Editor-in-Chief
Manabu Shimada (Hiroshima University)

Associate Editor-in-Chiefs
Masahiro Shishido (Yamagata University)
Ken-Ichiro Sotowa (The University of Tokushima)

Editors
Choji Fukuhara (Shizuoka University)
Toshitaka Funazukuri (Chuo University)
Yoshihiro Hashimoto (Nagoya Institute of Technology)
Shunji Homma (Saitama University)
Jun-ichi Horiuchi (Kyoto Institute of Technology)
Yoshinori Itaya (Gifu University)
Masashi Iwata (Osaka Prefecture University)
Noriho Kamiya (Kyushu University)
In-Beum Lee (Pohang University of Science and Technology (POSTEC))
Kouji Maeda (University of Hyogo)
Hideyuki Matsumoto (National Institute of Advanced Industrial Science and Technology (AIST))
Michiaki Matsumoto (Doshisha University)
Nobuyoshi Nakagawa (Gunma University)
Tsuguhiko Nakagawa (Okayama Prefectural University)
Yasuya Nakayama (Kyushu University)
Masaru Noda (Fukuoka University)
Mikihiro Nomura (Shibaura Institute of Technology)
Eika W. Qian (Tokyo University of Agriculture and Technology)
Yuji Sakai (Kogakuin University)
Noriaki Sano (Kyoto University)
Naomi Shibasaki-Kitakawa (Tohoku University)
Hiroshi Suzuki (Kobe University)
Nobuhide Takahashi (Shinshu University)
Kazuhiro Takeda (Shizuoka University)
Shigeki Takishima (Hiroshima University)
Yoshifumi Tsuge (Kyushu University)
Tomoya Tsuji (Nihon University)
Shigeyuki Uemiya (Gifu University)
Da-Ming Wang (National Taiwan University)
Takayuki Watanabe (Kyushu University)
Takuji Yamamoto (University of Hyogo)
Tetsuya Yamamoto (Nagoya University)
Masahiro Yoshida (Kagoshima University)
Yasuo Yoshimi (Shibaura Institute of Technology)
Miki Yoshimune (National Institute of Advanced Industrial Science and Technology (AIST))

Editorial office:
The Society of Chemical Engineers, Japan
Kyoritsu Building, 4-6-19, Kohinata, Bunkyo-ku
Tokyo 112-0006, Japan
journal@scej.org

AIMS AND SCOPE:

Journal of Chemical Engineering of Japan, an official publication of the Society of Chemical Engineers, Japan, is dedicated to providing timely original research results in the broad field of chemical engineering ranging from fundamental principles to practical applications. Subject areas of this journal are listed below. Research works presented in the journal are considered to have significant and lasting value in chemical engineering.

Physical Properties and Physical Chemistry
Transport Phenomena and Fluid Engineering
Particle Engineering
Separation Engineering
Thermal Engineering
Chemical Reaction Engineering
Process Systems Engineering and Safety
Biochemical Food and Medical Engineering
Micro and Nano Systems
Materials Engineering and Interfacial Phenomena
Energy
Environment
Engineering Education

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Solid–liquid suspensions in stirred tanks are common unit operations in many process industries. The complex flow characteristics of these systems, such as two-phase turbulence and interphase interaction, make the corresponding numerical simulations complicated and challenging. This paper presents a review of models dealing with the continuous and discrete phases of solid–liquid suspensions and summarizes the applications for simulating related flow phenomena, including velocity and turbulence components, solids concentration, just-suspended speed, cloud height, optimization of geometrical parameters, and particle shape and type. Perspectives concerning different modeling approaches are presented, and the Eulerian–Lagrangian approach with resolved particles is highlighted to address the underlying suspension mechanisms in stirred tanks.

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The present study investigates how solids affect the hydrodynamic characteristics in gas-liquid-solid flow in a cubic tank with a flat square base (length T=230 mm) using two-dimensional particle image velocimetry (PIV). The fluid was stirred by a half elliptical disk turbine (HEDT) of diameter D=77 mm. Flow fields at three different gas holdups (maximum 3.73%) were investigated, with the particle volumetric fraction up to 1.6%. The results show that the particles have a more significant influence on turbulent flow in solid–liquid two-phase flow and three-phase flow with 1.42% gas holdup than in the three-phase flow with 3.73% gas holdup. In multi-phase flow, the velocity of continuous phase is greatly influenced by the concentration of dispersed phase, but is rarely influenced by its density. However, the turbulent kinetic energy is affected by both of them.

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The shape, rise velocity and drag coefficient of a single drop with a diameter from 1.9 to 10.5 mm rising in Newtonian fluids are discussed, where the drops Reynolds numbers are from 0.002 to 1,000. The deformation of drops and its effect on the terminal velocities and drag coefficients are considered. The results for terminal velocity and drag coefficient are compared with the previous correlations of both bubble and drop motions in Newtonian system. We obtained the frequency spectrums on the lateral oscillation of the drops with different diameters by using Fourier analysis to investigate the effect of the resonance frequency and the vortex trail on the oscillation of the drops. The results show that the maximal response frequencies of the drops are shifted to the low-frequency part when the drop diameter increases. Particle image velocimetry was used to quantify the liquid velocity flow field around the drops, and the effect of the wake behind the drop may cause pulsating–pressure distribution over the surface of the drop, which leads to the change of the maximal frequencies on the response oscillation.

