A method for preparing high-grade lithium phosphate from lithium precipitation mother liquor

Abstract

This invention discloses a method for preparing high-grade lithium phosphate from lithium precipitation mother liquor. Using lithium precipitation mother liquor as raw material, it is mixed and reacted with sodium dihydrogen phosphate dihydrate solution to obtain a lithium phosphate slurry. After pressure filtration, heating, slurry washing, washing, flash drying, and packaging, the high-grade lithium phosphate product is finally produced. This method is not only effective and practical, but also improves the quality of lithium phosphate products, meeting the needs of downstream customers. It also increases the recycling rate of lithium precipitation mother liquor, reduces external discharge, and achieves a lithium-free, green, closed-loop production process from salt fields to lithium phosphate products.

Description

Technical Field

[0001] This invention relates to the technical field of high-grade lithium phosphate preparation methods, specifically to a method for preparing high-grade lithium phosphate from lithium precipitation mother liquor. Background Technology

[0002] While the increasingly sophisticated lithium extraction technology from salt lakes has greatly promoted the development of the new energy industry, a problem remains: lithium is sometimes lost due to entrainment in the mother liquor discharged after lithium carbonate production from salt lakes. To prevent this loss, lithium salt products are typically prepared from the mother liquor, especially since it is favored for its low impurity content after removing calcium, magnesium, and boron. The industry of producing crude lithium phosphate from this mother liquor has experienced explosive growth. However, the preparation of lithium phosphate from the mother liquor can introduce new impurities depending on the precipitant used, making it difficult to meet the needs of downstream customers. Without further processing, the product cannot be directly used in the new energy field.

[0003] In summary, there is a particular need for a method to prepare high-grade lithium phosphate based on lithium precipitation mother liquor, in order to solve the problem that the lithium phosphate products produced by existing processes are of low quality and cannot meet the requirements of downstream customers. Summary of the Invention

[0004] Based on the above-mentioned technical problems, the purpose of this invention is to provide a method for preparing high-grade lithium phosphate from lithium precipitation mother liquor.

[0005] This invention protects a method for preparing high-grade lithium phosphate from lithium precipitation mother liquor. The method uses lithium precipitation mother liquor as raw material, mixes and reacts it with sodium dihydrogen phosphate dihydrate solution to obtain a lithium phosphate slurry. After pressure filtration, heating, slurry washing, washing, flash drying, and packaging, a high-grade lithium phosphate product is finally produced. The specific steps include the following:

[0006] Step 1, Adjusting and heating the lithium precipitation mother liquor: Adjust the lithium precipitation mother liquor to an alkaline pH ≥ 12 and heat it to 70-90℃;

[0007] Step 2, Preparation of sodium dihydrogen phosphate dihydrate solution: Prepare sodium dihydrogen phosphate dihydrate solution by mixing pure water and sodium dihydrogen phosphate dihydrate at a liquid-to-solid ratio of 2:1.

[0008] Step 3, Precipitation Conversion: The above lithium precipitation mother liquor and sodium dihydrogen phosphate dihydrate solution are mixed to form a lithium phosphate slurry, and the Li content in the lithium precipitation mother liquor is detected. + Content, PO4 in sodium dihydrogen phosphate dihydrate solution 3- To determine the content, adjust the amount of sodium dihydrogen phosphate dihydrate solution added based on the measured data, and the reaction time is 50–70 min.

[0009] Step 4, Filtration separation: The fully reacted lithium phosphate slurry is separated by a filter press to obtain wet lithium phosphate;

[0010] Step 5, RO water heating: Heat the RO water used for washing the wet lithium phosphate product to 50-55℃;

[0011] Step 6, Washing: After pressure filtration and separation of the lithium phosphate slurry, pour the wet lithium phosphate into the reactor, and simultaneously add constant temperature water at a solid-liquid ratio of 1:4-7. Stir and wash for 20-40 minutes at a stirring speed of 100-300 r / min to remove Na from the wet lithium phosphate. + Cl - The wet material is obtained by filtration and then used for later use.

