Method for recovering magnesium through cooperative treatment of dolomite and aluminum electrolysis overhaul slag

Abstract

The invention provides a method for recycling magnesium through cooperative treatment of dolomite and aluminum electrolysis overhaul slag, and belongs to the field of solid waste resource utilization. The method comprises the following steps: mixing dolomite and aluminum electrolysis overhaul slag according to a set mass ratio to obtain a mixed material; and under the vacuum condition, the mixed material is subjected to a high-temperature roasting reaction, and the magnesium element in the mixed material is recycled. On one hand, the dolomite is decomposed at high temperature to generate CaO, the CaO reacts with fluoride in the aluminum electrolysis overhaul slag to generate CaF2, and therefore the fluorine fixing effect is achieved, and fluoride pollution is prevented; meanwhile, cyanide in the overhaul slag is decomposed into harmless C and N2 under a high-temperature condition, so that harmless treatment of the overhaul slag is realized; on the other hand, carbon in the overhaul slag can reduce MgO in the dolomite into magnesium steam. Therefore, based on the fluorine fixing property of calcium in the dolomite and the reducibility of carbon in the overhaul slag, the magnesium in the dolomite is efficiently extracted while the harmless treatment of the aluminum electrolysis overhaul slag is realized.

Description

Technical Field

[0001] The present application relates to the technical field of solid waste resource utilization, and in particular to a method for recovering magnesium by co-processing dolomite and aluminum electrolysis overhaul slag. Background Art

[0002] Magnesium and magnesium alloys are considered to be the most promising "green engineering materials" in the 21st century. In recent years, with the continuous development of my country's material technology, the application field of magnesium alloys has been continuously expanded, and the demand for magnesium has been continuously increasing, which has greatly promoted the progress of magnesium smelting metal. At present, there are two main methods for preparing magnesium metal: electrolysis and thermal reduction. At present, more than 80% of magnesium in my country is produced by the Pidgeon method (silicon thermal reduction method). The technology is relatively mature, but this method uses ferrosilicon as a reducing agent, which is expensive and energy-intensive.

[0003] Overhaul slag is waste slag produced during the maintenance of aluminum electrolytic cells. Its main components include carbon blocks, fluorides, alumina, silicon dioxide, cyanides, etc. Because it contains a large amount of soluble fluorides and cyanides, it is extremely harmful to the environment and has been included in the "National List of Hazardous Wastes". For hazardous waste overhaul slag with leaching toxicity, it must be harmlessly treated before it can be discharged. At present, my country mainly uses landfill method to treat overhaul slag, but this method is costly, and soluble fluorides and cyanides cause serious pollution to the land and groundwater. Therefore, how to achieve harmless treatment of aluminum electrolysis overhaul slag while efficiently extracting magnesium from dolomite is a technical problem that needs to be solved urgently. Summary of the invention

[0004] The present application provides a method for recovering magnesium by co-processing dolomite and aluminum electrolysis overhaul slag, so as to solve the following technical problem: how to efficiently extract magnesium from dolomite while achieving harmless treatment of aluminum electrolysis overhaul slag.

[0005] The present application provides a method for recovering magnesium by co-processing dolomite and aluminum electrolysis overhaul slag, the method comprising:

[0006] Mixing dolomite and aluminum electrolysis overhaul slag according to a set mass ratio to obtain a mixed material; the set mass ratio is (2-6):1; and

[0007] Under vacuum conditions, the mixed material is subjected to a high-temperature calcination reaction to recover the magnesium element in the mixed material.

[0008] Optionally, the set mass ratio is 4:1.

[0009] Optionally, the chemical composition of the aluminum electrolysis overhaul slag includes, by mass: Na3AlF6: 5 to 6 parts, NaF: 20 to 26 parts, C: 40 to 50 parts, CaF2: 1.5 to 3 parts, SiO2: 10 to 15 parts, and Al2O3: 2 to 4 parts.

[0010] Optionally, the particle size of the aluminum electrolysis overhaul slag is 200 mesh to 250 mesh.

[0011] Optionally, the chemical composition of the dolomite includes, by mass: MgO: 20 to 25 parts, CaO: 25 to 35 parts, SiO2: 1 to 3 parts, Fe2O3: 2 to 5 parts, and Al2O3: 0.5 to 2 parts.

