Method for recycling 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 recycling overhaul slag and chromium-containing aluminum mud. The overhaul slag contains fluoride, cyanide and carbon, the chromium-containing aluminum mud contains aluminum and hexavalent chromium, and the method comprises the following steps: carrying out redox reaction on inorganic acid, the chromium-containing aluminum mud and the overhaul slag to obtain a decyanation material containing fluoride, carbon, aluminum and chromium; carrying out a precipitation reaction on the decyanation material by using a calcium-containing alkaline oxide to obtain a precipitation material containing chromium, aluminum, carbon and fluorine; carrying out chlorination reaction on the precipitation material by using preheated chlorine to obtain aluminum-containing chlorinated flue gas and chromium-containing chlorinated slag; separating and purifying the aluminum-containing chlorinated flue gas to obtain an aluminum-containing solid phase; and washing the chromium-containing chlorination slag to obtain a trivalent chromium-containing solution. According to the method, the chromium-containing aluminum mud and the overhaul slag are used as raw materials, and the removal effect of toxic elements in the overhaul slag and the chromium-containing aluminum mud and the recovery rate of valuable elements such as aluminum and chromium can be synchronously improved through the oxidation-reduction reaction, the precipitation reaction and the chlorination reaction.

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 recycling overhaul slag and chromium-aluminum mud. Background Art

[0002] The electrolytic aluminum process produces 30kg to 50kg of overhaul slag for every ton of primary aluminum produced. The specific composition of the overhaul slag varies due to differences in electrolyte composition, current capacity, operating procedures, and lining replacement time during the aluminum electrolysis process. However, the main components of the overhaul slag are basically the same, including carbon, fluoride, and a small amount of sodium, aluminum, calcium, iron, silicon, and cyanide. Based on the characteristics of overhaul slag containing a large amount of soluble fluoride and a small amount of cyanide, the overhaul slag has been listed as a hazardous waste; therefore, if the overhaul slag is directly stored or landfilled, it will seriously affect the environment and even endanger human health. This leads to the harmless treatment and high-value utilization of overhaul slag, which is 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] Chromium-aluminum mud contains rich chromium and aluminum resources. By using appropriate methods to comprehensively utilize them, we can not only eliminate environmental pollution, but also effectively promote the green and sustainable development of the chromium salt industry. At present, the coordinated utilization of overhaul slag and chromium-aluminum mud is mainly direct use, which makes it difficult to effectively remove the toxic elements and recover the valuable elements aluminum and chromium. Summary of the invention

[0004] The present application provides a method for recycling overhaul slag and chromium-aluminium mud to solve the following technical problem: how to simultaneously improve the removal effect of toxic elements in overhaul slag and chromium-aluminium mud and the recovery rate of valuable elements.

[0005] In a first aspect, the present application provides a method for recycling overhaul slag and chromium-containing aluminum mud, wherein the overhaul slag contains fluoride, cyanide and carbon, and the chromium-containing aluminum mud contains aluminum 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 and chromium;

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

[0008] The preheated chlorine gas is mixed with the precipitate, and under the action of the carbon in the precipitate, the preheated chlorine gas is reacted with the chromium and aluminum in the precipitate to obtain aluminum-containing chlorinated fume and chromium-containing chlorinated slag;

[0009] Separating and purifying the aluminum-containing chlorinated flue gas to obtain an aluminum-containing solid phase;

[0010] The chromium-containing chloride slag is washed to obtain a trivalent chromium-containing solution.

[0011] Optionally, the temperature of the chlorination reaction is 500° C. to 900° C., and the time of the chlorination reaction is 0.5 h to 3 h.

[0012] Optionally, the chlorination reaction is carried out under microwave heating.

[0013] 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.

[0014] 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.

[0015] Optionally, the pH of the precipitation reaction is 8-11.

[0016] Optionally, the separation and purification of the aluminum-containing chlorinated flue gas to obtain an aluminum-containing solid phase comprises the steps of:

[0017] The aluminum-containing chlorinated flue gas is subjected to multi-stage condensation separation to obtain an aluminum-containing solid phase and liquid chlorine;

[0018] The liquid chlorine is gasified to obtain chlorine gas.

