A processing method of lithium mica sulfate calcine

Abstract

This invention discloses a processing method for calcined lepidolite sulfate clinker, relating to the field of lithium salt extraction technology. The method includes the following steps: constructing at least three processing units connected in series, including a first-end processing unit, a middle processing unit, and a last-end processing unit; adding the calcined lepidolite sulfate clinker from the first-end processing unit and adding washing water from the last-end processing unit, causing the solid and liquid phases to form a countercurrent contact; collecting the overflow liquid after solid-liquid separation from the first-end processing unit as the finished lithium-rich solution; continuously or intermittently drawing a portion of the circulating liquid sideflow from the middle processing unit and sending it to an impurity removal unit; in the impurity removal unit, first performing defluorination treatment; after treatment, freezing and crystallizing the defluorinated liquid to separate the precipitated alkali metal sulfates, obtaining a purified liquid; preheating the purified liquid and returning it to the middle processing unit for circulation. This invention achieves efficient lithium recovery while avoiding impurity blockage, ensuring long-term stable system operation.

Description

Technical Field

[0001] This invention relates to the field of lithium salt extraction technology, specifically to a processing method for roasted lithium mica sulfate clinker. Background Technology

[0002] Currently, the industrial process commonly uses a single-stage stirred leaching process to treat lepidolite sulfate roasted clinker. The resulting leachate has a low lithium concentration (typically only 3-5 g / L), requiring extensive evaporation and concentration before subsequent lithium precipitation, resulting in high energy consumption and cost. To increase the lithium concentration in the leachate, existing technologies employ mother liquor circulation or multi-stage countercurrent washing. However, in closed-loop circulation, impurities such as potassium, sodium, fluorine, and aluminum in the clinker accumulate rapidly, leading to decreased product purity, blockage of pipes and filter media, reduced solid-liquid separation efficiency, and inability to operate the system continuously and stably. To address these issues, existing technologies also employ defluorination or freeze crystallization to remove impurities. However, defluorination alone cannot effectively control the accumulation of soluble salts such as potassium and sodium. Furthermore, freeze crystallization alone, without defluorination, allows fluoride ions to react with components such as silicon and aluminum to form dense scale layers like fluorosilicates and cryolite, which adhere to the inner walls of the equipment, affecting heat exchange efficiency and requiring frequent shutdowns for cleaning. Therefore, while enriching the lithium concentration through multi-stage countercurrent leaching, it is necessary to simultaneously remove various impurities such as fluorine, potassium, and sodium that accumulate in the circulating system. Summary of the Invention

[0003] In view of the shortcomings of the prior art, the present invention proposes a processing method for lepidolite sulfate roasted clinker, which aims to solve the technical problem that, in the process of multi-stage countercurrent leaching of lepidolite sulfate roasted clinker to enrich lithium concentration, impurities such as potassium, sodium, fluorine, and aluminum accumulate continuously with the circulation, resulting in decreased product purity, equipment scaling and blockage, reduced solid-liquid separation efficiency, and difficulty in long-term stable operation of the system.

[0004] To achieve the above objectives, this invention proposes a processing method for calcined lithium mica sulfate clinker, comprising the following steps: Step S1: Construct at least three processing units in series, including a first-end processing unit, a middle processing unit, and a last-end processing unit. Lithium mica sulfate roasted clinker is added from the first-end processing unit, and washing water is added from the last-end processing unit, so that the solid phase and the liquid phase form a countercurrent contact. Step S2: Collect the overflow liquid after solid-liquid separation in the first-end processing unit as the finished lithium-rich solution; Step S3: A portion of the circulating liquid side flow is continuously or intermittently drawn from the central processing unit and sent to the impurity removal unit; Step S4: In the impurity removal unit, defluorination treatment is performed first. After the treatment is completed, the obtained defluorinated liquid is frozen and crystallized. After separating the precipitated alkali metal sulfates, a purified liquid is obtained. Step S5: After preheating the purified liquid, it is returned to the central processing unit to participate in the circulation.

[0005] In one embodiment, in step S3, the amount of circulating liquid drawn out is 5 to 20% of the overflow volume of the central treatment unit.

[0006] In one embodiment, step S4 includes the following steps: first, adding alkali to adjust the pH to 10-12, then adding a defluorinating agent for defluorination treatment, and after the pH stabilizes to 6-7, adding a flocculant for solid-liquid separation to obtain a defluorinated clear liquid.

[0007] In one embodiment, the amount of the defluorinating agent added is 8-15‰ of the circulating liquid side flow rate; And / or, the amount of flocculant added is 1 to 3‰ of the side flow rate of the lithium mica sulfur circulating liquid.

[0008] In one embodiment, in step S4, the temperature of the freeze-crystallization is 0~10°C; And / or, the alkali metal sulfate is mainly a double salt of sodium sulfate decahydrate and potassium sulfate.

[0009] In one embodiment, in step S5, the preheating involves preheating the purified liquid to 40~80°C.

