Method for purifying tellurium by fluidization process

Abstract

The invention relates to a fluidization process method for purifying tellurium. The method sequentially comprises the steps of fluidized oxidation roasting, reduction roasting, fluidized chlorination reaction, electrolytic purification, resource recycling and the like. The method comprises the following steps: firstly, carrying out fluidized roasting on crude tellurium powder in an oxygen-enriched atmosphere, and selectively removing volatile impurity selenium; and then adjusting the atmosphere for reduction roasting, reducing tellurium and other metal oxides into simple substances, and meanwhile, converting non-metal impurities into high-melting-point residues for subsequent removal. Afterwards, tellurium and impurity metal are converted into gaseous chloride through a fluidization chlorination reaction, and chloride crystals are collected through condensation. The obtained chloride is electrolyzed in an anhydrous solvent, tellurium is selectively deposited into high-purity metal, and impurities are reserved in electrolyte; chlorine released in the electrolysis process is recycled, and the electrolyte is also purified and supplemented regularly; the method realizes efficient purification of tellurium and cyclic utilization of resources, and has the advantages of high operation continuity, high purity, environmental friendliness and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of metallurgical engineering, and in particular relates to a method for purifying tellurium by a fluidized process. Background Art

[0002] Tellurium is an important rare earth metal. Due to its unique semiconductor properties and good photoelectric and thermoelectric properties, it is widely used in many strategic emerging industries, such as solar photovoltaic materials, thermoelectric conversion materials, infrared detectors, photoelectric switches and low-melting-point alloys. With the development of clean energy and high-performance electronic devices, the demand for tellurium continues to grow, especially the increasing requirements for its purity, generally requiring a high purity level of 5N (99.999%) or above, and some high-end applications even require 6N (99.9999%) level.

[0003] Currently, the main industrial preparation methods for high-purity tellurium include vacuum distillation, zone melting, and electrolytic refining. While vacuum distillation and zone melting can effectively improve purity, they suffer from high energy consumption, low efficiency, complex equipment, and difficulty in continuous production. Electrolysis, as a wet purification method, can recover relatively high-purity tellurium, but it is highly dependent on pretreatment processes. Inadequate separation of impurities can easily lead to reduced electrolysis efficiency and even substandard product purity. In particular, the impurity element selenium, due to its similar physical and chemical properties to tellurium, easily co-sublimes with tellurium during the sublimation process, making purity difficult to control. Furthermore, elements such as iron, magnesium, and silicon are often mixed into the raw materials in the form of oxides and silicates. These elements have high melting points and strong chemical stability, making them difficult to completely remove using conventional physical or chemical separation methods, severely impacting the purity and electrical properties of the final product.

[0004] In recent years, fluidized bed roasting, as a highly efficient gas-solid phase reaction technology, has gradually shown broad application prospects in the fields of metallurgy and rare metal purification due to its good material dispersion, fast reaction rate, high heat and mass transfer efficiency, and strong process temperature controllability. If fluidized bed roasting is combined with the subsequent chlorination-condensation-electrolysis process, it can not only achieve efficient oxidation and volatilization of Se, but also promote the removal of impurities such as Fe, Si, and Mg after forming stable compounds in the solid phase, providing a good prerequisite for subsequent selective conversion of chlorides and electrochemical purification. Therefore, this type of coupled process route is particularly suitable for the treatment of crude tellurium raw materials with high impurity content and complex components, and provides new ideas and technical paths for the green, continuous, and large-scale preparation of high-purity tellurium. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the deficiencies and defects mentioned in the above background technology and provide a method for efficiently removing impurities such as Se, Fe, Si, and Mg to prepare high-purity tellurium. To solve the above technical problem, the technical solution proposed by the present invention is as follows: A method for purifying tellurium using a fluidized process comprises the following steps: (1) Fluidized oxidation roasting to remove Se: The coarse tellurium powder crushed to a particle size of 1-2 mm is fed into a fluidized roasting furnace, and oxygen-rich gas is blown in to preferentially oxidize selenium into SeO2 gas, which is then discharged with the tail gas; the selenium is recovered through the tail gas treatment system.

