Upgrade of Methane from Landfill Gas by Pressure Swing Adsorption

This work focuses on the production of pipeline grade methane from landfill gas (LFG). Vacuum pressure swing adsorption technology using a kinetic adsorbent, Carbon Molecular Sieve 3K (Takeda), was employed for the separation of methane−carbon dioxide mixture. Adsorption equilibrium and kinetics of methane and carbon dioxide are reported at 298, 308, and 323 to model the adsorption-based process. A four-step Skarstrom-type cycle was employed comprising pressurization, feed, counter-current blowdown, and counter-current purge with product. Co-current pressurization with feed stream and counter-current pressurization with product were evaluated. The separation of a mixture of CH4 (55%)−CO2 (45%) was tested using two different four-step cycles: pressurization with feed stream, feed, blowdown, and purge with product and pressurization with product, feed, blowdown, and purge with product. The results indicate that purity of methane higher than 96% can be obtained with recovery higher than 75%. The difference of the performance in the non-adiabatic and adiabatic cases was also studied. It was observed that the temperature in the column increases allowing a faster and more important desorption of carbon dioxide in the blowdown step, retaining more CO2 in the column and improving methane purity and recovery.