The regeneration process of a sulfided dolomite with steam and carbon dioxide was analyzed in a thermogravimetric system at temperatures between 475 and 650 degreesC, Different gas concentrations from 5 to 40% and different H2O/CO2 ratios were used to isolate the effect of the different gases on the regeneration process. The morphological changes of the sorbent during regeneration and cyclic sulfidation/regeneration reactions were followed by SEM-EDX analysis, which indicated a grain structure inside the particle. The changing grain size model with a variable diffusivity in the CaCO3 product layer was used to predict the experimental data, and to obtain the kinetic parameters of the regeneration reaction. The sintering of the CaCO3 has showed to be responsible of the changes in the solid diffusivity along the time, the H2O being the more important sintering agent on the process. Finally, the dolomite was subject to the calcination/sulfidation/regeneration process during 20 cycles and no activity loss was detected along the successive cycles.