A comprehensive utilization method for clay-type lithium deposits

Abstract

This invention relates to the field of metal production and refining technology, and discloses a comprehensive utilization method for clay-type lithium ore, comprising the following steps: grinding pretreatment: clay-type lithium ore is fed into a ball mill for ball milling, controlling the fineness of the ore powder to be -200 mesh, accounting for 70% to 85%, to obtain clay-type lithium ore powder; blank roasting: the clay-type lithium ore powder obtained in the grinding pretreatment step is placed in a roasting device and roasted without additives at a roasting temperature of 500-700℃ for 1-4 hours to obtain roasted ore powder; sulfuric acid leaching: the roasted ore powder obtained in the blank roasting is mixed with sulfuric acid solution, and leached with stirring for 1-3 hours at a leaching temperature of 80-95℃, a liquid-to-solid ratio of 2-5 L / kg, and a sulfuric acid concentration of 2-4 mol / L. After the reaction, the mixture is filtered and washed. Through blank roasting, sulfuric acid leaching, and multi-stage impurity removal processes, while extracting lithium to prepare battery-grade lithium carbonate products, the aluminum in the leaching solution is converted into aluminum ammonium sulfate, avoiding resource waste caused by single lithium extraction.

Description

Technical Field

[0001] This invention relates to the field of metal production and refining technology, specifically to a comprehensive utilization method for clay-type lithium ore. Background Technology

[0002] Lithium, an indispensable energy storage metal in modern industry, is widely used in energy storage devices and advanced battery technology due to its excellent electrochemical activity and ultra-low redox potential. Global demand for lithium is surging with the rapid development of the new energy industry. Currently, the global lithium supply chain mainly relies on brine deposits and pegmatite lithium deposits (such as spodumene and lepidolite). Clay-type lithium deposits, as a potential lithium resource with wide distribution and large reserves, are particularly abundant in the southwestern Sichuan, Yunnan, and Guizhou regions of my country. Strengthening the research and development of its utilization technology is of great significance in alleviating the contradiction between lithium resource supply and demand. Existing lithium extraction processes from clay-type lithium ores can be broadly categorized into three types: additive roasting-leaching, blank roasting-leaching, and field-enhanced leaching. However, each type of process has significant drawbacks: in the sulfuric acid-enhanced leaching process, the problem of efficient separation of aluminum and lithium has not been effectively solved, resulting in limited lithium recovery rates; while the sodium salt roasting-leaching process can improve lithium leaching rates to some extent, it generates a large amount of waste residue, and the disposal and effective utilization of this waste residue has become a major bottleneck for industrial applications; the field-enhanced leaching process is only suitable for a small amount of clay-type lithium ores that exist in the form of lithium ion adsorption, and it generally suffers from low lithium recovery rates. To date, there have been no successful cases of industrial application of clay-type lithium ores.

[0003] Meanwhile, clay-type lithium ore is characterized by low lithium oxide content (mostly 0.2% to 0.8%) and its main constituent elements being silicon and aluminum (followed by iron, calcium, magnesium, etc.). If only lithium is extracted, a huge amount of waste residue will be generated. It is estimated that producing 1 ton of battery-grade lithium carbonate product that meets the YS / T582-2013 standard will generate 144 tons of waste residue, which will not only cause serious waste of resources, but also exacerbate the environmental burden. Therefore, the comprehensive utilization of valuable elements such as lithium and aluminum in clay-type lithium ore to reduce waste residue and wastewater discharge has become the key to improving its economic and social value and reducing its environmental impact.

[0004] While existing patented technologies attempt to address the aforementioned problems, such as the clay lithium ore processing method disclosed in patent CN119101806A, which involves mixing and roasting clay lithium ore with metal salts followed by acid leaching, and then enriching lithium through leaching solution circulation or removing impurities and concentrating before cooling and crystallizing to obtain sodium sulfate decahydrate, this method introduces a large amount of sodium ions into the solution, requiring additional processing of the byproduct sodium sulfate and easily causing lithium entrainment loss. Similarly, the low-grade clay-type lithium resource comprehensive utilization process disclosed in patent CN116356159B, which involves roasting, acid leaching, adding ammonium sulfate to prepare crude aluminum ammonium sulfate, and then concentrating and removing impurities from the lithium-rich crystallization tail liquid before lithium precipitation, also faces the challenges of introducing sodium ions and processing the byproduct sodium sulfate. The method for preparing battery-grade lithium carbonate from clay-type lithium ore disclosed in 119080035B obtains alumina and lithium-containing solutions through calcination leaching. However, it introduces additives such as NaCl during the process. Furthermore, due to the high ionic strength of the solution during the lithium solution concentration stage, it can only choose high-energy-consuming evaporation concentration or complex extraction concentration processes, making it difficult to adopt more environmentally friendly and low-cost membrane concentration processes. At the same time, the lithium recovery rate in the purification and concentration stages of the acid-enhanced leaching process is usually only about 73%. The overall process suffers from high energy consumption, low lithium recovery rate, large amount of slag per unit product, and difficulty in treating "three wastes" (waste gas, wastewater, and solid waste), which cannot meet the actual needs of green, efficient, and large-scale comprehensive utilization of clay-type lithium ore.

[0005] Therefore, those skilled in the art have proposed a comprehensive utilization method for clay-type lithium ore to solve the above problems. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a comprehensive utilization method for clay-type lithium ore, solving the problems of low lithium content in clay-type lithium ore leachate and difficulty in separating lithium from aluminum.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a comprehensive utilization method for clay-type lithium ore, characterized by comprising the following steps:

[0008] Grinding pretreatment: Clay-type lithium ore is fed into a ball mill for ball milling, and the fineness of the ore powder is controlled to be -200 mesh, accounting for 70% to 85%, to obtain clay-type lithium ore powder;

[0009] Blank roasting: The clay-type lithium ore powder obtained in the grinding pretreatment step is placed in a roasting equipment and roasted without additives. The roasting temperature is 500-700℃ and the roasting time is 1-4h to obtain roasted ore powder.

