Calcium Hypochlorite from Slaked Lime and Cl2 (Sodium Method)

The process under analysis comprises three major sections: (1) Reaction; (2) Separation; and (3) Finishing.

Reaction. Initially, caustic soda solution is mixed with recycled bleach mother liquor, composed of Calcium Hypochlorite and sodium chloride dissolved in water. The resulting solution is combined with slaked lime to form a milk of lime slurry. Such milk is mixed with more liquor recycle and recycled bleach mother liquor. The resulting solution is supersatured with sodium chloride and Calcium Hypochlorite, initiating the precipitation of crystals. Then, the mixture is fed into a chlorinator along with gaseous chlorine, which reacts with calcium hydroxide and sodium hydroxide to form Calcium Hypochlorite and sodium chloride. In this way, new Calcium Hypochlorite and sodium chloride crystals are formed and the preexisting ones increase in size.

Separation. The chlorinator outlet slurry is fed at the midpoint of a two-stage upward flow cylindrical elutriator-classifier. Bleach mother liquor is fed at the bottom portion of the lower stage of the elutriator as the elutriating fluid. The upper stream of the elutriator, an aqueous slurry containing most of Calcium Hypochlorite, is sent to Calcium Hypochlorite centrifuge. The bottom product of the elutriator, an aqueous slurry containing the denser sodium chloride crystals, is centrifuged; the sodium chloride wet cake is then conveyed to an intermediate tank. The salt centrifuge mother liquor is sent to the Calcium Hypochlorite centrifuge.

Finishing. The wet cake from Calcium Hypochlorite centrifuge is dried in a turbo dryer; the gas from the dryer is scrubbed and released. Dry Calcium Hypochlorite is squeezed, prilled, and then classified; the oversize and undersize solids are returned for further processing, while the Calcium Hypochlorite product is directed for packaging.