A process for extracting lithium from bauxite by high-temperature sulfate roasting

Abstract

This invention discloses a process for extracting lithium from bauxite by high-temperature roasting with sulfate, comprising the following steps: S1, mixing bauxite powder and sulfate mixed salt additives to obtain a mixture, aging the mixture, and then roasting the aged mixture in a rotary kiln at high temperature to obtain clinker; S2, mixing the clinker obtained in step S1 with water and ball milling, then leaching with a dilute sulfuric acid aqueous solution to obtain a lithium sulfate solid-liquid mixture, and performing a first solid-liquid separation on the lithium sulfate solid-liquid mixture to obtain leaching residue and leaching liquid; This lithium extraction process has the advantages of simple operation, good control performance, high lithium purity, and high lithium recovery rate, achieving a balance between economic and environmental benefits, enabling comprehensive utilization of effective resources, and the entire process can achieve stable and continuous operation, making it easy to industrialize and scale up production.

Description

Technical Field

[0001] This invention relates to the field of alumina and its material processing, and more particularly to a process for extracting lithium from bauxite by high-temperature sulfate roasting. Background Technology

[0002] Besides the typical chemical elements aluminum, silicon, and iron, bauxite typically enriches itself with valuable metallic elements crucial to modern industry during its mineralization process, such as lithium, vanadium, potassium, gallium, scandium, titanium, niobium, and tantalum. This makes bauxite an important source of these key metal minerals. Currently, the main method for extracting lithium from bauxite is through chemical processing. Existing methods for lithium extraction from bauxite mainly include acid leaching and alkaline leaching. While acid and alkaline leaching are relatively common, they suffer from drawbacks such as complex operation, low purity of extracted lithium, high impurity content, low lithium recovery rate, and significant resource waste, hindering industrial-scale production. Summary of the Invention

[0003] The purpose of this invention is to provide a process for extracting lithium from bauxite by high-temperature sulfate roasting, in order to solve the problems mentioned in the background art.

[0004] To achieve the above objectives, the present invention provides the following technical solution:

[0005] A process for extracting lithium from bauxite by high-temperature sulfate roasting includes the following steps:

[0006] S1. A mixture of bauxite powder and sulfate mixed salt additives is obtained. The mixture is then aged and fed into a rotary kiln for roasting at high temperature to obtain clinker.

[0007] S2. The clinker obtained in step S1 is mixed with water and ball-milled, and then leached with dilute sulfuric acid aqueous solution to obtain lithium sulfate solid-liquid mixture. The lithium sulfate solid-liquid mixture is subjected to a first solid-liquid separation to obtain leaching residue and leaching liquid.

[0008] S3. After washing the leaching residue obtained in step S2, the washing liquid and the leaching liquid obtained in step S2 are combined, evaporated and concentrated to obtain a lithium production solution. The pH of the lithium production solution is adjusted to strong alkalinity, and then EDTA disodium and sodium carbonate aqueous solution are added to react. The reaction product undergoes a second solid-liquid separation to obtain a preliminary lithium solution and filter residue. The filter residue is used as raw material for aluminum plants.

[0009] S4. The preliminary lithium solution obtained in step S3 is purified to obtain a refined lithium solution.

[0010] Preferably, the mass ratio of bauxite powder to sulfate mixed salt additive in step S1 is (70-80):(20-30).

[0011] Preferably, the moisture content of the mixture in step S1 is ≤1wt%, and the proportion of 60-80 mesh particles is ≥80%.

[0012] Preferably, the aging temperature in step S1 is room temperature, and the time is ≥12h.

[0013] Preferably, the rotary kiln in step S1 uses one of water gas, natural gas, or pulverized coal as fuel, and the rotary kiln roasting temperature is 900℃~950℃, and the roasting time is 40~60min.

[0014] Preferably, in step S2, the mass ratio of clinker to water is (0.85-0.95):1, the pH of the dilute sulfuric acid aqueous solution is 3-4, the temperature is room temperature, and the time is 1-2 hours.

[0015] Preferably, the lithium content in the leaching residue after washing in step S3 is ≤0.09wt%, and the leaching residue after washing is used as raw material for aluminum plants.

[0016] Preferably, the pH value corresponding to the strong alkalinity in step S3 is ≥12.5, the reaction time is 30 min, and the temperature is 80-95℃.

[0017] Preferably, the carbonate concentration of the sodium carbonate aqueous solution in step S3 is 96-107 g / L, the amount of sodium carbonate aqueous solution used is 1.5-2.5 times the theoretical value, and the amount of disodium EDTA used is 1.5 times the theoretical value.

