Process for the mixed production of high and low purity oxygen

Claim 1

A process for simultaneously producing both high and low purity oxygen from a double column, double reboiler apparatus, the double columns being low and high pressure columns, and said low pressure column having a lower and an upper reboiler, which comprises: a) condensing a first compressed and cooled feed stream fraction containing at least nitrogen and oxygen in a reboiler located at the bottom of the lower pressure column; b) feeding at least a fraction of the resulting liquefied feed stream to either high or low pressure columns or both as feed; c) introducing a second fraction of a feed stream to a bottom of the high pressure column as gaseous feed, whereby a bottom oxygen-rich liquid stream and an overhead nitrogen-rich gaseous stream are formed; d) passing the oxygen-rich liquid stream to the low pressure column as feed; e) condensing the nitrogen-rich gaseous stream against a boiling liquid in an upper reboiler of the low pressure column, thereby serving as a second reboil for distillation; f) returning a portion of the condensed nitrogen-rich stream to the high pressure column as reflux, and passing at least a fraction of a remaining portion of the nitrogen-rich stream to the top of the low pressure column as reflux, whereby the low pressure column separates its feeds into bottom stream oxygen product and top stream-rich in nitrogen; g) recovering the bottom stream oxygen product as high purity liquid oxygen; and h) drawing from a tray or a stage between the two reboilers of the low pressure column, an oxygen product stream as low purity oxygen.