Membrane performance on electro-electrodialysis of HI-I-HO mixture for IS process

HI-I-HO溶液の電解電気透析法における膜性能

田中 伸幸 ; 八巻 徹也; 浅野 雅春; 寺井 隆幸*; 小貫 薫

Tanaka, Nobuyuki; Yamaki, Tetsuya; Asano, Masaharu; Terai, Takayuki*; Onuki, Kaoru

高温ガス炉の熱利用法の一つである熱化学水素製造法ISプロセスでは、ヨウ化水素(HI-I-HO溶液)環境においてイオン交換膜を用いた電解電気透析法によるヨウ化水素濃縮を行う。エネルギー効率向上を目指した運転条件の最適化のため、ヨウ化水素濃縮時におけるイオン交換膜の膜性能である輸率及び導電率のヨウ素濃度依存性について検討した。放射線グラフト膜を用いた実験結果からヨウ素濃度増加とともに、輸率は増加し、導電率は減少することがわかった。また、Nernst-Planck理論をもとにしたEEDモデルから、これらの傾向は膜中のIイオンの拡散係数の変化により説明できることが明らかとなった。

Research and development of a water-splitting hydrogen-production method, called iodine-sulfur (IS) process, has been conducting as one of the heat applications of high temperature gas-cooled reactor. Among the unit operations in this IS process, we have investigated electro-electrodialysis (EED) using an ion-exchange membrane to concentrate HI in an HI-I-HO mixture. Aiming at maximizing EED performance, new membrane materials were prepared by the radiation-induced graft polymerization and were examined in terms of their proton permeability through the membrane, i.e., transport number and conductivity at different iodine (I) concentrations in the HI-I-HO mixture. The transport number increased and the conductivity decreased with an increase in the feed I molality. The EED model derived by the Nernst-Planck theory suggested that this trend could be explained exclusively by the variation of diffusion coefficient of I.