Laminar Mixing Performances of a Stirred Tank Equipped with Helical Ribbon Agitator Subjected to Steady and Unsteady Rotational Speed

Abstract The flow characteristics and power consumption of corn stover particles in a helical ribbon stirred tank was investigated in the context of simultaneous saccharification and fermentation of corn stover at high solids loading. It was found that the particles in the tank can be divided into conveyed material and core material according to their flow characteristics. The flow of the former materials was frictional regime and the latter was intermediate flow; the conveyed material avalanched into the core at the top of granular bed. The granular bed dilated when the impeller was rotating, which was beneficial for the entrance of liquid enzyme into the solid phase and for the successful proceeding of the saccharification of the corn stover. The power of granular mixing was linearly proportional to the impeller rotational speed due to the discrete characteristic of the particles and flow dynamics of the conveyed material. The ratio of power consumption to the impeller rotational speed (P/N) was linear proportional to loading ratio and the dimensionless torque (M/mgR) was 0.48. The power consumption increased first and then decreased as the corn stover particles evolved from granular/wet granular to paste/slurry. The maximum power consumption was at 83 % (w/w) moisture content.

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Laminar Mixing in Stirred Tank Agitated by an Impeller Inclined

International Journal of Chemical Engineering ◽

10.1155/2012/858329 ◽

2012 ◽

Vol 2012 ◽

pp. 1-10 ◽

Cited By ~ 9

Author(s):

Koji Takahashi ◽

Yoshiharu Sugo ◽

Yasuyuki Takahata ◽

Hitoshi Sekine ◽

Masayuki Nakamura

Keyword(s):

Numerical Simulation ◽

Laminar Flow ◽

Mixing Time ◽

Flow Region ◽

Experimental Results ◽

Stirred Tank ◽

Simulation Methods ◽

Mixing Performance ◽

Laminar Mixing ◽

Numerical Simulation Methods

The mixing performance in a vessel agitated by an impeller that inclined itself, which is considered one of the typical ways to promote mixing performance by the spatial chaotic mixing, has been investigated experimentally and numerically. The mixing time was measured by the decolorization method and it was found that the inclined impeller could reduce mixing time compared to that obtained by the vertically located impeller in laminar flow region. The effect of eccentric position of inclined impeller on mixing time was also studied and a significant reduction of mixing time was observed. To confirm the experimental results, the velocity profiles were calculated numerically and two novel numerical simulation methods were proposed.

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The simplest stirred tank for laminar mixing: Mixing in a vessel agitated by an off-centered angled disc

AIChE Journal ◽

10.1002/aic.14064 ◽

2013 ◽

Vol 59 (8) ◽

pp. 3092-3108 ◽

Cited By ~ 12

Author(s):

D. Bulnes-Abundis ◽

M. M. Alvarez

Keyword(s):

Stirred Tank ◽

Laminar Mixing

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Laminar Mixing in Eccentric Stirred Tank Systems

The Canadian Journal of Chemical Engineering ◽

10.1002/cjce.5450800418 ◽

2008 ◽

Vol 80 (4) ◽

pp. 546-557 ◽

Cited By ~ 65

Author(s):

Mario M. Alvarez ◽

Paulo E. Arratia ◽

Fernando J. Muzzio

Keyword(s):

Stirred Tank ◽

Laminar Mixing

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Effect of Impeller Speed Perturbation in a Rushton Impeller Stirred Tank

Journal of Fluids Engineering ◽

10.1115/1.4006471 ◽

2012 ◽

Vol 134 (6) ◽

Cited By ~ 1

Author(s):

Somnath Roy ◽

Sumanta Acharya

Keyword(s):

Kinetic Energy ◽

Turbulent Kinetic Energy ◽

Rotational Speed ◽

Stirred Tank ◽

Azimuthal Direction ◽

Mean Flow ◽

Eddy Simulation ◽

Large Eddy ◽

The Mean ◽

Rushton Impeller

Flow inside an unbaffled Rushton-impeller stirred tank reactor (STR) is perturbed using a time dependent impeller rotational speed. Large eddy simulation (LES) revealed that the perturbation increased the width of impeller jet compared to the constant rotational speed cases. The turbulent fluctuations were also observed to be enhanced in the perturbed flow and showed higher values of production and convection of turbulent kinetic energy. Changes in the mean flow-field during the perturbation cycle are investigated. The trailing edge vortices were observed to propagate farther both in the radial and azimuthal direction in the perturbed case. Production of turbulent kinetic energy is observed to be related to the breakup of the impeller jet in the perturbed case. Dissipation of turbulent kinetic energy is augmented due to the perturbation ensuring a better mixing at the molecular scale.

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