Coating and its preparation method, coating, carbon anode

Abstract

This application relates to a coating, a preparation method thereof, a coating layer, and a carbon anode. The raw material components of the coating include: alumina, potassium feldspar, aluminum dihydrogen phosphate, and inorganic silicone resin; wherein, by mass fraction, the content of the alumina is 30% to 40%, the content of the potassium feldspar is 10% to 30%, the content of the aluminum dihydrogen phosphate is 30 to 40%, and the content of the inorganic silicone resin is 5% to 15%. The content of this application solves the technical problem that the existing carbon anode is prone to react with air, resulting in oxidation and burning loss of the anode carbon block.

Description

Technical Field

[0001] This application relates to the technical field of coatings, and particularly to a coating, a preparation method thereof, a coating layer, and a carbon anode. Background Art

[0002] The carbon anode is known as the "heart" of the aluminum electrolysis cell, and its quality has a great impact on technical and economic indicators such as aluminum electrolysis production, current efficiency, power consumption, raw material consumption, and product quality.

[0003] During the production of electrolytic aluminum, the anode carbon block, as a consumable material for electrochemical reactions, participates in electrochemical reactions under high temperature and current, generating carbon dioxide and discharging it from the electrolysis cell. The theoretical consumption of carbon anode per ton of electrolytic aluminum is about 334 kg, but the actual consumption is much greater than 334 kg. The main reason for the excessive consumption of the carbon anode is the non-electrolytic consumption of the anode carbon block, that is, the reaction of the anode carbon block with oxygen and carbon dioxide in the air, resulting in the oxidation and burning loss of the anode carbon block. This will not only increase the consumption of the anode, but also increase carbon emissions and cause environmental pollution. Summary of the Invention

[0004] This application provides a coating, a preparation method thereof, a coating layer, and a carbon anode to solve the technical problem that the existing carbon anode is prone to react with air, resulting in the oxidation and burning loss of the anode carbon block.

[0005] In a first aspect, this application provides a coating, and the raw material components of the coating include:

[0006] aluminum oxide, potassium feldspar, aluminum dihydrogen phosphate, and inorganic silicone resin; wherein, by mass fraction,

[0007] the content of the aluminum oxide is 30% - 40%, the content of the potassium feldspar is 10% - 30%, the content of the aluminum dihydrogen phosphate is 30 - 40%, and the content of the inorganic silicone resin is 5 - 15%.

[0008] Optionally, the content of the aluminum oxide is 33% - 35%, the content of the potassium feldspar is 20% - 22%, the content of the aluminum dihydrogen phosphate is 32% - 34%, and the content of the inorganic silicone resin is 11% - 13%.

[0009] Optionally, the content of the aluminum oxide is 35%, the content of the potassium feldspar is 20%, the content of the aluminum dihydrogen phosphate is 34%, and the content of the inorganic silicone resin is 11%.

[0010] Optionally, the particle size of the aluminum oxide is 500 mesh - 800 mesh.

[0011] Optionally, the particle size of the potassium feldspar is 400 mesh - 500 mesh.

[0012] In a second aspect, the present application provides a coating formed from the coating material according to any one of the embodiments of the first aspect.

[0013] In a third aspect, the present application provides a carbon anode, characterized in that the carbon anode includes a carbon anode matrix and a coating according to any one of the embodiments of the second aspect attached to at least a part of the surface of the carbon anode matrix.

[0014] In a fourth aspect, the present application provides a method for preparing the coating material according to any one of the embodiments of the first aspect, the method comprising:

[0015] Performing a first stirring and mixing on aluminum dihydrogen phosphate and an inorganic silicone resin to obtain a mixed material;

[0016] Performing a second stirring and mixing on the mixed material with alumina and potassium feldspar to obtain the coating material.

