JPS56123386A - Method and apparatus for electrolysis of salt - Google Patents

Abstract

PURPOSE:To improve electrolytic current efficiency by partitioning the inside of an electrolytic cell for aqueous salt soln. with plural cation exchange membranes to constitute an anode chamber, an intermediate chamber and a cathode chamber, and performing electrolysis while passing raw liquid, dilute NaOH soln. and concd. NaOH soln. respectively. CONSTITUTION:Two sheets of cation exchange membranes 3a, 3b which have high current efficiency exclusively to an alkaline solution of low concn., are small in electric resistance and have durability are disposed between the anode 2 and cathode 1 of an electrolytic cell producing chlorine and NaOH by electrolyzing an aqueous soln. of salt, whereby an anode chamber (raw liquid chamber) 6, an intermediate chamber 5, and a cathode chamber 4 are formed. The raw liquid of the aqueous soln. of salt is circulated and supplied to the chamber 6 via an anolyte holding tank 2 and a gas-liquid separating chamber 11; an aqueous soln. contg. NaOH of high concn. is circulated and supplied to the chamber 4 via a catholyte holding tank 9 and a gas-liquid separating chamber 10, and an aqueous soln. of the NaOH having a concn. of 1/2-1/50 the catholyte concn. is circulated and supplied to the chamber 5 via an intermediate liquid holding tank 8. Gaseous chlorine and NaOH are produced at higher current efficiency than in the prior art.