Method for recycling overhauled slag and chromium-containing aluminum sludge

Abstract

The application relates to the technical field of hazardous waste resource utilization, in particular to a method for recycling and utilizing overhauling slag and chromium-containing aluminum sludge; the overhauling slag contains fluorides, cyanides and carbon, and the chromium-containing aluminum sludge contains aluminum and hexavalent chromium; the method comprises the following steps: performing an oxidation-reduction reaction on inorganic acid, the chromium-containing aluminum sludge and the overhauling slag to obtain decyanated material containing fluorides, carbon, aluminum and chromium; performing a precipitation reaction on the decyanated material by using calcium-containing alkaline oxides to obtain precipitated material containing chromium, aluminum, carbon and fluorides; performing a chlorination reaction on the precipitated material by using preheated chlorine to obtain aluminum-containing chlorination flue gas and chromium-containing chlorination slag; performing separation and purification on the aluminum-containing chlorination flue gas to obtain aluminum-containing solid phase; and performing washing on the chromium-containing chlorination slag to obtain trivalent chromium-containing solution. The method can simultaneously improve the removal effect of toxic elements and the recovery rate of valuable elements such as aluminum and chromium of the overhauling slag and the chromium-containing aluminum sludge by oxidation-reduction reaction, precipitation reaction and chlorination reaction.

Description

TECHNICAL FIELD

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

[0002] The electrolytic aluminum process produces 30kg-50kg of overhaul slag per ton of primary aluminum produced. Due to differences in electrolyte composition, current capacity, operation process, and lining replacement time in the electrolytic aluminum process, the specific composition of the overhaul slag is different, but the main components of the overhaul slag are basically the same. These main components include carbon, fluoride, and a small amount of sodium, aluminum, calcium, iron, silicon, and cyanide. Based on the characteristics of the overhaul slag containing a large amount of soluble fluoride and a small amount of cyanide, the overhaul slag has been listed as hazardous waste. Therefore, if the overhaul slag is directly stored or landfilled, it will seriously affect the environment and even harm human health, which makes the harmless treatment and high-value utilization of the overhaul slag important for the green and high-quality development of the aluminum industry. In addition, the main methods for industrial production of sodium dichromate are calcium roasting and calcium-free roasting. Compared with the calcium roasting method, the calcium-free roasting method is cleaner and more efficient. However, in the calcium-free roasting method, aluminum-silicon compounds will react with soda ash to form a large amount of sodium silicate and sodium aluminate, which will enter the alkaline leaching solution and produce a large amount of chromium-containing aluminum sludge, about 5-10 times that of the calcium roasting method. Chromium-containing aluminum sludge generally contains hexavalent chromium, which makes the chromium-containing aluminum sludge have strong toxicity. Therefore, the chromium-containing aluminum sludge is listed as hazardous waste, and if it is directly stored or discharged, it will cause serious harm to the environment.

[0003] The chromium-containing aluminum sludge contains rich chromium and aluminum resources. Through appropriate methods for comprehensive utilization, not only can the environmental pollution be eliminated, but also the green and sustainable development of the chromium salt industry can be effectively promoted. At present, the collaborative utilization of overhaul slag and chromium-containing aluminum sludge mainly uses directly, which is difficult to effectively remove toxic elements and recover valuable elements of aluminum and chromium. SUMMARY

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

[0005] In a first aspect, the present application provides a method for recycling overhaul slag and chromium-containing aluminum sludge, the overhaul slag containing fluoride, cyanide and carbon, and the chromium-containing aluminum sludge containing aluminum and hexavalent chromium, the method comprising:

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

[0007] carrying out a precipitation reaction on the de-cyanide material using a calcium-containing alkaline oxide to obtain a precipitate containing chromium, aluminum, carbon and fluorine;

[0008] mixing preheated chlorine gas with the precipitate to carry out a chlorination reaction on the chromium and aluminum in the precipitate under the action of the carbon in the precipitate, to obtain aluminum-containing chlorination flue gas and chromium-containing chlorination residue;

[0009] carrying out separation and purification on the aluminum-containing chlorination flue gas to obtain an aluminum-containing solid phase;

[0010] carrying out washing on the chromium-containing chlorination residue to obtain a trivalent chromium-containing solution.

