Simultaneous optimization of solvent composition and operation parameters for sulfolane aromatic extractive distillation processes

BTXs (benzene, toluene and xylenes), used widely as basic chemical intermediates, are separated generally from petroleum naphtha, coking naphtha, and pyrolysis gasoline. These oil fractions contain aromatic and non-aromatic hydrocarbons between C5 to C8 in which certain components have approximate boiling points and form azeotropes. Extractive distillation (ED) is one of the most attractive approaches for separating azeotropic mixtures with approximate boiling points. The aromatic ED technique aided by sulfolane used widely in recent years because of its simple process flowsheet, small equipment investment and high energy efficiency. The solvent and operating parameters are the cores of ED process in the economical design. Some results were published to rapidly screen the solvents as well as process parameter optimization for ED separating process, but few contributions have been reported to optimize an extractive distillation from the view of simultaneous optimization of the solvent composition and operation parameters for process economics. In this work, we propose a systematic optimization approach for energy saving of sulfolane aromatic ED processes based on process simulation and genetic algorithm (GA) optimization. The NRTL property method and rigorous unit models in Aspen Plus are used to simulate the ED processes. In particular, considering multi-variable and their interaction, a coordinating strategy is proposed to optimize the solvent composition and significant operating parameters for the ED processes by combining Aspen Plus with MATLAB. Under given separation specifications, the energy consumption and separation efficiency are investigated and optimized by GA optimization. The results show that the through the above optimization, the minimum heating utility of the ED process is significantly reduced by 29.2%.