Sulfur capture by limestone under simulated oxyfiring fluidized bed combustion conditions

Attrition/fragmentation of limestone under simulated fluidized bed oxyfiring conditions was investigated by means of an experimental protocol that had been previously developed for characterization of attrition/fragmentation of sorbents in air-blown atmospheric fluidized bed combustors. The protocol was based on the use of different and mutually complementary techniques. The extent and pattern of attrition by surface wear in the dense phase of a fluidized bed was assessed in experiments carried out with a bench scale fluidized bed combustor under simulated oxyfiring conditions. Sorbent samples generated during simulated oxyfiring tests were further characterized from the standpoint of fragmentation upon high velocity impact by means of a purposely designed particle impactor. Comparison of results with those previously obtained with the same limestone under air-blown atmospheric fluidized bed combustion conditions highlighted the profound differences in the attrition and fragmentation extents and patterns associated with oxyfiring and the role played by the different attrition/fragmentation paths. Noteworthy, attrition/fragmentation enhanced particle sulfation by continuously regenerating the exposed particle surface.