A device for separating and concentrating lithium salts

Abstract

The utility model relates to a kind of lithium salt separation and concentration device, including the filter assembly, ultrafiltration membrane assembly, nanofiltration separation system and reverse osmosis separation system connected in turn;Nanofiltration separation system includes three-stage nanofiltration membrane separation unit, and three-stage nanofiltration membrane separation unit is connected in turn in sequence.By adopting filter assembly and ultrafiltration membrane assembly combination as the pretreatment of raw material liquid, it is small, and degree of automation is high.Nanofiltration separation system has the function of selective retention to different salt or solute, by selecting different membrane through three-stage nanofiltration membrane separation unit, to control the water production ratio of permeate and concentrated solution, can effectively improve the concentration of lithium ion in raw water, so that its concentration can reach the requirement of making battery and other devices.At the same time, it saves cost.

Description

Technical Field

[0001] This utility model relates to the field of solution separation and purification technology, and in particular to an apparatus for lithium salt separation and concentration. Background Technology

[0002] Currently, with the rapid development of new energy vehicles, electronic devices, and energy storage technologies, the application of lithium in the field of new energy materials has received high attention. Lithium carbonate, as an important material for the cathode of lithium batteries, has a particularly critical production process.

[0003] New energy batteries include lithium nickel cobalt manganese oxide batteries, lithium cobalt oxide batteries, and lithium iron phosphate batteries. A single battery cell comprises a casing, electrolyte, positive electrode material, and negative electrode material. Lithium carbonate is a crucial raw material for the positive electrode material, and its quality significantly impacts battery performance. In my country, the main raw materials for lithium carbonate production include salt lake brine, spodumene, lepidolite, and spent lithium batteries. While salt lake brine has abundant reserves, its complex composition and low lithium grade, coupled with the difficulty in separating magnesium (the diagonal element of lithium) due to their similar chemical properties, result in low direct lithium recovery during production. Furthermore, the production process easily generates large amounts of wastewater and waste residue containing heavy metals, which are difficult and costly to treat, and can easily lead to environmental pollution and ecological damage.

[0004] The current mainstream production method is sulfuric acid leaching. This involves high-temperature calcination to transform the lithium crystal phase in spodumene concentrate to the β-type. After crushing in a ball mill, the lithium is mixed evenly with excess concentrated sulfuric acid and then roasted together. After cooling, lithium sulfate and other metal sulfate salts are co-leached. The leachate is then purified and precipitated with soda ash to produce lithium carbonate. The resulting lithium sulfate solution requires further purification and concentration. For example, Chinese patent CN 210559425 U discloses a high-purity lithium hydroxide production system, including a primary neutralization filtration system, a secondary neutralization filtration system, and a separation and concentration system connected in sequence. The primary neutralization filtration system includes a lithium salt leaching solution neutralization tank, a first coarse filter, and a first precision filter connected in sequence. The secondary neutralization filtration system includes a solution preparation tank, a second coarse filter, a filtrate storage tank, and a second precision filter connected in sequence. The separation and concentration system includes a freeze separation device, a third precision filter, a membrane separation and impurity removal system, a primary evaporation system, a centrifuge device, a third coarse filter, and a secondary evaporation system connected in sequence. The membrane separation and impurity removal system includes an alkali-resistant nanofiltration membrane filter and an alkali-resistant reverse osmosis membrane filter connected in sequence. However, the pretreatment filtration process is relatively complex, has a low degree of automation, and the simple separation and concentration system cannot effectively control the concentration of the recovered lithium solution, requiring additional production steps, making the process cumbersome. Summary of the Invention

[0005] The purpose of this invention is to provide an apparatus for lithium salt separation and concentration to solve the problems described in the background section.

[0006] To achieve the objective of this utility model, the technical solution is as follows:

[0007] A lithium salt separation and concentration apparatus includes a filter assembly, an ultrafiltration membrane assembly, a nanofiltration separation system, and a reverse osmosis separation system connected in sequence; the nanofiltration separation system includes three nanofiltration membrane separation units connected in series.

[0008] Furthermore, the lithium salt separation and concentration apparatus also includes a nanofiltration concentrate tank; the outlet on the filtration side of the first-stage nanofiltration membrane separation unit is connected to the inlet of the second-stage nanofiltration membrane separation unit, and the outlet on the filtration side of the second-stage nanofiltration membrane separation unit is connected to the inlet of the third-stage nanofiltration membrane separation unit; the outlet on the filtration side of the third-stage nanofiltration membrane separation unit is connected to the nanofiltration concentrate tank; and the outlet on the permeate side of each stage nanofiltration membrane separation unit is connected to the inlet of the reverse osmosis separation system.

[0009] Furthermore, the first-stage nanofiltration membrane separation unit uses a reverse osmosis membrane, while the second-stage and third-stage nanofiltration membrane separation units both use monovalent ion-selective nanofiltration membranes.

