2.Final Energy Efficiency

7/29/2019 2.Final Energy Efficiency

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PRESENTATION

ON

EFFICIENCY IMPRVEMENT IN COALFIRED THERMAL POWER STATION


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WHY ENERGY EFFICIENCY IS IMPORTANT ?

Depleting fossil fuel

Optimum plant utilization

Global warming Designated consumer

Generate more energy with same fuel


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EFFICIENCY IMPROVEMENT CAN

GIVE YOU

For an average increase of 1 % in theEfficiency would result in:-

Coal savings of approx. 11 million tons per annum

worth Rs.13,000 Million

CO2 reduction about 13.5 million tons per annum

Lower generation cost per kWh as more efficient

the unit works, the more economical it is.


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MAJOR CAUSE OF

INEFFICENCY IN POWER PLANT

High Flue gas exit Temp

Excessive amount of excess air(O2)

Poor Mill/Burners performance causinghigh unburnt carbon in fly and bottom ash

Poor insulation

Poor house Keeping

Poor instrumentation and automation


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MAJOR CAUSE OF INEFFICENCY IN

POWER PLANT(Cont---)

Not running the units on design parameter

Heaters not in service or poorperformance of regenerative system

Poor condenser vacuum

Excessive DM water consumption-passing and leakages

Use of Reheat spray to control ReheatTemperature

Poor Cylinder Efficiency of turbine


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HOW TO ACHIEVE ENERGY

EFFICIENCY ?

Adopt state of the art technologies

Adopt cutting edge technologies

Review & Re-engineering of the existingsystems

Bench Marking

Energy Auditing


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CAN WE IMPROVE EFFICIENCY?

-Yes ,provided we shed the myths and

believe in applying result oriented

efforts.

-Work out to identify & quantify the cost

of hidden losses.

-Bring in requisite operational behavioral

change.


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SOME OF THE MYTHS

High PLF & availability translates into

Optimum Efficiency

Heat rate is the responsibility of Efficiency

Management Group at Stations Equipment maintenance to be taken-up

based on periodic overhaul schedule

Boiler performance degradations has norelation to Turbine Cycle performance


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Some of the Myths contd

Design heat rate is the best achievable heat rate.

Efficiency tests are the same as performance

guarantee test.

Heat rate improvement requires large investment.

Results follow immediately after testing is

completed.

Heat rate is the responsibility of Energy &Efficiency Management Group (EEMG) atStations.

Station instruments are accurate for monitoring

heat rate parameters.


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contd

Design is not the best achievableperformance

Predicted performance based on Turbine Heat BalanceDiagrams and Boiler Efficiency at different loads

Design is based on specific ambient conditions thatvary throughout the year

Actual initial performance could be different from designor changes might have been made to plant

Current performance to be compared to an achievableexpected value to establish efficiency gaps


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SYNERGIZE OPERATION

OF UNIT

- Need to clearly understand the relation between

performance & fuel ,operation and design

parameters.

- -Operational behavior and performance- Impacts of operating efficiency of Boiler, Turbine

and their auxiliaries on Net Unit Heat Rate,

- Maximum Achievable Load, Maintenance,&- Availability.


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SOME CRITICAL FACTORS AFFECTING

BOILER PERFORMANCE

-Fuel;-Heating Value, Moisture Contents, AshComposition, Ash Contents,& Volatile Matter.

-Operational Parameter:-Level of Excess Air,&operating Condition of Burner Tilt Mechanism.

-Design:-Heating input per plan area, Height ofBoiler, Platens & pendants heat transfer Surfaces,

Burner & wind Box design.


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BEHAVIOURAL IMPACTS

-Low heat value results in over firing of fuel causing more heatavailability for super heater and re-heater thus more attemprationspray requirement. Hence increase in THR, overloading of ashhandling system, fans and increased soot blowing

-Moisture content increase causes increase in heat transfer to S.H,and R.H. Hence again increase in attempration spray and THR.

-Ash composition and contents increases damage to pressure partssurfaces because of melting behavior of low fusion ash temperature ofblended coal in particular.

-In consistency in fired fuel characteristics results in variation inexcess air requirement thereby increasing stack loss and hence boilerefficiency reduction, overloading of ID Fan and ultimately unit loadlimitation.

-High heat value causes excessive radiant heat transfer to water wallsthereby leaving lesser heat for super heater and re-heater.

Contd.


