Limestone attrition and fragmentation under simulated oxyfiring fluidized bed combustion conditions

Attrition/fragmentation of limestone under simulated FB oxyfiring conditions is investigated by means of an experimental protocol that has already been applied in the past to the characterization of attrition/fragmentation of sorbents in air-blown atmospheric fluidized bed combustors. The protocol is 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 has been assessed in experiments carried out with a bench scale FB combustor under simulated oxyfiring conditions. Sorbent samples generated during simulated oxyfiring tests have been 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 FB combustion conditions highlights the profound differences in the attrition and fragmentation extents and patterns associated with oxyfiring and the different role played by the different attrition/fragmentation paths. Noteworthy, attrition/fragmentation enhance particle sulfation by continuously regenerating the exposed particle surface.