Synthesis of refinery desulfurization solvent network with multi-stage solvent regeneration

Increasing process of sour crude oil and demand of low-sulfur oil products expand the desulfurization units in refineries, which raises the desulfurization solvent circulation as well as the energy cost for solvent regeneration. In this work, synthesis of desulfurization solvent network with multi-stage solvent regeneration is investigated to reduce the energy cost. Firstly, this work presents superstructures for desulfurization solvent network with regeneration considering one-stage structure, two-stage cascaded structure, and two-stage parallel structure, respectively. Next, mathematical models for the three cases are formulated as nonlinear programming problems where the objective function aims to minimize the total energy consumption. Finally, a case study is conducted to illustrate the proposed method. The results show that the two-stage structures reduce more energy costs than the one-stage structure by 7.65% and 8.46%, respectively, which means that two-stage regeneration is more attractive. Besides, the parallel structure is better than the cascaded structure, because the energy requirement for solvent regeneration is more sensitive to the outlet concentration of hydrogen sulfide than the inlet concentration.