Separation of organic vapors by means of membranes

In many production processes it is impossible to prevent the occurrence of flue gas streams containing solvents even if production-oriented environmen tal protection measures are implemented consistently. This means that there is still an urgent need to minimize emissions by cleaning solvent-loaded p rocess and flue gas streams. The thermal, catalytic or biological oxidation procedures that destroy organic solvents should only be used in cases wher e recovery is not reasonably possible. The procedures of choice are those t hat enable the solvent to be recovered and recycled, In the last ten years, major progress in the field of membrane separation technology has made gas permeation an interesting alternative to the conventional methods. The com bination of a membrane separation step with direct or indirect condensation results in a hybrid process permitting gentle and contamination-free recov ery of the organic components. The following article is a brief summary of the fundamental principles of the permeation of gas/vapor mixtures through polymer membranes.