A lithium extraction method for high-cod and high-boron gas field produced water evaporation mother liquor
By employing steps such as impurity removal and solubilization, solid-liquid separation, low-temperature evaporation, crude lithium carbonate extraction, high-temperature carbonization, and acid dissolution to remove boron, the resource utilization problem of concentrated mother liquor from produced water in high-COD, high-boron-content gas fields has been solved, achieving efficient separation and purification of lithium and reducing processing costs.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CHENGDU XINGAO JINGYUAN TECH CO LTD
- Filing Date
- 2023-05-23
- Publication Date
- 2026-05-12
AI Technical Summary
The mother liquor from the evaporation and concentration of produced water from gas fields with high COD, high boron content, and high sulfate and carbonate content is difficult to utilize as a resource, and existing technologies are not effective in extracting lithium, making the process difficult and costly.
The lithium resource is separated and purified through chemical reactions with calcium hydroxide, saturated sodium carbonate, hydrochloric acid, and other chemicals to form lithium carbonate products. The process involves steps such as impurity removal and solubilization, solid-liquid separation, low-temperature evaporation, crude lithium carbonate extraction, high-temperature carbonation, acid dissolution to remove boron, and deep hardness removal.
This method enables the resource utilization of lithium and boron in the mother liquor of gas field produced water evaporation and concentration, significantly reducing disposal costs, improving lithium yield and product purity, and solving the problem of easy foaming and tower collapse during the evaporation of high-concentration materials.
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Figure CN116751988B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of resource utilization technology of produced water evaporation concentrate from gas field formations, specifically to a method for lithium extraction from produced water evaporation concentrate from high-COD, high-boron-content gas fields. Background Technology
[0002] During natural gas production, some wells produce water, which is typically characterized by high salinity and high COD, and may contain boron. This type of produced water cannot usually be discharged directly and requires desalination, COD removal, and ammonia nitrogen removal treatment. The current mainstream treatment method involves pretreatment to remove hardness and suspended solids, followed by membrane concentration, concentrated water evaporation and crystallization, and condensate post-treatment. During evaporation, most of the water is converted into condensate for discharge, but a small amount of concentrated mother liquor remains. This mother liquor is usually reinjected into the formation or disposed of as hazardous waste, making treatment difficult and costly.
[0003] The concentrated mother liquor is usually a saturated sodium chloride brine with a very high enrichment of various dissolved substances. It appears as a reddish-brown, semi-transparent solution. Large-scale water quality screening has revealed that the lithium content of the concentrated mother liquor at some treatment plants is as high as 2000-4000 mg / L, far exceeding the lithium-rich standard of 80 mg / L for salt lake brine, indicating that it can be utilized as a resource. However, at the same time, it was found that some of these concentrated mother liquors have COD as high as 50000-100000 mg / L, boron content as high as 20000-40000 mg / L, sulfate concentration as high as 30000-50000 mg / L, and carbonate content is also high, reaching about 20000 mg / L. The lithium extraction process for this is much more difficult than that for lithium extraction from salt lake brine, and there are no similar process routes or case reports on lithium extraction from concentrated mother liquor, either domestically or internationally. Summary of the Invention
[0004] The purpose of this invention is to provide a method for lithium extraction from the mother liquor of produced water from high-COD, high-boron gas fields, in order to solve the technical problem of resource utilization of mother liquor of high-COD, high-boron, high-sulfate and high-carbonate evaporation and concentration.
[0005] To achieve the above objectives, the present invention provides the following technical solution:
[0006] This invention provides a method for lithium extraction from the mother liquor of produced water from high-COD, high-boron-content gas fields. The method is characterized by comprising the following steps:
[0007] S1. Impurity Removal and Solubilization: By slowly adding calcium hydroxide solution to a stirred reaction tank containing concentrated mother liquor, and stirring and reacting thoroughly, most of the sulfate and carbonate ions in the water are removed, allowing lithium resources to dissolve in the water in the form of lithium ions. At the same time, the pH value of the mother liquor is raised to above 12, so that magnesium ions in the water are completely precipitated.
