation from the menu bar. The Simulation window heading changes to Simulation (Transferring Design..), and Aspen Pinch sets up the files necessary to perform a simple simulation. For more information on the number and content of these files, see Data Files Used in Simple Simulation on page 10-14. 3. From the menu bar, select Network and Run Simulation to run the simulation of your network. Aspen Pinch calculates the performance of each exchanger within the network. Once the calculations are complete, the heading in the Simulation window changes to Simulation Report, and the window contains the results of the simulation calculations, as shown in the previous section. For more details about the report, see The Simulation Report on page 10-22.

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Omitting Exchangers from the Simulation You may want to omit some heat exchangers or blocks in your simulation and subsequent optimization and not recalculate their associated conditions, perhaps because of some site constraints. To omit blocks from your simulation/optimization: 1. With the Simulation window active, from the menu bar select Simulation and Simulation Blocks. The Editing Blocks to Simulate window appears, showing a summary of each block:

Blocks are the various pieces of equipment, stream mixers, and stream splits in the network design. This window also contains information about block types and connectivity. 2. If you want to omit a block from your simulation, change the YES next to the block name to NO. Double-click on the YES field, and select NO from the dropdown menu. 3. Once you have reviewed the Editing Blocks to Simulate window, close the window. When Aspen Pinch prompts you to save the data, answer Yes. You can now run the network simulation/optimization with your specified blocks omitted.

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Data Files Used in Simple Simulation While performing simulation or optimization, Aspen Pinch requires stream and network data in a different form from that used in targeting and network design. More data files are required because of the additional data needed for a detailed evaluation of a heat exchanger network. Detailed analysis will be described later. The additional information required to perform a simple simulation, over and above the data required for targeting and network design, is minimal. Hence, although some additional files are created for simple simulation, there is little additional data contained in them when compared to the targeting and network design data. Aspen Pinch can automatically transfer the data used in targeting and network design into a form more suitable for simulation/optimization calculations, as explained earlier in this chapter. As the network is transferred into the form required for simple simulation, several data files are automatically created, as follows: simulation stream data; Hfilm table; physical property sets data; total enthalpy table; simple HXER data; mixer block and flow splitter block. Each file is discussed in detail below.

Simulation Stream Data The purpose of the Simulation Stream Data file is to describe in detail the process streams which exchange heat. See Figure 10-2 for information on where the file fits into the overall description of stream information. The Simulation Stream Data file contains any detailed information that is available about stream pressure and pseudo-component flows, namely hydrocarbon and nonhydrocarbon flows, water liquid and vapor flows, and noncondensable flow. The Simulation Stream Data file should not be confused with the Stream Data file, which describes only simple stream information such as temperatures, duty, and heat transfer coefficient. One example where the simulation stream data file is useful is for refinery streams. For such streams, Aspen Pinch allows the user to enter the stream API gravity and UOP characterization factor into the Simulation Stream Data. From this, Aspen Pinch calculates detailed physical properties for the stream. Alternatively, if the physical property information for a stream is available either in tabular form or as an equation, the Simulation Stream Data file points Aspen Pinch to the appropriate Aspen Pinch physical property data set for that stream. This physical property data set describes where such property data can be found. See Figure 10-2 for more information on this link.

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The information in the Simulation Stream Data file is most relevant to detailed simulation/optimization. For simple simulation, it should be regarded as a file that is required but which contains no additional information over the Stream Data file. You can view the Simulation Stream Data by selecting Data and Simulation Streams from the menu bar. As an alternative, in the Case Manager window, double-click on the Simulation Stream Data file. Here is a sample Simulation Stream Data file:

The following table provides some additional information on this data: Line 1, StreamID

This must match the ID of a stream in your Stream Data.

Line 2, Temp

Stream Temperature.

Line 4, PPSet

Tells Aspen Pinch the name of the file which describes the stream’s physical property files. See Figure 10-2 for more information on this link.

Line 9, UOPK

The UOP characterization factor. Aspen Pinch uses this and the API gravity (line 7) to calculate physical properties for refinery-type streams.

Hfilm Table The heat transfer coefficient data from the Stream Data is incorporated into a new Hfilm Table. This table is only used for simple simulation, and not for detailed simulation and optimization. If you want to use different values for heat transfer coefficients during simple simulation, you should edit this Hfilm table and enter your preferred values.

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The Editing Hfilm Table can be viewed if the Simulation window is active, by selecting Data, Tabular Properties and Film Coefficient from the menu bar. Alternatively, in the Case Manager window, double-click Hfilm Table. Here is a sample Hfilm Table:

Physical Property Sets Data You may have physical property data for one or all of your process streams in the heat exchanger network. If so, you can enter these into Aspen Pinch. The Physical Property Sets data file tells Aspen Pinch where to look for stream physical properties. It tells Aspen Pinch whether the data is in table form or represented by an equation. See Figure 10-2 for a pictorial overview to see where the Physical Property Sets data fits into the overall suite of data. With the simulation window active, you can view the Editing Physical Property Sets window by selecting Data and Physical Property Sets from the menu bar. As an alternative, in the Case Manager window, double-click Physical Property Sets.

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Here is a sample Physical Property Sets file:

The PPSetID is the physical property calculation method ID. It tells Aspen Pinch where to look for physical property data for each stream. This ID corresponds to a PPSetID in the Simulation Stream Data (see Figure 10-2). The physical properties that can be entered in Aspen Pinch are listed in the preceding graphic. Property data can be supplied either in table form or as an equation. If you have tabular data, you should enter an ID for the property in the PPSets form. The first letter of this ID must be the letter T. If you want Aspen Pinch to calculate a physical property using your own equation, the first letter of the ID must be the letter E. For example, in the previously illustrated PPSets file, for the stream with a PPSetID of HOT1, Aspen Pinch will look up the total enthalpy values in a table with identifier THOT1. For a simple simulation, you need use only the enthalpies. Other physical properties are not required, as shown in the PPSet Table above.

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Total Enthalpy Table The previously illustrated physical property set (PPSets) Table tells Aspen Pinch that, for the stream with a PPSetID of HOT1, total enthalpy values can be found in a table with identifier THOT1. The corresponding Total Enthalpy Table would look as follows:

Total stream enthalpies (vapor plus liquid enthalpies) for all streams are stored in this table. The table is automatically generated when you transfer your network data into a form suitable for simulation (see page 10-11). The table gives the identifier and corresponding temperatures, pressures, and total enthalpy values. To view the Total Enthalpy Table, select Data, Tabular Properties and Total Enthalpy from the menu bar. As an alternative, in the Case Manager window, double-click on Total Enthalpy Table.

Simple Heat Exchanger (HXER) Block For simple simulation, each heat exchanger is modeled as a simple heat exchanger whose operating conditions are calculated from surface area, duty, temperatures, and user-supplied heat transfer coefficients. The details of exchanger geometry are not accounted for. Details for each simple heat exchanger are entered in a Simple Heat Exchanger (Hxer) Block file.

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The easiest way to generate Simple Heat Exchanger block data for your network is to first develop the design using Aspen Pinch’s Network Design tool, then let Aspen Pinch automatically transfer the network into the form required for simulation and optimization. This procedure was described earlier in this chapter. When Aspen Pinch does this, it places all hot streams nominally on the tube side and all cold streams on the shell side. It also places all process streams in utility exchangers on the shell side. This stream side allocation is a convention Aspen Pinch uses to organize the network and stream data. It does not affect the results for Simple Heat Exchanger blocks. With the simulation window active, you can view the Simple Hxer Block file by selecting Data, Block Data and Simple Heat Exchanger from the menu bar. As an alternative, in the Case Manager window, double-click Simple Hxer Block. A Simple Hxer Block file might look as follows, in Record Format:

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The following table provides additional information on this window: Lines 2-5

Stream IDs describing the connectivity of the heat exchanger. This is described in more detail below.

Line 6, OldNew

If a new design, the exchanger is NEW. In a retrofit, the exchanger could be either NEW or OLD.

Line 7, USID

Utility ID - only required if the exchanger is a heater or cooler. A utility with the same Utility ID must be present in the UTILITY file.

Line 9, Option

Specify one of the following based on the values you already know, or want to specify: AREA

Specify exchanger area

TAPP

Specify minimum approach temperature

SHELTEMP

specify shell side outlet temperature

HEATDUTY

specify heat exchanger duty

Lines 11 - 14

Based on your entry in line 9, Option, specify the corresponding value for one of Area, Tapp, ShelTemp or HeatDuty. You can specify several of these, but only the value corresponding to your OPTION will be used by Aspen Pinch in calculations. Note that the heat duty value is positive, if the shell side is heated, and negative if the shell side is cooled. In utility exchangers modeled as simple heat exchangers, process streams are specified as flowing on the shell side. Hence, for a cooler where heat is removed from the process stream on the shell side, the heat duty is a negative number.

