KINETICS OF THE CALCIUM-SULFATE DECOMPOSITION

The decomposition of fine calcium sulphate particles was studied in a thermogravimetric system at isothermal and nonisothermal conditions. A wide range of experimental conditions were tested; temperature (from 1300 to 1530 K), oxygen concentration (from 0 to 21%) and sulphur diox ide concentration (from 0 to 5000 ppm). The conversion-time curves are linear in shape. The presence of oxygen and sulphur dioxide strongly affects the reaction kinetics, retarding the decomposition. The change of reaction rate with temperature is affected by the type of decompos ition atmosphere. Thus, different values of activation energy were mea sured from the initial reaction rates: 81 kcal mol(-1) (in N-2), 132 k cal mol(-1) (in 5% O-2) and 212 kcal mol(-1) (in 0.3% SO2). It was fou nd that the decomposition reaction is chemically controlled at the exp erimental conditions analysed. A model based in the shrinking unreacte d core model (flat plate shape) was developed to describe the kinetics of the reaction. A good agreement between the experimental data and t hose predicted by the model was found.