真空变压吸附提纯沼气中甲烷的过程模拟  

Simulation on Vacuum Pressure Swing Adsorption Processes for CH_4 Separation from Biogas

作　　者：田相龙 王之婧 刘晓勤 马正飞 

机构地区：[1]南京工业大学化工学院材料化学工程国家重点实验室,江苏南京210009

出　　处：《高校化学工程学报》2018年第1期44-53,共10页Journal of Chemical Engineering of Chinese Universities

基　　金：国家重点基础研究发展计划(2013CB733504)

摘　　要：采用真空变压吸附工艺(VPSA)从组成为60%(V)CH_4、30%(V)CO_2和30%(V)N2的沼气中获得纯度大于95%的CH_4,以满足车用燃料的要求。通过测定CH_4、CO_2及N2在13X分子筛和碳分子筛(CMS)吸附剂上的吸附性能,将提纯CH_4的VPSA工艺分为两个阶段:第一阶段以13X分子筛为吸附剂,采用六床七步法以脱除CO_2;第二阶段以CMS为吸附剂,采用三床六步法以脱除N2。选择数学模型分别对CH_4、CO_2及N2混合气在13X和CMS上的穿透曲线计算,并与实验值进行对比,以验证其可靠性。基于所选数学模型,对两段VPSA工艺进行模拟,可获得CH_4纯度为99%,总回收率为65%;考察第一段工艺的操作压力及第二段工艺的吸附动力学参数对CH_4纯度和回收率的影响。结果表明:吸附压力升高,脱附压力降低有利于提高CH_4的纯度,但其回收率会降低;当CMS具备对CH_4吸附速率较低、N2吸附速率较高的吸附特性时,可获得纯度大于99%的CH_4,这对CMS吸附剂的研发有一定的指导作用。In order to meet vehicle gas requirements, a vacuum pressure swing adsorption(VPSA) method was proposed to acquire high purity CH_4(over 95%) from biogas composed of 60%(V) CH_4, 30%(V) CO_2 and 30%(V) N_2. The adsorption of CH_4, CO_2, and N_2 using 13 X and CMS was measured, and the vacuum pressure swing adsorption(VPSA) process was divided in two stages based on the adsorption results. In the first stage, the 13 X molecule sieve was used as the adsorbent for CO_2 removal by a six-bed seven-step process. In the second stage, carbon molecule sieve(CMS) was employed as the adsorbent for N2 capture by a three-bed six-step process. The breakthrough curves of CH_4, CO_2 and N2 mixtures on 13 X and CMS were calculated by mathematical models and compared with experimental values. The results demonstrate that the calculated values are in good agreement with that of experiments, which validates the accuracy and reliability of the mathematical models. Simulation results show that CH_4 purity of 99% with a total recovery of 65% is achieved. The effects of operating pressure in the first stage and adsorption dynamic parameters of CH_4 and N2 in the second stage on purity and recovery of CH_4 were discussed. The results show that higher adsorption pressure and lower desorption pressure lead to the improvement of purity but decrease of recovery. When CMS shows fast adsorption of N2 and slow adsorption of CH_4,the purity of CH_4 can achieve 99%, and this can be used as guidance for the development of CMS.

关 键 词：沼气提纯 CO2及N2脱除 真空变压吸附 吸附剂 

分 类 号：TQ202[化学工程—有机化工]