CN109790045B - Method for producing smelting-grade aluminum oxide (embodiment mode) - Google Patents
Method for producing smelting-grade aluminum oxide (embodiment mode) Download PDFInfo
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- CN109790045B CN109790045B CN201780060150.3A CN201780060150A CN109790045B CN 109790045 B CN109790045 B CN 109790045B CN 201780060150 A CN201780060150 A CN 201780060150A CN 109790045 B CN109790045 B CN 109790045B
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- 238000004519 manufacturing process Methods 0.000 title claims description 17
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 title abstract description 5
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims abstract description 112
- 238000000034 method Methods 0.000 claims abstract description 99
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims abstract description 96
- 230000008569 process Effects 0.000 claims abstract description 76
- 239000002699 waste material Substances 0.000 claims abstract description 74
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 claims abstract description 55
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims abstract description 52
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 45
- 229910052782 aluminium Inorganic materials 0.000 claims abstract description 39
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims abstract description 37
- 238000002386 leaching Methods 0.000 claims abstract description 31
- 239000007788 liquid Substances 0.000 claims abstract description 30
- 239000012535 impurity Substances 0.000 claims abstract description 27
- 239000002994 raw material Substances 0.000 claims abstract description 27
- 239000000377 silicon dioxide Substances 0.000 claims abstract description 26
- JGDITNMASUZKPW-UHFFFAOYSA-K aluminium trichloride hexahydrate Chemical compound O.O.O.O.O.O.Cl[Al](Cl)Cl JGDITNMASUZKPW-UHFFFAOYSA-K 0.000 claims abstract description 23
- 238000001354 calcination Methods 0.000 claims abstract description 22
- 239000000047 product Substances 0.000 claims abstract description 22
- 238000005406 washing Methods 0.000 claims abstract description 22
- 239000000460 chlorine Substances 0.000 claims abstract description 20
- 229910052801 chlorine Inorganic materials 0.000 claims abstract description 19
- 239000002244 precipitate Substances 0.000 claims abstract description 19
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 claims abstract description 18
- 230000002378 acidificating effect Effects 0.000 claims abstract description 16
- WNROFYMDJYEPJX-UHFFFAOYSA-K aluminium hydroxide Chemical compound [OH-].[OH-].[OH-].[Al+3] WNROFYMDJYEPJX-UHFFFAOYSA-K 0.000 claims abstract description 15
- 239000013078 crystal Substances 0.000 claims abstract description 15
- 238000001556 precipitation Methods 0.000 claims abstract description 13
- 239000004411 aluminium Substances 0.000 claims abstract description 12
- 239000002002 slurry Substances 0.000 claims abstract description 12
- 229910021502 aluminium hydroxide Inorganic materials 0.000 claims abstract description 10
- 230000001376 precipitating effect Effects 0.000 claims abstract description 9
- 150000001875 compounds Chemical class 0.000 claims abstract description 8
- 239000013067 intermediate product Substances 0.000 claims abstract description 8
- 150000004645 aluminates Chemical class 0.000 claims abstract description 6
- 239000000243 solution Substances 0.000 claims description 51
- VSCWAEJMTAWNJL-UHFFFAOYSA-K aluminium trichloride Chemical compound Cl[Al](Cl)Cl VSCWAEJMTAWNJL-UHFFFAOYSA-K 0.000 claims description 40
- IXCSERBJSXMMFS-UHFFFAOYSA-N hydrogen chloride Substances Cl.Cl IXCSERBJSXMMFS-UHFFFAOYSA-N 0.000 claims description 37
- 229910000041 hydrogen chloride Inorganic materials 0.000 claims description 37
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 claims description 24
- 239000003513 alkali Substances 0.000 claims description 19
- 229940009861 aluminum chloride hexahydrate Drugs 0.000 claims description 19
- 238000009283 thermal hydrolysis Methods 0.000 claims description 19
- 239000002253 acid Substances 0.000 claims description 18
- WCUXLLCKKVVCTQ-UHFFFAOYSA-M Potassium chloride Chemical compound [Cl-].[K+] WCUXLLCKKVVCTQ-UHFFFAOYSA-M 0.000 claims description 17
- 239000003517 fume Substances 0.000 claims description 15
- 238000005868 electrolysis reaction Methods 0.000 claims description 13
- 239000012528 membrane Substances 0.000 claims description 13
- 229940063656 aluminum chloride Drugs 0.000 claims description 12
- 229910052742 iron Inorganic materials 0.000 claims description 12
- 239000011780 sodium chloride Substances 0.000 claims description 12
- 238000004131 Bayer process Methods 0.000 claims description 11
- 238000010521 absorption reaction Methods 0.000 claims description 11
- 239000007789 gas Substances 0.000 claims description 11
- 229910052791 calcium Inorganic materials 0.000 claims description 9
- 239000001103 potassium chloride Substances 0.000 claims description 9
- 235000011164 potassium chloride Nutrition 0.000 claims description 9
- 238000002425 crystallisation Methods 0.000 claims description 8
- 230000008025 crystallization Effects 0.000 claims description 8
- 150000001805 chlorine compounds Chemical class 0.000 claims description 7
- 229910052749 magnesium Inorganic materials 0.000 claims description 7
- 238000005185 salting out Methods 0.000 claims description 7
- 150000008044 alkali metal hydroxides Chemical class 0.000 claims description 6
- 229910052751 metal Inorganic materials 0.000 claims description 6
- 239000002184 metal Substances 0.000 claims description 6
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims description 5
- 229910001514 alkali metal chloride Inorganic materials 0.000 claims description 5
- 239000001257 hydrogen Substances 0.000 claims description 5
- 229910052739 hydrogen Inorganic materials 0.000 claims description 5
- 239000007864 aqueous solution Substances 0.000 claims description 4
- 238000000605 extraction Methods 0.000 claims description 4
- 238000000227 grinding Methods 0.000 claims description 4
- 150000002739 metals Chemical class 0.000 claims description 4
- 238000000926 separation method Methods 0.000 claims description 4
- 229910001854 alkali hydroxide Inorganic materials 0.000 claims description 3
- 238000009835 boiling Methods 0.000 claims description 3
- 230000007062 hydrolysis Effects 0.000 claims description 3
- 238000006460 hydrolysis reaction Methods 0.000 claims description 3
- 238000002360 preparation method Methods 0.000 claims description 3
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 claims description 2
- 150000007513 acids Chemical class 0.000 claims description 2
- 239000012141 concentrate Substances 0.000 claims description 2
- 238000001035 drying Methods 0.000 claims description 2
- 239000013505 freshwater Substances 0.000 claims description 2
- 229910000288 alkali metal carbonate Inorganic materials 0.000 claims 1
