PROCESS FOR CONCENTRATION OF CAUSTIC ALKALI SOLUTION PRODUCED BY ION EXCHANGE MEMBRANE TYPE ELECTROLYSIS

摘要

An alkali metal hydroxide soln. obtained from the anode compartment in the electrolysis of aq. alkali chloride soln. is conce. in a series of concn. units. Each of these units comprises a heat-exchange stage for the exchange between the aq. alkali hydroxide soln. of the cathode compartment and the anolyte of the anode compartment. Also, it compriese a vaporliq. sepn. step for evapn. of the hot hydroxide soln. which is passed successively with increasing concn. from the 1st to the next concn. unit to obtain a concd. alkali hydroxide soln. in the last unit. aq. alkali chloride soln. is recycled into the anode compartment.