Stabilization of extra rich CH4/O2 flame in a two-section porous medium and the thermal partial oxidation characteristics thereof

Abstract

Fuel-rich CH4/O2 flames in a two-section porous medium burner were experimentally investigated for its application to the production of high concentration H2/CO syngas. The burner was made up of two axially-stacked silicon carbide foams having different pore sizes. Various flame behaviors, such as stable flame, flashback and blowout, were observed and, for the stable flame, temperature distributions and reformate compositions were measured. Results showed that the flame was stable in a sideway V-shape region on the domain of equivalence ratio and filtration velocity. Especially, it was found that the maximum equivalence ratio of the upper stable region was larger than the fuel-rich flammability limit showing characteristics of submerged combustion in porous media, which made the reaction closer to the stoichiometric partial oxidation. The reformate composition was measured for various conditions and maximum mole fraction of H2 and CO was 55.5 % and 28.0 % in dry basis being much higher than the air oxidant case. From these results, the reforming performance such as CH4 conversion, selectivity and yield of H2, CO, and energy conversion efficiency were evaluated. The equilibrium and the adiabatic planar flame were simulated as references to investigate the characteristics of partial oxidation reforming. The results may indicate that the porous media burner can be practically applied in producing high concentration H2/CO syngas, if it is designed to ensure minimum heat loss and enough residence time.