Study of Isothermal Behaviour of Natural Tunisian Dolomite Under Controlled Pressure of Carbon Dioxide

Abstract

The first half decomposition of natural Tunisian dolomite sample, was investigated by thermogravimetric measurements and in situ X-Ray diffraction, in controlled CO₂ pressure (20 < PCO₂ < 500h Pa) and in isothermal conditions (in the temperature range 823-1023 K). The thermograms exhibited two consecutive weight losses, corresponding to fractional conversion ranges of 0-0.2 and 0.2-1. A decelerating effect of was observed only during the second weight loss. In situ X-ray diffraction results indicate that crystal lattice of dolomite undergoes, during the thermal treatment, a dilatation along the c direction, then it decomposes progressively into poor crystalline MgO and a magnesian calcite Mg_0.052Ca_0.948 CO₃. The characterization of the final product using SEM and XPS has shown that MgO could precipitate at the surface of CaCO₃.