Deminerlise Plant

7/27/2019 Deminerlise Plant

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DEMINERALISATION PLANT

DM PLANT


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WATER TREATMENT

Introduction:- The natural water containssolid, liquid and gaseous impurities andtherefore, this water cannot be used for

the generation of steam in the boilers. Impurities in water:-

1. Undissolved and suspended solid2. Dissolved salt and minerals3. Dissolved gases4. Others materials oil and acids


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Undissolved and suspended solid Turbidity and Sediment:- Turbidity in the water is suspended insoluble matter including

coarse particle (mud, sediment, sand etc.) that settle rapidly on standing. Amount rangefrom almost zero in most ground water and 60000 ppm in muddy and turbulent river water.The turbidity of feed water should not exceed 5 ppm. These materials can be removed by

settling, coagulation and filtration. their presence is undesirable because heating orevaporation produces hard stony scale deposits in the heating surface & clog fluid system.A standard amount measurement of hardness is taken as being the amount of CalciumCarbonate(CaCO3) in the water and is referred to in part per million (ppm).

Sodium and Potassium salts:- These are extremely soluble in water and do not depositunless highly concentrated. Their presence is troublesome as they are alkaline in natureand accelerate the corrosion.

Chlorides:- Majority of the chlorides cause increased corrosive action of water.

Iron:- most common soluble iron in water is ferrous bicarbonate. The water containingferrous bicarbonate deposits becomes yellowish and reddish sediment of ferric hydroxideif exposed to air. Majority of ground water contains less than 5 ppm but even 0.3 ppm cancreate trouble in the feed water system by soft scale formation and accelerating thecorrosion.

Manganese:- It also occurs in similar form as Iron and it is also equally troublesome.

Silica:- Most natural water contains silica ranging from 1 to 100 ppm. Its presence is highlyobjectionable as it forms very hard scale in boilers and forms insoluble deposits on turbine

blades. In modern high pressure boilers its presence is reduced as low as 10 -15 ppb. Microbiological growth:- Various growth occurs in surface water. The micro- organism

include diatoms, molds, bacterial slimes, algae, manganese & sulphate reducing bacteriaand many others. These can cause coating on heat exchanger and clog the flow passageand reduce the heat transfer rates.

Colour:- Surface water form swampy areas become highly colored due to decayingvegetation. Color of feed water is objectionable as it causes foaming in boilers and mayinterfere with treatment processes. It is generally removed by chlorination or adsorption by

activated carbon.


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Dissolved salt and minerals Calcium and Magnesium Salts:- The calcium and Magnesium salts in the

water in the form of carbonates, bicarbonates, and sulphates and chlorides.The presence of these salts is recognized by the hardness of the water. The

hardness of the water is classified as temporary and permanent hardness.The temporary hardness is caused by the bicarbonates of Calcium andMagnesium and can be removed by boiling. The boiling converts the solublebicarbonates into less soluble carbonates which can be removed by simpleblow down method. The permanent hardness of the water is caused by thepresence of chlorides, sulphtes and nitrates of calcium and magnesium andthey can not be removed just by boiling because they form a hard scale on

heating surfaces. Others:-Any salt which dissolved in water solids into positively charged

Cations and negatively charged Anion and since these permits to conductelectricity, these salts are called electrolytes. Some of the most commonCations are Ca, Mg, Na and Fe and rarely ammonium manganese. ThisCations are associated with Anions like Bicarbonates, carbonates,Hydroxides ( the sum of which is termed as alkalinity), sulphates and

Chlorides. Presence of nitrates and phosphates is normally not verycommon. In the water treatment field, the preferred method of expression ofthese dissolved impurities is in terms of Equivalent Calcium carbonate,abbreviated to as CaCO3. This is because CaCO3 is a good commondenominator as it has a molecular weight of 100, which facilitatescalculation, temperature and pressures.


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Dissolved gases

Oxygen :- It is present in surface water in dissolved formwith variable percentage depending upon the watertemperature and other solid contents in water. Itspresence is highly objectionable as it is corrosive to iron,Zinc, brass and other metals. It causes corrosion and

pitting of water lines, boiler exchanger. Its effect isfurther accelerated at high temperatures.

