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WO2024084233A1 - Production de produits chimiques de qualité pour batterie - Google Patents

Production de produits chimiques de qualité pour batterie Download PDF

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Publication number
WO2024084233A1
WO2024084233A1 PCT/GB2023/052735 GB2023052735W WO2024084233A1 WO 2024084233 A1 WO2024084233 A1 WO 2024084233A1 GB 2023052735 W GB2023052735 W GB 2023052735W WO 2024084233 A1 WO2024084233 A1 WO 2024084233A1
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WO
WIPO (PCT)
Prior art keywords
lithium
mica
liquor
salt
sulphate
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Application number
PCT/GB2023/052735
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English (en)
Inventor
Roderick SMITH
Andrew Smith
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Research By British Lithium Ltd
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Filing date
Publication date
Application filed by Research By British Lithium Ltd filed Critical Research By British Lithium Ltd
Publication of WO2024084233A1 publication Critical patent/WO2024084233A1/fr

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
    • C01D15/00—Lithium compounds
    • C01D15/08—Carbonates; Bicarbonates
    • 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
    • C22B1/00—Preliminary treatment of ores or scrap
    • C22B1/02—Roasting processes
    • C22B1/06—Sulfating roasting
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
    • C01D15/00—Lithium compounds
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
    • C01D15/00—Lithium compounds
    • C01D15/02—Oxides; Hydroxides
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
    • C01D15/00—Lithium compounds
    • C01D15/06—Sulfates; Sulfites
    • 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
    • C01F11/00—Compounds of calcium, strontium, or barium
    • C01F11/18—Carbonates
    • 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
    • C22B1/00—Preliminary treatment of ores or scrap
    • C22B1/02—Roasting processes
    • 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
    • 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
    • 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
    • C22B3/24—Treatment or purification of solutions, e.g. obtained by leaching by physical processes, e.g. by filtration, by magnetic means, or by thermal decomposition by adsorption on solid substances, e.g. by extraction with solid resins
    • 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
    • C22B3/42—Treatment or purification of solutions, e.g. obtained by leaching by ion-exchange extraction
    • 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

Definitions

  • the present invention relates to a process for the calcination of lithium-micas and extraction and purification of battery grade lithium carbonate using a sustainable sulphate-based route, and to lithium-mica-containing compositions useful as reagents in said calcination process.
  • BACKGROUND OF INVENTION Currently, the main sources of lithium used to make battery chemicals are salar brines enriched in lithium salts and hard rock deposits containing spodumene. Lithium from salar brines requires pumping and evaporation of vast quantities of water to extract and concentrate brines before impurity removal to produce a final lithium salt product.
  • Spodumene a lithium-bearing pyroxene mineral
  • Lithium micas could be an alternative hard rock source of lithium salts, but these hard rock sources never been exploited commercially other than for glass making). These lithium micas occur within granites in Europe and elsewhere, and with granite containing gangue minerals, principally quartz and feldspar. Exploiting these deposits commercially requires the formulation of economic and environmentally sustainable methods for extraction of and production of high-grade lithium salts of saleable quality from these micas.
  • Lithium micas present an important potential source of lithium that is likely to grow in significance as the demand for lithium is expected to increase considerably in light of a worldwide effort to reduce carbon emissions.
  • Lithium micas are structurally classed as tri-octahedral micas and can exist in a solution series whose end members are polylithionite (KLi2AlSi4O10(F,OH)2; potassium lithium aluminium silicate fluorite hydroxide) and siderophyllite (KFe2Al(Al2Si2)O10(F,OH)2; potassium iron aluminium silicate hydroxide fluoride) ⁇ .
  • Zinnwaldite KLiFeAl(AlSi3)O10(OH,F)2; potassium lithium iron aluminium silicate hydroxide fluoride
  • lepidolite K(Li, Al)3(Al, Si, Rb)4O10(F, OH)2 are examples of mica that forms part of this solid solution series.
  • These lithium micas contain a wider range of elements than spodumene, the conventional hard rock source of lithium, which is LiAl(Si 2 O 6 ) (lithium aluminium inosilicate). Lithium micas are consequently less rich in lithium than spodumene, more complex to process and contain elements which may contaminate the desired end product.
  • the lower Li content and more complex mineralogy of lithium micas compared to spodumene gives rise to the need for an extraction process to generate brine or pregnant leach solution from lithium-mica minerals that affords improved recovery of lithium at a lower cost and environmental impact through reduced and more targeted use of reagents and more optimised calcining conditions, bringing fewer contaminants into solution.
  • One known method for the extraction of lithium salts from lithium micas relies on elevated temperature leaching of lithium micas in sulphuric acid, either at atmospheric pressure or in an autoclave or other device to increase pressure.
  • the present invention provides a process for producing precipitated or crystallised lithium carbonate from lithium-mica, the process comprising: i.
  • lithium-mica preferably lithium mica concentrate
  • a reagent or mixture of reagents comprising one or more of: calcium carbonate and/or sulphate salt(s) in a functional ratio to produce a lithium mica-reagent mixture
  • optionally pelletising the lithium mica-reagent mixture to provide pelletised lithium mica-reagent mixture
  • calcine filter cake optionally further comprising heat recovery/cooling of the hot calcine discharge, prior to leaching, to provide a calcine-product comprising lithium sulphate and/or lithium potassium sulphate; iv. leaching the hot calcine discharge or calcine-product for a functional time and having a functional pulp density in an aqueous leach liquor to provide a lithium-enriched leach liquor; v. filtering the lithium-enriched leach liquor to produce a leachate (also herein referred to as leachate liquor) and a filter leach residue (herein also referred to as “calcine filter cake”); vi.
  • At least one carbonate salt preferably a Group I metal carbonate, for example sodium carbonate
  • at least one carbonate salt preferably a Group I metal carbonate, for example sodium carbonate
  • removing impurities from the concentrated leachate in a second stage impurity removal step comprising addition of calcium hydroxide and calcium carbonate, and optional treatment with activated alumina, to provide a second reduced impurity containing leachate; ix.adding a carbonate source to the leachate liquor and/or concentrated leachate and/or second reduced impurity containing leachate to produce a crude lithium carbonate slurry comprising lithium carbonate precipitate, and subsequently filtering the lithium carbonate slurry to provide a first spent liquor and crude lithium carbonate; x.dissolving the crude lithium carbonate in water with a stream of carbon dioxide gas bubbling therethrough to produce lithium bicarbonate containing liquor; xi.optionally passing the lithium bicarbonate containing liquor through an ion exchange column to provide a purified lithium bicarbonate containing solution with a reduced concentration of, preferably substantially free of, calcium and other divalent cations; xii.
