A solid fluorine fixation system and method for extracting lithium from lepidolite

Abstract

A fluorine fixation system for extracting lithium from lepidolite, belonging to the field of new energy processing technology. The system includes a drying device, a preheating device, a fluorine fixation device, a cooling device and a purification device. The dirty flue gas outlet end of the drying device is connected to the purification device, and the material outlet end of the drying device is sequentially connected to the preheating device, the fluorine fixation device and the cooling device. A method for extracting lithium by the fluorine fixation system for extracting lithium from lepidolite includes the following steps: Step 1, drying; Step 2, preheating; Step 3, fluorine fixation; Step 4, cooling. Through this technology, lepidolite can fully react for fluorine fixation, improving the conversion rate of lepidolite in subsequent leaching processes. It has low heat consumption, large production capacity, simple system, low operating cost and high recovery rate of lithium.

Description

Technical Field

[0001] The present invention belongs to the technical field of new energy processing, and particularly relates to a fluorine fixation system and method for extracting lithium from lepidolite. Background Art

[0002] At present, in the field of new energy, lithium carbonate, which is used as the cathode material for lithium batteries, has a rapidly increasing demand, and various enterprises are actively and quickly carrying out research on lithium batteries. Although China has rich lepidolite resources, its grade is low, and due to the presence of fluoride ions, it is almost impossible to directly extract lithium from lepidolite. Therefore, pretreatment of fluoride ions is required. The currently adopted method is the tunnel kiln fluorine fixation method, which involves first pulverizing, then extrusion molding, then heating for fluorine fixation, and finally grinding and leaching. The tunnel kiln fluorine fixation method has the disadvantages of small production capacity, complex system, high construction investment, and high operating cost.

[0003] Patent No. CN 216205184 U discloses "a rotary kiln for roasting lepidolite", and its disadvantages are as follows: only a vertical preheating cylinder is provided, with a scattered material inclined plate inside, and a heating cover is provided outside the calcination section of the rotary kiln, and heat is recovered through a heat exchanger. The entire system only focuses on the recovery of waste heat in the calcination section of the rotary kiln, and a single vertical preheating cylinder cannot fully preheat the materials with the heat of the system, and does not have the effect of directly reducing energy consumption and cost.

[0004] Patent No. CN 103922355 B discloses "a device and preparation process for producing spodumene", and its disadvantages are as follows: although the waste gas of the rotary kiln is used for preheating through the design of a coarse particle suspension preheater, reducing energy consumption, the temperature of spodumene after heat exchange is only 370 - 380 °C. To complete the conversion of spodumene from α-spodumene to β-spodumene, the main heating stage is still completed in the rotary kiln. The rotary kiln has low thermal efficiency and high energy consumption, and cannot achieve better economic and environmental protection benefits.

[0005] Therefore, it is necessary to invent a fluorine fixation system and method for extracting lithium from lepidolite to solve the above problems. Summary of the Invention

[0006] The purpose of the present invention is to provide a fluorine fixation system and method for extracting lithium from lepidolite, enabling the lepidolite to fully react for fluorine fixation, improving the conversion rate of lepidolite in subsequent leaching processes, having low heat consumption, large production capacity, simple system, low operating cost, and high lithium recovery rate.

[0007] To achieve the above purpose, the present invention adopts the following technical solutions:

[0008] A fluorine fixation system for extracting lithium from lepidolite, comprising a drying device, a preheating device, a fluorine fixation device, a cooling device and a purification device. The dirty flue gas outlet end of the drying device is connected to the purification device, and the material outlet end of the drying device is sequentially connected to the preheating device, the fluorine fixation device and the cooling device.

[0009] The drying device includes a drying and dispersing machine and a cyclone preheater. The material outlet of the drying and dispersing machine is connected to the material inlet of the cyclone preheater. A wet material inlet, a drying air inlet and a drying flue gas inlet are respectively arranged on the drying and dispersing machine. A dry material outlet and a dirty flue gas outlet are respectively arranged on the cyclone preheater. The drying and dispersing machine can be replaced by a Venturi dryer, a vertical mill or a device with drying and dispersing functions.

