JOURNAL OF CHEMICAL ENGINEERING OF JAPAN
Print ISSN : 0021-9592
Volume 42 , Issue 11
Special Issue for the 2nd Asian Conference of Mixing
Showing 1-12 articles out of 12 articles from the selected issue
  • Koji Takahashi, Meguru Kaminoyama, Yutaka Tada
    Type: Preface
    2009 Volume 42 Issue 11 Pages 788
    Published: November 20, 2009
    Released: November 20, 2009
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    This special issue is an outcome of the 2nd Asian Conference on Mixing (ACOM) held in Yonezawa, Japan on October 7–9, 2008. The main objectives of this conference were to provide a forum for the exchange of information and promote and facilitate academic discussions, collaboration and interactions between participants from Asia and other countries in advancing polymer engineering and mixing technology. This conference consisted of 5 plenary lectures by authorized researchers and 35 scientific papers (18 oral and 17 poster presentations) by scientists and engineers from 7 countries. During the conference, the scientific committee was held to decide that next conference will be held at Korea in October 2010.

    The Fluid & Particle Processing Division, the Society of Chemical Engineers, Japan decided to publish this special issue in the Journal of Chemical Engineering of Japan (JCEJ). All the manuscripts were refereed following the standard procedure for papers submitted to the regular issues of the JCEJ. Eleven papers including one review paper were approved for publication by the referees.

    More than 32 professionals worked as referees for peer reviewing the submitted manuscripts. We, the editors for this special issue, are highly grateful to those referees for their collaboration in the reviewing process. We also express our appreciation to Prof. Yoshiyuki Yamashita at Tokyo University of Agriculture and Technology, the Editor-in-Chief of the JCEJ, for his solid support and to Ms. Yamashita in the editorial office for her persistent devotion to the preparation of this special issue.
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  • Alvin William Nienow
    Type: Journal Review
    2009 Volume 42 Issue 11 Pages 789-796
    Published: November 20, 2009
    Released: November 20, 2009
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    This paper considers recent work, mainly from the University of Birmingham, on stirred bench scale bioreactors. It focuses on mixing as it affects biological performance on scale-up, particularly the impact of stress on organisms as a result of fluid dynamic phenomena (mixing), namely mechanical stresses or spatial and temporal inhomogeneities. The work uses new experimental techniques (flow cytometry and advanced image analysis) and covers mycelial, bacterial (both including GMO’s) and yeast (including beer) fermentations and animal cell culture in batch, fed-batch and chemostat conditions. By using gas blending to control dissolved oxygen (dO2), the impact of mechanical stresses due to agitation and aeration can be decoupled from dO2 effects. With mycelia, image analysis of all biomass shows damage from mechanical stresses generated by agitation but not by aeration; and that productivity may be affected. Also, on scale-up, such damage is reduced. With yeast and bacteria, flow cytometry does not indicate damage. On the other hand, plant scale studies with E. coli give lower biomass but higher cell viability compared to the well-mixed bench-scale. When the locally high nutrient, low dO2 and high pH values found on the plant scale near feed points are simulated at bench-scale, similar results to plant scale are obtained. Similar scale-down results are obtained with a recombinant E. coli. Simulated large-scale beer production, where the inhomogeneities are associated with yeast distribution and temperature, also indicates a poorer performance. Though perceived to be more sensitive to mechanical stresses, somewhat similar conclusions can be drawn for animal cell culture, with stresses associated with bursting bubbles being potentially the most significant. These perceptions lead to problems associated with high dissolved carbon dioxide (pCO2) and osmolality in large-scale cell culture. A related topic is the search for ‘low shear’ impellers, a concept useful to mixer manufacturers but misleading to users.
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  • Maya Farhat, Louis Fradette, Hiro Horiguchi, Ryuichi Yatomi, Philippe ...
    Type: Research Paper
    2009 Volume 42 Issue 11 Pages 797-803
    Published: November 20, 2009
    Released: November 20, 2009
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    The mixing performance of the Superblend coaxial mixer consisting of a Maxblend® impeller and a helical ribbon mounted on two independently actuated coaxial shafts are experimentally investigated. The work focuses on the effect of the rotating modes (co- and counter-rotating) in the laminar, transition and turbulent flow regimes, and the performance is compared with previously studied dual shaft coaxial mixers. Power consumption and mixing time experiments using a discoloration technique have been conducted using Newtonian aqueous solutions of corn syrup. Based on mixing efficiency criteria, this study confirms that the co-rotating mode consistently yields the best results in the laminar and early transition regimes. Recent power correlations introduced by our group for coaxial mixers have been tested for their applicability and they are proven to be readily applicable for the Superblend. This work demonstrates the remarkable efficiency of the Superblend and its superiority when compared to standard coaxial mixers based on different mixing efficiency criteria.
