Method and system for preparing lithium carbonate by roasting lithium mica composite sulfate

Abstract

A method and system for preparing lithium carbonate by calcining lepidolite composite sulfate, the method comprising: step 1, mixing lepidolite and sulfate and calcining to obtain calcined material, wherein the mass ratio of lepidolite to sulfate is 1:(0.5-3); step 2, leaching lithium ions from the calcined material in a leaching agent to obtain a lithium-containing leachate; step 3, adding sodium carbonate solution to the lithium-containing leachate, stirring and reacting to obtain a precipitate mother liquor and lithium carbonate, recycling the precipitate mother liquor, and recovering the lithium carbonate. This application improves lithium extraction efficiency and lithium carbonate purity by optimizing the ratio of sulfate to lepidolite; by optimizing the calcination process, higher lithium conversion rate, lithium extraction efficiency, and extraction purity can be achieved, while significantly reducing energy consumption, lowering costs, and reducing environmental impact.

Description

Technical Field

[0001] This application relates to the field of lithium extraction technology, and in particular to a method and system for preparing lithium carbonate by roasting lepidolite composite sulfate. Background Technology

[0002] Lepidolite, also known as lepidolite, is an important mineral resource containing abundant rare metals such as lithium, sodium, potassium, rubidium, cesium, and aluminum. Lepidolite is the most common lithium mineral and a crucial source of lithium for lithium extraction. Lithium and its salts are fundamental materials for lithium-ion batteries, earning it the title of "industrial MSG" and "energy star" from scientists. It is the best material for producing lithium-ion batteries and a vital metal for developing new energy sources and materials. Therefore, the comprehensive development and utilization of lepidolite has significant economic and strategic value.

[0003] Traditional methods for extracting lithium typically involve roasting and acid leaching of lepidolite. However, these methods suffer from low extraction efficiency, high costs, and severe environmental pollution, and therefore urgently need improvement. Summary of the Invention

[0004] In view of this, in order to solve at least one of the above-mentioned defects, embodiments of this application provide a method for preparing lithium carbonate by calcination of lithium mica composite sulfate, which can improve...

[0005] Additionally, this application also provides a system for preparing lithium carbonate by roasting lepidolite composite sulfate as described above.

[0006] This application provides a method for preparing lithium carbonate by roasting lithium mica composite sulfate, including:

[0007] Step 1: Mix lepidolite and sulfate and calcine to obtain calcined material, wherein the mass ratio of lepidolite to sulfate is 1:(0.5-3);

[0008] Step 2: Leach lithium ions from the roasted material in a leaching agent to obtain a lithium-containing leachate; and

[0009] Step 3: Add sodium carbonate solution to the lithium-containing leachate, stir and react to obtain precipitate mother liquor and lithium carbonate, recycle the precipitate mother liquor and recover the lithium carbonate.

[0010] In some possible embodiments, the sulfate includes sodium sulfate, potassium sulfate, calcium sulfate, and magnesium sulfate, and

[0011] The formulation of lepidolite complex sulfate, calculated as a percentage by weight, includes:

[0012] Lithium mica: 50-80%;

[0013] Sodium sulfate: 5-20%;

[0014] Potassium sulfate: 5-20%;

[0015] Calcium sulfate: 2-10%; and

[0016] Magnesium sulfate: 2-10%.

[0017] In some possible embodiments, in step 2, the calcination temperature is 800℃~900℃ and the calcination time is 1 hour~2 hours.

[0018] In some possible embodiments, in step 3, the leaching agent includes sulfuric acid;

[0019] The leaching temperature is 80℃~100℃, and the leaching time is 2 hours~4 hours;

[0020] The volume ratio of the leaching agent to the calcined material is (3-10):1.

[0021] In some possible embodiments, prior to step 1, the method further includes:

[0022] The lepidolite is purified by electrochemical etching, the electrochemical etching method comprising:

[0023] An electrolyte is added to an electrochemical cell, with lepidolite as the anode and an inert metal as the cathode, and electrochemical etching is carried out under the protection of an inert gas.

[0024] The concentration of the electrolyte is 0.5M to 2M;

[0025] The flow rate of the inert gas is 1–5 L / min;

[0026] The parameters for the electrochemical etching are: initial voltage of 1–5 V, and current density of 50–200 Ma / cm². 2 The etching time is 1 to 6 hours, and the temperature of the electrolyte is room temperature to 40°C.

[0027] In some possible embodiments, the method further includes, in steps 1 to 3:

[0028] The waste heat from steps 1 to 3 is recovered and recycled; and / or,

[0029] Renewable energy sources are used as a portion of the energy supply in steps 1 to 3.

[0030] In some possible embodiments, a heat exchanger is used in step 1 to recover the waste heat generated during the roasting process;

[0031] In steps 2 and 3, a heat pump system is used to recover the heat energy generated during the leaching and purification processes, and the heat energy is recycled.

[0032] In some possible embodiments, heat recovery using the heat pump system includes the steps of:

[0033] Heat source identification: Identify the available heat sources in the leaching and purification processes, and measure the temperature and available thermal energy of the heat sources to obtain the design parameters of the heat pump system;

[0034] Heat sink selection: Determining the location where the heat energy can be transferred and utilized;

[0035] Heat pump type selection: Select the heat pump type based on the temperature difference between the heat source and the heat sink;

[0036] The capacity and efficiency of the heat pump system are determined based on the design parameters, the heat sink, and the type of heat pump.

