Abstract Coalbed methane (CBM) recovery and CO2 storage have always been important topics of study for clean energy utilization and environmental governance. To enhance CBM recovery, CO2/N2 injection is applied in coal mining, especially CO2 injection enhanced coalbed methane (CO2-ECBM). CO2 injection not only improves the production of CBM but also helps to reduce the greenhouse effect. As there are differences between CO2 injection and N2 injection, the advantages of CO2 should be studied in depth. The adsorbed methane accounts for more than 80% of total methane, and the amount of variation adsorbed methane is the key to CO2/N2 injection. In this paper, the desorption rate of adsorbed methane, the replacement ratio and the residual mixed gas content are discussed to evaluate the effect of CO2/N2 injection. After CO2/N2 injection, the desorption rate of adsorbed methane could be enhanced. The results also show that CO2 injection is better than N2 injection for enhanced coalbed methane (ECBM) recovery; however, the residual mixed gas content could be increased after CO2 injection. Moreover, anthracite (QC) could be more suitable for CO2 injection because of the value of replacement ratio. The influences of temperature and injection pressure are also empirically studied. Increasing both temperature and pressure could not significantly enhance the desorption rate of adsorbed methane significant. Increasing the temperature could reduce the residual mixed gas content; however, it is difficult to induce ECBM recovery with increasing temperatures. Increasing the injection pressure could cause a slight increase of the desorption rate of the adsorbed methane; however, higher injection pressure corresponds to greater economic cost. Thus, the most suitable injection pressure is twice as much as the initial pressure of methane.

中文翻译：

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煤中二氧化碳注入：温度和压力的优势和影响

摘要 煤层气回收和二氧化碳封存一直是清洁能源利用和环境治理的重要研究课题。为提高煤层气采收率，在煤矿开采中应用了 CO2/N2 注入，尤其是 CO2 注入强化煤层气（CO2-ECBM）。CO2 注入不仅提高了煤层气的产量，而且有助于减少温室效应。由于CO2注入和N2注入存在差异，因此应深入研究CO2的优势。吸附甲烷占甲烷总量的80%以上，吸附甲烷的变化量是CO2/N2注入的关键。本文通过讨论吸附甲烷的解吸率、置换率和残余混合气含量来评价CO2/N2注入的效果。CO2/N2 注入后，可提高吸附甲烷的解吸率。结果还表明，对于提高煤层气（ECBM）采收率，CO2 注入优于 N2 注入；然而，在注入 CO2 后，残余混合气含量可能会增加。此外，由于替代率的价值，无烟煤 (QC) 可能更适合注入 CO2。还根据经验研究了温度和注射压力的影响。增加温度和压力不能显着提高吸附甲烷的解吸速率。提高温度可降低残留混合气含量；然而，随着温度的升高，很难诱导 ECBM 恢复。增加注入压力可使吸附甲烷的解吸速率略有增加；然而，更高的注射压力对应更高的经济成本。因此，最合适的注入压力是甲烷初始压力的两倍。