On this day in 1953 Ralph W. Brown was granted the patent for PRECIPITATION OF ALUMINUM HYDROXIDE. U.S. Patent No. 2,653,858.
The principal method used heretofore in the production of aluminum hydroxide has been to dissolve alumina from bauxite by means of an aqueous caustic soda solution, and then precipitate aluminum hydroxide by auto-precipitation from the resultant sodium aluminate solution by adding previously precipitated particles of aluminum hydroxide to the solution to act as “seed” particles in the precipitation of aluminum hydroxide from the solution, and agitating the solution. It has been customary to effect agitation of the solution by means of a stirrer, gas lift or pump, and to carry out the precipitation process as a batch operation in which sodium aluminate solution and the “seed” particles are fed into a tank in which the solution is thus agitated for a suitable time, after which the spent solution and precipitated aluminum hydroxide are removed from the tank.
It has also been proposed to carry out auto-precipitation of the aluminum hydroxide from sodium aluminate solutions by a continuous process in which fresh solution is fed continuously to a precipitation tank from which there is a continuous overflow of solution to a succeeding precipitation tank, the solution and aluminum hydroxide suspended therein being kept agitated in the tanks by means of pumps. (See U. S. Patent 1,943,785.) However in order to precipitate aluminum hydroxide by auto-precipitation with maximum efficiency, and to produce a precipitate of relatively uniform size, it is desirable to control closely the amount and size of the particles of aluminum hydroxide available in the precipitation tanks to act as “seed” in the precipitation of further hydroxide.
