An Analysis of the Single-Stage Gaseous Permeation Process

Abstract

A theoretical analysis of the single-stage permeation process is presented. A unified mathematical formulation and calculation methods are given for various feed-permeate flow patterns (countercurrent, cocurrent, cross flow) with two permeable components Including the case with a nonpermeable fraction in the feed and a purge stream in the permeate. It is confirmed that the countercurrent flow pattern is always the best and that the cross-flow pattern is always intermediate with respect to membrane area, enrichment, or recovery. It is shown that the permeate/feed concentration ratio cannot be larger than the smallest of the permeability ratio, the feed/permeate pressure ratio, or the reciprocal of the feed concentration. For a given recovery of the more permeable component, the required membrane area decreases with Increasing permeabilities of both components. Purging on the permeate side of the membrane with a small gas stream can, in some cases, greatly reduce the membrane area requirement without diluting the permeate stream significantly. The effectiveness of purging generally increases with decreasing feed concentration and with Increasing membrane selectivity relative to the feed/permeate pressure ratio.

Modeling multicomponent gas separation using hollow‐fiber membrane contactors

“…As expected, purging the permeate of a hollow-fiber membrane separator acts to increase the driving force for mass transfer and higher recovery at a fixed residue purity is observed when recovery is based on residue flow rate at the module exit R / F (Li et al, 1990;Pan and Habgood. 1974;Wang et al, 1992).…”

“…Permeate purging can be used to assist the removal of low concentrations of highly permeable impurities in a feed gas mixture. The use of permeate purging to reduce required membrane area for such applications has been described in general (Pan and Habgood, 1974) and for the removal of CO, from sealed life support systems such as submarines and space capsules (Li et al, 1990). Membrane-based air drying is practiced using permeate purging to enhance the rate of removal of water from the feed gas (Wang et al, 1992).…”

A new liquid membrane technique for gas separation

“…Pan and Habgood (1974) analyzed binary mixture permeation in a flat membrane permeator with an impermeable sweep gas and no pressure drop in either gas stream. Stern and Leone (1980) treated the permeation separation of a quaternary mixture without any sweep gas or flow pressure drop.…”

Ternary gas mixture separation in two‐membrane permeators

“…Although the data and simulation do not match well for the quantity ys,co2 in countercurrent mode, the simulations and other data indicate that the permeator performs better in countercurrent mode than in cocurrent mode. This should indeed be the case if one considers the two-membrane permeator to be equivalent to a combination of two single-membrane permeators integrated locally, since for the latter, countercurrent flow is almost always better (Walawender and Stern, 1972;Pan and Habgood, 1974;Antonson et al, 1977;Sengupta and Sirkar, 1984).…”