WO2022221903A1 - Procédé de formation d'alumine de haute pureté - Google Patents

Procédé de formation d'alumine de haute pureté Download PDF

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Publication number
WO2022221903A1
WO2022221903A1 PCT/AU2022/050302 AU2022050302W WO2022221903A1 WO 2022221903 A1 WO2022221903 A1 WO 2022221903A1 AU 2022050302 W AU2022050302 W AU 2022050302W WO 2022221903 A1 WO2022221903 A1 WO 2022221903A1
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WIPO (PCT)
Prior art keywords
aluminium
cans
metal material
cooled metal
precipitate
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PCT/AU2022/050302
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English (en)
Inventor
Bernardus Willem Ziegelaar
Original Assignee
Dingo HPA Pty Ltd
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Filing date
Publication date
Priority claimed from AU2021901141A external-priority patent/AU2021901141A0/en
Application filed by Dingo HPA Pty Ltd filed Critical Dingo HPA Pty Ltd
Publication of WO2022221903A1 publication Critical patent/WO2022221903A1/fr

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B09—DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
    • B09B—DISPOSAL OF SOLID WASTE NOT OTHERWISE PROVIDED FOR
    • B09B3/00—Destroying solid waste or transforming solid waste into something useful or harmless
    • B09B3/40—Destroying solid waste or transforming solid waste into something useful or harmless involving thermal treatment, e.g. evaporation
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F7/00—Compounds of aluminium
    • C01F7/02—Aluminium oxide; Aluminium hydroxide; Aluminates
    • C01F7/30—Preparation of aluminium oxide or hydroxide by thermal decomposition or by hydrolysis or oxidation of aluminium compounds
    • C01F7/306—Thermal decomposition of hydrated chlorides, e.g. of aluminium trichloride hexahydrate
    • 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
    • C01F7/141—Aluminium oxide or hydroxide from alkali metal aluminates from aqueous aluminate solutions by neutralisation with an acidic agent
    • 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
    • C01F7/42—Preparation of aluminium oxide or hydroxide from metallic aluminium, e.g. by oxidation
    • C01F7/428—Preparation of aluminium oxide or hydroxide from metallic aluminium, e.g. by oxidation by oxidation in an aqueous solution
    • 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
    • C01F7/44—Dehydration of aluminium oxide or hydroxide, i.e. all conversions of one form into another involving a loss of water
    • C01F7/441—Dehydration of aluminium oxide or hydroxide, i.e. all conversions of one form into another involving a loss of water by calcination
    • 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
    • C22B21/00—Obtaining aluminium
    • C22B21/0084—Obtaining aluminium melting and handling molten aluminium
    • C22B21/0092—Remelting scrap, skimmings or any secondary source aluminium
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B09—DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
    • B09B—DISPOSAL OF SOLID WASTE NOT OTHERWISE PROVIDED FOR
    • B09B2101/00—Type of solid waste
    • B09B2101/10—Cans
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B09—DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
    • B09B—DISPOSAL OF SOLID WASTE NOT OTHERWISE PROVIDED FOR
    • B09B3/00—Destroying solid waste or transforming solid waste into something useful or harmless
    • B09B3/70—Chemical treatment, e.g. pH adjustment or oxidation
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/80—Compositional purity
    • 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
    • C22B21/0084—Obtaining aluminium melting and handling molten aluminium
    • 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
    • C22B7/00—Working up raw materials other than ores, e.g. scrap, to produce non-ferrous metals and compounds thereof; Methods of a general interest or applied to the winning of more than two metals
    • C22B7/001—Dry processes
    • C22B7/003—Dry processes only remelting, e.g. of chips, borings, turnings; apparatus used therefor
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F27—FURNACES; KILNS; OVENS; RETORTS
    • F27B—FURNACES, KILNS, OVENS, OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
    • F27B9/00—Furnaces through which the charge is moved mechanically, e.g. of tunnel type; Similar furnaces in which the charge moves by gravity
    • F27B9/04—Furnaces through which the charge is moved mechanically, e.g. of tunnel type; Similar furnaces in which the charge moves by gravity adapted for treating the charge in vacuum or special atmosphere
    • F27B9/045—Furnaces with controlled atmosphere
    • F27B9/047—Furnaces with controlled atmosphere the atmosphere consisting of protective gases

Definitions

  • the present invention relates to a process for forming high purity alumina (HPA).
