Solar energy driven plateau salt lake lithium extraction system and regulation method thereof

Abstract

This invention relates to a solar-driven lithium extraction system for high-altitude salt lakes and its regulation method, belonging to the field of multi-energy complementary technology and automatic regulation for lithium extraction from salt lake brine. The system optimizes the regulation of the lithium extraction system by optimizing the configuration of osmotic salinity gradient power generation, photovoltaic thermal energy, and the hot water and electricity from solar collectors. During the weak sunlight hours of 6-8 AM, a concentrated magnesium solution from the previous lithium extraction process is used as the draw solution for the osmotic salinity gradient power generation system. This concentrates the brine and generates electricity, which heats the solution in the NH4HCO3 regenerator. The system then switches to the NH4HCO3 draw solution mode, solving the startup power issue. From 8-10 AM, as sunlight intensifies, the photovoltaic thermal energy preheats the brine, and electricity heats the hot water in the backup water tank. The flow rate of the evaporating hot water is adjusted according to the water temperature, shortening the response time. From 10-3 PM, when sunlight is strongest, the hot water from the solar collectors provides a heat source for evaporation, concentration, and crystallization, while photovoltaic thermal and electrical energy heat the backup water tank. From 3-6 PM, as sunlight weakens, the backup water tank and the hot water storage tank work together to extend the designed operating time.

Description

Technical Field

[0001] This invention relates to a solar-driven lithium extraction system for high-altitude salt lakes and its regulation method, belonging to the technical field of lithium extraction and automatic regulation in salt lakes. Background Technology

[0002] Lithium-ion batteries have become an important energy storage device for the future. my country's lithium resources mainly come from salt lakes and ores, with ores accounting for only 15% of the total reserves. The high-temperature decomposition process for lithium extraction from ores consumes a large amount of fossil fuels, and the solid waste residue after extraction pollutes the environment. Salt lake lithium resources are far greater than ores, making the development of low-carbon, high-efficiency salt lake lithium extraction technology crucial for ensuring the security of my country's lithium resources.

[0003] Lithium-bearing salt lakes, accounting for 71.9% of my country's total lithium resources, are located at high altitudes on the Qinghai-Tibet Plateau. These high-altitude salt lakes have low lithium content, and the Qinghai-Tibet Plateau lacks electricity and fossil fuels. Traditional methods such as adsorption, electrochemical, evaporation crystallization, and precipitation are unsuitable for lithium extraction from Qinghai-Tibet Plateau salt lakes due to their high energy consumption and fossil fuel requirements. Furthermore, the chemical reagents used in extraction methods can damage the fragile ecosystem of the Qinghai-Tibet Plateau. Utilizing the abundant solar energy resources of the Qinghai-Tibet Plateau for lithium extraction from salt lakes has become a suitable technology for the characteristics and natural environment of high-altitude salt lake brine. However, the low energy density and intermittent nature of solar energy make dynamic regulation of solar-driven high-altitude salt lake lithium extraction systems a pressing issue that needs to be addressed.

[0004] Chinese patent CN117847609B discloses an energy supply system suitable for lithium extraction from salt lakes and a method for supplying energy using it. The system includes a lithium extraction unit, a water supply unit, a heating unit, a heat exchange unit, a steam supply unit, and a lithium extraction plant. It utilizes waste heat based on the principle of orderly cascaded energy utilization. However, the system's units cannot be dynamically adjusted according to different operating conditions, affecting the system's operating efficiency and energy utilization rate.

[0005] Chinese patent CN117303633A discloses a comprehensive recovery system for lithium, potassium, and sodium resources in salt lake brine. It utilizes membrane technology to separate divalent ions such as calcium, magnesium, and carbonate from the brine, and then recovers potassium and sodium resources through adsorption, membrane technology, and evaporation concentration. Chinese patent CN118127349A discloses a lithium extraction method and apparatus suitable for high-lithium-concentration carbonate-type salt lake brine. It utilizes a downstream bipolar membrane device to reuse the adsorption tail liquid, supplementing the upstream adsorption process with hydrochloric acid and sodium hydroxide produced from its electrolysis, thus achieving a closed-loop process. These methods focus on the reuse of tail liquid from lithium extraction in salt lakes and do not address reducing the energy costs of lithium extraction from salt lakes.

[0006] Chinese patent CN115962586B discloses a direct solar adsorption brine concentration and refrigeration system and its usage method, which integrates an adsorber with a solar collector to adsorb and desorb the evaporated brine.

[0007] Chinese patent CN118420032A discloses a lithium extraction device utilizing solar energy in a salt lake. This adsorption device uses solar energy to extract lithium while simultaneously producing fresh water. The efficiency of the above lithium extraction systems is limited by variations in sunlight intensity; the discontinuity and instability of sunlight make it difficult for these two lithium extraction systems to operate continuously and efficiently.

[0008] Chinese patent CN 111620357 A proposes a system for extracting lithium concentrate using photoelectric heating combined with continuous countercurrent heat exchange and floating salt-drying. This system builds upon the traditional method of artificially drying salt to form high-concentration brine. It utilizes clean electricity, such as photovoltaic or wind power, to heat the brine, accelerating evaporation and crystallization. Natural evaporation and crystallization then further enhance the lithium concentrate extraction. However, in the Qinghai-Tibet Plateau, where the average annual temperature is 4°C, the heat loss from heating the brine in an open, atmospheric-pressure vessel using photovoltaic or wind power is excessive. Furthermore, the steam generated from the brine evaporation, which consumes high-quality electricity, is directly released into the atmosphere, resulting in ineffective heat utilization. Shortening the lithium extraction cycle in the salt lake comes at the cost of consuming high-quality clean energy and low energy efficiency, making it difficult to effectively increase the cost of lithium extraction from the salt lake.

[0009] Chinese patent CN 111268754 A proposes an interface evaporation system that couples and enhances solar-driven photothermal-salt gradient power generation. The solar photothermal film evaporates seawater, thereby creating a concentration difference in the solution on both sides of the ion-permeable membrane of the salinity gradient power generation module. The salinity gradient power generation module uses the concentration difference generated by this evaporation process to generate electricity and feeds the electrical energy back to the solar photothermal film in situ to heat the solar photothermal film with Joule heating, thereby increasing the evaporation temperature of the solar photothermal film. This patent utilizes solar energy for continuous seawater desalination, aiming to continuously obtain fresh water, rather than to obtain high-concentration brine. This is because salinity gradient power generation uses a solar thermal membrane to evaporate seawater to form a concentrated solution, rather than utilizing natural salinity gradient energy. During salinity gradient power generation, water molecules in the low-concentration seawater will pass through the ion-permeable membrane and enter the concentrated solution on the other side to dilute the concentrated solution. Furthermore, the power generation efficiency of salinity gradient energy is low, and the increased evaporation rate of the solar thermal membrane is insufficient to offset the dilution effect of the concentrated solution. As a result, the concentrated solution side of the ion-permeable membrane maintains a relatively constant concentration. This system is not suitable for lithium extraction from high-altitude salt lakes to obtain high-concentration brine. In this system, the volume of concentrated solution remains constant without flow, making continuous concentration of salt lake brine impossible. For the low-temperature salt lake brine of the Qinghai-Tibet Plateau, a large amount of heat energy is required to achieve evaporation, resulting in low evaporation efficiency. Water molecules in the low-temperature salt lake brine on the other side of the ion-permeable membrane will then consume the heat generated by the solar thermal membrane after passing through the ion-permeable membrane into the concentrated solution, further reducing the thermal efficiency of the system.

