Process and device for extracting lithium from brine

Abstract

The invention discloses a process and a device for extracting lithium from brine, and the process comprises the following steps: S1, mixing and adsorbing the brine and an aluminum adsorbent, and transferring to a filter bed for solid-liquid separation to obtain an adsorbent bed layer; s2, carrying out nanofiltration treatment on the brine to remove divalent anions and divalent cations to obtain nanofiltration produced water as a transformation agent; s3, leaching the adsorbent bed layer treated in the step S1 by adopting the transformation agent; the brine in the step S1 and the step S2 is independently raw brine or brine obtained after the raw brine is pretreated. According to the method, the nanofiltration produced water of the brine is used as the transformation agent, a salt solution does not need to be additionally prepared as the transformation agent, and the transformation cost is low; in the step S1, the original halogen and the adsorbent can be directly mixed and adsorbed, the original halogen does not need to be pretreated, direct lithium extraction of the original halogen can be realized, and the whole process can be continuously implemented; the process is dynamically carried out on a belt filter, and the adsorbent bed layer can quickly and thoroughly dehydrate, so that mixing of effluent in each step is avoided to the greatest extent.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium extraction from brine, and particularly relates to a lithium extraction process and device from brine. Background Art

[0002] Lithium resources are widely used in multiple fields such as aviation and new energy, and are important resources required for the development of current high-tech industries.

[0003] Extracting lithium from salt lake brine is an important way to obtain lithium resources. However, the raw brine contains a large amount of anions with large ionic radii. If the raw brine is directly mixed with the adsorbent, it will cause the adsorbent to be poisoned. Therefore, before mixing with the adsorbent, the raw brine is usually pretreated, such as evaporation and concentration, so that a part of carbonate, sulfate, etc. will precipitate, reducing the pressure on the adsorbent; and then the pretreated brine is further processed.

[0004] However, in the pretreated brine, lithium ions still exist in the form of lithium carbonate or lithium sulfate. This form has a strong binding force with the adsorbent, making it difficult to regenerate the adsorbent. Therefore, in the prior art, after mixing the pretreated brine with the adsorbent for adsorption, a high-concentration salt solution is first used to pre-wash the adsorbent, and then conventional washing and desorption operations are carried out.

[0005] The purpose of pre-washing is to reduce the binding force between the lithium salt and the adsorbent. The high-concentration salt solution used for pre-washing can be artificially prepared. For example, the high-concentration salt solution used in CN115814465A is zinc chloride, copper chloride, zirconium oxychloride, sodium chloride, potassium chloride, magnesium chloride, calcium chloride, aluminum chloride, ammonium magnesium sulfate, zinc sulfate, sodium sulfate, potassium sulfate, magnesium sulfate, copper sulfate, magnesium nitrate, sodium nitrate, potassium nitrate, calcium nitrate, copper nitrate, zinc nitrate, etc. with a concentration greater than 150 g / L; the high-concentration salt solution used in CN117987665A is a sodium chloride solution with a chloride ion concentration greater than 80 g / L; it can also be prepared from the raw brine. For example, the Chinese invention patent with the publication number CN114196840B discloses using a solution containing divalent cation salts (such as magnesium chloride solution, calcium chloride solution, the tail liquid after lithium extraction from old brine or the concentrated solution of brine nanofiltration) for pre-washing.

[0006] The deficiencies of the prior art are as follows: (1) Pretreatment of the raw brine is required before mixing it with the adsorbent for adsorption, and the steps are complicated; (2) A large amount of salt is consumed in the artificially prepared high-concentration salt solution, which makes the pre-washing cost very high. Although the tail liquid after lithium extraction from the old brine prepared from the raw brine or the concentrated liquid of brine nanofiltration has a relatively lower cost, the sodium-lithium ratio and lithium recovery rate in the lithium eluate still need to be improved; (3) Steps such as adsorption and pre-washing are carried out in an adsorption column or adsorption tower. In this case, the adsorbent is not resistant to high pressure, so the pre-washing is carried out slowly under normal pressure, which not only takes a long time, but also between each step (adsorption step, pre-washing step, washing step), the adsorbent cannot be fully dehydrated, resulting in the mixing of the effluent. Summary of the Invention

[0007] The object of the present invention is to provide a process and device for extracting lithium from brine. This process can directly carry out the lithium extraction operation on the raw brine, and has low engineering cost and is easy to implement, and can avoid the mixing of the effluent of each step to the greatest extent.