- 150000008041 alkali metal carbonates Chemical class 0.000 claims 1
- 238000001816 cooling Methods 0.000 claims 1
- 239000000498 cooling water Substances 0.000 claims 1
- 238000005265 energy consumption Methods 0.000 abstract description 9
- 238000005272 metallurgy Methods 0.000 abstract description 2
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 22
- 239000003518 caustics Substances 0.000 description 15
- 239000000463 material Substances 0.000 description 13
- 229910052710 silicon Inorganic materials 0.000 description 11
- 239000010703 silicon Substances 0.000 description 11
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 10
- 239000011575 calcium Substances 0.000 description 8
- 239000011734 sodium Substances 0.000 description 8
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 7
- 239000002585 base Substances 0.000 description 7
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 description 6
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 description 6
- NLYAJNPCOHFWQQ-UHFFFAOYSA-N kaolin Chemical compound O.O.O=[Al]O[Si](=O)O[Si](=O)O[Al]=O NLYAJNPCOHFWQQ-UHFFFAOYSA-N 0.000 description 6
- 239000011777 magnesium Substances 0.000 description 6
- 239000000203 mixture Substances 0.000 description 6
- 239000005995 Aluminium silicate Substances 0.000 description 5
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 5
- KKCBUQHMOMHUOY-UHFFFAOYSA-N Na2O Inorganic materials [O-2].[Na+].[Na+] KKCBUQHMOMHUOY-UHFFFAOYSA-N 0.000 description 5
- 238000003723 Smelting Methods 0.000 description 5
- 235000012211 aluminium silicate Nutrition 0.000 description 5
- 229910052681 coesite Inorganic materials 0.000 description 5
- 229910052906 cristobalite Inorganic materials 0.000 description 5
- 238000001704 evaporation Methods 0.000 description 5
- 239000011591 potassium Substances 0.000 description 5
- 229910052700 potassium Inorganic materials 0.000 description 5
- 229910052708 sodium Inorganic materials 0.000 description 5
- 229910052682 stishovite Inorganic materials 0.000 description 5
- 229910052905 tridymite Inorganic materials 0.000 description 5
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 4
- TWRXJAOTZQYOKJ-UHFFFAOYSA-L Magnesium chloride Chemical compound [Mg+2].[Cl-].[Cl-] TWRXJAOTZQYOKJ-UHFFFAOYSA-L 0.000 description 4
- 238000002474 experimental method Methods 0.000 description 4
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 4
- 238000013178 mathematical model Methods 0.000 description 4
- 239000012071 phase Substances 0.000 description 4
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 3
- 229910001570 bauxite Inorganic materials 0.000 description 3
- 239000001110 calcium chloride Substances 0.000 description 3
- 229910001628 calcium chloride Inorganic materials 0.000 description 3
- 230000029087 digestion Effects 0.000 description 3
- 230000008020 evaporation Effects 0.000 description 3
- 239000000446 fuel Substances 0.000 description 3
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N iron oxide Inorganic materials [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 3
- 239000007791 liquid phase Substances 0.000 description 3
- 239000002245 particle Substances 0.000 description 3
- 239000011574 phosphorus Substances 0.000 description 3
- 229910052698 phosphorus Inorganic materials 0.000 description 3
- 238000012545 processing Methods 0.000 description 3
- 239000010454 slate Substances 0.000 description 3
- 239000010802 sludge Substances 0.000 description 3
- 239000007790 solid phase Substances 0.000 description 3
- UXVMQQNJUSDDNG-UHFFFAOYSA-L Calcium chloride Chemical compound [Cl-].[Cl-].[Ca+2] UXVMQQNJUSDDNG-UHFFFAOYSA-L 0.000 description 2
- 229910021578 Iron(III) chloride Inorganic materials 0.000 description 2
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 2
- 238000009825 accumulation Methods 0.000 description 2
- 238000004364 calculation method Methods 0.000 description 2
- 238000002485 combustion reaction Methods 0.000 description 2
- QDOXWKRWXJOMAK-UHFFFAOYSA-N dichromium trioxide Chemical compound O=[Cr]O[Cr]=O QDOXWKRWXJOMAK-UHFFFAOYSA-N 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 239000012467 final product Substances 0.000 description 2
- RBTARNINKXHZNM-UHFFFAOYSA-K iron trichloride Chemical compound Cl[Fe](Cl)Cl RBTARNINKXHZNM-UHFFFAOYSA-K 0.000 description 2
- 229910001629 magnesium chloride Inorganic materials 0.000 description 2
- -1 phosphorus compound Chemical class 0.000 description 2
- 238000011084 recovery Methods 0.000 description 2
- 238000001953 recrystallisation Methods 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- 230000008929 regeneration Effects 0.000 description 2
- 238000011069 regeneration method Methods 0.000 description 2
- 238000005245 sintering Methods 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- KZBUYRJDOAKODT-UHFFFAOYSA-N Chlorine Chemical compound ClCl KZBUYRJDOAKODT-UHFFFAOYSA-N 0.000 description 1
- 229910010068 TiCl2 Inorganic materials 0.000 description 1
- 238000010306 acid treatment Methods 0.000 description 1
- 239000012670 alkaline solution Substances 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 229940043430 calcium compound Drugs 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 150000001804 chlorine Chemical class 0.000 description 1
- 239000003245 coal Substances 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 239000010881 fly ash Substances 0.000 description 1
- 238000003837 high-temperature calcination Methods 0.000 description 1
- 150000004677 hydrates Chemical class 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 229910052622 kaolinite Inorganic materials 0.000 description 1
- 238000009533 lab test Methods 0.000 description 1
- 150000002681 magnesium compounds Chemical class 0.000 description 1
- 229910001510 metal chloride Inorganic materials 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000012452 mother liquor Substances 0.000 description 1
- 229910052664 nepheline Inorganic materials 0.000 description 1
- 239000010434 nepheline Substances 0.000 description 1
- NDLPOXTZKUMGOV-UHFFFAOYSA-N oxo(oxoferriooxy)iron hydrate Chemical compound O.O=[Fe]O[Fe]=O NDLPOXTZKUMGOV-UHFFFAOYSA-N 0.000 description 1
- 230000000704 physical effect Effects 0.000 description 1
- 238000010298 pulverizing process Methods 0.000 description 1
- 238000000746 purification Methods 0.000 description 1
- 238000007670 refining Methods 0.000 description 1
- 230000001172 regenerating effect Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 239000004576 sand Substances 0.000 description 1
- 238000009738 saturating Methods 0.000 description 1
- 238000010187 selection method Methods 0.000 description 1
- 239000011265 semifinished product Substances 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 238000010561 standard procedure Methods 0.000 description 1
- 239000007858 starting material Substances 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- QAOWNCQODCNURD-UHFFFAOYSA-N sulfuric acid Substances OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 1
