1. Prado, O.A; Jørgensen, S.B. and Jonsson, G. 1 /17 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. Prado, O.A; Jørgensen, S.B. and Jonsson, G. 2 /17 Introduction and motivation REED process REED module modelling Simulation results - static analysis - dynamic analysis Conclusions Outline Introduction and motivation REED process REED module modelling Simulation Results Conclusions

3. Prado, O.A; Jørgensen, S.B. and Jonsson, G. 3 /17 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) Introduction and motivation REED process REED module modelling Simulation Results Conclusions Applications Demand Design Operation

4. Prado, O.A; Jørgensen, S.B. and Jonsson, G. 4 /17 How can it be done? Due to LAB are impaired by lactates, continuous removal of biotoxic lactate will intensify the process Starting point: Precipitation Solvent extraction Adsorption Direct distillation Membrane separation processes Studied alternative: Integrated bioreactor with electrically driven membrane separation processes Substrate Bioreactor Membrane separation processes Broth + Lactate Broth Lactic acid 80% costs downstream - Very selective - Aseptic - No by-products Introduction and motivation REED process REED module modelling Simulation Results Conclusions Lactic acid production Alternatives Process description

5. Prado, O.A; Jørgensen, S.B. and Jonsson, G. 5 /17 Continuous Reverse Electro-Enhanced Dialysis (REED) process In situ lactate removal Introduction and motivation REED process REED module modelling Simulation Results Conclusions Lactic acid production Alternatives Process description Model based study for optimization of the design and operation Operation at higher cell densities Facilitates the pH control

6. Prado, O.A; Jørgensen, S.B. and Jonsson, G. 6 /17 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 Definition: Module with AEM where the current is periodically reversed Only AEM Imposing electrical field Current reversal – Destabilization of fouling What is REED? Introduction and motivation REED process REED module modelling Simulation Results Conclusions REED description How REED works

7. Prado, O.A; Jørgensen, S.B. and Jonsson, G. 7 /17 Introduction and motivation REED process REED module modelling Simulation Results Conclusions REED description How REED works

8. Prado, O.A; Jørgensen, S.B. and Jonsson, G. 8 /17 REED cell description Modelling Model tuning Cell in the REED stack Convective transport in y-direction Diffusion and migration in x-direction CSTR in series model Irreversible thermodynamics approach Introduction and motivation REED process REED module modelling Simulation Results Conclusions Phenomena involved: simultaneous diffusion, convection, electrophoretic transport of ions, plus ion dissociation and equilibrium at the membrane surface

9. Prado, O.A; Jørgensen, S.B. and Jonsson, G. 9 /17 Mass balances: Flux: Nernst-Planck Equilibrium at the interface: Model: Solution: Asymmetric 7-point difference equations System of DAE’s Conditions: Electroneutrality Current carried by ions No accumulation at the interfaces System of multiregion PDAE Introduction and motivation REED process REED module modelling Simulation Results Conclusions REED cell description Modelling Model tuning

10. Prado, O.A; Jørgensen, S.B. and Jonsson, G. 10 /17 Introduction and motivation REED process REED module modelling Simulation Results Conclusions REED cell description Modelling Model tuning Prado Rubio, O.A. et al. Lactic Acid Recovery in Electro-Enhanced Dialysis: Modelling and Validation. Accepted to ESCAPE-19. Estimated parameters:

11. Prado, O.A; Jørgensen, S.B. and Jonsson, G. 11 /17 AEM1 AEM2 Dialysate Feed Anode (+) Cathode (-) OH - L - L - - - L - Na + + + Introduction and motivation REED process REED module modelling Simulation Results Conclusions Competitive ion transport Fluxes enhancement Operation under current reversal

12. Prado, O.A; Jørgensen, S.B. and Jonsson, G. 12 /17 Max Donnan Dialysis flux Saturation of the current Introduction and motivation REED process REED module modelling Simulation Results Conclusions Total lactate fluxes imposing an external potential gradient Sonin, A. and Grossman, G. (1972). Ion Transport through Layered Ion Exchange Membranes. Journal of Physical Chemistry, 76(26), 3996-4006. Prado Rubio, O.A. et al. Lactic Acid Recovery in Electro-Enhanced Dialysis: Modelling and Validation. Accepted to ESCAPE-19. Competitive ion transport Fluxes enhancement Operation under current reversal

13. Prado, O.A; Jørgensen, S.B. and Jonsson, G. 13 /17 Pseudo-steady state Maximum separation Donnan dialysis Introduction and motivation REED process REED module modelling Simulation Results Conclusions Competitive ion transport Fluxes enhancement Operation under current reversal

14. Prado, O.A; Jørgensen, S.B. and Jonsson, G. 14 /17 Max recovery Concentration profiles are almost developed Price of long time operation ? Introduction and motivation REED process REED module modelling Simulation Results Conclusions Competitive ion transport Fluxes enhancement Operation under current reversal DD max recovery

15. Prado, O.A; Jørgensen, S.B. and Jonsson, G. 15 /17 Zone where it will be unfeasible to operate at constant current density Maximum potential gradient Operation: constant ΔV → J↓ Introduction and motivation REED process REED module modelling Simulation Results Conclusions Competitive ion transport Fluxes enhancement Operation under current reversal From experimental data

16. Prado, O.A; Jørgensen, S.B. and Jonsson, G. 16 /17 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. Introduction and motivation REED process REED module modelling Simulation Results Conclusions

17. Prado, O.A; Jørgensen, S.B. and Jonsson, G. 17 /17 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. Acknowledgments: This project is carried out within the Bioproduction project which is financed by the 6th Framework Programme, EU.