(445a) Economic Plantwide Control Design Procedure

A general systematic top-down procedure for an effective plantwide control system design for economically optimal operation of a process over a large throughput range is synthesized. As throughput is increased, operating constraints become active one by one at the optimum steady state till maximum plant throughput where maximum number of constraints is active. The crucial step in the systematic procedure is to design a control system for economic process operation at maximum throughput. In step 1 of the procedure control loops for tight control of active constraints and economically dominant CVs are implemented, then in Step 2 inventory control loops are set followed. Step 3 involves control loop configurations for throughput manipulation so that the setpoints that becomes unconstrained at lower throughput can take up additional close-by economic CV control for throughput manipulation. Step 4 involves control structure reconfiguration to eliminate fragile / unconventional inventory control loops resulting from above 3 steps. The procedure is applied on a realistic chemical process.