Secondary lithium precipitation system for producing lithium carbonate by sulfuric acid method

Abstract

The utility model discloses a secondary lithium precipitation system for producing lithium carbonate by a sulfuric acid method, and solves the technical problem that battery-grade lithium carbonate cannot be recycled from primary lithium precipitation mother liquor in the prior art. The device comprises a primary lithium precipitation mother liquor clear liquid tank, decarburization evaporation equipment connected out of the primary lithium precipitation mother liquor clear liquid tank, an MVR freezing crystallizer connected out of the decarburization evaporation equipment, a secondary lithium precipitation reaction kettle connected out of the MVR freezing crystallizer, and lithium carbonate roughing equipment connected out of the secondary lithium precipitation reaction kettle, the lithium carbonate roughing equipment is connected to lithium carbonate refining equipment for refining battery-grade lithium carbonate, the decarburization evaporation equipment is connected with a concentrated sulfuric acid conveying pipe, and the secondary lithium precipitation reaction kettle is connected to a sodium carbonate head tank. According to the utility model, the glaserite can be separated from the primary lithium precipitation mother liquor through decarbonization and evaporation, then the byproduct high-purity sodium sulfate product is obtained through MVR freezing crystallization, and finally the battery-grade lithium carbonate is obtained through the lithium carbonate refining equipment, so that the device is suitable for industrial application and has great economic value.

Description

Technical Field

[0001] The utility model belongs to the technical field of lithium carbonate production, and specifically relates to a secondary lithium precipitation system for producing lithium carbonate by a sulfuric acid process. Background Art

[0002] In the prior art, there are two main processes for extracting lithium from lithium ore: the lime method and the sulfuric acid method. The main principle of the sulfuric acid method is to use sulfuric acid to dissolve the metal oxides in the lithium ore to generate sulfates to obtain acidified clinker. After pulping and impurity removal, the acidified clinker is subjected to a lithium precipitation process, and the precipitate is refined to obtain lithium carbonate; the mother liquor after the first lithium precipitation still contains some lithium ions and impurities. In the prior art, the mother liquor after the first lithium precipitation is usually treated with a secondary lithium precipitation method to recover lithium ions, but the obtained lithium carbonate is usually industrial grade, and the by-product is a mixed salt of sodium potassium sulfate, and the overall economic value is not high.

[0003] Compared with industrial-grade lithium carbonate, battery-grade lithium carbonate has higher purity requirements. Battery-grade lithium carbonate is a raw material used in the production of lithium-ion batteries, and its purity requirement is usually above 99.9%, and its impurity content requirement is higher. Therefore, providing a secondary lithium precipitation system for producing lithium carbonate by sulfuric acid method, which can obtain high-purity battery-grade lithium carbonate from the primary lithium precipitation mother liquor and produce high-purity salt as a by-product, has become a technical problem that needs to be solved urgently by technicians in this field. Utility Model Content

[0004] The technical problem to be solved by the utility model is to provide a secondary lithium precipitation system for producing lithium carbonate by sulfuric acid method, so as to solve the technical problem that battery-grade lithium carbonate cannot be recovered from the primary lithium precipitation mother liquor in the prior art.

[0005] In order to achieve the above purpose, the technical solution adopted by the utility model is as follows:

[0006] A secondary lithium precipitation system for producing lithium carbonate by a sulfuric acid process comprises a primary lithium precipitation mother liquor clear liquid tank, a decarbonization evaporation device connected to the primary lithium precipitation mother liquor clear liquid tank, an MVR freezing crystallizer connected to the decarbonization evaporation device, a secondary lithium precipitation reactor connected to the MVR freezing crystallizer, and a lithium carbonate crude equipment connected to the secondary lithium precipitation reactor; the lithium carbonate crude equipment is connected to a lithium carbonate refining device for refining battery-grade lithium carbonate, the decarbonization evaporation device is connected to a concentrated sulfuric acid delivery pipe, and the secondary lithium precipitation reactor is connected to a sodium carbonate high-level tank.