  • the process of the present invention provides high purity lithium carbonate for use, for example, in batteries.
  • the present invention provides an efficient process for the production of high purity lithium carbonate from lithium mica.
  • lithium mica concentrate is used herein to refer to a product of beneficiation whereby a material consisting of lithium mica is beneficiated to selectively remove gangue materials thereby increasing the concentration of lithium mica in the remaining material producing a lithium mica concentrate.
  • lithium mica is herein used to refer to lithium mica or lithium mica concentrate.
  • particle size and particle size distribution values stated herein are as determined by the particle’s ability to pass through a sieve aperture of the stated value during sieve analysis. Unless otherwise stated, values stated herein are on a weight-by-weight basis.
  • high purity lithium carbonate means lithium carbonate with a purity of at least 97% Li2CO3
  • steps of the process are preferably acid free.
  • the leaching step of the process is acid free.
  • the process is preferably acid free (i.e. free from the use of acid in any process steps). It is to be noted that calcination in this process can mean roasting, and vice-versa.
  • calcination in this process can mean roasting, and vice-versa.
  • the lithium mica preferably lithium mica concentrate, has a P80 value (i.e. the particle size at which 80% of the lithium mica will pass when screened) of 450 ⁇ m or smaller.
  • the particles of the lithium mica have a particle size of greater than 15 ⁇ m in diameter. It has been found by the inventor’s testwork that the method of the present invention can be used to extract the desired lithium salts from lithium mica without requiring the lithium mica to be finely ground prior to calcination. As a result, the method of the present invention does not require the use of a costly and high energy consuming grinding or milling process. According to a further aspect of the present invention, there is provided a lithium mica concentrate as defined above. According to further aspect of the present invention, there is provided the use of the lithium mica, preferably lithium mica concentrate, as defined above in a calcination process, and in particular in a calcination process as herein described.
  • a lithium mica-reagent mixture comprising a lithium mica, preferably a lithium mica concentrate, as herein defined with a reagent or mixture of reagents comprising one or more of: calcium carbonate and/or sulphate salt(s) in a functional ratio to produce a lithium mica-reagent mixture.
  • a lithium mica-reagent mixture as herein described in a calcination process, and in particular in a calcination process as herein described.
  • the reagent or mixture of reagents comprises one or more of: calcium carbonate and/or make-up sulphate-salt, optionally further comprising mixed-salt by-product (for example recycled mixed sulphate salts and/or recycled mixed calcium salts).
  • the reagent or mixture of reagents is preferably free from hydrated lime.
  • the term “mixed salt by-product” is used herein to refer to salts, and in particular sulphate salts and/or calcium salts, recovered during one or more stages of the process.
  • the term “mixed salt by-product” may refer to the mixed salt by-product, produced by the recovery stage (xiii) described herein.
  • the process may therefore further comprise recovering mixed salts from one or more stages of the process and recycling the recovered mixed salts into one or more other stages of the process, for example into the reagent mixing step (i).
  • sulphate salt(s) is used herein to refer to the combination of: make-up sulphate salt and mixed salt by-product.
  • the make-up sulphate salt is calcium sulphate, for example gypsum. Calcium sulphate is cheap and readily available in the form of for example mined naturally occurring gypsum or synthetic gypsum, thereby significantly reducing processing costs.
  • the sulphate salt(s) for example calcium sulphate, such as for example present within gypsum
  • one or more sulphate salt(s) such as for example present within the mixed salt by-product, ⁇
  • the mixed salt by-product comprises (preferably predominantly comprises), for example consist of, a double salt of sodium and potassium sulphate.
  • the mixed recycled calcium salts comprise one or more of (preferably each of): calcium carbonate and/or calcium sulphate.
  • calcium carbonate is provided in the form of limestone CaCO3.
  • Limestone is readily commercially available and has a reduced associated cost compared to lime CaO or hydrated lime Ca(OH)2.
  • the commonly used alternative of hydrated lime would introduce water to the calciner, increasing energy consumption.
  • the use of limestone within the process of the present invention therefore has reduced associated processing costs.
  • calcium carbonate may be partly substituted with calcium oxide or calcium hydroxide such that the stoichiometric amount of calcium present is the same as had pure calcium carbonate been used.
  • the mixture of reagents and lithium mica are mixed together prior to being pelletised.
  • the lithium mica and one or more reagents may be mixed together in a pug mixer.
  • the ratio of lithium mica to calcium carbonate within the mixture is preferably within the range of 6: 1 and 6: 3, preferably between 6:1.5 and 6:2.5 (based on the dry mass of the components).
  • the ratio of mica to gypsum to calcium carbonate is within the range of between 6: x: 1 and 6: x: 3.
  • the ratio of lithium mica to sulphate salt(s) present within the mixture is within the range of 6: 1 and 6: 5 (based on the dry mass of the components).
  • the ratio of mica to sulphate salt to calcium carbonate is within the range of between 6: 1: x and 6: 5: x.
  • a lithium mica- reagent mixture for example a pelletised lithium-mica reagent mixture
  • a lithium mica- reagent mixture comprising a ratio of mica to calcium carbonate within the mixture within the range of 6: 1 and 6: 3, preferably between 6:1.5 and 6:2.5.
  • a lithium mica- reagent mixture for example a pelletised lithium-mica reagent mixture
  • a ratio of mica to gypsum to calcium carbonate within the range of between 6: x: 1 and 6: x: 3.
  • a lithium mica- reagent mixture for example a pelletised lithium-mica reagent mixture
  • a lithium mica- reagent mixture comprising a ratio of lithium mica to sulphate salt(s) within the range of 6: 1 and 6: 5.
  • a lithium mica- reagent mixture for example a pelletised lithium-mica reagent mixture
  • a ratio of mica to gypsum to sulphate salt(s) is within the range of between 6: x: 1 and 6: x: 5.
