Editor-in-Chief
Takao Tsukada (Tohoku University)

Associate (Editor-in-Cheifs)
Manabu Shimada (Hiroshima University)
Masahiro Shishido (Yamagata University)

Editors
Ryuichi Egashira (Tokyo Institute of Technology)
Jun Fukai (Kyushu University)
Choji Fukuhara (Shizuoka University)
Toshitaka Funazukuri (Chuo University)
Takayuki Hirai (Osaka University)
Jun-ichi Horiuchi (Kitami Institute of Technology)
Eiji Iritani (Nagoya University)
Yoshinori Itaya (Gifu University)
Noriho Kamiya (Kyushu University)
In-Beum Lee (Pohang University of Science and Technology (POSTEC))
Kouji Maeda (University of Hyogo)
Hideyuki Matsumoto (Tokyo Institute of Technology)
Nobuyoshi Nakagawa (Gunma University)
Masaru Noda (Fukuoka University)
Hiroyasu Ogino (Osaka Prefecture University)
Mitsuhiro Ohta (The University of Tokushima)
Eika W. Qian (Tokyo University of Agriculture and Technology)
Yuji Sakai (Kogakuin University)
Noriaki Sano (Kyoto University)
Naomi Shibasaki-Kitakawa (Tohoku University)
Ken-Ichiro Sotowa (The University of Tokushima)
Hiroshi Suzuki (Kobe University)
Nobuhide Takahashi (Shinshu University)
Shigeki Takishima (Hiroshima University)
Yoshifumi Tsuge (Kyushu University)
Tomoya Tsuji (Nihon University)
Da-Ming Wang (National Taiwan University)
Takuji Yamamoto (University of Hyogo)
Yoshiyuki Yamashita (Tokyo University of Agriculture and 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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Distillation is a common energy-intensive process. Accordingly, it is the first process to be addressed to improve the energy efficiency over both the short- and long-term. Recent studies and industrial applications have proven that advanced process integration and process intensification techniques such as the use of a thermally coupled distillation sequence (TCDS) and a dividing wall column (DWC) require the lowest amount of energy for the separation of mixtures into pure product streams. This paper reviews some energy-efficient distillation technologies that can be used in a retrofit design. The research on and implementation of retrofits using a TCDS and DWC are reviewed. This report proposes coupled schemes as alternatives to using a Petlyuk column that do not have the classical problem of controlling the vapor transfer from one column to another and have not previously been proposed for retrofits. These schemes are expected to make significant contributions to improving the energy efficiency and mitigating CO₂ emission in the retrofitting of distillation systems. The authors evaluated a solution for retrofitting azeotropic and extractive distillation systems. Various issues such as the constraints, techno-economic analysis, controllability, and operability are discussed briefly to provide more insight into the application of TCDS and DWC technologies in the retrofit.

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The author starts by reviewing papers regarding studies of solid–liquid mixing and dispersion states, essential for slurry fluid mixing, by both experimental and numerically analytical approaches, and subsequently reviews papers regarding visualization of the cavern and the flow state of slurry system fluids by CFD and ERT, as it is impossible to use an optical visualization approach for such fluids because they are usually opaque and non-light-transmitting.

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This study summarizes crystallization technology when using a Taylor vortex flow. A Taylor vortex is created in the gap between two co-axially positioned cylinders based on the rotation of the inner cylinder. Due to its unique periodic flow motion, a Taylor vortex has a significant influence on the processes of nucleation, growth, and agglomeration breakage in various crystallizations, including reaction recrystallization, drowning-out crystallization, and cooling crystallization. In the gas–liquid reaction crystallization of calcium carbonate, the mass transfer at the gas–liquid interface is greatly facilitated by a Taylor vortex, resulting in small crystals with a uniform size and morphology. Further, due to molecular alignment by the periodic Taylor vortex motion, the polymorphic nucleation of stable crystals is also promoted. This effect of molecular alignment by a Taylor vortex is demonstrated by the phase transformation of sulfamerazine. Furthermore, the Taylor vortex flow in a Taylor crystallizer improves the productivity of crystallization when compared with the random turbulent eddy flow in an MSMPR crystallizer. Consequently, the high performance of a Taylor crystallizer using a Taylor vortex has strong potential for application to various crystallizations.

