WO2008067594A1 - Elimination des impuretés de la bauxite - Google Patents

Elimination des impuretés de la bauxite Download PDF

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Publication number
WO2008067594A1
WO2008067594A1 PCT/AU2007/001866 AU2007001866W WO2008067594A1 WO 2008067594 A1 WO2008067594 A1 WO 2008067594A1 AU 2007001866 W AU2007001866 W AU 2007001866W WO 2008067594 A1 WO2008067594 A1 WO 2008067594A1
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WIPO (PCT)
Prior art keywords
leach solution
bauxite
solution
pregnant leach
impurities
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PCT/AU2007/001866
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English (en)
Inventor
Steven Philip Rosenberg
Stephen Charles Grocott
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Bhp Billiton Aluminium Australia Pty Ltd
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Filing date
Publication date
Priority claimed from AU2006906832A external-priority patent/AU2006906832A0/en
Application filed by Bhp Billiton Aluminium Australia Pty Ltd filed Critical Bhp Billiton Aluminium Australia Pty Ltd
Priority to AU2007329174A priority Critical patent/AU2007329174A1/en
Publication of WO2008067594A1 publication Critical patent/WO2008067594A1/fr

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B3/00—Extraction of metal compounds from ores or concentrates by wet processes
    • C22B3/04—Extraction of metal compounds from ores or concentrates by wet processes by leaching
    • C22B3/12—Extraction of metal compounds from ores or concentrates by wet processes by leaching in inorganic alkaline solutions
    • 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
    • C01F7/06—Preparation of alkali metal aluminates; Aluminium oxide or hydroxide therefrom by treating aluminous minerals or waste-like raw materials with alkali hydroxide, e.g. leaching of bauxite according to the Bayer process
    • C01F7/0613—Pretreatment of the minerals, e.g. grinding
    • 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
    • C01F7/06—Preparation of alkali metal aluminates; Aluminium oxide or hydroxide therefrom by treating aluminous minerals or waste-like raw materials with alkali hydroxide, e.g. leaching of bauxite according to the Bayer process
    • C01F7/062—Digestion
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B21/00—Obtaining aluminium
    • C22B21/0007—Preliminary treatment of ores or scrap or any other metal source
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B3/00—Extraction of metal compounds from ores or concentrates by wet processes
    • C22B3/20—Treatment or purification of solutions, e.g. obtained by leaching
    • C22B3/22—Treatment or purification of solutions, e.g. obtained by leaching by physical processes, e.g. by filtration, by magnetic means, or by thermal decomposition
    • 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

Definitions

  • the present invention relates to a process for purification of bauxite by removal of impurities upstream of the Bayer process.
  • metallurgical alumina is produced from bauxite via the Bayer process.
  • run-of-mine bauxite is crushed and transported without further treatment to an alumina refinery where it is milled in contact with recycled caustic liquor.
  • a portion of the aluminous minerals within the bauxite begins to dissolve under these conditions, as do a range of impurities that are also present in bauxite.
  • bauxite will contain silicious minerals (such as clay minerals), organics (such as humic and fulvic acids and their degradation products) and a variety of inorganic minerals from which sulphate, carbonate and various halides go into solution in the caustic liquor used in the Bayer process.
  • silicious minerals such as clay minerals
  • organics such as humic and fulvic acids and their degradation products
  • inorganic minerals from which sulphate, carbonate and various halides go into solution in the caustic liquor used in the Bayer process.
  • Some of the organic impurities present in the bauxite may also degrade during this process, forming carbonate, oxalate and other anions in Bayer liquors.
  • the clarified supersaturated aluminate solution is encouraged to precipitate via further cooling and seeding with recycled aluminium trihydroxide.
  • the precipitated aluminium trihydroxide is classified using cyclones or gravity separation, and the product-sized material washed and calcined to form metallurgical alumina. Under-sized material is recycled as seed, and the "spent" liquor that remains after precipitation is recycled to the mills and digestion circuit.
  • washing process leads to the removal of water-soluble impurities from the bauxite and removal of impurities which are bound loosely to the bauxite and are thus readily liberated from the surface of the bauxite. Washing with water also helps increase the removal of finely divided minerals such as clay in the form of slime.
  • Washing with water is not effective in removing impurities which are weakly acidic, have a high molecular weight, are hydrophobic or that are chemically bound to or adsorbed on the bauxite. Consequently, such impurities remain within the bauxite and are only liberated when subjected to the Bayer process within an alumina refinery. It is known at a laboratory scale to wash bauxite in a mild caustic solution to remove some of the impurities present in the bauxite, however to our knowledge this procedure has not been used on an industrial scale. The very large volume of contaminated alkaline washings that would be produced when bauxite is washed with a dilute caustic solution presents a water balance issue that is not easily resolved.
