A process for the production of metallurgical grade alumina from an aluminium-containing feed material by chlorination-bayer process

Abstract

The application relates to a method for producing metallurgical-grade aluminum oxide by chlorination-bayer process of aluminum-containing raw materials, and belongs to the technical field of metallurgical-grade aluminum oxide preparation. The method is characterized by ball making, chlorination, condensation separation, purification and refining and alkali dissolution roasting, and can prepare metallurgical-grade aluminum oxide. In the preparation process, chlorine gas and alkali liquor are recycled, no acid and alkali waste liquid is discharged, and the reaction efficiency is high; the whole process reduces the amount of flue gas, ensures the heat balance of the packing bed reaction device; the chlorination efficiency of the aluminum-containing raw materials reaches more than 90%; in the alkali dissolution process, the raw material is light active aluminum oxide, and a tubular stirring reactor is used, and the dissolution effect is improved by more than 30% compared with a traditional kettle type reactor, so that the application is an efficient aluminum-containing resource utilization method without red mud.

Description

Technical Field

[0001] This invention belongs to the field of metallurgical grade alumina preparation technology, and relates to a method for producing metallurgical grade alumina from aluminum-containing raw materials using the chlorination-Bayer process. Background Technology

[0002] Metallurgical grade alumina is a raw material used in the electrolytic production of metallic aluminum. Currently, in the alumina preparation industry, 90% of metallurgical grade alumina is produced through the Bayer process.

[0003] As the world's largest alumina producer, China's demand for bauxite is increasing. Furthermore, most of China's bauxite is difficult to mine, and is mostly low-grade, making smelting challenging. To maintain normal production at alumina plants, my country needs to import large quantities of high-grade bauxite annually.

[0004] When processing bauxite using the Bayer process, pre-desiliconization is required. Subsequently, during the leaching process, 3% to 7% of lime by weight of the ore is added to promote the dissolution of gibbsite monohydrate. The leaching conditions are more stringent than for other types of bauxite, with leaching temperatures of 240–260°C or higher (280–300°C) and sodium hydroxide alkali solution concentrations of 180–250 g / L.

[0005] Patent CN101054626A discloses a leaching method for monohydrate gibbsite-type bauxite. Before leaching, the bauxite is pretreated with alkaline solution, calcium ferrite, and lime, followed by solid-liquid separation. The separated solids are then leached using the conventional Bayer process. This technology consumes a large amount of lime, has high economic costs, and a complex process, making it difficult to promote.

[0006] Patent CN112158869A discloses a leaching method for monohydrate gibbsite-type bauxite. The method involves uniformly mixing monohydrate gibbsite-type bauxite with circulating mother liquor for pre-desiliconization. The resulting pre-desiliconized slurry is then uniformly mixed with dealkalized red mud and subjected to high-temperature leaching. The leached slurry undergoes dilution and desiliconization, followed by red mud sedimentation, separation, and washing to obtain red mud. The red mud is then dealkalized with lime to obtain dealkalized red mud, with some of the dealkalized red mud returned to the high-temperature leaching step. While this technology significantly reduces the amount of lime added and waste emissions, it still requires high-temperature leaching, resulting in high energy consumption and red mud emissions.

[0007] Red mud, a solid residue produced after alumina extraction from the Bayer process, is mainly disposed of through stockpiling. Faced with increasingly serious environmental pollution, patent CN103030160A discloses a method and apparatus for recovering alumina and sodium oxide from Bayer process red mud. This method utilizes a high molecular weight ratio, high alkali concentration sodium aluminate solution, enabling rapid alumina extraction under mild operating conditions. The alumina recovery rate from red mud reaches over 85%, effectively preventing or even eliminating equipment scaling and other problems. By achieving a highly efficient crystallization process for the intermediate product hydrated sodium aluminate, the circulation efficiency of the alkali-soluble medium can be significantly improved. The complete phase transformation during the alumina extraction reaction allows the sodium oxide recovery process to be carried out at low temperature and normal pressure. After a secondary sodium removal reaction, the final sodium oxide content in the red mud is no higher than 1%, far lower than the 6%–8% sodium oxide content of Bayer process red mud. This allows red mud to be used in large proportions for the preparation of cement, bricks and roadbed materials, concrete admixtures, environmental remediation materials, and other fillers, potentially solving problems related to the resource utilization of red mud and its potential environmental hazards. The application uses an excessively high concentration of alkali solution, placing high demands on the equipment. Furthermore, during the leaching process, most of the silica enters the solution, increasing its viscosity and surface tension, which is detrimental to subsequent liquid-solid separation. This also results in the consumption of a large amount of lime, high economic costs, and a complex process, hindering its widespread adoption.

[0008] Patent CN104649304A discloses a method and apparatus for alkaline extraction of aluminum and obtaining dealkali-treated red mud, comprising: (1) preparing raw materials according to a raw material formula, the raw materials including aluminum-containing raw materials, sodium oxide precursor and magnesium oxide precursor, and optionally calcium oxide precursor; (2) roasting the raw materials at 800-1300℃ to obtain sintered clinker; (3) obtaining red mud and leachate by leaching and solid-liquid separation of the sintered clinker; (4) obtaining aluminum hydroxide by desiliconization and carbonization of the leachate; (5) dealkali-treating the red mud to obtain dealkali-treated red mud containing magnesium silicate. This technology requires a large addition of lime and a roasting process, resulting in a large amount of slag discharge, high energy consumption, and cannot achieve comprehensive utilization of multiple metals such as silicon, iron, titanium, calcium, gallium, sodium, and scandium in the red mud.

[0009] Patent CN114150098A discloses a method for preparing pre-melted calcium aluminate and metallic iron from iron ore by reducing it with secondary aluminum ash, belonging to the field of solid waste resource utilization. This method involves mixing secondary aluminum ash, quicklime, and iron ore powder. The aluminum nitride and metallic aluminum in the secondary aluminum ash are used to reduce iron oxides in the iron ore at high temperatures. After slag-metal separation, pre-melted calcium aluminate and metallic iron are obtained. This invention fully utilizes the reducing properties of aluminum nitride and metallic aluminum in the secondary aluminum ash to reduce iron oxides in the iron ore to metallic iron, oxidize aluminum nitride to aluminum oxide and nitrogen, and oxidize metallic aluminum to aluminum oxide. This avoids the pollution caused by ammonia gas produced by the hydrolysis of aluminum nitride and the safety hazards posed by the spontaneous combustion of aluminum.

[0010] Patent CN113880567A discloses a method for preparing magnesium aluminum spinel from aluminum ash, comprising the following steps: (1) proportioning; (2) ball milling; (3) stirring; (4) dehydration; (5) pre-drying; (6) molding; (7) drying; and (8) calcination. This method utilizes aluminum ash and alumina to synthesize magnesium aluminum spinel, achieving comprehensive utilization of aluminum ash, reducing environmental pollution, and simultaneously obtaining high-quality, simple, and low-cost magnesium aluminum spinel.

