Modified coal pitch, preparation method and prebaked anode

Abstract

The invention provides modified coal pitch, a preparation method and a prebaked anode, and belongs to the field of carbon anodes for aluminum. The method comprises the following steps: heating coal pitch to a set temperature; adding a modifier into the coal pitch with a set temperature to obtain a mixture; the mass ratio of the coal pitch to the modifier is (95-99): (1-5); and stirring the mixture for a set time at the set temperature so as to polymerize the light components and the short-chain components in the coal pitch to form long-chain macromolecules, thereby obtaining the modified coal pitch. By modifying the coal pitch, light components and short-chain components in the coal pitch can be polymerized into long-chain macromolecules, volatilization of the light components in the coking process of the coal pitch is reduced, and the coking value of the coal pitch is further increased. Therefore, the modified coal pitch is used for replacing traditional coal pitch to serve as a binder to prepare the prebaked anode, the coking value of the coal pitch can be effectively increased, the quality of the anode is improved, and a guarantee is provided for production of high-quality anodes.

Description

Technical Field

[0001] The present application relates to the technical field of carbon anodes for aluminum, and in particular to a modified coal tar pitch, a preparation method, and a prebaked anode. Background Art

[0002] Prebaked anodes for aluminum are an important component of the electrolytic cell and are called the "heart" of the electrolytic cell. Traditional prebaked anodes for aluminum are composed of aggregate coke particles, powder and coal tar. The aggregate coke particles are calcined petroleum coke particles, and a small number of residual anode particles are also used by a small number of companies. The powder is calcined petroleum coke powder, and coal tar is used as a binder to connect the aggregate coke particles and powder together.

[0003] Coal tar pitch, as a pre-baked anode binder for aluminum electrolysis, has an important influence on the quality of the anode. During the roasting process, organic components such as aromatics in coal tar pitch will undergo pyrolysis and polycondensation reactions and gradually convert into coke. These cokes can be filled in the gaps of aggregates to increase the density of the anode and further improve the strength of the anode. Moreover, the generated coke also participates in the conductive process of the anode, which helps the anode to conduct current well during the electrolysis process. This places certain requirements on the coking value of coal tar pitch. The higher the coking value, the better the anode quality. With the change of process, the coking value of coal tar pitch in my country is relatively low, basically at 50% to 55%. The low coking value of coal tar pitch will result in a relatively small amount of coke formed during the roasting process of the anode, and it is easy to cause slag and block falling, thereby affecting the normal use of the anode in the electrolytic cell. Due to the low coking value, the corrosion resistance and oxidation resistance of the anode are poor. During the electrolysis process, the consumption rate of the anode will accelerate, shortening the service life of the anode. Therefore, how to improve the coking value of coal tar pitch as a pre-baked anode binder for aluminum electrolysis is a technical problem that needs to be solved urgently. Summary of the invention

[0004] The present application provides a modified coal tar pitch and a preparation method, and a prebaked anode to solve the following technical problem: how to improve the coking value of coal tar pitch used as a prebaked anode binder for aluminum electrolysis.

[0005] In a first aspect, the present invention provides a method for preparing a modified coal tar pitch, the method comprising:

[0006] The coal tar is heated to a set temperature;

[0007] Adding a modifier to the coal tar pitch having a set temperature to obtain a mixture; the mass ratio of the coal tar pitch to the modifier is (95-99):(1-5); and

[0008] At the set temperature, the mixture is stirred for a set time to polymerize the light components and short-chain components in the coal tar pitch to form long-chain macromolecules to obtain modified coal tar pitch.

[0009] Optionally, the modifier includes one or more of a copper-containing compound, carbon black, petroleum asphalt, sulfur compound, boron-containing compound, p-tolualdehyde, fluorine-containing compound, chlorobenzene compound, and hexahydroxymethylmelamine hexamethyl ether.

[0010] Optionally, the copper-containing compound includes one or more of copper sulfate, copper hydroxide, and copper bromide;

[0011] The sulfur compound includes one or more of sulfur trioxide, sodium sulfite, and copper sulfide;

[0012] The boron-containing compound includes one or more of boric acid and borate;

[0013] The fluorine-containing compound includes one or more of aluminum fluoride, sodium fluoride, and sulfur hexafluoride;

[0014] The chlorobenzene compound includes one or more of chlorobenzene and dichlorobenzene.

[0015] Optionally, the set temperature is 150°C to 180°C.

