Method for synergistically recovering valuable elements of overhaul slag and chromium-containing aluminum mud

Abstract

The invention relates to the technical field of hazardous waste resource utilization, in particular to a method for synergistically recovering valuable elements of overhaul slag and chromium-containing aluminum mud. The method comprises the following steps: mixing inorganic acid, chromium-containing aluminum mud and overhaul slag to obtain a decyanation material; carrying out a precipitation reaction on the decyanation material by using an alkaline component to obtain a precipitation material; mixing the first preheated silicon tetrachloride with the precipitation material to obtain first chlorinated flue gas and first chromium-containing chlorinated slag; mixing the second preheated silicon tetrachloride with the first chromium-containing chlorinated slag to obtain second chlorinated flue gas and second chromium-containing chlorinated slag; respectively separating and purifying the first chlorinated flue gas and the second chlorinated flue gas to obtain an aluminum-containing solid phase, an iron-containing solid phase and silicon tetrafluoride; and washing the second chromium-containing chloride slag to obtain a trivalent chromium-containing solution. According to the method, the removal rate of toxic elements of the overhaul slag and the chromium-containing aluminum mud can be synchronously increased to 99.95% or above, and the recovery rate of valuable elements such as aluminum, iron and chromium can be synchronously increased to 95% or above.

Description

Technical Field

[0001] The present application relates to the technical field of resource utilization of hazardous wastes, and in particular to a method for collaboratively recovering valuable elements from overhaul slag and chromium-aluminum-containing mud. Background Art

[0002] The inner lining of the electrolytic aluminum cell is corroded by electrolytes, high-temperature aluminum liquid, etc. for a long time, which makes it easy for the electrolyte to penetrate into the inner lining of the electrolytic aluminum cell, causing damage, deformation, or even rupture of the inner lining. In order to avoid further damage to the inner lining, the material of the penetrated part needs to be replaced, and the replaced material is called overhaul slag. At present, the main components of overhaul slag include waste cathode carbon blocks, waste refractory materials, and waste insulation materials. The weight content of carbon in the waste cathode carbon blocks is 30% to 70%, the weight content of fluoride is 30% to 50%, and the weight content of cyanide is about 0.2%. The main components of waste refractory materials and waste insulation materials include silicon nitride and silicon carbide. In addition, the overhaul slag also contains trace amounts of cyanide, which may be formed by the reaction of sodium intruding into the ends and edges of the electrolytic aluminum cell with nitrogen in the air at a high temperature of 800°C. Although differences in electrolyte composition, current capacity, operating procedures, and lining replacement time of aluminum electrolytic cells will lead to differences in the specific composition of overhaul slag, the main components of overhaul slag are basically the same at this stage, including carbon, fluoride, and a small amount of sodium, aluminum, calcium, iron, silicon, lithium, and cyanide. Due to the fact that overhaul slag contains a large amount of soluble fluoride and cyanide, overhaul slag has been listed as hazardous waste. Direct storage or landfill treatment of overhaul slag will seriously affect the environment and even endanger human health. Therefore, the harmless treatment and high-value utilization of overhaul slag are of great significance to the green and high-quality development of the aluminum industry. In addition, there are two main methods for industrial production of sodium dichromate: calcium roasting method and calcium-free roasting method. Compared with calcium roasting method, calcium-free roasting method is cleaner and more efficient. However, since aluminum silicon compounds in calcium-free roasting will react with soda ash to form more sodium silicate and sodium aluminate, these sodium silicate and sodium aluminate will enter the alkaline leachate and produce a large amount of chromium-containing aluminum mud, which is about 5 to 10 times that of calcium roasting method; chromium-containing aluminum mud generally contains hexavalent chromium, which makes chromium-containing aluminum mud highly toxic, so chromium-containing aluminum mud is listed as hazardous waste. If the chromium-containing aluminum mud is directly piled up or discharged directly, it will cause serious harm to the environment.

[0003] At present, overhaul slag and chromium-aluminum mud are generally treated directly, mainly for harmless treatment. The current technology makes it difficult to effectively recycle chromium, aluminum and iron simultaneously. Summary of the invention

[0004] The present application provides a method for collaboratively recovering valuable elements from overhaul slag and chromium-aluminium mud to solve the following technical problem: how to improve the recovery rate of chromium, aluminium and iron from overhaul slag and chromium-aluminium mud.

