关键词: 离子液体, 纳滤, 闪蒸, 能耗, 工艺模拟, 分离回收

Abstract: The highly efficient and low-cost recovery of ionic liquid from the solution remains an issue to realize the reuse of ionic liquid. This work proposes the coupling process combining nanofiltration and vacuum flash evaporation for recovery of ionic liquid in solution. The lower concentration of ionic liquid aqueous solution is concentrated through nanofiltration technology, and then the higher concentration of ionic liquid aqueous solution is treated by the vacuum flash evaporation process to obtain the pure ionic liquid and realize the efficient separation and recovery of ionic liquid. 1-methyl-3-octylimidazolium tetrafluoroborate ([C8Mim][BF4]) and 1-ethyl-3-methylimidazolium tetrafluoroborate ([C2Mim][BF4]) were used as model compounds to explore the recovery effect of the coupling technology by process simulation. Based on the literature reported data on the previous researches, the main physical properties of ionic liquid and ionic liquid-water thermodynamic models were constructed by the regression method. A model of the coupled process of the separation and recovery technology for ionic liquid was established by Aspen Plus simulation software. The influences of different operating conditions on the process separation performance were investigated by the parametrical sensitivities analysis. Then the optimal scenario could be obtained. At the same time, the heat exchanger network of the coupling process was modified which could increase the energy efficiency and reduce the cooling and heating utilities consumption. Moreover, the energy consumption of different processes were analyzed and evaluated to clarify the separation and recovery advantages of the novel coupling process. The results showed that the heating utilities of [C8Mim][BF4] and [C2Mim][BF4] were 11% and 13% of those of the initial scenarios, and the cooling utilities were 15% and 19% of those of the initial scenarios after the heat exchanger network modification. The lowest comprehensive energy consumption of the 2 stage membrane separation-flash evaporation coupling process was 3.9 GJthermal-eq/t IL ([C8Mim][BF4]) and 4.5 GJthermal-eq/t IL ([C2Mim][BF4]), which was only 20% ([C8Mim][BF4]) and 27% ([C2Mim][BF4]) of the direct vacuum flash evaporation process. The results of this study can provide theoretical basis and guidance for the future industrial application of ionic liquid recovery process.

Key words: ionic liquid, nanofiltration, vacuum flash evaporation, energy consumption, process simulation, recovery and separation