Method for extracting lithium carbonate from a mixed salt of low-grade lithium carbonate, potassium chloride, and sodium chloride

Abstract

The method for extracting lithium carbonate from a mixed salt of low-grade lithium carbonate, potassium chloride, and sodium chloride includes the following steps: (1) Grinding: Grinding the mixed salt of low-grade potassium chloride, sodium chloride, and lithium carbonate obtained by sun-drying in a salt field to obtain a slurry; (2) Screening: Screening the slurry in a screening machine or hydrocyclone to obtain gangue minerals and slurry; (3) Separation of lithium carbonate from potassium chloride and sodium chloride: Sending the slurry into a flotation machine, adding a lithium carbonate cationic collector for flotation, and refining to obtain refined lithium carbonate concentrate; (4) Washing, filtering, and drying: Washing and filtering the obtained refined lithium carbonate concentrate, collecting the solid, and drying the solid to obtain crude lithium carbonate product. The process of this invention is simple, the amount of ore fed into flotation is small, the flotation time is short, the lithium carbonate crude product obtained has high lithium carbonate purity, low cost, and high recovery rate.

Description

Technical Field

[0001] This invention relates to a method for extracting lithium carbonate, and more particularly to a method for extracting lithium carbonate from a mixed salt of low-grade lithium carbonate, potassium chloride, and sodium chloride. Background Technology

[0002] Lithium is an important strategic resource, widely used in batteries, ceramics, glass, lubricants, refrigerants, the nuclear industry, and optoelectronics. With the continuous development of electronic products such as computers, digital cameras, and mobile phones, as well as electric vehicles, the battery industry has become the largest consumer of lithium resources. Furthermore, the application of lithium carbonate is one of the effective ways for the ceramics industry to reduce energy consumption and promote environmental protection, which will further increase the demand for lithium. At the same time, various new uses for lithium in glass are constantly being discovered, and the demand for lithium in the glass industry will continue to grow.

[0003] my country possesses abundant lithium resources, with the Zabuye Salt Lake being a prime example. The Zabuye Salt Lake has yielded qualified lithium carbonate products through a solar pond process; however, the low efficiency and low recovery rate of this process limit the plant's capacity, especially for low-grade lithium carbonate mixed salts. Therefore, developing an efficient and economical method for the comprehensive utilization of lithium carbonate salt lakes is of great significance.

[0004] CN102120592B discloses a method for extracting lithium carbonate using a mixed salt flotation of NaCl and lithium carbonate, comprising the following steps: (1) grinding the mixed salt of NaCl and lithium carbonate; (2) feeding the slurry obtained in step (1) into a flotation machine, adjusting the pH value to alkaline, adding lithium carbonate collector at a dosage of 200g / t to 350g / t of slurry, stirring for 2-4 minutes, and then performing aerated flotation; (3) performing 1-2 cleaning processes on the lithium carbonate rough concentrate obtained in step (2), filtering, and drying to obtain industrial-grade crude lithium carbonate. The raw ore is a mixed salt of sodium chloride and lithium carbonate, targeting Li... + For lithium carbonate ores with high content, the grinding-flotation process is used. The amount of ore fed into the flotation process is large, the flotation time is long, the resulting crude lithium carbonate product has low purity, and the production cost is high.

