The heat treatment and particle size effects in the thermal decomposition of dolomite for separation of constituents

Abstract

The effect of particle size and heat treatment on partial decomposition of dolomite for the extraction of calcite has been investigated. Isothermal firing trials varying the soaking period were performed for dolomite at temperatures between 1013–1033 K according to schedules derived from thermogravimetric analysis (TGA). Samples of dolomite representing three size fractions were used. It is shown that, the optimum heat treatment for reducing the residual MgO in extracted CaCO₃ and maximising the yield of CaCO₃ is accomplished at 1013 K. A soaking time of 160 min seems adequate. The highest degree of partial decomposition was obtained for the 150 μm size fraction of dolomite. A single processing cycle performed under the optimised conditions coupled with relatively short periods of hydration and re-carbonation (24 h, 15 min) yielded CaCO₃ with 7˙5% MgO from a dolomite containing 23˙6% MgO.