Session VI -Clean Coal Technologies and Electricity-BHEL

7/28/2019 Session VI -Clean Coal Technologies and Electricity-BHEL

1/39


2/39

Bharat Heavy Electricals Limited, Tiruchirappalli

Clean Coal Technologies - September 2008

Hydro

Oil

Pulverised Coal Fludised Bed

Technology

Coal Gas

Steam Power Plants

Boiler + Turbine

Open Cycle

(Gas Turbine)

Combined Cycle

GT + ST

Gas Turbine Based

Power Plants

Thermal Nuclear Non Conventional

Power Generation Options


3/39



Thermal Power -Market Requirements

Low cost of generation

Minimum emission of Pollutants

Suitability for different quality of fuelSuitability for differing modes of operation and grid conditions

High Reliability & Availability

Increased use of IT

Low life cycle cost

Plant Life Extension & Capacity upgrades

Higher size Units

Shorter Delivery time

Power Plant Equipment Manufacturers to respond by employing the right

technologies


4/39



Sustainable, economic power generation thru efficient use oflocally available fuels, in an environmentally friendly fashion.

India - Coal the desirable choice abundantly available, lowcost

Coal Based Generation- Emissions/Pollutants to beminimised

9 Particulates

9 Carbon Dioxide

9 Oxides of Nitrogen

9 Sulfur dioxide

Thermal Power- Choice of fuel


5/39



Indian CoalsChallenges in Boiler Design

Widely varying properties makes equipment selection costly

and sub-optimum

High Ash with high Quartz; highly abrasive Erosion/wear

reduces boiler component life

Low Sulphur content - high electrical resistivity of Ash

Low Heating Value more coal burnt for the same output


6/39



Indian Coals Properties

Range

Ash 25 - 50%

SiO2+ Al2 03 in Ash 80 - 92%

Moisture 8 - 20%

Volatile Matter 18 - 30%

Sulphur 0.2 1.0%

Heating Value (HHV) 2500 - 5000 Kcal/Kg


7/39



Indian coal Vs Average International Coals

Coal/Ash Quantity For 500 MW Unit

INDIAN INT.

COAL COAL

Heat Duty MKcal/h 1080 1080

Fuel Fired MKcal/h 1250 1240

HHV Kcal/Kg 3800 6000

Quantity of Coal t/h 329 207

Average Ash Content % 40 8

Quantity of Ash t/h 132 17

The 8 fold increase in the ash passing thru an Indian coal fired boiler,

warrants incorporation of special design features for high availability.


8/39



Coal Fired Boilers

Design for Eco-friendly Power Generation


9/39



Burn less fuel

9 Improve Plant efficiency

Minimise generation of pollutants

9 Choice of appropriate combustion system, fuels

9 Choice of boiler technologies like Fluidised Bed

combustion

Capture pollutants before leaving the boiler9 Dust Collectors , De-sulfurisation plants, De-Nox plants.

Towards Eco-friendly use of coal .


10/39



2.0

1.5

0.4

0.7

2.0

7.2 %

Turbine Efficiency

Condenser Pressure

Process Optimisation

Steam Parameters

Feed Water Temperature

(FWT, feed heater arrangement)

0.6 Measures on Steam generator

240-

280bar

ev

opora

torpressure

55

50

45

40

35

BHEL CC+ Units

Efficien

cy,

%

20001980 19901960301950 1970

Year

250bar

/550C/

570C

260bar

/580C/

600C

280bar

/600C/

620C

Basis 38 %

175bar

/540C/540C

Efficiency Development ofpower plants in Europe Efficiency Improvement ofSteam power plants

Source: VGB Power Tech 11/2003

Plant Efficiency Improvement


11/39



Plant Efficiency ImprovementBoiler Side Measures

Designing for Supercritical Steam ParametersDesigning for minimum:

RH spray

SH spray (if tapped off before feed heaters)