[0010] The preheating device includes N separating heat exchangers and a preheating furnace, where N≥1. The material outlet of the separating heat exchanger is connected to the material inlet of the preheating furnace. A dry material inlet, a preheating flue gas inlet and a drying flue gas outlet are respectively arranged on the separating heat exchanger. A hot material outlet, a fuel II inlet and a tertiary air inlet are respectively arranged on the preheating furnace. The preheating furnace requires fuel II, and the fuel II is sent into the preheating device by a diffusion type high-efficiency burner. The separating heat exchanger adopts one or a combination of a cyclone preheater, a cyclone separator and a cyclone dust collector.

[0011] The purification device includes a dust collector, a denitration tower, a desulfurization tower, a defluorination tower, a induced draft fan and a chimney. The dust collector, the denitration tower, the desulfurization tower, the defluorination tower, the induced draft fan and the chimney are sequentially connected through pipelines. The dust collector is one of a bag filter, a metal filter bag dust collector and an electrostatic bag dust collector.

[0012] The fluorine fixation device is provided with a hot material inlet, a hot clinker outlet, a fuel I inlet, a secondary air inlet and a preheating flue gas outlet. The fluorine fixation device is a rotary reactor. The rotary reactor requires fuel I, which is sent into the rotary reactor by a high-efficiency burner. The high-efficiency burner is one of a partial premixed burner and a diffusion burner.

[0013] The cooling device is a grate cooler. The cooling device is provided with a hot clinker inlet, a cold clinker outlet, a cooling air inlet, a secondary air outlet, a tertiary air outlet and a drying air outlet.

[0014] The dry material outlet of the cyclone preheater is connected to the dry material inlet of the separation heat exchanger. The drying air inlet of the drying and dispersing machine is connected to the drying air outlet of the cooling device. The drying flue gas inlet of the drying and dispersing machine is connected to the drying flue gas outlet of the separation heat exchanger. The dirty flue gas outlet of the cyclone preheater is connected to the dirty flue gas inlet on the dust collector in the purification device. The clean flue gas outlet of the chimney in the purification device is used to discharge clean flue gas. The wet material inlet of the drying and dispersing machine is used to add wet material. The hot material outlet of the preheating furnace is connected to the hot material inlet of the fluorine fixation device. The tertiary air inlet of the preheating furnace is connected to the tertiary air outlet of the cooling device. The preheated flue gas inlet of the separation heat exchanger is connected to the preheated flue gas outlet of the fluorine fixation device. The hot clinker outlet of the fluorine fixation device is connected to the hot clinker inlet of the cooling device. The secondary air inlet of the fluorine fixation device is connected to the secondary air outlet of the cooling device. The fuel II inlet of the preheating furnace is used to add fuel II. The fuel I inlet of the fluorine fixation device is used to add fuel I and the required primary air. The cooling air inlet of the cooling device is used to add cooling air, and the cooling air is ambient air.

[0015] The wet material is a mixture of raw materials and additive I, additive II, and additive III. The raw material is lithium mica powder, additive I is a sulfate containing sodium or potassium elements, additive II is calcium carbonate, and additive III is sodium hydroxide.

[0016] Both fuel I and fuel II are gaseous fuels or liquid fuels. When they are gaseous fuels, the primary air serves as premixed air. When they are liquid fuels, the primary air serves as atomizing air, and the primary air is ambient air.

[0017] The cold clinker discharged from the cold clinker outlet of the cooling device has a temperature of ≤80°C.

[0018] A method for extracting lithium using a fluorine fixation system for extracting lithium from lithium mica includes the following steps:

[0019] Step 1, drying:

[0020] The wet material is transported through the wet material inlet of the drying device into the drying device. The drying air generated in the cooling device is output through the drying air outlet, flows through the drying air inlet of the drying device, and enters the drying device. The drying flue gas generated in the preheating device is output through the drying flue gas outlet, flows through the drying flue gas inlet of the drying device, and enters the drying device. The wet material is heated under the dual action of the drying air and drying flue gas in the drying device. The wet material is dried and separated in the drying and dispersing machine and the cyclone preheater. The dried dry material enters the preheating device. The dirty flue gas generated during this process is output through the dirty flue gas outlet of the drying device, enters the purification device through the dirty flue gas inlet for treatment, and the treated clean flue gas is sent into the chimney and discharged into the atmosphere through the induced draft fan.

