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

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

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.