[0006] (2) Adjust the oxygen potential for reduction roasting: Switch the atmosphere to a reducing gas to reduce oxides such as tellurium to simple substances. At the same time, impurities such as Si and Mg form high-melting-point oxides and remain in the residue for subsequent removal.

[0007] (3) Fluidized chlorination reaction: Chlorine (Cl2) is introduced into the material after reduction roasting, and the temperature is controlled at 300–400°C. Tellurium and iron form gaseous TeCl4 and FeCl3, which enter the condensation system to collect the generated mixed chloride crystals.

[0008] (4) Chloride dissolution and electrolytic purification: Dissolve the mixed chloride in anhydrous acetonitrile and perform electrolysis in an inert atmosphere. 4 ⁺ is preferentially reduced and precipitated as high-purity tellurium plates, while Fe³⁺ remains in the electrolyte.

[0009] (5) Chlorine gas circulation and waste liquid treatment: The Cl2 gas released during the electrolysis process is condensed and refluxed for the front-end chlorination reaction, reducing the consumption of chlorine source; the electrolyte is regularly filtered to remove impurity oxides and electrolyte is added to maintain the stability of the system.

[0010] Preferably, the tellurium ingot in step (1) comprises 35-50 ppm Se, 60-270 ppm Fe, 1200-1450 ppm Si, 45-55 ppm Al, and 6-20 ppm Mg by mass.

[0011] Preferably, the crushing in step (1) is to crush the tellurium ingot in a crusher, and the mass of particles with a particle size of 1-2 mm accounts for more than 95%; when the particle size is too large, the particle mass is large and the surface area is small, and it is difficult for the airflow to fully lift and evenly disperse it, resulting in insufficient reaction and seriously affecting the heat and mass transfer efficiency of the reaction; if the particle size is too small, it will lead to difficulty in gas-solid separation, increased friction between particles, and the bed may fluctuate violently, making it impossible to maintain a stable flow state, affecting continuous operation.

[0012] Preferably, the oxygen-rich gas (e.g., air) in step (1) is introduced at a rate of 5,000-15,000 L / min per ton of material mass. When the oxygen-rich gas introduction rate is low, insufficient supply of oxygen-rich gas will result in the inability to fully oxidize volatile impurities such as Se and S into volatile oxides (e.g., SeO2), significantly reducing the impurity removal efficiency and affecting the tellurium purity. Excessively high gas velocity will blow some fine particles out of the reactor, causing tellurium raw material loss and increasing the burden of tail gas purification. Excessively fast gas flow will destroy the fluidization balance, resulting in problems such as "spurting," "flying bed," or "reactor vibration," causing unstable operation and even damage to the equipment.

[0013] Preferably, the roasting temperature in step (1) is 200-300°C, and the roasting time is 1-3.5h. When the roasting temperature is too low, the oxidation reaction rate of Se and S is extremely slow at low temperature, and volatile oxides such as SeO2 are not easily generated, which affects the impurity removal efficiency. When the roasting temperature is too high, high-temperature roasting places higher requirements on the furnace lining material and hot air system, and the operating cost increases. In addition, high temperature may promote complex reactions between impurities and tellurium, forming compounds that are difficult to remove.

[0014] Preferably, the reducing agent in step (2) is one or more of hydrogen, water gas and natural gas, and the rate of introducing the reducing agent per ton of material is 150 L / (t·min)-600 L / (t·min), the injection time is 0.5-1.5 h, and the roasting temperature is 350-450°C; when the reducing agent introduction rate is too low, the reaction rate is slow due to insufficient reducing gas, and the oxide reduction is incomplete, which affects the recovery rate of elemental tellurium; when the reducing agent introduction rate is too high, it is easy to cause material blowing, insufficient gas-solid contact, excessive heat load, and energy waste.

