Method for efficiently and cleanly extracting lithium from low-grade lepidolite

Abstract

The application discloses a kind of low-grade lepidolite efficient clean lithium extraction methods, comprising the following steps: S1: lithium mica ore is mixed with sodium potassium sulfate, calcium sulfate, calcium hydroxide, lime, quartz uniformly, then mixed raw material is pressed into brick billet;S2, the brick billet is stacked, preheating drying, high-temperature calcination, cooling, crushing, powder after grinding to obtain fine powder clinker;S3: the fine powder clinker is immersed with water liquid, then through solid-liquid separation to obtain leaching solution;The application can accelerate the solid-phase reconstruction reaction of lepidolite by using sodium sulfate potassium salt, thereby improving the conversion rate of lithium;On the other hand, by adding quartz, the free energy of the solid-phase reaction between lepidolite and sulfate can be effectively reduced, so that low-grade lepidolite can also have a good transformation rate;Adding lime and calcium hydroxide is significantly better than adding calcium carbonate, not only can effectively absorb the HF gas generated in the reaction, but also can avoid the reduction of lithium leaching due to the combination of fluorine and lithium, which is beneficial to improve the leaching rate of lithium.

Description

TECHNICAL FIELD

[0001] The present application relates to a method for efficiently and cleanly extracting lithium from low-grade lepidolite. BACKGROUND

[0002] Lithium and its compounds are indispensable materials in modern industry, and have important applications in the fields of batteries, ceramics, lubricants, etc. Although China has abundant lithium resources, most of which are contained in salt lake brine, the production capacity cannot meet the demand of the rapid development of the new energy industry due to the limitations of resource endowment and geographical location and climate. Ore lithium extraction has become an important source of lithium products, and the development and utilization of lepidolite resources are of great significance to the sustainable development of lithium resources. At present, the phenomenon of "poor, fine and impure" lepidolite is common in some areas, so we have to face the extraction of lithium from low-grade lepidolite. The main lepidolite lithium extraction processes include limestone calcination, chloride calcination, sulfate calcination, sulfuric acid leaching and pressure leaching.

[0003] The existing low-grade lepidolite lithium extraction process requires 3 times the amount of limestone than lepidolite, which consumes a lot of energy and produces a large amount of slag. The chloride calcination method is not environmentally friendly due to serious equipment corrosion. The sulfuric acid leaching method is relatively mature, but it has problems such as difficulty in removing impurities from the leaching solution and equipment corrosion. The sulfate method is the most popular process at present, which basically produces lithium carbonate through the process of "calcination-leaching-impurity removal-precipitation-washing-filtration", but the main auxiliary materials used are potassium sulfate and calcium sulfate, which are expensive, so it is necessary to develop an economical, efficient and environmentally friendly lithium extraction process with high comprehensive recovery rate. Therefore, we propose a method for efficiently and cleanly extracting lithium from low-grade lepidolite. SUMMARY

[0004] The present application aims to provide a method for efficiently and cleanly extracting lithium from low-grade lepidolite, which solves the problems of high energy consumption, environmental pollution, impurity removal difficulty and high processing cost in the existing low-grade lepidolite lithium extraction process.

[0005] To achieve the above-mentioned purpose, the present application provides the following technical solution: a method for efficiently and cleanly extracting lithium from low-grade lepidolite, comprising the following steps:

[0006] S1: Mix lepidolite ore with sodium potassium sulfate, calcium sulfate, calcium hydroxide, lime and quartz uniformly, and then press the mixed raw material into a brick;

[0007] S2, After the brick is stacked, preheated and dried, high-temperature calcined, cooled, crushed and ground into powder, a fine powder is obtained;

[0008] S3: The fine powder is leached with water, and the leaching solution is obtained by solid-liquid separation;

[0009] S4: The leachate is purified, concentrated, lithium precipitated, and centrifuged to obtain crude lithium carbonate and lithium precipitated mother liquor. Then, the crude lithium carbonate is washed, dried, and pulverized to obtain battery-grade lithium carbonate.

[0010] S5: The mother liquor after lithium precipitation is decarbonized, neutralized, and concentrated to obtain recovered sodium and potassium sulfate and concentrated mother liquor. Then, the recovered sodium and potassium sulfate is returned to S1 for mixing, and the concentrated mother liquor is returned to S4.

[0011] The use of sodium sulfate and potassium sulfate can accelerate the solid-phase reconstruction reaction of lepidolite, thereby improving the lithium conversion rate. On the other hand, the addition of quartz can effectively reduce the solid-phase reaction free energy between lepidolite and sulfate, allowing even low-grade lepidolite to have a good conversion rate. The addition of lime and calcium hydroxide is significantly better than the addition of calcium carbonate. It can not only effectively absorb the HF gas generated in the reaction, which can avoid the reduction of lithium leaching due to the combination of fluorine and lithium, thus improving the lithium leaching rate, but also effectively absorb SO2 and SO3 generated in the roasting process, reducing the pressure of tail gas treatment and benefiting the environment. The addition of lime can effectively increase the melting point of sodium sulfate, preventing the formation of a glassy state in the reaction above 880℃, which would lead to a decrease in the conversion rate.