[0010] In one embodiment, in step S1, the leaching temperature of the first-end treatment unit is 80~95°C, and the leaching temperature decreases step by step along the series connection direction of the treatment units; the tail-end treatment unit is a room temperature washing unit. And / or, the leaching liquid-to-solid ratio of the first-end treatment unit is 2~5:1, the leaching liquid-to-solid ratio of the middle-end treatment unit is 1~3:1, and the washing liquid-to-solid ratio of the tail-end treatment unit is 1~3:1. And / or, the leaching time of the first-end treatment unit is 1~3h, the leaching liquid-to-solid ratio of the middle-end treatment unit is 1~3:1, and the washing time of the tail-end treatment unit is 1~3h.

[0011] In one embodiment, the method further includes step S6: by monitoring the concentration of fluoride ions and / or potassium ions and / or sodium ions in the circulating liquid online, when the concentration of fluoride ions and / or potassium ions and / or sodium ions exceeds a preset threshold, the amount of circulating liquid side flow drawn out in step S3 and / or the amount of washing water added in step S1 is increased.

[0012] In one embodiment, the preset threshold for the fluoride ion concentration is less than 3 mg / L; And / or, the preset threshold for the potassium ion concentration is less than 10 g / L; And / or, the preset threshold for sodium ion concentration is less than 16 g / L.

[0013] The present invention also proposes a method for preparing lithium-containing products using the processing method of calcined lithium mica sulfate clinker as described above.

[0014] One or more technical solutions proposed in this invention have at least the following technical effects: This invention achieves efficient enrichment of lithium ions in the leachate and synergistic balance of interfering components such as potassium, sodium, and fluorine within the system by constructing at least three processing units in series, including a first-end processing unit, a middle processing unit, and a tail-end processing unit, and by cooperating with a bypass purification circuit for side-flow extraction and step-by-step removal of impurities. Specifically, the countercurrent contact and the clean water washing in the tail-end treatment unit ensure that the lithium concentration of the finished lithium-rich solution remains stable at 8-9 g / L or higher, directly meeting the requirements for lithium precipitation feed. The main content of lithium carbonate is consistently above 99.2%, while the loss of soluble lithium in the final residue can be controlled below 0.001%, significantly improving the total lithium recovery rate. The side stream, after undergoing defluorination and freeze crystallization treatments, returns to the main circulation, effectively controlling the fluoride ion concentration in the circulating liquid at 1.8-2.4 mg / L. This effectively avoids the impact of fluoride corrosion and fluorine-aluminum complexes on the purity of the precipitated lithium product. Furthermore, by removing alkali metal sulfate complex salts through an open circuit, blockage and filtration performance deterioration caused by salt precipitation are prevented, allowing the system to operate continuously and stably for over 30 days. The purity of the byproduct alkali metal sulfate is not less than 98%, achieving resource recovery of potassium and sodium. Therefore, this invention effectively solves the problem of impurity accumulation while ensuring high lithium concentration and long-term stable operation, combining high process efficiency, operational reliability, and economy. Attached Figure Description

[0015] 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. The drawings described below are only some embodiments of the present invention. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 A schematic diagram of the process flow for the processing method of calcined lithium mica sulfate clinker provided by the present invention.

[0017] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0018] It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially. Furthermore, the meaning of "and / or" throughout the text includes three parallel solutions; for example, "A and / or B" includes solution A, or solution B, or a solution where both A and B are satisfied simultaneously. 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 a combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention. 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.

[0020] The technical problem solved by this invention is that existing single-stage stirred leaching methods for lepidolite sulfate roasted clinker result in low lithium concentration and high evaporation energy consumption. While mother liquor circulation or multi-stage countercurrent washing can enrich lithium concentration, impurities such as potassium, sodium, fluorine, and aluminum in the lepidolite clinker accumulate continuously in closed-loop circulation, leading to decreased product purity, scaling and clogging of pipes and filter media, reduced solid-liquid separation efficiency, and difficulty in long-term stable system operation. Existing single defluorination treatment cannot effectively control the accumulation of soluble salts such as potassium and sodium. After system operation, excessive salt content still leads to increased slurry viscosity and decreased filtration performance, affecting lithium recovery rate and product purity. Although single freeze crystallization treatment can precipitate some alkali metal sulfates, fluoride ions in the undefluorinated circulating liquid react with components such as silicon and aluminum during freeze crystallization to form dense scale layers such as fluorosilicates and cryolite, which adhere to the inner wall of the equipment, affecting heat exchange efficiency and requiring frequent shutdowns for cleaning.

[0021] To address the aforementioned technical problems, this invention proposes a processing method for calcined lithium mica sulfate clinker, comprising the following steps: Step S1: Construct at least three processing units in series, including a first-end processing unit, a middle processing unit, and a last-end processing unit. Lithium mica sulfate roasted clinker is added from the first-end processing unit, and washing water is added from the last-end processing unit, so that the solid phase and the liquid phase form a countercurrent contact. Step S2: Collect the overflow liquid after solid-liquid separation in the first-end processing unit as the finished lithium-rich solution; Step S3: A portion of the circulating liquid side flow is continuously or intermittently drawn from the central processing unit and sent to the impurity removal unit; Step S4: In the impurity removal unit, defluorination treatment is performed first. After the treatment is completed, the obtained defluorinated liquid is frozen and crystallized. After separating the precipitated alkali metal sulfates, a purified liquid is obtained. Step S5: After preheating the purified liquid, it is returned to the central processing unit to participate in the circulation.

