A method for synergistically recovering valuable elements from spent catalyst sludge and chromium-containing aluminum mud

Abstract

The application relates to the technical field of hazardous waste resource utilization, in particular to a method for cooperatively recovering valuable elements in overhauling slag and chromium-containing aluminum mud; the method comprises the following steps: mixing inorganic acid, chromium-containing aluminum mud and overhauling slag to obtain decyanated materials; using an alkaline component to carry out precipitation reaction on the decyanated materials to obtain precipitated materials; mixing first preheated silicon tetrachloride with the precipitated materials to obtain first chlorination flue gas and first chromium-containing chlorination slag; mixing second preheated silicon tetrachloride with the first chromium-containing chlorination slag to obtain second chlorination flue gas and second chromium-containing chlorination slag; respectively separating and purifying the first chlorination flue gas and the second chlorination flue gas to obtain aluminum-containing solid phase, iron-containing solid phase and silicon tetrafluoride; and washing the second chromium-containing chlorination slag to obtain a trivalent chromium-containing solution. The method can simultaneously improve the removal rate of toxic elements in the overhauling slag and the chromium-containing aluminum mud to more than 99.95% and the recovery rate of valuable elements such as aluminum, iron and chromium to more than 95%.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of hazardous waste resource utilization, and particularly relates to a method for cooperatively recovering valuable elements of overhauling slag and chromium-containing aluminum sludge. BACKGROUND

[0002] The inner lining of an electrolytic aluminum tank is long-term eroded by electrolyte and high-temperature aluminum liquid, so that the electrolyte easily penetrates into the inner lining of the electrolytic aluminum tank, causing damage, deformation and even rupture of the inner lining. In order to avoid further damage to the inner lining, the penetrated material needs to be replaced, and the replaced material is called overhauling slag. The main components of the overhauling slag at present stage include waste cathode carbon block, waste refractory material and waste insulation material, etc., wherein the weight content of carbon in the waste cathode carbon block is 30% to 70%, the weight content of fluoride is 30% to 50%, and the weight content of cyanide is about 0.2%, and the main components of the waste refractory material and the waste insulation material both include silicon nitride and silicon carbide. In addition, the overhauling slag also contains trace amounts of cyanide, which may be formed by the reaction of sodium and nitrogen in the air at 800°C under high-temperature conditions. Although the differences in electrolyte composition, current capacity, operation process and inner lining replacement time of the electrolytic aluminum tank may cause differences in the specific components of the overhauling slag, the main components of the overhauling slag at present stage are basically the same, and all contain carbon, fluoride and small amounts of sodium, aluminum, calcium, iron, silicon, lithium and cyanide. Based on the characteristic that the overhauling slag contains a large amount of soluble fluoride and cyanide, the overhauling slag has been listed as hazardous waste, and direct storage or landfill treatment of the overhauling slag will seriously affect the environment and even harm human health, so harmless treatment and high-value utilization of the overhauling slag are of great significance to the green and high-quality development of the aluminum industry. In addition, the main methods for industrial production of sodium dichromate are calcium roasting method and calcium-free roasting method. Compared with the calcium roasting method, the calcium-free roasting method is more clean and efficient. However, in the calcium-free roasting method, aluminum silicon compounds will react with soda to form a large amount of sodium silicate and sodium aluminate, which will enter the alkaline leaching solution and produce a large amount of chromium-containing aluminum sludge, about 5 to 10 times of that of the calcium roasting method. Chromium-containing aluminum sludge generally contains hexavalent chromium, which makes the chromium-containing aluminum sludge have strong toxicity, so the chromium-containing aluminum sludge is listed as hazardous waste, and direct storage or direct discharge of the chromium-containing aluminum sludge will cause serious harm to the environment.

[0003] At present, the overhauling slag and chromium-containing aluminum sludge are mainly directly treated, mainly for harmless treatment, and the current technology cannot effectively recover chromium, aluminum and iron simultaneously. SUMMARY

[0004] The present application provides a method for cooperatively recovering valuable elements of overhauling slag and chromium-containing aluminum sludge, to solve the technical problem of how to improve the recovery rate of chromium, aluminum and iron in the overhauling slag and chromium-containing aluminum sludge.

[0005] In a first aspect, the present application provides a method for recovering valuable elements from a chromium-containing aluminum sludge and a maintenance slag, wherein the maintenance slag contains fluoride, cyanide, iron and carbon, and the chromium-containing aluminum sludge contains aluminum, iron and hexavalent chromium, and the method comprises:

[0006] mixing an inorganic acid, the chromium-containing aluminum sludge and the maintenance slag to make the hexavalent chromium and the cyanide undergo a redox reaction in an acidic environment to obtain a de-cyanated material containing fluoride, carbon, aluminum, iron and chromium;

[0007] subjecting the de-cyanated material to a precipitation reaction using an alkaline component to obtain a precipitated material containing carbon, aluminum, chromium, iron and fluoride;

[0008] mixing a first preheated silicon tetrachloride with the precipitated material to make the first preheated silicon tetrachloride and the iron and fluoride in the precipitated material undergo a first chlorination reaction under the action of the carbon in the precipitated material to obtain a first chlorination flue gas containing iron and fluoride and a first chromium-containing chlorination residue containing chromium, aluminum, carbon and fluoride;

[0009] mixing a second preheated silicon tetrachloride with the first chromium-containing chlorination residue to make the second preheated silicon tetrachloride and the chromium, aluminum and fluoride in the first chromium-containing chlorination residue undergo a second chlorination reaction under the action of the carbon in the first chromium-containing chlorination residue to obtain a second chlorination flue gas containing aluminum and fluoride and a second chromium-containing chlorination residue;

[0010] separating and purifying the first chlorination flue gas and the second chlorination flue gas, respectively, to obtain an aluminum-containing solid phase, an iron-containing solid phase and silicon tetrafluoride;

[0011] washing the second chromium-containing chlorination residue to obtain a trivalent chromium-containing solution.

[0012] Optionally, the temperature of the first chlorination reaction is 500-700°C, and the time of the first chlorination reaction is 0.5-2h; and / or

[0013] the temperature of the second chlorination reaction is 800-900°C, and the time of the second chlorination reaction is 0.5-2h.

[0014] Optionally, the first chlorination reaction and the second chlorination reaction are both carried out by microwave heating.

[0015] Optionally, the pH of the redox reaction is 4-6, and the time of the redox reaction is 0.5-2h.