[0005] In a first aspect, the present application provides 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, and the method comprises:

[0006] Mixing an inorganic acid, the chromium-containing aluminum mud and the overhaul slag, so that the hexavalent chromium and the cyanide undergo an oxidation-reduction reaction in an acidic environment to obtain a decyanide material containing fluoride, carbon, aluminum, iron and chromium;

[0007] Using an alkaline component to carry out a precipitation reaction on the decyanation material to obtain a precipitate containing carbon, aluminum, chromium, iron and fluorine;

[0008] The first preheated silicon tetrachloride is mixed with the precipitate, and under the action of the carbon in the precipitate, the first preheated silicon tetrachloride and the iron and fluorine in the precipitate undergo a first chlorination reaction to obtain a first chlorinated flue gas containing iron and fluorine and a first chromium-containing chlorinated slag containing chromium, aluminum, carbon and fluorine;

[0009] mixing the second preheated silicon tetrachloride with the first chromium-containing chlorinated slag, and under the action of the carbon in the first chromium-containing chlorinated slag, causing the second preheated silicon tetrachloride to undergo a second chlorination reaction with chromium, aluminum and fluorine in the first chromium-containing chlorinated slag to obtain a second chlorinated fume containing aluminum and fluorine and a second chromium-containing chlorinated slag;

[0010] 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;

[0011] The second chromium-containing chloride slag is washed to obtain a trivalent chromium-containing solution.

[0012] Optionally, 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

[0013] 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.

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

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

[0016] Optionally, 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.

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

[0018] Optionally, the first chlorinated flue gas and the second chlorinated flue gas are separated and purified respectively to obtain an aluminum-containing solid phase, an iron-containing solid phase and silicon tetrafluoride, comprising the steps of:

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

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

[0021] combining the first gas-phase silicon tetrafluoride and the second gas-phase silicon tetrafluoride to obtain silicon tetrafluoride;

[0022] 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.

[0023] Optionally, 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 chlorinated flue gas containing iron and fluorine and obtain an iron-containing solid phase, the second cooling section is used to condense the first chlorinated flue gas containing iron and fluorine and obtain a first gas 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.

[0024] Optionally, the second multi-stage condensation includes a third cooling section and a fourth cooling section, 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 gas 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.

[0025] Optionally, before washing the second chromium-containing chlorinated slag to obtain the trivalent chromium-containing solution, after respectively 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 comprises:

[0026] Gasifying and classifying silicon tetrachloride to obtain first gas phase silicon tetrachloride and second gas phase silicon tetrachloride respectively;

[0027] introducing the first gaseous phase silicon tetrachloride and the first circulating gaseous phase silicon tetrachloride into the first chromium-containing chlorinated slag 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 chlorinated 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 embodiment of the present application provides a method for synergistically recovering valuable elements from overhaul slag and chromium-aluminum mud, which is intended to simultaneously treat overhaul slag (containing fluoride, cyanide, iron and carbon) and chromium-aluminum mud (containing aluminum, iron and hexavalent chromium), and achieve the removal of toxic elements and the recovery of valuable elements through a series of chemical reactions, including: an oxidation-reduction reaction step: mixing an inorganic acid, chromium-aluminum mud and overhaul slag, and using the acidic environment of the inorganic acid to promote the reaction of hexavalent chromium with cyanide, thereby removing cyanide. In this step, hexavalent chromium acts as an oxidant and undergoes an oxidation-reduction reaction with cyanide to generate harmless or low-toxic products. As a result, a decyanided material containing fluoride, carbon, aluminum, iron and chromium is obtained; precipitation reaction step: using an alkaline component (such as ammonia water or calcium oxide) to carry out a precipitation reaction on the decyanided material to remove chromium, aluminum, iron and fluoride therein; in addition, the precipitation reaction forms precipitates such as calcium fluoride, aluminum hydroxide, iron hydroxide, etc., thereby achieving the separation of these elements, and as a result, a precipitate containing carbon, aluminum, chromium, iron and fluorine (partially unprecipitated) is obtained. The chlorination reaction step comprises: using a first preheated chlorine gas to carry out a first chlorination reaction on the precipitate, using the 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 produces a first chlorinated flue gas containing iron and fluorine and a first chromium-containing chlorinated 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; in addition, the first chromium-containing chlorinated slag undergoes a second chlorination reaction, using the carbon of the first chromium-containing chlorinated 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 produces a second chlorinated flue gas containing aluminum and fluorine and a second chromium-containing chlorinated 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 chlorinated slag can be washed to obtain a trivalent chromium-containing solution, thereby realizing chromium recovery; therefore, the method removes toxic elements of overhaul slag and chromium-containing aluminum mud through redox reaction, and then through multiple chlorinations, aluminum, iron and chromium can be effectively recovered. 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 drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0033] Figure 1 A schematic flow chart of a method for collaboratively recovering valuable elements from overhaul slag and chromium-aluminum mud provided in an embodiment of the present application;

