doi:10.16186/j.cnki.1673-9787.2020.4.3

Received:2019/12/24

Revised:2020/02/08

Published:2020/07/15

Study on the influence of mixed gas on CH₄ replacement efficiency in coal

LYU Baoyan1, YANG Hongmin1,2, LYU Xiaolai1, QIU Xianglei1

1.School of Safety Science and Engineering， Henan Polytechnic University， Jiaozuo  454000 ， Henan， China;2.Engineering Research Center of the Ministry of Education for Coal Mine Disaster Prevention and Rescue and Disaster Relief， Jiaozuo  454000 ， Henan， China

Abstract:In order to explore the replacement efficiency of CH₄ and its influencing factors in different metamorphic coals， a self-built multi-gas replacement adsorption experimental device was used to carry out replacement CH₄ experiments in coal by mixed gas. The experimental coal samples were selected from three typical coal types ， such as anthracite ， lean coal and gas-fat coal， under conditions of different adsorption temperatures ， equilibrium pressures， injection pressures and composition ratio of injected gas. The results showed that under constant temperature conditions， with the increase of equilibrium pressure， the adsorption/desorption capacity of the mixed gas was of a monotonously increasing with increase of the adsorption strength of the replacement gas and the degree of coal metamorphism，i. e. ， > >> and V_无烟煤>V_瘦煤>V_气肥煤； Under a certain equilibrium pressure condition， the higher the temperature was， the smaller the adsorption/desorption capacity of the mixed gas had got； When the equilibrium pressure and temperature remained constant，with the injection pressure increases， the replacement efficiency of pure CO₂ gas for CH₄ would decrease. Compared with the injection of CO₂ gas， the replacement efficiency of the mixed gas was better， i. e. ， the higher the nitrogen content in the mixed gas was， the better the replacement efficiency of methane was. The enlightenment obtained from this experiment was that underground coal seam gas injection to replace coal seam CH₄ did not necessarily pursue its high injection pressure. As long as the gas injection source ratio was appropriate， low injection pressure could also achieve better coal seam gas recovery rate.

Key words:mixed gas;temperature;balancing pressure;injection pressure;CH₄ in coal;replacement efficiency

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