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Myagmarjav, O.; 田中 伸幸; 野村 幹弘*; 野口 弘喜; 今井 良行; 上地 優; 久保 真治; 竹上 弘彰
Progress in Nuclear Energy, 137, p.103772_1 - 103772_7, 2021/07
被引用回数：6 パーセンタイル：72.21(Nuclear Science & Technology)Hydrogen production from nuclear energy has attracted considerable interest as a clean energy solution to address the challenges of climate change and environmental sustainability. With respect to the large-scale and economical production of hydrogen using nuclear energy, the thermochemical water-splitting iodine-sulfur (IS) process is a promising method. The IS process uses sulfur and iodine compounds to decompose water into its elemental constituents, hydrogen and oxygen, by using three coupled chemical reactions: the Bunsen reaction; sulfuric acid decomposition; and hydrogen iodide (HI) decomposition. The decomposition of HI is the efficiency-determining step of the process. In this work, a membrane reactor with a silica membrane closed on one end was designed, and its potential for hydrogen production from HI decomposition was explored. In the reactor-module design, only one end of the membrane tube was fixed, while the closed-end of the tube was freely suspended to avoid thermal expansion effects. The closed-end silica membranes were prepared for the first time by a counter-diffusion chemical vapor deposition of hexyltrimethoxysilane. In application, HI conversion of greater than 0.60 was achieved at a decomposition temperature of 400
C. Thus, the membrane reactor with closed-end silica membrane was shown to produce a successful equilibrium shift in the production of hydrogen via HI decomposition in the thermochemical IS process.
Myagmarjav, O.; 田中 伸幸; 野村 幹弘*; 久保 真治
International Journal of Hydrogen Energy, 44(59), p.30832 - 30839, 2019/11
被引用回数：10 パーセンタイル：33.23(Chemistry, Physical)In this study, the catalytic decomposition of hydrogen iodide was theoretically and experimentally investigated in a silica-based ceramic membrane reactor to assess the reactors suitability for thermochemical hydrogen production. The silica membranes were fabricated by depositing a thin silica layer onto the surface of porous alumina ceramic support tubes via counter-diffusion chemical vapor deposition of hexyltrimethoxysilane. The performance of the silica-based ceramic membrane reactor was evaluated by exploring important operating parameters such as the flow rates of the hydrogen iodide feed and the nitrogen sweep gas. The influence of the flow rates on the hydrogen iodide decomposition conversion was investigated in the lower range of the investigated feed flow rates and in the higher range of the sweep-gas flow rates. The experimental data agreed with the simulation results reasonably well, and both highlighted the possibility of achieving a conversion greater than 0.70 at decomposition temperature of 400C. Therefore, the developed silica-based ceramic membrane reactor could enhance the total thermal efficiency of the thermochemical process.
Myagmarjav, O.; 岩月 仁; 田中 伸幸; 野口 弘喜; 上地 優; 井岡 郁夫; 久保 真治; 野村 幹弘*; 八巻 徹也*; 澤田 真一*; et al.
International Journal of Hydrogen Energy, 44(35), p.19141 - 19152, 2019/07
被引用回数：16 パーセンタイル：49.6(Chemistry, Physical)Thermochemical hydrogen production has attracted considerable interest as a clean energy solution to address the challenges of climate change and environmental sustainability. The thermochemical water-splitting iodine-sulfur (IS) process uses heat from nuclear or solar power and thus is a promising next-generation thermochemical hydrogen production method that is independent of fossil fuels and can provide energy security. This paper presents the current state of research and development of the IS process based on membrane techniques using solar energy at a medium temperature of 600C. Membrane design strategies have the most potential for making the IS process using solar energy highly efficient and economical and are illustrated here in detail. Three aspects of membrane design proposed herein for the IS process have led to a considerable improvement of the total thermal efficiency of the process: membrane reactors, membranes, and reaction catalysts. Experimental studies in the applications of these membrane design techniques to the Bunsen reaction, sulfuric acid decomposition, and hydrogen iodide decomposition are discussed.
Myagmarjav, O.; 田中 伸幸; 野村 幹弘*; 久保 真治
International Journal of Hydrogen Energy, 44(21), p.10207 - 10217, 2019/04
被引用回数：15 パーセンタイル：47.35(Chemistry, Physical)The potential of the silica membrane reactors for use in the decomposition of hydrogen iodide (HI) was investigated by simulation with the aim of producing CO
-free hydrogen via the thermochemical water-splitting iodine-sulfur process. Simulation model validation was done using the data derived from an experimental membrane reactor. The simulated results showed good agreement with the experimental findings. The important process parameters determining the performance of the membrane reactor used for HI decomposition, namely, reaction temperature, total pressures on both the feed side and the permeate side, and HI feed flow rate were investigated theoretically by means of a simulation. It was found that the conversion of HI decomposition can be improved by up to four times (80%) or greater than the equilibrium conversion (20%) at 400C by employing a membrane reactor equipped with a tubular silica membrane. The features to design the membrane reactor module for HI decomposition of thermochemical iodine-sulfur process were discussed under a wide range of operation conditions by evaluating the relationship between HI conversion and number of membrane tubes.