[0034] Figure 2 A detailed schematic diagram of a method for collaboratively recovering valuable elements from overhaul slag and chromium-aluminum mud provided in an embodiment of the present application;

[0035] Figure 3 A schematic diagram of the actual process flow of a method for collaboratively recovering valuable elements from overhaul slag and chromium-aluminum-containing mud provided in an embodiment of the present application. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0037] Various embodiments of the present application may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity and should not be understood as a rigid limitation on the scope of the present application; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within 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 within the range, such as 1, 2, 3, 4, 5 and 6, which applies regardless of the range; in addition, whenever a numerical range is indicated in this document, it is meant to include any cited number (fractional or integer) within the indicated range.

[0038] In this document, the terms including "including" and "including" mean "including but not limited to". Relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. "And / or" describes the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone; where A and B can be singular or plural. "At least one" means one or more, and "plurality" means two or more; "at least one", "at least one of the following" or similar expressions, refers to any combination of these items, including any combination of single or plural items; for example, "at least one of a, b, or c", or "at least one of a, b, and c" can all mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple. "Parts" such as parts by weight and parts by mass indicate the proportional relationship between the components. In the proportional relationship involved in this article, the parameters that need to be described by proportion should be understood as the first term of the proportional formula in the order of description, and the proportional numbers should be understood as the second term of the proportional formula. For example, if the mass ratio of substance A, substance B and substance C is 1:2:3, then substance A, substance B and substance C should correspond to the proportional numbers in the proportional formula in the order of description, that is, the mass of substance A: the mass of substance B: the mass of substance C

[0039] =1:2:3.

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

[0041] Figure 1 A schematic flow chart of a method for collaboratively recovering valuable elements from overhaul slag and chromium-aluminum-containing mud provided in an embodiment of the present application is exemplarily shown;

[0042] like Figure 1 As shown, the embodiment of the present application provides a method for collaboratively 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, and the method comprises:

[0043] S1. Mixing an inorganic acid, the chromium-containing aluminum mud and the overhaul slag, so that the hexavalent chromium and the cyanide undergo an oxidation-reduction reaction in an acidic environment to obtain a decyanide material containing fluoride, carbon, aluminum, iron and chromium;

[0044] S2. using an alkaline component to carry out a precipitation reaction of the decyanation material to obtain a precipitate containing carbon, aluminum, chromium, iron and fluorine;

[0045] S3. mixing the first preheated silicon tetrachloride with the precipitate, and under the action of the carbon in the precipitate, subjecting the first preheated silicon tetrachloride to a first chlorination reaction with the 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;

[0046] S4. mixing the 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 obtain a second chlorinated fume containing aluminum and fluorine and a second chromium-containing chlorinated slag;

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

[0048] S6. Washing the second chromium-containing chloride slag to obtain a trivalent chromium-containing solution.

[0049] It should be noted that the carbon in the overhaul slag can significantly improve the fluidization quality of the chromium-aluminum mud and can effectively promote the redox reaction; the carbon in the overhaul slag can be carbon or silicon carbide; when the carbon in the overhaul slag is carbon, there will be partial loss of carbon during the first chlorination reaction and the second chlorination reaction, and when the carbon in the overhaul slag is silicon carbide, based on the stable characteristics of silicon carbide, the loss of silicon carbide during the first chlorination reaction and the second chlorination reaction is relatively small.

[0050] It should be noted that the precipitate needs to be purified before the chlorination reaction to remove moisture from the precipitate and avoid loss of preheated chlorine. The purification process may be a drying process.

[0051] It should be noted that the temperature of the first preheated silicon tetrachloride can be lower than the working temperature of the first chlorination reaction. The temperature of the first preheated silicon tetrachloride is determined according to the actual heat exchange conditions. 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 during the microwave heating stage of the first chlorination reaction. Similarly, the temperature of the second preheated silicon tetrachloride also needs to be clearly controlled.

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

[0053] It should be noted that the inorganic acid may be hydrochloric acid 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 chloride salt, iron-containing chloride salt and aluminum-containing chloride salt.

