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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The electrochemical oxidation of carbon was studied in a direct carbon fuel cell (DCFC) using a carbon/carbonate slurry stirred by Ar bubbling. First, a single carbon pellet in contact with an anode in molten carbonate was observed during discharge. Bubbles were produced from the carbon during the discharge, indicating that the electrochemical oxidation of the carbon was advanced. The performance of the DCFC using activated carbon was then studied. By increasing the Ar bubbling flow rate (Q_bub) from 25 to 50 mL/min, the overpotential increased at high current density where the concentration polarization appeared; whereas, the overpotential at Q_bub=25 mL/min was almost the same as that at Q_bub=50 mL/min at lower current density than 20 mA/cm² and coulombic efficiency increased from 78 to 93% at 20 mA/cm². The bubbling optimization is expected to improve DCFC performance. Coulombic and voltage efficiencies decreased with increasing the current density, while the power density remained the same. The performance of the DCFC using coal chars was also studied. Ar bubbling was effective in the DCFC using coal chars.

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Improvement in the reduction kinetics and stabilities resulting in longer lifetimes are required for practical application of energy conversion and storage systems using redox reaction of metal oxides such as chemical looping systems. It has been previously reported that using oxide ion conductors as supports can improve the redox reactions of metal oxides. To evaluate which physical properties (such as oxide ion transport and electron transport) can affect the redox reaction kinetics of Fe₂O₃, reduction kinetic analyses of Fe₂O₃ reduction by hydrogen were performed. The experiments were conducted using various supports such as CaTi_1–xFe_xO₃ (CTFO, as a mixed ionic and electronic conductor), yttlia-stabilized zirconia (YSZ, as a pure oxide ionic conductor) and Al₂O₃ as a reference (insulator). The results showed that reduction of Fe₂O₃ with CTFO or YSZ as a support was greatly improved compared with Al₂O₃. Oxidation measurements of the Fe/supports by water vapor, i.e. hydrogen production by a steam-iron reaction, showed that CTFO was highly effective at increasing oxidation. Modeling analyses based on the oxygen chemical potential distributions of the Fe₂O₃/supports were also performed to analyze the effect of the supports quantitatively. Calculations assuming high electron and oxygen transport at the interface supported the experimental results. The results suggest that the transport properties at the interface were derived from a highly conducting phase and that oxide ionic conductivity is the predominant factor in the improvement. Sensitivity analysis using various parameters was also conducted and the mechanism for the improvements was discussed.

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For the CH₄ enrichment from biogas mainly consisting of CO₂, CH₄ and water vapor, the effect of water vapor on the separation performance by pressure swing adsorption, PSA, was experimentally investigated using three different adsorbents. Zeolite 13X, which has satisfactory adsorption ability for CO₂, SAPO-34, which shows superior water vapor adsorption/desorption characteristics, and the carbon molecular sieve (CMS), which is a hydrophobic adsorbent, were employed as adsorbents. It was found that the separation performance of zeolite 13X significantly decreased when water vapor was contained in the simulated biogas. The separation performance of SAPO-34 also decreased when water vapor was contained in the simulated gas, however, the decay of separation performance was partly inhibited due to its ease of water vapor desorption. CMS showed no separation performance decay even though the water vapor was contained in mixed gas since the amount of adsorbed water onto the CMS was low. From these results, it was suggested that the CMS is suitable as an adsorbent for the biogas separation containing water vapor.

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For the expansion of ammonia utilization, the fast absorption and fixation of NH₃ is required to prevent damage from leakage. In this study, ammonia absorption with NiCl₂ is the focus for NH₃ fixation, because it can absorb ammonia in low concentration with high fixation capacity. Thermogravimetric studies were performed on NH₃ absorption with NiCl₂ at temperatures of 303–383 K and NH₃ pressures of 23–84 kPa. As a result, it was found that initial particle sizes smaller than 355 µm had little influence on the NH₃ absorption rate. Ammonia absorption with NiCl₂ was enhanced with increasing temperature and NH₃ pressure, but it proceeded more slowly at 383 K compared to at 363 K. The absorption rate expression was determined for the NiCl₂/NiCl₂·6NH₃ reaction based on the grain model. The determined reaction rate constant and reaction order concerning NH₃ pressure had different temperature dependence between 303–323 K and over 323 K. The estimated conversion reasonably agreed with the experimental data.