- 150000003467 sulfuric acid derivatives Chemical class 0.000 description 1
- 239000000725 suspension Substances 0.000 description 1
- ZWYDDDAMNQQZHD-UHFFFAOYSA-L titanium(ii) chloride Chemical compound [Cl-].[Cl-].[Ti+2] ZWYDDDAMNQQZHD-UHFFFAOYSA-L 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
- C01F7/00—Compounds of aluminium
- C01F7/02—Aluminium oxide; Aluminium hydroxide; Aluminates
- C01F7/20—Preparation of aluminium oxide or hydroxide from aluminous ores using acids or salts
- C01F7/22—Preparation of aluminium oxide or hydroxide from aluminous ores using acids or salts with halides or halogen acids
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
- C01F7/00—Compounds of aluminium
- C01F7/02—Aluminium oxide; Aluminium hydroxide; Aluminates
- C01F7/30—Preparation of aluminium oxide or hydroxide by thermal decomposition or by hydrolysis or oxidation of aluminium compounds
- C01F7/306—Thermal decomposition of hydrated chlorides, e.g. of aluminium trichloride hexahydrate
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Life Sciences & Earth Sciences (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Geology (AREA)
- Inorganic Chemistry (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Geochemistry & Mineralogy (AREA)
- Compounds Of Alkaline-Earth Elements, Aluminum Or Rare-Earth Metals (AREA)
Abstract
The invention relates to metallurgy. Some embodiments of a method of producing metallurgical grade alumina are presented, providing the following operations: extracting an aluminium-containing feedstock with hydrochloric acid, separating the resulting chloride slurry into a spent silica precipitate and a clarified chloride solution, crystallizing aluminium chloride hexahydrate from the clarified chloride solution, thermally precipitating the aluminium chloride hexahydrate into alumina, which is then calcined to produce crude alumina as an intermediate product, leaching the crude alumina with an alkaline waste liquor and precipitating the resulting aluminate solution, washing and then calcining the separated aluminium hydroxide, concentrating the waste liquor leaving the precipitation zone and the water used to wash the aluminium hydroxide to produce an alkaline waste liquor which is returned to the intermediate alumina product leaching stage. In this case, about 15% of the acidic waste liquid is thermally hydrolyzed, the chloride ion concentration in the crude aluminum oxide is maintained at 0.2-5.0%, the chloride ion concentration in the alkaline waste liquid is maintained at 40-90 g/L, and the waste liquid leaving the precipitation zone (10-40% by weight of the total flow) is concentrated until the crystals of chlorine-containing compounds to be removed from the process are separated. The spent liquor is used mainly for leaching aluminium-containing raw materials, only a portion of which is sent to remove impurities by pyrohydrolysis. The technical result is that the quality of the alumina is better and the energy consumption is lower when the smelting-grade alumina is produced by low-grade raw materials.
Description
The present invention relates to the field of metallurgy, and more particularly to an acidic process for producing alumina and can be used to treat low grade high silicon aluminous feedstock, including waste such as fly ash from coal combustion. Smelting-grade aluminum oxide and its semi-finished product (aluminum hydroxide) have wide industrial application, and are mainly used for producing aluminum metal.
Alumina refiners around the world use primarily bayer technology to remove low silicon (bayer) bauxite (where Al is present)2O3/SiO2Concentration ratio (alumina to silica) not less than 3) to produce high quality metallurgical grade alumina. When the ratio of alumina to silica is in the range of 3-7, a bayer-sintering combined process must be used, which is a more energy-consuming process. For high silica aluminum-containing feedstocks, such as nepheline and kaolin, the industry uses only a sintering process, which has an energy cost about 5 times higher than that of the bayer process.
Meanwhile, acidic processes for producing alumina from high silicon, aluminum-containing feedstocks are being developed. Among them, the hydrochloric acid method is currently considered as the most reasonable method.
It is well known that alumina can be produced from high silica bauxite by the hydrochloric acid process which involves calcining an aluminium-containing feedstock at temperatures up to 700 ℃, treating it with hydrochloric acid, saturating a clear chloride solution with gaseous hydrogen chloride to produce aluminium chloride hexahydrate (AlCl)3·6H2O) salting out, calcining aluminium chloride to produce alumina (aluminum), pyrohydrolysis of the spent liquor, and rectification of the absorbed hydrochloric acid, including the return of hydrogen chloride in the acid treatment stage, and salting out in aqueous and gaseous form, respectively (Elsner D., Jenkins D.H. and Sinha H.N. aluminum via hydrochloric acid level of high silicon basic-processes severity. light measures, 1984, page 411-.
According to the known method, only the rectified hydrochloric acid is sent to the raw material treatment zone, which eliminates impurities (for example) in the acid cycleIron, sodium, potassium, calcium, etc.) and minimize their content in aluminum chloride hexahydrate. In the crystallization of AlCl3·6H2After O, the impurities are removed as oxides by complete pyrohydrolysis of the waste liquid. Nevertheless, the phosphorus content in the final product is 1.5 times higher than the allowable limit for smelting grade alumina.
The disadvantages of this process should also include very complex equipment and process flow and many expensive equipment to provide complete regeneration of the hydrochloric acid, which requires high capital expenditures to build an alumina refinery using this technology. In the crystallization of AlCl3·6H2The area where the complete thermal hydrolysis of the spent liquor is carried out after O is a very energy consuming area and the fuel costs add significantly to the production costs.
In addition, the alumina produced by calcining aluminum chloride hexahydrate is substantially different from the conventional smelting-grade alumina in particle strength, easy pulverization, 1.5 to 3 times lower bulk density, and completely different in rheological characteristics (very poor in fluidity), thus causing problems during its transportation and during electrolytic production of aluminum. When such alumina is calcined, it is almost impossible to obtain both low levels of residual chlorine and alpha phase, which is one of the main requirements for metallurgical grade alumina. As shown by the authors of the known processes, if the starting material contains any phosphorus compound, almost its entire volume will go into the final product.
