Filtration

TRAINING ON FILTRATION

FOR DARSAYT STP OPERATORS PREPARED BY:

DAUD DOMINADOR VELASCO INSTRUMENT SUPERVISOR OWSC

AUGUST 2008

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CONTENT

Filtration… … … … … … … … … … … … … … … … … … … . 1 Fitration Diagram… … … … … … … … … … … … … … … … .1 Methods… … … … … … … … … … … … … … … … … … … … 2 Flowing… … … … … … … … … … … … … … … … … … … … .2 Gravity Filtration… … … … … … … … … … … … … … … … ..2 Procedure for Gravity Filtration… … … … … … … … … … ...3 Filter Media… … … … … … … … … … … … … … … … … … ..4 Backwashing… … … … … … … … … … … … … … … … … … 4 Gravity Filter… … … … … … … … … … … … … … … … … … 5 Darsayt Filtration system… … … … … … … … … … … … … .6 Darsayt Filter Backwashing Procedures… … … … … … … ..7-11 Darsayt TE system P&ID… … … … … … … … … … … … … .12

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PREFACE

This training document is written to establish operation training module to be use from time to time it is needed. In 2007, after rehabilitation of the filter, training was conducted for several times and it was successfully satisfied the operation specifically filtration. More than one year the system operated at the highest reliability and availability. Other reason why this training needs was establish is to prevent failure of operation which was happened in 2006, Darsayt filter was blown and severe damage occur resulting to costly rehabilitation and cost more than 200,000.000 OR. This module begins by defining filtration, methods, procedures including the start up procedure. My sincere hope is that this document will not only stimulate interest in the field of operation but will also help technician with respect to troubleshooting. My special thanks go to Mr. Faiz Al Maskiry, Mr. James Hestad and Mr. Salem Al Hajery for supporting me to materialize this training requirements.

Daud Velasco

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FILTRATION Filtration is a mechanical or physical operation which is used for the separation of solids from fluids (liquids or gases) by interposing a medium to fluid flow through which the fluid can pass, but the solids (or at least part of the solids) in the fluid are retained. It has to be emphasized that the separation is NOT complete, and it will depend on the pore size and the thickness of the medium as well as the mechanisms that occur during filtration. •

Filtration is used for the purification of fluids: for instance separating dust from the atmosphere to clean ambient air.

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Filtration, as a physical operation is very important in chemistry for the separation of materials of different chemical composition in solution (or solids which can be dissolved) by first using a reagent to precipitate one of the materials and then use a filter to separate the solid from the other material(s).

Filtration diagram

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Methods There are many different methods of filtration; all aim to attain the separation of substances. This is achieved by some form of interaction between the substance or objects to be removed and the filter. In addition the substance that is to pass through the filter must be a fluid, i.e. a liquid or gas. The simplest method of filtration is to pass a solution of a solid and fluid through a porous interface so that the solid is trapped, while the fluid passes through. This principle relies upon the size difference between the particles making up the fluid, and the particles making up the solid.

Flowing Liquids usually flow through the filter by gravity. This is the simplest method, and can be seen in Darsayt Filtration system, this is usually the most economical method.

Gravity Filtration Gravity filtration is the method of choice to remove solid impurities from an organic liquid. The "impurity" can be a drying agent or an undesired side product or leftover reactant. Gravity filtration can be used to collect solid product, although generally vacuum filtration is used for this purpose because it is faster.

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Procedure for standard gravity filtration 1) Select and fold the filter paper Select the size of filter paper that, when folded, will be a few millimeters below the rim of your glass funnel. Fold the paper into a cone by first folding it in half, and then in half again, as shown.

2) Filter the solution Support the glass funnel in a ring or place it in the neck of an Erlenmeyer flask. Wet the filter paper with a few milliliters of the solvent to be used in the following procedure. Wetting the paper holds it in place against the glass funnel. Pour the mixture to be filtered through the funnel, in portions if necessary.

Note: fluted filter paper is often better for gravity filtration with organic solvents 3

Filter media The type of filter media is a bed of granular material which retains the solid particles as it passes. This type allows the solid particles, i.e. the residue, to be collected intact, this is less prone to clogging due to the greater surface area where the particles can be trapped. Also, when the solid particles are very fine, it is often cheaper and easier to discard the contaminated granules. Filter media can be cleaned by backwashing. Backwash is the backwards flow of air or water..

