A method for extracting lithium carbonate from lithium ore

Abstract

The present application relates to the technical field of lithium carbonate preparation, and specifically discloses a method for extracting lithium carbonate from lithium ore. The method comprises the following steps: crushing the lithium ore, adding sodium sulfate, calcium oxide, graphite powder, and carbon fiber to mix, and obtaining a mixed material; heating the mixed material under inert gas protection, calcining the mixed material, cooling it to room temperature by introducing an oxygen-containing gas, and cooling it to room temperature to obtain a calcined material; adding ethanol to the calcined material, mixing it, ball milling it, heating it to remove the ethanol, and obtaining a fine powder; leaching the fine powder to obtain a lithium leachate; removing impurities from the lithium leachate, precipitating lithium, filtering, washing, and drying it to obtain lithium carbonate. The calcined material obtained by this method is free of sintering, is easy to ball mill, and the average particle size of the obtained fine powder is less than 50 μm, which is easy to leach lithium, with a lithium leaching rate of >98%, which is easy to precipitate lithium, increases the yield of lithium carbonate, and increases the purity of lithium carbonate to >99.5%, which has market application and economic value.

Description

Technical Field

[0001] The present application relates to the technical field of lithium carbonate preparation, and more specifically, to a method for extracting lithium carbonate from lithium ore. Background Art

[0002] Lithium carbonate is an inorganic compound and an important chemical raw material. With the development of China's new energy, lithium carbonate, as a basic raw material, has seen its production and demand continue to increase. Lithium carbonate is mainly extracted from lithium ore or salt lake brine. For the extraction of lithium carbonate from lithium ore, lithium ore often uses lepidolite, spodumene, petalite, etc., and the main extraction methods include sulfate method, limestone sintering method, sulfuric acid method, etc. For lithium ore, lithium carbonate is extracted using the sulfate method. First, the lithium ore is crushed to obtain a powder. Then, sodium sulfate is added to the powder and roasted at high temperature to react the lithium ore and sodium sulfate to obtain a roasted material. The roasted material is then ground to obtain a fine powder. The fine powder is then leached, impurities are removed, and lithium is precipitated to obtain lithium carbonate. The applicant found in actual processing that the powder and sodium sulfate are prone to sintering under high-temperature roasting, which seriously affects the grinding of the roasted material and reduces the lithium leaching rate, thereby reducing the lithium carbonate production. Summary of the Invention

[0003] In order to reduce the sintering of roasted materials and improve the lithium leaching rate, the present application provides a method for extracting lithium carbonate from lithium ore.

[0004] In a first aspect, the present application provides a method for extracting lithium carbonate from lithium ore, using the following technical solution:

[0005] A method for extracting lithium carbonate from lithium ore comprises the following steps:

[0006] S1. Crushing and sieving lithium ore to obtain powder;

[0007] S2. Adding sodium sulfate, calcium oxide, graphite powder, and carbon fiber to the powder and mixing to obtain a mixed material;

[0008] S3. Under the protection of inert gas, the mixture is heated to 1000-1100° C., kept at this temperature for 3-5 hours, then cooled to 340-360° C., and then oxygen-containing gas is introduced, kept at this temperature for 1-3 hours, and then cooled to room temperature to obtain a calcined material;

[0009] S4, adding ethanol to the roasted material and mixing, then ball milling, heating to remove the ethanol, to obtain a fine powder;

[0010] S5, leaching the fine powder with a sulfuric acid solution to obtain a lithium leachate;

[0011] S6. Remove impurities from the lithium leaching solution, then use a carbonate solution to precipitate lithium, filter, wash, and dry to obtain lithium carbonate.

[0012] The method of extracting lithium carbonate from lithium ore in the present application greatly improves the sintering condition of the mixed material, makes the roasted material free of sintering, facilitates ball milling, makes the average particle size of the fine powder less than 50 μm, facilitates lithium leaching, and the lithium leaching rate is greater than 98%, facilitates lithium precipitation, increases the output of lithium carbonate, and makes the purity of lithium carbonate greater than 99.5%, showing good performance.

