Supercritical Steam Generators for Cleaner Environment

Bharat Heavy Electricals Limited, Tiruchirapalli

PowerPowerPowerPower----Gen India, 2012Gen India, 2012Gen India, 2012Gen India, 2012 BHELs Role in Cleaner Environment



Contents

BHEL Steam Generators

Design Features of Supercritical Once Thro Boilers

Major Systems

Startup System

Pressure part Arrangement

Firing System

High Temperature Materials

Major Differences between Supercritical and Subcritical Boilers



BHEL Utility Units - A SummaryUnit Rating, MW

No. MW No. MW

30 4 120 4 120

60 16 960 16 960

67.5 9 607.5 8 540

70 14 980 9 630

80 14 1120 3 240

100 6 600 6 600

110 39 4290 39 4290

120 31 3720 27 3240

125 7 875 1 125

130 2 260 2 260

150 17 2550 0 0

200 24 4800 20 4000

210 116 24360 114 23940

250 58 14500 34 8500

270 34 9180 0 0

300 1 300 0 0

500 82 41000 54 27000

525 6 3150 2 1050

600 22 13200 0 0

660 12 7920 0 0

700 1 700 0 0

800 4 3200 0 0

TOTAL 519 138393 339 75495

Contracted Commissioned

62 % Total

Installed

Capacity of

India is

Contributed by

BHEL Utility

Sets



Unit Contracted Commissioned

VU 40 46 45

VU 40 S 15 15

VU 60 38 19

MU 3 3

VP 23 16

V2R 17 17

HRSG 177 121

AFBC 72 59

CFBC 28 10

Others 28 28

Total 447 333

BHEL Industrial Units - A Summary



After supplying more than 950 boilers,

BHEL is currently adopting

Advanced Steam Cycles to Improve the

Environmental & Economic Performance of

Indias Power Generation



Once Through Supercritical Technology for

Higher Unit Ratings 660 MW to 1000 MW

BHEL under license from Alstom offers Once through supercritical

technology to Indian power utilities with the following benefits

Increased efficiency

Lower Fuel consumption

Lower emission levels of CO2 NOX SOX

Lower operating costs

Greater operational flexibility

These benefits are possible because of the higher steam pressures

and temperatures which are the hallmark of the technology



Reference List of Supercritical Boilers

NTPC / BARH 2 x 660MW

APPDCL / Krishnapatnam 2 x 800 MW

PPGCL / BARA 3 x 660 MW

RPCL / Yermaras 2 x 800 MW

RPCL / Edlapur 1 x 800 MW

KPCL / Bellary 1 x 700 MW

LPGCL/Lalithpur- BHL 3 x 660 MW

DB Power / Singrauli 2 x 660 MW

NTPC / Mouda St. II 2 x 660 MW

18 Boilers

Contracted



Design Features of 660 MW

Supercritical Boilers for

Indian Coal Fired Power Stations



Salient Features of Boiler

Pulverised coal fired

Once through, evaporator suitable for

variable pressure operation

Single reheat

Tilting Tangential firing System

Dry Bottom

Balanced draft furnace

Side mill layout



Dry Bottom

Balanced draft furnace

High performance Bowl Mills

Two Nos. of Axial FD Fans

Two Nos. of Axial PA Fans

Two Nos. of Axial ID Fans

ESP to meet reqd. outlet concentration

Salient Features of Boiler (Contd.)



Boiler Parameters

Description Unit 660 MW (Supercritical)

500 MW

(Sub critical)