[0016] Optionally, the weight of the cyanide in the de-cyanated material is less than or equal to 0.05% of the weight of the de-cyanated material, and the weight of the hexavalent chromium in the de-cyanated material is less than or equal to 0.05% of the weight of the de-cyanated material.

[0017] Optionally, the pH of the precipitation reaction is 8-11.

[0018] Optionally, the separating and purifying the first chlorination flue gas and the second chlorination flue gas respectively to obtain an aluminum-containing solid phase, an iron-containing solid phase, and silicon tetrafluoride comprises the following steps:

[0019] The first chlorination flue gas is subjected to first multi-stage condensation to obtain an iron-containing solid phase, first circulating liquid-phase silicon tetrachloride, and first gas-phase silicon tetrafluoride.

[0020] The second chlorination flue gas is subjected to second multi-stage condensation to obtain an aluminum-containing solid phase, second circulating liquid-phase silicon tetrachloride, and second gas-phase silicon tetrafluoride.

[0021] The first gas-phase silicon tetrafluoride and the second gas-phase silicon tetrafluoride are combined to obtain silicon tetrafluoride.

[0022] The first circulating liquid-phase silicon tetrachloride and the second circulating liquid-phase silicon tetrachloride are respectively subjected to gasification to obtain first circulating gas-phase silicon tetrachloride and second circulating gas-phase silicon tetrachloride.

[0023] Optionally, the first multi-stage condensation comprises a first cooling section and a second cooling section, the first cooling section is used for condensing the iron- and fluorine-containing first chlorination flue gas and obtaining an iron-containing solid phase, and the second cooling section is used for condensing the iron- and fluorine-containing first chlorination flue gas and obtaining first gas-phase silicon tetrafluoride and first circulating liquid-phase silicon tetrachloride respectively, the temperature of the first cooling section is 70-290°C, and the temperature of the second cooling section is 20-50°C.

[0024] Optionally, the second multi-stage condensation comprises a third cooling section and a fourth cooling section, the third cooling section is used for condensing the aluminum- and fluorine-containing second chlorination flue gas and obtaining an aluminum-containing solid phase, and the fourth cooling section is used for condensing the aluminum- and fluorine-containing second chlorination flue gas and obtaining second gas-phase silicon tetrafluoride and second circulating liquid-phase silicon tetrachloride respectively, the temperature of the third cooling section is 70-170°C, and the temperature of the fourth cooling section is 20-50°C.

[0025] Optionally, before the washing the second chromium-containing chlorination residue to obtain a trivalent chromium-containing solution, and after the gasification of the first circulating liquid-phase silicon tetrachloride and the second circulating liquid-phase silicon tetrachloride to obtain first circulating gas-phase silicon tetrachloride and second circulating gas-phase silicon tetrachloride, the method comprises the following steps:

[0026] The silicon tetrachloride is subjected to gasification and classification to obtain first gas-phase silicon tetrachloride and second gas-phase silicon tetrachloride respectively;

[0027] The first gas-phase silicon tetrachloride and the first circulating gas-phase silicon tetrachloride are respectively introduced into the first chromium-containing chlorination residue for heat exchange to obtain first preheated silicon tetrachloride.

[0028] The second gaseous phase silicon tetrachloride and the second circulating gaseous phase silicon tetrachloride are respectively introduced into the second chromium-containing chloride slag for heat exchange to obtain second preheated silicon tetrachloride.

[0029] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0030] The present invention provides a method for the synergistic recovery of valuable elements from overhaul slag and chromium-aluminum mud. This method aims to simultaneously treat overhaul slag (containing fluoride, cyanide, iron, and carbon) and chromium-aluminum mud (containing aluminum, iron, and hexavalent chromium) to remove toxic elements and recover valuable elements through a series of chemical reactions. The method includes the following steps: a redox reaction step: mixing an inorganic acid, chromium-aluminum mud, and overhaul slag, and utilizing the acidic environment of the inorganic acid to promote the reaction between hexavalent chromium and cyanide, thereby removing the cyanide. In this step, hexavalent chromium acts as an oxidant and undergoes a redox reaction with cyanide to produce harmless or low-toxic products. As a result, a decyanide material containing fluoride, carbon, aluminum, iron and chromium is obtained; a precipitation reaction step: using an alkaline component (such as ammonia water or calcium oxide) to perform a precipitation reaction on the decyanide material to remove chromium, aluminum, iron and fluoride therein; in addition, the precipitation reaction forms precipitates such as calcium fluoride, aluminum hydroxide, and iron hydroxide, thereby achieving the separation of these elements, and as a result, a precipitate material containing carbon, aluminum, chromium, iron and fluorine (partially unprecipitated) is obtained. The method comprises the following steps: performing a first chlorination reaction on the precipitate using a first preheated chlorine gas, utilizing carbon in the precipitate as a heating medium to promote the reaction of chromium, iron and aluminum to generate iron-containing chloride salt, chromium-containing chloride salt and aluminum-containing chloride salt; the first chlorination reaction generates a first chlorinated flue gas containing iron and fluorine and a first chromium-containing chloride slag containing chromium, aluminum, carbon and fluorine, and the first chlorinated flue gas can be further purified through subsequent steps to obtain an iron-containing solid phase and silicon tetrafluoride; the first chromium-containing chloride slag is subjected to a second chlorination reaction, utilizing carbon in the first chromium-containing chloride slag as a heating medium to promote the reaction of chromium and aluminum to generate chromium-containing chloride salt and aluminum-containing chloride salt, the second chlorination reaction generates a second chlorinated flue gas containing aluminum and fluorine and a second chromium-containing chloride slag containing chromium, and the second chlorinated flue gas can be further purified through subsequent steps to obtain an aluminum-containing solid phase and silicon tetrafluoride, and the second chromium-containing chloride slag can be washed to obtain a trivalent chromium-containing solution, thereby realizing chromium recovery; therefore, the method removes toxic elements from the overhaul slag and the chromium-aluminum mud through redox reactions, and then effectively recovers aluminum, iron and chromium through multiple chlorinations. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, for those of ordinary skill in the art, other drawings can also be obtained based on these drawings without any creative effort.

[0033] Figure 1 A process flow diagram of a method for cooperatively recovering valuable elements in overhaul slag and chromium-containing aluminum sludge provided by the embodiment of the present application;

[0034] Figure 2 A detailed process flow diagram of a method for cooperatively recovering valuable elements in overhaul slag and chromium-containing aluminum sludge provided by the embodiment of the present application;

[0035] Figure 3 An actual process flow diagram of a method for cooperatively recovering valuable elements in overhaul slag and chromium-containing aluminum sludge provided by the embodiment of the present application. DETAILED DESCRIPTION

[0036] In order to make the objectives, technical solutions and advantages of the embodiments of the present application clearer, the following will combine the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without any creative effort fall within the scope of protection of the present application.