[0018] Preferably, the purification in step S4 uses chelating resin D401 to remove impurities from calcium and magnesium ions. In the refined lithium solution, the total content of calcium and magnesium ions is ≤5ppm and the lithium ion content is ≥10g / L. When the lithium ion content is <10g / L, the process returns to step S3 for evaporation and concentration.

[0019] Compared with the prior art, the beneficial effects of the present invention are:

[0020] The lithium extraction process from bauxite using a rotary kiln provided in this application involves pre-treating bauxite through coarse, medium, and fine crushing and grinding to obtain bauxite powder. The bauxite powder is then mixed with sulfate mixed salt additives to obtain a mixture, which is aged and then fed into a rotary kiln for roasting under boiling conditions to obtain clinker. The clinker is mixed with water and ball-milled, then leached with a dilute sulfuric acid aqueous solution to obtain a lithium sulfate solid-liquid mixture. A first solid-liquid separation is performed to obtain leaching residue and leachate. The leaching residue is washed, and the washing liquid and leachate are combined, evaporated, and concentrated to obtain a lithium-producing solution. The pH of the lithium-producing solution is adjusted to strongly alkaline, and then an aqueous solution of disodium EDTA and sodium carbonate is added for reaction. The reaction product undergoes a second solid-liquid separation to obtain a preliminary lithium solution and filter residue. The preliminary lithium solution is purified to obtain a refined lithium solution, and the filter residue is used as raw material for aluminum plants. This lithium extraction process has the advantages of simple operation, good control performance, high lithium purity, and high lithium recovery rate. It achieves a balance between economic and environmental benefits, enables comprehensive utilization of effective resources, and allows the entire process to operate stably and continuously, making it easy to industrialize and scale up production. Attached Figure Description

[0021] Figure 1 This is a process flow diagram of the present invention;

[0022] Figure 2 This is a record of lithium extraction experiments using the process described in this invention;

[0023] Figure 3 This table compares the lithium carbonate detection results of the examples and comparative examples. Detailed Implementation

[0024] To make the technical problems solved, technical solutions, and beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0025] A process for extracting lithium from bauxite by high-temperature sulfate roasting, the process flow is as follows: Figure 1 As shown, the process experiment record is as follows: Figure 2 As shown, it includes the following steps:

[0026] S1. After coarse crushing, medium crushing, fine crushing and grinding pretreatment processes, bauxite powder is obtained. The bauxite powder and sulfate mixed salt additives are mixed to obtain a mixture. The mixture is aged and then fed into a rotary kiln for roasting at high temperature to obtain clinker.

[0027] S2. The clinker obtained in step S1 is mixed with water and ball-milled, and then leached with dilute sulfuric acid aqueous solution to obtain lithium sulfate solid-liquid mixture. The lithium sulfate solid-liquid mixture is subjected to the first solid-liquid separation to obtain leaching residue and leaching liquid.

[0028] S3. After washing the leaching residue obtained in step S2, the washing liquid and the leaching liquid obtained in step S2 are combined, evaporated and concentrated to obtain a lithium production solution. The pH of the lithium production solution is adjusted to strong alkalinity, and then EDTA disodium and sodium carbonate aqueous solution are added to react. The reaction product undergoes a second solid-liquid separation to obtain a preliminary lithium solution and filter residue. The filter residue is used as raw material for aluminum plants.

[0029] S4. The preliminary lithium solution obtained in step S3 is purified to obtain a refined lithium solution.

[0030] The reaction mechanism is as follows:

[0031] High-temperature roasting in a rotary kiln involves the efficient extraction of soluble lithium sulfate, which is formed by the transfer of valuable lithium ions and sodium and potassium ions from a mixed salt of sulfates in bauxite under molten ground conditions.

[0032] In an optional embodiment, the mass ratio of bauxite powder to sulfate mixed salt additive in step S1 is (70-80):(20-30).

[0033] Optionally, the mass ratio of bauxite and sulfate mixed salt additives can be any value between 70:30, 65:35, 80:20, or (70-80): (20-30).

[0034] In an optional embodiment, the moisture content of the mixture in step S1 is ≤1wt%, and the proportion of 60-80 mesh particles is ≥80%.

[0035] Optionally, the moisture content of the mixture can be any value of 0.1wt%, 0.5wt%, 1wt%, or ≤1wt%, and the proportion of 60-80 mesh particles can be any value of 80%, 90%, or not less than 80%.

[0036] In one optional implementation, the aging temperature in step S1 is room temperature, and the time is ≥12h.