  • the lithium mica-reagent mixture is heated to cause a series of solid- to-solid reactions to extract and convert the insoluble lithium contained in the lithium mica into water soluble lithium sulphate and/or lithium potassium sulphate.
  • the functional temperature of the calcining step is preferably within the range of about 750 o C to 1,100 o C, preferably within the range of 800 o C to 1,050 o C, preferably within the range of 850 o C to 1,000 o C.
  • the lithium mica-reagent mixture is preferably not milled prior to the calcination step.
  • the particle size distribution of the particles of the lithium mica-reagent mixture to be calcined is unaltered from the particle size distribution of the particles of lithium mica-reagent mixture prepared in step i).
  • the process comprising calcining a lithium mica-reagent mixture comprising particles having a maximum particle size distribution of P90 (i.e. the particle size at which 90% of the mixture will pass when screened) passing 400 ⁇ m.
  • the lithium mica-reagent mixture has a P80 value (i.e. the particle size at which 80% of the mixture will pass when screened) of 300 ⁇ m.
  • the lithium mica-reagent has a particle size distribution in which less than 25% of the particles have a particle size smaller than 20 ⁇ m.
  • the lithium mica-reagent mixture is pelletised before calcination. It has been found by the inventor’s testwork that pelletising the lithium-mica-reagent mixture increases the recovery of lithium to solution, which the applicant believe is related to an increase in the rate of the solid-to-solid reaction and also decreasing dust loss from the calciner.
  • the lithium mica-reagent mixture for example pelletised lithium mica-reagent mixture, is heated prior to calcination.
  • the heat may be provided by any suitable heat source.
  • the heat source is provided from excess heat or waste streams generated during the process, for example by off-gas generated from the calciner unit during the calcination step.
  • the process may therefore further comprise recycling one or more waste streams comprising excess heat, the waste streams being generated by the process (for example recycling off-gas generated by the calciner) to heat the lithium mica-reagent mixture (for example pelletised lithium mica-reagent mixture) prior to calcination.
  • the functional time for the calcining step is preferably between 15 minutes and 360 minutes. The functional time is dependent on the temperature ramp up profile. For example, if the temperature rises slowly towards the target temperature, the time period for calcining increases.
  • the calcining step occurs within either a direct fired rotary kiln/calciner, or an indirectly heated electric furnace.
  • the process of the present invention eliminates a step within the conventional lithium extraction process. Ideally, the process of the present invention is therefore free of milling, grinding or crushing of the mica prior to calcining.
  • the increased surface area of the calcine discharge increases the leaching recovery rate of the product, increasing the percentage lithium recovery and decreasing cost.
  • the process of the present invention has also been found by the inventor’s testwork to reduce fluorine gas evolution.
  • the fluorine content in the feed source for the calcining step, in the leach residue and in the leachate liquor was assayed during the inventor’s testwork.
  • HF hydrofluoric acid
  • the calcium carbonate in the feed mixture is preferably present at a level in excess of stoichiometric requirements.
  • the presence of alkaline substances in the calcine feed such as calcium carbonate can help to neutralise the generated hydrofluoric acid.
  • the present invention therefore provides a process for extracting lithium from lithium mica with reduced or no generation of fluorine gas or HF.
  • the hot calcine discharge is discharged straight into leach liquor without the need for cooling.
  • heat recovery/cooling is achieved by using methods other than indirect cooling
  • the heated, calcine discharge is deposited into the aqueous leaching liquor without the requirement for prior cooling.
  • cooling may be employed to cool the calcine discharge to > 100 o C without the use of indirect cooling. Handling and transportation of hot materials, such as materials heated to temperatures within or over, for example 150 o C, can be time consuming, dangerous and difficult which can lead to loss of product.
  • the heated, calcine discharge is cooled, by for example spraying the calcination vessel with water, to a temperature which facilitates easier handling and transportation.
  • This cooling step can however be costly and waste energy and water.
  • Calcine discharge may contain sintered or fused product which is not readily amenable to leaching.
  • Cooled calcine discharge may be hot-milled in order to break up and reduce the particle size prior to leaching in order to increase leach recovery. Milling of heated, calcined materials can be difficult to achieve and requires the use of an additional milling circuit which introduces additional process complexity and reduced plant availability, together with associated operating, energy and capital costs.
  • the present invention reduces, preferably eliminates, the need for a cooling step of the calcine discharge between the calcining step and the leaching step.
  • the calcine discharge is discharged directly, without additional cooling prior to discharge, into the leach liquor.
  • the present invention also provides a fluid or slurry, for ease of transportation, in the form of a slurry of calcine discharge and lithium enriched leach liquor.
  • Transportation of a fluid or slurry is much easier to handle and results in a lower risk of loss of product during transportation between process steps.
  • the direct deposition of the heated, calcine discharge into significantly cooler aqueous leaching liquor causes rapid generation of steam and thermal shock which effectively breaks apart calcined material which has been sintered or fused during calcination causing the product to break at least partially into fragments.
  • the expansion of steam bubbles created during deposition of the calcine discharge into the aqueous leaching liquor causes thermal fracture of the particles aiding processability of the quenched, leached, calcine discharge containing lithium.
  • the hot calcine discharge comprising water soluble lithium sulphate and/or lithium potassium sulphate produced in the hot calcination step (ii) (or calcine product produced in step (iii)) is leached with aqueous leach-liquor (for example water leach liquor) to create aqueous lithium ions in solution.
  • aqueous leach-liquor for example water leach liquor
  • the lithium enriched leach liquor is used in step (v).
  • the aqueous leach liquor may have a neutral pH, for example the aqueous leach liquor may comprise water having a neutral pH.
  • neutral pH is used herein to refer to a pH between 6.0 and 8.0.
  • the leach liquor such as for example water
  • the leach liquor is preferably free of pH modifiers, in particular, free from the addition of acid.
  • the leach liquor may comprise recycled wash water from previous batches.
  • the aqueous leach liquor may comprise an aqueous liquor comprising an alkaline pH.
  • the process of the present invention has been found by the inventor’s testwork to achieve >80% recovery of lithium into the lithium-enriched leach liquor solution.
