Method for removing impurities in magnesium liquid by using carbon-based refining agent

Abstract

The invention discloses a method for removing impurities in magnesium liquid by using a carbon-based refining agent, which comprises the following steps of: melting crude magnesium in a crucible into which protective gas is introduced to obtain crude magnesium liquid, and adding the carbon-based refining agent for refining when the refining temperature of the crude magnesium liquid is reached to obtain refined magnesium liquid at the upper part of the crucible. The method for removing the impurities in the magnesium liquid by using the carbon-based refining agent has the advantages of good impurity removal effect, zero environmental pollution and high practical application value, and solves the problems of environmental pollution, magnesium liquid pollution, equipment corrosion and the like of the refining agent with complex components in the existing magnesium refining technology.

Description

Technical Field

[0001] The present invention relates to the technical field of magnesium metal smelting, and in particular to a method for removing impurities from magnesium liquid by utilizing a carbon-based refining agent. Background Art

[0002] As the lightest structural engineering metal, magnesium is hailed as the "21st century green engineering material." Magnesium, due to its abundant resources, is gaining increasing attention. The demand for lightweight structures and environmental protection, in particular, has fueled the rapid development of the magnesium industry. With the increasing research and industrialization of high-quality magnesium alloys by domestic and international magnesium alloy processing companies, the demand for pure magnesium has increased significantly in recent years.

[0003] Currently, the main methods for purifying magnesium metal include flux refining, sedimentation refining, additive refining, vacuum distillation, zone smelting, and electrolytic refining. Flux refining and sedimentation refining are methods for refining crude magnesium, and magnesium plants employ either method. The flux used in flux refining is mostly composed of chloride salts and contains some water of crystallization. When in contact with the high-temperature magnesium melt, it easily produces large amounts of harmful gases such as Cl2, HCl, and HF, which corrode smelting equipment and plant, pose a health risk, and pollute the environment. Sedimentation refining also suffers from low production efficiency and ineffective impurity removal.

[0004] Chinese Patent No. 201010193468.9 discloses a new method for refining magnesium metal. This method utilizes a flux-free refining process, exploiting the physical property differences between solid inclusions and the melt to purify crude magnesium. This method offers advantages such as reduced energy consumption and production costs, as well as continuous melting and alloying. However, flux-free refining has yet to be industrialized. Chinese Patent No. 201620030985.7 discloses a novel magnesium metal refining system. This method and apparatus achieve continuous feeding, but the process is complex, prolongs refining time, and fails to improve production efficiency. Chinese Patent No. 202211486316.7 discloses a liquid magnesium refining device and method. This refining device enables secondary refining of liquid magnesium, increasing the purity of refined magnesium to 99.98%. While these methods can refine magnesium metal to a certain extent, they fail to address the environmental pollution and equipment corrosion caused by refining agents. Therefore, how to produce pure magnesium in a green, low-carbon, efficient, and low-cost manner is an urgent problem for those skilled in the art. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for removing impurities from magnesium liquid using a carbon-based refining agent, so as to solve the problems of large amounts of environmental pollution and equipment corrosion caused by the above-mentioned magnesium refining method.

[0006] To achieve the above object, the present invention provides a method for removing impurities from magnesium liquid using a carbon-based refining agent, comprising the following steps:

[0007] Crude magnesium is placed in a crucible filled with protective gas for melting to obtain crude magnesium liquid. When the refining temperature of the crude magnesium liquid is reached, a carbon-based refining agent is added for refining to obtain refined magnesium liquid on the upper part of the crucible.

[0008] Preferably, the refining temperature is 680-720°C.

[0009] Preferably, the heating rate of the melting is 5 to 20° C. / min.

[0010] Preferably, the carbon-based refining agent is added in an amount of 1-5% by weight of the crude magnesium. The carbon-based refining agent is a carbon-containing material with an average particle size of 4-8 mesh. The carbon-containing material can be a series of carbon-based materials with high specific surface area and unsaturated bonds, such as activated carbon, graphene, carbon nanotubes, and amorphous carbon. The carbon-based refining agent in the present invention is not limited to its source or shape, and can be spherical, cylindrical, or honeycomb.

