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