AU2022100082B4 - Optimized semi-dry process for sintering of aluminosilicates in the production of alumina - Google Patents
Optimized semi-dry process for sintering of aluminosilicates in the production of alumina Download PDFInfo
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- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 title claims description 9
- 238000005245 sintering Methods 0.000 title description 23
- 238000001035 drying Methods 0.000 title description 8
- 229910000323 aluminium silicate Inorganic materials 0.000 title description 6
- 238000004519 manufacturing process Methods 0.000 title description 3
- 238000001354 calcination Methods 0.000 claims abstract description 47
- BWHMMNNQKKPAPP-UHFFFAOYSA-L potassium carbonate Chemical compound [K+].[K+].[O-]C([O-])=O BWHMMNNQKKPAPP-UHFFFAOYSA-L 0.000 claims abstract description 30
- CDBYLPFSWZWCQE-UHFFFAOYSA-L sodium carbonate Substances [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 claims abstract description 27
- 239000000203 mixture Substances 0.000 claims abstract description 20
- 229910000029 sodium carbonate Inorganic materials 0.000 claims abstract description 16
- 229910052782 aluminium Inorganic materials 0.000 claims abstract description 14
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims abstract description 14
- 238000002156 mixing Methods 0.000 claims abstract description 14
- 229910000027 potassium carbonate Inorganic materials 0.000 claims abstract description 14
- 235000019738 Limestone Nutrition 0.000 claims abstract description 13
- 239000006028 limestone Substances 0.000 claims abstract description 13
- 239000004411 aluminium Substances 0.000 claims abstract description 4
- 239000007789 gas Substances 0.000 claims description 31
- 238000010438 heat treatment Methods 0.000 claims description 21
- 239000008187 granular material Substances 0.000 claims description 15
- 238000005469 granulation Methods 0.000 claims description 15
- 230000003179 granulation Effects 0.000 claims description 15
- 238000004064 recycling Methods 0.000 claims description 14
- 230000003134 recirculating effect Effects 0.000 claims description 12
- 239000012266 salt solution Substances 0.000 claims description 8
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 4
- 238000001816 cooling Methods 0.000 claims description 4
- KKCBUQHMOMHUOY-UHFFFAOYSA-N Na2O Inorganic materials [O-2].[Na+].[Na+] KKCBUQHMOMHUOY-UHFFFAOYSA-N 0.000 claims description 3
- 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 abstract description 7
- 238000000034 method Methods 0.000 description 23
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 10
- 235000011181 potassium carbonates Nutrition 0.000 description 9
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 9
- 239000012717 electrostatic precipitator Substances 0.000 description 8
- 238000005265 energy consumption Methods 0.000 description 8
- 235000017550 sodium carbonate Nutrition 0.000 description 7
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 6
- 239000000463 material Substances 0.000 description 6
- 238000013459 approach Methods 0.000 description 5
- 230000008901 benefit Effects 0.000 description 5
- 239000003518 caustics Substances 0.000 description 5
- 239000000377 silicon dioxide Substances 0.000 description 5
- 239000000243 solution Substances 0.000 description 5
- 238000012546 transfer Methods 0.000 description 5
- 239000002245 particle Substances 0.000 description 4
- 150000003839 salts Chemical class 0.000 description 4
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 3
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 3
- 229910052799 carbon Inorganic materials 0.000 description 3
- HNPSIPDUKPIQMN-UHFFFAOYSA-N dioxosilane;oxo(oxoalumanyloxy)alumane Chemical compound O=[Si]=O.O=[Al]O[Al]=O HNPSIPDUKPIQMN-UHFFFAOYSA-N 0.000 description 3
- 239000000428 dust Substances 0.000 description 3
- 238000002844 melting Methods 0.000 description 3
- 230000008018 melting Effects 0.000 description 3
- 229910052760 oxygen Inorganic materials 0.000 description 3
- 239000001301 oxygen Substances 0.000 description 3
- 239000008188 pellet Substances 0.000 description 3
- 229910052710 silicon Inorganic materials 0.000 description 3
- 239000010703 silicon Substances 0.000 description 3
- 238000004131 Bayer process Methods 0.000 description 2
- VTYYLEPIZMXCLO-UHFFFAOYSA-L Calcium carbonate Chemical compound [Ca+2].[O-]C([O-])=O VTYYLEPIZMXCLO-UHFFFAOYSA-L 0.000 description 2
- 239000003513 alkali Substances 0.000 description 2