[0037] Installation and integration of heat pump systems; and

[0038] The heat pump system is equipped with an intelligent control system to monitor and adjust the operating parameters of the heat pump system in real time.

[0039] This application also provides a system for preparing lithium carbonate by roasting lepidolite composite sulfate as described above. The system includes a roasting furnace, a leaching tank, and a lithium precipitation tank connected in sequence, and the system is a closed-loop system.

[0040] In some possible embodiments, the system further includes an electrochemical etching device, a heat exchanger, and a heat pump system, wherein the electrochemical etching device is used to purify the lepidolite, the heat exchanger is used to recover the waste heat generated in step 1, and the heat pump system is used to recover the heat energy generated in steps 2 and 3 and to recycle the heat energy.

[0041] The method for preparing lithium carbonate by roasting lepidolite composite sulfate provided in this application can improve the lithium extraction efficiency and lithium carbonate purity by optimizing the ratio of sulfate to lepidolite. By optimizing the roasting process, higher lithium conversion rate, lithium extraction efficiency, and extraction purity can be achieved, while significantly reducing energy consumption, lowering costs, and reducing environmental impact. The use of a closed-loop system can reduce waste gas emissions and recover and reuse heat energy, further reducing energy consumption and environmental pollution. In addition, the purification of lepidolite raw materials using erosion optimization technology can effectively improve the conversion and leaching efficiency of lithium ions in lepidolite, save energy, and improve the purity of the final product. Attached Figure Description

[0042] Figure 1 This is a flowchart of a method for preparing lithium carbonate by roasting lepidolite composite sulfate according to an embodiment of this application.

[0043] Figure 2 This is a framework diagram of a system for preparing lithium carbonate by roasting lepidolite composite sulfate according to an embodiment of this application.

[0044] Explanation of main component symbols

[0045] A system for preparing lithium carbonate by roasting lepidolite composite sulfate 100; roasting furnace 1; rotary furnace 2; leaching tank 3; lithium precipitation tank 4; electrochemical etching equipment 5; heat exchanger 6; heat pump system 7; controller 8. Detailed Implementation

[0046] The following specific embodiments illustrate the implementation of this application. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification. Although the description of this application is presented in conjunction with embodiments, this does not mean that the features of this application are limited to this embodiment. On the contrary, the purpose of describing the application in conjunction with embodiments is to cover other options or modifications that may be derived based on the claims of this application. To provide a thorough understanding of this application, many specific details will be included in the following description. This application may also be implemented without using these details. Furthermore, to avoid confusion or obscuring the focus of this application, some specific details will be omitted in the description. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other.

[0047] In the following description, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "multiple" means two or more.

[0048] The embodiments of this application are described below with reference to the accompanying drawings. Unless otherwise specified, the data range values ​​recorded in this application shall include the end values.

[0049] Please see Figure 1 This application provides a method for preparing lithium carbonate by roasting lepidolite composite sulfate, comprising:

[0050] Step 1: Lithium mica and sulfate are mixed and calcined to obtain calcined material, wherein the mass ratio of lithium mica to sulfate is 1:(0.5-3).

[0051] Step 2: Leach lithium ions from the roasted material in a leaching agent to obtain a lithium-containing leachate.

[0052] Step 3: Add sodium carbonate solution to the lithium-containing leachate, stir and react to obtain precipitate mother liquor and lithium carbonate, recycle the precipitate mother liquor and recover the lithium carbonate.

[0053] Step 1 is the roasting process of lepidolite composite sulfate. Steps 2 and 3 are the lithium leaching and purification steps, respectively. After roasting the lepidolite composite sulfate, the key steps are lithium leaching and purification. This process involves transferring lithium from the roasted solid material into a solution and obtaining high-purity lithium carbonate through a series of purification steps.

[0054] In step 1, the sulfate is a complex sulfate, and the ratio and preparation of the complex sulfate are key steps that directly affect the lithium extraction efficiency and product quality.

[0055] In some embodiments, the mass ratio of lepidolite to sulfate can be further 1:(0.5-2), or further 1:(0.5-1). Exemplarily, the mass ratio of lepidolite to sulfate can be 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1, 1:1.2, 1:1.4, 1:1.6, 1:1.8, 1:2, 1:2.2, 1:2.4, 1:2.6, 1:2.8, or 1:3, etc. By controlling the mass ratio of lepidolite to sulfate, lithium can be fully transferred out of the lepidolite, which is beneficial to improving the lithium transfer efficiency.

[0056] In some embodiments, considering factors such as the chemical composition of lepidolite, process efficiency, and environmental friendliness, sodium sulfate, potassium sulfate, calcium sulfate, and magnesium sulfate are selected as the composite sulfate. The formulation of the lepidolite composite sulfate, calculated by mass percentage, includes: lepidolite: 50-80%; sodium sulfate: 5-20%; potassium sulfate: 5-20%; calcium sulfate: 2-10%; and magnesium sulfate: 2-10%. Selecting these sulfates as the composite sulfate is environmentally friendly, has low corrosiveness to equipment, and reduces safety hazards to operators. Furthermore, by precisely controlling the ratio of the composite sulfate to lepidolite, the roasting process can be optimized, effectively improving the reactivity of lepidolite, thereby increasing the lithium conversion and leaching rates.

