Biogas to Fuel by Vacuum Pressure Swing Adsorption I. Behavior of Equilibrium and Kinetic-Based Adsorbents

Purification of biogas by vacuum pressure swing adsorption was evaluated to produce fuel grade methane (FGM). Two different adsorbents were employed to evaluate the process performance with equilibrium- and kinetic-based adsorbents. Carbon molecular sieve 3K was employed as the example of a kinetic...

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Bibliographic Details
Published in:Industrial & engineering chemistry research 2007-06, Vol.46 (13), p.4595-4605
Main Authors: Grande, Carlos A, Rodrigues, Alírio E
Format: Article
Language:English
Subjects:
Adsorption
Applied sciences
Chemical engineering
Exact sciences and technology
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Summary:Purification of biogas by vacuum pressure swing adsorption was evaluated to produce fuel grade methane (FGM). Two different adsorbents were employed to evaluate the process performance with equilibrium- and kinetic-based adsorbents. Carbon molecular sieve 3K was employed as the example of a kinetic adsorbent because methane diffusion is extremely small. A five-step cycle configuration (feed, intermediate depressurization, blowdown, purge, and pressurization) was employed to compare with results obtained with a four-step cycle without intermediate depressurization. The effect of different operating variables like step times and pressure conditions of the cycle was analyzed. We have employed zeolite 13X as the equilibrium-based adsorbent (much higher capacity for CO2 with fast diffusion of both gases). Different operating conditions as well as a new cycle configuration were evaluated. Methane with purity over 98% was obtained with both adsorbents. The CMS 3K adsorbent showed much higher methane recovery (close to 80%) compared to those obtained with zeolite 13X (close to 60%) because of low adsorption in the pressurization step and because the stream exiting the intermediate depressurization step can be considered as being a product.
ISSN:0888-5885
1520-5045
DOI:10.1021/ie061341+