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IMPACTS contd-Normally excess air ranges from 15% to 30% of stoichiometric air.

-High O2 % and presence of CO at ID Fan outlet are indicator of airin leakages and improper combustion in furnace.

-Poorly effective damper control also is the cause of higher SEC offans both primary and secondary.

-The quality and purity of feed water and make up water is alsorequired to be maintained in a meticulous way by limiting blow downlosses to nearly 1% and by checking the passing and leakages ofvalves. However, maximum 3% of flow can be taken as make up forthese causes including soot blowing requirements.

-Soot blowing is dependent on ash contents and is unit specific.Intelligently devised soot blowing can result in saving the fuel.

Contd.


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IMPACTS contd

-Cascading effects on efficiency, loading and

availability because of following systems and

equipments performance also needed to be

looked into. The systems are:-Fuel receiving, preparation and handling systems.

Pulverizing system

Air Heater

Fans

Electrostatic Precipitator

Fly ash handling system

Bottom ash handling system

Waste disposal system


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PERFORMANCE IMPACTS ON STEAM

CYCLE , UNIT HEAT RATE,&OUT PUT

Various design & operating parameters of

a unit are responsible for its cycle

performance, heat rate,& out put.


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CRITICAL FACTORS AFFECTING

CYCLE PERFORMANCE

1. Re-heater & its system pressure drop

2. Extraction line pressure drop

3. Make up

4. Turbine exhaust pressure

5. Air preheat

6. Condensate sub-cooling

7. S/H & R/H spray flows

8. Wet Bulb Temp.

9. Top Heaters out of service

10. H.P. heater drain pump

11. Type of BFP drives& method of flow control


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RH & ITS SYSTEM PRESSURE DROP.

- Every one 1% decrease in drop can

improve THR and output by 0.1% & 0.3%

respectively.

- Normally designed for pressure drop

equivalent to 10% of HP exhaust pressure


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EXTRACTION LINE PRESSURE

DROP

Permissible pressure drop between stage

pressure & Shell pressure is maximum

6%.

For every 2% increase in this pressure

drop, THR would be poorer by 0.09%.


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Cyclemake up.

- Acceptable value of make up water is 3%

to offset cycle water losses.

- For every 1% increase in make up 0.4%

increase in THR & 0.2% reduction on

output is there.


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EXHAUST PRESSURE

Increase & decrease in exhaust pressure

do affect the THR.

Though no valid thumb rule has been

devised so far, however last stage bladedesign & exhaust area of turbine do affect

the impact of changing exhaust pressure.


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AIR PRE-HEAT.

Air preheat of combustion air before entry to

regenerative air heater is done with either with

steam coil air pre - heater or hot water pre

heating coil to maintain AVERAGE COLD &TEMPERATURE (ACET) to escape dew point

temperature complications.

Condensate retrieval is necessary to avoid

deterioration to THR depending upon unit loadand combustion pre heating duty.


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CONDENSATE SUB-COOLING

For 30% total flow and 2.5 deg C sub-

cooling ,an increase of 0.001% in THR can

be there for every subsequent 10%

increase in flow.


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R.H & S.H. SPRAY FLOW

. Spray water whether drawn from BFP or

after the final heater, it is always less the

generative and less productive as well.

Every 1% spray flow, correction need to

be done in THR & load computed from the

curvessupplied with the machine.


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TOP HEATER OUT OF SERVICE.

Extraction steam flow meant for top heater

is required to pass through turbine thereby

increasing the output. But at the same

time final feed water tamp. Is loweredresulting in poor THR.


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HPH DRAIN PUMP

Retrieval of drip from HPH 6 & 7 is

important for load even around 50%.

Drain pump when deployed can improve

the THR by 2.5kCal/kwh.


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BFP DRIVE SELECTION

. Though four options are available for

choosing the suitable BFP drive and

control concepts.

. Adoption of turbine driven BFP to suit the

design requirements can improve THR by

0.56% and output by 0.58%.


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PERFORMANCE MONITORING

-Analyze the poor efficiency areas from previous record .

-Zero down to specific system and then to component.

-Carry out performance/diagnostic study as suggested in

the Auditing Manual & operating manual. -Devise a unit specific efficiency control sheet for few

terminal conditions (Act vs Des).

-Monitor once per shift to know the operating efficiency

and check any deterioration.


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Thank You

Documents

2.Final Energy Efficiency