Upload
sensubhasis58
View
143
Download
0
Embed Size (px)
Citation preview
SUPER CRITICAL
WHY-SUPER CRITICAL
AS PER MARKET REQUIREMENTS-*HIGH AVAILABILITY & RELIABILITY.*HIGHEST ECONOMICALLY ACHIEVABLE PLANT-HIGHEST EFFICIENCY AND LOWEST HEAT RATE.*SUITABLE FOR DIFFERENT MODES OF OPERATION.*SUITABLE FOR DIFFERENT QUALITY OF FUEL.*ABILITY TO OPERATE UNDER ADVERSE GRID CONDITIONS / FLUCTUATIONS.*MINIMUM EMISSION OF POLLUTANTS.*LOWEST LIFE CYCLE COST.
Supercritical cycles are more efficient
Heat rate improvement vs. steam conditions (single reheat)
1000/1000°F 538/538°C
1050/1050°F 565/565°C
1075/1110°F
580/600°C1110/1145°F 600/618°C
5%
2600 3475
4350 5225 psi
10%
Heat rate improvement
40 °F or 22 °C = 1.25 % improvement
Subcritical Supercritical and UltraSupercritical
1110/1110°F 600/600°C
179 240 300 360
- Lower Fuel Consumption and Lower Emissions/ kWh -- Lower Fuel Consumption and Lower Emissions/ kWh -
Sub. vs. Supercritical Cycle Impact on Emissions
Plant Efficiency, %*
Plant Efficiency, %
Fuel Consumption/Total Emissionsincluding CO2
Subcritical Supercritical 34 - 37 37 - 41
Plant Efficiency, Btu / kw-hr 10,000 - 9,200 9,200 - 8,300
34%
Base
37%
Base-8%
41%
Base-17%
* HHV Basis
Annual Fuel Cost Savings
0
2
4
6
8
10
12
14
16
20 25 30 35 40 45 50
42%
40%
38%
36%
Efficiency
Coal Price USD/Short Ton
Compared to 34% subcritical efficiency, 11,000 BTU/lb coal, 80% capacity factor
500 MW Unit
An
nua
l Fu
el S
avin
gs,
MU
SD
Boiler-Cycle Thermodynamics
3208
2865
1800
Pre
ssur
e
Ps i
a
Enthalpy BTU/lb
CARNOT ENGINE (CARNOT ENGINE (FRENCH ENGINEER SODI CARNOT 1824)FRENCH ENGINEER SODI CARNOT 1824)
•1-2 - Isothermal Expansion at T1ºK
•2-3 - Adiabatic Expansion up to T2ºK
•3-4 - Isothermal Compression at T2ºK
•4-1 - Adiabatic Expansion up to T1ºK
For Carnot Cycle η = 1 - T2 T1
T1 = Temp. of heat source where
T2 = Temp. of heat sink
Carnot Cycle gives maximum possible thermal
efficiency which can be obtained between any two
Given temperature limits.
1
1
2
34S
T T1
T2
CARNOT ENGINECARNOT ENGINE
RANKINE CYCLE
• The Carnot Cycle is theoretically most efficient, but it is having practical difficulties.
• For steam power plant, practical thermal cycle was suggested by Rankine, called Ideal cycle.
3-3’ – BFP raises pressure from p2 to p1
3’-4 – Heating In feed heaters & eco
4 -1 – Heating In boiler
1-2 – Work done in Turbine from p1 to p2
2-3- HEAT REJECTION IN CONDENSER
1
23
3’
4
T
S
T1
T2
p1
p2
THERMAL EFFICIENCY OF RANKINE CYCLE Q1-Q2 W Useful work• η = ------- = --- = ----------------
Q1 Q Heat supplied
Rejected Heat • η = 1 - -------------------- Useful Heat
T1 - T2 T2• η Carnot = -------- = 1 - ---
T1 T1
• To achieve more efficiency T2 should be as low as possible
and T1 should be as high as possible
THERMAL POWER
WE REQURIED HIGHER CYCLE EFFICIENCY FOR:-•CONSERVATION OF FUEL RESOURCES.•REDUCTION OF ATMOSPHERIC POLLUTANTS- OXIDES OF
SULPHER AND NITROGEN(NOX. & SOX)•REDUCTION IN CORBAN DIA OXIDE EMISSION(RELATED TO
GLOBAL WARMING).•BETTER ECONOMY IN POWER GENERATION AS FUEL COSTS
ARE HIGH AND POLLUTION CONTROL REQUIREMENTS ARE STRINGENT.
