Process for extracting lithium from lepidolite through low-temperature roasting

Abstract

The invention discloses a process for extracting lithium from lepidolite through low-temperature roasting, which comprises the following steps: uniformly mixing lepidolite mineral powder with ferrous sulfate, sodium sulfate and calcium oxide, roasting at 800-900 DEG C for 1-2 hours, and cooling to room temperature to obtain a roasted material; adding water into the roasted material to prepare slurry, performing wet grinding to obtain ball-milled slurry, performing water leaching on the slurry, and performing suction filtration to obtain lithium sulfate leaching liquid and leaching residues; treating the leaching solution to obtain a lithium precipitation pre-solution, and further carrying out lithium precipitation reaction to obtain a lithium carbonate crude product; and finally, mixing the crude lithium carbonate product with deionized water, heating, stirring, washing and carrying out solid-liquid separation to obtain a battery-grade lithium carbonate product. The lithium extraction process of the lepidolite can be realized under the roasting condition of 800-900 DEG C, and the roasting temperature is effectively reduced; meanwhile, on the basis of the low-temperature roasting condition, Li2SO4 and LiKSO4 can still be extracted to the maximum extent, and release of SO2, SO3 and HF is avoided.

Description

Technical Field

[0001] The invention belongs to the field of lithium extraction technology of lepidolite, and in particular relates to a lithium extraction technology of lepidolite by low-temperature roasting. Background Art

[0002] Lithium is known as the "green energy metal" and "white oil" that will change the world in the 21st century. At present, there are sulfuric acid method, sulfate roasting method, limestone method and other methods for extracting lithium using lithium mica as raw material. Among them, the limestone method has been basically eliminated due to the large amount of slag flow and low lithium recovery rate. The sulfuric acid method is to roast lithium mica at 900℃, pass water vapor to defluorinate, and then roast it with 98% concentrated sulfuric acid at 300℃ for 2h. This method has a high leaching rate, but due to the high roasting temperature, the environmental pressure is high. The sulfate roasting method mainly mixes lithium mica with sulfates such as potassium sulfate, sodium sulfate or calcium sulfate and roasts them at high temperature. This method is versatile and simple in process; but this method has relatively high energy consumption, large amount of slag and is difficult to use, high cost and kiln agglomeration problem, which leads to problems in industrial continuous production. At present, the sulfate roasting method uses sodium sulfate, calcium sulfate, and calcium carbonate as roasting auxiliary materials. The roasting temperature is above 950°C, and the energy consumption is relatively high. In order to solve the problem of high roasting temperature and high energy consumption, sodium sulfate, calcium sulfate, calcium carbonate and other sulfates are used to roast with lithium mica. Since sodium sulfate, calcium sulfate, calcium carbonate and other sulfates and lithium mica are all solid powder particles, powder particles are prone to aggregation, which in turn affects the lithium extraction effect.

[0003] Based on this, a new type of lithium extraction process is now studied to achieve low-temperature sintering to achieve the lithium extraction effect while improving the lithium extraction rate, thereby achieving sufficient lithium extraction. Summary of the invention

[0004] Purpose of the invention: The technical problem to be solved by the present invention is to provide a lithium extraction process for lithium mica roasting which can achieve the lithium extraction effect by low-temperature sintering while improving the lithium extraction rate, thereby achieving sufficient lithium extraction.

[0005] Technical solution: The process for extracting lithium from lepidolite by low-temperature roasting of the present invention comprises the following steps:

[0006] (1) mixing lithium mica ore powder with ferrous sulfate, sodium sulfate and calcium oxide, calcining at 800-900° C. for 1-2 h and cooling to room temperature to obtain a calcined material;

[0007] (2) adding water to the roasted material to prepare a slurry, and wet-grinding the slurry to obtain a ball-milled slurry; then leaching the slurry with water, and filtering to obtain a lithium sulfate leaching solution and a leaching residue;

[0008] (3) treating the leaching solution to obtain a lithium precipitation pre-liquid, and further subjecting the lithium precipitation reaction to obtain a crude lithium carbonate product; finally, mixing the crude lithium carbonate product with deionized water, heating and stirring, washing, and solid-liquid separation to obtain a battery-grade lithium carbonate product.