[0010] Sulfuric acid leaching: The roasted ore powder obtained from the blank roasting is mixed with sulfuric acid solution, and leached for 1 to 3 hours under the conditions of leaching temperature of 80-95℃, liquid-solid ratio of 2-5L / kg and sulfuric acid concentration of 2-4mol / L. After the reaction is completed, the mixture is filtered and washed, and the leachate and silicon-aluminum-rich leaching residue are collected separately.

[0011] Preparation of pre-aluminum removal and ammonium aluminum sulfate: Ammonium sulfate is slowly added to the leachate obtained in the sulfuric acid leaching step, and the excess ammonium sulfate coefficient is controlled at 0.7-0.9. The addition time is 15-45 min. After the addition is completed, the mixture is stirred at room temperature for 1-2 h. After the reaction is completed, the mixture is filtered and washed, and the pre-aluminum removal solution and ammonium aluminum sulfate concentrate are collected separately.

[0012] Aluminum and iron removal: Add No. 1 impurity removal agent to the pre-aluminum removal liquid, wherein No. 1 impurity removal agent is calcium hydroxide or calcium carbonate, heat to 30-50℃, stir to adjust the pH of the solution to 6.0-8.0, and react at a constant temperature for 15-45 minutes. After the reaction is completed, filter and wash, and collect the aluminum and iron removal liquid and the iron-rich aluminum slag separately.

[0013] Magnesium removal: Add No. 2 impurity removal agent to the aluminum-iron removal liquid obtained in the aluminum-iron removal step. The No. 2 impurity removal agent is calcium hydroxide or lime milk. Heat to 75-90℃, stir to adjust the pH of the solution to 10.5-11.5, and react at a constant temperature for 15-45 minutes. After the reaction is completed, filter and wash, and collect the magnesium removal liquid and magnesium-rich slag separately.

[0014] Calcium removal: Add No. 3 impurity remover to the magnesium removal solution. The No. 3 impurity remover is sodium carbonate, potassium carbonate or sodium bicarbonate. Heat to 75-90℃ and control the excess coefficient of No. 3 impurity remover to 1.5-2.5. Stir the reaction at a constant temperature for 0.5-1.5 hours. After the reaction is completed, filter and wash to collect the lithium purification solution.

[0015] Membrane concentration: The obtained lithium purification solution is passed into a membrane concentration device, and the lithium concentration ratio is controlled at 10-19 times. The lithium concentrate and permeate are collected separately.

[0016] Preparation of battery-grade lithium carbonate: The obtained lithium concentrate is subjected to lithium precipitation, carbonization and pyrolysis treatment in sequence to obtain battery-grade lithium carbonate product with Li2CO3 content ≥99.5%;

[0017] Washing water circulation: The washing water generated from filtration and washing is controlled at a mass ratio of 1.4-1.7:1 to the corresponding slag weight, and the washing water is returned to the previous process for recycling.

[0018] Preferably, the grinding pretreatment step uses wet ball milling with a ball mill speed of 200-300 r / min, a ball-to-material ratio of 5-8:1, and the ball milling media is the permeate produced in the membrane concentration step.

[0019] Preferably, the blank roasting equipment used is a rotary kiln or muffle furnace, with a roasting heating rate of 5-10℃ / min, and after roasting, the temperature is reduced to room temperature at a rate of 3-5℃ / min.

[0020] Preferably, the sulfuric acid leaching is carried out by segmented stirring: the stirring rate is 150-200 r / min for the first 0.5-1 h, and the stirring rate is 80-120 r / min for the next 1-2.5 h; the filtration is carried out by plate and frame filter press with a filtration pressure of 0.3-0.5 MPa, and the washing is carried out 2-3 times, with each washing time being 15-20 min.

[0021] Preferably, in the process of pre-aluminum removal and preparation of ammonium aluminum sulfate, ammonium sulfate is added dropwise at a rate of 5-10 mL / min, and the stirring rate at room temperature is 60-100 r / min; the purity of the refined ammonium aluminum sulfate product is ≥98%, wherein the Al2O3 content is 12%-15% and the SO3 content is 38%-42%.

[0022] Preferably, in the process of removing aluminum and iron, the amount of No. 1 impurity remover added satisfies the following conditions: aluminum ion removal rate ≥ 99.5% and iron ion removal rate ≥ 94% in the solution; in the process of removing magnesium, the amount of No. 2 impurity remover added satisfies the following condition: magnesium ion removal rate ≥ 99% in the solution.

[0023] Preferably, the calcium removal can be replaced by cationic chelating resin adsorption: the cationic chelating resin is of the aminophosphonic acid type or carboxylic acid type, the amount of resin is 0.1-0.3 times the volume of the magnesium removal liquid, adsorption is carried out at 25-40℃ for 1-2 hours, and the resin is desorbed with 0.5-1mol / L hydrochloric acid solution after adsorption.

[0024] Preferably, the membrane concentration equipment used for membrane concentration is a reverse osmosis membrane, and the lithium concentration in the lithium concentrate is 8-10 g / L.

[0025] Preferably, the specific process for preparing battery-grade lithium carbonate is as follows: during lithium precipitation, an ammonium carbonate solution is added to the lithium concentrate, and the molar ratio of ammonium carbonate to lithium is controlled at 1.2-1.5:1. The mixture is stirred and reacted at 70-85°C for 1-2 hours; during carbonation, carbon dioxide is introduced into the lithium carbonate precipitate obtained from lithium precipitation, and the partial pressure of carbon dioxide is controlled at 0.2-0.5 MPa and the temperature at 30-50°C for 0.5-1 hours; during pyrolysis, the lithium bicarbonate solution obtained from carbonation is heated to 90-110°C and kept at that temperature for 1-2 hours; the lithium carbonate precipitate is washed using the permeate generated by membrane concentration, and the washing is performed 3-4 times, with the amount of washing solution used each time being 1-1.5 times the mass of the precipitate; the lithium carbonate crystals obtained after pyrolysis are dried at 100-120°C and under a vacuum of -0.09 to -0.07 MPa for 2-3 hours.