  • US Patent 4,519,989 describes a process in organic impurities are removed from bauxite by washing the bauxite using an aqueous solution containing dissolved caustic soda, sodium carbonate or mixtures thereof in an amount up to about 80 g/1 total alkali content (expressed in terms of the sodium carbonate equivalent) and filtered to separate the purified bauxite solids from the spent washing solution.
  • a mild caustic solution is used to ensure that little or no aluminium is removed.
  • the process is carried out at an elevated temperature in the range of about 70°C - 110°C.
  • a rinse solution containing degradation products of the organic contaminants is then separated from the washed bauxite and treated to eliminate organic components.
  • the spent washing solution is subjected first to wet oxidation to oxidise the extracted organic sodium salts, ostensibly to sodium carbonate, with simultaneous or subsequent addition of lime to causticise the sodium carbonate, thereby regenerating the wash solution.
  • a principal disadvantage of the process of US Patent 4,519,989 is that any alkali consumed in the extraction of inorganic impurities that are invariably also present in the bauxite cannot be regenerated in this way, with the result that the recycled wash solution quickly becomes ineffective through the accumulation of these impurities.
  • a process for the removal of impurities from bauxite comprising the steps of: a) leaching a bauxite ore using a leach solution to remove impurities from the bauxite ore and form a leached bauxite ore and pregnant leach solution containing said impurities in solution; b) removing the leached bauxite ore from the pregnant leach solution of step a) using a solid-liquid separation process to produce a clarified pregnant leach solution; and c) concentrating the clarified pregnant leach solution of step b) to produce a concentrated impurity solution and recover a purified recycle stream comprising at least water for recycling to step a).
  • the leach solution comprises an alkaline solution that dissolves impurities from the bauxite ore, the total amount of alkali present in the alkaline solution being sufficient to allow leaching to proceed to completion, and the leaching of step a) is conducted at a pH of at least about 9.
  • the leaching of step a) may be conducted at a pH selected from the group consisting of at least 9.5, at least 10, at least 10.5, at least 11, at least 11.5, at least 12 and at least 12.5.
  • the concentrating of the clarified pregnant leach solution of step c) comprises using evaporation.
  • the concentrating of the clarified pregnant leach solution of step c) comprises using ultrafiltration.
  • the concentrating of the clarified pregnant leach solution of step c) comprises using nanofiltration.
  • the concentrating of the clarified pregnant leach solution of step c) may comprise using filtration to remove impurities from the recycled stream, wherein the impurities removed using filtration include at least one of humates, sulphates, carbonates, halides and oxalates.
  • the concentrating of the clarified pregnant leach solution of step c) further comprises using reverse osmosis.
  • the concentrating of the clarified pregnant leach solution of step c) further comprises using at least one of ultrafiltration and nanofiltration prior to using reverse osmosis.
  • the process further comprises removing suspended solids from the clarified pregnant leach solution prior to the concentrating the clarified pregnant leach solution of step c).
  • the process further comprises d) subjecting the concentrated impurity solution of step c) to an impurity removal process to recover purified leach solution for recycling to step a).
  • Step d) may be conducted using at least one of a liquor burner, a causticisation process, wet oxidation, catalytic wet oxidation, salting out, and ion exchange.
  • the process may further comprise e) reducing the particle size of at least some of the bauxite ore prior to leaching of the bauxite ore in step a).
  • the bauxite ore may be reduced to a particle size of no greater than about 1 millimetre prior to the leaching of the bauxite ore in step a).
  • the recycled stream comprising water that is produced from concentrating of the clarified pregnant leach solution of step c) is combined with the bauxite ore during step e).
  • the process further comprises f) feeding the leached bauxite ore from step b) to an alumina refining process.
  • Step f) may further comprise combining the leached bauxite ore from step b) with a liquor to form a slurry that is fed to the alumina refining process.
  • the leach solution of step a) may be saturated with alumina.
  • a system for removing impurities from bauxite comprising: a leach tank configured to receive and combine a bauxite ore and a leach solution to facilitate the leaching of the bauxite ore and the formation of a pregnant leach solution in the leach tank; a solid-liquid separator oriented to receive the slurry of leached bauxite and pregnant leach solution from the leach tank, wherein the solid-liquid separator is further configured to separate leached bauxite from the pregnant leach solution so as to form a clarified pregnant leach solution; and a concentrating section oriented to receive the clarified pregnant leach solution from the solid-liquid separator, wherein the concentrating section is configured to separate and recover a recycle stream comprising water from the clarified pregnant leach solution and to recycle
  • the concentrating section separates the recycle stream comprising water from the clarified pregnant leach solution by evaporation.