[0012] Optionally, the particle size of the dolomite is 200-250 mesh.

[0013] Optionally, subjecting the mixed material to a high temperature roasting reaction to recover the magnesium element in the mixed material comprises:

[0014] The mixed material is subjected to a high temperature calcination reaction so that the magnesium in the mixed material is converted into magnesium vapor;

[0015] The magnesium vapor is condensed to obtain a recovered product containing magnesium element.

[0016] Optionally, the calcination temperature of the high-temperature calcination reaction is 950° C. to 1350° C., and the calcination time of the high-temperature calcination reaction is 2 h to 3.5 h.

[0017] Optionally, the calcination pressure of the high temperature calcination reaction is 5Pa to 25Pa.

[0018] Optionally, the conversion rate of the magnesium into magnesium vapor is ≥90%, and the mass of the magnesium element is ≥80% of the total mass of the recyclate.

[0019] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0020] The present application provides a method for recovering magnesium by co-processing dolomite and aluminum electrolytic overhaul slag, comprising: mixing dolomite and aluminum electrolytic overhaul slag according to a set mass ratio to obtain a mixed material; the set mass ratio is (2-6):1; and subjecting the mixed material to a high-temperature roasting reaction under vacuum conditions to recover the magnesium element in the mixed material. On the one hand, the calcium in the dolomite decomposes at high temperature to generate CaO, and CaO reacts with the fluoride in the aluminum electrolytic overhaul slag to generate insoluble CaF2, thereby playing a role in fluorine fixation and preventing fluoride pollution; at the same time, the cyanide in the overhaul slag decomposes under high temperature conditions into harmless C and N2, thereby achieving harmless treatment of the overhaul slag; on the other hand, the carbon in the overhaul slag can reduce the MgO in the dolomite to magnesium vapor, thereby achieving magnesium extraction. Therefore, based on the fluorine fixation property of calcium in dolomite and the reducibility of carbon in the overhaul slag, while achieving harmless treatment of aluminum electrolytic overhaul slag, magnesium in the dolomite is efficiently extracted. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] 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.

[0022] In order to more clearly illustrate the embodiments of the present application or the technical solutions in 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.

[0023] Figure 1 A flow chart of a method for recovering magnesium by co-processing dolomite and aluminum electrolysis overhaul slag provided in an embodiment of the present application;

[0024] Figure 2 A schematic diagram of a method for recovering magnesium by co-processing dolomite and aluminum electrolysis overhaul slag provided in an embodiment of the present application. DETAILED DESCRIPTION

[0025] 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.

[0026] 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, the range description should be considered to have specifically disclosed all possible sub-ranges and single numerical values ​​within the range. For example, the range description from 1 to 6 should be considered to have 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 apply regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0027] In addition, in the description of the specification of the present application, the terms "including", "comprising", etc. mean "including but not limited to". In this article, relational terms such as "first" and "second", etc. 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. In this article, "and / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. Wherein A and B can be singular or plural. In this article, "at least one" means one or more, and "plurality" means two or more. "At least one", "the following at least one item (items)" or similar expressions refer to any combination of these items, including any combination of single items (items) or plural items (items). For example, "at least one of a, b, or c", or "at least one of a, b, and c", can all represent: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, 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, 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 one-to-one with 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 = 1:2:3.

[0028] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0029] Figure 1 A flow chart of a method for recovering magnesium by co-processing dolomite and aluminum electrolysis overhaul slag provided in an embodiment of the present application; Figure 2 A schematic diagram of a method for recovering magnesium by co-processing dolomite and aluminum electrolysis overhaul slag provided in an embodiment of the present application.

[0030] See also Figure 1 and Figure 2 The present application provides a method for recovering magnesium by co-processing dolomite and aluminum electrolysis overhaul slag, the method comprising:

[0031] S1, mixing dolomite and aluminum electrolysis overhaul slag according to a set mass ratio to obtain a mixed material; the set mass ratio is (2-6):1; and

[0032] In some embodiments, the set mass ratio is 4:1.

