Distillate-bottoms control of middle-vessel distillation columns

The performance of a middle-vessel distillation column subject to distillat e-bottoms (DB) control configurations is analyzed. DB-controlled columns, w here the distillate flow rate is manipulated to control the distillate comp osition and the bottoms flow rate is manipulated to control the bottoms com position, have been labeled as inoperable for continuous distillation. In t his paper, two DB-control configurations for a middle-vessel column (MVC) a re shown to overcome the deficiencies commonly associated with DB control. In the first configuration, the feed flow rate from the middle vessel is fi xed and the flow rate of the heating medium controls the sump level. In the second "on-demand" configuration, the feed flow rate from the middle vesse l is manipulated to control the sump level. To demonstrate the effectivenes s of these configurations, the distillation of a near-ideal binary mixture is examined.