•HIGHER CYCLE EFFICIENCY CAN BE ACIEVED BY -HIGHER LIVE STEAM PARAMETERS,REDUCTION IN CONDENSER ABSOLUTE PRESSURE AND ADOPTION OF DOUBLE REHEAT CYCLE.
FUEL FOR STEAM POWER PLANTS
CAOL & LIGNITE:-*ABUNDANT AVAILABILITY*LOWER COST.*WILL CONTINUE AS THE MAIN FUELS IN MANY COUNTRIES.MEASURES TO IMPROVE PLANT EFFICIENCY AND REDUCE HEAT RATE:-*MINIMUM RH SPRAY*MINIMUM SH SPRAY(IF TAPPING BEFORE FEED HEATERS)*MINIMUM FLUE GAS TEMP. AT APH OUTLET.*MINIMUM EXCESS AIR AT APH OUTLET*MINIMUM UNBURNT CARBON LOSS(AT FLY & BOTTAM ASH)*REDUCING AUXILIARY POWER CONSUMPTION.
IMPROVEMENT IN CYCLE EFFICIENCY
APPROXIMATE IMPROVEMENT IN CYCLE EFFICIENCYPRESSURE-0.005% PER BARTEMP -0.011% PER Deg. KIMPLICATION OF HIGHER STEAM PARAMETERS ON BOILER*BOILER TYPE*MATERIALS*RELIABILITY & AVAILABILITY
TYPES OF BOILERS*DRUM TYPE:-STEAM GENERATION IN FURANCE WATER WALL,EVAPORATION END POINT & SEPERATION OF STEAM & WATER TAKES PLACE AT DRUM,SEPERATED WATER MIXED WITH INCOMIMG FEED WATER.
NATURAL CIRCULATION BOILER-CIRCULATION THRU WATER WALL BY THERMO- SIPHON EFFECT.
CONTROLLED CIRCULATION BOILER- AT HIGHER OPERATING PR. BUT BELOW CRITICAL PR.THERMO –SIPHONEFFECT SUPPLEMENTED BY CONTROLLED CIRCULATION PUMPS.*FOR DRUM TYPE BOILER THE GASES AT THE COMBUSTION CHAMBER OUTLET CAN NOT BE COOLED BELOW A CERTAIN VALUE(TEMP).*DIMENSIONING OF THE HEATING SURFACES OF BOILERS HAVING FIXED EVAPORATION END POINT MUST BE DONE PRECISELY.*GENERATION OF STEAM AND SPRAYING QUANTITY IN SH CHANGES ,IF OPERATING POINT DEVIATES FROM THE DESIGN POINT.
Increase of Cycle Efficiency due to Steam Parameters
300241
175 538 / 538
538 / 566
566 / 566
580 / 600
600 / 620
6,77
5,79
3,74
5,74
4,81
2,76
4,26
3,44
1,47
3,37
2,64
0,75
2,42
1,78
00
1
2
3
4
5
6
7
8
9
10
HP / RH outlet temperature [deg. C]Pressure [bar]
Increase of efficiency [%]
500 MW Steam GeneratorCoal Consumption and Emissions
SubcriticalUnit
SupercriticalUnit
Coal Saving t/year Base 68800
CO2 Reduction t/year Base 88270
SO2 Reduction t/year Base 385
Basis:
Cycle Efficiency % Base +1.0
No. of operatinghrs.
Hrs./year 8000 8000
Steam generation process
Definition of Supercritical DesignEvaporator pressure (MCR) 222 bar Supercritical Design
Source: Siemens
ONCE THROUGH BOILER CONCEPT
THE MASS FLOW RATE THROUGH ALL HEAT TRANSFER CIRCUITS FROM ECONOMISER INLET TO SUPER HEATER OUTLET IS KEPT SAME EXCEPT AT LOW LOADS WHEREIN RECIRCULATION IS RESTORED TO PROTECT THE WATER WALL SYSTEM.*ONCE-THROUGH FLOW THROUGH ALL SECTIONS OF BOILER(ECO,WW,SH).*BOILER FEED PUMP PROVIDES THE DRIVING HEAD.*IT IS SUITABLE FOR SUB CRITICAL AND SUPER CRITICAL
PRESSURES.
