Experimental study on inhibition of spontaneous combustion of coal by gas mixture

In order to investigate the influence of gas mixture (O2/N2 and O2/N2/CO2) on the spontaneous combustion characteristics of coal, synchronous thermal analyzers, temperature programmed gas chromatography/infrared spectrometers were used to study the characteristic temperature, thermal effect/indicator gas, and functional group changes of coal under gas mixture. The results show that under O2/N2 atmosphere, with the increase of N2 volume fraction, the characteristic temperature point lags behind, TG, DTG, DSC all shift towards high temperature, heat release decreases, activation energy during combustion stage increases, final oxygen consumption and CO volume fraction of coal decrease, hydroxyl groups in coal increase, and the content of aliphatic hydrocarbons, oxygen-containing functional groups, and aromatic hydrocarbons shows a decreasing trend; under O2/N2/CO2 atmosphere, as CO2 increases, the characteristic temperature point shifts backward, the heat release decreases, the activation energy during the combustion stage decreases, the oxygen consumption and CO volume fraction both decrease, hydroxyl and fatty hydrocarbons increase, and the content of oxygen-containing functional groups decreases; when the volume fraction of O2 is the same, the peak weight loss rate, oxygen consumption, and CO volume fraction in the O2/N2/CO2 mixture are all lower than those in O2/N2; −OH is easily oxidized and undergoes dehydration reaction. Coal releases less heat in the initial stage of the reaction, but rapidly increases in the later stage. CO is mainly generated by −C=O.