Modelling and simulation of hollow fiber membrane vacuum regeneration for CO2 desorption processes using ionic liquids

Abstract

A novel modelling and simulation framework on CO2 desorption process from post-combustion CO2 capture was developed by a coupled membrane vacuum regeneration technology (MVR) and four imidazolium ionic liquids (ILs) with remarkably different viscosity values. The ILs 1-ethyl-3-methylimidazolium acetate ([emim][Ac]), 1-butyl-3-methylimidazolium acetate ([bmim][Ac]), 1-butyl-3- methylimidazolium isobutyrate ([bmim][i-but]), 1-butyl-3-methylimidazolium glycinate ([bmim][GLY]) were selected. COSMO based/Aspen Plus methodology was effectively implemented to estimate the physical and chemical CO2 absorption parameters by kinetic and thermodynamic models fitted to experimental data to design the regeneration process in Aspen Plus software. The membrane contactor unit for solvent regeneration was custom-built and successfully imported into the simulation tool, as no model library for the MVR existed yet in the commercial package for the steady state process flowsheet simulation. The effect on CO2 desorbed flux and process performance was evaluated for the comparison purpose between ILs at different operational conditions. High temperature, vacuum level and module length are beneficial to the solvent regeneration process, while low liquid flow-rate increases the CO2 desorption flux but also decrease the process performance. The viscosity, CO2 solubility and reaction enthalpy were identified as key thermodynamic properties of IL selection. The IL ([emim][Ac]) presented the highest regeneration performance (around 92% at 313 K and vacuum pressure of 0.04 bar) with a total energy consumption of 0.62 MJ·kgCO2-1, which is lower than conventional amino-based high temperature regeneration process (1.55 MJ·kgCO2-1). These results pointed out the interest of the membrane vacuum regeneration technology based on ILs compared to the conventional solvent-based thermal regeneration, but further techno-economic evaluation is further needed to ensure the competitiveness of this novel CO2 desorption approach to the large-scale application.