Evaluation of control systems and energy conservation techniques for distillation columns

Two methodologies are currently being used to design control systems for distillation columns. One method approaches the problem from a control loop interaction, sensitivity, and stability point-of-view. The other method considers the incentive (or lack of incentive) for dual product composition control by comparing the cost of the more complex control scheme to the cost of the additional energy used with a simpler, overfractioning control scheme. The purpose of this study is to merge both methods into one, more complete design methodology that considers both control loop interactions and energy costs. The methodology is applied to several practical distillation column examples to demonstrate its use in distillation column control system design.