"On the combustion and soot processes in a fluidized bed - Like furnace"

The combustion and soot processes in a fluidized-bed (FB)-like furnace are studied numerically. Fuel considered is methane. The simulation results obt ained show that the most important sooting region in the furnace is the low er circulating region formed between the secondary air jets and the primary inlet of the furnace (referred to here as the FB-region). The most importa nt factor affecting the soot formation in this FB-region are local temperat ures in the stagnation point-like flow region formed in the middle of the f urnace between the two opposing secondary air jets. These temperatures affe ct soot inception in this region, as well as local temperatures in the FB-r egion. Turbulent temperature fluctuations are high enough, so that they hav e important favoring effects on soot formation in the important sooting reg ions indicated above. By accounting for radiation heat transfer in the simu lation, temperatures in the hottest sites along the central symmetry plane of the furnace are reduced, roughly, by about 100 K. This has significant a dverse consequences on total soot amounts generated; soot amounts generated in this case are about 10 rimes lower than those predicted when radiation effects are ignored. Nevertheless, soot levels in the furnace, even under r adiating conditions, are still clearly higher than those typical for normal methane diffusion flames under atmospheric pressure. Tn contrast to the ca se when radiation is not simulated, under radiating conditions decoupling s oot from the gas phase is found to have almost no noticeable impact on loca l temperatures and species concentrations. In this case, however, less heat will be radiated to the walls and to colder regions in the furnace.