Real time optimization of chemical processes: A comparison of closed versus open form equations using commercial simulation packages

The main objective of this research was to compare the use of closed and open form equation based process simulation packages as the process models in real time optimization. Currently, both closed form equation based, or sequential modular, and open form equation based, or equation-oriented, process simulators have been suggested for use in real time optimization, but not implemented.; Two real time optimizers were developed for an industrial refinery stabilizer-splitter process using ASPEN PLUS, a sequential modular process simulator, and SPEEDUP, an equation-oriented process simulator.; After testing the two real time optimizers, it was concluded that neither ASPEN PLUS nor SPEEDUP in their present form were robust enough for an industrial on-line application. The equation-oriented simulator, however, was able to find better objective function values using approximately half as many cycles of the real time optimizer than the sequential modular simulator. The sequential modular simulator had difficulty in converging the economic optimization problem when inequality constraints became violated. Problems were also encountered converging the tear stream blocks in ASPEN PLUS for some operating conditions. The SPEEDUP real time optimizer required weighting factors in the objective functions for both data reconciliation and economic optimization due to a lack of tuning parameters for the SRQP optimization algorithm and possible flowsheet variable scaling problems.; From the development of the two real time optimizers, it was concluded that sequential modular simulators are quicker and easier to use than equation oriented simulators. However, they are not as flexible with respect to the choice of manipulated variables for optimization and convergence of flowsheet recycle loops and tear streams. The development of the real time optimizers also provides a "test bed" for future research into real time optimization.; Overall, despite the added difficulty in developing and converging an equation-oriented process flowsheet model, the added flexibility in terms of variable specification, robust and rapid tear stream convergence, and more powerful optimization algorithms make the equation-oriented process simulator a more attractive tool for real time optimization, provided the problems encountered can be overcome. Equation oriented process simulation packages have also already been used in advanced model based control, scheduling and process operation analysis which has the advantage of providing the same user-interface and models for all process modelling performed.; Several other runs were performed with the ASPEN PLUS real time optimizer testing changes in the economic objective function parameters and the effect of process disturbances. Also, a sensitivity study of the economic objective function stream prices was performed which showed that in every case tested, the real time optimizer was able to find a better operating point after change in economic parameters. (Abstract shortened by UMI.)...