[0037] In an optional embodiment, in step S1, the rotary kiln uses one of water gas, natural gas, or pulverized coal as fuel, and the rotary kiln roasting temperature is 900℃~950℃, and the roasting time is 40~60min.

[0038] Optionally, the rotary kiln firing temperature can be any value between 900℃, 910℃, 920℃, 950℃, or 900℃~950℃, and the firing time can be any value between 40min, 50min, 60min, or 40~60min.

[0039] In one optional embodiment, the mass ratio of clinker to water in step S2 is (0.85-0.95):1, the pH of the leaching solution of the dilute sulfuric acid is 3-4, the temperature is room temperature, and the time is 1-2 hours.

[0040] Optionally, the mass ratio of clinker to water can be any value between 0.85:1, 0.87:1, 0.9:1, 0.95:1, or (0.85 to 0.95):1; the pH of the dilute sulfuric acid aqueous solution leaching can be any value between 3, 3.5, 4, or 3 to 4; and the leaching time can be any value between 1 hour, 1.5 hours, 2 hours, or 1 hour to 2 hours.

[0041] In an optional embodiment, the lithium content in the leaching residue after washing in step S3 is ≤0.09wt%, and the leaching residue after washing is used as raw material for aluminum plants.

[0042] In an optional embodiment, the pH corresponding to the strong alkalinity in step S3 is ≥12.5, the reaction time is 30 min, and the temperature is 80–95 °C.

[0043] In an optional embodiment, the carbonate concentration of the sodium carbonate aqueous solution in step S3 is 96-107 g / L, the amount of sodium carbonate aqueous solution used is 1.5-2.5 times the theoretical value, and the amount of disodium EDTA used is 1.5 times the theoretical value.

[0044] Optionally, the carbonate concentration of the sodium carbonate aqueous solution can be 96 g / L, 100 g / L, or 107 g / L, or any value between 96 and 107 g / L, and the amount of sodium carbonate aqueous solution can be 1.5 times, 2 times, or 2.5 times, or any value between 1.5 and 2.5 times the theoretical value.

[0045] In an optional embodiment, in step S4, chelating resin D401 is used to remove impurities from calcium and magnesium ions. In the refined lithium solution, the total content of calcium and magnesium ions is ≤5ppm and the lithium ion content is ≥10g / L. When the lithium ion content is <10g / L, the process returns to step S3 for evaporation and concentration. Example

[0046] A process for extracting lithium from bauxite by high-temperature sulfate roasting includes the following steps:

[0047] Bauxite is first coarsely crushed into particles with a diameter of 6-7 cm. Next, the coarsely crushed bauxite is medium-crushed into particles with a diameter of 4-5 cm. Then, the medium-crushed bauxite is finely crushed into particles with a diameter of 1-2 cm. Finally, the finely crushed bauxite is ground and powdered for pre-treatment. The powdered bauxite, after sieving, has a particle size distribution of ≥90% (80 mesh). Bauxite and a sulfate mixed salt additive are mixed at a mass ratio of 70:30. The sulfate mixed salt is of industrial grade. The material, initially in the form of a fine powder, was mixed with a screw mixer for 40 minutes to form a mixture with a moisture content of 0.95% and a particle size distribution of 81.7% (80 mesh). The mixture was then conveyed to a high-level silo via a screw conveyor and aged for 14 hours. Following this, the mixture underwent mechanical activation pretreatment using water gas as fuel. The aged mixture was fed into the rotary kiln from the kiln tail and discharged from the kiln head. The residence time of the mixture inside the rotary kiln was 60 minutes. The calcination temperature was 900℃±10℃, and the operation was stable. The calcined clinker was then thoroughly ball-milled with water. A dilute sulfuric acid solution with a pH of 4 was prepared for leaching and washing. After ball milling, a soluble lithium sulfate solid-liquid mixture was formed. The mass ratio of calcined clinker to water was controlled at 0.85:1, the leaching water temperature was room temperature, and the leaching time was 1 hour. The lithium sulfate solid-liquid mixture was subjected to a first solid-liquid separation using a filtration device to obtain leaching residue and leachate. The leaching residue was subjected to three reverse washings using a belt filter to control the lithium ion concentration in the leaching residue to 0.09 wt%. The washed leaching residue was used as raw material for aluminum plants. The prepared leachate and washing liquid were combined to form lithium production solution A. Lithium production solution A was evaporated and concentrated to obtain lithium production solution B. To obtain qualified refined lithium solution, appropriate amounts of sodium hydroxide and lime milk were added to lithium production solution B to adjust the alkalinity to 12.5. 1.5 times the theoretical value of disodium EDTA and 2 times the theoretical value of sodium carbonate aqueous solution (carbonate concentration of 95 g / L) were added for reaction. The reaction time was 30 min, and the reaction temperature was 90℃. A second solid-liquid separation was performed using a plate and frame filter press to remove impurities such as Ca. 2+ Mg 2+ Fe 3+ Mn 2+ Al 3+ The solution contains trivalent and divalent metal ions. The filtrate is a preliminary lithium solution. The filter residue is acidified, washed, and recycled for use as raw material in aluminum plants. The preliminary lithium solution from the previous step is then further purified and impurities removed using chelating resin D401 to remove Ca... 2+ Mg 2+ After removal and purification, a refined lithium solution is obtained. The refined lithium solution contains Ca. 2+ Mg 2+With an ion concentration ≤5ppm, the chelating resin D401 can be recycled after alkaline washing, acid washing, and water washing. The refined lithium solution has a lithium ion concentration of 11.20g / L, and serves as the raw material for the subsequent lithium precipitation module to prepare battery-grade lithium carbonate and battery-grade lithium hydroxide. In practice, this lithium extraction process has a high production operating rate, sustainable production, and achieves a safe, stable, and good operating condition. Example