[0017] The above technical solutions provided by the embodiments of the present application have the following advantages compared with the prior art:

[0018] For the coating material provided by the embodiments of the present application, alumina is used as an antioxidant. Alumina can form a diaphragm on the anode surface and at the same time fill the voids on the anode surface, isolating oxygen from entering the voids to participate in the oxidation reaction; potassium feldspar is used as an antioxidant, and potassium feldspar has the characteristic of melting secondarily to form a glaze surface under the roasting temperature condition of (930 - 960 °C), thereby ensuring that the coating material can be tightly combined with the anode surface and will not delaminate; alumina and potassium feldspar cooperate to achieve strong antioxidant properties of the coating material and form a glaze surface, making the coating more dense; aluminum dihydrogen phosphate is used as a binder, having adhesiveness, environmental friendliness and no impurity introduction, and having antioxidant properties; inorganic silicone resin is used as a binder, having adhesiveness and environmental friendliness; aluminum dihydrogen phosphate and inorganic silicone resin cooperate to achieve strong adhesiveness of the coating material, enhancing the viscosity of the coating and enabling it to firmly adhere to the anode surface without falling off. In summary, the technical problem that the existing carbon anode is prone to react with air and cause oxidation and burning damage of the anode carbon block is solved. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The accompanying drawings herein are incorporated into the specification and constitute a part of this specification, showing embodiments consistent with the present application and used together with the specification to explain the principles of the present application.

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, other drawings can also be obtained based on these drawings without creative efforts.

[0021] Figure 1 It is a schematic flow chart of a method for preparing a coating material provided by an embodiment of the present application;

[0022] Figure 2 This is a comparison diagram after burning between the carbon anode with a coating and the carbon anode without a coating provided by the embodiments of the present application; wherein, white - the carbon anode with a coating, black - the carbon anode without a coating. Detailed implementation manners

[0023] To make the objectives, technical solutions and advantages of the embodiments of the present application clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present application with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative efforts shall fall within the scope of protection of the present application.

[0024] The various embodiments of the present application may exist 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 construed as a rigid limitation on the scope of the present application; therefore, it should be considered that the described range description has specifically disclosed all possible sub - ranges and individual values within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub - ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and individual numbers within the range, such as 1, 2, 3, 4, 5, and 6, and this applies regardless of the range. Additionally, whenever a numerical range is indicated herein, it means including any cited number (fraction or integer) within the indicated range.

[0025] In this application, unless otherwise stated, the orientation terms such as "upper" and "lower" specifically refer to the drawing directions in the attached drawings. Additionally, in the description of this application's specification, terms such as "include" and "comprise" mean "including but not limited to". In this text, relational terms such as "first" and "second" 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 text, "and / or" describes the association relationship of associated objects and indicates that three relationships can exist. For example, A and / or B can mean: A exists alone, A and B exist simultaneously, or B exists alone. Here, A and B can be singular or plural. In this text, "at least one" means one or more, and "multiple" means two or more. "At least one kind", "at least one of the following items (pieces)" or similar expressions refer to any combination of these items, including any combination of single item (piece) or plural items (pieces). For example, "at least one of a, b, or c", or "at least one of a, b, and c" can both mean: a, b, c, a - b (i.e., a and b), a - c, b - c, or a - b - c, where a, b, and c can be single or multiple respectively.

[0026] Unless otherwise specifically stated, various raw materials, reagents, instruments, equipment, etc. used in this application can be obtained through market purchases or can be prepared by existing methods.

[0027] In a first aspect, this application provides a coating, and the raw material components of the coating include:

[0028] aluminum oxide, potassium feldspar, aluminum dihydrogen phosphate, and inorganic silicone resin; wherein, by mass fraction,

[0029] the content of the aluminum oxide is 30% - 40%, the content of the potassium feldspar is 10% - 30%, the content of the aluminum dihydrogen phosphate is 30 - 40%, and the content of the inorganic silicone resin is 5 - 15%.

