Comprehensive study on bituminous coal oxidation by TGA–DTA–FTIR experiment

The spontaneous combustion of coal can have serious consequences. Bituminous coal is especially problematic as it produces a large amount of smoke comparative to other coals. Variable heating rate thermogravimetry analysis–differential thermal analysis–Fourier transform infrared spectroscopy experiments (TGA–DTA–FTIR) were conducted on three kinds of bituminous coals to study the change rule of weight, heat, and generated gas during the entire oxidation process from slow self-heating to burn out. Experimental results indicate that weight, heat, and gas release are in mutual correspondence at stages 1-4 in the oxidation process. However, change in generated gas lags behind weight and heat changes in the last stage. The main gas products of the oxidation process are CO, CO2, H2O, and CH4.The process of gas release depends on the reaction characteristics of related active structures. The concentration of generated gas from the same coal is CO2>H2O>CO>CH4. CO2 accounts for about 90% of the total amount of gas. The relationships between absorbance and temperature of generated gases in the rapid generation stage are linear or binomial, R2 are higher than 0.95. A comparison of the experimental results on different bituminous coals shows that when volatile matter is high, the characteristic temperatures are low and the concentration of generated gas and rate of heat release are high.