Method and system for extracting lithium from lepidolite ore through low-temperature salt-free fluidized roasting

Abstract

The invention provides a method and system for extracting lithium from lepidolite ore through low-temperature salt-free fluidized roasting, and the method comprises the following steps: S1, providing lepidolite ore particles; s2, the lepidolite ore particles and fluidizing gas are subjected to fluidized roasting treatment, Li-F ore phases in the lepidolite ore particles are dissociated to release fluorine ions, the fluorine ions and hydrogen ions are combined to generate hydrogen fluoride gas, the hydrogen fluoride gas is diffused into a gas phase from the interiors of the lepidolite ore particles, and roasted clinker and fluorine-containing tail gas are obtained; wherein the fluidizing gas comprises water vapor, and the volume percentage content of the water vapor in the fluidizing gas is not less than 30%. According to the method, the lepidolite ore particles can be dissociated under the conditions that the temperature is low and other auxiliaries do not need to be added, so that the method is low in energy consumption, and the amount of generated smelting slag is small.

Description

Technical Field

[0001] The present application belongs to the technical field of lithium-containing mineral processing, and specifically relates to a method and system for low-temperature salt-free fluidized roasting and lithium extraction of lithium mica ore. Background Art

[0002] Lithium is known as the "white oil" of the 21st century. Lithium and its compounds are widely used in lithium batteries, ceramics, glass, aluminum smelting, medicine and other industrial fields. In recent years, with the widespread application of lithium-ion batteries in portable electronic devices, electric vehicles, space technology and defense industry, the demand for lithium has increased. my country has abundant lepidolite resources, but the low-grade Li2O content is generally less than 2wt%, resulting in 30 to 60 tons of slag per ton of lithium carbonate. Moreover, since the slag contains toxic elements such as fluorine, beryllium and thallium, it poses a serious environmental safety risk. Therefore, how to reduce the amount of smelting slag, energy consumption and the content of easily lost toxic components in smelting lepidolite is of great significance to the green and high-quality utilization of my country's lithium resources. Summary of the invention

[0003] In view of this, the present application provides a method and system for low-temperature salt-free fluidized roasting and lithium extraction of lepidolite ore, aiming to reduce the amount of smelting slag and energy consumption in smelting lepidolite ore.

[0004] In a first aspect, the present application provides a method for extracting lithium by low-temperature salt-free fluidized roasting of lepidolite ore, comprising the following steps: Step S1: providing lepidolite particles; Step S2: preheating the lithium mica ore particles and the fluidizing gas respectively, so that the temperature of the preheated lithium mica ore particles is 700-790° C. and the temperature of the preheated fluidizing gas is 700-850° C., and fluidizing roasting the preheated lithium mica ore particles and the fluidizing gas so that the Li-F mineral phase in the lithium mica ore particles dissociates and releases fluoride ions, and the fluoride ions combine with hydrogen ions to generate hydrogen fluoride gas that diffuses from the inside of the lithium mica ore particles to the gas phase, thereby obtaining roasted clinker and fluorine-containing tail gas; wherein the fluidizing gas includes water vapor, and the volume percentage of the water vapor in the fluidizing gas is not less than 30%.

[0005] Based on the present application, the method preheats the lithium mica ore particles and the fluidizing gas containing a water vapor volume percentage of not less than 30% to the above temperature, and then performs a fluidized roasting treatment, wherein the preheating treatment is conducive to the rapid adsorption of water vapor on the surface of the lithium mica particles and its inward diffusion, thereby promoting the subsequent full dissociation of the lithium mica ore particles. At the same time, the temperature of the preheated lithium mica ore particles is 700-790°C, which can reduce the dissociation of the lithium mica ore particles during the preheating process to release HF and other toxic metal elements (such as thallium, etc.), reduce the erosion of the preheating device and the pipeline, and in addition, because the preheating device is not connected to the tail gas treatment unit The preheating temperature of the lithium mica ore particles is controlled within the above range, which can also reduce the pollution to the environment; the temperature of the fluidized gas after preheating is 700-850°C, and the higher temperature fluidized gas can further promote the rapid adsorption of water vapor on the surface of the lithium mica particles and diffuse inward; during the fluidized roasting process, the Li-F phase dissociation in the lithium mica ore particles can be enhanced under high water vapor partial pressure, and the fluidized roasting process can also further enhance the dissociation effect, thereby achieving the dissociation of the lithium mica ore particles at a lower temperature without adding other additives, so the energy consumption of the method is low and the amount of smelting slag produced is small. In addition, the full dissociation of the lithium mica ore particles is conducive to reducing the content of the easily lost toxic components in the roasted clinker and improving the recovery rate of the lithium element. At the same time, the lower reaction temperature can also reduce the erosion of the reaction device by HF in the gas phase.

[0006] In some embodiments, the volume percentage of the water vapor in the fluidizing gas is not less than 40%; preferably, not less than 50%.

[0007] In some embodiments, in step S1, the average particle size of the lepidolite particles is 0.1-0.5 mm.

[0008] In some embodiments, in step S2, the conditions of the fluidized calcination treatment include: the temperature of the fluidized calcination is 810-850° C., and the time of the fluidized calcination is 0.5-2 h.

[0009] In some embodiments, in step S2, the conditions of the fluidized roasting treatment include: the lepidolite ore particles are in countercurrent contact with the fluidizing gas.

[0010] In some embodiments, the step S2 further comprises: before the fluidized roasting treatment, preheating the lepidolite ore particles and the fluidizing gas respectively, so that the temperature of the preheated lepidolite ore particles is 700-790°C and the temperature of the preheated fluidizing gas is 700-850°C.

[0011] In some embodiments, the method further includes: Step S3: subjecting the roasted clinker to acid leaching using an acid solution to fix the lithium element in the roasted clinker into the leaching solution, and filtering to obtain leaching residue and the leaching solution.

[0012] In some embodiments, the acid solution is an aqueous sulfuric acid solution, and the concentration of the aqueous sulfuric acid solution is 0.1-5 mol / L; preferably, 0.3-3 mol / L; further preferably, 0.5-1.5 mol / L.

[0013] In some embodiments, the conditions for the acid leaching treatment include: a solid-liquid ratio of 0.5:5, and an acid leaching time of 0.5 to 3 hours; preferably, the solid-liquid ratio is 0.5:2; further preferably, the solid-liquid ratio is 0.5:1; preferably, the acid leaching time is 0.5 to 2 hours; further preferably, the acid leaching time is 0.5 to 1 hour.

[0014] In some embodiments, the method further includes: Step S4: adding benzoate to the leachate to convert the Al element in the leachate into aluminum benzoate precipitate, and filtering to obtain aluminum benzoate particles and lithium-rich leachate.

[0015] In some embodiments, the benzoate includes one or more of sodium benzoate, potassium benzoate, magnesium benzoate, and calcium benzoate.

[0016] In some embodiments, the process further includes: step S5: reacting the fluorine-containing tail gas with a metal oxide, so that the hydrogen fluoride in the fluorine-containing tail gas reacts with the metal oxide to generate metal fluoride, thereby obtaining defluorinated tail gas and metal fluoride; wherein the metal oxide includes at least one of CaO, Al2O3, MgO, ZnO, Fe2O3, FeO, Fe3O4, CuO, NiO, CoO, Co2O3, Co3O4, TiO2, Ti4O7, WO3, and MoO3; preferably Al2O3.

[0017] In some embodiments, the conditions for the reaction of the fluorine-containing tail gas with the metal oxide include: a reaction temperature of 200-800°C and a reaction time of 0.1-5h; preferably, the reaction temperature is 200-600°C; further preferably, the reaction temperature is 200-400°C; preferably, the reaction time is 0.2-2h; further preferably, the reaction time is 0.5-1h.

[0018] In some embodiments, the particle size of the metal oxide is 0.1-3 mm; preferably, 0.3-2 mm; more preferably, 0.5-1 mm.

[0019] In some embodiments, the method further includes: step S6: reacting the defluorinated tail gas with a thallium adsorbent, so that the thallium element in the defluorinated tail gas reacts with the thallium adsorbent to generate a thallium compound, thereby obtaining purified tail gas and thallium compounds; wherein the thallium adsorbent includes metal sulfide.