[0009] The present invention is based on the use of sodium sulfate and calcium oxide to extract lithium. By adding ferrous sulfate, ferrous sulfate will be completely decomposed into Fe2O3, SO2 and SO3 under 800-900°C roasting conditions. The generated SO2 and SO3 gases, on the one hand, provide a gas channel for the ion exchange reaction between sodium sulfate and lepidolite. With the flow of gas, the reaction contact area between sodium sulfate and lepidolite is increased, the ion exchange reaction rate is increased, and the Na in Na2SO4 is reduced to 2.5% at a lower roasting temperature. + Li in lepidolite + It is easier to undergo ion exchange reaction, achieving a simultaneous increase in lithium extraction rate under lower roasting conditions. On the other hand, the SO2 and SO3 gases produced themselves react with lithium mica to produce gas-solid reaction, thereby destroying the crystal structure of lithium mica and promoting the Na in sodium sulfate. + Li in lepidolite + The ion exchange reaction further improves the efficiency of lithium extraction and avoids the release of SO2 and SO3 gases. The Fe2O3 produced by the decomposition of ferrous sulfate will not dissolve into the leaching solution, avoiding the introduction of soluble impurities, which helps to reduce impurities in the lithium precipitation solution and improve the quality of lithium carbonate products.

[0010] In addition, due to the small amount of fluorine contained in lithium mica, a small amount of hydrogen fluoride gas will appear during the heating process. Adding a small amount of calcium oxide can absorb this hydrogen fluoride gas to prevent the hydrogen fluoride gas from overflowing and polluting the environment. Calcium oxide is a high melting point substance, which can avoid sintering and glass caused by high temperature of the raw materials during the heating process.

[0011] Furthermore, in step (1) of the lithium extraction process of the present invention, the lithium mica ore powder, ferrous sulfate, sodium sulfate and calcium oxide are mixed in a ratio of (50-60%): (27-33%): (8-12%): (5-7%).

[0012] Furthermore, in step (2) of the lithium extraction process of the present invention, the liquid-to-solid ratio of water to the roasted material is (0.8-1):1.

[0013] Furthermore, in step (2) of the lithium extraction process of the present invention, during the wet grinding, the particle size of the material is controlled to be 60-200 mesh.

[0014] Furthermore, in step (2) of the lithium extraction process of the present invention, the leaching temperature of the water leaching is 50-80°C, and the leaching time is 30min-1h.

[0015] Furthermore, in step (3) of the lithium extraction process of the present invention, the lithium precipitation reaction is to inject the lithium precipitation pre-liquid into a saturated sodium carbonate solution and react at a temperature of 80-95° C. for 3-5 hours.

[0016] Furthermore, in step (3) of the lithium extraction process of the present invention, the heating and stirring is carried out at a temperature of 90-98° C. and stirring for 30-60 minutes.

[0017] Furthermore, in step (1) of the lithium extraction process of the present invention, the water content of the lithium mica ore powder is 3-7%, and the particle size is 90-100 mesh.

[0018] Furthermore, in step (1) of the lithium extraction process of the present invention, the particle size of the ferrous sulfate is less than 150 um.

[0019] Beneficial effects: Compared with the prior art, the significant advantages of the present invention are: the lithium extraction process of the lithium mica can be achieved under the roasting condition of 800-900°C (the existing temperature needs to reach above 950°C), which effectively reduces the roasting temperature, reduces the natural gas energy consumption, and reduces the production cost; and at the same time, based on the low-temperature roasting condition, it is still possible to extract Li2SO4 and LiKSO4 to the maximum extent, and avoid the release of SO2, SO3 and HF, reducing environmental pollution. DETAILED DESCRIPTION

[0020] The technical solution of the present invention is further described in detail below in conjunction with embodiments.