[0054] It should be noted that the alkaline component can be ammonia water or an alkaline metal oxide. When the alkaline metal oxide is calcium oxide, the fluorine in the precipitate exists in the form of calcium fluoride. In this case, the product obtained by the precipitation reaction includes, in addition to the precipitate, a waste liquid containing calcium and other unreacted impurities. The waste liquid can be subjected to subsequent treatment to obtain a harmless waste liquid. When the alkaline component is ammonia water, the precipitated fluorine exists in the form of fluorine of a compound (aluminum fluoride). In this case, the product obtained by the precipitation reaction includes, in addition to the precipitate, a mixed solution formed by some unreacted ammonia water and soluble fluorine. The mixed solution needs to be treated with a calcium-containing compound (generally calcium oxide) first, and then subjected to subsequent treatment to obtain a harmless waste liquid.

[0055] It should be noted that the second chromium-containing chloride slag can be washed to remove chromium chloride, thereby obtaining a high-purity trivalent chromium-containing solution.

[0056] It should be noted that the overhaul slag needs to be ground before use to control the particle size of the overhaul slag to <10μm; the overhaul slag at this particle size has a higher specific surface area, and the overhaul slag with a higher specific surface area can increase the area of ​​its reaction contact surface with the chromium-aluminum mud, so that the cyanide in the overhaul slag can fully undergo redox reaction with the hexavalent chromium in the chromium-aluminum mud.

[0057] It should be noted that the first preheated silicon tetrachloride and the second preheated silicon tetrachloride can use silicon tetrachloride, a hazardous waste generated in the polysilicon production process, as the chlorinating agent.

[0058] It should be noted that the tailings of the second chromium-containing chloride slag after washing can be used as harmless tailings in multiple fields such as construction and filler.

[0059] In summary, the embodiment of the present application provides a method for synergistically recovering valuable elements from overhaul slag and chromium-aluminum mud. The method can effectively remove toxic elements (such as cyanide and hexavalent chromium) from overhaul slag and chromium-aluminum mud through oxidation-reduction reaction, precipitation reaction and chlorination reaction, and realize efficient recovery of valuable elements (such as aluminum, iron and chromium). Specifically:

[0060] (1) Removal of toxic elements: Through redox reactions and precipitation reactions, cyanide and hexavalent chromium are converted into harmless or low-toxic 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, and high-purity valuable element products are obtained through subsequent purification steps.

[0062] (3) Environmentally friendly: The by-products produced during the entire process (such as ammonia, carbon dioxide, silicon tetrafluoride, etc.) are harmless or low-toxic substances and meet environmental protection requirements.

[0063] Therefore, this method realizes the synchronous recycling of valuable elements in overhaul slag and chromium-aluminum mud through a series of chemical reactions, which not only improves the removal effect of toxic elements, but also effectively improves the recovery rate of valuable elements, and realizes efficient recycling of resources. This provides a new idea and method for solving the problem of industrial waste, and helps to achieve sustainable utilization of resources and environmental protection.

[0064] In some optional embodiments, 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

[0065] 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.

[0066] In these embodiments, the temperature of the first chlorination reaction can be 500°C to 700°C, and the time of the second chlorination reaction can be 0.5h to 2h. Under the action of the carbon of the precipitate, the first preheated silicon tetrachloride and the iron and fluorine of the precipitate are fully reacted through the first chlorination reaction 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°C to 900°C, and the time of the second chlorination reaction can be 0.5h to 2h. Under the action of the carbon of the first chromium-containing chloride slag, the second chlorination reaction is used to promote the chromium, aluminum and fluorine of the second preheated silicon tetrachloride and the first chromium-containing chloride slag to fully react 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 may 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 0.5 h, 1.0 h, 1.5 h or 2.0 h.

[0069] The temperature of the second chlorination reaction may 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 second chlorination reaction time can be 0.5 h, 1.0 h, 1.5 h or 2.0 h.

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

[0072] In these embodiments, the first chlorination reaction and the second chlorination reaction are both carried out by microwave heating. During the microwave heating process, the carbon of the precipitate and the carbon of the first chromium-containing chlorination slag can be used as a high-efficiency absorbing material to absorb and preserve the energy transmitted by microwave heating. The carbon with sufficient energy can not only promote the rapid heating of the precipitate and the first chromium-containing chlorination slag, so as to promote the temperature of the precipitate to meet the requirements of the first chlorination reaction and the temperature of the first chromium-containing chlorination slag to meet the requirements of the second chlorination reaction, but also can evenly disperse other materials of the precipitate during the microwave heating stage; in addition, the carbon of the precipitate and the carbon of the first chromium-containing chlorination slag can also be used as a carbon source to increase the intensity of the first chlorination reaction and the second chlorination reaction, so as to promote the reaction of chromium, iron, aluminum and fluorine to generate chromium-containing chloride salt, aluminum-containing chloride salt, iron-containing chloride salt and silicon tetrafluoride.

