Advanced control practice in the chemical process industry: A view from industry

Abstract

This paper presents a commentary on the status of application of modern control theories to industrial chemical processes. The difficulties encountered in the implementation of advanced control to chemical reactors are critically examined in order to determine the reasons for its limited success to date. Chemical processes, very often poorly understood because of the physicochemical complexities, are nonlinear, highly interacting, spacially dependent, and continuously disturbed by many uncharacterized noises. It is time-consuming and expensive to develop advanced control methods for these systems because few of the available theories can be applied directly. Thus, we often find it difficult to economically justify advanced control projects.

Design Concepts for Process Control

“…Weekman (1974) discusses an interesting case (Kurihara, 1967) in which an optimum design led to a controller which is not usable in a plant. On the other hand it gave useful information for improving controller design.…”

Potential use of advanced process control for safety purposes during attack of a process plant

“…This translates to larger 'safety margins' when establishing set points for CVs operating near a constraint. The result is reduced profitability as the economic operating point frequently lies at the intersection of constraints [4].…”

Steady-state multiplicity analysis of two-stage-riser catalytic pyrolysis processes

“…Based on the same mathematical model of the open-loop FCC unit, Oliveira validated that there was only one steady state for the parameters utilized (Oliveira, 1994). Actually, the reason for the unusual multiple steady states associated with Iscol's model was the peculiarity of a temperature cubic term in the coke-make correlation (Lee and Weekman, 1976). Following previous contributions, cracking kinetics and a simplified fluid dynamic representation were incorporated into the FCC unit's model to analyze the multiple steady states and the corresponding local (in) stabilities (Elnashaie and Kim, 1979).…”