[0057] In some embodiments, other additives besides sulfates may be added to the lepidolite raw material, such as carbonate additives, oxidants, silicate additives, fluxes, and organic additives. Among these, carbonate additives, such as calcium carbonate, sodium carbonate, and magnesium carbonate, can decompose at high temperatures, releasing carbon dioxide gas, thereby reducing agglomeration and improving the porosity of the calcined material. Oxidants, such as nitrates (e.g., sodium nitrate or potassium nitrate), release oxygen at high temperatures, promoting the combustion and decomposition of organic matter and reducing agglomeration and ring formation. Silicate additives, such as sodium silicate (water glass), can form a low-melting-point glass phase at high temperatures, helping to prevent excessive sintering and agglomeration of the material. Fluxes, such as boric acid or fluorides (e.g., sodium fluoride, calcium fluoride), lower the melting point of the material at high temperatures, helping to improve the calcination process and reduce agglomeration. Organic additives such as sawdust, carbon powder, or other organic materials burn during roasting, creating pores that increase the porosity of the roasted material, facilitating subsequent processing and lithium leaching. Therefore, the addition of these additives can reduce material agglomeration and rotary kiln ring formation during roasting, while also making the roasted material more porous, easier to crush, and facilitating lithium ion leaching. Selecting appropriate additives and adjusting their dosage is crucial for improving roasting efficiency and lithium extraction. Furthermore, both environmental and economic factors must be considered when selecting additives.

[0058] Before step 1, the method further includes: purifying lepidolite using erosion optimization to improve the efficiency and purity of the lepidolite purification process.

[0059] Improving the purification efficiency of lepidolite using erosion optimization technology includes: determining key parameters in the purification process and applying erosion optimization technology.

[0060] Step A1: Determine the key parameters in the purification process. The specific method is as follows:

[0061] Analysis of existing process problems: The existing process for lepidolite purification is analyzed to identify potential bottlenecks in the current purification process, such as difficulty in improving the efficiency of lithium extraction from lepidolite and low purity of extracted lithium carbonate.

[0062] Define the goals of erosion optimization: Based on the problem to be solved, define the goals of erosion optimization, namely, clarify that erosion optimization should focus on improving purification efficiency, reducing energy consumption, and improving the purity of the final product.

[0063] Step A2: Applying Erosion Optimization Techniques: This requires careful consideration of the material's chemical properties and the characteristics of the erosion process. The following is a more detailed description of the steps:

[0064] Step 1: Select a suitable erosion optimization method

[0065] First, assess the chemical properties of lepidolite: analyze the chemical composition and structure of lepidolite in detail to determine the most suitable melting method (e.g., chemical melting, electrochemical melting, or physical melting).

[0066] Secondly, select the etchant: based on the solubility characteristics of lepidolite, select a suitable etchant, such as a strong acid, strong alkali, or a specific solvent.

[0067] Finally, consider the erosion environment: determine the environmental conditions required during the erosion process, such as temperature, pressure, and atmosphere (inert gas protection, oxidizing or reducing atmosphere).

[0068] Step 2: Optimize erosion parameters

[0069] First, temperature and pressure control: Determine the optimal temperature and pressure settings during the melting process to optimize melting efficiency and reduce unnecessary material loss.

[0070] Secondly, adjust the flux concentration and flow rate.

[0071] Precise control of the concentration and flow rate of the etchant is essential to achieve optimal etchant action and minimize side reactions.

[0072] Secondly, time control: Determine the optimal duration of the erosion process to ensure sufficient purification while avoiding resource waste caused by excessive erosion.

[0073] Finally, continuous monitoring and adjustment: monitor the melting process in real time and adjust parameters as needed to ensure the stability and repeatability of the process.

[0074] Step 3, Post-etching treatment

[0075] Cleaning and Neutralization: After etching is complete, thoroughly clean the product to remove any residual etching agent. If necessary, use an appropriate neutralizing agent to neutralize any acidic or alkaline substances produced during the etching process.

[0076] Drying and Separation: The purified lepidolite is dried to remove moisture. Appropriate separation techniques (such as centrifugation and filtration) are used to separate the purified product from the byproducts.

[0077] Quality control: quality inspection and process adjustment

[0078] Qualitative and quantitative analyses are performed on the purified product to ensure it meets the expected purity and quality standards. Based on the quality test results, necessary adjustments can be made to the etching process to ensure consistent product quality and process reliability.

[0079] The purification process of lepidolite using the etching optimization technique in this application is a multi-step, multi-parameter integrated process. By precisely controlling each step, the purification efficiency of lepidolite can be significantly improved, while ensuring high product purity and good economic benefits. When implementing this technology, close attention needs to be paid to the adjustment of process parameters and quality control to achieve the best results.

[0080] Specifically, this embodiment uses the application of electrochemical etching optimization to purify lepidolite as an example to explain step A2 (application of etching optimization technology) in detail.

[0081] A strong acid solution (such as sulfuric acid or hydrochloric acid) is selected as the etchant. An inert gas (such as argon or nitrogen) is used for protection throughout the etch process to prevent oxidation and contamination.

[0082] Step 1: Setting up the electrochemical etching system

[0083] An electrochemical cell is used, with lepidolite as the anode and an inert metal (such as platinum) as the cathode. The electrolyte can be a strong acid, with a concentration of approximately 0.5 M to 2 M.

[0084] Step 2, inert gas protection

[0085] Argon or nitrogen gas is introduced into the upper part of the electrochemical tank, and the flow rate is controlled at 1-5 L / min.

[0086] Step 3: Optimization of electrochemical erosion parameters

[0087] Voltage and current control: The initial voltage can be set between 1-5V and gradually adjusted according to the progress of the erosion reaction. The current density can be controlled between 50-200mA / cm². 2 .