Carbon dioxide:- The river water contains 50 ppm andwell contain 2 to 50 ppm of CO2. it also causes thecorrosion of stream, water and condensate lines. It also

helps to accelerate the corrosion action of oxygen. Theother gases are H2 S, CH4 ,N2 and many others but theirpercentages are negligible, therefore, their effects arenot discussed here.


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Others materials oil and acids

Free mineral acid:- Usually present as sulfuric

or hydrochloric acid and causes corrosion. The

presence is reduced by neutralization with

alkalies. Oil :- Generally, the lubricating oil is carried with

steam into the condenser and through the feed

system to the boiler. It causes sludge, scale and

foaming in boilers. It is generally removed bystrainers and baffle separators.


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Terminology Total alkalinity or M- Alkalinity:- Alkalinity to methyl Orange indicator

P Alkalinity:-Alkalinity to phenolphthalein indicator

EMA:- The equivalent Mineral acidity a measure of the natural salt

( Chloride+sulphate+Nitrate) content of raw water. The test for FMA gives a check on the operating action of SAC unit.

Rinsing should be stopped when the FMA is 10% to 15% higherthan EMA.

Whenever Sulfuric acid is used as regenerant, effluent contains thesulphates of Ca, Mg & Na. calcium sulphate has a low solubility and

precipitation may occur in the resin bed. The capacity is proportional to the Total Cation content of the raw

water. TC= M alkalinity+EMA or( ALK+ Cl,SO4 & No3)

1 ppm of NaOH in the SBA outlet water results in conductivity of6 mS/cm and a Ph of more than 8.3. The P alkalinity figure will givethe sodium slip.

Silica being a weak acid in less easily removed than mineral acids. TA= EMA+M ALK+free Co2 or EMA+Silica+6 ppm CO2 .

If the cation exchange resin exhaust first, the treated waterconductivity will rise. At exhaustion of the Cation resin the treatedwater Ph will increase. If the anion resin exhaust s first , the treatedwater Ph will decrease.


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ACTIVATED CARBON FILTER It is mild steel vessel painted with epoxy based paint. Bell mouth

type single arm distributor is provided for inlet. Bottom collectingsystem is of header lateral type. Header is of mild steel and screwedwith PVC laterals. Small holes are drilled throughout the lateral.Bottom dish end filled with concrete. Different layers of under bedmaterial charged to prevent carbon leak. Each layer consist ofdifferent sizes of pebbles with bigger size at the bottom most andfine silex on top.

1 to 1 pebbles 100 mm

to 1/4 pebbles 100 mm

3/8 to 1/8 pebbles 100 mm

to 1/10 crushed gravel 100 mm

Activated carbon 1250 mm

Regeneration is done two stages Backwash Flow rate 62 m/hr.

Rinse Flow rate 90 m/hr.


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DM STRONG ACID CATION This is mild steel vessel lined internally with rubber. A calibrated

orifice board in the drain sump is also provided for controllingvarious regeneration flows. The middle and bottom collecting systemare of header lateral type. The header is of mild steel rubber linedand rubber covered to which PVC lateral are fitted. Strainers whichprevent resin from escaping are screwed to the bottom of thelaterals. Mark V strainers have been used for bottom collectingsystem whereas mark 801 strainers for middle collector. Bottomdished portion is filled with concrete. The vessel is charged with

strongly cationic resin (INDION 225). Indion 225 is in a bead formand is a cross linked polymer )Polystyrene Divinyl Benzene). Whenthe quality of outlet water from SAC with respect to Sodium ions isdeteriorated, then the unit should be regenerated.

Backwash:- Backwash operation is carried out to loosen bed and toremove the suspended impurities from the resin. Backwash

operation is carried out once in 7 regeneration or when pressuredrop across the unit increases beyond acceptable limits of 0.5kg/cm whichever occurs earlier. When backwash is given, doublequantity of acid is to be injected to ensure bottom layer of resin ishighly regenerated. Flow- 55M/Hr)


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DM STRONG ACID CATIONSub surface Wash:- The sub surface wash is carried out for each

regeneration. Flow- 55M/Hr and for 5 minutes)Acid Pre Injection:-This stage is carried out to set the power water

flow and down flow to the required conditions before injecting acid.