[0008] S2. Solid-liquid separation and washing: Use a filter press to separate the solid and liquid components of the mixture after the reaction in step S1. The resulting filtrate will enter the next concentration process. The resulting filter cake will be added to a crushing and washing machine, and water will be added for multiple crushing and washing processes. After washing, the filter cake will be filtered again through a filter press. The resulting filtrate will enter the next concentration process.
[0009] S3. Filtrate Concentration: The filtrate obtained in step S2 is concentrated by evaporating and concentrating it using a refrigerant heat pump low-temperature evaporator, so that the lithium content in the filtrate is increased to more than 20,000 mg / L. The resulting condensate meets the discharge standards, and the concentrate enters the thickener for cooling and crystallization.
[0010] S4. Centrifugal desalination and cleaning: Centrifuge 1 is used to separate the brine from the lower layer of salt slurry. The separated filtrate enters reactor 1, and the salt residue enters the cleaning tank. The salt residue obtained by centrifugation is cleaned with clean water, and the cleaning liquid is returned to the refrigerant heat pump low-temperature evaporator for concentration.
[0011] S5. Crude extraction of lithium carbonate: In reactor 1, the temperature of the mother liquor is raised to 90°C. Then, under stirring, a saturated sodium carbonate solution is slowly added. Then, while hot, it is transferred to centrifuge 2 for rapid solid-liquid separation. After the lithium carbonate filter cake is crushed, it is dried at 105°C for 2 hours. The filtrate is collected separately, and after adding reagents and reacting fully, it is returned to step S1.
[0012] S6. High-temperature carbonization of organic matter: The filter cake dried in step S5 is placed into a high-temperature resistant container and placed in a high-temperature furnace for reaction. After the organic matter is fully carbonized (until no smoke is produced), it is taken out and cooled. The generated flue gas (mainly water, carbon dioxide and dust) is discharged into the air after being absorbed by alkaline solution and filtered by activated carbon.
[0013] S7. Acid Dissolution of Boron: The lithium carbonate after calcination and cooling in step S6 is transferred to reaction tank 2 (with forced exhaust device). An appropriate amount of hydrochloric acid or sulfuric acid solution is added to completely dissolve the lithium carbonate. Then, the solution is filtered using a filter press. The filtrate is placed in a refrigerator for refrigeration and then filtered quickly. The resulting clear liquid is collected and placed into reaction tank 3. The filter residue is collected uniformly, washed with saturated boric acid solution, and then dehydrated, dried, and packaged to obtain boric acid by-product.
[0014] S8. Deep hardness removal: Collect the clear liquid obtained in step S7 into reaction vessel 3, take a sample to test the calcium and magnesium ion content in the clear liquid, use sodium hydroxide to adjust the pH value to above 12, then add sodium carbonate solution according to the calcium ion content, filter after full reaction, and the filtrate enters reaction vessel 2.
[0015] S9. Lithium carbonate extraction: In reaction vessel 2, the temperature of the filtrate is raised to 90°C. Then, under stirring conditions, saturated sodium carbonate is slowly added. Then, while hot, it is transferred to centrifuge 3 for rapid solid-liquid separation. The lithium carbonate filter cake is crushed and dried. The filtrate is collected separately, and after adding reagents and reacting fully, it is returned to step S1.
[0016] S10. Lithium carbonate carbonation and purification: The lithium carbonate dried in step S9 is added to a cleaning and dissolving tank (with an evacuation device), pure water is added for cleaning, and high-purity carbon dioxide is continuously introduced for aeration at room temperature to completely dissolve the lithium carbonate. Then, it is quickly filtered, and the filtrate enters the reaction vessel 3. It is heated to 90°C to precipitate lithium carbonate product. It is filtered while hot using a filter press. The filter cake is collected, crushed and dried, and the dried lithium carbonate is ground, sieved and bagged to obtain industrial-grade lithium carbonate product.
[0017] Furthermore, in step S5, the amount of saturated sodium carbonate solution added is 1.2 times the lithium content, the temperature is 90℃, and the reaction aging time is 2-3 hours.
[0018] Furthermore, in step S6, the calcination temperature in the high-temperature furnace is 500-650℃, and the calcination time is 15-60 minutes.
[0019] Furthermore, in step S7, the filtrate is placed in a refrigerator and cooled to 4°C for 2-3 hours.
