Analysis of gas characteristics and generation rules of coal spontaneous combustion in goaf

At present，there are few researches on coal spontaneous combustion with different metamorphic degree under environment conditions of simulated gradually heated goaf. Taking 4 kinds of metamorphic coal samples, such as coke lean coal, gas-fat coal, anthracite coal and fat coke coal as example, the experiment of coal spontaneous combustion was carried out by using simulation system of coal spontaneous combustion to study combustion characteristics of coal and generation rules of spontaneous combustion gas under goaf environment. Experiment results show that when coke lean coal, gas-fat coal, anthracite and fat coke coal are warmed up, the temperature will rise "S" type. The early temperature will have a slow accumulation process at first and then start to heat up quickly, and finally tend to balance at 300 ℃, and then slowly rising. Different coal samples produce volatile gases such as hydrocarbons and carbon oxides during the spontaneous combustion process and the rate of formation is affected by temperature, as well as the maximum and minimum two inflection points are present. The temperature rise curve of anthracite coal is similar to a straight line, and the gas curve does not fluctuate obviously with temperature. Large amounts of CO and CH4 are produced in spontaneous combustion of gas-fat coal and fat coke coal, the rate of CO production of gas-fat coal is the fastest, the maximum volume fraction of CO can reach 8%; and the rate of CH4 production of fat coke coal is the fastest, the maximum volume fraction of CH4 can reach 14%. The volume fraction of CO and CO2 produced by coke lean coal and anthracite is about 2% and 4% respectively.