[0008] A process for extracting lithium from brine, which comprises the following steps:

[0009] S1: After mixing and adsorbing the brine with an aluminum-based adsorbent, transfer it to a filter bed for solid-liquid separation to obtain an adsorbent bed layer;

[0010] S2: Perform nanofiltration treatment on the brine to remove divalent anions and divalent cations, and obtain the nanofiltration product water as a transformation agent;

[0011] S3: Use this transformation agent to wash the adsorbent bed layer after step S1;

[0012] In steps S1 and S2, the brine is independently the raw brine or the brine obtained by pretreating the raw brine.

[0013] The present invention uses the nanofiltration product water (i.e., nanofiltration fresh water) obtained by performing nanofiltration treatment on the brine as a transformation agent, without the need to additionally prepare a salt solution as a transformation agent, and the transformation cost is low. And the present invention finds that when using this transformation agent to wash the adsorbent bed layer after mixing and adsorption, not only can step S1 directly mix and adsorb the raw brine with the adsorbent, eliminating any pretreatment operation on the raw brine, and realizing the direct lithium extraction from the raw brine (obviously, the process of the present invention can also carry out the lithium extraction operation on the pretreated raw brine), and the whole process can be continuously implemented; moreover, both the sodium-lithium ratio and lithium recovery rate in the final lithium eluate can be greatly improved.

[0014] Meanwhile, the lithium extraction process of the present invention is carried out dynamically on equipment with a filter bed such as a belt filter. In each step, the adsorbent bed layer can be dehydrated quickly and relatively thoroughly (a vacuum extraction device or the like can be used to extract the liquid contained in the adsorbent bed layer, such as brine, transformation agent, etc.). Therefore, the water discharged in each step is relatively independent, and the situation where the water discharged in each step is confused is avoided to the greatest extent.

[0015] In the above-mentioned brine lithium extraction process, at the end of steps S1 and S3, the water content of the adsorbent bed layer (with a thickness of 5 - 30 cm) is less than 40%.

[0016] In step S2 of the above-mentioned brine lithium extraction process, the nanofiltration is single-stage nanofiltration or multi-stage nanofiltration to make the removal rate of divalent anions greater than 80%;

[0017] The divalent anions at least include one or more of sulfate, carbonate, and arsenate.

[0018] In step S2 or S3 of the above-mentioned brine lithium extraction process, the pH of the transformation agent is adjusted to 4 - 6. First, the transformation agent is adjusted to acidic and then the adsorbent bed layer is rinsed.

[0019] Preferably, the above-mentioned brine lithium extraction process further includes: collecting the water discharged in step S3, obtaining secondary nanofiltration product water after re-nanofiltration, and adding the secondary nanofiltration product water to the transformation agent in step S2 for recycling.

[0020] Further preferably, the dosage of the secondary nanofiltration product water is 3 - 5% of the transformation agent.

[0021] Preferably, the above-mentioned brine lithium extraction process further includes:

[0022] Step S4: Rinsing the adsorbent bed layer with a salt washing solution and collecting the washing water;

[0023] At the end of step S4, the water content of the adsorbent bed layer is less than 40%;

[0024] Step S5: Rinsing the adsorbent bed layer passing through step S1 with the washing water before the transformation agent;

[0025] The dosage of the washing water is 5 - 10% of the brine dosage in step S1.

[0026] Returning the washing water generated by washing with the salt washing solution and using it between steps S1 and S3 can displace the brine on the surface of the adsorbent after step S1, achieving the purpose of pre-salt washing. In this way, on the one hand, the salt washing pressure in step S4 can be reduced, the consumption of the salt washing solution in step S4 can be saved, and the salt washing efficiency can be improved; on the other hand, the consumption of the transformation agent in step S3 can also be saved, and the energy consumption of nanofiltration can be saved.

[0027] In this case, the dosage of the transformation agent in step S3 is 10-15% of the dosage of the brine in step S1; the dosage of the salt washing liquid in step S4 is 5-10% of the dosage of the brine in step S1.

