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DAWOOD HERCULES CHEMICALS LIMITEDCANAL WATER SYSTEM PURPOSEPurpose of canal water system is to provide raw water for water treatment plant. Advantage of canal water over tubewell water is that use of this water results in saving of local and imported water conditioning chemicals. This is due to the fact that quality of canal water is better than tubewell water as it has lesser dissolved salts and solids.Water from canal enters in the first pit and then enters two 18 R.C.C. pipes through two gate valves. Then it passes through the 2nd, 3rd and 4th pit and ultimately into the settling tank. Screens are fitted at moga inlet and in the 3rd pit to separate debris and floating material. .All particles heavier than water possess a tendency to settle due to influence of gravity. The specific gravity of suspended particles is one of the main factors governing the rate of settling.The main purpose of settling is to effect clarification of water by permitting settling of suspended matter and consequent reduction in turbidity. Settling is of value chiefly in the removal of course particles which settle rapidly and which can be more economically removed. A secondary result is removal of bacteria. Percentage of bacteria removal generally closely parallels turbidity removal.Residence time (2-4 hours) is provided in the settling tank for the suspended solids to settle down in the bottom and cleaner water (Max. turbidity = 40) is pumped to Raw Water Filters.For very small particles, which has very poor settling rate, alum as coagulant is added at moga. It is thought that precipitation of alum produces finely divided precipitates of hydrous oxide which are positively charged. Neutralization of the positive charges by negative ions such as sulfate and chloride in the water causes coalescence of the fine particles, thus forming gelatinous vapours precipitate of large volume.Al2 (SO4)3 + 3 Ca (HCO3)22 Al (OH)3 + 3CaSO4 + 6 CO2

Al2 (SO4)3 + 3 Na2CO3 + 3H2O2 Al (OH)3 + 3Na2SO4 + 3 CO2

Al2 (SO4)3 + 3 Ca (OH)22 Al (OH)3 + 3CaSO4

1-7% Alum is added in a controlled quantity through P-436 A/B at Moga. Polyelectrolyte is fed to the 3rd pit to enhance the settling rate in addition to alum. Poly electrolytes are high molecular weight water soluble polymers that contain groups capable of undergoing electrolytic dissociation to give a highly charged large molecular weight ion. Poly electrolyte is fed in controlled amount through P - 441. A slurry pump is used intermittently for the removal of slurry from the tank. P-434 A/B/C pumps this water to the filtration unit F-403 B, C, D.EQUIPMENT:I.MP-434 A/B/C (Canal Water Pumps) PUMP SPECIFICATION:Make:K.S.BR.P.M:14509

Flow:1100 G.P.M.Head:266 ft.H.P.:91.37Type:7-stages vertical centrifugalMOTOR SPECIFICATIONS:9

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Make: Voltage: Amps: H.P.: R.P.M.: Cycles/Sec :Make: Voltage: Amps: H.P.: R.P.M.: Cycles/See:II.MP-435 SIEMENS (MP-434 A/B)

380 140 100 147050U.S. Electrical Motors (MP-434 C) 380149 100 1470509

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MOTOR SPECIFICATIONS:9

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Make: Voltage: H.P.: R.P.M.: Cycles/See: Westinghouse, USA 38020 1470509

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Pump is single stage ordinary impeller with long shaft centrifugal type.III.MP-436 A/B (Alum Injection Pumps)MOTOR SPECIFICATIONS:

9

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Make: Voltage: H.P.:R.P.M.: Cycles/See: Time Rating: General Electric Company 240/4601/2172560Continuous9

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PUMP SPECIFICATIONS:Make:Milton Roy Co U.S.A.Type:Controlled Volume Pump. (Single stage Reciprocating Diaphragm type)Capacity:70 G.P.H. or 1.17 GPMPressure:100 #IV.ALUM PREPARATION TANK:Capacity:3300 gallons

Height:108"9

Width:96"Material:Mild steel/rubber lined Tank is fitted with an agitator.V.ALUM FEED TANK:Capacity:600 Approx. gallons

Height:60"Width:54"Material:Mild steel/rubber lined Tank is fitted with an agitator.VI. SETTLING TANK:

Total capacityEffective DepthLength X WidthResidence Time for water Material:2000 g.p.m.:12', Max depth = 17':73' X 40':2 hours:R.C.C.

START UP PROCEDURES:I.ALUM BATCH PREPARATION:Add 100 Kg. of alum for every 10" of water added in the preparation tank.

Start Agitator after water is added up to the required level.Add required quantity of alum.After all the alum is dissolved take sample and check concentration. It should be 1 - 7 percent.II.P-436 A/B (Alum Pump)Open all the valves between pump suction and tank out let. Open discharge valve.

Set pump stroke at minimum.Check that alum solution level in the tank is O.K. Check oil in the pump.Start alum pump.Check that flow actually has established.Increase alum pump stroke as required.III.P-435 (Slurry Pump)Open inlet valve.