[0021] Step 2, preheating:

[0022] The dry material is output through the dry material outlet of the drying device and enters the preheating device through the dry material inlet of the preheating device. The preheating device consists of an N-stage cyclone preheater and a preheating furnace. Fuel II is introduced into the preheating device through the fuel II inlet of the preheating device. The tertiary air generated in the cooling device is output through the tertiary air outlet of the cooling device and introduced into the preheating device through the tertiary air inlet of the preheating device. The preheated flue gas generated in the fluorine fixation device is discharged through the preheated flue gas outlet of the fluorine fixation device and introduced into the preheating device through the preheated flue gas inlet of the preheating device. The dry material is heated into hot material by the heat generated from fuel combustion, the combustion products of the tertiary air, and the preheated flue gas discharged from the fluorine fixation device;

[0023] Step 3, fluorine fixation:

[0024] The hot material is output through the hot material outlet of the preheating device and enters the fluorine fixation device through the hot material inlet of the fluorine fixation device. The fluorine fixation device is a rotary reactor. Fuel I and primary air enter the fluorine fixation device through the fuel I inlet of the fluorine fixation device. The secondary air generated in the cooling device is discharged through the secondary air outlet of the cooling device and flows through the secondary air inlet of the fluorine fixation device to enter the fluorine fixation device. The combustion products generated by the combustion of Fuel I, primary air, and secondary air in the fluorine fixation device heat and fix the fluorine in the hot material. The ratio of premixed primary air to the total air volume is 6-15%, and the ratio of secondary air to the total air volume is 85-94%;

[0025] The basic reaction formula for fluorine fixation:

[0026] CaCO3 + 2HF → CaF2↓ + CO2↑ + H2O↑, fluorine fixation rate ≥ 99.5%;

[0027] Step 4, cooling:

[0028] The hot clinker is output through the hot clinker outlet, enters the cooling device through the hot clinker inlet, and cooling air is introduced through the cooling air inlet to cool the hot clinker in the cooling device, so that the temperature of the cold clinker is reduced to below 80°C. At the same time, the cooling air is heated, that is, the drying air in the cooling device recovers the low-temperature section heat, and the secondary air and tertiary air in the cooling device recover the high-temperature section heat. The cooled cold clinker is discharged through the cold clinker outlet of the cooling device.

[0029] The lepidolite powder described in Step 1 is pre-ground to a fineness of ≤ 0.1 mm in advance. The ratio of lepidolite powder to additive in the wet material is 1:0.5 - 1.5. The drying time of the wet material is 5 - 60 s. The temperature of the drying air and drying flue gas is 300 - 400°C, and the temperature of the dirty flue gas and dry material is 110 - 150°C.

[0030] The temperature of the clean flue gas described in Step 1 is 110 - 150°C, and the particulate matter in the clean flue gas ≤ 10 mg / m 3, nitrogen oxides ≤ 50 mg / m 3 , sulfur dioxide ≤ 20 mg / m 3 , hydrogen fluoride ≤ 3 mg / m 3 .

[0031] The temperature of the tertiary air described in Step 2 is 600 - 700 °C, the temperature of the preheated flue gas discharged from the fluorine fixation device is 800 - 870 °C, the temperature of the dried flue gas discharged from the preheating device is 300 - 400 °C, the temperature of the hot material is 800 - 870 °C, and the residence time of the dry material in the preheating device is 20 - 60 s.

[0032] The primary air described in Step 3 is ambient air, the temperature of the secondary air is 800 - 850 °C, the temperature of the preheated flue gas discharged from the fluorine fixation device is 800 - 870 °C, the temperature of the hot clinker after rotary reaction is 900 - 950 °C, and the residence time of the hot material in the fluorine fixation device is 60 - 120 min.

