WO1998058876A1 - Process for production of monohydrate alumina from supersaturated aluminate solutions - Google Patents

Process for production of monohydrate alumina from supersaturated aluminate solutions Download PDF

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Publication number
WO1998058876A1
WO1998058876A1 PCT/GR1998/000019 GR9800019W WO9858876A1 WO 1998058876 A1 WO1998058876 A1 WO 1998058876A1 GR 9800019 W GR9800019 W GR 9800019W WO 9858876 A1 WO9858876 A1 WO 9858876A1
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WIPO (PCT)
Prior art keywords
boehmite
precipitation
alumina
monohydrate alumina
sodium aluminate
Prior art date
Application number
PCT/GR1998/000019
Other languages
French (fr)
Inventor
Ioannis Paspaliaris
Dimitrios Panias
Christoforos Skoufadis
Dimitrios Ballas
George Panou
George Rigas
Kostas Kalaitzoglou
Arnold Coppieters
Antonios Kontopoulos
Original Assignee
National Technical University Of Athens (Ntua)
Hellenic Alumina Industry S.A. (E.L.V.A.)
Universite Libre De Bruxelles
Kontopoulou, Konstantina
Kontopoulou, Eliza
Kontopoulou, Marianna
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
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Application filed by National Technical University Of Athens (Ntua), Hellenic Alumina Industry S.A. (E.L.V.A.), Universite Libre De Bruxelles, Kontopoulou, Konstantina, Kontopoulou, Eliza, Kontopoulou, Marianna filed Critical National Technical University Of Athens (Ntua)
Priority to CA002294478A priority Critical patent/CA2294478A1/en
Priority to AU77833/98A priority patent/AU7783398A/en
Priority to EP98925868A priority patent/EP0996590A1/en
Publication of WO1998058876A1 publication Critical patent/WO1998058876A1/en

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    • 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
    • C01F7/04—Preparation of alkali metal aluminates; Aluminium oxide or hydroxide therefrom
    • C01F7/14—Aluminium oxide or hydroxide from alkali metal aluminates
    • C01F7/144—Aluminium oxide or hydroxide from alkali metal aluminates from aqueous aluminate solutions by precipitation due to cooling, e.g. as part of the Bayer process

Definitions

  • the current invention is referred to a new aluminium precipitation process from supersaturated aluminate solutions at temperatures lower than 100°C in which aluminium is precipitated with the form of monohydrate alumina (Al 2 O 3 .H 2 O).
  • Bayer process is used almost exclusively for the extraction of alumina from bauxites.
  • the essential steps of the Bayer process are:
  • Precipitation of aluminum hydroxide (gibbsite, AJ O 3 .3H 2 O) from the pregnant liquor according to the following equation. Precipitation is effected by cooling the solution to 55 - 60°C, thus causing supersaturation, and by introducing small gibbsite particles as seeds.
  • Al 2 O 3 .3H 2 O ( .) Al2 ⁇ 3(s , + 3H 2 O
  • the new process which is analytically described in the current invention, is a highly innovative variation of the Bayer process whereby, at the precipitation step, alumina monohydrate (Al 2 O 3 H 2 O) rather than t ⁇ hydrate is precipitated at atmospheric conditions
  • alumina monohydrate Al 2 O 3 H 2 O
  • the mam feature of this method is the production of a material needed substantially lower amounts of energy during the calcination stage
  • the technical characteristics of the new process are the following
  • Alumina concentration in supersaturated aluminate solution is varied, typically but not exclusively, in the region 60-250g/l
  • the initial seed ratio (SR), grams of added boehmite/grams of dissolved alumina, is varied, typically but not exclusively, in the region 0-5
  • the precipitation of the monohydrate alumina can be carried out with or without glycerol or any other alcohol addition at concentration varied, typically but not exclusively in the region
  • the aluminate solution is similar to the one that is used by the Bayer process
  • concentrations of Al 2 O ⁇ , and Na 2 O are 132g/l and 120g/l respectively
  • the precipitate was mineralogicaly characterized as pure monohydrate alumina (boehmite)
  • the concentrations of Al 2 O and Na 2 O in the aluminate solution are 99g/l and 90g/l respectively Monohydrate alumina (boehmite) seeds are added in the solution with a ratio of 1,76 The resulting pulp is mantained by mechanical agitation at 300min " ' for 96 hours During the test, systematic sampling is carried out and the samples are analysed for Al O 3 The results of this test are given in Table 2
  • the concentrations of Al 2 O 3 and Na 2 O in the aluminate solution are l lOg/l and lOOg/l respectively
  • the precipitate was mineralogicaly characterized as pure monohydrate alumina (boehmite)
  • Example 4 A detailed example concerning the application of the process at starting temperature near but always under 100°C is the following
  • the concentrations of Al 2 O 3 and Na 2 O in the aluminate solution are 132g/l and 120g/l respectively
  • Monohydrate alumina (boehmite) seeds are added in the solution with a ratio of 1,76
  • the resulting pulp is mantained by mechanical agitation at 300min " ' for 96 hours at 95°C
  • the temperature of the pulp is lowered by 10°C, every 24 hours, until the final value of 60°C
  • the precipitate was mineralogicaly characterized as pure monohydrate alumina (boehmite)
  • the concentrations of Al 2 O 3 and Na 2 O in the aluminate solution are 179g/l and 160g/l respectively
  • the precipitate was mineralogicaly characterized as pure monohydrate alumina (boehmite)
  • the concentrations of Al 2 O, and Na 2 O in the aluminate solution are 179g/l and I60g/l respectively Glycerol is also added at concentration of 0,9mole/kg of monohydrate alumina
  • Monohydrate alumina (boehmite) seeds are added in the solution with a ratio of 2, 10
  • the resulting pulp is mantained by mechanical agitation at 300min " ' for 48 hours at 90°C
  • the precipitate was mineralogicaly characterized as pure monohydrate alumina (boehmite)
  • the precipitate was mineralogicaly characterized as pure monohydrate alumina (boehmite)
  • the above method comprises a highly innovative variation of the precipitation step in the current Bayer process It has a lot of advantages, the most important of them is the significant energy savings during the calcination stage for the following reasons