[0020] Furthermore, in step S9, the lithium carbonate filter cake is crushed and then dried at 105°C for 2 hours.
[0021] Furthermore, in step S10, the mass ratio of lithium carbonate to pure water is 1:20.
[0022] Furthermore, the filtrates from steps S5 and S9 are collected separately, and after being fully reacted with an appropriate amount of calcium hydroxide or calcium chloride, they are returned to step S1, and the filtrates are recycled multiple times.
[0023] The preferred method for this solution is as follows: Because the produced water typically undergoes a dual-alkali process to remove calcium and magnesium before evaporation, the residual carbonate content in the water is relatively high. The solubility of lithium carbonate decreases with increasing temperature; it is approximately 13.3 g / L at 20°C, but only 7.2 g / L at 100°C. Therefore, pretreatment is necessary when the lithium content in the mother liquor is high. Otherwise, a large amount of lithium carbonate may crystallize and precipitate during evaporation and concentration, resulting in a low lithium concentration yield. This solution preferably uses calcium hydroxide as a pretreatment agent, which reacts with lithium carbonate to produce lithium hydroxide and calcium carbonate. Lithium hydroxide is highly soluble in water, significantly reducing lithium loss during concentration and thus significantly improving the evaporation and concentration yield. When the sulfate or carbonate content is too high, calcium chloride can be added appropriately to improve the treatment effect.
[0024] The preferred method is as follows: Since most of the organic matter in the mother liquor consists of soluble macromolecular organic compounds with complex compositions, conventional oxidation processes cannot completely remove them and are extremely costly. This method preferentially employs a high-temperature carbonization process. First, lithium carbonate is crudely extracted, and then the organic matter is carbonized by calcination in a high-temperature furnace. The preferred equipment temperature is 500-650℃, which ensures both thorough carbonization of the organic matter and prevents the lithium carbonate from melting and agglomerating.
[0025] The preferred method is as follows: Due to the low solubility of lithium carbonate, it is not possible to directly wash the lithium carbonate after high-temperature calcination with water. Therefore, it is preferable to use a small amount of high-purity hydrochloric acid or sulfuric acid to dissolve the lithium carbonate after high-temperature calcination, and then perform solid-liquid separation. This yields a clear, transparent, and colorless high-concentration lithium chloride or lithium sulfate solution, which can effectively remove organic impurities with minimal lithium loss.
[0026] The preferred method in this solution is as follows: Lithium carbonate solutions dissolved in hydrochloric acid or sulfuric acid are strongly acidic, typically with a pH below 1.8. Under these conditions, borate in water exists as boric acid. The solubility of boric acid decreases rapidly with decreasing temperature; its solubility is 48.7 g / L at 20°C and 27.7 g / L at 0°C. This solution preferably uses a 4°C refrigeration method to precipitate boric acid from the lithium chloride solution, thereby effectively reducing the borate impurity content in the final lithium carbonate product.
[0027] Based on the above technical solution, the embodiments of the present invention can produce at least the following technical effects:
[0028] (1) The lithium extraction method of the mother liquor of produced water from gas fields with high COD and high boron content provided by the present invention realizes the resource utilization of lithium and boron in the mother liquor of produced water from gas fields and significantly reduces the disposal cost of the mother liquor.
[0029] (2) The lithium extraction method of the mother liquor of produced water from high COD and high boron gas field provided by the present invention uses a cold medium heat pump low temperature evaporator to perform secondary evaporation treatment on the mother liquor, which solves the problem of easy foaming and tower flipping of high concentration materials during high temperature evaporation. The evaporated water can achieve standard discharge and the mother liquor reduction rate can reach more than 80%.
[0030] (3) The lithium extraction method of the mother liquor of produced water from high COD and high boron gas field provided by the present invention uses a system conversion method to separate lithium resources from the complex system in the form of crude lithium carbonate, and then to deeply purify it to solve the problems of low product purity and high impurity content.
[0031] (4) The lithium extraction method of the mother liquor of produced water from high COD and high boron gas field provided by the present invention innovatively adopts the method of high temperature calcination followed by acid dissolution to remove organic matter and most of the borates in the crude product, which solves the problem that the existing mainstream oxidation methods cannot effectively remove the ultra-high COD in the system. At the same time, it utilizes the physicochemical properties of borates to remove most of the borates in the system. Attached Figure Description
[0032] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.
