A system for preparing high-purity lithium carbonate

Abstract

The utility model provides a kind of preparation system of high-purity lithium carbonate, the preparation system includes sodium carbonate preparation tank, calcium adding tank, sodium hydroxide adding tank, intermediate tank, membrane filtration device, refined water tank, lithium precipitation kettle device, filter washing device, post-processing device and packaging device connected in sequence;Intermediate tank is used to carry out buffer treatment to the coarse sodium carbonate solution after sodium hydroxide adding tank processing;Membrane filtration device is provided with filter water outlet, and filter water outlet is connected to the water inlet of refined water tank;Lithium precipitation kettle device is provided with water inlet and lithium solution import, and water inlet is connected to the water outlet of refined water tank, and lithium solution import is used to add lithium-containing solution to lithium precipitation kettle device.The preparation system provided by the utility model, by purifying raw materials, removing impurities as one of auxiliary units in lithium precipitation process, to ensure the purity of lithium carbonate, with the advantages of short process, strong applicability etc..

Description

Technical Field

[0001] This invention belongs to the field of high-purity lithium carbonate preparation technology, and relates to a high-purity lithium carbonate preparation system. Background Technology

[0002] In the process of lithium extraction from salt lake brine, a lithium-rich solution is obtained by separation and concentration through methods such as adsorption, membrane extraction, and solution extraction. After removing impurities such as calcium and magnesium, a lithium-containing solution is obtained and reacted with sodium carbonate to precipitate lithium. After filtration, washing, and drying, a high-purity lithium carbonate product is obtained.

[0003] In the preparation of lithium carbonate, the quality of lithium carbonate is often greatly affected by the raw materials. One of the key processes is the precipitation reaction between lithium chloride and sodium carbonate. For economic reasons, industrial-grade sodium carbonate is often used as a raw material for lithium carbonate production. However, due to its process characteristics, industrial-grade sodium carbonate products have higher and more fluctuating calcium and magnesium ion content. The calcium and magnesium ion content in industrial-grade sodium carbonate is one of the important factors affecting its quality. During the lithium precipitation process, calcium carbonate and magnesium carbonate impurities are inevitably introduced into the final lithium carbonate product, making it difficult to control the calcium and magnesium ion content, resulting in fluctuating product quality and failing to meet the standards for battery-grade lithium carbonate. Therefore, purifying the sodium carbonate solution in lithium carbonate production to remove calcium and magnesium ions is of great significance for preparing high-purity lithium carbonate products.

[0004] Currently, although there are reports on purification methods for sodium carbonate solutions in lithium carbonate production, namely using sodium hydroxide to remove calcium and magnesium ions from the sodium carbonate solution, followed by filtration to remove calcium carbonate and magnesium hydroxide, this method is limited by the filtration precision of the equipment. The calcium and magnesium ion content in the purified sodium carbonate solution does not meet the standards and fluctuates significantly. The filtration equipment also suffers from severe clogging due to magnesium hydroxide colloids, requiring frequent cleaning and consuming large amounts of water. Furthermore, the effluent often requires subsequent resin-based calcium and magnesium ion removal as a backup measure. However, resin-based calcium and magnesium ion removal requires a certain amount of acid and alkali reagents during saturation regeneration, resulting in high costs. Additionally, the sodium carbonate solution used for lithium precipitation often requires high temperatures and concentrations, placing high demands on the equipment selected for sodium carbonate solution purification. The resins used are limited to expensive chelating resins available on the market. Since it is a carbonate system, chelating resins are not very effective at removing calcium ions in a calcium carbonate system. Other methods may introduce other impurities that affect product quality, resulting in less than ideal results.

[0005] Therefore, it is crucial to develop and design a novel system for preparing high-purity lithium carbonate. Utility Model Content

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a high-purity lithium carbonate preparation system. By purifying raw materials and removing impurities as an auxiliary unit in the lithium precipitation process, the system ensures the purity of lithium carbonate and has advantages such as short process and strong applicability.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] This invention provides a high-purity lithium carbonate preparation system, which includes a sodium carbonate preparation tank, a calcium addition tank, a sodium hydroxide addition tank, an intermediate tank, a membrane filtration device, a purified water tank, a lithium precipitation vessel, a filtration and washing device, a post-treatment device, and a packaging device connected in sequence.

