1. M1 Master Nuclear Energy 29th June 2015
Modelling and simulation of a microfluidic solvent extraction process using a CFD software
M1 Master Nuclear Energy
29th June 2015
Student: Vera De la Cruz Gerardo
Supervisors: Siméon Cavadias, Clarisse Mariet and Gérard Cote
Referee: Eric Royer

2. Presentation display Global Objective Procedure
Extraction Process and Microfluidics
Difficulties and constraints
CFD Software
Flow Patterns tried
Previous works
Results
Assumptions-Modelling
Conclusions

3. General Objective
Simulation of a solvent extraction process in a Y-Y shaped microfluidic device, using the COMSOL Multiphysics software.

4. Industry Laboratories Extraction Process
Figure 1: Solvent extraction procedure with an additional Stripping step in the end.
Source: Solvent Extraction Cours notes, Pr. D. Pareau, Ecole Centrale Paris fall 2014.

5. Why a microchip? Microfluidics
 Small amounts of fluids ( 10 −18 − 10 −09 litres)
 Dimensions of tens to hundreds of micrometers.
Work with small volume
Better performance with lower power
Precise mixing/dosage
Ease of disposing of device and fluids
Can be integrated with other devices – lab on a chip
Minimize dead space, void volume and sample carryover
Reduce cost of reagents and power consumption
High surface to volume ratio / Low Reynolds number

6. Features CFD software Dynamic interface
Worldwide well-known software in the science field
Constant improvement
Specific websites and blogs
Dynamic interface

7. Previous Research Works
Research Cooperation Project
HDR
Clarisse Mariet
M1 Student
Sean Robertson

8. Geometry and assumptions used
Constant all along the microchannel
𝜌 𝑎,𝑜 → 𝐷𝑒𝑛𝑠𝑖𝑡𝑦 𝜇 𝑎,𝑜 →𝐷𝑦𝑛𝑎𝑚𝑖𝑐 𝑣𝑖𝑠𝑐𝑜𝑠𝑖𝑡𝑦 𝜎→ 𝑆𝑢𝑟𝑓𝑎𝑐𝑒 𝑡𝑒𝑛𝑠𝑖𝑜𝑛
Defined for each one of the phases
𝐷 𝑈𝑟𝑎𝑛𝑖𝑢𝑚 → 𝐷 𝐶𝑜𝑚𝑝𝑙𝑒𝑥 →
Uranium diffusion
coefficient
Complex diffusion
coefficient

9. Complex Formation Reaction
𝑈 𝑂 2 𝐶𝑙 𝑛 2−𝑛 + 𝑛−2 𝑅 4 𝑁 + , 𝐶𝑙 − → 𝑅 4 𝑁 + 𝑛−2 𝑈 𝑂 2 𝐶𝑙 𝑛 2−𝑛 + 𝑛−2 𝐶𝑙 −
for 𝑛≥3
Simplification
𝜕𝐶 𝜕𝑡 = 𝑘 1 𝐴−0.1709𝐶
A  Uranium concentration
C  Complex concentration
𝑘 1  Mass transfer global
coefficient
Relation
𝑹 𝑼𝒓𝒂𝒏𝒊𝒖𝒎 =− 𝒌 𝟏 𝑨−𝟎.𝟏𝟕𝟎𝟗𝑪
𝑹 𝑪𝒐𝒎𝒑𝒍𝒆𝒙 = 𝒌 𝟏 𝑨−𝟎.𝟏𝟕𝟎𝟗𝑪
Uranium reaction rate
Complex reaction rate

10. Physics Application modes
Fluid Flow
Laminar Two-Phase Flow Level Set
Chemical Species Transport
Transport of Diluted Species
Laminar Two-Phase Flow Level Set  Laminar flow
Moving interface
Immiscibility.
Transport of diluted Species  Diluted species diffusion phenomena
Complexation reaction

11. Study steps
Steady state

12. The solutions obtained from the software are based on three pillars
HOW THE SOFTWARE WORKS?
1° Model Equations
2° Treatment of the Interface
3° Boundary conditions setting
The solutions obtained from the software are based on three pillars

13. Table 1. Numerical stabilization parameters to be considered
First difficulties
No convergence
Physical settings
Numerical stabilization parameters
Table 1. Numerical stabilization parameters to be considered
Symbol
Definition
Parameter 𝛾
Reinitialization parameter
𝜖 𝑙𝑠
Parameter controlling interface thickness
Memory and time
Mesh optimization

14. Mesh Optimization Conditions to take into account
Immiscibility between the organic and the aqueous phases
Strong kinetics present in the interface region
Conditions to take into account
Sequence type: Physics-controlled mesh
Element size: Extremely coarse
Sequence type: Physics-controlled mesh
Element size: Fine
User-controlled mesh

15. Simulation models – flow patterns
Two basic flow patterns can be defined for all fluid systems
COUNTER CURRENT FLOW
CO-CURRENT FLOW
Internal Surface and Fluids properties
Initial fluid
Flow rates
Dispersed Flow
Continuous Co-current
Flow
Continuous
Counter-current Flow

16. 1) Co-current flow with moving interface, Laminar flow
In a first trial the objective was to observe how the interface changed its appearance and to obtain the required time for its stabilization.

17. 1) Co-current flow with moving interface, Laminar flow + chemical species transport
Stationary study after the flow stabilization and a time dependent study in parallel with the laminar flow study.

18. Interface instability
2) Counter current flow
Interface instability

19. 2) Wettability and contact-angle
This surface characteristic is defined by the surface wettability, characterized by the contact angle.
Figure 2: Contact angle, graphic definition.

20. 3) Co-current droplet formation
Phase initialization  Droplet Formation  Kinetics reaction in the interface

21. 3) Co-current droplet formation
The variations of the Uranium and the Complex concentrations can be observed in next figures.

22. Conclusions
The software utilized in the simulations executed in this report is a very useful tool that allows the users and researchers to obtain faster and cheaper results as compared to traditional experiments.
The several scientific fields in which microfluidics are used allow the radiochemists to take advantage of the innovations and the constant research carried out with regards to this kind of technology.
In previous works the phases interface had been considered fixed and the formation of droplets had not been studied. The results obtained for this last case in this report permit analyzing the essential characteristics of the extraction process in a microdevice for this flow pattern and are suitable to be modified for different parameters values.
One of the next objectives in order to improve the yields of the microdevices is to calculate and verify the relation between the inlet uranium concentration and the length necessary to extract it.
Although the surface hydrophobicity has been one of the topics more studied during the last years because of its relevance concerning the microfluidics the software available to date is not able to consider this aspect.

23. Thank you for your attention!