Hr Vdu Process

Vacuum Distillation Unit - Process

Sujit K Ghosh

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Introduction: Refinery Overview • Refining Objective:  High volume Fuels / Lube production  Flexible operation for different crudes  Proactive on environmental issues  Maximize higher value distillate yield

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Introduction: Refinery Overview • RefineryTypes:  Simple:  Processing specific range of crude to middle distillates  CDU & VDU, FCCU / Hydrocracker, Catalytic Reformer, Hydrogen Plant

 Complex:  Processing variety of crude making a range of high value added products  CDU & VDU, Visbreaker, Lube extraction, FCCU, Delayed Coker, Catalytic Reformer, Sulphur Plant, Bitumen Plant

 Integrated:  Refinery + Petrochemical

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Refinery Feed Stock •

Crude Oil: –

mixture of large number of hydrocarbons 1. Paraffins : normal and iso paraffins  Methane, Ethane, Butane, iso-butane

2. Napthenes : Cycloalkanes / Sat. ring structure  Methyl cyclo pentane

3. Aromatics : Benzene Ring & its derivatives  Benzene, Toluene

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Refinery Feed Stock •

Crude Assay: –

Used to evaluate crude for processing  Crude assay Determines  Refinery Configuration  Product Yield Analysis

–

Assay Content:  Key Crude oil properties  Boiling Point curve including properties of fractions  Chracterization factor (k)  Density Curve  Sulphur & Nitrogen content  Other contaminants

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Vacuum Distillation •

Why Vacuum unit ? –

Further fractionation of Reduced Crude Oil (RCO) ex ADU/CDU residue to get heavier distillates : 1. 2.

• •

For Lube feed stock For Cracking for high value fuel distillates.

Recovery of distillates from RCO without Vacuum leads to coking/ cracking and quite energy intensive. Higher temperature operation requires : - Special metallurgy & higher cost. - Higher protection for equipment & personnel

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Vacuum Distillation 

Product Routings: Distillates:    

HSD Pool FCC Feed Hydrocracker Feed Lube Processing

Vacuum Residue  Lube Processing ( PDA extraction)  Visbreaker / Thermal cracker Feed  Bitumen

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Vacuum Distillation •

VDU Types: Fuel Based

Lube Based

Prepares feedstock for FCC, Hydrocracker

Prepares feedstock for Lube Processing

Products:

Products:

1. 2. 3. 4. 5.

1. 2. 3. 4. 5. 6.

Diesel LVGO HVGO Slop Vacuum Residue

Gas Oil/Diesel Spindle Oil Light Oil Intermediate Oil Heavy Oil Vacuum Residue

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Vacuum Distillation •

Vacuum Column Types:

Dry

Damp Wet

Top/Flash Press (mm Hga) 8 / 24

25 / 42

75 /95

Heater Outlet Temp (oC)

420

405

395

Steam

Nil

Medium Highest

Column Dia

Highest

Medium Least

Transfer Line

Highest

Least

Medium

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Vacuum Distillation: Column Types •

Dry Vacuum Features:  

•

Wet Vacuum Features:    



Higher Heater Outlet temp (COT) More ejector steam Used for Lube Stocks where Flash Point of Products are to be met Reduces Heater Outlet temp (COT) requirement due to partial pressure of steam Lesser Ejector steam Marginally better yield of distillates and controllability due to steam

Economics normally in favour of Damp Vacuum Haldia Refinery Igniting Minds... Energizing Lives…

Vacuum Distillation: Distillate Specification KV ([email protected])

(oC)

CCR (Wt %)

Gas Oil

1.3-1.6

120

-

Spindle Oil

3.5-3.6

160+

-

Light Oil

6.0 min

200+

-

Inter Oil

9.0-11.0

230-240

-

Heavy Oil

19.0-24.0

240-260

2.4 max

1200+

300-320

18-20

Short Residue

•

Flash Point

Lube VDU Columns are typically wet vacuum as:  

Products need to meet Flash Point spec Better product separation (Sharp Cut) required

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VDU: Process Description Block Diagram: Furnace Feed Booster

Pre-heat Train

OSBL Feed Pump GO

Ejector

Vacuum Column

SO

SO LO IO

LN IN

HO

HN SR

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What is Vacuum Distillation?