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

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

[0013] Optionally, the pH of the oxidation-reduction reaction is 4-6, and the time of the oxidation-reduction reaction is 0.5-2h.

[0014] Optionally, the weight of cyanide in the de-cyanide material is less than or equal to 0.05% of the weight of the de-cyanide material, and the weight of hexavalent chromium in the de-cyanide material is less than or equal to 0.05% of the weight of the de-cyanide material.

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

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

[0017] carrying out multi-stage condensation separation on the aluminum-containing chlorination flue gas to obtain an aluminum-containing solid phase and liquid chlorine;

[0018] carrying out gasification on the liquid chlorine to obtain chlorine gas.

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

[0020] Optionally, in the case that the overhauling slag further comprises iron and silicon, the multi-stage condensing separation further comprises a third cooling section and a fourth cooling section, the third cooling section is used for condensing the aluminum-containing chlorination flue gas and obtaining an iron-containing solid phase, and the fourth cooling section is used for condensing the aluminum-containing chlorination flue gas and obtaining a silicon-containing liquid phase; the temperature of the third cooling section is 190-290 ℃, and the temperature of the fourth cooling section is 20-50 ℃.

[0021] Optionally, after the liquid chlorine is gasified to obtain chlorine gas, the method further comprises:

[0022] The chlorine gas is introduced into the chromium-containing chlorination slag to exchange heat, and preheated chlorine gas is obtained.

[0023] Compared with the prior art, the above technical solution provided by the embodiments of the present application has the following advantages:

[0024] The method for recycling overhauling slag and chromium-containing aluminum mud provided by the embodiments of the present application aims to simultaneously process overhauling slag (containing fluoride, cyanide and carbon) and chromium-containing aluminum mud (containing aluminum and hexavalent chromium), and realizes the removal of toxic elements and the recovery of valuable elements through a series of chemical reactions, including: an oxidation-reduction reaction step: mixing inorganic acid, chromium-containing aluminum mud and overhauling slag, and promoting the reaction of hexavalent chromium and cyanide in the acidic environment of the inorganic acid, so as to remove the cyanide. In this step, hexavalent chromium acts as an oxidizing agent and undergoes an oxidation-reduction reaction with cyanide to generate harmless or low-toxicity products. As a result, de-cyanated material containing fluoride, carbon, aluminum and chromium is obtained; a precipitation reaction step: using calcium-containing alkaline oxide (such as calcium oxide) to perform a precipitation reaction on the de-cyanated material to remove chromium, aluminum and fluoride therein; in addition, the precipitation reaction forms calcium fluoride, aluminum hydroxide and other precipitates, so as to realize the separation of these elements, and as a result, precipitated material containing chromium, aluminum, carbon and fluoride (partially unprecipitated) is obtained. A chlorination reaction step: using preheated chlorine gas to perform a chlorination reaction on the precipitated material, using carbon in the precipitated material as a heating medium to promote the reaction of chromium and aluminum to generate chromium-containing chlorides and aluminum-containing chlorides; 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 to obtain an aluminum-containing solid phase through a subsequent step, and the chromium-containing chlorination slag can be washed to obtain a trivalent chromium-containing solution, realizing the recovery of chromium. BRIEF DESCRIPTION OF DRAWINGS

[0025] The accompanying drawings, which are incorporated into and form a part of the specification, illustrate one embodiment consistent with the present application and, together with the description, serve to explain the principles of the application.

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, for those of ordinary skill in the art, other drawings can also be obtained based on these drawings without any creative effort.

[0027] Figure 1 A process flow diagram of a method for recycling overhaul slag and chromium-containing aluminum sludge according to an embodiment of the present application;

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

[0029] Figure 3 A practical process flow diagram of a method for recycling overhaul slag and chromium-containing aluminum sludge according to an embodiment of the present application. DETAILED DESCRIPTION

[0030] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the following will combine the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without any creative effort fall within the scope of protection of the present application.

[0031] Various embodiments of the present application can exist in the form of a range; it should be understood that the description in the form of a range is merely for the convenience and brevity, and should not be understood as a hard limit on the scope of the present application; therefore, it should be considered that the described range has specifically disclosed all possible sub-ranges and single values 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 described range, such as 1, 2, 3, 4, 5 and 6, which applies to any range; in addition, whenever a numerical range is indicated in this document, it refers to any cited number (fraction or integer) within the indicated range.