[0012] Step 7, Washing: Wash the wet lithium phosphate material after slurrying with warm water at 45-55℃ in small amounts and multiple times, while testing the indicators of the wet lithium phosphate material. Stop washing after the required indicators are met.

[0013] Step 8, flash drying, conveying and packaging: The wet lithium phosphate material after washing and meeting the standards in Step 7 is flash dried to ensure that the moisture content of the dry lithium phosphate material is ≤2%, thereby obtaining a high-grade lithium phosphate product, which is then conveyed and packaged.

[0014] Furthermore, in step 1, a plate heat exchanger is used for circulating heating, and NaOH is used for adjustment; the lithium content in the lithium precipitation mother liquor is 1.0-2.0 g / L.

[0015] Furthermore, in step 5, a plate heat exchanger is used for cyclic heating.

[0016] Furthermore, in step 6, the constant temperature water added to the reactor is 45-55°C.

[0017] Furthermore, in step 7, the required main content of the obtained lithium phosphate product is 97-98%, and the lithium phosphate yield reaches over 98%. - The content decreased to 0.02-0.04%, Na + The content decreased to 0.70-0.90%.

[0018] Furthermore, in step 7, the warm water can be the washing liquid after sizing, so as to achieve the purpose of recycling and saving water.

[0019] Compared with existing technologies, the present invention has the following beneficial effects:

[0020] The method of this invention has a simple process flow, low production cost, and no by-product precipitation throughout the process. It is not only effective and practical, but also improves the quality of lithium phosphate products, meets the needs of downstream customers, and increases the recovery rate of lithium precipitation mother liquor, reducing external discharge. It achieves a green closed-loop production effect with zero lithium discharge from salt fields to lithium phosphate products. Moreover, it also improves the overall yield of lithium phosphate, further increasing production revenue and significantly increasing profit margins. Attached Figure Description

[0021] Figure 1 This is a process flow diagram of the method of the present invention. Detailed Implementation

[0022] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] Example 1

[0024] A method for preparing high-grade lithium phosphate from lithium precipitation mother liquor involves using lithium precipitation mother liquor as raw material, mixing and reacting it with sodium dihydrogen phosphate dihydrate solution to obtain lithium phosphate slurry. After pressure filtration, heating, slurry washing, washing, flash drying, and packaging, the final product is high-grade lithium phosphate. The specific steps include the following:

[0025] Step 1, Adjusting and heating the lithium precipitation mother liquor: Adjust the lithium precipitation mother liquor (the lithium content in the lithium precipitation mother liquor is 1.42g / L) to alkaline pH=12 with NaOH, and use a plate heat exchanger to circulate and heat it to 75℃;

[0026] Step 2, Preparation of sodium dihydrogen phosphate dihydrate solution: Prepare sodium dihydrogen phosphate dihydrate solution by mixing pure water and sodium dihydrogen phosphate dihydrate at a liquid-to-solid ratio of 2:1.

[0027] Step 3, Precipitation Conversion: The above lithium precipitation mother liquor and sodium dihydrogen phosphate dihydrate solution are mixed to form a lithium phosphate slurry, and the Li content in the lithium precipitation mother liquor is detected. + Content, PO4 in sodium dihydrogen phosphate dihydrate solution 3- To determine the content, adjust the amount of sodium dihydrogen phosphate dihydrate solution added based on the measured data, and the reaction time is 60 min.

[0028] Step 4, Filtration separation: The fully reacted lithium phosphate slurry is separated by a filter press to obtain wet lithium phosphate;

[0029] Step 5, RO water heating: The RO water used for washing wet lithium phosphate products is heated to 50°C by circulating it through a plate heat exchanger.

[0030] Step 6, Washing: After pressure filtration and separation of the lithium phosphate slurry, pour the wet lithium phosphate into the reactor, and simultaneously add 50℃ constant temperature water at a solid-liquid ratio of 1:5. Stir and wash for 30 minutes at a stirring speed of 200 r / min to remove Na from the wet lithium phosphate. + Cl - The wet material is obtained by filtration and then used for later use.

