Multiobjective optimization of an industrial nylon-6 semibatch reactor system using genetic algorithm

Multiobjective Pareto optimal solutions for three different grades of nylon -6 produced in an industrial semibatch reactor are obtained by using the ad apted Non-dominated Sorting Genetic Algorithm (adapted NSGA). The two objec tive functions minimized are the total reaction time and the concentration of undesirable cyclic dimer in the product, while simultaneously attaining desired values of the monomer conversion and the number average chain lengt h. The control variables used are the fractional valve opening f(t) and the jacket fluid temperature T-J. The study shows a marked improvement over cu rrent industrial operation. It is found that the optimal values of the cycl ic dimer concentration in the product are worse (higher) when the reactor-c ontrol valve system is studied than when the reactor is considered alone. T his is because the control valve leads to additional constraints. The techn ique used is quite general and can be used to study other reactor systems a s well. (C) 1999 John Wiley & Sons, Inc.