2. Closure to Furnace Analysis P M V Subbarao Professor Mechanical Engineering Department Verification of Simplified Analysis……

3. Furnace Energy Balance Water walls Economizer Furnace Enthalpy to be lost by hot gases:

4. Other Radiative Exits of A Furnace

7. Platen Superheater Platen Superheater : Flat panels of tubes located in the upper part of the furnace, where the gas temperature is high. The tubes of the platen SH receive very high radiation as well as a heavy dust burden. Mechanism of HT : High Radiation & Low convection Thermal Structure: –No. of platens –No. of tubes in a platen –Dia of a tube –Length of a tube

8. Geometry of Thermal Structure : Platen SH The outer diameter of platen SH is in the range of 32 – 42 mm. The platens are usually widely spaced, S 1 = 500 – 900 mm. The tubes within a platen are closely spaced, S 2 /d = 1.1. The number of parallel tubes in a platen is in the range of 15 – 35. Design Problem: To find out –Length of tubes. –Number of PSHs. Design Constraints: Max. allowable steam flow rates.

10. Thermal Balance Equation for Platen SH Energy given out by flue gas: Energy absorption for a Platen SH: The radiative heat coming from the furnace may not be completely absorbed by PSH. The gas in PSH tube matrix radiates some heat out to next section.

11. Radiation coming from furnace Radiation lost from PSH b is the width of PSH. Radiation energy emitted by gas in tube space.

12. The convective heat lost by flue gas Overall Coefficient of Heat Transfer, Convection Heat Transfer in PSH

13. Ash Deposition Coefficient 1.non-slagging coal, 2. Medium Slagging Coal with soot blowing, 3. Medium slagging coal without soot blowing, 4. Combustible shale.

14. 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 : n ex.gas = P+Q+R+T+U+V 100 X CV of fuel =  n ex. Gas h f,gas Calculate Adiabatic Flame Temperature. Calculate total heat transfer area of furnace, A fur

15. Furnace Characterization Criteria M Temperature Field Coefficient T ad or T fl Theoretical combustion temperature T out Furnace Exit Gas Temperature A fur Total surface area of furnace m c Flow rate of fuel

16. 1225 1200 1175 1150 1125 1100 0C0C

17. Effect of Coal Quality on Furnace Size

18. Burner Flame Hot Exhaust gases Furnace Exit Heat Radiation & Convection

19. Structure of Furnace Wall