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12. Modelling of precipitation process by hybrid large eddy simulation - multizonal approach Application to uranium oxalate

Author

Bertrand, M., Plasari, E., Lebaigue, O., Lamarque N, ., Ducros, F., Muhr, H., CEA-Direction des Energies (ex-Direction de l'Energie Nucléaire) (CEA-DES (ex-DEN)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Ecole Nationale Supérieure des Industries Chimiques (ENSIC), Université de Lorraine (UL), China Earthquake Administration (CEA), CERFACS [Toulouse], Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Réactions et Génie des Procédés (LRGP), Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), and Centre Européen de Recherche et de Formation Avancée en Calcul Scientifique (CERFACS)

Subjects
[PHYS.NUCL]Physics [physics]/Nuclear Theory [nucl-th], Hydrometallurgy, Uranium oxalate CFD Micromixing, [PHYS.NEXP]Physics [physics]/Nuclear Experiment [nucl-ex], Modelling
Abstract

International audience; A modelling approach dedicated to precipitation processes has been developed to control the quality of the solid particles formed and to support design of industrial reactors. Precipitation reactions are well known to be very fast and highly sensitive to mixing effects. That is why modelling relies on the coupling of chemistry and hydrodynamics. The precipitation chemistry involves thermodynamic data and kinetic laws while the hydrodynamics inside the precipitator is described using a Computational Fluid Dynamics (CFD) approach. Currently a key issue for modelling a precipitation process arises from turbulence and chemistry coupling. Different methodologies are proposed in the literature ranging from hybrid methods based on multizonal models to a fully coupling, in which the population balance equations are directly implemented into a CFD code. In the hybrid modelling, the multizonal model that comprises several perfectly mixed compartments can be parameterised using CFD. Under these conditions, this multiscale method offers a practical compromise between simplified models based on idealised mixing description and the computationally expensive CFD solution. Consequently we have developed a multizonal approach in which hydrodynamic information is entirely extracted from Large Eddy Simulations. This modelling is applied to simulate the precipitation of actinide oxalates.

Published
2017

15. Modelling approach for a precipitation process: application to the tetravalent uranium oxalate precipitation.

Author

Bertrand M., Proceedings of Uranium sessions at Alta 2011 Perth, Australia 26-May-1127-May-11, Ducros F., Lamarque N., Lebaigue O., Plasari E., Bertrand M., Proceedings of Uranium sessions at Alta 2011 Perth, Australia 26-May-1127-May-11, Ducros F., Lamarque N., Lebaigue O., and Plasari E.

Abstract

Oxalic precipitation is used to process radioactive wastes or to recover actinides from a multicomponent solution. Uranium oxalate can be precipitated by mixing a uranium(IV) solution in nitric acid with oxalic acid solution. A computer simulation method was used to investigate the effect of various parameters on the precipitation process using kinetic laws and a hydrodynamic model based on the large eddy simulation approach. Experiment kinetic and nucleation studies were also carried out. A population balance approach was used to describe the dynamics of the precipitation process. A vortex reactor was used for the hydrodynamic modelling and the population balance inside the precipitator was solved based on hydrodynamic parameters computed using computational fluid dynamics. Two reagent feeding point locations were investigated, in the free and forced vortex zones. The computational conditions were a residence time of 10 minutes, temperature of 25 degrees C, tetravalent uranium oxide properties of molar crystal mass of 0.522, volume shape factor of 0.1 and density of 2 600 kg/m3 and injection of reagents under stoichiometric conditions. The feeding location had a strong effect on particle diameter, with uranium(IV) oxalate exhibiting a lengthened platelet shape with sizes of about 10 micrometers in the free vortex zone and about 1 micrometre in the forced vortex zone. The free vortex enhances the growth process while the forced vortex is characterised by high supersaturation and enhances nucleation phenomena resulting in small crystals., Oxalic precipitation is used to process radioactive wastes or to recover actinides from a multicomponent solution. Uranium oxalate can be precipitated by mixing a uranium(IV) solution in nitric acid with oxalic acid solution. A computer simulation method was used to investigate the effect of various parameters on the precipitation process using kinetic laws and a hydrodynamic model based on the large eddy simulation approach. Experiment kinetic and nucleation studies were also carried out. A population balance approach was used to describe the dynamics of the precipitation process. A vortex reactor was used for the hydrodynamic modelling and the population balance inside the precipitator was solved based on hydrodynamic parameters computed using computational fluid dynamics. Two reagent feeding point locations were investigated, in the free and forced vortex zones. The computational conditions were a residence time of 10 minutes, temperature of 25 degrees C, tetravalent uranium oxide properties of molar crystal mass of 0.522, volume shape factor of 0.1 and density of 2 600 kg/m3 and injection of reagents under stoichiometric conditions. The feeding location had a strong effect on particle diameter, with uranium(IV) oxalate exhibiting a lengthened platelet shape with sizes of about 10 micrometers in the free vortex zone and about 1 micrometre in the forced vortex zone. The free vortex enhances the growth process while the forced vortex is characterised by high supersaturation and enhances nucleation phenomena resulting in small crystals.

Published
2011

25. Towards new studies in two-phase thermal-hydraulics for industrial applications

Author

Lebaigue, O. and Hervieu, E.

Abstract

This paper gives a short presentation of the FASTNET team preliminary conclusions. This team tried to define a scientific strategy aimed at developing thermal-hydraulics in the nuclear and on-nuclear industry fields. The reflections were mainly conducted as a three stage process: - the identification of industrial problems, whose better resolution rely on a knowledge improvement in thermalhydraulics, - a state-of the-art analysis, which led to identify the actual limitations (and their origin) for the different components of the thermal-hydraulics expertise (physical rnodeling, numerical simulation, instrumentation, analytical and validation experiments), - the proposition of a coherent strategy to develop expertise in all these fields of thermal-hydraulics. This paper is a summarized version of a more detailed progress report. The work is still in progress...

Published
1998

27. A versatile technology for colloidal crystal transfer using parylene coatings and hydrosoluble polymers.

Author

Ushkov AA, Dellea O, Lebaigue O, Poncelet O, Verrier I, Lefkir Y, and Jourlin Y

Abstract

We propose a novel versatile colloidal crystal transfer technique compatible with a wide range of water-insoluble substrates regardless of their size, material, and wettability. There are no inherent limitations on colloidal particles material and size. The method possibilities are demonstrated via the colloidal transfer on quartz, glass substrates with a flat and curved surface, and via the fabrication of 3D colloidal structure with 5 overlaid colloidal monolayers. The process occurs at a room temperature in water and is independent from the illumination conditions, which makes it ideal for experimental manipulations with sensitive functional substrates. We performed the nanosphere photolithography process on a photosensitive substrate with a transferred colloidal monolayer. The metallized hexagonal arrays of nanopores demonstrated a clear resonant plasmonic behavior. We believe that due to its high integration possibilities the proposed transfer technique will find applications in a large-area surface nanotexturing, plasmonics, and will speed up a device fabrication process., (© 2022 IOP Publishing Ltd.)

Published
2022
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