Device and method for recovering and extracting lithium from calcium and magnesium slag with low energy consumption

Abstract

The invention provides a device and a method for recovering and extracting lithium from calcium and magnesium slag with low energy consumption, and belongs to the technical field of lithium resource recovery and energy utilization. The low-energy-consumption recovery and lithium extraction device for the calcium and magnesium slag comprises a dynamic stirring and washing separation system, a nanofiltration membrane calcium removal system, a two-stage membrane concentration system, an acid clinker slurrying reaction system and a closed water circulation system. The method comprises the following steps: stirring and washing calcium and magnesium slag to separate out a lithium-containing solution, sequentially removing calcium by a nanofiltration system and directionally concentrating lithium ions by a membrane to obtain a high-concentration lithium sulfate solution, and recycling purified water. According to the device, through process coupling and resource circulation design, the problems of low lithium recovery rate, high evaporation energy consumption, large waste residue and waste water discharge amount and the like in a traditional calcium and magnesium slag lithium extraction process are solved, the subsequent lithium salt production cost is remarkably reduced, and the device is suitable for calcium and magnesium slag treatment in various scenes such as salt lake and ore lithium extraction.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium resource recovery and energy utilization, and particularly to a device and method for low-energy consumption recovery and lithium extraction from calcium-magnesium slag. Background Art

[0002] In the processes of many lithium ore processing, lithium extraction from salt lakes and related industries, a large amount of calcium-magnesium slag containing lithium is generated. If these waste residues are directly discarded, it will not only cause serious waste of lithium resources, but also may bring environmental problems. Traditional treatment methods often cannot effectively separate lithium from calcium and magnesium components, and have huge energy consumption in the subsequent lithium purification process, and the consumption of water resources cannot be reasonably controlled, making it difficult to meet the requirements of sustainable development.

[0003] Currently known lithium extraction processes from calcium-magnesium slag mostly involve chemical precipitation methods, resin adsorption methods or extraction methods for impurity removal, such as dissolving and pulping followed by multi-stage impurity removal of calcium and magnesium ions, and then adding carbonate to precipitate lithium in the lithium-containing solution after impurity removal to obtain lithium carbonate products. For example, patents CN116639715A, CN109455744B, CN109735709B, CN116835614A and "Research on Preparation of Battery-grade Lithium Carbonate from Calcium-Magnesium Slag in the Recycling Process of Waste Lithium-Ion Batteries", etc., all involve impurity removal means. There is also a method of mixing lithium-containing waste residue with calcium-magnesium slag and adding it to a soluble chloride salt solution for reaction to obtain a lithium chloride solution, such as patent CN115141933B. These methods all have the disadvantages of long process, complex lithium extraction technology and high cost. In particular, patent CN116639715A also involves returning the tail liquid after lithium extraction from the washing liquid of calcium-magnesium slag to the system, which may lead to salt accumulation and affect subsequent processes.

[0004] Therefore, how to obtain a lithium extraction device and method with low energy consumption and simple process is a technical problem that needs to be solved currently. Summary of the Invention

[0005] The purpose of the present invention is to provide a device and method for low-energy consumption recovery and lithium extraction from calcium-magnesium slag to solve the above technical problems.

[0006] To achieve the above invention purpose, the present invention provides the following technical solutions:

[0007] The present invention provides a device for low-energy consumption recovery and lithium extraction from calcium-magnesium slag, comprising a dynamic stirring and washing separation system, a nanofiltration membrane calcium removal system 6, a two-stage membrane concentration system 7 and an acid clinker pulping reaction system connected in sequence;

[0008] The dynamic stirring and washing separation system comprises a washing tank 2 with adjustable stirring speed and a solid-liquid separation device 3.

[0009] Further, a closed-loop water circulation system is formed between the dynamic stirring and separation system and the two-stage membrane concentration system 7. In the closed-loop water circulation system, the two-stage membrane concentration system 7 is sequentially connected to the dynamic stirring and separation system via the microfiltration unit 10 and the pH adjustment unit 11 to form a closed-loop circulation.

[0010] Further, the nanofiltration membrane calcium removal system 6 includes an adsorption unit, and the adsorption unit uses a surface-modified molecular sieve material.