Line 24 UCalc

Calculation method for overall heat transfer coefficient. If the U value is to be calculated from the values in the Hfilm Table, specify HFILM. If you want to supply a value, specify SUPPLIED

Line 25, UValue

If you set UCalc = SUPPLIED in line 24, enter a U value here.

Line 29, CostCorr

Enter a cost correlation type. It is strongly recommended that you enter USER and then supply a USER cost law ID in the User Heat Exchanger Cost Data file.

The Simple Hxer Block file in Table format looks as follows:

You can see the connectivity between heat exchangers, represented in the preceding graphic by the S numbers. These correspond to substreams in the heat exchanger network and allow Aspen Pinch to understand the connectivity of streams to heat exchangers within the network.

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The heat exchanger network that corresponds to this Simple Hxer Block file is given here:

Mixer Blocks Mixer blocks are simple files that allow Aspen Pinch to understand which streams are mixed. With the simulation window active, you can view the Mixer Block file by selecting Data, Block Data and Stream Mixer from the menu bar. As an alternative, in the Case Manager window, double-click Mixer Block. A Simple Mixer Block file follows, describing the mixer in the previously illustrated Network Design Grid:

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Flow Splitter Blocks Flow Splitter blocks are simple files that allow Aspen Pinch to understand which streams should be split, and what the split fraction should be. With the simulation window active, you can view the Flow Splitter Block file by selecting Data, Block Data and Flow Splitter from the menu bar. As an alternative, in the Case Manager window, double-click Flow Splitter Block. A Simple Flow Splitter Block file follows, describing the splitter in the previously illustrated Network Design Grid:

The Simulation Report After a HEN simulation is completed successfully, the Simulation window changes to Simulation Report. The contents of the simulation Report vary, depending on whether simple or detailed simulation or optimization is performed. The elements of the report in each case are as follows:

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Table of Contents

Allows you to quickly move to those parts of the report of particular interest.

Block Convergence Status

Indicates which blocks have converged results and the corresponding residual error. If some blocks don’t converge, you may need to rerun the simulation, or increase the simulation tolerance slightly.

Unit Operation Block Section

The calculated conditions and connectivity information of each unit operation block are presented, including heat exchangers, flow splitters/mixers and any other types of equipment.

Cost and Size Section

The size, equipment cost and associated operating costs for each unit operation block are tabulated. The costs associated with process and utility streams are also listed.

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Simulation Report Tools Some Aspen Pinch simulation/optimization reports can be quite long. Aspen Pinch has several tools to help you quickly review and move within the information in your simulation/optimization report. These report tools can be accessed from the following popup menu that appears when you right-click your mouse in the report window:

The following sections describe each item of this popup menu.

Find Text To find text in your report: 1. Select Find from the popup menu. A Find window appears. 2. Enter the text you want to find in the box provided within the window. Qualify your find operation by selecting either the Up or Down button in the Direction box, and by selecting the Match Case box. If you want to search using the wildcard character *, select the Use Pattern Matching box.

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3. Click the Find Next button in the Find window. If Aspen Pinch finds the text, the cursor position in the Simulation Report window will move to that text.

Set Bookmarks You can set bookmarks to move easily within the report. For example, you can set a bookmark called Exchangers at the beginning of the detailed exchanger reports, or a bookmark called Coolers at the start of the cooler reports. To set bookmarks: 1. Move the cursor to the position in your report where you want to place the bookmark. Right-click the mouse button and select Bookmark from the popup menu that appears. A Bookmark dialog box appears:

2. Enter the name you want to give the bookmark, then click the Add button in the bookmark window. If you have several bookmarks, each will be listed. This helps you pick a unique bookmark name. To delete or go to other bookmarks, highlight the bookmark name you want to delete or go to, then click either the Delete or Go To boxes. Multiple bookmarks in the Bookmark window can be listed in alphabetical or positional order. Select your preference by clicking either the Name or Position buttons in the Sort By box.

Go To Aspen Pinch allows you to quickly move within a simulation/optimization report, using line numbers or bookmarks. To use the Go To facility: 1. Right-click the mouse button in the report window. From the popup menu that appears, select Go To. The Go To dialog box appears:

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2. To move to a given line using a line number, click the Line button, then enter the line number in the Line Number field. Finally click the Go To button. The cursor moves in the simulation report window to the beginning of your specified line. To move to a given bookmark, click the Bookmark button, then select the bookmark you want to go to in the Bookmark box:

Finally, click the Go To button. The cursor moves in the simulation report window to the bookmark position you specified.

Snapshot Aspen Pinch enables you to take a snapshot of your simulation/optimization report, perhaps for comparison with another report later in your analysis. To take a snapshot of the report, right-click the mouse button in the report window and select Snapshot from the menu that appears. A new window is created titled Snapshot of Simulation Report and containing a copy of your report.

Refresh Report If you want to refresh your report view, right-click the mouse button in the report window and select Refresh from the menu that appears.

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Formatting Aspen Pinch allows you to edit your report format in the following ways: Set Tab Spacing — Enables you to set the number of character columns between tabs. With the report window active, from the menu bar, select View and Set Tab Stops. Select Font — Enables you to change the fonts used in the report. Right-click the mouse button in the report window, and from the menu that appears, select Font.

Printing To print your Simulation Report, right-click the mouse button in the report window and from the pop-up menu that appears, select Print. To preview your Simulation Report print, right-click the mouse button in the report window. From the popup menu that appears, select Print Preview. If you want to change the appearance of your printed report: 1. Close the print preview window. 2. From the menu bar, select File and Page Setup. Adjust the page setup to your requirements. 3. From the menu bar, select File and Print Setup. Adjust the print setup to your requirements. 4. Preview the report again. If the preview shows the report in the format you want, select the Print button from within Print Preview.

Detailed HEN Simulation For a detailed simulation, the geometry of some or all heat exchangers is considered. This includes design values for shell diameters, tube diameters, baffle spacing, and so on. Detailed stream physical properties are required to perform such calculations, in order to accurately model pressure drops and heat transfer coefficients.

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Aspen Pinch’s detailed HEN simulation feature is not limited to modeling heat exchangers. Many other unit operations can be included, such as furnaces, decanters, pumps and flash drums. If you import your data from an Aspen Plus simulation, only streams and heat exchangers will be imported. Unit operations such as flash drums, decanters, pumps, compressors, motors and turbines will not be imported, and should be created separately within Aspen Pinch. Detailed simulation can be run in either rating mode or design mode. In rating mode, the exchanger designs have been set and Aspen Pinch is used to predict the performance of the network. In design mode, duty and temperatures are known for individual heat exchangers. The details of the design, such as tube length and number of tubes, are not yet known and have to be determined. The following sections discuss both modes of operation. You can also model heat exchangers using Aspen B-JAC. These, too, can be run in either simulation or design mode. In simulation mode, the heat exchanger geometry is specified in Aspen B-JAC and you reference the Hetran file (with a .bjt suffix) in Aspen Pinch.

Before You Start a Detailed HEN Simulation Before you start a detailed HEN simulation, you need all the information summarized in Figure 10-1.

Specifying Your Heat Exchanger Network The simplest way to specify your heat exchanger network is to first follow the steps outlined in Performing a Simple Simulation. When you do so, you will obtain a network for simulation that comprises simple heat exchangers or detailed Aspen B-JAC Hetran exchangers. If all of your exchangers are simple exchangers, you should simulate your network as a simple network to make sure all inputs are correct. After your network simulates without errors as a simple simulation, you are ready to convert your network to consider detailed heat exchanger models and perhaps other unit operations. To use an Aspen B-JAC heat exchanger in your simulation: Complete the B-JAC Hetran form as described in Chapter 8. If you have already done this in Network Design, the B-JAC information is already present.

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If you simulated the network in Network Design and your simulation contains unit operations other splitters, mixers, and Hetran exchangers (the unit operations present in Netwwork Design), you will need to manually change the Hot Side and Cold Side Stream Ids to maintain the connectivity between unit operations. If you have not simulated the network in Network Design you need to make sure that you enter the Hot Side and Cold Side Stream Ids correctly:

Stream Ids:

To add an Aspen Pinch detailed heat exchanger block into your simulation model: 1. With the Simulation window active, view the simple heat exchanger information by selecting Data, Block Data and Simple Heat Exchanger from the menu bar. 2. In the same way, view the detailed heat exchanger information by selecting Data, Block Data and Detailed Heat Exchanger from the menu bar. If you have not done a simulation or optimization with detailed heat exchanger or other unit operations in your current case, the fields within this window will be empty. 3. View the Simple and Detailed heat exchanger windows simultaneously in record format by selecting Window and Tile from the menu bar.