  • HPA high purity alumina
  • High purity Alumina is the pure form of aluminium oxide (AI203).
  • the size and morphology of the crystallites of the aluminium oxides are an important trait of these aluminas. Nearly half of the 30,000 tonnes of alumina that is produced annually is used to manufacture sapphires.
  • HPA for the formation of sapphires as well as for the manufacture of e.g. LED and semiconductor substrates, for the formation of lamps, and in polishing, and in the formation of lithium-ion battery separator coatings.
  • the price and performance of HPA varies according to the degree of purity.
  • HPA The purity of HPA can be categorised as 99.9% (3N), 99.99% (4N), 99.999 (5N) and 99.9999 (6N).
  • Impurities of 0.1% in 3N HPA, and 0.01% in 4N HPA, (and so on) depend on the original source of the aluminium used to create the HPA product.
  • 6N HPA there is 1 g of impurity for every tonne of material.
  • the impurities found alongside Al in most mined ores are reasonably consistent. Where mineral ores are the feedstock for the formation of HPA, the most common impurities that need to be removed are iron and silicon.
  • HPA feedstocks for the formation of 4N (and higher) HPA include aluminium ingots (metal) and aluminium containing minerals such as kaolin.
  • the chemical processes used to form the HPA from these feedstocks can include various of solvent extraction, acid leaching, precipitation/crystallisation and calcination.
  • HPA The most common process for the formation of HPA, consists in dissolving Bayer gibbsite in an excess of sulphuric acid, neutralizing it in ammonia in the form of NhUAI (S0 4 ) 2 ,12H 2 0, crystallizing it by cooling, then calcining it at more than 1000°C leaving a very friable residue of AI 2 O 3 .
  • the chloride process consists of dissolving pure alumina in hydrochloric acid (HCI) and precipitating the hexahydrated aluminium chloride, the calcination of which leaves alumina as a residue.
  • HCI hydrochloric acid
  • the present invention provides a method of manufacturing high purity alumina of at least 4N using de-coated aluminium cans as the only source of aluminium in the feedstock.
  • a method of manufacturing high purity alumina of at least 4N from aluminium cans comprising the steps of increasing the temperature of the aluminium cans in a non-oxidising atmosphere to form a molten material; separating molten metal from the molten material and allowing the molten metal to cool to a cooled metal material; forming discrete particles of the cooled metal material optionally by milling; dissolving discrete particles of the cooled metal material thereby forming a solution of the cooled metal material; precipitating an aluminium compound from the solution of the cooled metal material and recovering precipitate of the aluminium compound; washing the precipitate of the aluminium compound to form a washed product; and calcining the washed product to produce a high purity alumina.
  • the step of increasing the temperature of the aluminium cans in a non-oxidising atmosphere comprises hearing to the cans to above the melting point of aluminium.
  • the increase in temperature de-coats the cans by melting the polymer layer.
  • the polymer coating waste in the molten material is separated/removed from the molten metal,
  • the aluminium cans are shredded prior to increasing their temperature.
  • the shredded can material can be heated to around 500 degrees Centigrade in order to de-coat the cans.
  • the step of dissolving the discrete particles can be undertaken in an alkaline digest or in an acid digest.
  • a method of manufacturing high purity alumina of at least 4N from aluminium cans comprising the steps of increasing the temperature of the aluminium cans in a non-oxidising atmosphere to form a molten material; separating molten metal from the molten material and allowing the molten metal to cool to a cooled metal material; forming discrete particles of the cooled metal material; dissolving discrete particles of the cooled metal material in an alkaline digest thereby forming an alkaline solution of the cooled metal material; precipitating alloy metals from the alkaline solution of the cooled metal material by adjusting the pH towards a more acidic pH, optionally between about 9.5 to 10, to produce precipitated impurities and a filtrate; preferably removing the precipitated impurities.
  • the removal could be by filtration or other means, e.g. centrifuging, to separate the precipitated impurities from the clear liquor; precipitating aluminium hydroxide trihydrate (gibbsite) from the filtrate and recovering precipitate of the aluminium hydroxide trihydrate (gibbsite); washing the precipitate of aluminium hydroxide trihydrate (gibbsite) to form a washed product; and optionally treating the washed product by either or both of dihydroxylation and an acid digest to form a further treated washed product.
