660 mw super critical unit operation experiences

ADANI POWER MAHARASHTRA LIMITED5 X 660MW

SUPER CRITICAL UNITOPERATION EXPERIENCES

Presented by BHASKARPRASAD

What is Supercritical What is Supercritical Technology ?Technology ?

The critical point in steam water cycle is nothing but the thermodynamic state where there is no clear distinction between the Water and Steam phase in the Rankine Cycle

Water reaches to this state at a

pressure above 22.1 Mpa.

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Rankine Cycle Supercritical

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Diff. Between Subcritical & Supercritical units

Major changes are boiler area, water chemistry and steam turbine metallurgy.

Subcritical Unit The power plant Rankine cycle operating

pressure below 18 MPa in the evaporator part of the boiler

Cycle medium is non homogeneous mixture of water and steam in the boiler. The boiler cycle is known as subcritical.

The steam needs to be separated from water, using steam drum.

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Controlled CirculationControlled Circulation Once Through SystemOnce Through SystemV/sV/s

Supercritical Boiler Features There are two design features utilized in boiler water

wall design for once through supercritical boilers

The spiral tube furnace arrangement:

The modern supercritical once through furnace water wall are exposed to the higher heat flux of all heat absorbing surface

Intense radiant heat from the furnace firing zone or fireball. Spiral tube wall design (wrapped around the unit) helps to

increase the adequate mass flow of steam/water mixture through each tube

Mass flow improves heat transfer between the tube metal and the fluid inside, so the tube metal is sufficiently cooled despite of the high heat flux.

Boiler pressure parts weight is lower than the subcritical boiler

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Supercritical Boiler FeaturesThe vertical tube furnace arrangement:

The vertical tube designs are used for larger units with internal ribbed tube to enhance heat transfer.

Suitable for making high-pressure boiler to improve the efficiency by preventing the forming of steel film

Improved materials helps the maximum steam cycle performance at the furnace wall exit, superheated and reheated outlets tubes

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RIBBED TUBES RIBBED TUBES

•Generate swirl flow

•Centrifugal action

•Result water force towards the wall

•Expensive --- Slight increase in P

•Generate swirl flow

•Centrifugal action

•Result water force towards the wall

•Expensive --- Slight increase in P

LTRH LTRH

Inlet HDRInlet HDR

FRH FRH

Inlet HDRInlet HDR

LTRH LTRH

Outlet HDROutlet HDR

FRH FRH

Outlet HDROutlet HDR

Emergency DSHEmergency DSH

Micro flow Micro flow DSHDSH

Eco Eco Inlet Inlet HeaderHeader

Eco Header Eco Header Under Under LTRHLTRH

Eco Header Eco Header

Under LTSHUnder LTSH

Eco HDR or Eco HDR or Hanger (F&R) Hanger (F&R) Under LTSHUnder LTSH

BandBand

Eco Eco Hanger Hanger

OutletOutlet

Water Water wall wall lower lower headerheader

Spiral Spiral Water Water wallswalls

Transition Transition Intermediate Intermediate Header & Header & WallsWalls

Vertical Vertical Walls & Walls & Upper Upper HeaderHeader

SeparatorsSeparators

Roof I/HRoof I/H Back pass Back pass F&R WallF&R Wall

Back pass Back pass O HDRO HDR

Back pass Back pass side walls & side walls & Upper HDRUpper HDR

Divisional Divisional Upper I/HUpper I/H

Divisional Divisional Wall, Spacer Wall, Spacer tube & Lower tube & Lower HDRHDR

LTSHLTSH

I/O I/O HDRHDR

Platen Platen SHSH

FSHFSH

I/O I/O HDRHDR

StorageStorage

Tank & Tank & BCPBCP

Back pass extended Back pass extended side wallsside walls

Butterfly panelButterfly panel

HPTIPTLPTC

ONDENSER

FEED WATER

FRS

STORAGE TANK

SEPARATOR

BWRP

Spiral

water

walls

MS LINE

HRH LINE

VERTICAL WW

ECO I/L

ECO JUNCTION HDR

ECO HGR O/L HDR

FUR LOWER HDR

FUR ROOF I/L HDR

DIV PANELS SH PLATEN SH

FINAL RH

FINAL SH

LTRH

ECONOMISER

292°C,

411°C,

411°C,

492°C,

571°C, 254 Bar

329°

C,

45K

sc

569°C,

G

LPT

FIREBALL

BURNER

Theoratical ArrangementTangential Corner Fired Unit

PF FIRING OPTIONS - COMPARISON

BURNER

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Benefits of Supercritical Unit