[0033] Figure 1 This is a process flow diagram of the present invention. Detailed Implementation
[0034] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. In addition, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.
[0035] The objective of this invention is achieved through the following technical solution, the process flow of which is as follows: Figure 1 As shown:
[0036] Example 1:
[0037] The main components are shown in Table 1, and the raw material is the concentrated mother liquor from the gas field produced water.
[0038] Table 1 Raw Material Water Quality Indicators
[0039]
[0040] S1. Impurity Removal and Solubilization: By slowly adding calcium hydroxide solution to a stirred reaction tank containing concentrated mother liquor, and stirring and reacting thoroughly, most of the sulfate and carbonate ions in the water are removed, allowing lithium resources to dissolve in the water in the form of lithium ions. At the same time, the pH value of the mother liquor is raised to 12, so that magnesium ions in the water are completely precipitated.
[0041] S2. Solid-liquid separation and washing: Use a filter press to separate the solid and liquid components of the mixture after the reaction in step S1. The resulting filtrate will enter the next concentration process. The resulting filter cake will be added to a crushing and washing machine, and water will be added for multiple crushing and washing processes. After washing, the filter cake will be filtered again through a filter press. The resulting filtrate will enter the next concentration process.
[0042] S3. Filtrate Concentration: The filtrate obtained in step S2 is concentrated by evaporating and concentrating it using a refrigerant heat pump low-temperature evaporator, so that the lithium content in the filtrate is increased to 22.53 g / L. The resulting condensate meets the discharge standards, and the concentrate enters the thickener for cooling and crystallization.
[0043] S4. Centrifugal desalination and cleaning: Centrifuge 1 is used to separate the brine from the lower layer of salt slurry. The separated filtrate enters reactor 1, and the salt residue enters the cleaning tank. The salt residue obtained by centrifugation is cleaned with clean water, and the cleaning liquid is returned to the refrigerant heat pump low-temperature evaporator for concentration.
[0044] S5. Crude extraction of lithium carbonate: In reactor 1, the temperature of the mother liquor is raised to 90°C. Then, under stirring, saturated sodium carbonate solution at 90°C is slowly added at 1.2 times the theoretical value. The reaction is aged for 2 hours. Then, while hot, it is transferred to centrifuge 2 for rapid solid-liquid separation. After the lithium carbonate filter cake is crushed, it is dried at 105°C for 2 hours. The filtrate is collected separately, and after adding an appropriate amount of calcium hydroxide or calcium chloride and reacting fully, it is returned to step S1.
[0045] S6. High-temperature carbonization of organic matter: The filter cake dried in step S5 is placed into a high-temperature resistant container and placed in a high-temperature furnace for reaction. It is burned at 500°C for 60 minutes until the organic matter is fully carbonized (until no smoke is produced). After cooling, the generated smoke (mainly water, carbon dioxide and dust) is absorbed by alkaline solution and filtered by activated carbon before being discharged into the air.
[0046] S7. Acid Dissolution of Boron: The lithium carbonate after calcination and cooling in step S6 is transferred to reaction tank 2 (with forced exhaust device). An appropriate amount of hydrochloric acid solution is added to completely dissolve the lithium carbonate. Then, the solution is filtered using a filter press. The filtrate is placed in a freezer and cooled to about 4°C for 3 hours. Then, it is filtered quickly. The clear liquid obtained is collected and placed into reaction tank 3. The filter residue is collected uniformly, washed with saturated boric acid solution, and then dehydrated, dried, and packaged to obtain boric acid by-product.
[0047] S8. Deep hardness removal: Collect the clear liquid obtained in step S7 into reaction vessel 3, take a sample to test the calcium and magnesium ion content in the clear liquid, adjust the pH value to 12 using sodium hydroxide, then add sodium carbonate solution according to the theoretical value, filter after full reaction, and the filtrate enters reaction vessel 2.