- 229910001570 bauxite Inorganic materials 0.000 description 2
- 239000011230 binding agent Substances 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 150000004649 carbonic acid derivatives Chemical class 0.000 description 2
- 238000003763 carbonization Methods 0.000 description 2
- 229910052681 coesite Inorganic materials 0.000 description 2
- 230000000875 corresponding effect Effects 0.000 description 2
- 229910052906 cristobalite Inorganic materials 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 238000001704 evaporation Methods 0.000 description 2
- 230000008020 evaporation Effects 0.000 description 2
- 238000000265 homogenisation Methods 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 229910052664 nepheline Inorganic materials 0.000 description 2
- 239000010434 nepheline Substances 0.000 description 2
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 description 2
- 235000015320 potassium carbonate Nutrition 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- 235000012239 silicon dioxide Nutrition 0.000 description 2
- 239000007787 solid Substances 0.000 description 2
- 239000008247 solid mixture Substances 0.000 description 2
- 229910052682 stishovite Inorganic materials 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- 229910052905 tridymite Inorganic materials 0.000 description 2
- 235000008733 Citrus aurantifolia Nutrition 0.000 description 1
- 229910000503 Na-aluminosilicate Inorganic materials 0.000 description 1
- 235000011941 Tilia x europaea Nutrition 0.000 description 1
- 229910000272 alkali metal oxide Inorganic materials 0.000 description 1
- WNROFYMDJYEPJX-UHFFFAOYSA-K aluminium hydroxide Chemical compound [OH-].[OH-].[OH-].[Al+3] WNROFYMDJYEPJX-UHFFFAOYSA-K 0.000 description 1
- ANBBXQWFNXMHLD-UHFFFAOYSA-N aluminum;sodium;oxygen(2-) Chemical compound [O-2].[O-2].[Na+].[Al+3] ANBBXQWFNXMHLD-UHFFFAOYSA-N 0.000 description 1
- 239000002585 base Substances 0.000 description 1
- 235000010216 calcium carbonate Nutrition 0.000 description 1
- 229910000019 calcium carbonate Inorganic materials 0.000 description 1
- 239000000378 calcium silicate Substances 0.000 description 1
- 229910052918 calcium silicate Inorganic materials 0.000 description 1
- OYACROKNLOSFPA-UHFFFAOYSA-N calcium;dioxido(oxo)silane Chemical compound [Ca+2].[O-][Si]([O-])=O OYACROKNLOSFPA-UHFFFAOYSA-N 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000003245 coal Substances 0.000 description 1
- 230000000295 complement effect Effects 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 230000001276 controlling effect Effects 0.000 description 1
- 230000002596 correlated effect Effects 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- 239000003546 flue gas Substances 0.000 description 1
- 238000005243 fluidization Methods 0.000 description 1
- 239000004571 lime Substances 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 238000011020 pilot scale process Methods 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 238000009877 rendering Methods 0.000 description 1
- 239000011734 sodium Substances 0.000 description 1
- 229910052708 sodium Inorganic materials 0.000 description 1
- 229910001388 sodium aluminate Inorganic materials 0.000 description 1
- 235000012217 sodium aluminium silicate Nutrition 0.000 description 1
- 235000011182 sodium carbonates Nutrition 0.000 description 1
- 238000007669 thermal treatment Methods 0.000 description 1
- 230000001131 transforming effect Effects 0.000 description 1
- 229910052882 wollastonite Inorganic materials 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J6/00—Heat treatments such as Calcining; Fusing ; Pyrolysis
- B01J6/001—Calcining
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J6/00—Heat treatments such as Calcining; Fusing ; Pyrolysis
- B01J6/001—Calcining
- B01J6/002—Calcining using rotating drums
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J8/00—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes
- B01J8/18—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with fluidised particles
- B01J8/20—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with fluidised particles with liquid as a fluidising medium
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J8/00—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes
- B01J8/18—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with fluidised particles
- B01J8/20—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with fluidised particles with liquid as a fluidising medium