[0020] In the second aspect, the present application provides a system for low-temperature salt-free fluidized roasting and lithium extraction of lithium mica ore, comprising: a mineral powder feeding unit for transporting lithium mica ore particles; a water vapor generating unit for generating water vapor; a first reaction unit, the first reaction unit being connected to the mineral powder feeding unit and the water vapor generating unit, respectively, and being used as a reaction place between the lithium mica ore particles and the fluidizing gas including water vapor; a mineral powder preheating unit, the mineral powder preheating unit connecting the mineral powder feeding unit with the first reaction unit, and the mineral powder preheating unit connecting the water vapor generating unit, and being used to preheat the lithium mica ore particles and transport them to the first reaction unit, and the heat of the generated high-temperature gas is used for the water vapor generating unit to generate high-temperature steam; a gas preheating unit, the gas preheating unit connecting the water vapor generating unit with the first reactor unit, and being used to preheat the fluidizing gas and transport it to the first reaction unit.

[0021] Based on the present application, the system can be used for low-temperature salt-free fluidized roasting and lithium extraction of lithium mica ore in the first aspect, so the energy consumption and smelting slag amount of lithium mica ore can be reduced by the system.

[0022] In some embodiments, it also includes: a clinker cooling unit connected to the first reaction unit, and the clinker cooling unit connects the water vapor generating unit to the gas preheating unit, and is used to heat the sensible heat of the clinker obtained by the reaction of the first reaction unit with water vapor from the water vapor generating unit, and cool the clinker.

[0023] In some embodiments, it further includes: a leaching and filtering unit connected to the roasted clinker cooling unit, which is used to leach the lithium element in the roasted clinker into the leaching solution and separate it from the leaching residue.

[0024] In some embodiments, the method further includes: a tail gas treatment unit connected to the first reaction unit, for treating the fluorine-containing tail gas generated after the reaction in the first reaction unit.

[0025] In some embodiments, the mineral powder feeding unit includes a raw material bin and a screw feeder, the discharge port of the raw material bin is connected to the feed port of the screw feeder, and the discharge port of the screw feeder is connected to the mineral powder preheating unit.

[0026] In some embodiments, the first reaction unit includes a feed valve, a fluidized bed roaster, a roaster separator and a discharge valve, the feed port of the fluidized bed roaster is connected to the mineral powder feed unit through the feed valve, the discharge port of the fluidized bed roaster is connected to the roasted clinker cooling unit through the discharge valve, the air inlet of the roaster separator is connected to the air outlet of the fluidized bed roaster, and the air outlet of the roaster separator is connected to the exhaust gas treatment unit.

[0027] In some embodiments, a transverse baffle internal component is provided inside the fluidized bed roaster for regulating the residence time of the lepidolite ore particles in the constant temperature section of the fluidized bed roaster; preferably, 2 to 5 levels of transverse baffles are provided.

[0028] In some embodiments, the fluidizing section of the fluidized bed roasting furnace is provided with a plurality of supplementary heat burners for supplementing the heat of the fluidized bed roasting furnace to adjust the fluidized roasting temperature.

[0029] In some embodiments, the water vapor generating unit comprises a steam boiler, a steam outlet of the steam boiler is connected to the roasting clinker cooling unit, and the steam boiler is connected to the mineral powder preheating unit.

[0030] In some embodiments, the mineral powder preheating unit includes a combustion chamber, a cyclone preheater and a cyclone separator, the air outlet of the combustion chamber is connected to the air inlet of the cyclone preheater, the air outlet of the cyclone preheater is connected to the air inlet of the cyclone separator, the air outlet of the cyclone separator is connected to the water vapor generating unit, the feed port of the cyclone preheater 3 is connected to the mineral powder feed unit, and the discharge port of the cyclone preheater is connected to the first reaction unit.

[0031] In some embodiments, the cyclone preheater is a 3-4 stage cyclone preheater.

[0032] In some embodiments, the discharge port of the cyclone separator is connected to the feed port of the cyclone preheater, so as to transport the lithium mica ore particles separated from the gas phase to the cyclone preheater for preheating; the gas outlet of the cyclone separator is connected to a bag dust collector, so as to collect the lithium mica ore particles separated from the gas phase.

[0033] In some embodiments, the bag dust collector is connected to the mineral powder feeding unit via a feeder.

[0034] In some embodiments, the roasted clinker cooling unit includes a cyclone cooler and a cyclone cooling separator, the feed inlet of the cyclone cooler is connected to the first reaction unit, the discharge port of the cyclone cooler is connected to the leaching filtration unit, the air inlet of the cyclone cooler is connected to the water vapor generating unit, the air outlet of the cyclone cooler is connected to the air inlet of the cyclone cooling separator, and the air outlet of the cyclone cooling separator is connected to the gas preheating unit.

[0035] In some embodiments, the gas preheating unit comprises a hot blast furnace, an air inlet of the hot blast furnace is connected to the roasting clinker cooling unit, and an air outlet of the hot blast furnace is connected to the first reaction unit.

[0036] In some embodiments, the leaching and filtration unit includes a leaching device and a filtration device, the feed inlet of the leaching device is connected to the roasted clinker cooling unit, and the discharge port of the leaching device is connected to the filtration device.

[0037] In some embodiments, the exhaust gas treatment unit includes a second reaction device for absorbing hydrogen fluoride in the exhaust gas; and an exhaust gas purification device for absorbing thallium in the exhaust gas; the air inlet of the second reaction device is connected to the first reaction unit, and the air outlet of the second reaction device is connected to the exhaust gas purification device.

[0038] In some embodiments, the second reaction device is at least one of a fluidized bed reactor, a moving bed reactor or a fixed bed reactor; preferably, it is a moving bed reactor.

[0039] In some embodiments, an air induction unit is further included, which is connected to the tail gas treatment unit and the water vapor generation unit respectively, and is used to control the flow direction of the gas in the system.

[0040] In some embodiments, the air-inducing unit includes an air-inducing fan.

[0041] Compared with the prior art, the beneficial effects of this application are: (1) The method and system provided in this application can significantly reduce lithium smelting slag and reduce the fluorine content in the smelting slag; (2) The method and system provided in this application use low-temperature roasting and do not require the addition of sulfate roasting aids, which can significantly reduce roasting energy consumption; (3) The system provided by the present application has a high heat utilization rate. The high-temperature roasted clinker can be used to preheat the water of the steam boiler to generate high-temperature steam, and the sensible heat of the roasted clinker can be recovered; (4) The method and system provided in the present application have high resource utilization rate. Solid adsorbent is used to absorb the fluorine-containing thallium tail gas discharged from the fluidized bed roasting system and recover fluorine and thallium resources. Acid leaching is used, and lithium, rubidium and cesium valuable elements can be leached simultaneously. The lithium, rubidium and cesium leaching rates are >90%, and the aluminum leaching rate is >30%. Further, aluminum and lithium are separated by coordination regulation to obtain aluminum salt and lithium salt products. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 A schematic diagram of the structure of a system for low-temperature, salt-free fluidized roasting and lithium extraction of lepidolite ore provided in one embodiment of the present application.

[0043] Among them, 1-raw material bin, 2-screw feeder; 3-cyclone preheater; 4-first reaction unit; 5-second reaction device; 6-roasting clinker cooling unit; 7-hot blast furnace; 8-combustion chamber; 9-steam boiler; 10-exhaust gas purification device; 11-induced draft fan; 12-leaching device; 13-filtering device. DETAILED DESCRIPTION

[0044] In order to make the purpose, technical solution and advantages of the present application more clear, the present application is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described here are only used to explain the present application and are not used to limit the present application.

[0045] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the implementation or examples are included in at least one implementation or example of the present application. In this specification, the schematic representation of the above terms does not necessarily refer to the same implementation or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or more implementations or examples in a suitable manner.

[0046] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of this application, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0047] The lithium in lepidolite exists in the complex form of fluoroaluminosilicate, and the mineral structure is very dense. It is necessary to pre-treat the lepidolite with high-temperature steam roasting and defluorination to convert the valuable elements such as lithium, potassium, rubidium and cesium combined with fluorine into their respective oxides. After defluorination, its structure is loose, grindable, and conducive to improving the leaching rate of lithium. Therefore, the roasting and defluorination pretreatment of lepidolite plays an important role in the subsequent grinding, leaching of lithium and other processing of lepidolite.