[0088] Erosion time: Depending on the thickness and purity requirements of the lepidolite, the erosion time can be controlled between 1 and 6 hours.

[0089] Temperature control: The temperature of the electrolyte can be maintained between room temperature and 40°C.

[0090] Stirring and Flowing: The electrolyte is gently stirred to maintain a uniform electrochemical reaction environment.

[0091] Step 4: Post-processing and analysis

[0092] Cleaning and neutralization: After the etching is completed, use deionized water to clean the etching products, and then neutralize the residual acidity with a weak alkaline solution.

[0093] Drying and separation: The purified lepidolite is dried and then separated by physical methods (such as filtration).

[0094] Quality inspection: X-ray diffraction, electron microscopy and other methods are used to analyze the purity and microstructure of the product.

[0095] Evaluation and adjustment of erosion optimization effects: Monitor purification efficiency and product quality, and use appropriate analytical and detection methods (such as X-ray diffraction and electron microscopy) to evaluate the quality of purified lepidolite.

[0096] Optimization and Adjustment: Based on the evaluation results, the erosion parameters are further adjusted and optimized.

[0097] Step 5: Integrate erosion optimization technology into the overall process of lithium carbonate preparation.

[0098] Ensure process continuity: Ensure seamless integration of erosion optimization technology with the preceding and subsequent process steps of lithium carbonate preparation to maintain the efficiency and stability of the entire production process.

[0099] Environmental and safety factors are taken into consideration: Environmental protection and operational safety are taken into account during the optimization process to ensure that erosion optimization does not introduce additional environmental or safety risks.

[0100] This embodiment demonstrates that, through the steps described above, leaching optimization technology can be effectively applied to the purification process of lepidolite to improve the conversion and leaching efficiency of lithium ions in lepidolite, save energy, and enhance the purity of the final product. This approach requires adjustments based on specific production conditions and equipment capabilities to ensure optimal implementation results.

[0101] In step 1, the roasting process aims to promote the chemical reaction between sulfate and lepidolite through high-temperature treatment, thereby releasing lithium ions and facilitating the subsequent leaching process. Process control during roasting is crucial to the conversion rate of lithium in lepidolite, leaching efficiency, and purity of lithium carbonate.

[0102] In some embodiments, the calcination temperature is 800℃~900℃, further 820℃~860℃, for example, the calcination temperature can be 800℃, 810℃, 820℃, 830℃, 840℃, 850℃, 860℃, 870℃, 880℃, 890℃, or 900℃. If the calcination temperature is too low, the chemical reaction cannot be fully activated; while if the calcination temperature is too high, it may lead to the volatilization of lithium ions or unnecessary energy waste. Therefore, this embodiment controls the calcination temperature within the above temperature range, which allows the lepidolite to undergo a sufficient chemical reaction, improving the lithium conversion rate, while also reducing the volatilization of converted lithium ions and reducing energy consumption. Furthermore, by controlling the heating rate to ensure a uniform increase in calcination temperature, it is possible to ensure that the material is heated evenly during the calcination process, improving reaction efficiency and making the reaction more complete, avoiding localized overheating or non-reaction due to excessively rapid heating, and preventing the lepidolite raw material from breaking or agglomerating due to excessively rapid temperature rise.

[0103] In some embodiments, the calcination time can be 1 to 2 hours, more specifically 1 to 1.5 hours. For example, the calcination temperature can be 1 hour, 1.1 hours, 1.2 hours, 1.3 hours, 1.4 hours, 1.5 hours, 1.6 hours, 1.7 hours, 1.8 hours, 1.9 hours, or 2 hours, etc. If the calcination time is too short, the reaction will be incomplete; if the calcination time is too long, it may lead to energy waste without significant improvement. Therefore, this embodiment controls the calcination time within the above range, which allows for the full conversion of lithium ions in the lepidolite while saving energy and improving efficiency.

[0104] In some embodiments, atmosphere control is also required during the roasting process to maintain a slightly oxidizing atmosphere and prevent the reduction and loss of lithium in the lepidolite.

[0105] In some embodiments, the roasting process requires the use of a roasting furnace capable of withstanding high temperatures and possessing good chemical stability to ensure the safety and efficiency of the process. Simultaneously, certain environmental protection measures should be implemented, ensuring adequate ventilation during the preparation process to prevent sulfate dust from posing health risks to operators.

[0106] Specifically, step 1 includes the following steps:

[0107] Preheating: Slowly heat the container containing the mixture to the calcination temperature to prevent the material from breaking or clumping due to excessively rapid temperature rise.

[0108] Temperature maintenance: Maintain the set roasting temperature for a period of time to ensure the complete chemical reaction.

[0109] Cooling: After calcination, allow the material to cool naturally to room temperature in a closed environment to prevent the loss of lithium ions through volatilization.

[0110] Post-processing: The cooled material is crushed and screened to obtain roasted powder of suitable particle size, in preparation for the subsequent leaching process.

[0111] During the roasting process in step 1, the quality of the sulfate raw materials used needs to be tested regularly to ensure their purity and reactivity. This embodiment optimizes the roasting process in step 1, enabling the release of lithium from lepidolite at a higher efficiency, thus providing a good foundation for subsequent leaching and purification steps.

[0112] In step 2, leaching conditions (such as the type of leaching agent, leaching temperature, leaching time, and the ratio of leaching agent to solids) will affect the leaching rate of lithium ions in the calcined material.