[0022] It should be noted that the present invention constructs at least three processing units in series, including a first-end processing unit, a middle processing unit, and a last-end processing unit, so that the fresh clinker and the washing water form a solid-liquid phase countercurrent contact. The concentration gradient in the stepwise leaching process drives lithium ions to accumulate in the first-end processing unit, while the clean water washing in the last-end processing unit maximizes the recovery of soluble lithium in the residue, thereby increasing the lithium concentration of the finished lithium-rich solution to a level where lithium can be directly deposited.

[0023] Based on this, in response to the problem that impurities such as potassium, sodium, fluorine, and aluminum accumulate continuously with the number of cycles in a closed-loop system, a portion of the circulating liquid is drawn from the central processing unit and sent to the impurity removal unit. First, defluorination is performed to prevent it from corroding the subsequent freeze crystallization equipment and generating fluorine-containing crystals. Then, alkali metal sulfates are precipitated and opened up by cooling and freeze crystallization. The purified liquid is returned to the leaching system. In this way, while maintaining the enrichment of lithium concentration in the main route, impurity ions are removed from the system stepwise in solid form.

[0024] A schematic diagram of the process flow of the method of the present invention is shown below. Figure 1 As shown.

[0025] Furthermore, by monitoring the concentration of fluoride ions and / or potassium ions and / or sodium ions in the circulating liquid online, when the concentration exceeds a preset threshold, the side flow outflow and / or the amount of washing water added are increased to achieve dynamic balance control of the total amount of impurities in the system, thereby ensuring the long-term stability of the multi-stage countercurrent system under high lithium concentration operation.

[0026] In one embodiment, in step S3, the amount of circulating liquid drawn from the side is 5-20% of the overflow volume of the central processing unit, which can be 5%, 8%, 10%, 12%, 15%, 17%, 20%, etc. When the amount of circulating liquid drawn from the side is less than 5%, the bypass treatment volume is insufficient to effectively reduce the continuously accumulating impurity ions such as potassium, sodium, and fluorine in the system, the impurity balance will be broken, and the system stability cannot be maintained; when it is more than 20%, the circulating liquid is over-extracted, resulting in insufficient total liquid phase in the main leaching route, an imbalance in the solid-liquid ratio, and affecting the lithium leaching efficiency and washing effect.

[0027] In one embodiment, step S4, the defluorination treatment includes: first, adding alkali to adjust the pH to 10-12, then adding a defluorinating agent for defluorination treatment; after the pH stabilizes to 6-7, adding a flocculant for solid-liquid separation to obtain a defluorinated clear liquid. The defluorination reaction efficiency is highest under strongly alkaline conditions, where fluoride ions fully react with the defluorinating agent components to form fluoride precipitates. Subsequently, the defluorinating agent hydrolyzes, consuming alkalinity and causing the pH to naturally drop back to the near-neutral range. At this point, the flocculant exhibits optimal flocculation and sedimentation effects in a weakly acidic to neutral environment, effectively achieving solid-liquid separation.

[0028] In one embodiment, the amount of defluorinating agent added is 8-15‰ of the circulating liquid side flow rate, which can be 8‰, 10‰, 12‰, 15‰, etc. When the amount of defluorinating agent is less than 8‰, the defluorination reaction is incomplete, and the residual fluoride ions will cause corrosion to the equipment and form fluorosilicate scale after entering the freezing crystallization stage; when it is more than 15‰, excessive solid phase residue is introduced, increasing the load of subsequent solid-liquid separation and the cost of reagents.

[0029] In one embodiment, the amount of flocculant added is 1 to 3‰ of the circulating liquid side flow rate, which can be 1‰, 2‰, or 3‰, etc. When the amount of flocculant is less than 1‰, the floc formation is insufficient and the settling speed is slow; when it is more than 3‰, it increases the viscosity of the solution, which is not conducive to filtration.

[0030] In one embodiment, in step S4, the temperature for freeze crystallization is 0~10℃, which can be 0℃, 2℃, 4℃, 6℃, 8℃, 10℃, etc. The solubility of alkali metal sulfates within this temperature range decreases significantly with decreasing temperature, allowing for efficient crystallization and precipitation as sodium sulfate decahydrate and potassium sulfate double salts. Below 0℃, energy consumption increases significantly, and ice crystals may precipitate, interfering with separation. Above 10℃, the amount of sulfate crystallized is insufficient, and the impurity removal effect decreases dramatically.

[0031] In one embodiment, the alkali metal sulfate is mainly a double salt of sodium sulfate decahydrate and potassium sulfate.

[0032] In one embodiment, in step S5, the preheating involves preheating the purified liquid to 40-80°C, which can be 40°C, 50°C, 60°C, 70°C, 80°C, etc. Preheating the purified liquid before return prevents the low-temperature cryogenic liquid from impacting the thermal regime of the leaching system, ensuring stable leaching temperatures in each treatment unit, and simultaneously achieving energy cascade utilization.

[0033] In one embodiment, in step S1, the leaching temperature of the first-end treatment unit is 80~95℃, which can be 80℃, 85℃, 90℃, 95℃, etc., and the leaching temperature decreases step by step along the series connection direction of the treatment units. The tail-end treatment unit is a room temperature washing unit.