[0026] This invention provides a comprehensive utilization method for clay-type lithium ore. It has the following beneficial effects:

[0027] 1. This invention achieves efficient cascade utilization of clay-type lithium resources. Through blank roasting, sulfuric acid leaching, and multi-stage impurity removal processes, while extracting lithium to prepare battery-grade lithium carbonate products, aluminum in the leachate is converted into aluminum ammonium sulfate concentrate. This product can be widely used in water treatment, food processing, or high-purity alumina preparation, effectively recovering valuable elements from clay-type lithium ores, avoiding resource waste caused by single lithium extraction, and significantly improving the comprehensive economic value of clay-type lithium ores.

[0028] 2. This invention emphasizes green environmental protection and resource recycling throughout the entire process. By controlling the amount of ammonium sulfate added and using calcium salt stepwise impurity removal, no difficult-to-treat foreign cations are introduced into the system. Moreover, the leaching residue can be used as a building material admixture or soil amendment matrix after simple treatment. The iron-aluminum-rich slag and magnesium-rich slag generated during the impurity removal process can also be used in building materials or soil-related fields. At the same time, the permeate generated by membrane concentration and the filtration and washing water of each process are all recycled and reused, which greatly reduces the consumption of production water and the amount of solid waste residue discharged, and reduces the environmental impact of clay-type lithium mining.

[0029] 3. This invention effectively solves the problems of low lithium concentration, difficulty in separating lithium from impurities, and high energy consumption in the concentration of clay-type lithium ore leachate by optimizing the impurity removal and concentration processes: the precise control of ammonium sulfate dosage in the pre-aluminum removal stage reduces the ionic strength of the solution, and the subsequent step-by-step impurity removal further optimizes the solution system, creating suitable conditions for the membrane concentration process and achieving efficient concentration of lithium solution, which significantly reduces energy consumption compared with the traditional evaporation concentration process; at the same time, the multi-stage impurity removal process ensures the purity of the lithium purification solution, providing a guarantee for the subsequent preparation of high-purity battery-grade lithium carbonate, and improving the lithium recovery rate and product quality stability.

[0030] 4. The method of the present invention has strong practicality and operability, the connection between each process is reasonable, the key process parameters are clear and easy to control. For example, the operating conditions of grinding, roasting, leaching and impurity removal do not require special and complicated equipment, and conventional industrial equipment can meet the production needs. Attached Figure Description

[0031] Figure 1 This is the overall flowchart of the present invention. Detailed Implementation

[0032] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. 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.

[0033] Please see the appendix Figure 1This invention provides a comprehensive utilization method for clay-type lithium ore.

[0034] Example 1 (Clay-type lithium deposit in Yunnan)

[0035] 1.1 Raw material parameters

[0036] The main components of a clay-type lithium deposit in Yunnan Province are: Li2O 0.25%, SiO2 37.05%, Al2O3 40.04%, TFe 2.3%, MgO 0.36%, and CaO 0.25%. The lithium element is mainly found in independent minerals (lithium chlorite) and interlayer adsorption states, with a low proportion of lattice-state lithium and extremely low content of harmful impurities such as heavy metals.

[0037] 1.2 Process Steps and Parameters

[0038] Grinding pretreatment: Take 1000g of the above clay-type lithium ore and put it into a ball mill for wet ball milling. The ball mill speed is 250r / min, the ball-to-material ratio is 6:1, and the ball milling media is the permeate produced in the subsequent membrane concentration step. The fineness of the ore powder is controlled to be -200 mesh, accounting for 77%, to obtain clay-type lithium ore powder.

[0039] Blank roasting: Clay-type lithium ore powder was placed in a muffle furnace and heated to 500°C at a heating rate of 8°C / min without additives. It was then roasted at a constant temperature for 4 hours and then cooled to room temperature at a rate of 4°C / min to obtain 932.4g of roasted ore powder.

[0040] Sulfuric acid leaching: Roasted ore powder was mixed with 4 mol / L sulfuric acid solution, and the liquid-solid ratio was controlled at 2 L / kg and the leaching temperature at 80℃. The leaching was carried out by staged stirring (stirring rate of 180 r / min for the first 0.8 h and stirring rate of 100 r / min for the next 2.2 h) for 3 h. After the reaction, the mixture was filtered by a plate and frame filter press (filtration pressure of 0.4 MPa) and washed twice (each washing time of 18 min). 1716.4 mL of leachate (Li concentration of 573.1 mg / L) and 846.0 g of silica-alumina-rich leaching residue (SiO2 43.8%, Al2O3 30.6%) were collected.

[0041] Pre-aluminum removal and preparation of ammonium aluminum sulfate: Ammonium sulfate was added dropwise to the leaching solution at a rate of 8 mL / min, with the excess ammonium sulfate coefficient controlled at 0.9 and the addition time being 45 min. After the addition was completed, the mixture was stirred at 80 r / min for 2 h at room temperature (25℃). After the reaction was completed, the mixture was filtered and washed, and 1493.3 mL of pre-aluminum removal solution (Li concentration 646.8 mg / L) and 896.1 g of refined ammonium aluminum sulfate product were collected.

[0042] Removal of aluminum and iron: Add No. 1 impurity remover (calcium hydroxide) to the pre-aluminum removal solution, heat to 50℃, stir to adjust the pH of the solution to 6.0, and react at a constant temperature for 45 min; after the reaction is completed, filter and wash, and collect 1390.3 mL of aluminum and iron removal solution (Li concentration 691.9 mg / L) and 79.2 g of iron-rich aluminum slag (Al2O3 39.48%, CaO 17.8%, SO3 31.4%).

[0043] Magnesium removal: Add No. 2 impurity removal agent (lime milk) to the aluminum-removed iron liquid, heat to 90℃, stir to adjust the pH of the solution to 10.5, and react at a constant temperature for 45 min; after the reaction is completed, filter and wash, and collect 1347.4 mL of magnesium removal liquid (Li concentration 713.3 mg / L) and 40.6 g of magnesium-rich slag (MgO 6.3%, CaO 33.4%, SO3 45.6%).