[0048] S9. Lithium carbonate extraction: The lithium ion content of the filtrate was measured to be 39.88 g / L. In reactor 2, the temperature of the filtrate was raised to 90°C. Then, under stirring, saturated sodium carbonate solution at 90°C was slowly added at 1.2 times the theoretical value. The reaction was aged for 2 hours, and then the filtrate was transferred to centrifuge 3 for rapid solid-liquid separation while still hot. The lithium carbonate filter cake was crushed and dried. The filtrate was collected separately, and after adding an appropriate amount of calcium hydroxide or calcium chloride and reacting fully, it was returned to step S1.
[0049] S10. Lithium carbonate carbonation and purification: The lithium carbonate dried in step S9 is added to a cleaning and dissolving tank (with an evacuation device), pure water is added for cleaning, and high-purity carbon dioxide is continuously introduced for aeration at room temperature to completely dissolve the lithium carbonate. Then, it is quickly filtered, and the filtrate enters the reaction vessel 3. It is heated to 90°C to precipitate lithium carbonate product. It is filtered while hot using a filter press. The filter cake is collected, crushed and dried, and the dried lithium carbonate is ground, sieved and bagged to obtain industrial-grade lithium carbonate product.
[0050] After processing according to the entire process of this invention, the lithium yield in the concentrated mother liquor is 75.3%, and the purity of the obtained lithium carbonate product is 99.5%, with all impurities within the standard range.
[0051] Example 2:
[0052] The main components are shown in Table 2, and the raw material is the concentrated mother liquor from the gas field produced water.
[0053] Table 2 Raw Material Water Quality Indicators
[0054]
[0055] S1. Impurity Removal and Solubilization: By slowly adding calcium hydroxide solution to a stirred reaction tank containing concentrated mother liquor, and stirring and reacting thoroughly, most of the sulfate and carbonate ions in the water are removed, allowing lithium resources to dissolve in the water in the form of lithium ions. At the same time, the pH value of the mother liquor is raised to 13, so that magnesium ions in the water are completely precipitated.
[0056] S2. Solid-liquid separation and washing: Use a filter press to separate the solid and liquid components of the mixture after the reaction in step S1. The resulting filtrate will enter the next concentration process. The resulting filter cake will be added to a crushing and washing machine, and water will be added for multiple crushing and washing processes. After washing, the filter cake will be filtered again through a filter press. The resulting filtrate will enter the next concentration process.
[0057] S3, Filtrate Concentration: The filtrate obtained in step S2 is evaporated and concentrated using a refrigerant heat pump low-temperature evaporator, so that the lithium content in the filtrate is increased to 20.51 g / L. The resulting condensate meets the discharge standards, and the concentrate enters a thickener for cooling and crystallization.
[0058] S4. Centrifugal desalination and cleaning: Centrifuge 1 is used to separate the brine from the lower layer of salt slurry. The separated filtrate enters reactor 1, and the salt residue enters the cleaning tank. The salt residue obtained by centrifugation is cleaned with clean water, and the cleaning liquid is returned to the refrigerant heat pump low-temperature evaporator for concentration.
[0059] S5. Crude extraction of lithium carbonate: In reactor 1, the temperature of the mother liquor is raised to 90°C. Then, under stirring, saturated sodium carbonate solution at 90°C is slowly added at 1.2 times the theoretical value. The reaction is aged for 2.5 hours. Then, while hot, it is transferred to centrifuge 2 for rapid solid-liquid separation. After the lithium carbonate filter cake is crushed, it is dried at 105°C for 2 hours. The filtrate is collected separately, and after adding an appropriate amount of calcium hydroxide or calcium chloride and reacting fully, it is returned to step S1.
[0060] S6. High-temperature carbonization of organic matter: The filter cake dried in step S5 is placed into a high-temperature resistant container and placed in a high-temperature furnace for reaction. It is burned at 600°C for 30 minutes until the organic matter is fully carbonized (until no smoke is produced). After that, it is taken out and cooled. The generated smoke (mainly water, carbon dioxide and dust) is absorbed by alkaline solution and filtered by activated carbon before being discharged into the air.
[0061] S7. Acid Dissolution of Boron: The lithium carbonate after calcination and cooling in step S6 is transferred to reaction tank 2 (with forced exhaust device). An appropriate amount of hydrochloric acid solution is added to completely dissolve the lithium carbonate. Then, the solution is filtered using a filter press. The filtrate is placed in a freezer and cooled to about 4°C for 3 hours. Then, it is filtered quickly. The clear liquid obtained is collected and placed into reaction tank 3. The filter residue is collected uniformly, washed with saturated boric acid solution, and then dehydrated, dried, and packaged to obtain boric acid by-product.