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4. Select the simple heat exchanger that you want to convert to a detailed exchanger, using the Next Record and Previous Record buttons on the Edit toolbar. The detailed heat exchanger has to have the same connectivity as the simple exchanger. Use the Copy and Paste features of Aspen Pinch to copy the connectivity data (lines 2 to 5) from the simple heat exchanger:

to the detailed heat exchanger (lines 2 to 5):

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5. In the detailed exchanger window, complete the exchanger name in the BlkID field. The name must be different to the simple heat exchanger name. However, it is recommended that the name be similar so that you can keep track of your simulation exchangers. 6. Copy the SpecType from the simple (line 9) to the detailed heat exchanger (line 11) window. Depending on the spectype - AREA, TAPP, SHELTEMP, DUTY, copy the corresponding value from the simple (lines 11 to 14) to the detailed exchanger (lines 13 to 16) window. For more information on detailed heat exchanger data requirements, see the section Aspen B-JAC Hetran Exchanger on page 10-40. 7. Use the verify button on the Edit toolbar to check your input: 8. Complete the procedure for any other heat exchanger you want to model in detail. After completing this procedure, you will have some exchangers that can be modeled either by simple or detailed simulation blocks. See the next section to select either the simple exchanger model or the detailed exchanger model in your simulation. The procedure described here has focussed on transferring simple exchanger data to a detailed exchanger model. However, the data can also be transferred to any other Aspen Pinch model types available. A full list of these other block types is given in Figure 10-3.

Specifying Which Blocks to Simulate After you have created some detailed heat exchangers as in the last section, you can model such exchangers either using the simple exchanger model or the detailed exchanger model. To select which block models are used in the simulation: 1. With the simulation window open, from the menu bar select Network and Simulation Blocks. The Editing Blocks to Simulate window appears:

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2. For the same heat exchanger, enter Select=YES for one of the exchanger models, and Select=NO for the other exchanger model. In this example, the simple model (Model=SHXER) for exchanger HX06 is not selected, but the detailed model (Model=HXER) for the same exchanger is. 3. Close the window. Aspen Pinch will guide you as to whether to save or cancel your changes.

Specifying Utility Data Enter your utility data in the same way as described in the chapter Working with Projects, Cases and Data.

Specifying Equipment Cost Data You should have cost equations for each type of equipment used in your heat exchanger network. These equations help Aspen Pinch determine a cost for each piece of equipment, depending on its size. The types of equipment which require a cost equation are summarized in Figure 10-4. Each cost equation should be in the form: Actual Cost = Mobiliz + RefCost * (Size) Exponent

– Or – (Actual Cost) / RefCost = (Size / Refsize) Exponent

To view the cost data for each equipment type, with the simulation window active, select from the menu bar Data and Economic. The following menu appears, from which you can select the block model you want:

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The following figure provides an example of the cost data for the detailed heat exchanger (User Heat Exchanger Cost):

Specifying Economic Data Enter your economic data in the same way as described in the chapter Working with Projects, Cases and Data.

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Specifying Physical Property Sets Data For simple simulation, there is no need to enter detailed physical properties about any of the process streams. However, detailed simulation does require detailed physical properties to calculate pressure drops and heat transfer coefficients. The relationships between the various physical property data files is given in Figure 10-2. Your physical property data can be either in table or equation format. If you have an Aspen Plus simulation of your streams, then you can import the physical property data for these streams directly into Aspen Pinch. However, as your data may be in some other format, you may have to enter the data manually. To see what physical properties are required, let's look at an example. Before you start to enter physical properties into Aspen Pinch, you should have all your data in tabular or equation form. This example assumes that you have been through the steps outlined above and successfully completed a simple HEN simulation. To put your physical properties into the form needed by Aspen Pinch for simulation: 1. View your Simulation Stream Data, by selecting Data and Simulation Streams from the menu bar. The Editing Simulation Stream Data window appears:

Each simulation stream will have a Physical Property Set ID, generated when you transferred the network design into the form required by Aspen Pinch for simulation. This ID tells Aspen Pinch the name of the file that contains the location of the physical property data.

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Note

If you know either the API gravity or the specific gravity at 15/4 and the UOP characterization factor for a particular stream, these can be entered in the Simulation Stream Data file above. Aspen Pinch can calculate properties directly from these. In such a case, a Physical Property Set ID for that particular stream is not then required.

2. Leave the Editing Simulation Stream Data window open. View the Physical Property Sets data by selecting Data and Physical Property Sets from the menu bar. The Editing Physical Property Sets window appears:

This file tells Aspen Pinch where to find the physical properties for each property set. Your file will already have an entry in line 2, telling Aspen Pinch where to find total enthalpy data. 3. Add to this table the identifiers for each of the physical property tables you will specify. In the example above, Physical Property Set SVR1 has tabular liquid viscosity data with label TLVIS2, tabular liquid density data with label TLDENS1, tabular liquid thermal conductivity data with label TLTHC1, and tabular surface tension data with label TSUR1. These data entries are required for a liquid stream in a detailed heat exchanger. If the stream also contains some vapor, similar entries are required in the rows beginning with letter V. Vapor fraction data is also required (line 3). 4. Enter tabular data into the various property data files, using the labels you set for each property in step 3.

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To enter property data, with the simulation window active, select Data and Tabular Properties from the menu bar. The following menu appears:

From the full list of properties that appears, select the property you want to enter. An Editing Property Table appears:

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More details about entering tabular properties can be found in the next section. 5. Enter your property data into the table, using the labels you specified in step 3. There is a single, separate file for each property. In the case of say liquid viscosity, you must enter all viscosity values into the table. For more details on tabular properties, see the next section. 6. Repeat step 5 for each property. The properties required for a stream flowing through a detailed heat exchanger are enthalpy, viscosity, density, thermal conductivity and surface tension. If two phases are present, both liquid and vapor values for these properties are required, together with details on vapor fraction.

Detailed Physical Property Data The arrangement of physical property data is explained in Figure 10-2 and in Specifying Physical Property Sets Data on page 10-33. Physical properties that can be entered into Aspen Pinch are: total, liquid and vapor enthalpy; heat transfer coefficient; hydrocarbon, non-hydrocarbon, and steam vapor fraction; liquid and vapor viscosity; liquid and vapor density; liquid and vapor thermal conductivity; and surface tension. For a detailed heat exchanger, all of these properties are required, with the exception of heat transfer coefficient. You can enter physical property data in either tabular format or equation format. All physical property data, in either format, should be on a mass basis and in SI units, that is, Kelvin, J/Kg, Kg / m3 , Pa-sec, W/mK, N/m. If any stream is twophase, both liquid and vapor properties must be given, together with values for vapor fraction. Detailed physical property data in tabular form can be created when you import stream data from Aspen Plus directly into Aspen Pinch. See the chapter Importing and Segmenting Data for more information.

Property Data in Table Format To create a property data file in which to enter your tabular physical property data: 1. With the Simulation window active, select Data and Tabular Properties from the menu bar. 2. Select the property you want from the resulting menu. For example, in table format, the physical property data for liquid viscosity looks like this:

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3. Enter a temperature and pressure for each property value you have. The temperatures and pressure should correspond to the associated stream. The data for one property across all streams are stored in one file. Hence, in the previous graphic, we see liquid viscosity data for 2 streams. Different streams have different TabID names (See Specifying Physical Property Sets Data on page 10-33).

Property Data in Equation Format To create a property data file in which to enter your physical property data in equation format: 1. With the Simulation window active, from the menu bar, select Data and Equation Constants:

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2. Select the property you want from the resulting menu. In equation format, the physical property data looks like this:

The unique Equation ID is also present in the Physical Property Sets file (see Specifying Physical Property Sets Data on page 10-33). 3. Enter the constants that describe the property in the fields given. Each physical property has the same equation format as shown in the preceding figure.

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Detailed Block Data In detailed simulation, Aspen Pinch will calculate equipment sizes and heat exchanger geometries in some detail, providing you specify that such detailed information is required. This section shows you the specifications required by each detailed unit operation. A summary of the detailed block data that might be specified is given in Figure 10-3. The feed(s) to and product(s) from each block are identified by stream names, as explained earlier in the section Simple Heat Exchanger Block. To access block data files with the Simulation window open, from the menu bar select Data and Block Data. Select the data file required from the resulting menu:

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Aspen B-JAC Hetran Exchanger See Chapter 8 for a complete description of the Aspen B-JAC input form.