[0113] In some embodiments, sulfuric acid is typically used as a leaching agent because it can effectively extract lithium from the roasted product.

[0114] In some embodiments, the leaching temperature is 80°C to 100°C, more specifically 85°C to 95°C. For example, the leaching temperature can be 80°C, 85°C, 90°C, 95°C, or 100°C. Leaching under these temperature conditions can accelerate the reaction rate and improve the lithium leaching efficiency.

[0115] In some embodiments, the leaching time can be 2 to 4 hours to ensure sufficient leaching of lithium.

[0116] In some embodiments, the volume ratio of the leaching agent to the calcined material can be 10:1 to ensure sufficient contact and reaction.

[0117] In some embodiments, continuous stirring is required during the leaching process to ensure a uniform reaction.

[0118] In some embodiments, after the leaching reaction is completed, the solid and liquid are separated, and the lithium-containing leachate is collected.

[0119] Step 3 is the purification process, mainly involving the purification of the lithium-containing leachate and the precipitation of lithium carbonate, specifically including the following steps:

[0120] Step 1: Remove impurities

[0121] Impurity elements (such as iron, calcium, and magnesium) in the solution are removed by methods such as precipitation and ion exchange. Sodium carbonate or sodium bicarbonate is used to adjust the pH value to precipitate and remove insoluble impurities.

[0122] Specifically, during pH adjustment, the pH value is typically maintained between 8 and 11. Within this range, the hydroxide precipitates formed by most heavy metal ions (such as iron, calcium, and magnesium) are stable and can be effectively separated from the solution. More specifically, different metal ions have their own optimal pH precipitation ranges. For example, removing calcium and magnesium usually requires a pH between 9 and 10, while iron precipitation may require a slightly higher pH. Therefore, the pH can be adjusted according to the specific heavy metal impurities present during the reaction. Adjusting the pH value achieves the following beneficial effects: 1. Impurity removal: By adjusting the pH value, heavy metal ions and other insoluble impurities in the solution can be effectively precipitated and removed, thereby improving the purity of lithium ions. 2. Increased lithium recovery rate: Removing impurities that affect lithium extraction through precipitation improves lithium recovery efficiency. 3. Reduced processing difficulty and cost: Impurities precipitated within an appropriate pH range are easier to separate and process, reducing the difficulty and cost of subsequent purification steps. 4. Environmentally friendly: This method does not require the use of harmful chemicals and is relatively environmentally friendly.

[0123] Step 2, Concentration

[0124] The lithium concentration is increased by concentrating lithium-containing leachate through methods such as evaporation or reverse osmosis.

[0125] Step 3, precipitation of lithium carbonate

[0126] Sodium carbonate is added to a concentrated lithium-containing leachate to produce lithium carbonate precipitate. The precipitation efficiency and purity of lithium carbonate are optimized by controlling the pH and temperature. Furthermore, the resulting mother liquor can be recycled after treatment.

[0127] Specifically, the pH value is generally controlled between 10 and 11. Within this pH range, lithium carbonate exhibits high precipitation efficiency and effectively reduces interference from other metal ions. Furthermore, depending on the specific composition and concentration of the leachate, the pH value may need fine-tuning to improve precipitation efficiency and achieve optimal precipitation results. The temperature is typically controlled between 50°C and 70°C. Temperature control affects both the precipitation rate and crystal quality. Fine-tuning is performed within this temperature range based on specific experimental conditions to achieve the optimal temperature, ensuring the best growth and purity of lithium carbonate crystals.

[0128] By controlling the pH and temperature within the above ranges in this step, the following beneficial effects can be achieved: 1. Improved precipitation efficiency: Appropriate pH and temperature help improve the precipitation efficiency of lithium carbonate. 2. Optimized purity: Controlled conditions can reduce the co-precipitation of other ions, improving the purity of lithium carbonate. 3. Reduced energy consumption: Reasonable temperature control helps save energy and reduce operating costs. 4. Mother liquor recycling: Controlling pH and temperature allows for the maximum recovery of residual lithium ions in the mother liquor, improving resource utilization.

[0129] Step 4, Washing and Drying

[0130] The precipitated lithium carbonate is washed multiple times to remove residual impurities. The washed lithium carbonate is then dried to obtain the finished product.

[0131] The following aspects should also be noted during the entire lithium carbonate preparation process:

[0132] Firstly, environmental protection measures: attention should be paid to wastewater treatment and exhaust gas control in order to reduce the impact on the environment.

[0133] Secondly, safe operation: When using corrosive chemicals such as sulfuric acid, appropriate safety measures should be taken.

[0134] Thirdly, process monitoring: throughout the leaching and purification process, samples are taken and analyzed regularly to monitor process efficiency and product quality.

[0135] Regarding the first aspect

[0136] Specifically, this embodiment adopts a closed-loop system to reduce exhaust gas emissions; and reasonably recycles and utilizes waste residue from the process to reduce environmental pollution.

[0137] Implementing effective environmental protection measures is crucial in steps 1 through 3 (calcination of lepidolite composite sulfate and leaching and purification of lithium). These measures aim to reduce environmental impact, ensure process sustainability, and comply with relevant environmental regulations.

[0138] 1) Regarding waste gas treatment

[0139] Step 1: Treatment of roasting exhaust gas: Use high-efficiency dust removal equipment to capture the dust generated during the roasting process. Specifically, acidic substances and harmful gases in the exhaust gas can be removed using a wet scrubbing tower or spray tower. Appropriate emission reduction measures should be taken for any SOx and NOx gases that may be generated.

