Alumina crystal growth additive
AssigneeNalco Chemical Company
InventorWilliam J. Roe
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Abstract
A method of modifying crystal structure of alumina trihydrate crystallizing from saturated Bayer liquors, which method includes the treatment of the saturated Bayer liquors with a crystal modifying amount of a polysaccharide, preferably a dextran.
Claims9
An improved method of producing coarser aluminum trihydrate crystals, said crystals having a reduced content of crystallites having a crystal size below negative 325 mesh relative to crystals obtained in the absence of crystal modifying treatment, in the alumina trihydrate precipitation step of a Bayer process operating to produce alumina trihydrate crystals from bauxite ores, which method comprises treating caustic pregnant Bayer process liquor;
- after red mud separation, and prior to, or simultaneously with seeding the pregnant liquors;
- with an effective crystal modifying amount, ranging between about 0.1 ppm to about 1,000 ppm, based on the total weight of the caustic Bayer process liquors, of dextran having a weight average molecular weight ranging between about 50,000 to about 40,000,000 and having a degree of branching less than 5 weight percent of the total weight of the dextran.
Dependencies are inferred from the claim text.