Detailed Heat Exchanger To view or enter detailed heat exchanger information: Select Detailed Heat Exchanger from the menu above. An Editing Detailed Hxer Block window appears, in which you can view and edit your detailed heat exchanger data:

The following table presents additional notes on the Editing Detailed Hxer Block window: Lines 2-5

Stream Ids describing the connectivity of the heat exchanger. For more information, see Simple Heat Exchanger (HXER) Block on page 10-18.

Line 7, HxType

If a new design, the exchanger is NEW. In a retrofit, the exchanger could be either NEW or OLD.

Line 8, Rigorous

Enter YES for rigorous (heat exchanger design accounted for) or NO for shortcut (details of exchanger design not considered).

Line 9, TubeCorr

Specify either GILMOUR (default) or SHAH (horizontal) method for calculation of tube-side film coefficient. continued

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Line 11

Specification type. Choose from the following: SHELTEMP Specify shell side outlet temperature. The HxType in line 7 must be NEW. TUBETEMP

Specify tube side outlet temperature. This option is not valid if the exchanger is either a heater or cooler. The HxType in line 7 must be NEW.

SIMULAT

Perform a rating calculation for the exiting heat exchanger. If you choose this option, the HxType in line 7 must be OLD. Also, in rating mode you must enter all exchanger geometry.

HEATDUTY

Specify exchanger duty. The HxType in line 7 must be NEW.

Line 13, Area

Surface area to be used if Rigorous = NO. (line 8).

Lines 14-16

Enter a value based on your SpecType in line 11. If you specified HEATDUTY, use positive duty when heat is added to shell side; use negative duty when heat is removed from shell side

Line 18, ShelType

Pick the TEMA shell type for the exchanger, from E, F, X, K.

Line 31, FTMin

The minimum allowable temperature difference correction factor. The default value is 0.85.

Line 35, DefTube

If the default values for tube inside and outside diameters and tube pitch distance are to be used in design, select YES. The default values are selected by Aspen Pinch, based on the properties and flow of fluid, and on the maximum allowable tube side pressure drop. If the default values are not to be used, select NO. If you specify NO, you must enter tube values to be used by Aspen Pinch in lines 58 (TubeID), 59 (TubeOD) and 66 (Tpitch).

Line 36, DefPatt

If the default value for tube pattern is to be used in design, select YES. The default value is selected by Aspen Pinch, based on the properties and flow of fluid, and on the maximum allowable shell side pressure drop. If the default tube pattern is not to be used, select NO. If you specify NO, you must enter the tube pattern to be used by Aspen Pinch in line 63 (Pattern).

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Line 37, AdjBafTy

If the default value for baffle type is to be used in design, select YES. The default value is selected by Aspen Pinch, based on the properties and flow of fluid, and on the maximum allowable shell side pressure drop. If the default baffle type is not to be used, select NO. If you specify NO, you must enter the baffle type to be used by Aspen Pinch in line 44 (BafType).

Line 38, AdjNTPas

If the default value for number of tube passes is to be used in design, select YES. The default value is selected by Aspen Pinch, based on the properties and flow of fluid, and on the maximum allowable pressure drops. If the default number of tube passes is not to be used, select NO. If you specify NO, you must enter the number of tube passes to be used by Aspen Pinch in line 21, (NTPass).

Line 44, BafType

Baffle type. Select from CONVEN - conventional segmental, NOTUBE - Crossflow with no tubes in cut, TRIPLE - triple segmental baffle, CLOVER — cloverleaf or orifice baffles.

Line 77, CorrType

Cost correlation type. Choose one from: USER User-supplied cost law. See lines 80-92 (Recommended) FIXED

Aspen Pinch in-built fixed tube exchanger cost law

FLOAT

Aspen Pinch in-built floating head exchanger cost law

KETTLE

Aspen Pinch in-built kettle reboiler exchanger cost law

UBEND

Aspen Pinch in-built U-bend exchanger cost law

Line 80, CostID

If you specified USER in line 77, you should either enter a CostID here, or enter cost equation into lines 81 to 92. If you enter a CostID here, it must correspond with a CostID in the Detailed Exchanger Cost Data files. See Specifying Equipment Cost Data.

Lines 81-92

If you specified USER in line 77, you should either enter cost data here, or enter a CostID in line 80.

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The detailed heat exchanger models can be run either in rating mode or design mode: Rating Mode — In rating mode, you provide detailed geometrical information about the heat exchanger, such as tube diameters, baffle spacing, and so on. Aspen Pinch calculates heat transfer coefficients, pressure drop, and overall exchanger performance. To run in rating mode, you should have specified: • HxType = OLD • Rigorous = YES • SpecType = SIMULAT • All exchanger geometry Design Mode — In design mode, you specify the desired operating conditions such as duty or shell/tube side outlet temperature, and Aspen Pinch calculates heat transfer coefficients, pressure drop and exchanger geometry. To run in design mode, you should have specified: • HxType = NEW • Rigorous = YES • SpecType = one of SHELTEMP, TUBETEMP or HEATDUTY • A value to match your selected SpecType • Design Mode control parameters = YES (lines 35 to 38). If you set any of these parameters equal to NO, you should list the design parameter values you wish to use later in the detailed heat exchanger form. • Maximum shell inside diameter • Maximum shell-side pressure drop • Shell side fouling resistance • Maximum tube length • Maximum tube-side pressure drop • Tube side fouling resistance • Tube wall thermal conductivity

Furnace/ Fired Heater Aspen Pinch contains separate models for a furnace and a fired heater. The data required for each model is very similar. Both have one inlet and one outlet process stream. With the simulation window active, the furnace/fired heater block files can be viewed by selecting from the menu bar, Data, Block Data and either Furnace or Fired Heater.

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Here is an example of a furnace block:

The following table provides some additional notes on the Editing Furnace (and fired heater) window: Line 4, SpecType

Specification type. Choose the variable you want to specify from: HEATDUTY

Heat duty

DELTAT

Temperature increase across furnace/fired heater

TSPEC

Furnace/Fired heater outlet temperature

Lines 6-8

Enter the value in one of these fields to correspond to your specification type in line 4.

Line 9, UtilID

The utility ID of the fuel used in the furnace/fired heater. This ID points to a Utility ID in the UTILITY file. Acceptable utility types are coal, gas and oil.

Line 10, CstCorr

Furnace/fired heater cost correlation. Enter one from the following list:: Furnace Cost Correlations:

USER

User-supplied cost law. See lines 16-28 (Recommended)

PROCESS

Aspen Pinch in-built process furnace cost law

PYROLY

Aspen Pinch in-built pyrolysis furnace cost law

REFORMER

Aspen Pinch in-built reformer furnace cost law

Fired Heater Cost Correlations: USER

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User supplied cost law, See lines 15-28 (Recommended)

CYLIND

Aspen Pinch in-built cylindrical fired heater cost law

DOWTHRM

Aspen Pinch in-built Dowtherm fired heater cost law

Line 13, Material

Select material from CARBSTL (carbon steel), CHROME, STAINLESS.

Line 16, CostID

Cost law to be used to cost furnace/fired heater. Enter this ID or fill out the cost equation data in lines 17 to 28. This CostID should match a cost law ID in the Furnace Cost Data or Fired Heater Cost Data files. See Specifying Equipment Cost Data on page 10-31.

Lines 17-28

Cost equation information for the furnace/fired heater. Fill out these lines if you are not specifying a CostID in line 16.

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Air Cooler An air cooler has one inlet process stream and one outlet process stream. With the simulation window active, the air cooler block file can be viewed by selecting Data, Block Data and Air Cooler from the menu bar:

The following table provides some additional notes on the Editing Air Cooler window: Line 4, SpecType

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Specification type. Choose the variable you want to specify from: HEATDUTY

Heat duty

DELTAT

Temperature decrease across air cooler (positive number)

TSPEC

Air cooler outlet temperature

Lines 6-8

Enter the value in one of these fields to correspond to your specification type in line 4.

Line 14, UtilID

The utility ID of the electricity used to drive the air cooler fan. This ID points to an electricity ID in the UTILITY file. This is needed to establish an operating cost for the air cooler.

Line 15, CstCorr

Air cooler cost correlation. Enter one from the following list: USER

User supplied cost law, See lines 20-36 (Recommended)

BUILTIN

Aspen Pinch in-built air cooler cost law

Line 17, Material

Select material from carbon steel, 304 stainless steel, 316 stainless steel, aluminum, copper and monel. To view the full material selection, click the right mouse button over the field and from the resulting menu, select List.

Line 20, CostID

Cost law to be used to cost air cooler. Enter this ID or fill out the cost equation data in lines 21 to 36. This CostID should match a cost law ID in the Air Cooler Cost Data files. See Specifying Equipment Cost Data on page 10-31.

Lines 21-36

Cost equation information for the air cooler. Fill out these lines if you are not specifying a CostID in line 20.