[0012] Preferably, in S1, the mass ratio of lepidolite to sodium potassium sulfate, calcium sulfate, calcium hydroxide, lime, and quartz on a dry basis is 100:(10-15):(30-35):(3-5):(3-5):(2-4).

[0013] This allows for the improvement of lithium leaching rate through appropriate combinations.

[0014] Preferably, in step S1, the lithium oxide grade of the lepidolite is 1.8-2.0%.

[0015] This facilitates the lithium extraction process from low-grade lithium mica ore.

[0016] Preferably, in S1: the calcium oxide content of lime is ≥80%, and the silicon dioxide content of quartz is ≥90%.

[0017] It facilitates the absorption of HF gas produced by the reaction, thus avoiding the reduction of lithium leaching due to the combination of fluorine and lithium.

[0018] Preferably, in step S1: the brick blank is pressed into a brick blank by a hydraulic brick-making machine, and the compressive strength of the brick blank is 23-25 ​​MPa.

[0019] This allows for more thorough contact between lepidolite and auxiliary materials, which is beneficial for solid-phase reaction. In addition, the use of tunnel kiln for roasting can precisely control the reaction temperature and reaction time, ensuring that the brick blanks are roasted into clinker, thereby improving the conversion rate.

[0020] Preferably, in S2, the temperature of high-temperature calcination is 900-950 DEG C, and the calcination time is 60-120 min.

[0021] The transformation rate and total recovery rate of the clinker lithium are ensured by the suitable calcination time.

[0022] Preferably, in S2, the fine powder clinker particle size is controlled to be more than 95% of -100 mesh.

[0023] The leaching effect is improved by the better contact area.

[0024] Preferably, in S3, the liquid-solid ratio of water immersion is controlled to be (1.2-1.5):1, the leaching time is 30-50 min, and the leaching temperature is 50 DEG C-80 DEG C.

[0025] Preferably, in S4, the lithium precipitation reaction temperature is 90-95 DEG C.

[0026] The lithium is precipitated by the lithium precipitation reaction, and the coarse lithium carbonate and the lithium precipitation mother liquor are obtained by centrifugal separation.

[0027] Preferably, in S5, the lithium precipitation mother liquor is decarburized by sulfuric acid to pH 5.5-6.5, and then neutralized to pH 7.5-8.5 by sodium hydroxide.

[0028] The lithium precipitation mother liquor is decarburized to adjust the pH value for neutralization.

[0029] Compared with the prior art, the present application has the beneficial effects that:

[0030] (1) The present application uses sodium sulfate potassium salt, which contains 8-12% of potassium sulfate, to accelerate the solid phase reconstruction reaction of lepidolite, thereby improving the conversion rate of lithium; on the other hand, the addition of quartz can effectively reduce the free energy of the solid phase reaction of lepidolite and sulfate, so that low-grade lepidolite can also have a good transformation rate; the addition of lime and calcium hydroxide is significantly better than the addition of calcium carbonate, which not only can effectively absorb the HF gas generated in the reaction, can avoid the reduction of lithium leaching due to the combination of fluorine and lithium, is conducive to improving the leaching rate of lithium, but also can effectively absorb SO2 and SO3 generated in the calcination process, reduce the tail gas treatment pressure, and is beneficial to environmental protection; the addition of lime can effectively improve the melting point of sodium sulfate, prevent the formation of glass state in the reaction above 880 DEG C, and reduce the transformation rate.

[0031] (2) The present application adopts the method of entering the tunnel kiln for calcination after pressing the bricks, which can make the contact between lepidolite and auxiliary materials more sufficient, is conducive to the solid phase reaction, and in addition, the tunnel kiln calcination can precisely control the reaction temperature and reaction time, ensure the clinker to be fired, and thereby improve the transformation rate.

[0032] (3) The amount of recovered sodium potassium sulfate is basically the same as the amount of sodium potassium sulfate used in the mixing, material circulation is achieved, and the method is more environmentally friendly, energy-saving, and cost-saving. DETAILED DESCRIPTION

[0033] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of the present application.

[0034] Embodiment 1

[0035] The present application provides a technical solution: a method for efficiently and cleanly extracting lithium from low-grade lepidolite, comprising the following steps:

[0036] S1: uniformly mix lepidolite ore with sodium potassium sulfate, calcium sulfate, calcium hydroxide, lime, and quartz, then press the mixed raw material into a brick billet, and the sodium potassium sulfate contains 8-12% potassium sulfate;

[0037] S2: after the brick billet is stacked, preheated and dried, high-temperature calcined, cooled, crushed, and ground into powder, a fine powder clinker is obtained;

[0038] S3: the fine powder clinker is leached with water, and a leaching solution is obtained through solid-liquid separation;

[0039] S4: the leaching solution is subjected to impurity removal, concentration, lithium precipitation, and centrifugal separation to obtain coarse lithium carbonate and a mother liquor after lithium precipitation, and then the coarse lithium carbonate is subjected to stirring washing, drying, and crushing to obtain battery-grade lithium carbonate, so as to ensure the effect of lithium extraction by impurity removal and reduce the influence of impurities;

[0040] S5: the mother liquor after lithium precipitation is subjected to decarburization, neutralization, and concentration to obtain recovered sodium potassium sulfate and a concentrated mother liquor, and then the recovered sodium potassium sulfate is returned to S1 for mixing, and the concentrated mother liquor is returned to S4.

