A device for extracting lithium from old salt lake brine

Abstract

The application discloses a kind of salt lake old brine lithium extraction devices, comprising: adsorption device, filter device, nanofiltration-reverse osmosis device, electrodialysis device, resin impurity removal device, MVR concentration device, crystallization reactor, solid-liquid separation device, washing and dewatering device, drying device, granulation and crushing device and demagnetization packaging device in series connection sequentially;Wherein, the device is used to carry out lithium adsorption to salt lake old brine, nanofiltration-reverse osmosis device is used to filter and concentrate lithium-rich solution obtained by adsorption device, and resin impurity removal device is used to remove calcium ions, magnesium ions and boron ions in lithium solution concentrated by electrodialysis device.The application realizes preliminary separation of magnesium and lithium by using adsorption device, adopts nanofiltration-reverse osmosis device to realize the purpose of concentrating and purifying lithium chloride solution mother liquor, and the high lithium mother liquor after concentration and purification can meet the index requirements of high-quality lithium carbonate product in the later process, with the advantage of lower production operation cost.

Description

Technical Field

[0001] This invention belongs to the field of lithium extraction technology from salt lake brine, specifically relating to a lithium extraction device from old salt lake brine. Background Technology

[0002] With the rapid development of the new energy industry, lithium resources have become one of the most valued strategic resources in the world, triggering an explosive growth in global demand for lithium resources. Currently, lithium resource production methods are mainly divided into two types: liquid lithium extraction and ore lithium extraction. Among them, liquid lithium extraction technology has significant advantages due to its low cost, short cycle, and low pollution, and is becoming the mainstream lithium extraction method.

[0003] In the lithium extraction industry from salt lakes, the efficient, economical, and environmentally friendly extraction of lithium from complex liquid lithium resources such as salt lake brine and underground leachate has become a key challenge. Traditional liquid lithium extraction methods, such as aluminate precipitation and solvent extraction, suffer from problems such as high consumption, long process flow, low lithium recovery rate, high environmental pollution risk, and high operating costs when processing low-grade brine with a high magnesium-to-lithium ratio. Membrane technology, when used alone, also faces challenges such as easy scaling and limited selectivity for the separation of monovalent ions. Summary of the Invention

[0004] The purpose of this invention is to provide a lithium extraction device from old brine in salt lakes, which improves the overall lithium ion yield, increases the capacity of the adsorption device and the utilization rate of the adsorbent, and significantly reduces the investment and production costs of lithium extraction from brine.

[0005] The purpose of this invention is to provide a lithium extraction device from old salt lake brine, comprising: an adsorption device, a filtration device, a nanofiltration-reverse osmosis device, an electrodialysis device, a resin impurity removal device, an MVR concentration device, a crystallization reactor, a solid-liquid separation device, a washing and dehydration device, a drying device, a granulation and pulverization device, and a demagnetizing and packaging device connected in series; wherein, the adsorption device is used to adsorb lithium from the old salt lake brine, the nanofiltration-reverse osmosis device is used to filter and concentrate the lithium-rich solution obtained by the adsorption device, and the resin impurity removal device is used to remove calcium ions, magnesium ions, and boron ions from the lithium solution concentrated by the electrodialysis device.

[0006] Preferably, the adsorption device includes multiple first continuous ion exchange beds arranged in parallel. Each first continuous ion exchange bed includes multiple functional zones, namely an adsorption zone, a rinsing zone, a desorption zone, and a top material zone. Each first continuous ion exchange bed also includes multiple adsorption columns, and each adsorption column can be switched sequentially between the adsorption zone, the rinsing zone, the desorption zone, and the top material zone.

[0007] Preferably, both the adsorption zone and the desorption zone have multiple adsorption column arrangement positions arranged in series, and multiple sets of the multiple adsorption column arrangement positions arranged in series are arranged in parallel. The rinsing zone includes multiple adsorption column arrangement positions arranged in series. Each adsorption column can switch between adsorption column arrangement positions corresponding to different functional zones.

[0008] Preferably, the first continuous excitation bed includes a base and a rotating disk, the rotating disk is rotatably disposed on the base, the adsorption column is fixed on the rotating disk, and the rotating disk switches between the adsorption column arrangement positions under the drive of the transmission mechanism.

[0009] Preferably, the nanofiltration-reverse osmosis device includes a main filtration system and a branch recovery system. The main filtration system includes a first nanofiltration unit, a first reverse osmosis unit, a second nanofiltration unit, a third nanofiltration unit, a second reverse osmosis unit, and a fourth nanofiltration unit connected in series. The branch recovery system includes a first branch nanofiltration unit, a second branch nanofiltration unit, a first branch reverse osmosis unit, and a second branch reverse osmosis unit. The first branch nanofiltration unit and the second branch nanofiltration unit are connected together. The first branch nanofiltration unit is also connected to the first nanofiltration unit. The first branch reverse osmosis unit is connected to both the first branch nanofiltration unit and the second branch nanofiltration unit. The second branch reverse osmosis unit is connected to the first reverse osmosis unit.