  • the pulp density of the leach-liquor is between 7% and 40%, preferably between 10% and 35%, for example between 15% and 30%.
  • the process further comprises agitation of the aqueous leach liquor during and/or after deposition of the heated, calcine discharge therein. Agitation may for example be provided by a rotary mixer.
  • Agitation may further aid the process of fragmenting particles of the calcine discharge containing lithium sulphate and/or lithium potassium sulphate within the leaching liquor to provide a slurry.
  • the heated, calcine discharge is deposited into the aqueous leaching liquor without hot milling of the dried calcine discharge product prior to leaching.
  • the leaching vessel is in communication with the first outlet of the first outlet to receive heated, calcine discharge without a milling device located therebetween.
  • the calcine discharge once added to the leach water forms a slurry which may be wet milled or attritioned to break apart residual unbroken pellets, sintered or fused lumps to improve the leaching performance.
  • Enriched leach liquor together with calcine discharge may be passed through an attrition scrubber or milling stage to help break apart any residual unbroken pellets, sintered or fused lumps. This milling stage is performed before the subsequent filtration.
  • the solubility of lithium sulphate is “retrograde” meaning it is inversely proportional to the temperature of the solvent solution. As such, any increase in the temperature of the leach liquor during leaching of lithium sulphate may result in precipitation of lithium sulphate thereby reducing the concentration of lithium sulphate within the liquor.
  • An increase in the temperature of the leach liquor may also increase the solubility of other abundant aqueous salts within the calcine discharge (or hot calcine discharge), such as for example potassium sulphate and rubidium sulphate.
  • An increase in the concentration of the other abundant aqueous salts within the liquor may therefore further reduce the solubility of lithium sulphate within the leach liquor and reduce the overall recovery of lithium from the lithium mica.
  • leaching of the calcine discharge (or hot calcine discharge) is at first conducted at high temperature, with subsequent stages of leaching at decreasing temperatures as the slurry returns to ambient temperature. This ensures the solubility of lithium sulphate increases as leaching proceeds, and lithium sulphate is therefore less likely to reprecipitate.
  • the aqueous leaching liquor is maintained at a temperature below a functional temperature.
  • the aqueous leaching liquor may be cooled during deposition of the calcine discharge or hot calcine discharge.
  • the aqueous leaching liquor is preferably maintained at a temperature of less 90 o C, preferably less than 60 o C, preferably less than 50 o C, for example less than 40 o C.
  • the calcine discharge (or hot calcine discharge) is preferably deposited into the aqueous leaching liquor at a flow rate which is sufficient to ensure that the temperature of the aqueous leaching liquor does not exceed for example 60 o C, preferably 50 o C, for example 40 o C.
  • the calcine discharge (or hot calcine discharge) resides within the aqueous leaching liquor for a functional residence time (soak time), such as preferably for at least 30 minutes, preferably for at least 60 minutes, for example for at least 2 hours.
  • a functional residence time such as preferably for at least 30 minutes, preferably for at least 60 minutes, for example for at least 2 hours.
  • the lithium enriched leach liquor is filtered to separate the filter leach residue (also referred to as the calcine filter cake) to produce a filtered/leachate herein referred to as the leachate liquor. After filtration, the filter leach residue may be washed, and the resultant wash water may be re-used in the process.
  • the resultant wash water may be introduced into, or used in place of, the aqueous leaching liquor (iv) for treatment of a further batch of calcine discharge or hot calcine discharge.
  • the wash water may contain residual lithium which was present on the filter leach residue.
  • the carbonate salt may be a Group I metal carbonate salt.
  • the carbonate salt is preferably one or more of: sodium carbonate and/or potassium carbonate.
  • the carbonate salt is sodium carbonate.
  • the Group I metal carbonate is present at a concentration of at least 0.5 ⁇ g/L of leachate, preferably at least 1 g/L of leachate for example between 1 g/L of leachate and 2 g/L of leachate.
  • concentration of the leachate liquor or the first impurity reduced leachate may be achieved by any suitable method in order to produce a concentrated leachate. In one embodiment, concentration of the leachate liquor or the first impurity reduced leachate is achieved by partial evaporation to increase the concentration of the dissolved lithium in the remaining solution to produce concentrated leachate.
  • evaporation of the leachate or the first impurity reduced leachate is carried out to achieve a target lithium tenure within the concentrated leachate of greater > 4 g /L Li.
  • the evaporated water from the leachate or the first impurity reduced leachate may be condensed and collected.
  • the collected, evaporated and hence purified water may be reused within the process.
  • the collected, evaporated water may be introduced into, or used in place of, the leach liquor (iv) for leaching further calcine discharge or hot calcine discharge thereby reducing contaminants introduced to the process while reducing water consumption.
  • the concentration of leachate liquor or first impurity reduced leachate may be achieved or partially achieved by the use of Reverse osmosis or nanofiltration (NF) processes. This may eliminate the need for an evaporation stage or reduce the size requirements saving cost.
  • NF nanofiltration
  • SECOND STAGE IMPURITY REMOVAL STEP The concentrated leachate is further purified by crystallisation of impurities on introduction of calcium hydroxide and sodium carbonate and further treatment with activate alumina. The resultant leachate is known as a second reduced impurity containing leachate. Ferrous sulphate may also be introduced to the concentrated leachate.
  • calcium hydroxide is added to the concentrated leachate followed by the addition of sodium carbonate.
  • the calcium hydroxide may be added to the concentrated leachate for a functional time period.
  • calcium hydroxide is added to the concentrated leachate for a functional time period, for example for a functional time period prior to the introduction of sodium carbonate.
  • the functional time period is at least 30 minutes.
  • Calcium hydroxide may be added to the concentrated leachate at any suitable addition rate.
  • calcium hydroxide is added to the concentrated leachate at an addition rate of at least 0.2 g / L of concentrated leachate.
  • Sodium carbonate may be added to the concentrated leachate at any suitable addition rate.
  • sodium carbonate is added to the concentrated leachate at an addition rate of at least 0.6 g / L of concentrated leachate.
  • Treatment of the concentrated leachate with activated alumina provides reduced fluorine containing leachate.
  • Activated alumina may remove fluorine present within the concentrated leachate.