[0009] The intermediate tank is used to buffer the crude sodium carbonate solution after it has been treated in the sodium hydroxide dosing tank.

[0010] The membrane filtration device is provided with a filtered water outlet, which is connected to the water inlet of the purified water tank.

[0011] The lithium precipitation vessel is equipped with a water inlet and a lithium solution inlet. The water inlet is connected to the water outlet of the refining water tank, and the lithium solution inlet is used to add a lithium-containing solution into the lithium precipitation vessel.

[0012] Preferably, the preparation system further includes a slag pool treatment device.

[0013] Preferably, the sludge treatment device includes a sludge tank body and a plate and frame filter press connected in sequence. The inlet of the sludge tank body is connected to the concentrate outlet of the membrane filter, and the outlet of the plate and frame filter press is connected to the inlet of the calcium addition and conditioning tank.

[0014] Preferably, the preparation system further includes a backwashing device.

[0015] Preferably, the inlet of the backwashing device is connected to the filtered water outlet of the membrane filtration device via a branch, and the outlet of the backwashing device is connected to the inlet of the membrane filtration device.

[0016] Preferably, the membrane filtration device is further provided with an unfiltered product water outlet, which is connected to the inlet of the intermediate tank.

[0017] Preferably, the membrane filtration device is provided with a filter element.

[0018] Preferably, the filter element is an organic membrane or an inorganic membrane.

[0019] Preferably, the organic membrane is a polytetrafluoroethylene membrane.

[0020] Preferably, the inorganic membrane is an alumina ceramic membrane.

[0021] Preferably, the pore size of the organic membrane is 0.2μm to 0.5μm.

[0022] Preferably, the filtration pore size of the inorganic membrane is 0.01μm to 0.1μm.

[0023] Preferably, the refined water tank is externally connected to a heat exchanger, which is used to heat the sodium carbonate solution in the refined water tank.

[0024] Preferably, the filtration and washing apparatus includes a filtration and washing device and a resizing and washing tank connected in sequence.

[0025] Preferably, the inlet of the filtration and washing device is connected to the outlet of the lithium precipitation vessel, and the outlet of the filtration and washing device is connected to the inlet of the re-slurry washing vessel; the re-slurry washing vessel is used to add pure water to wash the crude lithium carbonate in the re-slurry washing vessel multiple times to obtain refined lithium carbonate.

[0026] Preferably, the post-processing device includes a centrifuge device, a drying device, and an iron removal device connected in sequence.

[0027] Preferably, the inlet of the centrifuge is connected to the outlet of the re-slurry washing tank, the inlet of the drying device is connected to the outlet of the centrifuge, the outlet of the drying device is connected to the inlet of the iron removal device, and the outlet of the iron removal device is connected to the inlet of the packaging device.

[0028] Preferably, a first online detector is installed at the inlet of the calcium addition mixing tank.

[0029] Preferably, a second online detector is installed at the outlet of the sodium hydroxide dosing tank.

[0030] Preferably, a third online detector is installed at the outlet of the filtered water of the membrane filtration device.

[0031] The system refers to an equipment system, device system, or production device.

[0032] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of this utility model, nor is it intended to limit the scope of this utility model. Other features of this utility model will become readily apparent from the following description.

