Over View of Super Critcal

8/13/2019 Over View of Super Critcal

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Over view of Super Critical

SUPERCRTICAL TECHNOLOGY OVER VIEW

Presentation ByAJAY SHUKLADGM PMI


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Drivers For Ultra MegaPower Projects LARGE CAPACITY ADDITION PLANNED OVER

NEXT DECADE IN 11TH PLAN BEYOND PACE OF THERMAL CAPACITY ADDITION TO

INCREASE FROM ~ 5000 MW/Yr TO ~ 10,000 MW/Yr

ADVANCED PROVEN TECHNOLOGY WITH HIGHEFFICIENCY FOR

OPTIMAL USE OF RESOURCES HIGHER

EFFICIENCY

ECOFRIENDLY POWER GENERATION ECONOMY OF SCALE

OPERATIONAL FLEXIBILITY( Faster Start Up, Load

Cycling)


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CONTENTS Importance of Efficiency

What is Thermal cycle Efficiency

How to Increase Cycle efficiency

What is Super critical Boiler

Advantages & Disadvantages of Super critical Boiler

The SG 3 x 660 MW Boiler package

Comparison with 500 MW SG package


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IMPORTANCE OF EFFICIENCY

The cost of operating the Plant of 3 x 660 MW, one percentagepoint below the design point, will incur additional fuel cost ofRs. 20 Crores in a year.

The indirect costs for Maintenance, APC, Ash Dyke land etc.

will give additional burden of Rs. 2 Crores in a year. The environment will suffer on account of GHGs.

The life time loss is Rs. 660 Crores for efficiency lower by onepercentage point .

At Sipat, we gain an efficiency of 2.5 percentage point byadopting super critical technology in 1980 MW station, thussaving Rs. 1650 Crores in its life time.


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Trend in unit sizes & Cycle parameters

2008568/596256800 MW

2008568/596256660 MW

1985540/568179500 MW

1991540/540156250 MW1972(37.5%)540/540137 / 156200 / 210 MW

1966(35.7%)540/540139110 / 120 MW

1965(30.5%)5409660 / 70 MW

Year ofIntroduction

SHO/RHOTemperature

(Deg.C)

SHO Pressure(kg/cm2(a))

Unit Size


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QUEST FOR EFFICIENCY IMPROVEMENT

Since the time thermal power stations have been engineered,

there is a quest for efficiency improvement.

And supercritical parameters (Press. above 225Kg/cm2 andtemperature above 374.15 C) is an effort in that direction.

The selected supercritical parameters for Sipat Boiler are :

Pressure : 256 kg/cm2

Temperature : 540 C SH and 568C RH


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UNDERSTANDING THE THERMAL CYCLE

EFFICIENCY

Let us refresh our knowledge of thermodynamics laws

First Law states that the total energy of a system in all its formsremain constant.

Second Law states that it is impossible to construct an enginewhose sole purpose is to convert all the heat supplied to it intoequivalent amount of work. In other words, it is impossible toconvert all heat energy supplied to a system to work.


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EFFICIENCY & CARNOTS ENGINE

= work output from a system

heat input to the system

Because of 2nd Law of Thermodynamics # 100%

Hence, for some heat, which is not converted to work, heat sink

is necessary.

Thus = Q1 Q2Q1


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CARNOT ENGINE (FRENCH ENGINEER SODI CARNOT 1824)

1-2 - Isothermal Expansion at T1K

2-3 - Adiabatic Expansion upto T2K

3-4 - Isothermal Compression at T2K 4-1 - Adiabatic Expansion upto T1K

For Carnot Cycle = 1 - T2

T1T1 = Temp. of heat source

whereT2 = Temp. of heat sink

Carnot Cycle gives maximum possible thermal efficiency which

can be obtained between any two given temperature limits.