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  • Zauyah Zamzam, Koji Takahashi, Shoji Morinaga
    Type: Research Paper
    2009 Volume 42 Issue 11 Pages 804-809
    Published: November 20, 2009
    Released: November 20, 2009
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    Large impellers are commonly used for a wide range of liquid viscosities, and can mix well in a mixing tank thoroughly. However, large impellers are not the solution for all mixing problems. Therefore, to improve the mixing performance of large impellers, a new method should be investigated. In this research, unsteady agitation is subjected to a Maxblend® impeller, which is one of the most popular large impellers, and investigation has been experimentally carried out in two scales, namely small and large scale mixing tanks. A decolorization reaction is adopted to measure the mixing time, and a linear equation which correlates the dimensionless mixing time for unsteady agitation is proposed. The experimental results show that mixing time can be reduced in a stirred tank when unsteady stirring approaches are used. However, from the investigation of these two scales of stirred tank in term of their time periodic interval, we understand the difference of mixing performance for both scales.
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  • Juan Huang, Yuelong Ma, Gance Dai
    Type: Research Paper
    2009 Volume 42 Issue 11 Pages 810-818
    Published: November 20, 2009
    Released: November 20, 2009
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    Extensive investigations were carried out to determine the mixing time (tm) in bubble columns with diameter of 0.2, 0.3, 0.4 and 0.8 m equipped with different type of spargers for different aspect ratios (H/D) of 0.8–8. The superficial gas velocity (Ug) varied from 0.01 to 0.25 m/s. The effect of temperature variations in the range of 20–90°C and surface tension variations (50–70 N·m) on tm was investigated. Experiments proved that as Ug increased, tm decreased in the homogenous regime and leveled off in the heterogeneous regime in tap water systems at ambient and elevated temperatures. There existed a critical aspect ratio (H/D)cri = 2 where tm varied with H/D reversely. The sparger configuration had a weak effect on tm. By placing the gas distributor pipe at the off centered position, tm could be decreased. In acetic acid solution, there existed a “jump point” in the tm vs. Ug curve at Ucri = 0.1 m/s, and tm was 2–3 times that in the tap water system at this point under otherwise identical conditions. The effect of temperature was determined by distinguishing the test temperature into a far from the boiling point stage and a near the boiling point stage. tm decreased marginally in the former stage and drastically in the latter. The surface tension had no notable effect on the liquid phase mixing behavior. Empirical tm correlations were proposed for various pipe distributors by considering the effect of (H/D)cri.
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  • Hideki Tokanai, Hiroki Yabune, Eiji Harada, Masafumi Kuriyama
    Type: Research Paper
    2009 Volume 42 Issue 11 Pages 819-825
    Published: November 20, 2009
    Released: November 20, 2009
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    An experimental study has been carried out on the volume of the cavities formed behind pitched-blades of turbine impeller in an aerated agitated vessel with highly viscous Newtonian liquid. Some kinds of pitched-blade turbines with different diameters and inclination-angles are used to examine the effects of impeller configuration and operating conditions on the total volume of the stable cavities remaining behind the blades even after stopping aeration. The experimental results are provided for each type of impeller and discussed with the consideration on the forces acting on the cavity. A balance equation is proposed for the forces, such as buoyant force, inertia force caused by axial flow, and force arising from dynamic pressure. The balance equation results in the correlation equations for each stable cavity volume in the laminar or turbulent flow region, respectively.
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  • Mitsumasa Kimata, Waldemar Bujalski, Alvin William Nienow, Masahiro Ha ...
    Type: Short Communication
    2009 Volume 42 Issue 11 Pages 826-830
    Published: November 20, 2009
    Released: November 20, 2009
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    Synthesis of silica particles by hydrolysis of metal alkoxides in a liquid-phase reaction was investigated two small stirred glass vessels with different bottom geometries were used. It is known that the size of product particles is influenced by the reactant concentration and reaction temperature, but the effect of different configuration by agitators on the products has not been investigated to date. In this study, influence of flow patterns on the production of mondispersed silica particles was investigated on a laboratory scale by using glass flasks with two geometries (round- and flat-bottom) and varying the impeller speed. It was found that the agitation speed and the geometry of the reaction vessel can have a significant effect on the monodispersibility of the produced silica particles under some synthesis conditions. Both impeller speed and flow patterns developed in the liquid phase, which are related to the vessel geometry, can have a significant effect on the properties of the produced particles.
