The volatility of argon and oxygen are close and that makes the task of separation of argon from air in a cryogenic air separation plant difficult. It demands strict maintenance of different design and operating parameters of the plant. It is shown that the impurity in liquid oxygen is argon only and extraction of crude argon helps in having a better control in maintaining the liquid oxygen purity. In this paper we first analyze the crude argon column. Effects of variations of crude argon draw with different concentrations of nitrogen and argon in the feed to the crude argon column on the oxygen and nitrogen concentrations in the crude argon product have been studied. A double column with crude argon column attachment has been analyzed next. The effects of the draw of liquid nitrogen, gaseous oxygen and crude argon product on the argon, oxygen and nitrogen content on the crude argon feed and crude argon product draw have been presented. The importance of different design and operating parameters in an air separation plant has been discussed in detail with an aim to extract argon most efficiently. Results of plant simulation have been presented in appendices. Information contained in this paper would help the design and operating engineers to have a clearer understanding of the phenomena of argon extraction in a cryogenic air separation plant.
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