[0011] Patent CN112744850A discloses a method for the comprehensive utilization of secondary aluminum ash resources. This method uses a pyrometallurgical process to recover alumina from the aluminum ash and convert it into sodium aluminate clinker. This clinker can be sold directly or returned to the sodium aluminate leaching process in alumina production to directly produce industrial-grade alumina. This invention features easy process control, stable industrial production, high product added value, and zero waste discharge, thus realizing the resource utilization of secondary aluminum ash.

[0012] Existing aluminum ash utilization technologies often result in the discharge of ammonia nitrogen wastewater, acid and alkali waste liquids, and waste residue. This is because aluminum ash reacts with water as follows:

[0013] AlN + 3H₂O = NH₃ + Al(OH)₃

[0014] 2AlN + 4H2O = Al(OH)3 + NH4OH

[0015] Al5O6N+4H2O=2Al2O3+Al(OH)3+NH4OH

[0016] NH3 + H2O = NH4OH

[0017] The aforementioned reactions are one of the main reasons why aluminum ash is classified as hazardous waste, and they are also the main reactions involved in the pretreatment process of aluminum ash utilization. Avoiding secondary pollution from ammonia nitrogen wastewater, acid and alkali waste liquids, and waste residue during the aluminum ash utilization process is the bottleneck to achieving its clean utilization.

[0018] Coal-based slag refers to coal gangue, coal gasification slag, fly ash, and other byproducts generated during coal production, processing, and use. From an environmental perspective, the large-scale stockpiling of coal-based slag not only wastes land but also causes serious pollution to soil, water, and air, ultimately endangering human health. However, from a resource recycling perspective, coal-based slag contains abundant aluminum and silicon resources, along with associated valuable elements such as titanium, gallium, germanium, scandium, calcium, iron, and magnesium, making it a veritable "urban mineral" resource. Coal-based slag is an important supplement to my country's bauxite resources, and its utilization has attracted widespread attention from relevant professionals.

[0019] Patent CN1927716A discloses a method and apparatus for preparing alumina. The method uses circulating fluidized bed fly ash as raw material, which is dissolved in sulfuric acid or hydrochloric acid to obtain aluminum sulfate or aluminum chloride solution. Silicon impurities are removed, and then metallurgical grade alumina is prepared by concentration and crystallization, calcination, and alkali dissolution to remove iron.

[0020] Existing methods mostly use acid or alkali to extract alumina from coal-based slag, which generates a large amount of acidic or alkaline slag and poses a secondary pollution problem. The alkaline method for extracting coal-based slag produces a large amount of slag and cannot achieve the comprehensive utilization of various associated metal elements such as silicon, iron, titanium, calcium, magnesium, gallium, and germanium in coal-based slag. The acid method is difficult to prepare metallurgical-grade alumina. Summary of the Invention

[0021] To address the above problems, this invention provides a method for producing metallurgical-grade alumina from aluminum-containing raw materials using the chlorination-Bayer process, comprising the following steps:

[0022] Step 1. Pelletizing: The aluminum-containing raw materials, carbonaceous raw materials, and binders are made into pellets;

[0023] Step 2. Chlorination: The pellets are continuously added to the chlorination reactor through the feed airlock for chlorination. During the chlorination process, chlorine gas and air are introduced into the reactor, and finally high-temperature flue gas and solid slag are obtained.

[0024] Step 3. Condensation and separation: The high-temperature flue gas obtained from chlorination is condensed and separated by a multi-stage spiral propeller condenser after heat exchange. The first stage of condensation and separation yields crude ferric chloride, the second stage yields crude aluminum chloride, and the third stage yields crude silicon tetrachloride. The tail gas obtained from condensation is compressed to obtain liquid chlorine, which is then returned to the chlorination process for recycling.

[0025] Step 4. Purification and Refining: The crude aluminum chloride obtained from condensation is mixed with chloride salts to obtain a mixed chloride. Then, metallic aluminum powder is added to obtain a reducing distillation mixture. The gaseous aluminum chloride in the mixture is mixed with oxygen in a Venturi reactor for gas-phase oxidation to obtain light activated alumina, chlorine, and other residues. The chlorine is returned to the chlorination process for recycling. The crude silicon tetrachloride is continuously discharged in liquid form through a screw-propelled condenser for distillation to obtain high-purity silicon tetrachloride, titanium tetrachloride, and germanium tetrachloride. The high-purity silicon tetrachloride is reduced by zinc to produce polycrystalline silicon and chlorine. The chlorine is returned to the chlorination process for recycling. The rare and dispersed metal chlorides are enriched for further separation and purification to obtain rare earth chlorides and lithium chloride.

[0026] Step 5. Alkali dissolution and calcination: Light activated alumina is mixed with alkali solution or circulating mother liquor in a tubular stirred reactor for low-temperature dissolution. The resulting dissolution solution is subjected to seed crystal decomposition to obtain aluminum hydroxide and mother liquor. The aluminum hydroxide is then subjected to multi-stage cyclone calcination in a multi-stage cyclone heat exchanger to obtain metallurgical grade alumina.

[0027] In step 1, the aluminum-containing raw material is one or more of the following: gibbsite, boehmite, diaspore, kaolin, illite, pyrophyllite, red mud, fly ash, aluminum ash, coal gangue, and coal gasification slag; the carbonaceous raw material is one or more of the following: coking coal, coke fines, calcined petroleum coke, and biomass carbon; the binder is one or more of the following: polyvinyl alcohol, lignosulfonic acid, modified starch, and bentonite; the mass ratio of carbonaceous raw material to aluminum-containing raw material is (0.1-3):1; the amount of binder accounts for 1-5% of the total mass of the material.

[0028] In step 2, the chlorination reaction temperature is 600–1200℃, and the reaction time is 30–120 min. The ratio of oxygen to chlorine is (0.01–0.4):1; the chlorination efficiency of aluminum, silicon, iron, calcium, magnesium, lithium, gallium, and rare earth elements in the aluminum-containing raw materials is greater than 90%; the solid slag contains lithium chloride and scandium chloride.

[0029] In step 2, the chlorination reactor is one of a multi-hearth chlorination furnace, a multi-stage countercurrent cyclone separator, a continuous packed bed, or a polymer-stirred fluidized bed. The multi-hearth chlorination furnace and the continuous packed bed are equipped with a feed airlock at the top and a discharge airlock at the bottom, allowing for continuous chlorination. The multi-stage countercurrent cyclone separator can be a 2-N stage, depending on the actual requirements of the carbothermic chlorination reduction process. In the multi-stage countercurrent cyclone separator, aluminum-containing raw materials and carbon (solid phase) react countercurrently with chlorine, oxygen, carbon monoxide, and other gaseous phases. The chlorination reaction takes place during the heat exchange process. Compared with conventional aluminum chloride, the system's heat utilization rate reaches over 70%, and the chlorine utilization efficiency reaches over 99%. The polymer-type stirred fluidized bed is equipped with a top stirring impeller and a side stirring impeller. The top stirring shaft uses centrifugal force to separate fine particles back into the bed, preventing small particles from escaping. The side stirring shaft has a hollow internal structure, ensuring that solid particles enter the fluidized bed from the bottom of the stirring impeller. Compared with conventional fluidized beds, the large bubble rate is reduced to below 60%, the heat transfer efficiency is increased to over 30%, and the dust carrying rate is reduced to below 2%.

