Process to recover argon from oxygen-only air separation plant

Claim 1

In an existing process for producing oxygen by the separation of air wherein feed air is introduced to an oxygen production facility comprising a high pressure column in heat exchange relation with a low pressure column wherein vapor and liquid flow countercurrently and contact to effect the separation, the improvement comprising retrofitting said existing process to include argon recovery capability including the steps of: (A) withdrawing from the low pressure column a stream having a flow rate of from about 3 to 9 percent of that of the feed air, said stream comprising from about 10 to 18 percent argon, at most about 0.5 percent nitrogen and the remainder primarily oxygen; (B) introducing said stream as feed into an argon column having a top condenser and a bottom condenser and which is driven by an independent heat pump circuit comprising the steps of: (1) introducing cooled, compressed heat pump fluid as vapor to a heat exchanger where it is cooled to a high pressure cold condition, (2) introducing said high pressure cold vapor to said bottom condenser where it is condensed to a liquid, (3) expanding the liquid heat pump fluid and introducing it to the top condenser where it is vaporized, and, (4) withdrawing the heat pump fluid as vapor from the argon column and introducing it to said heat exchanger of step (1) where it is warmed; (C) separating said feed in said argon column by rectification into an argon-rich fraction and an oxygen-rich fraction; (D) withdrawing from said argon column at least a portion of said argon-rich fraction as product crude argon containing at least 96 mole percent argon; and (E) withdrawing at least a portion of said oxygen-rich fraction as product oxygen having an oxygen concentration of at least 99 mole percent.