Mathematical model for the calcination of CaCO3 under oxy-fuel combustion atmosphere

Abstract

In this thesis, the calcination of CaCO3 under oxy-fuel combustion atmosphere is modeled. At first, a reaction model that simultaneously takes into account the non-uniformity in the solid microstructure and the sintering phenomenon is developed. It predicts the evolution of grain size distribution by using population balances and represents the sintering as a phenomenon of grain combination. This model is validated with experimental data on the redox reactions of copper-based oxygen carriers, in which the sintering phenomenon has a remarkable importance. In addition, it was proposed a mathematical expression for the aggregation frequency that depends on physical meaningful variables and can be used to identify the operating mechanism in sintering. Afterwards, another model for the sintering of the CaO under N2 atmosphere is proposed. This one considers the non-uniformity of the pore size distribution and is used to determine the controlling mechanism in the CaO sintering. Furthermore, it can simulate the sintering of materials with bimodal pore size distributions, commonly found in the study of ceramics. Finally, the sintering model is modified in order to consider the catalytic effect of CO2 on the CaO sintering and then coupled to a reaction model with the aim of simulating the calcination of CaCO3 under CO2 atmosphere.