A solar cell for producing lithium carbonate concentrate and a method for lithium extraction

Abstract

This invention discloses a solar pond and lithium extraction method for producing lithium carbonate concentrate, belonging to the field of lithium extraction technology from carbonate-type salt lake brine. It addresses the problems of low lithium carbonate precipitation rate and poor lithium deposition effect in existing technologies for lithium extraction from carbonate-type salt lake brine. The solar pond of this invention includes a pond body, comprising a bottom plate at the bottom and side plates on the side walls. The side plates are inclined relative to the horizontal direction, and their inner sides have multiple protruding main facets extending from the bottom to the top of the pond, with the top angle of each facet being an obtuse angle. The lithium extraction method of this invention involves injecting lithium-rich brine and fresh water into the pond body, allowing it to stand for several days to obtain a three-layered salt gradient solar pond: a brine layer, a salt gradient layer, and a fresh water layer. The salt gradient solar pond absorbs solar energy, gradually increasing in temperature, and precipitating lithium carbonate concentrate. This invention can be used for lithium extraction from carbonate-type salt lake brine.

Description

Technical Field

[0001] This invention belongs to the field of lithium extraction technology from carbonate-type salt lake brine, and particularly relates to a solar pond for producing lithium carbonate concentrate and a lithium extraction method. Background Technology

[0002] With the expansion of the new energy vehicle and energy storage battery industries, the demand for lithium resources has surged, and my country's annual lithium salt consumption has continued to climb. Self-sufficiency has become crucial for the development of the new energy industry. Lithium extraction from salt lakes has become a key area due to its abundant resources and low cost (30%-50% lower than ore extraction), and technological innovation in brine lithium extraction is a research hotspot.

[0003] Currently, the traditional lithium extraction process for lithium-rich carbonate salt lakes using solar ponds is as follows:

[0004] The pool is constructed with clay and lined with a black geomembrane or high-density polyethylene liner.

[0005] The lithium-rich brine, which has been concentrated by evaporation in the salt field, is then filled with fresh water to form a three-layer structure.

[0006] After 20 to 60 days of heat storage, lithium carbonate crystallizes out.

[0007] However, the above process has significant bottlenecks: the pool structure is simple, relying solely on the black pad to absorb heat, resulting in a long heat storage cycle, low annual circulation, high freshwater consumption, low lithium carbonate precipitation rate, and poor lithium deposition effect. Summary of the Invention

[0008] Based on the above analysis, the embodiments of the present invention aim to provide a solar pool for producing lithium carbonate concentrate and a lithium extraction method, in order to solve the problems of low lithium carbonate precipitation rate and poor lithium precipitation effect in the existing technology of lithium extraction from carbonate-type salt lake brine.

[0009] The objective of this invention is mainly achieved through the following technical solutions.

[0010] The present invention provides a solar cell for producing lithium carbonate concentrate, comprising a cell body, a bottom plate disposed at the bottom of the solar cell and a side plate disposed on the side wall of the solar cell, the side plate being inclined relative to the horizontal direction, and the inner side of the side plate having multiple protruding main facets, the main facets being continuous from the bottom of the cell to the top of the cell, the top angle of the main facets being an obtuse angle.

[0011] Furthermore, each main facet has multiple protruding sub-facets on its inner side.

[0012] Furthermore, as the pool gradually approaches the bottom plate, the height of the main facet of the pool side plate gradually decreases, and the connection between the pool side plate and the bottom plate is a straight line.

[0013] Furthermore, the angle between the pool side plate and the pool bottom plate is 130°~150°.

[0014] Furthermore, an insulation layer is provided beneath both the pool bottom plate and the pool side plate.

[0015] Furthermore, the insulation layer includes a heat-absorbing and seepage-proof layer and a honeycomb layer stacked sequentially from bottom to top; wherein, the cross-sectional shape of the honeycomb layer along the direction from the top of the pool to the bottom of the pool is honeycomb-shaped.

[0016] Furthermore, the cellular layer comprises alternating hexagonal and rectangular cellular cells.

[0017] Furthermore, the hexagonal honeycomb cell includes a hexagonal cell matrix and a hexagonal insulating sleeve that encloses the hexagonal cell matrix; the rectangular honeycomb cell includes a rectangular cell matrix and a rectangular insulating sleeve that encloses the rectangular cell matrix.

