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Flow control in non-continuous chemical plants
Abstract
We consider general-purpose and flexible non-continuous chemical plants under deterministic feedback control. The aim of this research has been to develop hierarchical distributed feedback based control policies to: (1) organize and schedule flow between the different unit operations, (2) ensure the satisfaction of both safety as well as product constraints, and (3) achieve desirable performance. We begin by developing a lower bound on total storage required to meet demand rates. We also develop an upper bound on total storage required by an optimal policy. Next we propose a distributed feedback control scheme to organize flow in flexible non-continuous chemical plants. We show that this control scheme is stable, and can be implemented with fixed and finite storage. The performance of this policy in a limited number of simulations was close to optimal. When there are severe constraints on the size of the intermediate storage, a global supervisor can be implemented to prevent deadlock. We show that when the plant satisfies a sparsity property, the global supervisory control problem is tractable. The overall control system approach that we have developed for non-continuous chemical plants is based on a two-tiered structure--(1) a global supervisor ensures that process and safety constraints are satisfied, and also keeps the plant state trajectory steered away from dead-lock; and (2) local controllers are designed to maximize a distributed performance measure.
Subject Area
Chemical engineering|Systems science|Operations research
Recommended Citation
Srinivasan, Venkatesh, "Flow control in non-continuous chemical plants" (1992). Doctoral Dissertations Available from Proquest. AAI9219502.
https://scholarworks.umass.edu/dissertations/AAI9219502