[0030] In some embodiments, the content of the aluminum oxide is 33% - 35%, the content of the potassium feldspar is 20% - 22%, the content of the aluminum dihydrogen phosphate is 32% - 34%, and the content of the inorganic silicone resin is 11% - 13%.

[0031] In some embodiments, the content of the aluminum oxide is 35%, the content of the potassium feldspar is 20%, the content of the aluminum dihydrogen phosphate is 34%, and the content of the inorganic silicone resin is 11%.

[0032] In the embodiments of the present application, aluminum dihydrogen phosphate and inorganic silicone resin are used as binders, alumina and potassium feldspar are added, and a solution is formed under stirring conditions and sprayed on the anode surface. At the calcination temperature, it will melt again to form a glaze surface, which adheres to the anode surface densely and uniformly, reducing the contact between air and the anode surface, and thus alleviating the oxidation of the anode. The specific functions of the above-mentioned alumina, the above-mentioned potassium feldspar, the above-mentioned aluminum dihydrogen phosphate, and the above-mentioned inorganic silicone resin are as follows:

[0033] Selecting alumina as an antioxidant is economical and applicable to the aluminum electrolysis carbon anode without affecting the quality of electrolytic aluminum. Alumina can form a diaphragm on the anode surface and at the same time fill the voids on the anode surface, isolating oxygen from entering the voids to participate in the oxidation reaction. If the content of this alumina is too high, it will be disadvantageous to control the cost to a certain extent. If the content of this alumina is too low, it will cause the content of other components of the coating to be too high, which will be disadvantageous to be applied to the aluminum electrolysis carbon anode to a certain extent, and thus pollute the quality of electrolytic aluminum. Specifically, the content of this alumina can be 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, etc.

[0034] Selecting potassium feldspar (KAlSi3O8), usually also called orthoclase, belonging to the monoclinic system, as an antioxidant is economical, and using the characteristic that potassium feldspar melts again at the calcination temperature to form a glaze surface, thus ensuring that the coating can be tightly combined with the anode surface without delamination. If the content of this potassium feldspar is too high, it will be disadvantageous to be applied to the aluminum electrolysis carbon anode to a certain extent, and thus pollute the quality of electrolytic aluminum, and the cost is increased; if the content of this potassium feldspar is too low, it will be disadvantageous to damage the integrity of the glaze surface and unable to achieve the expected antioxidant effect. Specifically, the content of this potassium feldspar can be 10%, 12%, 14%, 16%, 18%, 20%, 22%, 24%, 26%, 28%, 30%, etc.

[0035] The combination of the above-mentioned alumina and the above-mentioned potassium feldspar forms a glaze surface, making the coating denser. The coating formed by pure alumina is not dense enough. Adding a certain amount of potassium feldspar will form a glaze surface, making the coating denser, which can effectively prevent oxygen from contacting the anode, and thus play an antioxidant role.

[0036] Aluminum dihydrogen phosphate is selected as the binder, which has adhesiveness, environmental friendliness, no impurity introduction and oxidation resistance. An appropriate amount of aluminum dihydrogen phosphate makes the coating have excellent adhesiveness and economy. If the content of aluminum dihydrogen phosphate is too high, it will affect the quality of aluminum dissociation to a certain extent and increase the cost; if the content of aluminum dihydrogen phosphate is too low, it will reduce the adhesiveness of the coating to a certain extent. Specifically, the content of aluminum dihydrogen phosphate can be 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, etc.

[0037] Inorganic silicone resin is selected as the binder, which has adhesiveness and environmental friendliness. An appropriate amount of inorganic silicone resin makes the coating have excellent adhesiveness and economy. If the content of inorganic silicone resin is too high, it will affect the quality of aluminum dissociation to a certain extent and increase the cost; if the content of inorganic silicone resin is too low, it will reduce the adhesiveness of the coating to a certain extent. Specifically, the content of inorganic silicone resin can be 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, etc.

