Method for extracting lithium carbonate from spodumene ore raw material

Abstract

The present invention relates to the field of chemistry and chemical engineering and can be used for extracting lithium carbonate from lithium-bearing spodumene ore for battery production. The method for extracting lithium carbonate from spodumene ore comprises sintering a mixture of precursors: α-spodumene concentrate, sodium carbonate and alumina — to obtain a sinter containing sodium aluminosilicate and lithium carbonate. The sinter is then ground and leached with water in a countercurrent process; the resulting lithium carbonate solution is separated from the sodium aluminosilicate and evaporated, the solid lithium carbonate precipitate is separated from the remaining liquid. The leaching water is sequentially heated first by the steam generated during evaporation and then by the gases released during sintering. The liquid remaining after separation of the solid lithium carbonate precipitate and the condensate after cooling of the steam are combined with the leaching water before its heating. The technical result of the claimed invention is the development of an industrial method for extracting lithium carbonate from spodumene ore with reduced energy consumption and material intensity, as well as a decrease in the amount of by-products.

Description

Method for extracting lithium carbonate from spodumene ore raw material

[0001] The present invention relates to the field of chemistry and chemical engineering and can be used for extracting lithium carbonate from lithium-bearing spodumene ore for battery production.

[0002] Conventional methods for extracting lithium carbonate from spodumene raw materials — including the lime, potassium-sulfate, and sulfuric-acid processes — have several disadvantages: high energy and material consumption, low lithium recovery rates, and the generation of large amounts of waste, including liquid effluents.

[0003] A known method for extracting lithium from spodumene ore includes the following stages of spodumene processing: ore beneficiation and concentrate production; high-temperature roasting using organic fuel or natural gas to activate the obtained concentrate; reagent-based sulfation of the activated concentrate to obtain a solution containing lithium sulfate; precipitation of impurities from the lithium sulfate solution using alkaline agents; evaporation of the purified lithium sulfate solution; and precipitation of lithium carbonate from it, yielding a residual sulfate brine.

[0004] In this method, ammonium bisulfate is used as the reagent for sulfation of the activated concentrate. The ammonium bisulfate is recovered during the evaporation of the residual sulfate brine, which results in crystallization of ammonium sulfate. The obtained crystals are then heated to 250–400°C. Lithium carbonate is precipitated from the purified lithium sulfate solution using ammonium carbonate, which is produced from ammonia released during the recovery of ammonium bisulfate and from carbon dioxide present in the flue gases generated during high-temperature roasting of the spodumene concentrate (Patent RU 2824841, IPC C22B 26 / 12, C22B 1 / 06, C01D 15 / 08, October 11, 2023; published August 14, 2024, Bulletin No. 23, https: / www.fips.ru / registers-doc- view / fips_servlet?DB=RUPAT&DocNumber=2824841&TypeFile=html).

[0005] The disadvantages of this known method include significant energy consumption associated with high-temperature phase transformation (>1000°C) and recovery of ammonium bisulfate, as well as increased environmental burden due to the generation of by-products requiring disposal — particularly the residual sulfate brine — and due to a complex multistage leaching process that produces large volumes of effluent. Moreover, the multi-stage nature of the process, which inherently increases the number of technological units, metal consumption, and system complexity, limits its scalability for industrial application.

[0006] A known direct leaching technology for spodumene raw material Lithium Hydroxide Process (Lithium Hydroxide Process, URL: https: / www.metso.com / globalassets / commodities / lithium-hydroxide-process-5069-03-24-en- mng.pdf, accessed April 8, 2025) involves leaching silicate minerals at 230–250 °C under a pressure of up to 40 bar, resulting in the formation of insoluble lithium aluminate and analcime sand. Subsequently, at 90–95 °C without pressure, the lithium aluminate reacts with an excess of caustic soda solution, converting into lithium hydroxide, which is then subjected to carbonation, while the analcime sand precipitates.

[0007] The number of process stages in this technology is significantly smaller compared to conventional methods, which helps reduce the amount of technological equipment. However, the metal consumption remains high due to the need for specialized autoclaves and corrosion-resistant materials required for operating with caustic soda solution under high-pressure and high-temperature conditions.

[0008] In addition, this technology is associated with high energy consumption during the high-parameter leaching stage and the additional carbonation stage of lithium hydroxide, with the environmental burden due to the need to neutralize and dispose of alkaline effluents and the accumulation of by-product analcime sand waste, which has limited industrial applications.