12

3

T

S

T244


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CARNOT ENGINE (CARNOT ENGINE (FRENCH ENGINEER SODI CARNOTFRENCH ENGINEER SODI CARNOT

1824)1824)

1-2 - Isothermal Expansion at T1K


3-4 - Isothermal Compression at T2K


For Carnot Cycle = 1 - T2T1T1 = Temp. of heat source

whereT2 = Temp. of heat sink

Carnot Cycle gives maximum possible thermalefficiency which can be obtained between any two

given temperature limits.

12

3

T

S

T244


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CONCLUSION ON CARNOTS CYCLE EFFICIENCY

No engine working on cyclic process is more efficient than

Carnots engine when working between same limits oftemperature.

All efforts should be made to come closer to Carnots cycle as

far as possible to achieve maximum efficiency out of any

thermal cycle.


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eff=(1-T2/T1)

T1

T2


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THERMAL EFFICIENCY OF RANKINE CYCLE

Q1-Q2 W Useful work = ------- = --- = ----------------

Q1 Q Heat suppliedRejected Heat

= 1 - --------------------Useful Heat

T1 - T2 T2 Carnot = -------- = 1 - ---

T1 T1

To achieve more efficiency T2 should be as low as possible and T1

should be as high as possible


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METHODS OF INCREASING RANKINE CYCLE

EFFICIENCY

Raising supply temperature by super heating.

Increasing the inlet temperature will raise the heat supply tothe cycle more than the heat rejection.

Raising inlet pressure of steam :

Increasing the pressure will mean increase in saturationtemperature at which steam evaporates thus increasing theaverage inlet temperature (T1)


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(Contd..)

Dropping the final pressure (or temperature) at which heat is

rejected.

Regenerative Heating : Heating the feed water pumped toBoiler by bleeding steam from turbine.

Reheat Cycle : Reheating of steam in boiler after it has already

expanded in HP Turbine will avoid moisture formation in LTTurbine. Also, more heat content of steam before IP Turbine,

will improve efficiency.


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WHY SUPERCRITICAL PRESSURE

The purpose of having high inlet steam pressure for turbine

has already been discussed in this presentation.

A Boiler operating at a pressure above critical point is

called SUPERCRITICAL BOILER

A point where boiling water and dry saturated lines meet sothat associated latent heat is zero, this point is called Critical

Point and occurs at 225 kg/cm2 (abs) 374.15 C

temperature.


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CRITICAL CONDITION

Definition

CRITICAL is a thermodynamic expressiondescribing the state of a substance beyond whichthere is no clear distinction between the liquid andgaseous phase.

The critical pressure & temperature for water are Pressure = 225.56 Kg / cm2

Temperature = 374.15 C


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WHAT IS SUPER CRITICAL

T

S

P1

Pcr

P2

Cycle of Super critical boiler

operating above critical pressure


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SC Steam generator

Boiler Steam Pressure

above the critical point Critical Point

221 bar, 374c

S

T

1

2

3

4

Entropy

Temperature

1-2 Feed Water Pumping Process2-

3 Heat addition in the Feed

Water Heaters & Boiler

3-4 Expansion in HP Turbine4-5 Reheating in Boiler5-

6

Expansion in IP & LP Turbine

6-1 Heat rejection in Condenser

5

6


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256K

g/cm

2

0

100

200

300

400

500

600

SUPER CRITICAL

BOILER CYCLE

WITH SH, RH &

Regenerationof SIPAT 3 x 660 MW

540C 568C

Steam flow :2225 T/Hr

Steam temp : 540 c

Steam Pres : 256 kg/cm2RH pre : 51.6 Kg/cm2

RH Temp : 568c

Feed water Temp : 291c

ENTROPY

TEMP


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SUPERCRITICAL BOILER

Supercritical pressure boiler has no drum and heat absorbing

surface being, in effect, one continuous tube, hence called once

through Supercritical pressure boilers.

The water in boiler is pressurized by Boiler Feed Pump, sensible

heat is added in feed heaters, economizer and furnace tubes, until

water attains saturation temperature and flashes instantaneouslyto dry saturated steam and super heating commences.