[0030] In step 3, the multi-stage spiral propulsion condenser has a spiral propeller at its center, with the outer edge of the propeller in contact with the inner wall of the condenser. The central shaft is a hollow structure. After condensation, the flue gas is discharged through the interior of the central shaft, and the chloride is discharged through the airlock at the bottom of the condenser to prevent chloride from adhering to the wall surface during condensation and to ensure continuous discharge and sealing of chloride. The condensation recovery efficiency of chloride and flue gas is greater than 99%, and the water absorption rate is less than 0.1%.

[0031] The first-stage spiral propeller condenser has a controlled temperature of 250–300℃, the second-stage spiral propeller condenser has a controlled temperature of 150–180℃, and the third-stage spiral propeller condenser has a controlled temperature of 0–50℃.

[0032] In step 3, the crude aluminum chloride obtained by chlorination contains gallium chloride; and the crude silicon tetrachloride contains titanium chloride.

[0033] In step 4, the chloride salt is one or more of lithium chloride, sodium chloride, and potassium chloride; the amount of crude aluminum chloride added is 10% to 60% of the total mass of the mixed chlorides, and the amount of metallic aluminum powder added is 1% to 10% of the total mass of the mixed chlorides; the reduction distillation temperature is 160 to 230°C, and the reduction distillation yields anhydrous aluminum chloride with a mass fraction greater than 99.9%; the rare dispersed metal chlorides are gallium chloride, ferric chloride, etc., as raw materials for further gallium extraction; the mass fractions of silicon tetrachloride, titanium tetrachloride, and germanium tetrachloride are greater than 99.9%;

[0034] In step 4, the oxygen flow rate is 0.1–10 L / min, the oxidation temperature is 150–800 °C, and the oxidation time is 15–100 min; thus, active amorphous alumina is obtained with a purity greater than 99.9%, a pore size greater than 7 nm, and a specific surface area greater than 60 m². 2 / g;

[0035] The oxygen introduced in step 4 is oxygen-enriched air with an oxygen content of 25% to 100%. The purpose of introducing oxygen in step 4 is twofold: first, to reduce the amount of flue gas, and second, to ensure the thermal balance of the packed bed reactor.

[0036] In step 5, the mass concentration of the alkali solution or circulating mother liquor is 100-200 g / L, and the dissolution temperature is 60-150℃. Compared with the Bayer process, the concentration of the alkali solution is reduced by more than 50%, the dissolution temperature is reduced by more than 50%, and the dissolution effect is improved by more than 30% compared with the traditional batch reactor. Compared with the dissolution obtained by the traditional Bayer process, the obtained dissolution directly meets the requirements of seed content (or carbon content) without the need for solid-liquid separation and refining stages, and there is no red mud discharge.

[0037] In step 5, the leaching solution undergoes seed decomposition in a seed tank or a jet-stirred reactor. The carbon dioxide utilization rate of the jet-stirred reactor is 60% higher than that of existing carbon decomposition equipment, and the decomposition temperature is 50℃~70℃.

[0038] In step 5, the multi-stage cyclone heat exchanger is a 2-N multi-stage counter-current cyclone; aluminum hydroxide is calcined by multi-stage cyclone to obtain metallurgical grade alumina. In the multi-stage counter-current cyclone, the aluminum hydroxide solid phase and the high-temperature flue gas complete the calcination process in a counter-current manner during the heat exchange process of the cyclone. The required calcination temperature is 800-1100℃ and the calcination time is 1s-10s. Its heat utilization efficiency is more than 80% higher than that of the traditional fluidized bed reactor.

[0039] The metallurgical grade alumina meets the industry standard for metallurgical grade alumina (YS / T 803-2012).

[0040] Compared with existing aluminum-containing raw material utilization technologies, the advantages of this invention are as follows:

[0041] (1) Environmentally friendly and low energy consumption. Chlorine and alkaline solution are recycled, and there is no discharge of acid and alkaline waste liquid. The anhydrous aluminum chloride obtained by chlorination is prone to forming a gaseous bimolecular structure. The light active alumina obtained after direct calcination cannot be directly used in aluminum electrolysis cells. Therefore, based on chlorination-oxidation, the light active alumina obtained is leached with alkaline solution, seed crystal decomposition, and calcined to obtain metallurgical grade alumina. Compared with the leaching solution obtained by the traditional Bayer process, the leaching solution obtained does not require solid-liquid separation and refining stages to directly obtain the leaching solution that meets the requirements of seed content (or carbon content). At the same time, there is no red mud discharge, which completely eliminates the global problem of red mud discharge in the Bayer process.

[0042] (2) High reaction efficiency: Reduces flue gas volume and ensures thermal balance of the packed bed reactor; the chlorination efficiency of aluminum-containing raw materials reaches over 90%, which is superior to existing acid and alkali processes; the alkali dissolution process uses light active oxygen alumina as raw material and utilizes a tubular stirred reactor, which improves the dissolution effect by more than 30% compared to the traditional batch reactor; the leaching liquid is processed through a seed tank or jet stirred reactor to obtain aluminum hydroxide, and the carbon dioxide utilization rate of the jet stirred reactor is 60% higher than that of existing carbon separation equipment; aluminum hydroxide is calcined by multi-stage cyclone to obtain metallurgical grade alumina, and its heat utilization efficiency is more than 80% higher than that of the traditional fluidized bed reactor.

[0043] (3) The multi-hearth chlorination furnace and continuous packed bed described in this method utilize feed and discharge airlocks to achieve continuous chlorination reaction; in the multi-stage countercurrent cyclone separator, the solid and gas phases undergo chlorination reaction in a countercurrent manner during heat exchange, achieving a system heat utilization rate of over 70% compared to conventional aluminum chloride; chlorine utilization efficiency reaches over 99%; the polymer-type stirred fluidized bed is equipped with top and side stirring impellers, reducing the large bubble rate by over 60%, increasing heat transfer efficiency by over 30%, and reducing dust carryover rate by less than 2% compared to conventional fluidized beds. Anhydrous aluminum chloride is condensed and recovered using a spiral propulsion condenser to prevent adhesion to the wall surface during condensation, ensuring continuous discharge and encapsulation of aluminum chloride powder. The condensation recovery efficiency of anhydrous aluminum chloride and flue gas is greater than 99%, and the water absorption rate of anhydrous aluminum chloride is less than 0.1%. Attached Figure Description

[0044] Figure 1 This is a schematic diagram of the process for producing metallurgical-grade alumina from aluminum-containing raw materials using the chlorination-Bayer process in an embodiment of the present invention.

[0045] Figure 2 This is a schematic diagram of a spiral-driven condenser.

[0046] Among them, 1-stirring motor; 2-spiral propulsion stirring paddle; 3-flue gas inlet; 4-airlock; 5-tank body; 6-flue gas outlet. Detailed Implementation

[0047] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0048] The bauxite used in the embodiments of the present invention has the following main components: Al2O3 63.85%, SiO2 12.84%, TiO2 2.93%, Fe2O3 3.64%, Ga2O3-40ppm, Sc2O3-30ppm, Li2O-120ppm, and the remainder are trace elements.

