| abstract |
The invention relates to a method and apparatus for producing pressurized oxygen by low-temperature separation of air in a distillation column system having a low-pressure column and a high-pressure column. All of the feed air is compressed to a first air pressure, at least 4 bar above the operating pressure of the high-pressure column. A first partial stream of the feed air, compressed to the first air pressure, is further compressed in a secondary compressor to a second higher air pressure, before being (pseudo-)liquefied and is introduced into the distillation system. A second partial stream of the feed air, compressed to the first air pressure, is cooled and depressurized in an expander, which drives the secondary compressor. A return stream is branched off from the (pseudo-)liquefied first partial stream, depressurized, heated and then introduced to the first partial stream upstream from the secondary compressor. |