Supercritical technology provides electricity generation at lower operating fuel cost (15-20 % reduction)

Higher unit cycle efficiency (40-44%) Superior environmental Performance (15 -20 % CO2 reduction)

Operating flexibility – Sliding pressure capability without loss of cycle efficiency

Increased availability, reliability, fuel flexibility and faster load

response capability

Lower water losses because no continuous blow down.

Reduced auxiliary power consumption

Environmental Benefits

Reduced carbon dioxide (CO2) and other greenhouse gas (GHG) emissions by 25 %, Provides carbon credit mainly due to less fuel consumption.

Emissions may be reduced by using

fuel through efficient generating electricity within the Rankine cycle.

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Boiler equipment

The capacity for APML project is 5x660MW. The boiler was designed and manufactured by Shanghai Boiler Works Limited. It is the full suspended Π—type, once-through boiler with the supercritical pressure, primary intermediate reheating, single furnace balanced ventilation, semi-enclosed arrangement, dry bottom, all-steel framework.

The model is SG-2111/25.4 － M986. 2111-Steam flow in TPH.2111-Steam flow in TPH. 25.4-Steam operating pressure in Mpa.25.4-Steam operating pressure in Mpa. M986-Boiler serial numberM986-Boiler serial number..

Super heater :16080m2Super heater :16080m2 Re heater :24402m2Re heater :24402m2 WW high temp :41290m2WW high temp :41290m2 WW intermediate:30054m2WW intermediate:30054m2 WW low temp :13095m2WW low temp :13095m2

sumsum :84439m2 :84439m2

Storage tanks & separators : 25.5m3Storage tanks & separators : 25.5m3 Water wall : 67m3Water wall : 67m3 Economizer : 138m3Economizer : 138m3 Super Heaters : 221m3Super Heaters : 221m3 Re Heaters : 370m3Re Heaters : 370m3

SumSum : 824m3 : 824m3

BoilerBoiler

The boiler start system is equipped with water circulating pump.

The steam separation takes place inside separator at initial condition.

Two separators for start-up and one separator water storage tank are engineered for each boiler.

The separators and the water storage tanks are set up on upper part of the boiler front vertically.

BoilerBoiler The main steam temperature is

controlled by water coal ratio and spray desuperheater.

The normal reheater steam temperature is controlled by dampers in second pass.

RH Spray desuperheating devices are provided for normal & emergency .

BoilerBoiler

Pulverizing system uses cold primary fan positive pressure direct blowing system. Eight HP1103 intermediate-speed bowl coal mills, Six mills in operation and Two on standby under TMCR & seven service, one standby under BMCR, are provided. Each coal mill is consistent with a layer of burner.

The system has two axial forced primary draft fans with moving blade pitch adjustment and two centrifugal seal air fans.

110-Bowl Dia. 3-No of rollers.

PERFORMANCE DATAPERFORMANCE DATA

FUEL DATAFUEL DATA

Gross as Received 3927 kcal/kg

Total Moisture 10 %

Ash Content 37 %

Volatile Matter 27.6 %

Fixed Carbon 25.4 %

Boiler Efficiency 87.19 % (GCV Basis)

Gross as Received 3927 kcal/kg

Total Moisture 10 %

Ash Content 37 %

Volatile Matter 27.6 %

Fixed Carbon 25.4 %

Boiler Efficiency 87.19 % (GCV Basis)

Boiler

The boiler draft fan system is equipped with two axial forced draft fans with moving blade pitch adjustment, two axial Induced draft fans and two tri-sector rotary air preheaters.

ESP

The ESP is equipped with double pass, 10 X 4,10 X 4 Two sets fields.

ESP having total 80 X 2 =160 hoppers.