Boiler Parameters - BMCR BMCR

SH steam flow t/h 2120 1625

SHO pressure kg/cm2(a) 256 179

SHO/RHO temp. oC 568/596 540/540

Feed water temp. oC 294 254



Description

(Source/Type)Unit Design Coal Worst Coal Best Coal

Proximate Analysis

Fixed Carbon % 26.00 23.00 32.00

Volatile matter % 19.00 18.00 22.00

Moisture % 15.00 17.00 12.00

Ash % 40.00 42.00 34.00

Total % 100 100 100

HHV kcal/kg 3300 2800 4000

Ultimate Analysis

Carbon % 31.37 28.93 40.08

Hydrogen % 3.40 2.40 3.50

Sulphur % 0.40 0.5 0.36

Nitrogen % 1.5 1.45 1.78

Oxygen(difference) % 7.75 7.26 8.03

Moisture % 15.0 17.0 12.0

Ash % 40.0 42.0 34.0

Carbonates + Phosphorous % 0.58 0.46 0.25

Hard Grove Index 55 50 60

Fuel Analysis - Coal



General Arrangement of Steam Generator Elevation



General Arrangement of Steam Generator Plan



Plan Area Loading kCal/h/m2 4.75x106

EPRS Loading kCal/h/m2 190,000

Volumetric Loading kCal/h/m2 106,920

Furnace Heat Loadings



NTPC / BARH 2 x 660 MW

CoalFuel

568 / 596 oC Temperature

255/54.65 kg/cm2 (g)Pressure

2120/1708.2 t/h.Steam Flow

Customer scopeDust Collector

2 Nos. Axial ReactionID Fan

2 Nos. Axial ReactionPA Fan

2 Nos. Axial ReactionFD Fan

4 Nos. Airheater

9 Nos. Bowl MillMill

Major Auxiliaries

Parameters at SHO / RHO

BARH II 2 x 660 MWProject

National Thermal Power CorporationCustomer



Customer Prayagraj Power Generation Company Limited

Project PRAYAGRAJ STPP, PHASE-I, 3x660 MW, BARA


Steam Flow 2095.4/1706.9 t/h.

Pressure 255/54.33 kg/cm2 (g)

Temperature 568 / 596 oC

Fuel Coal

Major Auxiliaries

Mill 7 Nos. Bowl Mill

Airheater 2 Nos. Tri-Sector AHs

FD Fan 2 Nos. Axial Reaction

PA Fan 2 Nos. Axial Reaction

ID Fan 2 Nos. Axial Reaction

Dust Collector Customer Scope

PPGCL / PRAYAGRAJ STPP, 3x660 MW, BARA



DB POWER (MP) LIMITED / Gorgi DBP - 2 x 660 MW

Customer DB POWER (Madhya Pradesh) Ltd.

ProjectGorgi DBP(MP)L 2x660 MW STPP, DEOSAR,

Singrauli


Steam Flow 2120.0/1696.1 t/h.



Fuel Coal

Major Auxiliaries






Dust Collector 4 Nos



CustomerLalitpur Power Generation Company

Limited

Project Lalitpur Super Critical TPP, 3x660 MW


Steam Flow 2110/1697.8 t/h.



Fuel Coal

Major Auxiliaries






Dust Collector 4 Nos.

LPGCL / LALITPUR SUPERCRITICAL TPP, 3 x 660 MW



Supercritical Boilers- Major Systems



SC Steam generator Boiler Steam Pressure above the critical point Critical Point

221 bar, 374 c

S

T

1

2

3

4

Entropy

T

e

m

p

e

r

a

t

u

r

e

1 - 2 Feed Water Pumping Process 2 - 3 Heat addition in the Feed

Water Heaters & Boiler 3 - 4 Expansion in HP Turbine 4 - 5 Reheating in Boiler 5 - 6 Expansion in IP & LP Turbine 6 - 1 Heat rejection in Condenser

5

6



Supercritical Boilers

Supercritical pressure boiler has no drum and heat absorbing

surface being, in effect, one continuous tube, in which the water &

steam generated in the furnace water walls passes through only

once 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 instantaneously

to dry saturated steam and super heating commences.



The Concept

The mass flow rate thru all heat transfer circuits from

Eco. inlet to SH outlet is kept same except at low loads

wherein recirculation is resorted to protect the water

wall system



Increased mass flow through spiral waterwall tubing, or improved heat transfer through rifled vertical wall tubing.

No fixed evaporator end point

No thick wall components

Features

Once Through Boiler Flow Diagram

Evaporator

Water separator

Feedwater

Economizer

FW-Pump

Live steam

Superheater



Once through Supercritical Boilers

Major differences from Drum type boiler :

Evaporator system

Low load Recirculation system

Separator



STEAM TO TURBINESTEAM TO TURBINE

SHSH

DRUM

SEPERATING

VESSEL

E

V

A

P

O

R

A

T

O

R

E

V

A

P

O

R

A

T

O

R

ECO.

ECO.

(LOW LOAD &

CIRCULATION PUMP

START-UP)

F

E

E

D

F

E

E

D

CIRCULATION TYPE

ASSISTED

Circulation Systems

Drum Type Once-through



Once -through Operating Range



Once -thru Boiler

Requirements :

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



Features of Once Through Steam Generator

To ensure adequate mass flow rates through water wall,

spirally wound water wall tubes are used.

Start-up and low load system up to 30-40% BMCR required.

Feed water quality requirements are very stringent.

Can be designed for both sub-critical and super-critical

pressures.