  • the washing can be to partially dehydroxylate the washed product, with further washing of the intermediate.
  • the washing can be conducted with hot deionised water and may be pressurised to obtain a water temperature over 100 and up to 250 degrees Centigrade; calcining the further treated washed product to produce a high purity alumina.
  • the process is undertaken with an acid digest.
  • a method of manufacturing high purity alumina of at least 4N from aluminium cans comprising the steps of increasing the temperature of the aluminium cans in a non-oxidising atmosphere to form a molten material; separating molten metal from the molten material and allowing the molten metal to cool to a cooled metal material; forming discrete particles of the cooled metal material; dissolving discrete particles of the cooled metal material in an acid digest thereby forming a solution of the cooled metal material; evaporating the acid and redissolving the remainder in a minimum amount of deionised water to provide a clear liquid phase, precipitating aluminium chlorohexahydrate from the clear liquid phase by sparging with hydrochloric acid gas, and recovering precipitate of the aluminium compound; heating the aluminium chlorohexahydrate to recover the hydrochloric acid and precipitate aluminium oxide; other steps may include washing the precipitate of aluminium compound to form a washed product; and calcining the washed
  • the washed product from the alkaline digest is subject to the acid digest process.
  • the washed product is: dissolved in an acid digest thereby forming a solution of the washed product; the method further includes the steps of evaporating the acid of the acid digest and redissolving the remainder in a minimum amount of deionised water to provide a clear liquid phase, precipitating aluminium chlorohexahydrate from the clear liquid phase by sparging with hydrochloric acid, and recovering precipitate of the aluminium compound; washing the precipitate of aluminium compound to form a further treated washed product; and calcining the further treated washed product to produce a high purity alumina.
  • the present method makes use of aluminium cans (sometimes referred to as aluminium containers) as a starting material for the production of HPA.
  • the aluminium cans may be scrap aluminium cans.
  • the scrap aluminium cans were previously used or intended for use as beverage cans.
  • the scrap aluminium cans were previously used or intended for use as food cans.
  • the scrap aluminium can may have been a container for any material, but the container is now empty and is available for recycling.
  • the container may have been used, or it might be a reject from a manufacturing line, so it was intended for use, but never actually progressed to use.
  • mixtures of different types of cans from different sources are used as a feedstock for the process.
  • the impurities in a man-made aluminium can is well-known. Accordingly, the present inventors have found that a certain sequence of processing steps is required in order to properly prepare the cans for treatment, and then to ensure complete removal of the impurities (including unexpected impurities) from the can material. The inventors have found that if the cans are not treated according to the present method, the plastic lining of the cans can contaminate the resultant product and may contribute to the impurity levels in the resultant product.
  • Aluminium cans comprise aluminium alongside other impurity elements such as magnesium and iron.
  • the different parts of the aluminium can may have different requirements including strength requirements.
  • the aluminium can lid for example, needs to be more rigid than the can body, so the elemental composition likely differs. Any aluminium ring pull/tag in the lid of the can must be the most rigid part of the can, so will comprise e.g. more magnesium together with the aluminium to provide the require structural rigidity.
  • the aluminium cans are principally made of three alloys.
  • Some manufacturers may use slightly different alloys. In theory, there is no need to separate the can lids from the body of the can prior to use in the process, as the only significant alloy variation is the Mg content. However, in embodiments, it may be necessary to remove the can lids prior to subjecting the aluminium cans to an embodiment of the method of the present invention.
  • the aluminium cans as provided may, in embodiments, have an inner food grade plastic lining.
  • the cans may have printing or decoration on their outside surfaces.
  • the inside and or outside surface of the cans may comprise one or more of paint, ink, paper, plastic and oil. If the can has been used it may also contain residue of the material that was in the can. Depending on where the can was sourced from, it may also be covered in dirt, sand or other material that contacted the can while it was treated as rubbish/scrap.
  • the aluminium cans Prior to heating, the aluminium cans can be shredded. The cans may then be de- coated by thermal de-coating involving heating and melting.
  • the aluminium cans are heated in a furnace or kiln.
  • the temperature of the cans in the furnace is increased to a temperature above the melting point of the aluminium (Al melting point 660.3 degrees Centigrade).
  • the temperature of the cans in the furnace can be increased to above 650 degrees Centigrade.
  • the temperature is increased to at least about 700 degrees Centigrade. More preferably, the temperature is increased to at least about 750, 800 or 850 degrees Centigrade.