[0011] Preferably, the refining includes a stirring refining stage and a static refining stage.

[0012] Preferably, during the stirring refining stage, the carbon-based refining agent undergoes physical adsorption and chemical adsorption with impurities in the magnesium solution.

[0013] Preferably, during the static refining stage, the impurities are adsorbed and then settle to the bottom of the crucible together with the carbon-based refining agent for removal.

[0014] The impurities contained in crude magnesium include oxides and metal impurities. The metal impurities include Al, Ca, Si and Mn. Carbon-based refining agents are added during the refining process. The surface of the carbon-based refining agent has a large number of pores. Even a small amount of carbon-based refining agent has a huge surface area. The oxide impurities in the crude magnesium will be physically adsorbed by the carbon-based refining agent. During the heating process, the carbon-based refining agent does not react with the magnesium liquid in the temperature range of 100-800°C, but can react with the impurities Al, Ca, Si and Mn in the magnesium liquid to generate compounds such as Al4C3, CaC2, SiC and Mn3C, thereby realizing the chemical adsorption of the carbon-based refining agent.

[0015] The chemical adsorption reactions between the metal impurities in the crude magnesium and C in the present invention are:

[0016] 4 / 3Al+C=1 / 3AlC3

[0017] Si+C=SiC

[0018] 1 / 2Ca+C=1 / 2CaC2

[0019] 3Mn+C=Mn3C.

[0020] Preferably, the stirring refining stage lasts for 5 to 30 minutes, and the standing refining stage lasts for 0.5 to 2.0 hours.

[0021] Preferably, the refined magnesium liquid flows out from the crucible mouth and is poured into a preheated casting mold under a protective atmosphere to obtain a magnesium ingot with a purity of 99.8-99.99%.

[0022] Therefore, the present invention adopts the above-mentioned method of removing impurities from magnesium liquid using a carbon-based refining agent, which has the following beneficial effects:

[0023] The method of removing impurities from magnesium liquid by using a carbon-based refining agent has good impurity removal effect, zero environmental pollution, high practical application value, and solves the problems of the existing magnesium refining technology such as the refining agent with complex components polluting the environment, magnesium liquid, and corroding equipment.

[0024] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The present invention is a process flow chart of a method for removing impurities from magnesium liquid using a carbon-based refining agent;

[0026] Figure 2 Figure 2 is a graph showing the relationship between Gibbs free energy and temperature for possible chemical adsorption reactions in crude magnesium solution. DETAILED DESCRIPTION

[0027] The present invention will be further described below. It should be noted that this embodiment is based on the technical solution and provides a detailed implementation method and specific operation process, but the present invention is not limited to this embodiment.

[0028] The present invention has no particular requirements for the type or source of the crude magnesium, and any method known to those skilled in the art can be used. Prior to heating and melting the crude magnesium, the present invention preferably further includes steps such as washing and drying the crude magnesium to remove impurities, dust, and oily substances on its surface.

[0029] Example 1

[0030] like Figure 1 As shown, a method for removing impurities from magnesium liquid using a carbon-based refining agent comprises the following steps:

[0031] The crude magnesium is placed in a crucible filled with protective gas for melting, and the heating rate of the melting is 10°C / min to obtain a crude magnesium liquid; when the refining temperature of the crude magnesium liquid reaches 700°C, a carbon-based refining agent is added, and the carbon-based refining agent is coconut shell activated carbon with an average particle size of 4 to 8 meshes, purchased from Pingdingshan Tanernuo New Materials Co., Ltd., and the amount of coconut shell activated carbon added is 0.5% of the weight of the crude magnesium. The coconut shell activated carbon and the crude magnesium liquid are mixed and stirred, and the coconut shell activated carbon is dispersed in the magnesium liquid and the two are fully contacted. The stirring and refining time is 0.5h; the coconut shell activated carbon and the crude magnesium are mixed and stirred. The impurities in the liquid undergo physical adsorption and chemical adsorption. Physical adsorption can adsorb some impurities (oxides). The coconut shell activated carbon does not react with the magnesium liquid, but can react with Al, Ca, Si and Mn in the magnesium liquid to generate compounds such as Al4C3, CaC2, SiC and Mn3C, and undergo chemical reaction for chemical adsorption. The activated carbon after adsorbing impurities is allowed to settle to the bottom of the crucible and removed. The static refining stage lasts for 0.5 hours. The pure refined magnesium liquid flows out from the crucible mouth and is poured into a preheated casting mold under a protective atmosphere to obtain a magnesium ingot with a purity of 99.84%.

