(49e) Pressure Vacuum Swing Adsorption Cycles for Landfill Methane Purification

Pressure vacuum swing adsorption cycles have been designed for the purification of methane out a stream previously enriched in methane from landfill gas at room temperature and 800 kPa and using BPL activated carbon as the adsorbent.  The feed stream contains 86 vol% methane with the remainder being either 14 vol% N₂ or 12 vol% N₂, 1 vol% CO₂ and 1 vol% O_2.  The product stream must contain at least 97 vol% CH₄ and less than 0.2 vol% O₂ and must recover more than 90% of the CH₄ fed.  This study will reveal the role of equalization, heavy reflux, countercurrent depressurization and light reflux steps. In particular, the role of countercurrent heavy reflux with recycle to the feed will be discussed. This study will also analyze the role of low pressure in the cycle and the influence of carbon dioxide and oxygen in the feed. In addition to the main performance parameters of CH₄, purity, CH₄ recovery and feed throughput, the separation costs will also be discussed.