Effect of feed composition on cryogenic distillation precooling configurations

Abstract

Precooling the feed of cryogenic distillation columns is achieved by using the cold distillate and bottoms streams. The distillate is typically removed from the top of the reflux drum as a vapor to reduce the condenser refrigeration heat duty. The bottoms stream is typically a liquid at a somewhat higher temperature than the distillate. The colder vapor distillate can only provide sensible heat removal. The warmer bottoms liquid stream can provide more heat removal because of vaporization.The purpose of this paper is to demonstrate that the appropriate arrangement of the precooling heat exchangers depends on the column feed composition. If the feed contains little light key component, the bottoms stream is large and the feed can be easily precooled. If the feed contains little heavy key component, the bottoms stream is small and precooling the feed is more difficult.