Recovery of perfluorinated compounds from the exhaust of semiconductors fabrications with recycle of vaccum pump dilutent

摘要

Fluorochemicals are separated and recovered from a feed gas stream (12, Fig.1; 50, Fig. 2; 80, Fig. 3) containing a diluent gas and fluorochemicals by a process in which recycled diluent-rich stream(s) (26,32; 62,70; 92) from the separation step(s) provide vacuum pump diluent for a vacuum pump (14; 52; 82) through which the feed gas stream is pumped prior to compression (20; 58; 86). In one embodiment (Fig. 1), the compressed gas mixture is separated in a membrane system (24) in one or more stages, where the membrane(s) is selectively more permeable to the diluent gas than the fluorochemicals, to result in a recycle permeate stream (26) rich in diluent gas and retentate (28) rich in fluorochemicals, and thereafter the retentate (28) is purified by distillation or adsorption resulting in a product stream (34) enriched in fluorochemicals and a recycle purified diluent stream (32). In another embodiment (Fig. 2), the compressed gas mixture is separated by adsorption (60) and subsequent distillation (68) and recycle vacuum pump diluent is provided by the vent stream (62) from the adsorption (60) and purified diluent (70) from the distillation (68). In a third embodiment (Fig. 3), the compressed gas mixture is separated by cryogenic distillation (68) and the resultant enriched diluent stream (92) recycled.