[0033] Compared with the prior art, the beneficial effects of this utility model are as follows:

[0034] In this invention, solid sodium carbonate is pre-prepared in a sodium carbonate preparation tank by adding heated demineralized water and recycled rinsing water from the lithium carbonate washing process during lithium precipitation. The concentration of calcium and magnesium ions in the sodium carbonate solution is further controlled by a calcium addition tank and a sodium hydroxide addition tank. After buffering in an intermediate tank, the solution flows to a membrane filtration device. The qualified refined sodium carbonate solution after membrane filtration is then processed through a refining tank, a lithium precipitation vessel, a filtration and washing device, a post-treatment device, and a packaging device to obtain a high-purity lithium carbonate product. The high-purity lithium carbonate preparation system provided by this invention uses the purification of raw materials to remove impurities as an auxiliary unit in the lithium precipitation process, thereby ensuring the purity of the lithium carbonate product. The overall process is short, the structure is simple, the operation is easy, and it has strong applicability. Attached Figure Description

[0035] To more clearly illustrate the technical solutions in the embodiments of this utility model, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0036] Figure 1 A schematic diagram of the structure of a high-purity lithium carbonate preparation system provided in a specific embodiment of this utility model;

[0037] Figure 2 A schematic diagram of the structure of a high-purity lithium carbonate preparation system, including a slag pool treatment device, provided for a specific embodiment of this utility model;

[0038] Figure 3 A schematic diagram of the structure of a high-purity lithium carbonate preparation system including a backwashing device, provided for a specific embodiment of this utility model;

[0039] Among them, 1-sodium carbonate preparation tank; 2-calcium addition tank; 3-sodium hydroxide addition tank; 4-intermediate tank; 5-membrane filtration device; 6-refined water tank; 7-lithium precipitation vessel device; 8-filtration and washing device; 9-post-treatment device; 10-packaging device; 11-first online detector; 12-second online detector; 13-third online detector; 14-slag pool body; 15-plate and frame filter press device; 16-backwashing device. Detailed Implementation

[0040] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of 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 should fall within the protection scope of the present invention.

[0041] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this utility model are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the utility model described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0042] It should be noted that, in the description of this utility model, unless otherwise explicitly specified and limited, the terms "set," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0043] The technical solution of this utility model will be further described below with reference to the accompanying drawings and specific embodiments.

[0044] In one specific embodiment, the present invention provides a system for preparing high-purity lithium carbonate, such as... Figure 1 As shown, the preparation system includes a sodium carbonate preparation tank 1, a calcium addition tank 2, a sodium hydroxide addition tank 3, an intermediate tank 4, a membrane filtration device 5, a purified water tank 6, a lithium precipitation reactor 7, a filtration and washing device 8, a post-treatment device 9, and a packaging device 10 connected in sequence. The intermediate tank 4 is used to buffer the crude sodium carbonate solution after treatment in the sodium hydroxide addition tank 3. The membrane filtration device 5 is provided with a filtered water outlet, which is connected to the inlet of the purified water tank 6. The lithium precipitation reactor 7 is provided with an inlet and a lithium solution inlet. The inlet is connected to the outlet of the purified water tank 6, and the lithium solution inlet is used to add a lithium-containing solution into the lithium precipitation reactor 7.

[0045] In this invention, solid sodium carbonate is conveyed to a sodium carbonate preparation tank via an automatic unpacking machine and a belt conveyor. Simultaneously, heated demineralized water and recycled rinsing water from the lithium carbonate washing process are added to the preparation tank. A mechanical stirrer can be installed inside the preparation tank. Precise control of the amount of solid sodium carbonate added, the amount of demineralized water, and the amount of rinsing water is required to maintain the sodium carbonate concentration in the prepared solution at 25-30% by weight and the solution temperature at 50-65°C, ultimately yielding a crude sodium carbonate solution.

[0046] In this invention, a crude sodium carbonate solution is pumped to a calcium addition tank 2. A first online monitoring instrument is installed at the front end of the calcium addition tank 2 to monitor the concentration of calcium and magnesium ions in the crude sodium carbonate solution. Based on the calcium and magnesium ion concentration detected by the first online monitoring instrument, a conditioning agent is added to the calcium addition tank 2. The conditioning agent can be a calcium-containing solution, such as calcium chloride, to control the weight ratio of calcium and magnesium ions in the calcium addition tank 2 to be greater than 2. A mechanical stirrer can be installed in the calcium addition tank 2 to control the reaction time between the crude sodium carbonate solution and the conditioning agent to approximately 60-90 minutes. The use of a calcium-containing solution as the conditioning agent, to control the weight ratio of calcium and magnesium ions in the calcium addition tank 2 to be greater than 2, and the reaction time of approximately 60-90 minutes, facilitates thorough mixing and reaction of the substances.