[0073] In some optional embodiments, the pH of the redox reaction is 4 to 6, and the time of the redox reaction is 0.5 h to 2 h;

[0074] In these embodiments, the pH of the redox reaction can be 4 to 6, and the time of the redox reaction can be 0.5 h to 2 h. In the acidic environment of inorganic acid, the hexavalent chromium of the chromium-aluminum mud and the cyanide of the overhaul slag can fully react to promote the oxidation of cyanide to generate harmless carbon dioxide and nitrogen and promote the hexavalent chromium to be reduced to harmless trivalent chromium, thereby effectively removing toxic elements in the chromium-aluminum mud and the overhaul slag.

[0075] The pH of the redox reaction may 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 redox reaction time may be 0.5 h, 1 h, 1.5 h or 2 h.

[0077] In some optional embodiments, 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;

[0078] In these embodiments, the weight of cyanide in the cyanide material can be less than or equal to 0.05% of the weight of the decyanide material, and the weight of hexavalent chromium in the decyanide material can be less than or equal to 0.05% of the weight of the decyanide material, which indicates that the hexavalent chromium of the chromium-aluminum mud and the cyanide of the overhaul slag have been fully reacted during the redox reaction.

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

[0080] In these embodiments, the pH of the precipitation reaction can be 8 to 11, which means 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 of the decyanide material into precipitate material; in addition, when the alkaline component is calcium oxide, the calcium of the calcium oxide can react with the fluorine of the decyanide material to obtain a calcium fluoride precipitate in an alkaline environment, thereby facilitating subsequent recovery and treatment.

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

[0082] Figure 2 A detailed schematic diagram of a method for collaboratively recovering valuable elements from overhaul slag and chromium-aluminum mud provided in an embodiment of the present application is exemplarily shown;

[0083] Figure 3 An actual flow chart of a method for collaboratively recovering valuable elements from overhaul slag and chromium-aluminum-containing mud provided in an embodiment of the present application is exemplarily shown;

[0084] In some optional embodiments, such as Figure 2 and Figure 3 As shown, the first chlorinated flue gas and the second chlorinated flue gas are separated and purified respectively to obtain an aluminum-containing solid phase, an iron-containing solid phase and silicon tetrafluoride, comprising the steps of:

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

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

[0087] S503. Combining the first gas phase silicon tetrafluoride and the second gas phase silicon tetrafluoride to obtain silicon tetrafluoride;

[0088] S504. 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;

[0089] In these embodiments, the separation and purification of different chlorinated flue gases uses a multi-stage condensation separation and gasification method. Through the first multi-stage condensation separation, the iron-containing solid phase of the first chlorinated flue gas containing iron and fluorine and silicon tetrafluoride can be condensed and precipitated according to the boiling point difference between the two, thereby realizing the recovery of iron and fluorine; through the second multi-stage condensation separation, the aluminum-containing solid phase of the second chlorinated flue gas containing aluminum and fluorine and silicon tetrafluoride can be condensed and precipitated according to the boiling point difference between the two, thereby realizing the recovery of aluminum and fluorine; in addition, the precipitated first circulating liquid phase silicon tetrachloride and the second circulating liquid phase silicon tetrachloride are gasified to realize the regeneration of silicon tetrachloride.

[0090] It should be noted that the gasification temperature may be 70°C to 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 chlorinated flue gas containing iron and fluorine and obtain an iron-containing solid phase, the second cooling section is used to condense the first chlorinated flue gas containing iron and fluorine and obtain a first gas 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;

[0092] In these embodiments, the first multi-stage condensation may include a first cooling section, and the first cooling section may be used to condense the first chlorinated flue gas containing iron and fluorine and obtain an iron-containing solid phase, and the temperature of the first cooling section may be 70°C to 290°C, and the iron chloride component may be condensed into an iron-containing solid phase according to the difference in boiling points between the iron chloride component and other components of the first chlorinated flue gas to achieve iron recovery; in addition, the first multi-stage condensation may include a second cooling section, and the second cooling section is used to condense the first chlorinated flue gas containing iron and fluorine and obtain a first gas phase silicon tetrafluoride and a first circulating liquid phase silicon tetrachloride, respectively, and the temperature of the second cooling section may be 20°C to 50°C, and the silicon tetrachloride component may be condensed into a first circulating liquid phase silicon tetrachloride according to the difference in boiling points between silicon tetrafluoride and silicon tetrachloride in the first chlorinated flue gas to achieve separation of silicon tetrafluoride and silicon tetrachloride, facilitating the subsequent regeneration of silicon tetrachloride by gasification, thereby facilitating the recycling of silicon tetrachloride.