[0140] Step 2: Waste gas control during the leaching process: Ensure good ventilation during operation to reduce the impact of sulfuric acid vapor and other volatile substances, and use gas recovery equipment to recover and treat acidic gases generated during the leaching process.

[0141] 2) Regarding wastewater treatment

[0142] Treatment of leaching wastewater in step 2: Wastewater treatment equipment is used to treat the wastewater containing heavy metals and other harmful substances through sedimentation, neutralization, and filtration. Reverse osmosis and electrodialysis technologies are used to recover lithium and other valuable components from the water, ensuring that the treated wastewater meets discharge standards.

[0143] Rainwater and surface water management: Install seepage prevention equipment to prevent industrial wastewater from mixing with surface water and rainwater, and treat collected rainwater to prevent pollutant discharge.

[0144] 3) Regarding solid waste management

[0145] Treatment of roasting residue in Step 1: Safely landfill the unusable roasting residue or seek other suitable treatment methods. Explore the possibility of using the roasting residue as building material or for other purposes.

[0146] Treatment of leaching residue in step 2: Safe handling of precipitates and leaching residues containing heavy metals. Research on the use of leaching residues for other industrial applications, such as building materials.

[0147] 4) Efficient recycling of energy and resources

[0148] Where possible, recover waste heat from the process for heating or steam generation. Optimize energy use by adopting energy-efficient equipment and technologies.

[0149] In steps 1 to 3, the method further includes: recovering the waste heat generated during the process of steps 1 to 3, and recycling the waste heat.

[0150] In step 1, a heat exchanger is used to recover waste heat generated during the roasting process. Specifically, the high-temperature exhaust gas produced during roasting can be recovered through a heat exchanger. For example, the recovered heat energy can be used to preheat the raw materials entering the roasting furnace, thereby reducing energy consumption during roasting; it can also be used to generate steam, which can be used in the factory's heating system or converted into electricity. Highly efficient heat exchange technology is applied to maximize the utilization of waste heat.

[0151] In steps 2 and 3, a heat pump system is used to recover the heat energy generated during the leaching and purification processes, and this heat energy is then recycled. The recovered heat energy can be used to heat other processes, such as washing or evaporation concentration. Using a heat pump system to recover heat energy during leaching and purification is an efficient and environmentally friendly practice. This method not only improves the overall energy efficiency of the process but also helps reduce carbon emissions and operating costs.

[0152] Specifically, heat energy recovery using a heat pump system includes the following steps:

[0153] Step 1, Heat Source Identification: Determine the available heat sources in the leaching and purification processes, such as the discharge temperature of the heated liquid, the heat emitted from the equipment surface, etc., and measure the temperature and available thermal energy of the heat source to obtain the design parameters of the heat pump system.

[0154] Step 2, Heat sink selection: Determine the location where the heat energy can be transferred and utilized, such as preheating raw materials, heating systems, or generating hot water.

[0155] Step 3, Heat Pump Type Selection: Select the heat pump type based on the temperature difference between the heat source and the heat sink, such as an air source, water source, or ground source heat pump. Process environment, cost-effectiveness, and maintenance requirements must also be considered.

[0156] Step 4: Determining the capacity and efficiency of the heat pump system: Based on the design parameters, the heat sink, and the type of heat pump, determine the capacity and efficiency of the heat pump system. Calculate the required heat pump capacity to ensure the system can meet the needs of heat energy recovery and utilization. Consider the heat pump's coefficient of performance (COP) to ensure efficient energy utilization.

[0157] Step 5: Installation and integration of the heat pump system. The heat pump system is installed near the process to reduce heat loss during transmission, while ensuring seamless integration of the heat pump system with the lithium carbonate preparation process provided in this application embodiment to achieve efficient operation.

[0158] Step 6: Equip the heat pump system with an intelligent control system to monitor and adjust its operating parameters in real time. This ensures the heat pump system can flexibly adjust heat recovery and supply according to process requirements.

[0159] Step 7, Operation and Maintenance

[0160] Operational monitoring: Regularly monitor the performance of the heat pump system to ensure its efficient operation. Track energy savings and emission reduction effects.

[0161] Regular maintenance: Regularly inspect and maintain the heat pump system to ensure its long-term stable operation. Replace or repair damaged parts promptly to ensure the system's high efficiency and reliability.

[0162] By following the steps above for heat energy recovery using a heat pump system, the heat energy generated during the leaching and purification processes can be effectively recovered, thereby improving the overall energy efficiency of the process and reducing environmental impact. In practical operation, the specific process conditions and site conditions should be considered to determine the most suitable heat pump system design and implementation plan.

[0163] The method also includes recycling thermal energy: recycling the thermal energy generated in the process to reduce the demand for external energy, optimize the process flow, and reduce thermal energy loss.

[0164] The method also includes the efficient use of electrical energy: variable frequency speed control technology is used in the electric motors and pumps used in the lithium carbonate preparation process to improve energy efficiency and reduce unnecessary energy consumption by precisely controlling the operating speed of the equipment.

[0165] The method also includes the implementation of an intelligent energy management system: This system monitors and optimizes energy use throughout the factory. Through data analysis and real-time monitoring, optimized energy allocation and utilization are achieved.

