Sawada, Shinichi*; Kimura, Takehiro*; Nishijima, Haruyuki*; Kodaira, Takahide*; Tanaka, Nobuyuki; Kubo, Shinji; Imabayashi, Shinichiro*; Nomura, Mikihiro*; Yamaki, Tetsuya*
International Journal of Hydrogen Energy, 45(27), p.13814 - 13820, 2020/05
An electrochemical membrane Bunsen reaction using a cation exchange membrane (CEM) is a key to achieving an iodine-sulfur (IS) thermochemical water splitting process for mass-production of hydrogen. In this study, we prepared both the radiation-grafted CEM with a high ion exchange capacity (IEC) and the highly-porous Au-electroplated anode, and then used them for the membrane Bunsen reaction to reduce the cell overvoltage. The high-IEC grafted CEM exhibited low resistivity for proton transport, while the porous Au anode had a large effective surface area for anodic SO oxidation reaction. As a result, the cell overvoltage for the membrane Bunsen reaction was significantly reduced to 0.21 V at 200 mA/cm, which was only one-third of that of the previous test using the commercial CEM and non-porous anode. From the analysis of the current-voltage characteristics, employment of the grafted CEM was found to be more effective for the overvoltage reduction compared to the porous Au anode.
Myagmarjav, O.; Tanaka, Nobuyuki; Nomura, Mikihiro*; Kubo, Shinji
International Journal of Hydrogen Energy, 44(59), p.30832 - 30839, 2019/11
Myagmarjav, O.; Iwatsuki, Jin; Tanaka, Nobuyuki; Noguchi, Hiroki; Kamiji, Yu; Ioka, Ikuo; Kubo, Shinji; Nomura, Mikihiro*; Yamaki, Tetsuya*; Sawada, Shinichi*; et al.
International Journal of Hydrogen Energy, 44(35), p.19141 - 19152, 2019/07
Noguchi, Hiroki; Takegami, Hiroaki; Kamiji, Yu; Tanaka, Nobuyuki; Iwatsuki, Jin; Kasahara, Seiji; Kubo, Shinji
International Journal of Hydrogen Energy, 44(25), p.12583 - 12592, 2019/05
JAEA has been conducting R&D on thermochemical water-splitting hydrogen production IS process to develop one of heat applications of high-temperature gas-cooled reactor. A test facility was constructed using corrosion-resistant industrial materials to verify integrity of the IS process components and to demonstrate continuous and stable hydrogen production. The performance of components installed in each section was confirmed. Subsequently, a trial operation of integration of the processing sections was successfully carried out for 8 hours with hydrogen production rate of approximately 10 NL/h. After that, hydrogen production operation was extended to 31 hours (approximately hydrogen production rate of 20 NL/h) by introducing a corrosion-resistance pump system with a developed shaft seal technology.
Myagmarjav, O.; Tanaka, Nobuyuki; Nomura, Mikihiro*; Kubo, Shinji
International Journal of Hydrogen Energy, 44(21), p.10207 - 10217, 2019/04
Myagmarjav, O.; Tanaka, Nobuyuki; Nomura, Mikihiro*; Kubo, Shinji
International Journal of Hydrogen Energy, 42(49), p.29091 - 29100, 2017/12
The catalytic decomposition of hydrogen iodide in a membrane reactor using silica membranes derived from hexyltrimethoxysilane (HTMOS) was investigated for the production of hydrogen in the thermochemical water splitting iodine-sulfur process. The silica membranes were prepared by counter-diffusion chemical vapor deposition using porous alumina support tubes in both the absence and presence of a -alumina layer. The silica membranes formed on -alumina-coated -alumina tubes displayed a higher H permeance than that formed directly on an -alumina tube. A silica membrane based on a 1.5 m-thick -alumina layer fabricated under deposition conditions of 450C, 1200 s, and a N carrier gas velocity of 0.044 m s exhibited a high H permeance of 9.4 10 mol Pa m s while maintaining an H/N selectivity of over 80.0. The performance of a membrane reactor based on an HTMOS-derived silica membrane was evaluated at 400C by measuring the HI conversion and H flow rates. The conversion was approximately 0.48 when the HI flow rate was 9.7 mL min.
Kasahara, Seiji; Iwatsuki, Jin; Takegami, Hiroaki; Tanaka, Nobuyuki; Noguchi, Hiroki; Kamiji, Yu; Onuki, Kaoru; Kubo, Shinji
International Journal of Hydrogen Energy, 42(19), p.13477 - 13485, 2017/05
Current R&D on the thermochemical water splitting iodine-sulfur (IS) process in Japan Atomic Energy Agency is summarized. Reactors were fabricated with industrial materials and verified by test operations: a Bunsen reactor, a HSO decomposer, and a HI decomposer. Reactors of industrial materials showed corrosion stability. Demonstration of the test facility verified integrity of process components and stability of hydrogen production. An 8 hours continuous operation of the total IS process was performed in February 2016 with H production rate of 10 L/h.