A method for extracting aluminum and iron from aluminum ore is known (patent CA2684696 published on 11/27/2008); the method comprises the steps of preparing an aluminum-containing raw material (kaolinite family shale), leaching the raw material with 6 moles of hydrochloric acid at 100-110 ℃, separating the obtained suspension into a solid phase and a liquid phase, distilling the washing water of the liquid phase and the solid phase to a degree of 90%, and regenerating hydrogen chloride by rectification and returning the hydrogen chloride to a leaching stage. The remaining 10% of the liquid phase is neutralized with caustic to a pH > 10 to produce an aluminum chloride solution and the ferric oxide precipitate is separated. The aluminum chloride solution is neutralized with hydrochloric acid to pH 3 ÷ 4 and the aluminum is separated by liquid extraction and then converted to aluminum hydroxide and oxide (alumina).
The process also requires a very large amount of thermal energy to provide for the entire liquid stream and wash water to be concentrated after the feedstock is consumed to the extent of 90%, and a large consumption of hydrochloric acid and caustic to selectively recover iron and aluminum from the liquid.
The closest to the claimed process is the acid-base combined process for the production of alumina by treatment of the raw material with hydrochloric acid, which involves separation of the silica precipitate, crystallization of aluminum chloride hexahydrate from a clear chloride solution, which is then calcined to produce an intermediate alumina product, which is called "virgin" or "crude" alumina by the authors due to the significant content of iron and other impurities (other than silicon). The intermediate alumina product is then leached with an alkaline waste liquor, the resulting mother liquor is precipitated, washed with water and the separated aluminium hydroxide is subsequently calcined, the waste liquor leaving the precipitation zone and the water used to wash the aluminium hydroxide are concentrated by boiling and an alkaline waste liquor is formed which is returned to the zone for leaching the intermediate alumina product (non-ferrous metals production reference. alumina refining. Moscow. Metallurgiya,1970, p. 236-237).
Basically, the treatment of the intermediate alumina product is an alkaline recrystallization according to a simplified bayer process scheme, which is used to remove iron/phosphorus and other impurities, and produces metallurgical grade alumina in terms of chemical composition and physical properties.
A serious disadvantage of the described procedure is that iron, sodium, potassium, calcium, magnesium and other impurities transported with the raw materials accumulate during the acid circulation and, under the process, the problem is solved by deep evaporation of the chloride solution and, to the greatest possible extent, chloride crystallization. After the crude alumina is calcined, a large amount of alkali chloride is sent to the Bayer alkali cycle; such chlorides will inevitably accumulate in the recycle stream and their removal is not provided.
Disadvantages of the known processes for producing alumina also include the overall high energy costs and the additional alkali losses of up to 36-37 kg/ton of alumina. For these reasons, the process has not been industrially applied.
The present invention is based on the following problems: a process was developed for the production of smelting grade alumina from low grade (high silicon) feedstock which allows processing of barren high silicon ores and waste materials.
The technical result is an improvement in the quality of alumina and a reduction in energy consumption when producing smelting-grade alumina from low-grade raw materials, in other words when processing barren high-silicon ores and wastes.
This problem is solved and the above technical results are achieved by the proposed method for producing metallurgical grade alumina, comprising the following stages:
extracting the aluminum-containing raw material by hydrochloric acid,
the resulting chloride slurry is separated into a waste silica precipitate and a clear chloride solution,
crystallizing aluminum chloride hexahydrate from the clear chloride solution,
aluminum chloride hexahydrate is thermally decomposed into alumina, which is then calcined to produce crude alumina as an intermediate product,
leaching crude alumina with alkaline waste liquor and precipitating the aluminate solution obtained,
the separated aluminum hydroxide is subjected to water washing and subsequent calcination, and
the spent liquor leaving the precipitation zone and the water used to wash the aluminium hydroxide are digested to form an alkaline spent liquor which is returned to the intermediate alumina product leaching stage.
In addition, to optimize the process, the chloride ion concentration in the intermediate alumina product should be maintained at a level of 0.2 to 5.0 wt.%, the chloride ion concentration in the alkaline waste liquor should be maintained at a level of 40 to 90g/L, and the waste liquor leaving the precipitation zone (10 to 40 wt.% of the total flow) should be concentrated until the chlorine-containing compound crystals to be removed from the process are separated.
According to one embodiment, a method of producing metallurgical grade alumina comprises the following stages:
grinding aluminum-containing raw material, extracting with hydrochloric acid (acid waste liquid),
the resulting chloride slurry is separated into a waste silica precipitate and a clear chloride solution,
crystallizing aluminum chloride hexahydrate from the clear chloride solution,
aluminum chloride hexahydrate is thermally decomposed into alumina, which is then calcined to produce crude alumina as an intermediate product,
crude alumina leaching with alkaline waste liquor and precipitating the resulting aluminate liquor and subsequently calcining the separated aluminium hydroxide, when about 15% of the acidic waste liquor is subjected to pyrohydrolysis, the chloride ion concentration in the crude alumina is maintained at 0.2-5.0% and the chloride ion concentration in the alkaline waste liquor is maintained at a level of 40-90 g/L, the precipitated alkaline waste liquor in an amount of 10-40% by weight of the total flow is boiled off until chlorine-containing compound crystals to be removed from the process are separated.
According to a second embodiment, the process for the production of metallurgical grade alumina comprises the following stages:
grinding the aluminum-containing raw material, leaching the aluminum-containing raw material by using hydrochloric acid waste liquid (acid waste liquid),
the resulting chloride slurry is separated into a waste silica precipitate and a clear aluminum chloride solution which are poured after washing with water, while water for washing purposes is supplied to a region where hydrogen chloride is adiabatically absorbed from the fumes produced by calcining aluminum chloride hexahydrate and the fumes produced by the thermal hydrolysis process, and the amount of washing water is determined by the amount of water used for adiabatic absorption,
crystallizing aluminum chloride hexahydrate from the clear aluminum chloride solution; after separating the crystals, supplying the resulting waste liquid to a rectification zone where the hydrogen chloride concentration in the waste liquid is reduced to form hydrogen chloride gas, drying the hydrogen chloride gas and then supplying to a salting-out zone; the waste liquid discharged from the rectification zone is divided into two unequal portions: the larger part is supplied directly to the preparation effluent, the other part is supplied to the removal of impurities by thermal hydrolysis,
aluminum chloride hexahydrate is thermally decomposed to form alumina, which is then calcined to produce crude alumina as an intermediate product, while the calcined fumes are absorbed by water used for washing the waste silica precipitate,
crude alumina leaching with alkaline spent liquor according to the bayer process and precipitating the resulting aluminate liquor,
the separated aluminum hydroxide is washed with water and then calcined,
the spent liquor leaving the precipitation zone and the water used for washing the aluminium hydroxide are boiled to concentrate to form an alkaline spent liquor to be returned to the intermediate alumina product leaching stage, and
the spent liquor is mainly used for leaching aluminium-containing raw materials, and only part of the spent liquor is subjected to thermal hydrolysis to remove impurities.