[0016] Optionally, the set time is 60 min to 120 min.

[0017] In a second aspect, the present application provides a modified coal tar pitch prepared by the method according to any one of the embodiments in the first aspect, and the modified coal tar pitch is a thermoplastic pitch.

[0018] In a third aspect, the present application provides a prebaked anode, which includes the modified coal tar pitch according to the second aspect and calcined petroleum coke; the mass ratio of the modified coal tar pitch to the calcined petroleum coke is (13 - 16):(84 - 87).

[0019] Optionally, the calcined petroleum coke consists of aggregate calcined petroleum coke and fine powder calcined petroleum coke, and the mass ratio of the aggregate calcined petroleum coke to the fine powder calcined petroleum coke is (55 - 75):(25 - 45).

[0020] Optionally, the particle size distribution of the aggregate calcined petroleum coke includes coarse coke of 8 mm - 5 mm, medium coke of 5 mm - 2 mm, and fine coke of 2 mm - 1 mm, and the mass ratio of the coarse coke, the medium coke, and the fine coke is (25 - 29):(17 - 21):(17 - 22).

[0021] Optionally, the prebaked anode satisfies the following properties: bulk density ≥ 1.57 g / cm 3 , resistivity is 55.4 μΩ·m to 56.8 μΩ·m, ash content is 0.28% - 0.31%, and air reaction residue rate ≥ 67%.

[0022] The above technical solution provided by the embodiments of the present application has the following advantages compared with the prior art:

[0023] The embodiments of the present application provide a preparation method of modified coal tar pitch. The method includes: heating the coal tar pitch to a set temperature; adding a modifier to the coal tar pitch at the set temperature to obtain a mixture; the mass ratio of the coal tar pitch to the modifier is (95-99):(1-5); and stirring the mixture at the set temperature for a set time to polymerize the light components and short-chain components in the coal tar pitch into long-chain macromolecules, thereby obtaining modified coal tar pitch. By modifying the coal tar pitch, the light components and short-chain components in the coal tar pitch can be polymerized into long-chain macromolecules, reducing the volatilization of the light components during the coking process of the coal tar pitch, and thus improving the coking value of the coal tar pitch. Therefore, using modified coal tar pitch instead of traditional coal tar pitch as a binder to prepare pre-baked anodes can effectively improve the coking value of the coal tar pitch, improve the quality of the anodes, and provide guarantee for the production of high-quality anodes. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The drawings here are incorporated into the specification and form a part of this specification, showing the embodiments consistent with the present application, and are used together with the specification to explain the principles of the present application.

[0025] 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 the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0026] Figure 1 It is a schematic flow chart of a preparation method of modified coal tar pitch provided by the embodiments of the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0027] 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 drawings in the embodiments of the present application. Obviously, the described embodiments are some, but not all, of the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present application.

[0028] 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 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, 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.

[0029] In addition, in the description of the specification of the present application, terms such as "comprising" and "including" mean "including but not limited to". In this document, 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 document, "and / or" describes the associated relationship of associated objects, indicating that three relationships can exist. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. Wherein A and B can be singular or plural. In this document, "at least one" means one or more, and "a plurality" means two or more. "At least one kind", "at least one of the following (items)" or similar expressions refer to any combination of these items, including any combination of single item (s) or plural items (s). For example, "at least one of a, b, or c", or "at least one of a, b, and c" can both represent: 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. The "parts representation method" such as parts by weight and parts by mass represents the proportional relationship between each component. In the proportional relationships involved in this document, the parameters that need to be described by proportion should be understood as the antecedents of the proportion formula in the order of description, and the proportional numbers should be understood as the consequents of the proportion formula. For example, if the mass ratio of substance A, substance B, and substance C is 1:2:3, then substance A, substance B, and substance C should correspond one by one with the proportional numbers in the proportion formula in the order of description, that is, the mass of substance A: the mass of substance B: the mass of substance C = 1:2:3.

[0030] Unless otherwise specifically stated, various raw materials, reagents, instruments, and equipment used in the present application can be obtained through market purchase or can be prepared by existing methods.

[0031] Figure 1 It is a schematic flow diagram of a preparation method of a modified coal tar pitch provided for the embodiments of the present application.

