Anode material for inert anode aluminum electrolysis process

Abstract

The invention belongs to the technical field of aluminum electrolysis, and relates to an inert anode block for preparing a corrosion-resistant film layer on the surface of a high-entropy alloy for aluminum electrolysis. The invention provides an inert anode for preparing an oxide film layer on the surface of an AlCrFeNiV high-entropy alloy anode block matrix and a preparation method of the inert anode. The manufacturing method of the metal ceramic inert anode is easy to operate, efficient and beneficial to application and popularization. According to the invention, a compact oxide layer of (Fe, Al, Cr) 2O3 / AB2O4 spinel / NiO is generated on the surface after the pre-oxidized alloy anode is oxidized for 24 hours in the air at the temperature of 960 DEG C, and the compact oxide layer has good high-temperature conductivity, electrochemical stability and corrosion resistance.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of aluminum electrolysis, and in particular to an inert anode material for aluminum electrolysis and a preparation method of a corrosion-resistant film layer on the surface of the high-entropy alloy. BACKGROUND

[0002] The aluminum electrolysis industry is a key emission reduction field for realizing the "double carbon" strategic goal of China. The current mainstream cryolite-alumina molten electrolysis process (Hall-Heroult method) has a significant carbon emission problem: the carbon anode used will react with oxygen ions generated in the electrolysis process, continuously consuming the anode and releasing a large amount of CO2. In contrast, the inert anode technology, due to its characteristic of not reacting with oxygen ions, not only completely eliminates the CO2 emissions caused by anode carbon consumption, but also produces high-purity oxygen as a byproduct for resource utilization. Therefore, developing high-performance inert anode materials and supporting electrolysis technology has great strategic significance for promoting the green transformation of the aluminum industry and achieving energy saving, carbon reduction and energy efficiency improvement.

[0003] Currently, inert anodes are mainly divided into three categories: alloy systems, oxide ceramic systems and metal ceramic systems. Compared with ceramic and metal ceramic materials, metal materials have the advantages of high strength, good thermal shock resistance, good electrical conductivity and good mechanical performance. The metal anode can generate a protective oxide layer on the surface through pre-oxidation method, which acts as a barrier to isolate the metal matrix from the strong corrosive Na3AlF6 molten salt and oxygen during the electrolysis process while retaining good electrical conductivity. Therefore, the research on the generation of the oxide layer of the alloy anode is of great significance to the development of inert anodes for aluminum electrolysis.

[0004] The inventor's published patent (CN 113249755 A) discloses a nickel-based alloy inert anode and a preparation method thereof. The prepared nickel-based alloy block is oxidized at high temperature in air to form a nickel-based alloy surface corrosion-resistant film on the surface of the anode. The anode material of the invention has strong corrosion resistance and electrical conductivity in the cryolite molten salt system. However, the present application prepares AlCrNiFeV high-entropy alloy blocks into spherical powders through plasma spheroidization, and then forms high-density anode blocks through powder metallurgy, and then performs high-temperature oxidation. The alloy surface oxide layer has a dense layer with high bulk density and good high-temperature electrical conductivity, which can significantly improve the service life of the inert anode. SUMMARY

[0005] The purpose of the present application is to provide an alloy inert anode preparation method and application for the aluminum electrolysis industry to solve the problems in the prior art. The inert anode has good corrosion resistance, high-temperature electrical conductivity and electrochemical stability, and can be used to reduce carbon emissions and improve energy utilization in the current aluminum electrolysis industry.

[0006] In order to achieve the above-mentioned purpose, the technical scheme provided by the present application is:

[0007] The application discloses a preparation method of inert anode material for aluminum electrolysis with a high-entropy alloy surface prepared with a corrosion-resistant film layer.

[0008] According to the preparation method of the inert anode material for aluminum electrolysis with the high-entropy alloy surface prepared with the corrosion-resistant film layer, the high-entropy alloy comprises Al, Cr, Fe, Ni and V.

[0009] According to the preparation method of the inert anode material for aluminum electrolysis with the high-entropy alloy surface prepared with the corrosion-resistant film layer, the particle size of the high-entropy alloy is 1-53 microns.

[0010] According to the preparation method of the modified cermet inert anode composite material for aluminum electrolysis, the method comprises the following steps.

[0011] S1: high-entropy alloy powder is mixed with a binder by ball milling and drying, and then sieved in a vacuum ball mill jar, and then cold-pressed to obtain a green body;

[0012] S2: the anode green body is heated to a sintering temperature in an inert atmosphere, and then naturally cooled to room temperature after being kept at the temperature for a certain time, so that the inert anode is obtained.

