Enhanced fluidized bed desulfurization by pre-treated 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 with 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 limestone and pre-treated lime sorbents. Two particle size ranges were tested under typical fluidized bed coal combustion conditions (T = 850°C; SO2 = 1800 ppm). 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.