GB565089A - Improvements in production of neutral calcium hypochlorite - Google Patents

Abstract

565,089. Calcium hypochlorite. MATHIESON ALKALI WORKS. Jan. 26, 1943, No. 1328. Convention date, Jan. 21, 1942. [Class 1 (iii)] Easily filtered slurries of neutral calcium hypochlorite are produced by simultaneously adding to a previously prepared slurry thereof, at rates which are substantially equivalent chemically, chlorine and a slurry of dibasic calcium hypochlorite, the liquid phase of the latter having a gravity of 30-47, preferably 40-44‹ Tw. The free lime content of the composite slurry is generally kept below 1.5 per cent by weight during the chlorination which is effected at 10-25, preferably 15-20‹ C. The dibasic slurry may be added continuously or intermittently to a neutral slurry, prepared initially by chlorination of lime or the dibasic compound until the free lime content is below 1.5, usually about 0.5 per cent by weight. The dibasic slurry may be prepared by chlorinating milk of lime, starting at room temperature and rising to 35-45‹ C. until substantially complete conversion when, if desired, part of the mother liquor may be drawn off after settling, and further chlorine added until the liquid phase has the desired gravity. The dibasic compound may be separated and resuspended. In a batch operation, when the reaction chamber is full, the addition of dibasic slurry is stopped, further chlorination to a lime content of 0.1-0.2 per cent effected if desired, and the neutral slurry removed leaving sufficient for the next operation. In continuous operation, four tanks may be used, milk of lime being chlorinated in the first at 30-40‹ C. to a gravity of 22-26‹ Tw., and further chlorinated in the next at 35-40‹ C. to a gravity of 40-47‹ Tw. The slurry is passed to the third tank containing the neutral slurry, while chlorine is introduced to keep the free lime content below 1.5 per cent, the product being finally reduced in lime content to, say, .05-.25 per cent by chlorine in the last tank, which may be cooled to, say, 0‹ C. Examples of batch and continuous operation are given.