  • the concentrating section may separate the recycle stream comprising water from the clarified pregnant leach solution by at least one of microfiltration, ultrafiltration, nanofiltration and reverse osmosis to remove impurities from the recycled stream, wherein the impurities removed include at least one of humates, sulphates, carbonates, halides and oxalates.
  • the system further comprises an impurity removal section oriented to receive a pregnant leach solution concentrated with impurities from the concentrating section, wherein the impurity removal section is configured to remove impurities from the concentrated pregnant leach solution to form a purified stream and to recycle the purified stream to the leach tank.
  • the impurity removal section removes impurities from the concentrated pregnant leach solution to form the purified stream using at least one of a liquor burner, a causticisation process, wet oxidation, catalytic wet oxidation, salting out, and ion exchange.
  • the system further comprises a size reduction section configured to receive and reduce a particle size of bauxite ore prior to delivery to the leach tank.
  • the size reduction section may reduce particle sizes of the bauxite ore to dimensions no greater than about 1 millimetre.
  • the size reduction section receives the recycle stream comprising water from the concentrating section and combines the recycle stream with the bauxite ore for delivery to the leach tank.
  • the system is oriented upstream from an alumina refinery and is configured to deliver the leached bauxite ore to the alumina refinery.
  • the system may further comprise a slurry tank oriented to receive the leached bauxite from the solid-liquid separator and combine the leached bauxite with a liquor to form a slurry for delivery to the alumina refinery.
  • a system for removing impurities from bauxite comprising: a means for leaching a bauxite ore by receiving and combining the bauxite ore and a leach solution to form a pregnant leach solution; a means for separating leached bauxite ore from the pregnant leach solution so as to form a clarified pregnant leach solution; and a means for concentrating the clarified pregnant leach solution by separating a stream comprising water from the clarified pregnant leach solution to form a concentrated impurity solution, wherein the stream comprising water is recycled to the means for leaching.
  • system further comprises a means for purifying the concentrated impurity solution to form a purified stream, wherein the purified stream is recycled to the means for leaching.
  • the system may further comprise a means for reducing particle sizes of the bauxite ore prior to delivery to the means for leaching.
  • Figure 1 is a schematic flowchart of a first embodiment of the present invention.
  • Figure 2 is a schematic flowchart of a second embodiment of the present invention.
  • leaching refers to the act of extracting, removing or liberating specific constituents from a solid ore by rendering them soluble.
  • a leach solution is a liquid that possesses the ability to leach specific constituents from the solid ore or a liquid which contains dissolved reactants that provide this capability.
  • pregnant leach solution refers to the leach solution after one or more specific constituents have been leached from the ore.
  • regenerable leach solution refers to a pregnant leach solution that has been subjected to a process to reduce the concentration of the specific constituents that have been leached from the ore to allow the leach solution to be recycled and reused in a subsequent leaching operation or within the Bayer process.
  • impurity in the context of the present invention refers to any species present in bauxite other than alumina values in the form of, for example, aluminium oxides, hydroxides or oxy-hydroxides.
  • concentrating in the context of the present invention refers to a process whereby a solution is made richer in impurities, reducing the overall volume of the solution, preferably through the removal of water from the solution.
  • aluminate Al(OH) 4 '
  • OH " hydroxyl
  • a “Bayer liquor” is generated by digesting (dissolving) bauxite in a caustic soda solution at elevated temperatures and pressures.
  • the principal constituents of a Bayer liquor are sodium aluminate and sodium hydroxide. All other constituents present in the liquor are considered to be “impurities", the bulk of which are present as soluble sodium salts.
  • A refers to the aluminium concentration of the liquor and more specifically to the concentration of sodium aluminate in the liquor, expressed as equivalent grams per litre (g/L) of alumina (Al 2 O 3 ).
  • C refers to the caustic concentration of the liquor, this being the sum of the sodium aluminate and sodium hydroxide content of the liquor expressed as equivalent grams per litre (g/L) concentration of sodium carbonate.
  • AJC is thus the ratio of alumina concentration to caustic concentration.
  • spent liquor refers to a Bayer liquor stream after the gibbsite precipitation stage and prior to digestion.
  • a spent liquor typically has a low AJC ratio.
  • green liquor or "pregnant liquor” refers to a Bayer liquor stream after digestion and prior to precipitation.
  • a pregnant liquor typically has a high AJC ratio.