[0049] The red mud used in the embodiments of the present invention has the following main components: Al2O3-23.85%, SiO2-19.84%, TiO2-2.93%, Fe2O3-6.64%, Ga2O3-30ppm, Sc2O3-80ppm, Li2O-60ppm, with the balance being impurities.

[0050] The aluminum ash used in the embodiments of the present invention has the following main components: Al-45.3%, MgO-10%, F-2.3%, Cl-15.3%, with the remainder being impurities.

[0051] The fly ash used in the embodiments of the present invention has the following main components: Al2O3-47.8%, SiO2-42.3%, MgO-1.21%, Fe2O3-3.51%, TiO2-2.3%, Ga2O3-80ppm, Sc2O3-30ppm, Li2O-400ppm, GeO2-32ppm, with the balance being impurities.

[0052] The main components of the coal gangue used in the embodiments of the present invention are shown in the table below: C-14.9%, O-48.3%, Al-11%, Si-19.3%, K-0.75%, Ca-1.07%, Fe-2.29%, with the balance being impurities;

[0053] The main components of the coal gasification slag used in the embodiments of the present invention are Al2O3-8.72%, SiO2-35.24%, MgO-1.54%, Fe2O3-5.73%, with the remainder being impurities;

[0054] The lightweight activated alumina described in this invention employs a tubular stirred reactor and a jet-type stirred reactor for the leaching solution, forming a gas-liquid-solid multiphase tubular stirred reactor.

[0055] The production process described in this invention is not limited to using this type of raw material; any raw material with aluminum as its main component can be produced using this technology.

[0056] The process flow for producing metallurgical-grade alumina from aluminum-containing raw materials using the chlorination-Bayer process in this embodiment of the invention is as follows: Figure 1 As shown, the spiral propulsion condenser is as follows: Figure 2 As shown.

[0057] Example 1

[0058] A method for producing metallurgical-grade alumina from aluminum-containing raw materials via the chlorination-Bayer process mainly includes the following steps:

[0059] (1) Bauxite, coking coal and modified starch are made into pellets in a certain proportion. The mass ratio of coking coal to bauxite is 0.1:1 and the amount of modified starch accounts for 1% of the total mass of the materials.

[0060] (2) The pellets were continuously fed into a multi-hearth chlorination furnace through a feed airlock and reacted at a chlorination temperature of 600℃ for 120 min with an oxygen to chlorine ratio of 0.05:1. Alumina, silicon oxide, iron oxide, titanium oxide, calcium oxide, magnesium oxide, scandium oxide, gallium oxide and vanadium oxide in bauxite reacted with chlorine to produce aluminum chloride, silicon chloride, iron chloride, titanium chloride, calcium chloride, magnesium chloride, scandium chloride, gallium chloride and vanadium chloride, respectively.

[0061] (3) The gaseous products obtained from chlorination are condensed and separated by a multi-stage spiral propeller condenser after heat exchange. The temperature of the first-stage spiral propeller condenser is controlled at 300℃ to obtain crude ferric chloride. The temperature of the second-stage spiral propeller condenser is controlled at 180℃ to obtain crude aluminum chloride and gallium chloride. The temperature of the third-stage spiral propeller condenser is controlled at 50℃ to obtain crude silicon tetrachloride and titanium chloride. The tail gas obtained from condensation is compressed to obtain liquid chlorine and returned to the chlorination process for recycling.

[0062] (4) The crude aluminum chloride obtained from condensation is mixed with lithium chloride to obtain a mixed chloride. Then, aluminum powder is added to obtain a reductive distillation mixture. The amount of crude aluminum chloride added is 20% of the total mass of the mixed chloride, and the amount of aluminum powder added is 2% of the total mass of the mixed chloride. The reductive distillation mixture is heated to 160°C, and the gaseous aluminum chloride obtained from the reductive distillation is mixed with oxygen in a Venturi reactor for gas-phase oxidation to prepare light active alumina and chlorine. The gaseous aluminum chloride is analyzed, and its mass percentage is 99.9%. The anhydrous aluminum chloride oxidation reaction temperature is 200°C, the gas-phase oxidation reaction time is 90 min, and the oxygen flow rate is 0.5 L / min. The chlorine is recycled back to the chlorination process. The resulting light active alumina has a purity of 99.9%, a pore size of 12.5 nm, and a specific surface area of ​​70.3 m². 2 / g.

[0063] (5) Low-temperature leaching was performed in a tubular stirred reactor using a mixture of 120 g / L sodium hydroxide solution and light activated alumina at 80 °C. Compared with the Bayer process, the concentration of the leaching alkali solution was reduced by more than 50%, the leaching temperature was reduced by 60%, and the leaching effect was improved by 30% compared with the traditional batch reactor. Sodium aluminate solution was used for seed decomposition in a seed tank or jet stirred reactor at 55 °C to obtain aluminum hydroxide and mother liquor. Aluminum hydroxide was calcined at 1000 °C for 1 second in a multi-stage cyclone heat exchanger to obtain metallurgical grade alumina.

[0064] After processing by this method, the chlorination efficiency of aluminum, silicon, iron, calcium, magnesium, lithium, gallium, vanadium, and rare earth elements in bauxite is greater than 90%. The chlorination solid phase products are separated to obtain vanadium chloride, rare earth chloride, calcium hydroxide, and magnesium hydroxide with a mass fraction of 99.9%. Alkali dissolution and roasting yield metallurgical grade alumina that meets the quality standards, titanium tetrachloride and germanium tetrachloride with a mass fraction of 99.9%, and gallium-rich raw materials.

[0065] Example 2

[0066] A method for producing metallurgical-grade alumina from aluminum-containing raw materials via the chlorination-Bayer process mainly includes the following steps:

[0067] (1) Fly ash, coking coal and bentonite are made into pellets in a certain proportion. The mass ratio of coking coal to fly ash is 2:1 and the amount of bentonite accounts for 1.5% of the total mass of the materials.

[0068] (2) The pellets were continuously added to the moving bed reactor through the feed airlock and reacted at a chlorination temperature of 1200℃ for 60 min with an oxygen to chlorine ratio of 0.1:1. Alumina, silicon oxide, iron oxide, titanium oxide, calcium oxide, magnesium oxide, scandium oxide, gallium oxide and vanadium oxide in bauxite reacted with chlorine to produce aluminum chloride, silicon chloride, iron chloride, titanium chloride, calcium chloride, magnesium chloride, scandium chloride, gallium chloride and vanadium chloride, respectively.

[0069] (3) The gaseous products obtained from chlorination are condensed and separated by a multi-stage spiral propeller condenser after heat exchange. The temperature of the first-stage spiral propeller condenser is controlled at 300℃ to obtain crude ferric chloride. The temperature of the second-stage spiral propeller condenser is controlled at 180℃ to obtain crude aluminum chloride and gallium oxide. The temperature of the third-stage spiral propeller condenser is controlled at below 50℃ to obtain crude silicon tetrachloride and titanium chloride. The tail gas obtained from condensation is mainly unreacted chlorine gas, etc., which is compressed to obtain liquid chlorine and returned to the chlorination process for recycling.