[0047] In this invention, the crude sodium carbonate solution after reaction in the calcium addition tank 2 flows into the sodium hydroxide addition tank 3. A second online detector 12 is installed at the outlet of the sodium hydroxide addition tank 3 to detect the alkalinity of OH. A refining agent, mainly sodium hydroxide solution, is added to the sodium hydroxide addition tank 3. The amount added is mainly based on the excess alkalinity of OH detected by the second online detector 12, which is 0.2~0.4 g / L. A mechanical stirrer can be installed in the sodium hydroxide addition tank 3.

[0048] In this invention, the crude sodium carbonate solution after the reaction in the sodium hydroxide addition tank 3 flows into the intermediate tank 4 for buffering. The buffering time is about 30 to 60 minutes, which can facilitate the full mixing and reaction of the substances.

[0049] In this invention, the crude sodium carbonate solution, after being buffered in the intermediate tank 4, enters the membrane filtration device 5 by gravity flow or pumping. Under pressure, the liquid in the membrane filtration device 5 is separated into a concentrated solution containing calcium and magnesium sludge, which is blocked by the filter element, and a permeate containing a small amount of calcium and magnesium, which passes through the filter element. The permeate is the refined sodium carbonate solution. A third online detector 3 is installed at the outlet of the membrane filtration device 5 to detect the calcium and magnesium ion concentration in the effluent. A calcium and magnesium ion concentration not exceeding 1 ppm is considered a qualified refined sodium carbonate solution; a concentration exceeding 1 ppm is considered an unqualified refined sodium carbonate solution. The unqualified refined sodium carbonate solution is returned to the intermediate tank 4 through the unfiltered product water outlet for circulation filtration. An automatic valve switches between the qualified and unqualified refined sodium carbonate solutions. Differential pressure gauges can be installed at both the inlet and outlet of the membrane filtration device 5. Based on the differential pressure readings, the filter element can be backwashed online to restore its filtration characteristics.

[0050] In this invention, a portion of the qualified refined sodium carbonate solution at point 5 of the membrane filtration device enters the refined water tank 6 for subsequent lithium precipitation, while the other portion enters the backwash tank as online backwash water.

[0051] In some implementations, such as Figure 2 As shown, the preparation system also includes a slag tank treatment device, which includes a slag tank body 14 and a plate and frame filter press 15 connected in sequence. The inlet of the slag tank body 14 is connected to the concentrate outlet of the membrane filter 5, and the outlet of the plate and frame filter press 15 is connected to the inlet of the calcium addition and mixing tank 2.

[0052] In this invention, the concentrated liquid from the membrane filtration device 5 can be discharged into the sludge tank body 14. A stirring device can be installed inside the sludge tank body 14. The stirring device can be an air or mechanical stirrer. The sludge in the sludge tank is sent to the plate and frame filter press 15 for mud-water separation by a high-pressure pump. The filtrate from the plate and frame filter press 15 is returned to the calcium addition and mixing tank 2 to recover carbonate ions. The filter cake from the plate and frame filter press 15 serves as the final calcium and magnesium mud outlet.

[0053] In some implementations, such as Figure 3 As shown, the preparation system also includes a backwashing device 16. The inlet of the backwashing device 16 is connected to the filtered water outlet of the membrane filtration device 5 via a branch, and the outlet of the backwashing device 16 is connected to the inlet of the membrane filtration device 5.

[0054] This invention does not impose any special limitations on the specific model and equipment form of the backwashing device 16. Those skilled in the art can make appropriate selections of the specific model and equipment form of the backwashing device 16 according to the actual situation.

[0055] In some embodiments, the membrane filtration device 5 is also provided with an unfiltered product water outlet, which is connected to the inlet of the intermediate tank 4.

