The sulphation reaction of the calcines produced from four limestone and one dolomite samples were investigated and modeled. The experiments were conducted in a thermogravimetric analyzer under isothermal conditions and in a gaseous atmosphere consisting of 15 vol% CO2, 0.35 vol% SO2 and balance of dry air by volume. The variation of reaction rate with temperature was determined by sulphating of calcines at three different temperatures: 1023, 1173 and 1273 K. Based on the initial sulphation rates, the apparent activation energies were calculated as 51.58, 145.20 and -37.79 kJ/mol for L01, L04 and D01 samples, respectively. The unreacted shrinking core model was chosen to describe this non-catalytic solid/gas (CaO/SO2) reaction mechanism. The experimental results were found to be correlated successfully by this model and diffusion through the calcium sulphate product layer is rate limiting.