[0032] The ICP-OES method was used to detect the content of each element in crude magnesium and magnesium ingots. The test results are shown in Tables 1 and 2.

[0033] Table 1 Chemical analysis test results of raw material crude magnesium

[0034] element Mg Ca Al Si Mn Fe content 93.40 0.2700 0.0510 0.0180 0.0140 0.0068 element Zn Cu Sn Pb Ni other content 0.0060 0.0028 0.0080 0.0067 0.0027 6.23

[0035] Table 2 ICP-OES test results of the magnesium ingot prepared in Example 1

[0036]

[0037]

[0038] It can be seen from Table 1 that the elements with higher impurity content in crude magnesium are Ca, Al, Si and Mn. It can be seen from Table 2 that after adding activated carbon for crude magnesium refining, the content of impurity elements Ca, Si and Mn are significantly reduced.

[0039] from Figure 2 It can be seen that the chemical reactions that may occur after adding activated carbon to the crude magnesium solution and heating it are as follows:

[0040]

[0041] The change in Gibbs free energy (ΔG) is a key parameter for measuring the spontaneity of a chemical reaction. Negative values ​​indicate a spontaneous reaction, while positive values ​​indicate a non-spontaneous reaction. Under heating conditions, carbon (C) and Al, Ca, Si, or Mn can react to form carbides. However, the positive Gibbs free energy for the chemical reaction between Mg and C indicates that no carbonization reaction occurs. Activated carbon can remove metallic impurities from crude magnesium through chemical adsorption.

[0042] Example 2

[0043] A method for removing impurities from magnesium liquid using a carbon-based refining agent comprises the following steps:

[0044] The crude magnesium is placed in a crucible filled with protective gas for melting, and the heating rate of the melting is 10°C / min to obtain a crude magnesium liquid. When the refining temperature of the crude magnesium liquid reaches 700°C, activated carbon is added. The activated carbon is coconut shell activated carbon with an average particle size of 4 to 8 meshes, purchased from Pingdingshan Tanernuo New Materials Co., Ltd. The amount of coconut shell activated carbon added is 1% of the weight of the crude magnesium. The coconut shell activated carbon and the crude magnesium liquid are stirred evenly, and the stirring and refining stage lasts for 0.5h. The coconut shell activated carbon undergoes physical adsorption and chemical adsorption with impurities in the magnesium liquid. Attached, physical adsorption can absorb some impurities (oxides). Coconut shell activated carbon does not react with magnesium liquid, but can react with Al, Ca, Si and Mn in the magnesium liquid to generate compounds such as Al4C3, CaC2, SiC and Mn3C, and chemical reaction occurs for chemical adsorption. The activated carbon after adsorbing impurities is removed by settling to the bottom of the crucible. The time of the static refining stage is 0.5h. The pure refined magnesium liquid flows out from the crucible mouth and is poured into a preheated casting mold under a protective atmosphere to obtain a magnesium ingot with a purity of 99.87%.

[0045] The crude magnesium raw material used in this example is the same as that in Example 1. The content of each element in the magnesium ingot is detected by ICP-OES method. The test results are shown in Table 3.

[0046] Table 3 ICP-OES test results of the magnesium ingot prepared in Example 2

[0047] element Mg Ca Al Si Mn Fe content 99.87 0.0635 0.0443 0.0013 0.0088 0.0024 element Zn Cu Sn Pb Ni other content 0.0034 ＜0.0005 0.0005 0.0010 ＜0.0005 -

[0048] It can be seen from Table 3 that after adding activated carbon for crude magnesium refining, the contents of impurity elements Ca, Si and Mn are significantly reduced.

