Critical Impeller Speed for Suspending Solids in Aerated Agitation Tanks

Zhu, Yonggang; Wu, Jie

doi:10.1002/cjce.5450800417

Cited by 30 publications

(13 citation statements)

References 13 publications

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“…The suspension of solid particles in a three phase gas-liquid-solid system has been studied by Zlokarnik and Judat (1969), Queneau et al (1975), Subbarao and Taneja (1979), Wiedmann and Efferding (1980), Chapman et al (1983), Wong et al (1987), Rewatkar et al (1991), Zhu and Wu (2002), and Dohi et al (2004). These studies have been critically reviewed by Kasat and Pandit (2005).…”

Section: Solid Suspension Studiesmentioning

confidence: 96%

“…In this method, computational domain is divided into impeller zone (rotating reference frame) and stationary zone (stationary reference frame). For all the simulations, the boundary of the rotating domain was positioned at r = 0.16 and 0.10 m z 0.24 m. For the case of Zhu and Wu (2002), the rotating domain was positioned at r = 0.12 and 0.08 m z 0.18 m. Tetrahedral elements were used for meshing the geometry and a good quality of mesh was ensured throughout the computational domain using the GAM-BIT mesh generation tool. As regards the particular mesh quality, we have been restricted to use tetra mesh elements due to more number of case studies and complex geometry.…”

Section: Referencesmentioning

confidence: 99%

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CFD simulations of gas–liquid–solid stirred reactor: Prediction of critical impeller speed for solid suspension

Murthy

Ghadge

Joshi

2007

Chemical Engineering Science

151

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Section: Solid Suspension Studiesmentioning

confidence: 96%

Section: Referencesmentioning

confidence: 99%

CFD simulations of gas–liquid–solid stirred reactor: Prediction of critical impeller speed for solid suspension

Murthy

Ghadge

Joshi

2007

Chemical Engineering Science

151

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“…Further more, the relation is in dimensional form and thus is system dependent, thereby limiting its use for scale-up. Zhu and Wu (2002)…”

Section: Correlations For N Js N Js N and N Jsg N Jsg Nmentioning

confidence: 99%

Review on Mixing Characteristics in Solid‐Liquid and Solid‐Liquid‐Gas Reactor Vessels

Kasat

Pandit

2005

Can J Chem Eng

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REVIEW In carrying out the physical mass transfer processes and chemical reactions in the gas-liquid-solid systems, in which liquid is the continuous phase and where the solid and gas phase are the discontinuous phases, there is often a need to suspend the solid particles in the presence of gas. Stirred tanks are often employed for this purpose as slurry reactors, especially for discontinuous/batch operations and for smaller production levels. The main task of the stirrer in an aerated suspension system is to suspend the solids particles completely so as to expose their total surface area for the reaction and/or for mass transfer, to disperse the gas uniformly throughout the vessel and to provide liquid mixing patterns for an intimate contact between the phases. Thus, mechanically agitated reactors are extensively used in the industry to handle the three-phase systems and fi nd application in a wide range of processes such as catalyzed oxidation and hydrogenation reactions, polymerization, evaporative crystallization, aerobic fermentation, froth fl oatation, microbial coal desulphurization, gold leaching, and bacterial sulphide oxidations. In all these applications, simultaneous dispersion of gas and the suspension of the solids by the impellers are of vital importance. Review on Mixing Characteristics in SolidReview on Mixing Characteristics in SolidLiquid and Solid-Liquid-Gas Reactor VesselsGopal R. Kasat and Aniruddha B. Pandit* Chemical Engineering Division, University Institute of Chemical Technology (UICT), University of Mumbai, Matunga, Mumbai 400-019, IndiaFor a reliable design of a three-phase stirred tank reactor, it is important to know the complex hydrodynamic problems (i.e. phase-phase interactions) associated with the demands of simultaneous gas dispersion and solids suspension with a single or multiple impellers. One of the most important parameters for the assessment of the performance of the impellers for solid suspension (both in the absence and in the presence of gas), is the minimum impeller speed required for the complete offbottom suspension of the solids in the vessel. (Zwietering, 1958;Wiedmann et al., 1980;Chapman et al., 1981 Chapman et al., , 1983Frijlink et al., 1990;Rewatkar et al., 1991a; Mechanically agitated reactors with single and multiple impeller systems are used in the industry for the various three-phase mixing processes such as crystallization, fermentation, and hydrogenation, etc. The paper reviews the experimental work reported in the literature along with different techniques used for the measurement of the specifi c quantities such as minimum or critical impeller speed for solid suspension. The work critically surveys the literature and makes specifi c recommendations for the use of appropriate correlations and conditions to be used for the success of such equipment. This assessment will put all the relevant literature on a common footing and will help to validate work reported earlier.Les réacteurs agités mécaniquement munis d'une seule turbine et de turbines mult...

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“…Flow regimes of liquid-solid stirred reactor (Kraume, 1992) proposed a correlation for the minimum impeller speed for complete suspension of solids on the basis of dimensional analysis of the results obtained from over a thousand experiments. Since then, numerous papers on determination of critical impeller speed for different operating conditions and different types of impellers have been published (Bohnet and Niesmak, 1980;Chapman et al, 1983a;Kraume, 1992) for liquid-solid stirred reactors, and a few of them (Zlokarnik & Judat, 1969;Chapman et al, 1983b;Warmoeskerken et al, 1984;Nienow et al, 1985;Bujalski et al, 1988;Wong et al, 1987;Frijlink et al, 1990;Rewatkar et al, 1991;Dylag & Talaga, 1994;Dutta & Pangarkar, 1995;Pantula & Ahmed, 1998;Zhu & Wu, 2002) have been extended towards the development of correlations for the critical impeller speed for gas-liquid-solid stirred reactors. According to the literature, in general, N jsg is always greater than N js .…”

Section: Introductionmentioning

confidence: 99%