[0031] Step 7, Washing: Wash the wet lithium phosphate material after slurry washing with 50℃ warm water (washing liquid after slurry washing) in small amounts multiple times, while testing the indicators of the wet lithium phosphate material. Stop washing after the required indicators are met; the required indicators for the obtained lithium phosphate product are: main content 97.68%, lithium phosphate yield ≥ 98.67%, and Cl - The content decreased to 0.031%, Na + The content decreased to 0.788%;

[0032] Step 8, flash drying, conveying and packaging: The wet lithium phosphate material after washing and meeting the standards in Step 7 is flash dried to ensure that the moisture content of the dry lithium phosphate material is ≤2%, thereby obtaining a high-grade lithium phosphate product, which is then conveyed and packaged.

[0033] Example 2

[0034] A method for preparing high-grade lithium phosphate from lithium precipitation mother liquor, comprising the following specific steps:

[0035] Step 1, Adjusting and heating the lithium precipitation mother liquor: Adjust the lithium precipitation mother liquor (the lithium content in the lithium precipitation mother liquor is 1.0g / L) to alkaline pH=12.5 with NaOH, and use a plate heat exchanger to circulate and heat it to 70℃;

[0036] Step 2, Preparation of sodium dihydrogen phosphate dihydrate solution: Prepare sodium dihydrogen phosphate dihydrate solution by mixing pure water and sodium dihydrogen phosphate dihydrate at a liquid-to-solid ratio of 2:1.

[0037] Step 3, Precipitation Conversion: The above lithium precipitation mother liquor and sodium dihydrogen phosphate dihydrate solution are mixed to form a lithium phosphate slurry, and the Li content in the lithium precipitation mother liquor is detected. + Content, PO4 in sodium dihydrogen phosphate dihydrate solution 3- To determine the content, adjust the amount of sodium dihydrogen phosphate dihydrate solution added based on the measured data, and the reaction time is 50 min.

[0038] Step 4, Filtration separation: The fully reacted lithium phosphate slurry is separated by a filter press to obtain wet lithium phosphate;

[0039] Step 5, RO water heating: The RO water used for washing wet lithium phosphate products is heated to 52°C by circulating it through a plate heat exchanger.

[0040] Step 6, Washing: After pressure filtration and separation of the lithium phosphate slurry, pour the wet lithium phosphate into the reactor, and simultaneously add 45℃ constant temperature water at a solid-liquid ratio of 1:6. Stir and wash for 40 minutes at a stirring speed of 300 r / min to remove Na from the wet lithium phosphate. + Cl - The wet material is obtained by filtration and then used for later use.

[0041] Step 7, Washing: Wash the wet lithium phosphate material after slurry washing with 45℃ warm water (washing liquid after slurry washing) in small amounts multiple times, while testing the indicators of the wet lithium phosphate material. Stop washing after the required indicators are met; the required indicators for the obtained lithium phosphate product are: main content of 97.36%, lithium phosphate yield of 98.48% or higher, and Cl... - The content decreased to 0.035%, Na + The content decreased to 0.84%;

[0042] Step 8, flash drying, conveying and packaging: The wet lithium phosphate material after washing and meeting the standards in Step 7 is flash dried to ensure that the moisture content of the dry lithium phosphate material is ≤2%, thereby obtaining a high-grade lithium phosphate product, which is then conveyed and packaged.

[0043] Example 3

[0044] A method for preparing high-grade lithium phosphate from lithium precipitation mother liquor, comprising the following specific steps:

[0045] Step 1, Adjusting and heating the lithium precipitation mother liquor: Adjust the lithium precipitation mother liquor (the lithium content in the lithium precipitation mother liquor is 1.5g / L) to alkaline pH=13 with NaOH, and use a plate heat exchanger to circulate and heat it to 80℃;

[0046] Step 2, Preparation of sodium dihydrogen phosphate dihydrate solution: Prepare sodium dihydrogen phosphate dihydrate solution by mixing pure water and sodium dihydrogen phosphate dihydrate at a liquid-to-solid ratio of 2:1.

