Editor-in-Chief: Yoshiyuki Yamashita (Tokyo University of Agriculture and Technology) Associate Editors-in-Chiefs: Hiroyuki Honda (Nagoya University) Takao Tsukada (Tohoku University)
Editors Tomohiro Akiyama (Hokkaido University) Georges Belfort (Rensselaer Polytechnic Institute) Jun Fukai (Kyushu University) Yutaka Genchi (National Institute of Advanced Industrial Science and Technology (AIST)) Takayuki Hirai (Osaka University) Masahiko Hirao (The University of Tokyo) In-Beum Lee (Pohang University of Science and Technology (POSTEC)) Eiji Iritani (Nagoya University) Hideo Kameyama (Tokyo University of Agriculture and Technology) Masahiro Kino-oka (Osaka University) Toshinori Kojima (Seikei University) Noriaki Kubota (Iwate University (Professor Emeritus)) Shin Mukai (Hokkaido University) Akinori Muto (Okayama University) Nobuyoshi Nakagawa (Gunma University) Satoru Nishiyama (Kobe University) Hiroyasu Ogino (Osaka Prefecture University) Naoto Ohmura (Kobe University) Mitsuhiro Ohta (Muroran Institute of Technology) Hiroshi Ooshima (Osaka City University) Noriaki Sano (Kyoto University) Manabu Shimada (Hiroshima University) Masahiro Shishido (Yamagata University) Shigeki Takishima (Hiroshima University) Richard Lee Smith, Jr. (Tohoku University) Yoshifumi Tsuge (Kyushu University) Da-Ming Wang (National Taiwan University)
Editorial office: The Society of Chemical Engineers, Japan Kyoritsu Building, 4-6-19, Kohinata, Bunkyo-ku Tokyo 112-0006, Japan firstname.lastname@example.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
The Instructions for Contributors and other information are available through our website (http://www.scej.org/jcej/).
This special issue, “IWPI 2008,” is an outcome of the International Workshop on Process Intensification 2008 held in Tokyo, Japan on October 15–18, 2008. This workshop had been organized as the second workshop on this research field in Asia and is held every two years. The main objectives of this workshop were to provide the current achievements and trends on process intensification and share the latest research results among participants. This workshop consisted of 1 plenary lecture, 9 keynote lectures, 22 oral presentations and 83 poster presentations.
All the manuscripts were refereed following the standard procedure for papers submitted to the regular issues of the JCEJ. Twenty papers were approved for publication by the referees.
More than 40 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 of Tokyo University of Agriculture and Technology, the Editor-in-Chief of the JCEJ, for solid support and to Ms. Kazuko Yamashita in the editorial office for her persistent devotion to the preparation of this special issue.
Elongation studies are very important for validating the constitutive equations that describe the rheological behavior of fluids. The relaxation of a stretched polymer chain in the flow field has not been investigated in detail thus far. We extended the constitutive equations for predicting the start-up behavior and the power law relationship between the steady-state elongational viscosities and the strain rate. We also determined the steady-state elongational viscosity by fitting the calculated results with the measured values. The calculated results show the power law relationship between the steady-state elongational viscosities and the strain rate. Furthermore, we used these constitutive equations to predict the overshoot of the viscosities and stresses at initial stages of the steady elongational or shear flows by considering only one parameter, the stretch relaxation time.
Formation of a liquid jet and droplets from a micro-capillary in another immiscible co-flowing ambient fluid is simulated numerically with a front-tracking/finite difference method. The transition from dripping to jetting is observed and the size of the resulting droplets is predicted. The predicted size in jetting mode is in close agreement with that from linear stability theory for a moving liquid jet in a co-flowing ambient fluid with the same speed as the jet. The transition between dripping and jetting are mapped on the diagram of the jet Weber number versus the ambient flow Capillary number. It is found that the viscosity ratio is an important parameter to distinguish the mode.
In this experimental study, the effect of a modified 4-alternating pitched blade turbine (4-APBT) on isolated mixing regions (IMRs) was studied using a Newtonian fluid at low Reynolds numbers. The dimensionless mixing time, Ntm, was measured using direct visualization of an acid–base reaction within the Newtonian fluid. The digital image analysis of the photographs revealed that the use of 4-APBT leads to smaller IMR structure volumes (less than 20% of total liquid volume) and reduced mixing time by 60% compared to those obtained with the 4-blade disc turbine (4-DT).