- B01J8/22—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with fluidised particles with liquid as a fluidising medium gas being introduced into the liquid
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J8/00—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes
- B01J8/18—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with fluidised particles
- B01J8/20—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with fluidised particles with liquid as a fluidising medium
- B01J8/22—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with fluidised particles with liquid as a fluidising medium gas being introduced into the liquid
- B01J8/224—Chemical or physical processes in general, conducted in the presence of fluids and solid particles; Apparatus for such processes with fluidised particles with liquid as a fluidising medium gas being introduced into the liquid the particles being subject to a circulatory movement
-
- 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)
- Chemical Kinetics & Catalysis (AREA)
- Engineering & Computer Science (AREA)
- Combustion & Propulsion (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Silicates, Zeolites, And Molecular Sieves (AREA)
- Compositions Of Oxide Ceramics (AREA)
Abstract
The invention relates to an apparatus for treating aluminium comprising at least one device for mixing (20,
22, 30, 40) aluminium ore with limestone and sodium and/or potassium carbonate to obtain a mixture and
a calcination reactor (60) for producing the calcine. A circulating fluidized bed reactor (50) is arranged
between the device for mixing (20, 22, 30. 40) and the calcination reactor (60) and in which the mixture is
pre-calcined.
Description
Optimized Semi-Dry Process for Sintering of Aluminosilicates in the Production of Alumina
Technical Field The present invention describes an apparatus for treating aluminum comprising at least one device for mixing aluminum ore with limestone and sodium and/or potassium carbonate to obtain a mixture and a calcination reactor for producing the calcine. The invention also relates to the corresponding process.
Background Art The production of metals and their salts often relies on thermal treatment of the mined ores, transforming the natural occurring metal salts into the corresponding oxides, which are, if desired, subject to further processes yielding the targeted product.
Aluminum oxide (A1203) is predominantly produced from bauxite in the Bayer process. The mined and milled ore is treated with sodium hydroxide at elevated temperatures of 150 to 200 °C forming soluble sodium aluminate (NaAIO2), which is precipitated as aluminum hydroxide (AI(OH)3) from the obtained supersaturated solution. In the following calcination step, A1203 is formed at temperatures >1000 0 C.
In order for the Bayer process to be economically feasible, the ore's silica content must be below 10%. Higher levels of silica result in the simultaneous dissolution of alumina and silica, forming insoluble sodium aluminosilicates in the process, which significantly increases the amount of sodium hydroxide per ton of produced A1203 and hence the overall yield.
The addition of limestone (CaCO3) to the raw ore in a manner that the CaO/SiO2 molar ratio equals 1 during the sintering procedure, while concomitantly keeping 19945986_1 (GHMatters) P118991.AU the caustic ratio M20/ A1203 (M'= K' or Na') at 2, allows the processing of aluminosilicates. The typical temperature range in the sintering process of 1200 to 1350 °C results in the formation of insoluble calcium silicate phases (CaSiO3).
The sintering process is classified as wet, semi-wet or dry sintering, depending on the water content of the feed. The industrially applied wet sintering process operates with a slurry-like feed with an approximate water content of 30 wt.-%. The semi-dry sintering demands the granulation of the feed material featuring a residual water content of 10-15 wt.-%. A dry sintering approach is possible, if the caustic ratio equals 2 and if only calcinated limestone must be added to adjust the CaO/SiO2 ratio accordingly.
The wet sintering ensures agglomerates and, therefore, easy handling. However, it also suffers from the sticky consistence of its feed material, which leads to a high energy demand due to additional evaporation energy. Kilns with long residence times have to be applied for drying, calcination and subsequent sintering, resulting in a high specific energy consumption of 1200-1300 kcal/kg(sinter).
