Modelling and simulation of a microfluidic solvent

extraction process using a CFD softwareM1 MASTER NUCLEAR ENERGY

29TH JUNE 2015

Student: Vera De la Cruz GerardoSupervisors: Siméon Cavadias, Clarisse Mariet and Gérard CoteReferee: Eric Royer

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PRESENTATION DISPLAY

I. Global Objective

II. Extraction Process and Microfluidics

III. CFD Software

IV. Previous works

V. Assumptions-Modelling

VI. Procedure

VII. Difficulties and constraints

VIII.Flow Patterns tried

IX. Results

X. Conclusions

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GENERAL OBJECTIVE

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

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EXTRACTION PROCESS

• Industry

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.

• Laboratories

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WHY A MICROCHIP?

Microfluidics Small amounts of fluids ( litres)

Dimensions of tens to hundreds of micrometers.

High surface to volume ratio / Low Reynolds number

Minimize dead space, void volume and sample carryover

Work with small volume

Ease of disposing of device and fluids

Precise mixing/dosage

Better performance with lower power

Reduce cost of reagents and power consumption

Can be integrated with other devices – lab on a chip

Features

Worldwide well-known software in the science

field

Constant improvement

Specific websites and blogs

Dynamic interface

CFD SOFTWARE

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PREVIOUS RESEARCH WORKS

Research Cooperation Project

HDR Clarisse Mariet

M1 Student Sean Robertson

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GEOMETRY AND ASSUMPTIONS USED

Defined for each one of the phases

Uranium diffusioncoefficient

Complex diffusioncoefficient

Constant all along the microchannel

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COMPLEX FORMATION REACTION

𝜕𝐶𝜕𝑡 =𝑘1 ( 𝐴−0.1709𝐶 )

A Uranium concentrationC Complex concentration Mass transfer global coefficient

for

Simplification

Relation

𝑹𝑼𝒓𝒂𝒏𝒊𝒖𝒎=−𝒌𝟏 ( 𝑨−𝟎.𝟏𝟕𝟎𝟗𝑪 ) 𝑹𝑪𝒐𝒎𝒑𝒍𝒆𝒙=𝒌𝟏 ( 𝑨−𝟎 .𝟏𝟕𝟎𝟗𝑪 )

Uranium reaction rate Complex reaction rate| PAGE 9

APPLICATION MODES

Physics

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

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STUDY STEPS

Steady state| PAGE 11

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HOW THE SOFTWARE WORKS?

The solutions obtained from the software are based on three pillars

1° Model Equations

2° Treatment of the Interface

3° Boundary conditions setting

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FIRST DIFFICULTIES

Physical settings

Symbol Definition

Parameter Reinitialization parameter

Parameter controlling interface thickness

Table 1. Numerical stabilization parameters to be considered

No convergence

Numerical stabilization parameters

Memory and time

Mesh optimization

MESH OPTIMIZATION

• Immiscibility between the organic and the aqueous phases

• Strong kinetics present in the interface region

Sequence type: Physics-controlled meshElement size: Extremely coarse

Sequence type: Physics-controlled meshElement size: Fine

User-controlled mesh

Conditions to take into account

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SIMULATION MODELS – FLOW PATTERNS

Two basic flow patterns can be defined for all fluid systems CO-CURRENT FLOWCOUNTER CURRENT FLOW

Internal Surface

and Fluids properties

Initial fluid

Continuous Counter-current Flow

Dispersed FlowContinuous Co-

current Flow

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.

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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.

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2) COUNTER CURRENT FLOW

Interface instability

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2) WETTABILITY AND CONTACT-ANGLE

Figure 2: Contact angle, graphic definition.

This surface characteristic is defined by the surface wettability, characterized by the contact angle.

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3) CO-CURRENT DROPLET FORMATION

Phase initialization Droplet Formation Kinetics reaction in the interface

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3) CO-CURRENT DROPLET FORMATION

The variations of the Uranium and the Complex concentrations can be observed in next figures.

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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.

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Thank you for your attention!

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