Method and device for extracting lithium carbonate from a lithium mixed solution

Abstract

The present application relates to the technical field of lithium extraction, and particularly relates to a method and device for extracting lithium carbonate from a lithium mixed solution, which comprises a feeding mechanism, the feeding mechanism comprises a storage box, the storage box is internally filled with lithium carbonate seed crystals, a feeding pipe is fixedly arranged at the lower end of the storage box, one end of the feeding pipe is in communication with the storage box, the other end is in communication with a pipeline, the inner diameter of the feeding pipe gradually increases from the end close to the storage box to the end away from the storage box, a blocking ball for blocking the feeding pipe is arranged in the feeding pipe, a spring is arranged in the storage box, one end of the spring is fixedly connected with the storage box, and the other end is fixedly connected with the blocking ball, and the present application effectively solves the problem that lithium carbonate is deposited on the heating pipe wall in the evaporator, thereby causing the lithium carbonate extraction rate to be not high.

Description

Technical Field

[0001] This invention relates to the field of lithium extraction technology, and in particular to a method and apparatus for extracting lithium carbonate from a lithium mixed solution. Background Technology

[0002] Lithium and its compounds have wide applications in energy, aerospace, metallurgy, ceramics, and other fields, playing a vital role in my country's national economic development. Among lithium and its compounds, lithium carbonate is the fundamental material for producing metallic lithium and lithium salts; other industrial lithium products are downstream products of lithium carbonate. Therefore, lithium carbonate is the most critical raw material in the lithium industry. However, due to limited production capacity in my country, much of the lithium carbonate needed is imported, severely restricting the development of the domestic lithium industry.

[0003] The commonly used process for producing lithium carbonate in existing technologies is the spodumene-sulfuric acid process. In this process, solid-liquid separation yields crude lithium carbonate and a lithium precipitation mother liquor. Because lithium carbonate has a certain solubility in this sodium sulfate solution system, the lithium precipitation mother liquor still contains lithium at a concentration of 6-7 g / L. This lithium must be recovered, so the lithium carbonate precipitation mother liquor needs to be evaporated and crystallized to obtain lithium carbonate. Since the lithium precipitation mother liquor contains some solid impurities, the resulting lithium carbonate will have low purity if not treated.

[0004] Therefore, an MVR evaporator for processing lithium precipitation mother liquor for lithium carbonate production is disclosed in application number CN202221993592.8. The MVR evaporator body includes an MVR evaporator body, wherein a feed pipe is detachably connected to the end of the feed pipe, a second feed pipe is installed on the top of the installation box, a drain hole is provided at the bottom of the installation box, a filter cylinder is fixedly connected to the bottom of the second feed pipe, a plurality of filter holes are provided on the surface of the filter cylinder, and a stirring mechanism is provided inside the filter cylinder.

[0005] The above solution filters the lithium precipitation mother liquor before it enters the MVR evaporator body by setting up an installation box, filter cartridge and stirring mechanism, thereby removing solid impurities from the lithium precipitation mother liquor and improving the purity of lithium carbonate crystals to a certain extent; however, during the evaporation process, some lithium carbonate will precipitate on the heating tube wall, which seriously affects the evaporation efficiency and equipment operating rate. Summary of the Invention

[0006] The purpose of this solution is to provide a method and apparatus for extracting lithium carbonate from a lithium mixed solution, in order to solve the problem of lithium carbonate deposition on the heating tube wall in the evaporator, which leads to a low lithium carbonate extraction rate.

[0007] To achieve the above objectives, this solution provides a method for extracting lithium carbonate from a lithium mixed solution, comprising the following steps:

[0008] Step S1: Crush, ball mill and sieve the spodumene, mix it evenly to obtain primary raw ore powder, and then perform crystal transformation roasting on the raw ore powder to obtain the primary roasted material.

