Macro- and micromixing studies in an unbaffled vessel agitated by a Rushton turbine

Assirelli, Melissa; Bujalski, W.; Eaglesham, Archie; Nienow, Alvin W.

doi:10.1016/j.ces.2007.07.074

Cited by 103 publications

(54 citation statements)

References 19 publications

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“…The change of the blade tip velocity of the impeller, v i , calculated with Equation (1), is added to the figure for comparison. The right vertical axes of the figure are scaled relative to the average impeller tip velocity, v iav , calculated using Equation (2). At 70 mm height, corresponding to upstream circulation flow, v z exhibited slight time-dependence and showed nearly unchanged values over M Yoshida et al Figure 3(a) shows that flow whose v z decreased considerably was observed to follow near the surface of the vessel bottom.…”

Section: Liquid Flow Pattern and Velocitiesmentioning

confidence: 91%

Liquid flow circulating within an unbaffled vessel agitated with an unsteady forward–reverse rotating impeller

Yoshida

Wakura

Yamagiwa

et al. 2010

J of Chemical Tech & Biotech

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Liquid-phase mixing is a common operation, often performed in vessels using mechanically rotating impellers. To enhance axial mixing the vessels are generally equipped with baffles; however, in industries where cleaning the vessel interior is a major concern, i.e. food and pharmaceuticals, and crystallization, where baffles can disturb particle growth, unbaffled vessels are preferred. One method of agitation in unbaffled vessels is an impeller that periodically changes either the direction or rate of rotation: so-called unsteady rotation.

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Section: Liquid Flow Pattern and Velocitiesmentioning

confidence: 91%

Liquid flow circulating within an unbaffled vessel agitated with an unsteady forward–reverse rotating impeller

Yoshida

Wakura

Yamagiwa

et al. 2010

J of Chemical Tech & Biotech

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“…However, in order to avoid aeration and vibration, the process setting below critical speed is desired. In the scale up process, when the large scale is used, the swirling and unstable flow conditions are observed when the central vortex reaches the impeller; it can also give rise to mechanical damage [3]. Conversion of impeller rotation kinetic energy to the potential energy (depth of vortex) can be used to determine the critical speed.…”

Section: Critical Speedmentioning

confidence: 99%

“…Although baffled tanks are widely used in industrial applications, there are cases in which the use of baffled tanks may be undesirable. Removing the baffles will change the flow characteristics and therefore the mixing rate, thus altering the effectiveness of the tank design for the reaction and phase contacting processes [2,3]. Formation of the central vortex on the liquid free surface in an unbaffled stirred tank is obvious when the vessel is operated without a top cover.…”

Section: Introductionmentioning

confidence: 99%

Vortex Depth Analysis in an Unbaffled Stirred Tank With Concave Blade Impeller

Devi¹,

Kumar²

2017

ChChT

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Abstract. 1 The present study was carried out by experimenting in a stirred tank of unbaffled system employed with concave blade impeller. In this study the influence of impeller diameter (d), tank diameter (D) and impeller clearance depth ( C ) on vortex depth is investigated at various impeller rotational speeds. The higher vortex depth is observed when the impeller is closer to the tank bottom. Relative vortex depth increases with the increase in the impeller diameter in all cases of impeller clearance depth at constant D. Smaller tank diameter gives higher relative vortex depth, when d is constant at different impeller clearance depths. Critical speed is found decreasing with the increase in C/D and d/D ratio. Finally, a scale up criteria for relative vortex depth has been developed, which is valid for geometrically similar conditions.

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“…Mechanically-stirred tanks are extensively used in the chemical and process industries, including applications in the production of chemicals, pharmaceuticals, foods, paper, minerals, metals and many others [3][4][5][6]. Typical operations which are usually carried out in mixing tanks include blending of liquids, contacting of a liquid with a gas or second immiscible liquid, solids suspension and chemical reactions.…”

Section: Introductionmentioning

confidence: 99%

Study of gas–liquid mixing in stirred vessel using electrical resistance tomography

Sher

Sajid

Tokay

et al. 2016

Asia-Pacific J Chem Eng

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Hamad (2016) Study of gas-liquid mixing in stirred vessel using electrical resistance tomography. Asia-Pacific Journal of Chemical Engineering . ISSN 1932ISSN -2143 Access from the University of Nottingham repository: http://eprints.nottingham.ac.uk/35359/1/Manuscript%20ERT.pdf Copyright and reuse:The Nottingham ePrints service makes this work by researchers of the University of Nottingham available open access under the following conditions. This article is made available under the University of Nottingham End User licence and may be reused according to the conditions of the licence. For more details see: http://eprints.nottingham.ac.uk/end_user_agreement.pdf A note on versions:The version presented here may differ from the published version or from the version of record. If you wish to cite this item you are advised to consult the publisher's version. Please see the repository url above for details on accessing the published version and note that access may require a subscription. AbstractThis study presents a full operation and optimisation of a mixing unit; an innovative approach is developed to address the behaviour of gas-liquid mixing by using Electrical Resistance Tomography (ERT). The validity of the method is investigated by developing the tomographic images using different numbers of baffles in a mixing unit. This technique provided clear visual evidence of better mixing that took place inside the gasliquid system and the effect of a different number of baffles on mixing characteristics. For optimum gas flow rate (m 3 /s) and power input (kW), the oxygen absorption rate in water was measured. Dynamic gassingout method was applied for five different gas flow rates and four different power inputs to find out mass transfer coefficient (KLa). The rest of the experiments with one up to four baffles were carried out at these optimum values of power input (2.0 kW) and gas flow rate (8.5×10 -4 m 3 /s). The experimental results and tomography visualisations showed that the gasliquid mixing with standard baffling provided near the optimal process performance and good mechanical stability, as higher mass transfer rates were obtained using a greater number of baffles. 2 mixing was remarkably reduced in the case of four baffles as compared to without any baffle. The process economics study showed that the increased cost of baffles installation accounts for less cost of energy input for agitation. The process economics have also revealed that the optimum numbers of baffles are four in the present mixing unit and the use of an optimum number of baffles reduced the energy input cost by 54%.

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Macro- and micromixing studies in an unbaffled vessel agitated by a Rushton turbine

Cited by 103 publications

References 19 publications

Liquid flow circulating within an unbaffled vessel agitated with an unsteady forward–reverse rotating impeller

Liquid flow circulating within an unbaffled vessel agitated with an unsteady forward–reverse rotating impeller

Vortex Depth Analysis in an Unbaffled Stirred Tank With Concave Blade Impeller

Study of gas–liquid mixing in stirred vessel using electrical resistance tomography

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