Physical simulation of precipitation of radioactive element oxalates by using the harmless neodymium oxalate for studying the agglomeration phenomena

Lalleman, Sophie; Bertrand, Murielle; Plasari, Edouard

doi:10.1016/j.jcrysgro.2011.01.079

Cited by 14 publications

(22 citation statements)

References 19 publications

(34 reference statements)

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“…We can observe that the agglomeration constant increases with the temperature. This phenomenon has already been observed in other works, for example with neodymium oxalate [11] or silica [25].…”

Section: Influence Of the Temperaturesupporting

confidence: 80%

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Agglomeration Mechanisms and Kinetics during the Carbonation of a Suspension of Lime in a Pilot Batch Reactor

Schnebelen¹,

Mozet²,

Jakob³

et al. 2015

CSTA

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The reaction studied in this work is the synthesis of nanometric size calcium carbonate particles by carbonation of a suspension of lime, which represents the most common industrial route. It consists in bubbling carbon dioxide in a suspension of lime to obtain precipitated calcium carbonate (PCC). PCC is a mineral filler with various applications: sealants, paints, paper, ink, pharmacy, cosmetics, food etc. However, there is a challenge related to the synthesis and the use of this precipitate: the agglomeration of the monoparticles. The aim of this work is then to understand the mechanisms of this phenomenon and to study its kinetics to improve the run of the process and the control of its impact on the final product. Experiments realized with a high concentration in sodium chloride (2 M) showed that the modification of the electrostatic environment did not change the particle size distribution and the morphology of the agglomerates. This indicates that the electrostatic interactions are not responsible for the agglomeration but the formation of crystalline bridges induced by the crystal growth. Thus, thanks to an agglomeration model including the crystal growth rate, the agglomeration kernel β and the agglomeration constant β0 can be determined using a mathematical treatment of the experimental particle size distributions. Finally, by varying the experimental conditions, it appears that the agglomeration constant increases with the temperature whereas there is an optimal value regarding the shear rate.

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Section: Influence Of the Temperaturesupporting

confidence: 80%

“…Regarding the temperature, we could cite [25] or [11] that worked on silica and neodymium oxalate respectively and observed an increase of the agglomeration kernel with temperature.…”

Section: Introductionmentioning

confidence: 99%

Agglomeration Mechanisms and Kinetics during the Carbonation of a Suspension of Lime in a Pilot Batch Reactor

Schnebelen¹,

Mozet²,

Jakob³

et al. 2015

CSTA

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“…Nucleation, crystal growth, and agglomeration kinetics are taken into account [30,31]. The computer simulation is an important tool for the design, the optimisation, and scale-up of new geometries, especially in nuclear environment where experiments are limited.…”

Section: Discussionmentioning

confidence: 99%

Mixing Study in an Unbaffled Stirred Precipitator Using LES Modelling

Bertrand

Parmentier

Lebaigue

et al. 2012

International Journal of Chemical Engineering

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This paper describes the CFD modelling of a reactor operating in the nuclear industry using LES approach. The reactor consists of an unbaffled stirred tank reactor in which plutonium precipitation reactions are carried out. The flow generated in such a precipitator is complex and there is very little information available in the literature about unbaffled reactors stirred with magnetic rod. That is why a hydrodynamic modelling has been developed using computational fluid dynamics (CFD) in order to get accurate description of mixing phenomena inside the precipitator and therefore to be able to predict the solid particle properties. Due to the strong turbulence anisotropy, the turbulence transport simulation is achieved by a large eddy simulation (LES) approach which gives unsteady solutions. The numerical simulations are performed in 3D using the Trio U code developed at the Commissariat a l'Énergie Atomique. The predictive performances of the modelling are analysed through a mixing phenomena study. Both experimental and numerical studies are performed. This work shows how hydrodynamics inside the reactor can have a noticeable effect on the precipitate properties and how LES modelling is a very effective tool for the process control.

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“…The monoparticles are agglomerated, but the agglomerates are "loose". In such a case, during precipitation, the solution is in contact with all elementary particles which make up the agglomerates, so that they can grow in the same way as single crystals in the suspension and consequently the agglomeration does not influence the specific surface area [9]. The laser diffraction granulometer can not measure the particle size distribution of calcium carbonate monoparticles.…”

Section: Introductionmentioning

confidence: 99%

Determination of Crystallization Kinetics and Size Distribution Parameters of Agglomerated Calcium Carbonate Nanoparticles during the Carbonation of a Suspension of Lime

Schnebelen¹,

Ricaud²,

Jakob³

et al. 2015

CSTA

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The reaction studied in this work is the synthesis of nanometric size calcium carbonate by carbonation of a suspension of lime, which represents the most common industrial route. The carbonation was proceeded in a pilot batch reactor. This article presents a method for the determination of nucleation and crystal growth rates of calcium carbonate by following two macroscopic parameters: the mass production rate by precipitation and the specific surface area. The results give a constant nucleation rate around 4 × 10 15 m −3 •s −1 and a decreasing crystal growth rate between 0.2 and 2 × 10 −10 m•s −1. It also provides the main characteristics of the monoparticle size distributions (i.e. the mean particle sizes and in situ coefficient of variation) in the agglomerates, which cannot be obtained by other known methods. For the carbonation carried out in this work, the mean mass particle size at the end of the reaction is about 300 nm and the coefficient of variation of 0.28 indicates a narrow particle size distribution of the monoparticles.

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Physical simulation of precipitation of radioactive element oxalates by using the harmless neodymium oxalate for studying the agglomeration phenomena

Cited by 14 publications

References 19 publications

Agglomeration Mechanisms and Kinetics during the Carbonation of a Suspension of Lime in a Pilot Batch Reactor

Agglomeration Mechanisms and Kinetics during the Carbonation of a Suspension of Lime in a Pilot Batch Reactor

Mixing Study in an Unbaffled Stirred Precipitator Using LES Modelling

Determination of Crystallization Kinetics and Size Distribution Parameters of Agglomerated Calcium Carbonate Nanoparticles during the Carbonation of a Suspension of Lime

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