Application of multi-index grey target decision method in prediction of coal temperature in goaf

Abstract

ABSTRACT The index gas analysis is an important method of predicting coal spontaneous combustion (CSC). The temperature programmed experiment was used to simulate the CSC process in goaf, and the characteristics of each index gas and coal temperature change were investigated. The corresponding relationship between the target center distance and the coal temperature was determined using the multi-index weighted gray target decision theory. The findings indicate that the selected gases (CO, C2H4, C2H6) and gas combination (format fire coefficient (R), φ(CO)/φ(CO2), φ(C2H4)/φ(CH4), φ(C2H4)/φ(C2H6)) can be used as index gases for CSC prediction. The critical temperature was 70°C and the dry cracking temperature was 110°C. The combined action of coal and oxygen is divided into three stages: slow oxidation (30–70°C), accelerated oxidation (70–110°C), and strong oxidation (after 110°C). The combination of the programmed temperature experiment and the weighted gray target decision theory model determines the relationship between the off-target distance and the coal temperature. The lower the degree of CSC, the better the decision scheme, and the smaller the off-target distance. The results of Xiaobaodang’s experimental analyses are applied to the field, and the actual coal temperature in the goaf is predicted to be between 37–62°C. The risk level of CSC in the goaf is determined more intuitively and precisely, providing a theoretical foundation for improving the mining area’s fire prevention and extinguishing scheme.