[0010] Preferably, the electrodialysis device includes two-stage electrodialysis units, each stage of the electrodialysis unit includes two sections of electrodialysis units, each section of the electrodialysis unit includes multiple electrodialyzers, the two sections of the electrodialysis unit are respectively a first section of electrodialysis unit and a second section of electrodialysis unit, the first section of electrodialysis unit is located upstream of the second section of electrodialysis unit, wherein the number of electrodialyzers in the first section of electrodialysis unit is greater than the number of electrodialyzers in the second section of electrodialysis unit.

[0011] Preferably, each of the electrodialysis units includes an electrodialysis tank, a cathode electrode chamber, and an anode electrode chamber, with the cathode electrode chamber and the anode electrode chamber located at opposite ends of the electrodialysis tank. The electrodialysis tank is provided with a plurality of alternately arranged anion exchange membranes and cation exchange membranes, and the electrodialysis tank stores electrolytes.

[0012] Preferably, the MVR concentration unit includes a raw material preheating unit, an evaporation separation unit, and a vapor compression unit. The raw material preheating unit includes a distilled water plate heat exchanger, a condensate heat exchanger, a non-condensable gas heat exchanger, and a fresh steam heat exchanger arranged in sequence. The evaporation separation unit includes a falling film heat exchanger and a separator. The inlet of the falling film heat exchanger is connected to the outlet of the raw material preheating unit. The vapor compression unit includes a steam scrubbing tower and a steam compressor connected in sequence. The inlet of the steam scrubbing tower is connected to the steam outlet of the separator, and the outlet of the steam compressor is connected to the inlet of the falling film heat exchanger.

[0013] Preferably, the solid-liquid separation device includes a thickener, which includes a drive shaft, a rake frame, and a lifting mechanism. The rake frame is located inside the thickener, and rake teeth are provided below the rake frame. The drive shaft is connected to the rake frame for driving the rake frame to rotate, and the lifting mechanism is used to drive the rake frame to move in the up and down direction.

[0014] Preferably, the lithium extraction device from old brine in salt lakes further includes: a lithium-sodium separation device for the recovered liquid, wherein the lithium-sodium separation device for the recovered liquid includes multiple second continuous ion exchange beds arranged in parallel, the inlet of the second continuous ion exchange bed is connected to the outlet of the thickener, and the outlet of the second continuous ion exchange bed is connected to the MVR concentration device.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0016] The lithium extraction device for old brine proposed in this invention improves the overall lithium-ion yield, increases the capacity of the adsorption device and the utilization rate of the adsorbent, and significantly reduces the investment and production costs of lithium extraction from brine. In addition, the adsorption device is used to achieve the initial separation of magnesium and lithium, and the nanofiltration-reverse osmosis device is used to achieve the purpose of concentrating and purifying the lithium chloride solution mother liquor. The concentrated and purified high-lithium mother liquor can meet the index requirements of the subsequent process for producing high-quality lithium carbonate products, and has the advantage of low production and operating costs.

[0017] This invention achieves the recovery of lithium precipitation mother liquor through a lithium-sodium separation device, and uses a lithium-sodium separation resin process to recover lithium from the lithium precipitation mother liquor. It has a high lithium recovery rate and virtually no environmental pollution. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the lithium extraction device from old brine in the salt lake in this invention;

[0019] Figure 2 This is a flowchart of the concentration filtration process using a nanofiltration-reverse osmosis device in this invention.

[0020] In the diagram: 1. Adsorption device; 2. Filtration device; 3. Nanofiltration-reverse osmosis device; 4. Electrodialysis device; 5. Resin impurity removal device; 6. MVR concentration device; 7. Crystallization reactor; 8. Solid-liquid separation device; 9. Washing and dehydration device; 10. Drying device; 11. Granulation and pulverization device; 12. Demagnetization and packaging device. Detailed Implementation

[0021] The invention will now be further described with reference to the accompanying drawings.

[0022] like Figures 1 to 2 As shown, this invention discloses a lithium extraction device from old salt lake brine, comprising: an adsorption device 1, a filtration device 2, a nanofiltration-reverse osmosis device 3, an electrodialysis device 4, a resin impurity removal device 5, an MVR concentration device 6, a crystallization reactor 7, a solid-liquid separation device 8, a washing and dehydration device 9, and a demagnetizing packaging device 12 connected in series. The old salt lake brine sequentially passes through the adsorption device 1, filtration device 2, nanofiltration-reverse osmosis device 3, electrodialysis device 4, resin impurity removal device 5, MVR concentration device 6, crystallization reactor 7, solid-liquid separation device 8, washing and dehydration device 9, and demagnetizing packaging device 12 for extracting lithium from the old salt lake brine.