Electrostatic precipitator （ efficiency≥99.80）

Boiler

Boiler deslagging system adopts Bottom ash clinker grinder. The wet process is adopted as the slurry removal method.

Ash system adopts a dense phase pneumatic conveying system with positive pressure for ash handling.

Unit-operation

The Turbine can be run with a fixed pressure OR sliding pressure mode.

When the boiler is running with low load or starting, sliding pressure is recommended to obtain a higher economic efficiency.

Boiler specificationBoiler specificationNO.NO. ItemItem SpecificationSpecification UnitUnit

11 modelmodel SG2111/25.4SG2111/25.4 －－ M986M986

22 modemode once-through boiler with supercritical pressureonce-through boiler with supercritical pressure

33 Superheated steam flowSuperheated steam flow 21112111 t/ht/h

44 Superheater outlet pressure Superheater outlet pressure 25.425.4 MPaMPa

55 Superheater outlet temperatureSuperheater outlet temperature 569569 ℃℃

66 Reheated steam flowReheated steam flow 1749.11749.1 t/ht/h

77 Reheater inlet pressureReheater inlet pressure 4.734.73 MPaMPa

88 Reheater outlet pressureReheater outlet pressure 4.494.49 MPaMPa

99 Reheater inlet temperatureReheater inlet temperature 324324 ℃℃

1010 Reheater outlet temperatureReheater outlet temperature 569569 ℃℃

Feedwater pressureFeedwater pressure 28.828.8 MPa.gMPa.g

1111 Feedwater temperatureFeedwater temperature 280280 ℃℃

1212 Separator’s steam temperature Separator’s steam temperature 421421 ℃℃

1313 Air preheater’s outlet air temperature, uncorrectedAir preheater’s outlet air temperature, uncorrectedAfter correctingAfter correcting

153.3153.3 ℃℃

147.2147.2 ℃℃

1414 Calculating thermal efficiency of boilerCalculating thermal efficiency of boiler 87.19%87.19% （（ BMCRBMCR ））

1515 Guarantee thermal efficiency of boilerGuarantee thermal efficiency of boiler 87.2%87.2% （（ BRLBRL ））

1616 Pulverizing typePulverizing type Cold primary fan positive pressure direct blowing Cold primary fan positive pressure direct blowing systemsystem

1717 Burner typeBurner type Corner-mounted tangential circle combustion , dry Corner-mounted tangential circle combustion , dry ash extractionash extraction

1818 Draft typeDraft type balanced ventilationbalanced ventilation

1919 Design fuelDesign fuel Indian coalIndian coal

2020 Check fuelCheck fuel Indian coalIndian coal

2121 100% BMCR Coal consumption (Design)100% BMCR Coal consumption (Design) 390.37390.37t/ht/h

100% BMCR Coal consumption (Worst)100% BMCR Coal consumption (Worst)466.90466.90 t/ht/h

100% BMCR Coal consumption (Best Coal)100% BMCR Coal consumption (Best Coal)337.80337.80 t/ht/h

2222 Fuel oil for startup and ignitionFuel oil for startup and ignition light diesel oil and heavy diesel oillight diesel oil and heavy diesel oil

2323 Superheated steam temperature adjustmentSuperheated steam temperature adjustment Ratio of coal and water, secondary spray Ratio of coal and water, secondary spray desuperheatingdesuperheating

2424 Reheated steam temperature adjustmentReheated steam temperature adjustment Burner Tilt controlling, Rear flue gas damper, Burner Tilt controlling, Rear flue gas damper, primary spray desuperheatingprimary spray desuperheating

Important parameters to control:

1. Water / coal ratio – 7:1

2. OHDR- 20 to 30

3. Maintaining Pressure at SH and RH - 25.4 & 4.45

4. Effect of Excess air

5. Water Chemistry

6. Tube metal temperatures

Difference in Operation 1. Boiler initial filling. 2. BCP filling and operation 3. Pressure and Temp rise rate w.r.t Metal

temps. 4. Change in Boiler operation phases in Unit

operation (Wet to Dry state, Subcritical once through to

super critical once through) 5. Boiler tube failures - identification 6. Chemistry parameters – methods of chemical

treatment 7. Unit startup and Shutdown(dry to wet opn) 8. Additional Protections for Boiler