This paper provides a case study on the selection of controlled variables for the implementation of real time optimization results in a crude unit heat exchanger network. Two different control strategies with 22 different control structures are evaluated. The idea is to select the controlled variables that give the best plant economic (smallest loss) when there are disturbances (self-optimizing control). The disturbances are correlated and a simple principal component analysis is used to generate a more realistic set of disturbance variations for evaluation of the different control structures. This analysis shows a large variation of loss for different control structures and that a control structure evaluation is necessary to collect the benefits from a RTO system.
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