System and method for producing aluminum fluoride from aluminum oxide

Abstract

This invention discloses a system and method for preparing aluminum fluoride from alumina. First, fine alumina powder is chlorinated to aluminum chloride in a fluidized bed with internal components using silicon chloride. Then, aluminum chloride is fluorinated with silicon fluoride in a fluidized bed with added seed powder to obtain aluminum fluoride and silicon chloride. The silicon chloride is recycled for the chlorination reaction. This invention uses silicon chloride as the chlorinating agent in the alumina chlorination reaction, eliminating the need for carbon preparation and pelletizing, simplifying operation, and facilitating product separation and purification. Using a fluidized bed as the chlorination and fluorination reactor results in rapid gas-solid phase mass and heat transfer and high reaction efficiency. The internal components in the chlorination reactor significantly improve fluidization quality and increase gas-solid contact efficiency. Adding seed powder to the fluorination reactor provides nucleation sites and a matrix, facilitating product collection. The silicon chloride, a byproduct of the fluorination reaction, can be recycled for the chlorination reaction, resulting in a high system recycling rate, effectively reducing production costs, and demonstrating good economic and social benefits.

Description

Technical Field

[0001] This invention belongs to the field of non-ferrous metallurgy and environmental protection, and specifically relates to a system and method for preparing aluminum fluoride from alumina. Background Technology

[0002] Aluminum fluoride is a major auxiliary material in the electrolytic aluminum production process, primarily used as an electrolyte conditioner and flux. As a conditioner, it can improve the conductivity of the electrolyte by adjusting the molecular ratio; as a flux, it can lower the melting point of alumina, control the thermal balance of the electrolysis process, and reduce power consumption. In addition, aluminum fluoride can also be used as a catalyst in organic synthesis and as a refractive index modifier for lenses or prisms.

[0003] Chinese patent application CN1830794A discloses a method for producing aluminum fluoride. Kaolinite is pulverized to 100-200 mesh and placed in a pressure reactor with a 200-300 g / L sulfuric acid solution. The reaction is carried out at 130-150°C for 1-2 hours to obtain an aluminum sulfate solution. This solution is then reacted with hydrofluoric acid and crystallized at 130-160°C. The resulting product is then washed, dried, and dehydrated to obtain aluminum fluoride. While this method yields aluminum fluoride with good physical properties, it requires concentrated sulfuric acid under heating and pressure, resulting in significant equipment investment and demanding operating conditions, making large-scale continuous production difficult. Chinese patent application CN101077788A discloses another method for producing aluminum fluoride, which involves mixing ammonium fluoroaluminate and aluminum hydroxide in a certain proportion and reacting the mixture at 500-600°C to obtain aluminum fluoride, along with byproducts ammonia and water vapor. This method, while simple in principle, produces aluminum fluoride through a one-step solid-solid reaction. However, it generates ammonia gas, causing significant pollution, and also suffers from slow reaction rates, easy decomposition of ammonium fluoroaluminate, and difficulty in separating and purifying the products, making industrial-scale production difficult. Chinese patent application CN101077789A discloses a method for producing aluminum fluoride, which involves vaporizing ammonium fluoride or ammonium bifluoride at 200-300℃ and then reacting it with aluminum hydroxide in a certain proportion in a fluidized bed reactor at 500-600℃ to obtain aluminum fluoride as a product and ammonia and water vapor as byproducts. This method, while simple in principle, also suffers from ammonia pollution, difficulty in separating and purifying the products, and equipment corrosion, making large-scale production difficult. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention aims to provide a system and method for preparing aluminum fluoride from alumina, which is simple to operate, uses simple equipment, is highly efficient and convenient, and is easy to control, enabling large-scale continuous production.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A system for preparing aluminum fluoride from alumina includes an alumina silo, an alumina feeder, a chlorination fluidized bed, a primary cyclone separator I, a secondary cyclone separator I, a return valve I, a tailings silo, a heat exchanger I, a gas heater I, an induced draft fan I, a condenser I, a gasifier I, a fluorination fluidized bed, a primary cyclone separator II, a secondary cyclone separator II, a return valve II, a product silo, a heat exchanger II, a gas heater II, an induced draft fan II, a condenser II, and a gasifier II;