  • the molten material formed can include the metal materials and the lining and or coating materials on the cans surfaces.
  • the lining and coating materials can be removed as volatile organic carbons (VOCs) thereby separating molten metal from the other molten materials.
  • VOCs volatile organic carbons
  • the VOCs generated can be collected and treated according to environmental regulations. Beverage can coatings have steadily been altered to mininimise VOC’s on recycling by the introduction of water based resins.
  • the increase in temperature is undertaken in a non-oxidising atmosphere.
  • the atmosphere during the increase in temperature is oxygen free. There may be some oxygen such as less than 15, 10 or 8 % oxygen but it is preferred that there is no oxygen.
  • the molten metal that forms following the increase in temperature is a mixture of molten aluminium, and molten impurities including but not necessarily limited to Magnesium (Mg), Iron (Fe), Manganese (Mn), Zinc (Zn), Silicon (Si), Copper (Cu), Titanium (Ti) and Chromium (Cr).
  • Other impurities include Gallium (Ga), Vanadium (V) and Yttrium (Y).
  • the molten material (which can include metalloids such as silicon) can be cooled into handleable solid pieces of metal such as bars or ingots.
  • the ingots that form on cooling of the molten metal will form according to the size and shape of a mould into which the molten metal is directed from the furnace.
  • the molten metal can run into the mould when released from the furnace and as it cools, it takes the shape of the mould and can subsequently be removed from the mould for further processing.
  • the mould comprises multiple small discrete areas for the molten metal, so that each ingot is essentially a small chip of cooled metal material (cm or mm in size).
  • the formation of discrete particles of the cooled metal material can comprise forming the discrete particles in a mould.
  • moulds form larger ingots into which the molten material will cool.
  • the large ingots (2-3 cm x 3-8 cm x 6-12 cm) of metal are then broken, chopped, cut, milled or otherwise treated to form discrete particles of cooled metal sometimes referred to as chips (mm or cm in size).
  • the chips can be sized in a range of from about 1 mm to about 2 mm. There can be smaller and larger chips, so the average size distribution is about 80 % in the range stated.
  • the formation of discrete particles of the cooled metal material can comprise milling the ingots in a ball mill.
  • the formation of discrete particles of the cooled metal material can comprise milling the ingots in a hammer mill.
  • the formation of discrete particles of the cooled metal material can comprise moving the ingots against a multi-bladed or pointed cutting tool in a lathe.
  • At least some of the discrete particles of cooled metal material once formed are dissolved in order to from a solution. Preferably, all of the discrete particles are dissolved. In some embodiment at least 99, 95, 90, 80 or 85 % of the discrete particles are dissolved with the remainder being undissolved. Any undissolved particles can be removed (e.g., by filtration) and added to a subsequent batch being processed by the method. There can be any number of batches being processed in a factory in a sequence.
  • the discrete particles of cooled metal material can be dissolved in an alkaline digest. 2AI°+2Na0H+2H 2 0 ® 2(NaAI0 3 ) +3H 2
  • Any hydrogen generated during the alkaline dissolution process can be captured for recycle or sale. Generally, there will be about 111 kg of hydrogen generated per tonne of Al.
  • alumina of high purity can be produced with a target of 99.99 as a minimum.
  • a high purity sodium aluminate can be produced, from which a high purity aluminium hydroxide trihydrate (gibbsite) can be produced.
  • the discrete particles of the cooled metal material are dissolved in a caustic solution containing sodium.
  • the caustic solution containing sodium can be sodium hydroxide (caustic soda).
  • the particles of metal material are dissolved at about 30g/L in a 20% caustic soda solution.
  • the fastest dissolution of Al is said to take place in a solution of 5.5N NaOH which contains 220 grams per litre of flake caustic soda.
  • 30, 40 or 50 % liquid caustic can be used for dissolution.
  • the dissolution of the molten metal will produce some insoluble hydroxides and de- silication products. These can be removed at various points as would be understood by the skilled person.
  • the main portion of the hydroxides will be magnesium plus some iron, manganese, chromium, and copper It has been found that silicon co-precipitates with the hydroxides.
  • the pH of the caustic solution of cooled metal material can be adjusted using an acid.
  • the pH can be adjusted to a pH of about 10.
  • the acid can be hydrochloric acid (HCI).
