Partial Control. 5. A Systematic Approach to the Concurrent Design and Scale-up of Complex Processes: The Role of Control System Design in Compensating for Significant Model Uncertainties

Abstract

In four previous papers of this series (Ind. Eng. Chem. Res. 1995, 34 (4), 1228−1243; 1995, 34 (4), 3014−3026; 1996, 35 (7), 2215−2233; 1997, 36 (3), 747−759) the concepts of partial control were presented on the basis of the assumption that model information adequate to characterize the process is available from existing units. In this paper the more difficult problem of utilizing the limited data from a laboratory or small pilot plant for the design of a new complex process is analyzed. The fluid catalytic cracker again serves as the main example. One faces large uncertainties during such a scale-up. Reducing them by building a big pilot plant is time-consuming and expensive. It is demonstrated how that uncertainty can be compensated for through concurrent design that is focused on providing proper manipulated variables for control. This achieves one of the main goals of control, namely, to compensate for model uncertainties. A design strategy is presented for the scale-up of complex processes with large model uncertainties, utilizing the concepts of partial control developed previously.