Open about 1/2 turn discharge valve.Start pump.Open discharge valve.Check that flow has actually established, Otherwise stop pump and check the cause.9

IV.P-434 A/B/C (Canal Water Pumps)Check that level in the settling tank is about 2" - 3" over the skimmer. Check oil level in the bearings of the motor.Check water for the glands. Add some if required to wet the glands properly. Close discharge valve.Open a little the valve for open drain.Start P-434.Check pressure on PI.Open the drain valve.Remember MINIMUM discharge pressure for the Pumps is 125 #.Let the pump run for sometime until turbidity at pump out let is normal. Get a sample checked from laboratory.Close drain valve and open discharge valve of the pump simultaneously.If the pump is to run after long time or after maintenance, get its amps checked. MAXIMUM Amps = 140.NORMAL OPERATION AND ALUM DOSING INSTRUCTIONS:Proper alum dosing is required for good flocculation and efficient removal/separation of suspended solids from canal water in the settling tank.To avoid carryover of suspended solids with canal water, it is required that water level in settling tank should be ONLY 2" - 4" high over the skimmer edge. Canal water should over flow the weir, located under the skimmer into the suction chamber of P-434 A/B/C.With the increase in the turbidity at inlet/outlet of settling tank, alum dose may be increased. Max. turbidity at the outlet of P-434 = 40. If the turbidity continues to increase even after increase of alum injection, then the canal water flow to Raw Water Filters should be reduced or stopped.Sulphate at inlet of Moga and at outlet of P-434 should be analysed by the laboratory and the difference in sulphate ions should not be more than 10 ppm.Alum dosing rate should be controlled so that sulphates and turbidity limits are not exceeded.SHUT DOWN PROCEDURES:I.P-436 A/B (Alum Pump)"STOP" button is pushed to stop this pump.

Close suction valve.Close discharge valve.Depending upon if both the pumps are to be stopped, close out let valve of feed tank.II.P-434 A/B/C (Canal Water Pumps)9

Close discharge valve of pump in operation. (Keep the discharge valve slightly open). Stop P-434 by push botton.Close completely the discharge valve.Check water level in settling tank whenever a pump is put out of operation and regulated the level by controlling the moga gates etc.6.EMERGENCY PROCEDURES:I.ELECTRIC FAILURE: In case of electric failure all pumps will trip.

Canal water operator should inform U.S.E. immediately. Moga gate should be closed when level in settling tank starts increasing.Operator should close discharge valves of P-434 and P-436 alongwith the inlet and outlet valves of P-435 if this is in operation.II.CHANGE IN SETTLING TANK LEVEL:Sudden change in settling tank level should be investigated immediately. This could be either due to failure of P-434 or due to change in moga level. In both cases inform U.S.E. and act according to the laid down procedures i.e.

In case of P-434 failure, close moga gate and close discharge valve of P-434. Stop alum injection (only when all three pumps fail). I one pump fails, try to start third pump and keep a watch on settling tank level.

If moga level has decreased, inform U.S .E. and increase discharge pressure of P-434.

In case of gradual decrease in settling tank level, check screens and if required clean them.

SAFETY PROCEDURES:Alum, on contact with skin, will cause irritation. If it happens, wash affected area thoroughly with water. Avoid contact of alum solution with eyes. Alum is harmful to eyes. Use chemical splash goggles and gloves while handling alum.9

COOLING WATER SYSTEMPurposeThe cooling Water System provides the Ammonia Unit, Urea Unit, Utility Unit, and Offsite users with a common, continuous, closed loop supply of 90F (maximum) cooling water as heat sink.Process GeneralThe special process coolant pumps, p-4 11 A, B & C, take suction from the cooling tower basin, located below the cooling tower, and pump cooling water to two separate supply headers. One header supplies the Ammonia Plant exclusively. The second header supplies cooling water to the Utility Plant, the Urea Plant, and all offsite users. The design circulating rates are as follows:Ammonia Plant28,000 gpmUrea Plant20,000 gpmUtility Plant & Offsite Users15,000 gpmTOTAL63,000 gpmSpent cooling water is returned to the Cooling Tower, CT-401, via two separate headers. A 30" header returns the Ammonia Plant cooling water to the south end of the cooling tower at a maximum temperature of 120 oF A 36" header returns cooling water from the other users to the north end of the cooling tower at a temperature of about 112oF. Both return headers extend across the entire length at the bottom of the tower, with each header manifold to feed each of the seven cells. Ambient air is drawn in through the sides of the tower by fans located at the top of each cell. This dry air stream continuously removes water vapor from the tower, effecting evaporative cooling of the water passing down through the tower. The moist air is discharged from the top of the tower, and the cooled water falls into the cooling tower basin, where it is redistributed through the cooling water system.The design evaporation and draft losses from the cooling tower amount to approximately 1600 gpm. The total design make-up required is about 2000 gpm.DESCRIPTION OF FACILITIES Cooling Tower, CT-401This unit is a Head Wrightson induced draft, crossflow, Model 67D- 1-6711 cooling tower. The unit has a rated capacity of 75,000 gpm, and a duty of 750 MM BTU/hr with a design wet bulb temperature of 82 oF and a return cooling water temperature of 110 oF. The tower consists of seven cells, each 36 feet long by 48 feet wide. The overall length is 217 feet. The height of the distribution headers above the basin curb is 41`-4".Fans in three of the seven cells have 150 HP motor drive, while the four remaining cells have 175 HP motor drives.Special Process coolant Pumps, P-411 A, B, & CThese three pumps are Machine Fabriek Stork Company Model HGT 100-90/70 horizontal centrifugal pumps. Each is rated for 39,000 gpm at a discharge pressure of 80 psig. The pumps operate at 735 rpm. Materials of construction are carbon steel for casing and impeller, 11-13% chrome steel for shaft sleeve and 11-15% chrome steel for the shaft.9