[0007] Furthermore, the decarbonization evaporation equipment includes a decarbonization kettle connected to the primary lithium precipitation mother liquor clear liquid tank, and an MVR evaporator connected to the decarbonization kettle; the concentrated sulfuric acid delivery pipe is connected to the decarbonization kettle, and the MVR evaporator is connected to the MVR freezing crystallizer.

[0008] Furthermore, the MVR evaporator is connected to a condensate water pool and a glauberite transmission line.

[0009] Furthermore, the MVR freezing crystallizer is connected to a sodium sulfate transmission line.

[0010] Furthermore, the lithium carbonate crude equipment includes a secondary lithium precipitation centrifuge A connected to the secondary lithium precipitation reactor, a secondary crude lithium carbonate slurry tank connected to the solid phase outlet of the secondary lithium precipitation centrifuge A, a secondary lithium precipitation and washing high-level tank connected to the secondary crude lithium carbonate slurry tank, and a secondary lithium precipitation and washing centrifuge connected to the secondary lithium precipitation and washing high-level tank; the solid phase outlet of the secondary lithium precipitation and washing centrifuge is connected to the lithium carbonate refining equipment.

[0011] Furthermore, the secondary crude lithium carbonate slurrying tank is connected to a pure water delivery pipe.

[0012] Furthermore, the liquid phase outlet of the secondary lithium precipitation centrifuge is connected to the primary lithium precipitation mother liquor clear liquid tank.

[0013] Furthermore, the liquid phase outlet of the secondary lithium washing centrifuge is connected to the plant's water recovery and recycling system.

[0014] Furthermore, the lithium carbonate refining equipment is a lithium carbonate carbonization thermal analysis system.

[0015] Compared with the prior art, the utility model has the following beneficial effects:

[0016] The utility model has a simple structure and a scientific and reasonable design. It can first decarbonize and evaporate the potassium glauberite from the primary lithium precipitation mother liquor, then obtain the by-product high-purity sodium sulfate product through MVR freezing crystallization, and finally obtain battery-grade lithium carbonate through lithium carbonate refining equipment. It effectively solves the technical problem that the traditional technology cannot prepare battery-grade lithium carbonate and by-product high-purity sodium sulfate products from the primary lithium precipitation mother liquor. Compared with the traditional technology that can only prepare industrial-grade lithium carbonate and by-product sodium potassium sulfate mixed salt from the primary lithium precipitation mother liquor, the utility model system is more suitable for industrial application and has great economic value. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a schematic diagram of the system structure of the utility model.

[0018] The names corresponding to the reference numerals are:

[0019] 1-primary lithium precipitation mother liquor clear liquid tank, 2-MVR freezing crystallizer, 3-secondary lithium precipitation reaction kettle, 4-concentrated sulfuric acid delivery pipe, 5-decarbonization kettle, 6-MVR evaporator, 7-condensate water pool, 8-glauberite external transmission line, 9-sodium sulfate external transmission line, 10-sodium carbonate high-level tank, 11-lithium carbonate carbonization thermal analysis system, 12-secondary lithium precipitation centrifuge, 13-secondary crude lithium carbonate slurry tank, 14-secondary lithium precipitation and washing high-level tank, 15-secondary lithium precipitation and washing centrifuge, 16-pure water delivery pipe. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical solution and advantages of the utility model more clear, the utility model is further described in detail below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the utility model.

[0021] Example 1.

