PowerPoint Presentation
Generation and Control of Vacuum in FurnaceP M V
SubbaraoProfessorMechanical Engineering DepartmentSafe and
Efficient Combustion Needs Appropriate Furnace Pressure
Development of Air & Flow Circuits
Pa
where p1 = total pressure drop from the furnace outlet to the
dust collector, Pa p2 = pressure drop after the dust collector, Pa
= ash content in the glue gas, kg/kg pa v = average pressure of the
gas, Pa pg o = flue gas density at standard conditions, kg/Nm3
Total gas side pressure dropThe 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
The pressure drop from the balance point of the furnace to the
chimney base is
prest = pexit + pgas Dpnd
where pexit = pressure drop up to the boiler outlet
DpPercent Boiler RatingFurnace, SH & RH LossesEconomizer
LossesDucts & dampers lossesDraught LossesTotal losses
ID fan power calculationID fan power is calculated as:
DpPercent Boiler RatingBurner LossesAPH LossesDucts &
dampers lossesAir Pressure LossesTotal losses
FD FanDuct APH DuctFurnaceDuctAPHBack
passESPIDFanChimneyDuctDuctModeling of 210 MW Draught
SystemPressure 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.Important variables along air and gas
path
Pressure Variation
DuctFD Fan Duct SCAPHAPHDuctWindBoxBoilerAPHESPID FanOff Design
Pressure VariationPressure Variation in Air & Gas Path at Part
Load-2000-1500-1000-50005001000150020002500123456789101112Path
ElementPressure (Pa)Calculated (168 MW)Design (168 MW)ID
FanESPBoilerAPHWindBoxDuctAPHDuctSCAPHDuct FD Fan
Operational Data of 210 MW plant
Effect of Furnace Vacuum on Boiler Efficiency
The net effect is saving in energy of 117.32 kW due to increase
in furnace vacuum from 58.9 Pa to 230.6 Pa.New Ideas for Future
Research FD FanDuct APH DuctFurnaceDuctAPHBack
passESPIDFanChimneyDuctDuctAnalysis of Flue Gas at the ID Fan
InletPartial pressure of each constituent in flue gas, pCO2 =
16.366209 kPapO2 = 1.138404 kPaPN2 = 68.142138 kPapSO2 = 0.036081
kPapH2O = 13.363218 kPa Mass flow rate of each constituent in
tons/hour is:Mass flow rate of O2 in the flue gas =13.2867 tphMass
flow rate of CO2 in the flue gas = 262.646 tphMass flow rate of N2
in the flue gas = 695.893 tphMass flow rate of SO2 in the flue gas
= 0.84219 tphMass flow rate of H20 in the flue gas = 118.33 tph
Energy Audit of Flue Gas Temperature of flue gas = 136 C
150oCDew point of water is (obtained based on partial pressure of
0.1336 bar) 51.59 CCooling 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.
Energy Potential of Flue Gas with 10% water RecoveryFlue 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 49.74 C KJ/kgMass flow rate of each constituent at
49.74 C ( kg/s)Total thermal power released
(MW)CO216.37606.323.69075527.853.690.2895O21.11374.4372.957229472.95.8678N268.14425193.303335.09193.317.3797S020.0364870.23413430.550.23410.0132H2013.36275232.8694259130.44411.57635.1270Energy
Potential of Flue Gas with 100% water RecoveryFlue 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)CO216.366209606.323.69075485.833.690.444698O21.138404374.4372.9572248.3572.959.198452N268.142138425193.303283.32193.327.38828S020.0360814870.23413399.580.23410.020468H2013.363218275232.86942501090.45671127.5086Model
Experimentation
Expected Performance of the heat exchangerCooling capacity of
the heat exchanger = 10 kWCooling load available with the heat
exchanger = 115.3 kJ/kg of flue gasAvailable rate of condensation
of the present heat exchanger = 37.85gms/kg of flue gas.
Experimental validation Flue Gas heat exchanger measured data:
DATEFLUE GASI/L JUST OUTSIDE ID DUCTFLUE GASI/L TO HEAT
EXCHANGERFLUE GASO/L TO HEAT EXCHANGERWATERI/L TO HEAT
EXCHANGERWATERO/L TO HEAT EXCHANGERDPWATER FLOWQTY. OF WATER
CONDENSEDTemp Ccm WCLPMlt.
/Hr.1.2.10103603029305121.11.2.10105653231325100.92.2.10121693130315121.12.2.10121823231324.2121Calculation
of Flue Gas Flow Rate
Dp (cm)Tin 0CDensity (kg/m3)Flow rate
(kg/sec)5601.0517540.0071595651.0362030.0071065691.0240890.0070654.2820.9866040.006355Gas
Flow rate (kg/sec)Mesured condensatekg/hrMesured
condensateg/secCondensate loading (gms/kg of
gas)0.0071591.10.30555642.678640.0071060.90.2535.179940.0070651.10.30555643.251260.00635510.27777843.70829Design
rate of condensate loading using present heat exchanger =
37.85gms/kg of flue gas.Calculation of Condensate Flow
rateCombustion and Draught ControlThe 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.
Furnace Draught
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. Furnace Draught Control
Windbox Pressure Control
Combustion Prediction & Control The Model for Combustion
Control
Parallel Control of Fuel & Air Flow Rate
Flow Ratio Control : Fuel Lead
Flow Ratio Control : Fuel Lead
Cross-limited Control System
Oxygen Trimming of Fuel/air ratio Control
Combined CO & O2 Trimming of Fuel/Air Ratio Control
Resistance to Air & Gas Flow Through Steam Generator
System