[0034] In one embodiment, the leaching liquid-to-solid ratio of the first-end treatment unit is 2 to 5:1, which can be 2:1, 3:1, 4:1, 5:1, etc.; the leaching liquid-to-solid ratio of the middle treatment unit is 1 to 3:1, which can be 1:1, 2:1, 3:1, etc.; and the washing liquid-to-solid ratio of the tail-end treatment unit is 1 to 3:1, which can be 1:1, 2:1, 3:1, etc.

[0035] The high temperature and high liquid-to-solid ratio of the initial treatment unit ensures efficient lithium dissolution and high concentration enrichment of the lithium-rich solution. The temperature of each subsequent treatment unit gradually decreases to meet the thermodynamic requirements of decreasing liquid-phase lithium concentration and decreasing residual lithium content in the slag during countercurrent flow. The room-temperature, low liquid-to-solid ratio washing in the tail-end treatment unit ensures that soluble lithium in the slag is fully replaced and recovered, while minimizing the amount of wash water used to maintain the lithium concentration balance of the entire system.

[0036] In one embodiment, the immersion time of the first-end treatment unit is 1 to 3 hours, which can be 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, etc.; the immersion time of the middle-end treatment unit is 1 to 3 hours, which can be 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, etc.; and the washing time of the tail-end treatment unit is 1 to 3 hours, which can be 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, etc.

[0037] In one embodiment, the method further includes step S6: by monitoring the concentration of fluoride ions and / or potassium ions and / or sodium ions in the circulating liquid online, when the concentration of fluoride ions and / or potassium ions and / or sodium ions exceeds a preset threshold, the amount of circulating liquid side flow drawn out in step S3 and / or the amount of washing water added in step S1 is increased.

[0038] It should be noted that the composition of lepidolite clinker inevitably fluctuates with the source of the ore, and the bypass treatment with fixed parameters cannot cope with the changes in impurity load caused by the fluctuation of raw materials. By monitoring the concentration of key impurities online and dynamically adjusting the bypass extraction amount or the amount of wash water added, the system can still keep the impurities within the high-efficiency leaching zone when facing composition fluctuations, achieve long-term adaptive and stable operation, and avoid system shutdown due to raw material fluctuations.

[0039] In one embodiment, the preset threshold for the fluoride ion concentration is less than 3 mg / L. A fluoride ion concentration below 3 mg / L effectively prevents the formation of fluoride-aluminum complexes, ensuring the purity of the lithium precipitated product.

[0040] In one embodiment, the preset threshold for the potassium ion concentration is less than 10 g / L.

[0041] In one embodiment, the preset threshold for sodium ion concentration is less than 16 g / L.

[0042] A potassium ion concentration below 10 g / L and a sodium ion concentration below 16 g / L ensure that potassium sulfate and sodium sulfate do not precipitate out under supersaturation at the system temperature, maintaining the unobstructed flow of pipelines, valves, and filter cloth, as well as the good filtration performance of the slurry.

[0043] The present invention also proposes a method for preparing lithium-containing products using the processing method of calcined lithium mica sulfate clinker as described above.

[0044] Example The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0045] Example 1 This embodiment uses calcined lithium mica sulfate clinker as raw material, containing 5.9% Li₂O, 3.1% F, 5.2% K₂O, and 2.5% Na₂O. A four-stage countercurrent leaching system is employed, and the specific steps are as follows: Step S1: Construct a four-stage leaching and solid-liquid separation system, using a belt filter for solid-liquid separation. Fresh clinker is added from stage 1, and wash water is added from stage 4. In stage 1, fresh clinker is added and slurried with overflow from stage 2, maintaining a liquid-to-solid ratio of 3:1 and a leaching temperature of 90°C for 2 hours with stirring. In stage 2, overflow from stage 3 is used to slurry the underflow from stage 1, maintaining a liquid-to-solid ratio of 3:1 and a leaching temperature of 80°C for 1 hour with stirring. In stage 3, overflow from stage 4 is used to slurry the underflow from stage 2, maintaining a liquid-to-solid ratio of 2:1 and a leaching temperature of 60°C for 1 hour with stirring. In stage 4, pure water is added to perform final washing of the underflow from stage 3, maintaining a liquid-to-solid ratio of 2:1 and stirring at room temperature for 1 hour. After washing, solid-liquid separation is achieved, yielding lithium slag and overflow.

[0046] Step S2: Collect the overflow liquid after the first-stage solid-liquid separation, which is the finished lithium-rich solution.

[0047] Step S3: 10% of the volume of circulating liquid is drawn from the overflow liquid after the second-stage solid-liquid separation and sent to the impurity removal unit.

[0048] In step S4, in the impurity removal unit, sodium hydroxide is first added to adjust the pH to 11. Then, a defluorinating agent (commercially available defluorinating agent) at a flow rate of 10‰ of the circulating liquid side flow rate is added for defluorination treatment. When the pH stabilizes at 6.5, a flocculant (commercially available flocculant) at a flow rate of 2‰ of the circulating liquid side flow rate is added for flocculation and precipitation. After solid-liquid separation, a defluorinated clear liquid is obtained. The defluorinated clear liquid is then pumped into a cryo-crystallizer and cooled to 5°C for cryo-crystallization, precipitating sodium sulfate decahydrate and potassium sulfate double salt. After centrifugation, a purified liquid is obtained.