In water treatment (backwashing) In terms of water treatment, backwash refers to the reversal pumping of water, and sometimes intermittent with compressed air, through the process. Filters get dirty and must be maintained. Filters can be rapid sand filters, pressure filters, granulated activated carbon (GAC) filters (Brita is GAC), combination of gravel, sand & anthracite, etc. To keep them functional, they have to be washed periodically. The process, called "backwashing," involves several steps. First, the filter is taken off line and the water is drained down to the filter bed. Then, the air wash cycle is started which pushes air up through the filter material causing the filter bed to appear to boil. This breaks up the compacted filter bed and forces the accumulated particles into suspension. After the air wash cycle stops, the backwash cycle starts with water flowing up through the filter bed. Clean water is passed through the filter bed in order to wash the material and remove most of the accumulated particles. This cycle continues a fixed time or until the turbidity of backwash water is below a set value. In some cases, the additional step of air/water wash (simultaneously) is done after air wash cycle and followed by rinse water wash. These use less water compare to traditional step and have higher removal efficiency which result the cleaner filter. Backwashing is a form of preventive maintenance to prevent further clogging of the filter medium. Backwashing in water treatment plants is an automated process, usually run by programmable logic controllers (PLCs). The backwash cycle is usually triggered when the differential pressure over the filter exceeds a set value. 4

GRAVITY FILTER

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DARSAYT FILTER BACKWASH PROCEDURES-OWSC Manual Operation 1. The backwash sequence can be operated entirely on ‘MANUAL’operation when the switch for respective filter in ‘Manual’ 2. All the valves are provided with OPEN and CLOSE Push Buttons on front of CP91. The respective valve can be opened and closed with this. 3. The limit switches for each valve are wired to CP91. Hence the status of valve position i.e. OPEN or CLOSE is indicated by lamps on front of CP91 4. The following can be operated in MANUAL Mode from CP91 A) Inlet penstock valve B) Filter Inlet Slide Gate Valve C) Filter outlet Butterfly Valve D) Air Inlet Saunders Valve E) Air Vent Valve 5. The following can be operated in MANUAL mode from Respective Electrical control Panel A) Backwash Pump B) Air Blower Auto Operation A) When the AUTO-MANUAL Switch for respective filters is in ‘AUTO’the respective filter the following conditions will apply. In AUTO position of selector switch, PLC will select the Filter backwashing in either 2 conditions - If contact from Differential Pressure Transmitter is closed on High Differential Pressure - If the filter has not been backwashed with in pre-programmed time. This time is User Settable. a) When differential pressure across any bed goes Higher than set point, that filter will commence backwash. (HIGH DP condition) b) The backwash is on PRIORITY START i. e. the first bed on HIGH differential will commence first. c) After the backwash, that filter will resume AUTO operation, if differential pressure is normal. D) If filter ‘A’is already is already backwash and another filter say ‘B’goes on HIGH DIFFERENTIAL, Then ‘B’will commence backwash only after ‘A’backwashed is completed, provided HIGH DP is still ON for ‘B’ One OVERRIDE pushbutton is provided for each filter. On pressing this button, that filter will go to backwash irrespective of position of Auto-Manual switch. (If no other filter is in Backwash)

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B) In case of normal differential pressure across any filter bed, the following will be the status; a) Inlet penstock valve ; OPEN b) Filter Inlet Slide Gate Valve ; CLOSE c) Filter Outlet Butterfly valve ; On Level Control (Level 0 to 100%, Valve opening from 0 to 100%) d) Air inlet Saunders valve ; CLOSE e) Air Vent valve ; OPEN All limit switches are directly wired to relays on 24vdc circuit. All the Solenoid is 230VAC circuit