[0038] The interaction between the above-mentioned aluminum dihydrogen phosphate and the above-mentioned inorganic silicone resin enhances the viscosity of the coating, enables it to firmly adhere to the anode surface and will not fall off; synergistically controls the increase in viscosity to ensure the adhesion of the coating and will not fall off. The above two binders make the coating raw materials free of impurities and will not introduce impurity elements into the electrolyte during the electrolytic aluminum process, improving the adhesion between the coating and the substrate and making the adhesion between the coating and the anode very good.

[0039] Preferably, the content of the above-mentioned alumina can be 33% - 35%, the content of the above-mentioned potassium feldspar can be 20% - 22%, the content of the above-mentioned aluminum dihydrogen phosphate can be 32% - 34%, and the content of the above-mentioned inorganic silicone resin can be 11% - 13%.

[0040] More preferably, the content of the above-mentioned alumina can be 35%, the content of the above-mentioned potassium feldspar can be 20%, the content of the above-mentioned aluminum dihydrogen phosphate can be 34%, and the content of the above-mentioned inorganic silicone resin can be 11%.

[0041] In some embodiments, the particle size of the alumina is 500 mesh - 800 mesh.

[0042] In some embodiments, the particle size of the potassium feldspar is 400 mesh - 500 mesh.

[0043] In the embodiments of the present application, appropriate particle sizes of alumina and potassium feldspar can ensure the compactness of the coating. If the particle size of the potassium feldspar is too high, to a certain extent, it will lead to a decrease in the compactness of the coating; if the particle size of the potassium feldspar is too low, to a certain extent, it will increase the amount of binder used, resulting in an increase in cost. Specifically, the particle size of the alumina can be 500 mesh, 550 mesh, 600 mesh, 650 mesh, 700 mesh, 750 mesh, 800 mesh, etc. Specifically, the particle size of the potassium feldspar can be 400 mesh, 420 mesh, 440 mesh, 460 mesh, 480 mesh, 500 mesh, etc.

[0044] Compared with the prior art, the coating material in the embodiments of the present application has the following advantages:

[0045] The raw materials used are cheap, easy to obtain, safe, environmentally friendly, with low production costs, simple production processes, and obvious antioxidant effects. Specifically, it can effectively block the contact between air and carbon dioxide and the carbon anode, greatly reducing the consumption of the carbon anode and extending the service life of the anode.

[0046] In a second aspect, the present application provides a coating, which is formed by the coating material according to any one of the embodiments of the first aspect.

[0047] In a third aspect, the present application provides a carbon anode, characterized in that the carbon anode includes a carbon anode matrix and a coating according to any one of the embodiments of the second aspect attached to at least a part of the surface of the carbon anode matrix.

[0048] In the embodiments of the present application, by using the spraying or brushing method, the antioxidant coating material is evenly brushed on the surface (0.5 mm) of the anode carbon block. After the coating material is dried, it can be put into the electrolytic cell for use. Under the temperature conditions of the electrolytic cell (930 - 960 °C), the coating material can form a dense crust layer, which can effectively block the contact between air and carbon dioxide and the carbon anode, greatly reducing the consumption of the carbon anode and extending the service life of the anode.

[0049] In a fourth aspect, the present application provides a method for preparing the coating material according to any one of the embodiments of the first aspect. Please refer to Figure 1 , the method includes:

[0050] S1. First, stir and mix aluminum dihydrogen phosphate and inorganic silicone resin to obtain a mixed material;

[0051] S2. Then, second, stir and mix the mixed material with alumina and potassium feldspar to obtain the coating material.

[0052] In the embodiments of the present application, the specific method for preparing the above coating material: Put aluminum dihydrogen phosphate and inorganic silicone resin into a blender, stir for 30 minutes to make them evenly mixed, then add alumina and potassium feldspar, and continue to stir for 60 minutes. After the stirring is completed, discharge the material to obtain the finished coating material.

