Abstract: The effective enrichment and utilization of low-concentration methane are of strategic importance for mitigating greenhouse gas emissions and improving the recovery efficiency of coal-associated resources. CH4, although a cleaner fuel relative to conventional fossil fuels, has a high global warming potential, and substantial quantities of coal mine methane in China remain underexploited despite its large proven reserves. Current regulatory requirements prohibit the discharge of drainage gas with methane concentrations above 8%, highlighting the necessity of developing technically viable enrichment processes. Among available gas separation technologies, pressure swing adsorption (PSA) has emerged as a promising method for CH4/N2 separation due to its low energy demand, operational simplicity, and strong adaptability to varying gas compositions. Existing studies have primarily focused on the purification of medium and high concentration methane mixtures, whereas systematic investigations targeting the enrichment of dilute methane streams are still limited. In this work, a four-tower, five-step PSA system (pressurization, adsorption, equalization depressurization, vacuum desorption, and equalization pressurization) was constructed to evaluate the separation performance for an 8vol% CH4/92vol% N2 feed mixture. Na-ZSM-5 molecular sieve was employed as the adsorbent owing to its representative adsorption characteristics for methane-nitrogen systems. The effects of adsorption time and feed flow rate were quantitatively examined with respect to product purity, recovery, and productivity. Experimental results demonstrated that, under optimal conditions (single-cycle throughput of 1.8×10-3 m3/kg, adsorption time of 540 s, and feed flow rate of 4 L/min), the CH4 purity in the product gas increased to 14.6% with a recovery of 83.0%, while a productivity of 0.82 m3/(h?tadsorbent) was obtained at a low energy consumption of 0.82 kWh/Nm3. These findings provide fundamental insights into the enrichment behavior of dilute methane mixtures under cyclic adsorption conditions and offer an empirical basis for the optimization and engineering application of PSA-based low-concentration methane utilization processes.

Key words: methane enrichment, adsorbent, zeolite molecular sieve, pressure swing adsorption process

摘要： 低浓度瓦斯(CH4)的富集回收利用对于减排温室气体和提升煤炭伴生资源利用率具有重要意义，利用变压吸附工艺是实现CH4富集的重要途径。构建了四塔五步(充压-吸附-均压降-真空-均压升)变压吸附实验装置，以Na-ZSM-5分子筛为吸附剂，8vol% CH4/92vol% N2混合气作为研究对象，系统探究了吸附时间和进料流量对富集性能的影响。结果表明，在单循环处理量为1.8×10-3 m3/kg、吸附时间540 s、进料流量4 L/min的最优工艺条件下，产品气CH4纯度达到14.6%，回收率保持83.0%，产率达到0.82 m3/(h?tadsorbent)，能耗约为0.82 kWh/Nm3。

关键词: 甲烷富集, 吸附剂, 沸石分子筛, 变压吸附工艺