[0010] Furthermore, the ratio of nanofiltration membranes in the three-stage nanofiltration membrane separation unit is 4:2:1.

[0011] Furthermore, the lithium salt separation and concentration apparatus also includes a reverse osmosis permeate tank; the permeate side outlet of the reverse osmosis separation system is connected to the reverse osmosis permeate tank, and the throttling side outlet is connected to the inlet of the nanofiltration separation system.

[0012] Furthermore, the outlet on the filtration side of the ultrafiltration membrane module is connected to the inlet of the ultrafiltration membrane module; the lithium salt separation and concentration device also includes a high-pressure pump, the outlet on the permeate side of the ultrafiltration membrane module is connected to the high-pressure pump, and the high-pressure pump is connected to the inlet of the nanofiltration separation system.

[0013] Furthermore, the lithium salt separation and concentration device also includes a raw water tank connected to a filter assembly; an alkali addition pipe and a pH detection tank are also provided on the pipeline connecting the raw water tank and the filter assembly.

[0014] Furthermore, the reverse osmosis separation system includes a two-stage reverse osmosis separation unit, which is connected in series. The outlet on the cut-off side of the first-stage reverse osmosis separation unit is connected to the inlet of the second-stage reverse osmosis separation unit, and the outlet on the cut-off side of the second-stage reverse osmosis separation unit is connected to the inlet of the nanofiltration separation system. The outlets on the permeate side of the first-stage and second-stage reverse osmosis separation units are connected to the reverse osmosis permeate tank.

[0015] Compared with the prior art, the significant advantages of this utility model are:

[0016] This device, employing a combination of filtration and ultrafiltration membrane modules for feed liquid pretreatment, offers advantages over traditional sedimentation tanks in terms of smaller footprint, higher automation, and higher efficiency. The ultrafiltration membrane modules utilize hollow fiber membranes with a large packing area, resulting in lower equipment investment costs. The separation process does not involve phase changes, reducing energy consumption. The separation process is driven only by low pressure, simplifying equipment and process flow, and facilitating operation, management, and maintenance. It has a wide range of applications, capable of handling solutes with molecular weights ranging from 1000 to 500,000 Daltons or sizes from 0.005 to 0.1 micrometers. This reduces civil engineering investment and increases the level of industrialization.

[0017] Nanofiltration separation systems selectively retain different salts or solutes. By varying their retention capabilities for monovalent and divalent ions, they can effectively increase the lithium ion concentration in the feed solution. Through a three-stage nanofiltration membrane separation unit, different membranes are selected to control the permeate and concentrate product water ratio, concentrating the lithium content in the raw water by 3-5 times or more, achieving a concentration sufficient for manufacturing batteries and other devices. This process also saves costs.

[0018] The reverse osmosis separation system further removes Ca from the feed solution. 2+ Mg 2+ These divalent ions block all soluble salts and organic matter with a molecular weight greater than 100, allowing only water molecules to pass through. The permeate is then reused as pure water. Resources are effectively utilized, resulting in significant economic benefits. Through industrial integration, the efficiency and cost of wastewater treatment are reduced. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the lithium salt separation and concentration device of this utility model.

[0020] Figure 2 This is a process flow diagram of the lithium salt separation and concentration device of this utility model.

[0021] Among them, 1 is the filtration component; 2 is the ultrafiltration membrane component; 3 is the nanofiltration separation system; 4 is the reverse osmosis separation system; 5 is the nanofiltration concentrate tank; and 6 is the reverse osmosis permeate tank. Detailed Implementation

[0022] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0023] like Figure 1 As shown, a lithium salt separation and concentration apparatus includes a filtration module 1, an ultrafiltration membrane module 2, a nanofiltration separation system 3, and a reverse osmosis separation system 4 connected in sequence. The filtration module 1 uses an activated carbon filter, such as a coconut shell activated carbon filter. The filtration module 1 adsorbs particles, suspended solids, and colloids from the feed liquid.

[0024] Ultrafiltration membrane module 2 uses a hollow fiber separation membrane. Specifically, the hollow fiber separation membrane can be made of polyvinylidene fluoride (PVDF) material. Ultrafiltration membrane module 2 can further remove organic impurities and some precipitates from the feed liquid.