Ideally suited for sliding pressure operation due to the absence

of thick walled components.



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 the tubes



Reduced number of tubes with pitch.

Increased mass flow.

Mass flow rate can be selected by number of tubes.

Features

Spiral Tube Arrangement



Once -thru Boiler - Furnace Wall



Spiral Water wall Tubing

Lateral Heat Flux Profile



Sliding Pressure Supercritical Design

Spiral Wall Windbox



Supercritical boiler Separated Over Fire Air (SOFA) assySupercritical boiler Separated Over Fire Air (SOFA) assySupercritical boiler Separated Over Fire Air (SOFA) assySupercritical boiler Separated Over Fire Air (SOFA) assy

Complex Burner Panel using 41.3 mm tubesComplex Burner Panel using 41.3 mm tubesComplex Burner Panel using 41.3 mm tubesComplex Burner Panel using 41.3 mm tubes

2020 complex multi2020 complex multi2020 complex multi2020 complex multi----plane tube bendsplane tube bendsplane tube bendsplane tube bends

12 bends in each 5.4 m length12 bends in each 5.4 m length12 bends in each 5.4 m length12 bends in each 5.4 m length

Fabrication of T22 tubes with Gr 12 scalloped platesFabrication of T22 tubes with Gr 12 scalloped platesFabrication of T22 tubes with Gr 12 scalloped platesFabrication of T22 tubes with Gr 12 scalloped plates

SOFA burner SOFA burner SOFA burner SOFA burner

panelpanelpanelpanel



SPIRAL WALL SUPPORT

Support Fingers

Spiral to Vertical Transition Area - Load TransferSliding Pressure Supercritical Design



Supercritical boiler Spiral Furnace Wall AssemblySupercritical boiler Spiral Furnace Wall AssemblySupercritical boiler Spiral Furnace Wall AssemblySupercritical boiler Spiral Furnace Wall Assembly

115 membrane wall panels using 41.3 mm tubes115 membrane wall panels using 41.3 mm tubes115 membrane wall panels using 41.3 mm tubes115 membrane wall panels using 41.3 mm tubes

5000 multi5000 multi5000 multi5000 multi----plane tube bends for wall openingsplane tube bends for wall openingsplane tube bends for wall openingsplane tube bends for wall openings

4500 tube butt joints for spiral4500 tube butt joints for spiral4500 tube butt joints for spiral4500 tube butt joints for spiral----vertical transitionvertical transitionvertical transitionvertical transition



Furnace Wall Designs

Spiral Wall Configuration Vertical Wall Configuration



Supercritical Boiler with Vertical wallUnit Mwe: 750

Max. Continuous Rating: 2522 t/h

SH Outlet Press: 262 bar

SH Outlet Temp: 568C

RH Outlet Temp: 596 C

Fuel: Sub-bituminous



SCREEN TUBESSMOOTH TUBING

FRONT WALLRIFLED TUBING

SMOOTH TUBINGFROM THIS ELEVATION

ALL WALLS

SIDE WALLRIFLED TUBING

REAR WALLRIFLED TUBING

ARCHRIFLED TUBING

HANGER TUBESSMOOTH TUBING

FRONT WALLRIFLED TUBING SIDE WALLRIFLED TUBING

Vertical Wall Sliding Pressure Supercritical Design



Vertical Furnace Wall Design

Vertical tube furnace walls will provide all the operational benefits

of the currently popular spiral design while significantly reducing

the cost and construction time for the furnace and providing some

reduction in pressure drop.



Vertical Wall Design - Advantages

The tubes are self supporting.

Transition headers at spiral/vertical interface are avoided.

Ash hopper tubing geometry simplified

Corners are easier to form

Reduced pressure drop, auxiliary power



Spiral Vs. Vertical Wall Comparison

Spiral Furnace System Applicable for all

size units

Benefits from averaging of lateral heat

absorption variation (each tube forms

a part of each furnace wall)

Simplified inlet header arrangement

Large number of operating units

Use of smooth bore tubing throughout

entire furnace wall system

One material utilized throughout

entire waterwall system

No individual tube orifices Less

maintenance & pluggage potential

Vertical Furnace Wall System Limited to

larger capacity units .

