Zhang Liankun, Kang Tianhe, Kang Jianting, Zhang Xiaoyu, Zhang Bin, Guo Junqing, Chai Zhaoyun
Key Laboratory of In Situ Property Improving Mining of Ministry of Education, Taiyuan University of Technology, Taiyuan 030024, PR China.
College of Safety and Emergency Management Engineering, Taiyuan University of Technology, Taiyuan 030024, PR China.
ACS Omega. 2021 Nov 16;6(47):31566-31577. doi: 10.1021/acsomega.1c04056. eCollection 2021 Nov 30.
To better understand the methane adsorption behavior after microwave exposure, the importance of quantitatively characterizing the effect of cyclical microwave exposure on the molecular structures of coals cannot be overemphasized, with implications for enhancing coalbed methane (CBM) extraction. Thus, cyclical microwave exposure experiments of three different metamorphic coals were conducted, and the methane adsorption capacity before and after each microwave exposure (10 in total) for 120 s was evaluated. Fourier transform infrared spectroscopy analysis and peak fitting technology were applied to quantitatively characterize the changes in the structural parameters of coal molecules. The results showed that after modification, the structural parameters like aromatic carbon fraction ( ), aromaticity ( and ), degree of condensation ( and ), and the maturity of organic matter ("") gradually increased with increasing exposure times, while the length of the aliphatic chain or its branching degree ( / ) and the hydrocarbon generating capacity ("") showed a decreasing trend. The Langmuir volume ( ) of three different rank coal samples decreased from 29.2, 32.8, and 40.4 mL/g to 25.7, 29.3, and 35.7 mL/g, respectively; the Langmuir pressure ( ) increased from 0.588, 0.844, and 0.942 MPa to 0.626, 1.007, and 1.139 MPa, respectively. The modification mechanism was investigated by analyzing the relationship between the methane adsorption behaviors and molecular structures in coals. The release of alkane side chains and the oxidation of oxygen-containing functional groups caused by microwave exposure decreased the number of methane adsorption sites. As a result, the methane adsorption capability decreased. In addition, the decomposition of minerals affects methane adsorption behaviors in coals. This work provides a basis for microwave modification of coal as well as in situ enhancement of CBM extraction using microwave exposure.
为了更好地理解微波辐照后甲烷的吸附行为，定量表征循环微波辐照对煤分子结构的影响对于提高煤层气（CBM）开采具有重要意义，怎么强调都不为过。因此，进行了三种不同变质程度煤的循环微波辐照实验，并评估了每次微波辐照（共10次）120秒前后的甲烷吸附能力。采用傅里叶变换红外光谱分析和峰拟合技术定量表征煤分子结构参数的变化。结果表明，改性后，芳香碳分数（ ）、芳香度（ 和 ）、缩合度（ 和 ）以及有机质成熟度（“”）等结构参数随辐照时间增加逐渐增大，而脂肪链长度或其支化度（ / ）和生烃能力（“”）呈下降趋势。三种不同煤阶煤样的朗缪尔体积（ ）分别从29.2、32.8和40.4 mL/g降至25.7、29.3和35.7 mL/g；朗缪尔压力（ ）分别从0.588、0.844和0.942 MPa升至0.626、1.007和1.139 MPa。通过分析煤中甲烷吸附行为与分子结构之间的关系，研究了改性机理。微波辐照导致烷烃侧链的释放和含氧官能团的氧化，减少了甲烷吸附位点。结果，甲烷吸附能力下降。此外，矿物的分解影响煤中甲烷的吸附行为。这项工作为煤的微波改性以及利用微波辐照原位强化煤层气开采提供了依据。