[0021] It should be noted that the core of the present invention is to use ferrous sulfate, sodium sulfate and calcium oxide to extract lithium from lepidolite. The subsequent process steps after lithium extraction are conventional steps in the art. For example, the processes of neutralization and impurity removal, deep impurity removal, concentration, and resin calcium removal of the leachate are well-known technical steps in the art, so the present invention will not describe them in detail.

[0022] Example 1

[0023] The lithium extraction process of lepidolite by low temperature roasting in Example 1 comprises the following steps:

[0024] (1) placing the lithium mica ore in a drying kiln and drying it to a moisture content of about 5%, and then dry-grinding it in a ball mill to obtain a lithium mica ore powder with a particle size of 90-100 mesh;

[0025] (2) dry-grinding the FeSO4·7H2O crystals by a ball mill to obtain ferrous sulfate crystals with a particle size of less than 150 μm;

[0026] (3) mixing lepidolite, ferrous sulfate, sodium sulfate and calcium oxide in a mass fraction ratio of 56:30:8:6, conveying the mixture to a rotary kiln for roasting by a belt conveyor, wherein the roasting temperature of the rotary kiln is 825° C., the roasting time is controlled to be 2 h, and the roasted material is cooled to room temperature by a cooling kiln, and the lithium conversion rate reaches 91.3%, wherein the conversion rate = (soluble lithium in clinker / total lithium in clinker) × 100%;

[0027] (4) The cooled calcined material is transported to a ball mill, and circulating water is added to prepare the slurry, and the solid-liquid ratio is adjusted to control the liquid-solid mass ratio of water to the calcined material to be 0.8:1, and wet-milled to a particle size of 60-200 mesh after ball milling;

[0028] (5) The slurry after ball milling is brought to a leaching kettle heated to 50 degrees for water immersion for 30 minutes to 1 hour. After water immersion, it is vacuum filtered with a belt filter to obtain lithium sulfate mother liquor and leaching residue. The leaching residue is rinsed three times with circulating water;

[0029] (6) subjecting the leaching solution to neutralization and impurity removal, deep impurity removal, concentration, resin decalcification and other processes to obtain a lithium precipitation pre-liquid; injecting the lithium precipitation pre-liquid into a saturated sodium carbonate solution, and reacting lithium precipitation at 90° C. for 3-5 hours to obtain a crude lithium carbonate product;

[0030] (7) Lithium carbonate washing: The crude lithium carbonate obtained in step (6) is mixed with deionized water, stirred at 90° C. for 30-60 min, and washed. After the reaction is completed, solid-liquid separation is performed to obtain a qualified battery-grade lithium carbonate product.

[0031] Example 2

[0032] The lithium extraction process of lepidolite by low temperature roasting in Example 2 comprises the following steps:

[0033] (1) placing the lithium mica ore in a drying kiln and drying it to a moisture content of about 5%, and then dry-grinding it in a ball mill to obtain a lithium mica ore powder with a particle size of 90-100 mesh;

[0034] (2) dry-grinding the FeSO4·7H2O crystals by a ball mill to obtain ferrous sulfate crystals with a particle size of less than 150 μm;

[0035] (3) mixing lepidolite, ferrous sulfate, sodium sulfate and calcium oxide in a mass fraction ratio of 58:28:9:5, conveying the mixture to a rotary kiln for roasting via a belt, wherein the roasting temperature of the rotary kiln is 800° C., the roasting time is controlled to be 2 h, and the roasted material is cooled to room temperature via a cooling kiln, and the lithium conversion rate reaches 90.6%;

[0036] (4) The cooled calcined material is transported to a ball mill, and circulating water is added to prepare the slurry, and the solid-liquid ratio is adjusted to control the liquid-solid mass ratio of water to the calcined material to be 1:1, and wet-milled to a particle size of 60-200 mesh after ball milling;

[0037] (5) The slurry after ball milling is brought to a leaching kettle heated to 50 degrees for water immersion. After water immersion, it is vacuum filtered with a belt filter to obtain lithium sulfate mother liquor and leaching residue. The leaching residue is washed three times with circulating water.

