The sulfurization characteristics of calcined calcite and dolomite were examined in a packed bed reactor. The calcination and sulfurization experiments were carried out in the temperature range of 973-1.173 K using particles of 1 mm mean diameter. The effects of diffusion coefficient of the reactant Ras (SO2) in the grain product layer, pressure and pore structure on the SO2, reactivity of the calcined samples were theoretically investigated in order to predict the sulfurization characteristics under typical coal combustion conditions. Similar CaO conversion levels were attained by calcined calcite and dolomite. increasing the total gas pressure resulted in a higher initial reaction rate of calcined calcite. while showed no significant influence on the ultimate SO2 sorption capacity. With the calcined dolomite, on the other hand, no effect on the initial reaction rate, nor the capacity, was found upon increasing the total gas pressure. During sulfurization, the observed lower initial rates and ultimate capacities at higher calcination and/or sulfurization temperatures were attributed to the sintering effect. Theoretical calculations showed that both the initial reaction rates and capacities increased with larger SO2 effective intraparticle diffusivities. Only the initial reaction rate : however, iras found to increase with increasing the SO2 grain product diffusivity.