New Beginning

WATER CHEMISTRY IN THERMAL POWER PLANT (OVER VIEW)

Presented by:Pradip Patel ESSAR POWER GUJARAT LTD - JAMNAGAR11Role of Chemistry in Power Plant

Water Chemistry is important

toAchieve higher operation efficiency Minimize corrosion and scale formation problemTo reduce plant down time.

High water quality standards are to be maintain particularly in high pressure boiler and upcoming super critical boiler.22 WATERThe purest available form is from water vapour in atmosphere , as rain, snow or produced by melting of ice.

This water on reaching the ground absorbs different types of gases from atmosphere like nitrogen, oxygen and to a lesser extent carbon dioxide.

Other gasses like ammonia, oxides of nitrogen and sulphur etc. also dissolves during rain depending upon the pollution level of the atmosphere.

Apart from this, the surface water travels to various places and catches organic matter, suspended solids etc.33 SOURCES OF WATERRivers, Lakes and reservoirs (Surface drainage water)

Underground water (shallow well, deep well, springs)

Rain water

Sea water

Snow melting44 MAIN IMPURITIES IN WATERNon dissolved & Non Ionic :Suspended (Macro size) Sand, dirt, silt. This contributes turbidity to raw water.

Colloidal Micro size particles (1 to 100 nm)

Dissolved & Ionic :Dissolved form Alkaline salts and neutral salts, organic matter,

Alkaline salts are mainly bicarbonates rarely carbonates and hydrates of calcium, magnesium and sodium.

Neutral salts are sulphates, chlorides, nitrates of calcium, magnesium and sodium.55TYPE OF WATER IN THERMAL POWER PLANTRaw Water

Process water

Boiler water

Cooling water

66WATER TREATMENT IN POWER PLANTExternal Treatment Internal Treatment

External treatmentPre TreatmentPost Treatment

Why Pre treatment Plant ?

Pretreatment is required for removing Floating Solids, Suspended Solids and Colloids.

77Pretreatment:

(1) Screening(2) Storage of raw water(3) Chlorination(4) Coagulation & FlocculationFiltration

88Water Flow Diagram9WaterIntakeRaw Water ReservoirIRaw Water ReservoirIIClarifier Tank-IClarifier tank-IIThickener/SettlerThickener/SettlerFiler Water Reservoir Tank

DMFDMFService Water Tank / DM Feed TankCooling Tower Make UpBlow DownDM PLANTDM Water For Boiler

9Coagulation & Flocculation Ferric Alum:(Alum, Ferric Chloride, PAC)Fe2Al2(SO4)3.18H2O+ Ca(HCO3)2---Fe(OH)3+3CaSO4+2Al(OH)3+6CO2

Hydrated Lime:-Ca(HCO3)2+Ca(OH)2------2CaCO3+2H2OMg(HCO3)2+2Ca(OH)2------Mg(OH)2+2CaCO3+2H2OMg(OH)2+Al(OH)3----- SLUDGE

Coagulation aid:-Poly electrolytes1010Why Post Treatment Plant?Dissolved Solids present in water is removed by Post Treatment. Like,Cation:Calcium, Magnesium, Sodium etc.Anion:Bi Carbonate, Carbonate, Sulphate, Chloride, Silica(1) Calcium bicarbonateCa(HCO3)2Scale(2) Calcium carbonateCaCO3Scale(3) Calcium chloride CaCl2Scale(4) Magnesium bicarbonate Mg(HCO3)2Scale (5) Magnesium carbonate MgCO3Scale(6) Magnesium chlorideMgCl2Scale

1111Different type Post treatment plant

MEDR.O(3) DM Plant etc.

1212WBASBAMBDGTWACSACD M Plant DMSTACFDEGASSER13Dissolved solids present in water are removed in DM plant by Ion exchange process and resin are used for this Ion exchange process.Depending upon the amount of water to be treated and quality of the filter water, different types of demineralization schemes are made. DM Water Specification pH : 6.5 6.9 Cond. (S/cm) -: < 1.0 SiO2 -: < 0.02 ppm

1414Service & RegenerationSERVICE:-Ion Exchange process in Cation Resin.R-H+ + CaCl2, MgSO4, NaCl --- R-Ca, Mg, Na + HCl, H2SO4, 2HCl Ion Exchange process in Anion Resin.R-OH- +HCl, H2SO4 ----- R-Cl,SO4 + H2O

REGENERATION:-Exhausted Cation exchange resin R-Ca, R-Na, R-Mg is converted back to its original form by passing HCl R-Mg + 2 HCl---- 2 R-H + MgCl2R-Na + HCl R-H + NaClAnion exchange resin is regenerated by treating with NaOHR-Cl + NaOH ----- R-OH + NaCl

1515BOILER WATER CHEMISTRY16Boiler Water Parameter17Sample Detail pHSp. Cond.SiO2PO4N2H4CCTHFe(s/cm)(ppm)(ppm)(ppm)(s/cm)(ppm)(ppm)F.W8.8-9.2< 5