[0070] (4) The crude aluminum chloride obtained from condensation is mixed with sodium chloride to obtain a mixed chloride. Then, metallic aluminum powder is added to obtain a reductive distillation mixture. The amount of crude aluminum chloride added is 30% of the total mass of the mixed chloride, and the amount of metallic aluminum powder added is 5% of the total mass of the mixed chloride. The reductive distillation mixture is heated to 170℃, and the gaseous aluminum chloride obtained from the reductive distillation is mixed with oxygen in a Venturi reactor for gas-phase oxidation to prepare light active alumina and chlorine. The gaseous aluminum chloride is analyzed, and its mass percentage is 99.9%. The reaction temperature for anhydrous aluminum chloride oxidation is 800℃, the gas-phase oxidation reaction time is 20 min, and the oxygen flow rate is 1 L / min. The chlorine is recycled back to the chlorination process. The resulting light active alumina has a purity of 99.9%, a pore size of 11.5 nm, and a specific surface area of ​​68.4 m². 2 / g.

[0071] (5) Low-temperature leaching was performed in a tubular stirred reactor using a mixture of 200 g / L sodium hydroxide solution and light activated alumina at 140 °C. Compared with the Bayer process, the concentration of the leaching alkali solution was reduced by 55%, the leaching temperature was reduced by 60%, and the leaching effect was improved by 40% compared with the traditional batch reactor. The molecular ratio of sodium oxide to alumina before leaching was 3.3, and the molecular ratio of sodium oxide to alumina after leaching was 1.3. Sodium aluminate solution was seeded in a seed tank or jet stirred reactor at 55 °C. Alumina was calcined at 1000 °C for 5 s in a multi-stage cyclone heat exchanger to obtain metallurgical grade alumina.

[0072] After treatment by this method, the chlorination efficiency of aluminum, silicon, iron, calcium, magnesium, lithium, gallium, vanadium, and rare earth elements in fly ash is greater than 92%. The chlorination solid phase products are separated to obtain vanadium chloride, rare earth chloride, calcium hydroxide, and magnesium hydroxide with a mass fraction of 99.9%. Alkali dissolution and roasting yield metallurgical grade alumina that meets the quality standards. Alkali dissolution of silicon oxide yields water glass with a modulus of 2.9, titanium tetrachloride and germanium tetrachloride with a mass fraction of 99.9%, and gallium-rich raw materials.

[0073] Example 3

[0074] A method for producing metallurgical-grade alumina from aluminum-containing raw materials via the chlorination-Bayer process mainly includes the following steps:

[0075] In this embodiment, the selected raw material is aluminum ash;

[0076] (1) Aluminum ash, coking coal, and lignosulfonate are pelletized in a certain proportion, with the mass ratio of coking coal to aluminum ash being 3:1; the amount of lignosulfonate used accounts for 1.5% of the total mass of the materials.

[0077] (2) The pellets were continuously added to the moving bed reactor through the feed airlock and reacted at a chlorination temperature of 1000℃ for 60 min with an oxygen to chlorine ratio of 0.15:1. The aluminum oxide, silicon oxide, iron oxide, calcium oxide and other components in the aluminum ash reacted with chlorine to produce aluminum chloride, silicon chloride, iron chloride and calcium chloride, respectively.

[0078] (3) The gaseous products obtained from chlorination are condensed and separated by a multi-stage spiral propeller condenser after heat exchange. The temperature of the first-stage spiral propeller condenser is controlled at 250℃ to obtain crude ferric chloride. The temperature of the second-stage spiral propeller condenser is controlled at 150℃ to obtain crude aluminum chloride and gallium oxide. The temperature of the third-stage spiral propeller condenser is controlled at 40℃ to obtain crude silicon tetrachloride. The tail gas obtained from condensation is mainly unreacted chlorine gas, which is compressed to obtain liquid chlorine and returned to the chlorination process for recycling.

[0079] (4) The crude aluminum chloride obtained from condensation is mixed with potassium chloride to obtain a mixed chloride. Then, metallic aluminum powder is added to obtain a reductive distillation mixture. The amount of crude aluminum chloride added is 40% of the total mass of the mixed chloride, and the amount of metallic aluminum powder added is 8% of the total mass of the mixed chloride. The reductive distillation mixture is heated to 190℃, and the gaseous aluminum chloride obtained from the reductive distillation is mixed with oxygen in a Venturi reactor for gas-phase oxidation to prepare light active alumina and chlorine. The gaseous aluminum chloride is analyzed, and its mass percentage is 99.9%. The reaction temperature for anhydrous aluminum chloride oxidation is 600℃, the gas-phase oxidation reaction time is 40 min, and the oxygen flow rate is 10 L / min. The chlorine is recycled back to the chlorination process. The resulting light active alumina has a purity of 99.9%, a pore size of 10.6 nm, and a specific surface area of ​​70.5 m². 2 / g.

[0080] (5) Low-temperature leaching was performed in a tubular stirred reactor using a mixture of 140 g / L sodium hydroxide solution and light activated alumina at 150 °C. Compared with the Bayer process, the concentration of the leaching alkali solution was reduced by 60%, the leaching temperature was reduced by 70%, and the leaching effect was improved by 30% compared with the traditional batch reactor. Sodium aluminate solution was used for seed decomposition in a seed tank or jet stirred reactor at 60 °C to obtain aluminum hydroxide and mother liquor. Aluminum hydroxide was calcined at 900 °C for 8 s in a multi-stage cyclone heat exchanger to obtain metallurgical grade alumina.

[0081] After treatment by this method, the chlorination efficiency of aluminum, silicon, calcium and magnesium in aluminum ash is greater than 93%; the chlorinated solid phase products are separated to obtain calcium hydroxide and magnesium hydroxide with a mass fraction greater than 99.9%; metallurgical grade alumina that meets the quality standard requirements is obtained; water glass with a modulus of 3.0 is obtained by alkaline dissolution of silicon oxide; titanium tetrachloride and germanium tetrachloride with a mass fraction greater than 99.9% are obtained; and gallium-rich raw materials are obtained.

[0082] Example 4

[0083] A method for producing metallurgical-grade alumina from aluminum-containing raw materials via the chlorination-Bayer process mainly includes the following steps:

[0084] In this embodiment, the raw material used is coal gangue;

[0085] (1) Coal gangue, calcined petroleum coke and polyvinyl alcohol are made into pellets in a certain proportion. The mass ratio of calcined petroleum coke to coal gangue is 2.5:1, and the amount of polyvinyl alcohol accounts for 5% of the total mass of the materials.

[0086] (2) Pellet pellets are continuously added to a moving bed reactor through a feed airlock. Alumina and silica in the coal gangue react with chlorine to produce aluminum chloride and silicon chloride. The chlorination reaction temperature is 1000℃, the reaction time is 120 min, and the ratio of oxygen to chlorine is 0.1:1.