[0053] The method for preparing the coating is realized based on the raw material components of the above coating. The raw material components of the coating can refer to the above embodiments. Since the method for preparing the coating adopts some or all of the technical solutions of the above embodiments, it has at least all the beneficial effects brought by the technical solutions of the above embodiments, which will not be elaborated one by one here.

[0054] The following further elaborates on this application in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate this application and not to limit the scope of this application. For the experimental methods without specific conditions noted in the following embodiments, they are generally determined according to national standards. If there are no corresponding national standards, they are carried out according to general international standards, conventional conditions, or the conditions recommended by the manufacturer.

[0055] Example 1

[0056] The components of the coating raw materials: It is composed of four raw materials, namely α-Al2O3, potassium feldspar, aluminum dihydrogen phosphate, and inorganic silicone resin. The proportions of each raw material are as follows: α-Al2O3 accounts for 33%, potassium feldspar accounts for 22%, aluminum dihydrogen phosphate accounts for 32%, and inorganic silicone resin accounts for 13%; among them, the particle size of α-Al2O3 is 600 mesh, and the particle size of potassium feldspar is 450 mesh.

[0057] The method for preparing the coating is as follows: Put 32% of aluminum dihydrogen phosphate and 13% of inorganic silicone resin based on the total weight of the coating into a blender, stir for 30 minutes to make them evenly mixed, then add 33% of α-Al2O3 and 22% of potassium feldspar based on the total weight of the coating, and continue to stir for 60 minutes. After the stirring is completed, discharge the material to obtain the finished coating.

[0058] Example 2

[0059] The components of the coating raw materials: It is composed of four raw materials, namely α-Al2O3, potassium feldspar, aluminum dihydrogen phosphate, and inorganic silicone resin. The proportions of each raw material are as follows: α-Al2O3 accounts for 35%, potassium feldspar accounts for 20%, aluminum dihydrogen phosphate accounts for 34%, and inorganic silicone resin accounts for 11%; among them, the particle size of α-Al2O3 is 600 mesh, and the particle size of potassium feldspar is 450 mesh.

[0060] The method for preparing the coating is as follows: Put 34% of aluminum dihydrogen phosphate and 11% of inorganic silicone resin based on the total weight of the coating into a blender, stir for 30 minutes to make them evenly mixed, then add 35% of α-Al2O3 and 20% of potassium feldspar based on the total weight of the coating, and continue to stir for 60 minutes. After the stirring is completed, discharge the material to obtain the finished coating.

[0061] Example 3

[0062] Components of the coating raw materials: It is composed of four raw materials, namely α-Al2O3, potassium feldspar, aluminum dihydrogen phosphate, and inorganic silicone resin. The proportions of each raw material are as follows: α-Al2O3 accounts for 40%, potassium feldspar accounts for 14%, aluminum dihydrogen phosphate accounts for 39%, and inorganic silicone resin accounts for 7%. Among them, the particle size of α-Al2O3 is 600 mesh, and the particle size of potassium feldspar is 450 mesh.

[0063] The preparation method of the coating is as follows: Put 39% of the total weight of the coating of aluminum dihydrogen phosphate and 7% of the inorganic silicone resin into a blender, stir for 30 minutes to make them evenly mixed, then add 40% of the total weight of the coating of α-Al2O3 and 14% of potassium feldspar, and continue to stir for 60 minutes. After the stirring is completed, discharge the material to obtain the finished coating.

[0064] Example 4

[0065] Components of the coating raw materials: It is composed of four raw materials, namely α-Al2O3, potassium feldspar, aluminum dihydrogen phosphate, and inorganic silicone resin. The proportions of each raw material are as follows: α-Al2O3 accounts for 30%, potassium feldspar accounts for 25%, aluminum dihydrogen phosphate accounts for 40%, and inorganic silicone resin accounts for 5%. Among them, the particle size of α-Al2O3 is 600 mesh, and the particle size of potassium feldspar is 450 mesh.