[0015] Preferably, the chlorine introduction rate in step (3) is 200-500 L / min per ton of reducing material mass; the chlorination temperature is 300-400 °C, and the chlorination time is 1-2.5 h; when the chlorine introduction rate is too low, the chlorination reaction power is insufficient, the chlorine partial pressure is low, and the tellurium chlorination conversion rate is low; and the chloride generation rate is slow, resulting in a decrease in yield and a prolonged reaction time; when the chlorine introduction rate is too high, the tail gas load and the pressure of the chlorine recovery system are increased, resulting in a waste of resources.

[0016] Preferably, the inert atmosphere in step (4) is high-purity argon or high-purity nitrogen, which is continuously introduced; the cathode is a platinum sheet and the anode is a stone mill rod; the inert atmosphere is used because in the electrolysis process, if there is oxygen or moisture, Te 4 ⁺It is easily oxidized to TeO2 or other unstable forms, affecting the reduction efficiency and deposition purity; and the metal tellurium formed under an inert atmosphere is deposited evenly, has good density, and is not easily mixed with oxides and impurities, thereby improving the purity and flatness of the final product.

[0017] Preferably, the electrolysis control voltage in step (4) is -0.3-0.6 V, the electrolysis temperature is 25-40 °C, and the electrolysis time is 0.5-1.5 h. Controlling the appropriate voltage can ensure the selective reduction of tellurium ions and avoid the occurrence of side reactions. 4 The reduction potential of Fe⁺ is higher, while the reduction potential of impurity ions such as Fe³⁺ is more negative; keeping the control voltage within the window range of -0.3--0.6 V can make Te 4 ⁺The tellurium is preferentially reduced while the impurity ions are not yet reduced, thereby effectively improving the purity of tellurium deposition.

[0018] This invention introduces fluidized bed roasting technology into the high-purity tellurium extraction process for the first time, combining chlorination reaction with electrolytic separation technology to form a highly efficient, green, and continuous tellurium purification process system with the following significant advantages: (1) Improving gas-solid reaction efficiency and selectivity: The fluidized bed roasting process introduces an upward airflow to suspend the powdered material, achieving highly uniform gas-solid contact and significantly improving the reaction rate and mass transfer efficiency. This process can precisely control the oxygen potential conditions to achieve selective oxidation and separation of target impurities, significantly improving the purification efficiency.

[0019] (2) Efficient removal of selenium impurities: Under suitable oxidizing atmosphere and temperature conditions, selenium can be preferentially oxidized to SeO2 and escape with the gas phase, with a removal rate of more than 95%. This effectively solves the technical problem of Se and Te being easily co-sublimated and difficult to separate in the traditional sublimation process, ensuring the purity of subsequent products.

[0020] (3) Selective chlorination promotes impurity migration and separation: At a suitable chlorination temperature (300-400 °C), tellurium and iron can be converted into volatile chlorides (such as TeCl4, FeCl3), and enriched by condensation to form separation intermediates, further improving the separation degree between metal impurities and target components, providing an effective pre-enrichment method for subsequent electrolytic separation.

[0021] (4) High purity and high efficiency of electrolytic recovery: By precisely controlling the electrolytic parameters, Te 4 Through selective deposition of Fe³⁺, we ​​obtain high-purity tellurium plates with dense structures and purity exceeding 5N, which can meet the application requirements of high-end electronic fields such as photovoltaics and thermoelectrics. At the same time, we avoid the co-deposition of impurity metals (such as Fe³⁺) and improve product quality.

[0022] (5) Resource recycling and green environmental protection: Chlorine can be recycled in a closed loop during the chlorination and electrolysis process, significantly reducing raw material consumption and environmental emissions; the entire process flow does not discharge heavy metal waste liquid, has good environmental protection and industrial scalability, is suitable for large-scale continuous production, and is both economical and sustainable.

