Ma Li, Mao Qisen, Wang Chang'an, Duan Zhonghui, Chen Meijing, Yang Fu, Liu Jiamiao, Wang Zhendong, Che Defu
Shaanxi Provincial Coal Geology Group Co. Ltd., Key Laboratory of Coal Resources Exploration and Comprehensive Utilization, Ministry of Natural and Resources, Xi'an 710026, China.
School of Electrical Engineering, Xi'an Jiaotong University, Xi'an 710049, China.
ACS Omega. 2022 Jul 13;7(29):25613-25624. doi: 10.1021/acsomega.2c02786. eCollection 2022 Jul 26.
Tar-rich coal has the potential to substitute the supply of oil-gas resources, which is abundant in China. The effective conversion of tar-rich coal into oil-gas products can promote coal utilization, reduce resource wastage, alleviate environmental pollution, and benefit carbon neutrality. Nevertheless, less work, if any, has been performed on the pyrolysis and mild oxidation behaviors of tar-rich coal in Northwestern China. The influences of limited oxygen addition and an extremely low heating rate on the micromorphology of the residual semi-coke are yet to be fully understood. Here, an experimental study on the pyrolysis and mild oxidation characteristics of tar-rich coal was conducted by the thermogravimetric analysis method, with further elucidation of the physical-chemical properties of the residual semi-coke. Experimental results show that an increase in the ultimate temperature of pyrolysis leads to a decline in the residue mass, while the mass loss from 500 to 550 °C presents the maximum elevation. Volatile matter is inclined to discharge from a certain direction, and the pores formed in various directions hold different possibilities. The organic components undergo both pyrolysis and slow oxidation with limited oxygen in the heating medium. Compared with an inert atmosphere, the mass loss under conditions of a small amount of O is brought forward but prolonged. Compared with a N atmosphere, the oxidation reactions of tar-rich coal are weakened in the presence of CO. A large decrease in the heating rate exerts an unfavorable effect on the production of total volatiles. An extremely low heating rate possibly brings about a change in the mechanism of chemical bond cracking during pyrolysis. More pores can be yielded in tar-rich coal with an increase in the heating rate, and the morphology of the residual semi-coke after pyrolysis is susceptible to the heating rate. The present study offers an improved understanding of the pyrolysis characteristics of tar-rich coal as well as insights into the efficient utilization of tar-rich coal.
富含焦油的煤炭具有替代油气资源供应的潜力，而中国的此类煤炭资源丰富。将富含焦油的煤炭有效转化为油气产品能够促进煤炭利用、减少资源浪费、减轻环境污染并助力碳中和。然而，中国西北部富含焦油煤炭的热解和温和氧化行为方面的研究工作极少，即便有也寥寥无几。有限氧气添加和极低加热速率对残余半焦微观形态的影响尚有待充分了解。在此，采用热重分析法对富含焦油煤炭的热解和温和氧化特性进行了实验研究，并进一步阐明了残余半焦的物理化学性质。实验结果表明，热解最终温度升高会导致残余物质量下降，而500至550℃之间的质量损失增幅最大。挥发物倾向于从特定方向排出，不同方向形成的孔隙具有不同的可能性。有机成分在加热介质中有限氧气存在下既发生热解又发生缓慢氧化。与惰性气氛相比，少量氧气条件下的质量损失提前但持续时间延长。与氮气气氛相比，一氧化碳存在时富含焦油煤炭的氧化反应减弱。加热速率大幅降低对总挥发物产率产生不利影响。极低的加热速率可能导致热解过程中化学键断裂机制发生变化。加热速率增加时，富含焦油煤炭中会产生更多孔隙，热解后残余半焦的形态易受加热速率影响。本研究增进了对富含焦油煤炭热解特性的理解，并为富含焦油煤炭的高效利用提供了见解。