[0009] Step S2: React the initial roasted material with sulfuric acid to leach out lithium sulfate solution;

[0010] Step S3: Add soda ash to lithium sulfate solution to react and generate lithium carbonate, and filter the lithium carbonate to obtain high-temperature mother liquor;

[0011] Step S4: Preheat the high-temperature mother liquor;

[0012] Step S5: Add lithium carbonate as a seed crystal to the high-temperature mother liquor;

[0013] Step S6: Evaporate and separate the high-temperature mother liquor using a forced circulation evaporator;

[0014] Step S7: Cool the high-temperature mother liquor after evaporation and separation to obtain lithium carbonate slurry.

[0015] The principle and beneficial effects of this scheme are as follows: Compared with the traditional lithium carbonate extraction process, this scheme adds lithium carbonate as a seed crystal to the high-temperature mother liquor. By utilizing the affinity of the crystal surface, which is the same as the scale, for the scale, the supersaturation of lithium carbonate in the solution is reduced. This allows the lithium carbonate molecules precipitated in the solution to preferentially attach to the suspended seed crystals instead of depositing on the inner wall of the heating tube, thereby improving the extraction rate of lithium carbonate. At the same time, it can also prevent the problem of low heating efficiency caused by the adhesion of lithium carbonate seed crystals on the heating tube.

[0016] Furthermore, the particle size of the primary raw ore powder after screening in step S1 is 170–180 μm.

[0017] Furthermore, the reaction temperature in step S2 is 240–260°C.

[0018] Furthermore, the forced circulation evaporator in step S6 includes a feed pump, a heat exchanger, an evaporator separator, a circulation pump, and a discharge pump. The output end of the feed pump is connected to the feed end of the heat exchanger, the output end of the heat exchanger is connected to the input end of the evaporator separator via a pipeline, the input end of the circulation pump is connected to the output end of the evaporator separator, the output end of the circulation pump is connected to the input end of the heat exchanger, and the output end of the evaporator separator is connected to the discharge pump. The high-temperature mother liquor in step S4 is preheated through the heat exchanger, the seed crystals in step S5 are added to the high-temperature mother liquor through a pipeline, the lithium carbonate slurry in step S7 is discharged through the discharge pump, and the remaining liquid enters the heat exchanger through the circulation pump for circulating evaporation.

[0019] Furthermore, an apparatus for extracting lithium carbonate from a lithium mixed solution according to the method of claim 4 is provided, wherein a feeding mechanism is provided between the heat exchanger and the evaporator separator, the feeding mechanism includes a storage box filled with lithium carbonate seed crystals, a feeding pipe fixedly provided at the lower end of the storage box, one end of the feeding pipe being connected to the storage box and the other end being connected to a pipeline, the inner diameter of the feeding pipe gradually increasing from the end near the storage box to the end away from the storage box, a sealing ball for sealing the feeding pipe being provided inside the feeding pipe, and a spring being provided inside the storage box, one end of the spring being fixedly connected to the storage box and the other end being fixedly connected to the sealing ball.

[0020] The principle of this scheme is as follows: the high-temperature mother liquor enters the heat exchanger through the feed pump for preheating, and then enters the evaporator separator through the pipeline for evaporation and crystallization. At the same time as the high-temperature mother liquor enters the evaporator separator from the heat exchanger, the high-temperature mother liquor generates a suction force on the feed pipe in the pipeline due to Bernoulli's principle. At this time, the sealing ball moves to one side of the pipeline, and the spring extends. The lithium carbonate seed crystals in the storage box flow from the feed pipe into the pipeline and enter the evaporator separator together with the high-temperature mother liquor for reaction. The lithium carbonate slurry obtained after crystallization flows out from the discharge pump, and the remaining liquid enters the heat exchanger for circulation through the circulation pump.