P-4 11 A & C are each driven by a 21 90HP, 5000 rpm Elliott steam turbine. the inlet steam is at a pressure of 600 psig and a temperature of 710 oF. Exhaust pressure is 60 psig. The water rate at design horse-power is 23.5 lb./hp-hr.P-41 1B is driven by a Siemens 2500 HP, 3000 volt, 3 phase, 50 hertz, totally enclosed fan-cooled induction motor.Process Coolant Chlorinator, CH-401Cooling towers are efficient air washers so that contamination of water with bacteria and algae is unavoidable. The silt and heat and sunlight in cooling tower provide ideal conditions for the growth of micro-organism.Three main groups of organism, which cause fouling, are algae, fungi and bacteria.Chlorine is the most widely employed agent for control of microbiological deposits. Fischer porter chlorinator feeds Cl2.This unit, manufactured by Fischer Porter, consists of a 15 KW electrically heated evaporator, model 71V1008: 15KW, and a 70C4500 series cabinet mounted chlorinator. Chlorinator capacity is 8000 lb/day of gaseous chlorine. The components are constructed from corrosion resistant materials mounted in a polyester impregnated fibreglass cabinet.Liquid chlorine is fed from two (2) 1000-pound storage cylinders to the evaporator, where the liquid is vaporized. Chlorine vapour enters the cooling water system through the chlorine Ejector, EJ-402. The evaporation rate may be manually set in the range of 400 to 8000 lb/day. (See Fischer-Porter Operating Manual in Design Data Section of this manual). Free chlorine of 0.8-1.2 is achieved at the end of chlorination.Inhibitor Chemical Feed Pumps, P-404 A & BThese pumps are Proportioneer Model 1731-30-9817 Simplex Propsuperb. Each pump has a manually adjustable capacity (with pump shut down) of 0 to 100.0 gallons per hour against a maximum discharge pressure of 100 psig. An internal relief valve set at 50 psig is provided with the pump. The pumps are constructed with ductile iron cylinders, Hypalon diaphragms, and type 316 stainless steel check valves. Each pump driver is a 1/2 HP, 220 volt, 1 phase, 50 hertz, T.E.F.C. motor.Inhibitor Process Vessel, TK-409This tank is a vertical cylindrical carbon steel vessel, with a hinged cover and a dished bottom. The tank has a capacity of 1000 gallons (72 inch I.D. x 72 inch straight side x 5/16 inch thick shell). A pump mounting platform, and anti-swirl baffles are provided with the tank. An agitator driven by a 1 HP, 220 volt, 1 phase, 50 hertz, explosion proof motor, is also provided with the tank.Note: This inhibitor is not used these days.Acid Feed Pump P-517 and Day Tank TK-507H2 SO4 is added in mixing trough ME-402 to control pH of the cooling water in the range of 6.4 - 6.8. This helps preventing dissolved salts from precipitating out, at high temperature, by increasing their solubility. Moreover in above mentioned pH range protective layer of Zn- chromate keeps intact. Acid is pumped from day tank TK-507 to ME-402 through acid feed pump P-5179

Cooling Tower Mix Trough, ME-402The mix trough is a rectangular fiber glass box, 20 inches wide, by 12 inches deep, extending along the suction pit of P-41 1 A,B,C, with an open top. The trough has vertical baffles spaced at two feet intervals from the make-up inlet end of the trough. The baffles provide sufficient residence time to mix the chemical solutions with the make-up water added to the trough.Cooling Water Slip Stream Filter, F-403 AA small stream from cooling water supply header is passed through a slip stream filter and then fed to cooling tower basin to maintain the suspended solids with in limit. Maximum inlet turbidity is 20 ppm while maximum turbidity at the outlet is 10 ppm. Construction detail is provided under heading of utility filters (F-403 B, C, D.)Special Cooling Tower Sump Pump, P-418This pump is located in a small sump in the cooling tower pump pit. Its purpose is to prevent large quantities of water from collecting in the pump pit. See flow diagram 40-R-2 1, frame 11 for its location.The pump is a Gould`s model 3171 1 1/4 * 1 1/2-8 vertical centrifugal pump. It has a rated capacity of 40 gpm at a differential head of 35 feet. The driver is a 1 1/2 HP, 1500 rpm, 380 volt, 3 phase, 50 hertz, T.E.F.C. motor.Chromate Feed SystemChromate batch of 22-25 % concentration is prepared in TK-426. 200 kg ZnO and 850 kg Sodium-Chromate is dissolved in water. H2SO4 is added to bring pH 1-1.4.This solution is transferred to day tank TK-410 from where it is feed to ME-402 with pump P-407 to maintain 18-22 ppm chromate in cooling water.Blow Down and Chromate RemovalA small portion of cooling water return is with drawn as blow down (to maintain the dissolved salts concentration, especially chlorides (80-100 ppm), within limit) and passed through electrochemical cells. ME-503 A-EElectrolysis principle is used in cell for producing ferrous ions which react with hexavalent chromium, present in cooling water passing through the cell and converts them into trivalent form. This trivalent chromium is in precipitated form and can be removed by settling.Cooling water enters the cells from bottom and overflows through 32 electrodes into drain line in into the pit from where it is pumped by P-530 A/B to the settling pond. Electro chemical cell is designed such that electric current is supplied to end electrodes only. Current passes through water by conduction. One side of electrodes act as cathode while other side act as anode. Deposition of hydroxyl ions in the form of chromic hydroxide on cathode occurs. A gelatinous film of hydroxide of iron and chromium deposits on cathode which hinders the current flow and decreases the efficiency. For maintaining optimum efficiency, chemical cleaning with 10 % H2SO4 once a day is done.Following reactions occur:At Anode:Fe = Fe +2 + 2 eAt Cathode:2H2O + 2e- = H2 + 2 OHFluid:3 Fe+2 + CrO4 + 4 H2O = 3Fe + Cr+3 + 8 OH9