[0011] Further, the two-stage membrane concentration system 7 includes a series-connected nanofiltration membrane and a reverse osmosis membrane.

[0012] Further, the acid clinker pulping reaction system includes a pH feedback adjustment unit 8 and an acid clinker pulping reaction tank 9.

[0013] The present invention also provides a method for low-energy consumption recovery and lithium extraction from calcium-magnesium slag, including the following steps:

[0014] 1) After mixing calcium-magnesium slag and water, a lithium-containing solution is obtained after separation by the dynamic stirring and separation system;

[0015] 2) After passing the lithium-containing solution through the nanofiltration membrane calcium removal system 6, the obtained filtrate enters the two-stage membrane concentration system 7 for concentration to obtain a lithium-rich concentrated phase and a low-lithium clear phase;

[0016] 3) The obtained lithium-rich concentrated phase is mixed with acid clinker through the acid clinker pulping reaction system, and the pH is monitored in real time by the pH feedback adjustment unit 8 to obtain a lithium sulfate solution; the obtained low-lithium clear phase returns to the dynamic stirring and separation system through the closed-loop water circulation system.

[0017] Further, the mass ratio of calcium to magnesium in the calcium-magnesium slag is 8-15:1; the solid-liquid ratio of the calcium-magnesium slag and water is 1:3-10.

[0018] Further, the concentration of lithium in the lithium-rich concentrated phase is 2.0-4.0 mol / L.

[0019] Further, the mass ratio of the lithium-rich concentrated phase to the acid clinker is 3-10:1, and the acid clinker is a spodumene acid clinker.

[0020] Further, the pH feedback adjustment unit 8 monitors the pH in real time and adjusts it to 2.5-3.0.

[0021] Advantages of the present invention:

[0022] 1. Compared with the existing multi-stage impurity removal technology for calcium-magnesium slag, the present invention can directly control the dynamic stirring parameters to achieve efficient selective leaching of lithium in calcium-magnesium slag, while suppressing the excessive dissolution of calcium and magnesium ions, thereby reducing the load of the subsequent calcium removal system and improving the lithium recovery rate.

[0023] 2. The lithium-rich concentrate after membrane concentration is incorporated into the slurrying system in the process of producing lithium sulfate from spodumene, directly producing a high-concentration lithium sulfate solution, significantly reducing the evaporation and crystallization energy consumption for subsequent production of lithium salts such as lithium hydroxide, lithium carbonate, and lithium chloride. The low-lithium clear phase after membrane concentration can be recycled to the calcium and magnesium slag scrubbing process to achieve zero wastewater discharge in the whole process. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic structural diagram of the device for low-energy consumption recovery and lithium extraction from calcium and magnesium slag of the present invention;

[0025] Among them, 1 is the calcium and magnesium slag bin; 2 is a scrubbing tank with adjustable stirring speed; 3 is a solid-liquid separation device; 4 is the waste residue discharge port; 5 is the washing liquid tank; 6 is the nanofiltration membrane calcium removal system; 7 is the double-stage membrane concentration system; 8 is the pH feedback adjustment unit; 9 is the acid clinker slurrying reaction tank; 10 is the microfiltration unit; 11 is the pH adjustment unit. DETAILED DESCRIPTION OF THE INVENTION

[0026] The present invention provides a device for low-energy consumption recovery and lithium extraction from calcium and magnesium slag, including a dynamic scrubbing and separation system, a nanofiltration membrane calcium removal system 6, a double-stage membrane concentration system 7, and an acid clinker slurrying reaction system connected in sequence;

[0027] The dynamic scrubbing and separation system includes a scrubbing tank 2 with adjustable stirring speed and a solid-liquid separation device 3.

[0028] In the present invention, a stirring device is provided in the scrubbing tank 2 with adjustable stirring speed. The stirring device destroys the agglomeration structure of the slag body through mechanical shear force, accelerates the dissolution of lithium ions, and at the same time avoids the release of impurities caused by excessive fragmentation. The connected solid-liquid separation device 3 realizes the efficient leaching of soluble lithium in calcium and magnesium slag and the primary solid-liquid separation.