[0033] The temperature of the hot clinker described in Step 4 is 900 - 950 °C, and the temperatures of the secondary air, tertiary air, and drying air are 800 - 850 °C, 600 - 700 °C, and 300 - 400 °C respectively.

[0034] Advantages of the present invention:

[0035] The present invention provides a fluorine fixation system and method for extracting lithium from lepidolite. Through this technology, lepidolite can fully react for fluorine fixation, improving the conversion rate of lepidolite in subsequent leaching processes. It has low heat consumption, large production capacity, simple system, low operating cost, and high lithium recovery rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a schematic diagram of a fluorine fixation system and method for extracting lithium from lepidolite according to the present invention;

[0037] In the figure, 1 - drying device, 2 - preheating device, 3 - fluorine fixation device, 4 - cooling device, 5 - purification device;

[0038] A - lepidolite, B - additive I, C - additive II, D - additive III, E - wet material, F - dry material, G - hot material, H - hot clinker, J - cold clinker, K - fuel II, L - fuel I, M - cooling air, N - secondary air, O - tertiary air, P - drying air, Q - primary air, R - preheated flue gas, S - dried flue gas, T - dirty flue gas, U - clean flue gas. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0039] The present invention will be further described in detail below with reference to the drawings and embodiments.

[0040] As Figure 1As shown in the figure, a fluorine fixation system for extracting lithium from lepidolite includes a drying device 1, a preheating device 2, a fluorine fixation device 3, a cooling device 4 and a purification device 5. The dirty flue gas outlet end of the drying device 1 is connected to the purification device 5, and the material outlet end of the drying device 1 is sequentially connected to the preheating device 2, the fluorine fixation device 3 and the cooling device 4.

[0041] The drying device 1 includes a drying and dispersing machine and a cyclone preheater. The material outlet of the drying and dispersing machine is connected to the material inlet of the cyclone preheater. A wet material inlet, a drying air inlet and a drying flue gas inlet are respectively arranged on the drying and dispersing machine. A dry material outlet and a dirty flue gas outlet are respectively arranged on the cyclone preheater. In this embodiment, the drying and dispersing machine is a Venturi dryer.

[0042] The preheating device 2 includes a separation heat exchanger and a preheating furnace. The material outlet of the separation heat exchanger is connected to the material inlet of the preheating furnace. A dry material inlet, a preheating flue gas inlet and a drying flue gas outlet are respectively arranged on the separation heat exchanger. A hot material outlet, a fuel II inlet and a tertiary air inlet are respectively arranged on the preheating furnace. The preheating furnace requires fuel II K, and fuel II K is sent into the preheating device 2 by a diffusion type high-efficiency burner. The separation heat exchanger is a cyclone preheater.

[0043] The purification device 5 includes a dust collector, a denitration tower, a desulfurization tower, a defluorination tower, a induced draft fan and a chimney. The dust collector, the denitration tower, the desulfurization tower, the defluorination tower, the induced draft fan and the chimney are sequentially connected through pipelines. The dust collector is a bag filter.

[0044] The fluorine fixation device 3 is provided with a hot material inlet, a hot clinker outlet, a fuel I inlet, a secondary air inlet and a preheating flue gas outlet. The fluorine fixation device 3 is a rotary reactor. The rotary reactor requires fuel I L, which is sent into the rotary reactor by a high-efficiency burner. The high-efficiency burner is a partial premixed burner.

[0045] The cooling device 4 is a grate cooler. The cooling device 4 is provided with a hot clinker inlet, a cold clinker outlet, a cooling air inlet, a secondary air outlet, a tertiary air outlet and a drying air outlet.