Injection rate 27.2 m/hr and down flow is 32.7 m/hr for 5 minutes.

Acid Injection/ Buffer Down flow:-HCL acid of 5% concentration is

injected at total flow of 32.7m/hr into SAC, by means of Ejector. The

acid is injected thorough SAC bottom collecting system and effluent is

taken out through middle collector to drain sump. During injection to

prevent fluidization of SAC bed, a down flow of 32.7 M/hr water is

maintained.

Up rinse/Displacement:- The excess acid in SAC unit after acid

injection is taken out by allowing the water to flow at 27.2 m/hr for 30minutes. with down flow of 32.7 m/hr.

Final Rinse:- This operation is carried out to remove excess acid and

librated cations from SAC unit. The operation is carried out for 5

minutes.


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DM SAC REGENERATIONStep Flow rate Inject flow Time

DM ACF m/hr m/hr Min.

Backwash 55 10

Rinse 90 2

DM SAC

Backwash (optional) 55 10

M/C flush 55 5

Acid pre injection 32.7 27.2 2

Acid Injection 32.7 32.7 20

Acid Displacement 1 32.7 27.2 30

Acid Displacement 2 54.4 54.4 22

Rinse 90 10


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DEGASSIFIER

Degassifier operation is

carried out to eliminate

free carbon dioxide in

decationised water by

giving a forced draft of airby means of fan blowers

at 55 mm WC. CO2 free

water is then collected in

degassed water tank andpumped to anion units.

Dia /

Height

1.4*3.5

Media Pall ring of

50mm*500mm

(HDPE)

Quantity 3 m


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WEAK BASE ANION This is mild steel vessel lined internally with rubber. A

calibrated orifice board in the drain sump is alsoprovided for controlling various regeneration flows. Thewater is distributed from the top inlet strainer assemblywith SS mesh fixed on it to prevent resin carry overduring backwash stage. Alkali distributor is provided with

three arms with inverted bends with PVC spacers andblank flange for proper distribution of regenerant duringregeneration. Bottom collecting system of WBA is ofheader and lateral type. It consists of mild steel rubberlined and rubber covered header into which PVC lateralswith mark 79 strainers are fitted. The vessel is charged

with Anion resin ( INDION 850).The regeneration of unitis done in thoroughfare with SBA. The outlet water isfree of Free Mineral Acidity with only silica and negligiblequantity of chloride present in it.


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STRONG BASE ANION This is mild steel vessel lined internally with rubber. A calibrated

orifice board in the drain sump is also provided for controllingvarious regeneration flows. The water is distributed from the top inletstrainer assembly with SS mesh fixed on it to prevent resin carryover during backwash stage. Regeneration inlet nozzle is providedmild steel rubber lined/ rubber cover bend with blank flange andspacer at the end to distribute the regenerant evenly on the resinbed. Bottom collecting system of SBA is of header and lateral type.

It consists of mild steel rubber lined and rubber covered header intowhich PVC laterals with mark V strainers are fitted. The vessel ischarged with strongly base Anion resin ( INDION FFIP) when thedesired output from the pair of WBA & SBA is obtained or when thequality of treated water from SBA outlet with respect to silica isdeteriorated then the unit should be regenerated in through farewith SBA using NaOH as regenerant


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STRONG BASE ANION SBA Backwash:- Flow 11.4 m/hr for 15 minutes

WBA Backwash:- Flow 11.4 m/hr for 10 minutes

Alkali Pre Injection:- This operation is carried out to set the powerwater flow rate before injecting alkali. Flow rate is 18.7 m/hr in WBAand 9.3 m/hr in SBA unit for 2 minutes.

Alkali Injection:- 4% caustic solution at flow rate of 11.2 m/hr isinjected in SBA unit for 30 minutes by means of primary andsecondary ejector.

Alkali Displacement :- The unused alkali in SBA unit after causticinjection is transferred to WBA with help of ejector (Through fare).Flow rate is 30m/hr for 30 minutes.

Rinse :- This operation is carried out to remove excess caustic andlibrated anions from both SBA & WBA units. The operation is carriedout simultaneously but independently. WBA unit is rinsed at 44 m/hrfor 40 minutes while SBA at 27 m/hr for 54 minutes.


