A model of the reaction between SO, and calcium-based slurries is presented. The model is coupled with an extensive model of the evaporation process and considers external SO, mass transfer and liquid-phase mass transfer of dissolved sulfur and calcium species in both the film surrounding the calcium particles and the bulk liquid phase. The model assumes that particles do not circulate within slurry droplets and that evaporation results in an accumulation of particles at the droplet surface that causes a shift in the controlling mechanisms. Agreement between the model and data available in the literature is excellent.

The extent of high temperature (900-1,3OO"C), short time ( t l s) SO, capture was found to be limited by temperature-dependent losses in the porosity of calcium based sorbents. At 970°C these porosity losses were caused by C0,-activated sintering. Sulfation of the sorbents either prevented or reduced the extent of porosity losses. Differences in SO2 capture between hydroxides from different commercial sources, and significantly lower levels of capture by calcium carbonates compared to hydroxides were attributed to differences in particle size and the degree of porosity loss. SummaryThe use of a CO-fired reactor allowed calcines (CaO) of CaCO, and Ca(OH),, to be sampled without significantly alter- Vol. 35, No. 6AIChE Journal

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