Changes in full characteristics of spontaneous coal combustion under influence of temperature-driven CO2 desorption

Abstract

In coal mine goafs, spontaneous coal combustion disaster is a heating process caused by coal oxidation. Many experiments have investigated the variation of coal oxidation characteristics under different inert conditions; however, the time precondition of the inert conditions is usually ignored. In this study, a porous material adsorbed with CO₂ is mixed with coal for the oxidative heating experiment to investigate its full influence on the coal oxidation characteristics. The experimental results show that CO₂ proactively desorbs from the porous material at a small increase in temperature. In the mixture sample, the CO₂ concentration increases sharply to 57080 ppm around 80 ∼ 90 °C, and the crossing point temperature moves to the high-temperature region with a maximum delay of 26.3 %, significantly slowing down the oxidation process of the coal. In addition, the composite decision index of the mixture sample increases by a maximum of 10.91 %, and the spontaneous combustion tendency of the coal changes from “Spontaneous combustion” to “Non-prone to spontaneous combustion”, essentially decreasing the spontaneous coal combustion capacity. The temperature-driven CO₂ desorption from the porous material dilutes the oxygen concentration to hinder the coal-oxygen composite reaction from the very beginning of coal oxidation process, presenting an advanced and efficient preventive effect.