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

Abstract

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.

Separation of He/N2/CH4 ternary mixtures by a triple‐reflux pressure swing adsorption process

“…The concentration of components in the feed gas stream is generally different from that in the reflux flow, resulting in the so-called "mixing problem," which manifests as the discontinuity of axial concentration curves at the injection position. The mixing problem has been reported and investigated in the open literature 23,42,44,48 and has been confirmed…”

“…The concentration of components in the feed gas stream is generally different from that in the upstream reflux flow, resulting in the so‐called “mixing problem,” which manifests as the discontinuity of axial concentration curves at the injection position. The mixing problem has been reported and investigated in the open literature 23,42,44,48 and has been confirmed to have negative impacts on the separation performance of the process. The effect of feed position ( Z F ) was investigated by changing the Z F between 0.4 and 0.9.…”

“…Several simulation studies on DR‐PSA have been reported, ranging from simplified analytical models 17,33–38 to rigorous nonisothermal numerical models 26–28,39–44 . Based on the equilibrium theory, 45 simplified analytical models revealed critical insights into the operating parameters and separation performance of DR‐PSA.…”

“…[29][30][31][32] Several simulation studies on DR-PSA have been reported, ranging from simplified analytical models 17,[33][34][35][36][37][38] to rigorous nonisothermal numerical models. [26][27][28][39][40][41][42][43][44] Based on the equilibrium theory, 45 simplified analytical models revealed critical insights into the operating parameters and separation performance of DR-PSA. However, the simplified assumptions of isothermal behavior, no axial pressure drop, complete separation, and local equilibrium lead to inaccurate predictions and very limited application.…”

Separation of Methane and Nitrogen Using Heavy Reflux Pressure Swing Adsorption: Experiments and Modeling

“…A range of novel PSA processes has been proposed and demonstrated, particularly for the purpose of upgrading dilute mixtures of CH 4 in N 2 or air. May et al investigated the separation of CH 4 and N 2 using dual-reflux PSA with activated carbon, Engelhard titanosilicate type 4 (ETS-4), and ionic liquidic zeolites as adsorbents via experiments and simulations. − Results showed that optimized DR-PSA processes using Norit RB3 adsorbents can upgrade dilute methane (2.4%) to 35.7%, leaving a clean nitrogen vent bearing 3000 ppmv methane, which is promising in the reduction of fugitive methane emissions. Guo et al employed a triple-reflux strategy to separate CH 4 /N 2 /He by opening a third channel on DR-PSA and achieved three high-purity streams simultaneously.…”