Numerical Simulation of Uranium Extraction from Nitric Acid Medium Using Hollow-Fiber Contactor

ABSTRACT

A two-dimensional axisymmetric computational fluid dynamics (CFD) model is presented to simulate uranium extraction from nitric acid medium using tri-n-butyl phosphate in n-dodecane in a hollow-fiber membrane contactor operated in non-dispersive solvent extraction mode. CFD model solves continuity and momentum-transport equations for the feed and shell sides and species transport equations for the feed side, shell side, as well as the membrane. Complex boundary conditions of flux continuity and concentration jump are implemented in the CFD model. The estimates of percentage of uranium extraction obtained from CFD simulations for different parametric conditions are compared with the experimental results, and a good agreement is observed. The validated CFD model is used to gain detailed insights into the hydrodynamics and mass transfer.

Abbreviations CFD: Computational fluid dynamics; NDSX: Non-dispersive solvent extraction; TBP: Tri n-butyl phosphate

KEYWORDS:

• Computational fluid dynamics (CFD)
• hollow-fiber contactor
• mass-transfer modeling
• numerical simulation
• uranium extraction

Acknowledgments

Authors would like thank to Shri K. V. Ravi, Chief Executive, NRB, BARC, Mumbai, Shri S. Pradhan, Dy. Chief Executive, NRB, BARC, Tarapur, Shri K. K. Singh, Project Director, INRPC, NRB, BARC, Tarapur and Shri K. T. Shenoy, Head, Chemical Engineering Division, BARC, Mumbai for their support and encouragement.

Nomenclature

C	=	Concentration of solute [mol/m3]
D	=	Diffusion coefficient [m2/s]
%E	=	Percentage extraction
[H+]	=	Acidity, [M]
J	=	Diffusive flux [mol/m2.s]
Kd	=	Distribution ratio
Kex	=	Equilibrium constant
L	=	Length of module [m]
ΔP	=	Pressure drop [Pa]
Q	=	Flow rate [Lph]
r	=	Radial direction of module
r1	=	Inner radius of lumen [m]
r2	=	Outer radius of lumen [m]
r3	=	Shell radius [m]
z	=	Axial direction of module
v	=	Velocity vector [m/s]
Greek Letters	=
$\mathrm{\Phi }$	=	Molar flux [mol/m2.s]
ρ	=	Density [kg/m3]
ε	=	Porosity [%]
η	=	Viscosity [Pa.s]
τ	=	Tortuosity
Subscripts	=
0	=	Initial/Inlet
f	=	Feed
m	=	Membrane
m-f	=	Membrane–feed interface
m-org	=	Membrane–organic interface
org	=	Organic