[0056] This invention does not impose any special limitations on the specific model and equipment form of the membrane filtration device 5. Those skilled in the art can make appropriate selections of the specific model and equipment form of the membrane filtration device 5 according to the actual situation.

[0057] In some embodiments, the membrane filtration device 5 is provided with a filter element, which is an organic membrane or an inorganic membrane. The organic membrane is a polytetrafluoroethylene membrane, and the inorganic membrane is an alumina ceramic membrane.

[0058] In some embodiments, the pore size of the organic membrane is 0.2μm to 0.5μm, for example, it can be 0.2μm, 0.25μm, 0.3μm, 0.35μm, 0.4μm, 0.45μm, 0.5μm, etc., but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0059] The organic membrane in this invention has a filtration pore size of 0.2μm to 0.5μm because this range is conducive to further filtration and separation of substances.

[0060] When an organic membrane is used as the filter element in this invention, the filtration pressure can be 0~100kPa, and the water inlet method can be gravity flow or pump delivery.

[0061] In some embodiments, the filtration pore size of the inorganic membrane is 0.01μm to 0.1μm, for example, it can be 0.01μm, 0.03μm, 0.05μm, 0.07μm, 0.09μm, 0.1μm, etc., but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0062] The inorganic membrane in this invention has a filtration pore size of 0.01μm to 0.1μm because this range is conducive to further filtration and separation of substances.

[0063] When an inorganic membrane is used as the filter element in this invention, the filtration pressure can be 0~1000kPa, and the water inlet can be delivered by a pump.

[0064] In some embodiments, a heat exchanger is connected to the purified water tank 6 to heat the sodium carbonate solution inside the purified water tank 6.

[0065] The qualified refined sodium carbonate solution from membrane filtration device 5 of this invention enters the purification tank 6 for purification treatment, and then is further heated to 75-85°C through a heat exchanger before entering the lithium precipitation vessel 7. Simultaneously, a heated lithium chloride solution is added to the lithium precipitation vessel 7. The sodium carbonate solution and lithium chloride solution in the lithium precipitation vessel undergo a chemical reaction to generate lithium carbonate. At the same time, the supersaturated lithium carbonate precipitates out, resulting in a saturated solution containing suspended lithium carbonate solids. The heating treatment via heat exchanger facilitates complete reaction and saves energy.

[0066] This invention does not impose any special limitations on the specific model and form of the heat exchanger. Those skilled in the art can make appropriate selections based on actual conditions.

[0067] In some embodiments, the filtration and washing apparatus 8 includes a filtration and washing device and a re-slurry washing vessel connected in sequence. The inlet of the filtration and washing device is connected to the outlet of the lithium precipitation vessel 7, and the outlet of the filtration and washing device is connected to the inlet of the re-slurry washing vessel. The re-slurry washing vessel is used to add pure water to wash the crude lithium carbonate in the re-slurry washing vessel multiple times to obtain refined lithium carbonate.

[0068] In this invention, the saturated solution containing suspended lithium carbonate solids obtained after treatment in the refining tank 6 is first filtered by a filtration and washing device to obtain crude lithium carbonate product and lithium-containing precipitated mother liquor. The lithium-containing precipitated mother liquor is then further recycled for lithium resources, and the crude lithium carbonate product enters a subsequent unit for further refining. The filtration and washing device can be a belt filter, a two-in-one washing and filtration device, etc.

[0069] In this invention, the crude lithium carbonate product obtained after filtration and washing is fed into a re-slurry washing kettle, and pure water is added to wash the crude lithium carbonate multiple times. The lithium carbonate obtained after washing is refined lithium carbonate and washing mother liquor. The washing mother liquor is used as supplementary water for the preparation of carbonate. After washing, the refined lithium carbonate is centrifuged, dried, iron removed, and packaged to finally obtain a high-purity lithium carbonate product.

[0070] In some embodiments, the post-processing device 9 includes a centrifuge, a drying device, and an iron removal device connected in sequence.