[0046] The dry material outlet of the cyclone preheater is connected to the dry material inlet of the separation heat exchanger. The drying air inlet of the drying and dispersing machine is connected to the drying air outlet of the cooling device 4. The drying flue gas inlet of the drying and dispersing machine is connected to the drying flue gas outlet of the separation heat exchanger. The dirty flue gas outlet of the cyclone preheater is connected to the dirty flue gas inlet on the dust collector in the purification device 5. The clean flue gas outlet of the chimney in the purification device 5 is used to discharge the clean flue gas U. The wet material inlet of the drying and dispersing machine is used to add the wet material E. The hot material outlet of the preheating furnace is connected to the hot material inlet of the fluorine fixation device 3. The tertiary air inlet of the preheating furnace is connected to the tertiary air outlet of the cooling device 4. The preheated flue gas inlet of the separation heat exchanger is connected to the preheated flue gas outlet of the fluorine fixation device 3. The hot clinker outlet of the fluorine fixation device 3 is connected to the hot clinker inlet of the cooling device 4. The secondary air inlet of the fluorine fixation device 3 is connected to the secondary air outlet of the cooling device 4. The fuel II inlet of the preheating furnace is used to add the fuel II K. The fuel I inlet of the fluorine fixation device 3 is used to add the fuel I L and the required primary air Q. The cooling air inlet of the cooling device 4 is used to add the cooling air M, and the cooling air M is ambient air.

[0047] The wet material E is a mixture of raw materials and additive I B, additive II C, and additive III D. The raw material is lithium mica A powder. Additive I B is a sodium-containing sulfate. Additive II C is calcium carbonate. Additive III D is sodium hydroxide.

[0048] Both the fuel I L and the fuel II K are gaseous fuels or liquid fuels. When they are gaseous fuels, the primary air Q serves as premixed air. When they are liquid fuels, the primary air Q serves as atomizing air, and the primary air Q is ambient air.

[0049] In the clean flue gas U purified by the purification device 5, the particulate matter ≤ 10 mg / m 3 , nitrogen oxides ≤ 50 mg / m 3 , sulfur dioxide ≤ 20 mg / m 3 , hydrogen fluoride ≤ 3 mg / m 3 . The cold clinker J is discharged from the cold clinker outlet of the cooling device 4, and the temperature of the cold clinker J ≤ 80 °C.

[0050] A method for extracting lithium using a fluorine fixation system for extracting lithium from lithium mica includes the following steps:

[0051] Step 1, drying:

[0052] The lithium mica A powder material is pre-ground to a fineness of ≤0.1 mm in advance, and the ratio of the lithium mica A powder material to the additive in the wet material E is 1:0.75; the normal-temperature wet material E is conveyed into the drying and dispersing machine through the wet material inlet of the drying and dispersing machine. The dry air P at 350 °C generated in the cooling device 4 is output through the dry air outlet and flows through the dry air inlet of the drying and dispersing machine into the drying and dispersing machine. The dry flue gas S at 350 °C generated in the separating heat exchanger is output through the dry flue gas outlet and flows through the dry flue gas inlet of the drying and dispersing machine into the drying and dispersing machine. The wet material E is heated under the dual action of the dry air P and the dry flue gas S in the drying device 1. The wet material E is dried and separated in the drying and dispersing machine and the cyclone preheater. The drying time is 30 s, and the dry material F at 125 °C after drying enters the separating heat exchanger of the preheating device 2. The dirty flue gas T at 125 °C generated during this process is output through the dirty flue gas outlet of the cyclone preheater and enters the purification device 5 through the dirty flue gas inlet for treatment. The clean flue gas U at 125 °C after treatment is sent into the chimney and discharged into the atmosphere through the induced draft fan. The particulate matter in the clean flue gas U is ≤10 mg / m 3 , nitrogen oxides are ≤50 mg / m 3 , sulfur dioxide is ≤20 mg / m 3 , hydrogen fluoride is ≤3 mg / m 3 ;

[0053] Step 2, preheating:

[0054] The dry material F is output through the dry material outlet of the cyclone separator and enters the separating heat exchanger through the dry material inlet of the separating heat exchanger. The preheating device 2 consists of a separating heat exchanger and a preheating furnace. The diffusion-type high-efficiency burner passes the fuel II K into the preheating furnace through the fuel II inlet of the preheating furnace. The tertiary air O at 650 °C generated in the cooling device 4 is output through the tertiary air outlet of the cooling device 4 and passes through the tertiary air inlet of the preheating furnace into the preheating furnace. The preheated flue gas R generated in the fluorine fixation device 3 is discharged through the preheated flue gas outlet of the fluorine fixation device 3 and passes through the preheated flue gas inlet of the separating heat exchanger into the preheating separator. The high-temperature flue gas generated by the combustion of the fuel II K and the tertiary air O and the preheated flue gas R at 835 °C discharged from the fluorine fixation device 3 heat the dry material F into the hot material G. The temperature of the hot material G is 835 °C, and the residence time of the dry material F in the preheating device 2 is 40 s; the dry flue gas S discharged from the preheating device 2 has a temperature of 350 °C;

[0055] Step 3, fluorine fixation:

[0056] The hot material G is output through the hot material outlet of the preheating furnace and enters the fluorine fixation device 3 through the hot material inlet of the fluorine fixation device 3. The fluorine fixation device 3 is a rotary reactor. The fuel I L and the primary air Q enter the fluorine fixation device 3 through the fuel I inlet of the fluorine fixation device 3. The primary air Q is ambient air. The secondary air N with a temperature of 825 °C generated in the cooling device 4 is discharged through the secondary air outlet of the cooling device 4 and flows through the secondary air inlet of the fluorine fixation device 3 to enter the fluorine fixation device 3. The combustion products generated by the combustion of the fuel I L, the primary air Q and the secondary air N in the fluorine fixation device 3 heat the hot material G to fix fluorine into the hot clinker H. The temperature of the hot clinker H after the rotary reaction is 925 °C. The residence time of the hot material G in the fluorine fixation device 3 is 90 min. The ratio of the premixed primary air Q to the total air volume is 7.5%, and the ratio of the secondary air N to the total air volume is 89.5%. The temperature of the preheated flue gas R discharged from the fluorine fixation device 3 is 835 °C.

[0057] The basic fluorine fixation reaction formula:

[0058] CaCO3 + 2HF → CaF2↓ + CO2↑ + H2O↑, the fluorine fixation rate ≥ 99.5%;

[0059] Step 4, cooling:

[0060] The hot clinker H with a temperature of 925 °C is output through the hot clinker outlet, enters the cooling device 4 through the hot clinker inlet, and cooling air M is introduced through the cooling air inlet to cool the hot clinker H in the cooling device 4, so that the temperature of the cold clinker J is reduced to below 80 °C. The cooling air M is heated at the same time, that is, the dry air P of the cooling device 4 recovers the heat of the low-temperature section, and the secondary air N and the tertiary air O of the cooling device 4 recover the heat of the high-temperature section. The cooled cold clinker J is discharged through the cold clinker outlet of the cooling device 4. The temperatures of the secondary air N, the tertiary air O and the dry air P are 825 °C, 650 °C and 350 °C respectively.