[0037] Various embodiments of the present application can exist in the form of a range; it should be understood that the description in the form of a range is only for the convenience and brevity, and should not be understood as a hard limit on the scope of the present application; therefore, it should be considered that the described range has specifically disclosed all possible sub-ranges and single values in the range; for example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers in the range, such as 1, 2, 3, 4, 5 and 6, which applies to any range; in addition, whenever a numerical range is indicated in this document, it refers to any cited number (fraction or integer) in the indicated range.

[0038] In this document, the terms "comprises", "comprising", "includes", "including" or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises, includes or includes elements or steps do not include only those elements or steps but can include other elements or steps not expressly listed or inherent to such process, method, article, or apparatus. The terms "first", "second", "third", etc. are used merely as labels, and are not intended to impose numerical requirements on their objects. The term "and / or", describing the relationship between associated objects, means that there can be three kinds of relationships, for example, A and / or B can mean that A exists alone, A and B exist together, B exists alone; wherein A and B can be singular or plural. "At least one" means one or more, "multiple" means two or more; "at least one" or "at least one of the following" or the like means any combination of the items, including single item or combination of multiple items; for example, "at least one of a, b, or c", or "at least one of a, b, and c", can mean a, b, c, a-b (i.e. a and b), a-c, b-c, or a-b-c, wherein a, b, and c can be single or multiple. The "parts ratio" such as weight parts, mass parts, etc. represents the proportional relationship between components. In the proportional relationship described in this document, the parameters that need to be described in order should be understood as the front item of the proportional formula, and the proportional number should be understood as the rear item of the proportional formula, for example, the mass ratio of substance A, substance B and substance C is 1:2:3, then substance A, substance B and substance C should be corresponding to the proportional number in the proportional formula in the order of description, i.e. the mass of substance A: the mass of substance B: the mass of substance C

[0039] =1:2:3.

[0040] Unless otherwise specified, the various raw materials, reagents, instruments and equipment used in this document can be purchased from the market or prepared by existing methods.

[0041] Figure 1 An exemplary flow chart of a method for cooperatively recovering valuable elements from overhaul slag and chromium-containing aluminum slurry is shown.

[0042] As shown in Figure 1 The present application provides a method for cooperatively recovering valuable elements from overhaul slag and chromium-containing aluminum slurry, wherein the overhaul slag contains fluoride, cyanide, iron and carbon, and the chromium-containing aluminum slurry contains aluminum, iron and hexavalent chromium, and the method comprises:

[0043] S1. Mixing inorganic acid, the chromium-containing aluminum slurry and the overhaul slag, so that the hexavalent chromium and the cyanide perform redox reaction in an acidic environment to obtain de-cyanated material containing fluoride, carbon, aluminum, iron and chromium;

[0044] S2. precipitating the de-cyanated material using a basic component to obtain a precipitated material containing carbon, aluminum, chromium, iron and fluorine;

[0045] S3. mixing the first preheated silicon tetrachloride with the precipitated material, and allowing the first preheated silicon tetrachloride to react with the iron and fluorine in the precipitated material under the action of the carbon in the precipitated material to obtain a first chlorination flue gas containing iron and fluorine and a first chromium-containing chlorination residue containing chromium, aluminum, carbon and fluorine;

[0046] S4. mixing the second preheated silicon tetrachloride with the first chromium-containing chlorination residue, and allowing the second preheated silicon tetrachloride to react with the chromium, aluminum and fluorine in the first chromium-containing chlorination residue under the action of the carbon in the first chromium-containing chlorination residue to obtain a second chlorination flue gas containing aluminum and fluorine and a second chromium-containing chlorination residue;

[0047] S5. separately purifying the first chlorination flue gas and the second chlorination flue gas to obtain an aluminum-containing solid phase, an iron-containing solid phase and silicon tetrafluoride;

[0048] S6. washing the second chromium-containing chlorination residue to obtain a trivalent chromium-containing solution.

[0049] It should be noted that the carbon in the overhaul residue can significantly improve the fluidization quality of the chromium-containing aluminum slurry and effectively promote the redox reaction; the carbon in the overhaul residue can be carbon or silicon carbide; in the case where the carbon in the overhaul residue is carbon, part of the carbon will be lost during the first chlorination reaction and the second chlorination reaction, and in the case where the carbon in the overhaul residue is silicon carbide, the amount of silicon carbide lost during the first chlorination reaction and the second chlorination reaction is small due to the stability of silicon carbide.

[0050] It should be noted that the precipitated material needs to be purified before chlorination reaction to remove the water in the precipitated material and avoid loss of preheated chlorine. The purification treatment can be drying treatment.

[0051] It should be noted that the temperature of the first preheated silicon tetrachloride can be less than the working temperature of the first chlorination reaction, and the temperature of the first preheated silicon tetrachloride is determined according to the actual heat exchange condition; no matter what the temperature of the first preheated silicon tetrachloride is, it can be quickly heated to the working temperature of the first chlorination reaction in the microwave heating stage of the first chlorination reaction; similarly, the temperature of the second preheated silicon tetrachloride also needs to be controlled.

[0052] It should be noted that the first chlorination reaction and the second chlorination reaction can be carried out in a gas-solid fluidized bed reactor, and the preheated chlorine and the precipitated material have the characteristics of high degree of mixing and contact, fast mass and heat transfer rate and high reaction efficiency in the gas-solid fluidized bed reactor.

[0053] It should be noted that the inorganic acid can be hydrochloric acid, which is used to cooperate with the first chlorination reaction of the first preheated silicon tetrachloride and the second chlorination reaction of the second preheated silicon tetrachloride to obtain chromium-containing chlorides, iron-containing chlorides, and aluminum-containing chlorides.

[0054] It should be noted that the basic component can be ammonia water or a basic metal oxide. When the basic metal oxide is calcium oxide, the fluorine in the precipitate exists in the form of calcium fluoride. At this time, the product obtained by the precipitation reaction has a waste liquid containing calcium and other unreacted impurities in addition to the precipitate. The waste liquid can be treated to obtain a harmless waste liquid. When the basic component is ammonia water, the precipitated fluorine exists in the form of fluorine in the compound (aluminum fluoride). At this time, the product obtained by the precipitation reaction has a mixed solution of partially unreacted ammonia water and soluble fluorine in addition to the precipitate. The mixed solution needs to be treated with a calcium-containing compound (usually calcium oxide) and then treated to obtain a harmless waste liquid.