[0048] A process for extracting lithium from bauxite by high-temperature sulfate roasting includes the following steps:

[0049] The bauxite is first coarsely crushed into particles with a diameter of 6-7 cm. Next, it undergoes medium crushing to produce particles with a diameter of 4-5 cm. This medium-crushed bauxite is then finely crushed to produce particles with a diameter of 1-2 cm. Finally, the finely crushed bauxite is ground and pre-treated with lithium. The powdered bauxite, after sieving, has a particle size distribution of ≥80% (70 mesh). Bauxite and sulfate additives are mixed at a mass ratio of 80:20 and stirred for 50 minutes using a screw mixer to form a mixture with a moisture content of 0.80% and a particle size distribution of 90% (80 mesh). The mixture is then conveyed to a high-level silo using a screw conveyor and aged for 16 hours. Following this, the mixture undergoes mechanical activation pretreatment using water gas as fuel. The aged mixture enters the rotary kiln from the kiln tail and exits from the kiln head. The mixture remains in the rotary kiln for 60 minutes. The roasting temperature is 940℃±10℃, and the operation is stable. The calcined clinker was thoroughly ball-milled with water until finely ground. A dilute sulfuric acid solution with a pH of 3 was then used for leaching and washing. After ball milling, a soluble lithium sulfate solid-liquid mixture was formed. The mass ratio of calcined clinker to water was controlled at 0.95:1, the leaching water temperature was room temperature, and the leaching time was 1 hour. The lithium sulfate solid-liquid mixture was then filtered to obtain leaching residue and leachate. The leaching residue underwent three reverse washings using a belt filter, controlling the lithium ion concentration in the leaching residue to 0.08 wt%. The washed leaching residue was used as raw material in an aluminum plant. The leachate and washing solution prepared above were combined to form lithium production solution A. Lithium production solution A was evaporated and concentrated to obtain lithium production solution B. To obtain qualified refined lithium solution, appropriate amounts of sodium hydroxide and lime milk were added to lithium production solution B to adjust the alkalinity to 12.9. Then, 1.5 times the theoretical value of disodium EDTA and 2 times the theoretical value of sodium carbonate aqueous solution (carbonate concentration of 100 g / L) were added for reaction. The reaction time was 30 min, and the reaction temperature was 95℃. A second solid-liquid separation was performed using a plate and frame filter press to remove impurities such as Ca. 2+ Mg 2+ Fe 3+ Mn 2+ Al 3+The solution contains trivalent and divalent metal ions. The filtrate is a preliminary lithium solution. The filter residue is acidified, washed, and recycled for use as raw material in aluminum plants. The preliminary lithium solution from the previous step is then further purified and impurities removed using chelating resin D401 to remove Ca... 2+ Mg 2+ After removal and purification, a refined lithium solution is obtained. The refined lithium solution contains Ca. 2+ Mg 2+ With an ion concentration ≤5ppm, the chelating resin D401 can be recycled after alkaline washing, acid washing, and water washing. The refined lithium solution has a lithium ion concentration of 12.20g / L, and this refined lithium solution becomes the raw material for the subsequent lithium precipitation module to prepare battery-grade lithium carbonate and battery-grade lithium hydroxide. In practice, this lithium extraction process operates well and is sustainable.

[0050] Comparative Example 1:

[0051] Unlike Example 1, the lithium extraction method is different. Instead of high-temperature roasting with sulfates, acid leaching is used. Industrial-grade sulfuric acid and bauxite are thoroughly mixed, resulting in a sulfuric acid content ≥98%. All other process parameters are controlled identically. Specific test data can be found in [link to relevant documentation]. Figure 3 .