[0033] In some embodiments, the chemical composition of the aluminum electrolysis overhaul slag includes, by mass: Na3AlF6: 5 to 6 parts, NaF: 20 to 26 parts, C: 40 to 50 parts, CaF2: 1.5 to 3 parts, SiO2: 10 to 15 parts, and Al2O3: 2 to 4 parts.

[0034] In some embodiments, the chemical composition of the dolomite includes, by mass: MgO: 20 to 25 parts, CaO: 25 to 35 parts, SiO2: 1 to 3 parts, Fe2O3: 2 to 5 parts, and Al2O3: 0.5 to 2 parts.

[0035] The main components of dolomite are MgCO3, CaCO3, etc., and the main components of overhaul slag are C, NaF, Na3AlF6, SiO2, soluble cyanide, etc. On the one hand, the calcium in dolomite (mainly in the form of CaCO3) decomposes to form CaO at high temperature. CaO has strong alkalinity and can react with fluoride in aluminum electrolysis overhaul slag to form insoluble CaF2, thereby playing a role in fluorine fixation and preventing fluoride pollution. On the other hand, overhaul slag contains a certain amount of carbon, which is reducible at high temperature and can participate in the reduction reaction to reduce MgO in dolomite to magnesium vapor, thereby realizing the extraction of magnesium. Dolomite and aluminum electrolysis overhaul slag are uniformly mixed in a mass ratio of (2 to 6): 1 to ensure the uniformity and efficiency of the reaction during high-temperature roasting and promote the reduction and volatilization of magnesium. At the same time, the cyanide in the overhaul slag decomposes into harmless C and N2 under high temperature conditions, realizing the harmless treatment of overhaul slag. Exemplarily, the mass ratio of dolomite to aluminum electrolysis overhaul slag can be 2:1, 3:1, 4:1, 5:1, 6:1, etc.

[0036] Therefore, based on the fluorine-fixing property of calcium in dolomite and the reducing property of carbon in overhaul slag, the present invention uniformly mixes the two materials, and undergoes a high-temperature vacuum induction roasting reaction to reduce and volatilize magnesium, which is then recovered through condensation. The fluorine is converted into insoluble calcium fluoride and exists in the slag, while the cyanide is decomposed into harmless substances under high temperature conditions. This method achieves efficient extraction of magnesium and harmless treatment of overhaul slag.

[0037] In some embodiments, the particle size of the aluminum electrolysis overhaul slag is 200 mesh to 250 mesh.

[0038] In some embodiments, the particle size of the dolomite is 200-250 mesh.

[0039] The particle size of the aluminum electrolysis overhaul slag is limited to 200 mesh to 250 mesh, and the particle size of the dolomite is limited to 200 mesh to 250 mesh, which is conducive to the full contact of the two material particles when the aluminum electrolysis overhaul slag and the dolomite are mixed, thereby facilitating the reduction reaction during the roasting process and promoting the reduction and volatilization of magnesium. Exemplarily, the particle size of the aluminum electrolysis overhaul slag can be 200 mesh, 210 mesh, 220 mesh, 230 mesh, 240 mesh, 250 mesh, etc., and the particle size of the dolomite can be 200 mesh, 210 mesh, 220 mesh, 230 mesh, 240 mesh, 250 mesh, etc.

[0040] S2. Under vacuum conditions, subjecting the mixed material to a high-temperature calcination reaction to recover the magnesium element in the mixed material.

[0041] High-temperature roasting reaction is a reaction process of solid materials at high temperature (lower than the melting temperature of the material), which will cause physical and chemical changes. This process may include oxidation, pyrolysis, reduction, halogenation and other reactions. High-temperature roasting in a vacuum environment can effectively reduce the interference of oxygen, improve the efficiency of the reduction reaction, and promote the volatilization of magnesium vapor. High-temperature roasting reaction can be carried out by induction heating, which can quickly and evenly heat the mixed material to ensure the stability and controllability of the reaction temperature.