[0019] Optionally, the multi-stage condensation separation includes a first cooling section and a second cooling section, the first cooling section is used to condense the aluminum-containing chlorinated flue gas and obtain an aluminum-containing solid phase, and the second cooling section is used to condense the aluminum-containing chlorinated flue gas and obtain liquid chlorine; the temperature of the first cooling section is 70°C to 170°C, and the temperature of the second cooling section is -70°C to -40°C.

[0020] Optionally, when the overhaul slag also includes iron and silicon, the multi-stage condensation separation also includes a third cooling section and a fourth cooling section, the third cooling section is used to condense the aluminum-containing chlorinated flue gas and obtain an iron-containing solid phase, and the fourth cooling section is used to condense the aluminum-containing chlorinated flue gas and obtain a silicon-containing liquid phase; the temperature of the third cooling section is 190°C to 290°C, and the temperature of the fourth cooling section is 20°C to 50°C.

[0021] Optionally, before washing the chromium-containing chlorinated slag to obtain the trivalent chromium-containing solution, after gasifying the liquid chlorine to obtain chlorine gas, the process comprises:

[0022] The chlorine gas is introduced into the chromium-containing chloride slag for heat exchange to obtain preheated chlorine gas.

[0023] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0024] The embodiment of the present application provides a method for recycling overhaul slag and chromium-containing aluminum mud, which is intended to simultaneously treat overhaul slag (containing fluoride, cyanide and carbon) and chromium-containing aluminum mud (containing aluminum 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-containing aluminum mud and overhaul slag, and using the acidic environment of the inorganic acid to promote the reaction of hexavalent chromium and cyanide, thereby removing cyanide. In this step, hexavalent chromium acts as an oxidant and undergoes an oxidation-reduction reaction with cyanide to generate a harmless or low-toxic product. As a result, a decyanide material containing fluoride, carbon, aluminum and chromium is obtained; a precipitation reaction step: using a calcium-containing alkaline oxide (such as calcium oxide) to perform a precipitation reaction on the decyanide material to remove chromium, aluminum and fluoride therein; in addition, the precipitation reaction forms precipitates such as calcium fluoride and aluminum hydroxide, thereby achieving the separation of these elements, and as a result, a precipitate material containing chromium, aluminum, carbon and fluorine (partially unprecipitated) is obtained. Chlorination reaction step: using preheated chlorine to carry out chlorination reaction on the precipitate, using the carbon in the precipitate as a heating medium to promote the reaction between chromium and aluminum to generate chromium-containing chloride salt and aluminum-containing chloride salt; the chlorination reaction produces aluminum-containing chlorination flue gas and chromium-containing chlorination slag, and the aluminum-containing chlorination flue gas can be further purified through subsequent steps to obtain an aluminum-containing solid phase, and the chromium-containing chlorination slag can be washed to obtain a trivalent chromium-containing solution to achieve chromium recovery. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] 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.

[0026] 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.

[0027] Figure 1 This is a schematic flow chart of a method for recycling overhaul slag and chromium-containing aluminum mud according to an embodiment of the present application;

[0028] Figure 2 A detailed schematic diagram of a method for recycling overhaul slag and chromium-containing aluminum mud according to an embodiment of the present application;

[0029] Figure 3 This is a schematic diagram of the actual process of a method for recycling overhaul slag and chromium-aluminum mud according to an embodiment of the present application. DETAILED DESCRIPTION

[0030] 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.

[0031] 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.

[0032] 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

[0033] =1:2:3.

[0034] 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.