A large bubble rising in a narrow fixed bed is visualized by the index matching method, which makes particles and cylinder invisible by matching the refractive index between the material and the liquid. The bubble velocity is nearly independent of size in the narrow bed while it decreases with size in the pipe. The velocity in the bed sensitively increases with a superficial liquid velocity while a notable dependency is not observed in the pipe. The bubble behavior is modeled by a VOF (volume of fluid) method associated with a high-fidelity CFD (computational fluid dynamics) model, which can treat hundreds of particles that are randomly packed in the bed without geometrical simplification. The CFD model is validated based on the comparison between experimental and numerical results.
Abstract Slurry containing hydrate particles as a phase-change material in the aqueous surfactant solution with counter-ion can be applied to construct a highly effective heat transport system by the combination of latent heat and drag-reducing effect. However, the efficiency of the system is influenced not only by thermal characteristics but also by the fluidity of the slurry, which is influenced by the size and concentration of the particles and the agglomerates. In this study, we first investigate the condition providing steady crystallized slurry. It has been found that crystallization attained steady state within 1 hour after the start of crystallization under a well-agitated condition. The viscosities and first normal stress differences of the steady crystallized slurry and saturated solution were measured to clarify the interaction between hydrate particle and micellar structure of surfactant. As a result, it turned out that the agglomeration of the hydrate particles was influenced by the size and strength of the micellar structure depends on the concentration of counter-ion. In particular, a slurry containing a large amount of counter-ion showed a drastic decrease in fluidity in a certain shear rate range probably due to agglomeration of entangled structures of surfactants.
Double-spiral-type equipment is proposed as a new compact heat exchanger. Initially, the behavior of heat transfer coefficients is quantitatively determined through experiments of the heat exchange between hot and cold water flows in the exchanger. Subsequently, the heat-recipient water is changed with phase change material (PCM)–water slurry to ascertain the effects of PCM-melting on heat transfer enhancement through direct measurements of heat transfer rates. By appropriately evaluating the physical properties of the slurries with PCM-melting, we finally propose a heat transfer correlation which is applicable to both the water and slurry flows.
The thermal characteristics of inorganic disodium hydrogen phosphate dodecahydrate (Na2HPO4·12H2O) slurries in a water/ethylene glycol mixture were investigated in an attempt to reduce the size of absorbers in absorption chillers. In order to find the optimal concentration of Na2HPO4·12H2O and the optimal weight ratio of ethylene glycol to the mixture for cooling the absorber, solubility, phase change temperature, and latent heat were measured. The obtained results indicated that the hydrate slurry has an appropriate phase change temperature and sufficient concentration at the working temperature of the absorber when the hydrate concentration and the weight ratio of ethylene glycol to the mixture are set to 50 wt% and 0.4, respectively. Under this condition, the particle characteristics of the slurries were also measured. The particle size was found to be rather small, and it increased gradually. Thus, inorganic Na2HPO4·12H2O can be used as a cooling medium of the absorber in an absorption chiller.
We investigate the surface deformation of polymeric coatings dried under interfacial stresses. The surface-tension-driven Marangoni stress drives the liquid from low-surface-tension regimes to high-surface-tension regimes. The results of our computations reveal that with an increase in the Biot number, three distinct deformation modes are formed: (i) one elevation and two depressions, (ii) flat interface, and (iii) one depression near the air impingement point. A new drying map is presented to show the manner in which the nonuniform thickness varies with the Biot and Marangoni numbers. The map helps us decide the optimum operating conditions for achieving uniform surface coatings.
Mixing patterns generated in stirred vessels for a wide range of Reynolds numbers were observed using a decolorization method based on the reaction between sodium thiosulfate and iodine. A relationship was established between the power number diagram (NP–Re diagram) and the shape of the isolated zone was observed. At low Reynolds numbers (laminar regime), the isolated zone resembled a doughnut ring, while a cylindrically rotating zone isolated at high Reynolds numbers (turbulent regime). Even with a small change in Reynolds number, the doughnut-ring-shaped isolated zone suddenly changed to a cylindrically rotating zone in an unbaffled vessel. The cylindrically rotating zone was not observed in baffled vessels at high Reynolds numbers. The clearance between the propeller impeller and the vessel bottom brought about a change in the mixing patterns, although the power consumption the remained constant.
