Performance Analysis of SG FurnaceP M V SubbaraoAssociate ProfessorMechanical Engineering DepartmentI I T DelhiThermal Performance analysis of A complex Geometry..

Analysis of the Last but One EffectFinal effect : Tfl gets changed to Furnace Exit GasTemperature.Due to energy lost by hot gases. Loss due to EnvironmentEnergy absorbed by water wallsEnergy lost by hot gasses from flame to exit.TflameTfe

Mixed Adiabatic Temperature of the Gases

Analyses of Coal

Computation of Adiabatic TemperatureSyipikJ/kmol.KMoles of Products of Combustion

Heat absorbed = g (energy liberated energy of gas at furnace exit).TflameTfeg is a loss factor.Analysis of the Last EffectDefine

Finally the successful radiative action to the water walls:Divide thought by Tad4:Define :

Furnace exit temperature is proportional to Flame Temperature.

Furnace Exit Gas TemperatureTemperature of gasses leaving the furnace.An important furnace performance parameter.Defines the ratio of furnace heat absorption to later (convective) heat absorption.High FEGT Compact furnace.Due to increase in fouling of water wall tubes:FEGT < Ash Deformation Temperature.FEGT = AST 100FEGT < 1100 0C Strong slagFEGT < 1200 0C Moderate slag

1225

1200

1175

1150

1125

11000CIt is very essential to know the mass flow rates ofFuel, Air and various flue gases for furtherPerformance Analysis!

Computation of FEGT for Indian SG & Coals

Performance of Analysis of FurnaceGet Fuel Ultimate Analysis.Compute Equivalent Chemical Formula.Select recommended Exhaust Gas composition.Carry out first law analysis to calculate Adiabatic Combustion Temperature.Total number of moles of wet exhaust gas for 100 kg of fuel : nex.gasHV of fuel +nair hair = Snex. Gashf,gasCalculate Adiabatic Flame Temperature.Calculate total heat transfer area of furnace, Afur & cross sectional area of furnace Across

FEGT of A Clean Furnace : A CorrelationThermal efficiency factor, y.M Temperature Field CoefficientTad Adiabatic combustion temperatureTFEGT Furnace Exit Gas TemperatureAfur Total surface area of furnacemc Flow rate of fuel

EconomizerFeed WaterThermal Structure of Steam GeneratorFinal Super HeaterTIT

FEGT : A Measure of Instantaneous Cleanliness of Furnace Walls

Turbine Inlet Steam Temperature Control System In practice, the turbine governing system maintains required main steam flow rate for a given load on the turbine.An appropriate control system is used to maintain turbine inlet temperature(TIT) within specified safe limits. The control of TIT is generally carried out by injecting water in the path of super heaters. This mixing chamber (attemperator) is placed at upstream of final super heater.

Flow controller

Furnace Cleanliness FactorThus the Real FEGT and capacity FEGT can be calculated using the plant data and instantaneous cleanliness factor can be calculated using following formula:

Uses of Actual FEGT Calculations for Performance Monitoring and AnalysisSuperheat steam temperature control : The final steam temperature is maintained by keeping the FEGT within the allowable limit.Coal ash corrosion control: Maintaining the FEGT a minimum of 600C, below the ash softening temperature can reduce the potential of super heater coal ash corrosion .Control of NOx production : It is essential for the operator to maintain the original design FEGT to minimize other side effects.

Effect of FEGT on NOx Emissions1504155016% rise in NOx due to 3% increase in FEGT.

Uses of Real FEGT Calculations for Performance Monitoring and AnalysisSoot blowing :FEGT can be used as the primary indicator to establish the scheme for automatic soot blowing (cleaning of heat transfer surfaces) or to alert the operator to start the manual soot-blowing operation. If FEGT exceeds the original design value, this indicates that the furnace is dirty and the operator should initiate the furnace soot blowing and the soot blowing should be stopped when FEGT has been reduced below the original design value. The over-blowing in the furnace is wasting the energy and can also create soot blower erosion problem in the water wall tube

ARRANGEMENT OF SOOT BLOWERS IN A 500MW

Basic Geometry of A FurnaceHeat exchange by Radiation Through Top opening of furnace: