Enhanced SO2 abatement with water-hydrated dolomitic particles



A dolomitic calcine was hydrated with liquid water and then recalcined as an effective sorbent toward SO2 removal. The hydrated/recalcined sorbent was tested for SO2 removal in a thermogravimetric analyzer under conditions applicable to an atmospheric fluidized-bed combustor: 1,123 K, 20 vol. % excess air, and 3,000 ppmv SO2. Specific pore surface areas and volumes of hydrated/recalcined dolomites, hydrated at 80°C for 1 h, increased by four and five times, respectively, compared to unhydrated dolomitic calcines. Due to these improved pore characteristics, the SO2 capture achieved by the hydrated/recalcined calcine, was 1.3–1.6 times higher than that of the unhydrated one after a 1-h exposure to SO2 concentrations of 0.11–0.31 vol. % at 1,073–1,173 K. In the hydrated/recalcined calcine CaO utilization was enhanced due to the absence of significant pore diffusional limitations, at least during the early reaction times, evidenced by the high apparent activation energy of 198 kJ/mol. On the contrary, the lower CaO utilization in the unhydrated calcine was presumably due to severe pore diffusional limitations, which dropped the apparent activation energy from 149 to 85 kJ/mol at > 1,123 K.