Due to the increasing demand for processing low-grade ores, larger volumes of material are being processed. Therefore, the size of flotation equipment has significantly increased for the past decades. The studies related to scale-up are and will remain to be crucial in terms of designing larger flotation equipment. One of the most important factors for flotation scaling-up is the “flotation rate constant”. Hence, the main aim of this investigation was to understand the scale-up criteria when the size of different laboratory-scale cells increases, using the Outotec GTK LabCell®. This was done by assessing the influence of impeller speed, as a hydrodynamic variable, on the flotation performance. Recovery was found to increase with an increase in the cell area to rotor diameter ratio. Flotation rate and recovery increased with an increase in the impeller speed until a certain point that it eventually decreased for the 2 l and 7.5 l cells. For the 4 l cell, the flotation rate and recovery decreased with increasing the impeller speed. The impeller speed of 1200 rpm allowed a successful scale-up based on the flotation rate constants and recovery when increasing the size of the cells. Maintaining the impeller speeds constant at 1300 rpm increased the flotation rate constants and recovery when increasing the cell size from both the 2 and 4 l cells to the 7.5 l cell. A further increase in the impeller speed to 1400 rpm also produced the flotation rate constants and recovery to increase as the cell size increased from both the 2 and 4 l cells to the 7.5 l cell. However, when increasing the cell size from 2 l to 4 l, good results were also observed for all impeller speeds. The products concentrate seem to become finer when decreasing the cell size, with only a few exceptions. The recovery of particles larger than 38 μm was found to differ considerably less among the different scales.

Un grand nombre d’industries (chimiques, pharmaceutiques et agroalimentaires) utilisent, produisent ou transforment des fluides complexes. Ce sont des fluides à viscosité élevée, souvent de comportement non-Newtonien. Leur préparation nécessite souvent une étape de chauffe suivie d’une étape de refroidissement. La chauffe est indispensable afin de faciliter la fabrication (réaction chimique et/ou transformation physico-chimique). Le refroidissement, ou encore l’étape de finition, consiste à amener les fluides jusqu’à une température proche de la température ambiante pour aborder l'étape de conditionnement. Le refroidissement est le plus souvent réalisé « in situ » dans la même cuve agitée, équipée d’une double enveloppe (utilisée pour la fabrication), mais des technologies en continu peuvent également être envisagées. Ces travaux de thèse portent sur la mise en place d’une méthodologie de pilotage de la vitesse d’agitation lors du refroidissement de fluides complexes dans des cuves agitées, ainsi que sur la comparaison des performances de la cuve agitée avec celles du mélangeur statique. Deux fluides de travail sont testés : Newtonien et viscoplastique, en régime d’écoulement laminaire et transitoire. Nous déterminons les limites de l’influence de l’agitation sur le transfert thermique, la durée de l’opération et la quantité d’énergie consommée. En premier lieu, le refroidissement est étudié à l’échelle laboratoire (réacteur de 0,6L). Il a été constaté que le changement de la vitesse d’agitation au cours du refroidissement affecte le profil de température. Cela a un impact avantageux sur le coût énergétique et/ ou la durée de refroidissement. Les tendances observées à l’échelle laboratoire sont transposées et validées à l’échelle pilote (réacteur de 60L). Puis deux types de mélangeurs statiques sont étudiés comme technologie en continu. Nous établissons des modèles de perte de charge que nous utilisons dans la détermination de l’énergie dépensée pour le refroidissement. Ensuite nous réalisons une comparaison de leurs performances en fonction des facteurs d’efficacité de transfert thermique et de consommation énergétique. Enfin, une brève analyse comparée est exposée, présentant les divers critères de choix entre la cuve agitée et la technologie en continu. / Highly viscous Newtonian and non-Newtonian fluids are frequently encountered in the process industries (like pharmaceutical, food and cosmetics). The preparing of such products involves heating and cooling steps. The heating stage is essential in order to facilitate the production (chemical reaction and/or physico-chemical transformation). The cooling step, named also final stage, leads the fluids to ambient temperature and prepares them for the conditioning. The cooling is mostly realized "in situ" in the same double jacketed stirred vessel, (used for the manufacturing), but continuous technologies may also be employed. This study aims to investigate the cooling of highly viscous fluids, and intends to define the best conditions for controlling the impeller speed (constant or variable) in a stirred vessel, as well as to compare the performances of the stirred vessel with those of the static mixer. Two fluids are tested: a Newtonian and a Non-Newtonian yield-stress fluid, in laminar and transitional conditions. The limits of the influence of the impeller speed on the heat transfer, the duration and the energy consumption are determined. In a first approach, the cooling is studied at small scale (0,6L vessel). The variation of the impeller speed during the cooling, affects the profile of temperature. This type of procedure has an advantageous impact on the energy cost and / or the duration of the cooling. The observed tendencies at a small scale are transposed and validated at a pilot scale (60L vessel). Two types of static mixers are studied as continuous technology. Models of pressure drop are established, which are used further in the determination of the energy consumption for the cooling. The performances of these two static mixers are compared, according to the factors of heat transfer efficiency and energy consumption. Finally, a brief comparative analysis is exposed, presenting diverse criteria of choice between the stirred tank and the continuous technology.