Centrifuges, Sedimenting

Axelsson, Hans; Madsen, Bent

doi:10.1002/14356007.c05_c02.pub2

Cited by 4 publications

(6 citation statements)

References 18 publications

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“…Windage exerts drag on the rotating body and additional power is taken up to overcome it. Windage is a function of the properties of the environment, geometry, and speed of rotation as given below:

P_{W} = k_{S} μ_{A}^{0.2} ρ_{A}^{0.8}^{3} ω^{3} D^{4.5}

where P W is the windage power (W); μ A and ρ A are the viscosity (Pa · s) and density (kg · m −3 ) of the surrounding atmosphere, respectively; D is the rotating body outer diameter (m); and k S is a shape constant. The power loss due to windage increases with G 3/2 for a given geometry, and lowering the centrifuge speed therefore reduces the windage power loss.…”

Section: Resultsmentioning

confidence: 99%

“…The horizontal SDC is widely used in the chemical and processing industries to separate materials based on specific gravity differences . It is relatively easy to maintain, can be automated, and requires no consumable replacement parts such as filter cloths.…”

Section: Introductionmentioning

confidence: 99%

“…The steady scrolling out of the solids from the centrifuge bowl enables continuous processing of suspensions over a wide range of flow rates. As a result, the SDC frequently finds application in mineral solids speciation and wastewater sludge treatment, and is also widely used in the food, pharmaceutical, and chemical industries . Other solid‐liquid separation technologies, including belt‐filter press and traditional filtration, do not have the capacity to handle the vast inventories of FFT and are hampered by the low permeability and blockage of the filter medium (fouling) by fine solids, which make up the bulk of FFT.…”

Section: Introductionmentioning

confidence: 99%

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Impact of preflocculation on scroll decanter centrifuge separation performance

Demoz

2017

Can J Chem Eng

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Industrial scroll decanter centrifuge (SDC) separation of the solids in fluid fine tailings (FFT) which have particles 10 mm and smaller in size require flocculant addition. Accordingly, the mechanism in the centrifuge is flocculation of the fine solid particles followed by sedimentation. Thus, feeding preflocculated material obviates the flocculation step inside the SDC resulting in improved process efficiency by reducing the power consumption and increasing the throughput capacity of each SDC. This work evaluated the separation performance of the SDC using inline static mixers to preflocculate oil sands FFT containing solids, 90 mass% of which are < 9 mm in size. The minimum G-forces required to achieve the industry benchmarks of < 1 mass% solids in the centrate water and > 97 % fines capture rate were 750 G without preflocculation and 400 G with preflocculation. Since power consumption by the SDC, as expected, was directly proportional to the G-force, the savings in power due to preflocculation amounted to 47 %. Preflocculation increased SDC throughput capacity by up to 50 %. Operating at lower G-force has the additional benefits of protecting the high-capital-cost SDC machine and reducing ambient noise levels.

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P_{W} = k_{S} μ_{A}^{0.2} ρ_{A}^{0.8}^{3} ω^{3} D^{4.5}

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Impact of preflocculation on scroll decanter centrifuge separation performance

Demoz

2017

Can J Chem Eng

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“…The disc stack separator was equipped either with 40 or 35° discs and operated at 10 000 rpm giving an area equivalent Σ of 1696, 2605, 2848, or 3049 m 2 and KQ values of 40, 61, 66, or 71, respectively. Σ in m 2 and the semiempirical KQ values were calculated according to the following equations :

true \sum = \frac{π ω^{2}}{g} \frac{2}{3} N (r_{2}^{3} - r_{1}^{3}) normalcot α

true KQ = \frac{280}{10^{6}} {(\frac{n}{1000})}^{1.5} N (r_{out}^{2.75} - r_{in}^{2.75}) normalcot α

…”

Section: Methodsmentioning

confidence: 99%

Flocculant Screening Method at Lab Scale for Application in Disc Stack Centrifuges with Hermetic Design

2018

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Chemicals produced using biotechnological methods like fermentation processes are obtained as complex diluted aqueous mixture, which still contains the production organism. Centrifugation is a commonly used technology for biomass separation. By flocculation, the settling velocity of microorganisms can be increased. Here, a laboratory flocculant screening method tailored for the separation of flocculated biomass in a fully hermetic disc stack centrifuge is described. The specific requirements of this process, namely, floc formation, floc stability, sliding behavior in the disc stack, and flowability of the sludge, were transferred to lab scale and validated in pilot tests. The qualitative results of the laboratory screening were in agreement with the processes at industrial scale.

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“…[190] In sedimentation centrifuges, the separation of the particles occurs by centrifugal settling. [191] The sedimentation rate of solid particles depends on the particle size, shape, density difference and viscosity of the suspension. The influence of the solution viscosity on the sedimentation velocity, v c , can be seen in the Stokes law,[ 11 , 180 , 191 ] where the gravitational force, g , is substituted by the centrifugal acceleration,

[Eq.…”

Section: Effect Of Polymer Solution Viscosity For Plastic Purification Recycling Processesmentioning

confidence: 99%

State‐Of‐The‐Art Quantification of Polymer Solution Viscosity for Plastic Waste Recycling

et al. 2021

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Solvent-based recycling is a promising approach for closed-loop recovery of plastic-containing waste. It avoids the energy cost to depolymerize the plastic but still allows to clean the polymer of contaminants and additives. However, viscosity plays an important role in handling the polymer solutions at high concentrations and in the cleaning steps. This Review addresses the viscosity behavior of polymer solutions, available data, and (mostly algebraic) models developed. The non-Newtonian viscosity models, such as the Carreau and Yasuda-Cohen-Armstrong models, pragmatically describe the viscosity of polymer solutions at different concentrations and shear rate ranges. This Review also describes how viscosity influences filtration and centrifugation processes, which are crucial steps in the cleaning of the polymer and includes a polystyrene/ styrene case study.

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Centrifuges, Sedimenting

Abstract: The article contains sections titled: 1. Introduction 2. Fundamentals … Show more

Cited by 4 publications

References 18 publications

Impact of preflocculation on scroll decanter centrifuge separation performance

Impact of preflocculation on scroll decanter centrifuge separation performance

Flocculant Screening Method at Lab Scale for Application in Disc Stack Centrifuges with Hermetic Design

State‐Of‐The‐Art Quantification of Polymer Solution Viscosity for Plastic Waste Recycling

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