[0010] Solar-driven lithium extraction systems from salt lakes suffer from the following problems: Existing technologies are only suitable for lithium extraction from salt lakes under designed solar illumination conditions, meaning that the thermal and electrical energy provided under given solar illumination conditions can meet the production needs of lithium extraction from salt lakes. However, the actual solar intensity varies significantly throughout the day. When solar intensity is weak in the morning and evening, the temperature of the brine in the salt lake is low, photovoltaic power generation is low, and the hot water produced by the solar collectors is also low, resulting in insufficient thermal and electrical energy to drive the lithium extraction system. Normal production can only proceed when the solar intensity is strong enough at noon to meet the energy requirements of the lithium extraction system. As a result, the daily production time according to the designed conditions is greatly reduced, and the production efficiency of lithium extraction from salt lakes is significantly decreased. Therefore, it is necessary to develop a method for adjusting the solar-driven lithium extraction system from high-altitude salt lakes based on solar illumination intensity. Summary of the Invention

[0011] To overcome the shortcomings of existing technologies, this invention proposes a solar-driven lithium extraction system from high-altitude salt lakes and its adjustment method. Based on changes in solar radiation intensity, the system, which couples solar-driven power generation and lithium extraction from the salt lake, is dynamically adjusted, achieving efficient and flexible operation of the high-altitude salt lake lithium extraction system throughout the entire daytime sunshine period.

[0012] The present invention adopts the following technical solution: a solar-driven lithium extraction system for high-altitude salt lakes, which includes an osmotic pressure gradient energy generation unit, a photovoltaic photothermal unit, a salt lake lithium extraction unit, and a regulation and control unit. In the osmotic pressure gradient energy generation unit, the forward osmosis membrane module is divided into a draw liquid side and a feed liquid side. The feed liquid side inlet is connected to the salt lake brine pump pipeline, and the feed liquid side outlet is connected to the tube side of the salt lake brine tank and the salt lake brine preheater. The extractor liquid outlet is connected in sequence to the turbine generator set and the NH4HCO3 extractor liquid regenerator. The regenerated extractor liquid outlet is connected back to the extractor liquid inlet via the extractor liquid pump pipeline. The concentrated magnesium solution tank is connected to the extractor liquid inlet via the concentrated magnesium solution regulating valve pipeline. The photovoltaic thermal unit includes a photovoltaic thermal module, a solar collector, a hot water storage tank, a backup water tank, and a regulating control unit; the electrical energy generated by the photovoltaic thermal module drives the heater embedded in the backup water tank through a cable; the solar collector is connected to the plate heat exchanger embedded in the hot water storage tank to supply heat to the hot water storage tank; In the lithium extraction unit of the salt lake, hot water in the backup water tank is connected to the plate evaporator via the hot water outlet of the backup water tank evaporation and concentration and the first shut-off valve of the backup water tank. Hot water in the storage water tank is connected to the plate evaporator via the hot water outlet of the storage water tank evaporation and concentration and the first shut-off valve of the storage water tank. After the hot water releases sensible heat, it is connected to the backup water tank and the storage water tank via the hot water return port of the backup water tank evaporation and concentration and the hot water return port of the storage water tank evaporation and concentration, respectively. After evaporation and concentration, the brine flows out from the plate evaporator and enters the adsorption tower. The salt lake brine is connected to the plate condenser from the salt lake brine preheater through a pipeline, and the condensate is connected to the fresh water tank from the plate condenser through a pipeline. After evaporation and concentration, the brine is connected to the upper part of the adsorption tower through a pipeline. The bottom of the adsorption tower is connected to the lithium solution tank. The outlet of the lithium solution tank is connected to the inlet of the nanofiltration membrane separation component via a nanofiltration booster pump. The outlet of the freshwater tank is connected to the inlet of the middle section of the adsorption tower and enters the tower for rinsing. After magnesium ions are removed, the lithium solution is connected from the outlet of the nanofiltration membrane separation component to the condenser of the multi-effect evaporator. The concentrated magnesium solution separated by the nanofiltration membrane separation component is connected to the nanofiltration discharge concentrated magnesium solution tank via a pipeline. The outlet of the nanofiltration discharge concentrated magnesium solution tank is connected to the concentrated magnesium solution tank of the osmotic pressure salinity gradient power generation unit. The condensate is connected from the condenser and the multi-effect evaporator to the fresh water tank via a pipeline. The hot water in the standby water tank is connected to the multi-effect evaporator via the standby water tank evaporation crystallization hot water outlet and the standby water tank second shut-off valve. The hot water in the hot water storage tank is connected to the multi-effect evaporator via the hot water storage tank evaporation crystallization hot water outlet and the hot water storage tank second shut-off valve. After the hot water releases sensible heat, it is connected to the standby water tank and the hot water storage tank via the standby water tank evaporation crystallization hot water return port and the hot water storage tank evaporation crystallization hot water return port, respectively. After evaporation and concentration, the concentrated lithium solution flows out from the concentrated lithium solution outlet of the multi-effect evaporator and is connected to the lithium carbonate precipitation component. The regulating and control unit is electrically connected to the evaporation and concentration hot water regulating valve, the evaporation and crystallization hot water regulating valve, the regenerator temperature signal controller, the standby water tank temperature signal controller, the hot water storage tank temperature signal controller, the concentrated magnesium solution regulating valve, and the NH4HCO3 regulating valve using a PLC controller. The evaporation and concentration hot water regulating valve is installed on the inlet pipe of the evaporation and concentration hot water, the evaporation and crystallization hot water regulating valve is installed on the inlet pipe of the evaporation and crystallization hot water, the regenerator temperature signal controller is installed inside the NH4HCO3 regenerator, the standby water tank temperature signal controller and the hot water storage tank temperature signal controller are installed inside the standby water tank and the hot water storage tank, respectively, the concentrated magnesium solution regulating valve is installed on the outlet pipe of the concentrated magnesium solution water tank, and the NH4HCO3 regulating valve is installed on the outlet pipe of the NH4HCO3 regenerator.

[0013] Furthermore, in the osmotic pressure salt gradient energy generation unit, the brine from the salt lake is pumped through a pipeline to the feed liquid side of the forward osmosis membrane module via the feed liquid side inlet, and then connected to the photovoltaic thermal unit via the brine tank from the feed liquid side outlet of the forward osmosis membrane module. The concentrated magnesium solution is connected to the draw liquid side of the forward osmosis membrane module via the concentrated magnesium solution tank outlet, the concentrated magnesium solution regulating valve, and the draw liquid side inlet. It is then connected to the turbine generator set via the draw liquid side outlet of the forward osmosis membrane module and the turbine generator set inlet. The diluted draw liquid is connected from the turbine generator set outlet to the draw liquid discharge valve, the draw liquid regeneration valve, and the regenerator inlet of the NH4HCO3 draw liquid. The concentrated draw liquid is connected to the draw liquid side of the forward osmosis membrane module via the regenerator draw liquid outlet, the NH4HCO3 regulating valve, the draw liquid pump, and the draw liquid side inlet of the forward osmosis membrane module. The regenerator freshwater outlet is connected to the freshwater tank in the brine lake lithium extraction unit via a pipeline.

