Nonlinear model based multivariable control of a debutanizer

The debutanizer column control is a major economic incentive to a refinery due to the importance of the product quality. The nonlinear model-based multivariable control on a debutanizer has shown to provide improved control performance of the top product and the bottom stream qualities using a steady-state process model with approximate dynamics. The control performance is much better than that achieved by the traditional PID-type control system. This paper outlines the non-linear control method applied to an industrial debutanizer and discusses the use of inferential models to predict the iso-pentane contents in the overhead stream and the Reid vapour pressure (RVP) in the bottom stream, in nonlinear control applications.