[0013] Sodium sulfate is added to the powder, reacting with it to form lithium sulfate. Graphite powder and acicular carbon fibers are also added to the powder. The synergistic effect of the two greatly improves the thermal conductivity of the mixture, reduces sintering and overburning, and eliminates sintering in the calcined material. The temperature is then lowered and an oxygen-containing gas is introduced. The graphite powder and carbon fibers react with the oxygen to produce gas, which forms pore channels, increasing the bulk of the calcined material and facilitating ball milling. This reduces the fine powder size, facilitates lithium leaching, improves the lithium leaching rate, and increases lithium carbonate production, thus possessing market applications and economic value.

[0014] Optionally, the mass content of lithium oxide in the lithium ore is 0.5-1.5%; the residue on a 100-mesh sieve of the powder is ≤1%; the particle size of the graphite powder is 50-100 μm; the diameter of the carbon fiber is 1-10 μm and the length is 100-500 μm.

[0015] By adopting the above technical solution, the lithium oxide content in lithium ore is limited, and the fluctuation of the lithium oxide content is controlled, thereby reducing the impact of excessive fluctuation on the effect, increasing the stability of lithium carbonate extraction, and ensuring the quality of lithium carbonate.

[0016] The 100-mesh sieve residue of the powder is also limited to facilitate the subsequent mixing and roasting of the raw materials. The particle size of the graphite powder and the diameter and length of the carbon fiber are limited to increase the uniformity of the raw material mixing and enhance the use effect of the graphite powder and carbon fiber.

[0017] Optionally, in step S2, the weight ratio of powder, sodium sulfate, calcium oxide, graphite powder and carbon fiber is 40:(20-30):(4-6):(4-6):(1-2).

[0018] By adopting the above technical solution, the weight ratio of powder, sodium sulfate, calcium oxide, graphite powder and carbon fiber is limited, which not only facilitates the reaction between powder and sodium sulfate, but also utilizes graphite powder and carbon fiber to increase heat transfer efficiency, facilitate temperature control, reduce sintering, facilitate subsequent ball milling, reduce fine powder particle size, and improve lithium leaching rate.

[0019] Optionally, in step S4, during the ball milling treatment, the weight ratio of the ball milling medium, the roasting material, and the ethanol is (3-5):(1-3):(1-2).

[0020] By adopting the above technical solution, the weight ratio of ball milling media, calcined material, and ethanol is controlled. The calcined material is milled with the ball milling media. The grinding and impact forces on the calcined material cause cracks, which then propagate and break into small particles. Combined with ethanol, the ethanol quickly penetrates the cracks, preventing them from closing and allowing them to spread rapidly, significantly improving milling efficiency.

[0021] In multiple embodiments, the weight ratio of ball milling media, roasting material, and ethanol is 4:2:1, and the weight ratio can also be set to 3:1:1, 3:1:2, 3:3:1, 3:3:2, 5:1:1, 5:1:2, 5:3:1, 5:3:2, etc. as needed.

[0022] Optionally, in step S4, during the ball milling process, the rotation speed is 400-600 r / min and the ball milling time is 60-80 min. Preferably, the rotation speed is 500 r / min and the ball milling time is 70 min.

[0023] By adopting the above technical solution, the rotation speed and ball milling time in the ball milling process are limited, which facilitates the control of the ball milling process.

[0024] Optionally, the ball milling medium is a zirconia ball, and the diameter of the zirconia ball is 10-50 mm. Preferably, the diameter of the zirconia ball is 20 mm.

[0025] By adopting the above technical solution, the material and diameter of the ball milling medium are limited, which facilitates the selection of the ball milling medium.

[0026] Optionally, step S5 specifically comprises: adding a sulfuric acid solution with a mass concentration of 50-60% to the fine powder, heating to 100-120° C., stirring for 4-6 hours, and filtering to obtain a first-stage leaching residue and a first-stage leaching filtrate;

[0027] Then, a sulfuric acid solution with a mass concentration of 50-60% is added to the primary leaching residue, the temperature is raised to 100-120° C., stirred for 2-4 hours, and filtered to obtain a secondary leaching residue and a secondary leaching filtrate;

[0028] Then, a sulfuric acid solution with a mass concentration of 50-60% is added to the secondary leaching residue, the temperature is raised to 100-120° C., stirred for 1-3 hours, and filtered to obtain a tertiary leaching residue and a tertiary leaching filtrate;

[0029] Then, the tertiary leaching residue is washed with a sulfuric acid solution having a mass concentration of 5-15%, and filtered to obtain a washing liquid;

[0030] Then, the primary leaching filtrate, the secondary leaching filtrate, the tertiary leaching filtrate and the washing liquid are mixed to obtain a lithium leaching solution.

