How Oversized Mixers Became an Industry Standard

Pretorius, Coenraad; Wicklein, Ed; Rauch-Williams, Tanja; Samstag, Randal W.; Sigmon, Cole

doi:10.2175/193864715819541710

Cited by 4 publications

(2 citation statements)

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“…where N p is the impeller power number which for a plane disk with gentle agitation, as is our case, is 0.6 [45], N is the rotation speed, and D and V are the diameter of the impeller and the working volume of the vessel, respectively. The density of the suspension ρ sus is calculated from:…”

Section: Of 15mentioning

confidence: 99%

Describing Mining Tailing Flocculation in Seawater by Population Balance Models: Effect of Mixing Intensity

Quezada¹,

Ayala

Leiva

et al. 2020

Metals

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A population balance model (PBM) is used to describe flocculation of particle tailings in seawater at pH 8 for a range of mixing intensities. The size of the aggregates is represented by the mean chord length, determined by the focused beam reflectance measurement (FBRM) technique. The PBM follows the dynamics of aggregation and breakage processes underlying flocculation and provides a good approximation to the temporal evolution of aggregate size. The structure of the aggregates during flocculation is described by a constant or time-dependent fractal dimension. The results revealed that the compensations between the aggregation and breakage rates lead to a correct representation of the flocculation kinetics of the tailings of particles in seawater and, in addition, that the representation of the flocculation kinetics in optimal conditions is equally good with a constant or variable fractal dimension. The aggregation and breakage functions and their corresponding parameters are sensitive to the choice of the fractal dimension of the aggregates, whether constant or time dependent, however, under optimal conditions, a constant fractal dimension is sufficient. The model is robust and predictive with a few parameters and can be used to find the optimal flocculation conditions at different mixing intensities, and the optimal flocculation time can be used for a cost-effective evaluation of the quality of the flocculant used.Metals 2020, 10, 240 2 of 15 the operational priorities is to close the water cycle, a process that can be successful with proper management of the thickening stages. Generally, the concentration stages are carried out at alkaline pH, which means that both particles and flocculant molecules (such as hydrolyzed polyacrylamide) carry anionic charges. Although reagents may have a low affinity with the particles, it is sufficient to form porous aggregates with low density, which facilitate the transport of the thick pulp from the bottom of the thickener to the tailing dams. The fact that industrial water has some ionic charge can be beneficial. There is evidence in the literature that the presence of ions in the liquor is necessary for adequate flocculation, because ions allow the adsorption of polymeric molecules on the charged surfaces [1][2][3]. There is also evidence that flocculants may exhibit different behaviors when interacting in saline media. For example, studies have indicated that flocculated kaolinite shows decreasing sedimentation rates in environments with high salinity [4,5], while other studies show the opposite [6]. We recently demonstrated that the increase in salinity promotes the adsorption of polyelectrolytes on mineral surfaces but decreases the size of the polymer in solution, resulting in a competitive effect that can benefit or impair particle agglomeration. Thus, varied behaviors are expected [7,8].There is great interest in studying flocculation from a microscopic level because the mechanisms involved during the aggregation of colloidal particles determine the efficiency of t...

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Section: Of 15mentioning

confidence: 99%

Describing Mining Tailing Flocculation in Seawater by Population Balance Models: Effect of Mixing Intensity

Quezada¹,

Ayala

Leiva

et al. 2020

Metals

View full text Add to dashboard Cite

show abstract

“…where N p is the impeller power number (0.6 in our case for a plane disk with gentle agitation [51]), N is the rotation speed, D and V are, respectively, the diameter of the impeller and the working volume of the vessel. The density of the suspension ρ sus is calculated from:…”

Section: Shear Ratementioning

confidence: 99%

Reducing the Magnesium Content from Seawater to Improve Tailing Flocculation: Description by Population Balance Models

Quezada¹,

Jeldres

Toro

et al. 2020

Metals

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Experimental assays and mathematical models, through population balance models (PBM), were used to characterize the particle aggregation of mining tailings flocculated in seawater. Three systems were considered for preparation of the slurries: i) Seawater at natural pH (pH 7.4), ii) seawater at pH 11, and iii) treated seawater at pH 11. The treated seawater had a reduced magnesium content in order to avoid the formation of solid complexes, which damage the concentration operations. For this, the pH of seawater was raised with lime before being used in the process—generating solid precipitates of magnesium that were removed by vacuum filtration. The mean size of the aggregates were represented by the mean chord length obtained with the Focused beam reflectance measurement (FBRM) technique, and their descriptions, obtained by the PBM, showed an aggregation and a breakage kernel had evolved. The fractal dimension and permeability were included in the model in order to improve the representation of the irregular structure of the aggregates. Then, five parameters were optimized: Three for the aggregation kernel and two for the breakage kernel. The results show that raising the pH from 8 to 11 was severely detrimental to the flocculation performance. Nevertheless, for pH 11, the aggregates slightly exceeded 100 µm, causing undesirable behaviour during the thickening operations. Interestingly, magnesium removal provided a suitable environment to perform the tailings flocculation at alkaline pH, making aggregates with sizes that exceeded 300 µm. Only the fractal dimension changed between pH 8 and treated seawater at pH 11—as reflected in the permeability outcomes. The PBM fitted well with the experimental data, and the parameters showed that the aggregation kernel was dominant at all-polymer dosages. The descriptive capacity of the model might have been utilized as a support in practical decisions regarding the best-operating requirements in the flocculation of copper tailings and water clarification.

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Analysis of the flocculation process of fine tailings particles in saltwater through a population balance model

Quezada¹,

Ramos

Jeldres

et al. 2020

Separation and Purification Technology

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How Oversized Mixers Became an Industry Standard

Cited by 4 publications

References 0 publications

Describing Mining Tailing Flocculation in Seawater by Population Balance Models: Effect of Mixing Intensity

Describing Mining Tailing Flocculation in Seawater by Population Balance Models: Effect of Mixing Intensity

Reducing the Magnesium Content from Seawater to Improve Tailing Flocculation: Description by Population Balance Models

Analysis of the flocculation process of fine tailings particles in saltwater through a population balance model

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