[0018] Furthermore, a first air vent is opened on the sidewall of the hexagonal honeycomb cell facing the foundation, a second air vent is opened on the sidewall connecting the hexagonal honeycomb cell and the rectangular honeycomb cell, no air vent is provided on the sidewall of the hexagonal honeycomb cell facing the interior of the solar pool, a third air vent is opened on the sidewall of the rectangular honeycomb cell facing the foundation, and a fourth air vent is opened on the sidewall connecting the rectangular honeycomb cell and the hexagonal honeycomb cell. The second and fourth air vents are connected. No air vent is provided on the sidewall of the rectangular honeycomb cell facing the interior of the solar pool. Through the first and third air vents, the gas generated by the geothermal effect can enter the hexagonal cell matrix and the rectangular cell matrix. Through the connected second and fourth air vents, the gas in the hexagonal cell matrix and the rectangular cell matrix can be gradually guided to the ground.

[0019] Furthermore, the solar pool also includes a retractable heat-insulating canopy located above the pool body.

[0020] The present invention also provides a lithium extraction method for producing lithium carbonate concentrate, using the aforementioned solar cell for producing lithium carbonate concentrate, and the lithium extraction method includes the following steps:

[0021] Step 1: Concentrate carbonate-type salt lake brine to form lithium-rich brine;

[0022] Step 2: Inject lithium-rich brine and fresh water into the pool respectively, let it stand for several days to obtain a three-layer salt gradient solar pool, which consists of a brine layer, a salt gradient layer and a fresh water layer.

[0023] Step 3: The salt gradient solar pool absorbs solar energy and gradually increases in temperature, precipitating lithium carbonate concentrate and completing the first lithium carbonate precipitation.

[0024] Furthermore, in step 1, Li in lithium-rich halide formation + Concentration greater than 1.5 g / L.

[0025] Furthermore, in step 2, the depth of lithium-rich halogen formation is 1.8m to 2.2m.

[0026] Furthermore, in step 3, the temperature is gradually increased to 45℃~65℃.

[0027] Furthermore, it also includes step 4: using feeding equipment such as a slurry pump, a rotary pump or a thick slurry pump to inject a sodium carbonate suspension at a temperature of 65℃~70℃ into the upper part of the brine layer, and then heating it again to precipitate lithium carbonate.

[0028] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0029] A) The solar cell for producing lithium carbonate concentrate provided by this invention has multiple protruding main facets distributed on the side plate of the cell. The arrangement of the main facets can capture light entering the solar cell from multiple different angles, thereby ensuring that the light can be effectively received regardless of the direction of incidence, allowing more light to directly enter the solar cell. In addition, the structure of multiple main facets can significantly increase the heat absorption area of ​​the solar cell, thereby significantly improving the solar energy absorption efficiency per unit area. The heating phase of the solar cell is significantly shortened, thereby effectively reducing the time of the entire production cycle and improving overall efficiency. In practical applications, the heating phase of the solar cell can be reduced by 24.5% to 38.8%.

[0030] B) The solar pool for producing lithium carbonate concentrate provided by the present invention has multiple edges on adjacent main facets. The edges can serve as nucleation regions, effectively reducing the nucleation threshold of lithium carbonate crystals, breaking the energy barrier of the liquid-solid interface, and thus promoting the preferential precipitation of lithium carbonate crystals at the edges, thereby accelerating the crystallization of lithium carbonate.

[0031] C) The solar pool for producing lithium carbonate concentrate provided by the present invention has multiple protruding sub-facets on the inner side of each main facet, which not only further increases the heat absorption area of ​​the solar pool and makes the absorption of solar energy more complete, but also greatly increases the number of facets. More facets mean more nucleation areas, which provides more favorable positions for the precipitation of lithium carbonate crystals, thereby further accelerating the crystallization speed of lithium carbonate and improving the precipitation rate of lithium carbonate.

[0032] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained through the embodiments described and the accompanying drawings, which are particularly pointed out. Attached Figure Description

[0033] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0034] Figure 1 A schematic diagram of the structure of a solar cell for producing lithium carbonate concentrate provided in an embodiment of the present invention;

[0035] Figure 2 A schematic diagram of the structure of the side plate of the solar cell in the production of lithium carbonate concentrate provided in an embodiment of the present invention;

[0036] Figure 3 A schematic diagram of the insulation layer in a solar pool for producing lithium carbonate concentrate, provided in an embodiment of the present invention;

[0037] Figure 4 This is a schematic diagram of the operation process of the lithium extraction method for producing lithium carbonate concentrate provided in an embodiment of the present invention.