[0038] (6) The leaching solution is subjected to the processes of neutralization and impurity removal, deep impurity removal, concentration, resin decalcification, etc. to obtain a lithium precipitation pre-liquid; the lithium precipitation pre-liquid is injected into a saturated sodium carbonate solution, and lithium precipitation reaction is carried out at a temperature of 90° C. for 3-5 hours to obtain a crude lithium carbonate product.

[0039] (7) Lithium carbonate washing: The crude lithium carbonate obtained in step (6) is mixed with deionized water, stirred at 90° C. for 30-60 min, and washed. After the reaction is completed, solid-liquid separation is performed to obtain a qualified battery-grade lithium carbonate product.

[0040] Comparative Example 1

[0041] The basic steps are the same as those in Example 1, except that only sodium sulfate and calcium oxide are used to extract lithium, which specifically includes the following steps:

[0042] (1) placing the lithium mica ore in a drying kiln and drying it to a moisture content of about 5%, and then dry-grinding it in a ball mill to obtain a lithium mica ore powder with a particle size of 90-100 mesh;

[0043] (2) mixing lithium mica, sodium sulfate and calcium oxide in a ratio of 65:25:10, conveying the mixture to a rotary kiln for roasting via a belt, wherein the roasting temperature of the rotary kiln is 900° C. and the roasting time is controlled to be 2 h. The roasted material is cooled to room temperature via a cooling kiln, and the lithium conversion rate reaches 75%;

[0044] (3) The cooled calcined material is transported to a ball mill, and circulating water is added to prepare the slurry, and the solid-liquid ratio is adjusted to control the liquid-solid mass ratio of water to the calcined material to be 0.8:1, and wet-milled to a particle size of 60-200 mesh after ball milling;

[0045] (4) The slurry after ball milling is brought to a leaching kettle heated to 50 degrees for water immersion, and after water immersion, vacuum filtration is performed using a belt filter to obtain a lithium sulfate mother liquor and leaching residue after filtration, and the leaching residue is rinsed three times with circulating water;

[0046] (5) subjecting the leaching solution to neutralization and impurity removal, deep impurity removal, concentration, resin decalcification and other processes to obtain a lithium precipitation pre-liquid; injecting the lithium precipitation pre-liquid into a saturated sodium carbonate solution, and reacting lithium precipitation at 90° C. for 3-5 hours to obtain a crude lithium carbonate product;

[0047] (6) Lithium carbonate washing: The crude lithium carbonate obtained in step (5) is mixed with deionized water, stirred at 90° C. for 30-60 min, and washed. After the reaction is completed, solid-liquid separation is performed to obtain a qualified battery-grade lithium carbonate product.

[0048] Comparative Example 2

[0049] The basic steps are the same as those in Example 1, except that only ferrous sulfate and calcium oxide are used to extract lithium, which specifically includes the following steps:

[0050] (1) placing the lithium mica ore in a drying kiln and drying it to a moisture content of about 5%, and then dry-grinding it in a ball mill to obtain a lithium mica ore powder with a particle size of 90-100 mesh;

[0051] (2) dry-grinding the FeSO4·7H2O crystals by a ball mill to obtain ferrous sulfate crystals with a particle size of less than 150 μm;

[0052] (3) mixing lithium mica, ferrous sulfate and calcium oxide in a ratio of 56:29:15, conveying the mixture to a rotary kiln for roasting via a belt, wherein the roasting temperature of the rotary kiln is 900° C. and the roasting time is controlled to be 2 h. The roasted material is cooled to room temperature via a cooling kiln, and the conversion rate reaches 78%;

[0053] (4) The cooled calcined material is transported to a ball mill, and circulating water is added to prepare the slurry, and the solid-liquid ratio is adjusted to control the liquid-solid mass ratio of water to the calcined material to be 0.8:1, and wet-milled to a particle size of 60-200 mesh after ball milling;

[0054] (5) The slurry after ball milling is brought to a leaching kettle heated to 50 degrees for water immersion, and after water immersion, vacuum filtration is performed using a belt filter to obtain a lithium sulfate mother liquor and leaching residue after filtration, and the leaching residue is rinsed three times with circulating water;

[0055] (6) subjecting the leaching solution to neutralization and impurity removal, deep impurity removal, concentration, resin decalcification and other processes to obtain a lithium precipitation pre-liquid; injecting the lithium precipitation pre-liquid into a saturated sodium carbonate solution, and reacting lithium precipitation at 90° C. for 3-5 hours to obtain a crude lithium carbonate product;

[0056] (7) Lithium carbonate washing: The crude lithium carbonate obtained in step (6) is mixed with deionized water, stirred at 90° C. for 30-60 min, and washed. After the reaction is completed, solid-liquid separation is performed to obtain a qualified battery-grade lithium carbonate product.