  • the concentrated leachate may be purified by treatment with activated alumina prior to introducing calcium hydroxide.
  • the concentrated leachate may be purified with activated alumina after the introduction of the additional reagent(s).
  • calcium hydroxide is introduced to the concentrated leachate, and subsequently treated with activated alumina.
  • diatomaceous earth may be used to assist with the filtration.
  • the filter leach residue may be washed to recover leachate liquor for introduction or recycling back to one or more steps in the process to reduce lithium losses and improve recovery.
  • At least one carbonate salt is added to the leachate liquor and/or concentrated leachate and/or second reduced impurity leachate to provide lithium carbonate slurry comprising lithium carbonate precipitate. Precipitation of crude carbonate occurs within the liquor.
  • at least one carbonate salt comprises sodium carbonate.
  • at least one carbonate salt is added to the concentrated leachate.
  • at least one carbonate salt is added to the leachate liquor and/or concentrated leachate and/or second reduced impurity leachate in such a way as to not cause localised fluctuations therein.
  • the at least one carbonate salt is added to the second reduced impurity containing leachate.
  • crystallisation may be aided by heating the liquor to a temperature of at least 90 o C to reduce the solubility of the crude lithium carbonate.
  • the crystallised crude lithium carbonate is separated from the slurry by filtration, for example in a centrifuge. After filtration, the crystallised crude lithium carbonate may be collected, and the spent liquor, referred to as the first spent liquor, may be recycled.
  • filtration may be replaced or complemented by a dewatering stage.
  • the crude lithium carbonate is washed to remove entrained liquor or leachate and to thereby removing further impurities. This wash water can be recycled back to the leaching stage (iv) to recover any dissolved lithium.
  • x) CRUDE LITHIUM CARBONATE DISSOLUTION STEP The crude lithium carbonate is dissolved into an aqueous solution (for example water) to provide a lithium bicarbonate containing liquor.
  • the dissolution of the crude lithium carbonate in an aqueous solution is aided by the introduction of carbon dioxide into the solution.
  • the solution is preferably cooled to a temperature of less than 20 o C.
  • the second spent liquor may be recycled for use in the crude dissolution stage.
  • xi) ION EXCHANGE PURIFICATION STEP The lithium bicarbonate liquor is further purified by the use of an ion-exchange column to provide a high purity lithium bicarbonate containing solution free of calcium and other divalent cations.
  • a highly selective chelating resin is used to remove calcium and other divalent cations from the lithium bicarbonate liquor.
  • the resin may be regenerated by treating it with diluted solutions of, for example, hydrochloric acid and sodium hydroxide.
  • FINAL LITHIUM CRYSTALLISATION STEP Lithium carbonate may be precipitated or crystallised from the high purity lithium bicarbonate containing solution obtained from the ion exchange column by increasing the temperature of the solution to take advantage of its retrograde solubility.
  • the temperature of the solution may be increased to at least 75 o C.
  • the temperature of the solution is preferably less than 98 o C.
  • the temperature of the solution is in the range of from 80 o C to 95 o C.
  • the solution is preferably maintained at the increased temperature for a period of at least 1 hour, for example between 1 hour and 3 hours.
  • the precipitated or crystallised lithium carbonate is removed from solution by a filtration device (preferably by a centrifuge) to produce high purity (battery-grade) lithium carbonate.
  • the remaining liquor also referred to herein as “second-spent-liquor” obtained from filtration of the solution still contains dissolved lithium.
  • the remaining liquor may be recovered and reintroduced into the process to improve lithium recovery.
  • the remaining liquor may be reintroduced as the aqueous solution (or as part of the aqueous solution) in the dissolution stage, thereby enabling the process to recover a higher yield of lithium from the lithium-mica.
  • the high purity lithium carbonate may be washed to remove any entrained liquor which future removes impurities.
  • filtration may be replaced or complemented by a dewatering stage.
  • MIXED SALT RECYCLING STEP The first-spent-liquor from the crude carbonate precipitation (ix) comprises an aqueous solution of sodium, potassium, lithium and sulphate ions amongst others.
  • the recovery of the dissolved sulphate ions to a solid is achieved by cooling the spent liquor obtained from the crude carbonate precipitation (ix) step to cause the precipitation and/or crystallisation of a mixed salt.
  • the salt mixture residue When filtered, the salt mixture residue is referred to as the mixed-salt-by-product; the remaining filtrate is called the third-spent- liquor.
  • the recovery of the dissolved sulphate ion to a solid is achieved by partial evaporation of the spent liquor, causing a mixed-salt precipitation.
  • the recycled mixed salt by-product preferably predominately comprises, for example consists of, a double salt of sodium and potassium sulphate, and may contain entrained lithium.
  • the recovery of mixed salt-by-product, for example sulphate salts, from the spent liquor preferably enables the mixture of sulphate salts to be recycled for use, optionally together with one or more additional sulphate salt(s), in the reagent mixing (i), thereby reducing costs associated with the supply of feed material whilst also reducing costs and environmental burdens associated with removal and disposal of waste products.
  • the process has lower associated material, operational and processing costs and less environmental impacts compared to conventional lithium extraction processes.
  • the process may also be more efficient than known conventional processes due to the ready supply and recovery of mixed sulphate salts as a calcining reagent.
  • part of the mixture of sulphate salts may bleed out (for example be rejected from the circuit) to control the balance of sodium and other impurities in the recycle liquor stream.
  • the third spent liquor may be recycled to the leaching stage, and as a such any remaining aqueous lithium ions present within the third spent liquor, remaining within the circuit of the process have another chance of being recovered to the lithium carbonate product.
  • the present invention preferably reduces the amount of lithium lost during the recovery process by ensuring that the spent liquor is recycled as a leaching water, thereby remaining within the system.
  • Figure 1 is a schematic illustration of a flow chart of one embodiment of the process of the present invention
  • Figure 2 is a schematic illustration of the reagent mixing and optional pelletising stage (i) according to one embodiment of the process of the present invention
  • Figure 3 is a schematic illustration of the calcination stage (ii) according to one embodiment of the present invention
  • Figure 4 is a schematic illustration of the leaching and filtration stage (iv) and (v) according to one embodiment of the present invention.