[0042] The main reaction equations in the high temperature roasting reaction of the mixed material are as follows:

[0043] MgCO3=MgO+CO2 (g)

[0044] CaCO3=CaO+CO2 (g)

[0045] MgO+C=Mg(g)+CO(g)

[0046] Na3AlF6=3NaF+AlF3

[0047] CaO+2NaF+SiO2=CaF2+Na2O·SiO2

[0048] During the high-temperature roasting process, dolomite decomposes to produce MgO and CaO, and then MgO is reduced to magnesium vapor, and CaO reacts with soluble fluoride salts to produce insoluble CaF2. In addition, the cyanide in the overhaul slag decomposes under high temperature conditions to produce non-toxic and harmless C and N2. The slag remaining after high-temperature roasting contains high-value calcium fluoride and other metal oxides or compounds, which can be further processed and utilized to extract useful components or as industrial raw materials.

[0049] In some embodiments, subjecting the mixed material to a high temperature roasting reaction to recover the magnesium element in the mixed material comprises:

[0050] The mixed material is subjected to a high temperature calcination reaction so that the magnesium in the mixed material is converted into magnesium vapor;

[0051] The magnesium vapor is condensed to obtain a recovered product containing magnesium element.

[0052] In some embodiments, the calcination temperature of the high temperature calcination reaction is 950° C. to 1350° C., and the calcination time of the high temperature calcination reaction is 2 h to 3.5 h.

[0053] The calcination temperature of the high-temperature calcination reaction is 950℃~1350℃, which is determined based on the physical and chemical properties of dolomite and aluminum electrolytic overhaul slag and the chemical reactions that may occur between them. In the temperature range of 950℃~1350℃, MgCO3 and CaCO3 in dolomite can be fully decomposed to generate MgO and CaO. At the same time, the carbon in the overhaul slag can exert its reducing property and reduce MgO to magnesium vapor. In addition, the reaction of fluoride with CaO and the decomposition of cyanide are also carried out more thoroughly within this temperature range. The calcination time is selected to ensure that the reactants can fully contact and react chemically. If the calcination time is less than 2h, the material may not react completely, resulting in a low volatilization rate of magnesium and poor recovery effect. However, if the calcination time is higher than 3.5h, although it can further promote the reaction, it often leads to a no significant increase in the recovery rate of magnesium, but increases energy consumption and production costs, and reduces the efficiency of the overall process. Illustratively, the calcination temperature of the high temperature calcination reaction can be 950°C, 1000°C, 1050°C, 1100°C, 1150°C, 1200°C, 1250°C, 1300°C, 1350°C, etc., and the calcination time of the high temperature calcination reaction can be 2h, 2.2h, 2.5h, 3h, 3.2h, 3.5h, etc.

[0054] In some embodiments, the calcination pressure of the high temperature calcination reaction is 5Pa to 25Pa.

[0055] The roasting pressure of the high temperature roasting reaction is limited to 5Pa to 25Pa, and the magnesium vapor can be efficiently volatilized and recovered. A pressure higher than 25Pa is not conducive to the volatilization of magnesium and the recovery rate is low. When the pressure is lower than 5Pa, the equipment requirements are high, the investment cost is large, and the improvement of the magnesium recovery rate is not obvious. Exemplarily, the roasting pressure of the high temperature roasting reaction can be 5Pa, 10Pa, 15Pa, 20Pa, 25Pa, etc.

[0056] In some embodiments, the conversion rate of the magnesium into magnesium vapor is ≥ 90%, and the mass of the magnesium element is ≥ 80% of the total mass of the recyclate.

[0057] In summary, the present application provides a method for recovering magnesium by co-processing dolomite with aluminum electrolysis overhaul slag. The core of the method is to mix dolomite with aluminum electrolysis overhaul slag in a certain proportion and perform a high-temperature roasting reaction under vacuum conditions to simultaneously achieve harmless treatment of aluminum electrolysis overhaul slag and efficient extraction of magnesium in dolomite. The technical advantages are as follows: 1. Harmless treatment: Through the coordinated treatment with dolomite, harmful substances such as fluoride, cyanide, etc. in aluminum electrolysis overhaul slag can be effectively decomposed or solidified during the high-temperature roasting process, thereby achieving harmless treatment; this helps to reduce the pollution of the electrolytic aluminum industry to the environment and meets the requirements of national environmental protection policies. 2. Efficient extraction of magnesium: Dolomite is one of the important raw materials for extracting magnesium; through the coordinated treatment with aluminum electrolysis overhaul slag, the magnesium element in dolomite can be efficiently extracted while treating the waste slag, thereby improving the comprehensive utilization efficiency of resources. 3. Energy saving and emission reduction: The high-temperature roasting reaction under vacuum conditions can reduce energy loss and gas emissions during the reaction process, which helps to reduce production costs and reduce environmental burdens.