[0032] As used herein, the terms "including," "comprising," and the like mean "including but not limited to." Relational terms such as "first" and "second" are used solely to distinguish one entity or operation from another, and do not necessarily require or imply any actual relationship or order between these entities or operations. "And / or" describes the association relationship between associated objects, indicating that three relationships can exist. 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, "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 each be single or plural. "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 figures 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 figures 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, all 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 according to 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. The method comprises:

[0037] S1. Mixing an inorganic acid, the chromium-containing aluminum mud and the overhaul slag to allow the hexavalent chromium to undergo an oxidation-reduction reaction with the cyanide in an acidic environment to obtain a decyanide material containing fluoride, carbon, aluminum and chromium;

[0038] S2. The decyanide material is subjected to a precipitation reaction using a calcium-containing alkaline oxide to obtain a precipitate containing chromium, aluminum, carbon and fluorine;

[0039] S3. mixing the preheated chlorine gas with the precipitated material, under the action of carbon in the precipitated material, to make the preheated chlorine gas react with chromium and aluminum in the precipitated material to obtain aluminum-containing chlorination flue gas and chromium-containing chlorination residue;

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

[0041] S5. washing the chromium-containing chlorination residue to obtain a trivalent chromium-containing solution.

[0042] It should be noted that the carbon in the overhaul residue can significantly improve the fluidization quality of the chromium-containing aluminum mud and effectively promote the progress of the oxidation-reduction reaction.

[0043] It should be noted that the precipitated material needs to be purified before the chlorination reaction to remove the water in the precipitated material to avoid the loss of preheated chlorine gas. The purification treatment can be drying treatment.

[0044] It should be noted that the temperature of the preheated chlorine gas can be less than the working temperature of the chlorination reaction. The temperature of the preheated chlorine gas is determined according to the actual heat exchange condition. No matter what the temperature of the preheated chlorine gas is, it can be quickly heated to the working temperature of the chlorination reaction in 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 precipitated material have the characteristics of high degree of mixing and contact, fast mass and heat transfer rate, and high reaction efficiency in the gas-solid fluidized bed reactor.

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

[0047] It should be noted that the product obtained by the precipitation reaction is a mixed solution of part of calcium chloride and sodium chloride in addition to the precipitated material. The mixed solution can be obtained by subsequent treatment to obtain a harmless waste liquid.

[0048] It should be noted that the chromium chloride and calcium fluoride in the chromium-containing chlorination residue can be separated after washing. In addition to the trivalent chromium-containing solution, calcium fluoride products can also be obtained.

[0049] It should be noted that the overhaul residue also needs to be ground before use to control the particle size of the overhaul residue to be less than 10 microns.

[0050] In summary, the method for recycling the overhaul residue and the chromium-containing aluminum mud according to the embodiments of the present application has the following advantages:

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

[0052] Cyanide is removed through redox reactions, reducing the content of toxic substances. 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, realizing aluminum recovery. The chromium-containing chlorinated slag can be washed to obtain a trivalent chromium solution, providing the possibility for further utilization of chromium.

[0055] This method, through a series of chemical reactions, achieves the simultaneous recycling of overhaul slag and chromium-aluminum sludge, effectively increasing the recovery rate of valuable elements while improving the removal of toxic elements. This provides a new approach to resolving industrial waste issues, contributing to the sustainable use 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 0.5 h to 3 h;

[0057] In these embodiments, the chlorination reaction temperature can be 500° C. to 900° C., and the chlorination reaction time 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 is 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 in the precipitate can serve as a high-efficiency absorbing material to absorb and preserve the energy transmitted by the microwave heating. Carbon with sufficient energy can not only promote the rapid heating of the precipitate to promote the temperature of the precipitate to meet the requirements of the chlorination reaction, but also can uniformly disperse other materials in the precipitate during the microwave heating stage; in addition, the carbon in the precipitate can also serve 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 4-6, and the time of the redox reaction is 0.5h-2h.

