Optimization of Trickle-Bed Reactors (TBRs) for Hydrodesulfurization (HDS) and Hydrodearomatization (HDA) of Diesel using Single and Multiple Objectives

Abstract

Abstract This article describes the formulation, solution and analysis of two single-objective optimization and one multi-objective optimization (MOO) problems on trickle-bed reactors (TBRs) involving hydrodesulfurization (HDS) and hydrodearomatization (HDA). The model used by Chowdhury et al. (AIChE J 2002;48:26) for TBR involving HDS and HDA is used in this study, to solve these optimization problems. The correctness of algorithm and the numerical procedure used in this study to solve the model equations are validated with the results of Chowdhury et al. (AIChE J 2002;48:26), before the model is used for optimization. Objective functions chosen in our optimization studies are minimization of sulfur concentration and maximization of total conversion of aromatics at the exit of TBR. Decision variables considered are reactor temperature, reactor pressure and liquid hourly space velocity (LHSV). Two single-objective optimization and one MOO problems are formulated and solved using simple genetic algorithm (SGA) and NSGA-II, respectively, to obtain the optimal values of reactor operating conditions. Pareto set for the MOO problem is generated which show that conflicting nature of the objective functions. Specifically, we have shown that the simultaneous minimization of exit sulfur and maximization of aromatics removal conflict each other in hydrotreating.