Heat-gas production characteristics of pre-oxidized coal and its experimental shortest period of spontaneous combustion
DOI:
https://doi.org/10.17159/Abstract
During the coal mining process, the re-ignition of old fire sources occurs frequently, which is essentially the secondary oxidation of coal with different pre-oxidation degrees. However, data is still scarce about the spontaneous combustion characteristics of pre-oxidized coal, which hinders the efficient prevention and control the re-ignition of old fire sources. Coal samples with different pre-oxidation degrees were prepared by oxidizing at different temperatures (50 oC, 120 oC, 200 oC) for different times (6h, 24h) and an experimental system was built to simulate the coal oxidation process and test its gas generation characteristics. A new method called guided-heating method was used to calculate the adiabatic oxidation temperature rise curve, based on which the experimental shortest period of spontaneous combustion was obtained, and the heat generation characteristic was calculated. It was found that the prediction of the spontaneous combustion risk of old fires should be based on the heat production characteristics of the pre-oxidized coal at 120 oC, as it had the highest value in the slow oxidation stage. Moreover, pre-oxidized coal samples have a higher absolute production of CO and a higher rate of CO production. When the CO indicator is used to judge the development stage of the old fire source, the critical value of the CO indicator should be adjusted accordingly, which is higher than that of the raw coal.
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