Elemental sulfur production during the regeneration of iron oxide high-temperature desulfurization sorbent

The production of elemental sulfur instead of SO? during the regeneration of high temperature desulfurization sorbents will improve the efficiency of advanced power generation processes such as the integrated gasification combined cycle (IGCC). While much research is directed at developing zinc-based sorbents because of the favorable thermodynamics of the ZnO-H2S reaction, SO2 is the inevitable product from ZnS regeneration. Iron-based sorbents, although less efficient for H2S removal, permit significant amounts of elemental sulfur to be formed during regeneration. A laboratory-scale fixed-bed reactor has been used to study the regeneration of FeS in steam-oxygen mixtures. The experimental results are interpreted on the basis of four simultaneous reactions. Oxygen reacts rapidly with FeS to produce SO2 and Fe2O3. Steam reacts to give Fe3O4 and H2S. Elemental sulfur is formed by the reaction between H2S and SO2, and additional O-2 is consumed in converting Fe3O4 to Fe2O3. The maximum yield of elemental sulfur, approximately 75% of theoretical, was achieved using a large H2O-to-O-2 ratio (200-to-1) at the lowest feasible regeneration temperature (600 degrees C), and using a small regeneration gas feed rate. (C) 1998 Elsevier Science B.V.