Effects of steam on the kinetics of calcium carbonate calcination

Abstract

The effects of the fraction of steam in the reactive gas atmosphere on the decomposition thermodynamics and kinetics of calcium carbonate are reported by systematic assessment of various combination of steam, nitrogen and carbon dioxide. The concentrations of steam, nitrogen and carbon dioxide were varied in the range of 10–90% while assessing the decomposition temperature of the calcium carbonate by means of thermogravimetric analysis. Two commercial samples of stock–lime (96.76% of CaCO3) and Type C sand (85.26% of CaCO3) were compared to investigate the effects of impurities and particle size on decomposition temperature. The effects of temperature and CO2 partial pressure on reaction conversion of CaCO3 were investigated for different concentrations of steam from 70% to 90% in various temperature ranges (830 °C–900 °C). This was used to obtained new kinetic parameters for the calcination reaction with steam and nitrogen at CO2 partial pressure of 0.1–0.4 and temperatures between 830 °C and 900 °C. The activation energy of 161.7 kJ mol−1 and 194.1 kJ mol−1 for calcination of CaCO3 with steam and N2, respectively, imply that steam has a catalytic effect on the calcination reactions. This is confirmed with XRD measurement, which show that no further products are formed after the calcination reaction with steam.