[0044] Calcium removal: Add No. 3 impurity removal agent (sodium carbonate) to the magnesium removal solution, heat to 60℃, control the excess sodium carbonate coefficient to 1.5, and stir the reaction at a constant temperature for 0.6h; after the reaction is completed, filter and wash, and collect 1167.2mL of lithium purification solution (Li concentration 813.6mg / L) and 1.4g of calcium-rich slag (CaO 55.3%).

[0045] Membrane concentration: reverse osmosis membrane, operating pressure 2MPa, concentration factor 17.1 times, lithium concentrate Li concentration 13.31g / L;

[0046] Preparation of battery-grade lithium carbonate: An ammonium carbonate solution (with a molar ratio of ammonium carbonate to lithium of 1.3:1) was added to a lithium concentrate and stirred at 75°C for 1.5 h to generate lithium carbonate precipitate. The precipitate was washed three times with a permeate solution (each wash solution was 1.2 times the mass of the precipitate). Carbon dioxide was bubbled into the precipitate (partial pressure 0.3 MPa, temperature 40°C) and reacted for 0.8 h to obtain a lithium bicarbonate solution. The lithium bicarbonate solution was heated to 100°C and held at that temperature for 1.5 h for pyrolysis. The resulting lithium carbonate crystals were dried at 110°C and a vacuum of -0.08 MPa for 2.5 h to obtain the battery-grade lithium carbonate product.

[0047] 1.3 Implementation Results

[0048] The purity of the ammonium aluminum sulfate product is 98.5%, with Al2O3 at 12.3% and SO3 at 38.6%, and 77.88% of the aluminum in the solution enters the product;

[0049] During the aluminum and iron removal process, the aluminum ion removal rate was 99.89% and the iron ion removal rate was 94.91%; during the magnesium removal process, the magnesium ion removal rate was 99.2%.

[0050] The lithium recovery rate from raw ore to lithium purification solution is 81.75%; the lithium recovery rate in the impurity removal and concentration process (steps 4-8) is 94.1%, and the lithium recovery rate increases to 98.1% after permeate reuse;

[0051] The final battery-grade lithium carbonate product contains 99.78% Li2CO3, and the remaining indicators meet the YS / T582-2013 standard.

[0052] Each ton of battery-grade lithium carbonate generates 136 tons of solid waste, and the production water recycling rate is 92%.

[0053] II. Example 2 (Clay-type lithium mine in Sichuan)

[0054] 2.1 Raw material parameters

[0055] The main components of the clay-type lithium deposit in Sichuan Province are: Li₂O 0.42%, SiO₂ 41.2%, Al₂O₃ 35.8%, TFe 1.9%, MgO 0.51%, and CaO 0.38%. The lithium element is mainly in the interlayer adsorption state, with a small amount of lepidolite associated minerals.

[0056] 2.2 Process Steps and Parameters

[0057] Grinding pretreatment: Take 1500g of this clay-type lithium ore and wet ball mill (speed 220r / min, ball-to-material ratio 5:1, medium is permeate) to control the fineness of the ore powder to -200 mesh 82%.

[0058] Blank roasting: Roasting without additives in a rotary kiln, heating rate 6℃ / min to 650℃, constant temperature roasting for 2h, cooling rate 3℃ / min to room temperature, to obtain 1415g of roasted mineral powder.

[0059] Sulfuric acid leaching: 3 mol / L sulfuric acid solution, liquid-to-solid ratio 3 L / kg, leaching at 85℃ for 2.5 h (stirring at 160 r / min for the first h and 90 r / min for the next 1.5 h), plate and frame filter press (0.35 MPa), washing 3 times (15 min each time), yielding 3820 mL of leachate (Li concentration 721.5 mg / L) and 1280 g of silica-alumina-rich leaching residue.

[0060] Preparation of pre-aluminum removal and ammonium aluminum sulfate: Ammonium sulfate dropping rate 6 mL / min, excess coefficient 0.8, feeding time 30 min, stirring at room temperature (23℃) at 70 r / min for 1.5 h, yielding 3250 mL of pre-aluminum removal solution (Li concentration 785.3 mg / L) and 1320 g of ammonium aluminum sulfate (purity 98.2%, Al2O3 13.1%, SO3 39.8%).

[0061] Removal of aluminum and iron: No. 1 impurity remover (calcium carbonate), heat to 40℃, adjust pH to 7.0, react for 30 min, to obtain 3100 mL of aluminum and iron removal liquid (Li concentration 802.6 mg / L) and 115 g of iron-rich aluminum slag (Al³⁺ removal rate 99.6%, Fe³⁺ removal rate 95.3%).

[0062] Magnesium removal: No. 2 impurity removal agent (calcium hydroxide), heated to 80℃, pH adjusted to 11.0, reacted for 30 min, yielding 3020 mL of magnesium removal solution (Li concentration 815.8 mg / L) and 68 g of magnesium-rich slag (Mg²⁺ removal rate 99.1%).

[0063] Calcium removal: No. 3 impurity remover (potassium carbonate), excess coefficient 2.0, reaction at 80℃ for 1 hour, yielding 2850 mL of lithium purification solution (Li concentration 832.4 mg / L) and 22 g of calcium-rich slag.

[0064] Membrane Concentration: The membrane concentration equipment was set to operate at a pressure of 2.5 MPa, a temperature of 35°C, and a flux of 25 L / (m²·h). Based on the initial Li concentration of the lithium purification solution (832.4 mg / L), 2850 mL of the lithium purification solution was passed into the membrane concentration equipment, ultimately collecting approximately 237.5 mL of lithium concentrate (Li concentration ≈ 9.99 g / L) and 2612.5 mL of permeate. To meet the requirements of the subsequent lithium precipitation process for feedstock concentration, the resulting lithium concentrate was further evaporated and concentrated at 60-80°C and a vacuum of -0.08 to -0.06 MPa to increase the lithium concentration to 20-25 g / L.

[0065] Preparation of battery-grade lithium carbonate: The ammonium carbonate to lithium molar ratio is 1.4:1, the reaction is carried out at 80℃ for 1.2h, the CO2 partial pressure is 0.4MPa, the carbonization is carried out at 45℃ for 0.6h, the pyrolysis is carried out at 95℃ for 1.8h, and the drying is carried out at 105℃ under vacuum (-0.09MPa) for 2h to obtain battery-grade lithium carbonate product.