Material and EquipmentA.Electro Chemical CellCell treating capacity 200 GPM flow of cooling water containing 15-20 ppm chromate. Cell is rubber lined internally and externally, wall thickness of rubber lining = 3/169

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B.ElectrodesM.S. Plates

48 X 11.75 X 3/32 30 Nos. 56 X 11.75 X 3/32 2 Nos. 125 ft2

Material:Size Electrode:Size of End Electrodes: Total area of contact:C.Rectifier9

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D.C. Power supply is adjustableInput Voltage:Three Phase, 380 V, 50 HZ.Input Current:0-25 Amp.Output Current:0 40 Amp.Rectifier Unit contains:On-off switch.Voltage and Amp. Meters.Potentiometer for increasing or decreasing output current.D.Acid TankM.S. Tank rubber lined internally. Dimensions:

Dia:42Height:60 Capacity: 375 Gallons.E.Acid Circulation Pump9

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Material of construction: Discharge Pressure:Capacity:Drive:H.P/Voltage:RPM:F.Piping & ValvesFor Acid Circulation: For C.W. Inlet To Cell:

For Cooling Water Discharge: from Cell: Alloy No.2040 PSIG. 30 GPM. TEFC Motor3/3 80 Volt 3000PVC Pipe and Valve-1-1/2M.S. Pipe rubber lined.Two diaphram valves polypropylene lined-4PVC Pipe and M.S. Globe Valve, Rubber Lined-669

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RAW WATER AND FILTERED WATER SYSTEMSPurposeThe raw water system furnishes water for all uses on the Dawood Hercules Plant site. The filtered water system distributes filtered raw water to the cooling tower, Water Treatment Unit and plant water header.Source of WaterFive wells P-406 A-E and canal water pumps P-434 A,B,C located on plant property are the source of raw water for the entire complex.Process GeneralThe nominal plant demand for water isCooling Water for Makeup:2100 gpmWater Treatment Unit Feed:700 gpmPotable Water Feed:300 gpmPlant Water Users:300 gpmTOTAL:3400 gpm

To meet this demand four of the five Filter Feed Pumps (P-406 A-E) and/or P-434 are used. One pump is a spare. Water pumped from the wells passes through the Utility Filters, F-403 B, C & D, in which suspended solids are removed and the turbidity is reduced to below five NTU.The filter effluent passes to the Filtered Water Process Vessel, TK, 407, which serves as a reservoir of filtered water for the following uses: demineralise unit, fire-water, plant water users and cooling water make-upThe special Utility Pumps, P-410 A & B take suction from TK-407 and pump filtered water through the plant water header to the Hypo chlorinator, the Water Treating Unit, and to the miscellaneous plant water users.DESCRIPTION OF FACILITIESFilter Feed Pumps - P-406 A, B, C, D & EEach is a KSB pump co., Model No. B12D-7 stage vertical centrifugal pump rated for 1200 gpm at discharge pressure of 85 psig at the well top. The pump operates at 1450 revolutions per minute. Pump materials are cast iron and carbon steel with the exception of the shaft and shaft sleeve, which are 13% chromium stainless steel. Each pump has a Newman (U.K.) 100 HP, 1500 rpm, 380 volt, 3 phase, 50 hertz, T.E.F.C. motor. In addition to the motor driver, P-406D has a 125 HP diesel engine driver with gear. P-406 E has 80 HP motor and capacity of 900 gpm. In addition it can be started with electric generator.Filtered Water Process Vessel, TK-407TK-407 is a vertical cylindrical vessel, 59`-0 21/32" diameter by 44`-3 15/32" straight side. It has a cone roof and is designed for atmospheric pressure at 1 50oF. This vessel has a capacity of 900,000 gallons, of which 245,000 gallons is a firewater reservoir. The usable plant water capacity is equivalent to approximately a 3 1/2 hour supply at 3000 gpm.69

Utility Filters, F-403 B, C, D,The Neptune Microfloc filter system consists of three horizontal, multicell, sand filters. Each unit is 96" in diameter and has an overall length of 28`-6". They are designed for a maximum working pressure of 100 psig at 150oF. All filters have a nominal 1500 gpm filtering capacity.Materials for the shell and internal supports are carbon steel. Internal piping is carbon steel and PVC. The purpose of raw water filters F-403 B,C & D is to filter the raw water (coming from P-406 A,B,C,D,E or P-434 A,B,C) to remove the suspended impurities. The filtered water, for the entire Complex, will contain less than 5 ppm of suspended solids.The filter system is explained by the sketch below. Special Utility Pumps, P-410 A & BP-4 10 A&B are Gould`s Model 3405 6*8-1 2G cast iron, horizontal centrifugal pumps, each rated for 1600 gpm at a differential head of 176 feet. The pumps operate at 2900 rpm. P-4 1 0A is driven by a direct connected 150 HP, 380 volt, 3 phase, 50 hertz, T.E.F.C. motor. P-4 1 0B is driven by an Elliott steam turbine, rated for 136 brake horsepower at 2950 rpm with a water rate of 41.6 lb/hphr. Inlet steam pressure is 600 psig. Exhaust steam pressure is 60 psig.69

