Abstract:

Natural gas as an efficient and clean fossil fuel plays an important role in the transformation of energy structure in China. Some conventional and unconventional natural gases contain excessive nitrogen, which could not meet the pipeline specification [nitrogen content < 4%(vol)] and decrease the heat value of natural gas. Therefore, nitrogen removal from natural gas is essential to achieve the efficient utilization of fossil fuel. Compared with traditional separation technologies such as cryogenic distillation and adsorption, the membrane-based gas separation technology possesses distinct advantages of operational flexibility, low investment and low energy consumption, exhibiting great potential in energy and environmental fields. The gas transport mechanisms suitable for CH₄-N₂ separation are introduced. Moreover, the developments of membrane materials and corresponding membranes for CH₄-N₂ separation are reviewed from CH₄-selective and N₂-selective membranes. Furthermore, the feasibility analysis of a two-stage membrane process with CH₄-selective or N₂-selective membrane is compared in different cases (nitrogen removal from conventional natural gas, shale gas and coalbed gas). Finally, prospects on membrane technology for CH₄-N₂ separation are presented.

Key words: natural gas, methane, nitrogen, membrane, separation, membrane process

摘要：

天然气作为一种高效、清洁的化石能源,在我国能源转型中扮演着重要角色。部分常规和非常规天然气含有较高浓度的氮气,会降低天然气的热值,无法满足管道输送的要求[氮气含量小于4%(体积分数)]。因此,天然气脱氮对实现化石能源的高效利用具有重要意义。相比于传统的气体分离技术,膜分离技术具有操作弹性大、投资少、能耗低等优点,在能源和环境领域均展现出广阔的应用前景。介绍了甲烷-氮气分离膜的传递机理,从甲烷优先渗透膜、氮气优先渗透膜两方面综述了甲烷-氮气膜分离技术的研究进展,同时针对不同的应用场合(常规天然气、页岩气和煤层气)进行了膜过程模拟研究,结合应用实例展望了膜技术在甲烷-氮气分离领域的发展及应用前景。

关键词: 天然气, 甲烷, 氮气, 膜, 分离, 膜过程