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WBA SBA REGENERATION

Operation WBA SBA Time

SBA Backwash 11.4 5

WBA Backwash 17.1 5

Caustic pre injection 18.7 9.3 2

Caustic injection 22.5 11.2 20

Caustic Displacement 18.7 9.3 18WBA Rinse 44 40

SBA Rinse 27 54


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CONDENSATE TREATMENT Urea and Ammonia process condensate is collected in a

buffer tank and then passed through activated carbonfilter and strong acid cation unit. The treated condensateis passed through the Degassifier tower and collected inDM water storage tank which is further polished withmixed bed units along with the turbine condensate andDM water. The condensate from turbine which is

normally clean is filtered by micron cartridge andpolished with mixed bed units.

TC:- Micro cartridge filter 3 No's

Capacity 120m/hr

This condensate may be lined up in DM /PW tank onquality.

APC/UPC :- CPU A/B Capacity 125m/hr

Mixed bed:- MB A/B/C/D Capacity 170 m/hr


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DM 2 FEED WATER ANALYSIS

Parameter APC UPC SC TCTurbidity 1 NTU 1 Nil Nil

NH3 40 ppm 20 4 4

Methanol 80 ppm Nil Nil Nil

Urea Nil 20 Nil Nil

CO2 40 ppm 20 Nil Nil

Oil/Grease Nil Nil Nil Nil

Fe 1 ppm Nil Nil Nil

Flow 114 m/Hr 98.4 60 260

Temp. 41C 45 52 52


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DM 2 Outlet Quality

Parameter Unit CPU MB

Oil Nil Nil

Turbidity NTU 1 Nil

Fe ppm 0.02 0.01

Conductivity 5 0.2

SiO2 ppm NA 0.02

NH3 ppm NA Nil


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CPU ACF It is mild steel vessel painted with epoxy based paint. Bell mouth

type single arm distributor is provided for inlet. Bottom collectingsystem is of header lateral type. Header is of mild steel paintedexternally and internally with epoxy and screwed with PVC laterals.Small holes are drilled throughout the lateral. Bottom dish end filledwith concrete. Different layers of under bed material charged toprevent carbon leak. Each layer consist of different sizes of pebbleswith bigger size at the bottom most and fine silex on top.

1 to 1 pebbles 100 mm to 1/4 pebbles 100 mm

3/8 to 1/8 pebbles 100 mm

to 1/10 crushed gravel 100 mm

Activated carbon 1250 mm

Regeneration is done two stages

Backwash Flow rate 72 m/hr.

Rinse Flow rate 72 m/hr.


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CPU SAC This is mild steel vessel lined internally with rubber. A calibrated

orifice board in the drain sump is also provided for controllingvarious regeneration flows. The middle and bottom collecting systemare of header lateral type. The header is of mild steel rubber linedand rubber covered to which PVC lateral are fitted. Strainers whichprevent resin from escaping are screwed to the bottom of thelaterals. Mark V strainers have been used for bottom collectingsystem whereas mark 801 strainers for middle collector. Bottomdished portion is filled with concrete. The vessel is charged with

strongly cationic resin (INDION 225). Indion 225 is in a bead formand is a cross linked polymer )Polystyrene Divinyl Benzene). Whenthe quality of outlet water from SAC with respect to Sodium ions isdeteriorated, then the unit should be regenerated.

Backwash:- Backwash operation is carried out to loosen bed and toremove the suspended impurities from the resin. Backwashoperation is carried out once in 7 regeneration or when pressuredrop across the unit increases beyond acceptable limits of 0.5kg/cm whichever occurs earlier. When backwash is given, doublequantity of acid is to be injected to ensure bottom layer of resin ishighly regenerated. Flow- 55M/Hr)


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CPU SAC Sub surface Wash:- The sub surface wash is carried out for each

regeneration. Flow- 55M/Hr and for 5 minutes) Acid Pre Injection:-This stage is carried out to set the power water

flow and down flow to the required conditions before injecting acid.Injection rate 30 m/hr and down flow is 32.7 m/hr for 2 minutes.

