MODELING REVERSE ELECTRO-ENHANCED DIALYSIS FOR INTEGRATION WITH LACTIC ACID FERMENTATION

1. MODELING REVERSE ELECTRO-ENHANCED DIALYSIS FOR INTEGRATION WITH LACTIC ACID FERMENTATION Oscar Andrés Prado Rubio, Sten Bay Jørgensen and Gunnar Jonsson Department of Chemical and Biochemical Engineering Technical University of Denmark NPCW09, Jan 29-30, 2009

2. Introduction and motivation REED process REED module modelling Simulation Results Conclusions Outline • Introduction and motivation • REED process • REED module modelling • Simulation results - static analysis - dynamic analysis • Conclusions

3. Introduction and motivation REED process REED module modelling Simulation Results Conclusions Lactic acid production Alternatives Process description Why Lactic acid production? pH regulator, emulsifying agent, animal feed supplement, solvent, electrolyte and Polylactic acid Synthetically by hydrolysis of lactonitrile ? Fermentation of carbohydrates by Lactic Acid Bacteria (LAB) Applications Demand Design Operation

4. Broth Substrate Lactic acid Broth + Lactate Membrane separation processes Bioreactor Introduction and motivation REED process REED module modelling Simulation Results Conclusions Lactic acid production Alternatives Process description Starting point: Due to LAB are impaired by lactates, continuous removal of biotoxic lactate will intensify the process How can it be done? Precipitation Solvent extraction Adsorption Direct distillation Membrane separation processes 80% costs downstream - Very selective - Aseptic - No by-products Studied alternative: Integrated bioreactor with electrically driven membrane separation processes

5. Introduction and motivation REED process REED module modelling Simulation Results Conclusions Lactic acid production Alternatives Process description Continuous Reverse Electro-Enhanced Dialysis (REED) process • In situ lactate removal Model based study for optimization of the design and operation • Operation at higher cell densities • Facilitates the pH control

6. Introduction and motivation REED process REED module modelling Simulation Results Conclusions REED description How REED works What is REED? Definition: Module with AEM where the current is periodically reversed Driving forces: Concentration and potential gradients across the membranes • Potential problems of electrically driven MSP • Divalent cations • Low fluxes in DD • Fouling in ED and DD Only AEM Imposing electrical field Current reversal – Destabilization of fouling

7. Introduction and motivation REED process REED module modelling Simulation Results Conclusions REED description How REED works

8. Introduction and motivation REED process REED module modelling Simulation Results Conclusions REED cell description Modelling Model tuning Cell in the REED stack Convective transport in y-direction CSTR in series model Diffusion and migration in x-direction Irreversible thermodynamics approach Phenomena involved: simultaneous diffusion, convection, electrophoretic transport of ions, plus ion dissociation and equilibrium at the membrane surface

9. Introduction and motivation REED process REED module modelling Simulation Results Conclusions REED cell description Modelling Model tuning Mass balances: • Conditions: • Electroneutrality • Current carried by ions • No accumulation at the interfaces Flux: Nernst-Planck System of multiregion PDAE Model: Equilibrium at the interface: Solution: Asymmetric 7-point difference equations System of DAE’s

10. Introduction and motivation REED process REED module modelling Simulation Results Conclusions REED cell description Modelling Model tuning Estimated parameters: Prado Rubio, O.A. et al. Lactic Acid Recovery in Electro-Enhanced Dialysis: Modelling and Validation. Accepted to ESCAPE-19.

11. - - OH OH - OH - L - - L L + + Na Na + Na Introduction and motivation REED process REED module modelling Simulation Results Conclusions Competitive ion transport Fluxes enhancement Operation under current reversal Anode (+) Cathode (-) AEM1 AEM2 Dialysate Feed Feed

12. Introduction and motivation REED process REED module modelling Simulation Results Conclusions Competitive ion transport Fluxes enhancement Operation under current reversal Total lactate fluxes imposing an external potential gradient Saturation of the current Max Donnan Dialysis flux Prado Rubio, O.A. et al. Lactic Acid Recovery in Electro-Enhanced Dialysis: Modelling and Validation. Accepted to ESCAPE-19. Sonin, A. and Grossman, G. (1972). Ion Transport through Layered Ion Exchange Membranes. Journal of Physical Chemistry, 76(26), 3996-4006.

13. Introduction and motivation REED process REED module modelling Simulation Results Conclusions Competitive ion transport Fluxes enhancement Operation under current reversal Pseudo-steady state Maximum separation Donnan dialysis

14. Introduction and motivation REED process REED module modelling Simulation Results Conclusions Competitive ion transport Fluxes enhancement Operation under current reversal Max recovery DD max recovery Concentration profiles are almost developed Price of long time operation ?

15. Introduction and motivation REED process REED module modelling Simulation Results Conclusions Competitive ion transport Fluxes enhancement Operation under current reversal From experimental data Zone where it will be unfeasible to operate at constant current density Operation: constant ΔV → J↓ Maximum potential gradient

16. Introduction and motivation REED process REED module modelling Simulation Results Conclusions • A dynamic model was derived from first principles for simultaneous transport of multiple ions across ion exchange membranes under current load conditions (including current reversal conditions). • The model has been tuned based on experimental data for dialytic recovery of monoprotic carboxylic ions. • The model is used to understand the competitive ion transport across anions exchange membranes under current load conditions. • The potential flux enhancement by imposing an electrical field is calculated. Lactate fluxes are increased up to 230% compared to Donnan dialysis operation. • Investigations of REED show that an optimal operating point represents a trade off between lactate recovery and energy consumption, subject to constraints. • This model is derived as a tool to optimize the design and operation of the REED module when it becomes integrated with a bioreactor for lactic acid production.

17. Acknowledgments: This project is carried out within the Bioproduction project which is financed by the 6th Framework Programme, EU. Thanks for your attention.... Your questions are welcome! References Fila, V. and Bouzek, K. (2003). A Mathematical Model of Multiple Ion Transport Across an Ion-Selective Membrane under Current Load Conditions. Journal of Applied Electrochemistry, 33, 675-684. Hongo, M.; Nomura, Y. and Iwahara, M. (1986). Novel Method of Lactic Acid Production by Electrodialysis Fermentation. Applied and Environmental Microbiology, 52(2), 314-319. Møllerhøj, M. (2006). Modeling the REED Process. Master’s thesis, Technical University of Denmark. Prado Rubio, O.A.; Jørgensen, S.B. and Jonsson, G. Lactic Acid Recovery in Electro-Enhanced Dialysis: Modelling and Validation. Accepted to ESCAPE-19. Rype, J. (2003). Modelling of Electrically Driven Processes. Ph.D. thesis, Technical University of Denmark. Sonin, A. and Grossman, G. (1972). Ion Transport through Layered Ion Exchange Membranes. Journal of Physical Chemistry, 76(26), 3996-4006. Zheleznov, A. (1998). Dialytic Transport of Carboxylic Acids through an Anion Exchange Membrane. Journal of Membrane Science, 139, 137-143.