Adsorptive separation of gas mixtures: Mechanistic view, sharp separation and process intensification

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• 作者：S.V. Sivakumar^a ; D.P. Rao^b ; ^{dprao@iitk.ac.in} ; ^{dprao1943@gmail.com}
• 关键词：Adsorption ; Moving bed ; SMB ; PSA ; Duplex PSA ; Molecular gate
• 刊名：Chemical Engineering and Processing
• 出版年：2012
• 期刊代码：15_02552701
• 类别：ce
• 出版时间：March, 2012
• 卷：53
• 期：Complete
• 页码：31-52
• 文件大小：2795 K

摘要

We present here a mechanistic view of adsorption processes for separation of gas mixtures. The moving-bed adsorber (abandoned due to practical difficulties) is shown to offer orders of magnitude higher productivity than the conventional pressure swing adsorption (PSA) and yields 鈥榩erfect separation鈥? To realize its potential in fixed beds, simulated moving bed (SMB) with pressure or thermal swing and 3-bed and 4-bed PSAs that emulate moving-bed adsorbers have been proposed. Based on their characteristics of phase equilibria and separating agents employed, a classification of adsorption processes has been proposed as 鈥榓bsorption like鈥? 鈥榙istillation like鈥?and 鈥榗hromatographic鈥?processes, which provides insight into these processes and a rational basis for their design. The mechanism of separation in moving bed, SMB and the conventional PSA are shown to be similar to that of either absorption or distillation. On the other hand, the duplex, molecular-gate and rapid PSAs are shown to share the same separation mechanism that is akin to heat-transfer mechanism in heat regenerators. Subtle but significant differences in the role of 鈥榬eflux鈥?in absorption-like and distillation-like processes and their implications in process design have been highlighted. Though process intensification in molecular-gate PSA and duplex PSA is modest compared to the SMB, they appear to hold promise since they are based on a proven technology. Their adaptability for absorption and extraction using immobilized solvent has been presented.