[0055] It should be noted that the second chromium-containing chlorination residue can be removed after washing to obtain a high-purity trivalent chromium-containing solution.

[0056] It should be noted that the overhaul residue needs to be ground before use to control the particle size of the overhaul residue to be less than 10 μm. The overhaul residue with a particle size of less than 10 μm has a high specific surface area. The high specific surface area of the overhaul residue can increase the contact area between the overhaul residue and the chromium-containing aluminum mud, which enables the cyanide in the overhaul residue to fully undergo an oxidation-reduction reaction with the hexavalent chromium in the chromium-containing aluminum mud.

[0057] It should be noted that the first preheated silicon tetrachloride and the second preheated silicon tetrachloride can be hazardous waste silicon tetrachloride generated in the production process of polysilicon.

[0058] It should be noted that the tailings of the second chromium-containing chlorination residue after washing can be used as harmless tailings for construction and filling and other fields.

[0059] In summary, the method for cooperatively recovering valuable elements from the overhaul residue and the chromium-containing aluminum mud according to the embodiments of the present application can effectively remove toxic elements (such as cyanide and hexavalent chromium) in the overhaul residue and the chromium-containing aluminum mud through oxidation-reduction reactions, precipitation reactions, and chlorination reactions, and achieve efficient recovery of valuable elements (such as aluminum, iron, and chromium). Specifically:

[0060] (1) Removal of toxic elements: Through oxidation-reduction reactions and precipitation reactions, cyanide and hexavalent chromium are converted into harmless or low-toxicity products, achieving effective removal of toxic elements.

[0061] (2) Recovery of valuable elements: Through multiple chlorination reactions, fluorine, aluminum, iron, and chromium are converted into corresponding chloride salts, respectively, and high-purity valuable element products are obtained through subsequent purification steps.

[0062] (3) Environmental friendliness: The by-products generated during the entire process (such as ammonia, carbon dioxide, silicon tetrafluoride, etc.) are harmless or low-toxicity substances, meeting environmental protection requirements.

[0063] Therefore, this method realizes the simultaneous recovery and utilization of valuable elements in the large repair slag and chromium-containing aluminum sludge through a series of chemical reactions, not only improving the removal effect of toxic elements, but also effectively improving the recovery rate of valuable elements, achieving efficient recovery of resources. This provides a new idea and method for solving the problem of industrial waste, which is helpful for realizing sustainable utilization of resources and environmental protection.

[0064] In some optional embodiments, the temperature of the first chlorination reaction is 500-700°C, and the time of the first chlorination reaction is 0.5-2h; and / or

[0065] The temperature of the second chlorination reaction is 800-900°C, and the time of the second chlorination reaction is 0.5-2h.

[0066] In these embodiments, the temperature of the first chlorination reaction can be 500-700°C, and the time of the chlorination reaction can be 0.5-2h, which facilitates the reaction between the first preheated silicon tetrachloride and the iron and fluorine in the precipitate under the action of carbon in the precipitate, to obtain iron-containing chloride salt and silicon tetrafluoride, thereby facilitating the subsequent second chlorination reaction and separation and purification; in addition, the temperature of the second chlorination reaction can be 800-900°C, and the time of the second chlorination reaction can be 0.5-2h, which facilitates the reaction between the second preheated silicon tetrachloride and the chromium, aluminum, and fluorine in the first chromium-containing chlorination slag under the action of carbon in the first chromium-containing chlorination slag, to obtain aluminum-containing chloride salt, chromium-containing chloride salt, and silicon tetrafluoride, thereby facilitating the subsequent separation, purification, and washing.

[0067] The temperature of the first chlorination reaction can be 500°C, 520°C, 540°C, 560°C, 580°C, 600°C, 620°C, 640°C, 660°C, 680°C, or 700°C.

[0068] The time of the first chlorination reaction can be 0.5h, 1.0h, 1.5h, or 2.0h.

[0069] The temperature of the second chlorination reaction can be 800°C, 810°C, 820°C, 830°C, 840°C, 850°C, 860°C, 870°C, 880°C, 890°C, or 900°C.

[0070] The time of the second chlorination reaction can be 0.5 h, 1.0 h, 1.5 h, or 2.0 h.

[0071] In some alternative embodiments, both the first chlorination reaction and the second chlorination reaction are performed by microwave heating.

[0072] In these embodiments, both the first chlorination reaction and the second chlorination reaction are performed by microwave heating, and during the microwave heating process, the carbon of the precipitate and the carbon of the first chromium-containing chlorination residue can act as high-efficiency wave-absorbing materials to absorb and store the energy transferred by the microwave heating. The carbon with sufficient energy can not only cause the precipitate and the first chromium-containing chlorination residue to be rapidly heated to cause the temperature of the precipitate to meet the requirements of the first chlorination reaction and the temperature of the first chromium-containing chlorination residue to meet the requirements of the second chlorination reaction, but also can uniformly disperse other materials of the precipitate during the microwave heating process. In addition, the carbon of the precipitate and the carbon of the first chromium-containing chlorination residue can also act as a carbon source to improve the strength of the first chlorination reaction and the second chlorination reaction to cause chromium, iron, aluminum, and fluorine to react to generate chromium-containing chlorides, aluminum-containing chlorides, iron-containing chlorides, and silicon tetrafluoride.

[0073] In some alternative embodiments, the pH of the oxidation-reduction reaction is 4-6, and the time of the oxidation-reduction reaction is 0.5 h-2 h.

[0074] In these embodiments, the pH of the oxidation-reduction reaction can be 4-6, and the time of the oxidation-reduction reaction can be 0.5 h-2 h. In the acidic environment of the inorganic acid, the hexavalent chromium of the chromium-containing aluminum sludge and the cyanide of the overhauling residue can be fully reacted to cause the cyanide to be oxidized to generate harmless carbon dioxide and nitrogen and cause the hexavalent chromium to be reduced to harmless trivalent chromium, thereby effectively removing the toxic elements in the chromium-containing aluminum sludge and the overhauling residue.

[0075] The pH of the oxidation-reduction reaction can be 4.0, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5.0, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9, or 6.0.

[0076] The time of the oxidation-reduction reaction can be 0.5 h, 1 h, 1.5 h, or 2 h.