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SH

DRUM

ECOHTRBFP

W/WALL

DOWN COMER

RISERS

Natural CirculationBoiler

W/WALL

BF

P

HTR ECO

SH

SEPERATOR

ONCE THROUGH SYSTEM


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SH

DRUM

ECOHTRBFP

W/WALL

DOWN COMER

RISERS

Natural CirculationBoiler

W/WALL

BF

P

HTR ECO

SH

SEPERATOR

ONCE THROUGH SYSTEM


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Types of boilers

Drum type

Once-through type


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Division of heating surfaces


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Drum type boiler

Steam generation takes place in furnace water walls

Fixed evaporation end point - the drum

Steam -water separation takes place in the drum

Separated water mixed with incoming feed water


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Drum type boiler

Natural Circulation Boiler Circulation thru water walls by

thermo-siphon effect

Controlled Circulation Boiler

At higher operating pressures

just below critical pressure levels,

thermo-siphon effect supplemented

by pumps


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500 MW Boiler Typical Arrangement


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540C, 255 Ksc


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HPT

IPTLPTC

O

N

D

E

N

S

E

R

FEED WATER

FRS

S

T

O

R

A

G

E

T

A

N

K

SEPARATOR

BWRP

Spiralwa

terwall

s

MS LINEHRH LINE

VERTICAL WW

ECO I/L

ECO

JUNCTIONHDR

ECO HGR O/LHDR

FUR LOWER HDR

FUR ROOF I/L

HDR

DIV PANELS SH PLATEN SH

FINAL RH

FINAL SH

LTRH

ECONOMISER

290C, 302 KSC

411C,

277Ksc411C,

275 Ksc

492C, 260 Ksc

540 C, 255 Ksc

305C,

49K

sc

457C, 49 Ksc

568C, 47

Ksc

G LPT


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Steam generation process


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Boiler-Cycle Thermodynamics

3208

2865

1800

Pres s

ure

Ps

ia

Enthalpy BTU/lb


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Over view of Super CriticalWell suited for < 2100 psi cycles

Natural Circulation System


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Over view of Super CriticalOptimum solution for reliable high pressure subcritical operation

Controlled Circulation System


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CONTROLLED CIRCULATION (Vs) ONCETHRU

CC OT

B il i h E


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Boiler with Evaporator system


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Once-thru BoilerMajor differences from Drum type boiler :

Evaporator system

Low load circulation system

Separator


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Once -thru Boiler

Evaporator system :

Formed by a number of parallel tubes

Tubes spirally wound around the furnace to reduce

number of tubes and to increase the mass flow rate

thru the tubes

Small tube diameter

Arrangement ensures high mass velocity thru thetubes

mp e ra n


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mp e ra n

Discharge System

To Condenser

WW

ECO

HPH

BFP

DeaeratorC

WL

C

HWL

SH

Separator

Flash

Tank

S U S i h R i l i


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Start-Up System with Recirculation

Added Cost vs.

Simplified Drain

System

Reduced Heat andWater Loss During

Start-Up

HPH

BFP

Deaerator

C

C

WW

ECO

To Condenser

C

HWL

SH

Start-Up SystemRecirculation Pump in Main Bypass Line

Separa

tor

Flash

Tank


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ADVANTAGES

OF

SUPER CRITICAL BOILER


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SUPERCRITICALTHERMAL CYCLE ADVANTAGES

(1)

Improvements in plant efficiency by more than

2 % Decrease in Coal Consumption

Reduction in Green House gases.

Overall reduction in Auxiliary Power

consumption.

Reduction in requirement of Ash dyke Land &Consumptive water.

SUPERCRITICAL ADVANTAGES (2)


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( )

Sliding pressure operation because of Once through

system . Even distribution of heat due to spiral wall

arrangement leading to less Boiler tube failure,

thereby improving system continuity and availability

of the station.

