Patent ID: 7175824
Filing Date: 2007-02-13
Classification: C01B

Abstract:
1. A method for the continuous manufacture, in a tank, of higher strength, low-salt, aqueous sodium hypochlorite bleach from lower strength aqueous sodium hypochlorite bleach that has some sodium hydroxide and is essentially free of sodium chloride (salt) crystals, the method comprising: A) continuously introducing into an inner reaction zone circumscribed by a baffle i) that is inside a side wall of the tank for separating the inner reaction zone from an outer calming zone between the baffle and the side wall of the tank so as to avoid disturbing liquid in the calming zone, ii) that is open at its bottom to provide for both the inner reaction zone and the outer calming zone to be open to a bottom zone below both inner and outer zones, and iii) that is open at its top to a top wall of the tank, to create, by continuous reaction in the inner reaction zone, higher-strength bleach in which salt crystals are precipitating to continuously replenish a slurry in the bottom zone; B) continuously withdrawing first and second portions of the slurry from the bottom zone, cooling the withdrawn first portion of the slurry, and re-introducing the cooled, withdrawn first portion of the slurry into the inner reaction zone as the recycle solution, while creating at the top of the calming zone, an essentially crystal-free mother liquor containing a weight percentage of sodium hypochlorite greater than that of the lower strength aqueous sodium hypochlorite bleach being introduced into the inner reaction zone; and C) separating substantially all salt crystals from the withdrawn second portion of the slurry and recovering the residual liquid as the higher-strength low-salt, aqueous sodium hypochlorite bleach.