[0035] Figure 1 A schematic flow chart of a method for recycling overhaul slag and chromium-containing aluminum mud in an embodiment of the present application is exemplarily shown;

[0036] like Figure 1 As shown, an embodiment of the present application provides a method for recycling overhaul slag and chromium-containing aluminum mud, wherein the overhaul slag contains fluoride, cyanide and carbon, and the chromium-containing aluminum mud contains aluminum and hexavalent chromium, and the method comprises:

[0037] 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 and chromium;

[0038] S2. using a calcium-containing alkaline oxide to carry out a precipitation reaction of the decyanation material to obtain a precipitate containing chromium, aluminum, carbon and fluorine;

[0039] S3. The preheated chlorine gas is mixed with the precipitate, and under the action of the carbon in the precipitate, the preheated chlorine gas is subjected to a chlorination reaction with the chromium and aluminum in the precipitate to obtain aluminum-containing chlorinated fume and chromium-containing chlorinated slag;

[0040] S4. separating and purifying the aluminum-containing chlorinated flue gas to obtain an aluminum-containing solid phase;

[0041] S5. Washing the chromium-containing chloride slag to obtain a trivalent chromium-containing solution.

[0042] 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.

[0043] 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.

[0044] It should be noted that the temperature of the preheated chlorine gas can be lower than the working temperature of the chlorination reaction. The temperature of the preheated chlorine gas is determined according to the actual heat exchange conditions. No matter what the temperature of the preheated chlorine gas is, it can be quickly heated to the working temperature of the chlorination reaction during the microwave heating stage of the chlorination reaction.

[0045] It should be noted that the 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.

[0046] It should be noted that the inorganic acid may be hydrochloric acid to cooperate with the final chlorination reaction of the preheated chlorine gas to obtain chromium-containing chloride salt and aluminum-containing chloride salt.

[0047] It should be noted that the product obtained from the precipitation reaction includes, in addition to the precipitate, a mixed solution of some calcium chloride and sodium chloride, and the mixed solution can be used to obtain harmless waste liquid through subsequent treatment.

[0048] It should be noted that the chromium-containing chloride slag can be washed to separate chromium chloride and calcium fluoride, and in addition to the trivalent chromium solution, a calcium fluoride product can also be obtained.

[0049] 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.

[0050] In summary, the method for recycling overhaul slag and chromium-containing aluminum mud in the embodiment of the present application has the following advantages:

[0051] 1. Improve the removal effect of toxic elements

[0052] The removal of cyanide through redox reactions reduces the content of toxic substances, and precipitation and chlorination reactions further remove elements such as fluoride, aluminum and chromium that may be harmful to the environment.

[0053] 2. Improve the recovery rate of valuable elements

[0054] The chlorination reaction uses the carbon in the precipitate as a heating medium, which promotes the conversion of chromium and aluminum and improves the recovery rate of valuable elements. In addition, the aluminum-containing chlorinated flue gas can be purified to obtain an aluminum-containing solid phase, thereby realizing aluminum recovery. The chromium-containing chlorinated slag can be washed to obtain a trivalent chromium solution, which provides the possibility for further utilization of chromium.

[0055] This method achieves the simultaneous recycling of 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 increases the recovery rate of valuable elements. 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.

[0056] In some optional embodiments, the temperature of the chlorination reaction is 500°C to 900°C, and the time of the chlorination reaction is 0.5h to 3h;

[0057] In these embodiments, the temperature of the chlorination reaction can be 500° C. to 900° C., and the time of the chlorination reaction can be 0.5 h to 3 h. Under the action of the carbon in the precipitate, the preheated chlorine gas and the chromium and aluminum in the precipitate are fully reacted to obtain chromium-containing chloride salts and aluminum-containing chloride salts, thereby facilitating subsequent separation, purification and washing.

[0058] The temperature of the chlorination reaction may be 500°C, 550°C, 600°C, 650°C, 700°C, 750°C, 800°C, 850°C or 900°C.

[0059] The chlorination reaction time can be 0.5 h, 1.5 h, 2.0 h, 2.5 h or 3.0 h.

[0060] In some optional embodiments, the chlorination reaction comprises being carried out under microwave heating.

