Sodium Chlorate Production

The process under analysis comprises two major sections: (1) Electrolysis and (2) Sodium Chlorate Recovery.

Electrolysis. In a salt dissolver, a brine solution is prepared from sodium chloride raw material and process water. After purification, the solution receives hydrochloric acid and sodium dichromate, which, respectively, increase cell efficiency and protect electrodes from corrosion. The purified, acidified solution is then subjected to electrolysis. At the cathodes, hydrogen gas is generated and released along with impregnated chlorine. The released gas is collected in a column that prevents chlorine emissions through caustic scrubbing. At the anodes, chlorine atoms generated combine with water and free ions forming hypochlorous acid and sodium hypochlorite. Hypochlorous acid and sodium hypochlorite then react forming sodium chlorate. Reaction tanks downstream the electrolytic cells provide a longer residence time for the chemical reaction between hypochlorous acid and sodium hypochlorite to take place. The cells liquor is finally transferred to the crystallizer in the Sodium Chlorate Recovery section.

Sodium Chlorate Recovery. Prior to crystallization, residual hypochlorites are eliminated through heating and addition of chemicals. The cells liquor, virtually free of hypochlorites, is heated, subjected to vacuum evaporation and finally crystallized under vacuum. The Sodium Chlorate crystals are recovered by centrifugation, washed, and fed to a dryer. Dry sodium chlorate is conveyed to silos before being packed into big bags.