ABSTRACT
Distillation columns are fairly complex units. They have several inputs and outputs, so they can present challenging multivariable control problems. Their dynamics are a mixture of very fast vapor flowrate changes, moderately fast liquid flowrate changes, slow temperature changes and very slow composition changes. The manipulated variables often have constraints because of column flooding limitations or heat exchanger limitations. Developing an effective control system for an individual column is not a trivial job. There are at least six loops involved on even the most simple column.