On the other hand, the dry sintering process for the sintering of nepheline to produce alumina is the most efficient approach in terms of energy consumption (650- 700 kcal/kg(sinter)). The major advantage in (most of) the dry process is the pre-calcination of the limestone in a flash pre-calciner prior to sintering in the rotary kiln. This allows for much higher throughputs and shorter rotary kilns, because the major part of the calcination does not take place in the kiln. However, the dry-sintering process is limited to ores featuring a caustic ratio of 2. An addition of the low melting carbonates (Na2CO3: 857 °C, K2CO3: 891 °C) causes material to stick to the furnace wall in the sintering process, rendering this process impossible, if the caustic ratio has to be adjusted.
19945986_1 (GHMatters) P118991.AU
A semi-dry sintering process is e.g., disclosed in CN 105 540 627. Therein, Bayer alkali red mud powder, lime, bauxite, soda ash and pulverized coal are mixed uniformly to be raw material pellets, and the raw material pellets are sintered to obtain the clinker of the alumina produced by the sintering process using two rotary kiln.
Such a semi-dry sintering approach attempt to combine the benefits of a wet and a fry sintering. This results in kilns of smaller dimensions and consequently a lower energy consumption of 800-900 kcal/kg(sinter) compared to the wet sinter approach.
However, an additional reduction of energy consumption, lower residence times and the handling of low melting alkalis is necessary in order to further reduce the process' energy consumption.
Summary
Disclosed herein is an apparatus for treating aluminum, the apparatus comprising: at least one granulator for mixing aluminum ore with limestone and sodium carbonate and/or potassium carbonate to obtain a mixture and to form granules of this mixture, said sodium carbonate and/or potassium carbonate being a salt solution, which is stored in granulation liquor tanks prior to use; a calcination reactor for producing a calcine; a circulating fluidized bed reactor arranged between the granulator and the calcination reactor and in which the granules are pre-calcined; and a cooler for cooling the calcine formed in the calcination reactor, the apparatus further comprising:
19945986_1 (GHMatters) P118991.AU a first recycling line for recirculating hot exhaust gases from the calcination reactor to the circulating fluidized bed reactor or to at least one pre-heating stage or to a dryer; a second recycling line for recirculating hot exhaust gases from the circulating fluidized bed reactor to at least one pre-heating stage or to a dryer; a third recycling line for recirculating hot exhaust gases from the cooler to the calcination reactor or to the circulating fluidized bed reactor or to at least one pre-heating stage or to a dryer; and a control unit for controlling the amount of aluminium ore and sodium carbonate and/or potassium carbonate mixed together, the control unit configured to ensure that the ratio R of (Na2O+K20)/Al203 is 0,95<R<1,05.
Broadly, the disclosure is directed to providing a plant for the handling of high silicon content aluminosilicate ores as an economically ecologically feasible process.
The plant can comprise an apparatus for treating aluminum comprising at least one device for mixing aluminum ore with limestone and sodium and/or potassium carbonate to obtain a mixture and a calcination reactor for producing the calcine, wherein a circulating fluidized bed reactor is arranged between the device for mixing and the calcination reactor and in which the mixture is pre-calcined. A first recycling line for recirculating hot exhaust gases can be provided from the calcination reactor in the circulating fluidized bed reactor and/or in at least one pre-heating stage and/or the dryer. A second recycling line for recirculating hot exhaust gases can be provided from the circulating fluidized bed reactor in at least one pre-heating stage and/or the dryer. A cooler can be provided for cooling the calcine formed in the calcination reactor and that a third recycling line for recirculating hot exhaust gases is provided from the cooler in the calcination reactor and/or in the circulating fluidized bed reactor and/or in at least one pre 19945986_1 (GHMatters) P118991.AU heating stage and/or a dryer, wherein the at least one pre-heating stage and/or a dryer.
According to the invention, the setup of the plant consists of at least one device for mixing the crude aluminum ore with limestone and sodium and/or potassium carbonate. It further comprises a calcination reactor for producing the calcine. The basic idea underlying the invention is that between mixing and calcination, a circulating fluidized bed reactor is foreseen to pre-calcine the mixture.
