Ppg Industries, Inc.

Duk S Chun

Clifford E Loehr

David A Stermole

Calcium hypochlorite particles and larger sodium chloride crystals are separated by passing an aqueous slurry containing such particles and crystals into a first classification zone comprising a two-stage substantially vertical elutriator-classifier. A first slurry in which the solid phase is predominantly calcium hypochlorite particles is removed from the upper stage of the first classification zone. A second slurry in which the solid phase is predominantly sodium chloride crystals is removed from the lower stage of the first classification zone and forwarded to a second classification zone comprising a two-stage substantially vertical elutriator-classifier. A slurry in which the solid phase is predominantly calcium hypochlorite particles is removed from the upper stage of the second classification zone and, in one embodiment, combined with overflow from the upper stage of the first classification zone. A slurry in which the solid phase is predominantly sodium chloride crystals is removed from the lower stage of the second classification zone. Elutriation fluid comprising a saturated solution of calcium hypochlorite and sodium chloride is introduced into the lower stages of each of the first and second classification zones.

Method for separating particulate calcium hypochlorite and sodium

Calcium hypochlorite particles and larger separable sodium chloride crystals produced in a process for manufacturing calcium hypochlorite are effectively separated by use of a staged upward-flow elutriator-classifier. In particular, an aqueous slurry of the calcium hypochlorite particles and sodium chloride crystals are introduced into about the midpoint of the classifier and elutriated with fluid substantially saturated in calcium hypochlorite and sodium chloride. A first slurry in which the solid phase is predominantly calcium hypochlorite, e.g., at least 95 weight percent, is removed as overflow from the top of the classifier, and a second slurry in which the solid phase is predominantly sodium chloride is removed as underflow from the bottom of the classifier. In one embodiment, the first slurry is separated into a wet cake of calcium hypochlorite and bleach mother liquor, a portion of which liquor is used as elutriating fluid. The second slurry is separated into a wet cake of sodium chloride and salt mother liquor, which liquor is recycled to the bottom of the classifier. The wet cake of sodium chloride is washed with a fluid unsaturated in calcium hypochlorite and the washed sodium chloride recovered.

Boron trichloride containing minor amounts of phosgene as an impurity is purified by contacting a vaporous stream thereof and at least a stoichiometric amount of hydrogen, based on the phosgene impurity, with a substantially metal-free carbon catalyst under substantially anhydrous conditions at temperatures of between about 300.degree. C. and about 700.degree. C.

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Uniontown, OH, United States of America

Duk S Chun