基于低浓度甲烷富集的变压吸附工艺流程优化模拟

Process simulation of pressure swing adsorption technology optimization based on low concentration methane enrichment

甲烷富集是开发利用低浓度煤层气的必要措施,变压吸附技术以其低能耗、低成本成为研究热点。基于Aspen adsorption流程模拟软件研究了氮气选择性吸附剂MIL-100(Cr)和甲烷选择性吸附剂Silicalite-1在常规双塔六步真空变压吸附(VPSA)工艺和增加缓冲罐优化的VPSA工艺下富集低浓度甲烷的过程。模拟结果表明增加缓冲罐优化的VPSA工艺可以有效提升甲烷回收率,在MIL-100(Cr)上甲烷回收率提升表现优于Silicalite-1。采用单次循环效率综合指标定量分析了吸附剂类型和工艺对甲烷富集效果的影响,增加缓冲罐优化的VPSA工艺在MIL-100(Cr)吸附剂上的单次循环效率提升超过30个百分点,Silicalite-1吸附剂单次循环效率降低1个百分点。综合分析表明Silicalite-1吸附剂适用于常规VPSA工艺富集低浓度甲烷,而MIL-100(Cr)吸附剂更适合增加缓冲罐优化的VPSA工艺富集低浓度甲烷。

Methane enrichment is a necessary measure to develop and utilize low concentration coalbed methane.Among many separation technologies,pressure swing adsorption technology has become the most widely used technology in recent years due to its advantages of low energy consumption and low cost.In order to better realize the methane enrichment effect(purity and recovery),it is necessary to study the relationship between the adsorbent and the pressure swing adsorption process,that is,to select a suitable pressure swing adsorption process for the adsorbent.This work uses Aspen adsorption process simulation software to study two different types of adsorbents(N2 selective adsorbent MIL-100(Cr)and CH4 selective adsorbent Silicalite-1)in common and optimal vacuum pressure swing adsorption(adding buffer tank).Simulation results shows that the optimal vacuum pressure swing adsorption process can effectively improve the CH4 recovery,and MIL-100(Cr)has a significantly better recovery improvement effect compared with Silicalite-1.However,when the CH4 content of the coalbed methane is less than 30%,CH4 recovery of 100%can be achieved by using Silicalite-1 adsorbent in the optimal vacuum pressure swing adsorption process.In the actual process of enriching coalbed methane,methane purity and recovery are very important indicators.Therefore,the single cycle efficiency index is proposed to comprehensively evaluate the efficiency of the methane enrichment process.The results show that compared with the common vacuum pressure swing adsorption process,the optimal vacuum pressure swing adsorption process using MIL-100(Cr)adsorbent has a single cycle efficiency improvement of more than 30 percentage point,while that of Silicalite-1 adsorbent even slightly decline 1 percentage point.Comparative analysis shows that the common vacuum pressure swing adsorption process is suitable for Silicalite-1 adsorbent,and the optimal vacuum pressure swing adsorption process with buffer tank is more suitable for MIL-100(Cr)adsorbent.