Half-calcination of dolomite. kinetics and structural changes

Since dolomite is an effective sorbent for the control of sulfur emissions in the fluidized-bed combustion and gasification of coal, the kinetics of the various reactions involved in the cyclic use of dolomite were studied, in particular, the half-calcination reaction was studied since the half calcined dolomite has a greater porosity and surface area than fully calcined dolomite. Thermogravimetric analysis was used to study the rate of the half calcination reaction and structural data was obtained by methods such as optical microscopy. The rate of half-calcination was a strong function of temperature and the geographic origin of the stone. It was also dependent, to a lesser extent, on total pressure, partial pressure of CO/sub 2/ and pellet size. The nucleation of the product phase, MgO or CaCO/sub 3/, may be the controlling mechanism, although stones from different geographic locations may have different controlling mechanisms. Low temperatures for the half-calcination reaction favored high rates for the subsequent sulfidation reaction.