[0007] The alumina silo, alumina feeder, and chlorination fluidized bed are connected sequentially along the material flow direction; the air inlet, air outlet, and discharge outlet of the chlorination fluidized bed are respectively connected to the air outlet of the gas heater I, the air inlet of the primary cyclone separator I, and the discharge outlet of the tailings silo; the discharge outlet of the primary cyclone separator I is connected to the discharge outlet of the return valve I; the air inlet, air outlet, and discharge outlet of the secondary cyclone separator I are respectively connected to the air outlet of the primary cyclone separator I, the hot air inlet of the heat exchanger I, and the discharge outlet of the return valve I; the discharge outlet of the return valve I is connected to the chlorination fluidized bed. The upper return port of the fluidized bed is connected; the air inlet of the return valve I is connected to the air outlet of the gas heater I; the air inlet of the gas heater I is connected to the hot air outlet of the heat exchanger I; the cold air outlet of the heat exchanger I is connected to the air inlet of the induced draft fan I; the air outlet of the induced draft fan I is connected to the air inlet of the condenser I; the air outlets of the condenser I and the gasifier II are both connected to the cold air inlet of the heat exchanger I; the dust outlet of the condenser I is connected to the feed inlet of the gasifier I; and the air outlet of the gasifier I is connected to the feed inlet of the fluorinated fluidized bed.

[0008] The inlet, outlet, and discharge port of the fluorinated fluidized bed are respectively connected to the outlet of the gas heater II, the inlet of the primary cyclone separator II, and the inlet of the product silo; the discharge port of the primary cyclone separator II is connected to the inlet of the return valve II; the inlet, outlet, and discharge port of the secondary cyclone separator II are respectively connected to the outlet of the primary cyclone separator II, the hot gas inlet of the heat exchanger II, and the inlet of the return valve II; the discharge port of the return valve II is connected to the fluorinated fluidized bed. The upper return port of the fluidized bed is connected, the air inlet of the return valve II is connected to the air outlet of the gas heater II, the air inlet of the gas heater II is connected to the hot air outlet of the heat exchanger II, the cold air outlet of the heat exchanger II is connected to the air inlet of the induced draft fan II, the air outlet of the induced draft fan II is connected to the air inlet of the condenser II, the air outlet of the condenser II is connected to the cold air inlet of the heat exchanger II, and the liquid outlet of the condenser II is connected to the feed inlet of the gasifier II.

[0009] The room temperature silicon chloride pipeline is connected to the feed inlet of vaporizer II, and the room temperature silicon fluoride pipeline is connected to the cold air inlet of heat exchanger II.

[0010] Furthermore, the chlorination fluidized bed is provided with internal components, which are in the form of a porous plate structure, a paddle structure, or a perforated paddle structure.

[0011] Furthermore, the fluorinated fluidized bed contains seed powder, which is aluminum fluoride with a particle size of 0.1-0.5 mm.

[0012] The present invention also provides a method for operating the above-mentioned system for preparing aluminum fluoride from alumina, the specific process of which is as follows:

[0013] Fine alumina powder is stored in an alumina silo and then fed into a chlorination fluidized bed via an alumina feeder.

[0014] Room temperature silicon chloride enters vaporizer II from the room temperature silicon chloride pipeline, is vaporized into gaseous silicon chloride in vaporizer II, and then enters gas heater I through heat exchanger I to be heated into high temperature silicon chloride. The high temperature silicon chloride then enters the chlorination fluidized bed.