Acid Injection/ Buffer Down flow:-HCL acid of 5% concentration isinjected at total flow of 17.4m/hr into SAC, by means of Ejector. The

acid is injected thorough SAC bottom collecting system and effluentis taken out through middle collector to drain sump. During injectionto prevent fluidization of SAC bed, a down flow of 17.4 M/hr water ismaintained.(20 minutes)

Up rinse/Displacement:- The excess acid in SAC unit after acidinjection is taken out by allowing the water to flow at 14.5m/hr for 30

minutes. with down flow of 17.4 m/hr. Final Rinse:- This operation is carried out to remove excess acidand librated cations from SAC unit. The operation is carried out for 5minutes.


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DM 1 CPU SAC REGENERATION

Operation Flow Inject flow Time

Backwash 34 10

M/C flush 34 5

Acid Pre injection 17.4 14.5 2

Acid injection 17.4 17.4 20

Acid Displacement 1 17.4 14.5 30Acid Displacement 2 29 29 22

Rinse 136 5


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DM 2 CPU SAC 1/2Step Flow injection Time

Backwash 56 m/hr NA 10 minute

Middle collector

flushing

56 NA 2

Settle Bed NA NA 2

Power water 31.8m/hr 26.5m/hr 2

Acid injection 31.8m/hr 26.5m/hr 20

Acid Rinse 31.8m/hr 26.5m/hr 25

Settle bed NA NA 2

Fast Rinse 165m/hr NA 20

Pre req isites to start CPU SAC


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Pre-requisites to start CPU SAC

regeneration

Select ACF 1/2 in auto service from key board

PCP 1/2 any one selected in auto

PDG 1/2 any one selected in auto

VA 2 of SAC is closed

MHL-1A/B is full

MHL-1A/B tank is selected

Select regeneration operation in auto mode

Select SAC program from the CRT keyboard Select SAC-1or 2 in regeneration mode from

CRT key board


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MICRO CARTIDGE FILTER

Number off 3

Model Cuno 10 micron

Material of construction MS (Epoxy painted)

Max/Min flow 120/72.5 m/hr

Pr drop in Min/max 0.5/1.5 kg/cm

Filter type Micro wynd polypropylene

No of Cartridge per

filter

30

Degree of filtration 10 microns

Mi d B d


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Mixed Bed

This is mild steel vessel lined internally with rubber. A calibratedorifice board in the drain sump is also provided for controlling various

regeneration flows. The middle and bottom collecting system are ofheader lateral type. The header is of mild steel rubber lined andrubber covered to which PVC lateral are fitted. Strainers whichprevent resin from escaping are screwed to the bottom of the laterals.Mark V strainers have been used for bottom collecting systemwhereas mark 801 strainers for middle collector. Inlet water distributoris of three arms with strainers to avoid escape of resin during

backwashing. Bottom dished portion is filled with concrete. Thevessel is charged with strongly cationic resin (INDION 225) andstrongly basic anion (FFIP). Cation resin is regenerated with HCL andanion resin with NaOH.

Backwash:- This operation is carried out to separate the resin prior toinjection of chemicals. Due to difference in densities, the resin get

separated in two layers during the backwashing, with cation forminglayer and anion forming layer.(10 minutes

Subsurface Wash:- This operation is carried out to clean the middlecollector strainers to ensure proper distribution / collection duringinjection of chemicals. (2 minutes


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MIXED BED Caustic pre injection:-water flow for caustic injection is established through alkali ejector.

Simultaneously water is fed to the unit through bottom collecting system. The effluent istaken out through middle collector system. This ensure minimum diffusion of caustic intocation resin. (2 minutes

Caustic injection:- Once the pre injection flows are established the 5 % alkali solution fromthe CDT is passed through anion resin by opening ejector suction valve.(15 minutes

Caustic Rinse / Up flow:- After completion of the caustic injection water is continued topass to displace / fully utilize the regenerants from pipe works and also through the resinbed.

Acid Pre injection:- Water flow for acid injection is established through acid ejector.Simultaneously water is fed from inlet and effluent taken out from bottom collecting system.

