PERFORMANCE OF HYDROCYCLONES WITH DIFFERENT GEOMETRIES Luiz G. M. Vieira,* Beatriz C. Silv´ erio, Jo˜ ao J. R. Damasceno and Marcos A. S. Barrozo School of Chemical Engineering, Federal University of Uberlˆ andia, Bloco K, Campus Santa Mˆ onica, POB 593, 38400-902 Uberlˆ andia, MG, Brazil Hydrocyclones belong to an important group of equipments designed to solid–liquid or liquid–liquid separation in a centrifugal field. It is possible to adapt a hydrocyclone to the accomplishment of several industrial activities depending on the geometrical relations among its main dimensions. The operation and design of these devices are relatively simple; however, the flow inside them is very complex and its prediction is very difficult. For that reason, most models that are used to predict hydrocyclone performance are empirical ones. The objective of this work was to study the influence of geometric variables in the performance of hydrocyclones, using CFD and response surface techniques. The obtained results show that it was possible to find an optimum hydrocyclone design, that is, geometric relationships that lead to Euler number and cut size in minimum levels. Les hdrocyclones appartiennent ` a un groupe important d’´ equipements conc ¸us pour la s´ eparation solide-liquide ou liquide-liquide dans un champ centrifuge. Il est possible d’adapter un hydrocyclone ` a la r´ ealisation de plusieurs activit´ es industrielles selon les relations g´ eom´ etriques dans ses dimensions principales. Le fonctionnement et la conception de ces dispositifs sont relativement simples; cependant, leur circulation interne est tr` es complexe et sa pr´ ediction est tr` es difficile. Pour cette raison, la plupart des mod` eles utilis´ es pour pr´ edire le rendement des hydrocyclones sont des mod` eles empiriques. L’objectif de ce travail ´ etait d’´ etudier l’influence des variables g´ eom´ etriques sur le rendement des hydrocyclones en utilisant une DFN et des techniques de surface de r´ eponse. Les r´ esultats obtenus indiquent qu’il ´ etait possible de trouver une conception d’hydrocyclones optimale, c.-` a-d. les relations g´ eom´ etriques qui m` enent au nombre d’Euler et ` a la mesure fixe ` a des niveaux minimaux. Keywords: hydrocyclone, CFD, response surface INTRODUCTION H ydrocyclones are an important device for the separation of solid–liquid suspensions (Schuetz et al., 2004). A typical conventional hydrocyclone consists of a conical section, open as its apex (at the bottom), joined to a cylindrical section which has a tangential inlet. The top of the cylindrical section is closed with a plate through which passes an axially mounted overflow pipe (vortex finder). Hydrocyclone operation is chiefly based on the differential density and high rotational velocities that are imparted as the suspension or slurry is injected tangentially into its upper part. The suspension takes on a swirling motion as it flows into the outer portion of the inverted cone. Some of the downward flow exits the hydrocyclone through the underflow with the heavy and/or coarse materials, while the rest reverses its vertical direction and swirls up and out of the vortex finder or overflow. Hydrocyclones are getting more and more interest from vari- ous industries, because of their advantages such as design and operational simplicity, high capacity (volumetric flow rate), low maintenance and operating costs, and small space of equipment (Chu et al., 2004). Despite the advantage of the conventional hydrocyclones, this device has undergone many modifications to enable it to meet specific process requirements (Souza et al., 2000; Vieira et al., 2005, 2007; Oliveira et al., 2009). Mainly due to the demand for hydrocyclones in applications where con- ventional configurations fail to meet process requirements. The hydrocyclone geometry is critical to achieve optimal separation performance. The flow behaviour in a hydrocyclone is quite complex. The internal flow in these devices is totally turbulent and presents high vorticity preservation, vortex breakdown, flow inversion, air core, etc. This complexity of its flow processes has led designers to rely on empirical equations to predict the equipment’s perfor- mance. These empirical relationships are derived from an analysis of experimental data and include the effect of operational and ∗ Author to whom correspondence may be addressed. E-mail address: luizgustavo@feq.ufu.br Can. J. Chem. Eng. 89:655–662, 2011 © 2011 Canadian Society for Chemical Engineering DOI 10.1002/cjce.20461 Published online 30 March 2011 in Wiley Online Library (wileyonlinelibrary.com). | VOLUME 89, AUGUST 2011 | | THE CANADIAN JOURNAL OF CHEMICAL ENGINEERING | 655 |