[0031] By adopting the above technical solution, the sulfuric acid solution is used for three soakings, and the sulfuric acid solution is used for washing, so that the lithium sulfate in the fine powder is fully leached and the lithium leaching rate is improved.

[0032] Furthermore, in step S5, during the filtration of the primary leaching residue, the amount of sulfuric acid solution used is 800-1200 g. Preferably, the amount of sulfuric acid solution used is 900-1100 g. More preferably, the amount of sulfuric acid solution used is 1000 g.

[0033] In the filtration process to obtain the secondary leaching residue, the amount of sulfuric acid solution used is 800-1200 g. Preferably, the amount of sulfuric acid solution used is 900-1100 g. More preferably, the amount of sulfuric acid solution used is 1000 g.

[0034] In the filtration process to obtain the tertiary leaching residue, the amount of sulfuric acid solution used is 800-1200 g. Preferably, the amount of sulfuric acid solution used is 900-1100 g. More preferably, the amount of sulfuric acid solution used is 1000 g.

[0035] Furthermore, in step S5, the washing is performed one to five times, and the amount of sulfuric acid solution used for each washing is 300-800 g. Preferably, the washing is performed three times, and the amount of sulfuric acid solution used for each washing is 500 g.

[0036] Optionally, step S6 specifically comprises: adding alkali to the lithium leachate to adjust the pH value to 7.5-8, filtering, adding polyacrylamide solution and mixing, adding alkali to adjust the pH value to 12.5-13, filtering, and then evaporating and concentrating, cooling to room temperature, adding disodium ethylenediaminetetraacetic acid solution and mixing, then cooling to 5-15° C., filtering, then heating to 90-100° C., adding saturated sodium carbonate solution until no precipitation is produced, stirring for 2 hours, filtering at a temperature of 90-100° C., washing, and drying to obtain lithium carbonate.

[0037] By adopting the above technical solution, alkali is added to the lithium leachate to adjust the pH value to 7.5-8, which can cause iron ions and aluminum ions to form a precipitate, and then filter to remove iron ions and aluminum ions. Polyacrylamide is added and the pH value is adjusted to 12.5-13, which can cause ferrous ions, calcium ions, magnesium ions, and manganese ions to form a precipitate, and the flocculation of polyacrylamide is coordinated, and filtration is coordinated to remove ferrous ions, calcium ions, magnesium ions, and manganese ions. Since the calcium hydroxide formed by calcium ions is slightly soluble in water, calcium hydroxide and calcium ions are also residual. At this time, evaporation and concentration are carried out, and calcium hydroxide is precipitated. Disodium ethylenediaminetetraacetic acid is added to chelate the calcium ions and stably disperse them in water. Filtering is coordinated to further remove calcium hydroxide and chelate a small amount of calcium ions and stably disperse them in water. Afterwards, the temperature is raised and sodium carbonate is added. Sodium carbonate and lithium sulfate form a lithium carbonate precipitate, which is then filtered and washed to obtain lithium carbonate. In this application, the lithium carbonate purity is >99% through the mutual coordination of each step.

[0038] Furthermore, in step S6, the washing is first performed one to five times with ethanol, with the amount of ethanol used in each wash being 300-800 g, and then one to five times with deionized water at a temperature of 90-100° C., with the amount of deionized water used in each wash being 300-800 g. More preferably, the washing is performed three times with ethanol, with the amount of ethanol used in each wash being 500 g, and then three times with deionized water at a temperature of 95° C., with the amount of deionized water used in each wash being 500 g.

[0039] Optionally, in step S6, the solution is evaporated and concentrated, and the temperature is lowered to room temperature to obtain a concentrated solution, wherein the mass concentration of lithium ions in the concentrated solution is 0.5-1%.

[0040] By adopting the above technical solution, the concentrated solution contains a large amount of lithium sulfate, which limits the lithium ions in the concentrated solution, facilitates the control of the evaporation concentration amount, and also facilitates the subsequent lithium precipitation.

[0041] Optionally, in step S6, the mass concentration of polyacrylamide in the polyacrylamide solution is 0.05-0.1%, and the weight ratio of the lithium leaching solution to the polyacrylamide solution is 100:(1-2);

[0042] The mass concentration of disodium edetate in the disodium edetate solution is 0.01-0.05%, and the weight ratio of the lithium leaching solution to the disodium edetate solution is 100:(1-2).

