Gas—liquid mixing studies with multiple up‐ and down‐pumping hydrofoil impellers: Power characteristics and mixing time

Hari-Prajitno, D.; Mishra, V. P.; Takenaka, Katsuhide; Bujalski, W.; Nienow, Alvin W.; McKemmie, J.

doi:10.1002/cjce.5450760612

Cited by 75 publications

(42 citation statements)

References 8 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Lately at Fg value of 0.07 and above an average decrease of about 4.4% in the ratio of Pg/P was observed; which ends up with Pg/P value of 0.4 against Fg, 0.17. This fall in Pg/P with rising gas flow Qg was linked with the evolving size of the gas occupied voids around the impeller blades, which has been comprehensively stated in the literature [26]. The power curve obtained is consistent with the one in the literature [27,38].…”

Section: Optimisation and Process Economics 341 Gassed To Un-gassedsupporting

confidence: 79%

See 1 more Smart Citation

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

Sher

Sajid

Tokay

et al. 2016

Asia-Pacific J Chem Eng

View full text Add to dashboard Cite

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%.

show abstract

Section: Optimisation and Process Economics 341 Gassed To Un-gassedsupporting

confidence: 79%

“…ERT has also been utilised to study the mixing behaviour of gas-liquid-solid systems, fibre suspensions, pulp mixing, polymer particles mixing and many more [19][20][21][22][23][24][25]. But less has been written about the use of ERT to study the gas-liquid mixing phenomena [26].…”

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

View full text Add to dashboard Cite

show abstract

“…In this application, the downpumping axial-flow impellers perform poorly. Also, the complete dispersion torque requirements of the downpumping axial-flow impellers are susceptible to large fluctuations as the rising gas flow opposes the liquid pumping of the impeller (Hari-Prajitno et al, 1998). The complete dispersion torques of the up-pumping axial-flow and radialflow impellers do not exhibit large fluctuations and are of similar magnitudes, with the up-pumping axial-flow impellers having lower torque requirements in general.…”

Section: S =mentioning

confidence: 86%

Agitator design for solids suspension under gassed conditions

Lehn

Myers

Barker³

1999

Can J Chem Eng

View full text Add to dashboard Cite

Design of mechanical agitators for solids suspension under gassed conditions can be achieved using a constant ungassed torque criterion if the solids suspension task is more difficult than the gas dispersion task. When gas dispersion is the more difficult task, design for complete gas dispersion will ensure solids suspension. Evidence supporting this approach is very strong for radial-flow impellers, but less so for up-pumping and down-pumping axial-flow impellers.La conception d'agitateurs mecaniques pour la suspension de solides en conditions aeries peut Ctre effectuee a I'aide d'un critere de couple non aere constant lorsque la suspension des solides est plus difficile a realiser que la dispersion du gaz. Lorsque la dispersion du gaz est plus difficile a realiser. une conception basee sur la dispersion complete du gaz assurera la suspension des solides. Les preuves soutenant cette approche sont tres evidentes pour les turbines a ecoulement radial, mais moins pour les turbines a ecoulement axial a pompage ascendant eta pompage descendant.Keywords: gassed solids suspension, solids suspension, gas dispersion, three-phase agitation.gitator design for three-phase (gassolid-liquid) opera-A tion is a challenging and industrially-relevant task. Chapman et al. (1983) investigated this problem in detail, relating the just-suspended speed to liquid and solid physical properties in a Zwietering-like (1958) manner. For radial-flow impellers they found that the increase in justsuspended speed under aerated conditionswas linearly related to the volumetric gas flow rate. Suchsoa simple relation was not found for up-pumping or downpumping axial-flow impellers. Frijlink et al. (1990) related the increase in just-suspended speed under aerated conditions to the cavity structure that forms on aerated impeller blades and the associated drop in impeller power draw. They correlated their gassed justsuspended speed data in the following manner:where the just-suspended power number was defined in terms of the liquid density:The exponent n of this correlation was found to be 1.1 for down-pumping axial-flow impellers, and 2 for radial-flow and up-pumping axial-flow impellers. Recently, Pantula and Ahmed (1 997) found these same exponents and pointed out that an exponent of 2, as found for radial-flow and up-pumping axial-flow impellers, corresponds to a constant torque criterion; that is, the just-suspended torque under gassed conditions is equal to the just-suspended torque under ungassed conditions *Author to whom correspondence may be addressed. E-mail address: **Present address: Fluent Inc., Lebanon, NH 03766, USA kmyersl @engr.udayton.edu (qsg = q s o ' where torque is defined as M = P/27ch9. There is no apparent physical meaning for an exponent of 1.1 as was found for down-pumping axial-flow impellers.The present work examines the constant-torque design criterion including comparison of the difficulty of the solids suspension and gas dispersion tasks. In addition, solid property effects are studied, since they were not considered b...

show abstract

“…Three types of turbines have been studied: a novel vertically-asymmetric concave-blade turbine [19,20] and pitched-blade turbines pumping either downwards or upwards. This latter mode is being considered very promising [21,22] because of the more stable flow field with respect to the standard, down-pumping operational mode. The flow behavior has been described in terms of the axial dispersion model.…”

Section: Introductionmentioning

confidence: 99%

Gas Flow Behavior in a Two‐Phase Reactor Stirred with Triple Turbines

Majirova¹,

Pinelli²,

Machoň³

et al. 2004

Chem Eng & Technol

View full text Add to dashboard Cite

Gas behavior was studied in a gas-liquid reactor stirred with multiple turbines. Triple PBTs pumping either down or up and BT-6's were used. The behavior of coalescing (water) and non-coalescing (sodium sulfate solution) systems was investigated. The gas phase behavior was characterized by means of the RTD and modeled with the axial dispersion model. This model was confirmed to interpret the experimental data well for water and satisfactorily for the coalescence-inhibiting solutions. The influence of the operating conditions, turbine type and system coalescing behavior on the model parameters is discussed. Comparison is also made with similar data regarding Rushton turbines and high-solidity ratio hydrofoils, as well as gas holdup.

show abstract

Gas—liquid mixing studies with multiple up‐ and down‐pumping hydrofoil impellers: Power characteristics and mixing time

Cited by 75 publications

References 8 publications

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

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

Agitator design for solids suspension under gassed conditions

Gas Flow Behavior in a Two‐Phase Reactor Stirred with Triple Turbines

Contact Info

Product

Resources

About