Low thermal stress in Turbine . The startup time is less for boiler.


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SUPERCRITICAL DISADVANTAGES

Higher power consumption of BFP

Higher feed water quality required.

More complex supporting and framing in Boiler

due to Spiral Wall tubes.

Slight higher capital cost.


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HISTORY & EVOLUTION

HISTORY


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HISTORY

.

DEVELOPED IN USA IN -1950S

INTRODUCED IN JAPAN IN -1960S

MORE THAN 110 UNITS IN OPERATION IN

JAPAN

SLIDING PRESSURE INTRODUCED IN JAPAN-

1980S

INITIAL PROBLEMS


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INITIAL PROBLEMS

SLAGGING PROBLEMS DUE TO INADEQUATE

FURNACE SIZE.

FAILURE OF FURNACE TUBES DUE TO

INAPPROPRIATE FLOW CIRCUITS. BYPASS OPERATION DURING STARTUP

STARTUP VALVES FAILURE / EROSION DUE TO LARGE

PRESSURE DIFFERENCE.

COMPARISION OF THERMAL CYCLE


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COMPARISION OF THERMAL CYCLE

EFFICIENCIES.

OPEN CYCLE EFFICIENCY - 14.68 %

WITH CONDENSER - 26.2 %

WITH SUPER HEAT 30.75 TO 34.15 %

WITH REHEAT - 34.2 TO 36.6 %

WITH SUPER CRITICAL PARAMETERS-

36.0 TO 39.15 %

INCREASE IN PLANT EFFICIENCY by SUPER


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INCREASE IN PLANT EFFICIENCY by SUPER

CRITICAL PARAMETERS

1.5

0.90.6

3.2

167 bar

538/538c250 bar

538/538250 bar

540/560c

250 bar

580/600c

250bar

566/566

c

1

2

3

4

5

6

.

Efficiency Increase

REQUIREMENTS OF SUPERCRITICAL


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REQUIREMENTS OF SUPERCRITICAL

TECHNOLOGY

REQUIREMENT OF HIGH STRENGTH MATERIALS.

OXYGENATED FEED WATER TREATMENT (OWT)

ADVANCED DIGITAL BASED CONTROL SYSTEMS

HIGHLY AUTOMATED OPERATION.

LOW LOAD CIRCULATION SYSTEM


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Boiler load %

40

100

W WFlow

%

40


60 80100



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Boiler load %

40

100

W WFlow

%

40


60 80100


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BOILER PARAMETERS

STEAM PARAMETERS UNDER BMCR CONDITION


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291.9FEED WATER TEMP AT ECONOMISER INLET8

565STEAM TEMP AT IP TURBINE INLET DEGC7

568STEAM TEMP AT REHEATER OUTLET DEG C

306.3STEAM TEMP AT HP TURBINE EXHAUST DEG C6

51.6STEAM PRESSURE AT HP TURBINE EXHAUST KG/CM25

1754STEAM FLOW TO REHEATER ( T/HR)8

1742.6STEAM FLOW TO REHEATER T/HR7

540TEMPERATURE AT SUPERHEATER OUTLET (DEG C)5

247PRESSURE AT HP TURBINE INLET KG/CM2 (ABS)4

256PRESSURE AT SUPER HEATER OUTLET KG/CM2 (ABS)3

2225STEAM FLOW AT SUPER HEATER OUTLET (T/HR)1

DESCRIPTIONSL

COMPARISION OF 660 MW Vs 500 MW BOILER


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255.2291.40CFEED WATER TEMP

46.151.17KG/CM2RH STEAM PRESS INLET

5405680CRH STEAM TEMP OUTLET

338.5303.70CRH STEAM TEMP INLET

1397.41742T/HRRH STEAM FLOW

5405400CSH STEAM TEMP

179256KG/CM2SH STEAM PR

16252225T/HRS/H STEAM FLOW

500660unitDescription


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Over View of Super Critcal

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