[0166] The method also includes utilizing renewable energy sources as a portion of the energy supply in steps 1 through 3. Where possible, renewable energy sources such as solar and wind power can be used as a partial energy supply. By integrating renewable energy, dependence on fossil fuels is reduced. Carbon footprint is reduced: overall carbon emissions are reduced through energy recovery and reuse. The use of clean energy and efficient technologies further reduces the environmental impact of the process. By implementing these energy recovery and reuse measures, not only can energy efficiency be significantly improved and operating costs reduced, but the environmental impact of the process can also be reduced, promoting the sustainable development of industrial production.

[0167] The method also includes the recycling of raw materials and chemicals: exploring the recovery and reuse of chemicals such as sulfuric acid, as well as the recovery of valuable components from wastewater and waste.

[0168] These environmental protection measures help minimize the environmental impact of the lithium extraction process, ensuring its sustainability and compliance with environmental regulations. Please feel free to ask any specific environmental challenges or questions.

[0169] Please see Figure 2 Based on the same technical concept, this application also provides a system 100 for preparing lithium carbonate by roasting lithium mica composite sulfate. The system 100 includes a roasting furnace 1, a rotary furnace 2, a leaching tank 3 and a lithium precipitation tank connected in sequence.

[0170] In some embodiments, the system 100 is a closed-loop system.

[0171] In some embodiments, the system 100 further includes an electrochemical etching device 5, a heat exchanger 6, and a heat pump system 7. The electrochemical etching device 5 is used to purify the lepidolite. The heat exchanger 6 is used to process the waste heat generated during the roasting process and convert it for other uses (e.g., generating steam, using it in a factory heating system, or converting it into electricity). The heat pump system 7 is used to recover the heat energy generated during the leaching and purification processes and to recycle the heat energy.

[0172] In some embodiments, the system further includes dust removal equipment, gas recovery equipment, wastewater treatment equipment, and seepage prevention equipment. The dust removal equipment is used to capture dust generated during the roasting process, and may include, for example, a wet scrubbing tower or a spray tower. The gas recovery equipment is used to recover and treat acidic gases generated during the leaching process. The wastewater treatment equipment is used to treat wastewater containing heavy metals and other harmful substances through sedimentation, neutralization, filtration, etc., and may use technologies such as reverse osmosis or electrodialysis for the above water treatment processes. The seepage prevention equipment is used to prevent industrial wastewater from mixing with surface water and rainwater, and to treat collected rainwater to prevent pollutant discharge.

[0173] Understandably, the system 100 also includes a controller 8 for system control of the coordinated operation between the aforementioned components.

[0174] The method for preparing lithium carbonate by roasting lepidolite composite sulfate provided in this application can improve the lithium extraction efficiency and the purity of lithium carbonate by optimizing the ratio of sulfate to lepidolite. By optimizing the roasting process, higher lithium conversion rate, lithium extraction efficiency and extraction purity can be achieved, while significantly reducing energy consumption, lowering costs and reducing environmental impact. The use of a closed-loop system can reduce waste gas emissions and recover and reuse heat energy, further reducing energy consumption and environmental pollution. In addition, the purification of lepidolite raw materials by using erosion optimization technology can effectively improve the conversion and leaching efficiency of lithium ions in lepidolite, save energy and improve the purity of the final product.

[0175] The technical solutions of the embodiments of this application will be further described below through specific examples.

[0176] Example 1: Optimized process for roasting lithium carbonate using lepidolite composite sulfate

[0177] Step 101, raw material pretreatment: Select high-grade lepidolite, perform electrochemical etching treatment, crushing and screening to obtain raw materials with suitable particle size.

[0178] Step 102, the ratio of compound sulfate to lepidolite: lepidolite: 1000 g; sodium sulfate (Na2SO4): 250 g; potassium sulfate (K2SO4): 150 g; calcium sulfate (CaSO4): 100 g; magnesium sulfate (MgSO4): 50 g.

[0179] Step 103: According to the above ratio, accurately weigh the composite sulfate and lepidolite and mix them thoroughly under dry conditions to ensure that the sulfate and lepidolite powder are evenly distributed.

[0180] Step 104, roasting

[0181] The roasting process parameters are: temperature: 850℃, time: 1.5 hours, while adopting efficient environmental protection measures and energy recycling measures.

[0182] Step 105, Leaching

[0183] Lithium leaching efficiency: approximately 85%

[0184] Step 106, purification and lithium carbonate precipitation

[0185] Lithium carbonate purity: 99.5%.

[0186] Among them, efficient environmental protection measures are adopted in steps 101 to 106 to significantly reduce the emission of waste gas and wastewater.

[0187] Comparative Example 1: Extraction of Lithium Carbonate using the Traditional Sulfuric Acid Process

[0188] The only difference between Comparative Example 1 and Example 1 is that the calcination process parameters are set differently, and the aforementioned efficient environmental protection measures, as well as the heat recovery and reuse measures, are not adopted. The calcination process parameters include: temperature: 800°C, time: 2 hours.

[0189] Lithium leaching efficiency in Comparative Example 1: approximately 70%; Lithium carbonate purity: 98%; Environmental impact: high emissions of exhaust gas and wastewater.

[0190] The experimental data obtained from Example 1 and Comparative Example 1 are shown below:

[0191] Firing effect

[0192] 1. Lithium content analysis before and after roasting:

[0193] In Example 1, the lithium content increased by approximately 30% before and after calcination, while in Comparative Example 1, the lithium content increased by only approximately 20% before and after calcination. This is because Example 1 optimized the calcination process, and the lepidolite was purified before calcination. Furthermore, the ratio of lepidolite to composite sulfate was optimized, which can effectively improve the conversion rate of lithium in lepidolite.