[0038] Figure label:

[0039] 1-Pool bottom plate; 2-Pool side plate; 201-First straight line; 202-Second straight line; 203-Third straight line; 3-Main facet; 4-Sub-facet; 5-Honeycomb layer; 501-Hexagonal honeycomb cell; 502-Rectangular honeycomb cell; 6-First air vent; 7-Second air vent; 8-Third air vent; 9-Fourth air vent; 10-Expanded polytetrafluoroethylene membrane; 11-Expandable heat-insulating awning; 12-Foundation. Detailed Implementation

[0040] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which constitute a part of the present invention and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0041] In a first aspect, the present invention provides a solar cell for producing lithium carbonate concentrate, see [link to previous article]. Figure 1 The system includes a pool body, which includes a bottom plate 1 at the bottom of the solar pool and a side plate 2 on the side wall of the solar pool. The side plate 2 is inclined relative to the horizontal direction. The inner side of the side plate 2 has multiple protruding main facets 3. The main facets 3 extend from the bottom of the pool to the top of the pool. The top angle of the main facets 3 is an obtuse angle.

[0042] Compared with existing technologies, the solar pool for producing lithium carbonate concentrate provided by this invention has several advantages. First, multiple protruding main facets 3 are distributed on the side plate 2 of the pool. The arrangement of the main facets 3 can capture light entering the solar pool from multiple different angles, thus ensuring that the light can be effectively received regardless of the direction of incidence, allowing more light to directly enter the solar pool. In addition, the structure of multiple main facets 3 can significantly increase the heat absorption area of ​​the solar pool, thereby significantly improving the solar energy absorption efficiency per unit area. The heating phase of the solar pool is significantly shortened, which effectively reduces the time of the entire production cycle and improves the overall efficiency. In practical applications, the heating phase of the solar pool can be reduced by 24.5% to 38.8%.

[0043] On the other hand, due to the existence of multiple edges on adjacent main facets 3, the edges can serve as nucleation regions, effectively reducing the nucleation threshold of lithium carbonate crystals, breaking the energy barrier of the liquid-solid interface, and thus promoting the preferential precipitation of lithium carbonate crystals at the edges, accelerating the crystallization of lithium carbonate.

[0044] It should be noted that, in order to further increase the number of edges, each main edge 3 has multiple protruding sub-edges 4 on its inner side. These multiple protruding sub-edges 4 on the inner side of each main edge 3 not only further increase the heat absorption area of ​​the solar pool, making solar energy absorption more complete, but also greatly increase the number of edges. More edges mean more nucleation regions, which provides more favorable locations for the precipitation of lithium carbonate crystals, thereby further accelerating the crystallization rate of lithium carbonate and improving the precipitation rate of lithium carbonate.

[0045] For example, along the horizontal direction, the cross-sectional line of the pool side plate 2 includes multiple straight lines forming a wavy line. The angle between two adjacent straight lines is an obtuse angle. For example, the cross-sectional line of the pool side plate 2 includes multiple segments of a first straight line 201, a second straight line 202, and a third straight line 203. The angle θ1 between the first straight line 201 and the second straight line 202 is 110°~130°, and the angle θ2 between the second straight line 202 and the third straight line 203 is 140°~160°. In this way, by adopting a wavy line shape, the number of main facets 3 can be increased as much as possible, thereby further increasing the heat absorption area of ​​the solar pool and improving the solar energy absorption efficiency. At the same time, the wavy line shape of the main facets 3 also makes the facet distribution more dense, providing more favorable positions for the nucleation of lithium carbonate crystals, which helps the rapid precipitation and growth of lithium carbonate crystals.

[0046] It should be noted that, in order to achieve the connection between the side plate 2 and the bottom plate 1, the height of the main facet 3 of the side plate 2 gradually decreases as it approaches the bottom plate 1, and the connection between the side plate 2 and the bottom plate 1 is a straight line. This straight connection not only ensures structural stability but also effectively prevents brine leakage at the junction of the bottom plate 1 and the side plate 2, improving the overall sealing performance of the solar pool.

[0047] For example, the angle between the pool side plate 2 and the pool bottom plate 1 is 130°~150°.

[0048] In one alternative embodiment, the top surfaces of the pool bottom plate 1 and the pool side plate 2 are provided with a light-absorbing and seepage-proof material layer to enhance solar energy utilization efficiency and prevent brine leakage. The light-absorbing and seepage-proof material layer can be achieved using materials available in the prior art, such as laying a black EPDM waterproof membrane made of EPDM material on the top surfaces of the pool bottom plate 1 and the pool side plate 2.

[0049] In order to ensure the temperature inside the solar cell, insulation layers are stacked under both the bottom plate 1 and the side plate 2. The insulation layers can effectively reduce the heat loss inside the solar cell and maintain a high temperature environment inside the solar cell, which is extremely beneficial for the crystallization and precipitation process of lithium carbonate.

