Application of LQ and IMC controllers to a packed‐bed reactor

Abstract A practical application of advanced, model‐based, multivariable control to a pilot plant packed‐bed reactor carrying out highly exothermic butane hydrogenolysis reactions is presented. The system is first stabilized by using butane flow rate to control the reactor hot‐spot temperature. Propane production and butane conversion are then controlled using multivariable controllers that manipulate the hot‐spot temperature set point and hydrogen flow rate. The controller designs are based on multivariable transfer function models developed using multivariable time series and process identification methods. Two types of multivariable controllers are applied. The first is an internal model controller (IMC) utilizing a stabilized approximation of the model inverse and a tunable exponential filter. The second is a linear‐quadratic (LQ) controller design using pulse transfer function models to characterize the process dynamics and autoregressive‐moving average models to characterize the disturbances. The optimal control solution was arrived at via a spectral factorization solution to the Wiener‐Hopf equations. The results indicate that both designs, if well tuned, provide good performance and robustness over a wide range of operation.