Study on the application of coal spontaneous combustion positive pressure beam tube classification monitoring and early warning

To improve the accuracy of early warning on coal spontaneous combustion (CSC), this paper, on the basis of the principle of preferential selection of index gases in CSC process, carries out fitting analysis of the variation curve of index gas data with coal temperature by combining logistic fitting model, then establishes a CSC graded warning system based on positive pressure beam tube monitoring, and determines CO, O₂, φ(CO)/φ(O₂), C₂H₄, C₂H₆, φ(C₂H₄)/φ(C₂H₆) as the index gases for predicting and forecasting CSC, and accurately divides the CSC process into seven levels of early warning: safe, gray, blue, yellow, orange, red, and black. Applying the CSC positive pressure beam tube monitoring system to Dongtan coal mine and analyzing the error by manual sampling and sampling by positive pressure beam tube system, we find that the error is less than 0.1%. Monitoring of several working faces, we get that the CO and CH₄ concentrations of 14,320 working face are higher than the normal level at the beginning of mining, and the 100 × CO/ΔO₂ value is higher than the gray warning threshold of 0.1, and the warning level is gray warning. After taking timely preventive measures against coal oxidation and warming, the CO and CH₄ concentrations return to the normal level and the warning level drops to the safe level. This paper improves the monitoring, identifying and early warning capabilities of underground CSC in its early stage.