Modeling of the isothermal sulphation reactions of natural sorbents

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.