Steam reactivation of FB spent sorbent for enhanced SO2 capture: the relationship between microstructural properties and sulphur uptake

This paper addresses the regeneration of the sulphur capture ability of FB spent SO2 sorbent particles by steam hydration. The process was characterized in terms of hydration degree, particle sulphation pattern, development of accessible porosity and extent of particle fragmentation. Steam reactivation experiments were carried out in a lab-scale fluidized bed reactor at 250°C for 10 and 30 minutes, and 3h. The sorbent particle size range was 0.4-0.6mm, and the bed was fluidized at 0.2m/s with a steam-N2 mixture. The effectiveness of sorbent reactivation was assessed by reinjecting the reactivated material into the FB reactor (fluidized at 0.8m/s) operated at 850°C under simulated desulphurization conditions (the fluidizing gas consisted of a SO2-O2-N2 mixture), and following the degree of calcium conversion and the attrition rate along with resulphation. The experimental results indicated that steam reactivation is effective in renewing the SO2 uptake ability of the exhausted sorbent particles. Moreover steam reactivation induces, in the samples investigated, a strong sulphur redistribution throughout the particle cross-section, which contributes to the enhancement of the sulphur capture ability of the reactivated sorbent.