[0023] In summary, the fluidization-chlorination-electrolysis coupling process proposed in the present invention is highly efficient, selective, and environmentally friendly, and can stably prepare electronic-grade high-purity tellurium. It fills the technical gap in traditional processes for processing crude tellurium with complex impurity systems, and has significant industrial application value and promotion prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION

[0025] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments, but the protection scope of the present invention is not limited to the contents described above.

[0026] Example 1 (1) Crushed tellurium powder (the mass percentage of particles with a particle size of 1.5 mm is greater than 95%) is fed into a fluidized bed roaster; oxygen-rich gas is blown in at a rate of 8000 L / min per ton of material mass, the roasting temperature is controlled at 200°C, and the roasting time is 3.5 hours; under these conditions, selenium (Se) is preferentially oxidized to SeO2 gas and discharged with the tail gas; the tail gas is collected by a condensation system to collect selenium vapor, and the recovery rate reaches 90%; hydrogen is introduced as a reducing gas, and the rate of reducing agent introduction per ton of material is 150 L / (t·min), the furnace temperature is controlled at 400°C, and the holding time is 1 hour; through the reduction reaction, tellurium and iron oxides are reduced to elemental tellurium, while impurities such as Si and Mg form high-melting-point oxides, which are retained in the roasting residue for subsequent treatment.

[0027] (2) Chlorine is introduced into the material after reduction roasting at a rate of 300 L / min per ton of material mass, the temperature is controlled at 250°C, and the chlorination reaction lasts for 1.5 hours; tellurium reacts with iron to generate gaseous TeCl4 and FeCl3, which enter the condensation system, and the collected mixed chloride crystals are filtered to obtain high-purity chloride; the mixed chloride is dissolved in anhydrous acetonitrile and electrolyzed under argon atmosphere, the electrolysis temperature is controlled at 30°C, the electrolysis voltage is -0.5V, and the electrolysis time is 1 hour; in this process, Te 4 The ⁺ ions are preferentially reduced and precipitated into high-purity tellurium plates, while Fe³⁺ is retained in the electrolyte, which is regularly filtered to remove impurity oxides.

[0028] (3) The Cl2 gas released during the electrolysis process is condensed and then refluxed to the chlorination reaction system, reducing the consumption of chlorine source; impurities in the electrolyte are regularly filtered and electrolyte is replenished to maintain the stability of the system.

[0029] The purity of the high-purity tellurium plate prepared in this embodiment is ≥99.99%. High oxygen rate + low temperature calcination optimizes selenium removal and stabilizes the electrolysis voltage. Example 2 (1) The coarse tellurium powder (the mass percentage of particles with a particle size of 1 mm is greater than 95%) is crushed into a fluidized bed roaster and oxygen-rich gas is blown in. The oxygen introduction rate is 6000 L / min per ton of material mass, the roasting temperature is controlled at 280℃, and the roasting time is 2.5 hours. Under these conditions, selenium is effectively oxidized to SeO2 gas and recovered through the tail gas treatment system. Water gas is introduced as the reducing gas, the ratio of hydrogen to carbon monoxide is 1:2, and the rate of introducing the reducing agent per ton of material is 200 L / (t·min). The furnace temperature is controlled at 350℃ and the blowing time is 0.5 hours. During the reduction process, tellurium oxide is reduced to elemental tellurium, and impurities such as Si and Mg remain in the form of oxides, waiting to be removed later.

[0030] (2) Chlorine gas was introduced into the material after reduction roasting at a rate of 400 L / min per ton of material mass. The temperature was controlled at 300 °C. The chlorination reaction lasted for 1.8 hours to form gaseous TeCl4 and FeCl3. The generated chloride crystals were collected in the condensation system. The collected chloride was dissolved in anhydrous acetonitrile and electrolyzed in a high-purity argon atmosphere at a temperature of 35 °C, an electrolysis voltage of -0.4 V, and an electrolysis time of 1.2 hours. During the electrolysis process, TeCl4 4 ⁺ is preferentially reduced to high-purity tellurium plates, and Fe³⁺ is retained in the electrolyte.