[0058] This method can achieve harmless treatment of aluminum electrolytic overhaul slag and efficiently extract magnesium from dolomite, with high technical feasibility and economic benefits. This is of great significance for promoting the sustainable development of the electrolytic aluminum industry and the magnesium industry.

[0059] The present application will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are intended only to illustrate the present application and are not intended to limit the scope of the present application. The experimental methods for which specific conditions are not specified in the following examples are usually measured according to industry standards. If there is no corresponding industry standard, then the conditions recommended by the manufacturer are followed.

[0060] Example 1

[0061] The raw materials used are dolomite concentrate and aluminum electrolysis overhaul slag, and their chemical compositions are shown in Table 1 and Table 2 respectively.

[0062] Table 1 Main chemical composition of dolomite (wt.%)

[0063] MgO CaO <![CDATA[SiO2]]> <![CDATA[Fe2O3]]> <![CDATA[Al2O3]]> 22.73 29.5 2.14 3.53 1.18

[0064] Table 2 Main chemical composition of overhaul slag (wt.%)

[0065] <![CDATA[Na3AlF6]]> NaF C <![CDATA[CaF2]]> <![CDATA[SiO2]]> <![CDATA[Al2O3]]> 5.4 23.7 45.5 2.11 13.6 2.9

[0066] The dolomite and the aluminum electrolytic overhaul slag are processed by a method for extracting magnesium through the coordinated treatment of dolomite and aluminum electrolytic overhaul slag, and the steps are as follows: first, the dolomite and the overhaul slag are crushed and ground to 200 mesh, and then uniformly mixed in a mass ratio of 4:1 to obtain a mixed material to be processed, and then the mixed material is placed in a vacuum induction furnace for high-temperature roasting. Under the conditions of a furnace pressure of 5 Pa, a roasting temperature of 1000° C., and a roasting time of 2.5 h, the volatilization rate of magnesium (the conversion rate of magnesium into magnesium vapor) is 94%, the magnesium vapor is collected and recovered in a condenser, and the magnesium content in the recovered material is 80.3%.

[0067] Example 2

[0068] The raw materials used are dolomite concentrate and aluminum electrolysis overhaul slag, and their chemical compositions are shown in Table 1 and Table 2 respectively.

[0069] The dolomite and overhaul slag are processed by a method for extracting magnesium through coordinated processing of dolomite and overhaul slag, and the steps are as follows: first, the dolomite and overhaul slag are crushed and ground to 200 mesh, and then uniformly mixed at a mass ratio of 4:1 to obtain a mixed material to be processed, and then the mixed material is placed in a vacuum induction furnace for high-temperature roasting. Under the conditions of a furnace pressure of 5 Pa, a roasting temperature of 1100° C., and a roasting time of 2.5 h, the volatilization rate of magnesium is 95.2%, and the magnesium vapor is collected and recovered in a condenser, and the magnesium content in the recovered material is 82.3%.

[0070] Example 3

[0071] The raw materials used are dolomite concentrate and aluminum electrolysis overhaul slag, and their chemical compositions are shown in Table 1 and Table 2 respectively.

[0072] The dolomite and overhaul slag are processed by a method for extracting magnesium through coordinated processing of dolomite and overhaul slag, and the steps are as follows: first, the dolomite and overhaul slag are crushed and ground into 250 meshes, and then uniformly mixed at a mass ratio of 4:1 to obtain a mixed material to be processed, and then the mixed material is placed in a vacuum induction furnace for high-temperature roasting. Under the conditions of a furnace pressure of 10Pa, a roasting temperature of 1100°C, and a roasting time of 3h, the volatilization rate of magnesium is 95.8%, and the magnesium vapor is collected and recovered in a condenser, and the magnesium content in the recovered material is 84.1%.

[0073] Example 4

[0074] The raw materials used are dolomite concentrate and aluminum electrolysis overhaul slag, and their chemical compositions are shown in Table 1 and Table 2 respectively.