Due to the outstanding heat and mass transfer in a circulating fluidized bed (CFB), it is possible to use alkalis with low melting points. In addition, tailored residence times can be set. Therefore, the overall energy consumption can be lowered. This particularly enables the handling of ore with a high silicon content above 5,5 wt.-%.
In the mixing step, raw aluminosilicate ore, limestone and recycled solids are being mixed with an aqueous M2CO3 (M'= Na+ or K+) solution, adjusting the caustic ratio to 2, while introducing enough moisture to bind all constituents for the subsequent granulation. It is also possible to combine the mixing and the granulation step in at least one granulator. It is also possible that the mixing takes part in a drying or a pre-heating. An energy-intensive drying step of the respective carbonates is obsolete, since they are introduced as a salt solution.
In a preferred embodiment, the obtained mixture is granulated in two series connected granulators. The formation of granulates encapsulate the Na2CO3/ K2CO3additive within the grains.
These small pellets considerably facilitate to establish a circulating fluidized bed. In addition, dust generation is less if the material is granulated. This was shown in pilot-scale sintering tests comparing semi-dry and dry process. Furthermore, 19945986_1 (GHMatters) P118991.AU granulating not only a reduction of the water content, but to re-integrate dust from downstream steps, making the process more resource efficient.
The Na2CO3/ K2CO3 solution added in the granulation process does not only provide the solid mixture with the required alkalis, but also acts as a binder and decisively enhances the granulation process. This was shown in a series of laboratory granulation tests.
The grain size is typically between typically 5-20mm, which is most preferred for fluidizing bed systems.
It is particularly preferred to use at least two granulators for a careful control of the final moisture content (preferably 10-13 wt.-% water content).
With regard to the final calcination step, the used reactor type could be a kiln. This has the advantage that rotary kiln belongs to a relatively cheap and very well known technology. However, it is also possible to use any kind of fluidizing bed reactor to improve heat and mass transfer.
In the present invention, a ratio R of (Na2O+K20)/Al203 is 0,95<R<1,05 to ensure a high product quality. Therefore, a control unit is used to control or regulate the amounts of ore and alkali mixed in the granulation.
Moreover, it is particularly preferred that the sodium and/or potassium carbonate is a salt solution stored in granulation liquor tanks. It is possible to admix water to control the solution's concentration. Therefore, it is also possible to work with a low- or supersaturated solution. Additional energy savings can be made by feeding the granulation tanks with a (oversaturated) salt solution from the salt plant of the refinery. This saves additional evaporation energy in the salt plant,
19945986_1 (GHMatters) P118991.AU which corresponds to roughly 30 kcal per kg of produced sinter (depending on the concentration of the salt solution).
In another embodiment, at least one, preferably 2 to 3 pre-heating stage for the mixture and/or the granules is provided. Typically, the material is heated from ambient temperature to about 200 °C. Thereby, it may be possible to further improve the energy efficiency, particularly by any heat-recycling concept.
In addition, or alternatively, a dryer for the mixture or granules is foreseen before the circulating fluidized bed reactor. Therefore, it is possible to reduce the water content, preferably to a value below 1 wt.-%, and, as a consequence, also the energy consumption. The granules have a very good drying behavior keeping the rotary dryer comparatively short.
The achieved mixture is preferably pre-calcined in the circulating fluidized bed reactor at 700 to 900 °C, preferably at 800 to 850 °C to achieve a sufficient rate of pre-calcination. The final calcination step in the calcination reactor typically takes place at 800 to 14000 C, preferably at 1000 to 1300 °C.
The mean residence time in the circulating fluidized bed reactor is between 15 and 25 minutes, preferably 20 +/- 2 minute and/or the mean residence time in the calcination reactor is between 30 and 200 minutes. These residence times, particularly if they are correlated, lowers operation temperatures and avoiding liquid fractions of alkaline.