[0005] CN 102921553 A discloses a method for flotation of lithium potassium sulfate from a mixture of lithium potassium sulfate and sodium chloride, characterized by the following steps: (1) grinding lithium potassium sulfate and NaCl mixed salt to a grinding mass concentration of 50% to 60%, the grinding medium being a co-saturated mother liquor of lithium potassium sulfate and NaCl mixed salt to obtain a slurry; (2) feeding the slurry obtained in step (1) into a flotation machine, the flotation process being one roughing and one scavenging or one roughing and two scavenging, the flotation medium being a co-saturated mother liquor of lithium potassium sulfate and NaCl mixed salt, amine flotation reagents being added directly during roughing and scavenging, and flotation being carried out after stirring evenly, the dosage of flotation reagents being: 200g / t raw ore to 300g / t raw ore added during the roughing stage, and 100g / t raw ore to 150g / t raw ore added during the first scavenging stage. For the raw ore, if two scavenging processes are performed, the dosage of the reagent used in the second scavenging process is 0.5 to 1 times that of the first scavenging process. The reagent is added as follows: the reagent is prepared into an aqueous solution, heated, and added to the ore pulp after complete dissolution. The flotation temperature is room temperature; the roughing time is 4 to 6 minutes, and each scavenging process takes 3 to 5 minutes. This method is applied to a mixed salt of lithium potassium sulfate and sodium chloride. + The content is relatively high, and the particle size is relatively coarse. The grinding fineness needs to reach -200 mesh with a content of 65-90%. The flotation process involves one roughing and one scavenging or one roughing and two scavenging. The flotation process is complex and time-consuming, and the amount of ore fed into the flotation is large. It is difficult to apply to the field of ultra-low grade lithium carbonate mixed salts, resulting in high production costs. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the above-mentioned defects of the prior art and provide a method for extracting lithium carbonate from a mixed salt of low-grade lithium carbonate, potassium chloride and sodium chloride, which is simple in process, requires a small amount of ore to be fed into the flotation, has a short flotation time, produces high-purity lithium carbonate crude product, has low cost and high recovery rate.

[0007] The technical solution adopted by this invention to solve its technical problem is a method for extracting lithium carbonate from a mixed salt of low-grade lithium carbonate, potassium chloride, and sodium chloride, comprising the following steps:

[0008] (1) Grinding: The low-grade potassium chloride, sodium chloride and lithium carbonate mixed salt obtained by spreading and drying in the salt field is ground. The grinding medium is the co-saturated mother liquor of potassium chloride, sodium chloride and lithium carbonate mixed salt to obtain slurry;

[0009] (2) Screening: The slurry obtained in step (1) is fed into a screening machine or hydrocyclone for screening to obtain large gangue minerals and fine slurry.

[0010] (3) Separation of lithium carbonate from potassium chloride and sodium chloride: The slurry material obtained in step (2) is fed into a flotation machine, and lithium carbonate cationic collector is added for flotation. The flotation foam is lithium carbonate rough concentrate (mainly composed of lithium carbonate and sodium chloride), and the product in the flotation tank is rough tailings (mainly composed of sodium chloride and potassium chloride). Then the lithium carbonate rough concentrate is further refined to obtain refined lithium carbonate concentrate.

[0011] (4) Washing, filtering and drying: Wash and filter the lithium carbonate concentrate obtained in step (3), collect the solid, and dry the solid to obtain crude lithium carbonate product.

[0012] Furthermore, in step (1), the low-grade potassium chloride, sodium chloride, and lithium carbonate mixed salt is Li + Low-grade lithium carbonate mixed salt with a content of ≤0.5%.

[0013] Furthermore, in step (1), the grinding method is ball milling, rod milling, autogenous milling, or semi-autogenous milling; the grinding time is <1.5 min. The grinding time is determined based on the grinding fineness to achieve the individual dissociation of most lithium carbonate particles and gangue mineral particles, and the gangue mineral particles are not excessively ground. This invention only requires a short grinding time.

[0014] Furthermore, in step (1), the grinding fineness is -100 mesh with a mass content ≤25%; the grinding mass concentration is 50-80%. The grinding fineness and grinding concentration can be adjusted according to the actual situation.

[0015] Furthermore, in step (2), the mesh size of the screening machine is 18 to 200 mesh.

[0016] Furthermore, in step (3), the flotation time is ≤3 min; the flotation temperature is 5~30℃. Excessive flotation time leads to waste of the flotation cell and also increases the amount of gangue minerals entrained.

[0017] Furthermore, in step (3), the lithium carbonate cationic collector is a fatty amine or its derivative with 12-20 hydrocarbon carbon atoms. This type of collector has a prominent selective collecting effect on the low-grade lithium carbonate ore of the present invention, and its selectivity is relatively higher than that of anionic collectors.