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Geology (AREA)
  • Inorganic Chemistry (AREA)
  • Compounds Of Alkaline-Earth Elements, Aluminum Or Rare-Earth Metals (AREA)

Abstract

Process for production of monohydrate alumina (boehmite) with precipitation from supersaturated sodium aluminate solutions starting at temperatures lower than 100 °C. The current invention is referred to a new aluminium precipitation process from supersaturated sodium aluminate solutions at temperatures lower than 100 °C in which aluminium is precipitated with the form of monohydrate alumina (boehmite, Al2O3.H2O). The process for production of monohydrate alumina (boehmite, Al2O3.H2O), from supersaturated sodium aluminate solutions, is characterised by precipitation at temperatures lower than 100 °C. The process comprises a highly innovative variation of the precipitation step in the current Bayer process in which it is achieved 40 % energy reduction in the calcination stage and more than 10 % total energy savings in the Bayer process.

Description

PROCESS FOR PRODUCΗON OF MONOHYDRATE ALUMINA FROM SUPERSATURATED ALUMINATE SOLUTIONS
The current invention is referred to a new aluminium precipitation process from supersaturated aluminate solutions at temperatures lower than 100°C in which aluminium is precipitated with the form of monohydrate alumina (Al2O3.H2O).
Bayer process is used almost exclusively for the extraction of alumina from bauxites. The essential steps of the Bayer process are:
• Digestion of bauxite by using sodium hydroxide at elevated temperatures and pressures in autoclaves.
Al(OH)3(s) + NaOH(aq) = NaAl(OH)4(„q)
• Precipitation of aluminum hydroxide (gibbsite, AJ O3.3H2O) from the pregnant liquor according to the following equation. Precipitation is effected by cooling the solution to 55 - 60°C, thus causing supersaturation, and by introducing small gibbsite particles as seeds.
2Al(OH)4 (1) = Al2O3.3H2O(5) + 2OH-(aq)
• Calcination of gibbsite at about 1000- 1200°C to produce smelter-grade alumina according to the following equation:
Al2O3.3H2O(.) = Al2θ3(s, + 3H2O
Energy cost of the Bayer process constitute about 30% of the alumina price. Total energy requirements in modern alumina plants amounts to about 12 GJ/t of alumina produced. 3 GJ/t Al O? of this, representing 25% of the total energy consumption, is used for calcination.
The new process, which is analytically described in the current invention, is a highly innovative variation of the Bayer process whereby, at the precipitation step, alumina monohydrate (Al2O3 H2O) rather than tπhydrate is precipitated at atmospheric conditions The mam feature of this method is the production of a material needed substantially lower amounts of energy during the calcination stage The technical characteristics of the new process are the following
• Precipitation of the monohydrate alumina (Boehmite) from supersaturated aluminate solutions is carried out at temperatures lower than 100°C, namely under atmospheric conditions
• Precipitation of the monohydrate alumina (Boehmite) from supersaturated aluminate solutions is carried out with cooling, starting the procedure at temperatures close to but lower than 100°C
• In a process variation, precipitation of the monohydrate alumina (Boehmite) from supersaturated aluminate solutions is carried out with cooling, starting the procedure at temperatures close to but lower than 100°C and with simultaneous use of ultrasounds with frequency varied, typically but not exclusively, in the region 20-50kHz
• Alumina concentration in supersaturated aluminate solution is varied, typically but not exclusively, in the region 60-250g/l
• Caustic concentration in supersaturated sodium aluminate solution, expressed as grams of Na2O per liter of solution, is varied, typically but not exclusively, in the region 50-250g/l
• The precipitation of the monohydrate alumina can be carried out without boehmite seed addition in the aluminate solution In this case, a time consuming induction period is observed
• In a process variation, precipitation of the monohydrate alumina (Boehmite) from supersaturated sodium aluminate solutions is carried out with the presence of boehmite seed
