Process for maximizing the recovery of argon from an air separation system at high argon recovery rates

A process for maximizing the recovery of argon at high argon recovery rates from an air separation system having a high and low pressure distillation column containing multiple distillation stages of rectification with the high pressure column providing a nitrogen rich reflux fluid to wash the rising vapors in the low pressure distillation column and having a separate sidearm column for argon recovery comprising the steps of:

• introducing an oxygen enriched fluid into said low pressure column at a feed point where comparable oxygen-nitrogen equilibrium exists;
• withdrawing a fluid feedstream from said low pressure column at a location where the argon content is relatively high for use as an input feedstream to said argon sidearm column;
• identifying each stage of rectification within said low pressure column between said feedstream location and said feed point which exhibits a relatively high sensitivity to process changes in said air separation system;
• selecting at least one of said identified stages of rectification which exhibits high sensitivity to process changes for monitoring the composition of said input feedstream to said argon sidearm column;
• formulating a model defining the relationship between the nitrogen content in said feedstream and a compositional variable in said low pressure column at said selected stage of rectification;
• measuring the compositional variable at said selected stage of rectification;
• computing the concentration of nitrogen in said input feedstream to said argon sidearm column from said model in accordance with the value of said measured compositional variable;
• and
• controlling the operation of said process in response to said computation of nitrogen in said input feedstream.