A new process for regeneration of calcium sulfide produced from coal gas desulfurization has been proposed. The regenerative process involves the exposure of calcium sulfide to alternating oxidizing and inert atmospheres. The process consists of two oxidation steps during which CaS is converted to CaSO4. Each oxidation step is followed by a regeneration step during which there occurs an apparent solid-solid reaction between CaS and CaSO4, which yields the products CaO and SO2. The mechanisms and kinetics for the oxidation of CaS particles,the reaction between CaS and CaSO4, and the overall regenerative process have been investigated with a thermogravimetric analyzer and mass spectrometer. The conversion of CaS to CaSO4 was 30% during the first oxidation step, whereas it reached as high as 71.6% in the next oxidation step. This amount comes very close to the stoichiometry for the reaction between CaS and CaSO4. The apparent solid-solid reaction was fairly rapid at >850 degrees C, and a high degree of fractional production was achieved. When the overall regenerative process was completed, similar to 95% of the CaS in the sample had been converted to CaO.