NOTE: In case of Air pressure failure, The PLC will stop backwash after preset time. On restoration of Air pressure back to normal, the sequence will back to normal, the sequence will commence from the beginning. In case of power failure, the PLC will stop. On restoration of power, PLC will perform logic based on its program and conditions at that time. BACKWASH SYSTEM AUTO OPERATION Backwash set point table; Filter bed # Set point Filter bed 1 0.5 Filter bed 2 0.5 Filter bed 3 0.8 Filter bed 4 0.9 Filter bed 5 1.0 Closed inlet penstock valve After 30 seconds = closed outlet valve, then Air release valve will close After 10 seconds = open backwash air inlet valve After 30 seconds = start air blower After 180 seconds = stop air blower After 10 seconds = close air inlet valve, then Air release valve will open After 30seconds = open backwash inlet valve After 10 seconds = start backwash pump After 180 seconds = stop backwash pump After 10 seconds = close backwash inlet valve After 30 seconds = open filter outlet valve After 100 seconds = open inlet penstock valve (on set point level control) BACWASH FINISH 8

FILTER BED TIMER SETTINGS-DARSAYT-OWSC

CLOSE FEEDBACK TIME FOR FIP OPEN FEEDBACK TIME FOR FOV CLOSE FOV AFTER CLOSE FEEDBACK TIME FOR FOV START AIR BLOWER AFTER STOP AIR BLOWER AFTER START BACKWASH PUMP AFTER STOP BACKWASH PUMP AFTER OPEN FILTER OUTLET VALVE OPEN FIP AFTER REPEAT BACKWASH AFTER

20 30 5 30 30 180 30 180 10 100 480

seconds seconds seconds seconds seconds seconds seconds seconds seconds seconds seconds

(T1) (T2) (T3) (T4) (T5) (T6) (T7) (T8) (T10) (T11) (T12)

Prepared by ; D. S. VELASCO Instrument Supervisor

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Darsayt Filter Checklist/SOP 1. TE tank normal level 2. Balancing Tank Level not high level 3. Backwash pump –Open path position (Discharge and suction valves open). Common discharge valve limited to 40 to 50% opening to reduce excessive flow of backwash pump. 4. Air Blower outlet valve –open 5. Instrument(compressor) air Supply –not less than 5bar 6. All Pneumatic valves/actuator individual instrument air supply isolating valves –Open 7. Air Blowers Circuit breaker (Power Supply) –ON 8. Backwash pumps Circuit breaker(power supply) –ON 9. Power Supply for PLC –ON 10. Before Performing backwashing, Valves are in normal position Penstock valve –open Outlet valve –Open Air Release valve –Open Air Blower valve –Close Backwash valve –Close 11. Perform backwashing (Manual/Forced Auto/Auto) In Manual; Air Blower control selector –Manual Backwash Pump control selector –Manual Filter # 1,2,3,4,&5 control selector –Manual (Perform backwashing base on manual procedures) In Forced Auto Backwash; Air Blower control selector –Auto Backwash Pump control selector –Auto Filter # 1,2,3,4,&5 Control selector –Manual (Push Forced Auto Backwashing Button of any filter you want to backwash) In Auto Backwashing; Air Blower control selector –Auto Backwash Pump control Selector –Auto Filter # 1,2,3,4&5 control selector –Auto (it’s an option to select what filter You want to put in auto mode) 12. After backwashing, Valves are in normal position Penstock valve –Open Outlet Valve –Open Air release valve –Open Air Blower –Close Backwash valve –Close (Make Sure valves are in normal position before leaving the area) BY: Daud 10

Darsayt Filter Backwash Procedures; Manual Mode 1. Close inlet penstock valve. 2. Close the Filter outlet valve. Confirm if it is closed, then 3. Close Air release valve 4. Open Air Blower valve (Air inlet valve), then 5. Start Air Blower. After 3 minutes 6. Stop Air Blower, then 7. Close Air Blower valve(Air inlet valve), then 8. Open Air release valve 9. Open Backwash inlet valve, then 10. Start Backwash pump(one pump only). Water level rising until it reached overflow, it means backwashing confirmed. After 3 minutes 11. Stop backwash pump 12. Close Backwash inlet valve. Confirmed if backwash inlet valve closed, then 13. Open Filter Outlet valve. Confirm if really open, Water level falling down. After 100seconds 14. Open inlet Penstock valve. Backwash finished..

Prepared by; Mr. D. S. Velasco Instrument Supervisor

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