[0043] By adopting the above technical solution, the usage of polyacrylamide and disodium edetate is limited, which facilitates the impurity removal treatment of the lithium leaching solution.

[0044] In summary, this application has at least the following beneficial effects:

[0045] The present invention relates to a method for extracting lithium carbonate from lithium ore, using sodium sulfate in the powder to facilitate the formation of lithium sulfate. Graphite powder and carbon fiber are used in the powder, utilizing the synergistic effect between the two to greatly improve the thermal conductivity of the mixed material and reduce the occurrence of overburning. After roasting, oxygen-containing gas is introduced, allowing the graphite powder and carbon fiber to react with oxygen to produce gas, forming pore channels, increasing the fluffiness of the roasted material, eliminating sintering, and facilitating ball milling. The fine powder particle size is reduced to an average particle size of less than 50 μm, facilitating lithium leaching, with a lithium leaching rate of >98%, facilitating lithium precipitation, increasing the output of lithium carbonate, and increasing the purity of lithium carbonate to >99.5%. The method has market application and economic value. DETAILED DESCRIPTION

[0046] To make this application easier to understand, the following examples will be used to further illustrate this application. These examples are for illustrative purposes only and are not intended to limit the scope of application of this application. Unless otherwise specified, the raw materials or components used in this application can be obtained through commercial channels or conventional methods.

[0047] Example

[0048] Example 1

[0049] A method for extracting lithium carbonate from lithium ore comprises the following steps:

[0050] S1. Crushing the lepidolite and passing it through a 100-mesh sieve to obtain a powder, wherein the sieve residue of the powder is 0.3% and the mass content of lithium oxide is 0.85%.

[0051] S2. Take 400 g of the powder obtained in step S1, add 250 g of sodium sulfate, 50 g of calcium oxide, 50 g of graphite powder, and 15 g of carbon fiber to the powder, and stir for 20 minutes to obtain a mixture.

[0052] Among them, the particle size of the graphite powder is 80 μm and is selected from Hebei Houkang Mineral Products Co., Ltd.; the diameter of the carbon fiber is 7 μm and the length is 400 μm, and is selected from Toray New Materials (Guangdong) Co., Ltd.

[0053] S3. Under nitrogen protection, the mixture obtained in step S2 was heated to 1050°C and kept at this temperature for 4 hours. The mixture was then cooled to 350°C, air was introduced, and kept at this temperature for 2 hours. The mixture was then cooled to 25°C to obtain a calcined material.

[0054] S4. Take the calcined material obtained in step S3, add ethanol to it, and stir for 20 minutes. Then, ball mill it at a speed of 500 rpm for 70 minutes. Then, heat it to 80°C, keep it at this temperature for 2 hours, and cool it to 25°C to obtain a fine powder.

[0055] In the ball milling process, the ball milling medium is zirconia balls with a diameter of 20 mm, and the weight ratio of the ball milling medium, the calcined material and the ethanol is 4:2:1.

[0056] S5. Take the fine powder obtained in step S4, add 1000 g of a 55% sulfuric acid solution to the fine powder, heat to 120° C., stir for 5 h, and filter to obtain a primary leaching residue and a primary leaching filtrate.

[0057] Then, 1000 g of a sulfuric acid solution with a mass concentration of 55% was added to the primary leaching residue, the temperature was raised to 120° C., stirred for 3 hours, and filtered to obtain a secondary leaching residue and a secondary leaching filtrate.

[0058] Then, 1000 g of a sulfuric acid solution with a mass concentration of 50-60% was added to the secondary leaching residue, the temperature was raised to 120° C., stirred for 2 hours, and filtered to obtain a tertiary leaching residue and a tertiary leaching filtrate.

[0059] Then, the tertiary leaching residue was washed three times with a sulfuric acid solution having a mass concentration of 10%, with 500 g of sulfuric acid solution used for each washing, and filtered to obtain a washing solution.

[0060] Then, the primary leaching filtrate, the secondary leaching filtrate, the tertiary leaching filtrate and the washing liquid are mixed and stirred for 10 minutes to obtain a lithium leaching solution.

[0061] S6. Take the lithium leachate obtained in step S5, add a saturated sodium hydroxide solution to the lithium leachate, adjust the pH value to 8, and filter to obtain a first-level impurity-removed filter residue and a first-level impurity-removed filtrate.

