Welcome

Combustion Optimization

Emerging Market Requirements Higher Availability & Reliability Highest Plant efficiency Lower Heat Rate Minimum Auxiliary Power Consumption Ability to operate under adverse grid conditions/fluctuation in demand Minimum emission of Pollutants

Measures to improve Plant Efficiency Boiler side: Minimum flue gas temperature at AH outlet Minimum excess air at AH outlet Minimum un-burnt Carbon loss Minimum RH spray Minimum SH spray Reduced Auxiliary Power Consumption

Measures to improve Plant Efficiency … Turbine side measures Higher steam parameters ( MS Pressure & SHO/RHO Steam Temp). Adoption of double reheat cycle Increasing feed water temperature with Enhanced Regenerative feed heating 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

Factors Influencing Various Losses 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

Methods to reduce unburnt carbon loss 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 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: FG Temp Excess air Level Mill reject rate and 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 FANS AH LEAK GAS TEMPERATURE DUCT LEAKAGES EXCESS AIR LOAD/ PLANT HEAT RATE DRAUGHT LOSS AH CHOKING FD FANS WIND BOX PR. PRESSURE LOSS SCAPH CHOKING PA FANS AH LEAKAGE PA HEADER PR. MILL AIR FLOW MILL COAL QTY. GCV COAL MOISTURE HGI COAL FINENESS MILL CONDITION

Capacity Reduction in a Boiler Fuel input Low cv coal Milling capacity Grinding capacity Drying capacity Carrying capacity Drive capacity Draught system ID fan limitations Pressure drops high AH choking Chimney back pressure high High volume AH leakages Duct leakages High gas temperatures Worn out impellers Metal temperatures high High spray requirements Fouling of surfaces

CASE STUDIES

Case Study-1 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-2 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.

THANK YOU