Low-temperature pyrolysis is one of the important ways to achieve clean and efficient utilization of lignite. Semi-coke as the solid product of pyrolysis is widely used in both industrial and civil clean fuels. In this study, three lignites from Inner Mongolia (SHM), Indonesia (YN) and Mongolia (WM), and their pyrolyzed semi-coke at 550℃ were used as samples to investigate the concentrationand composition changes of soluble polycyclic aromatic hydrocarbons (PAHs) by extraction combined with GC/ MS analysis. The resultsshowed that the concentrations of total PAHs ( ∑ PAHs), 16 US EPA priority PAHs ( ∑16PAHs) and their alkylated derivatives(∑aPAHs) of the three lignites were in the ranges of 4 362-125 635, 1 871-35 039 and 1 723-61 757 ng/ g, respectively. It revealedthat the concentration of PAHs in lignite from different sources was significantly different, and aPAHs were abundant in all lignite. The concentrations of ∑PAHs, ∑16PAHs and ∑aPAHs the three semi-cokes were in the ranges of 4 679-10 289, 1 831-6 354 and 744-2 737 ng/ g,respectively. The relative abundance of PAHs in the semi-cokes with respect to the corresponding lignites was different. SHM semi-cokehad a lower concentration of PAHs than SHM lignite, YN semi-coke had a higher concentration than YN lignite, and the PAHs content ofWM semi-coke were similar to that of raw coal, but the parent 16PAHs content of WM semi-coke were relatively higher than that of WMraw coal. The ∑aPAHs concentrations of three semi-cokes were all lower than the corresponding parent ∑16PAHs concentration, indicating that the PAHs retained in semi-coke were dominated by the more thermodynamically stable parent form. The composition of PAHs inboth lignite and semi-coke was dominated by 2-3 rings low molecular weight PAHs. Especially the concentration of naphthalene and alkylated naphthalenes in YN semi-coke was the main reason for the increase of the total concentration of PAHs. It indicated that cleavage reaction occurred within the coal molecule during pyrolysis and a large number of small molecules PAHs were generated. The different changes of soluble PAHs in different lignites and their semi-cokes not only reveal the different physical and chemical reactions of different coals during pyrolysis from the molecular level, but also reflect the differences in the macromolecular structural characteristics of coal.

卢梦仟(1997—),女,广西河池人,硕士研究生。E-mail:lmq1870091117@163.com

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LU Mengqian,LI Shan,SHI Yungu,et al. Characterization of soluble polycyclic aromatic hydrocarbons in lignite and itslow-temperature pyrolysis semi-coke[J].Clean Coal Technology,2023,29(11):58-65.