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This paper investigates the use of expanded graphite (EG) as a thermal conductivity enhancer for packed bed reactor materials in a chemical heat storage/pump system based on magnesium hydroxide (Mg(OH)₂) dehydration and magnesium oxide (MgO) hydration reactions. Composites of Mg(OH)₂ powder mixed with EG (hereafter termed EM composites) were developed by varying the mass mixing ratios of Mg(OH)₂ to EG (ψ). EM composites and pure Mg(OH)₂ powder were compacted in slab configurations (width 20 mm×length 100 mm×variable thickness 20–38 mm) and the thermal conductivities of the slabs were measured as a function of the slab density and ψ. Using EG as a thermal conductivity enhancer in the composite improved the thermal conductivity of the EM slab six-fold relative to that using pure Mg(OH)₂. Evaluation of the thermal effusivity and chemical heat storage capacity showed that EM prepared with a mass ratio of ψ=8 allowed achievement of good heat transfer performance without negatively impacting the chemical heat storage capacity.

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Absorption heat pumps (AHPs) operate by refrigeration techniques that use heat without a compressor. In this study, proposed is the innovative LiBr/H₂O AHP system which utilizes waste heat at 80°C to produce both hot air of 120°C (at least) and steam of 100–115°C. Air is heated directly by heat exchange in the absorber at the heating mode. Steam is produced by heat exchange with the absorption solution still having high temperature. The performance of a bench-scale AHP was evaluated under the continuous operation. By recovering heat of hot water at 80°C, the temperature of hot air achieved more than 120°C at the outlet of the absorber and that of steam became up to 115°C. The energy efficiency ratio, which is defined as the ratio of heat generated to the power consumed for pumping fluid, exceeded 20. The heat transfer rate in the absorber was dominated by an air stream through a bundle of tubes, and the temperature in the evaporator was a significantly sensitive factor to increase the temperature in this AHP system.

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In this study, calcium chloride-anodized alumina composites were examined for water vapor sorption properties. Porous alumina host matrices for calcium chloride impregnation were prepared by anodizing aluminum plates in an oxalic acid bath or a sulfuric acid bath. CaCl₂-alumina composites were obtained through calcination of the anodic alumina film impregnated with a CaCl₂ solution at 473 or 773 K. XRD analyses indicated that the type of host matrix and the calcination temperature made an effect on crystal states of calcium chloride in the composite layer. The composite calcined at 473 K, of which the host matrix was oxalic-acid anodized alumina film, contained calcium chloride anhydrate crystals. Water vapor sorption experiments showed that the composite with crystalline calcium chloride sorbed water vapor well, and its sorption isotherm had a shape similar to that of bulk CaCl₂. Therefore, the water sorption behavior of the CaCl₂-alumina composite strongly depends on the crystal states of calcium chloride in anodized alumina layer.

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A dual-fluidized bed experimental apparatus was operated to study coal combustion behavior under the Calcium Looping (CaL) process temperature conditions. This apparatus consisted of a fast fluidized bed regenerator and a bubbling fluidized bed carbonator. High-volatile bituminous coal and semi-anthracite were burned in oxygen-enriched air in the regenerator. The formation of CO and CO₂ in the carbonator caused by oxidation of char, which was transported from the regenerator with circulating bed material, was measured. Inert silica sand was employed as the bed material so that the produced CO₂ could be measured without being captured by the bed material. The effect of the O₂ concentration in the fluidizing gas of the carbonator on the formation of CO and CO₂ was evaluated. The formation rate of CO and CO₂ in the carbonator was governed by different controlling factors depending on coal rank. NOx formation in the regenerator was also measured. The oxygen concentration in the carbonator fluidizing gas had only a minor influence on NOx emissions from the regenerator irrespective of char consumption in the carbonator.

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The objectives in the present study are to elucidate the fundamental gasification characteristics of woody biomass with a mixture gas of CO₂ and H₂O. The effects of temperature and gasification agents on the gasification characteristics of woody biomass were experimentally studied using an electrically heated drop tube furnace. The co-gasification performance of CO₂ with H₂O was compared with the CO₂ or H₂O gasification performance alone. As a result, H₂ and CO concentrations increased with an increase of temperature under both the co- and single-gasification conditions. CO under the co-gasification condition was produced more than under the single-gasification condition. The H₂ formation showed the opposite tendency to the CO formation during the co-gasification. This synergistic effect is caused by the difference of the surface structure of the woody biomass particles by CO₂ from H₂O.