Once Through Boiler-Concept
MAJOR DIFFERENCES FROM DRUM TYPE BOILER
*EVAPORATOR SYSTEM.*LOW LOAD CIRCULATION SYSTEM.*SEPARATOR.
ONCE THROUGH BOILER EVAPORATOR SYSTEM
*FORMED BY NUMBER OF PARALLER TUBES.*TUBES SPIRALLY WOUND AROUND THE FURNACE TO REDUCE THE NO OF TUBES & INCREASE THE MASS FLOW RATE THROUGH THE TUBES.*SMALL TUBE DIAMETER.*ARRANGEMENT ENSURES HIGH MASS VELOCITY THROUGH THE TUBES.
CONTROLLED CIRCULATION (Vs) ONCE THRU’
CC OT
Once -thru Boiler - Furnace Wall
Furnace ArrangementFurnace Arrangement
VERTICAL TYPE
SPIRAL TYPE
FURNACE WALL
*INCREASED OPERATING PR INCREASES THE MEDIUM TEMP*INCREASED REGENERATIVE FEED HEATING INCREASES THE FLUID INLET TEMP.*LARGER FURNACES REQUIRED FOR NOx REDUCTION,INCREASES SH STEAM TEMP AT FURNACE WALL OUTLET.SPIRAL WALLADVANTAGESIT CAN BE USED IN BOILER OF ANY CAPACITY.IT IS HAVING MORE UNIFORM HEAT ABSORPTION AS THE TUBES PASSESTHROUGH ALL FURNACE WALLHENCE EVAPORATOR OUTLET STEAM TEMP. ARE MORE UNIFORM.DISADVANTAGES-FURNACE WALLS ARE NOT SELF SUPPORTED AS TUBES ARE INCLINED,EXTERNAL SUPPORT(STRAP SYSTEM) IS NEEDED,FABRICATION & INSTALLATIONARE DIFFECULT HENCE INCREASES THE COST.
VERTICAL WALL
VERTICAL WALLS ONE PASS*CAN BE USED IN LARGE CAPACITY BOILERS*FLOW THROUGH INDIVIDUAL EVAPORATOR TUBEDEPENDES ON THE TOTAL FLOW,TUBE SIZE ANDFURNACE PERIMETER.*THE STEAM TEMP LEAVING EVAPORATOR VARIESDEPENDING ON THE HEAT ABSORPTION.
VERTICAL WALL MULTI PASS*NOT SUTABLE FOR SLIDIND PR OPERATION.*TO AVOID SEPERATION OF STEAM AT SUB CRITICALPRESSURES THE EVAPORATOR IS KEPTAT SUPERCRITICAL PRESSURE AT ALL LOADS.
VERTICAL TUBE WITH VARIABLE PR. FURNACE WALL PROVIDES ALL THE OPERATIONAL BENEFITSOF THE CURRENTLY POPULER SPRIAL DESIGN WHILE SIGNIFICANTLY REDUCING THE COST & CONSTRUCTION TIME FOR THE FURNACE AND PROVIDING SOME REDUCTION IN PR. DROP.ADVANTAGES ARE- THE TUBES ARE SELF SUPPORTING,TRANSTION HEADERS AT SPRIAL/VERTICAL INTERFACE ARE AVOIDED,ASH HOPPER TUBING GEOMETRY SIMPLIFIED,EASIER FORMING OF CORNERS,REDUCED PRESSURE DROP(AUXILIARY POWER).
SUPER HEATERSINCREASE IN TUBE METAL TEMP.& PR IN FINAL SECTIONSWITH INCREASE IN OUTLET STEAM TEMP MAY CAUSE HIGHTEMP CORROSION AND STEAM SIDE OXIDATION
HIGHER TEMP. & PR. LEAD TO INCREASE IN THICKNESS OF-SHELL OF SEPARATOR,START-UP-SYSTEM COMPONENTS,SHOUTLET HEADER,MAIN STEAM PIPING.HIGHER THICKNESS RESULTS IN LARGER TEMP GRAIDIENTS ACROSS WALLS.