For a further reduction of the plant's energy demand, a first recycling line for recirculating hot exhaust gases is provided from the calcination reactor in the circulating fluidized bed reactor and/or in at least one pre-heating stage. Alternative or complementary a second recycling line for recirculating hot exhaust
19945986_1 (GHMatters) P118991.AU gases is provided from the circulating fluidized bed reactor in at least one pre heating stage.
For an even higher grade of optimizing the overall energy balance, at least one cooler is provided for cooling the calcine formed in the calcination reactor. Preferably, a third recycling line for recirculating hot exhaust gases is provided from the cooler in the calcination reactor and/or in the circulating fluidized bed reactor and/or in at least one pre-heating stage.
Moreover, a conduit feeds a gas with an oxygen content between 15 and 25% by weight as fluidizing gas into the circulating fluidized bed reactor. Thereby, the fluidizing gas simultaneously is used as an 02 source for chemical reactions. The use of air or oxygen-enriched air as a cheap oxygen source is preferred.
With regard to the circulating fluidized bed, it is also preferred that the circulating fluidized bed reactor is configured such that at least 70% by weight of the carbon contained in the ore is removed. Thereby, a reduction of the overall mass flow in the calcining step is achieved. Moreover, the carbon burning provides at least parts of the energy, which is required for the endothermic calcination, and which is optimally transported within the circulating fluidized bed.
Advantageously, in the process herein disclosed, the handling of high silicon content aluminosilicate ores based on a semi-dry sintering process may be possible. Combining the known advantages of the semi-dry base process over the established approaches is being achieved at a reasonable energy consumption.
Also disclosed herein in a second aspect is a process comprising the steps of (a) mixing aluminum ore with limestone and sodium and/or potassium carbonate to obtain a mixture and (b) calcining the mixture to calcine. As the essential step, 19945986_1 (GHMatters) P118991.AU between step (a) and step (b) the mixture is pre-calcined in a circulating fluidized bed.
Preferably, the moisture content of the mixture or granules introduced in the pre calcining is 10 to 15% by weight, which provides a good stability of the granules.
Moreover, in a preferred embodiment in the pre-calcining at least 70% by weight of the carbon contained in the ore is removed to reduce the overall mass flow.
Brief Description of the Drawings Further features, advantages and possible applications of the invention can be taken from the following description of the drawings and the exemplary embodiments. All features described and/or illustrated form the subject-matter of the invention per se or in any combination, independent of their inclusion in the claims or their back-reference.
In the drawings:
Fig. 1 shows schematically an embodiment of a plant in accordance with the present invention.
Detailed Description Figure 1 shows the principal structure of a plant in accordance with the invention. Via conduit 10, alumina ore is fed into a homogenization silo 11, wherein it is mixed with recycled solids and/or limestone from fed in via conduits 13 and 14 to create a mixture.
Conduit 15 feeds at least one granulation liquor tank with a salt solution consisting of sodium and potassium carbonates that can be diluted with water injected via conduit 16, if necessary. 19945986_1 (GHMatters) P118991.AU
The mixture as well as the made-up salt solution is then dosed via conduits 17 and 18 to a first granulator 20 where it fulfils three tasks: adding the required amount of alkalis to the solid mixture of limestone, nepheline and dust (and optionally some recycle materials from the process), providing the moisture for granulation and acting as a binder. In this embodiment, the granulator 20 also works as a mixing device. However, it is also possible to foresee an addition mixer before the granulator 20. It is very advisable but not necessary to have a second granulator 22, preferably connected in in series via conduit 21, to achieve the necessary granulation time, but also to have a good control over the final moisture. In this context, it is possible to add additional water via conduit 24.
Downwards the granulators 20, 22, the produces granules are fed via conduit 23 into a dryer 30. Therein, the wet granules are dried, often with hot flue gases from conduit 63. Preferably, the dryer 30 is designed as a rotary dryer.
The off-gases are passed via conduit 32 in an electrostatic precipitator 33 and from there via conduit 35 in a not-shown off-gas treatment. Via conduit 34, small particles filtered out in the electrostatic precipitator 33 are fed into conduit 45 for recycling.