[0050] It is worth noting that during the operation of the solar pond, due to the unevenness of the salt field bottom or the geothermal effect, air pockets are easily formed at the bottom of the membrane. In artificial mining, this can easily cause damage to the membrane, increasing leakage in the solar pond. Therefore, the structure of the insulation layer specifically includes a heat-absorbing and seepage-proof layer and a honeycomb layer 5 stacked sequentially from bottom to top. The honeycomb layer 5 has a honeycomb-shaped cross-section along the direction from the top to the bottom of the pond. In practical applications, the average temperature of the solar pond of this invention is 15°C to 18°C ​​higher than that of a traditional solar pond.

[0051] Specifically, the honeycomb layer 5 includes alternating hexagonal honeycomb cells 501 and rectangular honeycomb cells 502. This structure not only has high strength and can withstand certain pressure and deformation, preventing the film from being damaged and the solar pool from leakage caused by unevenness at the bottom of the salt field or geothermal effects; but also has a large number of closed cavities. These cavities can effectively prevent heat transfer, further reduce heat loss in the solar pool, improve the heat preservation effect, and provide more favorable temperature conditions for the crystallization and precipitation of lithium carbonate.

[0052] The structures of hexagonal honeycomb cells 501 and rectangular honeycomb cells 502 are basically the same, differing only in shape. Specifically, hexagonal honeycomb cell 501 includes a hexagonal cell matrix (e.g., a hexagonal high-density rock wool board) and a hexagonal insulation sleeve enclosing the hexagonal cell matrix. Correspondingly, rectangular honeycomb cell 502 includes a rectangular cell matrix (e.g., a rectangular high-density rock wool board) and a rectangular insulation sleeve enclosing the rectangular cell matrix. In this way, a multi-layered insulation barrier can be formed through the hexagonal and rectangular insulation sleeves.

[0053] To facilitate the smooth extraction of gases generated by the geothermal effect, a first vent 6 is provided on the sidewall of the hexagonal honeycomb cell 501 facing the foundation 12. A second vent 7 is provided on the sidewall connecting the hexagonal honeycomb cell 501 and the rectangular honeycomb cell 502. No vent is provided on the sidewall of the hexagonal honeycomb cell 501 facing the interior of the solar pool. A third vent 8 is provided on the sidewall of the rectangular honeycomb cell 502 facing the foundation 12. A fourth vent 9 is provided on the sidewall connecting the rectangular honeycomb cell 502 and the hexagonal honeycomb cell 501. The second vent 7 and the fourth vent 9 are connected. No vent is provided on the sidewall of the rectangular honeycomb cell 502 facing the interior of the solar pool. In this way, the gases generated by the geothermal effect can enter the hexagonal cell matrix and the rectangular cell matrix through the first vent 6 and the third vent 8. Through the connected second vent 7 and the fourth vent 9, the gases in the hexagonal cell matrix and the rectangular cell matrix can be gradually guided to the ground.

[0054] In order to improve the thermal insulation performance of the above-mentioned insulation layer, the insulation layer also includes an expanded polytetrafluoroethylene film 10 applied to the inner wall of the hexagonal honeycomb cell 501 and the rectangular honeycomb cell 502. It should be noted that the expanded polytetrafluoroethylene film 10 can be applied to the inner wall of the hexagonal honeycomb cell 501 and the rectangular honeycomb cell 502 as a whole, or it can be applied only to the positions of the first air vent 6, the second air vent 7, the third air vent 8 and the fourth air vent 9.

[0055] It should be noted that the expanded polytetrafluoroethylene membrane 10 has a three-dimensional network of interconnected micropores, and gas permeation depends on the pressure difference: under high pressure difference, convection transport is the main method, and the gas passes through the micropores quickly, significantly improving the permeability; under low pressure difference, molecular diffusion is the main method, and the permeability rate decreases significantly. In this way, when the amount of gas generated by the geothermal effect is small, the pressure difference between the foundation 12 and the hexagonal honeycomb cells 501 and rectangular honeycomb cells 502 is low, the air permeability rate of the expanded polytetrafluoroethylene membrane 10 is low, and the interiors of the hexagonal honeycomb cells 501 and rectangular honeycomb cells 502 are independent chambers, which can form multiple independent air layers, effectively preventing heat loss through gas flow and further enhancing the insulation effect of the insulation layer. When the amount of gas generated by the geothermal effect is large, the pressure difference between the foundation 12 and the hexagonal honeycomb cells 501 and rectangular honeycomb cells 502 is high, the air permeability rate of the expanded polytetrafluoroethylene membrane 10 increases, and the gas can be smoothly discharged through the air vents, avoiding damage to the insulation layer structure due to gas accumulation, while also maintaining a stable temperature environment inside the solar pool.

[0056] It should be noted that the insulation layer is made of materials with low thermal conductivity and good insulation performance, such as polyurethane foam board and rock wool board. These materials not only have significant insulation effects, but also have sufficient structural strength to withstand certain pressure and deformation, thereby ensuring the long-term stable operation of the solar pool.