[0021] The technical advantages of this solution are as follows: 1. This solution uses an evaporator separator for extraction, which effectively reduces the use of substances such as sulfuric acid and sodium hydroxide compared to traditional chemical purification processes; 2. Adding lithium carbonate seed crystals to the high-temperature mother liquor effectively reduces the deposition of lithium carbonate on the heating tube wall and the inner wall of the evaporator separator, thereby improving the extraction rate of lithium carbonate; 3. Setting the feeding mechanism between the heat exchanger and the evaporator separator, instead of adding it directly to the high-temperature mother liquor and then pumping it into the heat exchanger by the feed pump, effectively prevents lithium carbonate from depositing in the heat exchanger, thus reducing the extraction efficiency; at the same time, the feeding mechanism achieves automatic feeding through Bernoulli's principle during feeding, requiring no manual control, which is simple and convenient.

[0022] Furthermore, a heating tube is provided inside the evaporator separator, and a descaling mechanism is sleeved on the heating tube. The descaling mechanism includes a descaling ring, which is filled with wax. The descaling ring includes a solid layer and a deformable layer. The deformable layer is disposed on the inner ring of the descaling ring, and several scrapers are fixedly disposed on the side of the deformable layer near the heating tube. During operation, the high-temperature mother liquor is fed into the evaporator separator. When the heating tube starts heating, the wax inside the descaling ring melts. Since the density of the wax is lower than that of the high-temperature mother liquor, the descaling mechanism rises under the action of buoyancy and eventually floats to the top of the heating tube. After evaporation is completed, the evaporator separator cools the evaporated high-temperature mother liquor. At this time, the heating tube stops heating, the temperature of the high-temperature mother liquor decreases, and the wax gradually solidifies from a liquid state to a solid state. During the process of the wax becoming solid, its volume gradually increases, and the deformable layer extends inward, thus making the scraper stick tightly to the heating tube wall. After cooling is completed, the liquid and lithium carbonate crystals in the evaporator separator are discharged. The descaling ring moves downward as the liquid level decreases. During the downward movement, the scraper scrapes off the lithium carbonate crystals and other deposited impurities deposited on the heating tube, effectively preventing lithium carbonate and impurities from depositing on the heating tube wall.

[0023] Furthermore, the deformable layer includes a first deformable layer and a second deformable layer, which are respectively disposed at the upper and lower ends of the solid layer. By providing the first and second deformable layers, the heating tube wall can be scraped twice sequentially to ensure effective descaling.

[0024] Furthermore, the scrapers on the first and second deformable layers are arranged in an alternating pattern. This arrangement allows the deformable layers to scrape over a wider area, resulting in a better scraping effect.

[0025] Furthermore, the descaling ring is internally equipped with a retractable limiting post. One end of the limiting post is fixedly connected to the solid layer, and the other end is fixedly connected to the deformable layer. By limiting the deformable layer with the limiting post, it is possible to effectively prevent the scraper from shifting when the deformable layer extends inward, thereby affecting the scraping effect.

[0026] Furthermore, the scraper is a trapezoidal scraper, with the width of the scraper near the deformable layer being smaller than the width of the scraper away from the deformable layer. This design reduces the scraper volume while increasing the contact area between the scraper and the heating element, thus achieving a lighter descaling mechanism with better descaling effect. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the overall structure of this embodiment;

[0028] Figure 2 This is a partial structural diagram of the feeding mechanism in this embodiment;

[0029] Figure 3 This is a schematic diagram of the feeding mechanism in the feeding state according to this embodiment;

[0030] Figure 4 This is a schematic diagram of the internal structure of the evaporator separator in this embodiment;

[0031] Figure 5 This is a top view of the descaling mechanism in its initial state according to this embodiment;

[0032] Figure 6 This is a top view of the descaling mechanism in another state according to this embodiment;

[0033] Figure 7 This is a cross-sectional view of the descaling mechanism in its initial state according to this embodiment;

[0034] Figure 8 This is a cross-sectional view of the descaling mechanism in another state of this embodiment;

[0035] Figure 9 This is a schematic diagram of the process for extracting lithium carbonate from a lithium mixed solution in this embodiment. Detailed Implementation

[0036] The following detailed explanation illustrates the specific implementation methods:

[0037] The reference numerals in the accompanying drawings include: 1. Feed pump; 2. Heat exchanger; 3. Evaporator separator; 4. Circulation pump; 5. Discharge pump; 6. Feeding mechanism; 61. Storage box; 62. Lithium carbonate seed crystal; 63. Feeding pipe; 64. Spring; 65. Sealing ball; 7. Pipe; 8. Heating tube; 9. Descaling mechanism; 91. Solid layer; 92. Deformable layer; 921. First deformable layer; 922. Second deformable layer; 93. Scraper; 94. Limiting post.