[0049] Step S5: After preheating the purified liquid to 60°C, return it to the second-stage leaching system for circulation.

[0050] Step S6: During system operation, the concentration of fluoride ions in the circulating liquid is monitored online. When the concentration of fluoride ions exceeds 3 mg / L, the amount of circulating liquid drawn out from the side flow is increased.

[0051] Example 2 This embodiment uses the same lithium mica sulfate roasted clinker and four-stage countercurrent leaching system as Example 1. The specific steps are as follows: Step S1: Construct a four-stage leaching and solid-liquid separation system, using a belt filter for solid-liquid separation. Fresh clinker is added from stage 1, and wash water is added from stage 4. In stage 1, fresh clinker is added and slurried with overflow from stage 2, maintaining a liquid-to-solid ratio of 3:1 and a leaching temperature of 90°C for 2 hours with stirring. In stage 2, overflow from stage 3 is used to slurry the underflow from stage 1, maintaining a liquid-to-solid ratio of 3:1 and a leaching temperature of 80°C for 1 hour with stirring. In stage 3, overflow from stage 4 is used to slurry the underflow from stage 2, maintaining a liquid-to-solid ratio of 2:1 and a leaching temperature of 60°C for 1 hour with stirring. In stage 4, clean water is added to perform a final wash on the underflow from stage 3, maintaining a liquid-to-solid ratio of 2:1 and stirring at room temperature for 1 hour. After washing, solid-liquid separation is performed to obtain lithium slag and overflow.

[0052] Step S2: Collect the overflow liquid after the first-stage solid-liquid separation, which is the finished lithium-rich solution.

[0053] Step S3: 15% of the volume of circulating liquid is drawn from the overflow liquid after the third-stage solid-liquid separation and sent to the impurity removal unit.

[0054] In step S4, sodium hydroxide is first added to the impurity removal unit to adjust the pH to 11. Then, a defluorinating agent (commercially available defluorinating agent) equivalent to 10‰ of the circulating liquid side flow rate is added. When the pH stabilizes at 6.5, a flocculant (commercially available flocculant) equivalent to 2‰ of the circulating liquid side flow rate is added for flocculation and precipitation. After solid-liquid separation, a defluorinated clear liquid is obtained. The defluorinated clear liquid is then pumped into a cryo-crystallizer and cooled to 8°C for cryo-crystallization to precipitate sodium sulfate decahydrate and potassium sulfate double salt. After centrifugation, a purified liquid is obtained.

[0055] Step S5: After preheating the purified liquid to 55°C, return it to the third-stage leaching system for circulation.

[0056] Step S6: During system operation, the concentration of fluoride ions in the circulating liquid is monitored online. When the concentration of fluoride ions exceeds 3 mg / L, the amount of circulating liquid drawn out from the side flow is increased.

[0057] Example 3 This embodiment uses the same lithium mica sulfate roasted clinker and three-stage countercurrent leaching system as Example 1. The specific steps are as follows: Step S1: Construct a three-stage leaching and solid-liquid separation system, using a belt filter for solid-liquid separation. Fresh clinker is added in stage 1, and wash water is added in stage 3. In stage 1, fresh clinker is added and slurried with overflow from stage 2, maintaining a liquid-to-solid ratio of 3:1 and a leaching temperature of 90°C for 2 hours with stirring. In stage 2, overflow from stage 3 is used to slurry the underflow from stage 1, maintaining a liquid-to-solid ratio of 3:1 and a leaching temperature of 80°C for 1 hour with stirring. In stage 3, pure water is added to perform final washing of the underflow from stage 2, maintaining a liquid-to-solid ratio of 2:1 and stirring at room temperature for 1 hour. After washing, solid-liquid separation is achieved, yielding lithium slag and overflow.

[0058] Step S2: Collect the overflow liquid after the first-stage solid-liquid separation, which is the finished lithium-rich solution.

[0059] Step S3: 10% of the volume of circulating liquid is drawn from the overflow liquid after the second-stage solid-liquid separation and sent to the impurity removal unit.

[0060] In step S4, in the impurity removal unit, sodium hydroxide is first added to adjust the pH to 11. Then, a defluorinating agent (commercially available defluorinating agent) at a flow rate of 10‰ of the circulating liquid side flow rate is added for defluorination treatment. When the pH stabilizes at 6.5, a flocculant (commercially available flocculant) at a flow rate of 2‰ of the circulating liquid side flow rate is added for flocculation and precipitation. After solid-liquid separation, a defluorinated clear liquid is obtained. The defluorinated clear liquid is then pumped into a cryo-crystallizer and cooled to 5°C for cryo-crystallization, precipitating sodium sulfate decahydrate and potassium sulfate double salt. After centrifugation, a purified liquid is obtained.

[0061] Step S5: After preheating the purified liquid to 60°C, return it to the second-stage leaching system for circulation.

[0062] Step S6: During system operation, the concentration of fluoride ions in the circulating liquid is monitored online. When the concentration of fluoride ions exceeds 3 mg / L, the amount of circulating liquid drawn out from the side flow is increased.