[0077] In some alternative embodiments, the weight of the cyanide of the de-cyanide material is less than or equal to 0.05% of the weight of the de-cyanide material, and the weight of the hexavalent chromium of the de-cyanide material is less than or equal to 0.05% of the weight of the de-cyanide material.

[0078] In the embodiments, the weight of cyanide in the cyanide material can be less than or equal to 0.05% of the weight of the de-cyanide material, and the weight of hexavalent chromium in the de-cyanide material can be less than or equal to 0.05% of the weight of the de-cyanide material, which indicates that the hexavalent chromium in the chromium-containing aluminum sludge and the cyanide in the spent catalyst residue have been sufficiently reacted in the redox reaction.

[0079] In some optional embodiments, the pH of the precipitation reaction is 8-11.

[0080] In the embodiments, the pH of the precipitation reaction can be 8-11, which indicates that the precipitation reaction is carried out in an alkaline environment, and the alkaline environment can promote the conversion of aluminum, iron and chromium into hydroxide precipitates, thereby promoting the conversion of aluminum, iron and chromium in the de-cyanide material into the precipitate material; in addition, in the case of calcium oxide as the alkaline component, the calcium in the calcium oxide can react with the fluorine in the de-cyanide material in the alkaline environment to obtain calcium fluoride precipitate, thereby facilitating subsequent recovery and processing.

[0081] The pH of the precipitation reaction can be 8, 8.5, 9.0, 9.5, 10.0, 10.5, 11.0.

[0082] Figure 2 An example of a detailed flow diagram of a method for cooperatively recovering valuable elements from spent catalyst residue and chromium-containing aluminum sludge provided by the embodiments of the present application is shown;

[0083] Figure 3 An example of a detailed flow diagram of a method for cooperatively recovering valuable elements from spent catalyst residue and chromium-containing aluminum sludge provided by the embodiments of the present application is shown;

[0084] In some optional embodiments, as shown in Figure 2 and Figure 3 The separation and purification of the first chlorination flue gas and the second chlorination flue gas to obtain aluminum-containing solid phase, iron-containing solid phase and silicon tetrafluoride, respectively, includes the steps of:

[0085] S501. The first chlorination flue gas is subjected to first multi-stage condensation to obtain iron-containing solid phase, first circulating liquid phase silicon tetrachloride and first gaseous phase silicon tetrafluoride;

[0086] S502. The second chlorination flue gas is subjected to second multi-stage condensation to obtain aluminum-containing solid phase, second circulating liquid phase silicon tetrachloride and second gaseous phase silicon tetrafluoride;

[0087] S503. The first gaseous phase silicon tetrafluoride and the second gaseous phase silicon tetrafluoride are combined to obtain silicon tetrafluoride;

[0088] S504. The first circulating liquid phase silicon tetrachloride and the second circulating liquid phase silicon tetrachloride are separately subjected to gasification to obtain first circulating gaseous phase silicon tetrachloride and second circulating gaseous phase silicon tetrachloride.

[0089] In these embodiments, the separation and purification of different chlorination flue gas uses the way of multi-stage condensation separation and gasification. Through the first multi-stage condensation separation, iron and fluorine can be recovered according to the boiling point difference between the iron-containing solid phase and silicon tetrafluoride of the first chlorination flue gas containing iron and fluorine, so that the two can be condensed and precipitated. Through the second multi-stage condensation separation, aluminum and fluorine can be recovered according to the boiling point difference between the aluminum-containing solid phase and silicon tetrafluoride of the second chlorination flue gas containing aluminum and fluorine, so that the two can be condensed and precipitated. In addition, the first and second circulating liquid phase silicon tetrachloride precipitated can be gasified to realize the regeneration of silicon tetrachloride.

[0090] It should be noted that the temperature of the gasification can be 70-100°C.

[0091] In some optional embodiments, the first multi-stage condensation includes a first cooling section and a second cooling section, the first cooling section is used to condense the first chlorination flue gas containing iron and fluorine and obtain an iron-containing solid phase, and the second cooling section is used to condense the first chlorination flue gas containing iron and fluorine and obtain first gaseous silicon tetrafluoride and first circulating liquid phase silicon tetrachloride, respectively. The temperature of the first cooling section is 70-290°C, and the temperature of the second cooling section is 20-50°C.

[0092] In these embodiments, the first multi-stage condensation can include a first cooling section, and the first cooling section can be used to condense the first chlorination flue gas containing iron and fluorine and obtain an iron-containing solid phase, and the temperature of the first cooling section can be 70-290°C. The iron-containing component can be condensed into an iron-containing solid phase according to the boiling point difference between the iron-containing component and other components of the first chlorination flue gas, so as to realize the recovery of iron. In addition, the first multi-stage condensation can include a second cooling section, and the second cooling section is used to condense the first chlorination flue gas containing iron and fluorine and obtain first gaseous silicon tetrafluoride and first circulating liquid phase silicon tetrachloride, respectively. The temperature of the second cooling section can be 20-50°C. The silicon tetrachloride component can be condensed into first circulating liquid phase silicon tetrachloride according to the boiling point difference between the silicon tetrachloride and silicon tetrafluoride of the first chlorination flue gas, so as to realize the separation of silicon tetrachloride and silicon tetrafluoride, facilitate the regeneration of silicon tetrachloride through the way of gasification in the subsequent process, and thus be conducive to the recycling use of silicon tetrachloride.

[0093] The temperature of the first cooling section can be 70°C, 90°C, 110°C, 130°C, 150°C, 170°C, 190°C, 210°C, 230°C, 250°C, 270°C, or 290°C.

[0094] The temperature of the second cooling section can be 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, or 50°C.

[0095] In some optional embodiments, the second multi-stage condensation comprises a third cooling section and a fourth cooling section, the third cooling section is used for condensing the second chlorination flue gas containing aluminum and fluorine and obtaining an aluminum-containing solid phase, and the fourth cooling section is used for condensing the second chlorination flue gas containing aluminum and fluorine and obtaining second gaseous phase silicon tetrafluoride and second circulating liquid phase silicon tetrachloride, respectively; the temperature of the third cooling section is 70-170°C, and the temperature of the fourth cooling section is 20-50°C.

