THE THERMAL-DECOMPOSITION OF DOLOMITE

The thermal decomposition of dolomite, CaMg(CO3)2, has been studied by obtaining thermogravimetric and differential thermal analysis curves in various controlled atmospheres involving the use of N2)-CO2 mixtures. The DTG and DTA curves show two peaks: the first is associated with the formation of magnesia and calcite, the second with the decomposition of this calcite. The temperature of the second peak increases with increasing partial pressure of carbon dioxide, but the first peak behaves in an anomalous manner. At first it decreases in temperature with increasing partial pressure of carbon dioxide, reaching a minimum value between 10% and 20% carbon dioxide. Subsequently it increases, although the temperature at 1 atm of carbon dioxide is still below that in 1 atm of nitrogen. The addition of either ammonium chloride or sodium carbonate reduces the decomposition temperature of the first peak, liberating magnesite. It is proposed that the mechanism of the decomposition of dolomite is via the formation of the two separate carbonates of magnesium and calcium. © 1990.