[0014] Furthermore, the electrical energy generated by the photovoltaic and solar thermal components in the photovoltaic and solar thermal unit drives the brine pump, the extraction liquid pump, the nanofiltration membrane booster pump, and the heater embedded in the backup water tank via cables. The hot water generated by the photovoltaic and solar thermal components forms a natural circulation through the brine preheater. The brine is connected to the brine extraction unit via pipelines through the brine tank outlet and the brine preheater. The backup water tank evaporation and concentration hot water outlet and the backup water tank first shut-off valve are installed on the evaporation and concentration hot water inlet pipe. The backup water tank evaporation and concentration hot water return outlet and the backup water tank first return water shut-off valve are installed on the evaporation and concentration hot water return pipe. The backup water tank evaporation and crystallization hot water outlet and the backup water tank second shut-off valve are installed on the evaporation and crystallization hot water inlet pipe. The backup water tank evaporation and crystallization hot water return outlet and the backup water tank second return water shut-off valve are installed on the backup water tank evaporation and crystallization hot water return pipe.

[0015] Furthermore, in the solar collector, hot water from the solar collector outlet is connected to the solar collector inlet via the hot water side of the plate heat exchanger embedded in the hot water storage tank. The hot water outlet for evaporation and concentration and the first shut-off valve of the hot water storage tank are installed on the hot water inlet pipe for evaporation and concentration. The hot water return port for evaporation and concentration and the first return water shut-off valve of the hot water storage tank are installed on the hot water return pipe for evaporation and concentration. The hot water outlet for evaporation and crystallization and the second shut-off valve of the hot water storage tank are installed on the hot water inlet pipe for evaporation and crystallization. The hot water return port for evaporation and crystallization and the second return water shut-off valve of the hot water storage tank are installed on the hot water return pipe for evaporation and crystallization.

[0016] A method for regulating a solar-driven lithium extraction system from a high-altitude salt lake includes the following steps: In the first stage of the control unit, based on the quantitative relationship between the temperature measurement value and the set value of the regenerator temperature signal controller, the start-up time of the lithium extraction system in the high-altitude salt lake is shortened by switching the working mode of the draw liquid of the osmotic pressure salinity gradient power generation unit: when the temperature measurement value of the regenerator temperature signal controller is lower than the set value, the concentrated magnesium solution regulating valve is opened. The concentrated magnesium solution in the insulated tank after the initial adsorption and lithium extraction is used as the draw liquid of the osmotic pressure salinity gradient power generation unit. After being diluted in the forward osmosis membrane module, the draw liquid drives the turbine generator set to generate electricity, and then is discharged by the draw liquid discharge valve. The power output from the turbine generator set is used to heat the NH4HCO3 solution in the NH4HCO3 regenerator. When the temperature measurement value of the regenerator temperature signal controller reaches the set value, the concentrated magnesium solution regulating valve is closed and the NH4HCO3 regulating valve is opened. The concentrated NH4HCO3 solution in the NH4HCO3 regenerator is used as the draw liquid for the osmotic pressure salt gradient energy generation unit. The system is switched to a continuously operating NH4HCO3 draw liquid salt gradient energy generation system. The power output from the turbine generator set is regenerated by the NH4HCO3 in the NH4HCO3 draw liquid regenerator. In the second stage, the hot water produced by the photovoltaic thermal modules preheats the brine, which is initially concentrated at 0-5℃ and flows out from the feed liquid side of the forward osmosis membrane module, in the brine preheater. The electricity generated by the photovoltaic thermal modules is used to heat the hot water in the backup water tank. When the temperature measurement value of the backup water tank temperature signal controller reaches the set value, the first shut-off valve, the first return water shut-off valve, the second shut-off valve, and the second return water shut-off valve of the backup water tank are opened. The adjustment parameter is obtained based on the difference between the temperature measurement value and the set value of the backup water tank temperature signal controller. Based on the change relationship between the adjustment parameter and the hot water temperature measurement value of the backup water tank, the hot water flow rate for evaporation concentration and evaporation crystallization is calculated, and the opening degree of the evaporation concentration hot water regulating valve and the evaporation crystallization hot water regulating valve is adjusted until the preset conditions are met. In the third stage, when the temperature measurement value of the hot water storage tank temperature signal controller reaches the set value, the first shut-off valve, the first return water shut-off valve, the second shut-off valve, and the second return water shut-off valve of the hot water storage tank open. The hot water generated by the solar collector becomes the heat source for the lithium extraction system from the salt lake. The first shut-off valve, the first return water shut-off valve, the second shut-off valve, and the second return water shut-off valve of the backup water tank close. The hot water in the backup water tank is continuously heated by the electricity generated by the photovoltaic thermal module and stops supplying heat to the lithium extraction module from the salt lake. Based on the difference between the temperature measurement value and the set value of the hot water storage tank temperature signal controller, the opening degree of the evaporation and concentration hot water regulating valve and the evaporation and crystallization hot water regulating valve is adjusted according to the adjustment method in the steps. In the fourth stage, when the temperature measurement value of the hot water storage tank temperature signal controller is lower than the set value, the first shut-off valve, the first return water shut-off valve, the second shut-off valve, and the second return water shut-off valve of the backup water tank are opened. The hot water in the backup water tank with a temperature higher than the set value and the hot water in the hot water storage tank with a temperature lower than the set value are mixed to provide heat for the lithium extraction system in the salt lake. Based on the difference between the temperature measurement value and the set value of the hot water storage tank temperature signal controller and the backup water tank temperature signal controller, the opening degree of the evaporation and concentration hot water regulating valve and the evaporation and crystallization hot water regulating valve is adjusted according to the adjustment method in the steps.

[0017] Furthermore, the first phase is from 6:00 AM to 8:00 AM, the second phase is from 8:00 AM to 10:00 AM, the third phase is from 10:00 AM to 3:00 PM, and the fourth phase is from 3:00 PM to 6:00 PM.

[0018] Furthermore, the preset conditions in the steps are as follows: the lithium ion concentration in the brine after evaporation and concentration at the inlet of the adsorption tower reaches 1.0-1.2%, and the lithium ion concentration after desorption in the absorption tower reaches 1.5-2.0%, while the lithium ion concentration at the inlet of the lithium carbonate precipitation component reaches 3.0-3.5%; the plate evaporator evaporates 97-97.5% of the water in the salt lake brine, and the multi-effect evaporator evaporates 33-57% of the water in the adsorbed lithium solution; the fresh water produced by the plate evaporator and the multi-effect evaporator meets the fresh water consumption in the desorption process within the adsorption tower.

