1958 - 2008

GOLDEN JUBILEE YEAR

Dr. Gopal P. SinhaCentral Mech. Engg. Res. Institute

Durgapur, West Bengal

OPTIMIZING BOILER DESIGNS FOR

INDIGENOUS COAL

97500719005450050700

78037 81492115705

157107

Mar '01 Mar '03 Mar '07 Mar ''12

PeakRequirement(MW)

EnergyRequirement(MU)

INDIAN POWER SECTOR

Capacity to increase to 2,12,000 MW

By 2012, India’s peak demand would be 157,000 MW with energy requirement of 97,500 MU

Capacity in MW (1,32,329)

PRESENT ELECTRICITY SCENARIOInstalled Electricity Generation Capacity

(1st April 2007)

Note: Coal-based captive generation capacity of 8000 MW is

not included.

Absolute Value

Renewable (6%)Nuclear (3%)

Hydro (26%) Thermal (65%)

Thermal Capacity in MW(86015)

Oil (0.9%) Gas (10.3%)

Coal (53.7%)

PF

•DEMAND IS GROWING @ 7-8 %

•PER CAPITA CONSUMPTION 15 Kwh/yr 350Kwh/yr

•PROJECTED TO INCREASE TO 750 Kwh/yr BY 2012

•PEAK DEMAND TO REACH 157,000 MW BY 2012

100,000 MW ADDITIONAL CAPACITY REQUIRED

•COAL WILL CONTINUE TO DOMINATE POWER

GENERATION SCENARIO

POWER SECTOR SCENARIO

FUEL OPTIONS

Various Fuel Options for Power Generation are:

18000 – 20000 KJ/KgBiomass

10000 – 16000 toe*Uranium and Thorium

42000 - 47000 KJ/KgPetroleum

35000 – 40000 KJ/KgNatural Gas

15000 – 27000 KJ/KgLignite

15000 – 27000 KJ/KgCoal

Calorific ValuesVarious Fuels

*1 toe = 42 GJ

COAL - the main stay of India’s electricity supply

• Present generation capacity: 1,35,000 MW

• Projected ( 2032 ) 8,00,000 MW

• About 50 to 55 % of generation capacity will be coal based.

• Coal consumption is projected to increase 5 fold in 25 years.

• Estimated reserve: 255 billion tonnes

• Out of this 98 billion tonnes is of proven category.

< 0.5Phosphorus

0.3-8.3Sulphur

3-60Ash

Trace-5MgO

Trace-12CaO

2-20Fe2O3

15-36Al2O3

45-63SiO2

3-43Moisture

1-36V.M

38-60F.C

Wt % RangeIndian Coal

CONSTITUENT

-

0.3-3.8

5-19

Trace - 3

Trace - 12

3 - 27

18 - 29

30 - 61

2-37

3-37

29-81

Wt % RangeImported Coal

INDIAN VIS-À-VIS IMPORTED COAL CHARACTERISTICS

CONSUMPTION & SUPPLY OF COAL IN 2005-06

• Consumption 448.72 million tonnes (333.15) million tonnes

• Supply– Indigenous production 401.72 million tonnes

(307.16) million tonnes– Imports 41.67 million tonnes

(17.78) million tonnesTotal 443.39 million tonnes

Gap (domestic supply) 47.0 million tonnes (26.0 million tonnes)

Figures in brackets pertain to coal used in power generation

TO IMPROVE CONVERSION (EFFICIENCY)

• COST OF GENERATION

• GREEN HOUSE GASES EMISSION

• PARTICULATE EMISSION

• CLEAN COAL TECHNOLOGIES

FUTURE THERMAL GENERATION TECHNOLOGIES NEED

DIFFERENT VARIANTS OF FLUIDIZED BED COMBUSTORS

265 Mwe CFBC Power Plant

CFB BOILERSAtmospheric Circulating Fluidized Bed Combustion (CFBC) Boiler

•Solids lifted from bed, rise, return to bed

•Steam generation in convection section

•Benefits: more economical, better space utilization and efficient combustion

(Thermax Babcock & Wilcox Ltd, 2001)

• Low NOX (combustion temp. 850°C.)