Both embodiments of the method ensure the achievement of the overall technical result, namely an increase in the alumina quality and a reduction in the energy costs when producing metallurgical-grade alumina from low-grade raw materials.
As an additional measure, the following measures are preferably implemented:
the waste liquid discharged from the precipitation zone and the water used for washing the aluminium hydroxide are concentrated in two stages, the alkali carbonate is crystallized in the first stage and the alkali chloride is crystallized in the second stage.
Alkali metal chlorides (mainly sodium chloride and potassium chloride) are purified and subjected to membrane or diaphragm electrolysis in the form of an aqueous solution.
Chlorine and hydrogen formed during membrane or diaphragm electrolysis of an aqueous alkali chloride solution are used to synthesize hydrochloric acid which is sent to extract the initial aluminium-containing raw material, and part of the aqueous alkali hydroxide solution formed during membrane or diaphragm electrolysis of an aqueous alkali chloride solution is mixed with alkaline waste liquor which is returned to the intermediate alumina product leaching stage.
Part of the alkali metal hydroxide solution resulting from the membrane or diaphragm electrolysis of the aqueous alkali metal chloride solution is sent to neutralize the silica precipitate.
Drawings
FIG. 1-schematic alumina production process flow.
The invention is illustrated by the schematic alumina production process flow scheme shown in fig. 1, which clearly illustrates the reasonably optimal combination of acid and base cycles of the technique, both in flow and mode, which provides the achievement of technical results as a whole.
For example, crushed aluminum-containing materials (such as kaolin or kaolin slate) are subjected to acidic extraction (leaching) with spent hydrochloric acid under autoclave conditions. After leaching, the slurry was separated into a precipitate (Si material) containing about 90% silica and an aluminum chloride solution. The Si material washed with water was poured.
Water for washing Si material is supplied to the reaction system from calcination of aluminum chloride hexahydrate (ACH, AlCl)3·6H2O) and the zone of adiabatic absorption of hydrogen chloride (HCl) in the fumes generated by the thermal hydrolysis process. And the HCl concentration in the aluminum chloride solution reaches 17-19 percent. During the absorption, the aluminum chloride solution self-evaporates and removes from the circulation all the water supplied for washing the Si material, due to the large amount of heat released during the HCl absorption. It is to be noted that the amount of Si material washing water is determined by the amount of water that can be evaporated in the adiabatic absorption stage.
The aluminum chloride solution separated from the Si material was sent to a crystallization (salting out) zone where the hydrogen chloride gas produced by rectification bubbled through the solution and the HCl concentration in the solution reached 32%, with most (-95%) of the aluminum precipitating as aluminum chloride hexahydrate crystals. After separation of the crystals (crystallized particles), the resulting effluent is sent to a rectification zone where the HCl concentration in the effluent is reduced to about 22% -27% HCl) and gaseous HCl is formed, which is dried to-5% H2O content and supplied to the salting-out region. The waste liquid (containing 22% to 27% HCl) discharged from the rectification zone is divided into two unequal fractions: the larger part is directly supplied to the preparation of the acidic waste liquid; the other part is supplied to the removal of impurities by thermal hydrolysis.
The proportion of the spent liquor sent to pyrohydrolysis is determined by the allowable content of impurities in the spent liquor used for leaching. The proportion of waste liquid used for thermal hydrolysis is about 15%. It is noteworthy that the impurity content in the aluminium chloride solution is increased by a factor of about 6 compared to the impurity content when the ore is leached with pure hydrochloric acid. During the thermal hydrolysis, all the free acids contained in the spent liquor and the HCl formed by the hydrolysis of the metal (including Al, Fe, Ca, Mg) chlorides enter the gas phase. The thermal hydrolysis products will include smog and iron oxide (Fe)2O3) And partial Al, Ca, Mg oxides and other trace impurities. The fumes produced by the thermal hydrolysis contain the regenerated HCl and are sent to the zone where the HCl is absorbed by the washing water with the Si material.
The produced ACH is supplied to a calcination zone to produce crude alumina and a HCl-containing fume. The fumes resulting from the calcination process are conveyed to an absorption stage where the Si material washing water is used for absorption. To recover the losses, fresh acid is added to the spent liquor sent to the leaching stage; also, it may be added by washing the ACH product supplied for rectification.
Fresh water is added to hygienically purify the fumes generated by the calcination and pyrohydrolysis processes (and then used to wash the Si material).
The advantage of this process is that most of the spent liquor is used to leach the ore and only a portion of it is sent to remove impurities by thermal hydrolysis. There are no large and complex cook-up and salt rectification zones, the pyrohydrolysis zone is minimized and independent of the production of crude alumina, but rather for the partial removal of impurities, which significantly reduces energy costs.
It should be noted that the crude alumina according to the prior art process contains a minimum amount of impurities (including chlorides). In order to achieve this in the prior art processes, it is necessary to keep the aluminium chloride solution containing a minimum allowable level of impurities, such as iron and potassium, sodium, calcium, magnesium etc. which are dosed with the raw material; for this purpose, the acidic waste liquid should be purified from these impurities. For example, prior art methods have shown that it is difficult to perform such purification from iron. A common technique for doing this is thermal hydrolysis, in particular complete evaporation of the acidic waste liquid at temperatures up to 850 ℃, as shown by similar processes (Elsner d., Jenkins d.h. and Sinha h.n. aluminium via hydrochloric acid left of high silicon substrates-process severity metals, page 1984,423), so the energy costs are very high in this case.
According to the claimed process, the crude alumina is then conveyed for alkaline recrystallization based on the known bayer process. The product of the bayer process is alumina, which is converted to metallurgical grade alumina by calcination.
To prepare the spent liquor, fresh caustic is also added, the consumption of which depends on the mechanical losses of the spent sludge and the alumina product, and on the metal chlorides (AlCl) contained in the crude alumina3、FeCl3、MgCl2、CaCl2) Alkali loss during its decarburizing. In this case, NaCl and KCl contained in the crude alumina go directly into solution without causing any loss of alkali.
One particular feature of alkaline treatment of crude alumina by the bayer process (as opposed to the natural bauxite treatment process) is that little water is required to wash the slurry, since the amount of slurry formed is very small. Thus, the water balance in the alumina production process can be compensated without the entire spent liquor stream being made to boil out, since the amount of water added to wash the hydrates corresponds approximately to the amount of water removed with the alumina product. Furthermore, since a small amount of sludge does not require such a large amount of condensate to wash the sludge, heat can be recovered by autoclave leaching using a slurry-to-slurry heat exchanger without self-evaporation of the discharged slurry.