[0018] Furthermore, in step (3), the fatty amines and their derivatives include, but are not limited to, octadecylamine hydrochloride, octadecylamine acetate, dodecylamine hydrochloride and dodecylamine acetate.

[0019] Furthermore, in step (3), the amount of lithium carbonate cationic collector added is 50 g / t to 150 g / t of raw ore. Excessive collector will lead to an increase in the amount of potassium chloride and sodium chloride floating, reducing the quality of the concentrate product; insufficient collector will lead to a decrease in the recovery rate of lithium carbonate in the concentrate.

[0020] Furthermore, in step (3), the number of selections is 0 to 5.

[0021] Furthermore, in step (4), the solution used for washing is a saturated lithium carbonate mother liquor.

[0022] Furthermore, in step (4), the washing may, but is not limited to, using heated washing.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] (1) This invention uses a lithium carbonate cationic collector positive flotation process to extract lithium carbonate from a mixed salt of low-grade lithium carbonate, sodium chloride and potassium chloride, which shortens the flotation time and effectively improves the flotation efficiency. At the same time, it was found that lithium carbonate crystals are relatively finer than gangue minerals sodium chloride and potassium chloride, and their coexistence is not very close. The invention creatively adopts a short-time grinding-screening-short-time flotation process to extract lithium carbonate, which greatly reduces the process cost.

[0025] (2) The present invention can extract lithium carbonate from low-Li grade lithium carbonate mixed salt, and the purity of the crude lithium carbonate product obtained is as high as 98.99%, with a comprehensive recovery rate of 50.12~75.21%. Detailed Implementation

[0026] The present invention will be further described below with reference to specific embodiments. It should be noted that the described embodiments are merely some, not all, of the present invention, and these embodiments should not be construed as limiting the scope of protection of the claims of this application. Based on the embodiments of the present invention, all other modifications or alterations obtained by those skilled in the art without inventive effort are within the scope of protection of the claims of this application. Example 1

[0027] Li-containing salts were obtained from salt pan drying in a carbonate-type salt lake in my country. + 0.108%, K + 13.59%, Na + 24.251%, CO3 2- 1.326%, Cl - This embodiment describes a method for extracting lithium carbonate from a 46.80% lithium carbonate mixed salt, comprising the following steps:

[0028] (1) Grinding: The mixed salt of potassium chloride, sodium chloride and lithium carbonate obtained by spreading and drying in the salt field is ground for 40 seconds, and then ground to -100 mesh with 10% content. The grinding medium is the co-saturated mother liquor of potassium chloride, sodium chloride and lithium carbonate mixed salt. The grinding mass concentration is 60% to obtain slurry.

[0029] (2) Screening: The slurry obtained in step (1) is poured into an 80-mesh high-frequency vibrating screen for screening to obtain large gangue minerals on the screen and fine slurry on the screen.

[0030] (3) Separation of lithium carbonate from potassium chloride and sodium chloride: The slurry of fine particles obtained in step (2) is fed into a flotation machine, and 50 g / t of octadecylamine hydrochloride collector is added. After stirring for 3 min, aeration and flotation are performed. The flotation time is 2 min and the flotation temperature is 22℃. The flotation foam is the lithium carbonate rough concentrate (the main components are lithium carbonate and sodium chloride). Then the rough concentrate is refined 4 times to obtain refined lithium carbonate concentrate.

[0031] (4) Washing, filtering and drying: The lithium carbonate concentrate obtained in step (3) is washed three times at 50°C using lithium carbonate saturated mother liquor, filtered, the solid is collected and dried to obtain crude lithium carbonate product.

[0032] The test results showed that the crude lithium carbonate product contained 98.01 wt% lithium carbonate, with a comprehensive recovery rate of 50.12%. Example 2

[0033] A brine in my country was evaporated to obtain Li-containing... + 0.36%, K + 12.65%, Na + 23.23%, CO3 2- 2.13%, Cl - 46.57%, SO4 2- This embodiment describes a method for extracting lithium carbonate from a 0.15% lithium carbonate mixed salt, comprising the following steps:

[0034] (1) Grinding: The mixed salt of potassium chloride, sodium chloride and lithium carbonate obtained by spreading and drying in the salt field is ground for 1 minute, and then ground to -100 mesh with 20% content. The grinding medium is the co-saturated mother liquor of potassium chloride, sodium chloride and lithium carbonate mixed salt. The grinding mass concentration is 65% to obtain slurry.

