School of Safety Science and Engineering, Xi'an University of Science and Technology, Xian, Shaanxi, China.
Minist Land & Resources, Key Lab Coal Resources Explorat & Comprehens Uti, Xian, Shaanxi, China.
Environ Sci Pollut Res Int. 2023 Sep;30(41):94865-94877. doi: 10.1007/s11356-023-29107-2. Epub 2023 Aug 4.
The intrinsic reaction of coal with oxygen in the process of low-temperature oxidation is the main reaction path leading to self-heating and spontaneous combustion of coal. Most of the existing studies regard the coal oxidation as an overall reaction, ignoring the multi-path characteristics of coal low-temperature oxidation, and it is difficult to accurately explore the intrinsic reaction characteristics between coal with oxygen. Therefore, the low-temperature oxidation process of coal was studied by using a C80 microcalorimeter and in situ FTIR technology from the macro and micro levels. The "profile subtraction method" was used to study the coal-oxygen intrinsic reaction process, and the reaction heat effect and the change characteristics of key functional groups in the process were analyzed. Furthermore, the gray correlation analysis method was used to study the relevant characteristic parameters in the reaction process and grasp the essential structure-activity relationship. The experimental results show that, compared with the overall reaction process in air atmosphere, the change in the heat release of the coal-oxygen intrinsic reaction path has changed to different degrees, and the change in the slow oxidation stage is the most significant (the heat absorption decreases by 70.1-90.9%). In addition, the characteristic temperature points show different degrees of advance, of which the initial exothermic temperature point is the largest (about 21-46 °C), which directly leads to a significant shortening of the slow oxidation stage (30.1-47.4%). The changes of functional groups in the intrinsic reaction path are more regular. With the increase of temperature, the oxygen-containing functional groups -C=O and the aliphatic hydrocarbon functional groups -CH- and -CH showed a fluctuating trend of increasing and decreasing, respectively. The oxidation heat-contributing functional groups of coal are mainly related to the degree of metamorphism and the functional group reaction characteristics during the reaction. With the deepening of coalification degree, the main heat-contributing functional groups as a whole showed the change rule of oxygen-containing functional groups → aliphatic hydrocarbon functional groups → aromatic hydrocarbon functional groups. In addition, the change of -OH content in the three coal samples has a high correlation with the change of the total heat release of coal.
煤在低温氧化过程中与氧气的本征反应是导致煤自热和自燃的主要反应途径。大多数现有研究将煤氧化视为一个整体反应，忽略了煤低温氧化的多路径特性，难以准确探究煤与氧气的本征反应特性。因此，采用 C80 微量量热仪和原位 FTIR 技术从宏观和微观层面研究了煤的低温氧化过程。利用“谱线减差法”研究了煤氧本征反应过程，分析了反应热效应和过程中关键官能团的变化特征。进一步采用灰色关联分析方法研究了反应过程中的相关特征参数，掌握了本质的结构-活性关系。实验结果表明，与空气气氛下的整体反应过程相比，煤氧本征反应路径的放热量变化程度不同，且慢速氧化阶段的变化最为显著（吸热量减少了 70.1%90.9%）。此外，特征温度点呈现不同程度的提前，其中初始放热温度点最大（约 2146℃），这直接导致慢速氧化阶段明显缩短（30.1%~47.4%）。本征反应路径中官能团的变化更为规律。随着温度的升高，含氧官能团 -C=O 和脂肪族烃官能团 -CH-和 -CH 呈先增后减的波动趋势。煤的氧化放热官能团主要与煤在反应过程中的变质程度和官能团反应特性有关。随着煤化程度的加深，主要的放热官能团整体表现出含氧官能团→脂肪族烃官能团→芳香族烃官能团的变化规律。此外，三种煤样中 -OH 含量的变化与煤的总放热量变化具有高度相关性。