  • Free caustic is the caustic concentration minus the alumina concentration (C- A) with C and A each being expressed as equivalent grams per litre (g/L) concentration of sodium carbonate.
  • soda concentration minus caustic concentration gives the actual concentration of sodium carbonate (Na 2 CO 3 ) in the liquor, in grams per litre (g/L).
  • TOC total organic carbon which includes acetate, oxalate, and high molecular weight organics all present as sodium salts (Na.org), expressed as grams/litre.
  • Na 2 SO 4 refers to sodium sulphate.
  • Na 2 C 2 O 4 refers to sodium oxalate.
  • P90 refers to the size of a mesh screen which allows 90 percent of the particles to pass through.
  • the flow chart of Figure 1 illustrates one embodiment of the process for the removal of impurities from bauxite.
  • Bauxite 10 is fed to leach tank 20, in which the bauxite is subjected to leaching using an alkali solution 16 added to the leach tank 20 to dissolve impurities from the bauxite ore and form a pregnant leach solution in which said impurities are present in solution.
  • a slurry 24 is formed.
  • the slurry in the leach tank 20 is maintained at a level of pH of at least about 9 as described in greater detail below.
  • the pH during the step of leaching may be at least 9.5, or at least 10, or at least 10.5, or at least 11, or at least 11.5, or at least 12, or at least 12.5 in various embodiments of the present invention.
  • leaching need not be conducted in a tank or other vessel, but could equally be conducted using a heap leaching process, or within a pipeline.
  • the temperature of the slurry 24 within the leach tank 20 can vary widely, ranging from ambient up to the boiling point of the leach solution. For economic reasons, the temperature of the slurry 24 in leach tank 20 is held in the range of ambient temperature to 60° Celsius with ambient temperature or temperature of the recycled stream 62 or temperature of the alkali solution 16 being preferred, as this reduces the energy requirements of the process.
  • the leach tank 20 is provided with a suitable agitator 22 or other mixing equipment used to encourage mixing of the bauxite 10 with the alkali solution 16 to improve leaching kinetics.
  • the pH in the leach tank 20 can be raised by direct treatment of the slurry 24 by addition of concentrated alkali solution 18, or by adjusting the pH of the alkali leach solution 16 being added to the leach tank 20.
  • the mass ratio of the alkali leach solution 16 to bauxite 10 may be raised, in which case the pH of the alkali leach solution 16 being added to the leach tank 20 should be higher than 9 to counteract the effects of neutralization of the alkaline leach solution due to the presence of acidic impurities in the bauxite.
  • the alkali leach solution 16 added to the leach tank 20 may be any suitable liquid capable of leaching impurities from the bauxite.
  • the alkali leach solution 16 used to form the slurry 24 with the bauxite 10 is a sodium hydroxide (caustic) solution.
  • a caustic solution that is already saturated or nearly saturated with alumina, for example process water from an alumina refinery or refinery process lake water or similar dilute aqueous solution derived from the Bayer process.
  • alkaline leach solutions other than caustic solutions for example, using an alkaline leach solution containing sodium carbonate, ammonium hydroxide or potassium hydroxide, or mixtures thereof.
  • the residence time in the leach tank 20 is about one hour, however this will vary depending on such relevant factors as the type of bauxite, the bauxite particle size distribution and the pH of the slurry 24, and additional residence time may be required to achieve the desired extraction of impurities.
  • a plurality of leach tanks or other means could equally be used or arranged in series or parallel to achieve a required holding time and level of leaching of the slurry.
  • Supplementary dosing of the alkali leach solution 16 may be required for each of the vessels if the vessels are arranged in series, due to on-going reaction of the impurities with the leach solution.
  • the slurry 24 comprises leached bauxite and a leach solution containing impurities that have gone into solution or been entrained therein as suspended solids.
  • the slurry 24 is then directed to a solid-liquid separation section or process 30 to separate a stream of clarified pregnant leach solution 36 from the leached bauxite 32.
  • a drum filter 30 is depicted in Figure 1, it is to be understood that the separation of the leached bauxite 32 and clarified pregnant leach solution 36 from the slurry 24 may be any suitable device or process known to those skilled in the arts including gravity thickening, pressure filtration, centrifugation and the like.
  • washing of the leached bauxite 32 within the solid-liquid separation process 30 may be performed using wash water 34.
  • the wash water 34 may be from any convenient source, ranging from fresh water to the alkali leach solution 16.
  • Leached bauxite 32 may be stockpiled or transported as required, but in the example illustrated in Figure 1, the leached bauxite 32 is directed from the solid-liquid separation device 30 to a bauxite re-slurry tank 40, to which refinery spent liquor 42 (also referred to in the art as “liquor-to-mills” or “liquor-to-digestion") is added to form an alumina refinery feed slurry 46.