[0013] S3: the obtained inert anode is oxidized in air at 960 DEG C for 24 hours, so that a (Fe, Al, Cr)2O3 / AB2O4 spinel / NiO multilayer oxide film structure is formed on the surface.

[0014] According to the preparation method of the inert anode material for aluminum electrolysis with the high-entropy alloy surface prepared with the corrosion-resistant film layer, the dispersant is ethanol or deionized water in the step S1, and the mass ratio of the dispersant to the raw material is 2:1-6:1.

[0015] According to the preparation method of the inert anode material for aluminum electrolysis with the high-entropy alloy surface prepared with the corrosion-resistant film layer, the binder is polyvinyl alcohol in the step S1, and the addition amount of the binder is 1-10% of the mass of the high-entropy alloy powder.

[0016] According to the preparation method of the inert anode material for aluminum electrolysis with the high-entropy alloy surface prepared with the corrosion-resistant film layer, the cold-pressing pressure is 200-800 Mpa, and the pressure maintaining time is 5-20 min in the step S1.

[0017] The application discloses a preparation method of inert anode material for preparing corrosion-resistant film layer on the surface of high-entropy alloy for aluminum electrolysis according to claim 1, characterized in that the inert atmosphere in step S2 is argon, the sintering temperature is 1000-1600 DEG C, and the holding time is 4-12 h.

[0018] The application discloses a preparation method of inert anode material for preparing corrosion-resistant film layer on the surface of high-entropy alloy for aluminum electrolysis according to claim 1, characterized in that the inert atmosphere in step S2 is argon, the sintering temperature is 1000-1600 DEG C, and the holding time is 4-12 h.

[0019] Compared with the prior art, the application has the following advantages and positive effects:

[0020] 1. The alloy anode surface is prepared with a corrosion-resistant oxide film, characterized in that the inert anode is obtained by pre-oxidation to obtain a dense oxide layer, and a multilayer oxide film structure of (Fe, Al, Cr)2O3 / AB2O4 spinel / NiO is generated on the surface of the alloy after oxidation in air at 960 DEG C for 24 h.

[0021] 2. The metal inert anode has good electrochemical stability and molten salt corrosion resistance, and the cross section does not change after 36 h of molten salt corrosion at 960 DEG C. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 a is the appearance feature of the AlCrFeNiV high-entropy alloy powder obtained in example 1.

[0023] Figure 1 b is the surface morphology diagram of the metal inert anode before oxidation obtained in example 1.

[0024] Figure 1 c is the surface morphology diagram of the metal inert anode after oxidation for 24 h obtained in example 1.

[0025] Figure 2 c is the surface morphology diagram of the metal inert anode after oxidation for 24 h obtained in example 1. DETAILED DESCRIPTION

[0026] The application will be further described below by way of examples, but the application is not limited to the scope of the examples. In the following examples, the experimental methods without specific conditions are selected according to conventional methods and conditions or according to the product instructions.

[0027] Example 1 DETAILED DESCRIPTION

[0028] The application will be further described in the following by way of examples without limiting the application to the examples described. The experimental methods in the following examples, for which no specific conditions are indicated, are carried out according to standard methods and conditions, or according to the instructions of the commercial suppliers.

[0029] Example 1

[0030] The preparation method of the metal inert anode composite material for aluminum electrolysis in this example is as follows:

[0031] The metal inert anode material is composed of high-entropy alloy powder; wherein the high-entropy alloy powder is Al, Ni, Cr, Fe, and V five metal elements with different proportions of molar atomic ratio calculation and weighing. Arc furnace is used for smelting into button ingot, and then mechanical alloying is used for ball milling and crushing. The ball milling tank is vacuumed, argon gas is filled and washed repeatedly three times before ball milling operation to ensure that the ball milling dry milling process is in an inert gas protection environment. The ball milling speed is 400 r / min, the ball-to-material ratio is 3:1, and the ball milling is carried out for 12 h. The high-entropy alloy granulated powder is sent into the radio frequency plasma spheroidization powder system for spheroidization treatment to obtain spherical powder, such as Figure 1 a.

[0032] In the metal inert anode material, 2% PVA powder by mass fraction is added to the high-entropy alloy powder, and ball milling is carried out by a ball mill at a ball milling speed of 400 r / min. The ball-to-material ratio is 3:1, and the ball milling is carried out for 12 h. The dispersant is deionized water, which is dried in a 80 ℃ air drying oven for 24 h. The dried powder block is ball milled in a vacuum ball milling tank with a ball-to-material mass ratio of 3:1 for 4 h. The powder with uniform mixing and meeting the particle size requirements is obtained by filtering with a 100 mesh sieve.

