Research Of Spontaneous Combustion In Goaf Of Large Mining Height Working Face

In the process of coal mine production,spontaneous combustion of scattered coal in goaf with large mining height will cause a great threat to life and property safety.The study of spontaneous combustion index gas and flow field analysis in goaf play an important role in early prevention and prediction of spontaneous combustion of coal in goaf.The distribution of gas components in the working surface of large mining height is obviously stratified in the vertical direction.As a black box model,the goaf is often measured by sensors on the wall to measure temperature and concentration,and the specific location of the disaster point is difficult to predict.In the early stage of coal spontaneous combustion,there will be standard gas generation,which can be used as an analysis of the fire trend in goaf.Many scholars and experts have done a lot of research,but there are few studies on the spatial migration rule and prediction mode of the working face with large mining height.In view of the above problems,this paper mainly does the following research:Through coal program heating experiments,the gas production law during coal heating process was analyzed,and the three stages of coal oxidation were defined according to the temperature and corresponding gas production law(CO,CO2,CH4,C2H4,C2H6,and C3H8)at 90℃ and 150℃,and the oxygen consumption rate,carbon monoxide production rate,and temperature rise rate were fitted by regression analysis,and the early self-ignition indicator gas was selected.Based on the situation of the large mining height working face,a multi-field coupling model of coal self-ignition in the goaf of the large mining height was established using COMSOL multi-physics simulation software,and the flow field migration law in the goaf was analyzed.Combined with the traditional three-zone division method of self-ignition in goaf,the spatial distribution of the three zones of self-ignition in the goaf was defined,and the distribution of O2,CO,and temperature in the goaf in the large space area was explored.The change of oxygen concentration in the vertical direction was analyzed,and the range of the three regions distributed in the vertical direction was defined as the easily disaster-prone area,potential disasterprone area,and not easily disaster-prone area.The change law of CO concentration of self-ignition early indicator gas in the upper corner was also analyzed.Combined with the multiple parameters that affect disaster,the fuzzy hierarchy analysis method was used to analyze the target mine,and the safety evaluation result was a safe disaster mine.Based on the spatial analysis of the disaster point in the Ningtiaota large mining height coal seam,fire prevention and extinguishing measures such as nitrogen injection and grouting were proposed,and the simulation analysis of nitrogen injection effect was carried out,and fire prevention suggestions for the early stage of self-ignition in goaf were proposed.