Method and apparatus for separating air

摘要

Method and apparatus of separating an oxygen and nitrogen containing feed stream, for example, air, in higher and lower pressure columns. A crude liquid oxygen stream condenses nitrogen vapor in the higher pressure column for reflux purposes and results in the partial vaporization of the crude liquid oxygen stream to produce vapor and liquid fractions thereof. The liquid fraction condenses a lower pressure part of the feed stream and results in the liquid fraction being at least partially vaporized. Both the vapor fraction of the crude liquid oxygen stream and the liquid fraction after having been at least partially vaporized are introduced into the lower pressure column. Boil-up is produced within a bottom region of the lower pressure column by partially vaporizing an oxygen-rich liquid column bottoms against condensing a higher pressure part of the feed stream and then utilizing vapor or residual liquid as an oxygen product.