[0025] The nanofiltration separation system 3 includes three nanofiltration membrane separation units connected in series. Specifically, the outlet on the filtration side of the first-stage nanofiltration membrane separation unit is connected to the inlet of the second-stage unit, and the outlet on the filtration side of the second-stage unit is connected to the inlet of the third-stage unit. The outlet on the filtration side of the third-stage unit is connected to the nanofiltration concentrate tank 5. The outlet on the permeate side of each nanofiltration membrane separation unit is connected to the inlet of the reverse osmosis separation system 4. The first-stage nanofiltration membrane separation unit uses a reverse osmosis membrane to retain all dissolved salts. The second and third-stage nanofiltration membrane separation units use monovalent ion-selective nanofiltration membranes. + The solution is trapped. The nanofiltration separation system 3 separates the raw liquid filtered by the ultrafiltration membrane module 2 into two parts: permeate and concentrate. The Li in the concentrate on the intercepting side after three-stage nanofiltration treatment... + Li content ≥12g / L, Li in the permeate on the permeate side + The content is ≤0.6g / L. The nanofiltration membrane can have a pore size of 1nm and a molecular weight cutoff of 200~400. The nanofiltration separation system typically operates at a pressure of 1.0~10.0MPa and can treat Li in the original solution. + Lithium-containing solutions with a concentration of ≤3g / L.

[0026] Preferably, the ratio of nanofiltration membranes in the three-stage nanofiltration membrane separation unit is 4:2:1, which can effectively improve the recovery rate of produced water.

[0027] Reverse osmosis separation system 4 uses a reverse osmosis membrane to further remove Ca from the permeate supplied by nanofiltration separation system 3. 2+ Mg 2+ Divalent ions block all dissolved salts and organic matter with a molecular weight greater than 100, allowing only water molecules to pass through. The permeate from the reverse osmosis separation system 4 is reused as pure water. Furthermore, the permeate outlet of the reverse osmosis separation system 4 is connected to the reverse osmosis permeate tank 6, and the filtration outlet is connected to the inlet of the nanofiltration separation system 3. Preferably, the reverse osmosis separation system 4 may include a two-stage reverse osmosis separation unit, which is connected in series. That is, the filtration outlet of the first-stage reverse osmosis separation unit is connected to the inlet of the second-stage reverse osmosis separation unit, and the filtration outlet of the second-stage reverse osmosis separation unit is connected to the inlet of the nanofiltration separation system 3. The permeate outlets of the first-stage and second-stage reverse osmosis separation units are connected to the reverse osmosis permeate tank 6. After desalination by the reverse osmosis separation system 4, the Li in the permeate on the permeate side... + <5ppm, Na + <0.5ppm, Ca2+ <0.01ppm, Mg 2+ <0.01ppm, Cl - <0.01g / L, TDS<50mg / L, pure water is obtained for reuse.

[0028] Furthermore, the outlet on the retentate side of the ultrafiltration membrane module 2 is connected to the inlet of the ultrafiltration membrane module 2 for recirculation. The lithium salt separation and concentration device also includes a high-pressure pump, with the outlet on the permeate side of the ultrafiltration membrane module 2 connected to the high-pressure pump, which is connected to the inlet of the nanofiltration separation system 3.

[0029] Furthermore, the lithium salt separation and concentration device also includes a raw water tank, which is connected to the filter assembly 1. An alkali addition pipe and a pH detection tank are also provided on the pipeline connecting the raw water tank and the filter assembly 1 to facilitate the addition of alkali to neutralize the feed solution, real-time monitoring of the pre-membrane pH value, and adjustment to 6-9 to meet the membrane inlet requirements.

[0030] like Figure 2 The diagram illustrates the wastewater separation and concentration process of a lithium salt separation and concentration apparatus:

[0031] S1. Add alkali solution to the acidified feed solution to neutralize the pH of the feed solution to a level of 6-9 to meet the requirements for membrane entry. The feed solution is then separated and filtered through filter assembly 1 and ultrafiltration membrane assembly 2. The permeate from ultrafiltration membrane assembly 2 is sent to nanofiltration separation system 3 for filtration.

[0032] S2, Nanofiltration separation system 3 concentrates the solution through membrane concentration to obtain a solution with a lithium content that meets the standard;

[0033] S3. The permeate after nanofiltration enters the reverse osmosis separation system 4. The permeate of the reverse osmosis separation system 4 is used as pure water, and the concentrate is returned to the nanofiltration separation system 3 for recycling.

[0034] The concentrate retained by the nanofiltration membrane in step S2, Li + The concentration reached 12 g / L, a 4-fold concentration; Li permeated from the liquid + <0.6g / L, Ca 2+ <0.01ppm, Mg 2+ <0.01ppm, Fe 2+ <0.01ppm, Cl - <1.5g / L, SO4 2- The concentration is 200 pmm and the TDS is 3.2 g / L. Proceed to step S3.

[0035] In step S3, the Li in the permeate retained by the reverse osmosis membrane + <5ppm, Na + <0.5ppm, Ca 2+ <0.01ppm, Mg2+ <0.01ppm, Cl - <0.01g / L, TDS<50mg / L, pure water is obtained and reused in the workshop.

