posted on 2021-02-23, 19:04authored byYang Lei, Yuhang Zhou, Zhiqiang Wei, Yuqiu Chen, Fen Guo, Wei Yan
Extractive distillation (ED) can
be used to separate mixtures with
low relative volatilities that are even close to unity. It is widely
adopted for the separation of aromatics and nonaromatics in the petrochemical
industry. Selecting a suitable solvent is of paramount importance
to ED processes. Ionic liquids (ILs) are increasingly being considered
as potential options to replace organic solvents in ED processes due
to their favorable properties including high boiling points and extremely
low volatilities. In this work, a nonexperimental solvent screening
approach, i.e., computer-aided ionic liquid design (CAILD), is employed
to identify the optimal ILs. Using a novel design objective and several
structural and property constraints on IL, we have identified 1,3-dimethylpyridinium
tetrafluoroborate ([C1mPy][BF4]) as the best
IL solvent by solving a formulated CAILD-based mixed-integer nonlinear
programming problem. The separation performance of this IL is further
evaluated with rigorous process simulation in Aspen Plus. Besides,
process simulation of the aromatic ED process using sulfolane as the
benchmark organic solvent is performed. Furthermore, a systematic
analysis of the energy consumption and the process economy is conducted
by investigating the optimized simulation results of the studied aromatic
ED process. The [C1mPy][BF4]-based process with
an assumed IL price of 50 $/kg can reduce the capital cost by 35.2%,
the operating cost by 11.8%, and the total annual cost by 31.2%. The
IL price at the break-even point of replacing sulfolane with [C1mPy][BF4] in the aromatic ED process is 91.03 $/kg.