THE CALCINATION AND SULFATION BEHAVIOR OF SORBENTS IN FLUIDIZED-BED COMBUSTION

A study was performed on the effects of the CO2 partial pressure in the calcining gas and sorbent impurities on the structure of calcines produced and on subsequent sulphation behaviour under fluidized bed combustion conditions. It was found that the average pore size and the BET surface area were affected markedly by these two parameters, but their effect on pore volume was not significant. Increasing both parameters increased the average pore size and decreased the surface area as a consequence of sintering. During sulphation the presence of impurities delayed pore closure due to the formation of CaSO4. Hence, higher calcium utilization was achieved from the lower purity stones. The results highlight the importance of considering chemical composition in addition to initial physical properties in the selection of sorbents for use during fluidized bed coal combustion, since chemical composition controls, to a large extent, the physical properties developed upon calcination, and the structure of the calcine affects sulphation behaviour.