[0023] The system comprises the following components: an adsorption device 1 for adsorbing lithium from old brine in a salt lake; a filtration device 2 for removing mechanical impurities, insoluble solids, macromolecular organic matter, and microorganisms from the lithium-rich raw solution flowing out of the adsorption device 1; a nanofiltration-reverse osmosis device 3 for filtering and concentrating the high-lithium mother liquor obtained from the filtration device 2; an electrodialysis device 4 for concentrating the lithium-rich solution obtained from the nanofiltration-reverse osmosis device 3; a resin impurity removal device 5 for removing calcium, magnesium, and boron ions from the lithium solution concentrated by the electrodialysis device 4; an MVR concentration device 6 for concentrating the lithium solution obtained from the resin impurity removal device 5; a crystallization reactor 7 for crystallizing the lithium solution obtained from the MVR concentration device 6; and a solid-liquid separation device 8 for separating the solid from the solid from the solid in the crystallization reactor 7. The obtained solid-liquid solution is separated to obtain a solid and a liquid. The solid enters a washing and dehydration device 9, where it is washed and then dehydrated. The dehydrated solid then enters a drying device 10, where it is dried to remove moisture. After that, it enters a granulation and pulverization device 11, where it is pulverized. Finally, it enters a demagnetizing and packaging device 12, where it demagnetizes and packages the granular solid, ultimately obtaining qualified battery-grade lithium carbonate granules. The liquid enters a lithium-sodium recovery device to separate sodium and lithium ions. The solution containing lithium ions is recovered to an MVR concentration device 6 for further recovery and utilization of lithium ions.

[0024] For example, the washing and dehydration device 9 includes a horizontal scraper centrifuge; the drying device 10 includes an electrically heated rotary dryer; and the granulation and pulverizing device 11 includes an air jet mill.

[0025] Preferably, the adsorption device 1 includes multiple first continuous ion exchange beds arranged in parallel. Each first continuous ion exchange bed includes multiple functional zones, namely an adsorption zone, a rinsing zone, a desorption zone, and a top material zone. Each first continuous ion exchange bed also includes multiple adsorption columns, and each adsorption column can switch between the adsorption zone, the rinsing zone, the desorption zone, and the top material zone in sequence.

[0026] Both the adsorption zone and the desorption zone have multiple adsorption column arrangements connected in series, and multiple sets of these adsorption column arrangements are connected in parallel. The rinsing zone includes multiple adsorption column arrangements connected in series. Each adsorption column can switch between adsorption column arrangements corresponding to different functional zones.

[0027] For example, the adsorption zone has two adsorption column positions connected in series, and nine sets of these two-in-series adsorption column positions are arranged in parallel; the top material zone has one adsorption column position; the desorption zone has two adsorption column positions connected in series, and three sets of these two-in-series adsorption column positions are arranged in parallel; the rinsing zone has five adsorption column positions connected in series; each adsorption column position has one adsorption column. Each adsorption column can only switch between adsorption column positions corresponding to different functional zones.

[0028] Preferably, each first continuous excitation bed includes a base and a rotating disk. The rotating disk is rotatably mounted on the base, and the adsorption columns are fixed on the rotating disk. The rotating disk rotates between the adsorption column positions under the drive of the transmission mechanism.

[0029] For example, each adsorption column is equipped with a distribution valve, which includes a fixed valve and a rotary valve. The fixed valve is fixed to the base and is used to connect to the external material pipeline; the rotary valve is located above the adsorption column and is connected to each adsorption column by a snap-fit ​​connection to achieve synchronous rotation. The rotating disk serves as the carrier of the adsorption column and rotates continuously under the drive of the transmission mechanism. The sealing power system between the rotary valve and the fixed valve ensures that there is no leakage at the valve port.

[0030] After potassium extraction, the old brine is buffered in the old brine feed tank and then pumped into the first continuous ion exchange bed. Lithium chloride in the brine is adsorbed onto the adsorption columns in the adsorption zone. After a certain time, the adsorption columns are transferred to the adsorption column arrangement position in the rinsing zone. The tail brine flowing through the adsorption zone is returned to the salt field for reuse or used as raw material for extracting other products such as potassium, magnesium, boron, and bromine. In the rinsing zone, residual impurities on the adsorption columns and brine entrained in the adsorbent voids are washed away, and the rinsing agent is recovered into the brine. The brine is then passed back into the adsorption zone for adsorption. Afterward, the adsorption column is transferred to the adsorption column arrangement position in the desorption zone, where 40°C pure water is used to desorb the lithium chloride adsorbed on the adsorption column, obtaining a lithium-rich stock solution with a lithium content of over 0.7 g / L. Then, the adsorption column is transferred to the adsorption column arrangement position in the top feed zone. The top feed liquid is water or a dilute solution. While pushing the adsorption column to the desorption zone, the top feed liquid can also "push" the lithium chloride remaining in the adsorption column in the desorption zone back into the desorption water tank, improving product yield and concentration.

