Electrolytic manufacture of chlorine and sodium carbonate

Abstract

Manufacture of chlorine and sodium carbonate using a combination of electrolysis of an aqueous solution of sodium chloride in a diaphragm cell, carbonation of the caustic brine leaving the cell, and the ammonia-soda method of making sodium carbonate. An aqueous solution of sodium chloride is electrolyzed in at least one diaphragm cell to form a caustic brine. The caustic brine leaving the cell is carbonated and further treated. This is first done in a soda plant without ammonia by treating the caustic brine in at least one monocarbonation scrubber by reacting the caustic brine with a gas having a low carbon dioxide content without causing bicarbonate precipitation in the monocarbonation scrubber to form a monocarbonated caustic brine, and treating the monocarbonated caustic brine in at least one bicarbonation column by reacting at least part of it with gas rich in carbon dioxide to precipitate sodium bicarbonate in the bicarbonation column and to form a mother liquor. The precipitated sodium bicarbonate from the mother liquor is separated by filtration. The separated mother liquor is de-bicarbonated by converting the dissolved bicarbonate to carbonate. The de-bicarbonated mother liquor is saturated with respect to sodium chloride. Then the saturated liquor is treated in an ammonia-soda process for making sodium carbonate and the saturated liquor is used as at least a partial source of sodium chloride for such process.