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Pump A pump has one inlet and one outlet stream. With the simulation window active, the pump block file can be viewed by selecting Data, Block Data and Pump from the menu bar:

The following table provides some additional notes on the Editing Pump Blocks window: Line 4, Ptype

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Specification type. Choose the variable you want to specify from: DELTAP

Pressure increase across pump

POUT

Discharge pressure

PRATIO

Outlet to inlet pressure ratio

Lines 6-8

Enter the value in one of these fields to correspond to your specification type in line 4

Lines 9-26

Similar material and cost information.

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Compressor A compressor has one inlet and one outlet stream. With the simulation window active, the compressor block file can be viewed by selecting Data, Block Data and Compressor from the menu bar:

The following table provides some additional notes on the Editing Compressor Block window: Line 4, Ptype

Specification type. Choose the variable you want to specify from: DELTAP

Pressure increase across compressor

POUT

Discharge pressure

PRATIO

Outlet to inlet pressure ratio

Lines 6-8

Enter the value in one of these fields to correspond to your specification type in line 4

Line 12, UtilID

The utility ID of the electricity, steam or fuel utility used by the compressor driver. This ID points to an electricity, steam or fuel ID in the UTILITY file. This is needed to establish an operating cost for the compressor.

Line 16, CCstCorr Compressor Cost Correlation. Choose one from:

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USER

User supplied cost law, See lines 20-32 (Recommended)

CENTRIF

Aspen Pinch in-built centrifugal compressor cost law

RECIPRO

Aspen Pinch in-built reciprocating compressor cost law

Lines 18-32

Material and cost information for the compressor.

Lines 33-47

Material and cost information for the driver.

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Valve A valve has one inlet and one outlet stream. With the simulation window active, the valve block file can be viewed by selecting Data, Block Data and Valve from the menu bar:

Aspen Pinch does not calculate the capital cost of a valve block.

Flash A flash block separates one feed stream into one vapor and one liquid product. With the simulation window active, the flash block file can be viewed by selecting Data, Block Data and Flash from the menu bar:

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Aspen Pinch does not calculate the capital cost of a flash block. The following table provides additional notes on the Editing Flash Block window: Line 5, Mode

Lines 7-10

Flash calculation mode. Choose one method from: QP

Adiabatic flash based on supplied duty and pressure

TP

Isothermal flash based on supplied temperature and pressure

Enter the value in one of these fields to correspond to your calculation mode entered in line 5

Decanter/Desalter A decanter block separates one feed stream into one product without water, and a pure water product. You can use a decanter block to approximate the performance of a desalter. The temperature and pressure of the two products is assumed to be the same as the feed.

Aspen Pinch does not calculate the capital cost of a decanter block.

Stream Relation Aspen Pinch uses a stream relation block to manipulate the conditions of a stream. It can be used to change the flow, temperature, and pressure in a stream. This is useful if you want to account for other unit operations not covered by Aspen Pinch’s block models.

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With the simulation window active, you can view the stream relation block file by selecting Data, Block Data and Stream Relation from the menu bar:

Aspen Pinch does not calculate a capital cost for a stream relation block.

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The following table provides additional notes on the Editing Stream relation block: Line 5, Ftype

Line 11, TType

Line 17, PType

Flow relation method. Choose one method from: RELA

Adjust flow based on ratio outlet/inlet . Enter the flow ratio value in line 7 RelF.

DIFF

Adjust flow based on difference. Enter the flow difference in line 8, DifF.

ABS

Adjust flow to an absolute value. Enter the absolute value for flow in line 9, AbsF.

NONE

Make no adjustment to flow.

Temperature relation method. Choose one method from: RELA

Adjust temperature based on ratio outlet/inlet . Enter the temperature ratio value in line 13 RelT.

DIFF

Adjust temperature based on difference. Enter the temperature difference in line 14, DifT.

ABS

Adjust temperature to an absolute value. Enter the absolute value for temperature in line 15, AbsT.

NONE

Make no adjustment to temperature.

Pressure relation method. Choose one method from: RELA

Adjust pressure based on ratio outlet/inlet . Enter the pressure ratio value in line 19,RelP.

DIFF

Adjust pressure based on difference. Enter the pressure difference in line 20, DifP.

ABS

Adjust pressure to an absolute value. Enter the absolute value for pressure in line 21, AbsP.

NONE

Make no adjustment to pressure.

Component Splitter Aspen Pinch uses a component splitter block to separate one stream into two products. Its main purpose is to remove one or more pseudo components, such as noncondensables, from a feed. You specify the fraction of each component which is rejected into the second product. The temperatures and pressures of both products are assumed to be the same as the feed. With the simulation window active, you can view the component splitter block file by selecting Data, Block Data and Component Splitter from the menu bar:

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Aspen Pinch does not calculate a capital cost for a component splitter block.

Detailed HEN Simulation: Rating In rating mode you provide detailed geometrical information about the heat exchanger, such as tube diameters, baffle spacing, and so on. Aspen Pinch calculates heat transfer coefficients, pressure drop, and overall exchanger performance. To simulate your network in rating mode: 1. Complete the specification of the equipment in your network. Your network will comprise some detailed heat exchangers. It may also include some other Aspen Pinch block models. The recommended way to create a network for detailed simulation that includes detailed heat exchanger blocks is: Develop your design in Aspen Pinch’s Network Design feature. Specify any Aspen B-JAC heat exchangers there. Use Aspen Pinch to automatically transfer any simple heat exchangers in the network into a form that Aspen Pinch needs for simulation. Run the simple simulation successfully. If not already done, convert the resulting simple heat exchanger blocks into detailed heat exchanger blocks. This procedure applies to Aspen Pinch's detailed heat exchanger model and is described in detail earlier in this chapter. Make sure that any additional blocks you put into the network or which replace simple heat exchangers have correct connecting stream identifiers.

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Also, make sure that your detailed heat exchangers have the following data variables which are required for network evaluation in rating mode: • HxType = OLD • Rigorous = YES • SpecType = SIMULAT • All exchanger geometry (tube diameters, tube pitch, baffle type, etc) 2. Complete specifications for utility, equipment cost, and economic data. 3. Complete the physical property data, as outlined in Specifying Physical Property Sets Data on page 10-33. The physical property data required to model a detailed heat exchanger are: enthalpy; viscosity; density; thermal conductivity; surface tension. If two-phase flow is present, vapor fraction and vapor and liquid properties are also required. Physical property data can also be transferred from Aspen Plus to Aspen Pinch. See the chapter Importing and Segmenting Data. 4. Ensure that Aspen Pinch’s simulation feature is activated. If not, click the Simulation button of the Common toolbar: A blank window appears labeled Simulation. Select the blocks to be included in the detailed rating simulation by selecting Simulation and Simulation Blocks from the menu bar. The Editing Blocks to Simulate window appears:

In the Editing Blocks to Simulate window, select each block you want to include in your simulation by setting SELECT = YES. If you have a simple model and a detailed model for the same heat exchanger, set one of the SELECT values to YES and the other to NO. Close the Editing Blocks to Simulate window. Aspen Pinch will ask you whether you wish to save your selections. Click the YES box in response. Run your simulation by selecting Network and Simulate from the menu bar.

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Aspen Pinch calculates conditions in the network. After calculations are completed, the Simulation window label changes to Simulation Report, and the results of the simulation are displayed. If Simulation errors occur, a separate error window appears. See the section Errors and Diagnostics on page 10-66. Review the results of your simulation in the Simulation window. In addition to a Unit Operation Block and a Cost and Size Section, the report contains a Stream Information section and a Heat Exchanger Specifications Sheets section. These summarize the physical properties for each stream, and summarize the details of each heat exchanger, from exchanger geometry to pressure drops and thermal performance. You have completed a detailed rating simulation in Aspen Pinch.

Detailed HEN Simulation: Design In design mode, you specify the desired operating conditions such as duty or shell/tube side outlet temperature. From this data, Aspen Pinch calculates heat transfer coefficients, pressure drop, and exchanger geometry. To simulate your network in design mode, follow the steps outlined in Detailed HEN Simulation: Rating. Make sure in Step 1 that your detailed heat exchangers have the following data for Design Mode: • HxType = NEW • Rigorous = YES • SpecType = one of SHELTEMP, TUBETEMP or HEATDUTY • A value to match your selected SpecType • Design Mode control parameters = YES. If you set any of these parameters equal to NO, you should list the values you wish to use later in the detailed heat exchanger form. • Maximum shell inside diameter • Maximum shell-side pressure drop • Shell side fouling resistance • Maximum tube length • Maximum tube-side pressure drop • Tube side fouling resistance • Tube wall thermal conductivity

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Simple HEN Optimization Aspen Pinch allows you to optimize your heat exchanger network. The most common objective of using Aspen Pinch's optimization feature is to minimize total annualized cost of a heat exchanger network. In optimization, you set variables and design specifications. Aspen Pinch manipulates the variables to meet the specifications. The number of variables you set must be greater than the number of specifications. Do not confuse HEN optimization with the targeting optimization described in the chapter Targeting for a New Process. Targeting optimization calculates optimum heat recovery based on targets without any network design. HEN optimization calculates the optimum based on a fixed network configuration and minimizes its cost based on capital and energy costs.

