# US 9,517,944 B2 · Method for producing alumina

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- Number: US 9,517,944 B2
- Document ID: US9517944B2
- Status: Granted
- Kind: B2
- Application number: 14/415,958
- Filed: 2012-07-20
- Published: 2015-06-25
- Granted: 2016-12-13
- Earliest claimed: 2012-07-20
- Assignees: United Company RUSAL Engineering and Technology Centre LLC
- Applicants: Aleksandr Sergeevich Senyuta; Andrey Vladimirovich Panov
- Inventors: Aleksandr Sergeevich Senyuta; Andrey Vladimirovich Panov
- Web page: https://patentgrep.com/patent/US9517944B2

## CPC

- C01F 7/306: Thermal decomposition of hydrated chlorides, e.g. of aluminium trichloride hexahydrate
- C01F 7/34: Preparation of aluminium hydroxide by precipitation from solutions containing aluminium salts
- C01F 7/441: by calcination
- C01F 7/56: Chlorides (containing fluorine C01F7/52)
- C01G 49/06: Ferric oxide [Fe2O3]
- C22B 3/10: Hydrochloric acid {, other halogenated acids or salts thereof}
- C22B 3/44: by chemical processes (treatment or purification of solutions by liquid-liquid extraction C22B3/26, by ion-exchange extraction C22B3/42)
- C22B 21/0015: {by wet processes (C22B21/02, C22B21/04 and C22B21/06 take precedence)}
- C01P 2006/80: Compositional purity
- Y02P 10/20: Recycling
- C01F: COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS (metal hydrides {monoborane, diborane or addition complexes thereof} C01B6/00; salts of oxyacids of halogens C01B11/00; peroxides, salts of peroxyacids C01B15/00; sulfides or polysulfides of magnesium, calcium, strontium, or barium C01B17/42; thiosulfates, dithionites, polythionates C01B17/64; compounds containing selenium or tellurium C01B19/00; binary compounds of nitrogen with metals C01B21/06; azides C01B21/08; {compounds other than ammonia or cyanogen containing nitrogen and non-metals and optionally metals C01B21/082; amides or imides of silicon C01B21/087}; metal {imides or} amides C01B21/092, {C01B21/0923}; nitrites C01B21/50; {compounds of noble gases C01B23/0005}; phosphides C01B25/08; salts of oxyacids of phosphorus C01B25/16; carbides C01B32/90; compounds containing silicon C01B33/00; compounds containing boron C01B35/00; compounds having molecular sieve properties but not having base-exchange properties C01B37/00; compounds having molecular sieve and base-exchange properties, e.g. crystalline zeolites, C01B39/00; cyanides C01C3/08; salts of cyanic acid C01C3/14; salts of cyanamide C01C3/16; thiocyanates C01C3/20; {double sulfates of magnesium with sodium or potassium C01D5/12; with other alkali metals C01D15/00, C01D17/00})
- C01G: COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F (metal hydrides {monoborane, diborane or addition complexes thereof} C01B6/00; salts of oxyacids of halogens C01B11/00; peroxides, salts or peroxyacids C01B15/00; thiosulfates, dithionites, polythionates C01B17/64; compounds containing selenium, or tellurium C01B19/00; binary compounds of nitrogen with metals C01B21/06; azides C01B21/08; {compounds containing nitrogen, other non-metals and metal C01B21/082}; metal amides C01B21/092; nitrites C01B21/50; {compounds of noble gases C01B23/0005}; phosphides C01B25/08; salts of oxyacids of phosphorus C01B25/16; carbides C01B32/90; compounds containing silicon C01B33/00; compounds containing boron C01B35/00; compounds having molecular sieve properties but not having base-exchange properties C01B37/00; compounds having molecular sieve and base-exchange properties, e.g. crystalline zeolites, C01B39/00; cyanides C01C3/08; salts of cyanamide C01C3/16; thiocyanates C01C3/20)
- C22B: PRODUCTION AND REFINING OF METALS (electrolytic C25); PRETREATMENT OF RAW MATERIALS
- C01P: INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- Y02P: CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS

## Abstract

The invention relates to metallurgy, in particular to acidic methods for producing alumina, and can be used in processing low-grade aluminum-containing raw material. The method for producing alumina comprises roasting an aluminum-containing raw material, treating said material with hydrochloric acid, salting out aluminum chloride by saturating the clarified chloride solution with gaseous hydrogen chloride, calcining aluminum chloride to produce aluminum oxide, and pyrohydrolyzing the mother liquor, with the return of hydrogen chloride to the acid treatment and salting out stages. To improve the quality of the alumina and to reduce energy consumption, the aluminum chloride, precipitated during the salting-out process, is treated with aqueous ammonia, the resulting precipitate is sent to calcination, and the ammonium chloride solution is mixed with said aluminum-containing raw material before or during the roasting thereof, ammonia released during the roasting is dissolved in water, and the resulting aqueous ammonia is sent to the treatment of aluminum chloride. The ammonium chloride solution, prior to mixing with the aluminum-containing raw material, may be subjected to stepwise evaporation with the repeated use of heating steam. The ammonium chloride released during the evaporation can be mixed with the aluminum-containing raw material.

## Claims

### Claim 1

A method for producing alumina, comprising:
mixing and roasting an aluminum-containing raw material with an ammonium chloride solution to produce a roasted raw material wherein said roasted raw material undergoes partial thermal activation and the ammonium chloride undergoes decomposition;
dissolving the ammonia released during the roasting in water to form aqueous ammonia;
treating said roasted raw material with hydrochloric acid to produce a slurry comprising a solid phase and a clarified chloride solution;
salting out aluminum chloride by saturating the clarified chloride solution with gaseous hydrogen chloride to produce a mother liquor and aluminum chloride hexahydrate in crystalline form;
subjecting the aluminum choride hexahydrate in crystalline form to treatment by the aqueous ammonia previously produced, to forming boehmite and an ammonium chloride solution;
calcining the boehmite to produce aluminum oxide; and
pyrohydrolyzing the mother liquor to form hematite and hydrochloric acid, wherein the hydrochloric acid is used in the treating of the roasted raw material step and the salting out aluminum chloride step.

### Claim 2 (depends on 1)

The method according to claim 1, wherein the ammonium chloride solution, prior to mixing with the aluminum-containing raw material, is subjected to a stepwise evaporation with repeated use of heating steam.

### Claim 3 (depends on 2)

The method according to claim 2, wherein the ammonium chloride released during the stepwise evaporation is mixed with the aluminum-containing raw material.