Abstract: Carbon molecular sieves were selected to separate CH₄/CO₂ mixture by pressure swing adsorption. Adsorption isotherms of pure CH₄,CO₂ and N₂ gases on carbon molecular sieves were measured by the intelligent gravimetric analyzer apparatus(IGA-100,HIDEN)at 25℃,and the gas diffusion rates on the adsorbents were in the order of CO₂>N₂>CH₄. The breakthrough curves were measured by single fixed bed device. Pressures,flow rates and trace nitrogen(2%)were discussed to investigate separation performances,and adsorption mechanisms were also discussed. The results indicated that adsorption capacity of CO₂ and CH₄ on carbon molecular sieves were 35.9mL/g and 5.4mL/g respectively at pressure of 0.4MPa and flow rate of 200mL/min. The separation coefficient of CO₂/CH₄ reached 12.6,indicating that pure CH₄ could be collected from the fixed bed device,and the carbon molecular sieves could be well regenerated by vacuum desorption. These results suggested that carbon molecular sieves might be suitable for CO₂ removal from biogas. The diffusion rate of N₂ was faster than that of CH₄ on carbon molecular sieves; therefore it is possible to enrich CH₄ with high concentration through the fixed bed device.

Key words: biogas purification, pressure swing adsorption, decarbonization, carbon molecular sieve, methane

摘要： 选择碳分子筛,以CH₄和CO₂为原料气,对变压吸附法提纯沼气中生物甲烷的分离性能进行了研究。采用高精度智能重量分析仪IGA-100测定了25℃下CH₄、CO₂和N₂纯组分气体在碳分子筛上的吸附平衡等温线,计算了3种气体在碳分子筛内的扩散速率CO₂>N₂>CH₄。使用单塔变压吸附装置测量了动态吸附穿透曲线,考察了吸附压力、气体流量和少量氮气等因素对吸附分离的影响,并对吸附机理做了初步探讨。实验结果表明,在吸附压力为0.4MPa、气体流量为200mL/min时,在碳分子筛上CO₂穿透吸附量为35.9mL/g,CH₄穿透吸附量为5.4mL/g,CO₂/CH₄分离系数高达12.6,可直接从吸附塔顶富集纯净的CH₄,而且碳分子筛可以通过抽真空完全再生,是一种理想的吸附材料;在有少量氮气存在的实验条件下,由于碳分子筛对CH₄和N₂具有动力学分离效应,仍能在塔顶富集高浓度的CH₄。

关键词: 沼气提纯, 变压吸附, 脱碳, 碳分子筛, 甲烷