Methane Recovery By Dual Reflux Pressure Swing Adsorption

Methane Recovery by Dual Reflux Pressure Swing Adsorption

Gang Li¹, Thomas Saleman¹, Yechun Zhang², Eric May¹

¹ Centre for Energy, School of Mechanical & Chemical Engineering, The University of Western Australia, 35 Stirling Highway, Crawley WA 6009, Australia.

² Department of Chemical and Materials Engineering, The University of Auckland, Private Bag 92019, Auckland 1142, New Zealand

Email of presenting author: Kevin.li@uwa.edu.au

Methane accounts for the second largest anthropogenic greenhouse gas emission and it is 21 times more potent than carbon dioxide. A significant amount of methane is emitted to the atmosphere as a dilute vent in the energy sector. It will be a great advantage if this methane could be captured and utilized as a fuel (e.g. for lean combustion engines) while dramatically minimizing its emission foot print. Here we present an effective separation of a binary mixture of methane and nitrogen with a high performance dual reflux pressure swing adsorption apparatus (DRPSA, Figure 1) by running the stripping and rectifying cycles simultaneously. Feed gases with a broad methane composition range of 2.2 % to 74.4 % were experimented using novel ionic liquidic zeolite adsorbents with a pressure ratio of merely 3.6. We show this process was able to enrich the 2.2% dilute methane by more than 23 times into a methane rich product while producing a clean nitrogen vent stream containing less than 100 ppmv methane. A trade-off was observed between achieving a high nitrogen purity in the light product and a high methane enrichment in the heavy product. This work suggests DRPSA can efficiently capture dilute methane at relatively low energy consumption and significantly reduce CH₄ emission, showing a great commercialization potential in gas industry.

Figure  SEQ Figure \* ARABIC 1. Picture of the dual reflux pressure swing apparatus at UWA showing the interconnected two columns and the feed manifold.