Fan Haohao, Wang Kai, Zhai Xiaowei, Hu Lihong
School of Safety Science and Engineering, Xi'an University of Science and Technology, Xi'an 710054, China.
Shaanxi Key Laboratory of Prevention and Control of Coal Fire, Xi'an University of Science and Technology, Xi'an 710054, China.
ACS Omega. 2021 Jul 12;6(29):19170-19182. doi: 10.1021/acsomega.1c02520. eCollection 2021 Jul 27.
The phenomenon of spontaneous combustion of "oxidized coal" is common in mining processes of goafs, thick coal seams, and unsealing of closed fire areas. In order to study the reburning characteristics of coal with different oxidation degrees, the oxygen concentration in the pre-oxidation process was selected as the key influencing factor. Thermogravimetric analysis (TGA) and in situ Fourier-transform infrared (FT-IR) spectroscopy were used to study the macro- and microcharacteristics of raw and oxidized coal during the combustion stage. The results showed that the pre-oxidation treatment exhibited a dual effect on promoting and inhibiting the weight loss characteristics of oxidized coal. The apparent activation energy, , of the combustion reaction for the utilized coal samples was calculated using the Flynn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS) methods, and it was found that the average apparent activation energy ( ®) values of the oxidized coal samples were less in magnitude than that of the raw coal and that the coal sample with the pre-oxidized oxygen concentration of 15% was more prone to the combustion reaction. Using the correlation determination method of key active groups in the proposed coal combustion reaction, the key active groups affecting the weight change of the tested coal samples during the combustion stage were determined as -CH and C-O. The results can be helpful to prevent and control coal spontaneous combustion during re-mining and unsealing of closed fire areas.
“氧化煤”自燃现象在采空区、厚煤层开采以及封闭火区启封过程中较为常见。为研究不同氧化程度煤的再燃特性，选取预氧化过程中的氧气浓度作为关键影响因素。采用热重分析（TGA）和原位傅里叶变换红外（FT-IR）光谱法研究原煤和氧化煤在燃烧阶段的宏观和微观特性。结果表明，预氧化处理对氧化煤的失重特性具有促进和抑制双重作用。利用Flynn-Wall-Ozawa（FWO）法和Kissinger-Akahira-Sunose（KAS）法计算了所用煤样燃烧反应的表观活化能，发现氧化煤样的平均表观活化能（®）值在数值上小于原煤，且预氧化氧气浓度为15%的煤样更易发生燃烧反应。采用所提出的煤燃烧反应中关键活性基团的关联判定方法，确定了燃烧阶段影响被测煤样重量变化的关键活性基团为-CH和C-O。研究结果有助于在封闭火区复采和启封过程中防治煤炭自燃。