[0047] Step 3, Precipitation Conversion: The above lithium precipitation mother liquor and sodium dihydrogen phosphate dihydrate solution are mixed to form a lithium phosphate slurry, and the Li content in the lithium precipitation mother liquor is detected. + Content, PO4 in sodium dihydrogen phosphate dihydrate solution 3- To determine the content, adjust the amount of sodium dihydrogen phosphate dihydrate solution added based on the measured data, and the reaction time is 60 min.

[0048] Step 4, Filtration separation: The fully reacted lithium phosphate slurry is separated by a filter press to obtain wet lithium phosphate;

[0049] Step 5, RO water heating: The RO water used for washing the wet lithium phosphate product is heated to 54°C by circulating it using a plate heat exchanger.

[0050] Step 6, Washing: After pressure filtration and separation of the lithium phosphate slurry, pour the wet lithium phosphate into the reactor, and simultaneously add 50℃ constant temperature water at a solid-liquid ratio of 1:7. Stir and wash for 30 minutes at a stirring speed of 200 r / min to remove Na from the wet lithium phosphate. + Cl - The wet material is obtained by filtration and then used for later use.

[0051] Step 7, Washing: Wash the wet lithium phosphate material after slurry washing with 50℃ warm water (washing liquid after slurry washing) in small amounts multiple times, while testing the indicators of the wet lithium phosphate material. Stop washing after the required indicators are met; the required indicators for the obtained lithium phosphate product are: main content of 97.98%, lithium phosphate yield of 98.85% or higher, and Cl - The content decreased to 0.021%, Na + The content decreased to 0.073%;

[0052] Step 8, flash drying, conveying and packaging: The wet lithium phosphate material after washing and meeting the standards in Step 7 is flash dried to ensure that the moisture content of the dry lithium phosphate material is ≤2%, thereby obtaining a high-grade lithium phosphate product, which is then conveyed and packaged.

[0053] Example 4

[0054] A method for preparing high-grade lithium phosphate from lithium precipitation mother liquor, comprising the following specific steps:

[0055] Step 1, Adjusting and heating the lithium precipitation mother liquor: Adjust the lithium precipitation mother liquor (lithium content in the lithium precipitation mother liquor is 2.0g / L) to alkaline pH=13.5 with NaOH, and use a plate heat exchanger to circulate and heat it to 90℃;

[0056] Step 2, Preparation of sodium dihydrogen phosphate dihydrate solution: Prepare sodium dihydrogen phosphate dihydrate solution by mixing pure water and sodium dihydrogen phosphate dihydrate at a liquid-to-solid ratio of 2:1.

[0057] Step 3, Precipitation Conversion: The above lithium precipitation mother liquor and sodium dihydrogen phosphate dihydrate solution are mixed to form a lithium phosphate slurry, and the Li content in the lithium precipitation mother liquor is detected. + Content, PO4 in sodium dihydrogen phosphate dihydrate solution 3- To determine the content, adjust the amount of sodium dihydrogen phosphate dihydrate solution added based on the measured data, and the reaction time is 70 min.

[0058] Step 4, Filtration separation: The fully reacted lithium phosphate slurry is separated by a filter press to obtain wet lithium phosphate;

[0059] Step 5, RO water heating: The RO water used for washing wet lithium phosphate products is heated to 55°C by circulating it through a plate heat exchanger.

[0060] Step 6, Washing: After pressure filtration and separation of the lithium phosphate slurry, pour the wet lithium phosphate into the reactor, and simultaneously add 55℃ constant temperature water at a solid-liquid ratio of 1:4. Stir and wash for 20 minutes at a stirring speed of 100 r / min to remove Na from the wet lithium phosphate. + Cl - The wet material is obtained by filtration and then used for later use.