[0015] In the chlorination fluidized bed, fine alumina powder reacts with high-temperature silicon chloride to produce a mixed flue gas of aluminum chloride and silicon chloride, as well as chlorinated slag. The chlorinated slag enters the tailings silo. The mixed flue gas of aluminum chloride and silicon chloride, under the action of induced draft fan I, passes through a primary cyclone separator I and a secondary cyclone separator I for dust collection before entering heat exchanger I for cooling. The dust collected by the primary and secondary cyclone separators I is fluidized in the return valve I under the action of high-temperature silicon chloride and returned to the chlorination fluidized bed. After the dust removal, the mixed flue gas of aluminum chloride and silicon chloride is cooled by heat exchange and enters condenser I for condensation to obtain solid aluminum chloride and gaseous silicon chloride. The gaseous silicon chloride is sent to heat exchanger I and heated to hot silicon chloride by heat exchange with the mixed flue gas of aluminum chloride and silicon chloride after dust removal. Then it enters gas heater I for further heating to high-temperature silicon chloride. The solid aluminum chloride is gasified by gasifier I to obtain gaseous aluminum chloride and enters the fluorinated fluidized bed.

[0016] Room temperature silicon fluoride enters the gas heater II via heat exchanger II from the room temperature silicon fluoride pipeline and is heated to high temperature silicon fluoride. In the fluorinated fluidized bed, gaseous aluminum chloride reacts with the high temperature silicon fluoride to produce a mixed flue gas of silicon fluoride and silicon chloride, as well as aluminum fluoride. The aluminum fluoride enters the product silo. The mixed flue gas of silicon fluoride and silicon chloride, under the action of induced draft fan II, passes sequentially through primary cyclone separator II and secondary cyclone separator II for dust collection before entering heat exchanger II for cooling. The dust collected by primary and secondary cyclone separators II is fluidized in the return valve II under the action of high temperature silicon fluoride and returned to the fluorination process. In a fluidized bed, the mixed flue gas of silicon fluoride and silicon chloride after dust removal is cooled by heat exchange and then enters condenser II for condensation to obtain gaseous silicon fluoride and liquid silicon chloride. The liquid silicon chloride is sent to gasifier II for vaporization into gaseous silicon chloride. The gaseous silicon chloride enters heat exchanger I and is heated by heat exchange with the mixed flue gas of aluminum chloride and silicon chloride after dust removal to become hot silicon chloride. The hot silicon chloride enters gas heater I for further heating to become high-temperature silicon chloride. The gaseous silicon fluoride enters heat exchanger II and is heated by heat exchange with the mixed flue gas of silicon fluoride and silicon chloride after dust removal to become hot silicon fluoride. The hot silicon fluoride enters gas heater II for further heating to become high-temperature silicon fluoride.

[0017] Furthermore, the particle size of the alumina fine powder is less than 1 μm.

[0018] Furthermore, the chlorination reaction is carried out at a temperature of 700-900℃ for a time of 0.5-1h.

[0019] Furthermore, the fluorination reaction is carried out at a temperature of 500-700℃ for a time of 0.5-1h.

[0020] Furthermore, the condensing temperature in condenser I is 70-170℃, and the condensing temperature in condenser II is 20-50℃.

[0021] The beneficial effects of this invention are as follows:

[0022] 1. This invention uses silicon chloride as the chlorinating agent in the chlorination reaction of alumina, eliminating the need for carbon preparation and pelletizing, making the operation simple and the process straightforward, and the product is easy to separate and purify.

[0023] 2. This invention uses silicon fluoride as a fluorinating agent to react with gaseous aluminum chloride to prepare aluminum fluoride. The gas-gas reaction is highly efficient and rapid, and the silicon chloride byproduct of the fluorination reaction can be recycled for the chlorination reaction. The system has a high recycling rate and effectively reduces production costs.

[0024] 3. This invention uses a gas-solid fluidized bed as a chlorination and fluorination reactor, which has good gas-solid phase mixing and contact, fast mass and heat transfer rate, high reaction efficiency, and is convenient for continuous operation and large-scale processing.

[0025] 4. The present invention provides internal components in the chlorination reactor to break up bubbles and prevent fine particle agglomeration, which significantly improves fluidization quality and increases gas-solid contact efficiency; adding seed powder to the fluorination reactor can provide nucleation sites and matrix for the fluorination reaction, promote the fluorination reaction, and the product obtained from the reaction is easy to collect.

[0026] In summary, this invention provides a system and method for preparing aluminum fluoride from alumina that is easy to operate, uses simple equipment, is highly efficient and convenient, and is easy to control, enabling large-scale, continuous, and efficient production of aluminum fluoride. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the system structure in Embodiment 1 of the present invention. Detailed Implementation

[0028] The present invention will be further described below with reference to the accompanying drawings. It should be noted that this embodiment is based on the present technical solution and provides detailed implementation methods and specific operation processes, but the protection scope of the present invention is not limited to this embodiment.