  • the alumina refinery feed slurry 46 may be directed to any suitable point in the alumina refinery, such as the desilicators or mills.
  • Agitator 44 is used in the bauxite re- slurry tank 40 to assist in forming the alumina refinery feed slurry 46 and for maintaining the leached bauxite 32 in suspension.
  • the leached bauxite in the alumina refinery feed slurry 46 has an organic content that has been reduced by up to 20% or more favourably up to 40% or still more favourably up to 80% relative to the normal level of contaminants fed to an alumina refinery when the bauxite is not subjected to the process of the present invention. Since some oxalate normally forms in the Bayer process as a result of reactions of the organics present in the bauxite after it has entered the refinery, as a further consequence, the amount of oxalate that is otherwise formed in the refinery is also reduced. Moreover, adsorbed oxalate is removed from the bauxite during the leaching process.
  • the oxalate input into the alumina refinery is reduced by up to approximately 20% or more favourably up to 60% or still more favourably up to 90%.
  • the sulphate content can be reduced up to 50% or more favourably up to 100% compared to the normal run-of-mine bauxite fed to an alumina refinery.
  • the liquid underflow from the solid-liquid separation process 30 is a stream of clarified pregnant leach solution 36 which is laden with the impurities that have been leached from the bauxite.
  • the clarified pregnant leach solution 36 contains several grams per litre of TOC as well as a number of other impurities, with for example between 40 to 80% of the extractable organic carbon in the bauxite 10 reporting to the clarified pregnant leach solution 36. Left untreated, the clarified pregnant leach solution 36 would quickly reach a high concentration of impurities and would be unsuitable for re-use as an alkali leach solution 16.
  • the clarified pregnant leach solution 36 is treated to remove the impurities and regenerate the alkali leach solution 16.
  • the clarified pregnant leach solution 36 is pumped to a polishing section or process 50 in which residual fine suspended solids are removed.
  • the polishing process 50 comprises a combination of filtration and/or settling apparatus arranged to reduce the level of the residual suspended solids to less than 50 mg/L, preferably less than 10 mg/L or more preferably less than 2 mg/L.
  • the polished pregnant leach solution 52 is fed to an impurity concentration section or process 60 to generate a recyclable purified regenerated leach solution 62 and a concentrated impurity solution 64.
  • the impurity concentration process 60 could consist of an evaporator and condenser to generate the concentrated impurity solution 64 and the recyclable regenerated leach solution 62 respectively.
  • the impurity concentration process 60 is a membrane filtration system using membrane filtration processes such as microfiltration, ultrafiltration, nanofiltration or reverse osmosis, alone or in combination. The type of filtration process selected depends in part on the molecular weight cut-off (MWCO) of the impurities to be removed from the polished leach solution 52.
  • MWCO molecular weight cut-off
  • hydrostatic pressure is used to force the polished leach solution against a semipermeable membrane.
  • a retentate (or reject) stream corresponding to concentrated impurity solution 64 is retained on one side of the semipermeable membrane whilst a substantially clean permeate stream, corresponding to recyclable regenerated leach solution 62 passes through the membrane.
  • nanofiltration Whilst ultrafiltration is effective for reducing the concentration of high molecular weight organic species such as humates (in excess of approximately 1000 Daltons) within the polished leach solution 52, nanofiltration is preferred in order to remove smaller sized organic and inorganic impurities.
  • the molecular weight cutoff is between 100 and 1000 Daltons, such that rejection of the organic impurities such as humates, as well as some larger inorganic impurities dissolved in the polished leach solution 52, to the retentate stream 64 is very high.
  • the retentate stream 64 from the concentrating section 60 is highly concentrated with respect to humic materials and other impurities such as various organic salts, and also inorganic salts including sulphate, carbonate and oxalate.
  • Residual caustic in the polished leach solution 52 will report to both the retentate 64 and the permeate 62.
  • the caustic which reports to the permeate 62 is directly recovered for reuse by recycling the permeate 62 as a portion of the alkali leach solution 16 added to the leach tank 20.
  • Some fresh alkali leach solution 16 will be required to compensate for the volume of caustic reporting to the retentate 64, and to replace caustic consumed during the leaching process.
  • some additional caustic may be required, which can be provided in the form of a concentrated alkali solution 18 added to the leach tank 20.
  • the retentate stream 64 contains some residual caustic as well as a high concentration of the sodium salts of the various impurities that have been leached from the bauxite.