  • Figures 5A and 5B are graphs illustrating the relationship between lithium recovery and ground or unground lithium mica – reagent mixture
  • Figure 6 is a graph illustrating the relationship between lithium recovery and pulp density
  • Figure 7 is a graph illustrating the relationship between lithium recovery and leaching time
  • Figure 8 is a graph illustrating the relationship between lithium recovery and residence time using different ratios of lithium mica and reagent mixtures
  • Figure 9 is a graph illustrating the relationship between lithium recovery and quench time.
  • the process for extracting lithium from lithium mica comprises mixing lithium mica (86) with a mixture of reagents comprising a sulphate salt(s) (for example gypsum) (89) and calcium (for example carbonate (CaCO3) (88) in water, and optionally mixed-salt-by-product (230) recovered during the process, to provide a lithium mica reagent mixture.
  • the lithium mica reagent mixture may optionally be pelletised to produce pelletised lithium mica reagent mixture (74).
  • the amount of sulphate salt(s) and optionally mixed salt by-product may be present within the lithium mica reagent mixture such that the total amount of Sulphate (SO4-) contained is in stoichiometric excess in order to fully react with the lithium present within the lithium mica to form lithium sulphate.
  • Calcium carbonate may be provided in the form of limestone. Two mixtures were prepared: Mixture 1: the ratio of lithium mica to sulphate salt (within gypsum) to carbonate salt (within limestone) is 6: 3: 2; and Mixture 2: the ratio of lithium mica to sulphate salt (within gypsum) to carbonate salt (within limestone) is 3: 3: 1.
  • the ratio of lithium mica to carbonate salt(s) within the lithium mica reagent mixture is preferably within the range of 6: 1 and 6:3, preferably 6:1.5 and 6:2.5.
  • the ratio of lithium mica to sulphate salt(s) within the lithium mica reagent mixture is preferably within the range of 6: 1 and 6: 5.
  • the ratio of lithium mica to sulphate salt(s) to carbonate salt(s) within the lithium mica reagent mixture is preferably within the range of between 6: 1: x and 6: 5: x.
  • the ratio of lithium mica to sulphate salt(s) to carbonate salt(s) within the lithium mica reagent mixture is preferably within the range of between 6: 1: x and 6: 3: x.
  • the lithium mica and reagents are first mixed ahead of the pelletising stage
  • the lithium mica reagent mixture of pelletised lithium mica reagent mixture (74) is optionally preheated using the recovered heat or off gas (71) from the calciner.
  • the lithium mica- reagent mixture or pelletised lithium mica reagent mixture (74) may be heated to a functional temperature prior to being introduced into a calciner.
  • the pelletised lithium mica reagent mixture (74) is calcined within the calciner at a functional temperature for a functional time to provide a calcine discharge.
  • the preheated lithium mica-reagent mixture or preheated lithium mica reagent pellets (x) are calcined within a rotary kiln/calciner.
  • the mixture may be calcined in any suitable calcining vessel as is not to be limited to a rotary calciner.
  • the rotation speed of the calciner tube, and rotation speed of the screw feeder of the rotary calciner can each be varied.
  • the dynamics of the mixture within the calcining vessel, for example within the rotary calciner, is of importance to ensure sufficient mixing and blending of the material (for example the lithium mica-reagent mixture) to increase energy efficiency, to improve the desired chemical reactions and to reduce sintering of the mixture by preventing material from contacting inner walls of the vessel for prolonged periods of time.
  • the rotary parameters of the rotary calciner are each selected to provide a cascading mixing motion of the mixture within the vessel.
  • the rotary parameters of the calcining vessel 204 are optimised to maximise residence time inside the tube.
  • the speed of rotation is approximately 1 rpm, for example between 0.5 rpm and 2 rpm.
  • the lithium mica reagent mixture, or optionally the lithium mica-reagent pellets are heated to any suitable temperature within the calcining vessel within the range of about 750 o C to 1,100 o C.
  • the lithium mica-reagent mixture optionally the lithium mica reagent pellets may be heated to any suitable temperature within the calcining vessel, for example within the range of 800 o C to 1,100 o C, preferably within the range of 800 o C to 1,000 o C, preferably within the range 840 o C to 1,000 o C.
  • the calcining step is carried out such that the soak time (the time maintained at temperature to complete the desired reactions) is a period of between 30 and 50 minutes, however it is to be understood that the calcining step may be performed for any suitable duration, such as for example between 15 minutes and 120 minutes.
  • the calcine discharge comprising lithium sulphate and/or lithium potassium sulphate is obtained.
  • the lithium recovery percentage is dependent on a combination of reagent mixture, residence time and calcining temperature.
  • the calcine discharge can be added to the leach liquor at any temperature without the need for deliberate cooling.
  • the hot calcine discharge may however be cooled using heat recovery equipment, for example a rotary cooler or grate cooler, to an extent on completion of the calcining process and prior to deposition into the aqueous liquor for the purpose of heat recovery.
  • the ability to discharge the calcine discharge straight into an aqueous solution at any temperature removes the need for indirect cooling. Thus, any cooling can be for the sole purpose of energy recovery.
  • any required breakup of the particles can be in a wet state, by a combination thermal fragmentation (shock quenching), agitation of the leach vessel, attrition scrubbing. It can therefore be seen that the process of the present invention may eliminate the need to further hot mill or grind the heated calcine discharge on completion of the calcining stage and prior to leaching.
  • the heated, calcine discharge is deposited into the aqueous leaching liquor whilst the temperature difference between the calcine discharge and the aqueous leaching liquor is sufficient to cause thermal fracturing (shock quenching) of the calcine discharge.
  • the heated, calcine discharge may exit the calcining vessel directly, without any cooling, into the leaching vessel containing the leaching liquor.
  • the heated, calcine discharge may exit the calcining vessel at the temperature maintained during the calcining process.
  • the heated, calcine discharge preferably exits the cooler at a temperature in excess of 150 o C, preferably in excess of 200 o C, into an aqueous liquor at ambient temperature (or at least less than 60 o C).
  • the heated, calcine discharge may be discharged into an open-top pump and into the leaching vessel directly.