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The present study investigates the volumetric mass transfer coefficient (k_La) by the catalyzed sulfite oxidation method at various power inputs, superficial gas velocities, and temperatures in a fully baffled dished base stirred vessel of 0.48 m diameter. A 6-elliptical-blade disk turbine (HEDT) was used as the bottom impeller to disperse the incoming gas, with two up pumping 4-blade hydrofoil impeller (WH_U) above. The sodium sulfite concentration was maintained at 500–800 mol·m⁻³ and the cobalt catalyst concentration was kept at 0.001 mol·m⁻³. Results show that k_La increases with the increasing power consumption, superficial gas velocity, and temperature. The effect of power consumption on k_La is larger than that of superficial gas velocity on k_La. Temperature has an obvious effect on k_La with the largest exponent. The correlation k_La=7.37×10⁻⁵P_Tm^0.63V_S^0.34T_K^1.64 was obtained in the range of operating conditions used.

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The bioreactor configuration including a dual-impeller combination, spacing between the impellers, and the diameter of the ring sparger is optimized based on solid suspension (N_jsg) and gas dispersion (N_f and k_La) in this work. Then, the solid suspension and gas dispersion performance in this optimized bioreactor are systematically studied. It is found that a smaller sparger (D_s/T=0.32) achieves better performance in gas dispersion. A pitched-blade disc turbine down-pumping (PDTD) as a bottom impeller achieves the lowest N_jsg value, and has lower N_f value compared with PBTD (pitched blade turbine down-pumping) and TBHA (three-bladed helical agitator). Techmix 335 hydrofoil impeller down-pumping (TXD) as an upper impeller provides higher k_La values. TXD+PDTD are more suitable for the requirements of a bioreactor. k_La decreases slightly with increasing solid loading, which is beneficial to good gas dispersion in such bioleaching reactors with higher solid loadings (>20 wt%).

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In the present study, the results of simulations of solid–liquid mixing inside a stirred vessel with the Rushton turbine impeller are presented. The simulations are conducted by using the Lagragian model to track solid particles. Behaviors of particles are related to the flow formation inside the stirred vessel. The velocity fields at various positions are compared with the experimental data to validate of numerical simulations. Overall, the comparisons between the results show good agreement between the simulations and the experiments. The particle distributions are predicted by numerical simulation based on the validated flow field. In addition to evaluated degree of solid–liquid mixing, the inter-particle distance is introduced and adopted considering individual behavior of particles.

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Particle distribution and just-suspension speeds have been studied for SATAKE SUPERMIX® HR100 and HS604 impellers in comparison to a 45° pitched-blade turbine (4PBT) and propeller (3P) in a flat-base fully baffled cylindrical tank. The slurries were made up of 18.0 µm, 75.3 µm and 195.5 µm diameter PMMA particles in water, with solids loading ranging from 5 to 40% by weight.
Points of last suspension were either from the center, side, or annular region, and are directly related to the flow on the tank base, which could result from primary discharge or induced flow. Increasing impeller clearance from the base reduces the extent of flow for the 4PBT and 3P, such that at high clearances the main flow completely separates into two recirculating loops, with weaker secondary loops in the lower half of the tank. This led to the accumulation of particles at the tank center. By comparison, the HR100 generates a strong axial flow that was maintained at all clearances, thereby making it more advantageous in clearing particles at the tank center.
N_js increased with increasing C/D, particularly at high clearances for the 4PBT and 3P, while the HR100 is relatively less affected by clearance. At C/D=0.75 and 1.0, N_js for both the 4PBT and 3P are strongly affected by solids loading of 20 wt% and upwards. The HS604 has promising suspension performance in terms of stability with respect to changes in solids loading, and this is related to its discharge pattern that results from a very low clearance.

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Mechanical agitators are widely used for accelerating the dissolution of hydrophobically associating polymers. However, the polymer dissolution process is nonuniform, changing from multiphase low viscosity to single-phase high viscosity. A single agitator, either a hydrofoil for low viscosity or an anchor type for high viscosity, cannot be optimized for the polymer dissolution process. In this paper, the use of double agitators for the polymer dissolution process is investigated. The double agitators are composed of an inner hydrofoil impeller, suitable for low viscosity fluids, and an outer anchor and frame type impeller, suitable for high viscosity fluids. In addition, different kinds of combinations and interactions between the two agitators are studied. The experimental process is also simulated using the CFD software package FLUENT, and the results are compared with experimental results. The predicted power consumptions are consistent with the experimental results. The experimental and numerical results show that different agitators have different effects during the polymer dissolution process. Using the same rotation direction for the inner and outer impellers increases the overall circulation in the stirred tank and accelerates the dissolution of the hydrophobically associating polymer. The inner impeller with down-pumping is more effective than that with up-pumping in the double agitator system.

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Pump-mix mixers, widely used in rare earth extraction, are quite different from stirred tanks in their suction effect. The effects of impeller type, diameter, clearance, blade width, blade number, orifice diameter, orifice height and liquid flow rate at different impeller speeds on the head generated by a rotational impeller have been studied. Results show that Both sides Shrouded Turbine with Radial Trapezoidal Blade (BSTRTB) has the best performance for suction. Clearance and orifice height affect the suction head largely. At a large clearance and orifice height, the phenomenon of double recirculation loop flow pattern is observed with weak suction head and high power consumption. Further discussion of pump-mix action was then carried out on the flow pattern and the results show that a large amount of liquid in the low recirculation loop flows to the impeller and results in high power consumption and low head.

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