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Before You Start a Simple HEN Optimization Before you start a simple HEN optimization, you should specify HEN, utility data, exchanger cost data, economic data, and physical property sets data, as described in Before You Start a Simple HEN Simulation on page 10-8. For optimization, some additional convergence, variable and specification data is also required, as outlined in Figure 10-5.

Group of Variables 2 Single file which lists all variables in variable group 1: Group of Variables 1 Groupfile of which variables Single listsID all, variables Variable ID 1group 1: in variable Variable ID 2 ID No. 1 , Group of variables Variable ID 3 ID 1 Variable etc Variable ID 2 Variable ID 3 etc

Convergence Data Single file which lists for each convergenc block: block ID, Group of variables ID , Group of specifications ID , run mode (simulation/optimization/ Design) Group of Specifications 2 Single file which lists all specifications in variable group 1: Group of Specification 1 Group variables Single fileofwhich lists ID all,specifications Variable ID 1 group 1: in specification Variable ID 2 Group of Specifications ID No. 1 , Variable ID 3 Specification ID 1 etc Specification ID 2 Specification ID 3 etc

List of Variables Variable ID 1,Block or Stream name, variable name Variable ID 2,Block or Stream name, variable name Variable ID 3,Block or Stream name, variable name etc

List of Specifications Specification ID 1 ,Block or Stream name, Specification name Specification ID 2 ,Block or Stream name, Specification name Specification ID 3 ,Block or Stream name, Specification name etc

Figure 10-5. Arrangement of Aspen Pinch’s Simulation/Optimization Run Data

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Optimization Variables and Specifications Before you can optimize a HEN, you must specify the variables that Aspen Pinch should manipulate in the optimization to achieve the optimization objective. As the following table indicates, variables can be associated with both unit operation blocks and streams: Examples of block variables:

Approach temperature Heat Duty Overall heat transfer coefficient Shell side (process) outlet temperature Shell side pressure drop Exchanger heat transfer area Tube side pressure drop

Examples of stream variables:

Flow Temperature Pressure

For optimization, it is recommended that you set block variables rather than stream variables.

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Consider this example HEN:

If you want to minimize the cost of this network, the hot outlet temperatures of each process heat exchanger could be set as variables. The split flows through each branch on stream COLD1 could also be varied. These would be the variables that you would set and that Aspen Pinch would manipulate to try to minimize HEN cost. Note

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For optimization, the number of variables you set should always be greater than the number of specifications.

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Optimization Specifications You must also set specifications for your optimization. As indicated in the table below, specifications can be associated with both streams and unit operation blocks: Examples of block specifications:

Approach temperature Heat Duty Overall heat transfer coefficient Shell side (process) outlet temperature Shell side pressure drop Exchanger heat transfer area Tube side pressure drop

Examples of stream specifications:

Flow Temperature Pressure

Referring to the optimization of the HEN in the sample network design grid, the outlet temperatures of each process heat exchanger and the split flows have been set as variables. However, the target temperature of each stream still has to be satisfied. To ensure that such target temperatures are met, specifications are required. Aspen Pinch specifications are split into two categories: Implicit specifications:

If no variable is specified for a particular block, then the block specification is inferred to be the specification used in the heat exchanger block data file. For example, in the network example in this chapter, no variables were specified for the heater and cooler blocks. Hence, Aspen Pinch implies design specifications equal to the heater and cooler block specifications. For a utility exchanger, the implied specification is the process-side outlet temperature.

Explicit specifications:

Explicit specifications are required whenever a block takes part in optimization, and where some specification associated with the block still has to be achieved. For example, in the network example in this chapter, the heat exchanger HX04 has been included in optimization. However, the outlet temperature of the cold stream running through this exchanger still has to be 180°, so the stream can achieve its target temperature. Hence, this temperature must be explicitly set as a specification. Explicit specifications must be entered into Aspen Pinch.

For optimization, the number of variables you set should always be greater than the number of specifications.

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Performing a Simple Optimization In a simple optimization, heat exchanger models use surface area, user-supplied heat transfer coefficients, temperatures, and duty to establish optimized network conditions. Process streams are described by temperatures and duty. No detailed heat exchanger design information or detailed stream physical property information is required. As you go through the following procedure, it will be useful to keep referring to Figure 10-5, which shows the relationship between the various Aspen Pinch data files required for optimization, and also to the network presented in the network design grid. To perform a simple optimization: 1. Specify your HEN, Utility data, exchanger cost data, economic data and physical property sets data, as described in Before You Start a Simple HEN Simulation. 2. Perform a simple simulation, to make sure that you have correctly specified you network. 3. Determine the network variables. For example, consider the network presented above in Optimization Variables. The variables for an optimization on this network would be the shell-side outlet temperatures of each process exchanger and the split flow fractions in the split on stream COLD1. 4. Determine the explicit specifications. In the sample network presented earlier in Optimization Variables, only one explicit specification is required — the temperature of the stream leaving exchanger HX04 (exchanger HX04 is involved in the optimization, so it needs a specification to ensure that the cold side temperature is achieved). All other stream target temperatures can be achieved using heaters and coolers, which are implied specifications. 5. Enter the definition and bounds for each variable. With the simulation window active, from the menu bar select Data, Specifications/Variables and Variable Definitions. An Editing Simulation Variables window appears:

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The window above corresponds to the sample HEN in the network design grid. Each variable must have a unique identifier (VaryID). If the variable is a block variable, enter the associated block name and variable name. Choose the block variable name from the following list: • TAPP — Approach temperature • HEATDUTY — Heat duty • UVALUE — Overall heat transfer coefficient • SHELTEMP — Shell side (process) outlet temperature • SHELDP — Shell side pressure drop • AREA — Exchanger heat transfer area • TUBEDP — Tube side pressure drop If the variable is a stream variable, enter the stream name in the Stream field and enter an index in the SVindex field from the following list: • 1 — Flow rate • 2 — Temperature • 3 — Pressure Finally, for each variable, set lower and upper bounds in SI units (Kelvin, Pascals, Watts, W m2 K , kg/s). The bounds should be set at practical and feasible bounds that are wide enough to cover likely optimal results, but that are not so narrow that they would preclude some attractive network options. 6. Enter the simulation variable list data. This data allows all variables to be grouped together. Different variable lists can be created for each different optimization you might perform, perhaps to meet different optimization objectives. With the Simulation window active, from the menu bar, select Data, Specifications/Variables and Variable Lists. The Editing Simulation Variable List window appears:

This window corresponds to the sample HEN in this chapter. Enter a unique variable group ID in line 1, and then the list of variables you want included in this variable group below it.

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7. Enter the definition and bounds for each specification. From the menu bar and with the Simulation window active, select Data, Specifications/Variables and Specification Definition. The Editing Simulation Specifications window appears:

Again, the window above corresponds to the sample HEN in the network design grid. For each specification, specify a unique identifier (SpecID). If you want to set a block specification, enter the associated block name and specification name in lines 3 and 4. Choose the block specification name from the following list: • TAPP — Approach temperature • HEATDUTY — Heat duty • UVALUE — Overall heat transfer coefficient • SHELTEMP — Shell side (process) outlet temperature • SHELDP — Shell side pressure drop • AREA — Exchanger heat transfer area • TUBEDP — Tube side pressure drop If you want to set a stream specification, name the associated stream and enter a stream variable type ID and index in lines 6, 7, and 10, as described in the comments in the right column of the window. For each specification, set the corresponding value in SI units (Kelvin, Pascals, Watts, W m2 K , kg/s).

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Finally, in line 17 of the Editing Simulation Specifications window, specify whether the value given in line 16 is a maximum value for the specification (MAX), the exact value required (EQUAL), or a minimum value for the specification (MIN). 8. Specify how you want to group the specifications together. Aspen Pinch allows you to group together different design specifications. Having different groups allows different sets of specifications to be applied to the optimization, depending on the objective of your optimization (you may want to minimize total cost, or minimize only capital costs. From the menu bar and with the Simulation window active, select Data, Specifications/Variables and Specification Lists. An Editing Simulation Spec List window appears:

Again, the window above corresponds to the sample HEN in the network design grid. Enter a unique specification group ID in line 1, and then the list of specifications in that group below it. Enter convergence data and the variable and specification groups to use. From the menu bar and with the Simulation window active, select Data, Specifications/Variables and Convergence Data. The Editing Convergence Data window appears:

Again, the window above corresponds to the sample HEN in the network design grid.Enter a unique identifier in line 1 (BlkID). In lines 2 and 3, enter the IDs for the groups of variables and specifications to be applied in your optimization. Finally, specify OPTIMIZ in line 4. The other lines in this window control the number of calculations and tolerances. These should be left at their default values.

