Abstract: Aluminum hydroxide aggregated particles which have an average particle diameter of not less than 40 ?m, an average particle diameter as determined after pressing at 1,000 kg/cm2 of not more than 35 ?m, and an L value of slurry obtained by mixing 20 ml of glycerol and 10 g of the aluminum hydroxide aggregated particles of not more than 69, are obtained by a process comprising the steps of: (a) feeding a supersaturated aqueous sodium aluminate solution to a vessel, (b) adding aluminum hydroxide seeds to the supersaturated aqueous sodium aluminate solution, (c) stirring the seed-added solution in the vessel while continuously feeding an additional supersaturated aqueous sodium aluminate solution into the vessel to hydrolyze the supersaturated aqueous sodium aluminate solution, (d) separating the aluminum hydroxide aggregated particles from the aqueous sodium aluminate solution, and (e) continuously discharging the aqueous sodium aluminate solution out of the vessel.

Abstract: Aluminum hydroxide aggregated particles which have an average particle diameter of not less than 40 ?m, an average particle diameter as determined after pressing at 1,000 kg/cm2 of not more than 35 ?m, and an L value of slurry obtained by mixing 20 ml of glycerol and 10 g of the aluminum hydroxide aggregated particles of not more than 69, are obtained by a process comprising the steps of: (a) feeding a supersaturated aqueous sodium aluminate solution to a vessel, (b) adding aluminum hydroxide seeds to the supersaturated aqueous sodium aluminate solution, (c) stirring the seed-added solution in the vessel while continuously feeding an additional supersaturated aqueous sodium aluminate solution into the vessel to hydrolyze the supersaturated aqueous sodium aluminate solution, (d) separating the aluminum hydroxide aggregated particles from the aqueous sodium aluminate solution, and (e) continuously discharging the aqueous sodium aluminate solution out of the vessel.

Abstract: Aluminum hydroxide aggregated particles which have an average particle diameter of not less than 40 ?m, an average particle diameter as determined after pressing at 1,000 kg/cm2 of not more than 35 ?m, and an L value of slurry obtained by mixing 20 ml of glycerol and 10 g of the aluminum hydroxide aggregated particles of not more than 69, are obtained by a process comprising the steps of: (a) feeding a supersaturated aqueous sodium aluminate solution to a vessel, (b) adding aluminum hydroxide seeds to the supersaturated aqueous sodium aluminate solution, (c) stirring the seed-added solution in the vessel while continuously feeding an additional supersaturated aqueous sodium aluminate solution into the vessel to hydrolyze the supersaturated aqueous sodium aluminate solution, (d) separating the aluminum hydroxide aggregated particles from the aqueous sodium aluminate solution, and (e) continuously discharging the aqueous sodium aluminate solution out of the vessel.

Abstract: Aluminum hydroxide aggregated particles which have an average particle diameter of not less than 40 ?m, an average particle diameter as determined after processing at 1,000 kg/cm2 of not more than 35 ?m, and an L value of slurry obtained by mixing 20 ml of glycerol and 10 g of the aluminum hydroxide aggregated particles of not more than 69, are obtained by a process comprising the steps of: (a) feeding a supersaturated aqueous sodium aluminate solution to a vessel, (b) adding aluminum hydroxide seeds to the supersaturated aqueous sodium aluminate solution, (c) stirring the seed-added solution in the vessel while continuously feeding an additional supersaturated aqueous sodium aluminate solution into the vessel to hydrolyze the supersaturated aqueous sodium aluminate solution, (d) separating the aluminum hydroxide aggregated particles from the aqueous sodium aluminate solution, and (e) continuously discharging the aqueous sodium aluminate solution out of the vessel.

Abstract: Aluminum hydroxide aggregated particles which have an average particle diameter of not less than 40 ?m, an average particle diameter as determined after pressing at 1,000 kg/cm2 of not more than 35 ?m, and an L value of slurry obtained by mixing 20 ml of glycerol and 10 g of the aluminum hydroxide aggregated particles of not more than 69, are obtained by a process comprising the steps of: (a) feeding a supersaturated aqueous sodium aluminate solution to a vessel, (b) adding aluminum hydroxide seed to the supersaturated aqueous sodium aluminate solution, (c) stirring the seed-added solution n the vessel while continuously feeding an additional supersaturated aqueous sodium aluminate solution into the vessel to hydrolyze the supersaturated aqueous sodium aluminate solution, (d) separating the aluminum hydroxide aggregated particles from the aqueous sodium aluminate solution, and (e) continuously discharging the aqueous sodium aluminate solution out of the vessel.

Abstract: Aluminum hydroxide aggregated particles which have an average particle diameter of not less than 40 &mgr;m, an average particle diameter as determined after pressing at 1,000 kg/cm2 of not more than 35 &mgr;m, and an L value of slurry obtained by mixing 20 ml of glycerol and 10 g of the aluminum hydroxide aggregated particles of not more than 69, are obtained by a process comprising the steps of:

Abstract: An aluminum hydroxide having high purity with high brightness and a method for producing such an aluminum hydroxide are provided. The aluminum hydroxide may be produced by a method which comprises the steps of mixing a crude aluminum hydroxide with an alkaline solution to obtain a mixture thereof; heating the mixture to obtain a slurry in which a solid of aluminum hydroxide is present in an amount of from about 10% by weight to about 90% by weight based on the crude aluminum hydroxide to be used for the mixing; cooling the slurry to precipitate an aluminum hydroxide; and separating the resulting aluminum hydroxide from the slurry.

