(27f) Modeling Transport and Extraction Kinetics in Membrane Solvent Extraction of Biofuels for Sustainable Biorefineries

Sustainable manufacturing of biofuels and biochemicals are increasingly becoming important for transportation fuels including aviation fuels. Today’s biofuels manufacturing, including ethanol are highly energy, water and carbon intensive processes. Sustainable biorefineries of the future need to include strategies of advanced, process intensification approaches integrating one or more unit operations with conventional processes. Membrane Solvent Extraction (MSE) offers one such process intensification approach especially suitable for extracting biofuels and biochemicals from low concentration aqueous broths from bioprocessing. The advantages of MSE include the prevention of emulsion formation, the ability to use solvents potentially harmful to microorganisms at higher concentrations, and easy separation facilitated by high-boiling solvents. It also offers an advantage to be integrated with bioprocessing recirculating the extracted broth gaining additional advantages.

Here we present a transport and extraction model for the membrane solvent extraction process that is used to extract biofuels and biochemicals from dilute broth into organic solvents. The mathematical model considers convective transport in the aqueous and organic streams, liquid – liquid extraction or partitioning of the solutes of interest into the organic solvent and diffusion of the solute and solvent through the porous hollow fiber membrane layer. The instantaneous mass transfer and extraction kinetics are considered in the modeling. The MSE system can be run as a co-current or counter current system with the two phases on either side of the membrane walls.

The model equations are solved with appropriate initial and boundary conditions to obtain the extraction kinetics profile with solute concentrations with time as well as the membrane transfer flux vs time. The model predictions are compared with experimental results using biofuels containing broth solutions and selected organic solvent. The model can also predict the equilibrium concentrations and the corresponding partition coefficients and overall mass transfer coefficients for the system. This information can be used in the design and development of process intensification approaches using MSE for sustainable biorefineries.