[0071] This invention does not impose specific limitations on the models of the centrifugal device, drying device, and iron removal device. Those skilled in the art can adapt the specific models and equipment forms of the centrifugal device, drying device, and iron removal device according to actual conditions. The centrifugation rate of the centrifugal device, the drying temperature of the drying device, and the iron removal method of the iron removal device can all adopt conventional designs and are not specifically limited here.

[0072] In some embodiments, the inlet of the centrifuge is connected to the outlet of the re-slurry washing vessel, the inlet of the drying device is connected to the outlet of the centrifuge, the outlet of the drying device is connected to the inlet of the iron removal device, and the outlet of the iron removal device is connected to the inlet of the packaging device 10.

[0073] In some embodiments, a first online detector 11 is installed at the inlet of the calcium addition tank 2.

[0074] In some embodiments, a second online detector 12 is installed at the outlet of the sodium hydroxide dosing tank 3.

[0075] In some embodiments, a third online detector 3 is installed at the outlet of the filtered water of the membrane filtration device 5.

[0076] This utility model does not impose any special limitations on the specific models and quantities of the first online detector 11, the second online detector 12, and the third online detector 3. The first online detector 11, the second online detector 12, and the third online detector 3 can be the same or different, and those skilled in the art can make adaptive selections according to the actual situation.

[0077] Example 1

[0078] This embodiment provides a system for preparing high-purity lithium carbonate, wherein:

[0079] The system includes, in sequence, a sodium carbonate preparation tank 1, a calcium addition tank 2, a sodium hydroxide addition tank 3, an intermediate tank 4, a membrane filtration device 5, a purified water tank 6, a lithium precipitation reactor 7, a filtration and washing device 8, a post-treatment device 9, and a packaging device 10. The intermediate tank 4 is used to buffer the crude sodium carbonate solution after treatment in the sodium hydroxide addition tank 3. The membrane filtration device 5 is equipped with a filtered water outlet, which is connected to the inlet of the purified water tank 6. The lithium precipitation reactor 7 is equipped with an inlet and a lithium solution inlet. The inlet is connected to the outlet of the purified water tank 6, and the lithium solution inlet is used to add a lithium-containing solution into the lithium precipitation reactor 7.

[0080] The preparation system also includes a slag tank treatment device, which includes a slag tank body 14 and a plate and frame filter press 15 connected in sequence. The inlet of the slag tank body 14 is connected to the concentrate outlet of the membrane filter 5, and the outlet of the plate and frame filter press 15 is connected to the inlet of the calcium addition and conditioning tank 2.

[0081] The preparation system also includes a backwashing device 16, the inlet of which is connected to the filtered water outlet of the membrane filtration device 5 via a branch, and the outlet of which is connected to the inlet of the membrane filtration device 5.

[0082] The membrane filtration device 5 is also equipped with an unfiltered product water outlet, which is connected to the inlet of the intermediate tank 4. The membrane filtration device 5 is equipped with a filter element, which is an organic membrane. The organic membrane is a polytetrafluoroethylene membrane with a pore size of 0.3 μm.

[0083] The refined water tank 6 is connected to a heat exchanger, which is used to heat the sodium carbonate solution in the refined water tank 6.

[0084] The filtration and washing device 8 includes a filtration and washing equipment and a re-slurry washing kettle connected in sequence. The inlet of the filtration and washing equipment is connected to the outlet of the lithium precipitation kettle device 7, and the outlet of the filtration and washing equipment is connected to the inlet of the re-slurry washing kettle. The re-slurry washing kettle is used to add pure water to wash the crude lithium carbonate in the re-slurry washing kettle multiple times to obtain refined lithium carbonate.

[0085] The post-processing device 9 includes a centrifuge, a drying device, and an iron removal device connected in sequence. The inlet of the centrifuge is connected to the outlet of the re-slurry washing kettle, the inlet of the drying device is connected to the outlet of the centrifuge, the outlet of the drying device is connected to the inlet of the iron removal device, and the outlet of the iron removal device is connected to the inlet of the packaging device 10.

