Zheng Xu, Liu Jia, Liu Peng, Liu Xiaoping, Luo Ping, Hao Guangzu, Liu Hongwei, Cai Tingting
College of Safety and Emergency Management Engineering, Taiyuan University of Technology, Taiyuan 030024, China.
School of Resources and Safety Engineering, Chongqing University, Chongqing 400000, China.
ACS Omega. 2024 Jul 26;9(31):33679-33691. doi: 10.1021/acsomega.4c02310. eCollection 2024 Aug 6.
Low-oxygen (oxygen concentration below 18.5%) phenomena often occur in the top coal caving working face of ultrathick coal seams, posing a serious threat to the safety of workers. The characteristics of oxygen consumption and gas production at low-constant temperature and the corresponding functional group evolution of residual coal in goaf were studied by temperature-programmed and infrared spectrum experiments. The influence of different factors on the emission of low-oxygen gases was studied through numerical calculation. The results show that low-temperature oxygen consumption and gas production occurred when the coal was about 40 °C. When the temperature was constant, the oxygen consumption and gas production rate increased with the extension of time. In the early stage of coal oxidation, the aliphatic C-H components were attacked by oxygen molecules and reacted with them. The asymmetric methyl and methylene groups were more likely to oxidize and produce carbonyl compounds. With the increase of nitrogen injection, the overall width of the oxidation zone (oxygen concentration was defined as 10-18%) narrowed, and the range of the oxidation zone moved forward from the depth of the goaf. The oxygen concentration in the air return corner decreased gradually, and the low-oxygen area in the air return corner expanded gradually. The distance between the low-oxygen area of the working face and the air intake corner was gradually shortened. With the increase of air intake, the width of the oxidation zone increased and moved to the depth of goaf, and the degree of low oxygen in the air return corner increased. The research results are of great significance for the understanding and prevention of the low-oxygen phenomenon in ultrathick coal seams.
低氧（氧气浓度低于18.5%）现象在特厚煤层放顶煤工作面经常发生，对工人安全构成严重威胁。通过程序升温实验和红外光谱实验研究了采空区残留煤在低温恒温下的耗氧产气特征及相应官能团演化。通过数值计算研究了不同因素对低氧气体涌出的影响。结果表明，煤温约40℃时发生低温耗氧产气现象。恒温时，耗氧产气速率随时间延长而增大。煤氧化初期，脂肪族C-H组分受到氧分子攻击并与之反应，不对称甲基和亚甲基更易氧化并生成羰基化合物。随着注氮量增加，氧化带（氧气浓度定义为10% - 18%）整体宽度变窄，氧化带范围从采空区深部向前移动，回风隅角氧气浓度逐渐降低，回风隅角低氧区域逐渐扩大，工作面低氧区域与进风隅角的距离逐渐缩短。随着进风量增加，氧化带宽度增大并向采空区深部移动，回风隅角低氧程度增大。研究结果对认识和防治特厚煤层低氧现象具有重要意义。
