Hollow-fiber membrane-based rapid pressure swing absorption

A novel gas purification technique called rapid pressure swing absorption (RAPSAB) was developed by integrating the best features of membrane contacting, gas-liquid absorption, and pressure swing adsorption (PSA). In this cyclic separation process, a well-packed microporous hydrophobic hollow-fiber module was used to achieve nondispersive gas absorption from a high-pressure feed gas into a stationary absorbent liquid on the module shelf side during a certain part of the cycle followed by desorption of absorbed gases from the liquid in the rest of the cycle. The total cycle time varies between 20 s and upwards. Separation of mixtures of N-2 and CO2 (around 10%) where CO2 is the impurity to be removed was studied using absorbent liquid; such as pure water and a 19.5% aqueous solution of diethanolamine (DEA). Three RAPSAB cycles studied differ in the absorption part. Virtually pure N-2 streams were obtained with DEA as absorbent demonstrating the capability of bulk separation to very high levels of purification. Numerical models developed predict the extent of purification for pure wafer and the DEA solution for one of the simpler cycles. Model simulations describe the observed behavior well.