[0032] As Figure 1 shown, the present application provides a method for preparing modified coal tar pitch, the method comprising:

[0033] S1. Heating the coal tar pitch to a set temperature;

[0034] S2. Adding a modifier to the coal tar pitch at the set temperature to obtain a mixture; the mass ratio of the coal tar pitch to the modifier is (95-99):(1-5); and

[0035] In some embodiments, the modifier includes one or more of a copper-containing compound, carbon black, petroleum pitch, sulfur compound, boron-containing compound, p-methylbenzaldehyde, fluorine-containing compound, chlorobenzene compound, and hexahydroxymethylmelamine hexamethyl ether.

[0036] In some embodiments, the copper-containing compound includes one or more of copper sulfate, copper hydroxide, and copper bromide;

[0037] the sulfur compound includes one or more of sulfur trioxide, sodium sulfite, and copper sulfide;

[0038] the boron-containing compound includes one or more of boric acid and borate;

[0039] the fluorine-containing compound includes one or more of aluminum fluoride, sodium fluoride, and sulfur hexafluoride;

[0040] the chlorobenzene compound includes one or more of chlorobenzene and dichlorobenzene.

[0041] The modifier can increase the coking value of the coal tar pitch, mainly playing a role in polymerization. Adding the modifier can polymerize the light components and short-chain components in the coal tar pitch into long-chain macromolecules, reducing the volatilization of the light components during the coking process of the coal tar pitch, and thus increasing the coking value of the coal tar pitch. Exemplarily, the mass ratio of the coal tar pitch to the modifier can be 95:5, 96:4, 97:3, 98:2, 99:1, etc.

[0042] S3. Stirring the mixture for a set time at the set temperature to polymerize the light components and short-chain components in the coal tar pitch to form long-chain macromolecules, thereby obtaining modified coal tar pitch.

[0043] In some embodiments, the set temperature is 150°C to 180°C.

[0044] The heating temperature of the pitch is limited to 150°C to 180°C, which can ensure that the pitch is in a molten and flowing state, facilitating the uniform dispersion and reaction of the modifier. If the temperature is too low (<150°C), it will lead to high viscosity and uneven mixing; if the temperature is too high (>180°C), it will cause the decomposition or excessive polycondensation of the pitch, reducing the bonding performance. Exemplarily, the heating temperature of the pitch can be 150°C, 155°C, 160°C, 165°C, 170°C, 175°C, 180°C, etc.

[0045] In some embodiments, the set time is 60 min to 120 min.

[0046] Limiting the stirring time to 60 min to 120 min can ensure sufficient contact between the modifier and the pitch and avoid excessive energy consumption or excessive aging of the pitch. Exemplarily, the stirring time can be 60 min, 70 min, 80 min, 90 min, 100 min, 110 min, 120 min, etc.

[0047] Based on a general inventive concept, the present application provides a modified pitch prepared by the method described in any one of the above embodiments, and the modified pitch is a thermoplastic pitch.

[0048] This modified pitch is realized based on the above-described preparation method of the modified pitch. The specific steps of the preparation method of the modified pitch can refer to the above embodiments. Since this modified pitch adopts some or all of the technical solutions of the above embodiments, it at least has all the beneficial effects brought by the technical solutions of the above embodiments, which will not be elaborated herein one by one.

[0049] The present application provides a prebaked anode, which includes: the modified pitch described in the second aspect and calcined petroleum coke; the mass ratio of the modified pitch to the calcined petroleum coke is (13 - 16):(84 - 87).

[0050] By modifying the pitch in the embodiments of the present application, the light components and short-chain components in the pitch can be polymerized into long-chain macromolecules, reducing the volatilization of the light components during the coking process of the pitch, thereby increasing the coking value of the pitch; as the coking value of the pitch increases, the anode recovery rate increases, the bulk density increases, the compactness becomes better, and the overall quality of the anode is improved. Exemplarily, the mass ratio of the modified pitch to the calcined petroleum coke can be 13:87, 14:86, 15:85, 16:84, etc.

[0051] In some embodiments, the calcined petroleum coke is composed of aggregate calcined petroleum coke and fine powder calcined petroleum coke, and the mass ratio of the aggregate calcined petroleum coke to the fine powder calcined petroleum coke is (55 - 75):(25 - 45).

[0052] In some embodiments, the particle size distribution of the calcined petroleum coke for aggregate includes: coarse coke with a particle size of 8 mm to 5 mm, medium coke with a particle size of 5 mm to 2 mm, and fine coke with a particle size of 2 mm to 1 mm. The mass ratio of the coarse coke, the medium coke, and the fine coke is (25 - 29):(17 - 21):(17 - 22).

