Experimental and modeling study of H2S formation and evolution in air staged combustion of pulverized coal

Abstract High-concentration H2S formed in the reduction zone of pulverized coal air-staged combustion can result into the high temperature corrosion of water wall tube of boiler, so it is of great importance to accurately predict H2S concentration for the safe operation of boilers and burners. H2S formation and evolution depends on two steps: the sulfur release from coal conversion and gas-phase reactions of sulfur species. In this study, the sulfur release characteristics from the pyrolysis of 17 coals, including 5 lignite, 9 bituminous coals and 3 anthracites, are investigated in a drop tube furnace (DTF). Sulfur release model is developed to describe the relationship between sulfur release and coal types. A global gas-phase reaction mechanism of sulfur species composed of ten reactions is used to calculate and predict the formation and evolution of H2S, COS and SO2 in the reduction zone of pulverized coal air-staged combustion. A wide range of air-staged combustion experiments of 17 coals are conducted in the DTF at different temperatures and stoichiometric ratios to validate the developed model. The results show that the prediction errors of sulfur species, including SO2, H2S and COS, are within ± 30%, which indicates that the developed prediction model of sulfur species is of great assistance for CFD modeling of actual engineering application.