Abstract:

Coalbed methane(CBM)is a kind of unconventional natural gas.In China,CBM often contains air when it comes out of the well.Considering issues regarding safety,it is natural that oxygen must be removed firstly.Then,the effective enrichment of methane from methane-nitrogen mixture is one of the most important issues in the utilization of CBM.In this paper,a two-bed pressure swing adsorption(PSA)experimental apparatus was used to separate CH₄/N₂ mixture on a selected type of carbon molecular sieve(CMS)adsorbent.Owing to the kinetic separation mechanism on CMS,nitrogen is adsorbed on CMS,while methane with certain pressure is delivered out continuously.The influence of adsorption pressure,feed gas velocity and cycle time on the overall performance of the adsorption process was discussed.Feeding a mixture of 50% CH₄/50% N₂,methane purity of 95.45% was obtained;and 94.89% purity was obtained while feeding a mixture of 30% CH₄/70% N₂.The results show that all three parameters may affect the separation performance,and the later two have greater influences.It is easier to achieve methane purity above 90% at low adsorption pressure and low feed gas velocity.And the shorter the cycle time,the higher the methane purity is.

Key words: adsorption, separation, methane, nitrogen, carbon molecular sieve

摘要：

煤层气(CBM)是一种非常规天然气。在中国,煤层气在抽采出来时常混有空气。考虑到安全因素,氧气首先应该被去除。之后,煤层气利用的最重要步骤则是甲烷-氮气混合气体的甲烷高效提浓。本文搭建了双床变压吸附(PSA)装置,选择特定的炭分子筛(CMS)进行CH₄/N₂混合物分离实验研究。由于CMS的动力学吸附特性,氮被吸附在CMS上,带有一定压力的甲烷则连续输出。研究了吸附压力、进气速度和循环周期等因素对吸附过程整体性能的影响。从50% CH₄/50% N₂的原料气可以获得95.45%纯度的甲烷产品,而从30% CH₄/70% N₂的原料气可以获得94.89%纯度的甲烷产品。研究表明,以上3个参数都对分离性能有影响,其中后两者的影响更大。在较低吸附压力和较低进气速度时更容易获得纯度90%以上的甲烷产品。另外,循环周期越短,获得的甲烷纯度越高。

关键词: 吸附, 分离, 甲烷, 氮气, 炭分子筛