A novel geometry for solids drawdown in stirred tanks

Khazam, Oscar; Kresta, Suzanne M.

doi:10.1016/j.cherd.2008.09.013

Cited by 38 publications

(43 citation statements)

References 14 publications

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“…Khazam and Kresta found that performance of half‐depth baffles is very similar to that of full‐depth baffles. However, surface baffles have advantages like a significant reduction in critical agitation speed and a better distribution of solids . Wójtowicz compared the effect of several classical impellers and a single reciprocating disc on the drawdown and dispersing of floating particles.…”

Section: Introductionmentioning

confidence: 99%

“…However, surface baffles have advantages like a significant reduction in critical agitation speed and a better distribution of solids. [8] W ojtowicz compared the effect of several classical impellers and a single reciprocating disc on the drawdown and dispersing of floating particles. The research indicated that the power consumption of a vibromixer could be halved with an appropriate selection of disc diameter and off-bottom clearance.…”

Section: Introductionmentioning

confidence: 99%

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Experimental study on the mixing and dispersing of floating particles in viscous system

et al. 2016

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The effects of baffle configuration, impeller type, impeller diameter ratio, and immersion depth on the critical drawdown speed and power of floating particles were investigated by experiment, and the advantageous stirred vessel was determined on the basis of the low energy consumption principle. Furthermore, the effects of system viscosity, mean solid concentration, and particle size on the dispersing characteristic of floating particles were also researched with the advantageous stirred vessel. The results show that, (1) when the stirred vessel is equipped with a single baffle, the critical drawdown speed and power of floating particles are lower than those of others. (2) Among the propeller, six flat‐blade disc turbine (Rushton), and six 45° pitched‐blade turbine (PBT‐6), the Rushton turbine has the lowest critical drawdown speed, and the down‐pumping propeller (TXL) has the lowest critical drawdown power. (3) The critical drawdown speed and power are lower with a larger impeller diameter and a smaller immersion depth. (4) The critical drawdown speed and power increase with increasing system viscosity, mean solid concentration, and particle size. The experimental results provide useful guidelines for the advantageous design of the stirred vessel used for the dispersing of floating particles in a viscous system.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Experimental study on the mixing and dispersing of floating particles in viscous system

et al. 2016

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“…The secondary loop near the liquid surface is responsible for solids drawdown, but this loop is characterized by relatively low velocity, low turbulence and radially‐inward reverse flow near the surface. These flow characteristics were reported not applicable to solids drawdown . Although the particles can obtain enough energy from the secondary loop to move downward at low N , the interaction of these two loops just below the surface causes the particles to be caught in a vortex around the shaft.…”

Section: Mechanism Of Floating Solidsdrawdownmentioning

confidence: 78%

“…The primary reason is that this correlation is more suitable for their preferred configurations and cannot consider all the geometric or physical variables. Besides, the complex and dramatic interactions between the geometric variables make it unlikely that a simple empirical correlation could reliably predict N CS in even a small range of tank configurations …”

Section: Comparison With Empirical Correlationmentioning

confidence: 99%

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CFD simulation of complete drawdown of floating solids in a stirred tank

et al. 2014

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Computational fluid dynamics (CFD) simulations were carried out to find a CFD methodology to predict the critical impeller speed (NCS) for the complete drawdown of floating solids in a stirred tank with an up‐ and down‐pumping pitched blade turbine (PBTU and PBTD). CFD models along with six mixing parameters predicted that NCS was 7.5 rps and 5.8 rps, respectively, for PBTU and PBTD, when impeller submergence (S) was equal to half of the liquid height (H/2). Reasonable agreement was observed between CFD simulations and published empirical correlation. NCS was smaller for PBTD relative to PBTU at S = H/2, which agreed with results in the literature. The drawdown mechanisms based on the mean drag, turbulent fluctuations or large scale eddies failed to explain the difference in NCS between PBTU and PBTD. The flow patterns based on a simulated velocity field were further investigated and successfully accounted for this difference.

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Stirred Vessels

Khopkar

Ranade

2019

Chemical Engineering in the Pharmaceutical Industry

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A novel geometry for solids drawdown in stirred tanks

Cited by 38 publications

References 14 publications

Experimental study on the mixing and dispersing of floating particles in viscous system

Experimental study on the mixing and dispersing of floating particles in viscous system

CFD simulation of complete drawdown of floating solids in a stirred tank

Stirred Vessels

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