[0029] Example 1

[0030] This embodiment provides a system for preparing aluminum fluoride from alumina, such as... Figure 1 As shown, the system includes an alumina silo 1, an alumina feeder 2, a chlorination fluidized bed 3, internal components 4, a primary cyclone separator I 5, a secondary cyclone separator I 6, a return valve I 7, a tailings silo 8, a heat exchanger I 9, a gas heater I 10, an induced draft fan I 11, a condenser I 12, a gasifier I 13, a fluorinated fluidized bed 14, a seed powder 15, a primary cyclone separator II 16, a secondary cyclone separator II 17, a return valve II 18, a product silo 19, a heat exchanger II 20, a gas heater II 21, an induced draft fan II 22, a condenser II 23, and a gasifier II 24.

[0031] The alumina silo 1, alumina feeder 2, and chlorination fluidized bed 3 are connected sequentially along the material flow direction. The air inlet, air outlet, and discharge outlet of the chlorination fluidized bed 3 are respectively connected to the air outlet of the gas heater I10, the air inlet of the primary cyclone separator I5, and the discharge outlet of the tailings silo 8. The discharge outlet of the primary cyclone separator I5 is connected to the discharge outlet of the return valve I7. The air inlet, air outlet, and discharge outlet of the secondary cyclone separator I6 are respectively connected to the air outlet of the primary cyclone separator I5, the hot air inlet of the heat exchanger I9, and the discharge outlet of the return valve I7. The discharge outlet of the return valve I7 is connected to the upper return outlet of the chlorination fluidized bed 3, the air inlet of the return valve I7 is connected to the air outlet of the gas heater I10, and the air inlet of the gas heater I10 is connected to the heat exchanger I9. The heat exchanger I 9 is connected to the hot air outlet, and the cold air outlet of the heat exchanger I 9 is connected to the air inlet of the induced draft fan I 11; the air outlet of the induced draft fan I 11 is connected to the air inlet of the condenser I 12, the air outlet of the condenser I 12 and the air outlet of the vaporizer II 24 are both connected to the cold air inlet of the heat exchanger I 9, the dust outlet of the condenser I 112 is connected to the feed inlet of the vaporizer I 113, and the air outlet of the vaporizer I 113 is connected to the feed inlet of the fluorinated fluidized bed 14.

[0032] The inlet, outlet, and discharge port of the fluorinated fluidized bed 14 are respectively connected to the outlet of the gas heater II 21, the inlet of the primary cyclone separator II 16, and the inlet of the product silo 19; the discharge port of the primary cyclone separator II 16 is connected to the inlet of the return valve II 18; the inlet, outlet, and discharge port of the secondary cyclone separator II 17 are respectively connected to the outlet of the primary cyclone separator II 16, the hot gas inlet of the heat exchanger II 20, and the inlet of the return valve II 18; the discharge port of the return valve II 18 is connected to the upper return port of the fluorinated fluidized bed 14, the inlet of the return valve II 18 is connected to the outlet of the gas heater II 21, the inlet of the gas heater II 21 is connected to the hot gas outlet of the heat exchanger II 20, and the heat exchanger II 17... The cold air outlet of heat exchanger II 20 is connected to the air inlet of the induced draft fan II 22, the air outlet of the induced draft fan II 22 is connected to the air inlet of the condenser II 23, the air outlet of the condenser II 23 is connected to the cold air inlet of the heat exchanger II 20, and the liquid outlet of the condenser II 23 is connected to the feed inlet of the vaporizer II 24.

[0033] The room temperature silicon chloride pipeline is connected to the feed inlet of vaporizer II 24, and the room temperature silicon fluoride pipeline is connected to the cold air inlet of heat exchanger II 20.

[0034] In this embodiment, the chlorination fluidized bed 3 is provided with an internal component 4, which is a porous plate structure, a paddle structure or a perforated paddle structure, used to break up agglomerates, eliminate bubbles and enhance gas-solid contact.