[0061] Step 7, Washing: Wash the wet lithium phosphate material after slurry washing with 55℃ warm water (washing liquid after slurry washing) in small amounts multiple times, while testing the indicators of the wet lithium phosphate material. Stop washing after the required indicators are met; the required indicators for the obtained lithium phosphate product are a main content of 97.22% and a lithium phosphate yield of over 98.16%, Cl - The content decreased to 0.04%, Na + The content decreased to 0.90%;

[0062] Step 8: Flash dry the wet lithium phosphate material after washing in Step 7 to ensure that the moisture content of the dry lithium phosphate material is ≤2%, thereby obtaining a high-grade lithium phosphate product, which is then transported and packaged.

[0063] 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 method for preparing high-grade lithium phosphate from lithium precipitation mother liquor, characterized in that: Using lithium precipitation mother liquor as raw material, it is mixed and reacted with sodium dihydrogen phosphate dihydrate solution to obtain lithium phosphate slurry. After pressure filtration, heating, slurry washing, washing, flash drying, conveying and packaging, high-grade lithium phosphate product is finally produced. The specific steps include the following: Step 1, Adjusting and heating the lithium precipitation mother liquor: Adjust the lithium precipitation mother liquor to alkaline pH ≥ 12, and heat it to 70-90℃; use a plate heat exchanger for circulating heating, and adjust the temperature with NaOH; the lithium content in the lithium precipitation mother liquor is 1.0-2.0 g / L; Step 2, Preparation of sodium dihydrogen phosphate dihydrate solution: Prepare sodium dihydrogen phosphate dihydrate solution by mixing pure water and sodium dihydrogen phosphate dihydrate at a liquid-to-solid ratio of 2:

1. Step 3, precipitation conversion: the above lithium precipitation mother liquor and sodium dihydrogen phosphate dihydrate solution are mixed into lithium phosphate slurry, and the Li + content in the lithium precipitation mother liquor, the PO4 3- content in the sodium dihydrogen phosphate dihydrate solution is detected, the amount of sodium dihydrogen phosphate dihydrate solution is adjusted according to the measured data, and the reaction time is 50-70 min. Step 4, Filtration separation: The fully reacted lithium phosphate slurry is separated by a filter press to obtain wet lithium phosphate; Step 5, RO water heating: Heat the RO water used for washing the wet lithium phosphate product to 50-55℃; Step 6, slurry washing: after the lithium phosphate slurry is separated by pressure filtration, the lithium phosphate wet material is poured into a reaction kettle, constant temperature water is added according to a solid-liquid ratio of 1:4-7, and the lithium phosphate wet material is washed for 20-40 min at a stirring speed of 100-300 r / min to wash out Na + , Cl - from the lithium phosphate wet material, and then filtered to obtain the wet material for standby use; Step 7, Washing: Wash the wet lithium phosphate material after slurrying with warm water at 45-55℃ in small batches, while testing the indicators of the wet lithium phosphate material. Stop washing after the required indicators are met; the required indicators for the obtained lithium phosphate product are a main content of 97-98% and a lithium phosphate yield of over 98%. - The content decreased to 0.02-0.04%, Na + The content is reduced to 0.70-0.90%; the warm water can be the washing liquid after sizing. Step 8, flash drying, conveying and packaging: The wet lithium phosphate material after washing and meeting the standards in Step 7 is flash dried to ensure that the moisture content of the dry lithium phosphate material is ≤2%, thereby obtaining a high-grade lithium phosphate product, which is then conveyed and packaged.

2. The method for preparing high-grade lithium phosphate from lithium precipitation mother liquor according to claim 1, characterized in that: In step 5, a plate heat exchanger is used for cyclic heating.

3. The method for preparing high-grade lithium phosphate from lithium precipitation mother liquor according to claim 1, characterized in that: In step 6, the constant temperature water added to the reactor is 45-55°C.

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