Taylor-Couette contactor as miniaturized column for solvent extraction pilot tests

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Submitted on 17 Dec 2019

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Taylor-Couette contactor as miniaturized column for solvent extraction pilot tests

N. Verdin, S. Charton, H. Roussel, D. Maurel

To cite this version:

N. Verdin, S. Charton, H. Roussel, D. Maurel. Taylor-Couette contactor as miniaturized column for solvent extraction pilot tests. ATALANTE 2016 - Nuclear Chemistry for Sustainable Fuel Cycles, Jun 2016, Montpellier, France. ATALANTE 2016 - Nuclear Chemistry for Sustainable Fuel Cycles, 2016. �hal-02416311�

Introduction & motivation

[1] Lanoë, J.-Y., (2002), Lanoë, J. (2002). Proceedings ATALANTE 2012

[2] Nemri, M., Climent, E., Charton, S., Lanoë, J.-Y., Ode, D. (2012), Chem. Eng. Res. Des. 91, pp.2346-2354 [3] Nakase M., Takeshita K. (2012).. Procedia Chemistry 7, pp. 288-294

[4] Amokrane, A., Charton, S., Sheibat_Othman, N., Becker, J., Klein, J.-P., Puel, F., (2014) Can. Jal. Chem. Eng., 92(2), pp. 220-233

R ef er enc es

Scale-reduction is a strong issue for R&D studies, especially in the nuclear industry. In this aim, a miniaturized liquid-liquid extraction

column based on Taylor-Couette flow has been designed and tested [1]. The device consists in two concentric cylinders. The inner cylinder (OD 17 mm) is rotating while the outer one (ID 20 mm) is fixed. The column is operated at counter-current and the emulsion of the two immiscible liquid phases is provided by the shear-stress prevailing within the counter-rotating vortices. It is able to operate with the same

separation performances as a 10 times higher industrial pulsed column (operated at some m3/h) but with a flow-rate as low as some 100mL/h, thus involving minimal amounts of solvent and of radioactive materials.

The main objective of this study is to investigate the ability of numerical simulation to predict the wall effects on the emulsion achieved in Taylor-Couette flows. Many possible configurations in Liquid-Liquid Extraction R&D studies are tested: direct (O/W) or inverse (W/O) emulsion, high viscosity.

Hydrophilic extractor Hydrophobic extractor

Direct (O/W) Inverse (W/O) Direct (O/W) Inverse (W/O)

 Importance of the surface treatment !

Numerical simulation

• Boundary conditions Stator at rest

Rotating inner wall

Properties Aqueous phase (W) Low viscosity oil (O1) High viscosity oil (O2)

Kinematic viscosity ν (m2_.s-1_{) 9.52 10}-7 _{2.47 10}-6 _{1.44 10}-5

Surface tension with W, σ (N.m-1) / 10-2 2.2 10-2

Rotor rotation speed ω (rad.s-1_{) 85 (812rpm) 496 (4736 rpm)}

Reynolds (single-phase) 1137 (WVF) 438 (TVF Regime)

Conclusion & On-going work

Direct Emulsion (O/W) Regardless of the oil phase viscosity

 Droplets of non-wetting oil achieved (optimal)  Rings of wetting oil at the walls (unadapted) When wall properties are optimal

 Emulsification hindered by viscosity (larger droplets)

- Good agreement between numerical results and experimental observations: a wetting dispersed phase forms annular rings (local flooding) while a non wetting one allows efficient emulsification

- VOF simulations are time consuming (approx. 150h / case on 8 processors) and Drop Size Distribution (DSD) cannot be predicted

- Coupled CFD-PBE simulation (Euler-Euler + DQMOM), based on previous work on pulsed column [4] are currently implemented to predict the DSD

h = 3  

 Parametric Study

The study focuses on contact angle θ and the viscosity of the organic phase ν

Taylor-Couette contactor as miniaturized column for solvent

extraction: numerical study of liquid-liquid emulsions

Nicolas VERDIN, Sophie CHARTON, Hervé ROUSSEL, Didier MAUREL

However, in this small gap configuration, surface effects are

increased and might be detrimental for the process efficiency.

Preliminary tests, based on 2 columns with different wall properties (hydrophilic / hydrophobic) were made. Bad emulsification and local flooding were highlighted in some cases.

optimal unadapted optimal sub-optimal

• Dispersed phase initialisation

One-phase flow initialisation  convergence Then:



Aqueous phase Re 1137

Wavy Vortex Flow

 can turn to TVF

Organic phase Re 496

Taylor Vortex Flow

 can turn to high  TVF

Single-phase flow patterns _{Two-phase flow patterns}

Same rotation rate (812rpm)

Hydrophilic Hydrophobic Dir ect (O/W) In ver se (W/O) Hydrophilic Hydrophobic Low viscosity oil (O1) High viscosity oil (O2)

 

Inverse Emulsion (W/O) Effect of viscosity (continuous phase)

 Requires (very) high rotation speed (same Re)  Overcomes wall effect (no effect of the

contact angle)

When wall properties are optimal

 Emulsification more difficult with viscous oil

• Wall interactions

Wall Adhesion option

Contact angle of the dispersed phase θ = 20° (non wetting drop)

 = 110° (wetting drop)