3 Total gas side pressure drop Pawhere p1 = total pressure drop from the furnace outlet to thedust collector, Pap2 = pressure drop after the dust collector, Pa = ash content in the glue gas, kg/kgpa v = average pressure of the gas, Papg o = flue gas density at standard conditions, kg/Nm3
4 The ash fraction of the flue gas calculated as, where f h = ratio of fly ash in flue gas to total ash in the fuelA = ash content of working mass, %Vg = average volume of gas from furnace to dust collector calculated from the average excess air ratio, Nm3/kg of fuel
5 prest = pexit + pgas –Dpnd The pressure drop from the balance point of the furnace to the chimney base isprest = pexit + pgas –Dpndwhere pexit = pressure drop up to the boiler outlet
6 Draught Losses Dp Total losses Furnace, SH & RH Losses Economizer LossesDucts & dampers lossesPercent Boiler Rating
7 ID fan power calculation ID fan power is calculated as:
8 Air Pressure Losses Dp Total losses Burner Losses APH Losses Ducts & dampers lossesPercent Boiler Rating
9 Modeling of 210 MW Draught System FDFanDuctAPHFurnaceBackpassESPIDChimneyPressure drop calculation in air & gas path and its comparison with design value.Assessment of ID and FD fan power as a function of furnace pressure.
13 Pressure Variation Duct FD Fan SCAPH APH Duct Wind Box Boiler APH ESP ID FanDuct
14 Off Design Pressure Variation Pressure Variation in Air & Gas Path at Part Load-2000-1500-1000-5005001000150020002500123456789101112Path ElementPressure (Pa)Calculated (168 MW)Design (168 MW)ID FanESPBoilerAPHWindBoxDuctSCAPHFD Fan
21 The net effect is saving in energy of 117 The net effect is saving in energy of kW due to increase in furnace vacuum from 58.9 Pa to Pa.
22 New Ideas for Future Research FDFanDuctAPHFurnaceBackpassESPIDChimney
23 Analysis of Flue Gas at the ID Fan Inlet Partial pressure of each constituent in flue gas, pCO2 = kPa pO2 = kPa PN2 = kPa pSO2 = kPa pH2O = kPaMass flow rate of each constituent in tons/hour is: Mass flow rate of O2 in the flue gas = tph Mass flow rate of CO2 in the flue gas = tph Mass flow rate of N2 in the flue gas = tph Mass flow rate of SO2 in the flue gas = tph Mass flow rate of H20 in the flue gas = tph
24 Energy Audit of Flue Gas Temperature of flue gas = 136 ºC – 150oCDew point of water is (obtained based on partial pressure of bar) ºCCooling of the exhaust gas below the dew point will lead to continuous condensation of water vapour and reduction of flue gas volume and mass.The temperature of the flue gas in order to remove x% of the available moisture can be obtained using partial pressures of water.
25 Energy Potential of Flue Gas with 10% water Recovery Flue gas constituentsPartial pressure at 136 C in kPaEnthalpy* at 136 C (KJ/kg)Mass flow rate of each constituent at 136 C ( kg/s)Enthalpy*at C KJ/kgMass flow rate of each constituent at C ( kg/s)Total thermal power released (MW)CO216.37606.32527.853.690.2895O21.11374.4329472.95.8678N268.14425335.09193.3S020.036487430.550.23410.0132H2013.362752259130.44411.576
26 Energy Potential of Flue Gas with 100% water Recovery Flue gas constituentsPartial pressure at 136 C in kPaEnthalpy* at 136 C (KJ/kg)Mass flow rate of each constituent at 136 C ( kg/s)Enthalpy at 0 C (kJ/Kg)Mass flow rate at 0 C ( kg/s)Total thermal power released (MW)CO2606.32485.833.69O2374.43248.3572.95N2425283.32193.3S02487399.580.2341H2027522501
28 Expected Performance of the heat exchanger Cooling capacity of the heat exchanger = 10 kWCooling load available with the heat exchanger = kJ/kg of flue gasAvailable rate of condensation of the present heat exchanger = 37.85gms/kg of flue gas.
29 Experimental validation Flue Gas heat exchanger measured data:DATEFLUE GASI/L JUST OUTSIDE ID DUCTI/L TO HEAT EXCHANGERO/L TO HEAT EXCHANGERWATERI/L TO HEAT EXCHANGERO/L TO HEAT EXCHANGERDPWATER FLOWQTY OF WATER CONDENSEDTemp °Ccm WCLPMlt. /Hr.1.2.101036030295121.1105653231100.92.2.1012169824.21
30 Calculation of Flue Gas Flow Rate Dp (cm)Tin 0C Density (kg/m3) Flow rate (kg/sec)56065694.282Calculation of Condensate Flow rateGas Flow rate (kg/sec)Mesured condensatekg/hrg/secCondensate loading (gms/kg of gas)184.108.40.206Design rate of condensate loading using present heat exchanger = 37.85gms/kg of flue gas.
31 Combustion and Draught Control The control of combustion in a steam generator is extremely critical.Maximization of operational efficiency requires accurate combustion.Fuel consumption rate should exactly match the demand for steam.The variation of fuel flow rate should be executed safely.The rate of energy release should occur without any risk to the plant, personal or environment.
33 The ControlFurnace (draft) pressure control is used in balanced draft furnaces in order to regulate draft pressure.Draft pressure is affected by both the FD and ID fans.The FD fan is regulated by the combustion control loop, and its sole function is to provide combustion air to satisfy the firing rate.The ID fan is regulated by the furnace pressure control loop and its function is to remove combustion gases at a controlled rate such that draft pressure remains constant.