Combustion Characteristics of Coal Gangue under an Atmosphere of Coal Mine Methane

Abstract

Combustion characteristics of coal gangue under O2/N2 mixtures with different O2 concentrations and coal mine methane (CMM) conditions were investigated by using thermogravimetric analysis (TGA) and tube reactor tests. Calculation results for the combustion characteristic parameters show that ignition temperature, burnout temperature, and peak temperature increase, while the maximum and average combustion rates decrease with decreasing O2 concentrations. The mass loss decreases and comprehensive combustion characteristic index increases slightly when CH4 is present in the combustion atmosphere with equivalent O2 concentration. TGA and tube reactor tests indicate that the mass loss of coal gangue is mainly attributed to the combustion of volatile matter and of fixed carbon. A temperature rise to ∼650 °C markedly inhibits carbon combustion because of O2 consumption caused by combustion of CH4 and H2 produced from CH4 cracking. Kinetic parameters (apparent activation energy (E), reaction order, and frequency factor) were calculated for various atmospheres by direct linear regression of the kinetic equation from a single TGA curve. The E value of coal gangue combustion varies from 117.6 to 137.4 kJ/mol under different atmospheres, and is slightly higher in CMM than in the O2/N2 mixture with equivalent O2 concentration.