Use of surfactants in alumina precipitation in the bayer process
AssigneeNalco Chemical Company
InventorsDavid O. Owen, David C. Davis
Life of this patent
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Abstract
A method and composition for producing a more coarse alumina trihydrate crystal in a Bayer process pregnant liquor, involving the addition of approximately 5-400 mg/l of surfactant-oil, the oil dissolving the surfactant which can be selected from a host of surfactants which are stable in (hot) caustic solutions and capable of dispersing hydrophobic liquids in the Bayer liquor. The preferred embodiment involves the use of tall-oil fatty acids; a number of equivalent surfactants are established. The oil or hydrocarbon (hydrophobic) liquid can be selected from paraffinic oils, naphthenic oils, mineral seal oils, fuel oils, and bottoms or residue from a C.sub.10 alcohol distillation.
Claims4
In the method for producing alumina trihydrate crystals by crystallization of alumina trihydrate from a hot, caustic pregnant Bayer process liquor, to obtain a reduced percent of small size crystals of -325 mesh fraction thereby to increase the yield of crystals coarser than -325 mesh subsequently to be processed to yield aluminum, the improvement comprising the addition to the pregnant liquor, after red mud separation and immediately prior to crystallization of alumina trihydrate, of two mutually soluble components (A) and (B) in an amount effective to increase the yield of the coarser crystals, component (A) being a surfactant which will disperse component (B) in the pregnant liquor and component (B) being an oil in which the surfactant is dissolved and having a boiling point above the temperature prevailing alumina hydrate crystallization.
Dependencies are inferred from the claim text.