Dynamic multi-objective optimization of industrial radial-flow fixed-bed reactor of heavy paraffin dehydrogenation in LAB plant using NSGA-II method

• Dynamic multi-objective optimization of paraffin dehydrogenation using NSGA-II.
• Maximization of olefin production rate and selectivity as objective functions.
• Pareto optimal solutions with optimum values of both objective functions.
• 3D distributions of decision variables chromosomes during 29 days of operation.
• Highest olefin production rate and selectivity under optimal conditions.

Due to the increasing global demand for olefin production, the development of catalytic dehydrogenation of paraffins to olefins has attracted considerable attention in recent years. Thus, a dynamic multi-objective optimization of heavy paraffin dehydrogenation over Pt–Sn–Al2O3 catalyst for production of olefin in an industrial radial-flow fixed-bed reactor (RF-FBR) using non-dominated sorting genetic algorithm-II (NSGA-II) is the subject of this study. The optimization problem involves two objective functions namely, maximization of olefin production rate and selectivity. Two points, A′A′ and B′B′, are considered on the obtained Pareto optimal fronts. The result reveals that the midpoints of A′B′A′B′ have the approximate optimal values of both objective functions. Moreover, the 3D distributions of the optimized decision variables chromosomes are studied during 29 operating days. Concentrations of the chromosomes are increasing toward the lower limit of temperature and pressure, as well as higher limit of total molar flow rate. Optimization results give the optimum values of operating conditions, under which the maximum olefin production rate and selectivity can be obtained.