[0063] Example 4 This embodiment uses the same lithium mica sulfate roasted clinker and five-stage countercurrent leaching system as Example 1. The specific steps are as follows: Step S1: Construct a five-stage leaching and solid-liquid separation system, using a belt filter for solid-liquid separation. Fresh clinker is added from stage 1, and wash water is added from stage 5. In stage 1, fresh clinker is added and pulped with overflow from stage 2, maintaining a liquid-to-solid ratio of 3:1 and a leaching temperature of 90°C for 2 hours with stirring. In stage 2, overflow from stage 3 is used to pulp the underflow from stage 1, maintaining a liquid-to-solid ratio of 3:1 and a leaching temperature of 80°C for 1 hour with stirring. In stage 3, overflow from stage 4 is used to pulp the underflow from stage 2, maintaining a liquid-to-solid ratio of 2:1 and a leaching temperature of 60°C for 1 hour with stirring. In stage 4, overflow from stage 5 is used to pulp the underflow from stage 3, maintaining a liquid-to-solid ratio of 2:1 and a leaching temperature of 60°C for 1 hour with stirring. In the fifth stage, pure water is added to perform the final washing of the underflow from the fourth stage. The liquid-to-solid ratio is 2:1, and the mixture is stirred at room temperature for 1 hour. After washing, the solid and liquid are separated to obtain lithium slag and overflow liquid.

[0064] Step S2: Collect the overflow liquid after the first-stage solid-liquid separation, which is the finished lithium-rich solution.

[0065] Step S3: 10% of the volume of circulating liquid is drawn from the overflow liquid after the second-stage solid-liquid separation and sent to the impurity removal unit.

[0066] In step S4, in the impurity removal unit, sodium hydroxide is first added to adjust the pH to 11. Then, a defluorinating agent (commercially available defluorinating agent) at a flow rate of 10‰ of the circulating liquid side flow rate is added for defluorination treatment. When the pH stabilizes at 6.5, a flocculant (commercially available flocculant) at a flow rate of 2‰ of the circulating liquid side flow rate is added for flocculation and precipitation. After solid-liquid separation, a defluorinated clear liquid is obtained. The defluorinated clear liquid is then pumped into a cryo-crystallizer and cooled to 5°C for cryo-crystallization, precipitating sodium sulfate decahydrate and potassium sulfate double salt. After centrifugation, a purified liquid is obtained.

[0067] Step S5: After preheating the purified liquid to 60°C, return it to the second-stage leaching system for circulation.

[0068] Step S6: During system operation, the concentration of fluoride ions in the circulating liquid is monitored online. When the concentration of fluoride ions exceeds 3 mg / L, the amount of circulating liquid drawn out from the side flow is increased.

[0069] Comparative Example 1 This comparative example does not include a bypass for impurity removal; it only employs a four-stage countercurrent leaching cycle. The raw materials, number of stages, and leaching conditions are the same as in Example 1. The difference is that all overflow liquid is returned to the system circulation, and no circulating liquid is drawn off for defluorination and freeze crystallization. The specific steps are as follows: Step S1: Construct a four-stage leaching and solid-liquid separation system, using a belt filter for solid-liquid separation. Fresh clinker is added from stage 1, and wash water is added from stage 4. In stage 1, fresh clinker is added and slurried with overflow from stage 2, maintaining a liquid-to-solid ratio of 3:1 and a leaching temperature of 90°C for 2 hours with stirring. In stage 2, overflow from stage 3 is used to slurry the underflow from stage 1, maintaining a liquid-to-solid ratio of 3:1 and a leaching temperature of 80°C for 1 hour with stirring. In stage 3, overflow from stage 4 is used to slurry the underflow from stage 2, maintaining a liquid-to-solid ratio of 2:1 and a leaching temperature of 60°C for 1 hour with stirring. In stage 4, clean water is added to perform a final wash on the underflow from stage 3, maintaining a liquid-to-solid ratio of 2:1 and stirring at room temperature for 1 hour. After washing, solid-liquid separation is performed to obtain lithium slag and overflow.

[0070] Step S2: Collect the overflow liquid after the first-stage solid-liquid separation, which is the finished lithium-rich solution.

[0071] In step S3, all overflow liquid after solid-liquid separation at each stage is returned to the system for recycling, and the concentrations of fluoride ions and potassium ions in the overflow liquid are monitored.

[0072] Comparative Example 2 This comparative example uses a bypass for impurity removal, but only employs freeze crystallization treatment; no defluorinating agent is added for the defluorination reaction. All other conditions are the same as in Example 1. The specific steps are as follows: Step S1: Construct a four-stage leaching and solid-liquid separation system, using a belt filter for solid-liquid separation. Fresh clinker is added from stage 1, and wash water is added from stage 4. In stage 1, fresh clinker is added and slurried with overflow from stage 2, maintaining a liquid-to-solid ratio of 3:1 and a leaching temperature of 90°C for 2 hours with stirring. In stage 2, overflow from stage 3 is used to slurry the underflow from stage 1, maintaining a liquid-to-solid ratio of 3:1 and a leaching temperature of 80°C for 1 hour with stirring. In stage 3, overflow from stage 4 is used to slurry the underflow from stage 2, maintaining a liquid-to-solid ratio of 2:1 and a leaching temperature of 60°C for 1 hour with stirring. In stage 4, clean water is added to perform a final wash on the underflow from stage 3, maintaining a liquid-to-solid ratio of 2:1 and stirring at room temperature for 1 hour. After washing, solid-liquid separation is performed to obtain lithium slag and overflow.