[0022] like Figure 1 As shown, the utility model provides a secondary lithium precipitation system for producing lithium carbonate by the sulfuric acid method, comprising a primary lithium precipitation mother liquor clear liquid tank 1, a decarbonization evaporation device connected to the primary lithium precipitation mother liquor clear liquid tank 1, an MVR freezing crystallizer 2 connected to the decarbonization evaporation device, a secondary lithium precipitation reactor 3 connected to the MVR freezing crystallizer 2, and a lithium carbonate crude equipment connected to the secondary lithium precipitation reactor 3; the lithium carbonate crude equipment is connected to a lithium carbonate refining device for refining battery-grade lithium carbonate, the decarbonization evaporation device is connected to a concentrated sulfuric acid delivery pipe 4, and the secondary lithium precipitation reactor 3 is connected to a sodium carbonate high-level tank 10 for delivering sodium carbonate to the secondary lithium precipitation reactor 3 for lithium precipitation.

[0023] The utility model has a simple structure and a scientific and reasonable design. It can first decarbonize and evaporate the potassium glauberite from the primary lithium precipitation mother liquor, then obtain the by-product high-purity sodium sulfate product through MVR freezing crystallization, and finally obtain battery-grade lithium carbonate through lithium carbonate refining equipment. It effectively solves the technical problem that the traditional technology cannot prepare battery-grade lithium carbonate and by-product high-purity sodium sulfate products from the primary lithium precipitation mother liquor. Compared with the traditional technology that can only prepare industrial-grade lithium carbonate and by-product sodium potassium sulfate mixed salt from the primary lithium precipitation mother liquor, the utility model system is more suitable for industrial application and has great economic value.

[0024] Example 2.

[0025] like Figure 1 As shown, the utility model provides a secondary lithium precipitation system for producing lithium carbonate by sulfuric acid method, including a primary lithium precipitation mother liquor clear liquid tank 1, a decarbonization evaporation device connected from the primary lithium precipitation mother liquor clear liquid tank 1, an MVR freezing crystallizer 2 connected from the decarbonization evaporation device, a secondary lithium precipitation reactor 3 connected from the MVR freezing crystallizer 2, and a lithium carbonate crude equipment connected from the secondary lithium precipitation reactor 3; the lithium carbonate crude equipment is connected to a lithium carbonate refining device for refining battery-grade lithium carbonate, the decarbonization evaporation device is connected to a concentrated sulfuric acid delivery pipe 4, and the secondary lithium precipitation reactor 3 is connected to a sodium carbonate high-level tank 10.

[0026] The decarbonization evaporation equipment includes a decarbonization kettle 5 connected to the primary lithium precipitation mother liquor clear liquid tank 1, and an MVR evaporator 6 connected to the decarbonization kettle 5; a concentrated sulfuric acid delivery pipe 4 is connected to the decarbonization kettle 5, and the MVR evaporator 6 is connected to the MVR freezing crystallizer 2.

[0027] Based on Example 1, this Example 2 provides a more preferred structure of the decarbonization evaporation equipment. Specifically, the decarbonization evaporation equipment includes a decarbonization kettle 5 connected to the primary lithium precipitation mother liquor clear liquid tank 1, and an MVR evaporator 6 connected to the decarbonization kettle 5; a concentrated sulfuric acid delivery pipe 4 is connected to the decarbonization kettle 5, and the MVR evaporator 6 is connected to the MVR freezing crystallizer 2. Sulfuric acid solution is added to the primary lithium precipitation mother liquor to remove carbonate; the decarbonized mother liquor is concentrated using an MVR high-efficiency evaporator. The evaporated and concentrated mother liquor is cooled to separate potassium glauberite.

[0028] Example 3.

[0029] like Figure 1 As shown, the utility model provides a secondary lithium precipitation system for producing lithium carbonate by sulfuric acid method, including a primary lithium precipitation mother liquor clear liquid tank 1, a decarbonization evaporation device connected from the primary lithium precipitation mother liquor clear liquid tank 1, an MVR freezing crystallizer 2 connected from the decarbonization evaporation device, a secondary lithium precipitation reactor 3 connected from the MVR freezing crystallizer 2, and a lithium carbonate crude equipment connected from the secondary lithium precipitation reactor 3; the lithium carbonate crude equipment is connected to a lithium carbonate refining device for refining battery-grade lithium carbonate, the decarbonization evaporation device is connected to a concentrated sulfuric acid delivery pipe 4, and the secondary lithium precipitation reactor 3 is connected to a sodium carbonate high-level tank 10.