Through an electrical resistance tomography method, it was possible to determine the phase inversion phenomenon, from water-in-oil (50 vol%) to oil-in-water, by dynamically varying the impeller rotational speed in a stirred vessel attached with a 6-blade paddle impeller. Accordingly, it was found that the water-in-oil and oil-in-water states replace each other continuously and reversibly up to a certain point, and then the replacement become irreversible thereafter.
An effect of feed concentration on particle focusing in an arc microchannel is numerically examined. A macroscopic particle model, which does not need any drag and lift force correlations and hence can be regarded as quasi-direct numerical simulation, is employed to model interparticle collisions due to high shear rates in the microchannel. The model can take into account physical boundaries of particles in contact. In dilute conditions, all particle trajectories formed smooth inward spirals over the transverse plane. In dense flow conditions, the particle trajectories were distorted by collisions, and then the particle focusing declined. It suggests that a particle concentration, which is regarded as dilute in terms of volume concentration, can be regarded as hydraulically dense due to shear-induced particle collisions in a microchannel. It is predicted that the angle between particle-velocity vectors at successive time steps during collision is rather small. The importance of collision mechanism is discussed for the device application to various materials.
This paper reports the results of a computational fluid dynamics (CFD) simulation for a sequential heterogeneous catalytic reaction by comparing the reaction selectivity in a catalytic microreactor with that in a conventional catalytic packed-bed reactor. The comparative simulation revealed that the catalytic microreactor has an advantage over the conventional reactor in the diffusion control regime, and that the control of concentration distribution of reactants by molecular diffusion in the microspace can enhance the selectivity of the desired product. The concentration distribution was intentionally controlled by the shape of the microreactor. The yield of the desired product in the microreactor was 1.16 times that in the packed-bed reactor. CFD simulation of methanol decomposition was also performed by fitting the parameters with the experimental results. The results of the CFD simulation verified the advantage of the microreactor.
Emulsion polymerization of vinyl acetate with a compartment reactor consisting of 3 well-mixing compartments has been investigated. A step response method revealed that the mixing of this reactor is characterized by a 4 CSTRs-in-series model. Higher conversion of the vinyl acetate monomer is obtained by the compartment reactor than by a single CSTR since the restricted axial dispersion suppresses the effluent of unreacted monomer. The oscillation of the mean particle size induced by the co-presence of small and large particles is inhibited due to narrow residence time distribution of particles, and stable particle size distributions are obtained under steady state operation. Back-mixing causes polymerization with short mean residence time in the first compartment. Since there is little back-mixing, polymerization occurs in the first vessel even when the mean residence time of feed is so low that the polymerization did not occur in a single CSTR. The compartment reactor can be a possible method to convert the batch process into a continuous process.
The reforming of methane by carbon dioxide and the simultaneous permeation of hydrogen through a 0.1 mm thick palladium–silver alloy (25% Ag) have been carried out in a dielectric barrier discharges (DBDs) membrane reactor at room temperature and atmospheric pressure for the first time. In this study, the effects of feed ratio (CH4/CO2 ratio) and input energy density (flow variation and power variation) on reagent conversion, product selectivity, and specific energy requirement as well as separation efficiency were investigated. Carbon dioxide and methane conversions were enhanced by increasing the input power and decreasing the total flow rate. The H2/CO ratio could be controlled and depended on the concentration of CO2 in the feed gas. Further, the input energy density hardly influenced synthesis gas composition (H2/CO). The heat generated by DBD was used to separate pure hydrogen from the product stream by passing it through a Pd–Ag membrane.
The effect of the addition of compressed carbon dioxide in continuous hydrogenation of toluene has been evaluated with process simulation software and tested with a fixed-bed reactor. The simulation results show that the temperature rise is significantly suppressed in the presence of compressed carbon dioxide and that the equilibrium conversion of toluene (toluene/hydrogen = 1/3) reaches 99.9%, whereas around 60% in the absence of carbon dioxide. Experimental results show that the continuous hydrogenation of toluene (toluene/hydrogen/carbon dioxide = 1/3.1/31, inlet temperature: 20 °C, outlet temperature: <70 °C, and total pressure: 11 MPa) over activated carbon-supported rhodium catalysts proceeds without deactivation. The conversion of toluene reaches 99% and methylcyclohexane is the only product detected.