[0031] Preferably, the nanofiltration-reverse osmosis device 3 includes a main filtration system and a branch recovery system. The main filtration system includes a first nanofiltration unit, a first reverse osmosis unit, a second nanofiltration unit, a third nanofiltration unit, a second reverse osmosis unit, and a fourth nanofiltration unit connected in series. The branch recovery system includes a first branch nanofiltration unit, a second branch nanofiltration unit, a first branch reverse osmosis unit, and a second branch reverse osmosis unit. The first branch nanofiltration unit and the second branch nanofiltration unit are connected together. The first branch nanofiltration unit is also connected to the first nanofiltration unit. The first branch reverse osmosis unit is connected to both the first branch nanofiltration unit and the second branch nanofiltration unit. The second branch reverse osmosis unit is connected to the first reverse osmosis unit.

[0032] The lithium-rich solution after impurity filtration is first passed into the first nanofiltration unit. After filtration by the first nanofiltration unit, permeate and concentrate are obtained. The permeate is passed into the first reverse osmosis unit, and the concentrate is passed into the first branch nanofiltration unit.

[0033] After concentration in the first reverse osmosis unit, concentrated water and permeate are obtained. The concentrated water is then fed into the second nanofiltration unit, and the permeate is fed into the second branch reverse osmosis unit.

[0034] After filtration by the second nanofiltration unit, permeate and concentrate are obtained. The permeate is then passed into the third nanofiltration unit, and the concentrate is recycled into the lithium-rich solution after impurity filtration.

[0035] After filtration by the third nanofiltration unit, permeate and concentrate are obtained. The permeate is passed into the second reverse osmosis unit, and the concentrate is recycled back to the second nanofiltration unit.

[0036] After concentration in the second reverse osmosis unit, concentrated water and permeate are obtained. The concentrated water is then fed into the fourth nanofiltration unit, and the permeate is fed into the second branch reverse osmosis unit.

[0037] After filtration by the fourth nanofiltration unit, permeate and concentrate are obtained. The permeate is a qualified lithium-rich solution, and the concentrate is recycled to the second nanofiltration unit.

[0038] After filtration by the first branch nanofiltration unit, permeate and concentrate are obtained. The permeate is fed into the first branch reverse osmosis unit, and the concentrate is fed into the second branch nanofiltration unit.

[0039] After filtration by the second branch nanofiltration unit, permeate and concentrate are obtained. The permeate is fed into the first branch reverse osmosis unit, and the concentrate is discharged from the system.

[0040] After concentration by the first branch reverse osmosis unit, concentrated water and permeate are obtained. The concentrated water is recycled to the lithium-rich solution after impurity filtration, and the permeate is passed into the first branch nanofiltration unit.

[0041] After concentration in the second branch reverse osmosis unit, concentrate and permeate are obtained. The concentrate is recycled to the first reverse osmosis unit, and the permeate is recycled to the desorption zone of the first continuous cross-linked bed.

[0042] The final concentration of lithium-rich concentrate resulted in an outlet flow rate of 104 m³. 3 / h, lithium yield >98.5%, Li >7.7 g / L, Ca <30 mg / L, Mg <20 mg / L, SO4 2- <1 mg / L.

[0043] Magnesium-rich concentrate outlet water flow rate: 152m³ 3 / h, Li≤40mg / L, Ca+Mg>20g / L.

[0044] 1104m³ of pure water was recycled. 3 / h, water yield >80%, Li <5mg / L, conductivity <150μs / cm.

[0045] Preferably, the electrodialysis device 4 includes two-stage electrodialysis units, each stage of which includes two sections of electrodialysis units, and each section of electrodialysis unit includes multiple electrodialyzers. The two sections of electrodialysis units are respectively the first section of electrodialysis unit and the second section of electrodialysis unit. The first section of electrodialysis unit is located upstream of the second section of electrodialysis unit, wherein the number of electrodialyzers in the first section of electrodialysis unit is greater than the number of electrodialyzers in the second section of electrodialysis unit.

[0046] The electrodialysis unit 4 employs a two-stage electrodialysis unit. The first-stage electrodialysis unit is designed with two sections: the first section has seven electrodialyzers, and the second section has four electrodialyzers, for a total of eleven electrodialyzers. The second-stage electrodialysis unit is also designed with two sections: the first section has two electrodialyzers, and the second section has one electrodialyzer, for a total of three electrodialyzers. Each stage of the electrodialysis unit can operate simultaneously or independently.

[0047] In the nanofiltration-reverse osmosis unit 3, the incoming water first passes through a first-stage electrodialysis unit. The permeate from the first-stage electrodialysis unit is then sent to a second-stage electrodialysis unit, and the permeate from the second-stage electrodialysis unit is sent to a second-stage electrodialysis unit. The overflow concentrate from the first-stage and second-stage units is mixed, and the resulting concentrate is the final lithium-rich concentrate, which is then pumped out by a concentrate delivery pump.

