Flowsheet study of HI separation process from HI-HO-I solution in the thermochemical hydrogen production iodine-sulfur (IS) process

Kasahara, Seiji  ; Guo, H.*; Tanaka, Nobuyuki ; Imai, Yoshiyuki  ; Iwatsuki, Jin ; Kubo, Shinji  ; Onuki, Kaoru

Flowsheet investigation of the subsection of HI separation from HI-HO-I solution in the thermochemical hydrogen production iodine-sulfur (IS) process was performed. Concentration of HI by electro-electrodialysis (EED) and distillation of HI were applied. Experimental data of the EED cell applying Nafion membrane was used to establish heat/mass balance equations for the cell. Heat/mass balance of HI distillation column was calculated using ESP, a process simulation software. HI molality at the cathode outlet of the cell, pressure in the HI distillation column, and flow rate ratio of the feed to the subsection to distillate of the column were focused as variable parameters for minimum heat demand. Parameters of the EED membrane, electric resistance and upper limit of HI molality between outlet streams, had a great effect on the heat demand; improvement of the membrane parameters is important to reduce the heat demand.