[0073] Step S2: Collect the overflow liquid after the first-stage solid-liquid separation, which is the finished lithium-rich solution.

[0074] Step S3: 10% of the volume of circulating liquid is drawn from the overflow liquid after the second-stage solid-liquid separation and sent to the impurity removal unit.

[0075] In step S4, in the impurity removal unit, the circulating liquid is directly pumped into the freeze crystallizer and cooled to 5°C for freeze crystallization to precipitate sodium sulfate decahydrate and potassium sulfate double salt. After centrifugation, the purified liquid is obtained.

[0076] Step S5: After preheating the purified liquid to 55°C, return it to the second-stage leaching system for circulation.

[0077] Step S6: During system operation, monitor the concentrations of fluoride ions and potassium ions in the circulating fluid online.

[0078] Comparative Example 3 This comparative example uses a bypass for impurity removal, but only employs a defluorinating agent and does not undergo a freeze-crystallization process. All other conditions are the same as in Example 1. The specific steps are as follows: Step S1: Construct a four-stage leaching and solid-liquid separation system, using a belt filter for solid-liquid separation. Fresh clinker is added from stage 1, and wash water is added from stage 4. In stage 1, fresh clinker is added and slurried with overflow from stage 2, maintaining a liquid-to-solid ratio of 3:1 and a leaching temperature of 90°C for 2 hours with stirring. In stage 2, overflow from stage 3 is used to slurry the underflow from stage 1, maintaining a liquid-to-solid ratio of 3:1 and a leaching temperature of 80°C for 1 hour with stirring. In stage 3, overflow from stage 4 is used to slurry the underflow from stage 2, maintaining a liquid-to-solid ratio of 2:1 and a leaching temperature of 60°C for 1 hour with stirring. In stage 4, clean water is added to perform a final wash on the underflow from stage 3, maintaining a liquid-to-solid ratio of 2:1 and stirring at room temperature for 1 hour. After washing, solid-liquid separation is performed to obtain lithium slag and overflow.

[0079] Step S2: Collect the overflow liquid after the first-stage solid-liquid separation, which is the finished lithium-rich solution.

[0080] Step S3: 10% of the volume of circulating liquid is drawn from the overflow liquid after the second-stage solid-liquid separation and sent to the impurity removal unit.

[0081] In step S4, sodium hydroxide is first added to the impurity removal unit to adjust the pH to 11. Then, a defluorinating agent (commercially available defluorinating agent) equivalent to 10‰ of the circulating liquid side flow rate is added. When the pH stabilizes at 6.5, a flocculant (commercially available flocculant) equivalent to 2‰ of the circulating liquid side flow rate is added for flocculation and precipitation. After solid-liquid separation, a defluorinated clear liquid is obtained.

[0082] In step S5, the defluorinated solution is preheated to 60°C and then directly returned to the second-stage leaching system to participate in the circulation, without undergoing freeze crystallization treatment.

[0083] Step S6: During system operation, monitor the concentrations of fluoride ions and potassium ions in the circulating fluid online.

[0084] The ion concentrations in the lithium-rich leachates obtained from the above embodiments and comparative examples were measured, and the results are shown in Table 1. The system operational stability and product quality results for each embodiment and comparative example are shown in Table 2.

[0085] Table 1 Comparison of ion concentrations between each example and the comparative example

[0086] As shown in Table 1, after using a combined bypass treatment of defluorination and freeze crystallization in Examples 1-4, the concentration of fluoride ions in the circulating liquid was stably controlled below 2.0 mg / L, and the concentrations of potassium and sodium ions were within the controllable range of the process. The lithium ion concentration in the finished lithium-rich solution reached 8.01~8.68 g / L, achieving efficient enrichment of lithium and effective balance of impurity ions. In Comparative Example 1, without bypass impurity removal, the concentrations of fluoride, potassium, and sodium ions were significantly increased, with the fluoride ion concentration reaching 4.5 mg / L, indicating that impurities accumulate rapidly under closed-loop circulation. In Comparative Example 2, only freeze crystallization was performed without defluorination treatment. Although potassium and sodium ions were well controlled, the fluoride ion concentration still reached 3.9 mg / L, indicating that the absence of defluorination treatment would lead to a significant increase in fluoride ions in the system. In Comparative Example 3, only defluorination was performed without freeze crystallization, and the concentrations of potassium and sodium ions increased to about twice that of Example 1, while the lithium ion concentration was significantly lower, indicating that the absence of freeze crystallization would lead to a significant increase in sodium and potassium content and an increase in system viscosity, thereby affecting the lithium leaching rate. Therefore, it can be seen that the combined implementation of defluorination and freeze crystallization can simultaneously solve the problem of multiple impurity accumulation.