[0038] The basic implementation examples are as follows: Figure 1 :

[0039] An apparatus for extracting lithium carbonate from a lithium mixed solution includes a feed pump, a heat exchanger, an evaporator, a circulation pump, and a discharge pump. The feed pump is connected to the heat exchanger, and the heat exchanger is connected to the evaporator via a pipeline. One end of the circulation pump is connected to the evaporator, and the other end is connected to the heat exchanger. The evaporator is connected to the discharge pump. Since the above components are those of an existing forced circulation evaporator, they will not be described in detail here. The inner diameter of the middle section of the pipeline is smaller than that of the two ends. A feeding mechanism is provided above the pipeline, as shown in the attached diagram. Figure 2-3The feeding mechanism includes a storage box with an internal cavity filled with lithium carbonate seed crystals. A feeding tube is welded to the lower end of the storage box. One end of the feeding tube is connected to the storage box, and the other end is welded to the smaller diameter section of the pipe and connected to the pipe. The inner diameter of the feeding tube gradually increases from the end near the storage box to the end away from the storage box. A sealing ball is installed inside the feeding tube to seal the feeding tube. When there is no fluid flow in the pipe, the sealing ball is in a sealed state. A spring is installed inside the cavity to support and reset the sealing ball. One end of the spring is welded to the inner wall of the storage box, and the other end is welded to the sealing ball.

[0040] As attached Figure 4 The evaporator separator has a heating tube at the bottom, and a descaling mechanism is fitted onto the heating tube, as shown in the attached image. Figure 5-8 The descaling mechanism includes a descaling ring, specifically a hollow circular ring. The inner ring is closer to the heating element, and the outer ring is further away. The descaling ring also includes a solid layer and a deformable layer. The solid layer is made of a hard, corrosion-resistant material, such as corrosion-resistant stainless steel sheet, while the deformable layer can be made of elastic rubber. Those skilled in the art can select the appropriate materials for the solid and deformable layers based on specific conditions. The descaling ring is filled with wax. The deformable layer is located on the inner ring of the descaling ring. Several scrapers are adhered to the side of the deformable layer away from the solid layer. These scrapers are made of hard plastic and are trapezoidal in shape. The length of the side in contact with the deformable layer is shorter than the length of the side in contact with the heating element. When the wax is solid, the deformable layer contracts towards the heating element, and the scrapers combine to form a ring-shaped scraper that adheres to the outer wall of the heating element, ensuring complete coverage. To further ensure the descaling effect, see attached... Figure 7-8 The deformable layer includes a first deformable layer and a second deformable layer. The first deformable layer and the second deformable layer are respectively disposed at the upper end and the lower end of the solid layer. The scrapers on the first deformable layer and the second deformable layer are staggered to ensure that the heating tube can be completely covered when scraping. To prevent the scrapers from shifting when the deformable layer extends inward, several retractable limiting posts are provided inside the descaling ring. One end of the limiting post is welded to the solid layer, and the other end is bonded to the deformable layer.

