COMPARATIVE REACTIVITY OF CA(OH)(2)-DERIVED OXIDES FOR SO2 CAPTURE

The sulfation capacity of sorbents derived from fine hydrated lime powder (termed H-CaO) and those derived from carbonated H-CaO (termed C-CaO) were investigated. All calcination, carbonation and sulfation experiments were conducted in a thermogravimetric analyzer (TGA) under conditions closely simulating those prevailing in an atmospheric fluidized bed combustor (AFBC). The effect of such parameters as calcination and sulfation temperatures and active gas concentration on the capacity of SO2 removal were studied. The change in porosity with progress of the sulfation reaction was investigated for both H-CaO and C-CaO sorbents. N-2-adsorption/desorption isotherms showed that both H-CaO and C-CaO sorbents exhibited slit-shaped pores. The pore-size and specific surface area distribution curves indicated a higher reactivity of H-CaO calcines over that of C-CaO calcines at all reaction temperatures. The conversion of both H-CaO and C-CaO decreased with decreasing porosity and reached an ultimate value where the porosity approached zero. These ultimate conversions of both H-CaO and C-CaO were found to be 71 and 61%, respectively, at 1123 K and 0.31 vol% SO2 concentration.