combustion optimization bharat heavy electricals limited tiruchirapalli committed to make a better...

Combustion Optimization

Bharat Heavy Electricals Limited TIRUCHIRAPALLI

Committed to make a better world FIELD ENGINEERING SERVICES (FB)


Committed to making a better world FIELD ENGINEERING SERVICES (FB)

Emerging Market Requirements

1. Higher Availability & Reliability

2. Highest Plant efficiency

3. Lower Heat Rate

4. Minimum Auxiliary Power Consumption

5. Ability to operate under adverse grid conditions/fluctuation in demand

6. Minimum emission of Pollutants





Measures to improve Plant Efficiency

Boiler side:

1. Minimum flue gas temperature at AH outlet

2. Minimum excess air at AH outlet

3. Minimum un-burnt Carbon loss

4. Minimum RH spray

5. Minimum SH spray

6. Reduced Auxiliary Power Consumption





Measures to improve Plant Efficiency …

Turbine side measures

1. Higher steam parameters ( MS Pressure & SHO/RHO Steam Temp).

2. Adoption of double reheat cycle

3. Increasing feed water temperature with

Enhanced Regenerative feed heating

4. Increase in condenser vacuum





2a. Boiler - Various Losses

By Gas Dry Gas Loss

Loss due to Moisture in Gas

Due to Fuel Moisture

Due to moisture formed by H2 in fuel

Due to air moisture

By Ash Unburnt carbon Loss

Sensible heat loss in Fly ash

Sensible heat loss in Bottom ash

Other Loss Carbon monoxide Loss

Radiation Loss

Heat loss through Mill rejects





No Loss Factor

1 Dry Gas Loss Flue Gas Temperature, Excess Air & Fuel

2 Unburnt Carbon Loss In Ash

Ash in Fuel & Unburnt Carbon In Fly / Bottom Ash

3 Mill Reject Loss Reject Rate & CV Of Reject

4 Due to Moisture formed from Hydrogen

Hydrogen Content In Fuel & Flue Gas Temperature

5 Due to Fuel Moisture Moisture Content In Fuel & Flue Gas Temperature

6 Due to Air Moisture Humidity Of Combustion Air, Excess Air Level & Flue Gas Temperature

7 Radiation & Convection Loss

Insulation Of Boiler

8 Sensible Heat Loss In Ash Ash Temperature

Factors Influencing Various Losses





Ensure consistent mill fineness - +50, - 200

Good burner maintenance

Proper secondary air adjustment - SADC

Reduce PA air to the minimum possible – min PA velocity variation

Cut out oil support at higher loads where coal flame is stable as oil preferentially deplete o2 in the area and reduces ‘o2 ‘ for coal particles to burn

Check coal property and tune combustion

Keep boiler heat transfer surface clean so that losses can be reduced thus reducing the coal input

Methods to reduce unburnt carbon loss





Methods to reduce dry gas loss

Correct excess air High mill outlet temp. Better combustion – combustion tuning Arrest air ingress Air heater performance – leakage , proper

elements Cleanliness of the heat transfer surfaces





Optimization of Boiler Efficiency

1 HHV All Losses

2 FG APH out Temp Dry gas, Sensible heat in Ash, H2, Fuel and Air Moisture Loss

3 Excess air Dry gas, Unburnt & Air Moisture Loss

4 Fuel Moisture Fuel Moisture Loss

5 Air Moisture Air Moisture Loss

6 H2 in Fuel H2 Loss

7 Mill reject rate or GCV

Mill reject Loss

The Major parameters to be looked into for Better Efficiency:1. FG Temp

2. Excess air Level

3. Mill reject rate and

4. Unburnt carbon in ash

Control / Optimization of other parameters (i.e GCV, H2, Fuel moisture and Air Moisture) are not possible.





Major reasons for increase in APC

Operation of unit with higher excess air Air heater leakage Higher PA fan outlet pressure High mill fineness, more no. of mills Air ingress into boiler Pluggage in line / ducting Partialy blocked APH





Sources of air ingress

Furnace roof Expansion joints Air heaters Ducts Esp hoppers Peep holes Manholes Furnace bottom





Factors affecting APC - a summary

FACTORS AFFECTING AUXILIARY POWER

ID FANSAH LEAKGAS TEMPERATUREDUCT LEAKAGESEXCESS AIRLOAD/ PLANT HEAT RATEDRAUGHT LOSS

AH CHOKINGFD FANS

AH LEAKWIND BOX PR.EXCESS AIRLOAD/ PLANT HEAT RATEPRESSURE LOSS

AH CHOKINGSCAPH CHOKING

PA FANSAH LEAKAGEPA HEADER PR.MILL AIR FLOWPRESSURE LOSS

AH CHOKINGMILL

COAL QTY.GCVLOAD/ PLANT HEAT RATE

COALMOISTUREHGI

COAL FINENESSMILL CONDITION





Capacity Reduction in a BoilerFuel input

Low cv coalMilling capacity

Grinding capacityDrying capacityCarrying capacityDrive capacity

Draught systemID fan limitations

Pressure drops highAH chokingChimney back pressure high

High volumeAH leakagesDuct leakagesHigh gas temperatures

Worn out impellers

Metal temperatures highHigh spray requirementsFouling of surfaces



CASE STUDIES



Problem: Heavy clinkering build up upto S-panel /Bottom of burner

reported from many boilers Investigations: Poor mill fineness (50% through 200 mesh) Non-working of SADC as per control Poor coal quality – usage of ground stock Non- working of wall blowers Improper evacuation of bottom ash

Solution:After taking above corrective actions no further problems faced.

Case Study-1



Problem: Frequent choking of coal pipe Investigations: Clean air flow test Checking of orifice Calibration of coal flow/air flow -check Foreign material entrapped in classifier

( cloth)

Solution: Problem resolved after removal of foreign material from classifier.

Case Study-2





THANK YOU

combustion optimization bharat heavy electricals limited tiruchirapalli committed to make a better...

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