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Select the blocks to be included in your optimization. With the Simulation window active, from the menu bar, select Simulation and Simulation Blocks. The Editing Blocks to Simulate window appears:

The window above corresponds to the sample HEN. One of the blocks listed will be your convergence block (line 3 in this window). It should be selected with SELECT=YES. Run the optimization. From the menu bar, select Simulation and Run Simulation. Aspen Pinch performs the optimization calculations. Once these are completed, the Simulation window title changes to Simulation Report. 9. Review your results in the Simulation report window. Should simulation errors occur, a separate error window appears. See Errors and Diagnostics.

Detailed HEN Optimization In a detailed optimization, detailed heat exchanger models are used which include the geometrical features of the exchangers, such as tube diameters and baffle spacings. Detailed stream physical property information is also required, including physical properties such as viscosity and density over the full temperature range of the stream.

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To perform a detailed HEN optimization, follow the instructions given in Performing a Simple Optimization on page 10-59. You need to use detailed exchanger models for your heat exchanger blocks, but all the principles from this chapter apply.

Simulation to Meet a Design Specification You can use Aspen Pinch’s simulation feature to also satisfy design specifications, where you want to change the value of one variable to meet a certain specification. For example, you could set up a simulation where a stream flow could be varied to meet a certain temperature specification on the outlet of a heat exchanger. To meet such design specifications, the number of variables must equal the number of specifications. To set up a simulation to achieve a design specification, follow the steps in simple optimization.You will likely only have one variable and one specification. In your Simulation Specifications file, you should set the value of the specification. In the Convergence Data, set the run mode to be Simulation. Complete the simulation as if it were a simple optimization.

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Performing Simulation, Optimization and Design Runs for a Single Network Aspen Pinch allows you to keep simulation, optimization, and design data for a single network in the same Aspen Pinch case. For example, your convergence data file may look as follows, containing a design convergence block, a simulation convergence block, and even an optimization convergence block.

This data is stored in Aspen Pinch. However, different types of simulation/ optimization runs cannot all be processed at the same time. You should select only one of these each time you do a simulation or optimization. Use the Editing Select blocks window to select only one of the simulation/optimization blocks, as follows:

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Errors and Diagnostics If your simulation or optimization does not calculate correctly, a new simulation history window automatically appears to tell you the problem that has been encountered. If your simulation does converge successfully, this simulation history window won't appear automatically. However, you can view it by selecting from the menu bar Simulation and Diagnostics. The following is a list of some of the error messages you may see, and recommendations on how to fix the errors:

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Error Message

Hints

Line Search Failure

Perturbation factor from numerical derivatives is too high. Reduce the Pertfac value in the Convergence Data file. Generally, Pertfac should be at least 1.0E-06.

Stream XX is product from YY and other blocks

Check your block connectivities, in the Editing Blocks to Simulate file.

Missing or Duplicate PPSet XXX

Check your PPSet data labels in the Simulation Stream Data and PHYSICAL Property Sets file.

Utility Stream XX is not defined

Check utility and block data files

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Setting Diagnostic Levels You can set the amount of diagnostic information that is presented in the simulation history window, as follows: 1. With the Simulation window open, from the menu bar select Data, Specifications/Variables and Diagnostic Levels. An Editing Simulation Diag Levels window appears:

2. In the BlkID field, enter one of the following: The block identifier

The diagnostic levels will only apply to the identified block

The keyword 'GLOBAL'

The diagnostic levels will apply to the whole simulation

The keyword 'CVG'

The diagnostic levels will only apply to the convergence searches

3. In the BlkLev and StrmLev fields, enter a number from 0 to 9. 0 will result in very little diagnostic information being created. 9 will result in a full report of diagnostic information being created. 4. In the Basic, Input and Results fields, enter 1, if you want Aspen Pinch to produce diagnostic reports of basic information, input information and results.

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Index

component splitter 10-50 compressor 10-46 decanter 10-48 desalter 10-48 detailed heat exchanger 10-40 fired heater 10-42 flash 10-47 flow splitter 10-22 furnace 10-42 mixer 10-21 pump 10-45 simple heat exchanger 10-18 stream relation 10-48 valve 10-47

A

C

Air preheat 9-16 Alpha values in retrofit targeting 5-1,5-3 Annualization of capital costs 2-30 Area-energy plot 5-1 Aspen B-JAC requirements 7-7 Aspen Plus importing data from 4-2 importing heating/cooling curves 4-9 importing network from 4-9 importing properties from 4-9 selecting file to import 4-3 Auto Optimization report 3-25 Autosave 7-48

Capital cost annualization 2-30 Case discard changes to 1-7 save Data 1-7 Case specific units 2-5 Case trees 1-5 Cases child 1-5,1-7 copying data between 2-38 creating 2-4 creating description 2-11 data 1-7 defined 1-4 deleting 2-39 discarding 1-9 moving data between 2-37 parent 1-5,1-7 project 1-4 renaming 2-39 saving 1-9 selecting an existing case 2-36 Child case 1-5,1-7 Combustion air 9-16 Common Data toolbar 3-2 Composite curves balanced 3-3 exergy 3-5 grand 3-17 introduction 3-1 pinches in 3-4 shifted temperature 3-4 viewing 3-3 Coordinate values in plots 3-7 Cost data for heat exchanger 2-28

B Base directory selecting 2-34 setting 2-2 B-JAC application type 7-11 constraints 7-14 execution 7-16 options 7-15 process conditions 7-9 requirements 7-7 results file 7-10 sample results 7-17 shell specifications 7-12 specifying the type 7-8 tube specifications 7-13 Block data air cooler 10-44

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1

CP table 7-33,7-47 Creating case description 2-11 cases 2-4 projects 2-1 stream data 2-11,2-22,10-14 target data 2-10 units 2-8 Cross-Pinch Heat Transfer report 7-50

D data converting from other Aspen Pinch versions 2-40 updating for use in Windows 2-43 Data case description 2-11 converting from ADVENT 2-40 copying cases 2-38 creating target 2-10 DTmin 2-21 economic 2-29 editing 2-37 editing target 2-10 entering energy target 2-9 heat exchanger cost 2-28 inheritance 1-5 moving 2-37 report 2-33 searching 2-33 selecting a filter 2-9 stream 2-11,2-22,10-14 table and record format 2-32 utility 2-16,10-9 verifying 2-33 Data Extraction applying previous changes 4-7 applying rules 4-5 options from Aspen Plus 4-5 Default sets, changing 2-7 Design toolbars 7-3 Design tools for network design 7-32 Directories, setting a base directory 2-2 Dtmin creating a data file 2-21 values for total site targeting 6-2

E Economic data 2-29 furnace model 9-12

2

gas turbine model 9-12 refrigeration system 9-63 steam turbine 9-12 Economic Method 2-29,2-30 Edit toolbar 2-31 Editing existing data 2-37 heat exchangers 7-20 target data 2-10 Energy management and audit, total site targeting 6-1 Energy savings plot 5-6 Exergy 3-5 Exergy grand composite curve 3-18 Exhaust heat 9-18

F Features 1-3 Fired heater 9-2 Flame temperature 9-2 Flue gas 9-2 Furnace model air preheat 9-16 data required 9-4 economic data 9-12 example 9-3 overview 9-2 report 9-17 running in targeting 9-14 running standalone 9-13 utility data 9-11 varying stack temperature 9-15

G Gas turbine model data required 9-20 economic data 9-12 example 9-19 overview 9-18 report 9-34 running in targeting 9-33 running standalone 9-32 stack temperature 9-33 utility data 9-29 Global units 2-5 Grand composite curve 3-17 Grid lines in plots 3-10 Grid, network design 7-4

