Inert anode material, preparation method and application

Abstract

The application provides an inert anode material, a preparation method and application, and uses divalent metal hydroxide and trivalent metal hydroxide as raw materials, in-situ synthesizes spinel-based ceramic phase by using a cold sintering process, and adds metal powder as a metal phase to obtain the inert anode material containing the ceramic phase and the metal phase. The application uses the existence of the metal phase to increase the conductivity of the inert anode material, so that the inert anode material is more easily connected with an external circuit. Meanwhile, the application reduces the traditional sintering temperature by means of the cold sintering process, greatly reduces the sintering energy consumption, and reduces the production cost. The inert anode material prepared by using the preparation process has a wide application prospect in the technical field of electrolytic aluminum.

Description

Technical Field

[0001] This invention relates to the field of aluminum electrolysis technology, specifically to an inert anode material, its preparation method, and its application. Background Technology

[0002] Replacing carbon anodes with inert anodes can effectively solve the direct carbon emissions in primary aluminum production, making it a focus of attention and a research hotspot worldwide. Compared to carbon anodes, inert anodes do not participate in the reaction and therefore do not produce carbon dioxide, while also eliminating pollution generated during the carbon anode manufacturing process. However, because inert anodes operate in a high-temperature cryolite molten salt environment, the requirements for their conductivity are quite stringent.

[0003] Current research indicates that the most promising inert anode material for industrial application is the cermet anode, which uses spinel-type oxide as the ceramic phase and adds an appropriate amount of metallic phase to enhance the conductivity and thermal shock resistance of the ceramic matrix. Currently, the preparation of this anode typically involves powder mixing, granulation, isostatic pressing, machining, and sintering. This process is lengthy, with sintering temperatures usually exceeding 1200℃ and sintering cycles exceeding 40 hours, resulting in high energy consumption. This makes the production cost of inert anodes higher than that of carbon anodes, hindering the promotion of carbon-free aluminum electrolysis technology. Therefore, there is an urgent need for a low-energy-consumption, low-cost method for preparing spinel-type inert anode materials. Summary of the Invention

[0004] To address the problems of insufficient conductivity and high energy consumption in the production of current inert anode materials, this invention provides an inert anode material and its preparation method. The presence of a metallic phase increases the conductivity of the inert anode material, making it easier to connect to external circuits. Simultaneously, this invention utilizes a cold sintering process to reduce the traditional sintering temperature, significantly lowering sintering energy consumption and production costs. The inert anode material prepared using the process described in this invention has broad application prospects in the field of aluminum electrolysis.

[0005] The present invention achieves the above-mentioned technical objectives through the following technical means.

[0006] An inert anode material comprises a metallic phase and a ceramic phase; the metallic phase comprises one or more elements selected from Ni, Co, Fe, Cu, Mn, Al, and Cr, and the ceramic phase is a spinel-type oxide; the proportion of the metallic phase in the inert anode material is 5-50 wt%, and the proportion of the ceramic phase is 50-95 wt%.

[0007] Furthermore, the general formula of the spinel-type oxide is A x B 3-xO4, wherein A includes one or more elements selected from Ni, Mg, Zn, Cu, Mn, Co, and Sn, and B includes one or more elements selected from Fe, Al, Cr, and Co; 0.8 ≤ x ≤ 1.2.

[0008] The preparation method of the above-mentioned inert anode material includes the following steps:

[0009] S1: Prepare ceramic phase precursor powder by mixing divalent metal hydroxide and trivalent metal hydroxide in a molar ratio of x:(3-x), where 0.8≤x≤1.2;

[0010] S2: Add the metallic phase powder to the ceramic phase precursor powder to obtain a mixed powder, wherein the metallic phase powder accounts for 5-50% of the total mass of the mixed powder;

[0011] S3: Add a fluid additive to the mixed powder to obtain a fully wetted mixed powder;

[0012] S4: The mixed powder obtained in step S3 is cold sintered to obtain an inert anode material.

[0013] Further, the divalent metal hydroxide is one or more of Ni(OH)2, Mg(OH)2, Zn(OH)2, Cu(OH)2, Mn(OH)2, Co(OH)2, and Sn(OH)2; the trivalent metal hydroxide is one or more of Fe(OH)3, Al(OH)3, Cr(OH)3, and Co(OH)3.

[0014] Furthermore, the metallic phase powder includes one or more of Ni, Co, Fe, Cu, Mn, Al, and Cr powders.