[0066] The preparation method of the coating is as follows: Put 40% of the total weight of the coating of aluminum dihydrogen phosphate and 5% of the inorganic silicone resin into a blender, stir for 30 minutes to make them evenly mixed, then add 30% of the total weight of the coating of α-Al2O3 and 25% of potassium feldspar, and continue to stir for 60 minutes. After the stirring is completed, discharge the material to obtain the finished coating.

[0067] Example 5

[0068] Components of the coating raw materials: It is composed of four raw materials, namely α-Al2O3, potassium feldspar, aluminum dihydrogen phosphate, and inorganic silicone resin. The proportions of each raw material are as follows: α-Al2O3 accounts for 30%, potassium feldspar accounts for 30%, aluminum dihydrogen phosphate accounts for 30%, and inorganic silicone resin accounts for 10%. Among them, the particle size of α-Al2O3 is 600 mesh, and the particle size of potassium feldspar is 450 mesh.

[0069] The preparation method of the coating is as follows: Put 30% of the total weight of the coating of aluminum dihydrogen phosphate and 10% of the inorganic silicone resin into a blender, stir for 30 minutes to make them evenly mixed, then add 30% of the total weight of the coating of α-Al2O3 and 30% of potassium feldspar, and continue to stir for 60 minutes. After the stirring is completed, discharge the material to obtain the finished coating.

[0070] The coating prepared in the examples was applied to the surface of the anode carbon block by spraying or brushing methods, and the antioxidant coating was evenly brushed on the surface of the anode carbon block and directly placed in a furnace at 960 °C for 10 h. For Comparative Example 1, anode carbon blocks with the same properties were taken, without coating, and directly placed in a furnace under the same temperature conditions for roasting. The weight loss rates of the anode carbon blocks in Examples 1-5 and Comparative Example 1 were calculated, and the results are shown in Table 1.

[0071] Table 1 Weight loss rates of anode carbon blocks

[0072] Serial number Example 1 Example 2 Example 3 Example 4 Example 5 Comparative example 1 Weight before firing g 183.75 184.26 183.59 184.12 183.75 182.78 Weight after firing g 179.14 179.89 178.67 179.35 178.96 149.20 Weight loss g 4.61 4.37 4.92 4.77 4.79 33.58 Weight loss rate % 2.51 2.37 2.68 2.59 2.61 18.37

[0073] The appearance of the coating is white. Please refer to Figure 2 , for the comparison after roasting of the anodes in Examples 1-5 coated with the antioxidant coating and the anode without coating (Comparative Example 1), it can be clearly seen that the anode without coating (black) was damaged after roasting. Combining with Table 1, it shows that the coating formed by the coating provided in the examples significantly reduces the weight loss rate of the anode carbon block with this coating.

[0074] The above are only specific embodiments of the present application, enabling those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be obvious to those skilled in the art. 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 these embodiments shown herein, but rather to the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A carbon anode, characterized in that, The carbon anode includes a carbon anode matrix and a coating attached to at least a part of the surface of the carbon anode matrix. The coating material of the coating consists of the following raw material components: by mass fraction, the content of alumina is 33% - 35%, the content of potassium feldspar is 20% - 22%, the content of aluminum dihydrogen phosphate is 32% - 34%, and the content of inorganic silicone resin is 11% - 13%. The particle size of the alumina is 500 mesh - 800 mesh, and the particle size of the potassium feldspar is 400 mesh - 500 mesh. The coating is formed by spraying or brushing the coating material evenly on the surface of the anode carbon block with a thickness of 0.5 mm. The carbon anode is suitable for use in an electrolytic cell at a temperature of 930 - 960 °C.

2. The carbon anode according to claim 1, characterized in that, The content of the alumina is 35%, the content of the potassium feldspar is 20%, the content of the aluminum dihydrogen phosphate is 34%, and the content of the inorganic silicone resin is 11%.

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