[0048] The lithium extraction process of lepidolite has gone through the first generation limestone roasting method (CN94113302.8), the second generation acid roasting method (CN201310062852.9) and the third generation salt roasting technology (CN200910226661.5).

[0049] The first generation of roasting technology ball-mills and mixes limestone and lithium mica in a weight ratio of 3:1 in a ball mill, then roasts at 800~900℃ to obtain clinker, which is then quenched, finely ground, leached, filtered or centrifuged to obtain leachate and residue, and the leachate is evaporated, crystallized and centrifuged to obtain lithium hydroxide monohydrate. The lime roasting method has a simple process and low raw material price, but it has disadvantages such as low lithium content in the leachate, high evaporation energy consumption, low lithium recovery rate and high limestone ratio.

[0050] The second-generation acid roasting technology is gradually being replaced by the third-generation sulfate-assisted roasting process because the hydrofluoric acid produced during the roasting-leaching process causes serious corrosion to the equipment and the high content of impurity elements during the leaching process leads to a complex lithium precipitation process and a large loss of lithium, which seriously affects the overall recovery rate of lithium.

[0051] The third generation of salt-assisted roasting process converts lithium mica into soluble lithium sulfate through high-temperature roasting, and further obtains lithium carbonate through water leaching, impurity removal and carbonation. However, this process adds a large amount of roasting aids (>35%), resulting in large slag production (30-60 tons of slag / ton of lithium carbonate), high energy consumption (950-1100℃), low lithium yield (<80%) and other problems; at the same time, a large amount of lithium smelting slag cannot be used on a large scale due to the presence of toxic elements such as fluorine, beryllium and thallium, and can only be temporarily stored in the factory area, which has become a prominent problem in the development of salt roasting technology. In addition, due to high-temperature roasting (>950℃), the mineral phase of toxic components such as fluorine, beryllium and thallium will change, making it easy for them to enter the gas phase or liquid phase, which not only causes the waste of resources such as fluorine, beryllium and thallium, but also increases the difficulty of environmental governance.

[0052] The relevant technology uses a rotary kiln / tunnel kiln reactor to introduce air and natural gas to burn and generate water vapor for roasting. Since the raw materials used in the rotary kiln / tunnel kiln are millimeter-sized pellets or centimeter-sized block ore, the water vapor does not contact the lithium mica material sufficiently, inhibiting the adsorption of water vapor on the surface of the lithium mica, the inward diffusion or the migration of lithium-containing substances, resulting in low defluorination rate and incomplete dissociation of the lithium ore phase.

[0053] Based on this, the present application provides a method and system for extracting lithium by low-temperature salt-free fluidized roasting of lepidolite ore, which is used to overcome at least one of the above problems. The specific implementation methods of the present application are described in detail below.

[0054] Method for extracting lithium from lithium mica ore by low-temperature salt-free fluidized roasting In a first aspect, the present application provides a method for extracting lithium by low-temperature salt-free fluidized roasting of lepidolite ore, comprising the following steps: Step S1: providing lepidolite particles; Step S2: preheating the lithium mica ore particles and the fluidizing gas respectively, so that the temperature of the preheated lithium mica ore particles is 700-790°C and the temperature of the preheated fluidizing gas is 700-850°C, and the preheated lithium mica ore particles and the fluidizing gas are subjected to fluidized roasting treatment, so that the Li-F mineral phase in the lithium mica ore particles dissociates and releases fluoride ions, and the fluoride ions combine with hydrogen ions to generate hydrogen fluoride gas that diffuses from the inside of the lithium mica ore particles to the gas phase, thereby obtaining roasted clinker and fluorine-containing tail gas; wherein the fluidizing gas includes water vapor, and the volume percentage of water vapor in the fluidizing gas is not less than 30%.

[0055] Based on the present application, the method preheats the lithium mica ore particles and the fluidizing gas containing a water vapor volume percentage of not less than 30% to the above temperature, and then performs a fluidized roasting treatment, wherein the preheating treatment is conducive to the rapid adsorption of water vapor on the surface of the lithium mica particles and its inward diffusion, thereby promoting the subsequent full dissociation of the lithium mica ore particles. At the same time, the temperature of the preheated lithium mica ore particles is 700-790°C, which can reduce the dissociation of the lithium mica ore particles during the preheating process. Release of HF and other toxic metal elements (such as thallium, etc.) can reduce the erosion of the preheating device and pipelines. In addition, since the preheating device is not connected to the tail gas treatment unit, the preheating device is not connected to the tail gas treatment unit. The elements are connected, so the preheating temperature of the lithium mica ore particles is controlled within the above range to reduce pollution to the environment; the temperature of the fluidized gas after preheating is 700~850℃, and the higher temperature fluidized gas can further promote the rapid adsorption of water vapor on the surface of the lithium mica particles and diffuse inward; during the fluidized roasting process, the Li-F phase dissociation in the lithium mica ore particles can be enhanced under high water vapor partial pressure, and the fluidized roasting process can also further enhance the dissociation effect, thereby achieving the dissociation of the lithium mica ore particles at a lower temperature and without the need to add other additives. Therefore, the energy consumption of this method is low and the amount of smelting slag produced is small. In addition, the full dissociation of the lithium mica ore particles is conducive to reducing the content of easily lost toxic components in the roasted clinker and improving the recovery rate of lithium elements. At the same time, the lower reaction temperature can also reduce the erosion of the reaction device by HF in the gas phase.

[0056] It should also be noted that, generally speaking, the higher the volume percentage of water vapor in the fluidizing gas, the more conducive it is to the dissociation of the mineral phase structure in the lithium mica ore particles. Therefore, the present application does not make further requirements on the upper limit of the volume percentage of steam in the fluidizing gas.

[0057] In some embodiments, the volume percentage of water vapor in the fluidizing gas is not less than 40%; preferably, not less than 50%.

[0058] In some embodiments, in step S1, the average particle size of the lepidolite particles is 0.1-0.5 mm.

[0059] In some of the above embodiments, the lithium mica ore particles meeting the above particle size are more suitable for fluidized roasting, which can further increase the contact area with water vapor, promote the adsorption of water vapor on the surface of the lithium mica particles, diffuse inward or migrate lithium-containing substances, thereby further promoting the dissociation of the mineral phase and improving the defluorination rate. Therefore, the dissociation of the lithium mica ore particles can be achieved at a lower temperature, further reducing energy consumption and improving the recovery rate of lithium elements.

[0060] In some embodiments, in step S2, the conditions of fluidized roasting treatment include: the temperature of fluidized roasting is 810-850°C, and the time of fluidized roasting is 0.5-2h. Based on the above embodiment, under this condition, it is more conducive to the full dissociation of lithium mica particles, improve the recovery rate of lithium elements, and reduce the content of easily lost toxic components in the roasted clinker.

[0061] In some embodiments, in step S2, the conditions for fluidized roasting treatment include: countercurrent contact between the lepidolite particles and the fluidizing gas. Based on the above embodiments, the countercurrent contact can further promote the adsorption of water vapor on the surface of the lepidolite particles, promote the full dissociation of the lepidolite particles, further reduce energy consumption, and improve the recovery rate of lithium elements.

[0062] In some embodiments, step S2 further includes: before the fluidized roasting treatment, preheating the lithium mica ore particles and the fluidizing gas respectively, so that the temperature of the preheated lithium mica ore particles is 700-790° C., and the temperature of the preheated fluidizing gas is 700-850° C. Based on the above embodiment, the lithium mica ore particles and the fluidizing gas are preheated before the fluidized roasting treatment, which is conducive to the rapid adsorption of water vapor on the surface of the lithium mica particles and its inward diffusion, thereby further promoting the full dissociation of the lithium mica ore particles, and the preheating treatment is conducive to improving the utilization rate of heat.

[0063] In some embodiments, the method further comprises: step S3: subjecting the roasted clinker to acid leaching with an acid solution to fix the lithium element in the roasted clinker into the leachate, and filtering to obtain leached residue and leachate. Based on the above embodiment, the roasted clinker obtained by mineral phase dissociation is subjected to acid leaching to fix valuable metals such as lithium in the leachate for further separation and extraction.