[0053] Defining the mass ratio of the calcined petroleum coke for aggregate to the calcined petroleum coke for fine powder as (55 - 75):(25 - 45) and the particle size classification of the aggregate can ensure the close packing of particles, prevent the structure from loosening, and avoid an increase in porosity caused by insufficient binder. Exemplarily, the mass ratio of the calcined petroleum coke for aggregate to the calcined petroleum coke for fine powder can be 55:45, 60:40, 65:35, 70:30, 75:25, etc.

[0054] In some embodiments, the pre-baked anode satisfies the following properties: bulk density ≥ 1.57 g / cm 3 , resistivity is 55.4 μΩ·m to 56.8 μΩ·m, ash content is 0.28% to 0.31%, and the residual rate of air reaction ≥ 67%.

[0055] Thus, modifying the coal tar pitch in the embodiments of the present application can effectively solve the problem of low coking value of the coal tar pitch used for anodes, improve the properties such as strength, oxidation resistance, and denseness of the anodes, greatly improve the anode quality, and meet the usage requirements of electrolytic aluminum enterprises for anodes.

[0056] In some embodiments, the preparation method of the pre-baked anode includes:

[0057] Put the dry calcined petroleum coke into a mixer and mix it at room temperature for 20 min to 30 min;

[0058] Put the mixed dry material into a preheating pot and preheat it at 175°C to 185°C for 5 min to 15 min;

[0059] After the preheating is completed, add the dry material to a kneading pot and add the modified coal tar pitch, and mix it at 165°C to 185°C for 5 min to 20 min to obtain carbon paste;

[0060] Put the carbon paste into a mold and press it into shape. The mold temperature is 150°C to 165°C, and the pressure is 300 KN to 500 KN;

[0061] After the formed anode carbon block is cooled to room temperature, it is put into a roasting furnace for roasting. The roasting heating curve rises from room temperature to 250°C at 3°C / h to 5°C / h, from 250°C to 650°C at 2°C / h to 3°C / h, from 650°C to 950°C at 2°C / h to 5°C, and from 950°C to 1150°C at 4°C / h to 8°C / h, and is kept at 1150°C for 45 h to 55 h to obtain the pre-baked anode.

[0062] In summary, a modified coal tar pitch, a preparation method thereof, and a pre-baked anode provided by the embodiments of the present application have the following advantages:

[0063] (1) Significantly improve the coking value of coal tar pitch and optimize the compactness of the anode: Through the synergistic effect of multi-component modifiers such as copper-containing compounds, sulfur-containing compounds, and fluorine-containing compounds, the polymerization of light components and short-chain molecules in coal tar pitch is promoted to form a long-chain macromolecular structure, reducing the volatilization loss during the coking process and increasing the coking value. This improvement directly enhances the compactness and bulk density of the anode (≥1.57 g / cm 3 ), while reducing the porosity.

[0064] (2) The modified process parameters are precisely matched to ensure reaction efficiency and stability: The modification temperature is controlled at 150 - 180 °C, which not only ensures the molten fluidity of coal tar pitch but also avoids decomposition caused by high temperature. The modification time is controlled at 60 min - 120 min, which can ensure the full dispersion and reaction of the modifier. The modifier ratio is 1% - 5%, achieving efficient polymerization at a low addition amount and balancing performance and cost through optimized ratio.

[0065] (3) The anode aggregate and powder are synergistically optimized to improve the structural integrity: The aggregate is classified, and the coarse, medium, and fine particle sizes are used to achieve close packing. The ratio of aggregate to powder is controlled to ensure that the binder fully wraps the particles and improves the structural strength.

[0066] (4) The staged roasting process reduces defects and improves the finished product rate: The temperature control curve (segmented heating at 3 °C / h - 8 °C / h), slow heating (such as 3 - 5 °C / h before 250 °C) reduces cracks caused by too fast volatilization of volatile components, and the high-temperature section (950 °C - 1150 °C) accelerates graphitization to improve conductivity. Controlling the holding time at 45 h - 55 h can ensure complete coking reaction.

[0067] The following specific embodiments are used to further illustrate the present application. It should be understood that these embodiments are only used to illustrate the present application and not to limit the scope of the present application. The experimental methods without specific conditions noted in the following embodiments are usually determined according to industry standards. If there is no corresponding industry standard, they are carried out according to general international standards, conventional conditions, or conditions recommended by the manufacturer.

