This chapter presents three MS Excel programs, namely, EMOO (Excel based Multi-Objective Optimization), NDS (Non-Dominated Sorting) and PM (Performance Metrics) useful for Multi-Objective Optimization (MOO) studies. The EMOO program is for finding non-dominated solutions of a given MOO problem. It has both binary-coded and realcoded NSGA-II (Elitist Non-Dominated Sorting Genetic Algorithm), and two termination criteria based on chi-squared test and steady state detection. The known/true Pareto-optimal front for the application problems is not available unlike that for benchmark problems. Hence, a procedure for obtaining known/true Pareto-optimal front is described in this chapter. The NDS program is for non-dominated sorting and crowding distance calculations of the non-dominated solutions obtained from several optimization runs using same or different MOO programs. The PM program can be used to calculate the values of performance metrics between the non-dominated solutions obtained using a MOO program and the true/known Pareto optimal front. It is useful for comparing the performance of MOO programs to find the non-dominated
A rigorous model is developed for simulating an existing industrial hydrogen plant based on refinery off-gas, which is made up of liquefied petroleum gas and off-gas from the membrane separation unit in a petroleum refinery. The presence of higher hydrocarbons in the reaction system is accounted for in the model equations for bulk gas and catalyst pellet. The reformer model is validated against three sets of industrial plant data, with good agreement. Thereafter, multiobjective optimization is performed using the nondominated sorting genetic algorithm to predict sets of Pareto-optimal operating conditions for improved performance. For a fixed feed rate of off-gas to the unit, two or three objectives, namely, maximization of product hydrogen and export steam rates and minimization of the heat duty supplied to the steam reformer, are targeted simultaneously. The optimal heat flux profile in the steam reformer is distinct from that predicted for methane feed (Oh, P. P.; Ray, A. K.; Rangaiah, G. P. J. Chem. Eng. Jpn. 2001, 34 (11), 1341. The optimal results obtained are better than industrial operating data.
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