Matsumura, Daiju; Taniguchi, Masashi*; Tanaka, Hirohisa*; Nishihata, Yasuo
International Journal of Hydrogen Energy, 42(11), p.7749 - 7754, 2017/03
Myagmarjav, O.; Ikeda, Ayumi*; Tanaka, Nobuyuki; Kubo, Shinji; Nomura, Mikihiro*
International Journal of Hydrogen Energy, 42(9), p.6012 - 6023, 2017/03
Ebara, Shinji*; Takamura, Hiroyuki*; Hashizume, Hidetoshi*; Yamano, Hidemasa
International Journal of Hydrogen Energy, 41(17), p.7139 - 7145, 2016/05
In this study, a flow visualization and pressure measurement were conducted by using an experimental setup including test sections of 1/7-scale models of the cold-leg piping of Japan sodium-cooled reactor with high Reynolds number region up to about one million. Regarding the flow field, flow separation appeared in the intrados of the third elbow. However, the separation region was smaller than that observed in the first elbow in the direction normal to the mean flow and was larger in the streamwise direction. This can be considered because of the swirling flow generated downstream of the second elbow which flowed into the third elbow with a little reduction. From the pressure fluctuation test, it was found that prominent frequencies of the pressure fluctuation appeared at about 0.4 in Strouhal number, which corresponds to a nondimensional frequency, in the region from 0 D to 0.4 D downstream of the elbow outlet, where D is the diameter of the piping. And weak peaks of about 0.7 in Strouhal number were observed in the region far 0.75 D downstream of the outlet.
Fan, M.*; Xu, Y.*; Sakurai, Junya*; Demura, Masahiko*; Hirano, Toshiyuki*; Teraoka, Yuden; Yoshigoe, Akitaka
International Journal of Hydrogen Energy, 40(37), p.12663 - 12673, 2015/10
The catalytic properties of single-phase NiSn powder in the production of hydrogen via the decomposition of methanol were investigated in isothermal tests at 713, 793, and 873 K. The catalytic activity of NiSn significantly increased with time at 793 and 873 K, but not at 713 K, suggesting that NiSn is spontaneously activated at temperatures above 793 K. At these temperatures, NiSn showed high selectivity for H and CO production and low selectivity for CH, CO, and HO production, indicating that methanol decomposition was the main reaction, and that side reactions such as methanation and water-gas shift reaction were suppressed. Surface analysis revealed that fine NiSn particles were formed during the reaction, accompanied by a small amount of deposited carbon. The formation of these particles was suggested to be the cause for the spontaneous activation of NiSn.
Endo, Naruki*; Saita, Itoko*; Nakamura, Yumiko*; Saito, Hiroyuki; Machida, Akihiko
International Journal of Hydrogen Energy, 40(8), p.3283 - 3287, 2015/03
Kim, H.*; Sakaki, Koji*; Saita, Itoko*; Enoki, Hirotoshi*; Noguchi, Kazuo*; Machida, Akihiko; Watanuki, Tetsu; Nakamura, Yumiko*
International Journal of Hydrogen Energy, 39(20), p.10546 - 10551, 2014/07
The effect of the vanadium content on the cyclic stability of V-Ti binary alloys was investigated. VTi, 0.2 and 0.5 samples were hydrogenated and dehydrogenated at 410 K and 553 K respectively, for more than 100 times. During hydrogen cycling, reduction in the reversible hydrogen storage capacity was clearly observed from both samples. In addition, the shape of the pressure-composition-isotherm curves was significantly altered over the testing cycle period; the absorption and desorption plateaus got markedly inclined and the hysteresis became evidently smaller. We found that even after the hydrogen storage capacity of VTi was significantly reduced, at low enough temperature VTi was able to absorb hydrogen as much as it did at the first cycle.
Tanaka, Nobuyuki; Onuki, Kaoru; Kubo, Shinji
International Journal of Hydrogen Energy, 39(1), p.86 - 89, 2014/01
The effect of sulfuric acid on the concentration of HIx solution by electro-electrodialysis (EED) was examined for the thermochemical water-splitting iodine-sulfur process. Presence of sulfuric acid in the anolyte HIx solution did not affect the concentration behavior. However, sulfuric acid in the catholyte solution caused side reaction(s) producing whitish precipitates, which indicates that the sulfur compound should be removed prior to the EED operation.
Kubo, Shinji; Futakawa, Masatoshi; Ioka, Ikuo; Onuki, Kaoru; Yamaguchi, Akihisa*
International Journal of Hydrogen Energy, 38(16), p.6577 - 6585, 2013/05
Very harsh environments exist in the iodine-sulfur process for hydrogen production. Structural materials for sulfuric acid vaporizers and concentrators are exposed to high-temperature corrosive environments. Immersion tests were carried out to evaluate the corrosion resistance of ceramics and to evaluate corrosion-resistant metals exposed to environments of aqueous sulfuric acids at temperatures of 320, 380, and 460C, and pressure of 2 MPa. The aqueous sulfuric acid concentrations for the temperatures were 75, 85, and 95 wt%, respectively. Ceramic specimens of silicon carbides (SiC), silicon impregnated silicon carbides (Si-SiC), and silicon nitrides (SiN) showed excellent corrosion resistance from weight loss measurements after exposure to 75, 85, and 95 wt% sulfuric acid. High-silicon irons with silicon content of 20 wt% showed a fair measure of corrosion resistance. However, evidence of crack formation was detected via microscopy. Silicon enriched steels severely suffered from uniform corrosion with a corrosion rate in 95 wt% sulfuric acid of approximately 1 gmh. Among the tested materials, the ceramics SiC, Si-SiC, and SiN were found to be suitable candidates for structural materials in direct contact with the considered environments.