[0041] In S4, lime is first added to the leaching solution to remove iron, and the pH is controlled to be 7.5-8.5 to obtain a first purified solution. Pure alkali is then added to the first purified solution to remove impurities, and the amount of pure alkali added is 105-110% of the theoretical value of calcium and magnesium ions in the solution being converted into calcium carbonate and magnesium carbonate. After stirring and filtration, a second impurity removal residue and a second purified solution are obtained. The second purified solution is first concentrated to a lithium oxide concentration of 28-30 g / L by MVR, and then subjected to resin filtration for deep calcium and magnesium removal to obtain a purified complete solution. Pure alkali solution is added to the purified complete solution, and the amount of pure alkali used is 105-115% of the theoretical value of sodium carbonate required to convert all lithium ions in the solution into lithium carbonate.

[0042] Preferably, in S1: the mass fraction ratio of lepidolite, sodium potassium sulfate, calcium sulfate, calcium hydroxide, lime, quartz is 100: (10-15) : (30-35) : (3-5) : (3-5) : (2-4) on a dry basis.

[0043] Preferably, in S1: the lithium oxide grade of lepidolite is 1.8-2.0%.

[0044] Preferably, in S1: the calcium oxide main content of lime is ≥80%, and the silicon dioxide content of quartz is ≥90%.

[0045] Preferably, in S1: the green brick is pressed by a hydraulic brick press, and the compressive strength of the green brick is 23-25 MPa.

[0046] Preferably, in S2: the high-temperature roasting temperature is 900-950℃, and the roasting time is 60-120 min; in S3, the preheating and drying are performed using the waste heat of high-temperature roasting.

[0047] Preferably, in S2: the fine powder clinker particle size is controlled to be more than 95% of -100 mesh.

[0048] Preferably, in S3: the liquid-solid ratio is controlled to be (1.2-1.5) : 1, the leaching time is 30-50 min, the leaching temperature is 50℃-80℃, the filter residue is repeatedly washed with water twice, the filter residue is repeatedly washed with circulating water twice, the wash filtrate is returned step by step, and the lithium oxide content of the leaching liquid is ensured to be 15-20 g / L.

[0049] Preferably, in S4: the lithium precipitation reaction temperature is 90-95℃, the reaction time is 2-3h, the coarse lithium carbonate is obtained by centrifugal separation, the coarse lithium carbonate is stirred and washed with pure water at 90℃ or above for 30-60 min at a solid-liquid ratio of 1:3-4, and the battery-grade lithium carbonate is obtained by centrifugal separation and drying and crushing, and the washing water is used to prepare a soda solution.

[0050] Preferably, in S5: the mother liquor after lithium precipitation is decarburized to pH 5.5-6.5 with sulfuric acid, and then neutralized to pH 7.5-8.5 with sodium hydroxide, the neutralization reaction end point pH is controlled to be 7.5-8.5, the decarburized mother liquor is centrifugally separated after MVR concentration to obtain sodium potassium sulfate, which is used for mixing in S1, the amount of generated sodium potassium sulfate is balanced with the amount of sodium potassium sulfate used in S1, material circulation is realized, and the mother liquor after evaporation is repeatedly operated in S4.

[0051] Example 2

[0052] The present application provides a technical solution: a method for efficiently and cleanly extracting lithium from low-grade lepidolite, comprising the following steps:

[0053] S1, the lithium oxide grade is 2.0% lepidolite ore according to the mass fraction ratio of lepidolite:sodium potassium sulfate, calcium sulfate, calcium hydroxide, lime, quartz is 100:13:30:4:3:3, fully mixed, get mixed raw material, the mixed raw material is pressed into a brick by a hydraulic brick press, the compressive strength of the green brick is controlled to be 23.5Mpa;

[0054] S2, the green brick of S1 is stacked, dried by entering the preheating drying tunnel kiln through the kiln car, and calcined at high temperature by entering the calcining tunnel kiln, the calcining temperature is controlled to be 920℃, the high temperature calcining time is 70min, the calcined clinker is obtained, and then cooled in the cooling kiln, crushed, ground in the vertical mill, the ground powder particle size is controlled to be-100 mesh, accounting for 95%, and the fine powder clinker is obtained;

[0055] S3, the fine powder clinker obtained in S2 is added into the first washing residue filtrate for leaching, the liquid-solid ratio is controlled to be 1.2:1, the stirring leaching time is 30min, the leaching liquid is obtained by filtration, the residue is washed with circulating water for 2 times, the washing residue filtrate is returned step by step, and the leaching liquid is controlled to have a lithium oxide content of 15-20g / L.