[0066] 2.3 Implementation Results

[0067] The aluminum recovery rate in ammonium aluminum sulfate was 79.2%.

[0068] The lithium recovery rate from raw ore to lithium purification solution is 83.5%, and the lithium recovery rate from the impurity removal and concentration process is 95.3%.

[0069] The battery-grade lithium carbonate product has a Li2CO3 content of 99.65%, a waste residue of 132 tons per unit product, and a water recycling rate of 93%.

[0070] III. Example 3 (Clay-type lithium mine in Guizhou, calcium removal using cationic chelate resin adsorption method)

[0071] 3.1 Raw material parameters

[0072] The main components of a clay-type lithium deposit in Guizhou Province are: Li₂O 0.31%, SiO₂ 39.5%, Al₂O₃ 37.2%, TFe 2.1%, MgO 0.43%, and CaO 0.32%.

[0073] 3.2 Process steps and parameters (only the steps that differ from Example 1 are listed)

[0074] Calcium removal: Add aminophosphonic acid-type cationic chelating resin (0.2 times the volume of magnesium removal solution) to the magnesium removal solution and adsorb at 30℃ for 1.5h; after adsorption, desorb the resin with 0.8mol / L hydrochloric acid solution, filter and collect 2980mL of lithium purification solution (Li concentration 786.5mg / L).

[0075] Membrane concentration: Reverse osmosis membrane (sulfonated polyethersulfone) was used for treatment. The membrane concentration equipment was set to an operating pressure of 2.4 MPa, an operating temperature of 35°C, and a membrane flux of 24 L / (m²·h). 2980 mL of lithium purification solution was passed into the membrane concentration equipment, collecting approximately 248.3 mL of lithium concentrate (Li concentration ≈ 9.44 g / L) and 2731.7 mL of permeate. To meet the feed requirements of the lithium precipitation process, the lithium concentrate was further evaporated and concentrated at 60-80°C and a vacuum of -0.08 to -0.06 MPa, increasing the lithium concentration to 20–25 g / L.

[0076] 3.3 Implementation Results

[0077] Calcium ion removal rate: 99.7%;

[0078] The battery-grade lithium carbonate product has a Li2CO3 content of 99.72%, a lithium recovery rate of 96.1% in the impurity removal and concentration process, and a water recycling rate of 91%.

[0079] The test results are shown in Table 1 below:

[0080] Table 1 compares the key indicators of the present invention with those of existing technologies.

[0081] Validate Project Example 1 Example 2 Example 3 Existing technology (acid-enhanced leaching) Ammonium aluminum sulfate purity (%) 98.5 98.2 98.3 - (This product is not available) Aluminum recovery rate (%) 77.88 79.2 78.5 - (Unrecycled aluminum) Aluminum ion removal rate (%) 99.89 99.6 99.7 85-90 Magnesium ion removal rate (%) 99.2 99.1 99.3 90-95 Lithium recovery rate (%) from raw ore to lithium purification solution 81.75 83.5 82.8 65-70 Lithium recovery rate (%) in the impurity removal and concentration process 94.1 (98.1 after reuse) 95.3 96.1 Around 73 <![CDATA[Li2CO3 content of battery-grade lithium carbonate (%)]]> 99.78 99.65 99.72 95-98 Waste residue per unit product (tons / ton of lithium carbonate) 136 132 134 144 Production water recycling rate (%) 92 93 91 60-70

[0082] The following conclusions can be drawn from Table 1:

[0083] Significantly improved resource utilization rate: Compared with the existing acid-enhanced leaching process that does not recover aluminum from clay-type lithium ore, this invention achieves efficient recovery of aluminum resources through pre-aluminum removal and ammonium aluminum sulfate preparation processes. The aluminum recovery rate in Examples 1-3 reaches 77.88% to 79.2%, and the purity of the produced ammonium aluminum sulfate concentrate is ≥98.2%, which can meet the application needs of water treatment, high-purity alumina preparation and other fields. It breaks through the resource waste problem caused by the existing process that only extracts lithium, and greatly improves the comprehensive economic value of clay-type lithium ore.

[0084] Significantly improved impurity removal efficiency and lithium recovery rate: In terms of impurity removal, this invention employs a tiered impurity removal process of "pre-aluminum removal + aluminum and iron removal + magnesium removal + calcium removal," achieving an aluminum ion removal rate of 99.6%–99.89% and a magnesium ion removal rate of 99.1%–99.3%, significantly superior to the existing acid-enhanced leaching process's 85%–90% aluminum ion removal rate and 90%–95% magnesium ion removal rate. Regarding lithium recovery rate, this invention achieves a lithium recovery rate of 81.75%–83.5% from raw ore to lithium purification solution, and a lithium recovery rate of 94.1%–96.1% in the impurity removal and concentration process (which can be increased to 98.1% after permeate reuse), far exceeding the existing acid-enhanced leaching process's 65%–70% lithium recovery rate from raw ore to purification solution and approximately 73% lithium recovery rate in the impurity removal and concentration process. This effectively solves the core problems of difficult lithium separation and low lithium recovery rate in existing processes.

[0085] Superior Product Purity and Green Production Level: The battery-grade lithium carbonate products prepared by this invention have a Li2CO3 content of ≥99.65%, meeting the requirements of YS / T582-2013 standard, and the purity is higher than the 95%–98% purity of existing acid-enhanced leaching processes. In terms of environmental protection and energy consumption, the amount of solid waste generated per ton of battery-grade lithium carbonate by this invention is 114–120 tons, lower than the 144 tons of waste generated by existing processes, and the water recycling rate in production reaches 91%–93%, far higher than the 60%–70% water recycling rate of existing processes. At the same time, by replacing the high-energy-consuming evaporation concentration of existing processes with membrane concentration technology, the energy consumption of production is further reduced, realizing the green, low-consumption, and large-scale utilization of clay-type lithium ore.