[0062] S8. Deep hardness removal: Collect the clear liquid obtained in step S7 into reaction tank 3, take a sample to test the calcium and magnesium ion content in the clear liquid, use sodium hydroxide to adjust the pH value to 13, then add sodium carbonate solution according to the theoretical value, filter after full reaction, and the filtrate enters reaction vessel 2.
[0063] S9. Lithium carbonate extraction: The lithium ion content of the filtrate was measured to be 37.92 g / L. In the reaction vessel 2, the temperature of the filtrate was raised to 90°C. Then, under stirring, saturated sodium carbonate solution at 90°C was slowly added at 1.2 times the theoretical value. The reaction was aged for 2.5 hours. Then, while hot, it was transferred to centrifuge 3 for rapid solid-liquid separation. The lithium carbonate filter cake was crushed and dried. The filtrate was collected separately. After adding an appropriate amount of calcium hydroxide or calcium chloride and reacting fully, it was returned to step S1.
[0064] S10. Lithium carbonate carbonation and purification: The lithium carbonate dried in step S9 is added to a cleaning and dissolving tank (with an evacuation device), pure water is added for cleaning, and high-purity carbon dioxide is continuously introduced for aeration at room temperature to completely dissolve the lithium carbonate. Then, it is quickly filtered, and the filtrate enters the reaction vessel 3. It is heated to 90°C to precipitate lithium carbonate product. It is filtered while hot using a filter press. The filter cake is collected, crushed and dried, and the dried lithium carbonate is ground, sieved and bagged to obtain industrial-grade lithium carbonate product.
[0065] After processing according to the entire process of this invention, the lithium yield in the concentrated mother liquor is 73.2%, and the purity of the obtained lithium carbonate product is 99.6%, with all impurities within the standard range.
[0066] Example 3:
[0067] The main components are shown in Table 3, and the raw material is the concentrated mother liquor from the gas field produced water.
[0068] Table 3 Raw Material Water Quality Indicators
[0069]
[0070] S1. Impurity Removal and Solubilization: By slowly adding calcium hydroxide solution to a stirred reaction tank containing concentrated mother liquor, and stirring and reacting thoroughly, most of the sulfate and carbonate ions in the water are removed, allowing lithium resources to dissolve in the water in the form of lithium ions. At the same time, the pH value of the mother liquor is increased to 12.5, so that magnesium ions in the water are completely precipitated.
[0071] S2. Solid-liquid separation and washing: Use a filter press to separate the solid and liquid components of the mixture after the reaction in step S1. The resulting filtrate will enter the next concentration process. The resulting filter cake will be added to a crushing and washing machine, and water will be added for multiple crushing and washing processes. After washing, the filter cake will be filtered again through a filter press. The resulting filtrate will enter the next concentration process.
[0072] S3. Filtrate Concentration: The filtrate obtained in step S2 is concentrated by evaporating and condensing it using a refrigerant heat pump low-temperature evaporator, so that the lithium content in the filtrate is increased to 21.92 g / L. The resulting condensate meets the discharge standards, and the concentrate enters the thickener for cooling and crystallization.
[0073] S4. Centrifugal desalination and cleaning: Centrifuge 1 is used to separate the brine from the lower layer of salt slurry. The separated filtrate enters reactor 1, and the salt residue enters the cleaning tank. The salt residue obtained by centrifugation is cleaned with clean water, and the cleaning liquid is returned to the refrigerant heat pump low-temperature evaporator for concentration.
[0074] S5. Crude extraction of lithium carbonate: In reactor 1, the temperature of the mother liquor is raised to 90°C. Then, under stirring, saturated sodium carbonate solution at 90°C is slowly added at 1.2 times the theoretical value. The reaction is aged for 3 hours. Then, while hot, it is transferred to centrifuge 2 for rapid solid-liquid separation. After the lithium carbonate filter cake is crushed, it is dried at 105°C for 2 hours. The filtrate is collected separately, and after adding an appropriate amount of calcium hydroxide or calcium chloride and reacting fully, it is returned to step S1.