[0064] In some embodiments, the acid solution is an aqueous sulfuric acid solution, and the concentration of the aqueous sulfuric acid solution is 0.1-5 mol / L; preferably, 0.3-3 mol / L; further preferably, 0.5-1.5 mol / L.

[0065] In some embodiments, the conditions for acid leaching treatment include: a solid-liquid ratio of 0.5:5, and an acid leaching time of 0.5 to 3 hours; preferably, the solid-liquid ratio is 0.5:2; further preferably, the solid-liquid ratio is 0.5:1; preferably, the acid leaching time is 0.5 to 2 hours; further preferably, the acid leaching time is 0.5 to 1 hour.

[0066] In some embodiments, the method further includes: Step S4: adding benzoate to the leachate to convert the Al element in the leachate into aluminum benzoate precipitate, and filtering to obtain aluminum benzoate particles and lithium-rich leachate.

[0067] In some of the above embodiments, the inventors found that in addition to having a good sedimentation effect on the Al element, the converted aluminum benzoate precipitate has a small adsorption capacity for other metal elements in the leachate, such as lithium, rubidium, and cesium, and can effectively separate the Al element from other metal elements, thereby improving the purity of the product and at the same time improving the recovery rate of metal elements such as lithium, rubidium, and cesium.

[0068] In some embodiments, the benzoate salt includes at least one of sodium formate, potassium benzoate, magnesium benzoate, and calcium benzoate.

[0069] In some embodiments, the process further includes: step S5: reacting the fluorine-containing tail gas with a metal oxide, so that the hydrogen fluoride in the fluorine-containing tail gas reacts with the metal oxide to generate metal fluoride, thereby obtaining defluorinated tail gas and metal fluoride; wherein the metal oxide includes at least one of CaO, Al2O3, MgO, ZnO, Fe2O3, FeO, Fe3O4, CuO, NiO, CoO, Co2O3, Co3O4, TiO2, Ti4O7, WO3, and MoO3.

[0070] In some of the above embodiments, hydrogen fluoride in the fluorine-containing exhaust gas can react with metal oxides to generate metal fluorides, thereby fixing the fluorine element, which can reduce the corrosion of hydrogen fluoride on the reaction device and the pollution of the exhaust gas to the environment. At the same time, using metal oxides to fix the fluorine element can increase the resource utilization rate of the fluorine element.

[0071] In some embodiments, the conditions for the reaction of fluorine-containing tail gas with metal oxide include: reaction temperature of 200-800°C, reaction time of 0.1-5h. Based on the above embodiments, under this condition, metal oxide can fully react with hydrogen fluoride in fluorine-containing tail gas, improve the resource utilization rate of fluorine element, and reduce the pollution of tail gas to the environment. Preferably, the reaction temperature is 200-600°C; more preferably, the reaction temperature is 200-400°C; preferably, the reaction time is 0.2-2h; more preferably, the reaction time is 0.5-1h.

[0072] In some embodiments, the particle size of the metal oxide is 0.1-3 mm. Under this condition, the specific surface area of ​​the metal oxide is larger, which is more conducive to reacting with hydrogen fluoride in the fluorine-containing tail gas, further improving the resource utilization rate of the fluorine element and reducing the pollution of the tail gas to the environment. Preferably, it is 0.3-2 mm; more preferably, it is 0.5-1 mm.

[0073] In some embodiments, the method further comprises: step S6: reacting the defluorinated tail gas with a thallium adsorbent, so that the thallium element in the defluorinated tail gas reacts with the thallium adsorbent to generate a thallium compound, thereby obtaining purified tail gas and thallium compounds; wherein the thallium adsorbent comprises a metal sulfide. Based on the above embodiments, the defluorinated tail gas may also include a trace amount of thallium element, which is reacted and fixed with the thallium adsorbent to improve the resource utilization rate of the thallium element and reduce the pollution of the tail gas to the environment.

[0074] System for low temperature salt-free fluidized roasting and lithium extraction of lepidolite ore In the second aspect, the present application provides a system for low-temperature salt-free fluidized roasting and lithium extraction of lithium mica ore, comprising: a mineral powder feeding unit for transporting lithium mica ore particles; a water vapor generating unit for generating water vapor; a first reaction unit, the first reaction unit being connected to the mineral powder feeding unit and the water vapor generating unit, respectively, and being used as a reaction place between the lithium mica ore particles and the fluidizing gas including water vapor; a mineral powder preheating unit, the mineral powder preheating unit connecting the mineral powder feeding unit with the first reaction unit, and the mineral powder preheating unit connecting the water vapor generating unit, and being used to preheat the lithium mica ore particles and transport them to the first reaction unit, and the heat of the generated high-temperature gas is used for the water vapor generating unit to generate high-temperature steam; a gas preheating unit, the gas preheating unit connecting the water vapor generating unit with the first reactor unit, and being used to preheat the fluidizing gas and transport it to the first reaction unit.

[0075] Based on the present application, the system can be used for low-temperature salt-free fluidized roasting and lithium extraction of lithium mica ore in the first aspect, so the energy consumption and smelting slag amount of lithium mica ore can be reduced by the system.

[0076] In some embodiments, it also includes: a clinker cooling unit connected to the first reaction unit, and the clinker cooling unit connects the water vapor generating unit to the gas preheating unit, and is used to heat the sensible heat of the clinker obtained by the reaction of the first reaction unit with water vapor from the water vapor generating unit, and cool the clinker.

[0077] In some of the above embodiments, the roasted clinker needs to be cooled before acid leaching. At this time, the sensible heat of the roasted clinker obtained by the reaction in the first reaction unit can be used to heat the water vapor from the water vapor generating unit, increase the temperature of the water vapor, and cool the roasted clinker, thereby further improving the heat utilization efficiency of the system and reducing energy consumption.

[0078] In some embodiments, it further includes: a leaching filtration unit connected to the roasted clinker cooling unit, used to leach the lithium element in the roasted clinker into the leaching solution and separate it from the leaching residue.

[0079] In some embodiments, the method further comprises: a tail gas treatment unit connected to the first reaction unit for treating the fluorine-containing tail gas produced after the reaction in the first reaction unit. Based on the above embodiment, the tail gas treatment unit is directly connected to the first reaction unit, and the fluorine-containing tail gas produced by the reaction in the first reaction unit has a relatively high temperature. Under such conditions, tail gas treatment can improve the absorption and fixation efficiency of toxic substances in the tail gas.

[0080] In some embodiments, the mineral powder feeding unit includes a raw material bin 1 and a screw feeder 2, the discharge port of the raw material bin 1 is connected to the feed port of the screw feeder 2, and the discharge port of the screw feeder 2 is connected to the mineral powder preheating unit.

[0081] In some embodiments, the first reaction unit includes a feed valve, a fluidized bed roaster 4, a roaster separator and a discharge valve, the feed port of the fluidized bed roaster 4 is connected to the mineral powder feed unit through the feed valve, the discharge port of the fluidized bed roaster 4 is connected to the roasting clinker cooling unit through the discharge valve, the air inlet of the roaster separator is connected to the air outlet of the fluidized bed roaster 4, and the air outlet of the roaster separator is connected to the exhaust gas treatment unit.

[0082] In some embodiments, a transverse baffle internal component is provided inside the fluidized bed roasting furnace 4 for regulating the residence time of the lithium mica ore particles in the constant temperature section of the fluidized bed roasting furnace; preferably, 2 to 5 levels of transverse baffles are provided.

[0083] In some embodiments, the fluidizing section of the fluidized bed roasting furnace 4 is provided with a plurality of supplementary heat burners for supplementing the heat of the fluidized bed roasting furnace to adjust the fluidized roasting temperature.

[0084] In some embodiments, the water vapor generating unit includes a steam boiler 9, the steam outlet of the steam boiler 9 is connected to the roasting clinker cooling unit, and the steam boiler 9 is connected to the mineral powder preheating unit. Based on the above embodiment, the high-temperature gas from the mineral powder preheating unit can be used to generate water vapor in the steam boiler, and the water vapor generated by the steam boiler can be used to cool the roasting clinker.