• High heat transfer to boiler tubing, allowing a compact boiler

• High flexibility for using different grades of coal (including with high sulphur ash content)

• Possibility to burn low grade fuels, such as biomass, waste substances and to perform “co-combustion” of different types of fuels;

• Use of crushed fuel with relatively large particles, leading to reduced milling costs.

ADVANTAGE OF FLUIDIZED BED COMBUSTION POWER PLANTS

BIOMASS: POTENTIAL & USAGE, IN INDIA

35 MW273 MW

16, 000 MW3, 000 MW

Biomass Poweri. Gasifiersii.Co-generation

33.0 Million120 MillionImproved biomass chulhas (cook-stoves)

3.10 Million12 MillionBiogas plants

Usage (till Dec 2000)

Potential (Approx.)

Sources/Technologies

COMPARISON PF AND CFB BOILERS

Ash upto 70%

Ash upto45%

Fuel flexibility

<6<0.0001Coal size (mm)

80-90smallSOx capture (%)

50-200400-600Nox (ppm)

4039Generation efficiency (%)

95-9995-99Combustion Efficiency(%)

CFBPF

30

20

10

0800 900 1000 1100 1200

COAL PRICE Vs. IRR

COAL PRICE ( Rs/ ton)

CFB

PC

IRR

(%

)

INTERNAL RATE OF RETURN Vs. FUEL COST

•Engineering Design

•Cost Effectiveness

•Regulatory Compactness Codes and Standards

•Fuel

•Site Selection Distribution Cost

Future Demand

FACTORS AFFECTING BOILER DESIGN

Competitive Generation (Rs/Gcal)

CapacityReliabilityAvailability

ChemestryCalorific ValueCost / G.cal

Furnace Chamber Design

•Combustion Requirement

•Fuel Properties

•Heat Transfer Efficiency

•Metal Temperature

•Surface Area Exposed

•Emission Standards

Other Design Considerations

Superheater

Re-Heaters

Hot and Cold Gas Air Heaters

Economizer

Safety

BOILER DESIGN

SPECIAL FEATURES OF CFB BOILERS

•Fuel Flexibility

•High Combustion

•Efficient Sulphur Removal

•Low NOX Emission

•Smaller Furnace Cross-Section

•Common Material Used

•Cold start (6-7 Hours)

•Hot start (30-45 Miniutes)

•Turn Down (on load demand: 25%)

CHALLENGE TO OVERCOME

• EROSION & CORROSION

• WATERWALL

• SUPERHEATER

• OMEGA

• AIR NOZZLE

• CYCLONE TARGET

• EXPANSION JOINT

• BULL NOSE (for regulating circulation)

• VORTEX FINDER

• DEPOSIT ON TUBES /REFRACTORY & ECONOMISER

PROVEN REMEDIAL ACTION

• DESIGN MODIFICATION

• PROPER REFRACTORY(TYPE &

LINING)

• SECRIFICIAL/ HARD COATING

• BAFFLE PLATE & SEALED COVER

CONCLUSIONS• POWER REQUIREMENT TO DOUBLE IN NEXT 5-10 YEARS.

•COAL WILL CONTINUE TO DOMINATE THE POWER GENERATION SCENARIIO.

• DETERIORATING COAL QUALITY WILL BUILD UP PRESSURE FOR IMPORT, LEADING TO HIGH COST OF POWER.

• ENVIRONMENT NORMS AND CARBON CREDIT WILL MAKE G.H.G.E. A PROHIBITIVE AFFAIR.

SUBSTITUTE/ CONVERT PF WITH CFB TO FLEXIBLE COAL INPUT AND UPTO 20% BIOMASS FEED

•The Solution:

Candidate materials for turbine in Japan

Larger CFBC Installations World-wide