[0030] The decarbonization evaporation equipment includes a decarbonization kettle 5 connected to the primary lithium precipitation mother liquor clear liquid tank 1, and an MVR evaporator 6 connected to the decarbonization kettle 5; a concentrated sulfuric acid delivery pipe 4 is connected to the decarbonization kettle 5, and the MVR evaporator 6 is connected to the MVR freezing crystallizer 2.

[0031] The MVR evaporator 6 is connected to a condensate water pool 7 and a potassium glauberite transmission line 8 .

[0032] Based on Example 2, this Example 3 provides a more preferred structure of the MVR evaporator 6. Specifically, the MVR evaporator 6 is connected to a condensate pool 7 and a glauberite transmission line 8. The condensate of the MVR evaporator 6 enters the condensate pool 7, and the separated glauberite is output to the secondary lithium precipitation system through the glauberite transmission line 8.

[0033] Example 4.

[0034] like Figure 1As shown, the utility model provides a secondary lithium precipitation system for producing lithium carbonate by sulfuric acid method, including a primary lithium precipitation mother liquor clear liquid tank 1, a decarbonization evaporation device connected from the primary lithium precipitation mother liquor clear liquid tank 1, an MVR freezing crystallizer 2 connected from the decarbonization evaporation device, a secondary lithium precipitation reactor 3 connected from the MVR freezing crystallizer 2, and a lithium carbonate crude equipment connected from the secondary lithium precipitation reactor 3; the lithium carbonate crude equipment is connected to a lithium carbonate refining device for refining battery-grade lithium carbonate, the decarbonization evaporation device is connected to a concentrated sulfuric acid delivery pipe 4, and the secondary lithium precipitation reactor 3 is connected to a sodium carbonate high-level tank 10.

[0035] The MVR freezing crystallizer 2 is connected to a sodium sulfate transmission line 9.

[0036] Based on Example 1, this Example 4 provides a more preferred structure of the MVR freezing crystallizer 2. Specifically, the MVR freezing crystallizer 2 is connected to a sodium sulfate transmission line 9, and the by-product high-purity sodium sulfate product produced by the secondary lithium precipitation system is output to the secondary lithium precipitation system through the sodium sulfate transmission line 9.

[0037] Example 5.

[0038] like Figure 1 As shown, the utility model provides a secondary lithium precipitation system for producing lithium carbonate by sulfuric acid method, including a primary lithium precipitation mother liquor clear liquid tank 1, a decarbonization evaporation device connected from the primary lithium precipitation mother liquor clear liquid tank 1, an MVR freezing crystallizer 2 connected from the decarbonization evaporation device, a secondary lithium precipitation reactor 3 connected from the MVR freezing crystallizer 2, and a lithium carbonate crude equipment connected from the secondary lithium precipitation reactor 3; the lithium carbonate crude equipment is connected to a lithium carbonate refining device for refining battery-grade lithium carbonate, the decarbonization evaporation device is connected to a concentrated sulfuric acid delivery pipe 4, and the secondary lithium precipitation reactor 3 is connected to a sodium carbonate high-level tank 10.

[0039] The lithium carbonate crude equipment includes a secondary lithium precipitation centrifuge 12 connected to the secondary lithium precipitation reactor 3, a secondary crude lithium carbonate slurrying tank 13 connected to the solid phase outlet of the secondary lithium precipitation centrifuge 12, a secondary lithium precipitation and washing high-level tank 14 connected to the secondary crude lithium carbonate slurrying tank 13, and a secondary lithium precipitation and washing centrifuge 15 connected to the secondary lithium precipitation and washing high-level tank 14; the solid phase outlet of the secondary lithium precipitation and washing centrifuge 15 is connected to the lithium carbonate refining equipment.

