Argon condensation system and method

A method of condensing argon reflux within an air separation unit having an argon column, a lower pressure column and a higher pressure column, said method comprising the steps of:

• extracting a crude argon feed stream from the lower pressure column;
• distilling the crude argon feed stream in the argon column to produce an argon-rich vapor column overhead;
• directing at least a portion of the argon-rich vapor column overhead to a plurality of once-through heat exchangers;
• condensing the argon-rich vapor streams within condensation passages of the plurality of once-through heat exchangers such that argon-rich vapor streams composed of argon-rich vapor column overhead are condensed within condensation passages of the once-through heat exchangers to produce an argon-rich liquid product stream and argon-rich liquid reflux stream
• returning the argon-rich liquid reflux stream to the argon column as reflux;
• introducing one or more streams of crude liquid oxygen column bottoms from the higher pressure column into vaporization passages of the plurality of once-through heat exchangers to partially vaporize the crude liquid oxygen streams through indirect heat exchange with the argon-rich vapor streams to produce partially vaporized crude liquid oxygen streams
• introducing the partially vaporized crude liquid oxygen streams into the lower pressure column;
• sensing liquid flow rates of the crude liquid oxygen streams directed from the bottom of the higher pressure column to the vaporization passages of the plurality of once-through heat exchangers;
• controlling the flow rates of the crude liquid oxygen streams to the plurality of once-through heat exchangers in response to the sensed liquid flow rates and the level of the crude liquid oxygen bottoms in the higher pressure column;
• and
• controlling a feed stream flow rate of the crude argon feed stream in response to an air flow rate into the air separation unit and by controlling the reflux flow rate of the argon-rich liquid reflux by:
• (i) decreasing the reflux flow rate of the argon-rich liquid reflux stream when the feed stream flow rate is above a feed stream set point to thereby cause the argon-rich liquid reflux to back up into the condensation passages of the once-through heat exchanger causing an increase in pressure of the argon-rich vapor stream and within the argon column;
• and
• (ii) increasing the reflux flow rate of the argon-rich liquid reflux stream when the feed stream flow rate is below a feed stream set point to thereby cause a decrease in the pressure of the argon-rich vapor stream and within the argon column.