doi:10.16186/j.cnki.1673-9787.2019120041

Received:2019/12/14

Revised:2020/06/23

Published:2021/09/15

Law and quantitative evaluation of methane desorption hysteresis of coal seam in Huanglong coalfield

GAO Zheng1,2, MA Dongmin 1,2,3, CHEN Yue 1,2,3

1.College of Geology and Environment， Xi ’ an University of Science and Technology， Xi ’ an  710054 ， Shaanxi， China;2.Shaanxi Provincial Key Laboratory of Geological Support for Coal Green Exploitation， Xi’an  710054 ， Shaanxi， China;3.Key Laboratory of Coal Resources Exploration and Comprehensive Utilization， Ministry of Natural Resources， Xi ’an  710021 ， Shaanxi， China

Abstract:In order to study the law of methane desorption hysteresis and quantitative evaluation of coal reservoirs in Huanglongcoa lfie，samplesofcoal-3inGuojiaheminefiel，coal-4inDafosiminefieldandcoal-2in Huangling No.2 minefield were collected. Liquid nitrogen adsorption and isothermal adsorption/desorption experiments were adopted to analyze its pore structure characteristics and adsorption and desorption characteristics. Based on Langmuir equation and thermodynamic calculation results， the difference between the desorption hysteresis and the adsorption heat changes before and after adsorption/desorption was quantitatively evaluated. The results showed that ：The results showed that ： （1） When the temperature was the same， the coal adsorption capacity was DFS4， HL2，GJH3，and the residual adsorption capacity of coal was HL2 ，GJH3 ，DFS4.The effect of temperature on residual adsorption was slightly different. Temperature did not have a linear negative correlation with residual adsorption ， so the effect of temperature on desorption needed to be comprehensively considered；（2）Three coal samples ， DFS4 ，GJH3 ，HL2 had a desorption hysteresis coefficient of 0.4 ~0.6，HL2 coal sample had the largest desorption hysteresis coefficient and poor reversibility of adsorption/desorption at 20 ℃；CJH3 sample had the smallest desorption hysteresis coefficient and the best reversibility of adsorption/desorption ； the desorption hysteres was coefficient decreases with temperature increasing adsorption/desorption reversibility becomes better；（3）The medium heat of adsorption in the desorption process was greater than that of adsorption in the adsorption process. Desorption required supplemental heat from outside the system. The energy difference between the adsorption and desorption processes might be a key factor in the desorption hysteresis.

Key words:Huanglong coalfield;low rank coal;methane;residual adsorption capacity;desorption hysteresis coefficient;equivalent heat of adsorption

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