Less complicated windbox openings

Traditional furnace water wall support

system

Elimination of intermediate furnace wall

transition header

Less welding in the lower furnace wall

system

Easier to identify and repair tubes leaks

Lower water wall system pressure drop

thereby reducing required feed pump

power



Vertical Wall Wind box

Straight Tubes

Only a Few Bends at the Top and Bottom



Supercritical Boilers- Start-up and

Low load recirculation Systems



Simplified drain discharge system



Low load system with circulating pump



Start-up System



Separator Separator Separator Separator

vessel for vessel for vessel for vessel for

supercritical supercritical supercritical supercritical

steam generatorsteam generatorsteam generatorsteam generator



Overview of Firing Systems

Close-CoupledOverfire AirClose-CoupledOverfire Air

CFS Air Nozzle TipsCFS Air Nozzle Tips

Flame AttachmentCoal Nozzle TipFlame AttachmentCoal Nozzle Tip

NOx < 0.18 0.30 kg/Mkcal*NOx < 0.18 0.30 kg/Mkcal*Furnace DiagonalFurnace Diagonal

Separated Overfire AirSeparated Overfire Air

HP Pulverizerwith Dynamic Classifier

HP Pulverizerwith Dynamic Classifier

*NOx at furnace outlet



Wind Box arrangement



Upper SOFA on Walls

Lower SOFAin Corners

Tilt +/-30o

Yaw +/-20o

Plan View for SOFA arrangement



Pressure Parts Arrangement



Materials

in 660 MW

(Typical)



Pressure part660 MW

OTSC (Supercritical)

500 MW

(Sub-critical)

Drum Not applicable SA 299 (Carbon Steel)

Vertical Separator SA 335 P91 Not applicable

Water Walls SA 213 T22 SA 210 Gr C

Economiser SA 210 Gr C Sa 210 Gr C

SH T91, TP 347H T11/T22/T91/ TP 347H

RHT12/T23/T91/TP347H/

Super 304HT22, T91, TP 347H

Material Comparison



Air and gas Path



Salient Differences between Supercritical

and subcritical Boilers



Description 660 MW (Supercritical)

600/500 MW(Subcritical)

Circulation System

-Startup low load recirculation

System water walls

Once-Through

Vertical separator with One no.

startup Re-circulation pump

Spiral walls with Plain tubing

Controlled Circulation with

3x50%Boiler water circulating

pumps

Not applicable

Vertical walls with rifled tubing

SH / RH / ECONOMISER

system

- Pressure parts arrangement

- 2 stages of SH with SH platen

located above furnace and final

SH in horizontal pass.

- 2 stages of RH with low

temperature RH located in

second pass and RH finish

pendant located in horizontal

pass

- Single stage economizer

located in second pass below

low temperature RH.

- 3 stages of SH with low temp.

SH located in horizontal pass,

SH panel and SH platen located

above furnace.

- Single stage RH located in

horizontal pass

-Single stage economizer

located in second pass below

low temperature SH.

Gas velocity in pressure part,

m/s

10 10

Firing System Tilting tangential firing with

wind box located in four

corners of the furnace

Tilting tangential firing with

wind box located in four

corners of the furnace

Draft System Balanced draft Balanced draft



Description 660 MW (Supercritical)

600/500 MW(Subcritical)

Pulverisers 9 nos.HP bowl mill

9/10 nos. bowl mill

Airheaters 4 nos Bi-sector air heater system with 2 nos. primary&2 nos. secondary.

2 nos. Regenerative Trisector air heater system or 4 nos Bi-sector air heater system with 2 nos. primary&2 nos. secondary.

Fans Axial FD, Axial PA and Axial ID-2nos each

2 Axial FD, 2 Axial PA and 2 Radial ID with VFD

ESP outlet dust concentration

18 mg/Nm3 18 mg/Nm3



Higher pressure, higher SHO/RHO temperature and higher

feed water temperature has been adopted for improving the

cycle efficiency.

Drum has been eliminated and vertical separator with start-

up recirculation system is used for loads below 40% BMCR.

Two stage SH and two stage RH has been adopted.

Axial ID fans are used in place of radial ID with VFD.



SUMMARY

OTSC plants offer better cycle efficiency

Proven technologies leading to lower GHG emissions and lesser

fuel burnt

BHEL has the technology for offering 660/700/800 MW

supercritical units



Gearing-up to introduce Advanced Ultra

supercritical boilers (AUSC)

AUSC Boilers (300 ata, 700 C / 700 C) will

be developed based on OTSC technology

Test Facility (400 bar, 700 Deg. C) installed

and tests are on to collect critical design

data

BHEL is one among the Five MNCs to have

this facility

Member of the National Technology

Mission program to install AUSC plant by

2017

Advanced Ultra Super Critical Plants

Documents

Supercritical Steam Generators for Cleaner Environment