In order to remove chlorine from the bayer circuit, a combination of deep digestion and crystallization of a portion of the spent liquor is required. Only in Na2In the region with high O concentration, the solubility of NaCl in the caustic solution is obviously reduced; thus, we talk about deep concentration of a portion of the spent liquor to a caustic content of 25% to 33% (Na)2O)。
The amount of waste liquor supplied to the digestion zone is determined by the allowable level of chloride accumulation in the bayer process. The higher the acceptable level of chloride in the solution, the smaller the proportion of waste liquor sent to the digestion zone, and therefore the amount of water evaporated (and heat energy consumed) will be (the same as the chloride content of the crude alumina).
According to the experience of the authors, the allowable level of chloride in the spent liquor used in the Bayer process under industrial conditions is 90g/L (for chloride Cl ions)-)。
The crystalline sodium chloride and part of the potassium chloride separated after the concentration process are sent to known diaphragm or membrane electrolysis to release caustic and hydrogen and chlorine gas, from which hydrogen chloride gas is synthesized. Caustic and hydrogen chloride are returned to the acid and base portions of the process, respectively, to compensate for the inevitable loss of these reagents.
Thus, the claimed process is a closed loop process flow that enables the treatment of low grade (high silicon) aluminum containing feedstock to produce smelting grade alumina.
Since the crude alumina is an intermediate product, not a marketable product, the content of impurities such as iron, potassium, sodium, calcium, magnesium, etc. charged together with the raw material therein does not have to be the minimum allowable content. Thus, the concentration of these impurities in the acid cycle can be increased, which will reduce the cost of evaporation of the chloride solution. For this reason, in the crystallization stage, it is advisable to extract the aluminum chloride hexahydrate most fully and rapidly into the solid phase using simple equipment and easy-to-implement processes, without worrying about the purity of the crystalline ACH which is sent to the calcination zone to produce crude alumina. Furthermore, in order to completely decompose the chloride, deep calcination of the product during calcination is not required. On the one hand, this reduces the thermal costs associated with calcination; on the other hand, this does not allow for the formation of a poorly soluble alpha phase in the crude alumina. The residual chlorine, which is mainly represented by potassium chloride, sodium chloride, calcium chloride and magnesium chloride, is extracted with the crude alumina into the acid phase of the process where it will inevitably accumulate. However, researches carried out by the creators show that the accumulation of chloride ions in the alkaline waste liquid to the level of 40-90 g/L does not cause the performance of the Bayer process to be remarkably reduced. In order to avoid further chlorine build-up in the caustic cycle of the process, the portion of the spent liquor that is precipitated in an amount of 10% to 40% of the total flow rate is concentrated by boiling until the chlorine-containing compound crystals to be removed from the process are separated. Laboratory experiments and cycle calculations indicate that the process is sufficient to maintain the chloride ion concentration in the spent caustic liquor at the desired level and to ensure the water balance of the bayer process.
The selection method does not make it possible to determine the optimal combination of operating parameters of such a multilink loop technique as the claimed method. The creators solve this problem by using specially developed mathematical models of process mass-to-heat balance. At the same time, the inventors have surprisingly found that if impurities are deliberately allowed to accumulate in the acid and base cycles of the process and in the crude alumina (intermediate product from the acid cycle to the base cycle), the energy consumption in the form of fuel, heat and electrical energy can be reduced.
The numerical experiment performed according to the result of the optimized iterative calculation based on the above mathematical model finds the following: if about 15% is sent to the pyrohydrolysis zone, the content of impurities (iron, sodium, potassium, magnesium, calcium, etc.) is set at an equilibrium level, which does not reduce the aluminium recovery from the raw material to the crude alumina, but leads to an increase in the concentration of said impurities in the aluminium chloride hexahydrate and further in the crude alumina. However, when the crude alumina leaching is carried out in the caustic cycle of the process, iron, calcium and magnesium compounds go directly into the insoluble precipitate and are removed. In this case, it should be considered that the smaller the proportion of the acidic waste liquid sent to the thermal hydrolysis zone, the lower the energy costs associated with the combustion of the fuel in this zone.
As provided in the prior art processes, the costs associated with hot hydrolysis can be reduced if the crude alumina is subjected to deep high temperature calcination and washed with water to remove soluble chlorides prior to leaching in the bayer cycle. In this case, the chloride ion content in the crude alumina is reduced to parts per million and parts per thousand, but the content of the poorly soluble α alumina is increased. The alkali treatment is carried out by high-temperature autoclave leaching, thus leading to an increase in thermal energy consumption.
On the other hand, it is evident that if the process temperature or heat and mass exchange strength of the calcination zone is reduced, the energy consumption will be significantly reduced, but the chlorine content in the crude alumina will increase and this chlorine in the form of chloride ions will continue to accumulate in the caustic cycle of the process. The transfer of chlorine from the acid cycle to the caustic cycle will inevitably result in the loss of hydrochloric acid and caustic. In the claimed process, these losses are compensated by removing some of the potassium and sodium chloride from the caustic cycle and its electrolytic treatment (producing NaOH and also chlorine and hydrogen from which HCl is synthesized). However, such regeneration requires thermal energy when evaporating potassium chloride and sodium chloride from the alkaline solution, and also requires electric energy for electrolyzing these chloride aqueous solutions.
However, numerical experiments show that despite the complexity of optimizing the heat and mass balance of the process, the mathematical model developed by the authors allows for finding some unobvious interrelated alternative combinations of process parameters in the acid and base cycles, thereby minimizing energy consumption while maintaining the desired quality of the metallurgical grade alumina product. This can be achieved when the chloride ion concentration in the crude alumina is maintained at a level of 0.2-5.0 wt.%, the chloride ion concentration in the alkaline waste liquor is maintained at a level of 40-90 g/L, and the waste liquor leaving the precipitation zone (10-40 wt.% of the total flow) is boiled off until the chlorine-containing compound crystals to be removed from the process are separated. The claimed method was carried out experimentally in the presence of the optimum combination of the above process parameters.
Examples
540g of an aluminium-containing raw material (kaolin slate) are comminuted to a particle size of < 100 μm (the aluminium-containing raw material comprises, in% by weight, Al)2O3 27.1；SiO2 56.8；Fe2O3 2.0；Na2O 0.31；K2O＜0.15；TiO2 0.48；CaO 0.45；MgO 0.27；P2O5(ii) a 0.05; 11.8) and mixed with 1,650ml of 20% hydrochloric acid, placed in an autoclave and kept under stirring at 160 ℃ for 3 hours. The resulting chloride slurry was separated by filtration and the solid precipitate (waste Si material) was washed with water. The clear aluminum chloride solution was bubbled with dry hydrogen chloride gas at 70 ℃ until ACH crystals were separated and stopped. The crystallized ACH was separated from the spent liquor using a filter and calcined at 600 ℃ to produce crude alumina. The spent liquor was diluted with Si material wash water to free 20% HCl to produce, the acidic spent liquor was sent to repeat extraction of kaolin slate with acid, and all (cycles) of the above were repeated.