ONCE-THRU BOILER(LOW LOAD CIRCULATION SYSTEM)AT PART LOADS ONCE THRU FLOW NOT ADEQUATE TO COOL THE TUBES,SO TO MAINTAIN REQURIED MASS VELOCITIES BOILER OPERATES ON CIRCULATING MODE(EXCESS FLOW SUPPLIED BY FEED P/P OR A DEDICATED CIRCULATING P/P)
ONCE - THROUGH OPERATING RANGE
LOW LOAD SYSTEM WITH CIRC. PUMP
LOW LOAD SYSTEM WITH HEAT EXCHANGER
LOW LOAD CIRCULATION SYSTEM-THE EXESS FLOW OVER THE ONCE –THRU FLOW SEPARATEDAND RETURNED TO THE CONDENSER THRU HEAT EXCHANGER OR RECIRCULATED BACK TO THE BOILERDIRECTLY BY DEDICATED CIRCULATING PUMP.SEPERATOR:-SEPARATES STEAM AND WATER DURING THE CIRCULATING MODE OPERATION(RUNS DRY DURING ONCE-THRU FLOW MODE (SMALLER IN SIZE COMPARED TO DRUM).
Sliding Pressure Operation
Sliding Pressure Supercritical Operation
Pressure operation mode at boiler outlet
4350
3625
2900
2175
1450
725
0
ps
ig)
1
2
3 1. Constant Pressure Operation
2. Modified Sliding Pressure Operation
3. Pure Sliding Pressure Operation
ONCE-THRU BOILERS BETTER SUITED FOR SLIDING PR MODE*STEAM TEMP CAN BE MAINTAINED OVER WIDER LOAD RANGE UNDER SLIDING PR.*QUICK RESPONSE TO LOAD CHANGES.•*SHORTER START UP TIME.•*HIGHER TOLERANCE TO VARYING COAL QUALITY.•*SUITABLE FOR SUB & SUPER CRITICALPRESSURE.
First Fire to Turbine Synch,
Minute without Bypass System First Fire to Turbine Synch,Minute with Bypass System
Hot Start Up, after 2 hr shutdown 40 30 Warm Start Up, after 8 hr shutdown 65 45 Cold Start Up, after 36 hr shutdown 130 90
Faster Start-up Time with Supercritical Design
First Fire to Turbine Synch,
Minute without Bypass System First Fire to Turbine Synch,Minute with Bypass System
Hot Start Up, after 2 hr shutdown 40 30 Warm Start Up, after 8 hr shutdown 65 - 90 45 - 70 Cold Start Up, after 36 hr shutdown 180 - 260 140 - 220
Once - Thru
Drum
Once -thru BoilerRequirements : Stringent water quality
Different control system compared to drum type
Low load circulation system
Special design to support the spiral furnace wall weight
High pressure drop in pressure parts
Higher design pressure for components from feed pump
to separator
Sliding Pressure Supercritical Design
Spiral Wall System
Spiral Lower Furnace Wall
Vertical Upper Furnace Wall
Transition Header and Furnace Wall Forged Elbows
Spiral Waterwall Tubing
Lateral Heat Flux Profile
Spiral Tube and Vertical Tube Boiler
WATER WALL TUBING
SHSH
Final Eva.
SHSH SH
SH
X
BENSON ALSTOM
Spiral Type Boiler Vertical Type Boiler
1985
19601930
19652000+ ?
1930
Spiral FurnaceWindbox Panel
Spiral Wall Sliding Pressure Supercritical Design
Realising higher steam parameters is dependent, to a great extent on the availability of materials to withstand the demanding service conditions
Requirements of Materials for Supercritical cycles
• Strength to resist rupture at design condition• Fatigue strength to withstand cycling stresses• Ability to resist stress concentrations• Resistance to oxidation,corrosion and erosion• Ability to withstand damaging metallurgical
changes.• Ease of fabrication• Good physical properties to minimise thermal
stresses.
