Study of the agglomeration of alumina powders using in situ turbidimetry

Abstract : Kinetics of agglomeration of alumina powders in stirred aqueous solutions was studied by means of an in situ turbidity sensor. The effects of stirring rate, pH and concentration of additives were determined and analysed via a new model of browman and turbulent agglomeration in presence of interactions. Suspensions of solid powders in liquid media are used in many industrial processes, particularly in ceramics production. In most cases, it is of major interest to follow as continuously as possible the dispersion state of the suspension for practical reasons of control or characterisation, as well as for fundamental aims of interpretation or modelling. Turbidimetry is one of the few techniques compatible with the use of in situ sensors; in recent studies we proved that it can be used to obtain continuous information on the particle size distribution in solid-liquid media in which attrition or agglomeration take place. The possibility of in situ measurements is essential in agglomeration studies, because sampling may alter the hydrodynamic conditions and damage the agglomerates. In this paper, we present an experimental study of agglomeration of an alumina powder for ceramics materials. To this aim, we have designed a reactor equipped with a turbidimetric sensor. The effects of stirring rate, pH and additive concentrations on the dynamics of agglomeration are qualitatively and quantitatively determined. These experimental results arc then discussed with the help of a model. This model consists of three parts: 1) determination of agglomeration kernels in brownian and turbulent conditions; 2) solution of the population balance equation, taking into account agglomeration and setting; 3) calculation of the turbidity of the suspension. This model has been written, assuming compact agglomerates; the consequence of a possible fractal structure is then examined.
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Communication dans un congrès
Béatrice Biscans ; John Garside. 13th Symposium on Industrial Crystallization, Sep 1996, Toulouse, France. PROGEP, 2, pp.455-460, 1996
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Hubert Saint Raymond, Frédéric Gruy, Michel Cournil. Study of the agglomeration of alumina powders using in situ turbidimetry. Béatrice Biscans ; John Garside. 13th Symposium on Industrial Crystallization, Sep 1996, Toulouse, France. PROGEP, 2, pp.455-460, 1996. 〈emse-00625735〉

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