Regeneration of sulfated dolomite and limestone by reductive decomposition

Regeneration properties of sulfated dolomite and limestone samples were investigated. Natural stones were first fully calcined at 1223 K in a gaseous atmosphere consisting of CO₂ 15 vol. % and dry air 85 vol. %; second, sulfation of the calcines was achieved by reacting them with a gaseous mixture consisting of CO₂ 15 vol. %, SO₂ 0.35 vol. %, and a balance of dry air at 1223 K; last, sulfated calcines were regenerated at 1373 K by a reductive decomposition process. During regeneration a 3:1 volumetric ratio of CO₂ / CO was maintained in the reducing gaseous atmosphere to minimize CaS formation. It has been found that for the fine sulfation-generation cycles the reactivity of the limestone and dolomite samples remained at acceptable levels. Since the repeated sulfation-regeneration steps caused an important change on the crystal lattice, as compared to the fresh stones, sorbent reactivity was also changed.