[0087] (3) The gaseous products obtained from chlorination are condensed and separated by a multi-stage spiral propeller condenser after heat exchange. The temperature of the first-stage spiral propeller condenser is controlled at 280℃ to obtain crude ferric chloride. The temperature of the second-stage spiral propeller condenser is controlled at 160℃ to obtain crude aluminum chloride and gallium chloride. The temperature of the third-stage spiral propeller condenser is controlled at 10℃ to obtain crude silicon tetrachloride and titanium chloride. The tail gas obtained from condensation is mainly unreacted chlorine gas, which is compressed to obtain liquid chlorine and returned to the chlorination process for recycling.

[0088] (4) The crude aluminum chloride obtained from condensation is mixed with lithium chloride and sodium chloride to obtain a mixed chloride. Then, metallic aluminum powder is added to obtain a reductive distillation mixture. The mass ratio of crude aluminum chloride:lithium chloride:sodium chloride is 2:4:4, and the amount of metallic aluminum powder added is 8% of the total mass of the mixed chloride. The reductive distillation mixture is heated to 200℃, and the gaseous aluminum chloride obtained from the reductive distillation is mixed with oxygen in a Venturi reactor for gas-phase oxidation to prepare light active alumina and chlorine. The gaseous aluminum chloride is analyzed, and its mass percentage is 99.9%. The reaction temperature for anhydrous aluminum chloride oxidation is 500℃, and the gas-phase oxidation reaction time is 20 min. The oxygen flow rate is 0.5 L / min. The purity of the obtained light active alumina is 99.9%, the pore size is 12.6 nm, and the specific surface area is 70.6 m². 2 / g.

[0089] (5) Light activated alumina was leached at low temperature in a tubular stirred reactor. The sodium hydroxide solution used had a mass concentration of 180 g / L and a temperature of 180 °C. Compared with the Bayer process, the concentration of the leaching alkali solution was reduced by 55%, the leaching temperature was reduced by 50%, and the leaching effect was improved by 45% compared with the traditional batch reactor. Before leaching, the molecular ratio of sodium oxide to alumina was 3.3, and after leaching, the molecular ratio of sodium oxide to alumina was 1.4. Sodium aluminate solution was seeded in a seed tank or jet stirred reactor at a decomposition temperature of 60 °C to obtain aluminum hydroxide and mother liquor. Aluminum hydroxide was calcined at 850 °C for 10 s in a multi-stage cyclone heat exchanger to obtain metallurgical grade alumina.

[0090] After treatment by this method, the chlorination efficiency of aluminum, silicon, iron, calcium, magnesium, lithium, gallium, vanadium, and rare earth elements in coal gangue is greater than 93%; the chlorination solid phase products are separated to obtain vanadium chloride, rare earth chloride, calcium hydroxide, and magnesium hydroxide with a mass fraction greater than 99.9%; alkali dissolution and roasting yield metallurgical grade alumina that meets the quality standards, titanium tetrachloride and germanium tetrachloride with a mass fraction of 99.9%, and gallium-rich raw materials.

[0091] Example 5

[0092] A method for producing metallurgical-grade alumina from aluminum-containing raw materials via the chlorination-Bayer process includes the following steps:

[0093] In this embodiment, the raw material used is coal gasification slag;

[0094] (1) The coal gasification slag, coking coal, biomass carbon and kaolin are pressed into pellets in a certain proportion; wherein, by mass ratio, biomass carbon: coal gasification slag = 3:1, and the amount of polyvinyl alcohol accounts for 2.5% of the total mass of the materials.

[0095] (2) Pellets are continuously added to a moving bed reactor through a feed airlock, and chlorine gas is introduced to carry out gas-solid pellet chlorination. The reaction temperature is 800℃ and the reaction time is 120 min. The ratio of oxygen to chlorine is 0.1:1. Alumina, silicon oxide, iron oxide, titanium oxide, calcium oxide, magnesium oxide, scandium oxide, gallium oxide, vanadium oxide, etc. in bauxite react with chlorine gas to generate aluminum chloride, silicon chloride, iron chloride, titanium chloride, calcium chloride, magnesium chloride, scandium chloride, gallium chloride, vanadium chloride, etc.

[0096] (3) The gaseous products obtained from chlorination are condensed and separated by a multi-stage spiral propeller condenser after heat exchange. The temperature of the first-stage spiral propeller condenser is controlled at 260℃ to obtain crude ferric chloride. The temperature of the second-stage spiral propeller condenser is controlled at 150℃ to obtain crude aluminum chloride and gallium chloride. The temperature of the third-stage spiral propeller condenser is controlled at 20℃ to obtain crude silicon tetrachloride and titanium chloride. The tail gas obtained from condensation is compressed to obtain liquid chlorine and returned to the chlorination process for recycling.

[0097] (4) The crude aluminum chloride obtained from condensation is mixed with lithium chloride to obtain a mixed chloride. Then, aluminum powder is added to obtain a reductive distillation mixture. The amount of aluminum chloride added is 45% of the total mass of the mixed chloride, and the amount of aluminum powder added is 7% of the total mass of the mixed chloride. The reductive distillation mixture is heated to 220℃, and the gaseous aluminum chloride obtained from the reductive distillation is mixed with oxygen in a Venturi reactor for gas-phase oxidation to prepare light active alumina and chlorine. The gaseous aluminum chloride is analyzed, and its mass percentage is 99.9%. The anhydrous aluminum chloride oxidation reaction temperature is 700℃, the gas-phase oxidation reaction time is 30 min, and the oxygen flow rate is 0.5 L / min. The chlorine is recycled back to the chlorination process. The resulting light active alumina has a purity of 99.9%, a pore size of 12.5 nm, and a specific surface area of ​​70.8 m². 2 / g.

[0098] (5) Light activated alumina was leached at low temperature in a tubular stirred reactor using a sodium hydroxide solution with a mass concentration of 140 g / L at a temperature of 180 °C. Compared with the Bayer process, the concentration of the leaching alkali solution was reduced by 60%, the leaching temperature was reduced by 50%, and the leaching effect was improved by 30% compared with the traditional batch reactor. Sodium aluminate solution was decomposed into seeds in a seed tank or jet stirred reactor at a decomposition temperature of 60 °C to obtain aluminum hydroxide and mother liquor. The aluminum hydroxide was calcined at 950 °C for 10 s in a multi-stage cyclone heat exchanger to obtain metallurgical grade alumina.

[0099] After processing by this method, the chlorination efficiency of aluminum, silicon, iron, calcium, magnesium, lithium, gallium, vanadium, and rare earth elements in bauxite is greater than 93%. The chlorination solid phase products are separated to obtain vanadium chloride, rare earth chloride, calcium hydroxide, and magnesium hydroxide with a mass fraction of 99.9%. Alkali dissolution and roasting yield metallurgical grade alumina that meets the quality standards. Alkali dissolution of silicon oxide yields water glass with a modulus of 2.8, titanium tetrachloride and germanium tetrachloride with a mass fraction of 99.9%, and gallium-rich raw materials.

[0100] Example 6

[0101] A method for producing metallurgical-grade alumina from aluminum-containing raw materials via the chlorination-Bayer process mainly includes the following steps:

[0102] In this embodiment, the selected raw material is red mud.