[0040] Based on Example 1, this Example 5 provides a more preferred structure of the lithium carbonate crude equipment. Specifically, the lithium carbonate crude equipment includes a secondary lithium precipitation centrifuge 12 connected to the secondary lithium precipitation reactor 3, a secondary crude lithium carbonate slurry tank 13 connected to the solid phase outlet of the secondary lithium precipitation centrifuge 12, a secondary lithium precipitation high-level tank 14 connected to the secondary crude lithium carbonate slurry tank 13, and a secondary lithium precipitation centrifuge 15 connected to the secondary lithium precipitation high-level tank 14; the solid phase outlet of the secondary lithium precipitation centrifuge 15 is connected to the lithium carbonate refining equipment. The reactants coming out of the secondary lithium precipitation reactor 3 are sequentially processed by the secondary lithium precipitation centrifuge 12, the secondary crude lithium carbonate slurry tank 13, the secondary lithium precipitation high-level tank 14 and the secondary lithium precipitation centrifuge 15, and then sent to the carbonization thermal analysis system for carbonization thermal analysis to obtain battery-grade lithium carbonate.

[0041] Example 6.

[0042] like Figure 1 As shown, the utility model provides a secondary lithium precipitation system for producing lithium carbonate by sulfuric acid method, including a primary lithium precipitation mother liquor clear liquid tank 1, a decarbonization evaporation device connected from the primary lithium precipitation mother liquor clear liquid tank 1, an MVR freezing crystallizer 2 connected from the decarbonization evaporation device, a secondary lithium precipitation reactor 3 connected from the MVR freezing crystallizer 2, and a lithium carbonate crude equipment connected from the secondary lithium precipitation reactor 3; the lithium carbonate crude equipment is connected to a lithium carbonate refining device for refining battery-grade lithium carbonate, the decarbonization evaporation device is connected to a concentrated sulfuric acid delivery pipe 4, and the secondary lithium precipitation reactor 3 is connected to a sodium carbonate high-level tank 10.

[0043] The lithium carbonate crude equipment includes a secondary lithium precipitation centrifuge 12 connected to the secondary lithium precipitation reactor 3, a secondary crude lithium carbonate slurrying tank 13 connected to the solid phase outlet of the secondary lithium precipitation centrifuge 12, a secondary lithium precipitation and washing high-level tank 14 connected to the secondary crude lithium carbonate slurrying tank 13, and a secondary lithium precipitation and washing centrifuge 15 connected to the secondary lithium precipitation and washing high-level tank 14; the solid phase outlet of the secondary lithium precipitation and washing centrifuge 15 is connected to the lithium carbonate refining equipment.

[0044] The secondary crude lithium carbonate slurrying tank 13 is connected to a pure water delivery pipe 16 .

[0045] Based on Example 5, this Example 6 provides a more preferred structure of the secondary crude lithium carbonate slurry tank 13. Specifically, the secondary crude lithium carbonate slurry tank 13 is connected to a pure water delivery pipe 16 for delivering pure water to the secondary crude lithium carbonate slurry tank 13.

[0046] Example 7.

[0047] like Figure 1As shown, the utility model provides a secondary lithium precipitation system for producing lithium carbonate by sulfuric acid method, including a primary lithium precipitation mother liquor clear liquid tank 1, a decarbonization evaporation device connected from the primary lithium precipitation mother liquor clear liquid tank 1, an MVR freezing crystallizer 2 connected from the decarbonization evaporation device, a secondary lithium precipitation reactor 3 connected from the MVR freezing crystallizer 2, and a lithium carbonate crude equipment connected from the secondary lithium precipitation reactor 3; the lithium carbonate crude equipment is connected to a lithium carbonate refining device for refining battery-grade lithium carbonate, the decarbonization evaporation device is connected to a concentrated sulfuric acid delivery pipe 4, and the secondary lithium precipitation reactor 3 is connected to a sodium carbonate high-level tank 10.