THE POTABLE WATER SYSTEMPURPOSEThe purpose of potable water system is to provide filtered safe drinking water to the plant, maintenance, administration, housing and other similar areas of the complex. The drinking water is produced from sand filtered raw water by treating this with hypochlorite. The unit sketched below essentially consists of a hypochlorinator CH 401 & potable water process vessel TK-4 14.MATERIALS & EQUIPMENT Hypochlorinator CH-402Manufacturer:Wallace TiernanType:A-429 Automatic water operated.Note:This unit includes a 55 gal polyethylene drum and a hydraulic in-line feed pump.Potable Water Process Vessel TK-41469

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Type:Dimentions: Designe Pressure: Operating Pressure: Capacity:System as a whole.Source of water: Capacity: Horizontal cylindrical dished head carbon steel tank. I.D.= 9` & T.P. length = 21`75 psig 50 psig10,000 gallonsPlant water header at 80 psig. 300 gpm.69

FIRE WATER SYSTEM1.PurposeThe Fire Water System is designed to provide 1500 gpm of filtered raw water at a pressure of 100 psig to any hydrant or monitor. The looped fire water main extends to all areas in the plant, including the housing area. The Administration Building, the Cafeteria, Change House, Security Building, Product Storage Building and the Catalysts and Spare Parts Storage Building are each provided with an internal fire protection system, which is fed from the fire water loop.

2.Firewater SourceFirewater is obtained from the Filtered Water Process Vessel, TK-407, by the Special Fire Loop Pumps, P-501 A&B.

3.Process Generala.All process water oulet nozzles on TK-407 are located about twelve feet from the tank botton. This ensures a minimum twelve feet depth of filtered water or approximately 245,000 gallons; for the firewater reservoir.

The firewater pumps are designed to start automatically when fire water line pressure decreases to 135 psig. When firewater is not used, the pressure in the firewater loop is maintained bay special jockey pump P-528. If a demand for firewater develops, as a result of opening a hydrant or monitor, pressure in the firewater loop decreases. When pressure falls to 135 psig, P-501 A starts. If conditions are such that the pressure falls further to 120 psig P-501 B will start.

DESCRIPTION OF FACILITIES1.Special Fire Loop Pumps, P-501 A&BThese are each a Fairbanks Morse and Co., Model No. KP-98228, horizontal centrifugal pump designed to discharge 1500 gpm at 150 pounds per square inch. They operate at 1750 rpm. The pumps meet National Fire Protection Association requirements.P-501 A&B each have a Cummings Model NHRS-61 F diesel engine driver, designed to start manually or automatically. Once started, they must be manually shut off. Each engine driver has a 550 gallon fuel tank. (Refer to Fairbanks, Morse Operating Manual in the Design Data Section of this Manual).The firewater loop is designed so each hydrant overlaps the coverage of the two adjacent hydrants. Hydrant spacing varies from 200 feet in hazardous areas to three hundred feet maximum. Each hydrant has 150 feet of hose.Monitors, Model CJ-2- 1/2", are provided in the Ammonia and Urea Plants and in the Utility Steam Boiler Plant. The effective range of these monitors at 100 psig nozzle pressure is as follows:a.Straight Stream - 155 feetNarrow Fog - 70 feetWide Fog - 50 feet

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Periodic tests of the firewater pumps are required to check the operability of the automatic starting controls and the pumps. Both pumps should be tested weekly by opening a hydrant and allowing the pumps to start.The Catalyst and Spare Parts Storage Building and the empty bag storage section of the Urea Product Storage Building have wet pipe fused head sprinkler systems. The cooling tower is provided with a dry pilot deluge sprinkler system. The Administration Building, the Change House, the Cafeteria, and the Security Building have interior hose stations with not more than 75 feet of hose per station.69

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WATER TREATMENT SECTIONINTRODUCTIONThe demineralisation section consists of three strong acid cation exchangers, a degassifier; three weak base anion exchangers, three strong base anion exchangers and two mixed bed polishers respectively arranged in series. Two condensate polishers are also included in this section, located at NH3 unit to polish the condensate of 1500 psig steam system.The demineralisation process reduces essentially all of the total dissolved solids to 0.1 ppm or less. Silica is reduced to 0.005 ppm and iron is reduced to zero ppm. This water is supplied to the 1500 psig steam-generating unit in ammonia unit. In case of 600 psig boilers, the treated water is not subjected to the mixed bed polishing operation. This water contains a maximum of 6 ppm dissolved solids and 0.05-ppm silica. The system is illustrated in the sketch on next page.PURPOSE69

The high quality of feed water (almost nil silica content) is required for the high-pressure steam generation because at these high-pressure silica is dissolved in the steam and acts much like a gas. As steam generation pressures increase above 400 psig, the tendency for silica to be selectively carried into the steam increases in amounts proportionate to the amount of silica in the feed water. Silica in the steam deposit in turbines as the steam pressure drops through the turbine and results in a reduction of turbine efficiency which would result in costly shutdowns, also forms glassy scales on heat transfer surfaces and reduces effective heat transfer rate.1.Cation Unitsa.Description and Principles of Operation

