Investigation of the Influence of Moisture During Coal Self-Heating
During coal self-heating, the dehydration process and oxygen consumption by coal with different moisture content were analyzed. The oxidation process of aliphatic hydrocarbons, peroxyl radical, and nitrogen-, and sulfur-containing structures with/without water were evaluated by quantum chemical calculations. Our results indicate that the dehydration order of chemically adsorbed water is Ar-C(CH3)2OO·, C7H8S, C6H6S, C4H5N, Ar-CHO, Ar-CH2-OH, Ar-COOH, Ar-CH2OO·, and Ar-CH(CH3)OO·; the bituminous coal has a critical moisture range of 9.4-10.3% to maintain the balance with intrinsic reactivity. Below the critical moisture content, as moisture content decreases, the self-heating rate is the faster and the oxygen consumption rate is the greater; within 70 °C, without/with adsorbed water, the chemical adsorption of oxygen is respectively through sulfur- and oxygen-containing functional groups, and through C6H6S, C7H8S, Ar-CH2OH and Ar-CHO; at the temperature range of 70-110 °C, the oxidation of aliphatic hydrocarbons is the main reason for the oxygen consumption. Without adsorbed water, oxygen directly extracts H from the functional group to form ·OOH; peroxyl radical directly abstracts H from a nearby aliphatic structure. During the process, water acts as an H-transfer mediator. Adsorbed water promotes H abstraction by peroxyl radical from Ar-CH2OO· and Ar-CH(CH3)OO·, suppresses H abstraction by peroxyl radical from Ar-C(CH3)2OO·, promotes H abstraction by O2 from C4H5N and C7H8S, and suppresses H abstraction by O2 from thiophenol. The exothermic reactions mainly include the abstraction of H from C7H8S with adsorbed H2O by O2, and bond breakage in peroxyl radicals with/without adsorbed water, except Ar-CH(CH3)OO·
Year of publication: |
[2022]
|
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Authors: | Xi, Zhilin ; Xi, Ke ; Lu, Linping ; Li, Xue |
Publisher: |
[S.l.] : SSRN |
Saved in:
freely available
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