[0057] In practical applications, heat loss in solar ponds mainly consists of two parts: heat loss from the bottom and slopes of the pond, and heat loss from the surface. Water evaporation absorbs heat and carries away a significant amount of thermal energy. Furthermore, the windy conditions at night in the lake area exacerbate airflow above the pond, leading to increased convective heat dissipation and further increasing surface heat loss. To reduce brine evaporation and heat loss, the aforementioned solar ponds for producing lithium carbonate concentrate also include a retractable heat-insulating awning 11 installed above the pond. It should be noted that the retractable heat-insulating awning 11 can be adjusted according to weather conditions and production needs. During sunny days, the awning 11 is retracted to allow the pond to fully receive solar radiation and increase the temperature inside. At night or during cloudy / rainy weather, the awning 11 is extended to cover the pond, reducing heat loss through the top and preventing brine evaporation, thus maintaining a stable brine concentration within the pond. In practical applications, the installation of the retractable heat-insulating awning 11 reduces freshwater consumption by 22% to 31%.

[0058] Secondly, the present invention also provides a lithium extraction method for producing lithium carbonate concentrate, using the aforementioned solar cell for producing lithium carbonate concentrate.

[0059] The above lithium extraction method includes the following steps:

[0060] Step 1: [The text abruptly shifts to a seemingly unrelated topic:] ...carbonate-type salt lake high + Low CO3 2- The brine is concentrated through sun evaporation to form lithium-rich brine, in which Li... + Concentration greater than 1.5 g / L;

[0061] Step 2: Inject lithium-rich brine and fresh water into the pool, respectively. The depth of lithium-rich brine is 1.8m~2.2m. Let it stand for several days to obtain a three-layer salt gradient solar pool, which consists of a brine layer, a salt gradient layer and a fresh water layer.

[0062] Step 3: The salt gradient solar pond absorbs solar energy and gradually heats up to 45℃~65℃, precipitating lithium carbonate concentrate. When the Li in the brine layer... + Once the concentration drops below 0.8 g / L, the first lithium carbonate precipitation is complete.

[0063] Step 4: Using a slurry pump, rotary pump, or thick slurry pump, inject a sodium carbonate suspension at a temperature of 65℃~70℃ into the upper part of the brine layer to precipitate lithium carbonate a second time. The volume ratio of sodium carbonate suspension to lithium brine is 1:22~1:81, and the solid-liquid ratio of sodium carbonate suspension is 30%~45%. The injection time is between 2~3 hours of the day when the temperature is highest, for example, between 2 pm and 5 pm in Xinjiang. This period is the highest brine temperature of the day, which is conducive to the dissolution of sodium carbonate particles in sodium carbonate suspension and increases the concentration of carbonate in brine.

[0064] Step 5: Drain the brine and collect the lithium carbonate mixed salt.

[0065] Compared with the prior art, the present invention provides a lithium extraction method for producing lithium carbonate concentrate, which has essentially the same beneficial effects as the solar cell for producing lithium carbonate concentrate provided above, and will not be elaborated here.

[0066] Furthermore, in the above-mentioned lithium extraction method, sodium carbonate suspension is forcibly injected, and sodium carbonate dissolves in the brine layer, making the temperature and concentration field distribution of the solar cell more uniform. The heat of dissolution of sodium carbonate particles causes the temperature of the brine in the lithium deposition layer to rise again. Both of these factors accelerate the crystallization and precipitation of lithium carbonate in the solar cell, thereby significantly improving the lithium yield of the solar cell.

[0067] The above-mentioned lithium extraction method is simple, easy to operate, and highly effective. Moreover, it is economical and environmentally friendly, does not pollute the environment, and has broad application prospects.

[0068] Specifically, in step 4 above, the sodium carbonate suspension is prepared using the following method:

[0069] Step 41: Add water to the mixing tank;

[0070] Step 42: Turn on the heater of the mixing tank to heat the water in the stirrer. During the water heating process, gradually add sodium carbonate particles in 8 to 10 batches. When the water temperature reaches 65℃ to 70℃, a sodium carbonate suspension is obtained.

[0071] It should be noted that, to avoid aging and maintain the dispersibility of sodium carbonate particles, the sodium carbonate suspension mentioned above is prepared within 10 to 25 minutes. This ensures that the sodium carbonate particles maintain good dispersion in a short period, without significant agglomeration or precipitation. When injected into the upper part of the brine layer, the sodium carbonate particles are more evenly dispersed, allowing for sufficient contact and reaction with lithium ions in the brine, thus effectively improving the efficiency of secondary lithium carbonate precipitation. Simultaneously, by avoiding the aging process, the sodium carbonate in the suspension has higher activity, dissolving and releasing carbonate ions more quickly, further promoting the precipitation of lithium carbonate.