[0057] It can be seen from the above-mentioned Example 1, Example 2, Comparative Example 1 and Comparative Example 2 that the lithium conversion rate in lepidolite can reach more than 90% by adopting the lithium extraction process of the present invention. And in combination with Comparative Example 1 and Comparative Example 2, it can be seen that when only sodium sulfate and calcium oxide, or ferrous sulfate and calcium oxide are used for lithium extraction, the lithium conversion rate in lepidolite is less than 80%. This further verifies that the present invention can achieve an excellent lithium conversion rate by coordinating ferrous sulfate, sodium sulfate and calcium oxide for lithium extraction, and the three promote each other.

[0058] In addition to the above embodiments, the present invention adopts lithium mica ore powder, ferrous sulfate, sodium sulfate, and calcium oxide in the mass ratio of (50-60%): (27-33%): (8-12%): (5-7%), which can be calcined at 800-900°C for 1-2h to achieve a high lithium conversion rate.

Claims

1. A process for extracting lithium by low temperature roasting of lepidolite, characterized in that: The steps include: (1) mixing lithium mica ore powder with ferrous sulfate, sodium sulfate and calcium oxide, calcining at 800-900° C. for 1-2 h and cooling to room temperature to obtain a calcined material; (2) adding water to the roasted material to prepare a slurry, and wet-grinding the slurry to obtain a ball-milled slurry; then leaching the slurry with water, and filtering to obtain a lithium sulfate leaching solution and a leaching residue; (3) treating the leaching solution to obtain a lithium precipitation pre-liquid, and further subjecting the lithium precipitation reaction to obtain a crude lithium carbonate product; finally, mixing the crude lithium carbonate product with deionized water, heating and stirring, washing, and solid-liquid separation to obtain a battery-grade lithium carbonate product.

2. The process for extracting lithium by low temperature roasting of lepidolite according to claim 1, characterized in that: In step (1), the lepidolite powder, ferrous sulfate, sodium sulfate and calcium oxide are mixed in a ratio of (50-60%): (27-33%): (8-12%): (5-7%).

3. The process for extracting lithium by low temperature roasting of lepidolite according to claim 1, characterized in that: In step (2), the liquid-to-solid ratio of water to the roasted material is (0.8-1):

1.

4. The process for extracting lithium by low temperature roasting of lepidolite according to claim 1, characterized in that: In step (2), during the wet grinding, the particle size of the material is controlled to be 60-200 mesh.

5. The process for extracting lithium by low temperature roasting of lepidolite according to claim 1, characterized in that: In step (2), the leaching temperature of the water immersion is 50-80°C, and the leaching time is 30min-1h.

6. The process for extracting lithium by low temperature roasting of lepidolite according to claim 1, characterized in that: In step (3), the lithium precipitation reaction is to inject the lithium precipitation pre-liquid into a saturated sodium carbonate solution and react at a temperature of 80-95° C. for 3-5 hours.

7. The process for extracting lithium by low temperature roasting of lepidolite according to claim 1, characterized in that: In step (3), the heating and stirring is carried out at a temperature of 90-98° C. and stirring for 30-60 minutes.

8. The process for extracting lithium by low temperature roasting of lepidolite according to claim 1, characterized in that: In step (1), the water content of the lithium mica powder is 3-7%, and the particle size is 90-100 mesh.

9. The process for extracting lithium by low temperature roasting of lepidolite according to claim 1, characterized in that: In step (1), the particle size of ferrous sulfate is less than 150 um.