Abstract:

This paper firstly conducted the experiments for N₂/CH₄ separation using the vacuum pressure swing adsorption (VPSA) process based on the two-bed experimental set-up and the laboratory-made coconut shell-based activated carbon as adsorbent. The PSA mathematical models were verified by comparing the separation results of experiments and simulations employing gPROMS dynamic simulation software. On this basis, sensitivity analyses were made on the key decision variables affecting product CH₄ purity and recovery. Sensitivity analysis indicated that the product purity mainly depended on the raw gas flow and displacement gas flow, while product gas recovery required a good combination of the three key variables. The results showed that the purity of the product gas was mainly regulated by the raw gas flow and displacement gas flow, while a common action of the key variables was required in order to maximize the product gas recovery. Based on the results of the sensitivity analysis, the dynamic optimization was studied for PSA process under consideration. Under optimal conditions, the molar concentration of CH₄ may be enriched to 75% and product recovery can be enhanced to 97.08% with feed concentration of 35%. This optimal VPSA process has proved its practicality for the effective recycling of waste gas mixture.

Key words: activated carbon, VPSA, methane recovery, sensitivity analysis, optimization

摘要：

首先采用实验室自制椰壳活性炭为吸附剂,进行了氮气/甲烷(65%/35%)原料气的真空变压吸附工艺(VPSA)分离实验。通过对比实验和gPROMS 动态模拟软件的分离效果,对变压吸附数学模型进行了验证,证明了所采用数学模型的准确性。在此基础上,对影响产品气甲烷纯度、回收率的关键决策变量进行了灵敏度分析。分析结果表明:产品气纯度主要由原料气流量和置换气流量来进行调控,产品气回收率则需要关键变量共同的作用才能实现最大化。依据灵敏度分析结果,对两塔分离氮气甲烷混合气的变压吸附工艺进行了动态优化。在最优的工况下,可以将进料组成为35%的甲烷富集到75%,回收率达到97.08%;从而达到对于废混合气的高效回收利用。

关键词: 活性炭, 变压吸附, 甲烷回收, 灵敏度分析, 优化