The partial oxidation of benzene in a reaction-extraction system was studied. The system consisted of a reactor, an extractor and a regenerator. The reactor contained both a benzene phase and an aqueous phase. Benzene was partially oxidized to phenol in the aqueous phase and then extracted to benzene phase. Phenol was finally extracted from benzene in the extractor. The regenerator reduced the oxidation catalyst. The phenol production rate increased when oxidation catalyst concentration, regenerator temperature, circulation rate between the reactor and the regenerator were increased. Thus, the regenerator played an important role in this system.
For the biodiesel-fuel production by methanolysis, the reaction mixture is composed of a methyl-ester phase and a glycerol phase. One of the reactants, triglyceride, is mainly contained in the ester phase. The other reactant, methanol, is easily dissolved in the glycerol phase. Therefore, the methanol in the system is not effectively used for the reaction due to interface mass transfer resistance. An excess amount of methanol is required to increase the conversion in single-step operation. Since the glycerol phase is removed during the operation, a two-step batch operation can effectively intensify the process. In the present study, the optimal operating conditions to increase the conversion are obtained for the methanolysis of rapeseed oil using a KOH catalyst. The distribution ratio of methanol addition in the first step was about 0.8, which is confirmed by a simple reaction model.
The effect of Ti compounds on H2 desorption/ absorption of LiNH2/LiAlH4/MgH2 was investigated. The formation of NH3 from the decomposition of LiNH2 was suppressed by adding LiAlH4 and MgH2 to LiNH2. In addition, the onset desorption temperature of LiNH2/LiAlH4/MgH2 was lower than that of pure LiNH2, whose onset desorption temperature is approximately 473 K. It was observed that the reversibility of the ternary mixture improved when Ti compounds (TiO2, TiCl3, and Ti) were doped into it. The Ti-doped mixture exhibited the highest reversible H2 capacity (0.4 wt%) at 573 K. Small peaks corresponding to Mg(AlH4)2 and Mg(NH2)2 were revealed from the XRD patterns of the ternary mixture, and the presence of reversible phases in the mixture were indicated from these peaks.
An aqueous solution of ethanol was ultrasonically atomized, and the mist was recovered to obtain concentrated ethanol solution. The atomization vessel was vacuumed, and the recovery vessel was pressurized for enhancing mist generation and recovery. Batch operation was carried out with and without pressure control, and the results obtained were compared. The amounts of produced and recovered mist increased dramatically upon pressure control. The ethanol concentration in the collected liquid was higher in the presence of ultrasound irradiation than in its absence. It was suggested that production of very fine ethanol-rich droplets was facilitated at reduced pressures, and the recovery was enhanced at elevated pressures. The effect of pressure in the atomization vessel on the amount of mist production and the ethanol concentration in the collected liquid was examined in the presence and absence of ultrasound irradiation. Without ultrasound irradiation, only evaporation would occur. Comparison of the results obtained with and without ultrasound irradiation indicated that the formation of fine droplets affected ethanol separation. The amount of mist collected was 1.4 times the amount of vapor. The ethanol concentration in the collected mist exceeded that in the collected vapor by 5 mol%. The results also suggested that the formation of fine droplets affected the ethanol separation degree by ultrasonic atomization.
The aim of this research was to study the immobilization of lipase on chitosan by adsorption in order to examine the use of lipase as a catalyst in the transesterification of crude sunflower oil and Jatropha oil. The highest activity of immobilized lipase was found to be 857 U/g, and it corresponded to a glutaraldehyde concentration of 0.05%, pH 7, and a temperature of 37 °C. On the other hand, the activity of free lipase was 2,136 U/g. The optimum conditions for the transesterification of crude sunflower oil were as follows: oil-to-methanol molar ratio, 1:3; immobilized lipase, 100% (w/w of oil); water content, 20% (w/w of oil); shaking speed, 200 rpm; and temperature, 50 °C for 24 h. The maximum amount of methyl esters produced was 25%. When free lipase was used as the catalyst under the same conditions, the amount of methyl esters produced was 33%. The transesterification of Jatropha oil was also studied to compare the activities of the two types of lipases. Both types of lipases activate the tranesterification of sunflower oil more easily than the transesterification of Jatropha oil.