[0093] The temperature of the first cooling section may 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 may 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 includes a third cooling section and a fourth cooling section, the third cooling section is used to condense the second chlorinated flue gas containing aluminum and fluorine to obtain an aluminum-containing solid phase, and the fourth cooling section is used to condense the second chlorinated flue gas containing aluminum and fluorine to obtain a second gas 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;

[0096] In these embodiments, the second multi-stage condensation may include a third cooling section, and the third cooling section may be used to condense the second chlorinated flue gas containing aluminum and fluorine and obtain an aluminum-containing solid phase, and the temperature of the third cooling section may be 70°C to 170°C, and the aluminum chloride component is condensed into an aluminum-containing solid phase according to the difference in boiling points between the aluminum chloride component and other components of the second chlorinated flue gas to achieve aluminum recovery; in addition, the second multi-stage condensation may include a fourth cooling section, and the fourth cooling section may be used to condense the second chlorinated flue gas containing aluminum and fluorine and obtain a second gas phase silicon tetrafluoride and a second circulating liquid phase silicon tetrachloride, respectively, and the temperature of the fourth cooling section may be 20°C to 50°C, and the silicon tetrachloride component may be condensed into a second circulating liquid phase silicon tetrachloride according to the difference in boiling points between silicon tetrafluoride and silicon tetrachloride in the second chlorinated flue gas, thereby achieving separation of silicon tetrafluoride and silicon tetrachloride, facilitating subsequent regeneration of silicon tetrachloride by gasification, thereby facilitating the recycling of silicon tetrachloride.

[0097] The temperature of the third cooling section may 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 washing the second chromium-containing chlorinated slag to obtain a trivalent chromium-containing solution, after gasifying the first circulating liquid phase silicon tetrachloride and the second circulating liquid phase silicon tetrachloride to obtain a first circulating gas phase silicon tetrachloride and a second circulating gas phase silicon tetrachloride, the method comprises:

[0100] S601. The silicon tetrachloride is gasified and classified to obtain a first gas phase silicon tetrachloride and a second gas phase silicon tetrachloride;

[0101] S602. introducing the first gaseous silicon tetrachloride and the first circulating gaseous silicon tetrachloride into the first chromium-containing chlorinated slag for heat exchange to obtain first preheated silicon tetrachloride;

[0102] S603. introducing the second gaseous silicon tetrachloride and the second circulating gaseous silicon tetrachloride into the second chromium-containing chlorinated slag for heat exchange to 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 in conjunction with specific examples. The experimental methods in the following examples that do not specify specific conditions are usually measured in accordance with national standards / industry standards; if there are no corresponding national standards / industry standards, they are measured in accordance with common 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-aluminum mud, wherein the overhaul slag contains fluoride, cyanide, iron and carbon, and the chromium-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 decyanation 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 the carbon of the precipitate, the first preheated silicon tetrachloride and the iron and fluorine of the precipitate are subjected to a first chlorination reaction 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 of the first chromium-containing chloride slag, the second preheated silicon tetrachloride and the chromium, aluminum and fluorine of the first chromium-containing chloride slag are subjected to a second chlorination reaction to obtain a second chlorinated flue gas containing aluminum and fluorine and a second chromium-containing chloride slag;

[0111] S501. The first chlorinated flue gas containing iron and fluorine is subjected to a first multi-stage condensation to obtain an iron-containing solid phase, a first circulating liquid phase of silicon tetrachloride and a first gas phase of silicon tetrafluoride;

[0112] S502. The second chlorinated flue gas containing aluminum and fluorine is subjected to a second multi-stage condensation to obtain an aluminum-containing solid phase, a second circulating liquid phase silicon tetrachloride, and a second gas phase silicon tetrafluoride;

[0113] S503. Combining the first gas phase silicon tetrafluoride and the second gas phase silicon tetrafluoride to obtain silicon tetrafluoride;

[0114] S504. The first circulating liquid phase silicon tetrachloride and the second circulating liquid phase silicon tetrachloride are respectively gasified to obtain the first circulating gas phase silicon tetrachloride and the second circulating gas phase silicon tetrachloride;