[0063] In these embodiments, the pH of the redox reaction can be 4-6, and the time of the redox reaction can be 0.5h-2h, so that the hexavalent chromium in the chromium-containing aluminum sludge and the cyanide in the overhaul slag can be fully reacted in the acidic environment of the inorganic acid to facilitate the oxidation of the cyanide into harmless carbon dioxide and nitrogen and the reduction of the hexavalent chromium into harmless trivalent chromium, thereby effectively removing the toxic elements in the chromium-containing aluminum sludge and the overhaul slag.

[0064] The pH of the redox reaction can be 4.0, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5.0, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9, or 6.0.

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

[0066] In some optional embodiments, the weight of the cyanide in the de-cyanated material is less than or equal to 0.05% of the weight of the de-cyanated material, and the weight of the hexavalent chromium in the de-cyanated material is less than or equal to 0.05% of the weight of the de-cyanated material.

[0067] In these embodiments, the weight of the cyanide in the de-cyanated material can be less than or equal to 0.05% of the weight of the de-cyanated material, and the weight of the hexavalent chromium in the de-cyanated material can be less than or equal to 0.05% of the weight of the de-cyanated material, which indicates that the hexavalent chromium in the chromium-containing aluminum sludge and the cyanide in the overhaul slag have been fully reacted in the redox reaction.

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

[0069] In these embodiments, the pH of the precipitation reaction can be 8-11, which indicates that the precipitation reaction is carried out in an alkaline environment, and the alkaline environment can facilitate the conversion of aluminum and chromium into hydroxide precipitates, thereby facilitating the conversion of aluminum and chromium in the de-cyanated material into the precipitated material; in addition, the calcium in the calcium-containing oxide can carry out a precipitation reaction with the fluorine in the de-cyanated material to obtain calcium fluoride precipitated material in the alkaline environment, thereby facilitating subsequent recycling and processing.

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

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

[0072] Figure 3 A method for recycling overhaul slag and chromium-containing aluminum sludge according to an embodiment of the present application is exemplarily shown in an actual flowchart;

[0073] In some optional embodiments, as shown in Figure 2 and Figure 3 The separation and purification of the aluminum-containing chlorination flue gas to obtain an aluminum-containing solid phase comprises the following steps:

[0074] S401. The aluminum-containing chlorination 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, the separation and purification can use the multi-stage condensation separation and gasification mode. Through the multi-stage condensation separation, the aluminum-containing solid phase and the liquid chlorine can be condensed and precipitated according to the boiling point difference between them, so that the recovery of aluminum can be realized. In addition, the gasification of the precipitated liquid chlorine can realize the regeneration of chlorine gas.

[0077] In some optional embodiments, the multi-stage condensation separation comprises a first cooling section and a second cooling section. The first cooling section is used for condensing the aluminum-containing chlorination flue gas and obtaining an aluminum-containing solid phase. The second cooling section is used for condensing the aluminum-containing chlorination flue gas and obtaining liquid chlorine. The temperature of the first cooling section is 70-170°C, and the temperature of the second cooling section is -70- -40°C.

[0078] In these embodiments, the multi-stage condensation separation can comprise a first cooling section, the first cooling section is used for condensing the aluminum-containing chlorination flue gas and obtaining an aluminum-containing solid phase, and the temperature of the first cooling section can be 70-170°C. The aluminum-containing chlorination flue gas can be condensed into an aluminum-containing solid phase according to the boiling point difference between the aluminum chloride component and other components of the aluminum-containing chlorination flue gas, so as to realize the recovery of aluminum. In addition, the multi-stage condensation separation can comprise a second cooling section, the second cooling section is used for condensing the aluminum-containing chlorination flue gas and obtaining liquid chlorine, and the temperature of the second cooling section can be -70- -40°C. The chlorine component of the aluminum-containing chlorination flue gas can be condensed into liquid chlorine according to the boiling point difference between the chlorine gas and other components of the aluminum-containing chlorination flue gas, so as to facilitate the regeneration of chlorine gas through the gasification mode in the subsequent process, thereby facilitating the cyclic use of chlorine gas.