Flue gas temperature at AH outlet

Excess air at AH outlet

Unburnt Carbon loss

Fuel oil support for coal flame stabilisation

Auxiliary power consumption


12/39



Heat Rate Improvement

Steam Parameters Vs Cycle Efficiency

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]

Incr ease of efficiency [%]

Cycle efficiency with :

175 bar and 538/ 538 C = 38.0 % (BASE)

241 bar and 538/ 566 C = 38.0 x 1.0264 = 39%

Cycle efficiency with :

175 bar and 538/ 538 C = 38.0 % (BASE)

241 bar and 538/ 566 C = 38.0 x 1.0264 = 39%


13/39



Steam Power plant efficiency increases with increase in steam

pressure and temperature.

Power plant Cycles operating above critical pressure (221.2 bar)

are classified as Supercritical cycles

With higher cycle efficiency, the supercritical cycle offers the

advantage of burn less fuel for the same output and lower

emission.

Supercritical Cycles

Lesser Pollutants SOX , NOX & CO2


14/39




Steam Parameters - Global Trends

538 / 566

566 / 593

593 / 593

246

246

246

1991

1995

2000

Japan

545 / 560

580 / 600

285

270

1995

1999Germany

540 / 540580 / 580 / 580

250290

19911997

Denmark

Temp CPressure(bar)YearCountry

255 bar 568/596 Deg C commonly used presentlyUltra super critical units (parameters up to 375 bar & 700 C)with plant efficiency approaching combined cycle plants(50%+) are in development stage with parallel developmentin Materials


15/39




Steam Parameters - Trends in India

96ata

139 ata

179 ata

156 ata

50

100

150

200

250

300

1970 1975 1980 1985 1990 1995 2000 200

Year

SHOS

team

Pressure


16/39


17/39


18/39



Boiler Design forSupercritical Steam Parameters

Subcritical

Drum Type boiler

Supercritical

Once thru Boiler


19/39



Supercritical Boilers

Once thru Boiler technology facilitates adoption ofSupercritical parameters

Higher pressure & temperature stress the boiler componentsat a high level

New materials in use/trial operation to withstand thedemanding service conditions

9 T 91/P91

9 T 92/P92

9 T 23/T24

9 TP347HFG

9 Esshete 1250

Well established, mature

technology

Availability on par withsubcritical boilers


20/39


21/39



Optimum design of furnace, Reheater & Superheater minimises the spray for maintaining rated SH&RH steam

temperature

Optimum design of combustion chamber, pulverising system,firing equipment - minimises the need for high excess air at

boiler outlet & reduces the unburnt carbon in fuel.

Coal specific design of firing equipment reduces the

quantum of fuel oil support for coal flame stabilisation

Plant Efficiency ImprovementBoiler Side Measures


22/39



Plant Efficiency Improvement - Boiler Side Measures

Auxiliary Power Consumption Reduction

Use of High efficiency Boiler Auxiliaries

Axial Reaction fans

Bowl Mills

ESP with Intelligent operating systems

Use of High Efficiency Drives like VFD

Reduction in the duty of the auxiliaries by system design

optimisation


23/39



NOx generation reduced by:

Use of Fluidised bed combustion Technology

Use of Low NOx Burners/ firing systems

Use of techniques like air staging/fuel staging/

re-burning

Separate Over Fire Air (SOFA) system

Capturing the NOx in DeNOX plants located at tail end of theboiler

Towards Eco-friendly use of coal


24/39



Fluidised Bed Combustion Boilers

Technologies in vogue:

Bubbling Fluidised Bed Combustion (BFBC)

Circulating Fluidised Bed Combustion (CFBC)

9 Ideally suited for Low Grade fuels, Lignite, Pet coke

9 Does not need coal pulverisation system

9 Keeps SOx & NOx emissions low


25/39



Integrated Gasification Combined Cycle(IGCC)