[0115] S601. The silicon tetrachloride is gasified and classified to obtain a first gas phase silicon tetrachloride and a second gas phase silicon tetrachloride;

[0116] S602. The first gaseous silicon tetrachloride and the first circulating gaseous silicon tetrachloride are introduced into the first chromium-containing chloride slag for heat exchange to obtain a first preheated silicon tetrachloride;

[0117] S603. introducing the second gas phase silicon tetrafluoride and the second circulating gas phase silicon tetrachloride into the second chromium-containing chloride slag for heat exchange to obtain a second preheated silicon tetrachloride;

[0118] S6. Washing the second chromium-containing chloride slag to obtain a trivalent chromium-containing solution.

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

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

[0121] The first chlorination reaction and the second chlorination reaction are both carried out by microwave heating.

[0122] The pH value of the redox reaction is 4, and the time of the redox reaction is 0.5h.

[0123] 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.

[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 to condense the first chlorinated flue gas containing iron and fluorine and obtain an iron-containing solid phase. The second cooling section is used to condense the first chlorinated flue gas containing iron and fluorine and obtain a first gas phase silicon tetrafluoride and a first circulating liquid phase silicon tetrachloride, respectively. The temperature of the first cooling section is 70°C, and the temperature of the second cooling section is 20°C.

[0126] The second multi-stage condensation includes a third cooling section and a fourth cooling section. The third cooling section is used to condense the second chlorinated flue gas containing aluminum and fluorine and obtain an aluminum-containing solid phase. The fourth cooling section is used to condense the second chlorinated flue gas containing aluminum and fluorine and obtain a second gas phase silicon tetrafluoride and a second circulating liquid phase silicon tetrachloride respectively. The temperature of the third cooling section is 70°C, and the temperature of the fourth cooling section is 20°C.

[0127] The temperature of gasification is 70°C.

[0128] Example 2

[0129] Based on the contents disclosed in Example 1, the following modifications are further made:

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

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

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

[0133] The pH 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 to condense the first chlorinated flue gas containing iron and fluorine and obtain an iron-containing solid phase. The second cooling section is used to condense the first chlorinated flue gas containing iron and fluorine and obtain a first gas phase silicon tetrafluoride and a first circulating liquid phase silicon tetrachloride, respectively. The temperature of the first cooling section is 290°C, and the temperature of the second cooling section is 50°C.

[0135] The second multi-stage condensation includes a third cooling section and a fourth cooling section. The third cooling section is used to condense the second chlorinated flue gas containing aluminum and fluorine and obtain an aluminum-containing solid phase. The fourth cooling section is used to condense the second chlorinated flue gas containing aluminum and fluorine and obtain a second gas phase silicon tetrafluoride and a second circulating liquid phase silicon tetrachloride respectively. The temperature of the third cooling section is 170°C, and the temperature of the fourth cooling section is 50°C.

[0136] The temperature of gasification is 100°C.

[0137] Example 3

[0138] Based on the contents disclosed in Example 1, the following modifications are further made:

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

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

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

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

[0143] 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 chlorinated flue gas containing iron and fluorine and obtain an iron-containing solid phase. The second cooling section is used to condense the first chlorinated flue gas containing iron and fluorine and obtain a first gas phase silicon tetrafluoride and a first circulating liquid phase silicon tetrachloride, respectively. The temperature of the first cooling section is 150°C, and the temperature of the second cooling section is 30°C.

[0144] The second multi-stage condensation includes a third cooling section and a fourth cooling section. The third cooling section is used to condense the second chlorinated flue gas containing aluminum and fluorine and obtain an aluminum-containing solid phase. The fourth cooling section is used to condense the second chlorinated flue gas containing aluminum and fluorine and obtain a second gas phase silicon tetrafluoride and a second circulating liquid phase silicon tetrachloride respectively. The temperature of the third cooling section is 120°C, and the temperature of the fourth cooling section is 35°C.

[0145] The vaporization temperature is 85°C.

[0146] Related experiments and effect data:

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

[0148] Table 1 The recovery rate of valuable elements in each embodiment and the weight of cyanide and hexavalent chromium content of the decyanation material

[0149]

[0150]

[0151] As can be seen from Table 1, an embodiment of the present application provides a method for synergistically recovering valuable elements from overhaul slag and chromium-aluminum mud. The method uses chromium-aluminum mud and overhaul slag as raw materials and can simultaneously improve the removal rate of toxic elements in overhaul slag and chromium-aluminum mud to more than 99.95% and the recovery rate of valuable elements such as aluminum, iron and chromium to more than 95% through oxidation-reduction reaction, precipitation reaction and multiple chlorination reactions.

