WATER CHEMISTRY IN POWER PLANT

WATER CHEMISTRY IN POWER PLANT WATER CHEMISTRY IS A VERY IMPORTANT DISCIPLINE IN POWER SECTOR. TO ACHIEVE HIGHER OPERATION EFFICIENCY AND TO REDUCE PLANT DOWNTIME, HIGH WATER QUALITY STANDARDS ARE TO BE MAINTAINED

WATER CHEMISTRY IN POWER PLANTPRODUCTION OF : - --- D.M. WATER FOR BOILER MAKE-UP. --- FILTER WATER FOR SOFTENING PLANT, D.M. PLANT, DRINKING WATER AND A.C. COOLING SYSTEM.MONITORING OF STEAM/ WATER PARAMETERSH.P./L.P. DOSING.TESTING OF COAL.TESTING OF LUB OIL.

WATER CHEMISTRY IN POWER PLANTCIRCULATING WATER TREATMENTPOLLUTION MONITORINGSTACK MONITORINGAMBIENT AIRWATER EFFLUENTEFFLUENT TREATMENT PLANTCOMMISSIONING ACTIVITES

WATER FLOW DIAGRAM

D.M. PLANT

D.M. WATER QUALITYpH - 7.0 0.2CONDUCTIVITY < 0.2 mhoTDS - NILSiO2 < 20 ppb

WATER STEAM CYCLE (GAS PROJECT)

WATER STEAM CYCLE (THERMAL PROJECT)

WATER/STEAM CHEMISTRYPARAMETERS MONITOREDpHSilicaConductivityAfter Cation ConductivityDissolved OxygenSodiumCopperIron

WATER QUALITY

FEED WATERACC

WATER QUALITYCONDENSATE WATERACC

WATER QUALITYBOILER WATERConductivity

WATER QUALITYSTEAMACC

DISTRIBUTION RATIO BETWEEN STEAM & BOILER WATER AT pH 9.5 Drum PressureSilica in Boiler Water 194 Kg/Cm2 130 ppb176 Kg/Cm2 220 ppb159 Kg/Cm2 290 ppb 134 Kg/Cm2 500 ppb117 Kg/Cm2 1000 ppb100 Kg/Cm2 2220 ppb 65 Kg/Cm2 4000 ppb-- Boiller Drum Pressure is to be maintined as such,Silica value in Main Steam maintain bellow 20 ppb.

100

10-1

10-2

10-3

10-4

10-5

10-6

10-7226 220 200 180 160 140 120 100 50 40 30PRESSURE ( BAR)PARTITION COEFFICIENT KpSiO2NaOHNaClPARTITION COEFFICIENT AT DIFFERENT PRESSURES

SOURCES OF IMPURITIES IN STEAMBy evaporation from the boiler drumBy entrainment of boiler water droplets in saturated steam.As impurity present in feed water used in desuper heater spray.

EFFECTS OF SILICA

Silica has high partition coefficient, so it has tendency to deposit from steam onto turbine.

Silica can deposit on turbine blades specially on LP turbine, which can lead to significant loss of output.

H.P. DOSINGCOORDINATED PHOSPHATE CONTROL

Na3PO4+H2O Na2HPO4 + NaOHNa2HPO4+H2O NaH2PO4 + NaOHNaOH + HCl (As Impurity) NaCl + H2O

L.P.DOSINGAMMONIA & HYDRAZINE HYDRATE DOSING

AMMONIA IS USED TO INCREASE THE pH OF THE SYSTEM AND HYDRAZINE IS USED TO REMOVE THE OXYGENN2H4 + O2 N2 + H2O3N2H4 4NH3 + N2

CHEMICAL CONTROL OF GENERATOR STATOR WATER COOLING CIRCUITSGENERATOR STATOR COOLANT --- D.M. WATERSTATOR WATER PARAMETER TO BE MAINTAINED - pH 6.8 + .2 - K < 1.0 s/cm - Copper < 50 PPb - D.O. < 10 PPb in low D.O. regime 2.0 to 5.0 PPM in high D.O. regime

CORROSION OF COPPER There are two methods where the copper is best passivated and minimum corrosion is found. 1. Low dissolved oxygen regime. 2. High dissolved oxygen regime.

LOW D.O. REGIME - Limits below 10 PPb With low D.O. concentration, copper corrosion is inhibited by a passive film of Cuprous Oxide(Cu2O).

HIGH D.O. REGIME

- Limits 2 to 5 PPM With high D.O. concentration, copper corrosion is inhibited by a passive film of Cupric Oxide(CuO).

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