[0033] The obtained metal ceramic composite powder is cold pressed to obtain a green body at 600 MPa for 5 min. The metal inert anode composite material is obtained by sintering and holding at 1300 ℃ in a tube furnace under a protective atmosphere for 6 h. The inert anode block material is polished by line cutting, 600#, 1000#, and 2000# water sandpaper in turn. The treated sample is cleaned and dried in a vacuum drying oven to obtain the metal inert anode material, and the surface morphology is as shown in Figure 1 b.

[0034] The obtained metal inert anode material is sintered and held at 960 ℃ in a tube furnace under air atmosphere for

[0035] 24 h to obtain the final metal inert anode material, and the surface morphology is as shown in Figure 1 c.

[0036] The metal inert anode of the embodiment is electrolyzed in a small aluminum electrolysis cell at 960 DEG C for 24 hours before and after anodic oxidation, and the cell voltage is stabilized at about 3.5 V. In the aluminum electrolysis experiment, the electrode distance is constant at 3 cm, and the molten salt system is 90wt% Na3AlF6-5wt% Al2O3-5wt% CaF2.

[0037] After the inert anode sample of Example 1 is oxidized in air at 960 DEG C for 24 hours, the phase composition and apparent morphology of the sample are characterized by XRD, SEM, TEM and other characterization methods. The oxides corresponding to the oxidation film of the alloy anode are mainly (Fe, Al, Cr)2O3, AB2O4 spinel and NiO, Figure 2 The XRD patterns of the anode block before and after oxidation are compared.

[0038] Example 2

[0039] The preparation method of the metal inert anode composite material for aluminum electrolysis in the embodiment is as follows:

[0040] The metal inert anode material is composed of high-entropy alloy powder; wherein the high-entropy alloy powder is Al, Ni, Cr, Fe and V five metal elements with different proportions of molar atomic ratio calculation and weighing. The button ingot is melted by arc furnace, and then the button ingot is broken by mechanical alloying. Before ball milling, the ball milling tank is vacuumed, argon gas is filled and washed repeatedly three times to ensure that the ball milling process is in an inert gas protection environment. The ball milling speed is 400 r / min, the ball-to-material ratio is 3:1, and the ball milling is carried out for 12 h. The high-entropy alloy granulated powder is sent into the radio frequency plasma spheroidization powder system for spheroidization treatment to obtain spherical powder.

[0041] In the metal inert anode material, 2% PVA powder by mass fraction is added to the high-entropy alloy powder, and the ball mill is used for mixing, with a ball milling speed of 400 r / min. The ball-to-material ratio is 3:1, and the ball milling is carried out for 12 h. The dispersant is deionized water, which is dried in a 80 DEG C air drying oven for 24 h. The dried powder block is ball milled in a vacuum ball milling tank, with a ball-to-material mass ratio of 3:1, and ball milling for 4 h. The powder meeting the particle size requirements and uniformly mixed is obtained by filtering with a 100 mesh screen.

[0042] The obtained metal ceramic composite powder is cold pressed to obtain a green body at 600 MPa for 5 min. The metal inert anode composite material is obtained by sintering in a 1300 DEG C tube furnace under a protective atmosphere for 6 h. The inert anode block material is cut by wire cutting, and then polished with 600#, 1000# and 2000# water sandpaper in sequence. The treated sample is cleaned and dried in a vacuum drying oven to obtain the metal inert anode material.

[0043] The obtained metal inert anode material is sintered in a tube furnace at 960 ℃ under air atmosphere

[0044] 12 h, and the final metal inert anode material is obtained.

[0045] The metal inert anode of the embodiment is electrolyzed at 960 ℃ for 12 h in a small aluminum electrolysis cell after oxidation, and the cell voltage is stabilized at about 4 V. In the aluminum electrolysis experiment, the pole distance is constant at 3 cm, and the molten salt system is 90wt% Na3AlF6-5wt% Al2O3-5wt% CaF2.

[0046] The inert anode sample of Example 2 is characterized by XRD, SEM and other characterization methods after oxidation in air at 960 ℃ for 12 h. The oxides corresponding to the oxidation film of the alloy anode are mainly (Al, Cr)2O3 and AB2O4 spinel.

[0047] Example 3

[0048] The preparation method of the metal inert anode composite material for aluminum electrolysis in the embodiment is as follows:

[0049] The metal inert anode material is composed of high-entropy alloy powder, wherein the high-entropy alloy powder is composed of Al, Ni, Cr, Fe and V metal elements in different proportions of molar atomic ratio. The button ingot is melted by an arc furnace, and then the button ingot is broken by mechanical alloying. The ball milling tank is vacuumed, argon gas is filled and washed repeatedly three times before ball milling to ensure that the ball milling process is in an inert gas protection environment. The ball milling speed is 400 r / min, the ball-to-material ratio is 3:1, and the ball milling is performed for 12 h. The high-entropy alloy granulated powder is sent to a radio frequency plasma spheroidization powder system for spheroidization treatment to obtain spherical powder.