[0086] A first online detector 11 is installed at the inlet of the calcium addition tank 2, a second online detector 12 is installed at the outlet of the sodium hydroxide addition tank 3, and a third online detector 3 is installed at the outlet of the filtered water of the membrane filtration device 5.

[0087] Example 2

[0088] This embodiment provides a system for preparing high-purity lithium carbonate, wherein:

[0089] The system includes, in sequence, a sodium carbonate preparation tank 1, a calcium addition tank 2, a sodium hydroxide addition tank 3, an intermediate tank 4, a membrane filtration device 5, a purified water tank 6, a lithium precipitation reactor 7, a filtration and washing device 8, a post-treatment device 9, and a packaging device 10. The intermediate tank 4 is used to buffer the crude sodium carbonate solution after treatment in the sodium hydroxide addition tank 3. The membrane filtration device 5 is equipped with a filtered water outlet, which is connected to the inlet of the purified water tank 6. The lithium precipitation reactor 7 is equipped with an inlet and a lithium solution inlet. The inlet is connected to the outlet of the purified water tank 6, and the lithium solution inlet is used to add a lithium-containing solution into the lithium precipitation reactor 7.

[0090] The preparation system also includes a slag tank treatment device, which includes a slag tank body 14 and a plate and frame filter press 15 connected in sequence. The inlet of the slag tank body 14 is connected to the concentrate outlet of the membrane filter 5, and the outlet of the plate and frame filter press 15 is connected to the inlet of the calcium addition and conditioning tank 2.

[0091] The preparation system also includes a backwashing device 16, the inlet of which is connected to the filtered water outlet of the membrane filtration device 5 via a branch, and the outlet of which is connected to the inlet of the membrane filtration device 5.

[0092] The membrane filtration device 5 is also equipped with an unfiltered product water outlet, which is connected to the inlet of the intermediate tank 4. The membrane filtration device 5 is equipped with a filter element, which is an inorganic membrane, specifically an alumina ceramic membrane, with a pore size of 0.07 μm.

[0093] The refined water tank 6 is connected to a heat exchanger, which is used to heat the sodium carbonate solution in the refined water tank 6.

[0094] The filtration and washing device 8 includes a filtration and washing equipment and a re-slurry washing kettle connected in sequence. The inlet of the filtration and washing equipment is connected to the outlet of the lithium precipitation kettle device 7, and the outlet of the filtration and washing equipment is connected to the inlet of the re-slurry washing kettle. The re-slurry washing kettle is used to add pure water to wash the crude lithium carbonate in the re-slurry washing kettle multiple times to obtain refined lithium carbonate.

[0095] The post-processing device 9 includes a centrifuge, a drying device, and an iron removal device connected in sequence. The inlet of the centrifuge is connected to the outlet of the re-slurry washing kettle, the inlet of the drying device is connected to the outlet of the centrifuge, the outlet of the drying device is connected to the inlet of the iron removal device, and the outlet of the iron removal device is connected to the inlet of the packaging device 10.

[0096] A first online detector 11 is installed at the inlet of the calcium addition tank 2, a second online detector 12 is installed at the outlet of the sodium hydroxide addition tank 3, and a third online detector 3 is installed at the outlet of the filtered water of the membrane filtration device 5.

[0097] In summary, in this invention, solid sodium carbonate is pre-prepared in the sodium carbonate preparation tank 1 by adding heated demineralized water and recycled rinsing water from the lithium carbonate washing process during lithium precipitation. The concentration of calcium and magnesium ions in the sodium carbonate solution is further controlled by the calcium addition tank 2 and sodium hydroxide addition tank 3. After buffering in the intermediate tank 4, the solution flows to the membrane filtration device 5. The qualified refined sodium carbonate solution after treatment by the membrane filtration device 5 is then processed by the refining water tank 6, the lithium precipitation vessel device 7, the filtration and washing device 8, the post-treatment device 9, and the packaging device 10 to obtain a high-purity lithium carbonate product. The high-purity lithium carbonate preparation system provided by this invention uses the purification of raw materials to remove impurities as an auxiliary unit in the lithium precipitation process, thereby ensuring the purity of the lithium carbonate product. The overall process is short, the structure is simple, the operation is easy, and it has strong applicability.

