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Performance Analysis of SG Furnace

Performance Analysis of SG Furnace. P M V Subbarao Associate Professor Mechanical Engineering Department I I T Delhi. Thermal Performance analysis of A complex Geometry…. Analysis of the Last but One Effect. T fe. Final effect : T fl gets changed to Furnace Exit GasTemperature.

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Performance Analysis of SG Furnace

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  1. Performance Analysis of SG Furnace P M V Subbarao Associate Professor Mechanical Engineering Department I I T Delhi Thermal Performance analysis of A complex Geometry…..

  2. Analysis of the Last but One Effect Tfe • Final effect : Tfl gets changed to Furnace Exit GasTemperature. • Due to energy lost by hot gases. • Loss due to Environment • Energy absorbed by water walls • Energy lost by hot gasses from flame to exit. Tflame

  3. Mixed Adiabatic Temperature of the Gases

  4. Analyses of Coal

  5. Computation of Adiabatic Temperature Moles of Products of Combustion Syipi kJ/kmol.K

  6. Analysis of the Last Effect Define Tfe • Heat absorbed = g (energy liberated – energy of gas at furnace exit). g is a loss factor. Tflame

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

  8. Furnace exit temperature is proportional to Flame Temperature.

  9. Furnace Exit Gas Temperature • Temperature 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 – 100 • FEGT < 1100 0C – Strong slag • FEGT < 1200 0C – Moderate slag

  10. It is very essential to know the mass flow rates of Fuel, Air and various flue gases for further Performance Analysis! 1225 1200 1175 1150 1125 1100 0C

  11. Computation of FEGT for Indian SG & Coals

  12. Performance of Analysis of Furnace • Get 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.gas • HV of fuel +nair hair = Snex. Gashf,gas • Calculate Adiabatic Flame Temperature. • Calculate total heat transfer area of furnace, Afur & cross sectional area of furnace Across

  13. FEGT of A Clean Furnace : A Correlation • Thermal efficiency factor, y. • M Temperature Field Coefficient • Tad Adiabatic combustion temperature • TFEGT Furnace Exit Gas Temperature • Afur Total surface area of furnace • mc Flow rate of fuel

  14. Final Super Heater TIT Economizer Feed Water Thermal Structure of Steam Generator

  15. FEGT : A Measure of Instantaneous Cleanliness of Furnace Walls

  16. 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.

  17. Flow controller

  18. Furnace Cleanliness Factor Thus the Real FEGT and capacity FEGT can be calculated using the plant data and instantaneous cleanliness factor can be calculated using following formula:

  19. Uses of Actual FEGT Calculations for Performance Monitoring and Analysis • Superheat 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.

  20. Effect of FEGT on NOx Emissions 16% rise in NOx due to 3% increase in FEGT. 1504 1550

  21. Uses of Real FEGT Calculations for Performance Monitoring and Analysis • Soot 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

  22. ARRANGEMENT OF SOOT BLOWERS IN A 500MW

  23. Basic Geometry of A Furnace Heat exchange by Radiation Through Top opening of furnace:

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