| OCR Text |
Show the furnace hopper gas temperature, and the distribution of and total heat absorption in the furnace with and without the reburn N O x reduction system. No assessment was made on convective pass performance (superheat, reheat, or economizer sections) with the reburn system due to any changes in flue gas weights (mass flows), total boiler heat absorption (as compared to radiant furnace heat absorption), or changes in convective section boiler exit gas temperature (as compared to furnace exit gas temperatures) in this thermal performance analysis. The furnace thermal performance analysis was completed on the preliminary reburn system design utilizing a proprietary computer code schematically shown in Figure 4. The code determines, through a series of heat balance calculations, the heat transfer from the combustion products to the waterwalls, the corresponding gas temperatures, and the furnace outlet temperature of the combustion products. The combustion history and combustion products were determined based on a fuel analysis, fuel and air mass flow rates and injection locations, fuel particle size distribution, and a set of fuel char combustion kinetics. Mathematical Inputs Model Outputs Fuel Information • Particle Size Distribution (R) • Apparent Density (Pf) • Chemical Characteristics • Ash Characteristics Drop Tube Furnace System Information • Char Activation Energy (E) • Char Frequency Factor (A) • Fuel Swelling Factor (a) • Fuel Volatile Matter (VM DTFS) Boiler Information • Design Parameters • Operating Conditions Figure 4: Flow Diagram for Boiler Combustion Performance Model Simulation Both furnace gas temperature profiles and furnace waterwall/heat absorption profiles were generated as a result of the thermal analysis. These are shown in Figures 5 and 6, respectively. Since reburn system operation (with natural gas) was initially projected to increase the furnace exit gas temperature (FEGT), additional furnace performance analyses were conducted in an attempt to decrease or eliminate this predicted F E G T increase, which could negatively impact convection tube metal temperatures and require additional desuperheat and reheat sprays. Proprietary Computer Code • Temperature /Time History •Overall Fuel Combustion Efficiency • Percent Carbon in Fly ash • Percent Carbon Heat Loss • Heat Release/Heat Absorption Profile 7 |
