规整复合吸附剂真空变压吸附分离CH4/N2工艺模拟与分析

为减少甲烷排放，实现低浓度煤层气有效资源化利用，探究了使用规整复合吸附剂真空变压吸附富集低浓度煤层气的工艺。采用静态容积法测定了甲烷、氮气在规整复合吸附剂上的吸附等温线，同时建立了包括质量、热量和动量守恒在内的严格吸附床数学模型，设计了三塔连续进料的真空变压吸附工艺并进行模拟。分析了工艺达到循环稳态后吸附床层轴向温度分布和压力变化，并且探究了进料量、解吸压力、原料气中甲烷浓度和吸附压力对纯度、回收率、工艺能耗和吸附剂产率等工艺性能的影响。模拟结果表明，在进料量为100 L·min^-1，解吸压力为0.1 bar（1 bar=0.1 MPa），原料气甲烷浓度为30%，吸附压力为3 bar时可以生产纯度为59.07%，回收率为93.64%的富CH₄产品气，同时单位能耗为18.70 kJ·mol^-1，吸附剂产率为4.56 mol·h^-1·kg^-1。表明规整吸附剂对CH₄/N₂具有良好的吸附分离效果，能够实现低浓度煤层气中甲烷高效富集。

Simulation and analysis of CH4/N2 separation by vacuum pressure swing adsorption with structured composite adsorption media

To reduce methane emissions and achieve effective resource utilization of low concentration coalbed methane, the process of using a structured composite adsorbent for vacuum pressure swing adsorption to enrich low-concentration coal-bed methane was explored. The equilibrium adsorption capacities of pure gases (CH₄ and N₂) on the structured composite adsorption medium were measured under different pressures at a series of fixed temperatures by using the static volumetric method. Thus, a rigorous and reasonable mathematical model, including a set of conservation equation of mass, energy and momentum balances, was developed to precisely describe the dynamic behavior of multiple components in adsorption bed. A typical three-bed VPSA process with continuous feeding was designed and simulated. A comprehensive analysis was presented, relating to the process characteristics and performance such as temperature and pressure distribution in axial adsorption bed at cycle steady state. Additionally, effects of feed flow rate, desorption pressure, feed concentration and adsorption pressure on purity, recovery, energy consumption and productivity were investigated. The results showed that an effective separation performance of 59.07% CH₄ purity, 93.64% CH₄ recovery and 4.56 mol·h^-1·kg^-1 productivity with an energy consumption of 18.70 kJ·mol^-1, was finally got with the optimal parameters, while the feed flow rate, desorption pressure, feed concentration and adsorption pressure were 100 L·min^-1, 0.1 bar, 30% and 3 bar, respectively. Overall, this study indicated there is an effective adsorption and separation performance on CH₄/N₂ of structured composite adsorption media, which can achieve high-efficiency enrichment of methane in low concentration coalbed methane.