[0019] The above technical solution is characterized by: dynamically adjusting the solar-driven power generation and heating system and the lithium extraction system coupled with brine based on changes in solar irradiance. When solar irradiance is weak, the concentrated magnesium solution after previous lithium extraction is used as the draw solution for the osmotic pressure salinity gradient power generation system to initially concentrate the brine and generate electricity, thus solving the problem of the electrical energy required for starting the brine extraction system; the low-grade heat generated by the photovoltaic thermal modules is used to preheat the low-temperature brine, saving the hot water used for brine evaporation and concentration; the electrical energy generated by the photovoltaic thermal modules is used to heat the hot water in the backup water tank, and the hot water flow rate is rationally adjusted according to the relationship between the measured temperature in the backup water tank and the set value, shortening the response time for normal operation of the brine extraction system; the hot water in the storage tank and the backup water tank generated by the solar collector is used to replace steam as the heat source for the evaporation crystallization unit and the evaporation concentration unit, reducing the cycle of the natural evaporation crystallization process of the brine and lowering the heat consumption cost of brine extraction.

[0020] The beneficial effects of this invention are: this solar-driven lithium extraction system and its regulation method for high-altitude salt lakes achieve optimized regulation of the lithium extraction system for high-altitude salt lakes by rationally configuring the osmotic pressure salinity gradient power generation, photovoltaic thermal energy, and hot water and electricity produced by solar collectors, based on the intensity of sunlight. When sunlight intensity is weak between 6:00 and 8:00 AM, sufficient heat and electricity cannot be provided to the brine extraction system via photovoltaic (PV) thermal and solar collectors. Instead, the concentrated magnesium solution from the initial lithium extraction process, after insulated absorption, is used as the draw solution for the osmotic pressure gradient power generation system. This process initially concentrates the brine and generates electricity. The output electricity is used to heat the solution in the NH4HCO3 regenerator to 60°C, after which the system switches to a continuously operating NH4HCO3 draw solution osmotic pressure gradient power generation mode. This shortens the start-up time of the high-altitude brine extraction system and solves the power requirement for system startup without consuming external energy. Between 8:00 and 10:00 AM, as sunlight intensity gradually increases, the low-grade 40°C heat from the PV thermal modules is used to preheat the 0-5°C brine in the brine tank. This energy cascade utilization reduces the consumption of high-temperature hot water during the evaporation and concentration process. The electricity generated by the PV thermal modules is used to heat the hot water in the backup tank, raising its temperature. When the hot water reaches 70℃, it begins to provide heat for the evaporation, concentration, and crystallization processes of the lithium extraction unit in the salt lake. Based on the relationship between the temperature of the backup water tank and the set value, the flow rate of hot water for evaporation, concentration, and crystallization is rationally adjusted to shorten the time for evaporation and concentration of the salt lake brine and the lithium-containing solution to reach the set concentration, respectively, further shortening the response time of the normal operation of the lithium extraction system. From 10:00 to 15:00, the solar radiation intensity reaches its strongest point of the day, and the solar collectors are most efficient. The hot water generated by the solar collectors becomes the heat source for the evaporation, concentration, and crystallization processes of the lithium extraction system in the salt lake. The electricity generated by the photovoltaic thermal modules is used to heat the hot water in the backup water tank, storing heat for the subsequent lithium extraction system. From 15:00 to 18:00, the solar radiation intensity gradually weakens, and the heat provided by the solar collectors decreases, failing to meet the heat demand of the lithium extraction system. The backup water tank and the hot water storage tank work together to meet the heat demand of the lithium extraction system in the salt lake, extending the operating time of the lithium extraction system under the designed operating conditions. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of a solar-powered lithium extraction system from a high-altitude salt lake.

[0022] Figure 2 This is a diagram of the evaporation heat transfer coefficient of a plate evaporator.

[0023] Figure 3 This is a graph showing the change in the heat transfer coefficient of falling film evaporation with the duration of sunlight.

[0024] In the diagram: 0. Osmotic pressure salinity gradient power generation unit; 1. Photovoltaic thermal unit; 2. Lithium extraction unit from salt lake; 3. Concentrated magnesium solution tank; 3a. Concentrated magnesium solution tank inlet; 3b. Concentrated magnesium solution tank outlet; 4. Salt lake brine pump; 5. Concentrated magnesium solution regulating valve; 6. Draw liquid pump; 7. Forward osmosis membrane module; 7a. Feed liquid side inlet; 7b. Feed liquid side outlet; 7c. Draw liquid side inlet; 7d. Draw liquid side outlet; 8. Salt lake brine tank; 8a. Salt lake brine tank inlet; 8b. Salt lake brine tank outlet; 9. Turbine generator set; 9a. Turbine generator set inlet; 9b. Turbine generator set outlet; 9c. Draw liquid discharge regulating valve. 9d. Draw liquid regeneration regulating valve; 10. NH4HCO3 draw liquid regenerator; 10a. Regenerator inlet; 10b. Regenerator draw liquid outlet; 10c. Regenerator fresh water outlet; 10d. Regenerator temperature signal controller; 11. Photovoltaic thermal module; 11a. Photovoltaic thermal module outlet; 11b. Photovoltaic thermal module inlet; 12. Salt lake brine preheater; 13. Solar collector; 14. Hot water storage tank; 14a. Hot water storage tank embedded plate heat exchanger; 14b. Hot water storage tank evaporation and concentration hot water outlet; 14c. Hot water storage tank evaporation and concentration hot water return port; 14d. Hot water storage tank evaporation and crystallization hot water outlet; 14e. 14f, Hot water return port for evaporation and crystallization in the hot water storage tank; 14g, First shut-off valve for the hot water storage tank; 14h, Second shut-off valve for the hot water storage tank; 14i, Second shut-off valve for the hot water storage tank; 15, Temperature signal controller for the hot water storage tank; 16, Backup water tank; 16a, Built-in heater for the backup water tank; 16b, Hot water outlet for evaporation and concentration in the backup water tank; 16c, First shut-off valve for the backup water tank; 16d, Hot water return port for evaporation and concentration in the backup water tank; 16e, First shut-off valve for the backup water tank; 16f, Hot water outlet for evaporation and crystallization in the backup water tank; 16g, Second shut-off valve for the backup water tank; 16h, Backup water tank... 16i, Second return water shut-off valve of standby water tank, 16j, Temperature signal controller of standby water tank, 17, Regulating control unit, 18, Plate condenser, 19, Evaporation and concentration hot water regulating valve, 20, Plate evaporator, 21, Fresh water tank, 22, Adsorption tower, 23, Lithium solution tank, 24, Nanofiltration booster pump, 25, Nanofiltration membrane separation assembly, 26, Nanofiltration discharge concentrated magnesium solution tank, 27, Multi-effect evaporator condenser, 28, Multi-effect evaporator, 28a, Concentrated lithium solution outlet of multi-effect evaporator, 29, Evaporation and crystallization hot water regulating valve, 30, Lithium carbonate precipitation assembly, 31, NH4HCO3 regulating valve. Detailed Implementation

[0025] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0026] Figure 1 A schematic diagram of a solar-driven lithium extraction system from a high-altitude salt lake is shown. The system includes an osmotic pressure gradient energy generation unit 0, a photovoltaic thermal unit 1, a salt lake lithium extraction unit 2, and a regulation and control unit 17.