[0056] S4, the leaching liquid of S3 is first added into lime for iron removal, the pH is controlled to be 8-9, the first purification liquid and the first purification residue are obtained by filtration; the first purification liquid is further added into soda ash for impurity removal, the addition amount is 105-110% of the theoretical value of calcium and magnesium ions in the solution being converted into calcium carbonate and magnesium carbonate, stirring and filtration are carried out, the second impurity removal residue and the second purification liquid are obtained; the second purification liquid is further concentrated to a lithium oxide concentration of 28-30g / L by MVR, a lithium sulfate concentrate is obtained, the concentrate is filtered by resin for deep calcium and magnesium removal, and the purified completed liquid is obtained; the purified completed liquid is added into a soda ash solution, the amount of soda ash is 105-115% of the theoretical value of sodium carbonate required for converting all lithium ions in the solution into lithium carbonate, the lithium precipitation reaction temperature is controlled to be 95℃, the reaction time is 2h, and the crude lithium carbonate and the lithium precipitation mother liquor are obtained by centrifugal separation, the crude lithium carbonate is further stirred and washed twice by adding pure water at a solid-liquid ratio of 1:4 at 90℃, the stirring and washing time is 40min, the second washing lithium carbonate is obtained by centrifugal separation, the second washing lithium carbonate is dried and then airflow pulverized to obtain battery-grade lithium carbonate, and the first washing water is used for preparing the soda ash solution;

[0057] S5, the lithium precipitation mother liquor obtained in S4 is added into concentrated sulfuric acid for decarburization, the reaction end point pH is controlled to be 5.5-6.5, the decarburization mother liquor is further added into sodium hydroxide for neutralization, the reaction end point pH is controlled to be 7.5-8.5, the neutralization mother liquor is centrifugally separated after MVR concentration to obtain sodium sulfate potassium salt and concentrated mother liquor, the sodium sulfate potassium salt is returned to S1 for mixing, the amount of generated sodium sulfate potassium salt is balanced with the amount of sodium sulfate potassium salt used in S1, material circulation is realized, and the concentrated mother liquor is repeatedly operated in S4;

[0058] The transformation rate of the S2 clinker is detected, and the lithium oxide grade of the leaching residue is detected, wherein the calculation method of the transformation rate is as follows:

[0059]

[0060] The transformation rate of the clinker lithium in the above method is 89.7%, and the total lithium recovery rate is 76.3%.

[0061] Example 3

[0062] The present application provides a technical solution: a method for efficiently and cleanly extracting lithium from low-grade lepidolite, comprising the following steps:

[0063] S1, the lithium oxide grade of 1.95% lepidolite is fully mixed according to the mass fraction ratio of lepidolite:sodium potassium sulfate:calcium sulfate:calcium hydroxide:lime:quartz is 100:15:30:3:4:3, to obtain mixed raw material, the mixed raw material is pressed into a brick by a hydraulic brick press, and the compressive strength of the brick is controlled to be 24Mpa;

[0064] S2, the brick of S1 is stacked, dried by a preheating drying tunnel kiln through a kiln car, and high-temperature calcined by a firing tunnel kiln, the calcination temperature is controlled to be 930℃, the high-temperature calcination time is 80min, the fired clinker is obtained, and then cooled by a cooling kiln, crushed, ground by a vertical mill, the ground powder particle size is controlled to be-100 mesh accounting for 95%, and the fine powder clinker is obtained;

[0065] S3, the fine powder clinker obtained in S2 is added to the first washing residue filtrate for leaching, the liquid-solid ratio is controlled to be 1.2:1, the stirring leaching time is 30min, the leaching liquid is obtained by filtering, the filter residue is washed with circulating water for 2 times, the washing filtrate is returned step by step, and the leaching liquid lithium oxide content is ensured to be 15-20g / L.

[0066] S4, the leaching solution is first added with lime to remove iron, and the pH is controlled at 8-9, and filtration is performed to obtain a primary purified solution and a primary purified residue; the primary purified solution is further added with soda ash to remove impurities, and the amount of soda ash added is 105-110% of the theoretical value of the amount of calcium and magnesium ions in the solution converted into calcium carbonate and magnesium carbonate, and stirring and filtration are performed to obtain a secondary impurity removal residue and a secondary purified solution; the secondary purified solution is further concentrated by MVR to obtain a lithium sulfate concentrated solution with a lithium oxide concentration of 28-30 g / L, and the concentrated solution is subjected to resin filtration for deep calcium and magnesium removal to obtain a purified completed solution; the purified completed solution is added with a pure alkali solution, and the amount of pure alkali used is 105-115% of the theoretical value of the amount of sodium carbonate required for the conversion of all lithium ions in the solution into lithium carbonate, the lithium precipitation reaction temperature is controlled at 95℃, the reaction time is 2h, and centrifugal separation is performed to obtain crude lithium carbonate and a lithium precipitation mother liquor, and the crude lithium carbonate is further stirred and washed twice with pure water at a solid-liquid ratio of 1:4 at 90℃, the stirring and washing time is 40min, and centrifugal separation is performed to obtain two-washed lithium carbonate, and the two-washed lithium carbonate is dried and then subjected to airflow crushing to obtain battery-grade lithium carbonate, and the first washing water is used to prepare a pure alkali solution;