[0062] Then, a polyacrylamide solution with a mass concentration of 0.05% was added to the first-stage impurity removal filtrate, and the mixture was stirred for 20 minutes. A saturated sodium hydroxide solution was added, and the pH value was adjusted to 13. The mixture was filtered to obtain a second-stage impurity removal residue and a second-stage impurity removal filtrate.

[0063] The secondary impurity removal filtrate was evaporated and concentrated, and the temperature was reduced to 25° C. to obtain a concentrated solution, in which the mass concentration of lithium ions in the concentrated solution was 0.9%. Then, a disodium ethylenediaminetetraacetic acid solution with a mass concentration of 0.02% was added, and the mixture was stirred for 20 minutes. After that, the mixture was cooled to 15° C. and filtered to obtain a tertiary impurity removal residue and a tertiary impurity removal filtrate.

[0064] The tertiary impurity-removed filtrate was heated to 95° C., saturated sodium carbonate solution was added until no precipitation was generated, the mixture was stirred for 2 h, and filtered to obtain lithium carbonate precipitate.

[0065] The mixture was then washed three times with 500 g of ethanol each time, washed three times with deionized water at 95° C. each time, and dried at 100° C. to obtain lithium carbonate.

[0066] Among them, the weight ratio of lithium leachate and polyacrylamide solution is 100:1, and the average molecular weight of polyacrylamide in the polyacrylamide solution is 10 million Daltons; the weight ratio of lithium leachate and disodium ethylenediaminetetraacetic acid solution is 100:1.

[0067] Example 2

[0068] A method for extracting lithium carbonate from lithium ore, which differs from Example 1 in that, in step S2, the amounts of sodium sulfate, calcium oxide, graphite powder, and carbon fiber used are different.

[0069] Specifically, the usage amount of sodium sulfate is 200 g, the usage amount of calcium oxide is 60 g, the usage amount of graphite powder is 60 g, and the usage amount of carbon fiber is 10 g.

[0070] Example 3

[0071] A method for extracting lithium carbonate from lithium ore, which differs from Example 1 in that, in step S2, the amounts of sodium sulfate, calcium oxide, graphite powder, and carbon fiber used are different.

[0072] Specifically, the usage amount of sodium sulfate is 300 g, the usage amount of calcium oxide is 40 g, the usage amount of graphite powder is 40 g, and the usage amount of carbon fiber is 20 g.

[0073] Comparative Example

[0074] Comparative Example 1

[0075] A method for extracting lithium carbonate from lithium ore, which differs from Example 1 in that step S2 and step S3 are different.

[0076] Step S2 specifically comprises: taking 400 g of the powder obtained in step S1, adding 250 g of sodium sulfate and 50 g of calcium oxide to the powder, and stirring for 20 minutes to obtain a mixture.

[0077] Step S3 specifically comprises heating the mixed material obtained in step S2 to 1050° C., keeping the temperature for 4 hours, cooling the temperature to 350° C., keeping the temperature for 2 hours, and then cooling the temperature to 25° C. to obtain a calcined material.

[0078] Comparative Example 2

[0079] A method for extracting lithium carbonate from lithium ore, which differs from Example 1 in that step S2 and step S3 are different.

[0080] Step S2 specifically comprises: taking 400 g of the powder obtained in step S1, adding 250 g of sodium sulfate and 50 g of calcium oxide to the powder, and stirring for 20 minutes to obtain a mixture.

[0081] Step S3 specifically comprises heating the mixed material obtained in step S2 to 850° C., keeping the temperature for 4 hours, cooling the temperature to 350° C., keeping the temperature for 2 hours, and then cooling the temperature to 25° C. to obtain a calcined material.

[0082] Comparative Example 3

[0083] A method for extracting lithium carbonate from lithium ore, which differs from Example 1 in that step S3 is different.

[0084] Step S3 specifically comprises heating the mixed material obtained in step S2 to 1050° C., keeping the temperature for 4 hours, cooling the temperature to 350° C., keeping the temperature for 2 hours, and then cooling the temperature to 25° C. to obtain a calcined material.

[0085] Comparative Example 4

[0086] A method for extracting lithium carbonate from lithium ore, which differs from Example 1 in that, in step S2, an equal amount of graphite powder is used to replace carbon fiber.