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

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

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

[0082] In some alternative embodiments, when the overhaul slag further comprises iron and silicon, the multi-stage condensation separation further comprises a third cooling section and a fourth cooling section, the third cooling section is used for condensing the aluminum-containing chlorination flue gas and obtaining an iron-containing solid phase, and the fourth cooling section is used for condensing the aluminum-containing chlorination flue gas and obtaining a silicon-containing liquid phase; the temperature of the third cooling section is 190℃-290℃, and the temperature of the fourth cooling section is 20℃-50℃.

[0083] In these embodiments, when the overhaul slag further comprises iron and silicon, the multi-stage condensation separation can further comprise a third cooling section and a fourth cooling section, the third cooling section is used for condensing the aluminum-containing chlorination flue gas and obtaining an iron-containing solid phase, and the fourth cooling section is used for condensing the aluminum-containing chlorination flue gas and obtaining a silicon-containing liquid phase, and the temperature of the third cooling section can be 190℃-290℃, and the temperature of the fourth cooling section can be 20℃-50℃, according to the boiling point difference of the iron chloride and silicon tetrachloride and other components in the overhaul slag, the iron chloride and silicon tetrachloride are condensed into an iron chloride solid phase and a silicon tetrachloride liquid phase, so that the iron and silicon in the overhaul slag can be recovered.

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

[0085] The temperature of the fourth cooling section can be 20℃, 25℃, 30℃, 35℃, 40℃, 45℃, or 50℃.

[0086] In some alternative embodiments, after the liquid chlorine is gasified to obtain chlorine gas, and before the chromium-containing chlorination slag is washed to obtain a trivalent chromium-containing solution, the method comprises:

[0087] S501. Heat exchange of chlorine gas and the chromium-containing chlorination slag is performed to preheat the chlorine gas and obtain preheated chlorine gas;

[0088] In these embodiments, the heat exchange of chlorine gas and the chromium-containing chlorination slag can use the heat of the chromium-containing chlorination slag to preheat the chlorine gas, so as 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 with reference to specific examples. Experimental methods in the following examples where specific conditions are not specified are generally measured in accordance with national / industry standards. If there are no corresponding national / industry standards, the methods are carried out in accordance with commonly used international standards, conventional conditions, or conditions recommended by the manufacturer.

[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-containing aluminum mud and overhaul slag with a particle size of <10 μm to allow hexavalent chromium to undergo an oxidation-reduction reaction with cyanide in an acidic environment to obtain a decyanide material containing fluoride, carbon, aluminum and chromium;

[0093] S2. The decyanide 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 carbon in the precipitate, the preheated chlorine is reacted with 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 and the chromium-containing chloride slag are heat exchanged 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 of the redox reaction is 4, and the time of the redox reaction is 0.5 h.

[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 comprises a first cooling section and a second cooling section, the first cooling section is used for condensing the aluminum-containing chlorination flue gas and obtaining an aluminum-containing solid phase, and the second cooling section is used for condensing the aluminum-containing chlorination flue gas and obtaining liquid chlorine; the temperature of the first cooling section is 70℃, and the temperature of the second cooling section is -70℃.

[0105] The multi-stage condensation separation further comprises a third cooling section and a fourth cooling section, the third cooling section is used for condensing the aluminum-containing chlorination flue gas and obtaining an iron-containing solid phase, and the fourth cooling section is used for condensing the aluminum-containing chlorination flue gas and obtaining a silicon-containing liquid phase; the temperature of the third cooling section is 190℃, and the temperature of the fourth cooling section is 20℃.

[0106] Embodiment 2

[0107] On the basis of the disclosure in Embodiment 1, the following modifications are further made:

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

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

[0110] The pH value of the precipitation reaction is 11.

[0111] The multi-stage condensation separation comprises a first cooling section and a second cooling section, the first cooling section is used for condensing the aluminum-containing chlorination flue gas and obtaining an aluminum-containing solid phase, and the second cooling section is used for condensing the aluminum-containing chlorination flue gas and obtaining liquid chlorine; the temperature of the first cooling section is 170℃, and the temperature of the second cooling section is -40℃.

[0112] The multi-stage condensation separation further comprises a third cooling section and a fourth cooling section, the third cooling section is used for condensing the aluminum-containing chlorination flue gas and obtaining an iron-containing solid phase, and the fourth cooling section is used for condensing the aluminum-containing chlorination flue gas and obtaining a silicon-containing liquid phase; the temperature of the third cooling section is 290℃, and the temperature of the fourth cooling section is 50℃.