Low Alloy steels
• Can meet live steam temperatures of 540 Deg.C.
• Reduced creep strength at higher temperatures calls for high thickness
• Poor resistance to oxidation at high temperatures
• Good workability & high thermal conductivity
Austenitic steels
• Superior high temp. strength
• High Steam side oxidation
• High temperature corrosion
• Susceptibility to stress corrosion cracking
• Expensive.
New Materials
Optimised to achieve :
• Greater long-term rupture strength
• Improved resistance to high temperature corrosion
• Lower oxide film growth
T91/P91
• Bridged the gap between Low alloy ferritic steels and Austenitic steels
• Higher Creep strength compared to the earlier ferritic steels
• Lower thickness resulting from the higher creep strength advantageous in meeting transient temperature changes
T92/P92
• Development on T91/P91
• Creep rupture strength higher than T91/P91(20 to 30% higher at 600 Deg C)
• Will facilitate raising steam temperature by 20 deg C over T91/P91 capability
T23/T24
• Higher Creep Rupture Strength compared to T22.
• Potential candidate for use in evaporator walls.
Steam temperature range for Materials
MATERIAL LIVE STEAM TEMPERATURE
X20CrMo V12-1 < 565 Deg.C (< 545 Deg.C for SH)
X3CrNiMoN17-13
Esshete 1250
565 Deg.C – 580 Deg.C
TP 347 H FG, SUPER 304 H 580 Deg.C - 600 Deg.C
HR 3C (25 Cr 20 Ni Nb N)
AC 66 (27 Cr 30 Ni Nb Ce)
NF 709 (20 Cr 25 Ni Mo Nb Ti)
Incoclad 671/ Incoloy 800 HT
600 Deg.C - 620 Deg.C
Compound Tubes
Coextruded Tubes
Alloy 617 (NiCr 23 Co 12 Mo)
620 Deg.C – 720 Deg.C
Vertical Wall Furnace Design
SCREEN TUBES
SMOOTH TUBING
FRONT WALLRIFLED TUBING
3.0 ft. max.
1 1/8 in. on 1 5/8 in. centers(FRONT & SIDE WALLS)
SMOOTH TUBINGFROM THIS ELEVATIONALL WALLS
1 1/4 in. on 1 5/8 in. centers(FRONT & SIDE WALLS)
1 1/8 in. on 1 5/8 in. centers(FRONT, REAR & SIDE WALLS)
8.0 ft.
SIDE WALLRIFLEDTUBING
REAR WALLRIFLED TUBING
ARCHRIFLED TUBING
HANGER TUBESSMOOTH TUBING
SA213 T23
.
1-1/8” O.D. Rifled Tubing
1-1/4” O.D. Rifled Tubing
SA213 T12
MATERIAL ASME ALLOY OXIDATION LIMIT
Carbon Steel SA-178C/ D 455°C
SA-210 A-1/ C
Carbon-1/2 Mo SA-209 T-1A 482°C
1 Cr-1/2 Mo SA-213 T-12 552°C
2-1/4 Cr-1 Mo SA-213 T-22 593°C
2-1/4 Cr-1.6W-V-Cb SA-213 T-23 593°C
9 Cr-1 Mo-V SA-213 T91 650°C
9 Cr-2W SA-213 T92 650°C
18 Cr-8 Ni SA-213 TP304H 760°C
18 Cr-10 Ni-Cb SA-213 TP347H 760°C
18 Cr-9 Ni-3Cu-Cb-N SA-213 Super304H 760°C
25 Cr-20 Ni-Cb-N SA-213 HR3C >760°C
Boiler Pressure Part MaterialsTubing Oxidation Temperature Limits
WATER QUALITY FOR SUPER CRITICAL BOILERS
1. EFFECT OF SUPER CRITICAL PARAMETRS:
•IMPROVEMENT IN FUEL EFFIENCY AND HEAT RATE
•DECREASE IN SPECIFIC FUEL CONSUMPTION
&•REDUCTION IN EMISSION
THESE ARE THE DRIVING FACTORS FOR SUPER CRITICAL CYCLE
2.CRITICAL PARAMETERS
• SUPERCRITICAL BOILER OERATE AT PRESSURE >200 BAR AND TEMPERATURE IS >600 deg.C THEREFORE THE CONSTRUCTION OF MATERIALSHOULD HAVE HIGH MECHANICAL STRENGTH AND LOW CREEP.
