Air separation method and apparatus

摘要

A stream of air is compressed (in a compressor 14) and is purified in a unit 18. The compressed purified air is cooled in a heat exchanger 22 to a temperature suitable for its rectification and is separated in a rectification column 24 into an oxygen-enriched liquid bottom fraction and a nitrogen top fraction. A stream of oxygen-enriched liquid is withdrawn from the column 28, is expanded through a valve 48 and is indirectly heat exchanged in a condenser 30 with a first stream 32 of the nitrogen fraction so as to condense the latter. A resulting stream 54 of vaporized oxygen-enriched air is warmed in the main heat exchanger and a part of it may be used to regenerate the purification unit 18. The nitrogen condensate is used as reflux in the column 24. A second stream 36 of nitrogen is expanded in a turbine 50, is warmed in the heat exchanger 22, and is taken as a product at above atmospheric pressure.