[0067] S5, the lithium precipitation mother liquor is added with concentrated sulfuric acid for decarburization, and the reaction end point pH is controlled at 5.5-6.5, the decarburized mother liquor is further added with sodium hydroxide for neutralization, and the reaction end point pH is controlled at 7.5-8.5, the neutralized mother liquor is concentrated by MVR and then subjected to centrifugal separation to obtain a sodium sulfate potassium salt and a concentrated mother liquor, the sodium sulfate potassium salt is returned to S1 for mixing, and the amount of generated sodium sulfate potassium salt reaches the amount of sodium sulfate potassium salt used in S1 to achieve balance, realizing material circulation, and the concentrated mother liquor is subjected to the operation of S4 repeatedly;

[0068] The conversion rate of the clinker is detected, and the lithium oxide grade of the leaching residue, wherein the conversion rate is calculated as follows:

[0069]

[0070] Through detection, the conversion rate of lithium in the clinker obtained by the above method is 88.96%, and the total lithium recovery rate is 75.82%.

[0071] Example 4

[0072] The present application provides a technical solution: a method for efficiently and cleanly extracting lithium from low-grade lepidolite, comprising the following steps:

[0073] S1, the lithium oxide grade is 1.9% lepidolite ore, and the lepidolite is fully mixed with sodium potassium sulfate, calcium sulfate, calcium hydroxide, lime and quartz in a mass ratio of 100:15:31:4:4:3 to obtain mixed raw material, and the mixed raw material is pressed into a brick by a hydraulic brick press, and the compressive strength of the brick is controlled at 24Mpa;

[0074] S2, the brick of S1 is stacked, enters the preheating drying tunnel kiln through the kiln car, is dried, enters the firing tunnel kiln and is high-temperature calcined, the calcination temperature is controlled to be 950 DEG C, the high-temperature section calcination time is 90 min, the sintered clinker is obtained, after cooling in the cooling kiln, is broken, enters the vertical mill and is ground, the grinding granularity is controlled to be-100 mesh 95%, the fine powder clinker is obtained;

[0075] S3, the fine powder clinker obtained in S2 is added into the first washing residue filtrate and is leached, the liquid-solid ratio is controlled to be 1.3:1, the stirring leaching time is 30 min, the leaching liquid is obtained after filtration, the residue is washed with circulating water repeatedly 2 times, the washing residue filtrate is returned gradually, the leaching liquid is oxidized lithium content is ensured to be 15-20 g / L.

[0076] S4, the leaching liquid is first added with lime to remove iron, the pH is controlled to be 8-9, the first purification liquid and the first purification residue are obtained after filtration; the first purification liquid is added with soda ash to remove impurities, the addition amount is 105-110% of the theoretical value of the calcium and magnesium ions in the solution being converted into calcium carbonate and magnesium carbonate, stirring and filtration are carried out, the second impurity removal residue and the second purification liquid are obtained; the second purification liquid is concentrated to the lithium oxide concentration of 28-30 g / L through MVR, the lithium sulfate concentrated liquid is obtained, the concentrated liquid is filtered through resin to remove calcium and magnesium in depth, the purification completed liquid is obtained; the purification completed liquid is added with soda solution, the amount of soda is 105-115% of the theoretical value of the sodium carbonate required for converting all lithium ions in the solution into lithium carbonate, the lithium precipitation reaction temperature is controlled to be 95 DEG C, the reaction time is 2 h, the coarse lithium carbonate and the lithium precipitation mother liquor are obtained after centrifugal separation, the coarse lithium carbonate is stirred and washed twice at 90 DEG C by adding pure water with the solid-liquid ratio of 1:4, the stirring and washing time is 40 min, the second washing lithium carbonate is obtained after centrifugal separation, the second washing lithium carbonate is dried and then is air flow pulverized to obtain the battery-grade lithium carbonate, the first washing water is used to prepare the soda solution;

[0077] S5, the lithium precipitation mother liquor is added with concentrated sulfuric acid to remove carbon, the reaction end point pH is controlled to be 5.5-6.5, the carbon removal mother liquor is added with sodium hydroxide for neutralization, the reaction end point pH is controlled to be 7.5-8.5, the neutralization mother liquor is centrifugally separated after MVR concentration to obtain the sodium sulfate potassium salt and the concentrated mother liquor, the sodium sulfate potassium salt is returned to S1 for mixing, and the amount of the generated sodium sulfate potassium salt reaches the amount of the sodium sulfate potassium salt used in S1, so that the material circulation is realized, and the concentrated mother liquor is repeatedly operated in S4;

[0078] The sintered clinker is detected to obtain the transformation rate and the leaching residue lithium oxide grade, wherein the transformation rate is calculated as follows:

[0079]

[0080] After detection, the transformation rate of the lithium sintered clinker in the above method is 90.02%, and the total lithium recovery rate is 77.65%.