[0096] In these embodiments, the second multi-stage condensation can comprise a third cooling section, and the third cooling section can be used for condensing the second chlorination flue gas containing aluminum and fluorine and obtaining an aluminum-containing solid phase, and the temperature of the third cooling can be 70-170°C, and the aluminum chloride component in the second chlorination flue gas is condensed into the aluminum-containing solid phase according to the boiling point difference between the aluminum chloride component and other components to realize the recovery of aluminum; in addition, the second multi-stage condensation can comprise a fourth cooling section, and the fourth cooling section can be used for condensing the second chlorination flue gas containing aluminum and fluorine and obtaining second gaseous phase silicon tetrafluoride and second circulating liquid phase silicon tetrachloride, respectively, and the temperature of the fourth cooling section can be 20-50°C, and the silicon tetrachloride component in the second chlorination flue gas can be condensed into the second circulating liquid phase silicon tetrachloride according to the boiling point difference between the silicon tetrafluoride and the silicon tetrachloride to realize the separation of the silicon tetrafluoride and the silicon tetrachloride, facilitate the regeneration of the silicon tetrachloride by gasification in the subsequent process, and thus facilitate the recycling use of the silicon tetrachloride.

[0097] The temperature of the third cooling section can be 70°C, 90°C, 110°C, 130°C, 150°C, or 170°C.

[0098] The temperature of the fourth cooling section can be 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, or 50°C

[0099] In some optional embodiments, before the second chromium-containing chlorination residue is washed to obtain a trivalent chromium-containing solution, after the first circulating liquid phase silicon tetrachloride and the second circulating liquid phase silicon tetrachloride are respectively gasified to obtain first circulating gaseous phase silicon tetrachloride and second circulating gaseous phase silicon tetrachloride, the method comprises:

[0100] S601. Gasify and classify the silicon tetrachloride to obtain first gaseous phase silicon tetrachloride and second gaseous phase silicon tetrachloride, respectively;

[0101] S602. Pass the first gaseous phase silicon tetrachloride and the first circulating gaseous phase silicon tetrachloride into the first chromium-containing chlorination residue, respectively, to exchange heat and obtain first preheated silicon tetrachloride;

[0102] S603. Pass the second gaseous phase silicon tetrachloride and the second circulating gaseous phase silicon tetrachloride into the second chromium-containing chlorination residue, respectively, to exchange heat and obtain second preheated silicon tetrachloride;

[0103] In these embodiments, silicon tetrachloride is gasified and classified, and the first circulating gaseous phase silicon tetrachloride and the second circulating gaseous phase silicon tetrachloride can be fed according to the actual consumption of silicon tetrachloride in the first chlorination reaction and the second chlorination reaction. In addition, the heat of the first chromium-containing chloride slag is recovered by the first gaseous phase silicon tetrachloride and the first circulating gaseous phase silicon tetrachloride, and the heat of the second chromium-containing chloride slag is recovered by the second gaseous phase silicon tetrachloride and the second circulating gaseous phase silicon tetrachloride. The first gaseous phase silicon tetrachloride and the first circulating gaseous phase silicon tetrachloride can be preheated by the heat of the first chromium-containing chloride slag, and the second gaseous phase silicon tetrachloride and the second circulating gaseous phase silicon tetrachloride can be preheated by the heat of the second chromium-containing chloride slag to recover the heat of the first chlorination reaction and the second chlorination reaction, thereby reducing the overall energy consumption of the method and improving the thermal efficiency of the method.

[0104] The present application is further described below with reference to specific examples. Experimental methods in the following examples where specific conditions are not specified are generally measured in accordance with national / industry standards. If there are no corresponding national / industry standards, the methods are carried out in accordance with commonly used international standards, conventional conditions, or conditions recommended by the manufacturer.

[0105] Example 1

[0106] like Figure 2 A method for synergistically recovering valuable elements from overhaul slag and chromium-containing aluminum mud is shown, wherein the overhaul slag contains fluoride, cyanide, iron and carbon, and the chromium-containing aluminum mud contains aluminum, iron and hexavalent chromium, comprising:

[0107] S1. Mixing an inorganic acid, chromium-containing aluminum mud and overhaul slag (particle size less than 10 μm), allowing hexavalent chromium to undergo an oxidation-reduction reaction with cyanide in an acidic environment to obtain a decyanide material containing fluoride, carbon, aluminum, iron and chromium;

[0108] S2. The decyanide material is subjected to precipitation reaction using calcium oxide to obtain a precipitate containing carbon, aluminum, chromium, iron and fluorine;

[0109] S3. The first preheated silicon tetrachloride is mixed with the precipitate, and under the action of carbon in the precipitate, the first preheated silicon tetrachloride is subjected to a first chlorination reaction with iron and fluorine in the precipitate to obtain a first chlorinated flue gas containing iron and fluorine and a first chromium-containing chlorinated slag containing chromium, aluminum, carbon and fluorine;

[0110] S4. The second preheated silicon tetrachloride is mixed with the first chromium-containing chloride slag, and under the action of the carbon in the first chromium-containing chloride slag, the second preheated silicon tetrachloride and the first chromium-containing chloride slag undergo a second chlorination reaction of chromium, aluminum and fluorine to obtain a second chlorinated flue gas containing aluminum and fluorine and a second chromium-containing chloride slag;

[0111] S501. performing first multi-stage condensation on the first chlorination flue gas containing iron and fluorine to obtain an iron-containing solid phase, a first circulating liquid phase silicon tetrachloride, and a first gaseous phase silicon tetrafluoride;

[0112] S502. performing second multi-stage condensation on the second chlorination flue gas containing aluminum and fluorine to obtain an aluminum-containing solid phase, a second circulating liquid phase silicon tetrachloride, and a second gaseous phase silicon tetrafluoride;

[0113] S503. combining the first gaseous phase silicon tetrafluoride and the second gaseous phase silicon tetrafluoride to obtain silicon tetrafluoride;

[0114] S504. separately performing gasification on the first circulating liquid phase silicon tetrachloride and the second circulating liquid phase silicon tetrachloride to obtain first circulating gaseous phase silicon tetrachloride and second circulating gaseous phase silicon tetrachloride;

[0115] S601. performing gasification and classification on the silicon tetrachloride to obtain first gaseous phase silicon tetrachloride and second gaseous phase silicon tetrachloride, respectively;

[0116] S602. passing the first gaseous phase silicon tetrachloride and the first circulating gaseous phase silicon tetrachloride into the first chromium-containing chlorination residue for heat exchange to obtain first preheated silicon tetrachloride;

[0117] S603. passing the second gaseous phase silicon tetrafluoride and the second circulating gaseous phase silicon tetrachloride into the second chromium-containing chlorination residue for heat exchange to obtain second preheated silicon tetrachloride;

[0118] S6. performing washing on the second chromium-containing chlorination residue to obtain a trivalent chromium-containing solution.