[0087] Comparative Example 5

[0088] A method for extracting lithium carbonate from lithium ore, which differs from Example 1 in that, in step S2, an equal amount of carbon fiber is used to replace graphite powder.

[0089] Performance testing

[0090] (1) The calcined materials obtained in step S3 of Examples 1-3 and Comparative Examples 1-5 were taken as samples, and the sintering conditions of the samples were observed and recorded. The test results are shown in Table 1.

[0091] (2) The fine powder obtained in step S4 of Examples 1-3 and Comparative Examples 1-5 was taken as a sample, and the average particle size of the sample was tested. The test results are shown in Table 1.

[0092] (3) The lithium leaching solutions obtained in step S5 of Examples 1-3 and Comparative Examples 1-5 were respectively taken as samples, and the lithium ion content in the samples was detected. The lithium leaching rate was calculated based on the fact that the mass content of lithium oxide in lepidolite was 0.85%. The test results are shown in Table 1.

[0093] (4) The lithium carbonate obtained in step S6 of Examples 1-3 and Comparative Examples 1-5 was taken as a sample, and the purity of the lithium carbonate in the sample was tested. The test results are shown in Table 1.

[0094] Table 1 Test results

[0095]

[0096]

[0097] As can be seen from Table 1, the method for extracting lithium carbonate in this application does not cause sintering of the roasted material, facilitating ball milling. Furthermore, the fine powder has a relatively low particle size, with an average particle size of 38-48 μm, facilitating lithium leaching. It also has a high lithium leaching rate of 98.2-98.9%, facilitating lithium precipitation and increasing lithium carbonate production. The purity of the lithium carbonate is >99.5%, demonstrating excellent performance and meeting market demand.

[0098] In the method of Comparative Example 1, graphite powder and carbon fiber were not used in the raw materials of the mixture, and the roasting temperature was 1050°C, and no oxygen-containing gas was introduced after roasting; in the method of Comparative Example 2, graphite powder and carbon fiber were not used in the raw materials of the mixture, and the roasting temperature was 850°C, and no oxygen-containing gas was introduced after roasting. It can be seen from this that lowering the roasting temperature can improve the sintering of the roasted material to a certain extent, thereby reducing the average particle size of the fine powder. However, too low a roasting temperature may affect the reaction of lithium ore and sodium sulfate, and instead reduce the lithium leaching rate. Combined with Comparative Example 3, in the method of Comparative Example 3, graphite powder and carbon fiber were used in the raw materials of the mixture, and the roasting temperature was 1050°C, and no oxygen-containing gas was introduced after roasting. It can be seen from this that the use of graphite powder and carbon fiber in the raw materials of the mixture can also improve the sintering of the roasted material and increase the lithium leaching rate. In conjunction with Example 1, the method of Example 1 includes graphite powder and carbon fiber as raw materials for the mixture, a calcination temperature of 1050°C, and the introduction of an oxygen-containing gas after calcination. This demonstrates that the use of graphite powder and carbon fiber in the raw materials for the mixture, combined with the introduction of an oxygen-containing gas after calcination, prevents sintering of the calcined material, significantly reduces the particle size of the fine powder, and significantly improves the lithium leaching rate.

[0099] Comparison was made between Example 1 and Comparative Examples 4-5. The raw materials used in the mixture of Comparative Example 4 were graphite powder; the raw materials used in the mixture of Comparative Example 5 were carbon fibers; and the raw materials used in the mixture of Example 1 were both graphite powder and carbon fibers. This indicates that the use of both graphite powder and carbon fibers in the raw materials, and their synergistic effect, resulted in an average fine powder particle size of less than 50 μm and a lithium leaching rate of greater than 98%, demonstrating superior lithium carbonate extraction from lithium ore.

[0100] It should be noted that the embodiments described above are only used to explain the present application and do not constitute any limitation to the present application. The present application has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words, rather than restrictive words. The present application may be modified as specified within the scope of the claims of the present application, and the invention may be revised without departing from the scope and spirit of the present application. Although the present application described therein relates to specific methods, materials and embodiments, it does not mean that the present application is limited to the specific examples disclosed therein. On the contrary, the present application can be extended to all other methods and applications with the same function.