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  • Kenji Oda, Meguru Kaminoyama
    Type: Research Paper
    2009 Volume 42 Issue 11 Pages 831-838
    Published: November 20, 2009
    Released: November 20, 2009
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    A new mathematical model is developed to solve transport of FeO with an apparent redox reaction coupled with a model of thermal convection in a glass tank furnace. A numerical method is proposed to calculate the distribution of FeO with a non-equilibrium reaction in a flow field. Computer simulation enables prediction of the FeO concentration, thermal conductivity, and optical characteristics. It is apparent that chemical homogeneity is attained by residence time and temperature, and that it is more uniform than the mechanical homogeneity by glass flow.
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  • Mostafa Barigou, Fabio Chiti, Paulina Pianko-Oprych, Antonio Guida, Lu ...
    Type: Research Paper
    2009 Volume 42 Issue 11 Pages 839-846
    Published: November 20, 2009
    Released: November 20, 2009
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    Positron emission particle tracking (PEPT) is a new technique allowing the quantitative study of flow phenomena in three dimensions in opaque systems that cannot be studied by techniques based on optical methods such as particle image velocimetry (PIV) or Laser Doppler anemometry (LDA). Here, the technique is initially described along with studies validating the technique, comparing velocity profiles from a Rushton and a pitched blade turbine in turbulent transparent systems from PEPT with PIV and LDA. Subsequently, results are presented showing, for the first time, the spatial distribution of suspended particles of two sizes throughout the vessel; and velocity profiles for the solid and liquid phase in low viscosity and high solid concentration three-phase (s–g–l) systems under fully turbulent conditions. Finally, three-dimensional flow fields, occupancy maps and Poincaré maps are presented, again for the first time, arising from the mixing of two different non-Newtonian shear thinning yield stress slurries. Clearly, PEPT offers many possibilities for obtaining quantitative data previously unobtainable for a wide range of important mixing problems relevant to a broad spectrum of the process industries.
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  • Hiroshi Takeda, Yutaka Tada, Setsuro Hiraoka
    Type: Research Paper
    2009 Volume 42 Issue 11 Pages 847-856
    Published: November 20, 2009
    Released: November 20, 2009
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    Low-frequency fluctuations in agitated vessels are found to be unstable phenomena of flows. The fluctuations can be generated when flows are ejected from an impeller into rotating flows formed by the rotating impeller in which centrifugal force instabilities occur. It is also shown that low-frequency fluctuations can be represented by carrying out a direct numerical simulation and promote the mixing of fluids in agitated vessels.
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  • Yoshihito Kato, Yutaka Tada, Mami Inoue, Yuichiro Nagatsu, Young-Sei L ...
    Type: Short Communication
    2009 Volume 42 Issue 11 Pages 857-860
    Published: November 20, 2009
    Released: November 20, 2009
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    The hydrodynamics of a rotating baffled shaking cylindrical vessel was studied. When shaking frequency exceeded a critical value, the baffled shaking cylindrical vessel was operated in the out of phase mode and the wave height of liquid free surface in the vessel suddenly decreased. The mixing performance of the baffled vessel was lower than that of the nonbaffled vessel because of the sudden transition of the flow pattern in the baffled vessel from a rotational-wave type to a progressive-wave type at low shaking frequency. The shaking frequency can be correlated with the Froude number and the baffle conditions only, and it did not depend on the Reynolds number.
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  • Nobutatsu Katagiri, Shinichi Ookawara, Shiro Yoshikawa, Kohei Ogawa
    Type: Research Paper
    2009 Volume 42 Issue 11 Pages 861-867
    Published: November 20, 2009
    Released: November 20, 2009
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    Mixing spectrum is proposed as a new index to express the mixing performance from a new viewpoint. The mixing spectrum is a terminology by the authors and the concept was built by making use of whole mixing capacity index. That is, the mixing spectrum is interpreted as the contribution from each scale of moving distance of fluid to the whole mixing capacity of an impeller. Specifically, the mixing spectrum can be obtained based on the value of whole mixing capacity index that is calculated by changing the value of the smallest scale of moving distance of fluid little by little. From the results of a new index, it can be said that the whole mixing capacity increases as the impeller rotation speed increases regardless of impeller style, there is no noticeable influence of the impeller rotation speed to the probability density distribution of moving distance of fluid and the mixing spectrum index distribution in the position of the relative distance specific to each impeller and the value of mixing spectrum index at the peak increases according to the impeller rotation speed because of the increase of the value of the whole mixing capacity.
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