[0049] Example 3

[0050] A method for removing impurities from magnesium liquid using a carbon-based refining agent comprises the following steps:

[0051] The crude magnesium is placed in a crucible filled with protective gas for melting, and the heating rate of the melting is 10°C / min to obtain a crude magnesium liquid. When the refining temperature of the crude magnesium liquid reaches 700°C, activated carbon is added. The activated carbon is coconut shell activated carbon with an average particle size of 4 to 8 meshes, purchased from Pingdingshan Tanernuo New Materials Co., Ltd. The amount of coconut shell activated carbon added is 1.5% of the weight of the crude magnesium. The coconut shell activated carbon and the crude magnesium liquid are stirred evenly, and the stirring and refining stage lasts for 0.5h. The coconut shell activated carbon undergoes physical adsorption and chemical reaction with impurities in the crude magnesium liquid. Chemical adsorption: Physical adsorption can adsorb some impurities (oxides). Coconut shell activated carbon does not react with magnesium liquid, but can react with Al, Ca, Si and Mn in the magnesium liquid to generate compounds such as Al4C3, CaC2, SiC and Mn3C, and undergo chemical reaction for chemical adsorption. The activated carbon after adsorbing impurities is allowed to settle to the bottom of the crucible for removal. The standing refining stage lasts for 0.5h. The pure refined magnesium liquid flows out from the crucible mouth and is poured into a preheated casting mold under a protective atmosphere to obtain a magnesium ingot with a purity of 99.9%.

[0052] The crude magnesium raw material used in this example is the same as that in Example 1. The content of each element in the magnesium ingot is detected by ICP-OES method. The test results are shown in Table 4.

[0053] Table 4 ICP-OES test results of the magnesium ingot prepared in Example 3

[0054] element Mg Ca Al Si Mn Fe content 99.9 0.0163 0.0651 0.0038 0.0090 0.0016 element Zn Cu Sn Pb Ni other content 0.0034 0.0010 ＜0.0005 0.0009 0.0006 -

[0055] It can be seen from Table 4 that after adding activated carbon for crude magnesium refining, the contents of impurity elements Ca, Si and Mn are significantly reduced.

[0056] Example 4

[0057] A method for removing impurities from magnesium liquid using a carbon-based refining agent comprises the following steps:

[0058] The crude magnesium is placed in a crucible filled with protective gas for melting, and the heating rate of the melting is 10°C / min to obtain a crude magnesium liquid. When the refining temperature of the crude magnesium liquid reaches 700°C, activated carbon is added. The activated carbon is coconut shell activated carbon with an average particle size of 4 to 8 meshes, purchased from Pingdingshan Tanernuo New Materials Co., Ltd. The amount of coconut shell activated carbon added is 2% of the weight of the crude magnesium. The coconut shell activated carbon and the crude magnesium liquid are stirred evenly, and the stirring and refining stage lasts for 0.5h. The coconut shell activated carbon undergoes physical adsorption and chemical adsorption with impurities in the magnesium liquid. Attached, physical adsorption can absorb some impurities (oxides). Coconut shell activated carbon does not react with magnesium liquid, but can react with Al, Ca, Si and Mn in the magnesium liquid to generate compounds such as Al4C3, CaC2, SiC and Mn3C, and chemical reaction occurs for chemical adsorption. The activated carbon after adsorbing impurities is removed by settling to the bottom of the crucible. The time of the static refining stage is 0.5h. The pure refined magnesium liquid flows out from the crucible mouth and is poured into a preheated casting mold under a protective atmosphere to obtain a magnesium ingot with a purity of 99.92%.

[0059] The crude magnesium raw material used in this example is the same as that in Example 1. The content of each element in the magnesium ingot is detected by ICP-OES method. The test results are shown in Table 5.

[0060] Table 5 ICP-OES test results of the magnesium ingot prepared in Example 4

[0061] element Mg Ca Al Si Mn Fe content 99.92 0.0341 0.0307 0.0026 0.0055 0.0009 element Zn Cu Sn Pb Ni other content 0.0033 ＜0.0005 0.0012 0.0019 ＜0.0005 -

[0062] It can be seen from Table 5 that after adding activated carbon for crude magnesium refining, the contents of impurity elements Ca, Si and Mn are significantly reduced.