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Decomposition of Japanese cypress volatiles has been found to proceed efficiently under a prepared Ni loaded brown coal (LY-Ni) char at extremely low temperatures around 400–450°C. This temperature range is much lower than conventional gasification methods (600–800°C for catalytic and 800–950°C for non-catalytic). For the low temperature decomposition of biomass volatiles, the LY-Ni coal with about 20 wt% Ni loading content by ion-exchange and impregnation methods showed a higher activity when compared with the lower LY-Ni coal by ion-exchange only and the higher Ni content of 27 wt%. Nickel particles in the 20 wt% LY-Ni coal dispersed well in the brown coal, with a mean particle size of 5 nm after devolatilization treatment at temperatures of 400–500°C. In the presence of 20 wt% LY-Ni char, tarry materials converted fairly significantly into gases so that the carbon amount in tarry materials was less than 2% (based on carbon). Compared with the cases of sand, the LY-Ni char increased the total gases, mainly including H₂, CO, CO₂ and CH₄, by 3.5–4.5 times, and hydrogen practically by 5.4–6.9 times at decomposition temperatures of 450 to 600°C. Steam addition advanced the tarry materials gasification and carbon conversion into gas products greatly.

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Co-processing of heavy oil and a low-grade iron ore which contains a large amount of FeO(OH) is proposed to produce both light oil and a raw material for iron making called iron ore/carbon composite (IOC). When the mixture of the heavy oil, an oil sand bitumen’s vacuum tower bottom (VR) in this work, and the low-grade iron ore was heated up to 300°C, the VR filled up the layered 0.8 nm-wide pore space which was formed by the dehydration of FeO(OH). When the mixture was further heated over 400°C, the VR in the pore space was catalytically cracked to produce light oil in high yield. The resulting low-grade iron ore consisting of Fe₂O₃ and containing high-molecular-weight compounds, coke, in the pore space is expected to be utilized as a high quality IOC, as reported in our previous paper.

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The treatment of 1,4-dioxane in wastewater is presently an issue in Japan because the pollutant is non-biodegradable and has a high solubility in water. The Fenton process, carried out in darkness, was effective in treating 1,4-dioxane in low concentrations. However, the process cannot be applied in cases of high 1,4-dioxane concentrations because the Fenton reaction is completed within 15 min. Therefore, the photo-Fenton process was evaluated for treating 1,4-dioxane present in high concentrations. The ferrioxalate-mediated photo-Fenton process, which utilizes the reduction of Fe(III) ions through ligand–metal charge transfer, uses UVA- or white-LED-irradiation to reduce energy consumption. Fe(III) ions can be reduced to Fe(II) ions even under white LED irradiation, indicating that the Fenton reaction can occur continuously. In this case 1,4-dioxane at a concentration of 100 mg/L could be degraded to less than 0.5 mg/L, which is the discharge limit for wastewater. The amount of 1,4-dioxane degraded is linearly dependent on the amount of Fe(III) reduced. The use of white LED irradiation could reduce energy consumption by 40% compared with UVA irradiation. Considering that ambient room light can also be used for degradation, the utilization of white LED light for the degradation process has promise for achieving a further reduction in energy consumption.

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Flue gases contain elemental mercury formed by combustion/incineration processes, and it is difficult to remove them by conventional gas cleaning devices. Researchers have developed a few sorbent materials to capture gaseous elemental mercury. Our study also found two candidate sorbent materials using low-cost waste derived particles, a paper sludge incineration ash and a carbonized municipal solid waste char. The main objective of this study is to elucidate the capturing mechanisms of gaseous elemental mercury in these two sorbents. In order to analyze the chemical states of the mercury adsorbed on the sorbents, X-ray absorption near edge structure (XANES) analyses of the mercury captured by sorbents are conducted. The XANES spectra of the two sorbents were found to be similar to those of Hg₂Cl₂ and HgS standard chemicals, while the XANES spectrum of the commercialized activated carbon for mercury capture was similar to that of elemental mercury. These results suggest that the gaseous mercury is captured and fixed on the sorbents via oxidation by chlorine and sulfur present in the sorbents.

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