Endo, Naruki; Saito, Hiroyuki; Machida, Akihiko; Katayama, Yoshinori
International Journal of Hydrogen Energy, 38(16), p.6726 - 6729, 2013/05
Guo, H.*; Kasahara, Seiji; Tanaka, Nobuyuki; Onuki, Kaoru
International Journal of Hydrogen Energy, 37(19), p.13971 - 13982, 2012/10
Separation of HI from HI-I-HO mixture determines the efficiency of the IS process for thermochemical hydrogen production. Energy requirement of HI separation from HI-I-HO mixture using electro-electrodialysis (EED) and distillation was evaluated by a process simulation. For EED, ideal membrane properties and properties of the reported EED experiments using Nafion membrane were evaluated. Effects of the operating parameters on heat duty were estimated, which comprised column pressure, HI molality in the column feed, and the flow rate ratio of the input from the Bunsen section to distillate rate. Low column pressure and high HI molality in the column feed were preferable for the ideal-membrane case; column pressure of 1.0 MPa and optimized HI molality in the column feed were desired for the Nafion-membrane case. The flow rate ratio had little effect on the minimum heat duty in the ideal-membrane case; a value in the vicinity of the lower limit of the flow rate ratio was optimal for the Nafion-membrane case. Optimization of these parameters was also carried out. The minimum heat duty of the Nafion-membrane case was 3.0710 J/mol-HI, and that of the ideal-membrane case was 12.5% of the value.
Wang, L.*; Imai, Yoshiyuki; Tanaka, Nobuyuki; Kasahara, Seiji; Kubo, Shinji; Onuki, Kaoru; Chen, S.*; Zhang, P.*; Xu, J.*
International Journal of Hydrogen Energy, 37(17), p.12967 - 12972, 2012/09
Optimization of purification operation of the Bunsen reaction products, HSO phase and HIx phase, is one of the problems for industrialization of the thermochemical hydrogen production iodine-sulfur process. HI impurity is contained in HSO phase, and HSO impurity is in HIx phase: these impurities should be removed by purification. Effect of pressure on purification of these phases was simulated as an investigation of the operation by a chemical process simulator ESP with a thermodynamic database based on the Mixed Solvent Electrolyte model. The simulation was of the reaction equilibrium and phase equilibrium. As the result of the simulation in the range of 0.2-6 bar, effective removal of impurities and suppression of undesirable side reactions were suggested in the purification of HSO phase at below atmospheric pressure. On the other hand, advantageous pressure in the viewpoint of equilibrium was not found in purification of HIx phase.
Yamada, Reiji; Kumagai, Yuta
International Journal of Hydrogen Energy, 37(18), p.13272 - 13277, 2012/09
The effects of powder characteristics on H and HO2 productions in Co -radiolysis were studied in pure water and in 0.4M HSO aqueous solutions containing alumina powders. In 0.4 M HSO solution, the H yields strongly depended on alumina structures and decreased in the order of , , alumina, although the specific surface areas increased as , , . The yields increased with increasing specific surface area when compared am-alumina. In pure water, similar dependence was observed but not as strong as that for 0.4 M HSO solution. The HO yields were strongly decreased by adding the alumina powders in both water and 0.4 M HSO aqueous solution, although the amounts of decrease were almost neither correlated with specific surface areas nor structures. The enhancing H production was discussed in terms of the electron supply from alumina to aqueous solution as well as the adsorption of OH radicals on alumina surfaces.
Yamada, Reiji; Kumagai, Yuta; Nagaishi, Ryuji
International Journal of Hydrogen Energy, 36(18), p.11646 - 11653, 2011/09
The H and HO produced by Co -radiation at room temperature were measured in pure water and 0.4M HSO aqueous solution with alumina powder. By increasing the addition of alumina powder, a strong reduction of HO concentrations in the solutions was obtained, and the final product H yields were correspondingly enhanced. These enhancement and reduction effects were diminished in the subsequent -radiation when irradiated alumina powder was used. The effects were reversibly restored by washing the irradiated powder with purified water. In 0.4M HSO solution with alumina powder, the H yields increased by increasing the absorbed dose rate in the region of 1-5 kGy/hr. The radiation-enhanced H production correlated with the reduction of HO concentration could be brought about by the reduction of HO molecules and OH radicals in the solutions due to alumina powder.