Distillation under vacuum Condition

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What is Vacuum? • Any pressure below atmospheric. How is it expressed? 760 mmHg (a)  1 Atm  0 Kg/cm2 (g) 76 mmHg vac ? (760-76) mmHg absolute 76 mmHg abs ?  (760-76) mmHg vac

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Process Description

• • • • •

Five main sections The Pre-heat Train The Furnace The Vacuum Column The Side Strippers Auxilliary Systems

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Process Description Block Flow Diagram

Furnace Feed Booster

Pre-heat Train

Feed Pump GO

Ejector

Vacuum Column

SO

SO LO IO

LN IN

HO

HN SR

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Process Description The Pre-heat Train configuration is based on • Heat recovery plan & Product R/D temp before cooler • Heat Exchanger network configuration as per heat/ temperature potential of streams • Fouling characteristics, Corossivity of the liquid, flow, viscosity, metallurgy, etc RCO Feed Gas Oil

To Furnace IO

SR

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Process Description The Furnace • The required temperature for distillation is achieved in the furnace, the outlet of which directly goes to to the Flash zone of the vacuum distillation column. • The furnace is a balanced draft type and has the facility of dual firing (both Fuel gas & Fuel oil). Its has got two passes with flow control in each. • The feed stream from the pre-heat train enters the convection zone followed by the radiation zone. • Major part of the oil feed to the furnace gets vaporized before entering the vacuum column. Haldia Refinery Igniting Minds... Energizing Lives…

Process Description Vacuum Column features : • • • • • • • • • • • •

The distillation and stripping takes place in the vacuum column. Internals are normally packing/ tray type or both. Bottom section (stripping) are typically with trays (sieve). Downcomers are either side/central or both based on liquid load. Transfer line enters tangentially with impingement plate to reduce impact. Multi Product Draw. Side draws are provided with strippers to control flash point Typical turn down 60-65% Top and bottom section are SS cladded based on crude property. Top temperature maintained 15-20 C above the Dew Point Column Diameter higher as compared to ADU columns (?) Diameter fixed by capacity and height depends on degree of rectification.

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Process Description The Vacuum Column • Two reflux : • Top reflux • Bottom Reflux (Known as Pump Around).

• Pump Around: To remove heat from the column • Key parameters: – – – – –

Flash zone temperature/ pressure, Top temperature/pressure, Side draw temperatures PA return flow and tempearure Bottom tempearture Haldia Refinery Igniting Minds... Energizing Lives…

Process Description The Vacuum Column

To Ejectors Reflux Gas oil SO LO

RCO From Furnace

Vacuum Distillation Column

IO HO Vacuum Slop

Stripping Steam

SR/VR

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Process Description The Side Draw Strippers • Different cuts drawn from the vacuum column are routed to their respective Stripper columns. • Lighter components in the draws are stripped off the main product by using superheated steam. ```` Draw Temperatures • Spindle Oil stripper----210-240 C • Light Oil stripper-------250-280 C • Inter Oil stripper--------300-320 C • Heavy Oil Stripper-----340-360 C Haldia Refinery Igniting Minds... Energizing Lives…

Process Description The Side Draw Strippers • The bottom products from the Strippers are routed to their respective storage tanks after exchanging heat with the RCO Feed in the Pre- Heat exchanger Train and then Cooling Water Exchangers.

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Process Flow Diagrams

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Haldia Refinery Vacuum Distillation Unit PFD (furnace and fractionator circuit) Furnace recycle Ex p-9/9r FC-10A

FC-10B To Ejectors

FC-5 CW

FC-4

VB steam

Turbulising steam

Combustion air Ex APH

GO as reflux ex E-2A/B/C

VS steam FC-9 Turbulising steam

F-1

FC-8

#22

FC-102 Fuel gas

RCO ex F-1/F-2

Turbulising steam

F-2 P-113/113R

Burners

FC-209

IFO supply IFO return Atomising steam

Combustion air Ex APH

Fuel gas

VS steam

E-6A/B/C

SO toE-123 P-7/7R

#4 #1

VS steam LO to E-121

#12

P-6/6R

#8 IO draw

Over Flash

LC-04

P-5/5R #4 C-3 #1

#5

VS steam IO to E-7

FC-217

HO Ex P-8/7R as Demister Wash

Turbulising steam

RCO Ex E-11

FC-216

FC-11 PA draw

C-1

To burners

FC-201

LC-03

LO draw

#16

C-105

LC-101 C-2

#19

FC-202 Comb. air

#4 #1

SO draw

HV-01 DPC-03

P-3/3R

GO draw

#26

Burners

IFO supply PC-06 IFO return Atomising steam

GO to E-1A/B/C/D

E-128A/B

#4

P-9/9R

#1

FC-13

HO draw FC-10B Vac slop to E-9

LC-05

#4 C-4 #1

P-12/12R VS steam HO to E-9

VS STEAM Bot Quench Ex H-1A/B FC-12 SR to E-11

SR draw P-10/10R

P-8/7R

Haldia Refinery Vacuum Distillation Unit PFD (Feed preheat and product cooling section ) LO R/D

