A method was developed to recover elemental sulfur from smelter off-gas with high SO2 content. Based on thermodynamic simulation of reactions between some sulfides and SO2

calcium sulfide (CaS) was demonstrated to be a novel chemical desulfurizer. SO2 was reduced to elemental sulfur by reacting with CaS in temperature range from 400℃ to 650℃ and direct solid product was CaSO4 rather than CaO. The experimental desulfurization in a fixed bed reactor showed that reaction temperature had a strong effect on SO2 removal efficiency and sulfur recovery ratio. When temperature was increased within the range of 400℃ and 650℃

both SO2 removal efficiency and sulfur recovery ratio were raised gradually. When temperature was higher than 600℃

SO2 removal efficiency was approximately equal to sulfur recovery ratio. Increasing gas velocity reduced SO2 removal efficiency

sulfur recovery ratio

and difference between these two. SO2 removal efficiency remained at 99.8% at SO2 concentration below 1% but dropped sharply to 92.1% at SO2 concentration up to 3.45%. Average SO2 removal efficiency declined gradually when SO2 concentration was continuously increased. With increase of SO2 concentration

sulfur recovery ratio exhibited an optimal range. At late stage of desulfurization

large particle size of CaS decreased SO2 removal efficiency. SEM photos showed that desulfurizer particles agglomerated more obviously at increase of reaction temperature. XRD patterns verified sublimated elemental sulfur particles in the reduction of SO2 by CaS.