[0086] Comparative Example 1 (Conventional high ammonium salt excess coefficient aluminum removal process)

[0087] 1.1 Raw material parameters (completely consistent with Example 1)

[0088] The sample was taken from a clay-type lithium ore deposit in Yunnan Province. The main components are: Li2O 0.25%, SiO2 37.05%, Al2O3 40.04%, TFe 2.3%, MgO 0.36%, and CaO 0.25%. The lithium is mainly found in lithium chlorite and interlayer adsorption states, with a low proportion of lattice lithium and extremely low content of harmful impurities.

[0089] 1.2 Process steps and parameters (only the "pre-aluminum removal and preparation of ammonium aluminum sulfate" are adjusted; the remaining steps are the same as in Example 1)

[0090] Grinding pretreatment, blank roasting, and sulfuric acid leaching: Example 1 was completely replicated, and 1716.4 mL of leachate (Li concentration 573.1 mg / L, Al³⁺ concentration approximately 8.2 g / L) and 846.0 g of silica-alumina-rich leaching residue were finally obtained.

[0091] Pre-aluminum removal and preparation of ammonium aluminum sulfate (key adjustment: excess of conventional high ammonium salt): Adopting the industry-standard approach of "complete aluminum removal with high ammonium salt in one step", ammonium sulfate was added dropwise to the leaching solution at a rate of 8 mL / min, controlling the ammonium sulfate excess coefficient to be 2.0 (0.9 in Example 1), and the addition time was extended to 60 min (due to the increased amount of ammonium salt); the reaction was stirred at 80 r / min for 2 h at room temperature (25℃); after the reaction, the solution was filtered and washed, and 1520 mL of pre-aluminum removal solution (Li concentration 638.5 mg / L) and 1280 g of ammonium aluminum sulfate product (purity 97.5%, Al2O3 12.8%, SO3 39.2%) were collected.

[0092] Removal of aluminum and iron, and removal of magnesium (processes affected by high ammonium salts):

[0093] Aluminum and iron removal: Add No. 1 impurity removal agent (calcium hydroxide) to the pre-aluminum removal solution. Because the concentration of residual ammonium sulfate in the solution increased by 122% compared with Example 1 (excess ammonium salt did not react completely), the amount of calcium hydroxide needs to be increased to 1.9 times that of Example 1 in order to maintain pH 6.0. After reacting at a constant temperature for 45 min, collect 1410 mL of aluminum and iron removal solution (Li concentration 685.2 mg / L) and 98 g of iron-rich aluminum slag (23.7% increase compared with Example 1).

[0094] Magnesium removal: Add No. 2 impurity removal agent (lime milk) to the aluminum-removed iron liquid. As ammonium sulfate consumes alkali, the amount of lime milk needs to be increased to 1.8 times that of Example 1 to maintain pH 10.5. After reacting at a constant temperature for 45 minutes, collect 1360 mL of magnesium removal liquid (Li concentration 702.3 mg / L) and 58 g of magnesium-rich slag (42.9% more than in Example 1).

[0095] Calcium removal and membrane concentration: The amount of sodium carbonate used in the calcium removal step was increased by 30% compared to Example 1 (to offset the ion interference caused by high ammonium salts); the same nanofiltration membrane (aromatic polyamide material, operating pressure 2 MPa, temperature 30°C) was used for membrane concentration as in Example 1. However, due to the surge in residual ammonium sulfate in the solution, the Baume degree of the solution increased from 3.0°Bé in Example 1 to 6.8°Bé (the ionic strength doubled), and the membrane flux decreased from 22 L / (m²·h) to 14 L / (m²·h). The concentration factor could only reach 8 times (17.1 times in Example 1). Finally, 170 mL of lithium concentrate (Li concentration 6.2 g / L) and 1190 mL of permeate (Li concentration 52.8 mg / L) were collected.

[0096] Preparation of battery-grade lithium carbonate: Same as in Example 1, but due to the low lithium concentration in the concentrate and the high residual impurity ions (NH4⁺, SO4²⁻), the lithium precipitation reaction time is extended to 2.5 h, and the purity of the product decreases after pyrolysis.

[0097] The experimental results are shown in Table 2:

[0098] Table 2 is a comparison table between Comparative Example 2 and Example 1.

[0099] Key Indicators Comparative Example 1 (Conventional high ammonium salt in excess) Example 1 (An unconventional approach to the invention) Core reasons for the differences Ammonium salt aluminum removal excess coefficient 2.0 0.9 Conventional processes aim for complete aluminum removal in one step, while this technology controls the amount of ammonium salt used. Pre-aluminum removal rate of aluminum in one pass 95.8% (standard target) 80.3% (unconventional low removal rate) High ammonium salts can achieve high aluminum removal rates, but they introduce large amounts of ammonium sulfate. Dosage of magnesium-removing lime slurry 1.8 times that of Example 1 Standard dosage (1.0 times) Excessive ammonium sulfate consumes alkali, leading to a surge in the amount of impurity removal reagents. Magnesium-rich slag content 58g 40.6g Increased reagent usage plus ammonium salt reaction byproducts resulted in a 42.9% increase in residue. Baume degree of solution after magnesium removal 6.8°Bé 3.0°Bé Ammonium sulfate residue caused a sharp increase in ionic strength, doubling the Baume degree. Membrane Concentration Factor 8 times 17.1 times High Baume degrees inhibit membrane permeation efficiency, reducing concentration capacity by 53.2%. Li concentration after membrane concentration 6.2g / L 13.31g / L Low concentration efficiency and poor lithium enrichment effect Lithium recovery rate from raw ore to lithium concentrate 82.5% 98.1% (after permeate reuse) Reagent consumption plus membrane concentration losses reduced lithium recovery rate by 15.6 percentage points. <![CDATA[Li2CO3 content of battery-grade lithium carbonate]]> 99.2% 99.78% Residual impurity ions reduced product purity by 0.58 percentage points.

[0100] Comparative Example 2 (Conventional sodium salt replacement of calcium salt for impurity removal process)

[0101] 2.1 Raw material parameters (completely consistent with Example 1)

[0102] Similar to Comparative Example 1, a clay-type lithium ore from a certain area in Yunnan was used to ensure that only the "type of impurity remover" was a variable.

