| 摘要 |
PURPOSE:Efficiency of saline water electrolysis by ion-exchange method is enhanced, wherein low concentration NaOH supplied from the electrolytic bath is concentrated, providing condensed water which is partly utilized to produce hydrochloric acid used for pH adjustment in the anode chamber whereby an adequate amount of the rest of the water is supplied to the cathode chamber to adjust catholyte concentration. CONSTITUTION:Saline water is electrolyzed in the ion-exchange membrane electrolytic bath 1. The produced Cl2 and H2 are both partially passed to the HCl sybthetic tower 2 to produce HCl, which is introduced into the absorption column 3. Meanwhile, aqueous NaOH solution of relatively low concentration such as 18 to 25% is fed from the electrolytic bath 1 to the evaporator 4 such as counter-current type quadruple effective evaporator, where the NaOH solution is concentrated to about 48% solution. Evaporated water is condensed and the condensed water is fed to the absorption column 3 to absorb HCl. The produced hydrochloric acid is then partially utilized to adjust pH of the anode chamber. An adequate amount of the condensed water is supplied to the cathode chamber to adjust the concentration of NaOH to 18 to 25%. Further, the NaOH contained in the condensed water is recovered. |