[0009] The GLET-Medaro technology (Hard Rock Lithium Technology – HLT, URL: https: / medaromining.com / technology / , accessed April 8, 2025) is designed for the rapid production of high-purity lithium carbonate and / or high-purity lithium hydroxide monohydrate from various spodumene-rich concentrates (LiAlSi2O6).

[0010] The technology involves direct acid leaching under pressure using 40% nitric acid. The resulting insoluble silicon dioxide precipitate is filtered, counter-washed, and sent for drying and storage as a commercial product. The filtrate obtained after silica removal is fed to carbonation with carbon dioxide. The resulting lithium carbonate slurry is cooled to 20–30 °C and centrifuged. The lithium carbonate precipitate is washed with water and causticized with calcium hydroxide as an aqueous suspension at 90–95 °C. The formed calcium carbonate is dried after filtration or centrifugation and stored as a commercial by-product.

[0011] Part of the obtained lithium hydroxide is sent for carbonation to produce purified lithium carbonate (Li₂CO₃ > 99.5%) after recrystallization. The remaining portion of lithium hydroxide is cooled to 20–30 °C and centrifuged to separate the lithium hydroxide crystals as “raw” product, which are then dissolved in hot demineralized water and filtered to remove undissolved carbonates. The lithium hydroxide filtrate, after cooling to 40 °C, is fed into a vacuum crystallizer. The resulting pure lithium hydroxide monohydrate is centrifuged and dried. The mother liquors remaining after recrystallization and centrifugation are reused to dissolve new batches of the “raw” product.

[0012] Despite achieving high lithium recovery, this technology involves numerous technological stages, comparable in complexity to classical methods, and therefore does not significantly reduce the amount or metal intensity of the required process equipment. Moreover, the use of 40% nitric acid necessitates corrosion-resistant materials.

[0013] Additional drawbacks include the need for disposal of nitrate-containing effluents, management of calcium carbonate waste, and limited marketability of by-product silicon dioxide, all of which increase the already high energy consumption associated with energy-intensive stages such as heating, centrifugation, vacuum crystallization, and drying.Technical Problem

[0014] The technical problem addressed by the present invention is to eliminate the drawbacks of existing lithium extraction technologies. The achieved technical result consists in developing an industrial method for extracting lithium carbonate from spodumene ore characterized by reduced energy consumption and material intensity, as well as a decrease in the amount of by-products, including liquid effluents.Solution to Problem

[0015] The stated problem is solved, and the specified technical result is achieved by means of a method for extracting lithium carbonate from spodumene ore, which comprises sintering a mixture of precursors: α-spodumene concentrate, sodium carbonate, and alumina — to obtain a sinter containing sodium aluminosilicate and lithium carbonate. The sinter is then ground and leached with water in a countercurrent process. The resulting lithium carbonate solution is separated from sodium aluminosilicate and evaporated, the solid lithium carbonate precipitate is separated from the remaining liquid.

[0016] The leaching water is sequentially heated, first by the steam generated during evaporation, and then by the gases released during sintering. The liquid remaining after separation of the solid lithium carbonate precipitate together with the condensate after cooling of said steam is combined with the leaching water before its heating.

[0017] The use of water as the sole solvent eliminates the need for acids and other aggressive reagents, while the formation of a chemically stable by-product (sodium aluminosilicate) reduces requirements for corrosion-resistant materials, thereby decreasing material consumption and simplifying equipment maintenance. Heat recovery from the gases released during sintering and pre-heating of leaching water improve the overall energy efficiency of the process. Water recirculation lowers fresh-water consumption, reducing environmental impact.

[0018] For maximum lithium extraction as lithium carbonate, sintering the precursor mixture is preferably carried out at 730–770 °C for 3–6 hours.

[0019] Leaching with water is preferably performed at a ratio of 5–10 L of water per 1 kg of sinter for 30–60 minutes with intensive stirring to ensure complete dissolution of lithium carbonate. Using water as the only solvent in a minimal volume reduces wastewater generation and the energy required for its treatment.

[0020] Evaporation of the lithium carbonate solution is preferably performed at 70–100 °C for 1–3 hours, until the solid precipitate contained 5–20 wt.% residual moisture.