In this case, the precipitation process is drastically accelerated The initial seed ratio (SR), grams of added boehmite/grams of dissolved alumina, is varied, typically but not exclusively, in the region 0-5
• The precipitation of the monohydrate alumina can be carried out with or without glycerol or any other alcohol addition at concentration varied, typically but not exclusively in the region
0-5mol/kg boehmite seed
In the following, examples of the process application are presented
Example 1
A detailed example concerning the application of the process at temperatures below 100 C, is the precipitation of monohydrate alumina (boehmite) from a supersaturated aluminate solution at 90°C The aluminate solution is similar to the one that is used by the Bayer process The concentrations of Al2O~, and Na2O are 132g/l and 120g/l respectively
Monohydrate alumina (boehmite) seeds are added in the solution with a ratio of 1,76 The resulting pulp is mantained by mechanical agitation at 300mιn ' for 96 hours During the test, systematic sampling is carried out and the samples are analysed for Al2O~, The results of this test are given in Table 1
Table 1
Process for production of monohydrate alumina (boehmite) by precipitation from supersaturated aluminate solution at 90°C.
Figure imgf000005_0001
Figure imgf000006_0001
The precipitate was mineralogicaly characterized as pure monohydrate alumina (boehmite)
Example 2
Another detailed example concerning the application of the process at temperatures below 100°C, is the precipitation of monohydrate alumina (boehmite) from a supersaturated aluminate solution at 90°C
The concentrations of Al2O and Na2O in the aluminate solution are 99g/l and 90g/l respectively Monohydrate alumina (boehmite) seeds are added in the solution with a ratio of 1,76 The resulting pulp is mantained by mechanical agitation at 300min"' for 96 hours During the test, systematic sampling is carried out and the samples are analysed for Al O3 The results of this test are given in Table 2
Table 2
Process for production of monohydrate alumina (boehmite) by precipitation from supersaturated aluminate solution at 90°C.
Figure imgf000006_0002
The precipitate was mineralogicaly characterized as pure monohydrate alumina (boehmite) Example 3
Another detailed example concerning the application of the process at temperatures below
100°C, is the precipitation of monohydrate alumina (boehmite) from a supersaturated aluminate solution at 90°C
The concentrations of Al2O3 and Na2O in the aluminate solution are l lOg/l and lOOg/l respectively
Monohydrate alumina (boehmite) seeds are added in the solution with a ratio of 0,4 The resulting pulp is mantained by mechanical agitation at 300min"' for 96 hours During the test, systematic sampling is carried out and the samples are analysed for Al2O3 The results of this test are given in Table 3
Table 3
Process for production of monohydrate alumina (boehmite) by precipitation from supersaturated aluminate solution at 90°C.
Figure imgf000007_0001
The precipitate was mineralogicaly characterized as pure monohydrate alumina (boehmite)
Example 4 A detailed example concerning the application of the process at starting temperature near but always under 100°C is the following
The concentrations of Al2O3 and Na2O in the aluminate solution are 132g/l and 120g/l respectively
Monohydrate alumina (boehmite) seeds are added in the solution with a ratio of 1,76 The resulting pulp is mantained by mechanical agitation at 300min"' for 96 hours at 95°C The temperature of the pulp is lowered by 10°C, every 24 hours, until the final value of 60°C
During the test, daily sampling is carried out and the samples are analysed for Al2O~, The results of this test are given in Table 4
Table 4
Process for production of monohydrate alumina (boehmite) by precipitation from supersaturated aluminate solution with cooling from 95°C to 60°C.
Figure imgf000008_0001
The precipitate was mineralogicaly characterized as pure monohydrate alumina (boehmite)
Example 5
