| Abstract
| - Cryogenic air separation plants that produce argon in addition to oxygen and nitrogen use two heat-integrateddistillation columns and a side rectifier. The dynamics of the side rectifier are very slow because of threefactors: the large number of separation stages, the small amount of argon in the air feed, and the high productpurity. Currently, when the plant shuts down, the liquid inventory in the argon column drains into the upper(low-pressure) column. A normal start-up takes about 10 h to achieve argon product purity. The start-up timecan be reduced significantly by using storage vessels to collect the liquid that drains from the argon columnupon shutdown and reintroducing the liquid during the subsequent start-up. Compared to a 10 h start-up timewith no collection points, the time required to achieve argon product purity is reduced to 3.35 h by using 2collection points and is reduced to 2.23 h by using 6 collection points.
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