[0103] 2.2 Process steps and parameters (adjust the type of impurity removal agent for "aluminum and iron removal" and "magnesium removal", the remaining steps are the same as in Example 1)

[0104] Grinding pretreatment, blank roasting, sulfuric acid leaching, and pre-aluminum removal: Example 1 was completely replicated, and 1493.3 mL of pre-aluminum removal solution (Li concentration 646.8 mg / L, ammonium salt excess coefficient 0.9, aluminum removal rate in one step 80.3%) and 896.1 g of aluminum ammonium sulfate product were finally obtained.

[0105] Removal of aluminum and iron (key adjustment: sodium salt instead of calcium salt): Sodium hydroxide (sodium salt) was used instead of calcium hydroxide (calcium salt) in Example 1. The temperature was raised to 50°C, and the pH was adjusted to 6.0 by stirring (the amount of sodium hydroxide was only 0.6 times that of calcium hydroxide). The reaction was carried out at a constant temperature for 45 min. After filtration, 1420 mL of aluminum and iron removal liquid (Li concentration 680.5 mg / L) and 62 g of iron-rich aluminum slag were collected (21.7% less than in Example 1).

[0106] Magnesium removal (key adjustment: sodium salt instead of calcium salt): sodium hydroxide (sodium salt) was used instead of lime milk (calcium salt) in Example 1. The temperature was raised to 90°C, and the pH was adjusted to 10.5 by stirring (the amount of sodium hydroxide was 0.5 times that of lime milk). The reaction was carried out at a constant temperature for 45 min. After filtration, 1370 mL of magnesium removal solution (Li concentration 698.2 mg / L) and 32 g of magnesium-rich slag were collected (21.2% less than in Example 1).

[0107] Calcium removal and membrane concentration: The amount of sodium carbonate used in the calcium removal step was basically the same as in Example 1. However, due to the introduction of a large amount of sodium ions in the aluminum and iron removal and magnesium removal processes, the Na⁺ concentration in the solution increased from 0.06 g / L in Example 1 to 4.2 g / L, and the Baume degree of the solution increased from 3.0°Bé to 5.5°Bé. The same nanofiltration membrane as in Example 1 was used for membrane concentration. The membrane flux was reduced to 16 L / (m²·h), and the concentration factor could only reach 7 times (17.1 times in Example 1). Finally, 195 mL of lithium concentrate (Li concentration 5.8 g / L) and 1175 mL of permeate (Li concentration 58.5 mg / L) were collected.

[0108] Battery-grade lithium carbonate preparation: Due to the high residual Na⁺ in the concentrate, we attempted to further concentrate it by evaporation (simulating conventional processes), but sodium sulfate crystals precipitated at 55°C, resulting in lithium entrainment loss; finally, after lithium precipitation, carbonization, and pyrolysis, Na⁺ impurities were detected in the product.

[0109] The experimental results are compared with those of Example 1, as shown in Table 3:

[0110] Table 3 is a comparison table between Comparative Example 2 and Example 1.

[0111] Key Indicators Comparative Example 2 (Conventional sodium salt purification) Example 1 (Calcium Salt Cascade Impurity Removal of the Invention) Core reasons for the differences Types of aluminum and iron removal / magnesium removal agents Sodium hydroxide (sodium salt) Calcium hydroxide / lime milk (calcium salt) Conventional processes aim to reduce slag, while this technology prioritizes controlling ion accumulation. Total amount of slag after impurity removal 94g 119.8g (iron-aluminum slag + magnesium-rich slag) Sodium salts are converted into soluble sodium sulfate, resulting in a 21.5% reduction in slag volume. Na⁺ concentration in the solution after magnesium removal 4.2g / L 0.06g / L Sodium salt purification leads to severe accumulation of sodium ions. Baume degree of solution after magnesium removal 5.5°Bé 3.0°Bé Sodium ions increase ionic strength, raising the Baume degree by 83.3%. Membrane Concentration Factor 7 times 17.1 times The high Baume degree limiting membrane's enrichment capacity resulted in a 59.1% decrease in concentration factor. Evaporation Concentration Salt Deposition Temperature 55℃ (low temperature precipitation of sodium sulfate) No salt precipitation (stable at 80℃) Excess sodium ions lead to salting out, preventing evaporation and concentration. Lithium recovery rate from raw ore to lithium concentrate 80.2% 98.1% (after permeate reuse) Salting-out entrainment and membrane concentration losses reduced lithium recovery rate by 17.9 percentage points. Battery-grade lithium carbonate purity 99.1% (including Na⁺0.25%) 99.78% (Na⁺ not detected) Sodium ion residue, product does not meet standard (YS / T582-2013 requires Na⁺≤0.01%).

[0112] As shown in Table 3, although the conventional use of sodium salts to replace calcium salts for impurity removal can reduce the amount of residue by more than 20% (a short-term advantage), it will lead to the continuous accumulation of sodium ions in the solution: ① The Baume degree of the solution increases by more than 80%, and the membrane concentration factor decreases by nearly 60%, making it impossible to achieve efficient enrichment of lithium; ② Sodium salts precipitate at low temperatures during subsequent evaporation and concentration, causing lithium entrainment loss and significantly reducing the recovery rate; ③ The final product contains sodium ion impurities, which does not meet the purity standard of battery-grade lithium carbonate, and sodium ions cannot be removed by conventional processes, creating a contradiction of "reducing residue - reducing quality".

[0113] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A comprehensive utilization method of a clay-type lithium mine, characterized by, Includes the following steps: Grinding pretreatment: Clay-type lithium ore is fed into a ball mill for ball milling, and the fineness of the ore powder is controlled to be -200 mesh, accounting for 70% to 85%, to obtain clay-type lithium ore powder; Blank roasting: The clay-type lithium ore powder obtained in the grinding pretreatment step is placed in a roasting equipment and roasted without additives. The roasting temperature is 500-700℃ and the roasting time is 1-4h to obtain roasted ore powder. Sulfuric acid leaching: The roasted ore powder obtained from the blank roasting is mixed with sulfuric acid solution, and leached for 1 to 3 hours under the conditions of leaching temperature of 80-95℃, liquid-solid ratio of 2-5L / kg and sulfuric acid concentration of 2-4mol / L. After the reaction is completed, the mixture is filtered and washed, and the leachate and silicon-aluminum-rich leaching residue are collected separately. Preparation of pre-aluminum removal and ammonium aluminum sulfate: Ammonium sulfate is slowly added to the leachate obtained in the sulfuric acid leaching step, and the excess ammonium sulfate coefficient is controlled at 0.7-0.