[0081] Comparative Example 1

[0082] The present comparative example provides a method for efficient and clean lithium extraction from low-grade lepidolite, comprising the following steps:

[0083] S1, fully mix 2.0% lithium grade lithium oxide mica with sodium potassium sulfate, calcium sulfate, calcium hydroxide, lime, and quartz in a mass fraction ratio of 100:13:30:4:3:3 to obtain mixed raw material. The mixed raw material is pressed into a brick by a hydraulic brick press, and the compressive strength of the brick is controlled to be 23.5 MPa;

[0084] S2, the brick is stacked and dried in a preheating tunnel kiln, and then transferred to a firing tunnel kiln for high-temperature calcination. The calcination temperature is controlled to be 950°C, and the high-temperature calcination time is 70 min. The calcined clinker is cooled in a cooling kiln and then crushed. The crushed clinker is ground in a vertical mill, and the particle size of the ground powder is controlled to be 95% passing -100 mesh to obtain fine powder clinker;

[0085] S3, the fine powder clinker obtained in S2 is added to the first washing filtrate for leaching. The liquid-solid ratio is controlled to be 1.2:1, and the stirring leaching time is 30 min. The leaching liquid is obtained by filtration. The filter residue is washed with recycled water for 2 times, and the washing filtrate is returned step by step. The lithium oxide content of the leaching liquid is ensured to be 15-20 g / L.

[0086] S4, the leaching liquid is first added with lime to remove iron, and the pH is controlled to be 8-9. The first purification liquid and the first purification residue are obtained by filtration. The first purification liquid is then added with soda ash to remove impurities. The amount of soda ash added is 105-110% of the theoretical value of calcium and magnesium ions in the solution converted to calcium carbonate and magnesium carbonate. The mixture is stirred and filtered to obtain the second impurity removal residue and the second purification liquid. The second purification liquid is concentrated to a lithium oxide concentration of 28-30 g / L by MVR to obtain a lithium sulfate concentrate. The concentrate is filtered through a resin to remove calcium and magnesium in depth to obtain a purified completed liquid. The purified completed liquid is added with a pure alkali solution. The amount of pure alkali used is 105-115% of the theoretical value of sodium carbonate required to convert all lithium ions in the solution to lithium carbonate. The lithium precipitation reaction temperature is controlled to be 95°C, and the reaction time is 2 h. The crude lithium carbonate and the lithium precipitation mother liquor are obtained by centrifugal separation. The crude lithium carbonate is stirred and washed twice with pure water at 90°C at a solid-liquid ratio of 1:4. The stirring and washing time is 40 min. The second washing lithium carbonate is obtained by centrifugal separation. The second washing lithium carbonate is dried and then air-ground to obtain battery-grade lithium carbonate. The first washing water is used to prepare a pure alkali solution;

[0087] S5, the lithium-sinked mother liquor is added with concentrated sulfuric acid for decarburization, the reaction end-point pH is controlled at 5.5-6.5, the decarburization mother liquor is added with sodium hydroxide for neutralization, the reaction end-point pH is controlled at 7.5-8.5, the neutralized mother liquor is concentrated by MVR and then centrifuged to obtain sodium sulfate potassium salt and concentrated mother liquor, the sodium sulfate potassium salt is returned to S1 for mixing, and the amount of the generated sodium sulfate potassium salt reaches the amount of the sodium sulfate potassium salt used in S1 to achieve material circulation, and the concentrated mother liquor is repeatedly operated in S4;

[0088] The conversion rate of the clinker in S2 is detected, and the lithium oxide grade of the leaching residue is detected, wherein the conversion rate is calculated as follows:

[0089]

[0090] Compared with Example 2, the calcination temperature is increased from 920℃ to 950℃

[0091] It is detected that the conversion rate of lithium in the clinker is 91.32% and the total recovery rate is 78.08% by the above method.

[0092] Comparative Example 2

[0093] The present comparative example provides a method for efficiently and cleanly extracting lithium from low-grade lepidolite, comprising the following steps:

[0094] S1, lithium oxide grade 1.95% lepidolite ore is fully mixed according to the mass fraction ratio of lepidolite:sodium potassium sulfate, calcium sulfate, calcium hydroxide, lime, quartz as 100:10:30:3:4:3 to obtain mixed raw material, and the mixed raw material is pressed into a brick by a hydraulic brick press, and the compressive strength of the brick is controlled at 24Mpa;

[0095] S2, the brick of S1 is stacked and dried by a preheating drying tunnel kiln, and then transferred to a firing tunnel kiln for high-temperature calcination, and the calcination temperature is controlled at 930℃, and the high-temperature calcination time is 80min, to obtain fired clinker, which is then cooled in a cooling kiln and crushed, and then ground in a vertical mill to control the particle size of the ground powder to 95% of-100 mesh to obtain fine powder clinker;

[0096] S3, the fine powder clinker obtained in S2 is added to the first washing residue filtrate for leaching, the liquid-solid ratio is controlled at 1.2:1, the stirring leaching time is 30min, and the filtrate is obtained by filtration, the filter residue is washed with circulating water for 2 times, the washing filtrate is returned step by step, and the lithium oxide content of the leaching filtrate is ensured at 15-20g / L.

