The effect of oxygen concentration on the non-isothermal combustion of coal

By thermogravimetric experiments under various oxygen concentrations, oxygen-adsorption mass-gain and decomposition/combustion mass-loss stages of coal combustion were investigated. Apparent activation energies were calculated by Starink equation. The results indicate that mass change through oxygen-adsorption mass-gain stage to decomposition/combustion mass-loss stage consists of adsorption mass gain, oxidation/decomposition mass loss, and combustion mass loss. Combustion contributes more to mass loss than do oxidation/decomposition. Inhibition of oxygen concentration in thermal curves shows a linear relationship with oxygen concentration. Different characteristic temperatures show different variations towards oxygen concentrations. At oxygen-adsorption mass-gain stage, apparent activation energy increases with the conversion rate, however, the variations caused by oxygen concentrations were different for different coals. Apparent activation energy first increases and then decreases at decomposition/combustion mass-loss stage whereas it decreases with decreasing oxygen concentration. The conversion rate when the apparent energy reached the maximum increases with increasing oxygen concentration, but the corresponding temperature has little change.