Myagmarjav, O.; 田中 伸幸; 野村 幹弘*; 久保 真治
International Journal of Hydrogen Energy, 42(49), p.29091 - 29100, 2017/12
被引用回数：20 パーセンタイル：51.38(Chemistry, Physical)熱化学水素製造法ISプロセスにおいて水素生成する反応であるHI分解反応の分解率を向上させるため、水素分離膜を用いた膜反応器の適用を検討している。本研究では、高性能な水素分離膜を開発するため、HTMOSをシリカ源に用い
-アルミナ基材上に対向拡散CVD法を用いて製膜したシリカ膜の性能を調べた。-アルミナに直接製膜した膜よりも
-アルミナをコーティングした-アルミナ基材上に製膜した膜の方が、高い水素透過性を示すこと、および、450Cの製膜条件で高い水素選択性ならびに水素透過性が得られることを見い出した。さらに、製膜した膜を適用した膜反応器において、HI分解反応を行い、平衡分解率(20%)を超える0.48の水素転化率を得ることができた。
Hwang, G.; 小貫 薫
Journal of Membrane Science, 194(2), p.207 - 215, 2001/12
被引用回数：59 パーセンタイル：87.3(Engineering, Chemical)熱化学法ISプロセスの水素発生工程の高効率化を目的として、膜反応器によるヨウ化水素接触分解反応に関する理論的検討を行った。解析にあたり、H及びHIの透過係数は、試作したシリカ膜における実測値を用いた。実測困難なIの透過係数については、H/I選択性が分解率に及ぼす影響を調べて評価した。検討の結果、90%以上のヨウ化水素分解率の得られる条件が存在することを明らかにした。さらに、反応部体積と膜面積との比,無次元長さなどの反応器パラメータと分解率との関係を明らかにし、その結果をもとに膜反応器の設計指針を論じた。
Myagmarjav, O.; 池田 歩*; 野村 幹弘*; 久保 真治
no journal, ,
熱化学水素製造法ISプロセスにおけるHI分解反応のワンパス分解率を向上させるため、水素選択透過性シリカ膜を用いたメンブレンリアクターの開発を行っている。HI分解膜反応に必要な機能性を確認するため、水素選択透過性シリカ膜(直径10mm、アルミナ管の外表面にシリカを製膜した非対称膜、HI分解反応場から水素を分離させる)を製膜・作製し、これ用いてHI膜分解反応実験を行って膜を透過したガスの成分を調べた。ガスクロマトグラフィーにより透過ガスに水素が含まれていることを示すとともに、透過ガスを水に溶解させる吸収槽内に捕集されたHIがほとんどなかったことから、必要機能である、HI分解反応による水素生成、反応場からの水素の選択的分離を確認することができた。
Myagmarjav, O.; 田中 伸幸; 野村 幹弘*; 久保 真治
no journal, ,
This study deals with demonstration of experimental membrane reactor equipped with silica membrane in HI decomposition for thermochemical IS hydrogen production. The silica membrane was prepared by chemical vapor deposition method. We found that the developed membrane reactor offered a significant increase in HI conversion up to 40%. Elemental technology of the membrane reactor in HI decomposition was successfully demonstrated.
Myagmarjav, O.; 田中 伸幸; 野村 幹弘*; 久保 真治
no journal, ,
In this study, we propose an iodine-sulfur cycle, a promising thermochemical water splitting process for CO-free hydrogen production, with the aim of contributing low-carbon society. One important task is to improve efficiency of the iodine-sulfur process due to poor equilibrium of hydrogen iodide (HI) decomposition. Efficient separation of hydrogen using a membrane reactor is an effective method of improving the conversion of the HI decomposition. When hydrogen is removed selectively from reaction field with the use of membrane, chemical equilibrium of the reactions is shifted toward product side according to Le Chateliers principle, resulting in increased the conversion of the HI decomposition. We developed membrane reactor assembled with 95 mm long silica membrane in the HI decomposition. It was found that the conversion can be improved twice (50%) or greater than equilibrium conversion (20%) at 400C. Elemental technologies of the membrane reactors were demonstrated for the HI decomposition. The thermochemical iodine-sulfur process is expected to be part of future key technologies in coming low-carbon society by producing efficiently CO-free hydrogen in large-scale.
Myagmarjav, O.; 田中 伸幸; 野村 幹弘*; 久保 真治
no journal, ,
Recently, the inorganic membranes have been undergoing quick development and innovation, and becoming an attractive field of membrane separation technology including membrane reactors. The catalytic decomposition of hydrogen iodide (HI) has long been a candidate reaction for the application of membrane reactors. The decomposition of HI is an endothermic reaction and equilibrium conversions even high temperatures are low. The use of membrane reactors based on silica membranes provides the opportunity of increasing the HI-conversion. Design of the membrane reactor modules previously developed for HI decomposition tests was based on the membrane tube fixed to gas lines at each end of the membrane tube. This design was a suitable for short-size module but not viable in terms of long-size fabrication and the practical applications. In this work, a membrane reactor equipped with one-end-closed silica membrane was designed and a potential of the membrane reactor to HI decomposition was explored. The closed-one-ended silica membrane were prepared by a counter diffusion chemical vapor deposition method for the first time. Permeation performance of the one-end-closed silica membrane was investigated. On the basis of HI decomposition tests, the membrane reactor equipped with the one-end-closed silica membrane demonstrated to show a successful equilibrium shift in the production of hydrogen.