[0072] For example, the sodium carbonate suspension is injected horizontally, at the upper part of the brine layer, 20-30 cm from the surface of the salt gradient solar cell. This horizontal injection ensures rapid and uniform diffusion of the sodium carbonate suspension upon entering the brine layer, allowing for sufficient contact with lithium ions. Because the injection location is at the upper part of the brine layer and relatively close to the surface, the brine temperature in this area is relatively high, which facilitates the rapid dissolution of sodium carbonate particles, thereby increasing the carbonate concentration in the brine and providing more favorable conditions for secondary precipitation of lithium carbonate. Simultaneously, the horizontal injection method avoids direct impact of the sodium carbonate suspension on the bottom of the brine layer, reducing disturbance to the already precipitated lithium carbonate crystals, helping to maintain the stability of the precipitation and improve the purity of the final product.

[0073] The injection flow rate of the sodium carbonate suspension was 1.5 m / s. 3 / h~30m 3 By controlling the injection flow rate within the above range, the sodium carbonate suspension can move in a horizontal parabolic motion in the brine layer. This ensures that the sodium carbonate particles are fully dissolved in the brine layer during sedimentation, effectively avoiding disturbance and damage to the salt gradient layer.

[0074] The sodium carbonate suspension is injected intermittently. Within each cycle, the injection time is 12–18 minutes (e.g., 15 minutes), with a pause of 3–7 minutes (e.g., 5 minutes). This intermittent injection method allows for more complete diffusion and reaction of the sodium carbonate suspension in the brine layer. During the injection phase, the sodium carbonate suspension continuously enters the brine layer, contacting and reacting with lithium ions. As injection continues, the carbonate concentration in localized areas of the brine layer gradually increases, and lithium carbonate begins to precipitate. During the pause phase, the injected sodium carbonate suspension has sufficient time to further diffuse in the brine layer, resulting in a more uniform carbonate concentration throughout the brine layer and preventing excessively high or low concentrations in certain areas. Simultaneously, the intermittent injection method also prevents excessive local temperature fluctuations in the brine layer caused by continuous injection, maintaining a relatively stable temperature environment and providing favorable conditions for lithium carbonate crystallization.

[0075] To further improve the temperature and ion concentration uniformity of the brine layer, multiple injection ports for the sodium carbonate suspension are arranged in a ring. The injection direction of these ports is inclined radially relative to the ring, either clockwise or counterclockwise, causing the injected sodium carbonate suspension to swirl and create forced convection circulation within the brine layer, thereby increasing the Li content in the brine layer. + and CO3 2- This increases the chances of collision and combination, while also promoting a more uniform distribution of temperature and ion concentration in the brine layer of the solar pool, thereby accelerating the crystallization and precipitation of lithium carbonate in the solar pool.

[0076] Example 1

[0077] The solar cell for producing lithium carbonate concentrate provided in this embodiment includes a bottom plate and four side plates. The bottom plate is rectangular with a length-to-width ratio of 7:4, meaning that the longitudinal cross-section of the cell is an inverted trapezoid. The top opening of the cell is outwardly flared. The angle between the side plates and the bottom plate is 140°. The angle between the first straight line and the second straight line is 120°. The angle between the second straight line and the third straight line is 150°. The ridge line extends in a wavy pattern to the bottom plate. The connection between the bottom plate and the side plates is a straight line.

[0078] In the insulation layer, the gap between adjacent hexagonal honeycomb cells and rectangular honeycomb cells is 0mm. The joint angle between the two main edges of the hexagonal honeycomb cells and rectangular honeycomb cells after splicing is 150°. The side length of the hexagonal honeycomb cells and rectangular honeycomb cells is 60cm, the side distance is 10cm, and the height is 10cm.

[0079] The lithium extraction method for producing lithium carbonate concentrate in this embodiment is described in the following flowchart. Figure 4 The lithium extraction method includes the following steps:

[0080] Step A: The carbonate-type salt lake brine is concentrated by solar evaporation to form a lithium-rich brine. The lithium in the lithium-rich brine... + The concentration was 1.8 g / L. The lithium-rich brine was poured into the solar cell at a depth of 1.8 m.

[0081] Step B: Lay fresh water on the lithium-rich brine surface layer to form a brine layer, a salt gradient layer, and a fresh water layer from bottom to top in the solar cell;

[0082] Step C: Let it stand still. During the day, the retractable heat insulation awning is retracted, and the solar pool absorbs solar energy and stores heat. At night, the retractable heat insulation awning is extended to cover the surface of the solar pool, with a height of 25cm above the water surface. The temperature of the brine layer gradually rises to 50℃. After entering the stable heating and lithium precipitation stage, lithium carbonate is precipitated for the first time, and the lithium ion content in the brine drops to 0.8g / L.

