An approach for evaluation of grading forecasting index of coal spontaneous combustion by temperature-programmed analysis

Focused on the prediction and forecast index of coal spontaneous combustion, the temperature-programmed experiments were carried out to identify the releasing rule of the gaseous compounds with the consideration of coal particle sizes. Based on the method of growth rate analysis, critical and dry cracking temperatures were determined, dividing the coal low-temperature oxidation process into three stages. The critical temperature for the spontaneous combustion of the coal is in the range of 60 similar to 70 degrees C, with the dry cracking temperature ranging from 100 to 110 degrees C. It was found that the particle sizes had obvious effects on the release of gaseous compounds during the coal heating test. To reduce the influence of coal particle size on the forecasting of coal spontaneous combustion, the combination methods of coefficient of variation and the weighted grey relational analysis were proposed for the selection and evaluation of coal spontaneous combustion indexes. For the tested coal sample, CO2/CO was selected as the primary index and O-2/(CO +CO2) and CO2/O-2 as the alternative indexes. C2H4 and C2H6 were selected as the index gases to confirm that the coal oxidation reached the dry cracking temperature. This research could provide a reference for the determination of the grading forecasting index of coal spontaneous combustion.