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Fracturing of a layered compound, zirconium phosphate, with ultrasound at various power inputs (ultrasound power) was investigated. A horn mounted on the transducer with the frequency of 20 kHz was used and the fracturing rate was estimated by measuring the time course change of light transmittance of the zirconium phosphate aqueous suspension containing tetrabutylammonium hydroxide. After the transmittance was normalized by using initial and maximum values, the fracturing rate was formulated with the equation −r_f=k_fC/(K−C) based on the mass concentration of the layered compound particles, and the experimental results agreed well with the simulation results. A loop-type ultrasonic apparatus was employed. It consisted of interconnected 2 continuous stirred tanks with and without sonication, and the suspension in these tanks was circulated between them through 2 tubes. Every experimental result shows higher transmittance than the numerically predicted results. It is inferred that the circulating flow allowed the fracturing rate to be promoted.

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SiO₂-coated SnPt nanoparticle catalysts (SnPt@SiO₂), comprised of core SnPt bimetallic nanoparticles covered with a porous SiO₂ layer were prepared by a water-in-oil (w/o) microemulsion method. X-Ray diffraction studies of SnPt@SiO₂ (Sn/Pt=1.0) indicated that the SnPt bimetallic nanoparticles consisted of a Sn-doped Pt phase and a Sn₁Pt₁ alloy phase. Transmission electron microscopy demonstrated that the SnPt bimetallic nanoparticles were covered with a thin silica layer. A higher selectivity of cinnamyl alcohol mediated by SnPt@SiO₂ (Sn/Pt=1.0) catalysts was observed in comparison to Sn–Pt/SiO₂ catalysts prepared by conventional co-impregnation methods. The synergy effect between the SnPt bimetallic core nanoparticles and the porous structure of the SiO₂ layer increased the chemo-selective hydrogenation of cinnamaldehyde to cinnamyl alcohol.

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The decolorization process of methylene blue (MB), as a model pollutant for dye wastewaters, has been investigated using an LED-irradiated glass microreactor. The main part of the microreactor is a semi-elliptic microchannel with the width, depth and length of 100 microns, 40 microns and 50 cm, respectively. For the purpose of comparisons and exploration of surface effects, glass and polystyrene cuvettes are employed as a model of a batch vessel. It is found that MB was decolorized by UV light and, further, that the photochemical decolorization process was intensified, in terms of reaction rate, by using the microreactor. Especially, at high pH conditions, the process intensification is found to be more prominent due to surface interactions, which are enhanced in the microreactor due to its high specific surface area.

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A spherical high density polyethylene (HDPE) with a diameter of more than 0.2 µm was obtained from emulsion crystallization of an HDPE/1-dodecanol/triethylene glycol system. A multilamination type or split-and-recombine type micromixer was used for continuous production of HDPE particles. The micromixers provided a high heat and mass transfer rate between the HDPE/1-dodecanol solution and the cold immiscible nonsolvent triethylene glycol. This process could easily realize a supercooled uniform emulsion for HDPE crystallization. The particle size of HDPE could be controlled from the operating conditions of the continuous-flow micromixer system.

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The high-level performance of a large impeller can be combined with the advantages of an eccentric impeller by using the impeller at an eccentric position. In this study, the power consumption and mixing time for Maxblend, which is a type of large impeller, were investigated. The power consumption P and mixing time θ_M were measured under various eccentric conditions. The relationships between the power number (N_p) and Reynolds number (Re) and between the dimensionless mixing time (nθ_M) and Re were investigated. It was confirmed that a large amount of energy can be supplied to the mixing liquid in eccentric mixing based on the N_p–Re curves. In the laminar state, the value of nθ_M of eccentric mixing under suitable eccentric conditions was lower than that of concentric mixing with and without baffles. In this region, eccentric mixing was useful in terms of power consumption. On the other hand, the mixing efficiency based on the power consumption at L_E=0.04 m was almost the same as that of concentric mixing with baffles in the turbulent state, where Re>2500.

