Fluidized bed desulfurization using lime obtained after slow calcination of limestone particles

In this work we have tested the fluidized bed desulfurization performance of lime particles obtained by means of a proprietary limestone slow calcination pre-treatment technique. This performance was compared to that of the parent untreated limestone particles. The occurrence of particle fragmentation and attrition during the fluidized bed operation was also investigated with a specific test protocol for both raw limestone and pre-treated lime sorbent. Two particle size ranges were tested under typical fluidized bed coal combustion conditions. The experiments were complemented by porosimetric and morphological (SEM) analyses of the sorbent. Results showed that limestone pre-treatment was able to preserve the high mechanical strength of the parent particles as opposed to the fast in situ calcination typically active in fluidized beds. In addition, a high calcium reactivity and final conversion were observed for the pre-treated lime particles, leading to a SO2 capture capacity per unit mass of sorbent much higher than that obtained with the untreated limestone. Simple economic evaluations suggest that the use of the pre-treated lime in place of limestone can involve significant economies for fluidized bed coal combustor operators.