[0031] (3) The Cl2 gas generated during the electrolysis process is condensed and refluxed to the chlorination reaction system, reducing the consumption of chlorine source. The electrolyte is regularly filtered and replenished to ensure the stability of the electrolysis process.

[0032] The purity of the high-purity tellurium plate prepared in this example is 99.98%-99.99%. The medium oxygen rate and low electrolysis voltage lead to some impurities remaining. Example 3 (1) Crushed tellurium powder (the mass percentage of particles with a particle size of 1.8 mm is greater than 95%) is fed into a fluidized bed roaster, and oxygen-rich gas is blown in at a rate of 15,000 L / min per ton of material mass. The roasting temperature is controlled at 300°C and the roasting time is 1 hour. Selenium is oxidized to SeO2 gas, which is discharged into the tail gas system and recovered. Hydrogen is introduced as a reducing gas at a rate of 400 L / (t·min) per ton of material. The furnace temperature is controlled at 450°C and maintained for 1.5 hours. Through the reduction reaction, tellurium oxide is reduced to elemental tellurium, and impurities such as Si and Mg form high-melting-point oxides, which remain in the residue and are subsequently processed.

[0033] (2) Chlorine gas was introduced into the material after reduction roasting at a rate of 350 L / min per ton of material mass, the temperature was controlled at 4000 °C, and the chlorination reaction lasted for 2 hours; the generated gaseous TeCl4 and FeCl3 were collected, and the mixed chloride crystals were separated by the condensation system; the chloride was dissolved in anhydrous acetonitrile, the electrolysis temperature was 28 °C, the electrolysis voltage was -0.3 V, and the electrolysis time was 1.2 hours. During the electrolysis process, TeCl4 4 ⁺ is preferentially reduced to high-purity tellurium, and Fe³⁺ remains in the electrolyte.

[0034] (3) The released Cl2 gas is refluxed to the chlorination reaction system through condensation, reducing the consumption of chlorine source. The electrolyte is regularly filtered to remove impurities and the electrolyte is replenished.

[0035] The purity of the high-purity tellurium plate prepared in this example is 99.97%-99.98%. High-temperature calcination optimizes selenium removal, but fluctuations in reduction / electrolysis conditions reduce purity. Example 4 (1) The coarse tellurium powder (the mass percentage of particles with a particle size of 1.2 mm is greater than 95%) is crushed into a fluidized bed roaster. The oxygen introduction rate is 7000 L / min per ton of material mass, the roasting temperature is 270℃, and the roasting time is 2.5 hours. Selenium and other volatile impurities are removed by oxidation, and the tail gas is collected for selenium recovery. Hydrogen is introduced, and the rate of introducing the reducing agent per ton of material is 600 L / (t·min). The furnace temperature is controlled at 500℃ and the roasting time is 1.2 hours. Impurities such as Si and Fe are removed in this process to produce high-purity tellurium.

[0036] (2) Chlorine gas was introduced at a rate of 450 L / min per ton of material mass, the chlorination temperature was controlled at 330°C, the reaction time was 2 hours, and the generated mixed chloride was recovered by condensation; the mixed chloride was dissolved in anhydrous acetonitrile, and the electrolysis process was carried out at 25°C, the electrolysis voltage was -0.6 V, and the electrolysis time was 0.5 hours. High-purity tellurium was preferentially precipitated, and Fe impurities were retained.

[0037] (3) By condensing and refluxing the Cl2 gas to the front-end chlorination reaction system, the consumption of chlorine source is reduced, and the electrolyte is regularly filtered to remove impurities.

