Drying and pyrolysis are related to the composition of underground coal gasification product gas and the efficiency of gasificationworking surface. In order to investigate the expansion law of pyrolysis temperature field in dry distillation zone during undergroundcoal gasification process, the 300 mm raw coal block of Heshun lean coal and the artificially prepared Mengdong lignite block were selected as the research objects. The large size fixed-bed pyrolysis reaction device was used to conduct a single-sided constant temperatureheating experiment on bulk coal under N2 atmosphere. The temperature of each measuring point during the experiment was collected by atotal of 50 thermocouples evenly arranged in four layers of bulk coal, and the temperature field distribution map of bulk coal pyrolysis wasdrawn. The results show that the pyrolysis temperature field of bulk raw coal expands upward in a multi-parabolic shape with multi-fissures as the center, while the pyrolysis temperature field of artificial bulk coal moves upwards in an approximate horizontal shape.The movement rate of drying line and characteristic temperature line of bulk coal pyrolysis gradually decreases with the increase of the pyrolysis time, and the movement rate of drying line is greater than that of characteristic line. The heat transfer rate and the movement rate ofdrying line and characteristic temperature line of the bulk raw coal is higher than that of the artificial bulk coal. The movement rate of drying line and characteristic temperature line of bulk raw coal during pyrolysis for 6 h are 21.0 and 12.3 mm/ h, respectively. Due to the existence and development of fissures in the bulk raw coal,the cracks undergo convective heat transfer during pyrolysis, which improves theheat transfer rate of raw coal. At the same time, the fissure development and heat transfer promote each other, so that the pyrolysis temperature field of raw coal expands in a multi-parabolic shape with multiple fissures as the center. The movement rate of drying line and characteristic temperature line is improved by the fissure of raw coal , especially there is the significanteffect on drying line. Therefore, the development of fissures and the large amount of flue gas generated by combustion in the oxidation zone will strengthen the convective heattransfer in the coal seam and increase the expansion rate of the pyrolysis temperature field of underground coal gasification in the actualprocess of underground coal gasification.

苏倩倩(1991—),女,山西运城人,工程师,硕士研究生。E-mail:1253875260@qq.com

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SU Qianqian,LI Wenjun,CHEN Yanpeng,et al.Expansion law of temperature field during bulk coal pyrolysis[ J].CleanCoal Technology,2023,29(11):66-73.