Scale invariants in the preparation of reverse high internal phase ratio emulsions

Chemical Engineering Science, 2013 , 101 , 721-730.

Anna May-Masnou, Jordi Ribó-Besolí, Montserrat Porras, Alicia Maestro, Carme González, José María Gutiérrez.

Departament d’Enginyeria Química, Facultat de Química, Universitat de Barcelona, Martí i Franquès, 1-11, 08028, Barcelona, Catalunya, Spain.

Abstract

 How would you be sure that the product you have prepared in an industrial scale mixing vessel has the same properties than the product prepared in a 100 mL vessel in the laboratory? If the product obtained is not the right one, the economic or time loss can be important. For this reason, we thought that this problematic could be studied and optimized. In this study, we focused on the scale-up of the preparation of highly concentrated w/o emulsions. In these systems, the rheological behavior, stability and droplet size, strongly depend on the preparation method and installation used to prepare them.

We used a three-scale installation with geometric similarity, to study the influence of the vessel size (scale up) on the highly concentrated w/o emulsions prepared. The emulsions were prepared through the continuous addition method. The process variables that we studied were, apart from the scale, the surfactant concentration, the stirring rate and the flow rate of the added dispersed phase. The properties analyzed were the rheological parameters: viscoelasticity, viscosity and yield stress. Droplet size and stability were also monitored.

The problematic can be reduced to a simple question: which variables have to be kept constant in all the scales in order to obtain the same emulsion? One may think that what needs to be kept constant is the Reynolds number; others may go for the Froude number, the tip speed velocity or the stirring rate. In this study, we find, using design of experiments and multiple linear regressions, the scale invariants to prepare emulsions of this kind. The parameter takes into account the scale and the stirring rate.

The results obtained are useful in many different ways: to prepare emulsions at different scales and predict their rheological parameters before measuring them; to use the developed method for determining scale invariants to other emulsion systems, and to prepare easily emulsions at a higher scale knowing that the result will be a success.

 

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Figure Legend:  Installation used to prepare the emulsions: stirred vessel, stirrer, peristaltic pump.

Scale invariants in the preparation of reverse high internal phase ratio emulsions

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