[0027] In the osmotic pressure salinity gradient power generation unit 0, the brine from the salt lake is pumped by the brine pump 4 and connected via a pipeline to the feed liquid side of the forward osmosis membrane module 7 through the feed liquid side inlet 7a. Then, it is connected from the feed liquid side outlet 7b of the forward osmosis membrane module through the brine tank 8 to the photovoltaic thermal unit 1. The concentrated magnesium solution is connected sequentially to the draw liquid side of the forward osmosis membrane module 7 through the concentrated magnesium solution tank outlet 3b, the concentrated magnesium solution regulating valve 5, and the draw liquid side inlet 7c. Finally, it is connected from the draw liquid side outlet 7d of the forward osmosis membrane module to the turbine generator inlet 9a. The diluted draw liquid is connected to the turbine generator set 9. It is then connected from the turbine generator set outlet 9b to the draw liquid discharge regulating valve 9c, the draw liquid regeneration valve 9d, and the NH4HCO3 draw liquid regenerator inlet 10a. The concentrated draw liquid is connected to the draw liquid side of the forward osmosis membrane module 7 via the regenerator draw liquid outlet 10b, the NH4HCO3 regulating valve 31, the draw liquid pump 6, and the forward osmosis membrane module draw liquid side inlet 7c. The regenerator freshwater outlet 10c is connected to the freshwater tank 21 in the brine lithium extraction unit 2 via a pipeline.

[0028] In photovoltaic-thermal unit 1, the electrical energy generated by the photovoltaic-thermal module 11 drives the brine pump 4, the extractor pump 6, the nanofiltration booster pump 24, and the heater 16a embedded in the backup water tank via cables. The hot water generated by the photovoltaic-thermal module 11 forms a natural circulation through the brine preheater 12. The brine is connected to the lithium extraction unit 2 via pipelines through the brine tank outlet 8b and the brine preheater 12. The backup water tank evaporation and concentration hot water outlet 16b and the backup water tank first shut-off valve 16c are installed on the evaporation and concentration hot water inlet pipe. The backup water tank evaporation and concentration hot water return outlet 16d and the backup water tank first return water shut-off valve 16e are installed on the evaporation and concentration hot water return pipe. The backup water tank evaporation and crystallization hot water outlet 16f and the backup water tank second shut-off valve 16g are installed on the evaporation and crystallization hot water inlet pipe. The return water inlet 16h and the second return water shut-off valve 16i of the standby water tank are installed on the hot water return pipe of the standby water tank for evaporation and crystallization. The hot water in the solar collector is connected from the outlet of the solar collector 13 through the hot water side of the embedded plate heat exchanger 14a in the hot water storage tank to the inlet of the solar collector 13. The hot water outlet 14b of the hot water storage tank for evaporation and concentration and the first shut-off valve 14f of the hot water storage tank for evaporation and concentration are installed on the hot water inlet pipe for evaporation and concentration. The hot water return inlet 14c of the hot water storage tank for evaporation and concentration and the first return water shut-off valve 14g of the hot water storage tank for evaporation and concentration are installed on the hot water return pipe for evaporation and concentration. The hot water outlet 14d of the hot water storage tank for evaporation and crystallization and the second shut-off valve 14h of the hot water storage tank for evaporation and crystallization are installed on the hot water inlet pipe for evaporation and crystallization. The hot water return inlet 14e of the hot water storage tank for evaporation and crystallization and the second return water shut-off valve 14i of the hot water storage tank for evaporation and crystallization are installed on the hot water return pipe for evaporation and crystallization.

[0029] Hot water in the backup water tank 16 of the lithium extraction unit 2 of the salt lake is connected to the plate evaporator 20 via the backup water tank evaporation and concentration hot water outlet 16b and the backup water tank first shut-off valve 16c. Hot water in the hot water storage tank 14 is connected to the plate evaporator 20 via the hot water storage tank evaporation and concentration hot water outlet 14b and the hot water storage tank first shut-off valve 14f. After the hot water releases sensible heat, it is connected to the backup water tank 16 and the hot water storage tank 14 via the backup water tank evaporation and concentration hot water return port 16d and the hot water storage tank evaporation and concentration hot water return port 14c, respectively. After evaporation and concentration, the brine flows out of the plate evaporator 20 and enters the adsorption tower 22. The salt lake brine is connected to the plate condenser 18 from the salt lake brine preheater 12 through a pipeline. The condensate is connected to the fresh water tank 21 from the plate condenser 18 through a pipeline.

[0030] After evaporation and concentration, the brine is connected to the upper part of the adsorption tower 22 through a pipeline. The bottom of the adsorption tower 22 is connected to the inlet of the lithium solution tank 23. The lithium solution is connected to the inlet of the nanofiltration membrane separation component 25 through the outlet of the lithium solution tank 23 via the nanofiltration booster pump 24. The outlet of the fresh water tank 21 is connected to the middle section inlet of the adsorption tower 22 and enters the tower for rinsing.

[0031] The lithium solution after removing divalent magnesium ions is connected from the outlet of nanofiltration membrane separation component 25 to multi-effect evaporator condenser 27. The concentrated magnesium solution separated by nanofiltration membrane separation component 25 is connected via pipeline to nanofiltration discharge concentrated magnesium solution tank 26. The outlet of nanofiltration discharge concentrated magnesium solution tank 26 is connected to concentrated magnesium solution tank 3 of osmotic pressure salinity gradient energy generation unit 0. Condensate is connected from multi-effect evaporator condenser 27 and multi-effect evaporator 28 via pipeline to freshwater tank 21. Hot water in standby water tank 16 is evaporated and crystallized at hot water outlet 16f. The second shut-off valve 16g of the backup water tank is connected to the multi-effect evaporator 28. The hot water in the hot water storage tank 14 is connected to the multi-effect evaporator 28 via the hot water storage tank evaporation crystallization hot water outlet 14d and the hot water storage tank second shut-off valve 14h. After the hot water releases sensible heat, it is connected to the backup water tank 16 and the hot water storage tank 14 via the backup water tank evaporation crystallization hot water return port 16h and the hot water storage tank evaporation crystallization hot water return port 14e, respectively. After evaporation and concentration, the concentrated lithium solution flows out from the concentrated lithium solution outlet 28a of the multi-effect evaporator and is connected to the lithium carbonate precipitation assembly 30.

[0032] The regulating control unit 17 is electrically connected to the evaporation and concentration hot water regulating valve 19, the evaporation and crystallization hot water regulating valve 29, the regenerator temperature signal controller 10d, the standby water tank temperature signal controller 16j, the hot water storage tank temperature signal controller 15, the concentrated magnesium solution regulating valve 5, and the NH4HCO3 regulating valve 31 using a PLC controller. The evaporation and concentration hot water regulating valve 19 is installed on the hot water inlet pipe of the evaporation and concentration process, the evaporation and crystallization hot water regulating valve 29 is installed on the hot water inlet pipe of the evaporation and crystallization process, the regenerator temperature signal controller 10d is installed inside the NH4HCO3 extractant regenerator 10, the standby water tank temperature signal controller 16j and the hot water storage tank temperature signal controller 15 are installed inside the standby water tank 16 and the hot water storage tank 14, respectively, the concentrated magnesium solution regulating valve 5 is installed on the outlet pipe of the concentrated magnesium solution water tank 3, and the NH4HCO3 regulating valve 31 is installed on the outlet pipe of the NH4HCO3 extractant regenerator 10.