[0075] The dolomite and overhaul slag are processed by a method for extracting magnesium through coordinated treatment of dolomite and overhaul slag, and the steps are as follows: first, the dolomite and overhaul slag are crushed and ground into 250 meshes, and then uniformly mixed at a mass ratio of 4:1 to obtain a mixed material to be processed, and then the mixed material is placed in a vacuum induction furnace for high-temperature roasting. Under the conditions of a furnace pressure of 10Pa, a roasting temperature of 1200°C, and a roasting time of 3h, the volatilization rate of magnesium is 96.4%, and the magnesium vapor is collected and recovered in a condenser, and the magnesium content in the recovered material is 88.3%.

[0076] Example 5

[0077] The raw materials used are dolomite concentrate and aluminum electrolysis overhaul slag, and their chemical compositions are shown in Table 1 and Table 2 respectively.

[0078] The dolomite and overhaul slag are processed by a method for extracting magnesium through coordinated processing of dolomite and overhaul slag, and the steps are as follows: first, the dolomite and overhaul slag are crushed and ground into 250 meshes, and then uniformly mixed at a mass ratio of 4:1 to obtain a mixed material to be processed, and then the mixed material is placed in a vacuum induction furnace for high-temperature roasting. Under the conditions of a furnace pressure of 15 Pa, a roasting temperature of 1300° C., and a roasting time of 3 hours, the volatilization rate of magnesium is 97.1%, and the magnesium vapor is collected and recovered in a condenser, and the magnesium content in the recovered material is 90.2%.

[0079] Example 6

[0080] The raw materials used are dolomite concentrate and aluminum electrolysis overhaul slag, and their chemical compositions are shown in Table 1 and Table 2 respectively.

[0081] The dolomite and overhaul slag are processed by a method for extracting magnesium through coordinated processing of dolomite and overhaul slag, and the steps are as follows: first, the dolomite and overhaul slag are crushed and ground into 250 meshes, and then uniformly mixed at a mass ratio of 4:1 to obtain a mixed material to be processed, and then the mixed material is placed in a vacuum induction furnace for high-temperature roasting. Under the conditions of a furnace pressure of 5 Pa, a roasting temperature of 1350° C., and a roasting time of 3.5 hours, the volatilization rate of magnesium is 97.5%, and the magnesium vapor is collected and recovered in a condenser, and the magnesium content in the recovered material is 91.5%.

[0082] Example 7

[0083] The raw materials used are dolomite concentrate and aluminum electrolysis overhaul slag, and their chemical compositions are shown in Table 1 and Table 2 respectively.

[0084] The dolomite and overhaul slag are processed by a method for extracting magnesium through coordinated processing of dolomite and overhaul slag, and the steps are as follows: first, the dolomite and overhaul slag are crushed and ground into 250 meshes, and then uniformly mixed at a mass ratio of 2:1 to obtain a mixed material to be processed, and then the mixed material is placed in a vacuum induction furnace for high-temperature roasting. Under the conditions of a furnace pressure of 5 Pa, a roasting temperature of 1350° C., and a roasting time of 3.5 hours, the volatility of magnesium is 93.1%, and the magnesium vapor is collected and recovered in a condenser, and the magnesium content in the recovered material is 90.4%.

[0085] Example 8

[0086] The dolomite and overhaul slag are processed by a method for extracting magnesium through coordinated treatment of dolomite and overhaul slag, and the steps are as follows: first, the dolomite and overhaul slag are crushed and ground into 250 meshes, and then uniformly mixed at a mass ratio of 6:1 to obtain a mixed material to be processed, and then the mixed material is placed in a vacuum induction furnace for high-temperature roasting. Under the conditions of a furnace pressure of 5 Pa, a roasting temperature of 1350° C., and a roasting time of 3.5 hours, the volatility of magnesium is 98.4%, and the magnesium vapor is collected and recovered in a condenser, and the magnesium content in the recovered material is 92.2%.