  • the temperature difference between the heated, calcine discharge and the aqueous liquor may be at least 125 o C. It is to be understood that the greater the temperature difference, the potentially greater thermal fracturing of the product.
  • the temperature difference may for example be at least 150 o C, preferably at least 200 o C.
  • the direct deposition of the heated, calcine discharge into significantly cooler aqueous leaching liquor causes rapid generation of steam which causes thermal fragmentation effectively breaking apart the calcine discharge material which has been sintered or fused during calcination causing the product to break at least partially into fragments.
  • the expansion of steam bubbles created during deposition of the calcine discharge into the aqueous leaching liquor causes thermal fracture of the particles aiding the processability of the quenched, leached, lithium containing calcine discharge.
  • the heated, calcine discharge firstly breaks into fragments on deposition into the aqueous leaching liquor by thermal fragmentation, and the agitation further breaks these fragments apart to form a slurry providing an increased surface area thereby improving the efficiency of leaching of the material, for example by reducing leach time and increasing lithium recovery.
  • the agitation further breaks these fragments apart to form a slurry providing an increased surface area thereby improving the efficiency of leaching of the material, for example by reducing leach time and increasing lithium recovery.
  • the agitation dependent on a number of factors including: temperature of calcination, residence time during calcination, the temperature difference (on deposition) between the heated, calcine discharge and the aqueous leaching liquor, and residence time within the aqueous leaching liquor that the presence of additional agitation means in order to provide a slurry may not be required and may be achieved by thermal fragmentation alone.
  • the addition of attrition scrubbing, or wet milling maybe required to break up sintered or fused lumps of calcine discharge.
  • the direct deposition of the heated, calcine discharge eliminates the need for an extra dry- milling step of the calcine discharge and therefore reduces the complexity, energy consumption and associated costs of the process.
  • breaking down the particle size of the calcine discharge by direct deposition without the requirement to cool the product to for example temperatures below 150 o C prior to leaching) from the calcination kiln into the leaching liquor, the surface area to volume ratio of the particles increases significantly.
  • the increase in surface area to volume ratio of the calcine discharge containing lithium sulphate and/or lithium potassium sulphate particles improves leaching efficiency of the product as there is an increased surface area particle exposure to the leaching liquor, thereby reducing leaching time and increasing lithium recovery rates.
  • the calcium is present to aid the conversion process by raising the sintering temperature of the mixture as well as capturing gases that may evolve during the calcining process such as fluorine gas and hydrogen fluoride mist.
  • the calcium carbonate also binds with free silica preventing the back reaction of silica with lithium sulphate, thereby increasing lithium recovery.
  • the calcium is present to neutralise hydrofluoric acid which may be released from the lithium mica, so producing calcium fluoride, and preventing or reducing the emission to atmosphere of hydrofluoric acid.
  • the calcining process i.e. the addition of the sulphate salt(s) and calcium carbonate
  • the furnace or calciner may provide a controlled residence soak time of between 15 minutes and 120 minutes in the hot zone at the desired reaction temperature.
  • the calcine discharge 81 is subsequently exposed to leaching by introducing the calcine discharge 81 to a leaching vessel 82 comprising an aqueous leach liquor.
  • the leach process preferably uses water with a natural pH (for example a pH of approximately between 9 and 10), with no requirement for any pH adjustment.
  • the aqueous leach liquor leaches the calcine discharge 81 to produce a lithium enriched leach liquor 83.
  • the leaching step may be carried out at a temperature between 15°C and 65°C to produce a lithium-enriched leach liquor.
  • the leach vessel may be agitated, and the reaction may be left running for between 0.1 hrs and 24 hrs to reach the desired recovery of Li into the leach solution.
  • the leach reaction may be carried out continuously or batch-wise.
  • the leaching step is preferably done over a period of time between 1 hrs and 4 hrs, at ambient temperatures, up to 90°C and at less than 30% solids m/m (preferably greater than 10%). It is however to be understood that the leaching step may be carried out over any suitable time period, such as for example over a time period as short as 60 minutes, or over a time period as long as 24 hours.
  • the resultant lithium enriched leach liquor 83 may contain between 0.1 and 45 g/L, preferably between 5 g/L and 45 g/L of Li.
  • the lithium enriched leach liquor 83 is filtered using filtration device 90. Filtration may occur using any suitable means, including for example pressure filtration and vacuum filtration.
  • the filter leach residue or calcine filter cake 79 can be disposed of or used for further processing.
  • the solid filter leach residue or calcine filter cake 79 may be washed and the wash water 91 may be collected and recycled for use as (or as part of) the aqueous leach liquor in the leach vessel 82 of the leaching step.
  • the leachate 77 (or lithium enriched leachate liquor) may be optionally purified using a first stage impurity removal step 92.
  • Sodium carbonate, soda ash is added to the leachate 77 resulting in the precipitation of impurities, in the form of for example calcium carbonate.
  • the precipitated impurities are removed by filtration 93.
  • the first impurity reduced leachate 84 is then concentrated in step 87 by partial evaporation to provide a concentrated leachate 224.
  • the concentrate of lithium in solution is increased.
  • Impurities are then removed from the concentrated leachate 224 in a second stage impurity removal step 94 using a two-stage process comprising the addition of calcium hydroxide followed by treatment with activated alumina to produce a second impurity reduced leachate 99.
  • a carbonate source is then added to the second impurity reduced leachate (99) to provide a precipitated crude lithium carbonate slurry 121.
  • the slurry is then filtered to provide crude lithium carbonate 138 and a first-spent-liquor 102.
  • This first spent liquor 102 is then chilled to cause a mixed salt precipitation within the now chilled slurry 104.
  • the chilled slurry is then filtered to separate the mixed salts (Glauber Salt Dewatering) leaving behind the filtrate as the third spent liquor.
  • the mixed salts can be recycled 230 as a calcination reagent into the reagent mixing stage.
  • the third-spent-liquor can be recycled 106 to the leach water.
  • the crude lithium carbonate 138 is then added to distilled water with the resulting mixture chilled whilst a stream of carbon dioxide gas is bubbled through the solution to produce lithium bicarbonate containing liquor 141.
  • the lithium bicarbonate containing liquor 141 is passed through an ion exchange column as a polishing stage to remove additional impurities to produce a polished bicarbonate solution 185.
