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利用者:Phyllis8051/sandbox/硫黄ヨウ素反応

硫黄–ヨウ素サイクル （いおう–—そ）は3段からなる熱化学サイクルで、水素製造に用いられる。

硫黄ヨウ素反応は3つの化学反応からなっていて、水を原料として水素と酸素を生成する。反応に関係する他の物質はリサイクルされる。また、この反応は効率的な熱の供給源を必要とする。

反応過程

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H2O ½O2
↓ ↑
I2 → 反応 1 ← SO2+H2O ← 分離
↑ ↓ ↑
2HI ← 分離 → H2SO4 → 反応 2
↓
H2

以下の3つの反応で水素が生成される。

  1. I2 + SO2 + 2 H2O → 2 HI + H2SO4 (120 °C) ブンゼン反応
  2. 2 H2SO4 → 2 SO2 + 2 H2O + O2 (830 °C)
  3. 2 HI → I2 + H2 (450 °C)
    • 主生成物の水素はガスとして存在する。
正味の反応: 2 H2O → 2 H2 + O2

硫黄やヨウ素の化合物は、回収され繰り返し使用される。したがって、これらの反応は環になっていると考察できる。また、この反応は化学的熱エンジンである。高温吸熱反応である2と3に熱を入力すると、低温発熱反応である1から熱が出力される。入力された熱と出力される熱の差は、このサイクルで生成された水素の燃焼熱として出てくる。


利点と欠点

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硫黄–ヨウ素サイクルの特徴は以下の様なものがある： The characteristics of the S–I process can be described as follows:

  • 全過程が流体なので、連続運転に適している。
    • All fluid (liquids, gases) process, therefore well suited for continuous operation;
  • 50%程度の高い熱利用率になると予測されているが、少なくとも850℃以上の高温を必要とする。
    • High utilization of heat predicted (about 50%), but very high temperatures required (at least 850 °C);
  • 水素と酸素以外の副生成物や廃液が出ない完全閉鎖系
    • Completely closed system without byproducts or effluents (besides hydrogen and oxygen);
  • 腐食性のある物質を
    • Corrosive reagents used as intermediaries (iodine, sulfur dioxide, hydriodic acid, sulfuric acid); therefore, advanced materials needed for construction of process apparatus;
  • Suitable for application with solar, nuclear, and hybrid (e.g., solar-fossil) sources of heat;
  • More developed than competitive thermochemical processes (but still requiring significant development to be feasible on large scale).

研究

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The S–I cycle was invented at General Atomics in the 1970s.[1] The Japan Atomic Energy Agency (JAEA) has conducted successful experiments with the S–I cycle in the Helium cooled High Temperature Test Reactor,[2][3][4][5] a reactor which reached first criticality in 1998, JAEA have the aspiration of using further nuclear high-temperature generation IV reactors to produce industrial scale quantities of hydrogen. (The Japanese refer to the cycle as the IS cycle.) Plans have been made to test larger-scale automated systems for hydrogen production. Under an International Nuclear Energy Research Initiative (INERI) agreement, the French CEA, General Atomics and Sandia National Laboratories are jointly developing the sulfur-iodine process. Additional research is taking place at the Idaho National Laboratory, in Canada, Korea and Italy.

材質の努力

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The S–I cycle involves operations with corrosive chemicals at temperatures up to about 1,000 °C (1,830 °F). The selection of materials with sufficient corrosion resistance under the process conditions is of key importance to the economic viability of this process. The materials suggested include the following classes: refractory metals, reactive metals, superalloys, ceramics, polymers, and coatings.[6][7] Some materials suggested include tantalum alloys, niobium alloys, noble metals, high-silicon steels,[8] several nickel-based superalloys, mullite, silicon carbide (SiC), glass, silicon nitride (Si3N4), and others. Recent research on scaled prototyping suggests that new tantalum surface technologies may be a technically and economically feasible way to make larger scale installations.[9]

水素経済

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The sulfur-iodine cycle has been proposed as a way to supply hydrogen for a hydrogen-based economy. With an efficiency of around 50% it is more efficient than electrolysis, and it does not require hydrocarbons like current methods of steam reforming but requires heat from combustion, nuclear reactions, or solar heat concentrators.

関連項目

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  • 酸化セリウム(IV)–酸化セリウム(III)サイクル
  • 銅-塩素サイクル
  • 硫黄サイクルハイブリッド法
  • 高温電気分解
  • 酸化鉄サイクル
  • 酸化亜鉛サイクル
  • 高温ガス炉

脚注

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  1. ^ Besenbruch, G. 1982. General Atomic sulfur iodine thermochemical water-splitting process. Proceedings of the American Chemical Society, Div. Pet. Chem., 27(1):48-53.
  2. ^ “HTTR High Temperature engineering Test Reactor”. Httr.jaea.go.jp. 2014年1月23日閲覧。
  3. ^ https://smr.inl.gov/Document.ashx?path=DOCS%2FGCR-Int%2FNHDDELDER.pdf. Progress in Nuclear Energy Nuclear heat for hydrogen production: Coupling a very high/high temperature reactor to a hydrogen production plant. 2009
  4. ^ Status report 101 - Gas Turbine High Temperature Reactor (GTHTR300C)
  5. ^ JAEA’S VHTR FOR HYDROGEN AND ELECTRICITY COGENERATION : GTHTR300C
  6. ^ Paul Pickard, Sulfur-Iodine Thermochemical Cycle 2005 DOE Hydrogen Program Review
  7. ^ Wonga, B.; Buckingham, R. T.; Brown, L. C.; Russ, B. E.; Besenbruch, G. E.; Kaiparambil, A.; Santhanakrishnan, R.; Roy, Ajit (2007). “Construction materials development in sulfur–iodine thermochemical water-splitting process for hydrogen production”. International Journal of Hydrogen Energy 32 (4): 497–504. doi:10.1016/j.ijhydene.2006.06.058. 
  8. ^ Saramet info sheet
  9. ^ T. Drake, B. E. Russ, L. Brown, G. Besenbruch, "Tantalum Applications For Use In Scale Sulfur-Iodine Experiments", AIChE 2007 Fall Annual Meeting, 566a.

参考文献

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  • Paul M. Mathias and Lloyd C. Brown "Thermodynamics of the Sulfur-Iodine Cycle for Thermochemical Hydrogen Production", presented at the 68 th Annual Meeting of the Society of Chemical Engineers, Japan 23 March 2003. (PDF).
  • Atsuhiko TERADA; Jin IWATSUKI, Shuichi ISHIKURA, Hiroki NOGUCHI, Shinji KUBO, Hiroyuki OKUDA, Seiji KASAHARA, Nobuyuki TANAKA, Hiroyuki OTA, Kaoru ONUKI and Ryutaro HINO, "Development of Hydrogen Production Technology by Thermochemical Water Splitting IS Process Pilot Test Plan", Journal of Nuclear Science and Technology, Vol.44, No.3, p. 477–482 (2007). (PDF).

外部リンク

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