is further compressed in a second compressor 706 to produce stream 708 which is eventually introduced to distillation column 140 pump 736 is optional the type of vaporizer used may include but is not limited to an ambient or water bath vaporizer another source of heat may be employed to further preheat the feed to the expander 740 power from the expander may be at least partially recovered in a generator not shown if a generator is used then the second compressor 706 becomes optional expander 740 may directly or indirectly drive the second compressor 706 supplying at least a portion of the power for the second compressor the second compressor 706 may also be used upstream of compressor 102 or in any other compression service such as compressing cold or warm nitrogen enriched vapor product stream 120 recovered power also can be used to drive pumps power may be generated by vaporizing and expanding any cryogenic liquid within the process the comments below apply to all of the embodiments which are discussed above and illustrated in fig1 7 the nitrogen containing gas steam 100 can come from any source which may include but is not limited to atmospheric air a customer 39 s.