POWER PLANT CHEMISTRY( WATER TREATMENT FOR BOILERS)
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Transcript of POWER PLANT CHEMISTRY( WATER TREATMENT FOR BOILERS)
TREATMENT OF WATER FOR HIGH PRESSURE BOILERS& STEAM-WATER QUALITY PARAMETERS
BYDILIP [email protected]
POWER PLANT CHEMISTRY
PRETREATMENT PLANT
AERETOR
BY GANGA MAKEUP PUMPS
RIVER GANGA
•Suspended particles
•Dissolved inorganic salts
•Dissolved organic compounds
•Micro organisms &
•Dissolved gasses
IMPURITIES IN RAW WATER
AERATION
Exposing Water to Atmospheric air thereby
oxidizing some of the dissolved salts.
During aeration, two impurities viz. Ferrous
Bicarbonate and Manganous Bicarbonate are
oxidized as follows;
Fe(HCO3) + O2 -- FeO(OH) + CO2 + H2O
Mn(HCO3) + O2 --MnO2(OH) + CO2 + H2O
AERATION
Exposing Water to Atmospheric air thereby
oxidizing some of the dissolved salts.
During aeration, two impurities viz. Ferrous
Bicarbonate and Manganous Bicarbonate are
oxidized as follows;
Fe(HCO3) + O2 -- FeO(OH) + CO2 + H2O
Mn(HCO3) + O2 --MnO2(OH) + CO2 + H2O
•Alum Al2 (SO4)3, 18H2O : For coagulation.
•Lime Ca (OH)2 : To maintain the pH.
•Chlorine Cl2 : As a disinfectant.
DOSING OF CHEMICALS
Al2(SO4)3.18 H2O + 3 Ca(HCO3)2 =2AI(OH)3 + 3CaSO4 + 18H2O + 6CO2
Al2(SO4)3.18 H2O + 3 Ca(OH)2 = 2AI(OH)3 + 3CaSO4 + 18H2O
Cl2 + H2O HOCL + HCl
CLARIFIER
CASCADE AERATOR
Clarifier outlet turbidity < 20NTUClarifier outlet residual Cl2: 0.2-0.5 ppm
RAW WATER INLET
CLARIFIED WATER OUTLET
SLUDGE OUTLET
Clarified water turbidity < 20NTUClarified water residual Cl2: 0.2-0.5 ppm
CLARIFIER
Turbidity reduced
Micro-organisms are killed
GRAVITY SAND FILTER (GSF)
Sand
Gravel
Rapid rate gravity filtration is the most widely used technology for removing turbidity and microbial contaminants from pretreated surface water and groundwater.
FILTERATION
Filtered water turbidity < 5 NTUClarified water residual Cl2: 0.2-0.5 ppm
FOR DRINKING
FOR DEMINERALIZATIONTO DM PLANT
FILTERED WATER SUMP
Filtered water turbidity < 5 NTUClarified water residual Cl2: 0.2-0.5 ppm
REMAINING IMPURITIESDissolved inorganic salts
Dissolved gasses
Dissolved organic compounds
Degasser
FW water
ACF WAC SAC
WBASBA MB
CST
Processes …..
DEMINERALISATION STREAM
Degasser
FW water
ACF WAC SAC
WBA SBA MB
CST
ACFActs on principle of adsorption which is a surface active phenomenonIt removes residual turbidity (<2 NTU) of water to its 1/10 level.It removes organic molecules to control colour and odour.It removes free residual chlorine present in filtered water(0.5 ppm Nil)
Processes …..
Degasser
FW water
ACF WAC SAC
WBA SBAMB
CST
WAC resin is capable to exchange cations of alkalinity producing salts only
i.e., for carbonate hardness removal purpose.
2 R-COOH + Ca(HCO3)2 (RCOO)2Ca2+ 2 H2CO3
WAC resin can exchange ions only in neutral to alkaline pH range.
WAC results efficient TDS reduction in high carbonate hardness water.
Efficient regeneration takes place even with very dilute acid solution.
Processes …..
Degasser
FW water
ACF WAC SAC
WBA SBA MB
CST
SAC resin works over wide pH range & is capable to
exchange any type of cations present in salts as sulphonic
acid group is strongly acidic.
2 R-SO3-H+ + CaCl2 (RSO3)2Ca2+ 2 (H+ + Cl- )
Processes …..
Degasser
FW water
ACF WAC SAC
WBA SBAMB
CST
Water from the ex-cation contains carbonic acid which is very weak acid and
difficult to be removed by strongly basic anion resin and causing hindrance
to remove silicate ions from the bed.
The ex-cation water is trickled in fine streams from top of a tall tower
packed with rasching rings, and compressed air is passed from the bottom
Carbonic acid break into CO^ and water. carbon dioxide escapes into the
atmosphere. Water is pumped back to anion exchanger bed
Processes …..
