CO-based early warning threshold for coal spontaneous combustion

Abstract

Few studies have been involved in the CO-based early warning threshold, although carbon monoxide (CO) is a vital gas indicator for predicting coal spontaneous combustion. In this paper, based on the dependency relationship between CO concentration and coal temperature, a novel approach is proposed to determine the critical value of CO. Firstly, the low-temperature oxidation characteristics of coal samples were investigated through a temperature-programmed system, and the critical temperature of coal samples was analyzed. Furthermore, the functional relationship between CO emissions and coal temperature was investigated based on on-site measurements. Accordingly, the critical value of CO corresponding to the critical temperature was determined. Finally, the migration and generation behavior of CO was studied by combining with air seepage, component transport, thermal transfer, and exothermic reaction. The results show that when the coal temperature in goaf reaches the critical temperature of 53 °C, the CO concentration will reach 110.84 ppm. This concentration is the critical value of CO. The numerical simulation analysis of CO gas migration in goaf shows that when CO concentration reaches the critical value, the CO gas concentration in the corner of the upper corner, the return air flow, and extraction pipeline are 10.69 ppm, 7.91 ppm and 67.26 ppm, respectively. This concentration is the critical value of CO at the corresponding position. The approach established can meet the requirements of identification of spontaneous combustion potential of coal, and ensure the safety of mine production.