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H Heat and power models furnace 9-2 gas turbine 9-18 overview 9-1 refrigeration system 9-52 steam turbine 9-35 Heat exchanger cost data 2-28 Heat exchanger network automatic design 7-37 autosave feature 7-48 controlling a loop’s shifted duty 7-40 CP table 7-33,7-47 defaults 7-47 deleting heat exchangers 7-20 design grid 7-4 design parameters 7-46 design tools 7-32 designing 7-2 detailed simulation 10-2 display conventions 7-24 display style 7-48 driving force plots 7-33 editing heat exchangers 7-20 exchanger placement 7-7 exchanger profiles 7-47 heating/cooling profile 7-36 identify options 7-23 information display 7-22 match data method 7-17 multi-stream exchangers 7-27 network loops 7-38 network path 7-40 optimization 10-54 overview 7-1 plate-fin exchanger 7-30 printing networks and plots 7-52 printing reports 7-53 reinitialising 7-21 reports 7-49 restarting 7-21 shifted duty 7-42 simple simulation 10-2 simulation 10-8 specifying exchangers 7-7 stream data 7-5 temperature labels 7-46 tick off method 7-17 viewing stream data table 7-6

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Heat Exchanger Network plot tools 7-25 Heat Exchanger Network report 7-49 Heat Exchanger report 7-50 Heat exchangers deleting 7-20 duty 7-8,7-16,7-17 Heat integration study 1-1 Heating/cooling profile 7-36 Hide streams and utilities 7-4,7-5

I Import from Aspen Plus 4-2 from SuperTarget 4-15 Inherited data 1-5 Interface 1-6 Iteration Log File 8-7

L Loops and Paths excluded exchangers 7-44 order by duty 7-43 order by number 7-43 required exchangers 7-44 setting parameters 7-43

M Match (heat exchanger) 7-7 Match Constraints in retrofit design 8-6 Match data method 7-17 Minimum temperature difference for heat exchange 2-21

N Network design 7-1 Network loops 7-38 Network paths for heat exchanger network 7-40 Network Pinch 8-1 locating 8-8 report 8-9 New exchangers adding 8-13

3

O Optimization convergence data 10-62 detailed 10-63 errors 10-66 list of specifications 10-62 list of variables 10-60 selecting blocks 10-52,10-63 setting specifications 10-61 setting variables 10-59 simple 10-59 specifications 10-58 variables 10-56 Optimization range, setting for utilities 3-25 Optimization report 3-25 Optimizing DTmin/utility loads 3-22 utilities 3-22 utility loads for multiple utilities 3-25

P Parent case 1-5,1-7 Payback line 5-6 Physical properties data 10-16,10-33,10-36 equation format 10-37 list 10-36 sets 10-34 table format 10-36 total enthalpy 10-18 Pinches, working with 3-4 Plate-fin heat exchanger 7-30 Plots background color 3-10 color in 3-10 coordinate values 3-7 driving force 7-33 energy savings 5-6 grid lines 3-10 identifying streams in 3-7 printing 3-11,7-52 retrofit targeting 5-5 setting limits on axes 3-11 taking a snapshot of 3-9 text in 3-8 updating views 3-7 viewing 3-8 zooming 3-8 Pop-up menu

4

exchanger 7-22 network 7-5 Printing a targeting report 3-17 customizing data reports 2-34 data reports 2-34 heat exchanger network reports 7-53 networks 7-52 plots 3-11,7-52 Projects cases 1-4 creating 2-1 defined 1-4 existing 2-34

Q Quitting 1-9

R Record format 2-32 Records editing 2-32 inserting and deleting 2-32 moving between 2-32 Refrigeration system model data required 9-55 economic data 9-63 example 9-54 overview 9-52 report 9-67 running in targeting 9-67 running standalone 9-65 Repiping 8-12 Report bookmarks 3-14 find text 3-13 formatting 3-16 go to 3-15 printing 3-17,10-26 refresh 3-16 simulation 10-22 snapshot 3-16 split 3-16 tools 3-13,10-23 Reports Auto Optimization 3-25 Cross-Pinch Heat Transfer 7-50 Data 2-33 Furnace 9-17

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Gas Turbine 9-34 Heat Exchanger 7-50 heat exchanger network 7-53 Heat Exchanger Network 7-49 Network Design 7-51 Refrigeration System 9-67 Retrofit Targeting 5-7,5-8 Specific Payback 5-7 Steam Turbine 9-48 Targeting 3-12 Total Site 6-8 Resequencing 8-10 Retrofit Design duty bounds 8-5 losing options 8-4 match constraints 8-6 modification options 8-10 network pinch 8-1 solver controls 8-16 solver method 8-7 solver options 8-7 sorting out infeasibilities 8-17 temperature approach 8-4 Retrofit targeting alpha values 5-1,5-3 area efficiency 5-1 plots 5-5 reports 5-7 requirements 5-1 starting 5-1 switching units and shells 5-5 Retrofit Targeting reports 5-8 switching between constant and incremental alpha 5-5 Retrofit Targeting Info toolbar 5-3 Retrofit Targeting Views toolbar 5-3 Root directory selecting 2-34 setting 2-2

S Segmentation 4-9 streams, automatic 4-10 Segmentation toolbar 4-11 Segmenting streams adding segments 4-13 changing accuracy of automatic segmentation 4-14 deleting segments 4-13 interactive 4-11

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saving data 4-14 Segments, streams 2-16 Sets, defaults 2-7 Shell targeting FTmin 2-30 maximum area per shell 2-30 X parameter 2-30 Shifted duty 7-42 simulation report 10-23 Simulation choosing blocks 10-30 convergence data 10-55 copying exchanger data 10-29 cost information 10-7 data 10-3 design 10-5,10-26,10-42,10-53 design specifications 10-64 detailed 10-2 diagnostics 10-67 errors 10-66 heat transfer coefficients 10-15 network information 10-6 optimization 10-56 rating 10-5,10-26,10-42,10-51 report 10-11,10-22 report tools 10-23 run data 10-55 selecting blocks 10-13,10-52 simple 10-2,10-8,10-9 stream data 10-14,10-33 stream information 10-4 utility data 10-9 Source sink profiles 6-3,6-4 Specific Payback report 5-7 Stack temperature furnace model 9-15 gas turbine model 9-33 Starting 1-5 Steam turbine model data required 9-37 economic data 9-12 example 9-36 overview 9-35 report 9-48 running in targeting 9-47 running standalone 9-46 utility data 9-45 Stream data adding to network design 7-5 API gravity 10-14

5

creating 2-11,2-22,10-14 minimum requirements 2-11,2-22,10-14 optional 2-16 segments 2-16 simulation 10-14,10-33 UOP characterization 10-14 viewing 7-6 Stream names from Aspen Plus 4-6 Stream Splitting 8-14 Stream type utility 2-17 Streams adding segments 4-13 automatic segmentation 4-10 deleting segments 4-13 hide 7-4 interactive segmentation 4-11 mixing 7-27 plotting 3-7 saving segmented data 4-14 segmentation accuracy 4-14 segmenting 4-13 split flows 7-26 splitting 7-25 temperature control 7-42 SuperTarget importing data from 4-15

labels 7-46 stack 9-15,9-33 Text in plots 3-8 Tick off method 7-17 Toolbar Case Manager 2-2 retrofit 5-3 targeting 3-2,6-5 Total Site Common Data toolbar 6-3,6-4 Total Site Place Utility toolbar 6-3,6-4 Total Site Source Sink toolbar 6-3,6-4 Total site targeting cases 6-2,6-3,6-4 DTmin values 6-2 modifying data 6-7 overview 6-1 pockets 6-2 report 6-8 source sink profiles 6-3,6-4 starting 6-1 targeting one case 6-7 utilities 6-6 utility system audit 6-1 Total Site View toolbar 6-3,6-4 Turbines gas 9-18 steam 9-35

T

U

Table format 2-32 Target data creating 2-10 editing 2-10 entering 2-9 Targeting activating functions 3-2 composite curves 3-1 exergy grand composite curve 3-18 grand composite curve 3-17 report 3-12 report tools 3-13 shell 2-30 Targeting Common toolbar 3-2 Targeting Information toolbar 3-2 Targeting Operations toolbar 3-2 Targeting Optimization toolbar 3-22 Targeting Place Utility toolbar 3-19 Targeting View toolbar 3-2 Temperature flame 9-2

Undo 7-21 Units case specific 2-5 creating 2-8 customizing 2-7 default 2-7 global 2-5 project 2-4 standard 2-5 viewing 2-6 Unix, converting data from 2-40 User Pinch toolbar 3-2 Utilities connections to other utilities 2-19 creating data for 2-16,10-9 fixed flow rate 2-20 heat and power model connections 2-20 hide 7-4 optimizing 3-22 optional data 2-18 placing 3-19

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Aspen Pinch User Guide Version 10.2

placing for total site targeting 6-6 removing 3-19,3-21 setting duty of 3-21 setting optimization range of 3-25 stream type 2-17 types 2-18 Utility data furnace model 9-11 gas turbine model 9-29 steam turbine 9-45 Utility duty, changing 3-21 Utility system audit, total site targeting 6-1

Aspen Pinch User Guide Version 10.2

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Aspen Pinch User Guide Version 10.2