[0033] The system's processing method employs the following steps: (a) In the regulating control unit 17, when the sunlight intensity is weak between 6:00 and 8:00 AM, based on the quantitative relationship between the temperature measurement value of the regenerator temperature signal controller 10d and the set value of 60°C, the start-up time of the plateau salt lake lithium extraction system is shortened by switching the working mode of the draw liquid of the osmotic pressure salinity gradient power generation unit 0: when the temperature measurement value of the regenerator temperature signal controller 10d is lower than the set value of 60°C, the concentrated magnesium solution regulating valve 5 is opened, and the concentrated magnesium solution in the concentrated magnesium solution tank 3 after the initial adsorption and lithium extraction is used as the draw liquid of the osmotic pressure salinity gradient power generation unit 0. After being diluted in the forward osmosis membrane module 7, the draw liquid drives the turbine generator set 9 to generate electricity, and then the draw liquid is used to generate electricity. The system discharges through the external discharge valve 9c. The electrical energy output by the turbine generator set 9 is used to heat the NH4HCO3 solution in the NH4HCO3 extractant regenerator 10. When the temperature measurement value of the regenerator temperature signal controller 10d reaches the set value of 60°C, the concentrated magnesium solution regulating valve 5 closes and the NH4HCO3 regulating valve 31 opens. The concentrated NH4HCO3 solution in the NH4HCO3 extractant regenerator 10 is used as the extractant for the osmotic pressure salt gradient energy generation unit 0, switching to the continuously operating NH4HCO3 extractant salt gradient energy generation system. The electrical energy output by the turbine generator set 9 is regenerated by the NH4HCO3 in the NH4HCO3 extractant regenerator 10.

[0034] (b) When the intensity of sunlight gradually increases between 8 and 10 a.m., the 40°C hot water produced by the photovoltaic thermal module 11 preheats the 0-5°C pre-concentrated brine flowing out from the feed liquid side of the forward osmosis membrane module 7 in the brine preheater 12. The electrical energy produced by the photovoltaic thermal module 11 is used to heat the hot water in the backup water tank 16. When the temperature measurement value of the backup water tank temperature signal controller 16j reaches the set value of 70°C, the first shut-off valve 16c, the first return water shut-off valve 16e, the second shut-off valve 16g, and the second return water shut-off valve 16i of the backup water tank are opened. The adjustment parameter is obtained based on the difference between the temperature measurement value of the backup water tank temperature signal controller 16j and the set value of 70°C. The adjustment parameter and the backup water tank temperature signal controller 16j ... The relationship between the measured hot water temperature values ​​is used to calculate the hot water flow rates for evaporation concentration and evaporation crystallization. The opening degree of the evaporation concentration hot water regulating valve 19 and the evaporation crystallization hot water regulating valve 29 is adjusted until the following conditions are met: the lithium ion concentration in the brine after evaporation concentration at the inlet of adsorption tower 22 reaches 1.0-1.2% and the lithium ion concentration after desorption in adsorption tower 22 reaches 1.5-2.0%, and the lithium ion concentration at the inlet of lithium carbonate precipitation component 30 reaches 3.0-3.5%; plate evaporator 20 evaporates 97-97.5% of the water in the salt lake brine, and multi-effect evaporator 28 evaporates 33-57% of the water in the adsorbed lithium solution; the fresh water produced by plate evaporator 20 and multi-effect evaporator 28 meets the fresh water consumption of the desorption process in adsorption tower 22.

[0035] (c) When the solar radiation intensity is strongest between 10:00 and 15:00, the temperature measurement value of the hot water storage tank temperature signal controller 15 reaches the set value of 70°C. The first shut-off valve 14f, the first return water shut-off valve 14g, the second shut-off valve 14h, and the second return water shut-off valve 14i of the hot water storage tank are opened. The hot water generated by the solar collector 13 becomes the heat source for the lithium extraction system from the salt lake. The first shut-off valve 16c, the first return water shut-off valve 16e, the second shut-off valve 16g, and the second return water shut-off valve 16i of the backup water tank are closed. The hot water in the backup water tank 16 is continuously heated by the electrical energy generated by the photovoltaic thermal module 11 and stops supplying heat to the lithium extraction module from the salt lake. Based on the difference between the temperature measurement value of the hot water storage tank temperature signal controller 15 and the set value of 70°C, the opening degree of the evaporation and concentration hot water regulating valve 19 and the evaporation and crystallization hot water regulating valve 29 is adjusted according to the adjustment method in step (b).

[0036] (d) When the intensity of sunlight weakens between 3 PM and 6 PM, the temperature measurement value of the hot water storage tank temperature signal controller 15 is lower than the set value of 70°C. The first shut-off valve 16c, the first return water shut-off valve 16e, the second shut-off valve 16g, and the second return water shut-off valve 16i of the standby water tank are opened. The hot water in the standby water tank 16 with a temperature higher than 70°C and the hot water in the hot water storage tank 14 with a temperature lower than 70°C are mixed to provide heat for the lithium extraction system in the salt lake. Based on the difference between the temperature measurement value of the hot water storage tank temperature signal controller 15 and the standby water tank temperature signal controller 16j and the set value of 70°C, the opening degree of the evaporation and concentration hot water regulating valve 19 and the evaporation and crystallization hot water regulating valve 29 is adjusted according to the adjustment method in step (b).

[0037] Figure 2 This is a graph showing the evaporation heat transfer coefficient of a plate evaporator. The graph shows that the evaporation heat transfer coefficient of the evaporator increases first and then tends to stabilize as the flow rate increases under different brine flow rates.

[0038] Figure 3 This is a graph showing the change of the falling film evaporation heat transfer coefficient with the duration of sunlight. As can be seen from the graph, the heat transfer coefficient first increases and then decreases with the increase of the duration of sunlight, reaching its peak between 150 and 200 minutes of sunlight.

[0039] Using the above technical solution, the solar-driven power generation and heating system and the lithium extraction coupling system in the brine lake are dynamically adjusted according to changes in solar irradiance. When solar irradiance is weak, the concentrated magnesium solution after the initial lithium extraction, which is insulated and heated, is used as the extractant for osmotic pressure gradient energy generation, completing the initial concentration and power generation of the brine lake. This solves the problem of the electrical energy required to start the lithium extraction system in the brine lake without consuming external energy. As solar irradiance gradually increases, the low-grade heat generated by the photovoltaic thermal modules is used to preheat the brine lake in the brine lake tank. Through energy cascade utilization, the high-temperature hot water consumed in the evaporation concentration and evaporation crystallization processes is reduced. The electrical energy generated by the photovoltaic thermal modules is used to heat the hot water in the backup water tank to 70°C, based on the temperature of the backup water tank and the set temperature. By rationally adjusting the flow rates of hot water for evaporation concentration and evaporation crystallization, the response time of the lithium extraction system from the salt lake can be shortened. When the solar radiation intensity reaches its peak, the efficiency of the solar collectors is highest, and the hot water generated by the solar collectors becomes the heat source for evaporation concentration and evaporation crystallization in the lithium extraction system from the salt lake. The electricity generated by photovoltaic and solar thermal power is used to heat the hot water in the backup water tank as heat storage. As the solar radiation intensity gradually decreases, the heat provided by the solar collectors decreases, and the backup water tank and the hot water storage tank work together to meet the heat demand of the lithium extraction system from the salt lake, thus extending the operating time of the lithium extraction system under the designed operating conditions.