The previously filtered water to be treated is supplied from TK-407 through P-410 A, B and passes into a manifold, entering each vessel at the top, passing down flow through the resin beds. The vessels operate flooded so the incoming water displaces the contained water downward through the beds. (451 -UA- 1, UA-2 & UA-3). These vessels have a size of 10' X 8' - 6" side shell and are of carbon steel lined internally with 3/6" rubber sheeting. Each unit contains 400 cubic feet of exchange IRC-124 material, for a bed depth of 4.5 ft. The normal flow of water per unit through the exchangers is 233.3 gallons per minute and the maximum capacity is 700 gallons per minute. As the water flows downward through the beds of the cation exchangers, the metallic cations are taken from the water and retained by the bed exchange material. In doing so, an equivalent amount of hydrogen ions are exchanged to the anion radicals. When regenerated, acid used removes the accumulated metallic cations and restores the hydrogen to the exchanger.Examples:Ca (HCO3)2 + + 2RSO3H Mg (HCO3)2 + 2RSO3H Na HCO3 + RSO3H NaCl + RSO3 HNa2SO4 + 2RSO3H

(RSO3)2 Ca + 2H2CO3(RSO3)2 Mg + 2H2CO3RSO3Na + H2CO3 RSO3 Na + HCl2RSO3Na + H2SO4

RSO3H is strong acid cation exchange resinThe flow rates through the exchangers in normal operation are indicated on the flow indicators installed at the inlet to each of the exchangers and rates will respond to the demand for water as required by level control in the Degassifier tank 452-U via a level controller whose control valve is located at the outlet of the cations. A pressure controller in the raw filtered water inlet line to cations maintains a constant pressure through the exchanger train.2.The DegassifierA degassifier tank and tower are provided for the removal of carbon dioxide. When the raw filtered water is passed thru the hydrogen cation exchangers, the cations are removed and retained by the ion exchange material. The equivalent hydrogen ions given in exchange for the cations unite with the bicarbonate radical to form carbon dioxide and water. Although carbon dioxide can be removed in a strongly basic anion exchanger, (which is the subsequent

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demineralisation step), it is less costly to remove large amounts of carbon dioxide by mechanical means, rather than chemically.The water effluent from the cation exchangers enters the top of the tower and flow by gravity over the Rasching rings to the tank at the bottom. The flow of air from the blower is upward through the tower to help liberate the carbon dioxide from the water.The level controller on the storage tank controls the inlet flow to the degassifier. The signal from this controller, throttles a stainless steel control valve, located approximately 3 feet above grade on the outlet line from the cation exchangers. Water from the degassifier tank is pumped by degassifier booster pumps 452-UJ2 (or UJ2A) into the three primary Anion Exchangers. A pressure controller is provided to maintain a constant pressure on the inlet header. The control valve for this control is installed on a 2-inch line from the booster pump discharge, which releases back into degassifier storage tank.3.Anion UnitsThe purpose of primary anion is to remove chloride and sulphate, from degassifier effluent water. These vessels have a size of 8'-6" X 5'-6" and are of carbon steel, lined internally with 3/16" rubber sheeting. Each unit contains 165 ft3 of A-378 weak base resin upto a depth of 36".

R3NHCl + H2O

Primary Anion R3NHOH + HCl2R3NHOH + H2SO4(R3NH)2 SO4 + 2H2O69

Secondary AnionR4 NOH + H2CO3R4NOH + H2SiO3

R4NHCO3 + H2O

R4NHSiO3 + H2O

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The secondary anions remove silica and bicarbonates from the degassifier effluent water. Silica is removed effectively to 0.05 ppm and dissolved mineral content to 6 ppm. This procedure is generally similar to the regeneration of the cation exchangers, except that caustic is the regeneration medium.This is not quite low enough to meet the specification of 0.005 ppm, required for the 1500 psig generation facilities. However, the purity of the treated water from these exchangers does meet the specification required for the 600 psig generating systems and the quantity required (about 250 gallons per minute) is taken on flow control and sent to the 600 psig generating facility via a resin trap (455-U-2). The balance of the effluent from the secondary anion exchangers passes into the mixed bed make-up polishing unit from which the effluent purity will be within the limits desired for the 1500 psig generating system in the ammonia unit.These vessels have a size of 9'-6' X 5'-6" and are of carbon steel, lined internally with 3/16" rubber sheeting. Each unit contains 188 ft3 of IRA-402 weak base resin upto a depth of 36".69

4.Mixed Bed Make up Polishersa.Description and Principles of OperationThe mixed bed-polishing Unit, as the name implies, is an exchanger in which the strong Cation and Anion resins are combined in a mixed mass. It is employed for final polishing of the make up water charged to 101 F feed water drum for high pressure steam generation for which, as already mentioned, extremely pure water is required. The water passing downward through the bed contacts a long series of strong acid cation and strong base anion resins and results in a more nearly complete deionisation than in a series of Cation and Anion exchanger beds.