[0048] The permeate from the first-stage electrodialysis (stage 2) enters the second-stage electrodialysis (stage 1), and the permeate from the second-stage electrodialysis (stage 1) is sent to the second-stage electrodialysis (stage 2), while the permeate from the second-stage electrodialysis (stage 2) is discharged. The concentrate from the overflow of the stage 1 and stage 2 concentrates is mixed and then pumped back to the raw water tank via a reflux pump.

[0049] The outlet flow rate of the lithium-rich solution after concentration and impurity removal by the two-stage electrodialysis unit is approximately 34.7 m³. 3 / h, lithium recovery ≥99%, boron removal ≥86%, silicon removal ≥93%, Li ≥18g / L, boron ≤493mg / L, silicon ≤22mg / L. Electrodialysis desalination outlet flow rate is approximately 60.5m³. 3 / h, TDS approximately 670mg / L.

[0050] Preferably, each electrodialysis unit includes an electrodialysis tank, a cathode electrode chamber, and an anode electrode chamber, located at opposite ends of the electrodialysis tank. The electrodialysis tank contains multiple alternating anion exchange membranes and cation exchange membranes, and stores electrolytes. A desalination chamber and a concentration chamber are connected to the electrodialysis tank. The anion exchange membranes and cation exchange membranes divide the electrodialysis tank into alternating desalination and concentration chambers. When direct current is applied to the cathode and anode electrode chambers, various electrolyte ions migrate with the current. At this time, cations and anions in the electrodialysis tank migrate out through the cation and anion exchange membranes, respectively, thus purifying the solution in that chamber and reducing the salt concentration. This chamber is the desalination chamber. The concentration chamber is used to collect ions migrating from adjacent desalination chambers. Due to the selective permeability of the ion exchange membranes, ions migrating from the desalination chamber cannot migrate out after entering the concentration chamber, thus continuously accumulating in this chamber to form a high-concentration brine.

[0051] Preferably, the resin impurity removal device 5 includes a third continuous ion exchange bed and a fourth continuous ion exchange bed connected in series. The third continuous ion exchange bed is used to remove calcium ions and magnesium ions, and the fourth continuous ion exchange bed is used to remove boron ions.

[0052] The third continuous exchange bed comprises an adsorption zone and a regeneration zone. The adsorption zone has two resin column positions connected in series, while the regeneration zone has one resin column position. Each resin column position contains a resin column filled with calcium and magnesium chelating resin. This resin can adsorb divalent or higher-valent metal ions in solutions containing a large number of monovalent metal ions. The resin column can be switched between multiple resin column positions. The two resin columns in the adsorption zone can be used individually or in series. When the two columns are used in series, the working exchange capacity of the resin is higher, and the removal rate is also higher. The saturation capacity of the calcium and magnesium chelating resin can be used as the working capacity.

[0053] For example, the third continuous cross-linked bed has three resin columns, each with a packing depth of 18m³. 3 Resin, 54m in total 3 Resin. The operating mode is that the first and second stage resin columns are connected in series for adsorption, and the third stage resin column is used for regeneration. When the first stage resin column fails, it is cut off for regeneration. The second and third stage resin columns are connected in series and switched every 9 hours.

[0054] The lithium chloride solution is pumped from the top of the first-stage resin column into the second-stage resin column. The effluent passes through a series valve and enters the second-stage resin column from the top. The effluent from the bottom of the second-stage resin column enters the qualified solution tank after calcium and magnesium removal. The feed solution undergoes series adsorption through the first and second-stage resin columns, with the first-stage column serving as the primary adsorption column and the second-stage column as a guard column to ensure treatment accuracy.

[0055] When the first-stage resin column becomes saturated (or the adsorption feed reaches the process set value), the electrodialysis unit 4 automatically switches valves, and the second and third-stage resin columns are connected in series for adsorption, while the first-stage resin column enters the regeneration process. The first-stage resin column is regenerated using 6% hydrochloric acid to remove the calcium and magnesium ions adsorbed on the resin, thus restoring its adsorption performance. A dilute acid solution is prepared online by mixing pure water from a pure water tank and acid from a 31% hydrochloric acid tank. After acid addition, the acid is washed with pure water, and the effluent enters the front-end membrane section. Finally, after acid removal, a sodium hydroxide solution is used for circulation. Pure water and 32% liquid alkali are mixed online and then fed into the resin column, while the effluent enters the circulation tank, performing reverse circulation of the resin column.

[0056] The fourth continuous ion exchange bed includes an adsorption zone, a washing zone, and a regeneration zone. The adsorption zone has multiple resin column positions arranged in series, the washing zone has multiple resin column positions arranged in series, and the regeneration zone has multiple resin column positions arranged in series. Each resin column position is equipped with a resin column, and the resin columns switch between the resin column positions corresponding to different functional zones.

[0057] The fourth continuous exchanging bed is equipped with sixteen boron removal resin columns, each designed to be filled with 5.0 m³ of boron removal resin. 3 The total filling volume is 80.0 m³.3 The fourth continuous extrusion bed boron removal capacity is: boron content ≤0.5g / L, feed flow rate 36.7m³. 3 / h, the tower cutting time is 60min, and the boron content of the qualified liquid produced after boron removal is reduced to below 2mg / L.

