Separation of Landfill Gas CH4 from N2 Using Pressure Vacuum Swing Adsorption Cycles with Heavy Reflux

Abstract

Simulations were carried out to study the purification of CH4 from pretreated landfill gas containing 88 vol % CH4 and 12 vol % N2 using BPL activated carbon and three different four-bed four-step pressure vacuum swing adsorption (PVSA) cycles. All three PVSA cycle schedules included feed (F), heavy reflux (HR), countercurrent depressurization (CnD), and light product pressurization (LPP) steps. The light-end heavy-reflux plus recycle (LEHR–Rec) cycle had a HR step fed to the light end of a bed by a partial reflux of the product from the CnD step and a full recycle of the product from the HR step blended back with the feed. The heavy-end HR plus recycle (HEHR–Rec) cycle was the same as the LEHR–Rec cycle except the HR step was fed to the heavy end of a bed. The heavy-end HR (HEHR) cycle was the same as the HEHR–Rec cycle, except that it did not have Rec, so the product from the HR step was taken as light product. For all three PVSA cycles, increases in either the feed throughput or the HR reflux ratio cau...