[0035] In this embodiment, the fluorinated fluidized bed 14 is provided with seed powder 15, which is aluminum fluoride with a particle size of 0.1-0.5 mm, and is used to provide nucleation sites and matrix for the fluorination reaction.

[0036] Example 2

[0037] This embodiment provides a working method for the system for preparing aluminum fluoride from alumina as described in Embodiment 1. The specific process is as follows:

[0038] Fine alumina powder is stored in alumina silo 1 and enters chlorination fluidized bed 3 via alumina feeder 2;

[0039] Room temperature silicon chloride enters vaporizer II 24 from the room temperature silicon chloride pipeline, is vaporized into gaseous silicon chloride in vaporizer II 24, and then enters gas heater I10 through heat exchanger I 9 to be heated into high temperature silicon chloride, and the high temperature silicon chloride enters the chlorination fluidized bed 3;

[0040] Within the chlorination fluidized bed 3, fine alumina powder undergoes a chlorination reaction with high-temperature silicon chloride with the assistance of internal components to produce a mixed flue gas of aluminum chloride and silicon chloride, as well as chlorinated slag. The chlorinated slag enters the tailings silo 8. The mixed flue gas of aluminum chloride and silicon chloride, under the action of the induced draft fan I11, passes through a primary cyclone separator I5 and a secondary cyclone separator I6 for dust collection before entering the heat exchanger I9 for heat exchange and cooling. The dust collected by the primary cyclone separator I5 and the secondary cyclone separator I6 is fluidized in the return valve I7 under the action of high-temperature silicon chloride and returned to the chlorination fluidized bed 3. After heat exchange and cooling, the mixed flue gas of aluminum chloride and silicon chloride enters the condenser I12 for condensation to obtain solid aluminum chloride and gaseous silicon chloride. The gaseous silicon chloride is sent to the heat exchanger I9. The mixed flue gas of aluminum chloride and silicon chloride after dust removal in 9 is heated to hot silicon chloride by heat exchange, and then enters the gas heater I10 for further heating to high temperature silicon chloride. Solid aluminum chloride is gasified by gasifier I13 to obtain gas phase aluminum chloride and enters the fluorinated fluidized bed 14.

[0041] Room temperature silicon fluoride enters the gas heater II 21 via heat exchanger II 20 and is heated to high temperature silicon fluoride. In the fluorinated fluidized bed 14, gaseous aluminum chloride reacts with the high temperature silicon fluoride under the action of seed powder to produce a mixed flue gas of silicon fluoride and silicon chloride, as well as aluminum fluoride. The aluminum fluoride enters the product silo 19. The mixed flue gas of silicon fluoride and silicon chloride, under the action of induced draft fan II 22, passes through a primary cyclone separator II 16 and a secondary cyclone separator II 17 for dust collection before entering heat exchanger II 20 for cooling. The dust collected by the primary cyclone separator II 16 and the secondary cyclone separator II 17 is fluidized in the return valve II 18 under the action of high temperature silicon fluoride and returned to the fluorinated fluidized bed 14. The mixed flue gas of silicon fluoride and silicon chloride, after dust removal and cooling, enters condenser II. 23. Condensation yields gaseous silicon fluoride and liquid silicon chloride. Liquid silicon chloride is fed into vaporizer II 24 and vaporized into gaseous silicon chloride. Gaseous silicon chloride enters heat exchanger I 9 and is heated to hot silicon chloride by heat exchange with the mixed flue gas of aluminum chloride and silicon chloride after dust removal. Hot silicon chloride enters gas heater I 10 for further heating to high-temperature silicon chloride. Gaseous silicon fluoride enters heat exchanger II 20 and is heated to hot silicon fluoride by heat exchange with the mixed flue gas of silicon fluoride and silicon chloride after dust removal. Hot silicon fluoride enters gas heater II 21 for further heating to high-temperature silicon fluoride.

[0042] In this embodiment, the particle size of the alumina fine powder is less than 1 μm.

[0043] In this embodiment, the chlorination reaction was carried out at a temperature of 700°C for 1 hour.