[0040] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments, or make equivalent substitutions for some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A solar-driven lithium extraction system for high-altitude salt lakes, comprising an osmotic pressure salinity gradient power generation unit (0), a photovoltaic thermal unit (1), a salt lake lithium extraction unit (2), and a regulation and control unit (17), characterized in that: The forward osmosis membrane module (7) in the osmotic pressure salt gradient energy power generation unit (0) is divided into a draw liquid side and a feed liquid side. The feed liquid side inlet (7a) is connected to the brine pump (4) pipeline, and the feed liquid side outlet (7b) is connected to the brine tank (8) and the brine preheater (12) pipe side. The draw liquid outlet (7d) is connected in sequence to the turbine generator set (9) and the NH4HCO3 draw liquid regenerator (10). The draw liquid outlet (10b) of the regenerator is connected back to the draw liquid inlet (7c) via the draw liquid pump (6). The concentrated magnesium solution tank (3) is connected to the draw liquid inlet (7c) via the concentrated magnesium solution regulating valve (5). The photovoltaic thermal unit (1) includes a photovoltaic thermal module (11), a solar collector (13), a hot water storage tank (14), a backup water tank (16), and a regulating control unit (17); the electrical energy generated by the photovoltaic thermal module (11) drives the heater (16a) embedded in the backup water tank through a cable; the solar collector (13) is connected to the plate heat exchanger (14a) embedded in the hot water storage tank to provide heat to the hot water storage tank (14); In the lithium extraction unit (2) of the salt lake, the hot water in the backup water tank (16) is connected to the plate evaporator (20) via the backup water tank evaporation and concentration hot water outlet (16b) and the backup water tank first shut-off valve (16c). The hot water in the hot water storage tank (14) is connected to the plate evaporator (20) via the hot water storage tank evaporation and concentration hot water outlet (14b) and the hot water storage tank first shut-off valve (14f). After the hot water releases sensible heat, it is connected to the backup water tank (16) and the hot water storage tank (14) via the backup water tank evaporation and concentration hot water return port (16d) and the hot water storage tank evaporation and concentration hot water return port (14c), respectively. After evaporation and concentration, the brine flows out of the plate evaporator (20) and enters the adsorption tower (22). The salt lake brine is connected to the plate condenser (18) via a pipeline from the salt lake brine preheater (12). The condensate is connected to the fresh water tank (21) via a pipeline from the plate condenser (18). After evaporation and concentration, the brine is connected to the upper part of the adsorption tower (22) through a pipeline. The bottom of the adsorption tower (22) is connected to the lithium solution tank (23). The outlet of the lithium solution tank (23) is connected to the inlet of the nanofiltration membrane separation component (25) via the nanofiltration booster pump (24). The outlet of the fresh water tank (21) is connected to the middle section inlet of the adsorption tower (22) and enters the tower for rinsing. The lithium solution after magnesium ion removal is connected from the outlet of the nanofiltration membrane separation unit (25) to the multi-effect evaporator condenser (27). The concentrated magnesium solution separated by the nanofiltration membrane separation unit (25) is connected via a pipeline to the nanofiltration discharge concentrated magnesium solution tank (26). The outlet of the nanofiltration discharge concentrated magnesium solution tank (26) is connected to the concentrated magnesium solution tank (3) of the osmotic pressure salinity gradient power generation unit (0). Condensate is connected from the multi-effect evaporator condenser (27) and the multi-effect evaporator (28) via a pipeline to the fresh water tank (21). Hot water in the standby water tank (16) is evaporated and crystallized at the standby water tank outlet (16f) and the standby water tank outlet. The water tank is connected to the multi-effect evaporator (28) via the second shut-off valve (16g) of the water tank. The hot water in the hot water storage tank (14) is connected to the multi-effect evaporator (28) via the hot water storage tank evaporation crystallization hot water outlet (14d) and the hot water storage tank second shut-off valve (14h). After the hot water releases sensible heat, it is connected to the standby water tank (16) and the hot water storage tank (14e) via the standby water tank evaporation crystallization hot water return port (16h) and the hot water storage tank evaporation crystallization hot water return port (14e), respectively. After evaporation and concentration, the concentrated lithium solution flows out from the concentrated lithium solution outlet (28a) of the multi-effect evaporator and is connected to the lithium carbonate precipitation assembly (30). The regulating control unit (17) is electrically connected to the evaporation and concentration hot water regulating valve (19), the evaporation and crystallization hot water regulating valve (29), the regenerator temperature signal controller (10d), the standby water tank temperature signal controller (16j), the hot water storage tank temperature signal controller (15), the concentrated magnesium solution regulating valve (5), and the NH4HCO3 regulating valve (31) using a PLC controller. The evaporation and concentration hot water regulating valve (19) is installed on the evaporation and concentration hot water inlet pipe, the evaporation and crystallization hot water regulating valve (29) is installed on the evaporation and crystallization hot water inlet pipe, the regenerator temperature signal controller (10d) is installed in the NH4HCO3 extractor regenerator (10), the standby water tank temperature signal controller (16j) and the hot water storage tank temperature signal controller (15) are installed in the standby water tank (16) and the hot water storage tank (14), respectively, the concentrated magnesium solution regulating valve (5) is installed on the outlet pipe of the concentrated magnesium solution water tank (3), and the NH4HCO3 regulating valve (31) is installed on the outlet pipe of the NH4HCO3 extractor regenerator (10).

2. The solar-driven lithium extraction system for high-altitude salt lakes according to claim 1, characterized in that, In the osmotic pressure salt gradient energy generation unit (0), the salt lake brine is pumped by the salt lake brine pump (4) and connected to the feed liquid side of the forward osmosis membrane module (7) through the feed liquid side inlet (7a) of the forward osmosis membrane module, and then connected to the photovoltaic thermal unit (1) through the salt lake brine tank (8) from the feed liquid side outlet (7b) of the forward osmosis membrane module. The concentrated magnesium solution is connected to the draw liquid side of the forward osmosis membrane module (7) via the concentrated magnesium solution tank outlet (3b), the concentrated magnesium solution regulating valve (5), and the draw liquid side inlet (7c). It is then connected to the turbine generator set (9) via the draw liquid side outlet (7d) of the forward osmosis membrane module and the turbine generator set inlet (9a). The diluted draw liquid is connected from the turbine generator set outlet (9b) to the draw liquid discharge regulating valve (9c), the draw liquid regeneration regulating valve (9d), and the regenerator inlet (10a) of the NH4HCO3 draw liquid. The concentrated draw liquid is connected to the draw liquid side of the forward osmosis membrane module (7) via the regenerator draw liquid outlet (10b), the NH4HCO3 regulating valve (31), the draw liquid pump (6), and the draw liquid side inlet (7c) of the forward osmosis membrane module. The regenerator freshwater outlet (10c) is connected to the freshwater tank (21) in the salt lake lithium extraction unit (2) via a pipeline.