  • HCI hydrochloric acid
  • carbon dioxide can be bubbled into the alkaline solution to lower the pH .
  • Ionic species Fe, Cu, Mn, Mg, Cu will precipitate at high pH whilst those such as Zn will precipitate below Ph 10..
  • These precipitates can be removed from the filtrate.
  • the precipitates can be removed by decanting and or filtration or centrifuge.
  • the solids recovered as precipitate can be washed to recover any residual aluminium and sodium that might have value in other industrial processes. Tests will establish the composition of the removed precipitates and determine if the waste has any commercial value or waste cost.
  • the filtrate is recovered for further processing.
  • the yield of hydrate through the precipitator train is an important efficiency parameter. The greater the yield the more efficient the refinery.
  • the pregnant/green liquor entering precipitation (at 75-80°C) will have an aluminium content of 140 g/L (expressed as AI2O3) and the spent liquor exiting precipitation (at 55°C) a value of 50 g/L, giving a yield of 90 g/L.
  • the mechanism of precipitation involves a combination of agglomeration and growth.
  • the first stage of precipitation involves the sticking together of small seed particles to form agglomerates. This is a relatively rapid process, which is favoured by high alumina supersaturations and high temperatures.
  • the agglomerates so formed are of random shapes, and the overall strengths of the agglomerated particles are low. This is also the step in which most of the chemically included soda is incorporated into the hydrate crystals. It is therefore essential that the high yielding agglomeration stage is followed by a period of controlled growth. In this growth stage, as well as increasing in size the particles are strengthened, and their shapes are regularised. In addition, the overall soda content of the particles is diluted.
  • the Precipitator used to effect the precipitation can be similar to those used in the older plants i.e. tall vessels with a fluted bottom. However, the precipitation could be undertaken in a flat bottomed circular tank fitted with impellers for a slow stirring action as would be understood by the skilled person.
  • the gibbsite precipitate is recovered e.g. by filtration. Some precipitate from the process can be reserved for the provision of seeding material in subsequent precipitation.
  • the step of precipitating aluminium hydroxide trihydrate (gibbsite) from the filtrate is undertaken more than once by recovering the filtrate and adding further seed to the filtrate and then filtering the solution again.
  • the step of precipitating aluminium hydroxide trihydrate (gibbsite) from the filtrate is undertaken more than once such as 2, 3 or 4 times. In a preferred embodiment the precipitation is undertaken twice.
  • the gibbsite produced by precipitation of alumina produced from aluminium cans will have to be washed free from at least sodium (Na) to attain the 99.99% required.
  • the first step in this washing purification is to wash the gibbsite precipitate with water.
  • the water is deionised to avoid adding any impurities to the solution with the water. It is also preferred that all material in which reactions are undertaken are lined with non-contaminating surfaces such as Teflon to minimise the transfer of contamination into solution.
  • the washed precipitate can then be processed in various ways.
  • the washed precipitate is dehydroxylated at about 400, 450 or 500 degrees Centigrade, and then acid washed at high temperature under pressure and then filtered before being calcined.
  • the washed precipitate is subject to the acid digest aspect of the invention as set out below.
  • the washed precipitate treated by the acid digest process is treated in the same way as the discrete particles of the cooled metal material obtained fresh from the furnace.
  • the discrete particles of cooled metal material obtained from the furnace can be dissolved in an alkaline digest (such as NaOH).
  • an alkaline digest such as NaOH
  • Dissolution in an alkaline digest such as caustic soda is preferred because of the generation of a high pH solution which precipitates Fe, Mn, Cu and Mg as hydroxides, which can be removed by filtration.
  • the discrete particles of cooled metal material can be dissolved in an acid digest.
  • the acid of the digest can be a strong acid.
  • the acid can be hydrochloric acid (HCI).
  • HCI hydrochloric acid
  • the acid digest can take the solution to near dryness, at which point the solution is redissolved in a minimum quantity of deionised water and then filtered to provide a clear liquid phase.
  • the clear liquid phase can then be sparged with a chlorinated acid until precipitation of the chloride hexahydrate is complete.
  • the acid can be HCI.
  • the result is a precipitate of aluminium chlorohexahydrate (ACH) which can be filtered and collected.
  • ACH aluminium chlorohexahydrate
  • the ACH precipitate can be redissolved in a minimum amount of water and sparged again to repeat the precipitation of the ACH with increased purity.
