EFFICIENT PROCESS TO PRODUCE OXYGEN

摘要

The present invention relates to a process for the cryogenic distillation of air in a distillation column system that contains at least one distillation column wherei n the boil-up at the bottom of the distillation column producing the oxygen product is provide d by condensing a stream whose nitrogen concentration is equal to or greater than tha t in the feed air stream. The process of the present invention comprises the steps of: (a ) generating work energy which is at least ten percent (10%) of the overall refrig eration demand of the distillation column system by at least one of the following two me thods: (1) work expanding a first process stream with nitrogen content equal to or grea ter than that in the feed air and then condensing at least a portion of the expanded stre am by latent heat exchange with at least one of the two liquids: (i) a liquid at an in termediate height in the distillation column producing oxygen product; (ii) one of the liqu id feeds to this distillation column having an oxygen concentration equal to or preferably g reater than the concentration of oxygen in the feed air; and (2) condensing at least a second process stream with nitrogen content equal to or greater than that in the feed a ir by latent heat exchange with at least a portion of an oxygen-enriched liquid stream which has oxygen concentration equal to or preferably greater than the concentration o f oxygen in the feed air and which is also at a pressure greater than the pressure of the distillation column producing oxygen product, and after vaporization of at least a portion of oxygen-enriched liquid into a vapor fraction due to latent heat exchange, wor k expanding at least a portion of the resulting vapor stream; (b) work expanding a third process stream to produce additional work energy such that the total work genera ted along with step (a) exceeds the total refrigeration demand of the cryogenic plan t and if the third process system is the same as the first process system in step (a)(1), then at least a portion of the third process stream after work expansion is not condense d against either of the two liquid streams described in step (a)(1); and (c) using the work which is generated in excess of the refrigeration need of the distillation colum n system to cold compress a process stream at a temperature lower than the ambient temperatu re.