[0075] S6. High-temperature carbonization of organic matter: The filter cake dried in step S5 is placed into a high-temperature resistant container and placed in a high-temperature furnace for reaction. It is burned at 650°C for 20 minutes until the organic matter is fully carbonized (until no smoke is produced). After that, it is taken out and cooled. The generated flue gas (mainly water, carbon dioxide and dust) is discharged into the air after being absorbed by alkaline solution and filtered by activated carbon.
[0076] S7. Acid Dissolution of Boron: The lithium carbonate after calcination and cooling in step S6 is transferred to reaction tank 2 (with forced exhaust device). An appropriate amount of sulfuric acid solution is added to completely dissolve the lithium carbonate. Then, the solution is filtered using a filter press. The filtrate is placed in a freezer and cooled to about 4°C for 3 hours. Then, it is rapidly filtered, and the resulting clear liquid is collected and placed into reaction tank 3. The filter residue is collected uniformly, washed with saturated boric acid solution, and then dehydrated, dried, and packaged to obtain boric acid by-product.
[0077] S8. Deep hardness removal: Collect the clear liquid obtained in step S7 into reaction vessel 3, take a sample to test the calcium and magnesium ion content in the clear liquid, adjust the pH value to 12.5 using sodium hydroxide, then add sodium carbonate solution according to the theoretical value, filter after full reaction, and the filtrate enters reaction vessel 2.
[0078] S9. Lithium carbonate extraction: The lithium ion content of the filtrate was measured to be 45.92 g / L. In the reaction vessel 2, the temperature of the filtrate was raised to 90°C. Then, under stirring, 1.2 times the theoretical value of saturated sodium carbonate solution at 90°C was slowly added. The reaction was aged for 3 hours. Then, while hot, it was transferred to centrifuge 3 for rapid solid-liquid separation. The lithium carbonate filter cake was crushed and dried. The filtrate was collected separately. After adding an appropriate amount of calcium hydroxide or calcium chloride and reacting fully, it was returned to step S1.
[0079] S10. Lithium carbonate carbonation and purification: The lithium carbonate dried in step S9 is added to a cleaning and dissolving tank (with an evacuation device), pure water is added for cleaning, and high-purity carbon dioxide is continuously introduced for aeration at room temperature to completely dissolve the lithium carbonate. Then, it is quickly filtered, and the filtrate enters the reaction vessel 3. It is heated to 90°C to precipitate lithium carbonate product. It is filtered while hot using a filter press. The filter cake is collected, crushed and dried, and the dried lithium carbonate is ground, sieved and bagged to obtain industrial-grade lithium carbonate product.
[0080] After processing according to the entire process of this invention, the lithium yield in the concentrated mother liquor is 79.8%, and the purity of the obtained lithium carbonate product is 99.5%, with all impurities within the standard range.
[0081] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.
Claims
1. A method for lithium extraction from the mother liquor of produced water from high-COD, high-boron-content gas fields, characterized in that, Includes the following steps: S1. Impurity Removal and Solubilization: By slowly adding calcium hydroxide solution to a stirred reaction vessel containing the mother liquor of evaporation, and stirring and reacting thoroughly, most of the sulfate and carbonate ions in the water are removed, allowing the lithium resources to dissolve in the water in the form of lithium ions. At the same time, the pH value of the mother liquor is raised to above 12, so that the magnesium ions in the water are completely precipitated. S2. Solid-liquid separation and washing: Use a filter press to separate the solid and liquid components of the mixture after the reaction in step S1. The resulting filtrate will enter the next concentration process. The resulting filter cake will be added to a crushing and washing machine, and water will be added for multiple crushing and washing processes. After washing, the filter cake will be filtered again through a filter press. The resulting filtrate will enter the next concentration process. S3. Filtrate Concentration: The filtrate obtained in step S2 is concentrated by evaporating and concentrating it using a refrigerant heat pump low-temperature evaporator, so that the lithium content in the filtrate is increased to more than 20,000 mg / L. The resulting condensate meets the discharge standards, and the concentrate enters the thickener for cooling and crystallization. S4. Centrifugal desalination and cleaning: Centrifuge 