[0058] Adsorption Zone: The adsorption process employs two parallel sets and a single set of four columns in series in a forward operating mode. The feed solution after calcium and magnesium removal enters the boron removal feed tank from the boundary zone. The solution enters from the top of the first-stage adsorption column and flows forward into the second, third, and fourth-stage adsorption columns from the bottom. The adsorption effluent enters the qualified liquid tank from the bottom of the fourth-stage adsorption column. The adsorption operating pressure is controlled below 0.5 MPa.

[0059] Washing section: The washing section consists of two resin columns connected in series. The resin column that has been saturated with adsorption from the adsorption section is fed into the second stage of this section. Pure water is used to wash the residual boron-containing lithium chloride solution in the resin column starting from the first stage. The effluent is judged based on its conductivity. The liquid with high conductivity is returned to the raw material tank for continued adsorption and use, while the liquid with low conductivity is returned to the front-end electrodialysis for further treatment.

[0060] Regeneration zone: Five resin columns are connected in series for forward regeneration. The entire regeneration process is divided into three parts: acid regeneration, alkali conversion, and water washing of alkali.

[0061] Acid regeneration is carried out first. The feed solution from the alkali conversion zone is mixed online with 31% hydrochloric acid solution to form a 3-5% dilute acid solution, which enters from the top of the acid regeneration resin column. The effluent is judged by conductivity. The feed solution with low conductivity is returned to the condensate tank for continued use, while the desorbed solution with high conductivity is discharged.

[0062] After the acid addition is completed, the solution enters the alkali conversion process. The solution from the water washing alkali zone is mixed online with 32% liquid alkali to form a 3-5% dilute alkali solution. This solution enters the resin column from the upper part of the first stage of the alkali conversion process. The effluent passes through series valves and enters the second-stage resin column. The effluent from the second stage enters the acid regeneration zone for acid preparation and analysis.

[0063] After the alkali addition is completed, the process begins with the water washing process. The water from the MVR evaporator condensate tank is pumped into the first stage of the water washing process. The effluent then passes through a series valve to enter the second stage. The effluent from the second stage enters the alkali conversion zone for alkali preparation and use.

[0064] Qualified liquid replacement zone: Qualified liquid replacement is a single-column reverse operation. The qualified liquid after boron removal replaces the water in the column from the bottom of the resin column. The effluent is judged based on conductivity. Low conductivity effluent is returned to the condensate tank for continued use, while high conductivity effluent is returned to the electrodialysis section for further treatment.

[0065] Preferably, the MVR concentration unit 6 includes a raw material preheating unit, an evaporation separation unit, and a vapor compression unit. The raw material preheating unit includes a distilled water plate heat exchanger, a condensate heat exchanger, a non-condensable gas heat exchanger, and a fresh steam heat exchanger arranged in sequence. The evaporation separation unit includes a falling film heat exchanger and a separator. The inlet of the falling film heat exchanger is connected to the outlet of the raw material preheating unit. The vapor compression unit includes a steam scrubbing tower and a steam compressor connected in sequence. The inlet of the steam scrubbing tower is connected to the steam outlet of the separator, and the outlet of the steam compressor is connected to the inlet of the falling film heat exchanger.

[0066] The concentrated electrodialysis water from upstream, after boron, calcium, and magnesium removal, is mixed with the lithium-rich solution obtained from lithium and sodium separation and enters the feed tank. It is then pumped into heat exchangers, where it exchanges heat with distilled water, condensate, non-condensable gas, and fresh steam heat exchangers. Once preheated to the bubble point temperature, it enters a falling film heat exchanger for membrane evaporation. The evaporated concentrate and secondary steam undergo thorough gas-liquid separation in a separator. The product is discharged when the required concentration is achieved. The lithium-ion concentration in the discharged product is increased to no less than 35 g / L.

[0067] The secondary steam from the falling film separator is scrubbed in a steam scrubbing tower to remove any entrainment and foam before entering the MVR compression system. This ensures that the steam entering the steam compressor is free of entrainment, guaranteeing stable operation of the steam compressor. After compression, the secondary steam's temperature can be increased by approximately 20°C before returning to the falling film heat exchanger. During the material heating process, the secondary steam condenses into water, which flows to a condenser and is pumped by a distilled water pump into a distilled water plate heat exchanger to exchange heat with the raw material liquid before being discharged from the system. The conductivity of the secondary steam condensate is ≤150 μS / cm, and it is not mixed with the live steam condensate; it is recovered separately. After preheating, the material enters the evaporator and exchanges heat with the compressed steam (raised by 20°C) for evaporation, bringing the entire system to thermal equilibrium.