Claims

1. A fluorine fixation system for extracting lithium from lepidolite, characterized in that, It includes a drying device, a preheating device, a fluorine fixation device, a cooling device and a purification device. The dirty flue gas outlet end of the drying device is connected to the purification device, and the material outlet end of the drying device is sequentially connected to the preheating device, the fluorine fixation device and the cooling device; The drying device includes a drying and dispersing machine and a cyclone preheater. The material outlet of the drying and dispersing machine is connected to the material inlet of the cyclone preheater. A wet material inlet, a drying air inlet and a drying flue gas inlet are respectively arranged on the drying and dispersing machine, and a dry material outlet and a dirty flue gas outlet are respectively arranged on the cyclone preheater; The preheating device includes N separating heat exchangers and a preheating furnace, where N≥1. The material outlet of the separating heat exchanger is connected to the material inlet of the preheating furnace. A dry material inlet, a preheating flue gas inlet and a drying flue gas outlet are respectively arranged on the separating heat exchanger, and a hot material outlet, a fuel II inlet and a tertiary air inlet are respectively arranged on the preheating furnace; The purification device includes a dust collector, a denitration tower, a desulfurization tower, a defluorination tower, a induced draft fan and a chimney; The dust collector, the denitration tower, the desulfurization tower, the defluorination tower, the induced draft fan and the chimney are sequentially connected through pipelines; The fluorine fixation device is a rotary reactor, provided with a hot material inlet, a hot clinker outlet, a fuel I inlet, a secondary air inlet and a preheating flue gas outlet; The cooling device is provided with a hot clinker inlet, a cold clinker outlet, a cooling air inlet, a secondary air outlet, a tertiary air outlet and a drying air outlet; The dry material outlet of the cyclone preheater is connected to the dry material inlet of the separating heat exchanger. The drying air inlet of the drying and dispersing machine is connected to the drying air outlet of the cooling device. The drying flue gas inlet of the drying and dispersing machine is connected to the drying flue gas outlet of the separating heat exchanger. The dirty flue gas outlet of the cyclone preheater is connected to the dirty flue gas inlet on the dust collector in the purification device. The clean flue gas outlet of the chimney in the purification device is used to discharge clean flue gas. The wet material inlet of the drying and dispersing machine is used to add wet material. The hot material outlet of the preheating furnace is connected to the hot material inlet of the fluorine fixation device; The tertiary air inlet of the preheating furnace is connected to the tertiary air outlet of the cooling device; The preheating flue gas inlet of the separating heat exchanger is connected to the preheating flue gas outlet of the fluorine fixation device; The hot clinker outlet of the fluorine fixation device is connected to the hot clinker inlet of the cooling device; The secondary air inlet of the fluorine fixation device is connected to the secondary air outlet of the cooling device; The fuel II inlet of the preheating furnace is used to add fuel II; The fuel I inlet of the fluorine fixation device is used to add fuel I and the required primary air. The cooling air inlet of the cooling device is used to add cooling air, and the cooling air is ambient air.

2. The fluorine fixation system for extracting lithium from lepidolite according to claim 1, characterized in that: The drying and dispersing machine can be a Venturi dryer or a vertical mill; The separating heat exchanger adopts a cyclone preheater; The dust collector is one of a bag dust collector, a metal filter bag dust collector and an electric bag dust collector.

3. The fluorine fixation system for extracting lithium from lepidolite according to claim 1, characterized in that: Both the fuel I and the fuel II are gaseous fuels or liquid fuels. When they are gaseous fuels, the primary air serves as premixed air; When they are liquid fuels, the primary air serves as atomizing air, where the primary air is ambient air.

4. A method for extracting lithium using the fluorine fixation system for extracting lithium from lepidolite according to claim 2, characterized in that, It includes the following steps: Step 1, drying: The wet material is conveyed into the drying device through the wet material inlet of the drying device. The dry air generated in the cooling device is output through the dry air outlet, flows through the dry air inlet of the drying device, and enters the drying device. The dry flue gas generated in the preheating device is output through the dry flue gas outlet, flows through the dry flue gas inlet of the drying device, and enters the drying device. Under the dual action of the dry air and the dry flue gas in the drying device, the wet material is heated. The wet material is dried and separated in the drying and dispersing machine and the cyclone preheater. The dried dry material enters the preheating device. The dirty flue gas generated during this process is output through the dirty flue gas outlet of the drying device, enters the purification device through the dirty flue gas inlet for treatment, and the treated clean flue gas is sent into the chimney and discharged into the atmosphere by the induced draft fan; Step 2, Preheating: The dry material is output through the dry material outlet of the drying device and enters the preheating device through the dry material inlet of the preheating device. The preheating device consists of an N-stage cyclone preheater and a preheating furnace. Fuel II is introduced into the preheating device through the fuel II inlet of the preheating device. The tertiary air generated in the cooling device is output through the tertiary air outlet of the cooling device, flows through the tertiary air inlet of the preheating device, and is introduced into the preheating device. The preheated flue gas generated in the fluorine fixation device is discharged through the preheated flue gas outlet of the fluorine fixation device, flows through the preheated flue gas inlet of the preheating device, and is introduced into the preheating device. The dry material is heated into hot material by the heat generated by fuel combustion, the combustion products of the tertiary air, and the preheated flue gas discharged from the fluorine fixation device; Step 3, Fluorine Fixation: The hot material is output through the hot material outlet of the preheating device and enters the fluorine fixation device through the hot material inlet of the fluorine fixation device. The fluorine fixation device is a rotary reactor. Fuel I and primary air enter the fluorine fixation device through the fuel I inlet of the fluorine fixation device. The secondary air generated in the cooling device is discharged through the secondary air outlet of the cooling device, flows through the secondary air inlet of the fluorine fixation device, and enters the fluorine fixation device. The combustion products generated by the combustion of Fuel I, primary air, and secondary air in the fluorine fixation device heat and fix the hot material. The ratio of the premixed primary air to the total amount of air is 6 - 15%, and the ratio of the secondary air to the total amount of air is 85 - 94%; The basic reaction formula for fluorine fixation: CaCO3 + 2HF → CaF2↓ + CO2↑ + H2O↑, and the fluorine fixation rate ≥ 99.5%; Step 4, Cooling: The hot clinker is output through the hot clinker outlet, enters the cooling device through the hot clinker inlet, and cooling air is introduced through the cooling air inlet to cool the hot clinker in the cooling device, so that the temperature of the cold clinker is reduced to below 80°C. The cooling air is heated at the same time, that is, the dry air in the cooling device recovers the heat in the low-temperature section, and the secondary air and tertiary air in the cooling device recover the heat in the high-temperature section. The cooled cold clinker is discharged through the cold clinker outlet of the cooling device.