Another detailed example concerning the application of the process at starting temperature near but always under 100°C is the following
The concentrations of Al2O3 and Na2O in the aluminate solution are 179g/l and 160g/l respectively
Monohydrate alumina (boehmite) seeds are added in the solution with a ratio of 2,10 The resulting pulp is mantained by mechanical agitation at 300min_1 for 48 hours at 90°C Afterwards, the pulp is cooled at 70°C, where it remains for 24 hours and finally the pulp is cooled at 60°C, where it remains for 24 hours During the test, daily sampling is carried out and the samples are analysed for Al2O3 The results of this test are given in Table 5 Table 5
Process for production of monohydrate alumina (boehmite) by precipitation from supersaturated aluminate solution with cooling from 90°C to 60°C.
Figure imgf000009_0001
The precipitate was mineralogicaly characterized as pure monohydrate alumina (boehmite)
Example 6
A detailed example concerning the application of the process at starting temperature near but always under 100°C, with the addition of alcohol, is the following
The concentrations of Al2O, and Na2O in the aluminate solution are 179g/l and I60g/l respectively Glycerol is also added at concentration of 0,9mole/kg of monohydrate alumina
(boehmite) seeds
Monohydrate alumina (boehmite) seeds are added in the solution with a ratio of 2, 10 The resulting pulp is mantained by mechanical agitation at 300min"' for 48 hours at 90°C
Afterwards, the pulp is cooled at 70( C, where it remains for 24 hours and finally the pulp is cooled at 60°C, where it remains for 24 hours During the test, daily sampling is carried out and the samples are analysed for Al2O3 The results of this test are given in Table 6 Table 6
Process for production of monohydrate alumina (boehmite) by precipitation from supersaturated aluminate solution with cooling from 90°C to 60°C and addition of glycerol.
Figure imgf000010_0001
The precipitate was mineralogicaly characterized as pure monohydrate alumina (boehmite)
Example 7
A detailed example concerning the application of the process at starting temperature near but always under 100ϋC, with the addition of alcohol and use of ultrasounds, is the following The concentrations of Al2O3 and Na2O in the aluminate solution are 155 g/1 and 160g/l respectively Glycerol is also added at concentration of 0,4mole/kg of monohydrate alumina (boehmite) seeds
Monohydrate alumina (boehmite) seeds are added in the solution with a ratio of 2,42 The resulting pulp is mantained by mechanical agitation at 300mm"1 for 48 hours at 90υC Afterwards, the pulp is cooled at 70°C, where it remains for 48 hours Ultrasounds with frequency of 35kHz are applied only in the last 48 hours During the test, daily sampling is carried out and the samples are analysed for Al2O3 The results of this test are given in Table 7 Table 7
Process for production of monohydrate alumina (boehmite) by precipitation from supersaturated aluminate solution with cooling from 90°C to 60°C, addition of glycerol and use of ultrasounds.
Figure imgf000011_0001
The precipitate was mineralogicaly characterized as pure monohydrate alumina (boehmite)
The above method comprises a highly innovative variation of the precipitation step in the current Bayer process It has a lot of advantages, the most important of them is the significant energy savings during the calcination stage for the following reasons
(a) the enthalpy of dehydration of boehmite to alumina is significantly lower than that of gibbsite
A1203.3H20 → A1203 + 3H20 ΔH = 187 KJ/moleAl2O3
A1203. H20 → A1203 + H O ΔH = 72 KJ/ ole Al2O3
This means energy savings about 1 1 GJ/t Al2O3
(b) As boehmite contains one mole of water against three for gibbsite, the amount of the material to be calcined will be reduced by 360 kg/t of alumina produced This will result in additional energy savings of the order of 0 7 GJ/t Al2O3 as well as in increase in the calciner productivity The energy consumption during the calcination stage is reduced to 1.2 GJ/t Al2O , representing more than 40% energy reduction in the calcination stage and more than 10% total energy savings in the Bayer process.