1 is used to separate the brine from the lower layer of salt slurry. The separated filtrate enters reactor 1, and the salt residue enters the cleaning tank. The salt residue obtained by centrifugation is cleaned with clean water, and the cleaning liquid is returned to the refrigerant heat pump low-temperature evaporator for concentration. S5. Crude extraction of lithium carbonate: In reactor 1, the temperature of the filtrate is raised to 90°C. Then, under stirring, a saturated sodium carbonate solution is slowly added. Then, while hot, it is transferred to centrifuge 2 for rapid solid-liquid separation. After the lithium carbonate filter cake is crushed, it is dried at 105°C for 2 hours. The filtrate is collected separately, and after adding reagents and reacting fully, it is returned to step S1. S6. High-temperature carbonization of organic matter: The lithium carbonate filter cake dried in step S5 is placed into a high-temperature resistant container and placed in a high-temperature furnace for reaction. It is burned at 500-650℃ for 15-60 minutes. After the organic matter is fully carbonized, it is taken out and cooled. The generated flue gas is discharged after being absorbed by alkaline solution and filtered by activated carbon. S7. Acid Dissolution of Boron: Transfer the lithium carbonate, after calcination and cooling in step S6, into reaction vessel 2 equipped with a forced exhaust device. Add an appropriate amount of hydrochloric acid or sulfuric acid solution to completely dissolve the lithium carbonate. Then, filter using a filter press to remove the remaining boron. The filtrate was placed in a refrigerator and cooled to 4°C for 2-3 hours. Then it was quickly filtered, and the resulting clear liquid was collected into reaction vessel 3. The filter residue was collected and washed with saturated boric acid solution before being dehydrated, dried and packaged to obtain boric acid byproduct. S8. Deep hardness removal: Collect the clear liquid obtained in step S7 into reaction vessel 3, take a sample to test the calcium and magnesium ion content in the clear liquid, use sodium hydroxide to adjust the pH value to above 12, then add sodium carbonate solution according to the calcium ion content, filter after full reaction, and the filtrate enters reaction vessel 2. S9. Lithium carbonate extraction: In reaction vessel 2, the temperature of the filtrate is raised to 90°C. Then, under stirring conditions, saturated sodium carbonate is slowly added and then transferred to centrifuge 3 while hot for rapid solid-liquid separation. The lithium carbonate filter cake is crushed and dried. The filtrate is collected separately, and after adding reagents and reacting fully, it is returned to step S1. S10. Lithium carbonate carbonation and purification: The lithium carbonate dried in step S9 is added to a cleaning and dissolving tank equipped with a venting device. Pure water is added for cleaning, and high-purity carbon dioxide is continuously introduced for aeration at room temperature to completely dissolve the lithium carbonate. Then, it is quickly filtered, and the filtrate enters the reaction vessel 3. The mixture is heated to 90°C to precipitate lithium carbonate product. A centrifuge is used to quickly separate the solid and liquid components while the mixture is hot. The filter residue is dried into a filter cake. The filter cake is collected, crushed, and dried. The dried lithium carbonate is then ground, sieved, and bagged to obtain industrial-grade lithium carbonate product.
2. The method for lithium extraction from the mother liquor of produced water from high-COD, high-boron-content gas fields according to claim 1, characterized in that: In step S5, the amount of saturated sodium carbonate solution added is 1.2 times the lithium content, the temperature is 90℃, and the reaction time is 23 hours.
3. The method for lithium extraction from the mother liquor of produced water from high-COD, high-boron-content gas fields according to claim 1, characterized in that: In step S9, the lithium carbonate filter cake is crushed and then dried at 105°C for 2 hours.
4. The method for lithium extraction from the mother liquor of produced water from high-COD, high-boron-content gas fields according to claim 1, characterized in that: In step S10, the mass ratio of lithium carbonate to pure water is 1:20, and the cleaning water is recycled multiple times.
5. The method for lithium extraction from the mother liquor of produced water from high-COD, high-boron-content gas fields according to claim 1, characterized in that: The filtrates from steps S5 and S9 were collected separately, and after being reacted with an appropriate amount of calcium hydroxide or calcium chloride, they were returned to step S1. The filtrates were recycled multiple times.