Decoupling In Distillation

Abstract

Due to the dynamic characteristics of the distillation process, the control design by
process decoupling is suited especially for two point composition case. The proposed decoupling
method is a theoretical-experimental procedure that can be applied as a rule to two inputs - two
outputs processes. The purpose of the paper is to present a simple and robust decoupling
procedure, and to emphasize the advantages of distillation process control by decoupling
technique. The designed decoupler has a standard general structure, which can be implemented in
4x4 distinct variants, corresponding to the dynamic characteristics of process direct and crossed
channels. It has six tuning parameters: two time constants, two deadtimes and two gains, which
can be experimentally tuned in order to obtain better decoupling performance. The decoupler is
tested on two binary distillation columns, and the simulation results show that the proposed
decoupling method is a useful tool for composition decoupling. The applied technique can also
gain recognition in other areas of chemical process control, especially when relative gain array
elements are relatively small and larger than one.