Constraint control on distillation columns

✍ Scribed by A. Maarleveld; J.E. Rijnsdorp

• Publisher: Elsevier Science
• Year: 1970
• Tongue: English
• Weight: 657 KB
• Volume: 6
• Category: Article
• ISSN: 0005-1098
• DOI: 10.1016/0005-1098(70)90074-9

✦ Synopsis

Optimum control is often not at the "hilltop", but at the intersection of constraints. When these constraints shift with changes in operation, a self-adaptive control scheme is required.

Summary--Optimum operation of processes is often not at the "top of the hill", but at the intersection of constraints. When the process conditions change, other constraints can become critical; hence a control system making use of the constraint principle should be capable of automatically switching to another intersection. This is referred to as constraint control.

This idea has been worked out for a simple distillation column--where the column pressure and the feed preheating are the degrees of freedom available for optimization. The shifting of the constraints due to changes in throughput are illustrated in constraint diagrams.

As an example, constraint diagrams and a constraint control scheme for a deisopentanizer are discussed. The control scheme is not very complicated and can be realized by conventional means.