Abstract:

The carbon molecular sieve was adopted as adsorbent for biogas upgrading, and the morphologies of carbon molecular sieve were examined by scanning electron microscopy while the pore-size distribution was characterized by CO₂ adsorption at 273.15 K. With the volume method, the adsorption isotherms of carbon dioxide and methane on carbon molecular sieve were measured at 283.15, 303.15, and 323.15 K and at pressure up to 0.5 MPa, while the diffusion coefficient of carbon dioxide and methane on carbon molecular sieve were also determined. The breakthrough experiments were implemented on single fixed bed, and the effects of adsorption pressure and feed flow rate on the breakthrough curve of CO₂ were explored. Two-bed-six-step vacuum pressure swing adsorption (VPSA) process was carry out with the adsorption pressure of 0.3 MPa and the feed flow rate of 4 L·min-1. In addition, the effects of adsorption step time and product flush ratio on separation performances were also investigated. The experimental results show that the purity of methane could be achieved to 98% with a recovery of 82% when adsorption time was set to be 140 s with a product flush ratio of 0.05.

Key words: molecular sieve, vacuum pressure swing adsorption, biogas, methane, carbon dioxide

摘要：

以煤基碳分子筛为沼气净化吸附剂，借助扫描电镜观察了碳分子筛的表面形貌，并通过物理化学吸附仪表征了碳分子筛的孔径分布。基于静态容积法测定了CO₂与CH₄在碳分子筛的静态吸附量，并估算了CO₂与CH₄在碳分子筛的动力学扩散系数。单塔穿透实验考察了吸附压力与进料流量对原料气中CO₂穿透曲线的影响，选取吸附压力为0.3 MPa，进料流量为4 L·min-1进行两塔六步真空变压吸附提纯沼气的实验研究，并考察了吸附步骤时长与产品气冲洗率对CH₄富集效果的影响。实验结果表明，吸附步骤时长为140 s，冲洗率为0.05时，产品气中CH₄纯度可达98%，收率可达82%。

关键词: 分子筛, 真空变压吸附, 沼气, 甲烷, 二氧化碳