[0061] It should be noted that the chlorination reaction can be carried out under microwave heating. During the microwave heating process, the carbon of the precipitate can be used as a high-efficiency absorbing material to absorb and preserve the energy transmitted by microwave heating. Carbon with sufficient energy can not only cause the precipitate to be heated quickly, so that the temperature of the precipitate meets the requirements of the chlorination reaction, but also can evenly disperse other materials of the precipitate during the microwave heating stage; in addition, the carbon of the precipitate can also be used as a carbon source to increase the intensity of the chlorination reaction, so as to promote the reaction of chromium and aluminum to generate chromium-containing chloride salts and aluminum-containing chloride salts.

[0062] 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;

[0063] 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.

[0064] 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.

[0065] The redox reaction time can be 0.5 h, 1 h, 1.5 h or 2 h.

[0066] 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;

[0067] In these embodiments, the weight of cyanide in the decyanide 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.

[0068] In some optional embodiments, the pH of the precipitation reaction is 8 to 11;

[0069] 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 and chromium into hydroxide precipitates, thereby promoting the conversion of aluminum and chromium in the decyanide material into precipitates; in addition, in an alkaline environment, calcium containing calcium oxide can react with fluorine in the decyanide material to obtain calcium fluoride precipitate, thereby facilitating subsequent recovery and treatment.

[0070] The pH of the precipitation reaction can be 8, 8.5, 9.0, 9.5, 10.0, 10.5, or 11.0.

[0071] Figure 2A detailed schematic diagram of a method for recycling overhaul slag and chromium-containing aluminum mud in an embodiment of the present application is exemplarily shown;

[0072] Figure 3 An actual flow chart of a method for recycling overhaul slag and chromium-containing aluminum mud in an embodiment of the present application is exemplarily shown;

[0073] In some optional embodiments, such as Figure 2 and Figure 3 As shown, the aluminum-containing chlorinated flue gas is separated and purified to obtain an aluminum-containing solid phase, comprising the steps of:

[0074] S401. The aluminum-containing chlorinated flue gas is subjected to multi-stage condensation separation to obtain an aluminum-containing solid phase and liquid chlorine;

[0075] S402. The liquid chlorine is gasified to obtain chlorine gas;

[0076] In these embodiments, separation and purification can use multi-stage condensation separation and gasification. Through multi-stage condensation separation, the aluminum-containing solid phase and liquid chlorine in the aluminum-containing chlorinated flue gas can be condensed and precipitated according to the boiling point difference between the two, thereby realizing aluminum recovery; in addition, the precipitated liquid chlorine is gasified to realize chlorine regeneration.

[0077] In some optional embodiments, the multi-stage condensation separation includes a first cooling section and a second cooling section, the first cooling section is used to condense the aluminum-containing chlorinated flue gas to obtain an aluminum-containing solid phase, and the second cooling section is used to condense the aluminum-containing chlorinated flue gas to obtain liquid chlorine; the temperature of the first cooling section is 70°C to 170°C, and the temperature of the second cooling section is -70°C to -40°C;

[0078] In these embodiments, the multi-stage condensation separation may include a first cooling section, and the first cooling section is used to condense the aluminum-containing chlorinated flue gas and obtain an aluminum-containing solid phase, and the temperature of the first cooling section may be 70°C to 170°C, and the aluminum chloride component of the aluminum-containing chlorinated flue gas may be condensed into an aluminum-containing solid phase according to the difference in boiling points between the aluminum chloride component and other components of the aluminum-containing chlorinated flue gas to achieve aluminum recovery; in addition, the multi-stage condensation separation may include a second cooling section, and the second cooling section is used to condense the aluminum-containing chlorinated flue gas and obtain liquid chlorine, and the temperature of the second cooling section may be -70°C to -40°C, and the chlorine component of the aluminum-containing chlorinated flue gas may be condensed into liquid chlorine according to the difference in boiling points between the chlorine and other components of the aluminum-containing chlorinated flue gas, so as to facilitate the subsequent regeneration of chlorine by gasification, thereby facilitating the recycling of chlorine.

[0079] It should be noted that the second cooling section can separate gaseous carbon dioxide and liquid chlorine to achieve recovery of liquid chlorine.