[0085] In some embodiments, the mineral powder preheating unit includes a combustion chamber 8, a cyclone preheater 3 and a cyclone separator, the air outlet of the combustion chamber 8 is connected to the air inlet of the cyclone preheater 3, the air outlet of the cyclone preheater 3 is connected to the air inlet of the cyclone separator, the air outlet of the cyclone separator is connected to the water vapor generating unit, the feed inlet of the cyclone preheater 3 is connected to the mineral powder feed unit, and the discharge port of the cyclone preheater 3 is connected to the first reaction unit.

[0086] In some embodiments, the cyclone preheater 3 is a 3-4 stage cyclone preheater.

[0087] In some embodiments, the discharge port of the cyclone separator is connected to the feed port of the cyclone preheater 3, which is used to transport the lithium mica ore particles separated from the gas phase to the cyclone preheater for preheating; the gas outlet of the cyclone separator is connected to the bag dust collector, which is used to collect the lithium mica ore particles separated from the gas phase.

[0088] In some embodiments, the bag dust collector is connected to the mineral powder feeding unit via a feeder. Based on the above embodiments, the utilization rate of the lepidolite ore particles can be improved.

[0089] In some embodiments, the roasted clinker cooling unit 6 includes a cyclone cooler and a cyclone cooling separator, the feed port of the cyclone cooler is connected to the first reaction unit, the discharge port of the cyclone cooler is connected to the leaching and filtering unit, the air inlet of the cyclone cooler is connected to the water vapor generation unit, the air outlet of the cyclone cooler is connected to the air inlet of the cyclone cooling separator, and the air outlet of the cyclone cooling separator is connected to the gas preheating unit. Based on the above embodiments, the water vapor generated by the water vapor generation unit can be used to cool the roasted clinker in the cyclone cooler, and at the same time, the water vapor is heated by the roasted clinker and enters the gas preheating unit through the cyclone cooling separator, which can further improve the heat utilization rate of the system.

[0090] In some embodiments, the gas preheating unit includes a hot blast furnace 7, the air inlet of the hot blast furnace 7 is connected to the roasting clinker cooling unit 6, and the air outlet of the hot blast furnace 7 is connected to the first reaction unit. Based on the above embodiment, the hot blast furnace further heats the water vapor from the roasting clinker cooling unit 6 to the preheating temperature, and then passes it into the first reaction unit for reaction.

[0091] In some embodiments, the leaching and filtering unit includes a leaching device 12 and a filtering device 13 , the feed inlet of the leaching device 12 is connected to the roasting clinker cooling unit, and the discharge port of the leaching device 12 is connected to the filtering device 13 .

[0092] In some embodiments, the exhaust gas treatment unit includes a second reaction device 5 for absorbing hydrogen fluoride in the exhaust gas; and an exhaust gas purification device 10 for absorbing thallium in the exhaust gas; the air inlet of the second reaction device 5 is connected to the first reaction unit, and the air outlet of the second reaction device 5 is connected to the exhaust gas purification device 10.

[0093] In some embodiments, the second reaction device 5 is at least one of a fluidized bed reactor, a moving bed reactor or a fixed bed reactor; preferably, it is a moving bed reactor.

[0094] In some embodiments, an air induction unit is further included, which is connected to the tail gas treatment unit and the water vapor generation unit respectively, and is used to control the flow direction of the gas in the system. Based on the above embodiments, the gas passing through the tail gas treatment device also contains a certain amount of heat, which can be used by the water vapor generation unit to generate water vapor through the air induction device, thereby further improving the heat utilization rate and reducing energy consumption.

[0095] In some embodiments, the induced draft unit includes an induced draft fan 11 .

[0096] The scheme of the present application is described below in conjunction with the following specific examples. Unless otherwise specified, the raw materials used in the following examples are all from common commercial products, and the devices or equipment used are all purchased from conventional market sales channels.

[0097] Example 1 The schematic diagram of the structure of the system used for low-temperature salt-free fluidized roasting of lithium from lepidolite ore used in this embodiment is as follows: Figure 1 shown.

[0098] The system comprises: a mineral powder feeding unit comprises a raw material bin 1 and a screw feeder 2, a discharge port of the raw material bin 1 is connected to a feed port of the screw feeder 2, and a discharge port of the screw feeder 2 is connected to a mineral powder preheating unit; The mineral powder preheating unit includes a combustion chamber 8, a cyclone preheater 3 and a cyclone separator, the gas outlet of the combustion chamber 8 is connected to the gas inlet of the cyclone preheater 3, the gas outlet of the cyclone preheater 3 is connected to the gas inlet of the cyclone separator, the gas outlet of the cyclone separator is connected to the water vapor generation unit, the feed inlet of the cyclone preheater 3 is connected to the mineral powder feed unit, and the discharge port of the cyclone preheater 3 is connected to the first reaction unit; The first reaction unit includes a feed valve, a fluidized bed roaster 4, a roaster separator and a discharge valve. The feed port of the fluidized bed roaster 4 is connected to the ore powder feed unit through the feed valve, the discharge port of the fluidized bed roaster 4 is connected to the roasted clinker cooling unit 6 through the discharge valve, the air inlet of the roaster separator is connected to the air outlet of the fluidized bed roaster 4, and the air outlet of the roaster separator is connected to the tail gas treatment unit; The roasting clinker cooling unit 6 includes a cyclone cooler and a cyclone cooling separator, the feed port of the cyclone cooler is connected to the first reaction unit, the discharge port of the cyclone cooler is connected to the leaching and filtering unit, the air inlet of the cyclone cooler is connected to the water vapor generating unit, the air outlet of the cyclone cooler is connected to the air inlet of the cyclone cooling separator, and the air outlet of the cyclone cooling separator is connected to the gas preheating unit; The leaching and filtering unit comprises a leaching device 12 and a filtering device 13, wherein the feed port of the leaching device 12 is connected to the roasting clinker cooling unit, and the discharge port of the leaching device 12 is connected to the filtering device 13; The water vapor generating unit comprises a steam boiler 9, the steam outlet of the steam boiler 9 is connected to the roasting clinker cooling unit, and the steam boiler 9 is connected to the mineral powder preheating unit; The gas preheating unit comprises a hot blast furnace 7, the air inlet of the hot blast furnace 7 is connected to the roasting clinker cooling unit 6, and the air outlet of the hot blast furnace 7 is connected to the first reaction unit; The tail gas treatment unit includes a second reaction device 5 for absorbing hydrogen fluoride in the tail gas, and the second reaction device 5 is a moving bed reactor; and a tail gas purification device 10 for absorbing thallium in the tail gas; the air inlet of the second reaction device 5 is connected to the first reaction unit, and the air outlet of the second reaction device 5 is connected to the tail gas purification device 10.

[0099] The induced draft unit includes an induced draft fan 11, which is respectively connected to the tail gas treatment unit and the water vapor generation unit to control the flow direction of the gas in the system. The induced draft unit is respectively connected to the tail gas treatment unit and the water vapor generation unit to control the flow direction of the gas in the system.

