Membrane cell chlor-alkali process having improved overall efficiency

摘要

A process for the preparation of an alkali metal hydroxide and halogen from an alkali metal halide in a plurality of electrolytic cells, wherein each electrolytic cell is physically arranged in series with respect to the other electrolytic cells, the series having a first electrolytic cell and a last electrolytic cell, so that for a selected cell in the series, after the first electrolytic cell, catholyte alkali metal hydroxide from the catholyte chamber of a previous electrolytic cell is conveyed to the catholyte chamber of the selected electrolytic cell. The concentration of the alkali metal hydroxide is progressively increased toward a desired final concentration in the last cell through the series of electrolytic cells. Each electrolytic cell has an anolyte chamber containing an anode and a catholyte chamber containing a cathode, separated by a permselective membrane. The process of this invention is characterized by the improvement wherein the permselective membrane is employed to maximize cell power efficiency corresponding to the concentration of alkali metal hydroxide produced in the catholyte chamber of each cell.