Design rules for suspending concentrated mixtures of solids in stirred tanks

Ayranci, İnci; Kresta, Suzanne M.

doi:10.1016/j.cherd.2011.01.008

Cited by 56 publications

(53 citation statements)

References 18 publications

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“…The impeller speed was increased in steps of 3 rpm. After the system reached steady state (in 1 to 2 min), the bottom of the tank was observed for at least 30 s 53. This was repeated until the Zwietering criterion was satisfied.…”

Section: Methodsmentioning

confidence: 99%

“…According to the Zwietering criterion,50 complete off‐bottom suspension occurs when no particles stay on the bottom of the tank for more than 1 or 2 s. This impeller speed is called the just suspended speed ( N js ). If the solids concentration is less than 10 wt %, N js can be estimated using the Zwietering correlation While Zwietering included the effect of impeller diameter in his correlation; later studies have shown that N js also depends on the off‐bottom clearance 51–53. Because of this, the Zwietering constant ( S Z ) is a characteristic of both the impeller geometry and the tank configuration.…”

Section: Introductionmentioning

confidence: 99%

“…The power consumption at N js ( P js ) is Most of the literature on solids suspension focusses on determining S Z for various geometries, and on defining the key variables for this process objective. A recent article by Ayranci53 compares the power consumption of a range of geometries. The results show that P js may be a better indicator of impeller performance than S Z .…”

Section: Introductionmentioning

confidence: 99%

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Impeller characterization and selection: Balancing efficient hydrodynamics with process mixing requirements

et al. 2011

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Current literature relies almost exclusively on the power number to compare and characterize impellers. Industrial mixing requirements may rely on conditions far away from the impeller. A protocol is proposed to compare impellers designed for turbulent mixing on the basis of impeller hydrodynamic performance and mixing process objectives. A hydrofoil impeller (KPC), and a mixed‐flow impeller (45° down‐pumping PBT), each at two diameters, were used to test the protocol. Fourteen measures were considered. Five are recommended for full characterization: power number, momentum number, and peak rate of dissipation of turbulent kinetic energy to characterize conditions at the impeller; power at just‐suspended speed to compare the efficiency of solids suspension at the bottom of the tank; and point of air entrainment as a measure of turbulence penetration to the free surface. These five measures provide complete information about mixing performance and good differentiation between the impellers and geometries. © 2011 American Institute of Chemical Engineers AIChE J, 58: 2573–2588, 2012

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Impeller characterization and selection: Balancing efficient hydrodynamics with process mixing requirements

et al. 2011

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“…The other difference that arises from the two equations is that with the latter, e T;JS is constant on scale-up whilst with the former it falls. Where particles of different size and density are present, N JS behaves in a complex manner and cannot at present be predicted [42].…”

Section: Solid-liquid Systemsmentioning

confidence: 99%

Stirring and Stirred‐Tank Reactors

Nienow

2014

Chemie Ingenieur Technik

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Stirred-tank reactors are used throughout the process industry. They are not only applied in the chemical industry, but also in newer industrial sectors, such as biologics, pharmaceuticals, nanotechnology, and regenerative medicine. Certain features have not changed for many years, but the understanding of the physical processes occurring within has greatly increased. Since knowledge of the interaction between the physics of mixing, single-or multiphase, and the underlying science is critical, the physical processes of mixing/stirring are considered as they developed over the last~75 years.

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“…Montante et al combined experimental and computational (computational fluid dynamics, CFD) methods to study solids suspension in mixing tanks. Recent work on solids suspension in stirred tanks deals with mixtures of different types of particles and addresses important questions about the interaction between the different particle types.…”

Section: Introductionmentioning

confidence: 99%

Suspending a solid sphere in laminar inertial liquid flow—experiments and simulations

Gao

Bao

et al. 2015

AIChE Journal

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The critical conditions for the suspension of single, spherical solid particles by a liquid flow in a square container driven by a rotating disk have been determined. In the experiments, the motion of the sphere has been visualized quantitatively. The conditions are such that the flow in the container is laminar (Reynolds numbers based on the rotating disk characteristics are in the range 10 -40). The Archimedes numbers of the spheres are of order 1. The suspension process has also been numerically simulated with full resolution of the liquid flow, including the flow around the sphere, and the translational and rotational motion of the sphere. The simulations recover the critical conditions to within 3% in terms of the rotational speed of the disk. Also the sphere's trajectory in the container is reproduced well by the simulations.

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Design rules for suspending concentrated mixtures of solids in stirred tanks

Cited by 56 publications

References 18 publications

Impeller characterization and selection: Balancing efficient hydrodynamics with process mixing requirements

Impeller characterization and selection: Balancing efficient hydrodynamics with process mixing requirements

Stirring and Stirred‐Tank Reactors

Suspending a solid sphere in laminar inertial liquid flow—experiments and simulations

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