[0036] This device is suitable for collecting lithium sulfate solution generated during the production of lithium battery raw materials, as detailed below:

[0037] S1. Feed solution (lithium sulfate solution) 60 m3 / h is pumped into the raw water tank. The raw water contains 3.0 g / L lithium, 20 ppm calcium, 3.5 ppm magnesium, 21 g / L sulfate, and 13.6 g / L TDS. Sodium hydroxide is added in a metered manner to adjust the pH to 6-9 to meet the membrane feed requirements. Ultrafiltration is performed through filter module 1 and ultrafiltration membrane module 2. The operating pressure of ultrafiltration membrane module 2 is 0.15 MPa, and the membrane flux is 17.2 L / m2·h. It retains small particles and impurities and blocks colloids and proteins.

[0038] S2. The permeate from ultrafiltration is pressurized by a high-pressure pump and then enters the nanofiltration separation system 3 for nanofiltration. The operating pressure is 10.0 MPa, the membrane flux is 11.2 L / m2·h, the flow rate of the nanofiltration membrane concentrate is controlled at 8 m3 / h, and the flow rate of the permeate is 57 m3 / h. Li+ is retained in the concentrate. The lithium content in the permeate of the nanofiltration membrane is 0.5 g / L, and the lithium content in the retained concentrate is 12.2 g / L. The concentrate is pumped into the nanofiltration concentrate tank 5 for use as the finished product.

[0039] S3. The permeate from the nanofiltration membrane system enters the reverse osmosis system at an operating pressure of 6.0 MPa and a membrane flux of 31.8 L / m²·h. The concentrate at a flow rate of 5 m³ / h is returned to the nanofiltration unit for recycling. The permeate contains 5 ppm lithium, 0.01 ppm calcium, 0.01 ppm magnesium, and 21.4 mg / L TDS, and is then reused in the workshop.

Claims

1. An apparatus for lithium salt separation and concentration, characterized in that: The device includes a filter assembly (1), an ultrafiltration membrane assembly (2), a nanofiltration separation system (3), and a reverse osmosis separation system (4) connected in sequence. The nanofiltration separation system (3) includes three nanofiltration membrane separation units connected in series. The outlet of the first nanofiltration membrane separation unit is connected to the inlet of the second nanofiltration membrane separation unit, and the outlet of the second nanofiltration membrane separation unit is connected to the inlet of the third nanofiltration membrane separation unit. The outlet of each nanofiltration membrane separation unit is connected to the inlet of the reverse osmosis separation system (4). The outlet of the reverse osmosis separation system (4) is connected to the inlet of the nanofiltration separation system (3).

2. The apparatus for lithium salt separation and concentration according to claim 1, characterized in that: The lithium salt separation and concentration device also includes a nanofiltration concentrate tank (5); the outlet of the third-stage nanofiltration membrane separation unit is connected to the nanofiltration concentrate tank (5).

3. The apparatus for lithium salt separation and concentration according to claim 2, characterized in that: The first-stage nanofiltration membrane separation unit uses a reverse osmosis membrane, while the second-stage and third-stage nanofiltration membrane separation units both use monovalent ion-selective nanofiltration membranes.

4. The apparatus for lithium salt separation and concentration according to claim 3, characterized in that: The ratio of nanofiltration membranes in the three-stage nanofiltration membrane separation unit is 4:2:

1.

5. The apparatus for lithium salt separation and concentration according to claim 1, characterized in that: The lithium salt separation and concentration device also includes a reverse osmosis permeate tank (6); the permeate side outlet of the reverse osmosis separation system (4) is connected to the reverse osmosis permeate tank (6).

6. The apparatus for lithium salt separation and concentration according to claim 5, characterized in that: The outlet of the ultrafiltration membrane module (2) on the filtration side is connected to the inlet of the ultrafiltration membrane module (2); the lithium salt separation and concentration device also includes a high-pressure pump, the outlet of the ultrafiltration membrane module (2) on the permeate side is connected to the high-pressure pump, and the high-pressure pump is connected to the inlet of the nanofiltration separation system (3).

7. The apparatus for lithium salt separation and concentration according to claim 5, characterized in that: The lithium salt separation and concentration device also includes a raw water tank, which is connected to the filter assembly (1); an alkali addition pipe and a pH detection tank are also provided on the pipeline connecting the raw water tank and the filter assembly (1).

8. The apparatus for lithium salt separation and concentration according to claim 5, characterized in that: The reverse osmosis separation system (4) includes a two-stage reverse osmosis separation unit, and the two-stage reverse osmosis separation units are connected in series. The outlet of the first-stage reverse osmosis separation unit is connected to the inlet of the second-stage reverse osmosis separation unit, and the outlet of the second-stage reverse osmosis separation unit is connected to the inlet of the nanofiltration separation system (3). The outlets of the first-stage reverse osmosis separation unit and the second-stage reverse osmosis separation unit are connected to the reverse osmosis product water tank (6).

Images