3. The solar-driven lithium extraction system for high-altitude salt lakes according to claim 2, characterized in that, The photovoltaic thermal unit (1) generates electricity from the photovoltaic thermal module (11) to drive the brine pump (4), the extractor pump (6), the nanofiltration booster pump (24), and the heater (16a) embedded in the backup water tank via cables. The hot water generated by the photovoltaic thermal module (11) forms a natural circulation through the brine preheater (12). The brine is connected to the brine extraction unit (2) via pipelines through the brine tank outlet (8b) and the brine preheater (12). The backup water tank evaporates and concentrates the hot water outlet (16b) and the backup water tank first... The shut-off valve (16c) is installed on the hot water inlet pipe of the evaporation and concentration. The hot water return port (16d) of the standby water tank and the first return water shut-off valve (16e) of the standby water tank are installed on the hot water return pipe of the evaporation and concentration. The hot water outlet (16f) of the standby water tank and the second shut-off valve (16g) of the standby water tank are installed on the hot water inlet pipe of the evaporation and crystallization. The hot water return port (16h) of the standby water tank and the second return water shut-off valve (16i) of the standby water tank are installed on the hot water return pipe of the standby water tank.

4. The solar-driven lithium extraction system for high-altitude salt lakes according to claim 3, characterized in that, Hot water from the solar collector (13) outlet is connected to the solar collector (13) inlet via the hot water side of the embedded plate heat exchanger (14a) in the hot water storage tank. The hot water outlet (14b) and the first shut-off valve (14f) of the hot water storage tank are installed on the hot water inlet pipe of the hot water evaporation and concentration. The hot water return port (14c) and the first return water shut-off valve (14g) of the hot water storage tank are installed on the hot water return pipe of the hot water evaporation and concentration. The hot water outlet (14d) and the second shut-off valve (14h) of the hot water storage tank are installed on the hot water inlet pipe of the hot water evaporation and crystallization. The hot water return port (14e) and the second return water shut-off valve (14i) of the hot water storage tank are installed on the hot water return pipe of the hot water evaporation and crystallization.

5. A method for regulating a solar-driven lithium extraction system from a high-altitude salt lake as described in claim 4, characterized in that: (a) In the regulating control unit (17), in the first stage, based on the quantitative relationship between the temperature measurement value and the set value of the regenerator temperature signal controller (10d), the start-up time of the plateau salt lake lithium extraction system is shortened by switching the working mode of the draw liquid of the osmotic pressure salinity gradient power generation unit (0): when the temperature measurement value of the regenerator temperature signal controller (10d) is lower than the set value, the concentrated magnesium solution regulating valve (5) is opened, and the concentrated magnesium solution in the concentrated magnesium solution tank (3) after the initial adsorption and lithium extraction is used as the draw liquid of the osmotic pressure salinity gradient power generation unit (0). After the draw liquid is diluted in the forward osmosis membrane module (7), it drives the turbine generator set (9) to generate electricity, and then the draw liquid is discharged by the regulating valve (9c). The power output of the turbine generator set (9) is used to heat the NH4HCO3 solution in the NH4HCO3 extractant regenerator (10) when the temperature measurement value of the regenerator temperature signal controller (10d) reaches the set value. The concentrated magnesium solution regulating valve (5) is closed and the NH4HCO3 regulating valve (31) is opened. The concentrated NH4HCO3 solution in the NH4HCO3 extractant regenerator (10) is used as the extractant of the osmotic pressure salt gradient energy power generation unit (0). The system is switched to the continuously operating NH4HCO3 extractant salt gradient energy power generation system. The power output of the turbine generator set (9) is used to regenerate the NH4HCO3 in the NH4HCO3 extractant regenerator (10). (b) In the second stage, the hot water produced by the photovoltaic thermal module (11) preheats the salt lake brine that is initially concentrated at 0-5℃ flowing out from the feed liquid side of the forward osmosis membrane module (7) in the salt lake brine preheater (12). The electrical energy produced by the photovoltaic thermal module (11) is used to heat the hot water in the backup water tank (16). When the temperature measurement value of the backup water tank temperature signal controller (16j) reaches the set value, the backup water tank first shut-off valve (16c), the backup water tank first return water shut-off valve (16e), the backup water tank second shut-off valve (16g) and the backup water tank second return water shut-off valve (16i) are opened. The adjustment parameter is obtained based on the difference between the temperature measurement value of the backup water tank temperature signal controller (16j) and the set value. Based on the change relationship between the adjustment parameter and the hot water temperature measurement value of the backup water tank, the hot water flow rate of evaporation concentration and evaporation crystallization is calculated. The opening degree of the evaporation concentration hot water regulating valve (19) and the evaporation crystallization hot water regulating valve (29) is adjusted until the preset conditions are met. (c) In the third stage, when the temperature measurement value of the hot water storage tank temperature signal controller (15) reaches the set value, the first shut-off valve (14f), the first return water shut-off valve (14g), the second shut-off valve (14h), and the second return water shut-off valve (14i) of the hot water storage tank are opened. The hot water generated by the solar collector (13) becomes the heat source of the lithium extraction system in the salt lake. The first shut-off valve (16c), the first return water shut-off valve (16e), the second shut-off valve (16g), and the second return water shut-off valve (16i) of the backup water tank are closed. The hot water in the backup water tank (16) is continuously heated by the electricity generated by the photovoltaic thermal module (11) and stops supplying heat to the lithium extraction module in the salt lake. Based on the difference between the temperature measurement value and the set value of the hot water storage tank temperature signal controller (15), the opening degree of the evaporation and concentration hot water regulating valve (19) and the evaporation and crystallization hot water regulating valve (29) is adjusted according to the adjustment method in step (b). (d) In the fourth stage, when the temperature measurement value of the hot water storage tank temperature signal controller (15) is lower than the set value, the first shut-off valve (16c), the first return water shut-off valve (16e), the second shut-off valve (16g), and the second return water shut-off valve (16i) of the standby water tank are opened. The hot water in the standby water tank (16) with a temperature higher than the set value and the hot water in the hot water storage tank (14) with a temperature lower than the set value are mixed to provide heat for the lithium extraction system in the salt lake. Based on the difference between the temperature measurement value and the set value of the hot water storage tank temperature signal controller (15) and the standby water tank temperature signal controller (16j), the opening degree of the evaporation and concentration hot water regulating valve (19) and the evaporation and crystallization hot water regulating valve (29) is adjusted according to the adjustment method in step (b).

6. The adjustment method for a solar-driven lithium extraction system from a high-altitude salt lake according to claim 5, characterized in that: The first phase is from 6:00 AM to 8:00 AM, the second phase is from 8:00 AM to 10:00 AM, the third phase is from 10:00 AM to 3:00 PM, and the fourth phase is from 3:00 PM to 6:00 PM.

7. The adjustment method for a solar-driven lithium extraction system from a high-altitude salt lake according to claim 6, characterized in that, The preset conditions in step (b) are as follows: the lithium ion concentration in the brine after evaporation and concentration at the inlet of the adsorption tower (22) reaches 1.0-1.2% and the lithium ion concentration after desorption at the adsorption tower (22) reaches 1.5-2.0%, and the lithium ion concentration at the inlet of the lithium carbonate precipitation component (30) reaches 3.0-3.5%; the plate evaporator (20) evaporates 97-97.5% of the water in the salt lake brine, and the multi-effect evaporator (28) evaporates 33-57% of the water in the adsorbed lithium solution. The fresh water produced by the plate evaporator (20) and the multi-effect evaporator (28) meets the fresh water consumption of the desorption process in the adsorption tower (22).

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