[0119] The temperature of the first chlorination reaction is 500℃, and the time of the first chlorination reaction is 2h;

[0120] The temperature of the second chlorination reaction is 800℃, and the time of the second chlorination reaction is 2h.

[0121] Both the first chlorination reaction and the second chlorination reaction are performed in a microwave heating manner.

[0122] The pH of the oxidation-reduction reaction is 4, and the time of the oxidation-reduction reaction is 0.5h.

[0123] The weight of cyanide in the de-cyanated material is less than or equal to 0.05% of the weight of the de-cyanated material, and the weight of hexavalent chromium in the de-cyanated material is less than or equal to 0.05% of the weight of the de-cyanated material.

[0124] The pH of the precipitation reaction is 8.

[0125] The first multi-stage condensation includes a first cooling section and a second cooling section, the first cooling section is used for condensing the first chlorination flue gas containing iron and fluorine and obtaining an iron-containing solid phase, and the second cooling section is used for condensing the first chlorination flue gas containing iron and fluorine and obtaining a first gaseous phase silicon tetrafluoride and a first circulating liquid phase silicon tetrachloride respectively, the temperature of the first cooling section is 70℃, and the temperature of the second cooling section is 20℃.

[0126] The second multi-stage condensation includes a third cooling section and a fourth cooling section, the third cooling section is used for condensing the second chlorination flue gas containing aluminum and fluorine and obtaining an aluminum-containing solid phase, and the fourth cooling section is used for condensing the second chlorination flue gas containing aluminum and fluorine and obtaining a second gaseous phase silicon tetrafluoride and a second circulating liquid phase silicon tetrachloride respectively; the temperature of the third cooling section is 70℃, and the temperature of the fourth cooling section is 20℃.

[0127] The temperature of the gasification is 70℃.

[0128] Example 2

[0129] On the basis of the disclosure of Example 1, the following modifications are further made:

[0130] The temperature of the first chlorination reaction is 700℃, and the time of the first chlorination reaction is 0.5h;

[0131] The temperature of the second chlorination reaction is 900℃, and the time of the second chlorination reaction is 0.5h.

[0132] The pH value of the redox reaction is 6, and the time of the redox reaction is 2h.

[0133] The pH value of the precipitation reaction is 10.

[0134] The first multi-stage condensation includes a first cooling section and a second cooling section, the first cooling section is used for condensing the first chlorination flue gas containing iron and fluorine and obtaining an iron-containing solid phase, and the second cooling section is used for condensing the first chlorination flue gas containing iron and fluorine and obtaining a first gaseous phase silicon tetrafluoride and a first circulating liquid phase silicon tetrachloride respectively, the temperature of the first cooling section is 290℃, and the temperature of the second cooling section is 50℃.

[0135] The second multi-stage condensation includes a third cooling section and a fourth cooling section, the third cooling section is used for condensing the second chlorination flue gas containing aluminum and fluorine and obtaining an aluminum-containing solid phase, and the fourth cooling section is used for condensing the second chlorination flue gas containing aluminum and fluorine and obtaining a second gaseous phase silicon tetrafluoride and a second circulating liquid phase silicon tetrachloride respectively; the temperature of the third cooling section is 170℃, and the temperature of the fourth cooling section is 50℃.

[0136] The temperature of the gasification is 100℃.

[0137] Example 3

[0138] On the basis of the disclosure of Example 1, the following modifications are further made:

[0139] The temperature of the first chlorination reaction is 600 DEG C, and the time of the first chlorination reaction is 1h;

[0140] The temperature of the second chlorination reaction is 850 DEG C, and the time of the second chlorination reaction is 1h.

[0141] The pH of the redox reaction is 5, and the time of the redox reaction is 1h.

[0142] The pH of the precipitation reaction is 9.

[0143] The first multi-stage condensation includes a first cooling section and a second cooling section, the first cooling section is used for condensing the first chlorination flue gas containing iron and fluorine and obtaining an iron-containing solid phase, and the second cooling section is used for condensing the first chlorination flue gas containing iron and fluorine and obtaining a first gaseous phase silicon tetrafluoride and a first circulating liquid phase silicon tetrachloride respectively, the temperature of the first cooling section is 150 DEG C, and the temperature of the second cooling section is 30 DEG C.

[0144] The second multi-stage condensation includes a third cooling section and a fourth cooling section, the third cooling section is used for condensing the second chlorination flue gas containing aluminum and fluorine and obtaining an aluminum-containing solid phase, and the fourth cooling section is used for condensing the second chlorination flue gas containing aluminum and fluorine and obtaining a second gaseous phase silicon tetrafluoride and a second circulating liquid phase silicon tetrachloride respectively, the temperature of the third cooling section is 120 DEG C, and the temperature of the fourth cooling section is 35 DEG C.

[0145] The temperature of the gasification is 85 DEG C.

[0146] Related experiments and effect data:

[0147] The yields of aluminum elements in the aluminum-containing solid phase, iron elements in the iron-containing solid phase, and chromium elements in the trivalent chromium-containing solution obtained in each embodiment are counted, and the recovery rates of aluminum, iron, and chromium and other valuable elements are calculated, and the weight content of cyanide in the cyanide removal material and the weight content of hexavalent chromium are counted, and the results are shown in Table 1.

[0148] Table 1: Recovery rates of valuable elements and weight contents of cyanide and hexavalent chromium in cyanide removal materials of each embodiment

[0149]

[0150]

[0151] As shown in Table 1, the method provided by the embodiments of the present application can simultaneously improve the removal rate of toxic elements in the overhaul slag and the chromium-containing aluminum slurry to more than 99.95% and the recovery rate of aluminum, iron, and chromium and other valuable elements to more than 95% through the redox reaction, the precipitation reaction, and the multiple chlorination reactions.

[0152] In summary, the method for cooperatively recovering valuable elements of the overhaul slag and the chromium-containing aluminum sludge provided by the embodiments of the present application cooperatively detoxifies by using the redox characteristics of the chromium-containing aluminum sludge and the overhaul slag, and further recovers valuable elements such as aluminum, chromium and iron through multiple chlorination reactions. Therefore, the method not only realizes the harmless treatment of the overhaul slag and the chromium-containing aluminum sludge, but also effectively recovers valuable elements such as chromium, aluminum and iron of the two.