Degasser
FW water
ACF WAC SAC
WBA SBAMB
CST
Weak anion resins derive their functionality from primary (RNH2),secondary(R-NHR’)& tertiary amine (R3N)groups. The weak weak-base anion resins remove free minerals acidity(FMA) such as HCl & H2SO4 but doesn’t remove weakly ionized acids such silicic acid and bicarbonates
Processes …..
Degasser
FW water
ACF WAC SAC
WBA SBA MB
CST
The Strong base anion resins derived their functionality from quaternary ammonium exchange sites.These are capable of exchanging anions like Cl-,HCO3-,Silica.
Processes …..
Degasser
FW water
ACF WAC SAC
WBA SBA MB
CST
ex-anion water is fed to the mixed bed exchanger containing both cationic
resin and anionic resin.
This bed not only takes care of sodium slip from cation but also silica slip
from anion exchanger very effectively
The final output from the mixed bed is an extra-ordinarily pure water having
less than 0.2/Mho conductivity, H 7.0 and silica content less than 0.02 ppm.
Processes …..
CATIONS
Ca2+,Mg2+
Na+,Fe3+,
K+
ANIONS
Cl-,SO42-,
NO3-,CO3
2-
HCO3,SiO22
WATER
SAC
R-H+R-H+
R-H+
R-H+R-H+
R-H+
R-H+
CATIONS
H+
ANIONS
Cl-,SO42-,
NO3,CO32-
HCO3,SiO22-
AIR
DG
CATIONS
H+
ANIONS
Cl-,SO42-,
NO3-,SiO2
2-
WATER
WATER
R-OH-
R-OH- R-OH-
R-OH-
R-OH- R-OH-
CATIONS
H+
ANIONS
OH-
WBA+SBA
CO2
ION EXCHANGE - PROCESS CHEMISTRY
WAC +
REGENERATION PROCESS
R2-Ca2+ R2Mg2+
R-Na+ R-K+
R3-Fe+3 R3-Al+3
HCl
R-H+ R-H+
R-H+ R-H+
R-H+ R-H+NaCl,CaCl2 etc.
TO DRAIN
SAC SAC
R-Cl
R2-SO4
R-NO3
R-ClNaOH
TO DRAIN
R-OH-
R-OH- R-OH-
R-OH-
R-OH- R-OH-
SBA SBA+ WBA
R2-SiO2
R2-SiO2
R2-SiO2
WBA
Parameters pH Conductivity Turbidity Residual Chlorine
Silica
ACF 6.5 – 7.5 -- <2.0 NTU Nil --
Anion 6.5 – 8.0 <10 Nil Nil <200 ppb
Mixed Bed 6.5-7.0 <0.2 Nil Nil < 20 ppb
Why DM water can’t be used directly in boiler?
• - Principle says if water is acidic – Corrosive.
- Principle say if water is alkaline – Scale forming.
As DM water (also called as hungry water) is having no
salt, when it comes in contact with metal surface attacks the metal.
CONDENSER
CEP
LPH
DEAERATOR
HPH
ECONOMISER
WATER WALLS
BOILER DRUM
TURBOGENERATOR GT SWITCHYARD
BOTTOM RING HEADER
UPPER RING HEADER
DOWNCOMMERS
SH
TO STACK TO ESP BFP
CT
BFP
DOSING OF CHEMICALS TO PROTECT THE BOILER AND PREBOILER SYSTEM FROM CORROSION
BFP
AMMONIA IS USED TO INCREASE THE pH OF THE SYSTEM &NH3+ CO2 = (NH4)2CO3N2H4 + O2 =N2 + H2O3N2H4 =4NH3 + N2 ( this reaction takes place in the boiler
drum
AMMONIA DOSING
BFP
Tri-sodium phosphate hydrolyses & givesNa3PO4+H2O= Na2HPO4 + NaOHNa2HPO4+H2O= NaH2PO4 + NaOHNaOH + HCl (As Impurity)= NaCl + H2O
TRISODIUM PHOSPHATE DOSING IN BOILER DRUM
BFP
SAMPLING POINTS AND PARAMETERS
CONDENSATE SAMPLE COLLECTED FROM CEP DISCHARGEPH 9.0-9.2K 3.0-4.0 µs/cmSILICA 10 ppbDO <40 ppbNH3 1.0 ppmFe <10 ppbCu <3.0 ppb
BFP
SAMPLING POINTS AND PARAMETERS
FEED SAMPLE COLLECTED FROM ECONOMIZER INLETPH 9.0-9.2K 3.0-5.0 µs/cmACC 0.2 µs/cmSILICA 10 ppbDO <5 ppbFe <10 ppbCu <3.0 ppb
