抄録
This article reviews gas permeation mechanisms of membranes, problems in evaluation of membranes and designing methods of membrane modules and processes.
The gas permeability of porous membranes is generally expressed by the sum of surface flow, Knudsen flow and viscons flow. That of rubbery polymer membranes is described by the product of Henry's low solubility constant and Fick's law diffusion coefficient. However, permeation properties of glassy polymer membranes are dependent on gas concentration, and are analyzed by the dual mobility model postulating Henry's law species and Langmuir's law species. Commercial type membranes having anisotropic structure should be considered the contribution of various permeation mechanisms, using the resistance model.
The separation efficiency of membranes is affected by operating conditions. Specifically, the effect of concentration polarization phenomenon becomes significant problem with respective to high-flux membranes.
Flow patterns also affect the performance of membrane modules. Analyses of them are based on the designing equations, such as perfect mixing, cross flow, cocurrent flow and countercurrent flow models. Gas separation processes with high performance can be constructed using recycle module systems, such as one-unit recycle, two-unit series and continuous membrane column.