[0097] S4, the leaching solution is first added with lime to remove iron, and the pH is controlled at 8-9, and filtration is performed to obtain a primary purified solution and a primary purified residue; the primary purified solution is further added with soda ash to remove impurities, and the amount of soda ash added is 105-110% of the theoretical value of the amount of calcium and magnesium ions in the solution converted into calcium carbonate and magnesium carbonate, and stirring and filtration are performed to obtain a secondary impurity removal residue and a secondary purified solution; the secondary purified solution is further concentrated by MVR to obtain a lithium sulfate concentrate solution with a lithium oxide concentration of 28-30 g / L, and the concentrate solution is subjected to resin filtration for deep calcium and magnesium removal to obtain a purified completed solution; the purified completed solution is added with a pure alkali solution, and the amount of pure alkali used is 105-115% of the theoretical value of the amount of sodium carbonate required for the conversion of all lithium ions in the solution into lithium carbonate, the lithium precipitation reaction temperature is controlled at 95°C, the reaction time is 2 h, and centrifugal separation is performed to obtain crude lithium carbonate and a lithium precipitation mother liquor, and the crude lithium carbonate is further stirred and washed twice with pure water at a solid-liquid ratio of 1:4 at 90°C, the stirring and washing time is 40 min, and centrifugal separation is performed to obtain two-washed lithium carbonate, and the two-washed lithium carbonate is dried and then subjected to airflow crushing to obtain battery-grade lithium carbonate, and the first washing water is used to prepare a pure alkali solution;

[0098] S5, the lithium precipitation mother liquor is added with concentrated sulfuric acid for decarburization, and the reaction end point pH is controlled at 5.5-6.5, the decarburized mother liquor is further added with sodium hydroxide for neutralization, and the reaction end point pH is controlled at 7.5-8.5, the neutralized mother liquor is concentrated by MVR and then subjected to centrifugal separation to obtain a sodium sulfate potassium salt and a concentrated mother liquor, the sodium sulfate potassium salt is returned to S1 for mixing, and the amount of generated sodium sulfate potassium salt reaches the amount of sodium sulfate potassium salt used in S1 to achieve balance, realizing material circulation, and the concentrated mother liquor is subjected to the operation of S4 repeatedly;

[0099] The conversion rate of the clinker is detected, and the lithium oxide grade of the leaching residue, wherein the conversion rate is calculated as follows:

[0100]

[0101] Compared with Example 3, the sodium-potassium sulfate ratio is reduced.

[0102] It is detected that the conversion rate of lithium in the clinker obtained by the above method is 85.84%, and the total lithium recovery rate is 74.22%.

[0103] Comparative Example 3

[0104] The present embodiment provides a method for efficiently and cleanly extracting lithium from low-grade lepidolite, comprising the following steps:

[0105] S1, lithium oxide grade 1.9% lepidolite ore is fully mixed according to the mass fraction ratio of lepidolite:sodium-potassium sulfate, calcium sulfate, calcium hydroxide, lime, and quartz of 100:15:31:4:4:3 to obtain mixed raw material, and the mixed raw material is pressed into a brick by a hydraulic brick press, and the compressive strength of the brick is controlled at 24 Mpa;

[0106] S2, the brick of S1 is stacked, enters the preheating drying tunnel kiln through the kiln car, is dried, enters the firing tunnel kiln and is fired at high temperature, the firing temperature is controlled to be 950 DEG C, the firing time at high temperature is 60 min, the fired grog is obtained, after cooling in the cooling kiln, is broken, enters the vertical mill and is ground, the grinding granularity is controlled to be 95% of-100 mesh, the fine powder grog is obtained;

[0107] S3, the fine powder grog obtained in S2 is added into the first washing residue filtrate and is leached, the liquid-solid ratio is controlled to be 1.3:1, the stirring leaching time is 30 min, the leaching liquid is obtained after filtration, the residue is washed with circulating water for 2 times, the washing residue filtrate is returned gradually, the lithium oxide content of the leaching liquid is ensured to be 15-20 g / L.

