Importance

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Abstract

A process and apparatus for producing a gaseous oxygen product at a delivery pressure so as to contain a low concentration of heavy impurities in which compressed and purified air is cooled in a main heat exchanger to near dew point temperatures and then introduced into an air separation unit designed to rectify the air into a liquid oxygen fraction. The air separation unit comprises high and low pressure columns operatively associated with one another in a heat transfer relationship by provision of a condenser-reboiler. The liquid phase of the air being separated becomes increasingly more concentrated in heavy impurities as it descends within the low pressure column so that liquid oxygen collected in the sump of the condenser-reboiler becomes concentrated in the heavy impurities and the liquid phase flowing into the sump contains a low concentration of the heavy impurities. A product stream is withdrawn from the liquid phase before it reaches the sump and is pumped to the delivery pressure and then vaporized within the main heat exchanger. A purge stream of liquid oxygen from the sump is removed so that the impurity concentration level within the liquid oxygen does not reach its solubility limit.

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First Claim