Chemical Engineering Research & Design, Vol.78, No.4, 621-629, 2000
Constrained nonlinear multivariable control - Application to catalytic reforming process
In this paper, a constrained nonlinear multivariable control and optimization strategy for handling constraints has been proposed and applied in real time to the catalytic reforming reactor-section. A dynamic model of the catalytic reforming process was developed and used in nonlinear multivariable control application on the reactor section to provide target values for the reactor inlet temperature. The model results were tested in real-time application, and were used to improve the dynamic response of the model. The constrained nonlinear multivariable controller controls the weighted average inlet temperature (WAIT), while respecting the heater tube temperature constraints. An octane inferential model forming a closed-loop WAIT/octane quality control system sets WAIT. It has been shown that nonlinear multivariable control provided better disturbance rejection compared to traditional linear model-based control, reduced the octane deviation and variation in WAIT and maintained a very good control of WAIT. The same model is used for optimization and control, minimizing the modelling errors due to process/model mismatch.