[0153] In addition, the method for cooperatively recovering valuable elements of the overhaul slag and the chromium-containing aluminum sludge provided by the embodiments of the present application can improve the reaction rate and the reaction degree of the first chlorination reaction and the second chlorination reaction based on the characteristics that the carbon of the overhaul slag and the first chromium-containing chlorination slag has a fast heating rate and is uniformly heated, so as to promote the valuable elements such as aluminum, chromium, iron and fluorine of the precipitated material to be fully converted into aluminum-containing chlorides, chromium-containing chlorides, iron-containing chlorides and silicon tetrafluoride.

[0154] In addition, the method for cooperatively recovering valuable elements of the overhaul slag and the chromium-containing aluminum sludge provided by the embodiments of the present application can also recover the heat of the chromium-containing chlorination slag obtained through the chlorination reaction at each stage, and use the recovered heat to preheat silicon tetrachloride, so as to realize the recycling of heat and improve the energy utilization rate of the method. In addition, the method can also regenerate silicon tetrachloride through separation and purification, and therefore has good economic and social benefits.

[0155] The above only describes specific embodiments of the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined in the present application can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown in the present application, but will conform to the widest scope consistent with the principles and novel features of the present application.

Claims

1. A method for synergistically recovering valuable elements from overhaul slag and chromium-containing aluminum mud, wherein the overhaul slag contains fluoride, cyanide, iron, and carbon, and the chromium-containing aluminum mud contains aluminum, iron, and hexavalent chromium, the method comprising: Mixing an inorganic acid, the chromium-containing aluminum mud, and the overhaul slag to allow the hexavalent chromium to undergo an oxidation-reduction reaction with the cyanide in an acidic environment to obtain a decyanide material containing fluoride, carbon, aluminum, iron, and chromium; Using an alkaline component to carry out a precipitation reaction on the decyanided material to obtain a precipitate containing carbon, aluminum, chromium, iron and fluorine; mixing first preheated silicon tetrachloride with the precipitate, and subjecting the first preheated silicon tetrachloride to a first chlorination reaction with iron and fluorine in the precipitate under the action of carbon in the precipitate, to produce first chlorinated flue gas containing iron and fluorine and first chromium-containing chlorinated slag containing chromium, aluminum, carbon and fluorine; mixing a second preheated silicon tetrachloride with the first chromium-containing chlorinated slag, and subjecting the second preheated silicon tetrachloride to a second chlorination reaction with chromium, aluminum, and fluorine in the first chromium-containing chlorinated slag under the action of carbon in the first chromium-containing chlorinated slag, to produce a second chlorinated fume containing aluminum and fluorine and a second chromium-containing chlorinated slag; Separating and purifying the first chlorinated flue gas and the second chlorinated flue gas respectively to obtain an aluminum-containing solid phase, an iron-containing solid phase, and silicon tetrafluoride; The second chromium-containing chloride slag is washed to obtain a trivalent chromium-containing solution.

2. The method according to claim 1, wherein the temperature of the first chlorination reaction is 500° C. to 700° C., and the time of the first chlorination reaction is 0.5 h to 2 h; and / or The temperature of the second chlorination reaction is 800° C. to 900° C., and the time of the second chlorination reaction is 0.5 h to 2 h.

3. The method according to claim 1, wherein the first chlorination reaction and the second chlorination reaction are both carried out by microwave heating.

4. The method according to claim 1, wherein the pH of the redox reaction is 4 to 6, and the time of the redox reaction is 0.5 to 2 hours.

5. The method according to claim 1, wherein the weight of cyanide in the decyanation material is less than or equal to 0.05% of the weight of the decyanation material, and the weight of hexavalent chromium in the decyanation material is less than or equal to 0.05% of the weight of the decyanation material. The method according to claim 1 , wherein the pH of the precipitation reaction is 8 to 11.

7. The method according to claim 1, wherein the first chlorinated flue gas and the second chlorinated flue gas are separated and purified to obtain an aluminum-containing solid phase, an iron-containing solid phase, and silicon tetrafluoride, comprising the steps of: performing a first multi-stage condensation on the first chlorinated flue gas to obtain an iron-containing solid phase, a first circulating liquid phase silicon tetrachloride, and a first gaseous phase silicon tetrafluoride; subjecting the second chlorinated flue gas to a second multi-stage condensation to obtain an aluminum-containing solid phase, a second circulating liquid phase of silicon tetrachloride, and a second gaseous phase of silicon tetrafluoride; combining the first gas-phase silicon tetrafluoride and the second gas-phase silicon tetrafluoride to obtain silicon tetrafluoride; The first circulating liquid phase silicon tetrachloride and the second circulating liquid phase silicon tetrachloride are respectively gasified to obtain first circulating gas phase silicon tetrachloride and second circulating gas phase silicon tetrachloride.

8. The method according to claim 7, wherein the first multi-stage condensation comprises a first cooling section and a second cooling section, wherein the first cooling section is used to condense the first chlorinated flue gas containing iron and fluorine and obtain an iron-containing solid phase, and the second cooling section is used to condense the first chlorinated flue gas containing iron and fluorine and obtain a first gaseous phase silicon tetrafluoride and a first circulating liquid phase silicon tetrachloride, respectively. The temperature of the first cooling section is 70°C to 290°C, and the temperature of the second cooling section is 20°C to 50°C.

9. The method according to claim 7, wherein the second multi-stage condensation comprises a third cooling section and a fourth cooling section, wherein the third cooling section is used to condense the second chlorinated flue gas containing aluminum and fluorine and obtain an aluminum-containing solid phase, and the fourth cooling section is used to condense the second chlorinated flue gas containing aluminum and fluorine and obtain a second gaseous phase silicon tetrafluoride and a second circulating liquid phase silicon tetrachloride, respectively; the temperature of the third cooling section is 70°C to 170°C, and the temperature of the fourth cooling section is 20°C to 50°C.

10. The method according to any one of claims 7 to 9, wherein before washing the second chromium-containing chloride slag to obtain the trivalent chromium-containing solution, after gasifying the first circulating liquid phase silicon tetrachloride and the second circulating liquid phase silicon tetrachloride to obtain the first circulating gas phase silicon tetrachloride and the second circulating gas phase silicon tetrachloride, the method further comprises: Gasifying and classifying silicon tetrachloride to obtain first gaseous silicon tetrachloride and second gaseous silicon tetrachloride; introducing the first gaseous silicon tetrachloride and the first circulating gaseous silicon tetrachloride into the first chromium-containing chloride slag for heat exchange to obtain first preheated silicon tetrachloride; The second gaseous phase silicon tetrachloride and the second circulating gaseous phase silicon tetrachloride are respectively introduced into the second chromium-containing chloride slag for heat exchange to obtain second preheated silicon tetrachloride.

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