Experimental validation of a fluid dynamics based model of the UF Falcon concentrator in the ultrafine range

Abstract

Experimental validation of a fluid dynamics based model of the UF Falcon concentrator in the ultrafine range . (2012) Separation and Purification Technology, vol. 92. pp. 129-135. ISSN 1383-5866 Open Archive Toulouse Archive Ouverte (OATAO)OATAO is an open access repository that collects the work of Toulouse researchers and makes it freely available over the web where possible.Any correspondence concerning this service should be sent to the repository administrator: staff-oatao@inp-toulouse.fr The process of separating ultrafine particles, say below 80 lm, on the basis of density is a true technical challenge. Indeed, the separation process itself becomes very much size dependent with such fine particles, so that large enough density differentials are necessary for offsetting the strong particle size effect. Our study is concerned with understanding the limitations of the UF Falcon concentrator, an enhanced gravity separator specifically designed for treating slurries with ultrafines. To this end, based on a number of hypotheses, we have already derived and published a theoretical model of the UF Falcon concentrator for treating dilute suspensions. This paper presents the validation and calibration of this model, based on experimental measurements carried out under controlled conditions using a laboratory scale concentrator. By comparing measured and predicted separation results for particles with known size distribution and density, the work validates the key model hypotheses, thereby confirming our understanding of the physics of the separation process. Moreover, by changing operating conditions in a systematic manner, the work is able to calibrate the model so that it can be used to make quantitative prediction of the UF Falcons performance.

Experimental investigation into the kinetics of Falcon UF concentration: Implications for fluid dynamic-based modelling

“…These results confirm those obtained by Kroll-Rabotin et al (2012) with pure quartz, who showed that the tailings PSD remains unchanged for the first few minutes of the separation and then shifts towards the PSD of the feed [22]. This first phase of the separation during which ultrafine particles are rejected with a relatively constant PSD was taken to be a proof that the Falcon UF operates a steady state separation until the retention zone is full [22]. While it may be true for pure minerals, it seems that the opposite is observed here with more complex materials such as the industrial ores used in this study, exhibiting more heterogeneous compositions comprising high density metal-bearing minerals and gangue minerals displaying a range of low to medium specific gravities (Table 1).…”

“…These results confirm those obtained by Kroll-Rabotin et al (2012) with pure quartz, who showed that the tailings PSD remains unchanged for the first few minutes of the separation and then shifts towards the PSD of the feed [22]. This first phase of the separation during which ultrafine particles are rejected with a relatively constant PSD was taken to be a proof that the Falcon UF operates a steady state separation until the retention zone is full [22].…”

“…From Figure 5 to 9, it can be inferred that two separation mechanisms are at play. The differential settling of particles within the flowing film is the one mechanism that has been accounted for in the model developed by Kroll-Rabotin et al [22], which is responsible for the ejection of fine particles during the whole separation cycle. However, the non-uniform decrease of the yield after the concentrate bed results from another mechanism.…”

“…[19,20]. This model, which has been validated in laboratory conditions using pure-silica samples [22], relies on a number of assumptions, including the existence of a stationary separation stage before saturation and the no-resuspension of trapped particles in the bowl retention zone [19,20]. However, the model does not explain the increase in separation performance with time/feed mass before the bowl saturation as well as the potential evidences of resuspension as observed by some authors with industrial ores [6,11,12], who suggested that bed erosion phenomena may affect the efficiency of the separation over time.…”

Physical analysis and modeling of the Falcon concentrator for beneficiation of ultrafine particles

“…R min , R max and H bowl define the bowl geometry (base radius, radius at the outlet and height) and λ is a calibration constant. Experiments yielded a value of λ = 0.68 for a laboratory scale Falcon L40 equipped with a UF bowl (Kroll-Rabotin et al, 2011b). The need of a calibration constant has already been detailed extensively in Kroll-Rabotin et al (2011b): it actually only reflects the simplifications we have included in the model derivation such as:…”