[0052] Comparative Example 2:

[0053] Unlike Example 1, the lithium extraction method is different. Instead of high-temperature sulfate roasting, an alkaline leaching method is used. After thorough mixing of industrial-grade liquid alkali and bauxite, the main content of the liquid alkali is ≥31%. Other process parameters are controlled exactly the same. Specific test data can be found in [link to specific data]. Figure 3 .

[0054] Figure 3 This is a comparison table of the detection results of lithium extraction and preparation of lithium carbonate using the process method of the present invention in Examples 1 and 2 and Comparative Examples 1 and 2.

[0055] pass Figure 3 This demonstrates that the lithium extraction process provided in this application offers a better guarantee of the quality of battery-grade lithium carbonate compared to conventional acid and alkali leaching methods. Experimental comparisons using other processes, especially existing methods with identical preparation techniques and controlled technical parameters, show that lithium carbonate products prepared using bauxite acid or alkali leaching fail to meet national standards for their main lithium carbonate content, and some impurity levels deviate significantly from national standard requirements. However, as shown in Table 2, lithium carbonate products prepared using the process provided in this application fully meet the national standards for battery-grade lithium carbonate, achieving a balance between economic and environmental benefits and ensuring comprehensive utilization of resources.

[0056] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A process for extracting lithium from bauxite by high-temperature sulfate roasting, characterized in that, Includes the following steps: S1. A mixture of bauxite powder and sulfate mixed salt additives is obtained. The mixture is then aged and fed into a rotary kiln for roasting at high temperature to obtain clinker. S2. The clinker obtained in step S1 is mixed with water and ball-milled, and then leached with dilute sulfuric acid aqueous solution to obtain lithium sulfate solid-liquid mixture. The lithium sulfate solid-liquid mixture is subjected to a first solid-liquid separation to obtain leaching residue and leaching liquid. S3. After washing the leaching residue obtained in step S2, the washing liquid and the leaching liquid obtained in step S2 are combined, evaporated and concentrated to obtain a lithium production solution. The pH of the lithium production solution is adjusted to strong alkalinity, and then EDTA disodium and sodium carbonate aqueous solution are added to react. The reaction product undergoes a second solid-liquid separation to obtain a preliminary lithium solution and filter residue. The filter residue is used as raw material for aluminum plants. S4. The preliminary lithium solution obtained in step S3 is purified to obtain a refined lithium solution.

2. The lithium extraction process according to claim 1, characterized in that, The mass ratio of bauxite powder to sulfate mixed salt additive in step S1 is (70-80):(20-30).

3. The lithium extraction process according to claim 1, characterized in that, The moisture content of the mixture in step S1 is ≤1wt%, and the proportion of 60-80 mesh particles is ≥80%.

4. The lithium extraction process according to claim 1, characterized in that, In step S1, the aging temperature is room temperature and the time is ≥12h.

5. The lithium extraction process according to claim 1, characterized in that, The rotary kiln described in step S1 uses one of water gas, natural gas, or pulverized coal as fuel, and the rotary kiln roasting temperature is 900℃~950℃, and the roasting time is 40~60min.

6. The lithium extraction process according to claim 1, characterized in that, In step S2, the mass ratio of clinker to water is (0.85-0.95):1, the pH of the dilute sulfuric acid aqueous solution is 3-4, the temperature is room temperature, and the time is 1-2 hours.

7. The lithium extraction process according to claim 1, characterized in that, The lithium content in the leaching residue after washing in step S3 is ≤0.09wt%, and the leaching residue after washing is used as raw material for aluminum plants.

8. The lithium extraction process according to claim 1, characterized in that, In step S3, the strong alkalinity corresponds to a pH ≥ 12.5, the reaction time is 30 min, and the temperature is 80–95 °C.

9. The lithium extraction process according to claim 1, characterized in that, In step S3, the carbonate concentration of the sodium carbonate aqueous solution is 96-107 g / L, the amount of sodium carbonate aqueous solution used is 1.5-2.5 times the theoretical value, and the amount of disodium EDTA used is 1.5 times the theoretical value.

10. The lithium extraction process according to any one of claims 1 to 9, characterized in that, The purification process in step S4 uses chelating resin D401 to remove impurities from calcium and magnesium ions. In the refined lithium solution, the total content of calcium and magnesium ions is ≤5ppm and the lithium ion content is ≥10g / L. When the lithium ion content is <10g / L, the process returns to step S3 for evaporation and concentration.

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