[0028] The present invention also provides a brine lithium extraction device, which includes a frame, on which a filter bed is movably arranged, and the filter bed moves along a preset path, and an adsorption area, a transformation area, a first washing area and a desorption area are successively arranged on this path;

[0029] The following are provided on the frame:

[0030] A mixed adsorption mechanism, which is used to mix the adsorbent and the brine and output the suspension to the adsorption area;

[0031] A transformation mechanism, which is used to spray the transformation agent into the transformation area, and the transformation mechanism is connected to the first nanofiltration mechanism through a nanofiltration produced water output pipeline, and the first nanofiltration mechanism is used to perform nanofiltration on the brine and provide nanofiltration produced water to the transformation mechanism;

[0032] A first washing mechanism, which is used to spray the salt washing liquid into the first washing area;

[0033] A desorption mechanism, which is used to spray the desorption liquid into the desorption area.

[0034] Preferably, in the above-mentioned brine lithium extraction device, a second washing area is further arranged on the moving path of the filter bed between the adsorption area and the transformation area, and a second washing mechanism is further arranged on the frame above the second washing area;

[0035] A washing water collection mechanism for collecting the produced water in the first washing area is further arranged on the frame, and the washing water collection mechanism is used to supply the collected washing water to the second washing mechanism.

[0036] Compared with the prior art, the beneficial effects of the present invention are reflected in:

[0037] (1) The present invention uses the nanofiltration produced water (i.e., nanofiltration fresh water) obtained by performing nanofiltration treatment on the raw brine as the transformation agent, without the need to additionally prepare a salt solution as the transformation agent, and the transformation cost is low. And the present invention finds that when the transformation agent is used to wash the adsorbent bed after mixed adsorption, not only can the raw brine and the adsorbent be directly mixed and adsorbed in step S1, eliminating any pretreatment operation on the raw brine, and direct lithium extraction from the raw brine can be realized, and the whole process can be continuously implemented; moreover, the sodium-lithium ratio and lithium recovery rate in the final lithium eluate can be greatly improved.

[0038] (2) The lithium extraction process of the present invention is carried out dynamically on equipment with a filter bed such as a belt filter. In each step, the adsorbent bed layer can be dehydrated quickly and relatively thoroughly (a vacuum extraction device or the like can be used to extract the liquid contained in the adsorbent bed layer, such as brine, transformation agent, etc.). Therefore, the water discharged in each step is relatively independent, and the situation where the water discharged in each step is confused is avoided to the greatest extent.

[0039] (3) The present invention returns the washing water generated by washing the salt with the salt washing liquid and uses it between steps S1 and S3, which can replace the brine on the surface of the adsorbent after step S1, achieving the purpose of pre-washing the salt. In this way, on the one hand, the salt washing pressure in step S4 can be reduced, the consumption of the salt washing liquid in step S4 can be saved, and the salt washing efficiency can be improved; on the other hand, the consumption of the transformation agent in step S3 can also be saved, and the energy consumption of nanofiltration can be saved. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 is the first structural schematic diagram of a brine lithium extraction device of the present invention;

[0041] Figure 2 is the second structural schematic diagram of a brine lithium extraction device of the present invention;

[0042] Figure 3 is the third structural schematic diagram of a brine lithium extraction device of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0043] The technical solutions of the present invention will be further described in detail below with reference to the drawings and embodiments.

[0044] Embodiment 1

[0045] A brine lithium extraction process in this embodiment includes the following steps:

[0046] S1: After mixing and adsorbing the raw brine with the aluminum-based adsorbent, it is transferred to a belt filter for solid-liquid separation to obtain an adsorbent bed layer remaining on the belt filter;

[0047] Among them, the raw brine used in this embodiment is taken from a sulfate-type salt lake in Tibet, and the aluminum-based adsorbent used is a powder aluminum-based adsorbent. However, the raw brine and the aluminum-based adsorbent are only used as specific examples, and the present invention has no restrictions on the types, sources, and properties of the brine that the process can handle, and any brine can be processed; the aluminum-based adsorbent can also be specifically selected by those skilled in the art;

[0048] In this step, the adsorbent bed layer is formed by the adsorbent aggregating on the belt filter under the action of a vacuum extraction device after being separated from the raw brine, with a thickness of about 20 cm and a water content of less than 40%;

