SCT reaction kinetics model and diffusion for p.c. combustion in TGA

Abstract

Recently, the process of char burnout is extensively concerned. Global model used widely cannot predict the extent of char burnout at the later burning stage. For the need of predicting the burnout degree in industrial pulverized coal (p.c.) fired furnace by making use of the experimental data from such as thermogravimetry analysis (TGA) and drop tube furnace, based on the simple collision theory (SCT) of chemical reaction kinetics, the SCT model is educed. The p.c. combustion is considered as the results of strike and oxidation of oxygen molecules on the surface of p.c. particles, and the frequency of effective strike was determined by Boltzmann factor. Strike and oxidation occur on the oxygen accessible specific surface area (OASA). Chemical regime controlled is at temperature below 1200 K, and molecules diffusion regime controlled is at the temperature above 1600 K, at which OASA corresponds to the specific surface area with pore diameter more than 38 nm of p.c particles in coal-fired boiler. The OASA of p.c. particles increases with the char burning, for the particles swells, shrinks and cracks. The burning rates calculated based on SCT model have shown good correspondence with experimental data reported. 