BFP
SAMPLING POINTS AND PARAMETERS
BOILER DRUM(BD) SAMPLE COLLECTED FROM BOILER DRUMPH 9.1-9.4K <20 µs/cmSILICA 0.1 ppmPHOSPHATE 1.0-2.0 ppmCHLORIDE 0.5 ppm TDS 10 ppb
BFP
SAMPLING POINTS AND PARAMETERS
SATURATED STEAM SAMPLE COLLECTED FROM BOILER DRUM OUTLETPH 9.0-9.2K 3.0-5.0 µs/cmACC 0.2 ppmSILICA 10 ppbNa <5.0 ppbNH3 <1.0 ppmFe <10 ppbCu <3.0 ppb
BFP
SAMPLING POINTS AND PARAMETERS
MAIN STEAM SAMPLE COLLECTED FROM SUPER HEATER OUTLETPH 9.0-9.2K 3.0-5.0 µs/cmSILICA 10 ppbNa <5.0 ppbNH3 1.0 ppmFe <10 ppbCu <3.0 ppb
BFP
SAMPLING POINTS AND PARAMETERS
DEAERATOR OUTLET SAMPLEDO <5 ppb
GENERAL LAYOUT OF MAIN PLANT
FUEL SYSTEM
COAL UNLOADING
CRUSHER HOUSE
CONVEYOR BELT
COAL BUNKERS
COAL FEEDERS
COAL MILLS
FUEL SYSTEM
COAL HANDLING PLANT
CRUSHER HOUSE
CONVEYOR BELT
COAL BUNKERS
COAL MILLS PULVERIZED THE COAL INTO 75 µ SIZE
VARIOUS SIZED COAL
20 mm SIZE
FUEL SYSTEM
COAL HANDLING PLANT
CRUSHER HOUSE
CONVEYOR BELT
COAL BUNKERS
COAL MILLS PULVERIZED THE COAL INTO 75 µ SIZE
COAL SAMPLES COLLECTED FROM COAL FEEDER S FOR DETAILED ANALYSIS (PROXIMATE ANALYSIS & GCV)
PA FAN
AIR
AIR PREHEATER
HEATED AIR
COAL MILL
FD FAN
AIR
PA FAN
AIR
AIR PREHEATER
HEATED AIR
COAL MILL
FD FAN
AIR
Coal sample sampling point for
MILL FINENESS
PA FAN
AIR
AIR PREHEATER
HEATED AIR
COAL MILL
FD FAN
AIR
MILL FINENESS+50 3.00%-100-200 70%
PA FAN
AIR
AIR PREHEATER
HEATED AIR
COAL MILL
FD FAN
AIR
Oxygen % in flue gas>4% for efficient combustion of fuel
Bottom Ash Hopper
COAL MILL
Bottom Ash HopperSamples for determination of combustibles in bottom ash
Bottom Ash Hopper
COAL MILL
Combustibles in bottom ash <3.00%Combustibles in Fly ash <1.00%
ESPs
SAMPLING POINT FOR FLY ASH ANALYSIS
16 April 2015 PMI Revision 00 39
GENERATOR CHEMISTRY
Basic Generator Theory
GENERATOR PARTS
STATOR OF GENERATOR
ROTOR WINDING & ROTOR
GENERATOR PARTS
GENERATOR INTERNALS COOLING
STATOR COOLED BY PRIMARY WATER
GENERATOR INTERNALS COOLING
ROTOR COOLED BY HYDROGEN GASHYDROGEN PURITY MAINTAINED >97%
GENERATOR INTERNALS COOLING
LOWER FLAMABILITY LIMIT OF H2 4% H2 IN AIRUPPER FLAMABILITY LIMIT OF H2 74% H2 IN AIR
PRIMARY WATER SYSTEM
P W PUMPS
P W COOLERS
FILTERS
ALKALIZERION
EX
CH
AN
GE
R
GENERATOR WINDING
EXPANSION TANK
PRIMARY WATER SYSTEM
P W PUMPS
P W COOLERS
FILTERS
In Case Of Low PH (6.0-8.0) & High DO (<100ppb)Protective Layer formed in Winding is CuO
EXPANSION TANK
PRIMARY WATER SYSTEM
P W PUMPS
P W COOLERS
FILTERS
In Case Of High DO (Without alkalizer)Control limits arepH 6.0-8.0K <1.5 µs/cmCu <20ppbFe <20 ppb
EXPANSION TANK
PRIMARY WATER SYSTEM
P W PUMPS
P W COOLERS
FILTERS
ALKALIZERION
EX
CH
AN
GE
R
In Case Of High PH (8.5-9.0) & Low DO (<10 ppb)Protective Layer formed in Winding is Cu2O
EXPANSION TANK
PRIMARY WATER SYSTEM
P W PUMPS
P W COOLERS
FILTERS
ALKALIZERION
EX
CH
AN
GE
R
In Case Of High DO (With alkalizer)Control limits arepH 8.5-9.0K <2.2 µs/cmCu <20ppbFe <20 ppb
EXPANSION TANK