[0049] S2: Perform nanofiltration treatment on the raw brine to remove divalent anions and divalent cations, and obtain the nanofiltration product water as the transformation agent;

[0050] Specifically, another portion of the original brine is subjected to nanofiltration treatment, which can be single-stage nanofiltration, or two-stage or multi-stage nanofiltration. It is preferable that in the nanofiltration result, more than 80% of divalent anions (including sulfate, carbonate, arsenate, etc.) and divalent cations (including calcium ions, magnesium ions, etc.) are retained in the nanofiltration concentrate. The nanofiltration permeate that does not contain the above divalent cations and anions is used as the transformation agent. Before being applied to step S3, the pH of the transformation agent needs to be adjusted to the range of 4-6;

[0051] There is no absolute sequence between step S2 and step S1. For the transformation operation of step S3 to proceed smoothly after step S1, step S2 and step S1 can be carried out simultaneously, or even step S2 can be carried out first, and the prepared transformation agent is reserved;

[0052] S3: The transformation agent is used to wash the adsorbent bed after step S1;

[0053] Among them, the dosage of the transformation agent is 20% of the dosage of the original brine in step S1;

[0054] After washing, the water content of the adsorbent bed is also lower than 40%;

[0055] S4: The adsorbent bed is washed with a salt-washing solution;

[0056] Among them, the salt-washing solution is usually fresh water, and the dosage of the salt-washing solution is 15% of the dosage of the original brine in step S1;

[0057] Under the action of a vacuum device, the water content of the adsorbent bed after washing is also lower than 40%;

[0058] S5: The adsorbent bed is washed with a desorbing solution to obtain a lithium eluate;

[0059] Among them, the desorbing solution is usually fresh water, and the dosage of the desorbing solution is 200% of the dosage of the original brine in step S1 (the dosage of the desorbing solution depends on the lithium concentration. Desorption can only be carried out after the salt-washing is qualified, otherwise the amount of salt-washing water needs to be increased);

[0060] Under the action of a vacuum device, the water content of the adsorbent bed after washing is also lower than 40%.

[0061] Examples 2-3

[0062] The lithium extraction process from original brine in this example is basically the same as that in Example 1, with the difference being:

[0063] It also includes the following operations: collecting the effluent of step S3, subjecting it to nanofiltration treatment to obtain secondary nanofiltration product water, adding the secondary nanofiltration product water to the nanofiltration product water of step S2, and the dosage of the secondary nanofiltration product water is 3% or 5% of the nanofiltration product water. After mixing the two, adjust the pH to 4-6 for use as a transformation agent.

[0064] Examples 4-8

[0065] In this example, a process for extracting lithium from raw brine is basically the same as that in Example 1, except that:

[0066] It also includes the following operations: collecting the effluent of step S4, i.e., the washing water, and returning the washing water between step S1 and step S3 to rinse the adsorbent bed.

[0067] In this example, the dosages of the washing water, transformation agent, salt washing solution, and desorbing solution are shown in Table 1.

[0068] Table 1 Dosages of washing water, transformation agent, salt washing solution, and desorbing solution in Examples 4-8 (proportion of the dosage of raw brine in step S1 / %)

[0069] Group Washing water Conversion agent Salt washing solution Desorbed solution Example 4 5％ 15％ 5％ 200％ Example 5 8％ 12％ 8％ 200％ Example 6 10％ 10％ 10％ 200％ Example 7 5％ 10％ 5％ 200％ Example 8 10％ 15％ 10％ 200％

[0070] It can be seen that since a pre-salt washing step is added between the adsorption step and the transformation step in Examples 4-8, the dosages of the transformation agent and the salt washing solution are both less than those in Examples 1-3.

[0071] The salt-lithium ratio, magnesium-lithium ratio, lithium concentration, and lithium recovery rate of the lithium eluate obtained in Examples 1-8 were analyzed, and the results are shown in Table 2.