[0015] Furthermore, the fluid aid is a soluble salt solution of one or more metal ions from the divalent and trivalent metal hydroxides.

[0016] Furthermore, the fluid aid uses all metal salts as solutes, the concentration of the fluid aid is 0.5-4 mol / L, and the amount of fluid aid added is 1-10% of the total mass of the mixed powder.

[0017] Furthermore, the cold sintering parameters are: pressure value of 100-650MPa, temperature value of 150-500℃, and sintering time of 10min to 5h.

[0018] The application of the above-mentioned inert anode materials in electrolytic aluminum.

[0019] Unlike traditional sintering, cold sintering draws inspiration from the formation mechanism of minerals in nature. It involves applying external temperature and pressure, and by adding appropriate fluid additives, wetting and dissolving the particle surface, causing the particles to slide and rearrange under pressure and solution conditions. When the temperature rises, the particles are in a hydrothermal environment. The concentration difference between the liquid and solid phases provides a significant chemical driving force for the solid and liquid phases to reach equilibrium. Under pressure, the contact area between particles has a high chemical potential. Ionic substances or atomic clusters diffuse through the liquid and precipitate on particles located away from the stress contact area, forming deposition lattice sites, leading to grain deposition. The mass transfer during this process minimizes the excess surface free energy of the sample within the compact and eliminates porosity when the material forms a dense solid, thus densifying the material.

[0020] The beneficial effects of this invention are as follows:

[0021] 1. This invention, through in-situ cold sintering to synthesize ceramic and metallic phases, greatly simplifies the inert anode preparation process. Compared to traditional sintering processes, the sintering temperature is reduced by over 700°C, and the sintering cycle is shortened by over 35 hours, significantly reducing energy consumption and costs in inert anode production, improving anode production efficiency, and reducing carbon emissions during anode production. Simultaneously, the simplified process also reduces initial equipment investment, which is beneficial for the promotion of inert anodes and carbon-free aluminum electrolysis technology.

[0022] 2. In this invention, the presence of the metallic phase can transfer electrons, allowing the electrons released during the anodic reaction to be smoothly transferred to the external circuit through the metallic phase, increasing the conductivity of the anodic material. Furthermore, the metallic phase can form a dense oxide film during the cold sintering process, improving the corrosion resistance of the inert anodic material.

[0023] 3. This invention uses an inert anode to replace the traditional carbon anode, eliminating the need for frequent anode replacements during operation. The electrolysis process is simple to operate, reducing a significant amount of manual labor and facilitating the intelligent and automated implementation of aluminum electrolysis plants. Furthermore, the use of inert anodes can reduce the need for desulfurization and denitrification facilities and processes, thereby reducing the initial investment and operating costs of aluminum electrolysis plants. Attached Figure Description

[0024] Figure 1 The image shows the XRD pattern of the inert anode material prepared in Example 1 of this invention.

[0025] Figure 2 This is an electrochemical test diagram of the inert anode material prepared in Example 1 of the present invention;

[0026] Figure 3 The image shows the XRD pattern of the inert anode material prepared in Example 2 of this invention.

[0027] Figure 4 This is an electrochemical test diagram of the inert anode material prepared in Example 2 of the present invention;

[0028] Figure 5 The image shows the XRD pattern of the inert anode material prepared in Example 3 of this invention.

[0029] Figure 6 This is an electrochemical test diagram of the inert anode material prepared in Example 3 of the present invention. Detailed Implementation

[0030] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0031] Example 1

[0032] The preparation method of the inert anode material described in this embodiment is as follows:

[0033] S1: Ni(OH)2, Co(OH)2, Fe(OH)3, and Al(OH)3 were mixed in a molar ratio of 0.9:0.05:2:0.05 to obtain 40g of ceramic phase precursor powder.

[0034] S2: Add 20g of 70Ni25Cu4.5Al0.5Cr alloy powder to the ceramic phase precursor powder, and mix for 2 hours using a three-dimensional mixer to obtain a mixed powder.

[0035] S3: Add 6g of a 4mol / L aqueous solution of nickel nitrate to the mixed powder, and continue mixing for 1 hour using a three-dimensional mixer to obtain the mixed powder.

