Energy requirement of HI separation from HI-I-HO mixture using electro-electrodialysis and distillation

電解電気透析と蒸留を用いたHI-I-HO混合溶液からのHI分離の所要熱評価

Guo, H.*; 笠原 清司  ; 田中 伸幸 ; 小貫 薫

Guo, H.*; Kasahara, Seiji; Tanaka, Nobuyuki; Onuki, Kaoru

熱化学水素製造法ISプロセスにとって、HI-I-HO混合溶液からのHIの分離工程の所要熱がプロセス全体の熱効率に大きく影響する。電解電気透析(EED)と蒸留を用いたHI-I-HO混合溶液からのHI分離工程のシミュレーションを行い、EEDにおける理想的な分離膜とNafion膜の実験値を用いた現実的な分離膜の場合での所要熱評価を行った。操作パラメータとして、蒸留塔内圧,蒸留塔フィード内HI濃度,蒸留塔流出量に対する工程入口流量の比を検討した。理想的分離膜の場合、低圧,高フィードHI濃度が望ましかったのに対し、Nafion膜の場合、塔内圧は1.0MPaで十分で、フィードHI濃度は最適化を行うことが望まれた。流量比に関しては、理想的分離膜の場合その影響は小さかったが、Nafion膜の場合、到達しうる最小値付近に所要熱の最小値があった。これらの操作条件の最適化によって、Nafion膜の場合、所要熱は3.0710 J/mol-HIとなり、理想的分離膜の所要熱はその12.5%となった。

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.