[0041] In operation, the high-temperature mother liquor is preheated by a feed pump and then enters the evaporator separator through a pipeline for evaporation and crystallization. Simultaneously, the high-temperature mother liquor enters the evaporator separator from the heat exchanger, and due to Bernoulli's principle, it creates a suction force on the feeding pipe. At this time, the sealing ball moves to one side of the pipeline, and the spring extends. Lithium carbonate seed crystals in the storage box flow from the feeding pipe into the pipeline and enter the evaporator separator along with the high-temperature mother liquor for reaction. After feeding is complete, the spring contracts, causing the sealing ball to reset and seal the feeding pipe, achieving automatic feeding. After the high-temperature mother liquor enters the evaporator separator, the heating tube begins heating, melting the wax inside the descaling ring. Because the density of the wax is lower than that of the high-temperature mother liquor, the descaling mechanism rises under the buoyancy of the high-temperature mother liquor and eventually floats to the top of the heating tube, as shown in the attached diagram. Figure 5 and attached Figure 7 At this point, the scraper is not in close contact with the heating tube wall; after evaporation is complete, the evaporator cools the high-temperature mother liquor, at which point the heating tube stops heating, the temperature of the high-temperature mother liquor decreases, and the wax gradually solidifies from a liquid state to a solid state, as shown in the attached image. Figure 6 and attached Figure 8 As the wax solidifies, its volume gradually increases, and the deformable layer extends inward, causing several scrapers to form a ring and adhere tightly to the heating tube wall. After cooling, the lithium carbonate slurry in the evaporator is discharged through the discharge pump, and the remaining liquid is circulated into the heat exchanger through the circulation pump. The descaling ring moves downward as the liquid level decreases. During the downward movement, the scrapers on the second and first deformable layers scrape off the lithium carbonate crystals and other deposited impurities deposited on the heating tube, effectively preventing lithium carbonate and impurities from depositing on the heating tube wall.

[0042] This solution also discloses a method for extracting lithium carbonate from a lithium mixed solution, as shown in the attached diagram. Figure 9 As shown, it includes the following steps:

[0043] Step S1: Crush, ball mill and screen spodumene, mix evenly to obtain primary raw ore powder with a particle size of 175μm, and then perform crystal transformation roasting in a programmable box furnace to obtain the primary roasted material.

[0044] Step S2: The initial roasted material is reacted with sulfuric acid at 250°C to leach out lithium sulfate solution;

[0045] Step S3: Add excess soda ash to the lithium sulfate solution to react and generate lithium carbonate, and filter the lithium carbonate to obtain a high-temperature mother liquor;

[0046] Step S4: The high-temperature mother liquor is pumped into the heat exchange tubes of the heat exchanger by the feed pump for preheating;

[0047] Step S5: Lithium carbonate is added as a seed crystal to the high-temperature mother liquor through a feeding mechanism via a pipeline;

[0048] Step S6: The high-temperature mother liquor after adding lithium carbonate seeds is evaporated and separated by an evaporator separator;

[0049] Step S7: Cool the high-temperature mother liquor after evaporation and separation to obtain lithium carbonate slurry, which is discharged from the discharge pump. The remaining liquid is then pumped into the heat exchanger for circulating evaporation.