  • the precipitation, hydration and sparging cycle can be undertaken 1 , 2, 3 or more times.
  • the product can be calcined at about 350, 400 or 450 degrees Centigrade. Any HCI recovered during this calcination step can be recovered for reuse in the process. The product can then be washed and passed to the final calcination step.
  • the final calcination step comprises elevating the temperature of the purified precipitate to a temperature in the range of about 500 to about 1200 degrees Centigrade, preferably 500 to 1000 degrees Centigrade. Preferably the calcination is undertaken at least about 1000 degrees Centigrade. Without wishing to be limited by theory, it is thought that the final calcination step assists in reorganising the oxide structure of the HPA.
  • the calcined product can be acid and water washed and then dried.
  • a system of manufacturing high purity alumina of at least 4N using de-coated aluminium cans as the only source of aluminium in the feedstock comprising the steps of sourcing coated aluminium cans; de-coating the coated aluminium cans in a furnace by increasing the temperature of the aluminium cans in a non-oxidising atmosphere to form a molten material; separating molten metal from the molten material and allowing the molten metal to cool to a cooled metal material; subjecting the cooled metal material to a method or process optionally in accordance with any one of claims 1 to 10, wherein that method or process removes impurities from the cooled metal material, thereby leaving only highly pure aluminium in the resultant product.
  • Figure 1 is a flow diagram showing the alkaline digest embodiment of the present invention.
  • FIG. 2 is a flow diagram showing the acid digest embodiment of the present invention.
  • FIG. 3 is a flow diagram showing the hybrid embodiment of the present invention.
  • Figure 4 is a table showing the alloy content of sample aluminium cans.
  • a process according to an embodiment of the present invention is shown in Figure 1 .
  • the aluminium cans are acquired and brought to site 111.
  • the cans can be from any source.
  • the aluminium cans are optionally shredded and compressed and are then delivered into a furnace or kiln for heating 112.
  • the temperature of the cans in the furnace is increased to about 500, 600 or 700 degrees Centigrade for about 20, 30 or 60 minutes or longer
  • the molten material (which includes alloying metals and metalloids) can be cooled 113 into handleable solid pieces of metal such as bars or ingots.
  • the ingots are then milled using a lathe to form discrete particles 114. At least some of the discrete particles of cooled metal material once formed at 114 are dissolved to form a solution 115.
  • the process shows that the discrete particles of cooled metal material are dissolved in an alkaline digest.
  • Any hydrogen generated during the alkaline dissolution process can be captured for recycle or sale.
  • particles of metal material are dissolved at about 30g/L in a 20% caustic soda solution 115.
  • the pH of the caustic solution of cooled metal material is then adjusted using HCI acid 116.
  • the pH is adjusted to just below 10
  • Metals such as Fe, Cu, Mn, Mg, Cu will already have precipitated above pH 10 , Zn and other minor impurities will precipitate below 10 117. These precipitates can be removed from the filtrate by filtration 118.
  • the solids recovered as precipitate can be washed to recover any residual aluminium and sodium that might have value in other industrial processes 119.
  • the first stage of gibbsite precipitation involves the sticking together of small seed particles to form agglomerates.
  • the agglomerates so formed are of random shapes, and the overall strengths of the agglomerated particles are low.
  • the gibbsite precipitate is recovered e.g. by filtration 121.
  • the step of precipitating aluminium hydroxide trihydrate (gibbsite) from the filtrate is undertaken more than once 122 by recovering the filtrate and adding further seed to the filtrate and then filtering the solution again 123.
  • the gibbsite precipitate is washed with deionised water 124.
  • the washed precipitate can then be processed in various ways.
  • the washed precipitate is dehydroxylated at about 450 Centigrade 235, and then acid washed 236 before being calcined 130.
  • the acid may be hydrochloric, acetic or citric or a combination thereof.
  • the washing will be at elevated temperature and may be conducted when pressurised; the wash water will reach temperatures of up to 250 degrees Centigrade.
  • the washed precipitate is subject to the acid digest.
  • the washed precipitate treated by the acid digest process (125 to129) .
  • the discrete particles of cooled metal material obtained from the furnace can be dissolved in an alkaline digest (such as NaOH). This is represented by steps 115 to 124 of e.g. Figure 1 .
