OCR Text |
Show parameters were found for two cases. Then 6.7% of the fed methane is burned in the Precombustor, the mixed gas is preheated to 1880°F and a residence time of 10*2 to 1 second is required to generate soot precursors. When the feed methane burned in the Precombustor is increased to 9.1% of the feed methane, the mixed gas is preheated to 2420°F and the residence time required to generate soot precursors is reduced to 10~4 to 10~2 seconds. Flame (Combustion) Zone Radiation heat transfer from non-luminous and luminous flames has been determined for a model glass melting furnace using natural gas and industrial oxygen. Parametric calculations have been carried out to determine the effects of a number of independent variables on the heat transfer from the high luminosity burner. The basis for comparison was selected to be a non-luminous flame with H 2 O and C O 2 as the only important combustion products. In the luminous flame, soot was included as a radiating species. The model was first conducted in one dimension. The 1-D model does not account for radiative heat transfer in the axial, flow direction. Therefore, a quasi two dimensional (quasi 2- D ) model was developed to predict radiative heat transfer in the model furnace. This model was then coupled with the thermal energy model of the furnace to calculate temperature distribution and heat flux along the load. Parametric calculations were then performed to examine the effects of furnace design and operating parameters on the furnace performance. The quasi 2-D energy equation-based model employs the following, major assumptions: • Gas flow can be described by steady, laminar plug flow. • Heat transfer is by radiation and convection. Radiation heat transfer is quasi two dimensional - perpendicular to the load and in the direction of flow. • Heat losses by radiation through the entrance and exit ports are neglected. • Turbulence, mixing, and detailed chemical reactions are neglected. Fuel burnout is empirical. • Emission and absorption of radiation by soot particles is related to the soot volume fraction. • The crown is a gray, diffuse emitter and absorber of radiation, and interreflection of radiation between the crown and load is included. 12 |