[0050] The above are merely embodiments of the present invention. The invention is not limited to the fields covered by these embodiments. Commonly known structures and characteristics in the solutions are not described in detail here. Those skilled in the art are aware of all common technical knowledge in the field prior to the application date or priority date, are able to access all existing technologies in that field, and have the ability to apply conventional experimental methods prior to that date. Those skilled in the art can, under the guidance of this application, improve and implement this solution in combination with their own capabilities. Some typical known structures or methods should not be obstacles for those skilled in the art to implement this application. It should be noted that those skilled in the art can make several modifications and improvements without departing from the structure of the present invention. These should also be considered within the scope of protection of the present invention, and will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A method for extracting lithium carbonate from a lithium mixed solution, characterized in that: Includes the following steps: Step S1: Crush, ball mill and sieve the spodumene, mix it evenly to obtain primary raw ore powder, and then perform crystal transformation roasting on the raw ore powder to obtain the primary roasted material. Step S2: React the initial roasted material with sulfuric acid to leach out lithium sulfate solution; Step S3: Add soda ash to lithium sulfate solution to react and generate lithium carbonate, and filter the lithium carbonate to obtain high-temperature mother liquor; Step S4: Preheat the high-temperature mother liquor; Step S5: Add lithium carbonate as a seed crystal to the high-temperature mother liquor; Step S6: Evaporate and separate the high-temperature mother liquor using a forced circulation evaporator; Step S7: Cool the high-temperature mother liquor after evaporation and separation to obtain lithium carbonate slurry; The forced circulation evaporator in step S6 includes a feed pump, a heat exchanger, an evaporator separator, a circulation pump, and a discharge pump. The output end of the feed pump is connected to the feed end of the heat exchanger, and the output end of the heat exchanger is connected to the input end of the evaporator separator via a pipeline. The input end of the circulation pump is connected to the output end of the evaporator separator, and the output end of the circulation pump is connected to the input end of the heat exchanger. The output end of the evaporator separator is connected to the discharge pump. The high-temperature mother liquor in step S4 is preheated through the heat exchanger. The seed crystals in step S5 are added to the high-temperature mother liquor through a pipeline. The lithium carbonate slurry in step S7 is discharged through the discharge pump. Meanwhile, the remaining liquid enters the heat exchanger through a circulating pump for circulating evaporation; a feeding mechanism is provided between the heat exchanger and the evaporation separator, the feeding mechanism including a storage box, the storage box being filled with lithium carbonate seed crystals, a feeding pipe fixedly installed at the lower end of the storage box, one end of the feeding pipe being connected to the storage box and the other end being connected to a pipeline, the inner diameter of the feeding pipe gradually increasing from the end near the storage box to the end away from the storage box, a sealing ball for sealing the feeding pipe being installed inside the feeding pipe, and a spring being installed inside the storage box, one end of the spring being fixedly connected to the storage box and the other end being fixedly connected to the sealing ball; The evaporator separator is equipped with a heating tube, and a descaling mechanism is fitted onto the heating tube. The descaling mechanism includes a descaling ring filled with wax. The descaling ring comprises a solid layer and a deformable layer, with the deformable layer located on the inner ring. Several scrapers are fixedly mounted on the deformable layer near the heating tube. During operation, high-temperature mother liquor is introduced into the evaporator separator. When the heating tube begins to heat, the wax inside the descaling ring melts, and the descaling mechanism rises under buoyancy, eventually floating to the top of the heating tube. After evaporation is complete, the evaporation separation... The device cools the high-temperature mother liquor after evaporation. At this time, the heating tube stops heating, the temperature of the high-temperature mother liquor decreases, and the wax gradually solidifies from a liquid state to a solid state. During the process of wax becoming solid, its volume gradually increases, and the deformable layer extends inward, thus making the scraper stick tightly to the wall of the heating tube. After the cooling is completed, the liquid and lithium carbonate crystals in the evaporator are discharged. The descaling ring moves downward as the liquid level decreases. During the downward movement, the scraper scrapes off the lithium carbonate crystals and other deposited impurities deposited on the heating tube, effectively preventing lithium carbonate and impurities from depositing on the wall of the heating tube.

2. The method for extracting lithium carbonate from a lithium mixed solution according to claim 1, characterized in that: The particle size of the primary raw ore powder after screening in step S1 is 170-180 μm.

3. The method for extracting lithium carbonate from a lithium mixed solution according to claim 1, characterized in that: The reaction temperature in step S2 is 240–260 °C.

4. The method for extracting lithium carbonate from a lithium mixed solution according to claim 1, characterized in that: The deformable layer includes a first deformable layer and a second deformable layer, which are respectively disposed at the upper and lower ends of the solid layer.

5. The method for extracting lithium carbonate from a lithium mixed solution according to claim 4, characterized in that: The scrapers on the first deformable layer and the second deformable layer are arranged alternately.

6. The method for extracting lithium carbonate from a lithium mixed solution according to claim 1, characterized in that: The descaling ring is equipped with a retractable limiting post inside. One end of the limiting post is fixedly connected to the solid layer, and the other end is fixedly connected to the deformable layer.

7. The method for extracting lithium carbonate from a lithium mixed solution according to claim 1, characterized in that: The scraper is a trapezoidal scraper, and the width of the scraper on the side closer to the deformable layer is smaller than the width on the side farther away from the deformable layer.

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