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This study deals with fluid mixing process in the circular cross-section of a cylindrical vessel using a rotationally reciprocating (back and forth rotation) plate impeller from the view point of experimental visualization and numerical simulation. We have investigated the fluid deformation process with the visualization of streak lines. It has been found that a pair of vortices generated at the impeller tip plays a crucial role in stretching and folding of streak lines. Additionally, for effective overall mixing, we found that fluid needs to be dragged inward to the region near the mixing shaft, stretched and folded along the impeller plate, and then extensively deformed from the impeller tip. However, since the path of fluid inward motion is rarely disturbed by locally strong vortices generated at the conditions of small amplitude and short period, a poor mixing region expanded from the mixing shaft to the vessel wall, which made two separated mixing regions in a vessel. With increasing amplitude, the poor mixing region shrunk near the mixing shaft. In the case of the largest amplitude and longest period, fluid was effectively deformed everywhere in the vessel, which leads to a highly intensified mixing process.

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Silica has been modified with decyltrimethoxysilane at various temperatures to improve the dispersion of the silica particles in a silica–rubber composite. The modified silica samples are characterized by FT-IR and ²⁹Si CP/MAS NMR. With increasing treatment temperature, the chemical reaction between the silanol group of silica and the methoxy group of decyltrimethoxysilane is facilitated and the silica samples demonstrate very low water vapor adsorption capacities and good hydrophobicity compared to silica. The SBR rubber composite containing thermally modified silica shows improved silica particle dispersion. However, when physically mixed silica is used, the silica is mainly located on the surface and agglomerated.

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Silica sols can be continuously produced by the neutralization of sodium silicate with sulfuric acid using a Y-shaped reactor. The viscosity of the produced silica sols gradually increases, and gels are finally formed through the sol–gel transition. The gelation properties are significantly affected by the preparation conditions. Here we examined the effect of the dilution of silica sols by water in terms of the gelation properties of the silica sols and gels, using both dynamic viscoelasticity measurement and the creep test. Information that is needed to control the gelation properties of silica sols and gels for making silica materials into a product is also presented.

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Aluminum ammonium sulfate dodecahydrate (ammonium alum hydrate) slurries are promising latent heat media for high temperature applications. However, a major problem associated with materials developed specifically for high temperature use is sedimentation in the pipes of the device. Thus, the ability of poly vinyl alcohol (PVA) to prevent sedimentation and particle growth of ammonium alum hydrates has been investigated in this study. In order to increase the fluidity of the slurry, a cationic surfactant, behenyl trimethyl ammonium chloride, was used as a drag-reducing agent, and the interaction between the cationic surfactant and PVA was evaluated. The rheological properties of the slurries and solutions were investigated, and they indicated that the drag-reducing cationic surfactant was not disturbed by the PVA.

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In 1994, the first commercial application of surfactant drag reduction was conducted in Japan for the air conditioning system in the Shunan Regional Industry Promotion Center building. A commercially available drag-reducing additive (LSP-01) based on the mixture of a cationic surfactant, a counter ion, and corrosion inhibitors was developed based on the results of the project. Since 1995, LSP-01 has been used at more than 180 sites in building air conditioning systems throughout Japan. The drag-reducing technique was adopted recently for an air conditioning system in a skyscraper in Tokyo. Here, I measured the drag reduction and heat transfer characteristics during the cooling operation of a heat exchanger for a surfactant and a counter ion system, Ethoquad O/12 and NaSal. The analogy between the momentum and heat transfer for the drag-reducing flow is also discussed.