[0029] In the present invention, a closed-circuit water circulation system is formed between the dynamic scrubbing and separation system and the double-stage membrane concentration system 7. In the closed-circuit water circulation system, the double-stage membrane concentration system 7 is connected to the dynamic scrubbing and separation system via a microfiltration unit 10 and a pH adjustment unit 11 in sequence to form a closed-loop circulation.

[0030] In the present invention, the closed-circuit water circulation system includes a microfiltration purification unit 10 and a pH adjustment unit 11, which are used to remove trace residual impurities, adjust the acidity and alkalinity, etc., to meet the water use standards of specific process links in the system, realize zero discharge of process water and recovery of key components, and greatly reduce the water use cost.

[0031] In the present invention, the nanofiltration membrane calcium removal system 6 includes an adsorption unit, and the adsorption unit uses a surface-modified molecular sieve material.

[0032] In the present invention, the adsorption unit of the nanofiltration membrane calcium removal system 6 uses a surface-modified molecular sieve material to selectively intercept Ca2+ divalent metal ions such as calcium ions, etc., and achieve the directional enrichment of lithium ions, preliminarily purify the solution, and avoid scaling and blocking of pipelines caused by calcium salts, etc. in subsequent concentration and other processes.

[0033] In the present invention, the two-stage membrane concentration system 7 includes a nanofiltration membrane and a reverse osmosis membrane connected in series. In the first stage, a nanofiltration membrane with an appropriate molecular weight cut-off is used to further remove impurities such as residual fine colloids and macromolecular organic matters in the solution; in the second stage, a highly efficient reverse osmosis membrane is used. Under high pressure, water molecules overcome the osmotic pressure and pass through the reverse osmosis membrane to become purified water, which is discharged and recycled to the closed-loop water circulation module, while lithium ions are highly concentrated and retained, and finally a high-concentration lithium-containing solution is obtained. The two-stage membranes work together to gradually increase the lithium ion concentration, greatly improving the recovery efficiency of lithium resources.

[0034] In the present invention, the acid clinker slurrying reaction system includes a pH feedback adjustment unit 8 and an acid clinker slurrying reaction tank 9. The pH feedback adjustment unit 8 is used to monitor the pH value of the reaction system in real time and accurately control the addition amount of the lithium-rich solution.

[0035] The present invention also provides a method for low-energy consumption recovery and lithium extraction from calcium-magnesium slag, including the following steps:

[0036] 1) After mixing calcium-magnesium slag and water, a lithium-containing solution is obtained through separation by a dynamic stirring and washing separation system;

[0037] 2) After passing the lithium-containing solution through the nanofiltration membrane calcium removal system 6, the obtained filtrate enters the two-stage membrane concentration system 7 for concentration to obtain a lithium-rich concentrated phase and a low-lithium clear phase;

[0038] 3) The obtained lithium-rich concentrated phase is mixed with acid clinker through the acid clinker slurrying reaction system, and the pH is monitored in real time by the pH feedback adjustment unit 8 to obtain a lithium sulfate solution; the obtained low-lithium clear phase returns to the dynamic stirring and washing separation system through the closed-loop water circulation system.

[0039] In the present invention, the mass ratio of calcium to magnesium in the calcium-magnesium slag is 8-15:1, preferably 8:1 or 15:1; the solid-liquid ratio of the calcium-magnesium slag and water is 1:3-10, preferably 1:3.

[0040] In the present invention, the concentration of lithium in the lithium-rich concentrated phase is 2.0-4.0 mol / L, preferably 2.8-3.2 mol / L.

[0041] In the present invention, the mass ratio of the lithium-rich concentrated phase to the acid clinker is 3-10:1, preferably 5:1; the acid clinker is a spodumene acid clinker.

[0042] In the present invention, the pH feedback adjustment unit 8 monitors the pH in real time and adjusts it to 2.5-3.0, preferably 2.8.

[0043] The technical solutions provided by the present invention will be described in detail below in conjunction with embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0044] Example 1

[0045] Raw materials: Treatment of calcium-magnesium slag from lithium extraction from salt lakes (lithium content 0.8%, calcium-magnesium ratio 15:1, pH 8.2).