[0194] 2. Material loss rate:

[0195] In Example 1, the material loss rate was about 3%, while in Comparative Example 1, the material loss rate was about 5%. This is because Example 1 applied efficient energy recycling measures, which can effectively recycle the materials in the lithium carbonate preparation process, thereby reducing material loss.

[0196] Environmental impact

[0197] 1. The exhaust gas emission of Example 1 is 20 kg / ton of lithium, while the exhaust gas emission of Comparative Example 1 reaches 50 kg / ton of lithium. It can be seen that the efficient environmental protection measures adopted in Example 1 can effectively reduce exhaust gas emissions and reduce the impact on the environment.

[0198] 2. The wastewater discharge of Example 1 was 5 m3 / ton of lithium, while the wastewater discharge of Comparative Example 1 reached 10 m3 / ton of lithium. It can be seen that the efficient environmental protection measures adopted in Example 1 can effectively reduce the wastewater discharge and reduce the impact on the environment.

[0199] Therefore, compared with the traditional lithium carbonate process in Comparative Example 1, the optimized lithium mica composite sulfate roasting lithium carbonate process in Example 1 of this application not only improves the lithium conversion rate, leaching efficiency and lithium carbonate purity, but also significantly reduces the environmental impact, demonstrating the high efficiency and environmental advantages of the process.

[0200] It should be noted that the above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Where there is no conflict, the embodiments and features described in the embodiments of this application can be combined with each other. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for preparing lithium carbonate by roasting lithium mica composite sulfate, characterized in that, include: Step 1: Mix lepidolite and sulfate and calcine to obtain calcined material, wherein the mass ratio of lepidolite to sulfate is 1:(0.5~3). Step 2: The calcined material is placed in a leaching agent to leach lithium ions, obtaining a lithium-containing leachate; and Step 3: Add sodium carbonate solution to the lithium-containing leachate, stir and react to obtain precipitate mother liquor and lithium carbonate, recycle the precipitate mother liquor and recover the lithium carbonate; The sulfate comprises sodium sulfate, potassium sulfate, calcium sulfate, and magnesium sulfate, and the formulation of the lepidolite composite sulfate, calculated by mass percentage, includes: Lithium mica: 50~80%; Sodium sulfate: 5~20%; Potassium sulfate: 5~20%; Calcium sulfate: 2-10%; and Magnesium sulfate: 2~10%; In step 2, the calcination temperature is 800℃~900℃, and the calcination time is 1 hour~2 hours; Prior to step 1, the method further includes: The lepidolite is purified by electrochemical etching, the electrochemical etching method comprising: An electrolyte is added to an electrochemical cell, with lepidolite as the anode and an inert metal as the cathode, and electrochemical etching is carried out under the protection of an inert gas. The electrolyte is sulfuric acid or hydrochloric acid; The concentration of the electrolyte is 0.5M~2M; The flow rate of the inert gas is 1~5L / min; The parameters for the electrochemical etching are: initial voltage of 1~5V, current density of 50~200mA / cm². 2 The etching time is 1 to 6 hours, and the temperature of the electrolyte is room temperature to 40°C.

2. The method for preparing lithium carbonate by roasting lithium mica composite sulfate according to claim 1, characterized in that, In step 2, the leaching agent includes sulfuric acid; The leaching temperature is 80℃~100℃, and the leaching time is 2 hours~4 hours; The volume ratio of the leaching agent to the calcined material is (3~10):

1.

3. The method for preparing lithium carbonate by roasting lithium mica composite sulfate according to claim 1, characterized in that, In steps 1 to 3, the method further includes: The waste heat generated during steps 1 to 3 is recovered and recycled; and / or, Renewable energy sources are used as a portion of the energy supply in steps 1 to 3.

4. The method for preparing lithium carbonate by roasting lithium mica composite sulfate according to claim 3, characterized in that, In step 1, a heat exchanger is used to recover the waste heat generated during the roasting process; In steps 2 and 3, a heat pump system is used to recover the heat energy generated during the leaching and purification processes, and the heat energy is recycled.

5. The method for preparing lithium carbonate by roasting lithium mica composite sulfate according to claim 4, characterized in that, The heat energy recovery using the heat pump system includes the following steps: Heat source identification: Identify the available heat sources in the leaching and purification processes, and measure the temperature and available thermal energy of the heat sources to obtain the design parameters of the heat pump system; Heat sink selection: Determining the location where the heat energy can be transferred and utilized; Heat pump type selection: Select the heat pump type based on the temperature difference between the heat source and the heat sink; The capacity and efficiency of the heat pump system are determined based on the design parameters, the heat sink, and the type of heat pump. Installation and integration of heat pump systems; and The heat pump system is equipped with an intelligent control system to monitor and adjust the operating parameters of the heat pump system in real time.

6. A system for preparing lithium carbonate by roasting lepidolite composite sulfate as described in any one of claims 1-5, characterized in that, The system comprises a roasting furnace, a leaching tank, and a lithium deposition tank connected in sequence, and is a closed-loop system.

7. The system according to claim 6, characterized in that, It also includes an electrochemical etching device, a heat exchanger, and a heat pump system. The electrochemical etching device is used to purify the lepidolite, the heat exchanger is used to recover the waste heat generated in step 1, and the heat pump system is used to recover the heat energy generated in steps 2 and 3 and to recycle the heat energy.

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