CFD-aided optimization of the decomposition kinetics of cement raw meals under high CO2 concentrations

Abstract

Oxy-fuel combustion technology is a promising option for CO2 capture in the cement industry, as the cement raw meal decomposes to generate large amounts of CO2. Exploring the decomposition kinetics of raw meal under high CO2 concentrations is crucial for the design and operation optimization of precalciners. In this work, a new method is proposed to obtain the decomposition kinetics of cement raw meals. First, a real decomposition atmosphere, including the temperature and CO2 concentration in an actual precalciner, is simulated in an electric-heated down firing furnace (E-DFF), and the decomposition characteristics of raw meal at various temperatures (850–1050 °C) and CO2 concentrations (0–90 vol%) are investigated. Second, a detailed decomposition model of raw meal under high CO2 concentrations is developed, and this model considers gas adsorption and surface reactions, structural changes due to solid product formation, gas diffusion around the particle and particle temperature changes due to heat transfer and endothermic reactions. Third, the prediction model of raw meal decomposition is implemented into CFD software, and the kinetic parameters are determined via a CFD-aided optimization method in which a direct search algorithm is used to accelerate the optimization process. Finally, the optimized kinetics are verified over wide ranges of temperatures, residence times, and CO2 concentrations. The simulation results agree well with the experimental data, indicating that the developed model and obtained kinetic parameters could be applied for the application of oxy-fuel combustion technology in the cement industry.