After the above total 6 cycles, the contents of the acidic waste liquid components were stabilized as follows (%): AlCl3 20.5-21.5；FeCl3 3.9-4.2；TiCl2 0.001；CaCl20.4-0.48; NaCl 0.1-0.12; KCl 0.1-0.11. No decrease in the recovery rate of aluminum from the aluminum-containing raw material was observed, which was 95.5% to 97.5%. After each experiment, 15% of the volume of the waste liquid was replaced by pure hydrochloric acid (20% strength) to simulate the removal of impurities from the circulation by thermal hydrolysis or by treatment with concentrated sulfuric acid (forming low-soluble sulfates of the corresponding metals).
The average composition of the resulting waste Si material in weight percent is as follows: al (Al)2O3 2.0；SiO2 90.5；Fe2O3 0.16；Na2O 0.2；K2O＜0.15；TiO2 0.7；CaO 0.12；MgO＜0.025；P2O5；＜0.02；4.2。
After the composition of the acidic waste liquid is stable, performing another 10 times of circulation experiments; as a result, the creator produced crude alumina having the following composition (wt%): al (Al)2O3 86.0；SiO2 0.08；Fe2O3 2.9；Na2O 0.61；K2O＜0.15；<TiO20.05；CaO 0.3；MgO＜0.025；P2O5；0.06；Cl-3.5；7.0。
In order to produce metallurgical grade alumina from crude alumina by alkali treatment in the bayer cycle, 500g of crude alumina was dissolved in an alkaline green liquor having the following composition (g/L) in an autoclave at 150 ℃ for 2 hours: al (Al)2O3 102.0；Na2O 174.0；NaCl 63.3。
The content of the resulting filtered green liquor in g/L was as follows: al (Al)2O3 167.3；Na2O149.2; NaCl 57.7. The alumina was isolated by precipitation of the solution according to the bayer technique, which was washed with hot water (%) and calcined at 1,100 ℃ by the authors to produce alumina having the following chemical composition (%): al (Al)2O3 98.7；；SiO2 0.004；Fe2O30.008；Na2O 0.15；K2O 0.01；TiO2 0.001；CaO 0.004；MgO 0.0025；P2O5；0.0007；V2O50.0002；Cr2O3 0.0003 0.02；Cl-0.013。
In determining the physical and mechanical properties of the alumina using standard methods, the inventors have discovered the following:
despite the high chloride content of the caustic cycle, the alumina produced completely meets the Russian (GOST 30558-98 'smelting grade alumina') and international requirements for 'sand' smelting grade alumina.
In the absence of energy consumption data published in similar processes, in addition to similar processes (Elsner D., Jenkins D.H., and Sinha H.N.aluminum via hydrochloric acid leveling of high silicon substrates-Process leveling. light metals,1984, page 411-426), the authors calculated the heat and electrical energy consumed in the production of 1kg of alumina and compared the results to compare the energy savings of all the techniques mentioned in the present specification. The results are shown below.
Obviously, the proposed process is inferior to patent family 1 in terms of energy savings when processing high silica feedstock, however, the latter does not provide for the production of metallurgical grade alumina. Other patent families require higher energy consumption.
The energy savings specified by the claimed process can be best realized when about 15% of the acidic waste liquor is subjected to pyrohydrolysis, the chloride ion concentration in the intermediate alumina product is maintained at a level of 0.2-5.0 wt.%, the chloride ion concentration in the alkaline waste liquor is maintained at a level of 40-90 g/L, and the waste liquor leaving the precipitation zone (10-40 wt.% of the total flow) is concentrated until the chlorine-containing compound crystals to be removed from the process are separated. The specified concentrations and flow intervals were calculated based on a mathematical model of the overall mass balance of the acid and base portions of the process. The total calculated energy consumption at any combination of operating parameters does not exceed 41.2kJ/kg over the specified interval.
While the specification refers to certain embodiments, many modifications should be apparent to those skilled in the art and are not strictly limited to the examples, descriptions and process flows.
Claims (16)
1. A process for the production of metallurgical grade alumina, which comprises the following stages:
grinding aluminum-containing raw materials, extracting the raw materials by hydrochloric acid, wherein the hydrochloric acid is acidic waste liquid,
the resulting chloride slurry is separated into a waste silica precipitate and a clear chloride solution,
crystallizing aluminum chloride hexahydrate from the clear chloride solution,
aluminum chloride hexahydrate is thermally decomposed into alumina, which is then calcined to produce crude alumina as an intermediate product,
crude alumina leaching with alkaline waste liquor and precipitating the obtained aluminate solution, then calcining the separated aluminium hydroxide, simultaneously carrying out pyrohydrolysis on about 15% of the acidic waste liquor, keeping the chloride ion concentration in the crude alumina at 0.2-5.0% and the chloride ion concentration in the alkaline waste liquor at a level of 40-90 g/L, and boiling the precipitated alkaline waste liquor in an amount of 10-40 wt% of the total flow until separating chlorine-containing compound crystals to be removed from the process.
2. A process according to claim 1, wherein the alkaline waste liquor is concentrated in two stages, the alkali metal carbonate being crystallized in the first stage and the alkali metal chloride being crystallized in the second stage.
3. The method according to claim 2, wherein alkali chlorides, mainly sodium chloride and potassium chloride, are purified and subjected to membrane or diaphragm electrolysis in the form of an aqueous solution.
4. A process as claimed in claim 3 wherein the chlorine and hydrogen formed during membrane or diaphragm electrolysis of the aqueous alkali chloride solution is used to synthesise hydrochloric acid which is sent to the extraction of the initial aluminium-containing feedstock and part of the aqueous alkali hydroxide solution formed during membrane or diaphragm electrolysis of the aqueous alkali chloride solution is mixed with the alkaline waste liquor returned to the intermediate alumina product leaching stage.
5. A process according to claim 4, wherein part of the alkali metal hydroxide solution resulting from the membrane or diaphragm electrolysis of the aqueous alkali metal chloride solution is sent to neutralize the silica precipitate.