[0038] The purity of the high-purity tellurium plate prepared in this example is ≥99.995%, with balanced comprehensive parameters and optimal impurity control. Medium oxygen rate, efficient Si / Fe removal, complete separation of mixed chlorides, and low-temperature electrolysis to suppress side reactions Comparative Example 1 (1) Crude tellurium powder crushed to a particle size of 1.5 mm is fed into a fluidized bed roaster; oxygen-rich gas is blown in at a rate of 3000 L / min per ton of material mass, the roasting temperature is controlled at 350°C, and the roasting time is 3 hours; under these conditions, selenium (Se) is preferentially oxidized to SeO2 gas and discharged with the tail gas; the tail gas is collected by a condensation system to collect selenium vapor, with a recovery rate of only 60%; hydrogen is introduced as a reducing gas, and the rate of reducing agent introduction per ton of material is 100 L / (t·min), the furnace temperature is controlled at 500°C, and the holding time is 2 hours; under these conditions, impurities such as Si and Fe cannot be effectively removed, resulting in a high impurity content in subsequent steps.

[0039] (2) Chlorine is introduced into the material after reduction roasting at a rate of 300 L / min per ton of material mass, the temperature is controlled at 350°C, and the chlorination reaction lasts for 1.5 hours; tellurium reacts with iron to generate gaseous TeCl4 and FeCl3, which enter the condensation system, and the collected mixed chloride crystals are filtered to obtain high-purity chloride; the mixed chloride is dissolved in anhydrous acetonitrile and electrolyzed under argon atmosphere, the electrolysis temperature is controlled at 30°C, the electrolysis voltage is -0.5V, and the electrolysis time is 1 hour; in this process, Te 4 The ⁺ ions are preferentially reduced and precipitated into high-purity tellurium plates, while Fe³⁺ is retained in the electrolyte, which is regularly filtered to remove impurity oxides.

[0040] The purity of the high-purity tellurium plate prepared in this example is ≤99.9% (significant selenium residue and excessive Fe / Si impurities) By comparison, it can be seen that the oxidation roasting stage can achieve efficient removal of selenium and impurity control. When the oxygen introduction rate is higher, selenium (Se) is more fully oxidized to volatile SeO2, effectively separating selenium. The moderate temperature optimizes the formation and volatilization of SeO2 while avoiding impurity redeposition. The selenium removal rate of Examples 1-4 is significantly improved, and impurities such as Fe and Si remain stably in the slag phase in the form of high-melting-point oxides (purity ≥99.99% in Example 1 vs. ≤99.9% in Comparative Example 1).

[0041] In the reduction stage, impurities are selectively removed and the reduction efficiency is improved. Examples 1-4 use high-purity hydrogen (150-600 L / (t·min)), while Comparative Example 1 uses low-speed hydrogen (100 L / (t·min)). The high hydrogen rate accelerates the reduction of TeO2 to elemental Te, while suppressing the reduction of impurities such as Fe and Si, causing them to remain in the form of oxides. The reduction temperature of Examples 1 / 4 is 350-450°C, avoiding the high temperature of 500°C in Comparative Example 1 that causes excessive reduction of Te. Therefore, the residual Fe and Si in Examples 1 / 4 is less than 0.001%, while the impurity content in Comparative Example 1 is as high as 0.02%-0.05% due to the high temperature and inefficient reduction.

[0042] For efficient separation of mixed chlorides in the chlorination stage, the chlorine gas introduction rate and temperature are coordinated. Examples 1 / 4 use 200-500 L / (t·min) of chlorine gas, combined with a temperature of 300-400°C, to promote the chlorination reaction of Te (to produce TeCl4 and FeCl3) while avoiding side reactions (such as the formation of FeCl2). Condensation and filtration optimization: Examples 1-4 achieve efficient separation of TeCl4 and FeCl3 through multi-stage condensation and filtration, while Comparative Example 1 does not clearly define the graded treatment, which may result in residual FeCl3. Therefore, the electrolyte of Examples 1 / 4 has lower Fe³⁺ residual content and higher purity of tellurium deposited by electrolysis.

[0043] The electrolysis stage realizes the selective precipitation of high-purity tellurium, controls the electrolysis voltage and temperature to be stable, reduces side reactions (such as H2 precipitation), and ensures Te 4+ Priority reduction; Example 1 / 4 regularly filters Fe during electrolysis 3+ oxide, while Comparative Example 1 only relies on the natural sedimentation of the electrolyte, resulting in a higher Fe residue; the purity of the tellurium plate in Example 1 / 4 is ≥99.99%, while the purity of Comparative Example 1 is ≤99.9% due to the residual Fe³⁺.