[0035] (2) Screening: The slurry obtained in step (1) is poured into a 60-mesh high-frequency vibrating screen for screening to obtain large gangue minerals on the screen and fine slurry on the screen.

[0036] (3) Separation of lithium carbonate from potassium chloride and sodium chloride: The slurry of fine particles obtained in step (2) is fed into a flotation machine, and 58 g / t of octadecylamine hydrochloride collector is added. After stirring for 3 min, aeration and flotation are performed. The flotation time is 2 min 30 s and the flotation temperature is 22℃. The flotation foam is the lithium carbonate rough concentrate (the main components are lithium carbonate and sodium chloride). Then the rough concentrate is refined 3 times to obtain refined lithium carbonate concentrate.

[0037] (4) Washing, filtering and drying: The lithium carbonate concentrate obtained in step (3) is washed twice with lithium carbonate saturated mother liquor at 40°C, filtered, the solid is collected and dried to obtain crude lithium carbonate product.

[0038] The test results showed that the crude lithium carbonate product contained 98.01 wt% lithium carbonate, with a comprehensive recovery rate of 69.33%. Example 3

[0039] Li-containing salt was obtained from a salt lake in my country through salt field drying. + 0.41%, K + 11.78%, Na + 22.79%, CO3 2- 2.13%, Cl - 45.19%, SO4 2- This embodiment describes a method for extracting lithium carbonate from a 0.36% lithium carbonate mixed salt, comprising the following steps:

[0040] (1) Grinding: The mixed salt of potassium chloride, sodium chloride and lithium carbonate obtained by spreading and drying in the salt field is ground for 1 minute, and then ground to -100 mesh with 20% content. The grinding medium is the co-saturated mother liquor of potassium chloride, sodium chloride and lithium carbonate mixed salt. The grinding mass concentration is 65% to obtain slurry.

[0041] (2) Screening: The slurry obtained in step (1) is poured into a 60-mesh high-frequency vibrating screen for screening to obtain large gangue minerals on the screen and fine slurry on the screen.

[0042] (3) Separation of lithium carbonate from potassium chloride and sodium chloride: The slurry of fine particles obtained in step (2) is fed into a flotation machine, and 80 g / t of octadecylamine hydrochloride collector is added. After stirring for 3 min, aeration and flotation are performed. The flotation time is 3 min and the flotation temperature is 25℃. The flotation foam is the lithium carbonate rough concentrate (the main components are lithium carbonate and sodium chloride). Then the rough concentrate is refined twice to obtain refined lithium carbonate concentrate.

[0043] (4) Washing, filtering and drying: The lithium carbonate concentrate obtained in step (3) is washed three times at 60°C using lithium carbonate saturated mother liquor, filtered, the solid is collected and dried to obtain crude lithium carbonate product.

[0044] The test results showed that the crude lithium carbonate product contained 98.99 wt% lithium carbonate, with a comprehensive recovery rate of 75.21%.

Claims

1. A method for extracting lithium carbonate from a mixed salt of low-grade lithium carbonate, potassium chloride, and sodium chloride, characterized in that, Includes the following steps: (1) Grinding: The low-grade potassium chloride, sodium chloride and lithium carbonate mixed salt obtained by spreading and drying in the salt field is ground. The grinding medium is the co-saturated mother liquor of potassium chloride, sodium chloride and lithium carbonate mixed salt to obtain slurry; the grinding time is <1.5min; (2) Screening: The slurry obtained in step (1) is fed into a screening machine or hydrocyclone for screening to obtain large gangue minerals and fine slurry. (3) Separation of lithium carbonate from potassium chloride and sodium chloride: The fine particle slurry obtained in step (2) is fed into a flotation machine, and lithium carbonate cationic collector is added for flotation. The flotation foam is lithium carbonate rough concentrate. Then the lithium carbonate rough concentrate is further refined to obtain lithium carbonate refined concentrate. The flotation time is ≤3min. (4) Washing, filtering and drying: Wash and filter the lithium carbonate concentrate obtained in step (3), collect the solid, and dry the solid to obtain crude lithium carbonate product.