FC-21

E-127 CW

RCO Ex tanks

To VBU FC-20

B-1

To TK-761

P-1/1R

FC-15

E-1A

E-1C GO Ex P-3/3R

E-1B

CW

E-1D SO Ex P-7/7R

E-2A

GO to top reflux E-2B

FC-19 CW

SO to R/D

TC-06

TW

HO to R/D E-4A

E-122A/B

IO Ex P-12/12R

FC-12

To R/D FC-26

LC-02 SR to R/D FC-28

E-11

H-1A

E-10

Vac slop to PDA

To VBU To PDA

To VBU

Bot quen

H-1B

To VB steam header

SR Ex P-10/10R RCO to P-113/113R suction

FC-27

TW

E-9 TW

IO to VBU

Pump Around To # 18 of C-1

HO Ex P-8/7R

HO Ex P-8/7R Vac slop Ex P-9/9R

E-124A/B TW

E-4B

To HSD

IO to R/D

E-126A/B

E-6C

E-6A

E-7

FC-25

E-125A/B

E-14A/B CW

PA Ex P-6/6R

To Tar

FC-24

E-123 E-6B

FC-22

FC-23A

GO to R/D

E-2C

CW

FC-23

To Tar E-121

LO Ex P-5/5R

To VBU

To TK-761

DM water

Haldia Refinery Vacuum Distillation Unit PFD (Vacuum System)

Cooling Water Inlet Header E-128B

E-128A

PC-121

VM Steam to Ejectors PC-05

#26 #22 31C-1

CW

CW

PEJ

#19

Cooling Water Return Header

SEJ

CW

CW

Vent

E-129 E-130

CW P-101/101R B-3 coaleser

oil

Barometric legs B-2

water

B-7 seal pot

P-102/102R

Hot well

Hot well water to OWS/ Desalter

Hot well gas oil to HSD pool

Tempered water circuit

E-116A/B/C CW

E-125A/B

DM water B-105

IO

E-124A/B/C SR

VB steam

HO E-126A/B

Tempered water P-114A/B/C

Vac Slop

E-10

Auxilliary Systems The VDU has following auxilliary systems 2. The tempered water system 3. Steam generation and SR Cooling 4. Balanced Draft Furnace 5. Battery Limit product lines 6. Pumping systems 7. Vacuum System

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Auxiliary Systems The Tempered Water System :Why?

• • • •

Run down temperature @80 C Product congealing in nature. C/W higher scaling nature above 55 C. Less corrosive due to DM water/ Condensate

Make Up DM . Water

C/W

TW vessel

TW cooler

SR

SR

IO

TW pump

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HN

Auxiliary Systems Steam Generation and SR cooling

• •

Steam generation reboilers from SR stream. SR after Exchanging heat with RCO in 31 E 11 and 31 E 122 A/B enters 31-H- 1A/B where DM water recovers the heat from SR and generates steam at ~5 Kg/ Cm2 g and 151 C.

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Auxiliary Systems Balance Draft Furnace

Main Features: Process circuit: Turbo Steam

PHE Convection zone Radiation Zone Column Flue gas Circuit: Radiation Zone, Convection Zone, APH , ID fan, Stack Combustion Air Circuit: FD fan, SCAPH, APH, Burners Fuel Oil Circuit & Fuel gas circuit Haldia Refinery Igniting Minds... Energizing Lives…

Auxiliary Systems Battery Limit and Product lines

Feed, Products and utilities are routed through the Battery Limit. The product lines are provided with Flow control valves, Level control valves and necessary instrumentations like Temperature Transmitters, Pressure Transmitters, Pressure/ Temperature Gauges etc.

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Auxiliary Systems Vacuum System

Precondensers Primary ejectors Secondary ejectors Seal pot Barometric legs Hot Well (HW) Gas oil recovery system from HW

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Haldia Refinery Vacuum Distillation Unit PFD (Vacuum System)

Cooling Water Inlet Header E-128B

E-128A

PC-121

VM Steam to Ejectors PC-05

#26

SEJ

CW

CW

Cooling Water Return Header

PEJ

#22 31C-1

CW

#19 CW

Vent

E-129 E-130

CW

P-101/101R

B-3 coaleser

oil

water

B-7 seal pot

P-102/102R

Barometric legs B-2

Hot well

Hot well gas oil to HSD pool

Hot well water to OWS/ Desalter