[0080] The temperature of the first cooling section may be 70°C, 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C or 170°C.

[0081] The temperature of the second cooling section may be -70°C, -65°C, -60°C, -55°C, -50°C, -45°C or -40°C.

[0082] In some optional embodiments, when the overhaul slag also includes iron and silicon, the multi-stage condensation separation further includes a third cooling section and a fourth cooling section, the third cooling section is used to condense the aluminum-containing chlorinated flue gas to obtain an iron-containing solid phase, and the fourth cooling section is used to condense the aluminum-containing chlorinated flue gas to obtain a silicon-containing liquid phase; the temperature of the third cooling section is 190° C. to 290° C., and the temperature of the fourth cooling section is 20° C. to 50° C.;

[0083] In these embodiments, when the overhaul slag also includes iron and silicon, the multi-stage condensation separation may also include a third cooling section and a fourth cooling section, and the third cooling section is used to condense the aluminum-containing chlorinated flue gas and obtain an iron-containing solid phase, and the fourth cooling section is used to condense the aluminum-containing chlorinated flue gas and obtain a silicon-containing liquid phase, and the temperature of the third cooling section may be 190°C to 290°C, and the temperature of the fourth cooling section may be 20°C to 50°C, and the ferric chloride and silicon tetrachloride are condensed into a ferric chloride solid phase and a silicon tetrachloride liquid phase according to the difference in boiling points of ferric chloride and silicon tetrachloride and other components in the overhaul slag, thereby realizing the recovery of iron and silicon in the overhaul slag.

[0084] The temperature of the third cooling section may be 190°C, 195°C, 200°C, 205°C, 210°C, 215°C, 220°C, 225°C, 230°C, 235°C, 240°C, 245°C, 250°C, 255°C, 260°C, 265°C, 270°C, 275°C, 280°C, 285°C or 290°C.

[0085] The temperature of the fourth cooling stage may be 20°C, 25°C, 30°C, 35°C, 40°C, 45°C or 50°C.

[0086] In some optional embodiments, before washing the chromium-containing chlorinated slag to obtain a trivalent chromium-containing solution, after gasifying the liquid chlorine to obtain chlorine gas, the method further comprises:

[0087] S501. exchanging heat between the chlorine gas and the chromium-containing chloride slag to preheat the chlorine gas and obtain preheated chlorine gas;

[0088] In these embodiments, chlorine gas and chromium-containing chlorination slag are heat exchanged, and the heat of the chromium-containing chlorination slag can be used to preheat the chlorine gas to recover the heat of the chlorination reaction, thereby reducing the energy consumption of the method and improving the thermal efficiency of the method.

[0089] The present application is further described below in conjunction with specific examples. The experimental methods in the following examples where specific conditions are not specified 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.

[0090] Example 1

[0091] like Figure 2 A method for recycling overhaul slag and chromium-containing aluminum mud is shown, wherein the overhaul slag contains fluoride, iron, silicon, cyanide and carbon, and the chromium-containing aluminum mud contains aluminum and hexavalent chromium, comprising:

[0092] S1. Mixing an inorganic acid, chromium-aluminum mud and overhaul slag with a particle size of less than 10 μm, so that hexavalent chromium and cyanide undergo an oxidation-reduction reaction in an acidic environment to obtain a decyanide material containing fluoride, carbon, aluminum and chromium;

[0093] S2. The decyanation material is subjected to precipitation reaction using calcium oxide to obtain a precipitate containing chromium, aluminum, carbon and fluorine;

[0094] S3. The preheated chlorine is mixed with the precipitate, and under the action of the carbon in the precipitate, the preheated chlorine is reacted with the chromium and aluminum in the precipitate to obtain aluminum-containing chlorinated flue gas and chromium-containing chlorinated slag;

[0095] S401. The aluminum-containing chlorinated flue gas is subjected to multi-stage condensation separation to obtain an aluminum-containing solid phase and liquid chlorine;

[0096] S402. The liquid chlorine is gasified to obtain chlorine gas;

[0097] S501. The chlorine gas is heat exchanged with the chromium-containing chloride slag to preheat the chlorine gas and obtain preheated chlorine gas;

[0098] S5. Washing the chromium-containing chloride slag to obtain a trivalent chromium-containing solution.

