Cryogenic rectification system for producing dual purity oxygen

摘要

Producing lower purity oxygen and higher purity oxygen comprises (a) at least partially condensing a first feed air portion (13) and passing the resulting first feed air portion into a higher pressure column (2) of a double column which also comprises a lower pressure column (1); (b) at least partially condensing a second feed air portion (12) having a pressure less than that of the first feed air portion and passing the resulting second feed air portion into the higher pressure column; (c) separating feed air within the double column by cryogenic rectification to produce first oxygen richer fluid (25) and nitrogen richer fluid (40), (d) passing the first oxygen richer fluid from the double column into a first auxiliary column (3) and separating the first oxygen richer fluid within the first auxiliary column by cryogenic rectification to produce second oxygen richer fluid (28) having an oxygen concentration greater than that of the first oxygen richer fluid; (e) passing second oxygen richer fluid from the first auxiliary column into a second auxiliary column (4) and separating the second oxygen richer fluid within the second auxiliary column by cryogenic rectification into lower purity oxygen (29), having an oxygen concentration which is greater than that of the first oxygen richer fluid and less than that of the second oxygen richer fluid and into higher purity gaseous (31) and liquid (33) oxygen, having an oxygen concentration greater than that of the lower purity oxygen; (f) recovering lower oxygen and higher purity oxygen from the second auxiliary column. Also claimed is an appts. for producing lower and higher purity oxygen and a method and appts. having a single large auxiliary column which is useful when the oxygen product is required at low pressure.