  • concentration process 60 the volume of liquid in the retentate solution 64 has been greatly reduced compared with the volume of the clarified pregnant leach solution 36 which was separated from the leached bauxite 32 using solid/liquid separation process 30.
  • the retentate stream 64 is amenable to storage and further volume reduction in, for example, an evaporation pond or evaporator (not shown). However, in a preferred embodiment, the retentate stream 64 is directed to an impurity destruction section or process 70.
  • the caustic and alumina concentration of the retentate stream 64 is low, and the impurity concentration ratio to caustic and alumina concentrations of the retentate stream 64 is relatively high (compared with Bayer process liquors).
  • the impurity destruction process 70 is conducted using a liquor burner, wet oxidation, catalytic wet oxidation, an ion exchange process, a salting out process, the organic impurity removal process described in US Patent 6,555,077, the sulphate/oxalate removal process described in US Patent 6,743,403 or the causticisation process described in US Patent 6,743,403, either singly or in combination.
  • the contents of US Patent 6,555,077 and US Patent 6,743,403 are incorporated herein by reference in their entireties.
  • the products of the impurity destruction process 70 are a regenerated caustic stream 72 and a by-product stream 74 which may be either discarded or further processed for use elsewhere.
  • a regenerated caustic stream 72 When the recovered caustic stream 72 is recycled for use in the leach tank 20, this further reduces the caustic requirements for alkali leach solution 16 and concentrated alkali solution 18.
  • the bauxite was mixed with the leaching solutions to produce slurries containing 25-30% by weight of bauxite solids.
  • the slurries were leached in a leach tank in the form of a closed stainless steel vessel equipped with a motor- driven coaxial agitator operating at approximately 500 rpm, with the vessel placed in a thermostatically controlled water bath set at 6O 0 C. Leaching was conducted with a residence time of three hours.
  • a slurry comprising the leached bauxite and the pregnant leach solution containing impurities was subjected to solid/liquid separation using a centrifuge at 4000 rpm for 35 minutes to produce a leached bauxite and a clarified pregnant leach solution.
  • Samples of the clarified pregnant leach solution were retained for analysis and for subsequent production of the clean recycle stream and concentrated leach solution.
  • the leached bauxite solids were subsequently re-washed with deionised water and air dried at 8O 0 C prior to analysis to determine the residual impurity content.
  • a combination of the leached bauxite solids and clarified pregnant leach solution analyses were used to determine the leaching efficiency of several major impurities from the bauxite. Results of these tests are summarised in Table 1 below:
  • This solution 72 may be returned to the leach tank 20, or alternatively can be directed to the alumina refinery for use within the Bayer process.
  • FIG. 2 A second embodiment of the present invention is now described with reference to Figure 2 for which like reference numerals refer to like parts.
  • the flowchart of Figure 2 is the same as that for Figure 1 apart from the addition of a size reduction section or process 12 in which part or all of the bauxite 10 is subjected to comminution in the presence of a liquid.
  • the size reduction process 12 comprises a combination of milling and/or grinding apparatus arranged to reduce the size of the bauxite 10 to improve leaching yield and kinetics.
  • the bauxite 10 is ground to a P90 of about 1 millimetre where the term "P90" refers to the size of a mesh screen which allows 90 percent of the particles to pass through. It is worth noting that grinding of the bauxite to a P90 of about 1 millimetre would not normally be undertaken prior to transport of bauxite to an alumina refinery, as it is traditionally considered easier to transport coarse material than material that has been finely ground.
  • the bauxite 10 is ground to a P90 of about 300 micrometres to about 400 micrometres and leach tank 22 can be located adjacent to a mine with the leached bauxite slurry 46 being transported via a pipeline or other slurry transfer apparatus to a location adjacent to an alumina refinery.
  • the size reduction process 12 can be conducted at a location adjacent to a mine, with the ground or milled bauxite stream 14 being pumped for tens, hundreds or thousands of kilometres to an alumina refinery, the leach tank 22 being located adjacent to the alumina refinery.
  • the purified regenerated leach solution 62 is used as the liquid which is added to the bauxite in the size reduction process 12.
  • the size reduction process 12 incorporates a slimes separation, said slimes being circulated directly to the bauxite reslurry tank 40 if the alumina content of the slimes is high, or discarded if not.
  • Run-of-mine bauxite was ground to two size distributions, with P90 of lmm and
  • the bauxite samples were mixed with the leach solution to produce slurries containing 25-30% by weight of bauxite solids.
  • the slurries were leached in a leach tank in the form of a closed stainless steel vessel equipped with a motor-driven coaxial agitator operating at approximately 500 rpm, with the vessel placed in a thermostatically controlled water bath set at 6O 0 C. Leaching was conducted for a residence time of three hours.