[0068] The high-lithium mother liquor from MVR concentration unit 6 is filtered through a precision filter to remove large crystal particles and impurities. The filtered high-lithium mother liquor is then heated by a high-lithium mother liquor heat exchanger and enters a reaction crystallizer. There, it mixes, reacts, and crystallizes with a soda ash solution from the soda ash preparation section to produce lithium carbonate granular crystals. The resulting lithium carbonate slurry flows by gravity into a thickener.

[0069] Reaction equation: 2LiCl + Na₂CO₃ = 2NaCl + Li₂CO₃↓

[0070] The thickener includes a drive shaft, a rake frame, and a lifting mechanism. The rake frame is located inside the thickener, and rake teeth are provided below the rake frame. The drive shaft is connected to the rake frame for driving the rake frame to rotate, and the lifting mechanism is used to drive the rake frame to move in the up and down direction.

[0071] After thickening, the upper clear liquid flows by gravity into the filtrate tank, while the lower slurry, having reached the specified solids content, is pumped by the underflow pump of the thickener into the lithium carbonate slurry tank. From there, it is pumped into a horizontal scraper centrifuge for dehydration and washing. During washing, a second washing solution, a first washing solution, and hot water are introduced into the centrifuge according to a programmed flow. After three washing processes, the washing liquid and filtrate finally flow by gravity into the thickener. The lithium-precipitated filtrate in the filtrate tank is then pumped to the lithium-sodium separation section.

[0072] As more material settles to the bottom of the thickener and the bed thickens, the working resistance of the rake frame also increases. When the working resistance increases to 4MPa, the pressure sensor, time delay relay, and solenoid directional valve 2DT activate, cutting off the oil circuit of the hydraulic motor. At this time, the drive shaft stops rotating, and the rake lifting cylinder drives the rake frame to lift upward. After a delay of about 3 to 5 seconds, the solenoid valve resets, resumes oil supply to the hydraulic motor, and the drive shaft starts to rotate and work again. After the rake frame is raised, the working resistance decreases accordingly. When it drops below 4 MPa, the rake stops being raised. When the working resistance is less than 4 MPa, the rake frame stays at this height and rotates, scraping the material towards the center of the pool. As the working resistance gradually decreases, when it is less than 2 MPa, the 3DT solenoid valve is energized and reversed, and the rake frame automatically descends for 3-5 seconds and stops. The descent speed is controlled by a one-way shut-off valve. When the working resistance is still less than 2 MPa, the 3DT solenoid valve is energized again and reversed, and the rake frame descends again for 3-5 seconds and stops. When the working resistance is greater than 2 MPa, the rake frame stays at this height and rotates. When the working resistance increases again to the set 4 MPa, the rake frame is raised again, and the above actions are repeated, thus achieving the purpose of automatic rake raising and lowering.

[0073] Preferably, the lithium extraction device from old brine in salt lakes further includes: a lithium-sodium separation device for the recovered liquid, which includes multiple second continuous ion exchange beds arranged in parallel. The inlet of the second continuous ion exchange bed is connected to the outlet of the thickener, and the outlet of the second continuous ion exchange bed is connected to the MVR concentration device 6.

[0074] The lithium-sodium separation system for the recovered liquid includes two parallel continuous ion exchange beds. Each continuous ion exchange bed has twenty resin columns, including ten in the adsorption zone, five in the top feed zone, three in the desorption zone, and two in the water washing acid zone.

[0075] After cooling and filtration, the recovered liquid enters the raw material tank and is pumped to the resin column in parallel in the adsorption zone. The effluent enters the tail liquid tank. Then, the resin column is transferred to the top feeding zone, where unqualified liquid is used to top the resin column, replacing the lithium-rich liquid "entrained" in the resin and returning it to the raw material tank. This step improves the lithium yield of the system. The resin column is then transferred to the desorption zone, where the lithium on the resin column is desorbed. After that, the resin column is transferred to the water washing acid zone, where water from the pure water tank and concentrated hydrochloric acid from the hydrochloric acid tank are pumped and mixed to form a 3-5% dilute hydrochloric acid solution to wash and regenerate the resin column. The regenerated liquid is then judged by set parameters and enters the intermediate buffer tank and the qualified desorption liquid tank respectively. After the resin regains its adsorption capacity, it continues to enter the adsorption zone.

[0076] The above are merely preferred embodiments of the present invention and do not constitute any limitation on the present invention. Any equivalent substitutions or modifications made by those skilled in the art to the technical solutions and content disclosed in the present invention without departing from the scope of the present invention shall be deemed to have remained within the protection scope of the present invention.

Claims

1. A lithium extraction device from old brine in a salt lake, characterized in that, include: The following devices are connected in series: an adsorption device (1), a filtration device (2), a nanofiltration-reverse osmosis device (3), an electrodialysis device (4), a resin impurity removal device (5), an MVR concentration device (6), a crystallization reactor (7), a solid-liquid separation device (8), a washing and dehydration device (9), a drying device (10), a granulation and pulverization device (11), and a demagnetizing and packaging device (12). The adsorption device (1) is used to adsorb lithium from the old brine of the salt lake. The nanofiltration-reverse osmosis device (3) is used to filter and concentrate the lithium-rich solution obtained by the adsorption device (1). The resin impurity removal device (5) is used to remove calcium ions, magnesium ions, and boron ions from the lithium solution concentrated by the electrodialysis device (4).

