The influence of reactivation of spent SO2 sorbents on fragmentation upon resulphation in fluidized bed combustors

The relationship between calcination/sulphation and attrition/fragmentation of limestone-based SO2 sorbents in FB combustors has long been recognized, but only recently did attrition by impact receive consideration. Moreover, there is scarce information available on the propensity to undergo impact fragmentation upon resulphation by exhausted sorbents submitted to hydration/reactivation. The present study represents an original attempt to characterize this propensity. The limestone was pre-processed (sulphation at 850°C in a lab-scale FB, water-hydration for 3 h in a thermostatic bath, dehydration at 850°C in the FB) and subjected to impact test in a purposely designed apparatus, operated with different particle impact velocities. The particle size distribution of the debris was worked out to define a fragmentation index and a probability density function of the size of generated fragments. The effect of hydration/reactivation of spent sorbent on its impact fragmentation propensity was assessed, and results were discussed in the light of a mechanistic framework.