  • the process of the present invention is conducted prior to the traditional desilication process which is typically the first step after milling in the Bayer process. Accordingly, the leached bauxite, once it is fed to an alumina refinery, can be subjected to desilication in the usual fashion with the desilicated bauxite being subjected to digestion to recover alumina with red mud residue being discarded as waste from the Bayer process in the usual fashion.
  • the key difference between the traditional Bayer process and the present invention is that the impurity burden on the alumina refinery is greatly reduced by ensuring that the bauxite that is fed to the alumina refinery has already been treated to remove a large percentage of the impurities, particularly the organic and soluble inorganic impurities.
  • the process of the present invention takes place upstream of and outside of the Bayer process and indeed, this process can be conducted at a location that is remote from an alumina refinery by hundreds of kilometres and have nothing to do with the refinery in any way. However, it is advantageous for the process to be conducted at a location in the vicinity or at an alumina refinery.

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  • Geochemistry & Mineralogy (AREA)
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Abstract

Les impuretés sont éliminées de la bauxite en lixiviant un minerai de bauxite en utilisant une solution de lixiviation pour dissoudre les impuretés du minerai de bauxite et pour former une solution de lixiviation enrichie contenant les impuretés en solution, en éliminant le minerai de bauxite lixivié de la solution de lixiviation enrichie en utilisant un procédé de séparation solide-liquide afin de produire une solution de lixiviation enrichie clarifiée, et en concentrant la solution de lixiviation enrichie clarifiée afin de récupérer un flux de recyclage comprenant de l'eau pour le recyclage vers le procédé de lixiviation. De plus, la solution de lixiviation concentrée peut être soumise à un procédé d'élimination des impuretés afin de récupérer la solution de lixiviation purifiée pour un recyclage dans le procédé de lixiviation.
PCT/AU2007/001866 2006-12-07 2007-12-04 Elimination des impuretés de la bauxite WO2008067594A1 (fr)

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AU2006906832A AU2006906832A0 (en) 2006-12-07 Removal of Impurities from Bauxite

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Cited By (17)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8241594B2 (en) 2007-05-21 2012-08-14 Orbite Aluminae Inc. Processes for extracting aluminum and iron from aluminous ores
CN103128003A (zh) * 2011-12-05 2013-06-05 沈阳铝镁设计研究院有限公司 高硫铝土矿综合利用方法
WO2014075173A1 (fr) * 2012-11-14 2014-05-22 Orbite Aluminae Inc. Procédé de purification d'ions aluminium
US9023301B2 (en) 2012-01-10 2015-05-05 Orbite Aluminae Inc. Processes for treating red mud
US9150428B2 (en) 2011-06-03 2015-10-06 Orbite Aluminae Inc. Methods for separating iron ions from aluminum ions
US9181603B2 (en) 2012-03-29 2015-11-10 Orbite Technologies Inc. Processes for treating fly ashes
US9260767B2 (en) 2011-03-18 2016-02-16 Orbite Technologies Inc. Processes for recovering rare earth elements from aluminum-bearing materials
US9290828B2 (en) 2012-07-12 2016-03-22 Orbite Technologies Inc. Processes for preparing titanium oxide and various other products
US9353425B2 (en) 2012-09-26 2016-05-31 Orbite Technologies Inc. Processes for preparing alumina and magnesium chloride by HCl leaching of various materials
US9382600B2 (en) 2011-09-16 2016-07-05 Orbite Technologies Inc. Processes for preparing alumina and various other products
US9410227B2 (en) 2011-05-04 2016-08-09 Orbite Technologies Inc. Processes for recovering rare earth elements from various ores
WO2019161455A1 (fr) * 2018-02-23 2019-08-29 Rio Tinto Alcan International Limited Procédé bayer
CN113428883A (zh) * 2021-07-22 2021-09-24 昆明理工大学 一种铝土矿中硫和有机物的脱除方法
CN113716589A (zh) * 2021-10-09 2021-11-30 贵州华锦铝业有限公司 一种拜耳法氧化铝脱硫脱碳协同处理的方法及其系统
CN116002732A (zh) * 2023-02-20 2023-04-25 贵州晟达雅科技有限公司 一种消除铝土矿分离母液中有机杂质的工艺及装置