[0036] S4: The mixed powder obtained in step S3 is loaded into a cold sintering mold, the temperature is set to 480℃ and the pressure is 100MPa, and the ceramic phase (spinel oxide) and metal phase are synthesized in situ by cold sintering. The sintering time is 1h. After the sintering is completed, the pressure is released and the material is cooled to room temperature to obtain an inert anode material.

[0037] Figure 1 The figure shows the XRD pattern of the inert anode material prepared in this embodiment. As can be seen from the figure, Ni was synthesized in situ by cold sintering in this embodiment. 0.9 Co 0.05 Fe2Al 0.05 The relative density of the O4 spinel-type ceramic phase, measured using the Archimedes method, was 98.7% for the inert anode material.

[0038] The above-mentioned inert anode material was subjected to an electrolysis experiment at 100A in a KF-NaF-AlF3-Al2O3 electrolyte system, with CR = 1.35 and an anode current density of 0.8A / cm. 2The electrolysis voltage was 3.42V, and the test results were as follows: Figure 1 As shown, the electrolytic cell maintained a stable voltage during long-term operation at 800℃, indicating that the electrolyte system has good conductivity and thermal stability. After 250 minutes of operation, the electrolysis voltage was 3.45V, indicating low energy consumption and high electrolysis efficiency. The measured impurity content in the molten aluminum was less than 0.5%, demonstrating that the inert anode material effectively prevents the formation and accumulation of impurities, exhibiting high chemical stability and corrosion resistance.

[0039] Example 2

[0040] The preparation method of the inert anode material described in this embodiment is as follows:

[0041] S1: Ni(OH)2, Cu(OH)2, Mg(OH)2, Fe(OH)3, and Cr(OH)3 were mixed in a molar ratio of 1:0.05:0.05:1.85:0.05 to obtain 40g of ceramic phase precursor powder.

[0042] S2: Add 30g of 85Ni10Fe4.5Co0.5Mn alloy powder to ceramic phase precursor powder, and mix for 2 hours using a three-dimensional mixer to obtain mixed powder.

[0043] S3: Add 5g of a mixed salt solution of nickel nitrate and ferric nitrate to the mixed powder, wherein nickel nitrate and ferric nitrate are the solutes and the concentration of the mixed salt solution is 4mol / L. Continue mixing for 1 hour using a three-dimensional mixer to obtain the mixed powder. The molar ratio of nickel nitrate to ferric nitrate in the mixed salt solution is 1:2.

[0044] S4: The mixed powder obtained in step S3 is loaded into a cold sintering mold, the temperature is set to 300℃ and the pressure is 350MPa, and the ceramic phase (spinel oxide) and metal phase are synthesized in situ by cold sintering. The sintering time is 3h. After the sintering is completed, the pressure is released and cooled to room temperature to obtain an inert anode material.

[0045] Figure 3 The figure shows the XRD pattern of the inert anode material prepared in this embodiment. As can be seen from the figure, NiCu was synthesized in situ by cold sintering in this embodiment. 0.05 Mg 0.05 Fe 1.85 Cr 0.05 The relative density of the O4 spinel-type ceramic phase, measured using the Archimedes method, was 96.3% for the inert anode material.

[0046] The above-mentioned inert anode material was subjected to an electrolysis experiment at 100A in a KF-NaF-AlF3-Al2O3 electrolyte system, with CR = 1.5 and an anode current density of 1A / cm. 2 The electrolysis voltage was 3.74V, and the test results were as follows: Figure 4 As shown, the electrolytic cell maintained a stable voltage during long-term operation at 860℃, indicating that the electrolyte system has good conductivity and thermal stability. After 240 minutes of operation, the electrolysis voltage was 3.65V, indicating low energy consumption and high electrolysis efficiency. The measured impurity content in the molten aluminum was less than 0.3%, demonstrating that the inert anode material effectively prevents the formation and accumulation of impurities, exhibiting high chemical stability and corrosion resistance.

[0047] Example 3

[0048] The preparation method of the inert anode material described in this embodiment is as follows:

[0049] S1: Ni(OH)2, Mn(OH)2, Sn(OH)2, and Fe(OH)3 were mixed in a molar ratio of 0.9:0.05:0.05:2 to obtain 40g of ceramic phase precursor powder.

[0050] S2: Add 5g of Cu powder and 5g of Ni powder to the ceramic phase precursor powder, and mix for 2 hours using a three-dimensional mixer to obtain a mixed powder.