The dried granules fed via conduit 31 into a pre-heating section 40. It is preferred that that pre-heating section 40 comprises 2 or 3 stages. Further, consecutive venture / cyclone stages lead to particularly good results. For an improved energy concept, hot gases, fed in via conduit 53, preferably counter-current, can be used.
Via conduit 42, the off-gases from the pre-heating section 40 in an electrostatic precipitator 43. From there, preferably parts of the off-gases are withdrawn as exhaust gas via conduit 46 and 48 while the other part is transported via conduit
19945986_1 (GHMatters) P118991.AU
46 and 47 as a gas for carbonization. Filtered particles can be passed via conduit 44 and 45 into the first granulator 20.
After pre-heating the granules are passed via conduit 41 in a circulating fluidized bed reactor 50 for pre-calcining, which is in accordance with the invention to ensure the necessary very good heat and mass transfer. Therein, the granules are de-carbonization to a degree of minimum 80 wt.-%. The pre-calcined particles are fed via conduit 51 in a calcination reactor 60. Via conduit 78 and/or 52, fluidizing gas is injected over the bottom nozzle grid. It is preferred that around 20 vol-% of fluidization gas is fresh air, whereby this percentage of fresh air can deviate depending on the design of the circulating fluidized bed. Preferably, the bigger part of the fluidizing gas is air from a downward device transferred to the pre-calcination reactor via conduits 76, 78, a so-called tertiary air duct.
Moreover, it is possible to pass hot off-gases from the circulating fluidized bed with its high amount of off-gases into the pre-heating stage 40 via conduit 53. Therein, it can be used as a direct and/or indirect heat transfer medium. Thereby, also no separate off-gas handling is necessary.
The final sintering takes place in the calcining reactor 60, which is preferably designed as a rotary kiln to reduce the amount of hot gases in comparison with fluidized bed technology. Fresh air is fed into calcination reactor via conduit 62 while it is also possible to introduce hot gas from the downward cooler via conduits 76 and 77 to reduce the amount of energy to be supplied.
The resulting hot sinter is passed via conduit 61 into a cooler 70, where it is preferably air-cooled by a grate cooler. The cooler 70 is preferably cooled with air passed in via conduit 73. This air withdrawn and at least partly used as a heat transfer medium in the pre-calcination reactor 50 and the calcining reactor 60.
19945986_1 (GHMatters) P118991.AU
Further, air can be withdrawn via conduit 74 into an electrostatic precipitator 75 and from there via conduit 75 into a not-shown off-gas treatment.
Cooled product is withdrawn via conduits 71, 72, whereby it is possible to admix small particles filtered in the electrostatic precipitator 75.
It is to be understood that, if any prior art is referred to herein, such reference does not constitute an admission that the prior art forms a part of the common general knowledge in the art, in Australia or any other country.
In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word "comprise" or variations such as "comprises" or "comprising" is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention.
19945986_1 (GHMatters) P118991.AU
Reference numbers
10 conduit 11 homogenization silo 12 granulation liquor tank 13-18 conduit 20 granulator 21 conduit 22 granulator 23, 24 conduit 30 dryer 31, 32 conduit 33 electrostatic precipitator 34, 35 conduit 40 pre-heating section 41, 42 conduit 43 electrostatic precipitator 44-48 conduit 50 circulating fluidized bed reactor 51 conduit 60 calcining reactor 61, 62 conduit 70 cooler 71-74 conduit 75 electrostatic precipitator 76,77 conduit
19945986_1 (GHMatters) P118991.AU
Claims (3)
1. An apparatus for treating aluminum, the apparatus comprising: at least one granulator for mixing aluminum ore with limestone and sodium carbonate and/or potassium carbonate to obtain a mixture and to form granules of this mixture, said sodium carbonate and/or potassium carbonate being a salt solution, which is stored in granulation liquor tanks prior to use; a calcination reactor for producing a calcine; a circulating fluidized bed reactor arranged between the granulator and the calcination reactor and in which the granules are pre-calcined; and a cooler for cooling the calcine formed in the calcination reactor, the apparatus further comprising: a first recycling line for recirculating hot exhaust gases from the calcination reactor to the circulating fluidized bed reactor or to at least one pre-heating stage or to a dryer; a second recycling line for recirculating hot exhaust gases from the circulating fluidized bed reactor to at least one pre-heating stage or to a dryer; a third recycling line for recirculating hot exhaust gases from the cooler to the calcination reactor or to the circulating fluidized bed reactor or to at least one pre-heating stage or to a dryer; and a control unit for controlling the amount of aluminium ore and sodium carbonate and/or potassium carbonate mixed together, the control unit configured to ensure that the ratio R of (Na2O+K20)/Al203 is 0,95<R<1,05.