There is always some leakage of cations in a cation exchanger and this results in leakage of alkalinity (sodium hydroxide from sodium leakage) from the anion exchangers. In the mixed bed, cation and anion exchange take place almost simultaneously, which results, in effect, in a single irreversible reaction that goes very close to completion to produce water of almost theoretical chemical purity.The mixed bed polishers are two 5' X 7' carbon steel vessels, with stainless steel internals lined with 3/16" rubber sheeting.The exchange material in each of these units consists of 35 cubic feet of A 101 D 3 (strong acid) and 35 cubic feet of C-2 10 (strong base) resin. The normal flow per unit is 200 gpm and 400 gpm maximum. The flow per square foot of bed is 10 gpm (normal) and 20 gpm maximum. The total flow between regeneration is 2,016,000 gallons.Water from the mixed bed polishers is sent to the 157-F demineralized water storage tank on level control of LC-20 via the resin trap 455-U-1.5.Automation and InstrumentationThe instrumentation described below is generalized in presentation. The vendor of the water treatment plant supplies all of the instruments.

A PLC system is provided for operating and regeneration of trains, mix beds and condensate polishers.A programmable logic controller (PLC) is a user-friendly computer that carries out control functions of many types and levels of complexity.A PLC consists of a processor (CPU), power supply, Input/output modules, programmer (usually a PC) and chassis. PLC based control system was originally designed to replace relay logic system and solid state hard wired logic control panels. Their advantages over relay logic system are that they are easily programmed, highly reliable, flexible, relatively inexpensive, secure and able to communicate with other plant computers. Two panels (Panel view 900 in CCR and panel view 550 local) are provided for controlling and monitoring.An automatic silica analyser is mounted at the local control panel. The analyser is capable of detecting as little as 0.005 ppm of silica. The silica content is monitored in treated water to the ammonia plant and discharge line from the anion exchangers.Conductivity meters and a recorder are provided for monitoring conductivity at points downstream of the three primary anion exchangers, three secondary anion exchangers and69

outlets of the two make up mixed bed polishers and the condensate polishers (175-U 1 and 175-U 2) associated with the ammonia plant steam system.Pressure gauges are installed at suitable locations throughout the system. Three resin traps for removing entrained resin particles are furnished. The locations of these traps are at the outlet of the make up mixed bed polishers, outlet of the cation exchanger, anion exchangers and the condensate mixed bed polishers.6.MiscellaneousUtilities are supplied to the Water Treatment section. These consist of 55 psig steam, plant and instrument air and plant and cooling water. The chemicals used for regeneration, i.e. 50% caustic and 98% sulphuric acid and 34% HCL are also made available in the building.

Overflows and drains from regenerant vessels as well as drains from block and bleed valves do not enter the sewer connection but this material is disposed of to a neutralizing pit.7.REGENERATIONa.Cation ExchangersBasically, regeneration involves four separate steps consisting of backwash, introduction of regeneration chemicals, displacement and rinsing. It may be done manually or automatically. It is expected that the flow per unit between regeneration will approximate 336,000 gallons for cation exchangers (This quantity does not include the amount used for regeneration). Although rates and time period are given in the regeneration procedure which follows, they are approximated. The equipment vendors' operating instruction will specify precise rates and time periods for the different functions.

The backwashing is accomplished by diverting the inlet water from the top of the exchanger bed to the bottom of the bed. The backwash water effluent from the top is directed to the neutralization pit ME-504. As the water flows upward through the exchanger, the bed is loosened and expanded to facilitate washing of the exchange resin. If regeneration should prove to be ineffective, it is invariably the result of bed fouling with suspended matter. Proper backwash procedures should be strictly adhered to and are governed by backwash rate, temperature and the density of the ion exchanger. Excessive backwash rate must not be used in order to prevent loss of resin by carryover.When the backwash is completed, the bed will settle back down and regeneration with hydrochloric acid can be started.The dilute acid is introduced directly above the bed of the cation (strong acid) exchanger through the distributor and passes downwards through the bed. Ejector is used for injecting the acid solution. Excess regenerate passes out at the bottom. As the regenerant proceeds downwards through the beds, the cation radicals are removed from the resin and replaced by hydrogen. The waste chemicals are drawn off at the bottom of the exchanger and are directed to the neutralization pit ME-504.The cation units require about 2.75 MT of hydrochloric acid (oBe 5-6.5) for canal water and 3.5 MT for tube well water, but this amount is approximated and will depend on the impurities in the raw water. As already mentioned, the precise rates69

will be specified in the operating instructions issued by the equipment vendor. The injection period, most generally, is over in a 20 to 40 minutes period.Following reactions occur during regeneration.(RSO3)2 Ca + 2HCl (RSO3)2 Mg + 2HCl RSO3 Na + HCl