[0100] The above system is used for low-temperature salt-free fluidized roasting of lithium mica ore, including the following steps: (1) adding lithium mica ore particles with an average particle size of 0.45 mm into a raw material bin 1, and sending them to a cyclone preheater via a screw feeder. Natural gas and air in a combustion chamber 8 are fully in contact with each other to generate a combustion reaction to produce high-temperature hot flue gas, which is then sent to a cyclone preheater 3 to preheat the lithium mica ore particles to a temperature of 700° C.; (2) The cold water introduced from the water inlet of the steam boiler 9 exchanges heat with the high-temperature gas from the combustion chamber 8, and the steam discharged from the steam outlet of the steam boiler 9 is sent to the roasting clinker cooling unit 6 to cool the roasting clinker and heat the water vapor. The water vapor discharged from the top of the roasting clinker cooling system enters the hot blast furnace 7 to further increase the temperature, so that the temperature of the water vapor reaches 850°C; (3) The high-temperature lithium mica ore particles discharged from the bottom outlet of the cyclone preheater 3 enter the fluidized bed roaster 4 through the feed valve, and countercurrently contact and react with the water vapor from the bottom of the fluidized bed roaster 4. The fluidized section is provided with a plurality of supplementary heat burners to control the reaction temperature at 810°C. After the roasting reaction for 2 hours, roasted clinker and fluorine-containing tail gas are obtained; (4) The roasted clinker produced by the fluidized bed roasting furnace 4 enters the cyclone cooling system 6 through the discharge valve, and the roasted clinker is discharged after being cooled. The heat generated during the cooling process is used as a heat source for preheating the water vapor produced by the steam boiler 9; (5) The fluorine-containing tail gas generated by the fluidized bed roaster 4 is separated by the roaster separator, and the solid particles generated by the separation are returned to the fluidized bed roaster 4 to continue the roasting reaction. The gas generated by the separation enters the second reaction device 5, and the second reaction device 5 is loaded with MgO, which reacts with HF gas to produce MgF2. The solid fluorine reaction temperature is 800°C and the reaction time is 1.0h; the defluorinated gas enters the tail gas purification device 10 for thallium removal. The gas absorption device 10 is loaded with Na2S thallium adsorbent. The purified gas generated after thallium defluorination is discharged into the atmosphere through the induced draft fan 11; the HF-containing gas discharged from the fluidized bed roaster 4 is sent to the tail gas treatment unit for recovery, and the purified high-temperature tail gas (defluorination rate> 99%) is used to preheat water in the steam boiler 9 to produce high-temperature water vapor; (6) The roasted clinker discharged from the roasted clinker cooling unit 6 is sent to the leaching device 12 for acid leaching, and after leaching, it is sent to the filtering device 13 for filtration to produce leaching residue and leachate; sodium benzoate is added to the leachate until no precipitation is produced, and aluminum benzoate and lithium-rich leachate are obtained by filtration; sodium carbonate is added to the lithium-rich leachate to precipitate lithium to obtain lithium carbonate; an extractant is then added to the leachate after lithium extraction, and after multi-stage centrifugal extraction, the raffinate is collected in a residual water storage tank The loaded organic phase after extraction enters the water washing section. After multi-stage centrifugal water washing, the washing water flows into the residual water storage tank. The loaded organic phase after water washing enters the centrifugal stripping section. The regenerated extractant obtained after stripping enters the extractant storage tank for recycling. The washing water and the residual water are mixed and enter the extraction section again. The stripping water after stripping is further treated and recycled as the stripping agent. The rubidium and cesium after stripping are precipitated by adding sodium carbonate or introducing CO2 to obtain carbonates of rubidium and cesium.

[0101] In this embodiment, the lithium leaching rate is 95%, the comprehensive lithium recovery rate is 89%, the rubidium-cesium leaching rate is 92%, the comprehensive rubidium-cesium recovery rate is 86%, the fluorine-thallium resource utilization rate is 95%, the thallium emission in the flue gas is 40 ppb, and the HF emission is 0.6 ppm.

[0102] Example 2 The same system as in Example 1 is used for low-temperature salt-free fluidized roasting of lithium mica ore, comprising the following steps: (1) adding lithium mica ore particles with an average particle size of 0.15 mm into a raw material bin 1, and sending them to a cyclone preheater via a screw feeder. The natural gas and air in the combustion chamber 8 are fully in contact with each other to generate a combustion reaction to produce high-temperature hot flue gas. The generated high-temperature hot flue gas is sent to a cyclone preheater 3 to preheat the lithium mica ore particles to a temperature of 790°C. (2) The cold water introduced from the water inlet of the steam boiler 9 exchanges heat with the high-temperature gas from the combustion chamber 8, and the steam discharged from the steam outlet of the steam boiler 9 is sent to the roasting clinker cooling unit 6 to cool the roasting clinker and heat the water vapor. The water vapor discharged from the top of the roasting clinker cooling system enters the hot blast furnace 7 to further increase the temperature, so that the temperature of the water vapor reaches 850°C; (3) The high-temperature lithium mica ore particles discharged from the bottom outlet of the cyclone preheater 3 enter the fluidized bed roaster 4 through the feed valve, and are countercurrently contacted and reacted with the water vapor from the bottom of the fluidized bed roaster 4. A plurality of supplementary heat burners are provided in the fluidized section to control the reaction temperature at 850°C. After the roasting reaction is performed for 0.5h, roasted clinker and fluorine-containing tail gas are obtained; (4) The roasted clinker produced by the fluidized bed roasting furnace 4 enters the cyclone cooling system 6 through the discharge valve, and the roasted clinker is discharged after being cooled. The heat generated during the cooling process is used as a heat source for preheating the water vapor produced by the steam boiler 9; (5) The fluorine-containing tail gas generated by the fluidized bed roaster 4 is separated by the roaster separator, and the solid particles generated by the separation are returned to the fluidized bed roaster 4 to continue the roasting reaction. The gas generated by the separation enters the second reaction device 5, and CaO is loaded in the second reaction device 5 to react with HF gas to produce CaF2. The solid fluorine reaction temperature is 800°C and the reaction time is 0.5 h. The defluorinated gas enters the tail gas purification device 10 for thallium removal. The gas absorption device 10 is loaded with K2S adsorbent. The purified gas generated after defluorination and thallium removal is discharged into the atmosphere through the induced draft fan 11. The HF-containing gas discharged from the fluidized bed roaster 4 is sent to the tail gas treatment unit for recovery. The purified high-temperature tail gas (defluorination rate> 99%) is used to preheat water in the steam boiler 9 to produce high-temperature water vapor. (6) The roasted clinker discharged from the roasted clinker cooling unit 6 is sent to the leaching device 12 for acid leaching, and after leaching, it is sent to the filtering device 13 for filtration to produce leaching residue and leachate; sodium benzoate is added to the leachate until no precipitation is produced, and aluminum benzoate and lithium-rich leachate are obtained by filtration; sodium carbonate is added to the lithium-rich leachate to precipitate lithium to obtain lithium carbonate; an extractant is then added to the leachate after lithium extraction, and after multi-stage centrifugal extraction, the raffinate is collected in a residual water storage tank The loaded organic phase after extraction enters the water washing section. After multi-stage centrifugal water washing, the washing water flows into the residual water storage tank. The loaded organic phase after water washing enters the centrifugal stripping section. The regenerated extractant obtained after stripping enters the extractant storage tank for recycling. The washing water and the residual water are mixed and enter the extraction section again. The stripping water after stripping is further treated and recycled as the stripping agent. The rubidium and cesium after stripping are precipitated by adding sodium carbonate or introducing CO2 to obtain carbonates of rubidium and cesium.

[0103] In this embodiment, the lithium leaching rate is 91.5%, the comprehensive lithium recovery rate is 81%, the rubidium-cesium leaching rate is 91%, the comprehensive rubidium-cesium recovery rate is 86%, the fluorine-thallium resource utilization rate is 95%, the thallium emission in the flue gas is 45 ppb, and the HF emission is 0.8 ppm.