[0048] The lithium carbonate crude equipment includes a secondary lithium precipitation centrifuge 12 connected to the secondary lithium precipitation reactor 3, a secondary crude lithium carbonate slurrying tank 13 connected to the solid phase outlet of the secondary lithium precipitation centrifuge 12, a secondary lithium precipitation and washing high-level tank 14 connected to the secondary crude lithium carbonate slurrying tank 13, and a secondary lithium precipitation and washing centrifuge 15 connected to the secondary lithium precipitation and washing high-level tank 14; the solid phase outlet of the secondary lithium precipitation and washing centrifuge 15 is connected to the lithium carbonate refining equipment.

[0049] The liquid phase outlet of the secondary lithium precipitation centrifuge 12 is connected to the primary lithium precipitation mother liquor clear liquid tank 1.

[0050] Based on Example 5, this Example 7 provides a more preferred structure of the secondary lithium precipitation centrifuge 12. Specifically, the liquid phase outlet of the secondary lithium precipitation centrifuge 12 is connected to the primary lithium precipitation mother liquor clear liquid tank 1, and the mother liquor from the liquid phase outlet of the secondary lithium precipitation centrifuge 12 is combined with the primary lithium precipitation mother liquor clear liquid tank 1 for recycling.

[0051] Example 8.

[0052] like Figure 1 As shown, the utility model provides a secondary lithium precipitation system for producing lithium carbonate by sulfuric acid method, including a primary lithium precipitation mother liquor clear liquid tank 1, a decarbonization evaporation device connected from the primary lithium precipitation mother liquor clear liquid tank 1, an MVR freezing crystallizer 2 connected from the decarbonization evaporation device, a secondary lithium precipitation reactor 3 connected from the MVR freezing crystallizer 2, and a lithium carbonate crude equipment connected from the secondary lithium precipitation reactor 3; the lithium carbonate crude equipment is connected to a lithium carbonate refining device for refining battery-grade lithium carbonate, the decarbonization evaporation device is connected to a concentrated sulfuric acid delivery pipe 4, and the secondary lithium precipitation reactor 3 is connected to a sodium carbonate high-level tank 10.

[0053] The lithium carbonate crude equipment includes a secondary lithium precipitation centrifuge 12 connected to the secondary lithium precipitation reactor 3, a secondary crude lithium carbonate slurrying tank 13 connected to the solid phase outlet of the secondary lithium precipitation centrifuge 12, a secondary lithium precipitation and washing high-level tank 14 connected to the secondary crude lithium carbonate slurrying tank 13, and a secondary lithium precipitation and washing centrifuge 15 connected to the secondary lithium precipitation and washing high-level tank 14; the solid phase outlet of the secondary lithium precipitation and washing centrifuge 15 is connected to the lithium carbonate refining equipment.

[0054] The liquid phase outlet of the secondary lithium washing centrifuge 15 is connected to the plant water recycling system.

[0055] Based on Example 5, this Example 8 provides a more preferred structure of the secondary lithium washing centrifuge 15. Specifically, the liquid phase outlet of the secondary lithium washing centrifuge 15 is connected to the plant water recycling system to achieve water resource recycling.

[0056] Example 9.

[0057] like Figure 1 As shown, the utility model provides a secondary lithium precipitation system for producing lithium carbonate by sulfuric acid method, including a primary lithium precipitation mother liquor clear liquid tank 1, a decarbonization evaporation device connected from the primary lithium precipitation mother liquor clear liquid tank 1, an MVR freezing crystallizer 2 connected from the decarbonization evaporation device, a secondary lithium precipitation reactor 3 connected from the MVR freezing crystallizer 2, and a lithium carbonate crude equipment connected from the secondary lithium precipitation reactor 3; the lithium carbonate crude equipment is connected to a lithium carbonate refining device for refining battery-grade lithium carbonate, the decarbonization evaporation device is connected to a concentrated sulfuric acid delivery pipe 4, and the secondary lithium precipitation reactor 3 is connected to a sodium carbonate high-level tank 10.