  • the polished lithium bicarbonate carbonate solution 185 is then heated to around 95 o C to cause a precipitation of a high purity lithium carbonate 189 which is then washed to provide high grade lithium carbonate 196.
  • the process of the present invention is therefore more energy efficient, with lower associated time requirements, processing costs and operating costs, lower risk of material losses during extraction, and lower associated carbon footprint whilst achieving the same or improved recovery rates of lithium as conventional leaching of calcined lithium mica.
  • heated calcine discharge produced at a calcining temperature of between 900 o C and 1,000 o C, with a residence time of between 30 and 50 minutes produces similar lithium recovery (%) as reground calcine discharge at the same temperature, for example having a lithium recovery of between 35% and 90%.
  • Pulp density can be an important consideration in hydrometallurgical separation. Water evaporation to increase the concentration of liquors has a high associated operational and energy cost.
  • various pulp densities at different calcination conditions (calcination temperature and residence time) were evaluated.
  • Figure 6 shows that at 1,000 o C, with a residence time of 30 minutes, there is a small reduction in lithium recovery from 10% to 20% pulp density. The lithium recovery then plateaus to 30% pulp density.
  • Leaching time can also influence the lithium recovery rate.
  • the results of leaching time on lithium recovery are shown in Figure 7. It can be seen that in general, the longer the leaching time, the higher the lithium recovery. With an increased leaching time, the conglomerates of calcined discharge have longer to break apart, increasing the surface area and improving the dissolution of the lithium sulphate and/or lithium potassium sulphate contained in the calcine discharge.
  • the conglomeration and pelletisation is thought to occur as a result of calcium sulphate absorbing moisture.
  • Increasing the temperature has been found by the inventor’s testwork to improve lithium recovery, even with reduced residence time.
  • the process of the present may be carried out without requiring additional milling circuits whilst achieving high lithium recovery rates.
  • the lithium mica-reagent mixture was heated to temperatures within the calcining vessel of: 800 o C, 850 o C, 900 o C and 1,000 o C.
  • the feed source comprises a ratio of lithium mica to sulphate salt (preferably gypsum) to carbonate salt (preferably limestone) of 6: 3: 2 and heated during the calcining step to a temperature within the range of 800 o C to 1,100 o C.
  • a feed source comprising a ratio of lithium mica to sulphate salt (preferably gypsum) to carbonate salt (preferably limestone) of 6: 3: 2 and heating the mixture during the calcining step to a temperature within the range of 850 o C to 1,100 o C, preferably within the range of 900 o C to 1,000 o C, with a residence time of between 30 and 50 minutes, the lithium recovery has been found to be in the range of from 35% to 90%.
  • a feed source comprising a ratio of lithium mica to sulphate salt (preferably gypsum) to carbonate salt (preferably limestone) of 6: 3: 2 and heating the mixture during the calcining step to a temperature within the range of 850 o C to 1,100 o C, preferably within the range of 900 o C to 1,000 o C, with a residence time of between 30 and 50 minutes
  • a feed source comprising a ratio of lithium mica to sulphate salt (preferably gypsum) to carbonate salt (preferably limestone) of 6: 3: 2 and heating the mixture during the calcining step to a temperature within the range of 850 o C to 1,100 o C, preferably within the range of 900 o C to 1,000 o C, with a residence time of between 40 and 50 minutes, the lithium recovery has been found to be in the range of from 50% to 90%.
  • the feed source (Mixture B) comprises a ratio of lithium mica to sulphate salt (preferably gypsum) to carbonate salt (preferably limestone) of 3: 3: 1 and heated during the calcining step to a temperature within the range of 850 o C to 1,100 o C.
  • the lithium recovery has been found to be in the range of from 55% to 90%.
  • the lithium recovery has been found to be in the range of from 70% to 90%.
  • the calcining step was carried out for a period of between 30 and 50 minutes, however, it is to be understood that the calcining step may be performed for any suitable duration, such as for example between 15 minutes and 120 minutes.
  • the process of the present invention reduces the risk of loss of lithium during extraction. The number of steps of the process have been reduced therefore requiring less apparatus and increasing overall process availability.
  • the associated process and operating costs, labour and energy consumption of the apparatus and the process of the present invention are therefore reduced whilst the lithium recovery has been improved compared to conventional lithium mica extraction processes.
  • the process and apparatus of the present invention provide for improved lithium recovery from lithium mica providing for significant associated energy use, carbon emissions, time and cost savings.

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Abstract

La présente invention concerne un procédé de production de carbonate de lithium de pureté élevée à partir de lithium-mica. Le procédé comprend la granulation de lithium-mica avec un mélange de réactifs ; et la calcination du mélange de réactif lithium-mica granulé ; la lixiviation de la matière évacuée calcinée pour fournir une liqueur de lixiviation enrichie en lithium. La liqueur de lixiviation enrichie en lithium est filtrée pour produire un lixiviat et un résidu calciné filtré. Le lixiviat est en partie évaporé pour fournir un lixiviat concentré. Le lixiviat concentré est purifié à l'aide d'un procédé en deux étapes comprenant l'ajout d'hydroxyde de calcium et le traitement avec de l'alumine activée pour fournir un lixiviat contenant des quantités réduites d'impuretés. Une source de carbonate est ajoutée au lixiviat et/ou au lixiviat concentré et/ou au lixiviat contenant des quantités réduites d'impuretés pour produire une suspension de carbonate de lithium comprenant un précipité de carbonate de lithium. Le précipité de carbonate de lithium brut est éliminé par filtration laissant une liqueur résiduaire. Le carbonate de lithium brut est ensuite dissous dans de l'eau réfrigérée avec un courant de dioxyde de carbone gazeux à travers celui-ci pour produire une liqueur contenant du bicarbonate de lithium. La liqueur contenant du bicarbonate de lithium est ensuite passée à travers une colonne d'échange d'ions pour fournir un bicarbonate de lithium hautement purifié qui est ensuite chauffé jusqu'à une précipitation de carbonate de lithium de qualité élevée. La liqueur résiduaire est ensuite refroidie pour produire un sel de sulfate mixte, qui peut être utilisé dans le mélange de réactifs.
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