[0021] To prevent side reactions, it is advisable to measure and control the pH of the leaching water and / or ionic composition of the leaching water after water is mixed with the liquid after separation of the lithium carbonate precipitate and with the condensate after cooling of the steam.

[0022] For improved uniformity of sintering and enhanced reaction kinetics under stable temperature conditions, the precursor mixture may be additionally preheated before sintering.

[0023] To further increase process flexibility and stability, the leaching water can be additionally heated with superheated steam immediately before leaching.

[0024] To reduce harmful impurities, the gases released during sintering, after preliminary purification, can be used for carbonation of solid residues or wash waters.

[0025] Before sintering, to improve the yield of reaction products, the precursors can be further milled and then dried at 60–90 °C to remove residual moisture.

[0026] The method for extracting lithium carbonate from spodumene ore may also include before sintering granulation of the milled precursors in a granulator or press in order to increase the contact surface area between particles.

[0027] Fig.1

[0028] The claimed invention is illustrated by a block diagram shown in, using the following designations:

[0029] 1–26 –line;

[0030] 101, 102, 103, 600 – mill;

[0031] 201, 202, 203 – dryer;

[0032] 300 – mixer;

[0033] 400 – conveyor;

[0034] 500 – reactor furnace;

[0035] 700 – leaching reactor;

[0036] 801, 802, 803 – heat exchanger;

[0037] 901, 902 – filter;

[0038] 1000 – vacuum evaporation unit.

[0039] All precursors: α-spodumene concentrate, Na₂CO₃, and Al₂O₃ - are separately milled into fine powders with particle sizes below 75 µm in ball mills 101–103, into which they are fed through lines 1–3, respectively, to increase the contact surface area and accelerate subsequent reactions. The α-spodumene concentrate, supplied as ore, is preliminarily crushed in a jaw or cone crusher (not shown in).

[0040] The milled precursors are then delivered through lines 4–6 into dryers 201–203, for example, conveyor or fluidized-bed dryers, where they are dried at 60–90 °C to remove moisture that would otherwise slow down the reaction and cause side products.

[0041] The prepared precursors are then fed via lines 7–9 into a mixer 300 (such as a ribbon or planetary mixer) and thoroughly blended to achieve a homogeneous mixture. Optionally, the precursor mixture can be granulated (not shown in) to improve particle-to-particle contact and heated, e.g., with superheated steam, to enhance the kinetics of the solid-phase reaction.

[0042] The precursor mixture: α-spodumene concentrate, sodium carbonate, and alumina - is then conveyed via conveyor 400 into a reactor furnace 500, e.g., a rotary kiln or a moving-bed furnace, where sintering is carried out at 730–770 °C for 3–6 hours. During the solid-phase reaction, according to the equation

[0043] 2LiAlSi2O6+2Na2CO3+Al2O3→2Li2CO3+4NaAlSiO4, (1)

[0044] a sinter is formed that contains lithium carbonate and sodium aluminosilicate.

[0045] The resulting sinter exits the reactor furnace 500 via line 10, is ground in mill 600, and then delivered via line 11 to the leaching reactor 700, where it is treated countercurrently with water fed through line 26 at a ratio of 5–10 L of water per 1 kg of sinter for 30–60 minutes with intensive stirring. During leaching, lithium carbonate completely dissolves, while sodium aluminosilicate with minor impurities (mainly quartz) remains as a solid residue. The resulting suspension is sent through line 12 to a separation e.g., filtration in filter 901 or centrifugation. The solid sodium aluminosilicate residue is discharged via line 17 for further processing into a commercial by-product, suitable for use as raw material in construction or other industries. The lithium carbonate solution is transferred via line 13 to evaporation at 70–100 °C for 1–3 hours until the solid precipitate contained 5–20 wt.% residual moisture. Evaporation can be carried out in a rotary evaporator, a mechanically agitated evaporator, or a vacuum evaporation unit 1000.

[0046] The solid lithium carbonate precipitate is then separated from the residual moisture via filter 902 or centrifugation (line 14), yielding the target product discharged through line 15.

[0047] During the solid-phase reaction (Equation 1), carbon dioxide is released as a by-product at 400–450 °C. This hot gas is utilized via line 16 for heat recovery in heat exchanger 802, where it heats the leaching water supplied via line 22. The cooled gas (120–150 °C), after preliminary purification, is vented through an exhaust system or used for carbonation of solid residues or wash waters, reacting with trace metals (Fe, Ca) that form carbonates (not shown in).