Claims

1. A method for extracting lithium carbonate from lithium ore, characterized in that: The steps include: S1. Crushing and sieving lithium ore to obtain powder; S2. Adding sodium sulfate, calcium oxide, graphite powder, and carbon fiber to the powder and mixing to obtain a mixed material; S3. Under the protection of inert gas, the mixture is heated to 1000-1100° C., kept at this temperature for 3-5 hours, then cooled to 340-360° C., and then oxygen-containing gas is introduced, kept at this temperature for 1-3 hours, and then cooled to room temperature to obtain a calcined material; S4, adding ethanol to the roasted material and mixing, then ball milling, heating to remove the ethanol, to obtain a fine powder; S5, leaching the fine powder with a sulfuric acid solution to obtain a lithium leachate; S6. Remove impurities from the lithium leaching solution, then use a carbonate solution to precipitate lithium, filter, wash, and dry to obtain lithium carbonate.

2. A method for extracting lithium carbonate from lithium ore according to claim 1, characterized in that: The mass content of lithium oxide in the lithium ore is 0.5-1.5%; the residue on a 100-mesh sieve of the powder is ≤1%; the particle size of the graphite powder is 50-100 μm; the diameter of the carbon fiber is 1-10 μm and the length is 100-500 μm.

3. The method for extracting lithium carbonate from lithium ore according to claim 1, wherein: In step S2, the weight ratio of powder, sodium sulfate, calcium oxide, graphite powder and carbon fiber is 40:(20-30):(4-6):(4-6):(1-2).

4. The method for extracting lithium carbonate from lithium ore according to claim 1, wherein: In step S4, during the ball milling process, the weight ratio of the ball milling medium, the calcined material, and the ethanol is (3-5):(1-3):(1-2).

5. The method for extracting lithium carbonate from lithium ore according to claim 4, wherein: In step S4, during the ball milling process, the rotation speed is 400-600 r / min and the ball milling time is 60-80 min.

6. The method for extracting lithium carbonate from lithium ore according to claim 4, wherein: The ball milling medium is a zirconia ball, and the diameter of the zirconia ball is 10-50 mm.

7. The method for extracting lithium carbonate from lithium ore according to claim 1, wherein: Step S5 is specifically as follows: adding a sulfuric acid solution with a mass concentration of 50-60% to the fine powder, heating to 100-120° C., stirring for 4-6 hours, and filtering to obtain a first-stage leaching residue and a first-stage leaching filtrate; Then, a sulfuric acid solution with a mass concentration of 50-60% is added to the primary leaching residue, the temperature is raised to 100-120°C, stirred for 2-4 hours, and filtered to obtain a secondary leaching residue and a secondary leaching filtrate; Then, a sulfuric acid solution with a mass concentration of 50-60% is added to the secondary leaching residue, the temperature is raised to 100-120°C, stirred for 1-3 hours, and filtered to obtain a tertiary leaching residue and a tertiary leaching filtrate; Then, the tertiary leaching residue is washed with a sulfuric acid solution having a mass concentration of 5-15%, filtered, and a washing liquid is obtained; Then, the primary leaching filtrate, the secondary leaching filtrate, the tertiary leaching filtrate and the washing liquid are mixed to obtain a lithium leaching solution.

8. The method for extracting lithium carbonate from lithium ore according to claim 1, wherein: Step S6 is specifically as follows: adding alkali to the lithium leachate to adjust the pH value to 7.5-8, filtering, adding polyacrylamide solution and mixing, adding alkali to adjust the pH value to 12.5-13, filtering, then evaporating and concentrating, cooling to room temperature, adding disodium ethylenediaminetetraacetic acid solution and mixing, then cooling to 5-15° C., filtering, then heating to 90-100° C., adding saturated sodium carbonate solution until no precipitation is generated, stirring for 2 hours, filtering at a temperature of 90-100° C., washing, and drying to obtain lithium carbonate.

9. The method for extracting lithium carbonate from lithium ore according to claim 8, wherein: In step S6, the solution is evaporated and concentrated, and the temperature is lowered to room temperature to obtain a concentrated solution, in which the mass concentration of lithium ions is 0.5-1%.

10. The method for extracting lithium carbonate from lithium ore according to claim 8, wherein: In step S6, the mass concentration of polyacrylamide in the polyacrylamide solution is 0.05-0.1%, and the weight ratio of the lithium leaching solution to the polyacrylamide solution is 100:(1-2); The mass concentration of disodium edetate in the disodium edetate solution is 0.01-0.05%, and the weight ratio of the lithium leaching solution to the disodium edetate solution is 100:(1-2).

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