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In this study, we introduce a layer-by-layer (LbL) assembly method to prepare a reverse osmosis (RO) desalination membrane that consists of a hybrid combination of [polyelectrolyte (PE)/montmorillonite (MTM)]_n layers. First, adopting poly(allylamine hydrochloride) (PAH) for a PE layer, an RO test showed that the permeate flux of water through (PAH/MTM)_n multilayer-coated membranes decreased from ∼25.5 to ∼8.3 L·m⁻²·h⁻¹ with the increased bilayer number from n=9 to n=18. At the same time, the corresponding ion rejection with respect to NaCl is increased from ∼30 to ∼81%. Despite the increased ion rejection performance, (PAH/MTM)_n membranes exhibit a poor chlorine resistance, as frequently observed in commercial polyamide-based RO membranes. In our previous study, it was noted that the RO membranes, prepared just from the PE multilayers (i.e., [PAH/poly(acrylic acid) (PAA)]_n layers), showed a marked chlorine tolerance, but concomitantly very low permeate flux (∼4–5 L·m⁻²·h⁻¹). Considering the significant drawback in each case (poor chlorine tolerance for (PAH/MTM)_n layers and low permeate flux for (PAH/PAA)_n layers), we proposed to combine the layer constituents primarily by inserting PAH/PAA layers between two adjacent PAH/MTM layers. Indeed, the flux is maintained at ∼7.5±0.5 L·m⁻²·h⁻¹, comparable to commercial membranes, while the salt rejection ability is as high as ∼75±2.5% and the stability against the chlorine attack is well preserved with ∼74±5.0% ion rejection after the NaOCl treatment.

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In the present study, we investigate a framework for the application of genetic algorithm (GA) methods to reactive distillation (RD) process design. First, a computational method for hybrid simulation is proposed by linking a commercial process simulator with an in-house GA-based optimizer in order to accelerate the search for process designs showing high performance. When developing the hybrid simulation system, detailed methods for the GA operations of crossover, mutation, and selection were investigated to achieve a combination that maximizes the effectiveness of the simulation framework. Next, we investigate the designs obtained from the simulations for a case study, an RD process for acetyl acetate. The proposed GA method is shown to provide not only the lowest total annual cost (TAC) design, but also various alternative design solutions. Since the generation of alternative designs lets us consider many other factors, e.g., the distillate composition and the overall conversion of the product, we believe that the application of techniques such as multi-niche crowding (MNC) GA could be effective for searching simulataneously structural and operational conditions of multifunctional processes.

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Formation of compound droplets from a co-axial dual nozzle was simulated by a three-fluid front-tracking method. The device simulated in this study is the so-called flow-focusing device. Core and shell fluids, which are the constituents of a compound droplet, are injected from inner and outer nozzles, respectively. External fluid is also injected to drag the core and shell fluids and promote their breakup into droplets. The dripping–jetting transition was observed in a manner similar to the formation of simple droplets in two-fluid systems. The formation of compound droplets sometimes fails, and simple droplets with no core fluid are produced depending on the non-dimensional numbers. The transition between compound and simple droplets was examined by changing the Capillary number (Ca) of the core fluid and the ratio of the external fluid viscosity to the droplet fluid viscosity. When both the viscosity ratio and Ca are low, the droplets break off as simple droplets. When these numbers are moderate, compound droplets are formed. The Weber number of the core fluid also influences the formation of compound droplets.

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The characteristics of oxygen dissolution accelerated by the use of micro-bubbles in a viscoelastic fluid were studied. An aqueous solution of a combination of a cationic surfactant and of a counter-ion supplier was used as a viscoelastic fluid. Flow visualizations and measurements on the time variation of the oxygen concentration were performed. From the results, it was found that the dissolution of oxygen rapidly occurs by the use of microbubbles, but the dissolution becomes slow in a highly elastic fluid. The flow observation of bubbles in a highly elastic fluid showed a chaining effect with bubble ascension. Bubble chaining was found to accelerate the agglomeration of bubbles and decrease the apparent gas–liquid interface area. Thus, such a chaining effect was concluded to disturb the dissolution of oxygen.

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Unsteady operation is one of the process intensification methods applied to heterogeneous catalytic reactions. Periodic temperature cycling was investigated for 2-propanol (isopropyl alcohol; IPA) dehydrogenation using a microreactor with an anodized aluminum-supported platinum catalyst. A parametric study of the periodic temperature cycling was conducted experimentally and the reactivity under periodic temperature cycling was compared with the reactivity under steady-state operation. A new variable was introduced to evaluate the reactivity improvement under unsteady operation. It was found that a higher cycling temperature difference improved the reactivity. There was an optimum temperature range of around 140–150°C for periodic temperature cycling. It was found that a shorter cycling time was not necessary for reactivity improvement. The IPA adsorption rate and the rate of temperature change are important factors in periodic temperature cycling conditions.

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