3 Emerging Market Requirements Higher Availability & ReliabilityHighest Plant efficiencyLower Heat RateMinimum Auxiliary Power ConsumptionAbility to operate under adverse grid conditions/fluctuation in demandMinimum emission of Pollutants
4 Measures to improve Plant Efficiency Boiler side:Minimum flue gas temperature at AH outletMinimum excess air at AH outletMinimum un-burnt Carbon lossMinimum RH sprayMinimum SH sprayReduced Auxiliary Power Consumption
5 Measures to improve Plant Efficiency … Turbine side measuresHigher steam parameters( MS Pressure & SHO/RHO Steam Temp).Adoption of double reheat cycleIncreasing feed water temperature with Enhanced Regenerative feed heatingIncrease in condenser vacuum
6 2a. Boiler - Various Losses By Gas Dry Gas LossLoss due to Moisture in GasDue to Fuel MoistureDue to moisture formed by H2 in fuelDue to air moistureBy Ash Unburnt carbon LossSensible heat loss in Fly ashSensible heat loss in Bottom ashOther Loss Carbon monoxide LossRadiation LossHeat loss through Mill rejects
7 Factors Influencing Various Losses NoLossFactor1Dry Gas LossFlue Gas Temperature, Excess Air & Fuel2Unburnt Carbon Loss In AshAsh in Fuel & Unburnt Carbon In Fly / Bottom Ash3Mill Reject LossReject Rate & CV Of Reject4Due to Moisture formed from HydrogenHydrogen Content In Fuel & Flue Gas Temperature5Due to Fuel MoistureMoisture Content In Fuel & Flue Gas Temperature6Due to Air MoistureHumidity Of Combustion Air, Excess Air Level & Flue Gas Temperature7Radiation & Convection LossInsulation Of Boiler8Sensible Heat Loss In AshAsh Temperature
8 Methods to reduce unburnt carbon loss Ensure consistent mill fineness - +50, - 200Good burner maintenanceProper secondary air adjustment - SADCReduce PA air to the minimum possible – min PA velocity variationCut 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 burnCheck coal property and tune combustionKeep boiler heat transfer surface clean so that losses can be reduced thus reducing the coal input
9 Methods to reduce dry gas loss Correct excess airHigh mill outlet temp.Better combustion – combustion tuningArrest air ingressAir heater performance – leakage , proper elementsCleanliness of the heat transfer surfaces
10 Optimization of Boiler Efficiency 1HHV All Losses 2FG APH out Temp Dry gas, Sensible heat in Ash, H2, Fuel and Air Moisture Loss 3Excess air Dry gas, Unburnt & Air Moisture Loss 4Fuel Moisture Fuel Moisture Loss 5Air Moisture Air Moisture Loss 6H2 in Fuel H2 Loss 7Mill reject rate or GCV Mill reject Loss The Major parameters to be looked into for Better Efficiency:FG TempExcess air LevelMill reject rate andUnburnt carbon in ashControl / Optimization of other parameters (i.e GCV, H2, Fuel moisture and Air Moisture) are not possible.
11 Major reasons for increase in APC Operation of unit with higher excess airAir heater leakageHigher PA fan outlet pressureHigh mill fineness, more no. of millsAir ingress into boilerPluggage in line / ductingPartialy blocked APH
12 Sources of air ingress Furnace roof Expansion joints Air heaters Ducts Esp hoppersPeep holesManholesFurnace bottom
16 Case Study-1Problem:Heavy clinkering build up upto S-panel /Bottom of burner reported from many boilersInvestigations:Poor mill fineness (50% through 200 mesh)Non-working of SADC as per controlPoor coal quality – usage of ground stockNon- working of wall blowersImproper evacuation of bottom ashSolution:After taking above corrective actions no further problems faced.
17 Case Study-2 Problem: Frequent choking of coal pipe Investigations: Clean air flow testChecking of orificeCalibration of coal flow/air flow -checkForeign material entrapped in classifier ( cloth)Solution: Problem resolved after removal of foreign material from classifier.