FricDiff: A novel separation concept

Purity versus recovery in FricDiff separations for feed-side and sweep-side products

“…As such, it is the hydrocarbon most difficult to separate from hydrogen using FricDiff. In contrast to earlier applications of FricDiff [1][2][3][4], the product of interest, hydrogen, diffuses faster than hydrocarbon molecules and is thus recovered with the mass separating agent.…”

“…The main difference between the previously studied azeotropic mixtures [1][2][3][4] and the current system (hydrogen-hydrocarbon mixture) is the product outlet stream. In the azeotropic mixture case, the alcohol (either ethanol or isopropanol) is the product.…”

“…In previous work [1][2][3], FricDiff unit has been considered to be operating without any pressure difference over the porous barrier; however, it is observed that a pressure difference has a positive effect on purity (see below and [12]). With the pressure difference, convective forces affect the transport in addition to diffusional forces which was been pointed out by Schwertz [8] who developed the basics of diffusion-based separation processes.…”

“…Frictional Diffusion also called friction difference [1], FricDiff in short, is a recent revival and adaptation of mass diffusion [14] for separating gas (or vapor) mixtures. A FricDiff module consists of flows of a target gas mixture (feed side) and a mass separating agent (sweep side) separated by a nonselective porous layer (barrier).…”

“…The separation in FricDiff is based on a difference in diffusion coefficients. It has been shown that FricDiff allows for the breaking of azeotropes in mixtures [1][2][3].…”