Numerical Model of Sedimentation/Thickening with Inertial Effects

Karl, Joanna Robin; Wells, Scott A.

doi:10.1061/(asce)0733-9372(1999)125:9(792)

Cited by 17 publications

(7 citation statements)

References 21 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This regime is characterized by a sharp boundary between the suspension and the supernatant [11]. The solids subside as a more or less consolidated structure due to the fact that concentration is large enough to develop agglomerate contact as they settle [12]. Water movement is hindered by solid phase then clarification velocity decreases as a function of mass fraction [13].…”

Section: Zone B: Concentrated Suspensions (From 4 To 9% In Mass Fractionmentioning

confidence: 99%

Study of suspension settling: A approach to determine suspension classification and particle interactions

Vie

Azéma

Quantin

et al. 2007

Colloids and Surfaces A: Physicochemical and Engineering Aspect

View full text Add to dashboard Cite

The properties of mineral suspensions do not evolve linearly with particle mass fraction. For some critical concentrations these properties are abruptly modified due to a change of relative interparticle interaction force prevalence. Using kaolin and glass beads as model materials, physicochemical stability and rheological measurement have been carried out in order to propose a global and discriminant parameter enabling the nature of particle interactions to be identified. Different types of suspensions were studied namely: diluted suspensions, concentrated suspensions and solid suspensions. Physico-chemical stability, studied by optical dispersion analysis (Turbiscan MA 2000) enables the clarification rate to be measured and to propose a new global parameter, the "phase separation index". In addition, rheological analysis was realized by the means of viscous flow measurement. Behaviour of solid suspensions is satisfactorily described by Oswald de Waele power law in the whole range of concentration studied which tends to demonstrate that the interactions remains the same in this range.

show abstract

Section: Zone B: Concentrated Suspensions (From 4 To 9% In Mass Fractionmentioning

confidence: 99%

Study of suspension settling: A approach to determine suspension classification and particle interactions

Vie

Azéma

Quantin

et al. 2007

Colloids and Surfaces A: Physicochemical and Engineering Aspect

View full text Add to dashboard Cite

show abstract

“…The unified theory, inclusive of networked bed consolidation, has now been applied to a large range of dewatering simulations (Auzerais et al 1990;Howells et al 1990;Bergstrom et al 1992;Bürger & Wedland 1998;Bustos et al 1999;Karl 1999;Diehl 2000;Bürger et al 2001). In some cases this was for a continuous thickener (Landman et al 1988;Lester et al 2010).…”

Section: Prediction Of Thickener Throughputmentioning

confidence: 99%

Thickener modelling – from laboratory experiments to full-scale prediction of what comes out the bottom and how fast

Scales¹,

Crust²,

Usher³

2015

Proceedings of the 18th International Seminar on Paste and Thickened Tailings

View full text Add to dashboard Cite

Predicting full-scale thickener performance, including the solids flux and concentration delivered from a thickener underflow based solely on laboratory-scale experiments, has long been the holy grail of thickener design and operation. A number of researchers have developed both thickener models and laboratory characterisation techniques to measure sedimentation and compressional properties of flocculated suspensions. Combining these to produce predictions of actual performance generally results in an underestimation of the thickener solids flux, often by a factor of between 10 and 20. Consequently, a range of empirical methods and industry scalars has been developed to get around this discrepancy. Analysis of the reasons for the discrepancy shows that changes in aggregate structure in shear, due to inter-aggregate buffeting and shear induced by collisions with surfaces and rakes, causes the flocculated aggregate to change from a fractal to a denser non-fractal object as it progresses through the thickener. These changes are shear rate and solids concentration dependent and as such, very difficult to reproduce in the laboratory and then incorporate into thickener models. A method to quantify the time and shear rate dependent changes in aggregate structure is now available and a model has been developed that allows incorporation of this effect into modelling. The change in aggregate behaviour is incorporated through a shear rate dependent densification rate and final extent of aggregate densification. The latter parameter helps to define an upper limit in solids flux behaviour for a given solids underflow concentration. Using the new information, thickener models now predict a range of underflow solids flux outcomes between the upper (densified aggregate) and lower (undensified aggregate) limit for a particular underflow solids concentration, depending on the operational conditions. The difference in underflow solids flux between these two limits is significant and the actual outcome depends on the shear rate and time of shear, as well as total solids residence time in the thickener. The data indicate that for non-segregating flocculated suspensions, operational conditions that produce the optimum thickener underflow solids flux for a given flocculation condition can now be explored quantitatively without resorting to extensive pilot trials.

show abstract

“…This regime is characterized by a sharp boundary between the suspension and the supernatant [14]. The solids subside as a more or less consolidated structure due to the fact that concentration is large enough to develop agglomerate contact as they settle [15]. -Class IV: solid suspensions, in which all the agglomerates or unit particles form a contact network in the suspension.…”

Section: Typology Of Suspensionsmentioning

confidence: 99%

Settling of mineral aqueous suspensions. Classification and stability prediction by neural networks

Vie¹,

Johannet²,

Azéma³

2014

Colloids and Surfaces A: Physicochemical and Engineering Aspect

View full text Add to dashboard Cite

show abstract

Numerical Model of Sedimentation/Thickening with Inertial Effects

Cited by 17 publications

References 21 publications

Study of suspension settling: A approach to determine suspension classification and particle interactions

Study of suspension settling: A approach to determine suspension classification and particle interactions

Thickener modelling – from laboratory experiments to full-scale prediction of what comes out the bottom and how fast

Settling of mineral aqueous suspensions. Classification and stability prediction by neural networks

Contact Info

Product

Resources

About