CaCl2 + 2RSO3H MgCl2 + 2RSO3H NaCl + RSO3H

b.Anion ExchangersThe regeneration of an anion unit is normally done immediately after the completion of the cation unit regeneration in a given train. The need for regeneration is indicated by conductivity meters, which is provided for each anion exchanger outlet, or effluent water analysis. Sample points are also provided in the vicinity of these meters so that samples of the effluent can be analysed for silica, total dissolved solids and pH.The regeneration steps are essentially the same as for the cation exchangers except that caustic is injected instead of HCl. The backwash rate is somewhat less than that of the cation exchanger. First caustic of 5-6.5 oBe is injected, through ejector, to secondary anion and waste effluent is directed to neutralising pit ME-504. After injection to secondary anion is completed, waste outlet of secondary anion is diverted to primary anion caustic inlet and waste outlet of primary anion is sent to neutralising pit ME-504. This step is secondary to primary caustic injection. The anion units require about 13" (8 for secondary anion and 5 for secondary to primary anion) of day tank of 50% caustic soda for canal water and 17" (10 + 7 or 8 + 9 for secondary anion + secondary to primary anion injection) of day tank of 5-6.5o Be for tube well water. Following reactions occur during regeneration.In primary anionR3NHCl + NaOHR3NHOH + Na Cl(R3NH)2SO4 + 2Na OH2 R3NHOH + Na2SO4In secondary anionR4NHSiO3 + NaOHR4NOH + NaHSiO3R4NHCO3 + NaOHR4NOH + Na HCO3As already mentioned, the regeneration is mechanically and sequentially the same as the cation exchanger regeneration and should be done in like manner provided the previously mentioned exception and difference are incorporated. In the anion exchanger regeneration, the caustic soda (NaOH) reacts with the resin to remove the anion radical ions which forms a soluble salt with sodium (Na) and the hydroxide ion (OH) is retained by the resin for the restoration of its exchange power. Completion of the rinse period with degasified water will be indicated by the conductivity meter and by sample analysis.69

REGENERATION SEQUENCE OF A TRAINS.No.Operation & SequenceFlowRateGPMTimeCanalMin.TimeTubewellMin.1.Primary Anion backwash B/W inlet (5) & B/W.outlet (6) valves open all other closed8020902.Cation backwash B/W inlet (7) & B/W outlet(8) valves open all other closed.2909030

Or till water is clear3.Cation Acid injection Acid inlet (11) & Rinseoutlet (12) valves open all other closed.9045604.Cation acid displacement.Valve position same as in step 3.905050

Or till outlet oBe = nil5.Cation RinsingService inlet (1) & rinse outlet (12) Valves openall other closed23045456.Secondary Anion backwashB/W inlet (17) & B/W outlet (18) valves. Openall other closed.11520207.Secondary Anion caustic injection. Causticinlet (19) & rinse outlet (21) valves & BCV-1open all other closed.3640408.Secondary to primary caustic injectionCaustic inlet (19) rinse outlet (21)Caustic inlet (9) & rinse outlet (14)Valves open all other closed.3620209.Secondary to primary caustic displacementvalve position same as in step 8369090

Till oBe at P.anion = nil10.Primary Anion final rinsing Service inlet (3) &2304545

rinse outlet (14) valves open all other closed.Till conductivity < 10micro mhos/cm11.Secondary Anion final rinsing Service inlet (15)2304545

& rinse outlet valve (21 will be openTill conductivity is lessthan 5 micro mhos/cm andSiO2 < 0.05 ppm.

PRECAUTIONS FOR REGENERATION1.During backwash steps check that resin is not going out with water. If resin is going out stop regeneration immediately.69

2.During acid & caustic injection be careful about leakage to trains in service. Analysis of running trains should be performed continuously with 15 minutes interval. A sudden increase of conductivity for anion and disturbance of FMA for cation are indications of leakages. In such case isolate the affected train for rinsing.During caustic or acid injection, oBe of chemical being injected should be kept constant. Also check oBe at outlet.While handling chemicals safety rules should be observed i.e. goggles, gloves, helmet, rubber/safety boots & face shield is necessary.During rinsing steps check for resin going out. If resin comes out during rinsing, it might be due to a broken outlet distributor of vessel.Before taking a stand-by train in service, rinse it and analyse it.

c.Mixed Bed Make up PolishersIn order to regenerate the mixed bed unit, the cation and anion resins must be separated into individual beds by hydraulic classification. This is possible because the density of the anion resin is slightly less than the cation resin.A suggested stepwise procedure for the regeneration of a mixed bed unit is listed below. It is possible to do this manually or automatically. This procedure is not intended to supersede the regeneration procedure recommended by the equipment vendors, which must remain the final authority.The resin is back washed, which classifies the cation and anion resins to form two separate Beds. Excessive back wash rates can result in resin carry over to the waste stream sewer so care should be taken to avoid such an occurrence. Upon completion of the backwash period, the resins are allowed to settle and they form two separate beds with the anion resin on top. Looking into the lower sight glass at the cation/anion interface can make confirmation of the effectiveness of the hydraulic classification.Caustic of 5-6.5 oBe is injected on top of the anion resin bed. Ejectors are used to feed caustic solution from caustic day tank. 4" of the day tank is injected for canal water and 27" for tubewell water.CYCLE OF OPERATION CHARTS.No.OperationFlowRateGPMTimeMin.1.Back wash B/W inlet (24) & B/W outlet (25) valves open allother closed.60452.Caustic injection (oBe = 5 6.5) caustic inlet (26) rinse outlet(27) valves open all other closed.1730

4 of day tank

3.Caustic displacement valve position same as for step 2.17504.Acid injection (H2SO4) (oBe = 5 - 6.5) acid inlet (29) & rinseoutlet (27) valves open all other closed.1730

3 of day tank

5.Acid displacement, valve position same as for step 4

6.First Rinse Service inlet (22) & rinse outlet (27) valves openall other closed.200157.Blow down Rinse outlet (27) open and all other closed and-1069

air valve 31 open.

8.Air Mix Valve (32) & (44) open all other closed100 C.F.M.109.Final Rinsing20060

Tillconductivity