[0050] In the metal inert anode material, 2% PVA powder by mass fraction is added to the high-entropy alloy powder, and the ball mill is used for ball milling and mixing. The ball milling speed is 400 r / min. The ball-to-material ratio is 3:1, and the ball milling is performed for 12 h. The dispersant is anhydrous ethanol which is dried in a 80℃ air drying oven for 24 h. The dried powder block is ball milled in a vacuum ball milling tank, the ball-to-material mass ratio is 3:1, and the ball milling is performed for 4 h. The powder meeting the particle size requirements and uniformly mixed is obtained by filtering with a 100 mesh screen.

[0051] The obtained cermet composite powder is cold-pressed to obtain a green body under 600 MPa for 5 min, sintered at 1300 ℃ in a tube furnace under a protective atmosphere for 6 h to obtain a metal inert anode composite material, and then the inert anode block material is cut by wire, polished by 600#, 1000# and 2000# water sandpaper in sequence, cleaned and dried in a vacuum drying box to obtain the metal inert anode material.

[0052] The obtained metal inert anode material is sintered at 960 ℃ in a tube furnace under an air atmosphere for 24 h to obtain the final metal inert anode material.

[0053] The obtained metal inert anode material is sintered at 960 ℃ in a tube furnace under an air atmosphere for 24 h to obtain the final metal inert anode material.

[0054] The metal inert anode of the embodiment is electrolyzed at 960 ℃ in a small aluminum electrolysis cell before and after oxidation

[0055] The metal inert anode of the embodiment is electrolyzed at 960 ℃ in a small aluminum electrolysis cell before and after oxidation

[0056] After the inert anode sample of Example 3 is oxidized in air at 960 ℃ for 24 h, the phase composition and apparent morphology of the sample are characterized by XRD, SEM and other characterization methods. The oxides corresponding to the oxidation film of the alloy anode are mainly (Al,Cr)2O3, AB2O4 spinel and NiO.

Claims

1. A method for preparing an inert anode material for preparing a corrosion-resistant film layer on the surface of a high-entropy alloy for aluminum electrolysis, characterized by, The high-entropy alloy substrate and the surface corrosion-resistant film layer can be used as a whole as an aluminum electrolysis inert anode.

2. The method of claim 1, wherein the inert anode material for the preparation of a corrosion-resistant film layer on the surface of a high-entropy alloy for aluminum electrolysis is prepared by the steps of: The high-entropy alloy comprises five metal elements of Al, Cr, Fe, Ni and V. ​ 3. The method of claim 1, wherein the inert anode material is prepared by a process comprising: preparing a high-entropy alloy layer on a surface of the inert anode material; and preparing a corrosion-resistant film layer on the high-entropy alloy layer. The particle size of the high-entropy alloy is 1-53 microns.

4. The method of producing a modified cermet inert anode composite material for aluminum electrolysis according to any one of claims 1 to 3, characterized in that The method comprises the following steps: S1: high-entropy alloy powder is ball-mixed with a binder and dried, and then sieved in a vacuum ball mill jar, and then cold-pressed to obtain a green body; S2: the anode green body is heated to a sintering temperature in an inert atmosphere, and then naturally cooled to room temperature after being kept for a certain time, so that an inert anode is obtained. S3: the obtained inert anode is oxidized in air at 960 DEG C for 24 hours, so that a (Al, Cr)2O3 / AB2O4 spinel / NiO oxide film structure is formed on the surface.

5. The method of claim 1, wherein the method is characterized by: In step S1, the dispersant is ethanol or deionized water, and the mass ratio of the dispersant to the raw material is 2:1-6:

1.

6. The method of claim 1, wherein the method is characterized by: In step S1, the binder is polyvinyl alcohol, and the addition amount of the binder is 1-10% of the mass of the high-entropy alloy powder.

7. The method of claim 1, wherein the method is characterized by: In step S1, the cold-pressing pressure is 200-800 MPa, and the pressure holding time is 5-20 min.

8. The method of claim 1, wherein the method is characterized by: In step S2, the inert atmosphere is argon, the sintering temperature is 1000-1600 DEG C, and the holding time is 4-12 h.

9. The method of claim 1, wherein the method is characterized by: In step S3, the oxidation temperature is 960 DEG C, and the holding time is 24 h.

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