[0087] Comparative Example 1

[0088] The dolomite and overhaul slag are processed by a method for extracting magnesium through coordinated processing of dolomite and overhaul slag, and the steps are as follows: first, the dolomite and overhaul slag are crushed and ground into 250 meshes, and then uniformly mixed in a mass ratio of 1:1 to obtain a mixed material to be processed, and then the mixed material is placed in a vacuum induction furnace for high-temperature roasting. Under the conditions of a furnace pressure of 50 Pa, a roasting temperature of 850° C., and a roasting time of 3.5 hours, the volatility of magnesium is 68.3%, and the magnesium vapor is collected and recovered in a condenser, and the magnesium content in the recovered material is 78.5%.

[0089] In addition, one or more technical solutions in the embodiments of the present invention have at least the following technical effects or advantages:

[0090] In the embodiment of the present invention, CaO generated by dolomite at high temperature reacts with fluoride in aluminum electrolysis overhaul slag to generate insoluble CaF2, which effectively fixes the fluoride and prevents it from volatilizing into the environment and causing pollution. At the same time, cyanide in the overhaul slag is decomposed into harmless C and N2 under high temperature conditions, eliminating the potential harm of cyanide to the environment and human body.

[0091] In the embodiment of the present invention, the carbon in the overhaul slag is used as a reducing agent to reduce the MgO in the dolomite into magnesium vapor, which is then collected by condensation or the like, thereby achieving efficient recovery of the magnesium element.

[0092] In the embodiment of the present invention, the high temperature roasting reaction is carried out under vacuum conditions, the operation is relatively simple, and it is convenient for industrial production. At the same time, high temperature roasting is also one of the common solid waste treatment methods, and the technology is highly mature.

[0093] In the embodiment of the present invention, the potential threat to the environment is reduced by harmlessly treating the aluminum electrolysis overhaul slag. At the same time, since vacuum conditions are used in the magnesium recovery process, the emission risk of other harmful gases is also reduced. The aluminum electrolysis overhaul slag and dolomite, which may have been regarded as waste, are effectively and comprehensively utilized, which not only solves the problem of waste disposal, but also realizes the recycling of resources, which is in line with the concept of circular economy and sustainable development.

[0094] 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. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein 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 herein, but will conform to the widest range consistent with the principles and novel features applied for herein.

Claims

1. A method for recovering magnesium by co-processing dolomite and aluminum electrolysis overhaul slag, characterized in that: The method comprises: Mixing dolomite and aluminum electrolysis overhaul slag according to a set mass ratio to obtain a mixed material; the set mass ratio is (2-6):1; and Under vacuum conditions, the mixed material is subjected to a high-temperature calcination reaction to recover the magnesium element in the mixed material.

2. The method according to claim 1, characterized in that The set mass ratio is 4:

1.

3. The method according to claim 1, characterized in that Calculated by mass, the chemical composition of the aluminum electrolysis overhaul slag includes: Na3AlF6: 5 to 6 parts, NaF: 20 to 26 parts, C: 40 to 50 parts, CaF2: 1.5 to 3 parts, SiO2: 10 to 15 parts, and Al2O3: 2 to 4 parts.

4. The method according to claim 3, characterized in that The particle size of the aluminum electrolysis overhaul slag is 200-250 meshes.

5. The method according to claim 1, characterized in that Calculated by mass, the chemical composition of the dolomite includes: MgO: 20 to 25 parts, CaO: 25 to 35 parts, SiO2: 1 to 3 parts, Fe2O3: 2 to 5 parts, and Al2O3: 0.5 to 2 parts.

6. The method according to claim 5, characterized in that The particle size of the dolomite is 200-250 meshes.

7. The method according to claim 1, characterized in that The step of subjecting the mixed material to a high temperature roasting reaction to recover the magnesium element in the mixed material comprises: The mixed material is subjected to a high temperature roasting reaction so that the magnesium in the mixed material is converted into magnesium vapor; The magnesium vapor is condensed to obtain a recovered product containing magnesium element.

8. The method according to claim 7, characterized in that The calcination temperature of the high temperature calcination reaction is 950° C. to 1350° C., and the calcination time of the high temperature calcination reaction is 2 h to 3.5 h.

9. The method according to claim 7, characterized in that: The calcination pressure of the high temperature calcination reaction is 5Pa to 25Pa.

10. The method according to claim 7, characterized in that The conversion rate of the magnesium into the magnesium vapor is ≥90%, and the mass of the magnesium element is ≥80% of the total mass of the recyclate.

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