[0044] In this embodiment, the fluorination reaction was carried out at a temperature of 500°C for 1 hour.

[0045] In this embodiment, the condensation temperature in condenser I is 70°C, and the condensation temperature in condenser II is 20°C.

[0046] Example 3

[0047] This embodiment is basically the same as Embodiment 2, and the similarities will not be described again. The differences are as follows: In this embodiment, the chlorination reaction temperature is 900℃ and the time is 0.5h; the fluorination reaction temperature is 700℃ and the time is 0.5h; the condensation temperature in condenser I is 170℃ and the condensation temperature in condenser II is 50℃.

[0048] Example 4

[0049] This embodiment is basically the same as Embodiment 2, and the similarities will not be described again. The differences are as follows: In this embodiment, the chlorination reaction temperature is 800℃ and the time is 0.7h; the fluorination reaction temperature is 600℃ and the time is 0.7h; the condensation temperature in condenser I is 120℃ and the condensation temperature in condenser II is 30℃.

[0050] For those skilled in the art, various corresponding changes and modifications can be made based on the above technical solutions and concepts, and all such changes and modifications should be included within the protection scope of the claims of this invention.

Claims

1. A system for preparing aluminum fluoride from alumina, characterized in that, It includes an alumina silo, an alumina feeder, a chlorination fluidized bed, a primary cyclone separator I, a secondary cyclone separator I, a return valve I, a tailings silo, a heat exchanger I, a gas heater I, an induced draft fan I, a condenser I, a gasifier I, a fluorinated fluidized bed, a primary cyclone separator II, a secondary cyclone separator II, a return valve II, a product silo, a heat exchanger II, a gas heater II, an induced draft fan II, a condenser II, and a gasifier II; The alumina silo, alumina feeder, and chlorination fluidized bed are connected sequentially along the material flow direction; the air inlet, air outlet, and discharge outlet of the chlorination fluidized bed are respectively connected to the air outlet of the gas heater I, the air inlet of the primary cyclone separator I, and the discharge outlet of the tailings silo; the discharge outlet of the primary cyclone separator I is connected to the discharge outlet of the return valve I; the air inlet, air outlet, and discharge outlet of the secondary cyclone separator I are respectively connected to the air outlet of the primary cyclone separator I, the hot air inlet of the heat exchanger I, and the discharge outlet of the return valve I; the discharge outlet of the return valve I is connected to the chlorination fluidized bed. The upper return port of the fluidized bed is connected; the air inlet of the return valve I is connected to the air outlet of the gas heater I; the air inlet of the gas heater I is connected to the hot air outlet of the heat exchanger I; the cold air outlet of the heat exchanger I is connected to the air inlet of the induced draft fan I; the air outlet of the induced draft fan I is connected to the air inlet of the condenser I; the air outlets of the condenser I and the gasifier II are both connected to the cold air inlet of the heat exchanger I; the dust outlet of the condenser I is connected to the feed inlet of the gasifier I; and the air outlet of the gasifier I is connected to the feed inlet of the fluorinated fluidized bed. The inlet, outlet, and discharge port of the fluorinated fluidized bed are respectively connected to the outlet of the gas heater II, the inlet of the primary cyclone separator II, and the inlet of the product silo; the discharge port of the primary cyclone separator II is connected to the inlet of the return valve II; the inlet, outlet, and discharge port of the secondary cyclone separator II are respectively connected to the outlet of the primary cyclone separator II, the hot gas inlet of the heat exchanger II, and the inlet of the return valve II; the discharge port of the return valve II is connected to the fluorinated fluidized bed. The upper return port of the fluidized bed is connected, the air inlet of the return valve II is connected to the air outlet of the gas heater II, the air inlet of the gas heater II is connected to the hot air outlet of the heat exchanger II, the cold air outlet of the heat exchanger II is connected to the air inlet of the induced draft fan II, the air outlet of the induced draft fan II is connected to the air inlet of the condenser II, the air outlet of the condenser II is connected to the cold air inlet of the heat exchanger II, and the liquid outlet of the condenser II is connected to the feed inlet of the gasifier II. The room temperature silicon chloride pipeline is connected to the feed inlet of gasifier II, and the room temperature silicon fluoride pipeline is connected to the cold gas inlet of heat exchanger II; the chlorination fluidized bed is provided with internal components, which are porous plate structure, paddle structure or perforated paddle structure; the fluorination fluidized bed is provided with seed powder, which is aluminum fluoride with a particle size of 0.1-0.5 mm.