2. An apparatus according to claim 1, wherein the calcination reactor is a rotary kiln.
19945986_1 (GHMatters) P118991.AU
3. An apparatus according to claim 1 or claim 2, wherein: the circulating fluidized bed reactor is designed for an operation temperature between 700 and 900 °C;
the circulating fluidized bed reactor is designed for a mean residence time between 15 and 25 minutes; and/or the calcination reactor is designed for a mean residence time between 30 and 200 minutes.
19945986_1 (GHMatters) P118991.AU
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| AU2022100082A AU2022100082B4 (en) | 2019-11-26 | 2022-06-21 | Optimized semi-dry process for sintering of aluminosilicates in the production of alumina |
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| AUPCT/EP2019/082626 | 2019-11-26 | ||
| PCT/EP2019/082626 WO2021104613A1 (en) | 2019-11-26 | 2019-11-26 | Optimized semi-dry process for sintering of aluminosilicates in the production of alumina |
| AU2022100082A AU2022100082B4 (en) | 2019-11-26 | 2022-06-21 | Optimized semi-dry process for sintering of aluminosilicates in the production of alumina |
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| PCT/EP2019/082626 Division WO2021104613A1 (en) | 2019-11-26 | 2019-11-26 | Optimized semi-dry process for sintering of aluminosilicates in the production of alumina |
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| GB2144206A (en) * | 1983-07-28 | 1985-02-27 | Fives Cail Babcock | Calcination installation for producing various grades of alumina and a method of operation |
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| CN108314069A (en) * | 2018-05-08 | 2018-07-24 | 杨光华 | A kind of method of dry sintering dissolution aluminium oxide |
| CN110028091A (en) * | 2018-05-31 | 2019-07-19 | 沈阳铝镁设计研究院有限公司 | A kind of Bayer process red mud production aluminium oxide wet laid furnishes dry sintering technique |
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2022
- 2022-06-21 AU AU2022100082A patent/AU2022100082B4/en active Active
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2144206A (en) * | 1983-07-28 | 1985-02-27 | Fives Cail Babcock | Calcination installation for producing various grades of alumina and a method of operation |
| EP1575871B1 (en) * | 2002-12-23 | 2012-08-15 | Outotec Oyj | Process and plant for producing metal oxide from metal compounds |
| US20120052000A1 (en) * | 2009-01-26 | 2012-03-01 | Outotec Oyj | Process and plant for producing metal oxide from metal salts |
| WO2012062593A1 (en) * | 2010-11-08 | 2012-05-18 | Outotec Oyj | Process and plant for producing alumina from aluminum hydroxide |
| CN105540627A (en) * | 2016-01-19 | 2016-05-04 | 中国铝业股份有限公司 | Preparation method for clinker of alumina produced by sintering process |
| CN105565350A (en) * | 2016-02-06 | 2016-05-11 | 杭州锦江集团有限公司 | Method for producing aluminum oxide with high-alumina fly ash |
| CN108314069A (en) * | 2018-05-08 | 2018-07-24 | 杨光华 | A kind of method of dry sintering dissolution aluminium oxide |
| CN110028091A (en) * | 2018-05-31 | 2019-07-19 | 沈阳铝镁设计研究院有限公司 | A kind of Bayer process red mud production aluminium oxide wet laid furnishes dry sintering technique |
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| AU2022100082A4 (en) | 2022-07-28 |
| AU2022100082A6 (en) | 2022-09-22 |
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