| In the mining process of high gas and easy spontaneous combustion mine,for the old goaf with spontaneous combustion or the working face closed by spontaneous combustion,the pore structure of remaining roal will change after low temperature oxidation,and the pore structure of remaining coal with different particle size is also different,which leads to the change of adsorption characteristics of remaining coal to methane,oxygen and other gases in goaf.When the air leakage in the old goaf or the re-opening of the working face,the proportion of gas components in the goaf will change,so the influence of methane gas on the physical adsorption of oxygen by coal will also change.Therefore,based on the actual problems in the 81301 old goaf of Yangmei No.1 Coal Mine,through field measurement and laboratory research,the pore structure characteristics of remaining coal with different oxidation degree in the old goaf and the adsorption law of multi-component gas by remaining coal with different particle size or different oxidation degree were studied.First of all,the change rules of moisture,ash and volatile in the process of low temperature oxidation were studied by industrial analysis.the results showed that the content of moisture and volatile in coal samples decreased with the increase of oxidation temperature of coal samples.among them,the volatile content decreased slowly at first and then quickly,and the ash content increased slowly.In addition,the evolution characteristics of pore structure caused by low temperature oxidation were studied by liquid nitrogen adsorption experiments on coal samples with different oxidation degrees.the specific surface area and pore volume of pores in each scale were positively correlated with the oxidation temperature of coal samples.With the increase of oxidation temperature of coal samples,the specific surface area of micropores gradually increased,but the proportion decreased slightly,the specific surface area of micropores increased,the specific surface area of mesopore increased at first and then decreased,and both micropore volume and mesopore volume increased slowly.the increasing rate of micropore volume is first fast and then slow,the proportion of micropore and small pore volume increases gradually,and the proportion of mesopore volume decreases gradually.Secondly,the adsorption characteristics of single methane gas on coal samples with different particle sizes and different oxidation degrees at constant temperature or corresponding oxidation temperature were studied.the results show that the methane adsorption capacity increases gradually with the decrease of coal particle size;for coal samples with particle size less than 120 mesh,the methane adsorption capacity does not increase significantly with the further decrease of particle size,and the methane adsorption capacity of coal samples with high oxidation degree is larger at the same temperature.In the experiment of methane adsorption by low temperature oxidized coal at corresponding oxidation temperature,the effect of temperature on methane adsorption is greater than that of oxidation.Finally,the adsorption rules of multi-component gases on coal samples with different particle sizes and different oxidation degrees were studied under atmospheric pressure.the results show that the gas adsorption capacity of coal samples with different particle size and oxidation degree increases with the decrease of particle size.the order of adsorption capacity of coal samples with different particle size and oxidation degree to the three component gases is the same,which is CH4>N2>O2,indicating that the particle size and oxidation degree have no effect on the preference of coal adsorption gas.For the coal samples with smaller particle size,the oxygen adsorption capacity is more easily affected by the methane volume fraction;similarly,the oxygen adsorption capacity of the coal samples with higher oxidation degree is more easily affected by the methane volume fraction.The paper contains 30 figures,31 tables and 76 references. |
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