[0046] 1) Dynamic stirring and washing separation system: Mix the calcium-magnesium slag with recycled water at a solid-liquid ratio of 1:3, start variable-frequency stirring, and obtain a lithium-containing solution (lithium concentration 0.5 mol / L, calcium ion concentration 1200 ppm) and low-lithium residue (lithium content < 0.1%) after centrifugal separation;

[0047] 2) Nanofiltration membrane calcium removal system 6: The lithium-containing solution flows through a modified molecular sieve adsorption column, and the residual calcium ion content ≤ 10 ppm. The filtrate enters the bipolar membrane concentration system;

[0048] 3) Double-stage membrane concentration system 7: A nanofiltration membrane (cut-off molecular weight 200 Da) is connected in series with a reverse osmosis membrane (desalination rate ≥ 98%) and further concentrated to a lithium concentration of 2.8 mol / L. The low-lithium clear phase enters the closed-loop water circulation system;

[0049] 4) Acid clinker pulping system: Premix the lithium-rich concentrate (2.8 mol / L) with lithium spodumene acid clinker at a mass ratio of 5:1, transport it to the acid clinker pulping reaction tank 9, monitor and adjust the pH to 2.5 in real time, and react to generate a lithium sulfate solution (concentration 3.0 mol / L, purity ≥ 99.5%);

[0050] 5) Closed-loop water circulation system: The low-lithium clear phase is microfiltered to remove suspended solids and then neutralized to neutrality and returned to the dynamic stirring and washing separation system.

[0051] Example 2

[0052] Raw materials: Treatment of calcium-magnesium slag from lithium extraction from lithium spodumene (lithium content 1.2%, calcium-magnesium ratio 8:1).

[0053] 1) Dynamic stirring and washing separation system: Mix the calcium-magnesium slag with recycled water at a solid-liquid ratio of 1:3, start variable-frequency stirring, and obtain a lithium-containing solution (lithium concentration 0.7 mol / L, calcium ion concentration 1500 ppm) and low-lithium residue (lithium content < 0.1%) after centrifugal separation;

[0054] 2) Nanofiltration membrane calcium removal system 6: The lithium-containing solution flows through a modified molecular sieve adsorption column, and the residual calcium ion content ≤ 15 ppm. The filtrate enters the bipolar membrane concentration system;

[0055] 3) Double - stage membrane concentration system 7: A nanofiltration membrane (molecular weight cut - off 200 Da) is in series with a reverse osmosis membrane (salt rejection rate ≥ 98%), and it is further concentrated to a lithium concentration of 3.2 mol / L. The low - lithium clear phase enters the closed - loop water circulation system;

[0056] 4) Acid - cooked material pulping system: The lithium - rich concentrated phase (3.2 mol / L) and lithium spodumene acid - cooked material are premixed at a mass ratio of 5:1, and then transported to the acid - cooked material pulping reaction tank 9. The pH is monitored in real - time and adjusted to 3.0, and lithium sulfate solution (concentration 3.5 mol / L, purity ≥ 99.3%) is generated by the reaction;

[0057] 5) Closed - loop water circulation system: After the low - lithium clear phase removes suspended solids through microfiltration, it is neutralized to neutral and then returned to the dynamic stirring and separation system.

[0058] Example 3

[0059] Raw materials: Treatment of lithium - containing calcium - magnesium slag from lithium extraction from lithium spodumene (lithium content 1.0%, calcium - magnesium ratio 12:1).

[0060] 1) Dynamic stirring and separation system: The calcium - magnesium slag and recycled water are mixed at a solid - liquid ratio of 1:3, the variable - frequency stirring is started, and a lithium - containing solution (lithium concentration 0.6 mol / L, calcium ion concentration 1300 ppm) and low - lithium residue (lithium content < 0.1%) are obtained after centrifugal separation;

[0061] 2) Nanofiltration membrane calcium - removal system 6: The lithium - containing solution flows through a modified molecular sieve adsorption column, and the residual calcium ion content ≤ 13 ppm. The filtrate enters the bipolar membrane concentration system;

[0062] 3) Double - stage membrane concentration system 7: A nanofiltration membrane (molecular weight cut - off 200 Da) is in series with a reverse osmosis membrane (salt rejection rate ≥ 98%), and it is further concentrated to a lithium concentration of 3.0 mol / L. The low - lithium clear phase enters the closed - loop water circulation system;

[0063] 4) Acid - cooked material pulping system: The lithium - rich concentrated phase (3.0 mol / L) and lithium spodumene acid - cooked material are premixed at a mass ratio of 5:1, and then transported to the acid - cooked material pulping reaction tank 9. The pH is monitored in real - time and adjusted to 3.0, and lithium sulfate solution (concentration 3.4 mol / L, purity ≥ 99.5%) is generated by the reaction;

[0064] 5) Closed - loop water circulation system: After the low - lithium clear phase removes suspended solids through microfiltration, it is neutralized to neutral and then returned to the dynamic stirring and separation system.