[0087] Table 2 Comparison of system operation and product quality between each embodiment and the comparative example

[0088] As shown in Table 2, after bypass purification in Examples 1-4, the system maintained a continuous and stable operation cycle of over 12 days, with the lithium carbonate product purity consistently above 99.1%, the soluble lithium loss in the final slag as low as 0.001%, the total lithium recovery rate reaching 99.9%, and the purity of the by-product alkali metal sulfate reaching 99.9%, achieving high-quality recovery of potassium and sodium resources. Comparative Example 1, without bypass treatment, had a significantly shorter operating cycle, and both lithium carbonate purity and lithium recovery rate were significantly lower. Comparative Example 2 only underwent freeze crystallization without defluorination, resulting in all indicators being inferior to Example 1. Comparative Example 3 only underwent defluorination without freeze crystallization, resulting in the shortest operating cycle, the lowest lithium carbonate purity and lithium recovery rate, and the highest soluble lithium loss in the final slag. This indicates that without defluorination and freeze crystallization treatment of the overflow liquid, not only will the lithium carbonate purity fail to meet standards, but it will also lead to an increase in soluble lithium in the slag and a decrease in the lithium recovery rate.

[0089] The above results show that the present invention, through a multi-stage countercurrent leaching process combined with defluorination and freeze crystallization bypass purification, can ensure the efficient enrichment and recovery of lithium, extend the stable operation cycle of the system, and obtain high-purity by-products.

[0090] The above description is merely an exemplary embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention's specification and drawings under the technical concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A method for processing lithium mica sulfate roasted clinker, characterized in that, Includes the following steps: Step S1: Construct at least three processing units in series, including a first-end processing unit, a middle processing unit, and a last-end processing unit. Lithium mica sulfate roasted clinker is added from the first-end processing unit, and washing water is added from the last-end processing unit, so that the solid phase and the liquid phase form a countercurrent contact. Step S2: Collect the overflow liquid after solid-liquid separation in the first-end processing unit as the finished lithium-rich solution; Step S3: A portion of the circulating liquid side flow is continuously or intermittently drawn from the central processing unit and sent to the impurity removal unit; Step S4: In the impurity removal unit, defluorination treatment is performed first. After the treatment is completed, the obtained defluorinated liquid is frozen and crystallized. After separating the precipitated alkali metal sulfates, a purified liquid is obtained. Step S5: After preheating the purified liquid, it is returned to the central processing unit to participate in the circulation.

2. The processing method of lithium mica sulfate roasted clinker as described in claim 1, characterized in that, In step S3, the amount of circulating liquid drawn out is 5-20% of the overflow volume of the central treatment unit.

3. The processing method of lithium mica sulfate roasted clinker as described in claim 1, characterized in that, In step S4, the defluorination treatment includes: first adding alkali to adjust the pH to 10-12, then adding a defluorinating agent for defluorination treatment, and after the pH stabilizes to 6-7, adding a flocculant for solid-liquid separation to obtain a defluorinated clear liquid.

4. The processing method of lithium mica sulfate roasted clinker as described in claim 3, characterized in that, The amount of the defluorinating agent added is 8-15‰ of the circulating liquid side flow rate; And / or, the amount of flocculant added is 1 to 3‰ of the circulating liquid side flow rate.

5. The processing method of lithium mica sulfate roasted clinker as described in claim 1, characterized in that, In step S4, the temperature of the freeze-crystallization is 0~10℃; And / or, the alkali metal sulfate is mainly a double salt of sodium sulfate decahydrate and potassium sulfate.

6. The processing method of lithium mica sulfate roasted clinker as described in claim 1, characterized in that, In step S5, the preheating involves preheating the purified liquid to 40~80℃.

7. The processing method of lithium mica sulfate roasted clinker as described in claim 1, characterized in that, In step S1, the leaching temperature of the first-end treatment unit is 80~95℃, and the leaching temperature decreases step by step along the series connection direction of the treatment units. The tail-end treatment unit is a room temperature washing unit. And / or, the leaching liquid-to-solid ratio of the first-end treatment unit is 2~5:1, the leaching liquid-to-solid ratio of the middle treatment unit is 1~3:1, and the washing liquid-to-solid ratio of the tail-end treatment unit is 1~3:

1. And / or, the immersion time of the first-end treatment unit is 1-3 hours, the immersion time of the middle treatment unit is 1-3 hours, and the washing time of the tail-end treatment unit is 1-3 hours.

8. The processing method of lithium mica sulfate roasted clinker as described in claim 1, characterized in that, It also includes step S6: by monitoring the concentration of fluoride ions and / or potassium ions and / or sodium ions in the circulating liquid online, when the concentration of fluoride ions and / or potassium ions and / or sodium ions exceeds a preset threshold, the amount of circulating liquid side flow drawn out in step S3 and / or the amount of washing water added in step S1 is increased.

9. The processing method of lithium mica sulfate roasted clinker as described in claim 8, characterized in that, The preset threshold for the fluoride ion concentration is less than 3 mg / L; And / or, the preset threshold for the potassium ion concentration is less than 10 g / L; And / or, the preset threshold for sodium ion concentration is less than 16 g / L.

10. A lithium-containing product prepared by processing lithium mica sulfate roasted clinker as described in any one of claims 1 to 9.

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