Acid injection / Down flow:- Once the pre injection flows are established the 5 % acidsolution from the ADT is passed through cation resin by opening ejector suction valve.( 10minutes

Acid Rinse:- After completion of the acid injection water is continued to pass to displace /fully utilize the regenerants from pipe works and also through the resin bed.

Drain Down:- Water from the vessel is drained up to about 300 mm above the top surfaceof resin bed( approx half of top inspection window.) 10 minutes

Air Mix :- Air is passed from the bottom of the unit to mix the individual resin thoroughly.The mixing and movement of the resin bed can be observed through inspection windows.(10 minutes)

Final rinse :- DM water is taken from inlet and drained from the rinse outlet for specifiedtime to remove excess regenerants from the bed.. The unit is rinsed partially during thisoperation.

Rinse to Recycle:- To avoid wastage of water the rinsing is completed by recycling thewater back to DMT till the acceptable treated water quality is achieved.


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DM 1 MB REGENERATIONOperation Flow

m/hr

Inject flow

m/hr

Time

Backwash 34.2 10

M/C Flush 15.2 2

Acid Pre injection 5.7 19 1

Acid injection 5.7 22.8 10Acid Displacement 5.7 19.5 15

Caustic Pre injection 17.1 21.6 1

Caustic injection 17.1 26 15

Caustic Displacement 17.1 45.6 20

Drain down 5

Air Mix 456 10

Final Rinse 170 10

Rinse to Recycle 170 20


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DM 2 MB RegenerationStep Flow

m/hr

Injection

m/hr

Time

Middle collector flushing 35 NA 2

Backwash 35 Na 10

Settle bed NA Na 2

Power water 20.8 17.4 2

Alkali injection 20.8 17.4 15Alkali slow rinse 20.8 17.4 15

Settle bed Na NA 2

Acid power water 9 10 2

Acid injection 9 10 15

Acid slow rinse 9 10 15

Drain Down NA NA 4

Drain down cont. NA NA 1

Air Mixing NA NA 10

Refill NA NA 2

Fast Rinse 176 NA 10


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Pre-requisites to start MB

regeneration

MAK tank is full

MHL-2 tank is full

VA-2 of MB is closed

PDM 1/2/3/4 selected in auto PDG 1/2 selected in auto

BMB 1/2 selected in auto

Select regeneration in Auto mode

Select MB program from CRT key board

Select particular MB in regeneration mode


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Air scour & Open manhole

backwash Open the manhole

Drain water till level is about 300 mm above the resinbed

Insert the air hose halfway into resin bed

Start air scoring throughout the resin Continue operation for 15 minutes.

Give backwash

Drain the vessel

Scrape off 6 mm layer from the top of the resin bed anddiscard this.

Close the manhole cover.


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Alkaline Brine Treatment of

WBA/SBA Prepare solution of 10% NaCl and 2% NaOH making 3 bed volume

of WBA and SBA resin

Backwash the unit thoroughly and the alkali brine prepared wasinjected into SBA, letting the effluent coming out of SBA drain outlet.

After 10 minutes the brine is injected into WBA thoroughfare SBAswithout any power water and the effluent will come out from WBAand is drained.

One bed volume is let to pass through SBA and WBA.

Second bed volume of brine solution is allowed to pass through bothSBA & WBA units and when the units are full with solution , theinjection is stopped and allowed to soak for 12 hours.

After soaking the units, drain down the vessels and final part of thebrine solution is injected through both SBA &WBA. After completinginjection both units were rinsed at normal rinse flow rate till thechlorides in the effluent are nil. Then the units WBA/SBA were givendouble regeneration.


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Alkaline Brine Treatment of MB

Prepare solution of 10% NaCl and 2% NaOH making 3bed volume of MB resin

First the MB unit was backwashed and first batch wasinjected through alkali inlet distribution header letting theeffluent to come out through rinse outlet (VA6)

The second batch of brine solution is again injected intothe MB unit and is allowed to soak for12 hours.

After soaking the unit , the vessel is drained out and thefinal batch of brine solution is injected.

After that the unit should be rinsed thoroughly till theeffluent coming out contains nil chloride.

The MB unit was then given a double regeneration withdouble quantities of regenerant chemicals.

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Deminerlise Plant