[0083] Step D: Add water to the mixing tank, turn on the heater of the mixing tank, and heat the water in the mixer to 70°C. During the heating process, add 150-200 mesh sodium carbonate particles in 10 portions to obtain a sodium carbonate suspension with a solid-liquid ratio of 30%.

[0084] Step E: 20 minutes after the preparation of the sodium carbonate suspension, inject the 70℃ sodium carbonate suspension into the brine layer using a slurry pump. The outlet of the slurry pump should be placed horizontally, located 25 cm below the salt gradient layer (approximately above the brine layer). The sodium carbonate suspension should be injected at a flow rate of 10 m / s. 3 / h, inject sodium carbonate suspension for 15min, stop for 5min, the volume ratio of sodium carbonate suspension to lithium-rich halogen is 1:35;

[0085] Step F: Sodium carbonate particles dissolve in the brine layer, the brine layer is heated a second time, lithium carbonate crystals precipitate again, and the lithium ion concentration is considered to have dropped below 0.25 g / L, indicating that the lithium carbonate precipitation is complete.

[0086] Example 2

[0087] The solar cell for producing lithium carbonate concentrate provided in this embodiment includes a bottom plate and four side plates. The bottom plate is rectangular with a length-to-width ratio of 8:3, meaning that the longitudinal cross-section of the cell is an inverted trapezoid. The top opening of the cell is outwardly flared. The angle between the side plates and the bottom plate is 150°. The angle between the first straight line and the second straight line is 110°. The angle between the second straight line and the third straight line is 160°. The ridge line extends in a wavy pattern to the bottom plate. The connection between the bottom plate and the side plates is a straight line.

[0088] In the insulation layer, the gap between adjacent hexagonal and rectangular honeycomb cells is 0.1 mm. After the hexagonal and rectangular honeycomb cells are spliced ​​together, the joint angle between the two main edges is 150°. The side length of the hexagonal and rectangular honeycomb cells is 50 cm, the side distance is 8 cm, and the height is 8 cm.

[0089] The lithium extraction method of this embodiment includes the following steps:

[0090] Step A: The carbonate-type salt lake brine is concentrated by solar evaporation to form a lithium-rich brine. The lithium in the lithium-rich brine... + The concentration was 1.6 g / L. The lithium-rich brine was poured into the solar cell at a depth of 2.2 m.

[0091] Step B: Lay fresh water on the lithium-rich brine surface layer to form a brine layer, a salt gradient layer, and a fresh water layer from bottom to top in the solar cell;

[0092] Step C: Let it stand still. During the day, the retractable heat insulation awning is retracted, and the solar pool absorbs solar energy and stores heat. At night, the retractable heat insulation awning is extended to cover the surface of the solar pool, with a height of 35cm above the water surface. The temperature of the brine layer gradually rises to 60℃. After entering the stable heating and lithium precipitation stage, lithium carbonate is precipitated for the first time, and the lithium ion content in the brine drops to 0.8g / L.

[0093] Step D: Add water to the mixing tank, turn on the heater of the mixing tank, and heat the water in the mixer to 65°C. During the heating process, add 150-200 mesh sodium carbonate particles in 8 batches to obtain a sodium carbonate suspension with a solid-liquid ratio of 40%.

[0094] Step E: 15 minutes after the preparation of the sodium carbonate suspension, inject the 65℃ sodium carbonate suspension into the brine layer using a slurry pump. The outlet of the slurry pump should be placed horizontally, located 30 cm below the salt gradient layer (approximately above the brine layer). The sodium carbonate suspension should be injected at a flow rate of 25 m / s. 3 / h, inject sodium carbonate suspension for 17min, stop for 3min, the volume ratio of sodium carbonate suspension to lithium-rich halogen is 1:62;

[0095] Step F: Sodium carbonate particles dissolve in the brine layer, the brine layer is heated a second time, lithium carbonate crystals precipitate again, and the lithium ion concentration is considered to have dropped below 0.25 g / L, indicating that the lithium carbonate precipitation is complete.

[0096] Table 1. Comparison of performance indicators between traditional lithium extraction solar cells and solar cells of Examples 2 and 2.