[0108] S4, the leaching liquid is first added with lime to remove iron, the pH is controlled to be 8-9, the first purification liquid and the first purification residue are obtained after filtration, the first purification liquid is added with soda ash to remove impurities, the addition amount is 105-110% of the theoretical value of the calcium and magnesium ions in the solution being converted into calcium carbonate and magnesium carbonate, stirring and filtration are carried out, the second impurity removal residue and the second purification liquid are obtained, the second purification liquid is concentrated to the lithium oxide concentration of 28-30 g / L through MVR, the lithium sulfate concentrated liquid is obtained, the concentrated liquid is filtered through resin to remove calcium and magnesium in depth, the purification completed liquid is obtained, the purification completed liquid is added with soda ash solution, the amount of soda ash is 105-115% of the theoretical value of the sodium carbonate required for converting all lithium ions in the solution into lithium carbonate, the lithium precipitation reaction temperature is controlled to be 95 DEG C, the reaction time is 2 h, the coarse lithium carbonate and the mother liquor after lithium precipitation are obtained through centrifugal separation, the coarse lithium carbonate is stirred and washed twice at 90 DEG C by adding pure water with the solid-liquid ratio of 1:4, the stirring and washing time is 40 min, the second washing lithium carbonate is obtained through centrifugal separation, the second washing lithium carbonate is dried and then is air-ground to obtain the battery-grade lithium carbonate, the first washing water is used to prepare the soda ash solution;

[0109] S5, the mother liquor after lithium precipitation is added with concentrated sulfuric acid to remove carbon, the reaction end point pH is controlled to be 5.5-6.5, the carbon removal mother liquor is added with sodium hydroxide for neutralization, the reaction end point pH is controlled to be 7.5-8.5, the neutralization mother liquor is centrifugally separated after MVR concentration to obtain the sodium sulfate potassium salt and the concentrated mother liquor, the sodium sulfate potassium salt is returned to S1 for mixing, and the amount of the generated sodium sulfate potassium salt is balanced with the amount of the sodium sulfate potassium salt used in S1, the material circulation is realized, and the concentrated mother liquor is repeated in the operation of S4;

[0110] The conversion rate of S2 grog is detected, and the lithium oxide grade of the leaching residue, wherein the conversion rate is calculated as follows:

[0111]

[0112] Compared with example 4, the firing time is reduced from 90 min to 60 min.

[0113] The transformation rate of the above method for the calcined lithium is 86.07%, and the total recovery rate is 75.64%.

[0114] While embodiments of the application have been shown and described, it is to be understood that the embodiments described are merely divergences of the principles and spirit of the application and that numerous modifications, changes, substitutions, and alterations can be made thereto without departing from the spirit and scope of the application as defined by the appended claims and their equivalents.

Claims

1. A method for efficient and clean lithium extraction from low-grade lepidolite, characterized in that, Includes the following steps: S1: Mix lepidolite with sodium potassium sulfate, calcium sulfate, calcium hydroxide, lime, and quartz evenly, and then press the mixed raw material into brick blanks; S2. The brick blanks are stacked, preheated and dried, fired at high temperature, cooled, crushed and ground to obtain fine powder clinker; S3: The fine powder clinker is leached with water, and then the leachate is obtained by solid-liquid separation; S4: The leachate is purified, concentrated, lithium precipitated, and centrifuged to obtain crude lithium carbonate and lithium precipitated mother liquor. Then, the crude lithium carbonate is washed, dried, and pulverized to obtain battery-grade lithium carbonate. S5: The mother liquor after lithium precipitation is decarbonized, neutralized, and concentrated to obtain recovered sodium and potassium sulfate and concentrated mother liquor. Then, the recovered sodium and potassium sulfate is returned to S1 for mixing, and the concentrated mother liquor is returned to S4. In S1, the mass ratio of lepidolite to sodium potassium sulfate, calcium sulfate, calcium hydroxide, lime, and quartz on a dry basis is 100: (10-15): (30-35): (3-5): (3-5): (2-4); In S2: the calcination temperature is 950℃ and the calcination time is 60-120min.

2. The method for efficient and clean lithium extraction from low-grade lepidolite according to claim 1, characterized in that, In S1: the lithium oxide grade of the lepidolite is 1.8-2.0%.

3. The method for efficient and clean lithium extraction from low-grade lepidolite according to claim 1, characterized in that, In S1: the calcium oxide content of lime is ≥80%, and the silicon dioxide content of quartz is ≥90%.

4. The method for efficient and clean lithium extraction from low-grade lepidolite according to claim 1, characterized in that, In S1: brick blanks are formed by pressing with a hydraulic brick-making machine, and the compressive strength of the brick blanks is 23-25 ​​MPa.

5. The method for efficient and clean lithium extraction from low-grade lepidolite according to claim 1, characterized in that, In S2: the particle size of the fine clinker is controlled to be more than 95% of -100 mesh.

6. The method for efficient and clean lithium extraction from low-grade lepidolite according to claim 1, characterized in that, In S3: the water-to-solid ratio is controlled at (1.2-1.5):1, the leaching time is 30-50 min, and the leaching temperature is 50℃-80℃.

7. The method for efficient and clean lithium extraction from low-grade lepidolite according to claim 1, characterized in that, In S4, the lithium deposition reaction temperature is 90-95℃.

8. The method for efficient and clean lithium extraction from low-grade lepidolite according to claim 1, characterized in that, In S5: the mother liquor after lithium precipitation is decarbonized with sulfuric acid to a pH of 5.5-6.5, and then neutralized with sodium hydroxide to a pH of 7.5-8.5.

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