Process evaluation of swing strategies to recover N-ethylbutylamine after wet lipid extraction from microalgae

Abstract

N-ethylbutyl amine (EBA) has been reported as switchable solvent for the extraction of lipids from microalgae. To properly assess the technical feasibility as well as the sustainability of the lipid extraction process with EBA, solvent recovery is an essential process consideration. In this paper, opportunities for solvent recovery from both the aqueous raffinate stream and the solid algal residue were investigated, and two approaches for solvent recovery from the extracted lipids were investigated. In the first approach, CO2 switching is applied, which switches EBA from a neutral molecule into an ionic liquid that phase splits from the lipids. In the second approach, the strong effect on water solubility of EBA due to its lower critical solution temperature (LCST) behavior is used in a temperature swing back-extraction. For both approaches, a conceptual process was designed, and for all unit operations where important information was missing, the missing information was obtained by experiment and/or using process simulation software (Aspen Plus V8.8). From the conceptual process evaluation, it was concluded that the process making use of CO2 switching suffers from large solvent losses due to the switching mechanism. With the temperature swing back-extraction, it was much better possible to recover the EBA, and design a feasible process that costs 12.4 MJ/kg lipids, which considering the energy content of 1 kg lipids, is net energy gain of 22.4 MJ/kg lipids.