Stripping Columns to Regenerate Ionic Liquids and Selectively Recover Hydrocarbons Avoiding Vacuum Conditions

Abstract

There is a large number of liquid-liquid extraction processes where ionic liquids (ILs) are proposed as solvents. However, the development of the purification and IL regeneration units still represents a challenge. Several effective separation trains were proposed to regenerate ILs, but extreme vacuum is needed to achieve commercial standards, which demands extra energy and extra solvent consumptions due to recycling streams. In this proposal, the use of stripping columns stands as a promising IL regeneration technology to avoid vacuum conditions and to enhance the separation of the compounds that form the extract stream, explored in the aromatic-aliphatic separation. COSMO-based/Aspen Plus methodology is applied to extensively evaluate the role of the IL nature and easily evaluate the influence of the main operating variables, namely temperature feed, column pressure, reboiler heat, number of stages on the separation efficiency. A critical comparison between current proposal and the benchmark IL regeneration process is reported, analyzing the aromatic recovery, energy duty and operating cost. The use of two stripping columns for the IL regeneration stage evidences the potential of this new configuration, drawing a new paradigm in which mild conditions are enough to conceptual design new separation processes involving ILs.

Technoeconomic Assessment of a Biomass Pretreatment + Ionic Liquid Recovery Process with Aprotic and Choline Derived Ionic Liquids

“…In addition, the electricity cost is estimated to be 1.58 × 10 –5 $/kJ. These prices have been previously used in the literature . The software calculates the operating costs associated with each utility by considering the energy requirements of each process unit.…”

“…These prices have been previously used in the literature. 27 The software calculates the operating costs associated with each utility by considering the energy requirements of each process unit. Figure 5 represents the recovery operating costs, divided into electricity costs and heating utility requirements, at the most favorable conditions for both ILs and with the 4 feed streams composition, those resulting from washing the pretreated wood with different volumes of water.…”

“…Moreover, the operating costs needed for each simulation were determined with Aspen Plus Economics Analyzer. The vacuum costs have been estimated by a COMPRESSOR block carrying out the opposed pressure drop taking place in the process, as can be found in the literature. ,, Among all of the operating conditions that ensure that the simulation objectives are accomplished, those that minimized operating costs in each case have been selected.…”

“…Washing with different volumes of water affects the enzymatic digestibility and the IL recovery step. The IL regeneration represents a limiting role regarding the ionic liquid-based processes proposed in the literature . Although several solute recovery and IL regeneration approaches have been evaluated through simulation with Aspen Plus, e.g., stripping with hot gas, distillation columns, re-extraction with supercritical fluids, among others, , a series of flash distillation drums at vacuum conditions has been the most used technique to regenerate the ionic liquid for different processes involving ILs .…”

“…The IL regeneration represents a limiting role regarding the ionic liquid-based processes proposed in the literature. 27 Although several solute recovery and IL regeneration approaches have been evaluated through simulation with Aspen Plus, e.g., stripping with hot gas, distillation columns, re-extraction with supercritical fluids, among others, 28,29 a series of flash distillation drums at vacuum conditions has been the most used technique to regenerate the ionic liquid for different processes involving ILs. 30 Nevertheless, this work is the first time that an IL recovery simulation is performed in biorefinery streams, using the recovered IL from the pretreatment step to study the system and model it, allowing the analysis of the variables that affect the most to the process economy.…”