A BOUNDING PROCEDURE FOR THE MINIMUM NUMBER OF COLUMNS IN NONSHARP DISTILLATION SEQUENCES

When multicomponent products are to be produced from a single feed, it is frequently not necessary to separate the feed into pure-component products. Instead, column bypasses and nonsharp splits may be used to significantly reduce the cost of the distillation sequence. This paper describes a bounding procedure for the minimum number of columns in nonsharp split distillation sequences. Three bounds are established for the minimum number of columns. The first bound is determined from a degree of freedom analysis of the feed and product specifications. The second is determined from an analysis of the amount of separation that must be performed. The third bound is based on the minimum purity that the separation system must achieve. The procedures are illustrated for four sample problems. © 1989.