熱化学水素製造法ISプロセスのためのヨウ化水素濃縮用イオン交換膜の開発

Development of proton exchange membranes for HI concentration in thermochemical water-splitting IS process

田中 伸幸 ; 澤田 真一*; 越川 博*; 八巻 徹也*

Tanaka, Nobuyuki; Sawada, Shinichi*; Koshikawa, Hiroshi*; Yamaki, Tetsuya*

熱化学水素製造法ISプロセスの熱効率の向上を行う膜技術の開発が進められており、HI-I-HO (HIx)溶液のHI濃縮のため、カチオン交換膜を用いた電解電気透析法(EED)が適用されている。カチオン交換膜に対して、放射線グラフト重合法を用いることにより、イオン導電性を向上し、消費エネルギーを大幅に削減した。さらに、グラフト鎖に架橋を導入し、膜の膨潤を抑制することで、H選択性を向上させ、イオン導電率との両立を実現した。現在では、膨潤抑制効果がさらに期待できるイオン飛跡グラフト重合法を用いて、イオン交換膜の性能向上を進めている。

A thermochemical water-splitting iodine-sulfur process enables us to provide the Carbon-free hydrogen (H) at high-efficiency levels, and it uses high-temperature heat sources, including high-temperature gas-cooled reactors, solar heat, and more. The cation exchange membranes (CEMs) for the HI mediated electro-electrodialysis (EED) were developed using a radiation grafted polymerization method in order to improve the process efficiency of the IS process. High proton (H) conductivity and selectivity are required for the performance of CEMs to reduce the consumption energy for EED. The H conductivity of the radiation grafted CEMs were successfully improved by controlling the grafting amount, comparing with that of Nafion. Moreover, the H selectivity and water transport of the developed CEMs was improved by introducing the crosslinker. Currently, the further improvement of the membrane performance is underway by using the ion-track grafting technic.