Claims

1 A process for production of monohydrate alumina (boehmite, Al2O H2O), from supersaturated sodium aluminate solutions, characterised by precipitation starting at temperatures lower than 100°C
2 The process as defined by the claim 1, wherein precipitation takes place isothermally
3 The process as defined by the claim 1, wherein precipitation starts at temperature close to but lower than 100°C and afterwards the supersaturated sodium aluminate solutions is cooled to successively lower temperatures
4 The process as defined by the claims 1, 2 or 3, wherein precipitation is carried out with boehmite seed addition in the supersaturated sodium aluminate solutions The initial seed ratio (SR), grams of added boehmite/grams of dissolved alumina, is varied, typically but not exclusively, in the region 0-5 5 The process as defined by the claims 1, 2 or 3, wherein precipitation is carried out with simultaneous application of ultrasounds with frequencies varied, typically but not exclusively, in the region 20-50kHz
6 The process as defined by the claims 1 , 2 or 3 wherein the precipitation is carried out with addition of glycerol or any other alcohol, at concentration varied, typically but not exclusively, in the region 0-5mol/kg boehmite seed
7 The process as defined by the claims 1 -6, wherein the alumina concentration in the supersaturated sodium aluminate solution is varied, typically but not exclusively, in the region 60-250g/l
8 The process as defined by the claims 1-6, wherein the caustic concentration in the supersaturated sodium aluminate solution, expressed as grams of Na O per liter of solution, is varied, typically but not exclusively, in the region 50-250g/l.
PCT/GR1998/000019 1997-06-24 1998-06-23 Process for production of monohydrate alumina from supersaturated aluminate solutions WO1998058876A1 (en)

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CA002294478A CA2294478A1 (en) 1997-06-24 1998-06-23 Process for production of monohydrate alumina from supersaturated aluminate solutions
AU77833/98A AU7783398A (en) 1997-06-24 1998-06-23 Process for production of monohydrate alumina from supersaturated aluminate solutions
EP98925868A EP0996590A1 (en) 1997-06-24 1998-06-23 Process for production of monohydrate alumina from supersaturated aluminate solutions

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GR97100253 1997-06-24

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2008116259A1 (en) * 2007-03-27 2008-10-02 Alcoa Of Australia Limited Method for precipitating boehmite
WO2009039592A1 (en) * 2007-09-28 2009-04-02 Alcoa Of Australia Limited Method for precipitating boehmite from pre-precipitation bayer liquors
WO2019049668A1 (en) 2017-09-07 2019-03-14 株式会社Adeka Composition, and flame-retardant resin composition

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN116040667A (en) * 2023-02-22 2023-05-02 中国神华能源股份有限公司哈尔乌素露天煤矿 Micron-sized boehmite powder material and preparation method thereof

Citations (3)

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EP0015196A1 (en) * 1979-02-26 1980-09-03 Rhone-Poulenc Specialites Chimiques Process for the preparation of aqueous suspensions of alumina at least partially in the form of ultra-fine boehmite and their applications
US4595581A (en) * 1984-12-10 1986-06-17 Aluminum Company Of America Boehmite production by precipitation from sodium aluminate solution at elevated temperatures
EP0366825A1 (en) * 1988-11-04 1990-05-09 Vereinigte Aluminium-Werke Aktiengesellschaft Process for the preparation of fine platelike boehmite

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0015196A1 (en) * 1979-02-26 1980-09-03 Rhone-Poulenc Specialites Chimiques Process for the preparation of aqueous suspensions of alumina at least partially in the form of ultra-fine boehmite and their applications
US4595581A (en) * 1984-12-10 1986-06-17 Aluminum Company Of America Boehmite production by precipitation from sodium aluminate solution at elevated temperatures
EP0366825A1 (en) * 1988-11-04 1990-05-09 Vereinigte Aluminium-Werke Aktiengesellschaft Process for the preparation of fine platelike boehmite

Non-Patent Citations (2)

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ED: E. BARTHOLOMÉ ET AL.: "Ullmanns Encyklopädie der technischen Chemie; 4te Aufl.", 1974, VERLAG CHEMIE, WEINHEIM (DE), XP002077302 *
FILIPPOU D ET AL: "FROM BAYER PROCESS LIQUORS TO BOEHMITE AND, THEN, TO ALUMINA: AN ALTERNATIVE ROUTE FOR ALUMINA PRODUCTION?", 21 February 1993, LIGHT METALS, DENVER, FEB. 21 - 25, 1993, NR. MEETING 122, PAGE(S) 119 - 123, SUBODH K DAS, XP000379783 *

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2008116259A1 (en) * 2007-03-27 2008-10-02 Alcoa Of Australia Limited Method for precipitating boehmite
WO2009039592A1 (en) * 2007-09-28 2009-04-02 Alcoa Of Australia Limited Method for precipitating boehmite from pre-precipitation bayer liquors
WO2019049668A1 (en) 2017-09-07 2019-03-14 株式会社Adeka Composition, and flame-retardant resin composition
US11674037B2 (en) 2017-09-07 2023-06-13 Adeka Corporation Composition, and flame-retardant resin composition

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AU7783398A (en) 1999-01-04
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GR1002926B (en) 1998-06-16

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