[0113] Embodiment 3

[0114] On the basis of the disclosure in Embodiment 1, the following modifications are further made:

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

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

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

[0118] The multi-stage condensation separation comprises a first cooling section and a second cooling section, the first cooling section is used for condensing the aluminum-containing chlorination flue gas to obtain an aluminum-containing solid phase, and the second cooling section is used for condensing the aluminum-containing chlorination flue gas to obtain liquid chlorine; the temperature of the first cooling section is 120 DEG C, and the temperature of the second cooling section is -60 DEG C.

[0119] The multi-stage condensation separation further comprises a third cooling section and a fourth cooling section, the third cooling section is used for condensing the aluminum-containing chlorination flue gas to obtain an iron-containing solid phase, and the fourth cooling section is used for condensing the aluminum-containing chlorination flue gas to obtain a silicon-containing liquid phase; the temperature of the third cooling section is 250 DEG C, and the temperature of the fourth cooling section is 35 DEG C.

[0120] Related experiments and effect data:

[0121] The yields of aluminum elements in the aluminum-containing solid phases and chromium elements in the trivalent chromium-containing solutions obtained in the examples and the comparative examples are counted, and the recovery rates of the valuable elements such as aluminum and chromium are calculated, in addition, the weight contents of cyanide and hexavalent chromium in the cyanide-removing materials are counted, and the results are shown in Table 1.

[0122] Table 1: Recovery rates of valuable elements in the examples and the comparative examples and weight contents of cyanide and hexavalent chromium in the cyanide-removing materials

[0123]

[0124] As shown in Table 1, the method for recycling the overhaul slag and the chromium-containing aluminum sludge provided in the examples can simultaneously improve the removal rate of toxic elements in the overhaul slag and the chromium-containing aluminum sludge to more than 99.95% and the recovery rate of valuable elements such as aluminum and chromium to more than 95% through the oxidation-reduction reaction, the precipitation reaction and the chlorination reaction.

[0125] In summary, the method for recycling the overhaul slag and the chromium-containing aluminum sludge provided in the examples utilizes the oxidation-reduction characteristics of the chromium-containing aluminum sludge and the overhaul slag to cooperate with the detoxification, and further recovers valuable elements such as aluminum and chromium through the chlorination reaction, so that the method not only realizes the harmless treatment of the overhaul slag and the chromium-containing aluminum sludge, but also effectively recovers valuable elements such as chromium and aluminum in the two.

[0126] In addition, the method for recycling the overhaul slag and the chromium-containing aluminum sludge provided in the examples can improve the reaction rate and the reaction degree of the chlorination reaction based on the characteristics that the carbon in the overhaul slag has a fast heating rate and is uniformly heated, so as to promote the aluminum and the chromium in the precipitation material to be fully converted into aluminum-containing chlorides and chromium-containing chlorides.

[0127] In addition, the method for recycling the overhaul slag and the chromium-containing aluminum slurry provided by the embodiment of the present application can also recycle the heat of the chromium-containing chlorination slag obtained through chlorination reaction, and use the recycled heat to preheat chlorine, so that the heat is recycled and used, and the energy utilization rate of the method is improved; in addition, the method can also regenerate chlorine through separation and purification, and therefore the method has good economic and social benefits.

[0128] The above description is merely a specific implementation of the present application, which enables those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined in the present application can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown in the present application, but will conform to the widest scope consistent with the principles and novel features of the present application.

Claims

1. A method for 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 to allow the hexavalent chromium and the cyanide to undergo an oxidation-reduction reaction in an acidic environment to obtain a decyanide material containing fluoride, carbon, aluminum, and chromium; The decyanide material is subjected to a precipitation reaction using a calcium-containing alkaline oxide to obtain a precipitate containing chromium, aluminum, carbon and fluorine; mixing preheated chlorine with the precipitate, and causing the preheated chlorine to react with chromium and aluminum in the precipitate under the action of carbon in the precipitate to produce 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 to 2 hours.

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

7. The method according to claim 1, wherein the 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 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 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 and 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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