[0098] The specific embodiments described above do not constitute a limitation on the scope of protection of this utility model. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this utility model should be included within the scope of protection of this utility model.

Claims

1. A system for producing high purity lithium carbonate, characterized by, The preparation system includes a sodium carbonate preparation tank, a calcium addition tank, a sodium hydroxide addition tank, an intermediate tank, a membrane filtration device, a purified water tank, a lithium precipitation tank, a filtration and washing device, a post-treatment device, and a packaging device, which are connected in sequence. The intermediate tank is used to buffer the crude sodium carbonate solution after it has been treated in the sodium hydroxide dosing tank. The membrane filtration device is provided with a filtered water outlet, which is connected to the water inlet of the purified water tank. The lithium precipitation vessel is equipped with a water inlet and a lithium solution inlet. The water inlet is connected to the water outlet of the refining water tank, and the lithium solution inlet is used to add a lithium-containing solution into the lithium precipitation vessel.

2. The high-purity lithium carbonate preparation system according to claim 1, characterized in that, The preparation system also includes a slag pool treatment device; The sludge treatment device includes a sludge tank body and a plate and frame filter press connected in sequence. The inlet of the sludge tank body is connected to the concentrate outlet of the membrane filter press, and the outlet of the plate and frame filter press is connected to the inlet of the calcium addition and conditioning tank.

3. The high-purity lithium carbonate preparation system according to claim 1 or 2, characterized in that, The preparation system also includes a backwashing device; The inlet of the backwashing device is connected to the filtered water outlet of the membrane filtration device via a branch, and the outlet of the backwashing device is connected to the inlet of the membrane filtration device.

4. The high-purity lithium carbonate preparation system according to claim 1, characterized in that, The membrane filtration device is also provided with an unfiltered product water outlet, which is connected to the inlet of the intermediate tank.

5. The high-purity lithium carbonate preparation system according to claim 1 or 4, characterized in that, The membrane filtration device is equipped with a filter element; The filter element is an organic membrane or an inorganic membrane; The organic membrane is a polytetrafluoroethylene membrane; The inorganic membrane is an alumina ceramic membrane.

6. The high-purity lithium carbonate preparation system according to claim 5, characterized in that, The organic membrane has a filtration pore size of 0.2 μm to 0.5 μm; The inorganic membrane has a filtration pore size of 0.01 μm to 0.1 μm.

7. The high-purity lithium carbonate preparation system according to claim 1, characterized in that, The refined water tank is connected to a heat exchanger, which is used to heat the sodium carbonate solution in the refined water tank.

8. The high-purity lithium carbonate preparation system according to claim 1, characterized in that, The filtration and washing device includes a filtration and washing unit and a resizing and washing tank connected in sequence. The inlet of the filtration and washing equipment is connected to the outlet of the lithium precipitation reactor, and the outlet of the filtration and washing equipment is connected to the inlet of the re-slurry washing reactor. The resizing washing kettle is used to add pure water to wash the crude lithium carbonate in the resizing washing kettle multiple times to obtain refined lithium carbonate.

9. The high-purity lithium carbonate preparation system according to claim 8, characterized in that, The post-processing device includes a centrifuge device, a drying device, and an iron removal device connected in sequence. The inlet of the centrifuge is connected to the outlet of the re-slurry washing tank, the inlet of the drying device is connected to the outlet of the centrifuge, the outlet of the drying device is connected to the inlet of the iron removal device, and the outlet of the iron removal device is connected to the inlet of the packaging device.

10. The high-purity lithium carbonate preparation system according to claim 1, characterized in that, A first online detector is installed at the inlet of the calcium addition mixing tank; A second online detector is installed at the outlet of the sodium hydroxide dosing tank; A third online monitoring instrument is installed at the outlet of the filtered water of the membrane filtration device.

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