[0104] Example 3 The same system as in Example 1 is used for low-temperature salt-free fluidized roasting of lithium mica ore, comprising the following steps: (1) adding lithium mica ore particles with a particle size of no more than 0.5 mm into a raw material bin 1, and sending them to a cyclone preheater via a screw feeder. Natural gas and air in a combustion chamber 8 are fully in contact with each other to generate a combustion reaction to produce high-temperature hot flue gas, which is then sent to a cyclone preheater 3 to preheat the lithium mica ore particles to a temperature of 750° C.; (2) The cold water introduced from the water inlet of the steam boiler 9 exchanges heat with the high-temperature gas from the combustion chamber 8, and the steam discharged from the steam outlet of the steam boiler 9 is sent to the roasting clinker cooling unit 6 to cool the roasting clinker and heat the water vapor. The water vapor discharged from the top of the roasting clinker cooling system enters the hot blast furnace 7 to further increase the temperature, so that the temperature of the water vapor reaches 810°C; (3) The high-temperature lithium mica ore particles discharged from the bottom outlet of the cyclone preheater 3 enter the fluidized bed roaster 4 through the feed valve, and countercurrently contact and react with the water vapor from the bottom of the fluidized bed roaster 4. The fluidized section is provided with a plurality of supplementary heat burners to control the reaction temperature at 830°C. After the roasting reaction for 1 hour, roasted clinker and fluorine-containing tail gas are obtained; (4) The roasted clinker produced by the fluidized bed roasting furnace 4 enters the cyclone cooling system 6 through the discharge valve, and the roasted clinker is discharged after being cooled. The heat generated during the cooling process is used as a heat source for preheating the water vapor produced by the steam boiler 9; (5) The fluorine-containing tail gas generated by the fluidized bed roaster 4 is separated by the roaster separator, and the solid particles generated by the separation are returned to the fluidized bed roaster 4 to continue the roasting reaction. The gas generated by the separation enters the second reaction device 5, and MgO is loaded in the second reaction device 5 to react with HF gas to produce MgF2. The solid fluorine reaction temperature is 600°C and the reaction time is 1.5 h. The defluorinated gas enters the tail gas purification device 10 for thallium removal. The gas absorption device 10 is loaded with MoS2 thallium adsorbent. The purified gas generated after defluorination and thallium removal is discharged into the atmosphere through the induced draft fan 11. The HF-containing gas discharged from the fluidized bed roaster 4 is sent to the tail gas treatment unit for recovery. The purified high-temperature tail gas (defluorination rate> 99%) is used to preheat water in the steam boiler 9 to produce high-temperature water vapor. (6) The roasted clinker discharged from the roasted clinker cooling unit 6 is sent to the leaching device 12 for acid leaching, and after leaching, it is sent to the filtering device 13 for filtration to produce leaching residue and leachate; sodium benzoate is added to the leachate until no precipitation is produced, and aluminum benzoate and lithium-rich leachate are obtained by filtration; sodium carbonate is added to the lithium-rich leachate to precipitate lithium to obtain lithium carbonate; an extractant is then added to the leachate after lithium extraction, and after multi-stage centrifugal extraction, the raffinate is collected in a residual water storage tank The loaded organic phase after extraction enters the water washing section. After multi-stage centrifugal water washing, the washing water flows into the residual water storage tank. The loaded organic phase after water washing enters the centrifugal stripping section. The regenerated extractant obtained after stripping enters the extractant storage tank for recycling. The washing water and the residual water are mixed and enter the extraction section again. The stripping water after stripping is further treated and recycled as the stripping agent. The rubidium and cesium after stripping are precipitated by adding sodium carbonate or introducing CO2 to obtain carbonates of rubidium and cesium.

[0105] In this embodiment, the lithium leaching rate is 93.5%, the comprehensive lithium recovery rate is 82%, the rubidium-cesium leaching rate is 91%, the comprehensive rubidium-cesium recovery rate is 84%, the fluorine-thallium resource utilization rate is 96%, the thallium emission in the flue gas is 30 ppb, and the HF emission is 0.5 ppm.

[0106] Example 4 The same system as in Example 1 is used for low-temperature salt-free fluidized roasting of lithium mica ore, comprising the following steps: (1) adding lithium mica ore particles with an average particle size of 0.35 mm into a raw material bin 1, and sending them to a cyclone preheater via a screw feeder. The natural gas and air in the combustion chamber 8 are fully in contact with each other to generate a combustion reaction to produce high-temperature hot flue gas. The generated high-temperature hot flue gas is sent to a cyclone preheater 3 to preheat the lithium mica ore particles to a temperature of 710°C. (2) The cold water introduced from the water inlet of the steam boiler 9 exchanges heat with the high-temperature gas from the combustion chamber 8, and the steam discharged from the steam outlet of the steam boiler 9 is sent to the roasting clinker cooling unit 6 to cool the roasting clinker and heat the water vapor. The water vapor discharged from the top of the roasting clinker cooling system enters the hot blast furnace 7 to further increase the temperature, so that the temperature of the water vapor reaches 710°C; (3) The high-temperature lithium mica ore particles discharged from the bottom outlet of the cyclone preheater 3 enter the fluidized bed roaster 4 through the feed valve, and are countercurrently contacted and reacted with the water vapor from the bottom of the fluidized bed roaster 4. A plurality of supplementary heat burners are arranged in the fluidized section to control the reaction temperature at 8-15°C. After the roasting reaction for 2 hours, roasted clinker and fluorine-containing tail gas are obtained; (4) The roasted clinker produced by the fluidized bed roasting furnace 4 enters the cyclone cooling system 6 through the discharge valve, and the roasted clinker is discharged after being cooled. The heat generated during the cooling process is used as a heat source for preheating the water vapor produced by the steam boiler 9; (5) The fluorine-containing tail gas generated by the fluidized bed roaster 4 is separated by the roaster separator, and the solid particles generated by the separation are returned to the fluidized bed roaster 4 to continue the roasting reaction. The gas generated by the separation enters the second reaction device 5, and MgO is loaded in the second reaction device 5 to react with HF gas to produce MgF2. The solid fluorine reaction temperature is 220°C and the reaction time is 3.0 h. The defluorinated gas enters the tail gas purification device 10 for thallium removal. The gas absorption device 10 is loaded with WS2 thallium adsorbent. The purified gas generated after defluorination and thallium removal is discharged into the atmosphere through the induced draft fan 11. The HF-containing gas discharged from the fluidized bed roaster 4 is sent to the tail gas treatment unit for recovery. The purified high-temperature tail gas (defluorination rate> 99%) is used to preheat water in the steam boiler 9 to produce high-temperature water vapor. (6) The roasted clinker discharged from the roasted clinker cooling unit 6 is sent to the leaching device 12 for acid leaching, and after leaching, it is sent to the filtering device 13 for filtration to produce leaching residue and leachate; sodium benzoate is added to the leachate until no precipitation is produced, and aluminum benzoate and lithium-rich leachate are obtained by filtration; sodium carbonate is added to the lithium-rich leachate to precipitate lithium to obtain lithium carbonate; an extractant is then added to the leachate after lithium extraction, and after multi-stage centrifugal extraction, the raffinate is collected in a residual water storage tank The loaded organic phase after extraction enters the water washing section. After multi-stage centrifugal water washing, the washing water flows into the residual water storage tank. The loaded organic phase after water washing enters the centrifugal stripping section. The regenerated extractant obtained after stripping enters the extractant storage tank for recycling. The washing water and the residual water are mixed and enter the extraction section again. The stripping water after stripping is further treated and recycled as the stripping agent. The rubidium and cesium after stripping are precipitated by adding sodium carbonate or introducing CO2 to obtain carbonates of rubidium and cesium.

[0107] In this embodiment, the lithium leaching rate is 92%, the comprehensive lithium recovery rate is 82%, the rubidium-cesium leaching rate is 90.5%, the comprehensive rubidium-cesium recovery rate is 85%, the fluorine-thallium resource utilization rate is 97%, the thallium emission in the flue gas is 25 ppb, and the HF emission is 0.4 ppm.

[0108] Example 5 The same system as in Example 1 is used for low-temperature salt-free fluidized roasting of lithium mica ore, comprising the following steps: Steps (1) to (5) are the same as those in Example 1. (6) The roasted clinker discharged from the roasted clinker cooling unit 6 is sent to the leaching device 12 for acid leaching, and then sent to the filtering device 13 for filtration to produce leaching residue and leachate; sodium hydroxide is added to the leachate until the pH value of the solution is 4, and then filtered to obtain aluminum hydroxide precipitate and lithium-rich leachate; sodium carbonate is added to the lithium-rich leachate to precipitate lithium to obtain lithium carbonate; an extractant is then added to the leachate after lithium extraction, and after multi-stage centrifugal extraction, the raffinate is collected to the residual water storage In the tank, the loaded organic phase after extraction enters the water washing section. After multi-stage centrifugal water washing, the washing water flows into the residual water storage tank. The loaded organic phase after water washing enters the centrifugal stripping section. The regenerated extractant obtained after stripping enters the extractant storage tank for recycling. The washing water and the residual water are mixed and enter the extraction section again. The stripping water after stripping is further treated and recycled as the stripping agent. The rubidium and cesium after stripping are precipitated by adding sodium carbonate or introducing CO2 to obtain carbonates of rubidium and cesium.

[0109] In this embodiment, the lithium leaching rate is 95%, the comprehensive lithium recovery rate is 70%, the rubidium-cesium leaching rate is 92%, and the comprehensive rubidium-cesium recovery rate is 60%.

