Response Surface Methodology Applied to the Evaluation of the SO2 Sorption Process in Two Brazilian Limestones

This paper proposes a response surface methodology to evaluate the influence of the particle size and temperature as variables and their interaction on the sulfation process using two Brazilian limestones, a calcite (ICB) and a dolomite (DP). Experiments were performed according to an experimental design [central composite rotatable design (CCRD)] carried out on a thermogravimetric balance and a nitrogen adsorption porosimeter. In the SO 2 sorption process, DP was shown to be more efficient than ICB. The best results for both limestones in relation to conversion and Brunauer–Emmett–Teller (BET) surface area were obtained under central point conditions (545 μm and 850 °C for DP and 274 μm and 815 °C for ICB). The optimal values for conversion were 52% for DP and 37% for ICB. For BET surface area, the optimal values were 35 m 2 g –1 for DP and 45 m 2 g –1 for ICB. A relationship between conversion and pore size distribution has been established. The experiments that showed higher conversions also exhibited more pores in the region between 20 and 150 Å and larger BET surface area, indicating that the amount of smaller pores may be an important factor in the reactivity of limestones.