[0072] Table 2 Analysis of lithium eluate of each example

[0073] Group Salt-lithium ratio Magnesium-lithium ratio Lithium concentration (mg / L) Lithium recovery rate % Example 1 9.95 0.20 195 86.67 Example 2 10.24 0.21 204 85.78 Example 3 10.14 0.19 193 87.56 Example 4 10.35 0.22 199 93.33 Example 5 10.15 0.20 199 92.44 Example 6 10.04 0.21 218 90.67 Example 7 10.33 0.22 220 94.67 Example 8 9.97 0.19 195 91.56

[0074] It can be seen from Table 2 that adding a transformation step can improve the lithium recovery rate of the system. In Examples 4-8, the lithium recovery rate in the desorbing solution is above 90%, while the lithium recovery rate in Examples 1-3 is between 85-87%. This shows that after the adsorbent is transformed, the adsorption and desorption processes of the adsorbent are more thorough. During the desorption process, more lithium is desorbed into the desorbing solution, and the adsorption effect of lithium during the adsorption process is also enhanced, effectively reducing the poisoning risk of the adsorbent.

[0075] In addition, adding a pre-salt washing step not only reduces the dosages of the transformation agent and the salt washing solution, which is beneficial to improving the salt washing efficiency, but also helps to ensure the quality of the lithium eluate, and the salt-lithium ratio of the lithium eluate fluctuates slightly around 10:1.

[0076] It can be seen from Examples 1-3 that the effluent from step S3 can be recycled after nanofiltration treatment, which has little impact on the desorbent, effectively reducing the nanofiltration load of the brine and thus reducing the investment cost of nanofiltration.

[0077] Example 9

[0078] As Figure 1 shown, a brine lithium extraction device in this embodiment includes a frame 1, on which a filter cloth 2 is movably arranged, and the filter cloth 2 moves along a preset path. Figure 1 The path shown in is linear, but other forms of paths, such as circular, are also feasible. This embodiment has no requirements for the form of the path, and any form of path can be set with the following functional areas.

[0079] An adsorption area 100, a transformation area 200, a first washing area 300 and a desorption area 400 are successively arranged on the path. Correspondingly, a mixing adsorption mechanism 3, a transformation mechanism 4, a first washing mechanism 5 and a desorption mechanism 6 are successively installed on the frame 1 along the path.

[0080] Among them, the mixing adsorption mechanism 3 includes a mixing tank 31. After brine and adsorbent are respectively input into the mixing tank 31, they are stirred and mixed evenly, and then the suspension is output to the adsorption area 100 through a feeding port above the adsorption area 100.

[0081] On the filter cloth 2 running at a constant speed, the suspension discharged at a constant speed forms an adsorbent bed layer with a thickness of about 1.5-4 cm under the action of a vacuum pumping mechanism; when the suspension is continuously discharged, the adsorbent bed layer extends along the entire running path of the filter cloth 2, and when the suspension is intermittently discharged, multiple adsorbent bed layers with intervals between them will be formed on the filter cloth 2.

[0082] The transformation mechanism 4 includes a nanofiltration device 41, which is used for nanofiltration treatment of brine to obtain nanofiltration concentrate and nanofiltration fresh water respectively. After adjusting the pH value of the nanofiltration fresh water, the nanofiltration fresh water is sprayed onto the adsorbent bed layer by a spraying device above the transformation area 200 to realize the transformation of the adsorbent.

[0083] The first washing mechanism 5 sprays a salt washing solution onto the adsorbent bed layer by a spraying device above the first washing area 300, and the desorption mechanism 6 sprays a desorbent onto the adsorbent bed layer by a spraying device above the desorption area 400.

[0084] Below the adsorption area 100, the transformation area 200, the first washing area 300 and the desorption area 400, a brine collection mechanism 8, a transformation agent collection mechanism 9, a washing water collection mechanism 10 and an eluate collection mechanism 11 are respectively arranged to collect the effluent from each area.

[0085] Example 10

[0086] As Figure 2 shown, the lithium extraction device from bittern in this embodiment has basically the same structure as that in Embodiment 9, except that: a second washing area 500 located between the adsorption area 100 and the transformation area 200 is further provided on the moving path of the filter bed, a second washing mechanism 7 located above the second washing area 500 and a pre-washing water collection mechanism 13 located below the second washing area are further provided on the frame 1;

[0087] After the washing water collection mechanism 10 located below the first washing area 300 collects the washing water flowing out of the first washing area 300, the washing water is conveyed to the second washing mechanism 7 through the return pipe 12 and sprayed to the second washing area 500 by the second washing mechanism 7.