[0044] Through high oxygen rate, precise temperature control, and graded chlorination, the whole process of Se, Fe, Si and other impurities can be removed in a coordinated manner. High-purity hydrogen reduction can avoid secondary pollution, and low-temperature electrolysis can ensure the quality of Te 4+ Prioritized precipitation. The Cl2 cycle reduces raw material consumption, and parameter matching lowers energy consumption, making it suitable for industrial scale-up. The purity of the high-purity tellurium plates in Example 1 / 4 is ≥99.99%, significantly better than the ≤99.9% in Comparative Example 1, meeting the requirements of high-end electronic materials. Through multi-step parameter optimization and collaborative innovation, the process in this example solves the core issues of residual impurities, high energy consumption, and insufficient purity in the comparative example, providing a reliable technical solution for the industrial production of high-purity tellurium.

Claims

1. A method for purifying tellurium by a fluidized process, characterized in that: The specific steps include: (1) Fluidized oxidation roasting to remove Se: The crushed crude tellurium powder is fed into a fluidized roasting furnace for roasting, and oxygen-rich gas is blown in to preferentially oxidize selenium into SeO2 gas, which is then discharged with the tail gas. The tail gas is passed through a condensation system to collect selenium vapor; (2) Adjusting the oxygen potential for reduction roasting: introducing reducing gas into the collected selenium vapor for reduction; (3) Fluidized chlorination reaction: Chlorine is introduced into the material after reduction roasting, and the temperature is controlled at 300-400 ° C. Tellurium and iron form gaseous TeCl4 and FeCl3, which enter the condensation system to collect the generated mixed chloride crystals; (4) Chloride dissolution and electrolytic purification: Dissolve the mixed chloride in anhydrous acetonitrile and perform electrolysis in an inert atmosphere. 4 ⁺ is preferentially reduced and precipitated as high-purity tellurium plates, while Fe³⁺ remains in the electrolyte; (5) Chlorine gas circulation and waste liquid treatment: The Cl2 gas released during the electrolysis process is condensed and refluxed for the front-end chlorination reaction, reducing the consumption of chlorine source; the electrolyte is regularly filtered to remove impurity oxides and electrolyte is added to maintain the stability of the system.

2. The method for purifying tellurium by fluidized bed process according to claim 1, characterized in that: The mass proportion of particles with a particle size of 1-2 mm in the coarse tellurium powder after crushing in step (1) is greater than 95%.

3. The method for purifying tellurium by fluidized bed process according to claim 1, characterized in that: In step (1), the oxygen-rich gas is introduced at a rate of 5000-15000 L / min per ton of material mass; the roasting conditions are: roasting temperature of 200-300°C, and roasting time of 1-3.5h.

4. The method for purifying tellurium by fluidized bed process according to claim 1, characterized in that: The reducing gas in step (2) is one or more of hydrogen, water gas and natural gas. The rate of introducing the reducing agent per ton of material is 150 L / (t·min)-600 L / (t·min), the blowing time is 0.5-1.5 h, and the roasting temperature is 350-450°C.

5. The method for purifying tellurium by fluidized bed process according to claim 1, characterized in that: In step (3), the chlorine gas introduction rate is 200-500 L / min per ton of reducing material mass; and the chlorination time is 1-2.5 h.

6. The method for purifying tellurium by fluidized bed process according to claim 1, characterized in that: The inert atmosphere in step (4) is high-purity argon or high-purity nitrogen, which is continuously introduced, the cathode uses a platinum sheet, and the anode uses a stone mill rod.

7. The method for purifying tellurium by fluidized bed process according to claim 41, characterized in that: In step (4), the electrolysis control voltage is -0.3-0.6 V, the electrolysis temperature is 25-40 °C, and the electrolysis time is 0.5-1.5 h.

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