5. The method for extracting lithium using the fluorine fixation system for extracting lithium from lepidolite according to claim 4, characterized in that: The wet material is a mixture of raw materials and Additive I, Additive II, and Additive III; the raw material is lithium mica powder, Additive I is a sulfate containing sodium or potassium elements, Additive II is calcium carbonate, and Additive III is sodium hydroxide.

6. The method for extracting lithium using the fluorine fixation system for extracting lithium from lepidolite according to claim 5, characterized in that: The lepidolite powder described in Step 1 is pre-ground to a fineness of ≤ 0.1 mm in advance. The ratio of lepidolite powder to additive in the wet material is 1:0.5 - 1.5, and the drying time of the wet material is 5 - 60 s; the temperature of the drying air and drying flue gas is 300 - 400 °C; the temperature of the dirty flue gas and dry material is 110 - 150 °C; The temperature of the clean flue gas described in Step 1 is 110 - 150 °C, the particulate matter in the clean flue gas is ≤ 10 mg / m³, nitrogen oxides are ≤ 50 mg / m³, sulfur dioxide is ≤ 20 mg / m³, and hydrogen fluoride is ≤ 3 mg / m³.

7. The method for extracting lithium using the fluorine fixation system for extracting lithium from lepidolite according to claim 4, characterized in that: The temperature of the tertiary air described in Step 2 is 600 - 700 °C, the temperature of the preheated flue gas discharged from the fluorine fixation device is 800 - 870 °C, the temperature of the drying flue gas discharged from the preheating device is 300 - 400 °C, the temperature of the hot material is 800 - 870 °C, and the residence time of the dry material in the preheating device is 20 - 60 s.

8. The method for extracting lithium using the fluorine fixation system for extracting lithium from lepidolite according to claim 4, characterized in that: The primary air described in Step 3 is ambient air, the temperature of the secondary air is 800 - 850 °C, the temperature of the preheated flue gas discharged from the fluorine fixation device is 800 - 870 °C, the temperature of the hot clinker after rotary reaction is 900 - 950 °C, and the residence time of the hot material in the fluorine fixation device is 60 - 120 min.

9. The method for extracting lithium using the fluorine fixation system for extracting lithium from lepidolite according to claim 4, characterized in that: The temperature of the hot clinker described in Step 4 is 900 - 950 °C, the temperatures of the secondary air, tertiary air and drying air are 800 - 850 °C, 600 - 700 °C and 300 - 400 °C respectively, and the temperature of the cold clinker is ≤ 80 °C.

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