Rotary sloshing induced by impeller action in unbaffled stirred vessels

Busciglio, Antonio; Montante, Giuseppina Maria Rosa; Kracík, Tomáš; Moucha, T.; Paglianti, Alessandro

doi:10.1016/j.cej.2017.02.099

Cited by 13 publications

(6 citation statements)

References 18 publications

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“…Therefore, the vessel cannot be considered equal to three independent vessels. For instance, typical features of unbaffled vessels of low height-to-tank diameter ratio stirred with coaxial shafts, such as the macro-instabilities reported by Pieralisi et al 32 and Busciglio et al, 33 are not expected in the present configuration. Also, the feedstock distribution in the vessel volume depends on the location of the feed with respect to the rotating shafts, which will be different in the case of three independent vessels.…”

Section: Power Consumptionmentioning

confidence: 98%

Power Consumption and Fluid Mixing in a Scale-Down Geometry of a Stirred Digester for Biogas Production

et al. 2023

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A unconventional stirred tank of geometry typically adopted for the production of biogas is experimentally investigated with pseudo-plastic model fluids. The apparent viscosities of the fluids, based on the Metzner–Otto method, are in the range of 39–264 mPa·s, resulting in a range of rotational Reynolds number equal to 17–648. The power consumption of the three top-entering agitators is measured by a strain gauge technique, and the power number curve is obtained in the full range of flow regimes, going from laminar to fully turbulent conditions. The flow field measured by particle image velocimetry allows us to observe the fluid circulation patterns and their variations in different operative conditions. The measurements reveal relatively low axial and radial velocities, especially toward the bottom of the tank, that may hinder solid feedstock suspension and subsequent biogas production. Significant changes in the flow patterns are observed with small variations in the impeller speed and the mixture viscosity. The homogenization dynamics of a tracer obtained by planar laser-induced fluorescence leads us to estimate the dimensionless mixing time, a trend similar to that observed for conventional stirred vessel geometries. The detailed fluid dynamics information collected by a combination of different techniques can contribute to optimize the energy requirement and to avoid failure of the biogas production due to poor fluid mixing.

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Section: Power Consumptionmentioning

confidence: 98%

Power Consumption and Fluid Mixing in a Scale-Down Geometry of a Stirred Digester for Biogas Production

et al. 2023

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“…Impellers can be used in different mixing processes, such as blending of substances, generating gas-liquid exchange or suspending particles in a fluid medium [14]. Different types of impellers produce distinct flows that can be used for different purposes.…”

Section: Impeller Based Aerationmentioning

confidence: 99%

Vortex Impeller-Based Aeration of Groundwater

Griend

Warrener

Akker³

et al. 2022

Water

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Iron oxidation and removal from groundwater is a necessary and costly process in drinking water production. In most cases, iron removal is done via aeration, succeeded by precipitation. Most systems for aeration are based on increasing the interfacial area via injecting air in the system or spraying. Both methods have disadvantages, like clogging and formation of aerosols. In this study, a new vortex-based flow-through reactor consisting of a cylindrical tank with an impeller located at the bottom was studied regarding its aeration and iron oxidation capabilities in groundwater. During the aeration experiments, the flow rate, impeller rotation and aerated volume were varied. A nondimensional constant α was proposed to relate the system’s physical characteristics and its aeration capabilities, expressed in dissolved oxygen and system volumetric mass transfer coefficient (KLa). Three distinct operational regimes were defined: formation, complete and bubble regime. These regimes showed very specific characteristics regarding the air–water interface structure and the area to volume ratio, resulting in different aeration capabilities and iron oxidation efficiency values. The system presented KLa values similar to commercially available aeration systems, especially inside the bubble regime. By using dimensionless coefficients, the presented analysis provided the basis for the design of continuous impeller aeration and oxidation systems of arbitrary size.

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“…In this situation, the liquid phase will be forced to rotate strongly at the high speed of the impeller, which result in free‐surface fluctuations and the formation of large vortices, 20,21 has a significant impact on the flow and mixing processes 22,23 . Especially in a unbaffled stirred tank with free‐surface, it has been reported that the strong rotation of the liquid phase could disperse the air located at the top of the stirred tank into the liquid in the form of small bubbles, 22,24 when it would be improper to ignore the free‐surface. In CFD, the movement of gas–liquid free‐surface could be calculated by the volume of fluid (VOF) model 25,26 .…”

Section: Introductionmentioning

confidence: 99%

Study of free‐surface and solids suspension in top‐sealed tanks stirred by pitched blade turbine impellers through DEM‐VOF method

Bao

Kang

Wang

et al. 2022

Asia-Pacific J Chem Eng

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A coupled method of discrete element method (DEM) and volume of fluid (VOF) is applied to study the particle suspension in top‐sealed solid–liquid tanks with a free‐surface. VOF is used to track the gas–liquid free‐surface, and DEM is used to calculate the movement and interaction of particles. As the air between the cover and free‐surface in a sealed tank is very limited, the free‐surface evolution process that a big vortex is generated quickly and then shrinks to a smaller one in sealed stirred tanks is reported first in this paper. In addition, the effects of pitched blade turbine (PBT) with different blade pitched angles (including 30°, 45°, 60°, 75°, and 90°) on solid suspension, free‐surface, and power number are investigated. Finally, the relationships between particle motion and fluid flow during the stirring are studied carefully. Fluid flow plays a dominant role during the start‐up of the stirring; and then, due to the contact of particles, some particles could obtain the larger velocity than the fluid. The results obtained here are helpful to design the sealed stirred tanks with PBT.

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Rotary sloshing induced by impeller action in unbaffled stirred vessels

Cited by 13 publications

References 18 publications

Power Consumption and Fluid Mixing in a Scale-Down Geometry of a Stirred Digester for Biogas Production

Power Consumption and Fluid Mixing in a Scale-Down Geometry of a Stirred Digester for Biogas Production

Vortex Impeller-Based Aeration of Groundwater

Study of free‐surface and solids suspension in top‐sealed tanks stirred by pitched blade turbine impellers through DEM‐VOF method

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