5/20/2023 0 Comments Hydroxyl functional group![]() Generally speaking, the initial temperature of CO production from coal with the lower metamorphic degree is lower, and the concentration increases faster. The gases produced by oxidation at lower temperatures include CO and CO 2, while the gases produced at higher temperatures are mainly hydrocarbon gases. With the increase in temperature, the concentration of CO 2 increased exponentially and the concentration was much greater than that of CO. Some researchers, ,, ] suggested that CO 2 produced at a lower temperature is not produced by oxidation, but by desorption. In this way, the release of gas products will be clear in the process of CSC.ĬSC is a very complicated physicochemical process, with the emission of gaseous products including CO and CO 2, C xH y, H 2, H 2O, etc, ,, , ]. Hence, it is necessary to focus on the changes of active functional groups during low-temperature oxidization, to grasp the effect of active functional groups on the emissions of gas products. The gas products, produced in the process of coal oxidation, not only waste non-renewable coal resources, but also cause serious pollution to the environment. Coal with may generate various gaseous products in the process of CSC, due to the inherent features of spontaneous combustion, ,, ]. Coal oxidation takes place as soon as coal comes into contact with O 2 in the air. The coal spontaneous combustion (CSC) process contains complex physical and chemical reactions, which have been one of the important research topics for centuries. The research results establish the relationship between microscopic changes and macroscopic phenomena of low-rank coal during low-temperature oxidation process, and provide research ideas for understanding low-rank coal low-temperature oxidation process and revealing low-temperature oxidation mechanism. 100 ☌–200 ☌ is the key temperature for producing gases. And methyl/methylene groups made a great contribution to producing CH4. According to the grey correlation analysis, C O was mainly responsible for the formation of CO2 and CO. The initial contents of oxygen-containing functional groups in coal sample 1 are higher. The methyl/methylene content in coal sample 1 is significantly higher than that in coal sample 2 and the initial content of OH–OH in the two coal samples is similar. The relationship between the gases and the active functional groups of coal were explored by grey correlation analysis. In this paper, under the temperature of 30 ☌–350 ☌, the formation and release of small molecule gases and changes of active functional groups were investigated via TG-DSC, TG-IR and in-situ FTIR measurement on low-rank coal. The low-temperature oxidation of active groups in coal plays an important role in the release of small molecule gases during coal spontaneous combustion.
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