• AT SUPER CRITICAL CONDITION THE MEDIUM IS JUST A HOMOGENEOUS FLUID RATHER THAN WATER OR STEAM. THEREFORE USUALLY SUPERCRITICAL BOILER ARE OF ONCE THROUGH TYPE.
3.DEFINITION OF SUPERCRITICAL CONDITION
•CRITICAL CONDITION IS THERMODYNAMIC
EXPRESSION DESCRIBING THE STATE OF A
SUBSTANCE BEYOUND WHICH THERE IS NO
CLEAR DISTINCTION BETWEEN THE LIQUID AND GASEOUS PHASE.
4.REQUIREMENT OF WATER QUALITY
•THE CONTENTS OF DISSOLVED AND UNDISSOLVED SOLIDS AND OTHER MATERIAL SHOULD BE PRACTICALLY ZERO.•IN ORDER TO MAINTAIN ABOVE CONDITIONS CONTINUOUS PURIFICATION OF THE RETURN CONDENSATE BY MEANS OF CPU IS MANDETORY
•IT EMPLOY THE USE OF ALL VOLATILE TREATMENT IN ORDER TO MAINTAIN THE LOW TDS IN WATER.
•O.T. IS RECENT METHOD EMPLOYED FOR THE TREATMENT OF WATER/STEAM CYCLE
EFFECT OF CARBONIC ACID ON CORROSION RATE
10 ppm 8 ppm
5. MAKE UP WATER QUALITY
PARAMETERS SAMPLE TARGETFREQUENCYVALUE
------------------------------------------------------------------1. SODIUM , PPB C < 3
2. CONDUCTIVITY C < 0.1 S/CM3. SILICA , PPB C OR S < 10
4. CHLORIDE , PPB C OR S < 3
5. SULPHATE ,PPB D < 3------------------------------------------------------------------
6.CONDENSATE PUMP DISCHARGE
PARAMETERS SAMPLE TARGETFREQUENCY VALUE
---------------------------------------------------------------------------1.SODIUM, PPB C < 3
2.CATION CONDUCTIVITY C < 0.2 S/CM3.OXYGEN, PPB C < 10---------------------------------------------------------------------------
7. C.P.U OUTLET
PARAMETERS SAMPLE TARGETFRQUENCY VALUE
---------------------------------------------------------------------------1. SODIUM, PPB C < 2
2.CAT.CONDUCTIVITY C < 0.1 S/CM3. SILICA, PPB C OR S < 5
4. CHLORIDE, PPB S < 2
5. SULPHATE, PPB S <2(VALUE BASED ON EPRI GUIDELINES)---------------------------------------------------------------------------
8. FEED WATER
PARAMETERS SAMPLE AVT OTFREQUENCY
----------------------------------------------------------------------------------------------------------------------1. CATION CONDUCTIVITY C < 0.15 <0.15 S/CM2.HYDRAZINE, PPB C 10-15 -----
3. pH C 9.0-9.5 7.0-8.5
4. DISSOLVED OXYGEN, PPB C < 5 30-150
5. TOTAL IRON, PPB S < 2 <2
6. SILICA, PPB S <5 <5
7.SODUIM, PPB S < 2 < 2
8.CHLORIDE, PPB S < 2 < 2-----------------------------------------------------------------------------------------------
MAGNETITE FORMATION IN ALL VOLATILE TREATMENTCONTD
OXIDE FORMATION IN OXYGENETED CONDITIONCONTD
Cycle chemistry limit of boiler water during start up, normal operation and shutdown is shownbelow: 2 a-b
I -P T u rb in e L -P T u rb in e
H -P T u r b in eO R P
O R P
O R P
D e a e r a to r
H -P H e a te rs L -P H e a te rs
B o i le r R e h e a te rs
E c o n o m is e r
S u p e rH e a te r
C h e m ic a lfe e d
S te a mS a tu ra te d
O R P
C o n d e n s e r
H o tw e ll
O R P
F ig u re 5
S ta r tu p O p e ra t io n 1 H o u r S h u t D o w n
p H 8 .0 - 8 .5
(A s n e e d e d )N H p p b3
< 0 .1 5
O p p b2
> 9 .0
0 .2C a t io nC o n d u c t iv ityu s /c m
D o t te d l in e s re p re s e n ts o p t im u m s itu a t io n
c h e m is t r y in c lu d in g p a ra m e t r ic l im its s h o w n .