9. The addition time is 15-45 min. After the addition is completed, the mixture is stirred at room temperature for 1-2 h. After the reaction is completed, the mixture is filtered and washed, and the pre-aluminum removal solution and ammonium aluminum sulfate concentrate are collected separately. Aluminum and iron removal: Add No. 1 impurity removal agent to the pre-aluminum removal liquid, wherein No. 1 impurity removal agent is calcium hydroxide or calcium carbonate, heat to 30-50℃, stir to adjust the pH of the solution to 6.0-8.0, and react at a constant temperature for 15-45 minutes. After the reaction is completed, filter and wash, and collect the aluminum and iron removal liquid and the iron-rich aluminum slag separately. Magnesium removal: Add No. 2 impurity removal agent to the aluminum-iron removal liquid obtained in the aluminum-iron removal step. The No. 2 impurity removal agent is calcium hydroxide or lime milk. Heat to 75-90℃, stir to adjust the pH of the solution to 10.5-11.5, and react at a constant temperature for 15-45 minutes. After the reaction is completed, filter and wash, and collect the magnesium removal liquid and magnesium-rich slag separately. Calcium removal: Add No. 3 impurity remover to the magnesium removal solution. The No. 3 impurity remover is sodium carbonate, potassium carbonate or sodium bicarbonate. Heat to 75-90℃ and control the excess coefficient of No. 3 impurity remover to 1.5-2.

5. Stir the reaction at a constant temperature for 0.5-1.5 hours. After the reaction is completed, filter and wash to collect the lithium purification solution. Membrane concentration: The obtained lithium purification solution is passed into a membrane concentration device, and the lithium concentration ratio is controlled at 10-19 times. The lithium concentrate and permeate are collected separately. Preparation of battery-grade lithium carbonate: The obtained lithium concentrate is subjected to lithium precipitation, carbonization and pyrolysis treatment in sequence to obtain battery-grade lithium carbonate product with Li2CO3 content ≥99.5%; Washing water circulation: The washing water generated from filtration and washing is controlled at a mass ratio of 1.4-1.7:1 to the corresponding slag weight, and the washing water is returned to the previous process for recycling.

2. The comprehensive utilization method of a clay-type lithium mine according to claim 1, characterized in that, The grinding pretreatment step uses wet ball milling with a ball mill speed of 200-300 r / min and a ball-to-material ratio of 5-8:

1. The ball milling media is the permeate produced in the membrane concentration step.

3. The comprehensive utilization method of a clay-type lithium mine according to claim 1, characterized in that, The blank roasting uses a rotary kiln or muffle furnace, with a roasting heating rate of 5-10℃ / min, and after roasting, the temperature is reduced to room temperature at a rate of 3-5℃ / min.

4. The comprehensive utilization method of a clay-type lithium mine according to claim 1, characterized in that, The sulfuric acid leaching process employs segmented stirring: the stirring rate is 150-200 r / min for the first 0.5-1 h, and 80-120 r / min for the next 1-2.5 h; filtration is carried out using a plate and frame filter press with a filtration pressure of 0.3-0.5 MPa, and the washing is performed 2-3 times, with each washing lasting 15-20 min.

5. The comprehensive utilization method of a clay-type lithium mine according to claim 1, characterized in that, In the process of pre-aluminum removal and preparation of ammonium aluminum sulfate, ammonium sulfate is added dropwise at a rate of 5-10 mL / min, and the stirring speed at room temperature is 60-100 r / min.

6. The comprehensive utilization method of a clay-type lithium mine according to claim 1, characterized in that, In the process of removing aluminum and iron, the amount of No. 1 impurity remover added meets the following requirements: aluminum ion removal rate ≥ 99.5% and iron ion removal rate ≥ 94% in the solution; in the process of removing magnesium, the amount of No. 2 impurity remover added meets the following requirement: magnesium ion removal rate ≥ 99% in the solution.

7. The comprehensive utilization method of a clay-type lithium mine according to claim 1, characterized in that, The calcium removal method is replaced by cationic chelating resin adsorption: the cationic chelating resin is of the aminophosphonic acid type or carboxylic acid type, the amount of resin is 0.1-0.3 times the volume of magnesium removal liquid, adsorption is carried out at 25-40℃ for 1-2 hours, and the resin is desorbed with 0.5-1mol / L hydrochloric acid solution after adsorption.

8. The comprehensive utilization method of a clay-type lithium mine according to claim 1, characterized in that, The membrane concentration equipment used for the membrane concentration is a reverse osmosis membrane, and the lithium concentration in the lithium concentrate is 8-10 g / L.

9. The comprehensive utilization method of a clay-type lithium mine according to claim 1, characterized in that, The specific process for preparing battery-grade lithium carbonate is as follows: During lithium precipitation, ammonium carbonate solution is added to the lithium concentrate, and the molar ratio of ammonium carbonate to lithium is controlled at 1.2-1.5:

1. The mixture is stirred and reacted at 70-85℃ for 1-2 hours. During carbonization, carbon dioxide is introduced into the lithium carbonate precipitate obtained from lithium precipitation, and the partial pressure of carbon dioxide is controlled at 0.2-0.5 MPa and the temperature at 30-50℃. The reaction is carried out for 0.5-1 hours. During pyrolysis, the lithium bicarbonate solution obtained from carbonization is heated to 90-110℃ and kept at that temperature for 1-2 hours. The lithium carbonate precipitate is washed using the permeate generated by membrane concentration, and the washing is performed 3-4 times, with the amount of washing solution used each time being 1-1.5 times the mass of the precipitate. The lithium carbonate crystals obtained after pyrolysis are dried at 100-120℃ and under a vacuum of -0.09 to -0.07 MPa for 2-3 hours.

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