The emerging technology to utilise coal with the maximumefficiency

6.2 MWe capacity coal

based combined cycledemonstration facility atBHEL, Trichy

BHEL is now setting up a125 MW plant jointlywith a customer

Bh t H El t i l Li it d Ti hi lli


26/39



Integrated Gasification Combined Cycle

(IGCC)

Air

HRSG

Combustor

SynGas

Gasifier

Coal

Air


27/39

Bharat Hea Electricals Limited Tir chirappalli


28/39



Fuel evaluation test facility

Bharat Heavy Electricals Limited Tiruchirappalli


29/39



SFBTF of 10 Mkcal/h capacity is used for coalburner/nozzle development, evaluation of flame stability,combustion efficiency & turndown.

Solid Fuel Burning Test Facility



30/39



Existing Power PlantsPerformance Improvement

Existing Power PlantsPerformance Improvement


31/39



32/39



Availability & Reliability improved byAdoption of appropriate Operation & maintenance practices special focus on tube failure prevention, maintaining

proper combustion regimeUse of early warning systems:

9 Tube leak detection system, Operator alarms

9 Sophisticated Controls & Instrumentation

9 Vibration monitoring systems for high speed equipment

9 Equipment trip provisions

Operator TrainingRenovation of Boilers

Use of well proven equipment & design practices,Redundancy for Critical equipment

Results in lesser number of plant outages, start ups

Minimises fuel oil consumption

Results in lesser number of plant outages, start ups

Minimises fuel oil consumption



33/39



Boiler Operating Modes for

Improved Efficiency

Base Load

Cycling

Two-shift

Sliding pressure

Trip to house load

Designing to operate in different modes :- Improves part-load efficiency- Less number of plant start ups- Quicker plant start-ups Minimises fuel oil consumption



34/39



IT for Power Plant Applications

Increasingly used for :

Performance Optimisation

Residual Life Assessment

Emission analysis

Operator Training

Expert systems & Root cause analysis

Maintenance



35/39

y , pp


IT for Boiler PerformanceImprovement

Introduction of smart systems:

Performance Analysis, Diagnostics, Optimisation(PADO)System - provides operator guidance for optimisedperformance

Smart wall blowing system improves heat rate, minimisessteam erosion

Emission analysis

Expert systems & Root cause analysis



36/39

y , pp


Performance Improvement

Optimised OperationImproved Plant Efficiency by maintaining :

9 Minimum spray in Superheater/Reheater- use temperature control mechanisms

9 Rated steam parameters

9 Optimised combustion regime

9 Rated pulverised coal fineness

9 Minimum/zero oil support for coal flame stabilisation

Minimum Auxiliary Power consumption:

9 Optimum number of mills in service

9 Prevent air ingress into boiler

Minimise Down time:

9 Boiler maintenance techniques plan for shortest time

9 Reduce plant start up time

Minimise Emissions:

9 Maintain appropriate combustion air regimes

9 Flue gas conditioning for reduced emissions



37/39


Regain of lost capacity / Capacity augmentation

Reduced forced outages

Lesser maintenance requirement and time

Enhanced operational Efficiency

Improved Boiler Availability & reliabilty

Performance improvements

State-of-the-art upgrades

Reduced support fuel requirement

Enhanced life for Wear prone components

Reduced emissions

Renovation & Modernisation of boilers



38/39


Future Outlook

Coal & Lignite will continue to be main fuels for

Power Plants for some more decades

Economics will decide the optimum power plant cycle

parameters to be adopted.

Increasing focus on minimising Emissions, improving

efficiencies, fuel flexibility, enhanced Availability &

Reliability

Pulverized coal firing will continue to be the mainstay,

till other technologies mature into commercially viable

options

Boiler technology will continue the advance towards

increased efficiencies.



39/39


BharatHeavy ElectricalsLimitedTiruchirappalli

Documents

Session VI -Clean Coal Technologies and Electricity-BHEL