[0103] (1) Red mud, coking coal and bentonite are made into pellets in a certain proportion; during the preparation of pellets, the mass ratio of coking coal to red mud is 0.5:1, and the amount of bentonite accounts for 4% of the total mass of the materials.

[0104] (2) Pellet pellets are continuously added to a moving bed reactor through a feed airlock. Alumina, silicon oxide, iron oxide, titanium oxide, calcium oxide, magnesium oxide, scandium oxide, gallium oxide, vanadium oxide, etc. in the red mud react with chlorine to produce aluminum chloride, silicon chloride, iron chloride, titanium chloride, calcium chloride, magnesium chloride, scandium chloride, gallium chloride, vanadium chloride, etc. The chlorination reaction temperature is 1100℃, the reaction time is 50min, and the ratio of oxygen to chlorine is 0.1:1.

[0105] (3) The gaseous products obtained from chlorination are condensed and separated by a multi-stage spiral propeller condenser after heat exchange. The temperature of the first-stage spiral propeller condenser is controlled at 250℃ to obtain crude ferric chloride. The temperature of the second-stage spiral propeller condenser is controlled at 160℃ to obtain crude aluminum chloride and gallium oxide. The temperature of the third-stage spiral propeller condenser is controlled at 30℃ to obtain crude silicon tetrachloride and titanium chloride. The tail gas obtained from condensation is mainly unreacted chlorine gas, which is compressed to obtain liquid chlorine and returned to the chlorination cycle for reuse.

[0106] (4) The crude aluminum chloride obtained from condensation is mixed with potassium chloride to obtain a mixed chloride. Then, aluminum powder is added to obtain a reductive distillation mixture. The amount of crude aluminum chloride added is 25% of the total mass of the mixed chloride, and the amount of aluminum powder added is 9% of the total mass of the mixed chloride. The reductive distillation mixture is heated to 200℃, and the gaseous aluminum chloride obtained from the reductive distillation is mixed with oxygen in a Venturi reactor for gas-phase oxidation to prepare light active alumina and chlorine. The gaseous aluminum chloride is analyzed, and its mass percentage is 99.9%. The anhydrous aluminum chloride oxidation reaction temperature is 150℃, and the gas-phase oxidation reaction time is 100 min. The chlorine is recycled back to the chlorination process. The oxygen flow rate in the silicon tetrachloride calcination process is 2 L / min, the oxygen-enriched calcination temperature is 700℃, and the oxidation reaction time is 60 min. The resulting light active alumina has a purity of 99.9%, a pore size of 13.6 nm, and a specific surface area of ​​66.5 m². 2 / g.

[0107] (5) Light activated alumina is leached using a sodium hydroxide solution with a mass concentration of 160 g / L at a temperature of 180 °C. Compared with the Bayer process, the concentration of the leaching alkali solution is reduced by more than 50%, the leaching temperature is reduced by more than 50%, and the leaching effect is improved by more than 30% compared with the traditional batch reactor. Sodium aluminate solution is used for seed decomposition in a seed tank or jet-stirred reactor at a decomposition temperature of 60 °C to obtain aluminum hydroxide and mother liquor. The aluminum hydroxide is then calcined at 900 °C for 6 s in a multi-stage cyclone heat exchanger to obtain metallurgical grade alumina.

[0108] After treatment by this method, the chlorination efficiency of aluminum, silicon, iron, calcium, magnesium, lithium, gallium, vanadium, and rare earth elements in red mud is greater than 93%. The chlorination solid phase products are separated to obtain vanadium chloride, rare earth chloride, calcium hydroxide, and magnesium hydroxide with a mass fraction of 99.9%. Alkali dissolution and roasting yield metallurgical grade alumina that meets the quality standards. Alkali dissolution of silicon oxide yields water glass with a modulus of 2.8, titanium tetrachloride and germanium tetrachloride with a mass fraction greater than 99.9%, and gallium-rich raw materials.

[0109] Comparative Example 1

[0110] A method for producing alumina from low-grade bauxite includes the following steps:

[0111] When low-grade bauxite is leached by adding 120 g / L sodium hydroxide solution at 280℃, the alumina leaching rate in the bauxite is only 60.32%, the amount of red mud residue is 1.5 times that of the low-grade bauxite raw material, and the alkali content of the red mud reaches 3.52%.

[0112] Metallurgical-grade alumina was obtained by seed decomposition.

[0113] Although this method enables the utilization of low-grade bauxite, the process results in a large discharge of alkaline red mud, a significant alumina loss (up to 40%), and the generation of a large amount of alkaline red mud, making it impossible to achieve economical utilization of low-grade bauxite.

[0114] Comparative Example 2

[0115] Bauxite, calcined petroleum coke, and kaolin are pelletized in a certain proportion, wherein the mass ratio of calcined petroleum coke to bauxite is 1:1, and the amount of kaolin used accounts for 1.5% of the total mass of materials (bauxite, calcined petroleum coke, and kaolin).

[0116] Pellets were continuously added to a moving bed reactor through a feed airlock and reacted at a chlorination temperature of 900℃ for 120 minutes. Alumina, silicon oxide, iron oxide, titanium oxide, calcium oxide, scandium oxide, and other oxides in bauxite reacted with chlorine to produce aluminum chloride, silicon chloride, iron chloride, titanium chloride, calcium chloride, scandium chloride, and gallium chloride, respectively.

[0117] Scandium chloride and calcium chloride are enriched and recovered in the slag. The gaseous products obtained from chlorination are condensed and separated by a multi-stage spiral propeller condenser after heat exchange. The first-stage spiral propeller condenser is controlled at 300℃ to obtain crude ferric chloride. The second-stage spiral propeller condenser is controlled at 180℃ to obtain crude aluminum chloride and gallium oxide. The third-stage spiral propeller condenser is controlled at a temperature below 50℃ to obtain crude silicon tetrachloride and titanium chloride. The tail gas obtained from condensation is mainly unreacted chlorine gas, which is compressed to obtain liquid chlorine and returned to the chlorination process for recycling.

[0118] The obtained AlCl3 was prepared into an aluminum chloride solution with a concentration of 160 g / L. The electrolysis temperature was 30℃, the initial cell voltage was 5V, and the electrolysis time was 120 min. The particle size of the electroconversion products was less than 55 μm (D(50)) and the specific surface area was less than 8.14 m². 2 / g,

[0119] The resulting electroconversion products, after being calcined at 800℃ for 2 hours, showed an alumina particle size D(50) of less than 40 μm and an AlCl3 conversion rate of less than 10%.

[0120] The resulting alumina does not meet the quality requirements of the metallurgical grade alumina standard, and the chlorine gas generated by electrolysis cannot be recycled.