[0097] Temperature rise of the brine layer (°C) Average freshwater consumption (per day / time) Average warming duration (days) Average lithium yield (%) Traditional solar pool 30~40 25 9 35 Example 1 45~60 31 5 70.5 Example 2 45~59 33 6 71

[0098] As shown in Table 1, the brine layer temperature rise of Examples 1 and 2 is about 15-20°C higher than that of traditional solar cells, and the average heating time is shorter. The average lithium yield reaches 70.5% and 71%, respectively, which is significantly better than the average lithium yield of traditional lithium extraction solar cells. The lithium extraction method of this application improves the average lithium yield by about 36%.

[0099] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of this application. It should be understood that the above description is only a specific embodiment of this application and is not intended to limit the scope of protection of this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A solar cell for producing lithium carbonate concentrate, characterized in that, The system includes a pool body, which includes a bottom plate at the bottom of the solar pool and a side plate on the side wall of the solar pool. The side plate is inclined relative to the horizontal direction. The inner side of the side plate has multiple protruding main edges. The main edges extend from the bottom of the pool to the top of the pool. The top angle of the main edges is an obtuse angle. A heat insulation layer is provided below both the bottom plate and the side plate of the pool; the heat insulation layer includes a heat-absorbing and seepage-proof layer and a honeycomb layer stacked sequentially from bottom to top; the cross-sectional shape of the honeycomb layer along the direction from the top to the bottom of the pool is honeycomb-shaped; the honeycomb layer includes alternating hexagonal honeycomb cells and rectangular honeycomb cells; the hexagonal honeycomb cell includes a hexagonal cell base and a hexagonal heat insulation sleeve that wraps the hexagonal cell base, and the rectangular honeycomb cell includes a rectangular cell base and a rectangular heat insulation sleeve that wraps the rectangular cell base; The hexagonal honeycomb cell has a first air vent on its sidewall facing the foundation. The sidewall connecting the hexagonal honeycomb cell and the rectangular honeycomb cell has a second air vent. The sidewall facing the interior of the solar pool of the hexagonal honeycomb cell does not have an air vent. The sidewall facing the foundation of the rectangular honeycomb cell has a third air vent. The sidewall connecting the rectangular honeycomb cell and the hexagonal honeycomb cell has a fourth air vent. The second air vent and the fourth air vent are connected. The sidewall facing the interior of the solar pool of the rectangular honeycomb cell does not have an air vent. Gas generated by the geothermal effect enters the hexagonal cell matrix and the rectangular cell matrix through the first and third air vents. The gas in the hexagonal cell matrix and the rectangular cell matrix is ​​gradually guided to the ground through the connected second and fourth air vents. The insulation layer also includes an expanded polytetrafluoroethylene (ePTFE) membrane attached to the inner wall of the hexagonal and rectangular honeycomb cells. The ePTFE membrane is continuously attached to the inner wall of the hexagonal and rectangular honeycomb cells or only attached to the first, second, third, and fourth air vents. The ePTFE membrane has a three-dimensional network of interconnected micropores, and gas permeation is driven by the pressure difference.

2. The solar cell for producing lithium carbonate concentrate according to claim 1, characterized in that, Each main facet has multiple protruding sub-facets on its inner side.

3. The solar cell for producing lithium carbonate concentrate according to claim 1, characterized in that, As the pool gradually approaches the bottom plate, the height of the main facet of the pool side plate gradually decreases, and the connection between the pool side plate and the bottom plate is a straight line.

4. The solar cell for producing lithium carbonate concentrate according to claim 1, characterized in that, The angle between the side plate and the bottom plate of the pool is 130°~150°.

5. The solar cell for producing lithium carbonate concentrate according to claim 1, characterized in that, The solar pool also includes a retractable heat-insulating awning installed above the pool body.

6. A method for lithium extraction from lithium carbonate concentrate, characterized in that, The lithium extraction method using the solar cell for producing lithium carbonate concentrate as described in any one of claims 1 to 5 includes the following steps: Step 1: Concentrate carbonate-type salt lake brine to form lithium-rich brine; Step 2: Inject lithium-rich brine and fresh water into the pool respectively, let it stand for several days to obtain a three-layer salt gradient solar pool, which consists of a brine layer, a salt gradient layer and a fresh water layer. Step 3: The salt gradient solar pool absorbs solar energy and gradually increases in temperature, precipitating lithium carbonate concentrate and completing the first lithium carbonate precipitation.

7. The lithium extraction method for producing lithium carbonate concentrate according to claim 6, characterized in that, In step 1, the Li in the lithium-rich halide formation + Concentration greater than 1.5 g / L.

8. The lithium extraction method for producing lithium carbonate concentrate according to claim 6, characterized in that, In step 2, the depth of lithium-rich halogen formation is 1.8m to 2.2m.

9. The lithium extraction method for producing lithium carbonate concentrate according to claim 6, characterized in that, In step 3, the temperature is gradually increased to 45℃~65℃.

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