F ig u re 4 : S ta r t u p , o p e ra t io n & s h u t d o w n g u id a n c e fo r o x y g e n a te d
30-1500 00
CONTD.
CONTD.
•THE ALL VOLATILE TREATMENT OFFER GOOD PROCTECTION OF THE SYSTEM IN BOILER. BUT THE RATE OF INCREASE IN PRESSURE DROP ISCONSIDERABLE DUE TO DEPOSITION OF SCALE.THIS WARRANT REGUALR CHEMICAL CLEANING.
•OXYGENETED MODE OF TREATMENT OF FEED WATERRESULTED IN PRACTICALLY NO DEPOSITION OF SCALEIN BOILER SYSTEM.THEREFORE LONGER PERIOD OFOPERATION WITHOUT CLEANING.
9. RATIONALE FOR MONITORING TARGET PARAMETERS
MONITORING OF PARAMETERS ARE NECESSARY BECAUSE:
(a) pH : - CORROSION IS FUNCTION OF pH AND OXYGEN
- ALKALINE CONDITION INCREASES STABILITY OF MAGNETITE IN ALL VOLATILE TREATMENT
- IN O.T. STABILITY OF FeOOH IS IN RANGE OF pH 7-8.5
(b) SODIUM/CHLORIDE/SULPHATE:
- ARE THE MAJOR CORRODANT FOR TURBINE AND PRESSURE PARTS.
(c) DISSOLVEDOXYGEN:
- TO ENSURE THE FUNCTIONING OF DEAREATOR
- TO CONTROL THE AMOUNT OFHYDRAZINE IN FEED WATER.
(d) IRON: - THE CORROSION PRODUCT IN WATER/STEAM CYCLE
- INDICATES THE CORROSIVE CONDITIONS
(e) SP.CONDUCTIVITY/CATION CONDUCTIVITY:
- MOST IMPORTANT PARAMETER INDICATE THE LEVEL OF TREATMENT CHEMICAL AND INDICATION OF IMPURITIES.
Contd.
10. INSTRUMENTATION FOR WATER/STEAM CYCLE
INSTRUMENTATION FOR CORE PARAMETERS
LOCATION PARAMETERS RANGE ALARM-----------------------------------------------------------------------------------1.MAKE UP WATER CONDUCTIVITY 0 - 1 S/CM YES
2.CEP DISCHARGE SP.CONDUCTIVITY 0 - 10 S/CM YESCATION CONDUCTIVITY 0 - 1 S/CM YESSODIUM 0 -1,0 - 100 ppb YESD.O. 0 - 100 ppB YES
3.C.P.U.(OUTLET) AS IN S.No.2CHLORIDE 0 -10 ppb YES
--------------------------------------------------------------------------------------------------------------
4.FEED WATER pH 6 - 11 YESSILICA 0 -20 - 100ppb YESD.O. 0 -10 - 100 - 500ppb YESHYDRAZINE 0 -50 -100Pppb YESCAT.CONDUCTIVITY 0 -1 S/CM YESSP.CONDUCTIVITY 0 -10 S/CM YES
5.BOILER DRUM pH 6 - 11 YES (FOR DRUM TYPE) SILICA 0 -500 ppb YES
SP.CONDUCTIVITY 0 - 10 -20 S/CM YESCAT.CONDUCTIVITY 0 -1 S/CM YES
6.STEAM SP.CONDUCTIVITY 0 - 10 S/CM YES CAT.CONDUCTIVITY 0 -1 S/CM YES SODIUM 0 -10 ppB YES
--------------------------------------------------------------------------------------------------------
LOCATION PARAMETERS RANGE ALARM-----------------------------------------------------------------------------------
CONTD.
THANKS
THANKS