Claims

1. A method for producing metallurgical-grade alumina from aluminum-containing raw materials using the chlorination-Bayer process, characterized in that, Includes the following steps: Step 1. Pelletizing: The aluminum-containing raw materials, carbonaceous raw materials, and binder are made into pellets; the mass ratio of carbonaceous raw materials to aluminum-containing raw materials is (2~3):

1. Step 2. Chlorination: The pellets are continuously added to the chlorination reactor through the feed airlock for chlorination. During the chlorination process, chlorine gas and air are introduced into the reactor, and finally high-temperature flue gas and solid slag are obtained. The chlorination reaction temperature is 800~1200℃ and the reaction time is 30min~120min. Step 3. Condensation and separation: After heat exchange, the high-temperature flue gas obtained from chlorination is condensed and separated using a multi-stage spiral propeller condenser. The first stage of condensation and separation yields crude ferric chloride, the second stage yields crude aluminum chloride, and the third stage yields crude silicon tetrachloride. The tail gas obtained from condensation is compressed to obtain liquid chlorine, which is then returned to the chlorination process for recycling. Step 4. Purification and Refining: The crude aluminum chloride obtained from condensation is mixed with chloride salts to obtain a mixed chloride. Then, metallic aluminum powder is added to obtain a reducing distillation mixture. The gaseous aluminum chloride in the mixture is mixed with oxygen in a Venturi reactor for gas-phase oxidation to obtain light activated alumina, chlorine, and other residues. The chlorine is returned to the chlorination process for recycling. The crude silicon tetrachloride is continuously discharged in liquid form through a screw-propelled condenser for distillation to obtain high-purity silicon tetrachloride, titanium tetrachloride, and germanium tetrachloride. The high-purity silicon tetrachloride is reduced by zinc to produce polycrystalline silicon and chlorine. The chlorine is returned to the chlorination process for recycling. The rare and dispersed metal chlorides are enriched for further separation and purification to obtain rare earth chlorides and lithium chloride. Step 5. Alkali dissolution and calcination: Light activated alumina is mixed with alkali solution or circulating mother liquor in a tubular stirred reactor for low-temperature dissolution. The resulting dissolution solution is subjected to seed crystal decomposition to obtain aluminum hydroxide and mother liquor. The aluminum hydroxide is then subjected to multi-stage cyclone calcination in a multi-stage cyclone heat exchanger to obtain metallurgical grade alumina. In step 1, the aluminum-containing raw material is one or more of the following: gibbsite, boehmite, diaspore, kaolin, illite, pyrophyllite, red mud, fly ash, aluminum ash, coal gangue, and coal gasification slag; the carbonaceous raw material is one or more of the following: coking coal, coke fines, calcined petroleum coke, and biomass carbon; the binder is one or more of the following: polyvinyl alcohol, modified starch, and bentonite; the amount of binder used accounts for 1-5% of the total material mass. In step 2, the reactor is one of the following: a multi-hearth chlorination furnace, a multi-stage countercurrent cyclone separator, a continuous packed bed, or a polymer-type stirred fluidized bed. The ratio of oxygen to chlorine is (0.01~0.4):1; the chlorination efficiency of aluminum, silicon, iron, calcium, magnesium, lithium, gallium and rare earth elements in the aluminum-containing raw materials in the pellet chlorination reaction is greater than 90%; the solid slag contains lithium chloride and scandium chloride; In step 2, the multi-hearth chlorination furnace and the continuous packed bed are equipped with a feed airlock at the top and a discharge airlock at the bottom, so that the chlorination reaction can be carried out continuously by using the feed airlock and the discharge airlock. The multi-stage countercurrent cyclone separator can be a 2-N multi-stage countercurrent cyclone separator according to the actual needs of the carbothermic chlorination reduction process. In the multi-stage countercurrent cyclone separator, the solid phase and the gas phases of chlorine, oxygen and carbon monoxide undergo chlorination reaction in a countercurrent manner during the heat exchange process. The system heat utilization rate reaches more than 70%, and the chlorine utilization efficiency reaches more than 99%. The polymer-type stirred fluidized bed is equipped with a top stirring impeller and a side stirring impeller. The top stirring shaft uses centrifugal force to separate fine particles back into the bed to prevent small particles from escaping. The side stirring shaft has a hollow internal structure to ensure that solid particles enter the fluidized bed from the bottom of the stirring impeller. Compared with conventional fluidized beds, the large bubble rate is reduced to below 60%, the heat transfer efficiency is increased to above 30%, and the dust carrying rate is reduced to below 2%. The lightweight activated alumina has a purity greater than 99.9%, a pore size greater than 7 nm, and a specific surface area greater than 60 m². 2 / g; The chlorine gas obtained from roasting is returned to the carbothermic chlorination step 2 for recycling; In step 4, the amount of crude aluminum chloride added is 10% to 60% of the total mass of the mixed chloride, and the amount of metallic aluminum powder added is 1% to 10% of the total mass of the mixed chloride; the reduction distillation temperature is 160 to 230℃. In step 5, the dissolution temperature is 60~150℃, and the mass concentration of the alkali solution or circulating mother liquor is 100~200g / L.

2. The method for producing metallurgical-grade alumina from aluminum-containing raw materials using the chlorination-Bayer process according to claim 1, characterized in that, In step 3, the spiral propeller condenser has a spiral propeller at its center, with the outer edge of the propeller in contact with the inner wall of the condenser. The central shaft is hollow, and the flue gas is discharged through the interior of the central shaft after condensation. Chloride is discharged through the airlock at the bottom of the condenser to prevent chloride from adhering to the wall surface during condensation and to ensure continuous discharge and sealing of chloride. The condensation recovery efficiency of chloride and flue gas is greater than 99%, and the water absorption rate is less than 0.1%. The crude aluminum chloride contains ferric chloride and gallium chloride; the crude silicon chloride contains titanium chloride.

3. The method for producing metallurgical-grade alumina from aluminum-containing raw materials using the chlorination-Bayer process according to claim 1, characterized in that, In step 4, the chloride salt is one or more of lithium chloride, sodium chloride, and potassium chloride; the reducing distillation yields anhydrous aluminum chloride with a mass fraction greater than 99.9%; the rare dispersed metal chlorides are gallium chloride and ferric chloride, used as raw materials for further gallium extraction; the silicon tetrachloride, titanium tetrachloride, and germanium tetrachloride have a mass fraction greater than 99.9%. The oxygen is oxygen-enriched air with an oxygen content of 25% to 100%, a flow rate of 0.1 to 10 L / min, an oxidation temperature of 150 to 800℃, and an oxidation time of 15 to 100 min.

4. The method for producing metallurgical-grade alumina from aluminum-containing raw materials using the chlorination-Bayer process according to claim 1, characterized in that, In step 5, no red mud is discharged during the alkali dissolution process; the leaching solution is subjected to seed decomposition in a seed tank or a jet-stirred reactor, wherein the carbon dioxide utilization rate of the jet-stirred reactor is increased by 60% compared with the existing carbon separation equipment, and the decomposition temperature is 50℃~70℃. The multi-stage cyclone heat exchanger is a 2-N multi-stage counter-current cyclone. In the multi-stage counter-current cyclone, the aluminum hydroxide solid phase and the high-temperature flue gas complete the roasting process in the heat exchange process of the cyclone in a counter-current manner. The required roasting temperature is 800~1100℃ and the roasting time is 1s~10s. Its heat utilization efficiency is more than 80% higher than that of the traditional fluidized bed reactor.

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