  • the discrete particles of cooled metal material can be dissolved in an acid digest as shown in Figure 2 as steps 125 to 129 and in Figure 3 using like numbering (325 to 339).
  • the acid digest shown in Figure 2 (and also in part in Figure 3) can take the solution to near dryness 337, at which point the solution is redissolved in a minimum quantity of deionised water 338 and then filtered to provide a clear liquid phase 339.
  • the clear liquid phase can then be sparged with a HCI gas 326/126.
  • the result is a precipitate of aluminium hexachlorohydrate (ACH) which can be filtered and collected 327/127.
  • ACH aluminium hexachlorohydrate
  • the ACH precipitate can be redissolved in a minimum amount of water 338’ and sparged 3267 126’ again to repeat the precipitation of the ACH with increased purity.
  • the product can be calcined at 450 degrees Centigrade 328/128. Any HCI recovered during this calcination step can be recovered for reuse in the process as shown by the arrow in Figure 3. The product can then be washed 329/129 and passed to the final calcination step 130.
  • the final calcination step 130 comprises elevating the temperature of the purified precipitate to a temperature in the range of about 800 to about 1200 degrees Centigrade.
  • the calcined product can be acid 131 and water washed 132 and then dried 133.
  • Aluminium cans comprise aluminium alongside other impurity elements such as magnesium and iron.
  • the Table of Figure 4 shows the elemental analysis of an aluminium can that contained Coke ® and an aluminium can that contained beer. The elemental analysis of a standard aluminium ingot is also provided.

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Abstract

L'invention concerne un procédé de fabrication d'alumine de haute pureté d'au moins 4N à l'aide de boîtes d'aluminium dé-revêtues en tant que seule source d'aluminium dans la charge d'alimentation.
PCT/AU2022/050302 2021-04-19 2022-04-06 Procédé de formation d'alumine de haute pureté WO2022221903A1 (fr)

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Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1457242A (en) * 1974-04-08 1976-12-01 Aluminum Co Of America Method and apparatus for melting aluminum charge
US3999980A (en) * 1975-05-09 1976-12-28 The United States Of America As Represented By The Secretary Of The Interior Fluxless recovery of metallic aluminum from wastes
CA2227126A1 (fr) * 1997-01-15 1998-07-15 Bernd Kos Processus et dispositif pour fondre des metaux legers
US20070113705A1 (en) * 2005-11-22 2007-05-24 Tsl Engenharia, Manutencao E Preservacao Ambiental Ltda. Process and apparatus for use in recycling composite materials
CN106115755A (zh) * 2016-06-28 2016-11-16 上海滃泽科技有限公司 一种利用废铝制品升级制备高纯氧化铝的方法
CN206735820U (zh) * 2016-12-23 2017-12-12 袁伟昊 一种蓝宝石级高纯氧化铝块体、多晶锭制备装置
US20180162739A1 (en) * 2016-12-09 2018-06-14 Samhwa Yang Heng Co., Ltd. Method of manufacturing high-density beads of high-purity alumina
AU2019204216A1 (en) * 2014-02-26 2019-07-04 Altech Chemicals Australia Pty Ltd A method for the preparation of alumina

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1457242A (en) * 1974-04-08 1976-12-01 Aluminum Co Of America Method and apparatus for melting aluminum charge
US3999980A (en) * 1975-05-09 1976-12-28 The United States Of America As Represented By The Secretary Of The Interior Fluxless recovery of metallic aluminum from wastes
CA2227126A1 (fr) * 1997-01-15 1998-07-15 Bernd Kos Processus et dispositif pour fondre des metaux legers
US20070113705A1 (en) * 2005-11-22 2007-05-24 Tsl Engenharia, Manutencao E Preservacao Ambiental Ltda. Process and apparatus for use in recycling composite materials
AU2019204216A1 (en) * 2014-02-26 2019-07-04 Altech Chemicals Australia Pty Ltd A method for the preparation of alumina
CN106115755A (zh) * 2016-06-28 2016-11-16 上海滃泽科技有限公司 一种利用废铝制品升级制备高纯氧化铝的方法
US20180162739A1 (en) * 2016-12-09 2018-06-14 Samhwa Yang Heng Co., Ltd. Method of manufacturing high-density beads of high-purity alumina
CN206735820U (zh) * 2016-12-23 2017-12-12 袁伟昊 一种蓝宝石级高纯氧化铝块体、多晶锭制备装置

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