2. The lithium extraction device from old brine in salt lakes according to claim 1, characterized in that, The adsorption device (1) includes multiple first continuous ion exchange beds arranged in parallel. Each first continuous ion exchange bed includes multiple functional zones, namely an adsorption zone, a rinsing zone, a desorption zone and a top material zone. Each first continuous ion exchange bed also includes multiple adsorption columns, and each adsorption column can switch between the adsorption zone, the rinsing zone, the desorption zone and the top material zone in sequence.

3. The lithium extraction device from old brine in salt lakes according to claim 2, characterized in that, Both the adsorption zone and the desorption zone have multiple adsorption column arrangement positions arranged in series, and multiple sets of the multiple adsorption column arrangement positions arranged in series are arranged in parallel. The rinsing zone includes multiple adsorption column arrangement positions arranged in series. Each adsorption column can switch between adsorption column arrangement positions corresponding to different functional zones.

4. The lithium extraction device from old brine in salt lakes according to claim 3, characterized in that, The first continuous excitation bed includes a base and a rotating disk. The rotating disk is rotatably mounted on the base, and the adsorption columns are fixed on the rotating disk. The rotating disk switches between the positions of the adsorption columns under the drive of a transmission mechanism.

5. The lithium extraction device from old brine in salt lakes according to claim 1, characterized in that, The nanofiltration-reverse osmosis device (3) includes a main filtration system and a branch recovery system. The main filtration system includes a first nanofiltration unit, a first reverse osmosis unit, a second nanofiltration unit, a third-stage nanofiltration unit, a second reverse osmosis unit, and a fourth nanofiltration unit connected in series. The branch recovery system includes a first branch nanofiltration unit, a second branch nanofiltration unit, a first branch reverse osmosis unit, and a second branch reverse osmosis unit. The first branch nanofiltration unit and the second branch nanofiltration unit are connected. The first branch nanofiltration unit is also connected to the first nanofiltration unit. The first branch reverse osmosis unit is connected to both the first branch nanofiltration unit and the second branch nanofiltration unit. The second branch reverse osmosis unit is connected to the first reverse osmosis unit.

6. The lithium extraction device from old brine in salt lakes according to claim 1, characterized in that, The electrodialysis device (4) includes two stages of electrodialysis units. Each stage of the electrodialysis unit includes two sections of electrodialysis units. Each section of the electrodialysis unit includes multiple electrodialyzers. The two sections of the electrodialysis unit are respectively the first section of the electrodialysis unit and the second section of the electrodialysis unit. The first section of the electrodialysis unit is located upstream of the second section of the electrodialysis unit. The number of electrodialyzers in the first section of the electrodialysis unit is greater than the number of electrodialyzers in the second section of the electrodialysis unit.

7. The lithium extraction device from old brine in salt lakes according to claim 6, characterized in that, Each of the aforementioned electrodialysis units includes an electrodialysis tank, a cathode electrode chamber, and an anode electrode chamber, with the cathode electrode chamber and the anode electrode chamber located at opposite ends of the electrodialysis tank. The electrodialysis tank is equipped with multiple alternating anion exchange membranes and cation exchange membranes, and stores electrolytes within it.

8. The lithium extraction device from old brine in a salt lake according to claim 1, characterized in that, The MVR concentration unit (6) includes a raw material preheating unit, an evaporation separation unit, and a vapor compression unit. The raw material preheating unit includes a distilled water plate heat exchanger, a condensate heat exchanger, a non-condensable gas heat exchanger, and a fresh steam heat exchanger arranged in sequence. The evaporation separation unit includes a falling film heat exchanger and a separator. The inlet of the falling film heat exchanger is connected to the outlet of the raw material preheating unit. The vapor compression unit includes a steam scrubbing tower and a steam compressor connected in sequence. The inlet of the steam scrubbing tower is connected to the steam outlet of the separator, and the outlet of the steam compressor is connected to the inlet of the falling film heat exchanger.

9. The lithium extraction device from old brine in salt lakes according to claim 1, characterized in that, The solid-liquid separation device (8) includes a thickener, which includes a drive shaft, a rake frame and a lifting mechanism. The rake frame is located inside the thickener, and rake teeth are provided below the rake frame. The drive shaft is connected to the rake frame for driving the rake frame to rotate, and the lifting mechanism is used to drive the rake frame to move in the up and down direction.

10. The lithium extraction device from old brine in salt lakes according to claim 9, characterized in that, Also includes: The recovered liquid lithium-sodium separation device includes multiple second continuous ion exchange beds arranged in parallel. The inlet of the second continuous ion exchange bed is connected to the outlet of the thickener, and the outlet of the second continuous ion exchange bed is connected to the MVR concentration device (6).

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