Patent ID: 8640496
Filing Date: 2014-02-04
Classification: F25J

Abstract:
1. A method of separating air comprising: separating the air within a first air stream by introducing the first air stream into a first cryogenic air separation plant, the first cryogenic air separation plant employing a first main heat exchanger to cool the first air stream, after having been compressed and purified, to a temperature suitable for the distillation of the air within the first air stream and a higher pressure column and a lower pressure column to distill the air within the first air stream; withdrawing an oxygen-rich product stream from the lower pressure column, the oxygen-rich product stream being made up of an oxygen-rich liquid column bottoms produced in the lower pressure column; separating the air within a second air stream in a second cryogenic air separation plant independently of the separating of the air within the first cryogenic air separation plant with the use of a second main heat exchanger to cool the second air stream, after having been compressed and purified separately from the first air stream, to a temperature suitable for the distillation of the air with the second air stream and at least one other distillation column to distill the air within the second air stream such that an impure oxygen vapor stream is produced having an oxygen concentration between that of the oxygen-rich product stream and the air and a lower nitrogen concentration than the air; and introducing at least part of the impure oxygen vapor stream produced by the second cryogenic air separation plant into the lower pressure column of the first cryogenic air separation plant such that the at least part of the impure oxygen vapor stream, upon introduction into the lower pressure column, has the oxygen concentration and the lower nitrogen concentration of the impure oxygen vapor stream produced by the second cryogenic air separation plant and oxygen contained within the first air stream and the impure oxygen vapor stream is recovered in the oxygen-rich liquid column bottoms of the lower pressure column and is used in producing the oxygen-rich product stream.