[0099] The temperature of the chlorination reaction is 500°C, and the time of the chlorination reaction is 3 hours.

[0100] The chlorination reaction is carried out under microwave heating.

[0101] The pH value of the redox reaction is 4, and the time of the redox reaction is 0.5h.

[0102] 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.

[0103] The pH of the precipitation reaction is 8.

[0104] The multi-stage condensation separation includes a first cooling section and a second cooling section. The first cooling section is used to condense the aluminum-containing chlorinated flue gas and obtain an aluminum-containing solid phase, and the second cooling section is used to condense the aluminum-containing chlorinated flue gas and obtain liquid chlorine. The temperature of the first cooling section is 70°C, and the temperature of the second cooling section is -70°C.

[0105] The multi-stage condensation separation also includes a third cooling section and a fourth cooling section. The third cooling section is used to condense the aluminum-containing chlorinated flue gas and obtain an iron-containing solid phase, and the fourth cooling section is used to condense the aluminum-containing chlorinated flue gas and obtain a silicon-containing liquid phase. The temperature of the third cooling section is 190°C, and the temperature of the fourth cooling section is 20°C.

[0106] Example 2

[0107] Based on the contents disclosed in Example 1, the following modifications are further made:

[0108] The temperature of the chlorination reaction is 900°C, and the time of the chlorination reaction is 0.5h.

[0109] The pH value of the redox reaction is 6, and the time of the redox reaction is 2h.

[0110] The pH of the precipitation reaction was 11.

[0111] The multi-stage condensation separation includes a first cooling section and a second cooling section. The first cooling section is used to condense the aluminum-containing chlorinated flue gas and obtain an aluminum-containing solid phase, and the second cooling section is used to condense the aluminum-containing chlorinated flue gas and obtain liquid chlorine. The temperature of the first cooling section is 170°C, and the temperature of the second cooling section is -40°C.

[0112] The multi-stage condensation separation also includes a third cooling section and a fourth cooling section. The third cooling section is used to condense the aluminum-containing chlorinated flue gas and obtain an iron-containing solid phase, and the fourth cooling section is used to condense the aluminum-containing chlorinated flue gas and obtain a silicon-containing liquid phase. The temperature of the third cooling section is 290°C, and the temperature of the fourth cooling section is 50°C.

[0113] Example 3

[0114] Based on the contents disclosed in Example 1, the following modifications are further made:

[0115] The temperature of the chlorination reaction is 800°C, and the time of the chlorination reaction is 1.5h.

[0116] The pH value of the redox reaction is 5, and the time of the redox reaction is 1 h.

[0117] The pH of the precipitation reaction is 10.

[0118] The multi-stage condensation separation includes a first cooling section and a second cooling section. The first cooling section is used to condense the aluminum-containing chlorinated flue gas and obtain an aluminum-containing solid phase, and the second cooling section is used to condense the aluminum-containing chlorinated flue gas and obtain liquid chlorine. The temperature of the first cooling section is 120°C, and the temperature of the second cooling section is -60°C.

[0119] The multi-stage condensation separation also includes a third cooling section and a fourth cooling section. The third cooling section is used to condense the aluminum-containing chlorinated flue gas and obtain an iron-containing solid phase, and the fourth cooling section is used to condense the aluminum-containing chlorinated flue gas and obtain a silicon-containing liquid phase. The temperature of the third cooling section is 250°C, and the temperature of the fourth cooling section is 35°C.

[0120] Related experiments and effect data:

[0121] The yields of aluminum element in the aluminum-containing solid phase and chromium element in the trivalent chromium-containing solution obtained in each embodiment and comparative example were counted, and the recovery rates of valuable elements such as aluminum 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.

