Operation of chlor-alkali cells and anolyte liquid level control.

摘要

1,174,264. Electrolytic chlor-alkali diaphragm cells. HOOKER CHEMICAL CORP. Nov. 25, 1966 [Nov.29, 1965(3)], No.53015/66. Heading C7B. In a process for operating a group of chloralkali diaphragm cells in which a decomposition voltage is applied across the electrodes of the diaphragm cells, a solution of an alkali metal chloride is fed to the anolyte compartment of each of the cells at a rate in excess of the rate at which liquor flows through the diaphragm of the cells, the excess feed solution is withdrawn from the anolyte compartments of the cells and replenished by combining with additional amounts of an alkali metal chloride, hydrogen chloride, as gas or aqueous solution, or mixtures thereof, and the replenished solution of alkali metal chloride is returned to the anolyte compartments of the cells. The diaphragm cells used for carrying out the above process may comprise an anode compartment 46 containing anodes 56 and separated from the cathode compartment by diaphragm 50; brine inlet 52; chlorine outlet 54; alkali metal hydroxide outlet 49 and an anolyte withdrawal system 64. The anolyte withdrawal system may comprise a bent tube 64, as shown, which is rotatable about the axis of the opening 66, such that the level of anolyte maintained may be varied. Alternatively cells may be used in which the anolyte is withdrawn from a level beneath the surface thereof, Fig. 5 (not shown) the tube 70, indicated by (20) in Fig. 5, being provided with a variable level control by means of movable vertical overflow tube (28) positioned within the tube (20), which is also provided with a sight glass (40) through which the liquor withdrawn from the anolyte may be observed. The space above the anolyte and the space within the tube (20) and above the overflow tube are interconnected to equalize the pressure therein. The anolyte withdrawal systems are preferably formed of non-conductive materials resistant to chlorine attack, e.g. synthetic polymers such as polyvinyl chloride, chlorinated polyvinyl chloride, and chlorinated polyesters and rubbers; glass; ceramic material or metals such as tantalum or titanium.