2. The method for extracting lithium carbonate from a mixed salt of low-grade lithium carbonate, potassium chloride, and sodium chloride according to claim 1, characterized in that, In step (1), the low-grade potassium chloride, sodium chloride, and lithium carbonate mixed salt is Li + Low-grade lithium carbonate mixed salt with a content of ≤0.5%.

3. The method for extracting lithium carbonate from a mixed salt of low-grade lithium carbonate, potassium chloride, and sodium chloride according to claim 1 or 2, characterized in that, In step (1), the grinding method is ball milling, rod milling, autogenous milling, or semi-autogenous milling.

4. The method for extracting lithium carbonate from a mixed salt of low-grade lithium carbonate, potassium chloride, and sodium chloride according to claim 1 or 2, characterized in that, In step (1), the fineness of the grinding is -100 mesh with a mass content of ≤25%, and the mass concentration of the grinding is 50-80%.

5. The method for extracting lithium carbonate from a mixed salt of low-grade lithium carbonate, potassium chloride, and sodium chloride according to claim 3, characterized in that, In step (1), the fineness of the grinding is -100 mesh with a mass content of ≤25%, and the mass concentration of the grinding is 50-80%.

6. The method for extracting lithium carbonate from a mixed salt of low-grade lithium carbonate, potassium chloride, and sodium chloride according to claim 1 or 2, characterized in that, In step (2), the mesh size of the screening machine is 18 to 200 mesh.

7. The method for extracting lithium carbonate from a mixed salt of low-grade lithium carbonate, potassium chloride, and sodium chloride according to claim 1 or 2, characterized in that, In step (3), the flotation temperature is 5 to 30°C.

8. The method for extracting lithium carbonate from a mixed salt of low-grade lithium carbonate, potassium chloride, and sodium chloride according to claim 1 or 2, characterized in that, In step (3), the lithium carbonate cationic collector is a fatty amine or its derivative with 12-20 hydrocarbon carbon atoms.

9. The method for extracting lithium carbonate from a mixed salt of low-grade lithium carbonate, potassium chloride, and sodium chloride according to claim 8, characterized in that, In step (3), the fatty amine and its derivatives are at least one of octadecylamine hydrochloride, octadecylamine acetate, dodecylamine hydrochloride, and dodecylamine acetate.

10. The method for extracting lithium carbonate from a mixed salt of low-grade lithium carbonate, potassium chloride, and sodium chloride according to claim 1 or 2, characterized in that, In step (3), the amount of lithium carbonate cationic collector added is 50-150 g / t of raw ore.

11. The method for extracting lithium carbonate from a mixed salt of low-grade lithium carbonate, potassium chloride, and sodium chloride according to claim 1 or 2, characterized in that, In step (4), the washing solution used is a saturated lithium carbonate mother liquor.

12. The method for extracting lithium carbonate from a mixed salt of low-grade lithium carbonate, potassium chloride, and sodium chloride according to claim 3, characterized in that, In step (4), the washing solution used is a saturated lithium carbonate mother liquor.

13. The method for extracting lithium carbonate from a mixed salt of low-grade lithium carbonate, potassium chloride, and sodium chloride according to claim 4, characterized in that, In step (4), the washing solution used is a saturated lithium carbonate mother liquor.

14. The method for extracting lithium carbonate from a mixed salt of low-grade lithium carbonate, potassium chloride, and sodium chloride according to claim 6, characterized in that, In step (4), the washing solution used is a saturated lithium carbonate mother liquor.

15. The method for extracting lithium carbonate from a mixed salt of low-grade lithium carbonate, potassium chloride, and sodium chloride according to claim 7, characterized in that, In step (4), the washing solution used is a saturated lithium carbonate mother liquor.