[0048] The leaching water sequentially passes through several heat exchangers:

[0049] In heat exchanger 801 (line 22), it is heated from 15–20 °C to 40–50 °C by water vapor generated during lithium carbonate evaporation, which flows from the vacuum unit 1000 via line 18;

[0050] In heat exchanger 802 (line 23), it is further heated to 70–90 °C by CO₂ gas from the reactor furnace 500 via line 16;

[0051] Optionally, in heat exchanger 803, it is heated to 90–100 °C by superheated steam (line 25), which may also be used earlier to heat the precursor mixture before sintering (not shown in).

[0052] The heated water is then fed via line 26 into the leaching reactor 700, countercurrent to the crushed sinter entering via line 11. If additional heating is unnecessary, the water passes directly from heat exchanger 802 via line 26 to leaching reactor 700 through the bypass line 24.

[0053] The leaching water consists of:

[0054] Fresh water (line 21),

[0055] Liquid remaining after lithium carbonate separation (line 19 from filter 902), and

[0056] Condensate formed upon cooling of the water vapor from the vacuum unit 1000 (via 18 line) and / or the superheated steam from heat exchanger 803 (not shown in).

[0057] To prevent impurity accumulation, the circulating liquid streams (lines 19 and 20) are pre-purified, e.g., by filtration (not shown in), before mixing with the fresh water (line 21). To avoid undesired side reactions, flow rates are regulated, and the pH and / or ionic composition of the leaching water is measured and controlled on line 22.

[0058] The invention is further illustrated by calculated examples obtained through mathematical modeling of the proposed method for extracting lithium carbonate from spodumene ore.Examples

[0059] As raw material, a concentrate of α-spodumene with the following composition (wt.%) is used:

[0060] 69,6% α-spodumene (LiAlSi2O6) (Li2O content: 5,59%);

[0061] 18,8% quartz (SiO2);

[0062] 9,4% feldspar (Na AlSi3O8);2CO3

[0063] 2,2% mica (K(Li,Al)3(Al,Si,Rb)4O10(F,OH)2).

[0064] The milled and dried powders of concentrate, sodium carbonate, and alumina are mixed and fed into the reactor furnace, where they were maintained at 730 °C for 4 hours.

[0065] The resulting sinter, formed according to the solid-phase reaction (Equation 1), is ground and leached with water at a ratio of 5 L of water per 1 kg of sinter for 30 minutes with intensive stirring.

[0066] The resulting suspension, containing a lithium carbonate solution and a solid sodium aluminosilicate phase, is first filtered to separate the sodium aluminosilicate as a solid precipitate, while the remaining lithium carbonate solution is evaporated at 70 °C for 1 hour until the solid precipitate contained 5 wt.% residual moisture. The solid lithium carbonate precipitate is separated from the remaining liquid by filtration or centrifugation.

[0067] Assuming a maximum lithium recovery of up to 90,4% in the form of lithium carbonate according to Equation (1), the production of 100 t of lithium carbonate would require:

[0068] 371,7 t of α-spodumene concentrate,

[0069] 147,3 t of sodium carbonate, and

[0070] 57,3 t of alumina, as well as 2881 t of water for leaching.

[0071] The estimated energy consumption would be:

[0072] 403533 MJ for heating and maintaining the reactor furnace temperature,

[0073] 904073 MJ for leaching, and

[0074] 6865992 MJ for evaporation.

[0075] Thus, the total energy consumption for processing 1 kg of α-spodumene concentrate amounts to approximately 22 MJ / kg.

[0076] Example 2

[0077] As raw material is used the α-spodumene concentrate described in Example 1.

[0078] The milled and dried powders of concentrate, sodium carbonate, and alumina are mixed and fed into the reactor furnace, where they were held at 750 °C for 4 hours.

[0079] The resulting sinter, formed according to the solid-phase reaction (Equation 1), is ground and leached with water at a ratio of 8 L of water per 1 kg of sinter for 45 minutes with intensive stirring.

[0080] The obtained suspension, containing a lithium carbonate solution and a solid sodium aluminosilicate phase, is first filtered to separate the sodium aluminosilicate as a solid precipitate. The remaining lithium carbonate solution is then evaporated at 85 °C for 2 hours until the solid precipitate contained 12.5 wt.% residual moisture. The solid lithium carbonate precipitate is subsequently separated from the remaining liquid by filtration or centrifugation.