[0088] Embodiment 11

[0089] As Figure 3 shown, the lithium extraction device from bittern in this embodiment has basically the same structure as that in Embodiment 9 or 10, except that: the transformation agent collection mechanism 9 is connected to the nanofiltration device 14, and the output pipeline of the nanofiltration device 14 is connected to the output pipeline of the nanofiltration device 41 through a tee 15. After the nanofiltration device 14 nanofilters the water discharged from the transformation area to obtain secondary nanofiltration product water, after adjusting the pH, it flows back to the transformation area; a valve is provided at the tee 15 to adjust the flow ratio of the secondary nanofiltration product water and the nanofiltration product water.

Claims

1. A process for extracting lithium from brine, characterized in that, It includes the following steps: S1: After mixing and adsorbing brine with an aluminum-based adsorbent, transfer it to a filter bed for solid-liquid separation to obtain an adsorbent bed layer; S2: Perform nanofiltration treatment on the brine to remove divalent anions and divalent cations, and obtain nanofiltration produced water as a transformation agent; S3: Use the transformation agent to wash the adsorbent bed layer after step S1; In steps S1 and S2, the brine mentioned independently is raw brine or brine obtained after pretreatment of raw brine.

2. The brine lithium extraction process according to claim 1, characterized in that, At the end of steps S1 and S3, the water content of the adsorbent bed layer is less than 40%.

3. The brine lithium extraction process according to claim 1, characterized in that, In step S2, the nanofiltration is single-stage nanofiltration or multi-stage nanofiltration to make the removal rate of divalent anions greater than 80%; The divalent anions at least include one or more of sulfate, carbonate, and arsenate.

4. The brine lithium extraction process according to claim 1, characterized in that, In step S2 or S3, adjust the pH of the transformation agent to 4 - 6.

5. The brine lithium extraction process according to claim 1, characterized in that, The dosage of the transformation agent in step S3 is 10 - 15% of the dosage of brine in step S1.

6. The brine lithium extraction process according to claim 1, characterized in that, It also includes: Collect the effluent from step S3, obtain secondary nanofiltration produced water after re-nanofiltration, and add the secondary nanofiltration produced water to the transformation agent in step S2 for recycling.

7. The brine lithium extraction process according to claim 6, wherein, The dosage of the secondary nanofiltration produced water is 3 - 5% of the transformation agent.

8. The brine lithium extraction process according to claim 1, characterized in that, It also includes: Step S4: Use a salt-washing solution to wash the adsorbent bed layer and collect the washing water; The dosage of the salt-washing solution is 5 - 10% of the dosage of brine in step S1; at the end of step S4, the water content of the adsorbent bed layer is less than 40%; Step S5: Use the washing water to wash the adsorbent bed layer after step S1 before the transformation agent; The dosage of the washing water is 5 - 10% of the dosage of brine in step S1.

9. A brine lithium extraction device, comprising a frame (1), on which a filter bed is movably arranged, and the filter bed moves along a preset path, characterized in that, An adsorption zone (100), a transformation zone (200), a first washing zone (300), and a desorption zone (400) are successively provided on this path; On the frame (1), there are provided: A mixing and adsorption mechanism (3), which is used to mix the adsorbent and brine evenly and output the suspension to the adsorption zone (100); A transformation mechanism (4), which is used to spray the transformation agent into the transformation zone (200), and this transformation mechanism (4) is connected to the first nanofiltration mechanism through a nanofiltration produced water output pipeline, and the first nanofiltration mechanism is used to perform nanofiltration on the brine and provide nanofiltration produced water to the transformation mechanism (4); A first washing mechanism (5), which is used to spray the salt-washing solution into the first washing zone (300); A desorption mechanism (6), which is used to spray the desorbing solution into the desorption zone (400).

10. The brine lithium extraction device according to claim 9, wherein, A second washing zone (500) is also provided on the moving path of the filter bed in the adsorption zone (100) and the transformation zone (200), and a second washing mechanism (7) is also provided on the frame (1) above the second washing zone (500); A washing water collection mechanism (10) for collecting the effluent from the first washing zone (300) is also provided on the frame (1), and this washing water collection mechanism (10) is used to supply the collected washing water to the second washing mechanism (7).

Images