[0110] Compared with Example 1, the comprehensive recovery rate of lithium, rubidium and cesium can be effectively improved by using benzoate as the precipitant of Al element.

[0111] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the principles of the present application should be included in the protection scope of the present application.

Claims

1. A method for extracting lithium from lepidolite by low-temperature salt-free fluidized roasting. It is characterized in that The following steps are involved: Step S1: providing lepidolite particles; Step S2: preheating the lithium mica ore particles and the fluidizing gas respectively, so that the temperature of the preheated lithium mica ore particles is 700-790° C. and the temperature of the preheated fluidizing gas is 700-850° C., and fluidizing roasting the preheated lithium mica ore particles and the fluidizing gas so that the Li-F mineral phase in the lithium mica ore particles dissociates and releases fluoride ions, and the fluoride ions combine with hydrogen ions to generate hydrogen fluoride gas that diffuses from the inside of the lithium mica ore particles to the gas phase, thereby obtaining roasted clinker and fluorine-containing tail gas; Wherein, the fluidizing gas includes water vapor, and the volume percentage of the water vapor in the fluidizing gas is not less than 30%.

2. The method according to claim 1, It is characterized in that In the step S1, the average particle size of the lepidolite particles is 0.1-0.5 mm.

3. The method according to claim 1, It is characterized in that In the step S2, the conditions of the fluidized calcination treatment include: the temperature of the fluidized calcination is 810-850° C., and the time of the fluidized calcination is 0.5-2 hours.

4. The method according to claim 1, further comprising: include: Step S3: subjecting the roasted clinker to acid leaching treatment using an acid solution to fix the lithium element in the roasted clinker into the leaching solution, and filtering to obtain leaching residue and leaching solution; Wherein, the acid leaching treatment satisfies at least one of the following conditions: 1) The acid solution is a sulfuric acid aqueous solution, and the concentration of the sulfuric acid aqueous solution is 0.1-5 mol / L; 2) The conditions of the acid leaching treatment include: a solid-liquid ratio of 0.5:5 and an acid leaching time of 0.5 to 3 hours.

5. The method according to claim 4, further comprising: include: Step S4: adding benzoate to the leachate to convert the Al element in the leachate into aluminum benzoate precipitate, and filtering to obtain aluminum benzoate particles and lithium-rich leachate.

6. The method according to claim 1, It is characterized in that Also includes: Step S5: reacting the fluorine-containing tail gas with metal oxides, so that the hydrogen fluoride in the fluorine-containing tail gas reacts with the metal oxides to generate metal fluorides, thereby obtaining defluorinated tail gas and metal fluorides; wherein the metal oxides include CaO, Al 2 O 3 ,MgO,ZnO,Fe 2 O 3 ,FeO,Fe 3 O 4 、CuO、NiO、CoO、Co 2 O 3 、Co 3 O 4 、TiO 2 、Ti 4 O 7 , WO 3 、MoO 3 At least one of; The step S5 satisfies at least one of the following conditions: 1) The conditions for the reaction of the fluorine-containing tail gas with the metal oxide include: a reaction temperature of 200-800° C. and a reaction time of 0.1-5 h; 2) The particle size of the metal oxide is 0.1-3 mm.

7. The method according to claim 6, It is characterized in that Also includes: Step S5: reacting the defluorinated tail gas with a thallium adsorbent, so that the thallium element in the defluorinated tail gas reacts with the thallium adsorbent to generate a thallium compound, thereby obtaining purified tail gas and thallium compounds; wherein the thallium adsorbent includes metal sulfide.

8. A system for extracting lithium from lepidolite by low-temperature, salt-free fluidized roasting. It is characterized in that include: Mineral powder feeding unit, used to transport lepidolite ore particles; A water vapor generating unit, used for generating water vapor; A first reaction unit, the first reaction unit is connected to the ore powder feeding unit and the water vapor generating unit respectively, and is used as a reaction place for the lepidolite ore particles and the fluidizing gas including water vapor; A ore powder preheating unit, wherein the ore powder preheating unit connects the ore powder feeding unit with the first reaction unit, and the ore powder preheating unit is connected with a water vapor generation unit, and is used to preheat the lepidolite ore particles and then transport them to the first reaction unit, and the heat of the generated high-temperature gas is used for the water vapor generation unit to generate high-temperature steam; A gas preheating unit connects the steam generating unit with the first reactor unit and is used for preheating the fluidizing gas and then transporting it to the first reaction unit.

9. The system according to claim 8, It is characterized in that Also includes: The clinker cooling unit is connected to the first reaction unit, and the clinker cooling unit connects the water vapor generating unit and the gas preheating unit, and is used to heat the sensible heat of the clinker obtained by the reaction of the first reaction unit with water vapor from the water vapor generating unit, and cool the clinker.

10. The system according to claim 9, It is characterized in that Also includes: The leaching and filtering unit is connected to the roasted clinker cooling unit and is used to leach the lithium element in the roasted clinker and fix it into the leaching solution, and separate it from the leaching residue.

11. The system according to claim 8, It is characterized in that Also includes: The tail gas treatment unit is connected to the first reaction unit and is used to treat the fluorine-containing tail gas generated after the reaction in the first reaction unit.

12. A system according to any one of claims 8 to 11, It is characterized in that At least one of the following conditions is met: 1) The mineral powder feeding unit comprises a raw material bin (1) and a screw feeder (2), the discharge port of the raw material bin (1) is connected to the feed port of the screw feeder (2), and the discharge port of the screw feeder (2) is connected to the mineral powder preheating unit; 2) The first reaction unit comprises a feed valve, a fluidized bed roaster (4), a roaster separator and a discharge valve, wherein the feed port of the fluidized bed roaster (4) is connected to the ore powder feed unit via the feed valve, the discharge port of the fluidized bed roaster (4) is connected to the roasted clinker cooling unit via the discharge valve, the air inlet of the roaster separator is connected to the air outlet of the fluidized bed roaster (4), and the air outlet of the roaster separator is connected to the tail gas treatment unit; 3) the water vapor generation unit comprises a steam boiler (9), a steam outlet of the steam boiler (9) is connected to a roasting clinker cooling unit, and the steam boiler (9) is connected to a mineral powder preheating unit; 4) The mineral powder preheating unit comprises a combustion chamber (8), a cyclone preheater (3) and a cyclone separator, the gas outlet of the combustion chamber (8) is connected to the gas inlet of the cyclone preheater (3), the gas outlet of the cyclone preheater (3) is connected to the gas inlet of the cyclone separator, the gas outlet of the cyclone separator is connected to the water vapor generation unit, the feed inlet of the cyclone preheater 3 is connected to the mineral powder feed unit, and the discharge outlet of the cyclone preheater (3) is connected to the first reaction unit; 5) The roasted clinker cooling unit (6) comprises a cyclone cooler and a cyclone cooling separator, the feed inlet of the cyclone cooler is connected to the first reaction unit, the discharge port of the cyclone cooler is connected to the leaching and filtering unit, the air inlet of the cyclone cooler is connected to the water vapor generating unit, the air outlet of the cyclone cooler is connected to the air inlet of the cyclone cooling separator, and the air outlet of the cyclone cooling separator is connected to the gas preheating unit; 6) The gas preheating unit comprises a hot blast furnace (7), an air inlet of the hot blast furnace (7) is connected to the roasting clinker cooling unit (6), and an air outlet of the hot blast furnace (7) is connected to the first reaction unit; 7) The leaching and filtering unit comprises a leaching device (12) and a filtering device (13), wherein the feed port of the leaching device (12) is connected to the roasted clinker cooling unit, and the discharge port of the leaching device (12) is connected to the filtering device (13); 8) The tail gas treatment unit comprises a second reaction device (5) for absorbing hydrogen fluoride in the tail gas; and an exhaust gas purification device (10) for absorbing thallium in the exhaust gas; The air inlet of the second reaction device (5) is connected to the first reaction unit, and the air outlet of the second reaction device (5) is connected to the exhaust gas purification device (10); 9) It also includes an induced draft unit, which is connected to the tail gas treatment unit and the steam generation unit respectively, and is used to control the flow direction of the gas in the system.

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