[0081] Assuming a maximum lithium recovery of up to 90,4% in the form of lithium carbonate according to Equation (1), the production of 100 t of lithium carbonate requires:

[0082] 371,7 t of α-spodumene concentrate,

[0083] 147,3 t of sodium carbonate, and

[0084] 57,3 t of alumina, as well as 4610 t of water for leaching.

[0085] The energy consumption for this process is estimated as follows:

[0086] 415,189 MJ for heating and maintaining the reactor furnace temperature,

[0087] 1445171 MJ for leaching, and

[0088] 10481086 MJ for evaporation.

[0089] Thus, the total energy consumption for processing 1 kg of α-spodumene concentrate amounts to approximately 33,2 MJ / kg.

[0090] Example 3

[0091] As raw material is used the α-spodumene concentrate described in Example 1.

[0092] The milled and dried powders of concentrate, sodium carbonate and alumina are mixed and fed into the reactor furnace, where they were maintained at 770 °C for 4 hours.

[0093] The resulting sinter, formed according to the solid-phase reaction (Equation 1), is ground and leached with water at a ratio of 10 L of water per 1 kg of sinter for 60 minutes with intensive stirring.

[0094] The obtained suspension, containing a lithium carbonate solution and a solid sodium aluminosilicate phase, is first filtered to separate the sodium aluminosilicate as a solid precipitate. The remaining lithium carbonate solution is then evaporated at 100 °C for 3 hours until the solid precipitate contained 20 wt.% residual moisture. The solid lithium carbonate precipitate isseparated from the remaining liquid by filtration or centrifugation.

[0095] Assuming a maximum lithium recovery of up to 90,4% in the form of lithium carbonate according to Equation (1), the production of 100 t of lithium carbonate requires:

[0096] 371,7 t of α-spodumene concentrate,

[0097] 147,3 t of sodium carbonate, and

[0098] 57,3 t of alumina, as well as 5762 t of water for leaching.

[0099] The energy consumption for heating and maintaining temperature in the reactor furnace is estimated as follows:

[0100] 426966 MJ for heating and maintaining the reactor furnace temperature,

[0101] 1807939 MJ for leaching, and

[0102] 12482101 MJ for evaporation.

[0103] Thus, the total energy consumption for processing 1 kg of α-spodumene concentrate amounts to approximately 39,6 MJ / kg.

Claims

A method for extracting lithium carbonate from spodumene ore, comprising sintering a mixture of precursors: α-spodumene concentrate, sodium carbonate, and alumina — to obtain a sinter containing sodium aluminosilicate and lithium carbonate, wherein the sinter is ground and leached with water in a countercurrent process; the resulting lithium carbonate solution is separated from the sodium aluminosilicate and evaporated; the solid lithium carbonate precipitate is separated from the remaining liquid,wherein the leaching water is sequentially heated first by the steam generated during evaporation and then by the gases released during sintering, and the liquid remaining after separation of the solid lithium carbonate precipitate together with the condensate after cooling of said steam is combined with the leaching water before its heating.The method according to claim 1, wherein the sintering of the precursor mixture is carried out at a temperature of 730-770 °C for 3-6 hours.The method according to claim 1, wherein leaching with water is carried out at a ratio of 5-10 L of water per 1 kg of sinter for 30-60 minutes with intensive stirring.The method according to claim 1, wherein evaporation of the lithium carbonate solution is performed at 70-100 °C for 1-3 hours until the solid precipitate contained 5-20 wt.% residual moisture.The method according to claim 1, wherein the pH of the leaching water and / or ionic composition of the leaching water is measured and controlled after water is mixed with the liquid after separation of the lithium carbonate solid precipitate and with the condensate after cooling of the steam.The method according to claim 1, wherein before sintering the precursors are additionally milled and then dried at 60-90 °C to remove residual moisture.The method according to claim 6, wherein before sintering the milled precursors are granulated in a granulator or press.The method according to claim 1, wherein before sintering the precursor mixture is additionally preheated.The method according to claim 1, wherein immediately before leaching the water is additionally heated with superheated steam.The method according to claim 1, wherein the gases released during sintering, after preliminary purification, are used for carbonation of solid residues or wash waters.

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