[0063] Example 5

[0064] A method for removing impurities from magnesium liquid using a carbon-based refining agent comprises the following steps:

[0065] The crude magnesium is placed in a crucible filled with protective gas for melting, and the heating rate of the melting is 10°C / min to obtain a crude magnesium liquid. When the refining temperature of the crude magnesium liquid reaches 700°C, activated carbon is added. The activated carbon is coconut shell activated carbon with an average particle size of 4 to 8 meshes, purchased from Pingdingshan Tanernuo New Materials Co., Ltd. The amount of coconut shell activated carbon added is 4% of the weight of the crude magnesium. The coconut shell activated carbon and the crude magnesium liquid are stirred evenly, and the stirring and refining stage lasts for 0.5h. The coconut shell activated carbon undergoes physical adsorption and chemical adsorption with impurities in the magnesium liquid. Attached, physical adsorption can absorb some impurities (oxides). Coconut shell activated carbon does not react with magnesium liquid, but can react with Al, Ca, Si and Mn in the magnesium liquid to generate compounds such as Al4C3, CaC2, SiC and Mn3C, and undergo chemical reaction for chemical adsorption. The activated carbon after adsorbing impurities is allowed to settle to the bottom of the crucible for removal. The static refining stage lasts for 0.5h. The pure refined magnesium liquid flows out from the crucible mouth and is poured into a preheated casting mold under a protective atmosphere to obtain a magnesium ingot with a purity of 99.89%.

[0066] The crude magnesium raw material used in this example is the same as that in Example 1. The content of each element in the magnesium ingot is detected by ICP-OES method. The test results are shown in Table 5.

[0067] Table 5 ICP-OES test results of the magnesium ingot prepared in Example 4

[0068]

[0069]

[0070] As can be seen from Table 5, after adding 4% of the weight of crude magnesium to activated carbon for crude magnesium refining, although the content of impurity elements Ca, Si, and Mn is reduced, the purity of magnesium is not further increased.

[0071] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solutions of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for removing impurities from magnesium liquid using a carbon-based refining agent, characterized in that: The following steps are involved: Crude magnesium is placed in a crucible filled with protective gas for melting to obtain crude magnesium liquid. When the refining temperature of the crude magnesium liquid is reached, a carbon-based refining agent is added for refining to obtain refined magnesium liquid on the upper part of the crucible.

2. The method for removing impurities from magnesium liquid using a carbon-based refining agent according to claim 1, characterized in that: The refining temperature is 680~720℃.

3. The method for removing impurities from magnesium liquid using a carbon-based refining agent according to claim 1, characterized in that: The melting temperature rise rate is 5~20℃ / min.

4. The method for removing impurities from magnesium liquid using a carbon-based refining agent according to claim 1, wherein: The amount of the carbon-based refining agent added is 1-5% of the weight of the crude magnesium. The carbon-based refining agent is a carbon-containing substance, and the average particle size of the carbon-based refining agent is 4-8 meshes.

5. The method for removing impurities from magnesium liquid using a carbon-based refining agent according to claim 1, characterized in that: Refining includes stirring refining stage and static refining stage.

6. The method for removing impurities from magnesium liquid using a carbon-based refining agent according to claim 5, characterized in that: During the stirring refining stage, the carbon-based refining agent undergoes physical and chemical adsorption with the impurities in the magnesium liquid.

7. The method for removing impurities from magnesium liquid using a carbon-based refining agent according to claim 6, characterized in that: During the static refining stage, the impurities are adsorbed and then settle to the bottom of the crucible together with the carbon-based refining agent for removal.

8. The method for removing impurities from magnesium liquid using a carbon-based refining agent according to claim 5, characterized in that: The time for the stirring refining stage is 5 to 30 minutes, and the time for the static refining stage is 0.5 to 2.0 hours.

9. The method for removing impurities from magnesium liquid using a carbon-based refining agent according to claim 1, characterized in that: The refined magnesium liquid flows out from the crucible mouth and is poured into a preheated casting mold under a protective atmosphere to obtain a magnesium ingot with a purity of 99.8~99.99%.

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