WO2023220072A1 (fr) * 2022-05-09 2023-11-16 West Virginia University Board of Governors on behalf of West Virginia University Systèmes et procédés servant à extraire des minéraux critiques à partir de pré-concentrés préparés à partir d'un drainage minier acide
US12006225B2 (en) 2018-02-23 2024-06-11 Rio Tinto Alcan International Limited Bayer process

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WO2002051753A1 (fr) * 2000-12-22 2002-07-04 Queensland Alumina Limited Procede d'evacuation de contaminants de la liqueur bayer

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GB2140400A (en) * 1981-04-29 1984-11-28 Comalco Alu Treatment of aluminous materials to produce metallurgical grade alumina
US4519989A (en) * 1983-02-22 1985-05-28 Aluminum Company Of America Removal of organic contaminants from bauxite and other ores
US4650653A (en) * 1985-04-30 1987-03-17 Aluminium Pechiney Production of alumina from gibbsite-bearing bauxite of low reactive silica content
US4676959A (en) * 1986-01-06 1987-06-30 Aluminum Company Of America Bayer process for producing aluminum hydroxide having improved whiteness
WO1998022390A1 (fr) * 1996-11-20 1998-05-28 Comalco Aluminium Limited Procede pour separer la silice de la bauxite
WO2002051753A1 (fr) * 2000-12-22 2002-07-04 Queensland Alumina Limited Procede d'evacuation de contaminants de la liqueur bayer

Cited By (24)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8241594B2 (en) 2007-05-21 2012-08-14 Orbite Aluminae Inc. Processes for extracting aluminum and iron from aluminous ores
US8337789B2 (en) 2007-05-21 2012-12-25 Orsite Aluminae Inc. Processes for extracting aluminum from aluminous ores
US8597600B2 (en) 2007-05-21 2013-12-03 Orbite Aluminae Inc. Processes for extracting aluminum from aluminous ores
US9945009B2 (en) 2011-03-18 2018-04-17 Orbite Technologies Inc. Processes for recovering rare earth elements from aluminum-bearing materials
US9260767B2 (en) 2011-03-18 2016-02-16 Orbite Technologies Inc. Processes for recovering rare earth elements from aluminum-bearing materials
US9410227B2 (en) 2011-05-04 2016-08-09 Orbite Technologies Inc. Processes for recovering rare earth elements from various ores
US9150428B2 (en) 2011-06-03 2015-10-06 Orbite Aluminae Inc. Methods for separating iron ions from aluminum ions
US9382600B2 (en) 2011-09-16 2016-07-05 Orbite Technologies Inc. Processes for preparing alumina and various other products
US10174402B2 (en) 2011-09-16 2019-01-08 Orbite Technologies Inc. Processes for preparing alumina and various other products
CN103128003A (zh) * 2011-12-05 2013-06-05 沈阳铝镁设计研究院有限公司 高硫铝土矿综合利用方法
US9023301B2 (en) 2012-01-10 2015-05-05 Orbite Aluminae Inc. Processes for treating red mud
US9556500B2 (en) 2012-01-10 2017-01-31 Orbite Technologies Inc. Processes for treating red mud
US9181603B2 (en) 2012-03-29 2015-11-10 Orbite Technologies Inc. Processes for treating fly ashes
US9290828B2 (en) 2012-07-12 2016-03-22 Orbite Technologies Inc. Processes for preparing titanium oxide and various other products
US9353425B2 (en) 2012-09-26 2016-05-31 Orbite Technologies Inc. Processes for preparing alumina and magnesium chloride by HCl leaching of various materials
US9534274B2 (en) 2012-11-14 2017-01-03 Orbite Technologies Inc. Methods for purifying aluminium ions
WO2014075173A1 (fr) * 2012-11-14 2014-05-22 Orbite Aluminae Inc. Procédé de purification d'ions aluminium
WO2019161455A1 (fr) * 2018-02-23 2019-08-29 Rio Tinto Alcan International Limited Procédé bayer
CN111757852A (zh) * 2018-02-23 2020-10-09 力拓加铝国际有限公司 拜耳工艺
US12006225B2 (en) 2018-02-23 2024-06-11 Rio Tinto Alcan International Limited Bayer process
CN113428883A (zh) * 2021-07-22 2021-09-24 昆明理工大学 一种铝土矿中硫和有机物的脱除方法
CN113716589A (zh) * 2021-10-09 2021-11-30 贵州华锦铝业有限公司 一种拜耳法氧化铝脱硫脱碳协同处理的方法及其系统
WO2023220072A1 (fr) * 2022-05-09 2023-11-16 West Virginia University Board of Governors on behalf of West Virginia University Systèmes et procédés servant à extraire des minéraux critiques à partir de pré-concentrés préparés à partir d'un drainage minier acide
CN116002732A (zh) * 2023-02-20 2023-04-25 贵州晟达雅科技有限公司 一种消除铝土矿分离母液中有机杂质的工艺及装置

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