6. A process for the production of metallurgical grade alumina, which comprises the following stages:
grinding an aluminum-containing raw material, leaching the aluminum-containing raw material by using a hydrochloric acid waste liquid, wherein the hydrochloric acid waste liquid is an acidic waste liquid,
separating the resulting chloride slurry into a waste silica precipitate which is washed with water and poured, and a clarified aluminum chloride solution, wherein water for washing purposes is supplied to a region where hydrogen chloride is adiabatically absorbed from fumes produced by calcining aluminum chloride hexahydrate and fumes produced by a thermal hydrolysis process, and the amount of washing water is determined by the amount of water used for adiabatic absorption,
crystallizing aluminum chloride hexahydrate from the clear aluminum chloride solution; after separation of the crystals, the resulting spent liquor is supplied to a rectification zone where the hydrogen chloride concentration in the spent liquor is reduced to form hydrogen chloride gas, which is dried and then supplied to a salting-out zone; the waste liquid discharged from the rectification zone is divided into two unequal portions: the larger part is supplied directly for the preparation of the waste liquid, the other part is supplied for the removal of impurities by thermal hydrolysis,
aluminum chloride hexahydrate is thermally decomposed to form alumina, which is then calcined to produce crude alumina as an intermediate product, while the calcined fumes are absorbed by water used for washing the waste silica precipitate,
crude alumina leaching with alkaline spent liquor according to the bayer process and precipitating the resulting aluminate liquor,
the separated aluminum hydroxide is washed with water and then calcined, and
the spent liquor that has left the precipitation zone and the water that has been used to wash the aluminium hydroxide are boiled to concentrate to produce alkaline spent liquor that is returned to the intermediate alumina product leaching stage, and
the spent liquor is mainly used for leaching aluminium-containing raw materials, only a part of which is sent for removing impurities by thermal hydrolysis,
wherein the chloride ion concentration in the intermediate alumina product is maintained at a level of 0.2-5.0 wt.%, the chloride ion concentration in the alkaline waste liquor is maintained at a level of 40-90 g/L, and the waste liquor that has left the precipitation zone is concentrated until crystals of chlorine-containing compounds to be removed from the process are separated, the waste liquor that has left the precipitation zone being 10-40 wt.% of the total flow.
7. A process according to claim 6, wherein the waste liquor discharged from the settling zone and the water already used for washing purposes are both concentrated in two stages, alkali carbonate being crystallized in the first stage and alkali chloride being crystallized in the second stage.
8. The method according to claim 7, wherein alkali chlorides, mainly sodium chloride and potassium chloride, are purified and subjected to membrane or diaphragm electrolysis in the form of an aqueous solution.
9. A process as claimed in claim 8, wherein the chlorine and hydrogen formed during membrane or diaphragm electrolysis of the aqueous alkali chloride solution is used to synthesize hydrochloric acid which is sent to leach the initial aluminium-containing raw material, and part of the aqueous alkali hydroxide solution formed during membrane or diaphragm electrolysis of the aqueous alkali chloride solution is mixed with alkaline waste liquor returned to the intermediate alumina product leaching stage.
10. A process according to claim 9, wherein part of the alkali metal hydroxide solution produced by electrolysis of a membrane or diaphragm of an aqueous alkali metal chloride solution is sent to neutralize the silica precipitate.
11. The process according to claim 6, wherein the concentration of hydrogen chloride in the aluminium chloride solution reaches 17-19% and in this case, during absorption, the aluminium chloride solution self-evaporates due to the large amount of heat released during the absorption of HCl and all the water supplied for washing the waste silica precipitate is removed from the circulation.
12. The process as claimed in claim 6, wherein the aluminum chloride solution is sent to a crystallization zone, where the hydrogen chloride gas resulting from the rectification is bubbled through the solution and the concentration in the solution reaches about 32%, about 95% of the aluminum precipitating as aluminum chloride hexahydrate crystals.
13. A process as claimed in claim 6, wherein, after separation of the crystals, the resulting spent liquor is passed to a rectification zone, where the hydrogen chloride concentration in the spent liquor is reduced to form hydrogen chloride gas, which is dried to a water content of about 5%, and then to a salting-out zone, wherein the drying is carried out by cooling the gas with cooling water to a temperature of about 35 ℃.
14. A method according to claim 6, wherein the proportion of the spent liquor sent to pyrohydrolysis is determined by the allowable content of impurities in the spent liquor sent to leaching, and during pyrohydrolysis all free acids contained in the spent liquor and hydrogen chloride formed by the hydrolysis of chlorides of metals including Al, Fe, Ca, Mg enter the gas phase; the fumes resulting from the thermal hydrolysis contain regenerated hydrogen chloride and are sent to a zone where the hydrogen chloride is absorbed with water washing the waste silica precipitate.
15. A process according to claim 14, wherein the proportion of waste liquor sent to the thermal hydrolysis is about 15%.
16. A process as claimed in claim 6, wherein during the calcination to produce crude alumina and fumes containing hydrogen chloride, the fumes produced by the calcination process are conveyed to an absorption zone where they are absorbed with water washing the spent silica precipitate, while fresh acid is added to the spent liquor supplied to the leaching zone to compensate for losses and fresh water is added to sanitise the fumes produced by the calcination and pyrohydrolysis processes.
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| US3961030A (en) * | 1974-08-12 | 1976-06-01 | Freeport Minerals Company | Production of alumina from ores |
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Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
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| US4224287A (en) * | 1978-04-24 | 1980-09-23 | Veb Mansfeld Kombinat Wilhelm Pieck | Process for the preparation of pure aluminum oxide |
| CN1927716A (en) * | 2006-08-29 | 2007-03-14 | 吉林大学 | Preparation method of alumina |
| CN104507867A (en) * | 2012-07-20 | 2015-04-08 | 俄罗斯工程技术中心 | Method for producing alumina |
| CN103693665A (en) * | 2012-12-28 | 2014-04-02 | 中国神华能源股份有限公司 | Method for preparing high-purity aluminum oxide from fly ash |
| CN103738989A (en) * | 2012-12-28 | 2014-04-23 | 中国神华能源股份有限公司 | Method for producing alumina from low- and medium-grade bauxite |
| CN105121348A (en) * | 2013-02-04 | 2015-12-02 | 俄罗斯工程技术中心 | Aluminum oxide production method |
Also Published As
| Publication number | Publication date |
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| WO2018063029A1 (en) | 2018-04-05 |
| RU2647041C1 (en) | 2018-03-13 |
| CA3032938A1 (en) | 2018-04-05 |
| CA3118678C (en) | 2024-05-14 |
| CA3118678A1 (en) | 2018-04-05 |
| MY186787A (en) | 2021-08-20 |
| CN109790045A (en) | 2019-05-21 |
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