[0065] As can be seen from the above examples, the present invention provides a device and method for low - energy - consumption recovery and lithium extraction from calcium - magnesium slag. Through process coupling and resource - cycle design, the device of the present invention solves the problems of low lithium recovery rate, high evaporation energy consumption, and large discharge of waste residue and waste water in the traditional lithium - extraction process from calcium - magnesium slag, significantly reduces the subsequent production cost of lithium salts, and is applicable to the treatment of calcium - magnesium slag in various scenarios such as salt - lake and ore - based lithium extraction.

[0066] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A device for low - energy - consumption recovery and lithium extraction from calcium - magnesium slag, characterized in that, It includes a dynamic stirring and separation system, a nanofiltration membrane calcium removal system, a two-stage membrane concentration system, and an acid clinker pulping reaction system connected in sequence; The dynamic stirring and separation system includes a stirring tank with adjustable stirring speed and a solid-liquid separation device.

2. The lithium recovery device with low energy consumption from calcium-magnesium slag according to claim 1, wherein A closed-loop water circulation system is formed between the dynamic stirring and separation system and the two-stage membrane concentration system. In the closed-loop water circulation system, the two-stage membrane concentration system is connected to the dynamic stirring and separation system via a microfiltration unit and a pH adjustment unit in sequence to form a closed-loop circulation.

3. The lithium recovery device with low energy consumption from calcium-magnesium slag according to claim 2, characterized in that, The nanofiltration membrane calcium removal system contains an adsorption unit, and the adsorption unit uses a surface-modified molecular sieve material.

4. The lithium recovery device with low energy consumption from calcium-magnesium slag according to claim 3, characterized in that, The two-stage membrane concentration system contains a series-connected nanofiltration membrane and a reverse osmosis membrane.

5. The lithium recovery device with low energy consumption from calcium-magnesium slag according to claim 1 or 4, characterized in that, The acid clinker pulping reaction system contains a pH feedback adjustment unit and an acid clinker pulping reaction tank.

6. A method for low-energy consumption recovery and lithium extraction from calcium-magnesium slag, characterized in that, It includes the following steps: 1) After mixing calcium-magnesium slag and water, a lithium-containing solution is obtained after separation by the dynamic stirring and separation system; 2) After passing the lithium-containing solution through the nanofiltration membrane calcium removal system, the obtained filtrate enters the two-stage membrane concentration system for concentration to obtain a lithium-rich concentrated phase and a low-lithium clear phase; 3) The obtained lithium-rich concentrated phase is mixed with acid clinker in the acid clinker pulping reaction system, and the pH is monitored in real time by the pH feedback adjustment unit to obtain a lithium sulfate solution; the obtained low-lithium clear phase returns to the dynamic stirring and separation system through the closed-loop water circulation system.

7. The method for low-energy consumption recovery and lithium extraction from calcium-magnesium slag according to claim 6, characterized in that, The mass ratio of calcium to magnesium in the calcium-magnesium slag is 8-15:1; the solid-liquid ratio of the calcium-magnesium slag to water is 1:3-10.

8. The method for low-energy consumption recovery and lithium extraction from calcium-magnesium slag according to claim 6 or 7, characterized in that, The concentration of lithium in the lithium-rich concentrated phase is 2.0-4.0 mol / L.

9. The method for low-energy consumption recovery and lithium extraction from calcium-magnesium slag according to claim 8, characterized in that, The mass ratio of the lithium-rich concentrated phase to the acid clinker is 3-10:1, and the acid clinker is a spodumene acid clinker.

10. The method for low-energy consumption recovery and lithium extraction from calcium-magnesium slag according to claim 9, characterized in that, The pH feedback adjustment unit monitors the pH in real time and adjusts it to 2.5-3.0.

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