[0051] S3: Add 1g of a mixed salt solution of nickel nitrate and ferric nitrate to the mixed powder, wherein nickel nitrate and ferric nitrate are the solutes and the concentration of the mixed salt solution is 4mol / L. Continue mixing for 1 hour using a three-dimensional mixer to obtain the mixed powder. The molar ratio of nickel nitrate to ferric nitrate in the mixed salt solution is 1:2.

[0052] S4: The mixed powder obtained in step S3 is loaded into a cold sintering mold, the temperature is set to 150℃ and the pressure is 500MPa, and the ceramic phase (spinel oxide) and metal phase are synthesized in situ by cold sintering. The sintering time is 4h. After the sintering is completed, the pressure is released and the material is cooled to room temperature to obtain an inert anode material.

[0053] Figure 5 The figure shows the XRD pattern of the inert anode material prepared in this embodiment. As can be seen from the figure, Ni was synthesized in situ by cold sintering in this embodiment. 0.9 Mn 0.05 Sn 0.05 The Fe2O4 spinel-type ceramic phase, with a relative density of 96.5% for the inert anode material determined using the Archimedes method.

[0054] The above-mentioned inert anode material was subjected to an electrolysis experiment at 100A in a KF-NaF-AlF3-Al2O3 electrolyte system, with CR = 1.4 and an anode current density of 1A / cm. 2 The electrolysis voltage was 3.9V, and the test results were as follows: Figure 6As shown, the electrolytic cell maintained a stable voltage during long-term operation at 830℃, indicating that the electrolyte system has good conductivity and thermal stability. After 180 minutes of operation, the electrolysis voltage was 3.6V, indicating low energy consumption and high electrolysis efficiency. The measured impurity content in the molten aluminum was less than 0.4%, demonstrating that the inert anode material and electrolyte system effectively prevent the formation and accumulation of impurities, exhibiting high chemical stability and corrosion resistance.

[0055] The embodiments described above are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments. Any obvious improvements, substitutions or modifications that can be made by those skilled in the art without departing from the essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A method for preparing an inert anode material, characterized in that, Includes the following steps: S1: Prepare ceramic phase precursor powder by mixing divalent metal hydroxide and trivalent metal hydroxide in a molar ratio of x:(3-x), where 0.8≤x≤1.2; The divalent metal hydroxide is one or more of Ni(OH)2, Mg(OH)2, Zn(OH)2, Cu(OH)2, Mn(OH)2, Co(OH)2, and Sn(OH)2; the trivalent metal hydroxide is one or more of Fe(OH)3, Al(OH)3, Cr(OH)3, and Co(OH)3. S2: Add the metallic phase powder to the ceramic phase precursor powder to obtain a mixed powder, wherein the metallic phase powder accounts for 5-50% of the total mass of the mixed powder; the metallic phase powder includes one or more of Ni, Co, Fe, Cu, Mn, Al, and Cr powders; S3: Add a fluid additive to the mixed powder to obtain a fully wetted mixed powder; the fluid additive is a soluble salt solution of one or more metal ions among the divalent metal hydroxide and trivalent metal hydroxide; S4: The mixed powder obtained in step S3 is subjected to cold sintering. The cold sintering parameters are: pressure value of 100-650MPa, temperature value of 150-500℃, and sintering time of 10min~5h. An inert anode material was obtained.

2. The preparation method according to claim 1, characterized in that, The fluid additive uses all metal salts as solutes, and the concentration of the fluid additive is 0.5~4 mol / L. The amount of fluid additive added is 1-10% of the total mass of the mixed powder.

3. The inert anode material prepared by the preparation method according to any one of claims 1-2, characterized in that, It includes a metallic phase and a ceramic phase; the metallic phase includes one or more elements selected from Ni, Co, Fe, Cu, Mn, Al, and Cr, and the ceramic phase is a spinel-type oxide; the proportion of the metallic phase in the inert anode material is 5~50wt%, and the proportion of the ceramic phase is 50~95wt%.

4. The inert anode material according to claim 3, characterized in that, The general formula of the spinel-type oxide is A x B 3-x O4, wherein A includes one or more elements selected from Ni, Mg, Zn, Cu, Mn, Co, and Sn, and B includes one or more elements selected from Fe, Al, Cr, and Co; 0.8 ≤ x ≤ 1.

2.

5. The application of the inert anode material according to any one of claims 3 to 4 in electrolytic aluminum.

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