The sulfidation and regeneration of half-calcined dolomite

Abstract

High-temperature sulfur removal from fuel gas, such as in the Westinghouse fluidized bed coal gasification process, may be achieved using dolomite in the reaction ▪ Although the regeneration process reduced the sorbent requirement and solid waste handling, a major problem has been the difficulty in completing regeneration and the decrease in regenerability with sulfidation/regeneration cycles. Reactions were carried out in a pressurized TG system and structural information of the solid products was obtained employing scanning electron microscopy, energy dispersive analysis by X-ray, electron microprobe analysis, and X-ray diffraction. The morphological changes during half-calcination, sulfidation, regeneration and cyclic sulfidation/regeneration reactions were correlated with chemical kinetic measurements obtained from TGA. A reaction mechanism which postulates the migration and crystallite growth of MgO onto CaS crystals explains the deterioration in dolomite regenerability, and is supported by the kinetic TG measurements. Time at temperature, and desulfurization temperature are the significant variables which control the regenerability of the product calcium sulfide.