[0152] In summary, the embodiment of the present application provides a method for synergistically recovering valuable elements from overhaul slag and chromium-aluminum-containing mud. The method utilizes the redox characteristics of chromium-aluminum-containing mud and overhaul slag for synergistic "detoxification". In addition, valuable elements such as aluminum, chromium and iron are recovered through multiple chlorination reactions. Therefore, the method not only achieves the harmless treatment of overhaul slag and chromium-aluminum-containing mud, but also effectively recovers valuable elements such as chromium, aluminum and iron in the two.

[0153] In addition, the embodiment of the present application provides a method for synergistically recovering valuable elements from overhaul slag and chromium-aluminum mud. Based on the characteristics of fast heating rate and uniform heating of the carbon in the overhaul slag and the first chromium-containing chlorinated slag, the reaction rate and reaction degree of the first chlorination reaction and the second chlorination reaction can be improved, and the valuable elements such as aluminum, chromium, iron and fluorine in the precipitate are fully converted into aluminum-containing chloride salts, chromium-containing chloride salts, iron-containing chloride salts and silicon tetrafluoride.

[0154] In addition, the embodiment of the present application provides a method for synergistically recovering valuable elements from overhaul slag and chromium-aluminum mud. The method can also recover the heat of the chromium-containing chlorination slag obtained from the chlorination reaction at each stage, and use the recovered heat to preheat silicon tetrachloride, thereby realizing the recycling of heat and improving the energy utilization rate of the method; in addition, the method can also achieve the regeneration of silicon tetrachloride through separation and purification, so the method has good economic and social benefits.

[0155] The above description is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. It will be apparent to those skilled in the art that various modifications to these embodiments are possible, 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 the embodiments shown in the present application, but will conform to the widest range consistent with the principles and novel features applied for by the present application.

Claims

1. A method for synergistically recovering valuable elements from overhaul slag and chromium-aluminum mud, wherein the overhaul slag contains fluoride, cyanide, iron and carbon, and the chromium-aluminum mud contains aluminum, iron and hexavalent chromium, the method comprising: Mixing an inorganic acid, the chromium-containing aluminum mud and the overhaul slag, so that the hexavalent chromium and the cyanide undergo an oxidation-reduction reaction 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 decyanation material to obtain a precipitate containing carbon, aluminum, chromium, iron and fluorine; The first preheated silicon tetrachloride is mixed with the precipitate, and under the action of the carbon in the precipitate, the first preheated silicon tetrachloride and the iron and fluorine in the precipitate undergo a first chlorination reaction to obtain a first chlorinated flue gas containing iron and fluorine and a first chromium-containing chlorinated slag containing chromium, aluminum, carbon and fluorine; mixing the second preheated silicon tetrachloride with the first chromium-containing chlorinated slag, and under the action of the carbon in the first chromium-containing chlorinated slag, causing the second preheated silicon tetrachloride to undergo a second chlorination reaction with chromium, aluminum and fluorine in the first chromium-containing chlorinated slag to obtain 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 0.5h to 2h; 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 h to 2 h.

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.

6. 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: The first chlorinated flue gas is subjected to a first multi-stage condensation to obtain an iron-containing solid phase, a first circulating liquid phase silicon tetrachloride and a first gas phase silicon tetrafluoride; The second chlorinated flue gas is subjected to a second multi-stage condensation to obtain an aluminum-containing solid phase, a second circulating liquid phase silicon tetrachloride, and a second gas phase 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 gas phase silicon tetrafluoride and a first circulating liquid phase silicon tetrachloride, respectively, wherein 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 gas 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, before washing the second chromium-containing chlorinated slag to obtain a trivalent chromium-containing solution, after gasifying the first circulating liquid phase silicon tetrachloride and the second circulating liquid phase silicon tetrachloride to obtain a first circulating gas phase silicon tetrachloride and a second circulating gas phase silicon tetrachloride, comprising: Gasifying and classifying silicon tetrachloride to obtain first gas phase silicon tetrachloride and second gas phase silicon tetrachloride respectively; introducing the first gaseous phase silicon tetrachloride and the first circulating gaseous phase silicon tetrachloride into the first chromium-containing chlorinated 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 chlorinated slag for heat exchange to obtain second preheated silicon tetrachloride.

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