[0058] The lithium carbonate refining equipment is a lithium carbonate carbonization thermal analysis system 11.

[0059] This Example 9 provides a more preferred structure of the lithium carbonate refining equipment based on Example 1. Specifically, the lithium carbonate refining equipment is a lithium carbonate carbonization thermal analysis system 11, and the crude lithium carbonate from the lithium carbonate crude equipment has a purity of 92.4%. The crude lithium carbonate enters the lithium carbonate carbonization thermal analysis system 11 for carbonization thermal analysis to obtain battery-grade lithium carbonate.

[0060] The utility model provides a secondary lithium precipitation system for producing lithium carbonate by sulfuric acid method, and a secondary lithium precipitation method for producing lithium carbonate by sulfuric acid method adapted thereto, using the primary lithium precipitation mother liquor for producing lithium carbonate by sulfuric acid method as raw material, and the method comprises the following steps:

[0061] S1. Decarbonization and evaporation: The primary lithium precipitation mother liquor is decarbonized and then evaporated and concentrated. The primary lithium precipitation mother liquor enters the decarbonization kettle from the primary lithium precipitation mother liquor clear liquid tank, and sulfuric acid solution is added to the primary lithium precipitation mother liquor to make its pH value 4-8 to remove carbonate; the decarbonized mother liquor is concentrated using an MVR evaporator, and more preferably, concentrated to a lithium sulfate concentration of ≥30g / L.

[0062] S2. Separation of glauberite: The mother liquor after evaporation and concentration is cooled to 25°C±5°C, and glauberite crystals are precipitated. The glauberite slurry is sent out through the glauberite external transmission line, and the lithium sulfate concentration in the mother liquor is increased to 30-40g / L.

[0063] S3. Separation of sodium sulfate: The mother liquor after separation of potassium sulfate is cooled to ≤0°C in an MVR freezing crystallizer, sodium sulfate crystals are precipitated, and the sodium sulfate slurry is sent out through a sodium sulfate external transmission line; after separation of sodium sulfate, the sodium sulfate concentration in the mother liquor is reduced to below 50g / L, and the lithium sulfate concentration is increased to 50-90g / L. The separated sodium sulfate slurry is dehydrated and dried to obtain a sodium sulfate product, and the purity of the sodium sulfate product is ≥85%.

[0064] S4. Secondary lithium precipitation: The mother liquor after separation of sodium sulfate is sent to the secondary lithium precipitation reactor, sodium carbonate is added to it through the sodium carbonate high-level tank, the temperature is increased, and lithium is precipitated for the second time. The reaction liquid is centrifuged in the secondary lithium precipitation centrifuge, and the mother liquor after the secondary lithium precipitation is returned and combined with the mother liquor of the primary lithium precipitation, and steps S1-S4 are circulated; the centrifugal precipitation is crude lithium carbonate, and the purity is ≥90%.

[0065] The crude lithium carbonate enters the secondary crude lithium carbonate slurry tank for stirring, washing, centrifugation, and removal of soluble impurities. The centrifugal precipitate enters the lithium carbonate carbonization thermal analysis system for carbonization thermal analysis, and then the carbonization thermal analysis precipitate is dehydrated and dried to obtain battery-grade lithium carbonate.

[0066] The lithium sulfate content in the primary lithium precipitation mother liquor is less than or equal to 7wt.%, the sodium sulfate content is 5-27wt.%, and the potassium sulfate content is 8-19wt.%.