Abstract: The present invention provides a method for manufacturing aluminum hydroxide powder highly fillable in a resin as a filler, comprising the step of grinding raw aluminum hydroxide using a kneader mixer.

Abstract: In the production of alumina from aluminous ores containing alumina trihydrate and alumina monohydrate comprising a first-stage digestion by digesting alumina trihydrate from a slurry of the ores and a caustic solution and separating the resulting slurry into a caustic aluminate solution and an insoluble residue, and a second-stage digestion by digesting alumina monohydrate from a slurry of the insoluble residue separated in the first-stage digestion and a caustic solution, the present invention provides an improvement wherein scale formation onto a preheater for the slurry in the second-stage digestion is completely or substantially prevented and reduction in heat transfer coefficient of heat transfer surface is remarkably lowered. The improvement is attained by setting up a desilication reaction zone in the course of the first-stage digestion, whereby the slurry introduced into said zone is subjected to desilication reaction treatment.

Abstract: A highly efficient process for producing metallic gallium from a gallium containing alkali aluminate solution circulating in the Bayer process is disclosed. The process comprises subjecting an alkali aluminate solution to electrolysis, said solution being obtained by (1) cooling an alkali aluminate solution after the aluminum hydroxide separation step in the Bayer process in the presence or absence of at least one, as a seed, alkali salt of an element selected from vanadium and phosphorus, or complexes containing the alkali salt, in order to precipitate crystals of impurities containing vanadium, phosphorus, etc.

Abstract: Coarse grains of aluminum hydroxide having high resistance to disintegration to powder in a calcination step are continuously produced from a supersaturated sodium aluminate solution of the Bayer process through(1) a first precipitation step of adding recycle seed aluminum hydroxide to a supersaturated sodium aluminate solution having a molar ratio of Na.sub.2 O as caustic soda to Al.sub.2 O.sub.3 in solution of less than 1.8 supplied to a precipitation tank of substantially complete mixing type in a ratio of 30-150 kg of the recycle seed to 1 m.sup.3 of the solution, thereby partially decomposing the seed-added solution until the molar ratio of the solution reaches 2.0-2.4 while keeping the solution at 65.degree.-80.degree. C.

Abstract: Coarse grains of aluminum hydroxide are economically produced in a high yield from sodium aluminate solution by dividing supersaturated sodium aluminate solution being prepared by the Bayer process and having a molar ratio of Na.sub.2 O as caustic soda to Al.sub.2 O.sub.3 in solution of less than 1.8 into two streams, adding a portion of recycle seed aluminum hydroxide and fine grains of aluminum hydroxide as seed to one of the streams of sodium aluminate solution, partially decomposing the sodium aluminate solution until the molar ratio of the sodium solution reaches 1.8-2.6, adding to the resulting partially decomposed sodium aluminate slurry the other stream of sodium aluminate solution, which has been cooled to a temperature low enough to lower the temperature of the partially decomposed sodium aluminate slurry by at least 3.degree. C.

Abstract: Impurities such as organic substances, i.e. sodium oxalate and inorganic impurities, i.e.

Abstract: In the production of alumina from bauxite by the Bayer process, the present invention provides an improvement for effectively and economically removing organic substances from a circulating alkali aluminate solution by contacting the aluminate solution containing organic substances with molecular oxygen gas or a molecular oxygen-containing gas in the presence of copper ions as a catalyst at an elevated temperature, thereby oxidizing the organic substances, adding a chemical substance to the resulting aluminate solution which reacts with copper ions to deposit a water-insoluble precipitate, and separating the precipitate from the solution, and recycling the precipitate as a copper source to the above-mentioned wet oxidation procedure.

Abstract: In the production of alumina from aluminous ores by the Bayer process, the present invention provides an improvement for effectively and economically recovering caustic components consisting essentially of sodium aluminate from aluminum hydroxide cakes as seed classified from the product aluminum hydroxide by washing the seed with a washing liquor having a substantially saturated concentration of sodium oxalate and little content of caustic and then removing organic substances such as sodium oxalate from the washed seed by secondly washing said seed with hot water, thereby recovering caustic components without the dissolution of sodium oxalate from the seed into the recovered caustic solution and attaining the removal of sodium oxalate contaminant with high efficiency.

Abstract: An aqueous basic aluminum salt high in basicity can be continuously produced with a high conversion by passing a slurry of aluminum hydroxide, alumina-containing mineral or a mixture thereof and hydrochloric or nitric acid through a tubular reactor and then reacting the initial stage reaction product with the unreacted alumina in a holding treatment portion provided subsequent to the tubular reactor.