Model-based evaluation of a membrane-assisted hybrid extraction-distillation process for energy and cost-efficient purification of diluted aqueous streams
The concentration of diluted aqueous streams is an important task in bio-based production processes, as well as the recovery of valuable impurities prior to wastewater purification. Affinity-based separation processes, such as liquid-liquid extraction, are generally considered favorable to distillation, which however is regularly used for solvent recovery. To reduce the effort for a solvent-based extraction and improve the economic performance, an extended hybrid process concept is considered, which exploits energy-efficient pressure-driven membrane separations, i.e. reverse osmosis or nanofiltration, for preconcentration. The current work presents a systematic evaluation of this process for purification of a diluted aqueous γ-valerolactone stream, considering two solvents. The potential economic savings are first evaluated in a model-based assessment prior to an experimental screening of suitable membranes. Finally, a detailed economic evaluation of the processes is conducted by an optimization-based process design. The proposed approach allows to quickly identify a considerable saving potential for the membrane-assisted hybrid process.
