Capture of dilute methane with a novel dynamic-feed dual-reflux pressure swing adsorption process

Dual-reflux pressure swing adsorption (DR-PSA) is a state-of-art adsorption technology claiming to achieve both high product purity and recovery. However, its performance is inevitably limited by the gas mixing problem at the feed inlet position in adsorption columns, where a discontinuity in the columns' axial concentration profiles disturbs the separation. Here, we developed a dynamic-feed DR-PSA (DF-DR-PSA) process to solve the mixing problem and obtain better separation performance by introducing multiple feed inlets along the column. The DF-DR-PSA process was demonstrated by enrichment methane (CH4) from a binary gas mixture containing 2.4 mol.% CH4 in nitrogen (N2) using activated carbon material. Non-isothermal dynamic models were constructed to investigate the effects of operating parameters on the separation performance. The results showed the DF-DR-PSA process achieved both higher methane purity (53.5% vs. 47.5%) and recovery (81.1% vs. 72.2%) over the conventional DR-PSA process at the same energy consumption.