[0122] Table 1 The recovery rate of valuable elements and the weight of cyanide and hexavalent chromium content of the decyanide material in each embodiment and comparative example

[0123]

[0124] As can be seen from Table 1, an embodiment of the present application provides a method for recycling 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 and chromium to more than 95% through oxidation-reduction reaction, precipitation reaction and chlorination reaction.

[0125] In summary, the embodiment of the present application provides a method for recycling overhaul slag and chromium-aluminum mud. The method utilizes the redox properties of chromium-aluminum mud and overhaul slag for synergistic "detoxification". In addition, valuable elements such as aluminum and chromium are recovered through chlorination reaction. Therefore, the method not only achieves the harmless treatment of overhaul slag and chromium-aluminum mud, but also effectively recovers valuable elements such as chromium and aluminum in the two.

[0126] In addition, the embodiment of the present application provides a method for recycling overhaul slag and chromium-containing aluminum mud. Based on the characteristics of fast heating rate and uniform heating of the carbon in the overhaul slag, the reaction rate and degree of the chlorination reaction can be increased, thereby promoting the aluminum and chromium in the precipitate to be fully converted into aluminum-containing chloride salts and chromium-containing chloride salts.

[0127] In addition, the embodiment of the present application provides a method for recycling overhaul slag and chromium-containing aluminum mud. The method can also recover the heat of the chromium-containing chlorinated slag obtained by the chlorination reaction, and use the recovered heat to preheat the chlorine, thereby realizing the recycling of heat and improving the energy utilization rate of the method; in addition, the method can also regenerate chlorine by separation and purification, so the method has good economic and social benefits.

[0128] 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 recycling overhaul slag and chromium-containing aluminum mud, wherein the overhaul slag contains fluoride, cyanide and carbon, and the chromium-containing aluminum mud contains aluminum 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 and chromium; Using calcium-containing alkaline oxide to carry out precipitation reaction on the decyanation material to obtain a precipitate containing chromium, aluminum, carbon and fluorine; The preheated chlorine gas is mixed with the precipitate, and under the action of the carbon in the precipitate, the preheated chlorine gas is reacted with the chromium and aluminum in the precipitate to obtain aluminum-containing chlorinated fume and chromium-containing chlorinated slag; Separating and purifying the aluminum-containing chlorinated flue gas to obtain an aluminum-containing solid phase; The 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 chlorination reaction is 500°C to 900°C, and the time of the chlorination reaction is 0.5h to 3h.

3. The method according to claim 1, wherein the chlorination reaction is carried out under 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 aluminum-containing chlorinated flue gas is separated and purified to obtain an aluminum-containing solid phase, comprising the steps of: The aluminum-containing chlorinated flue gas is subjected to multi-stage condensation separation to obtain an aluminum-containing solid phase and liquid chlorine; The liquid chlorine is gasified to obtain chlorine gas.

8. The method according to claim 7, wherein the multi-stage condensation separation comprises a first cooling section and a second cooling section, wherein the first cooling section is used to condense the aluminum-containing chlorinated flue gas and obtain an aluminum-containing solid phase, and the second cooling section is used to condense the aluminum-containing chlorinated flue gas and obtain liquid chlorine; the temperature of the first cooling section is 70°C to 170°C, and the temperature of the second cooling section is -70°C to -40°C.

9. According to the method of claim 8, when the overhaul slag also includes iron and silicon, the multi-stage condensation separation also includes a third cooling section and a fourth cooling section, the third cooling section is used to condense the aluminum-containing chlorinated flue gas and obtain an iron-containing solid phase, and the fourth cooling section is used to condense the aluminum-containing chlorinated flue gas and obtain a silicon-containing liquid phase; the temperature of the third cooling section is 190°C to 290°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 chromium-containing chlorinated slag to obtain a trivalent chromium-containing solution, after gasifying the liquid chlorine to obtain chlorine gas, comprising: The chlorine gas is introduced into the chromium-containing chloride slag for heat exchange to obtain preheated chlorine gas.

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