[0067] Finally, it should be noted that the above embodiments are only preferred embodiments of the present invention to illustrate the technical solution of the present invention, rather than limiting it, and certainly not limiting the patent scope of the present invention; although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions recorded in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention; that is to say, any changes or embellishments made to the main design concept and spirit of the present invention that have no substantive significance, and the technical problems they solve are still consistent with the present invention, should be included in the protection scope of the present invention; in addition, the direct or indirect application of the technical solution of the present invention in other related technical fields is also included in the patent protection scope of the present invention.

Claims

1. A secondary lithium precipitation system for producing lithium carbonate by sulfuric acid process, characterized in that: The invention comprises a primary lithium precipitation mother liquor clear liquid tank (1), a decarbonization evaporation device connected to the primary lithium precipitation mother liquor clear liquid tank (1), an MVR freezing crystallizer (2) connected to the decarbonization evaporation device, a secondary lithium precipitation reaction kettle (3) connected to the MVR freezing crystallizer (2), and a lithium carbonate crude equipment connected to the secondary lithium precipitation reaction kettle (3); the lithium carbonate crude equipment is connected to a lithium carbonate refining device for refining battery-grade lithium carbonate, the decarbonization evaporation device is connected to a concentrated sulfuric acid delivery pipe (4), and the secondary lithium precipitation reaction kettle (3) is connected to a sodium carbonate high-level tank (10).

2. The secondary lithium precipitation system for producing lithium carbonate by sulfuric acid process according to claim 1, characterized in that: The decarbonization evaporation equipment comprises a decarbonization kettle (5) connected to a primary lithium precipitation mother liquor clear liquid tank (1), and an MVR evaporator (6) connected to the decarbonization kettle (5); a concentrated sulfuric acid delivery pipe (4) is connected to the decarbonization kettle (5), and the MVR evaporator (6) is connected to the MVR freezing crystallizer (2).

3. A secondary lithium precipitation system for producing lithium carbonate by sulfuric acid process according to claim 2, characterized in that: The MVR evaporator (6) is connected to a condensate water pool (7) and a glauberite transmission line (8).

4. The secondary lithium precipitation system for producing lithium carbonate by sulfuric acid process according to claim 1, characterized in that: The MVR freezing crystallizer (2) is connected to a sodium sulfate transmission line (9).

5. The secondary lithium precipitation system for producing lithium carbonate by sulfuric acid process according to claim 1, characterized in that: The lithium carbonate crude equipment comprises a secondary lithium precipitation centrifuge (12) connected to a secondary lithium precipitation reactor (3), a secondary crude lithium carbonate slurrying tank (13) connected to a solid phase outlet of the secondary lithium precipitation centrifuge (12), a secondary lithium precipitation high-level tank (14) connected to the secondary crude lithium carbonate slurrying tank (13), and a secondary lithium precipitation centrifuge (15) connected to the secondary lithium precipitation high-level tank (14); the solid phase outlet of the secondary lithium precipitation centrifuge (15) is connected to the lithium carbonate refining equipment.

6. A secondary lithium precipitation system for producing lithium carbonate by sulfuric acid process according to claim 5, characterized in that: The secondary crude lithium carbonate slurrying tank (13) is connected to a pure water delivery pipe (16).

7. A secondary lithium precipitation system for producing lithium carbonate by sulfuric acid process according to claim 5, characterized in that: The liquid phase outlet of the secondary lithium precipitation centrifuge (12) is connected to the primary lithium precipitation mother liquor clear liquid tank (1).

8. The secondary lithium precipitation system for producing lithium carbonate by sulfuric acid process according to claim 5, characterized in that: The liquid phase output from the secondary lithium washing centrifuge (15) is connected to the plant water recycling system.

9. The secondary lithium precipitation system for producing lithium carbonate by sulfuric acid process according to claim 1, characterized in that: The lithium carbonate refining equipment is a lithium carbonate carbonization thermal analysis system (11).

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