PERFORMANCES COMPARISON OF INTENSIFIED MIXERS AND MICROMIXERS
Special Symposium - EPIC-1: European Process Intensification Conference - 1
EPIC-1: Multifunctionality (MF-2)
Keywords: mixing, characterization,
FALK Laurent, COMMENGE Jean-Marc, LOMEL Sébastien*, RAMDANI Kamel*,
LSGC-ENSIC, 1 rue Grandville BP 2045, 54001 Nancy cedex, France
* RHODIA, Centre de Recherches & Technologies de Lyon
85 rue des Frères Perret BP 62 F-69162 Saint-Fons Cedex
The production of high added values molecules in the fine chemistry and pharmaceutical industry is essentially carried out in batch and semi batch stirred tanks, which conception has in fact not changed since hundreds of years. The chemical reactions are very often fast exothermic reactions involving complex reactions schemes which may induce selectivity and yield problems because of poor mixing efficiency of the stirred tank. Besides, it is known that for reactions with multiple consecutive or parallel stoichiometry, the introduction of the co-reagent by a feeding law is synonymous of selectivity loss if the desired product is an intermediate replacement product. To prevent selectivity problems induced by mixing, batch reactors work in diluted solvent environment which fatal consequences are the important use of solvent that is necessary to separate and to recycle.
For some years, there is an alternative in the use of these batch reactors, thanks to process intensification and to microreactors development. The idea consists in transposing the reactions into continuous small plug flow reactors equipped with intensive mixing devices.
These mixers are very often characterized by chemical test reactions, whose selectivity of the products is influenced by the mixing conditions. These methods are very convenient to use but they have the drawback to give an information about the mixing quality which is only the reflection of the reaction conditions: on fixed hydrodynamics conditions, i.e. mixing conditions, we have an impression, for a slow reaction, of an effective mixing while for a fast reaction, the mixing quality is lower.
Generally, the conditions of reaction (concentrations) are adapted to make the most sensitive possible measure of the characterized mixer. As a result, the comparison between the mixers is even often difficult, all the more impossible if different test reactions have been used. In spite of the numerous publications on these intensified mixers, it is still difficult to get a clear information on theses mixers. Furthermore test reactions are not the reactions used industrially, and the transposition is particularly delicate.
The objective of the present paper is to propose the comparison of mixers in term of mixing time, independent of the reactions conditions.
From a certain number of results of the literature on characteristic mixers, we compare all the devices on the same graph giving the mixing time as a function of a key parameter of the operating conditions, as the power rate dissipation per unit mass. The aimed objective is that a user can easily compare the technologies between them so as to choose the most appropriate for his process.
Presented Thursday 20, 11:40 to 12:00, in session EPIC-1: Multifunctionality (MF-2).