2. A method for operating the system for preparing aluminum fluoride from alumina as described in claim 1, characterized in that, The specific process is as follows: Fine alumina powder is stored in an alumina silo and then fed into a chlorination fluidized bed via an alumina feeder. Room temperature silicon chloride enters vaporizer II from the room temperature silicon chloride pipeline, is vaporized into gaseous silicon chloride in vaporizer II, and then enters gas heater I through heat exchanger I to be heated into high temperature silicon chloride. The high temperature silicon chloride then enters the chlorination fluidized bed. In the chlorination fluidized bed, fine alumina powder reacts with high-temperature silicon chloride to produce a mixed flue gas of aluminum chloride and silicon chloride, as well as chlorinated slag. The chlorinated slag enters the tailings silo. The mixed flue gas of aluminum chloride and silicon chloride, under the action of induced draft fan I, passes through a primary cyclone separator I and a secondary cyclone separator I for dust collection before entering heat exchanger I for cooling. The dust collected by the primary and secondary cyclone separators I is fluidized in the return valve I under the action of high-temperature silicon chloride and returned to the chlorination fluidized bed. After the dust removal, the mixed flue gas of aluminum chloride and silicon chloride is cooled by heat exchange and enters condenser I for condensation to obtain solid aluminum chloride and gaseous silicon chloride. The gaseous silicon chloride is sent to heat exchanger I and heated to hot silicon chloride by heat exchange with the mixed flue gas of aluminum chloride and silicon chloride after dust removal. Then it enters gas heater I for further heating to high-temperature silicon chloride. The solid aluminum chloride is gasified by gasifier I to obtain gaseous aluminum chloride and enters the fluorinated fluidized bed. Room temperature silicon fluoride enters the gas heater II via heat exchanger II from the room temperature silicon fluoride pipeline and is heated to high temperature silicon fluoride. In the fluorinated fluidized bed, gaseous aluminum chloride reacts with the high temperature silicon fluoride to produce a mixed flue gas of silicon fluoride and silicon chloride, as well as aluminum fluoride. The aluminum fluoride enters the product silo. The mixed flue gas of silicon fluoride and silicon chloride, under the action of induced draft fan II, passes sequentially through primary cyclone separator II and secondary cyclone separator II for dust collection before entering heat exchanger II for cooling. The dust collected by primary and secondary cyclone separators II is fluidized in the return valve II under the action of high temperature silicon fluoride and returned to the fluorination process. In a fluidized bed, the mixed flue gas of silicon fluoride and silicon chloride after dust removal is cooled by heat exchange and then enters condenser II for condensation to obtain gaseous silicon fluoride and liquid silicon chloride. The liquid silicon chloride is sent to gasifier II for vaporization into gaseous silicon chloride. The gaseous silicon chloride enters heat exchanger I and is heated by heat exchange with the mixed flue gas of aluminum chloride and silicon chloride after dust removal to become hot silicon chloride. The hot silicon chloride enters gas heater I for further heating to become high-temperature silicon chloride. The gaseous silicon fluoride enters heat exchanger II and is heated by heat exchange with the mixed flue gas of silicon fluoride and silicon chloride after dust removal to become hot silicon fluoride. The hot silicon fluoride enters gas heater II for further heating to become high-temperature silicon fluoride.

3. The working method according to claim 2, characterized in that, The particle size of the fine alumina powder is less than 1 μm.

4. The working method according to claim 2, characterized in that, The chlorination reaction is carried out at a temperature of 700-900℃ for 0.5-1h.

5. The working method according to claim 2, characterized in that, The fluorination reaction is carried out at a temperature of 500-700℃ for 0.5-1h.

6. The working method according to claim 2, characterized in that, The condensing temperature in condenser I is 70-170℃, and the condensing temperature in condenser II is 20-50℃.

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