Determination of the kinetic parameters of oxy-fuel combustion of coal with a high ash content

Abstract

The aim of this study was to determine the kinetic parameters of the oxy-fuel combustion of char from a Brazilian bituminous coal with a high ash content. The char, with a particle diameter of 715 μm, was prepared in a N2 atmosphere at 1173 K. The oxy-fuel combustion assays were performed using a thermobalance at different temperatures and O2/CO2 gas mixtures of different concentrations. According to the unreacted core model, the process is determined by chemical reaction at low temperatures, with an activation energy of 56.7 kJ.kmol-1, a reaction order of 0.5 at 973 K and a reaction order of 0.7 overall. The use of the continuous reaction model did not provide a good fit for the experimental data because the consumption of the particles during the reaction was not constant, as predicted by the model. According to the Langmuir-Hinshelwood model, the activation energy for the first step was 37.3 kJ.kmol-1.