[0068] Example 1

[0069] This embodiment provides a preparation method of an aluminum-carbon anode, including the following steps:

[0070] Coal tar pitch modification: Put 99 parts of coal tar pitch into a reaction kettle, heat up and maintain the temperature at 160 °C, then add 1 part of petroleum asphalt, turn on the stirring paddle, set the rotation speed at 300 r / min, set the stirring time at 75 min, and the required modified coal tar pitch can be obtained after stirring ends.

[0071] Raw material dry materials: Weigh 26 parts of calcined petroleum coke with a particle size of 8 mm to 5 mm, 19 parts of calcined petroleum coke with a particle size of 5 mm to 2 mm, 17 parts of calcined petroleum coke with a particle size of 2 mm to 1 mm, and 38 parts of fine powder calcined petroleum coke with a particle size ≤ 0.3 mm and put them into a mixer to mix evenly.

[0072] Anode preparation: Put 85 parts of dry materials into a kneader, then add 15 parts of modified coal tar pitch, knead at 175 °C for 10 min to obtain a paste. Put the paste into a mold and press it into shape with a pressure of 400 KN to obtain a green anode blank.

[0073] Anode baking: The prepared anode is cooled to room temperature, then the anode is placed in a baking furnace for baking. Heat from room temperature to 250 °C at a heating rate of 4 °C / h; heat to 650 °C at a heating rate of 2 °C / h; heat to 950 °C at a heating rate of 3 °C / h; heat to 1150 °C at a heating rate of 5 °C / h; keep the temperature at 1150 °C for 50 h; after baking, cool down slowly. After the temperature drops to 200 - 300 °C, the anode carbon block is taken out of the furnace, and the pre-baked anode is obtained.

[0074] Example 2

[0075] This example provides a preparation method of carbon anodes for aluminum, including the following steps:

[0076] Coal tar pitch modification: Put 98.5 parts of coal tar pitch into a reaction kettle, heat up and maintain the temperature at 166 °C, then add 1.5 parts of copper sulfate, turn on the stirring paddle, set the rotation speed at 350 r / min, set the stirring time at 70 min, and the required coal tar pitch can be obtained after stirring ends.

[0077] Raw material dry materials: Weigh 27 parts of calcined petroleum coke with a particle size of 8 mm to 5 mm, 18 parts of calcined petroleum coke with a particle size of 5 mm to 2 mm, 18 parts of calcined petroleum coke with a particle size of 2 mm to 1 mm, and 37 parts of fine powder calcined petroleum coke with a particle size ≤ 0.3 mm and put them into a mixer to mix evenly.

[0078] Anode preparation: Put 87 parts of dry materials into a kneader, then add 13 parts of modified coal tar pitch, knead at 170 °C for 15 min to obtain a paste. Put the paste into a mold and press it into shape with a pressure of 450 KN to obtain a green anode blank.

[0079] Anode baking: The prepared anode is cooled to room temperature, and then placed in a baking furnace for baking. It is heated from room temperature to 250°C at a heating rate of 5°C / h; heated to 650°C at a heating rate of 2.5°C / h; heated to 950°C at a heating rate of 4°C / h; heated to 1150°C at a heating rate of 5°C / h; kept at a temperature of 1150°C for 55 h; after baking, it is cooled slowly. After the temperature drops to 200 - 300°C, the anode carbon block is taken out of the furnace, and the pre-baked anode is obtained.

[0080] Example 3

[0081] This example provides a preparation method of carbon anodes for aluminum, including the following steps:

[0082] Modification of coal tar pitch: Take 96 parts of coal tar pitch and put it into a reaction kettle, heat up and keep the temperature at 175°C, then add 4 parts of aluminum fluoride, turn on the stirring paddle, set the rotation speed to 340 r / min, and set the stirring time to 75 min. After stirring, the required coal tar pitch is obtained.

[0083] Raw material dry materials: Weigh 25 parts of calcined petroleum coke with a particle size of 8 mm - 5 mm, 21 parts of calcined petroleum coke with a particle size of 5 mm - 2 mm, 18 parts of calcined petroleum coke with a particle size of 2 mm - 1 mm, and 36 parts of fine powder calcined petroleum coke with a particle size ≤ 0.3 mm, and put them into a mixer to mix evenly.

[0084] Anode preparation: Put 86 parts of dry materials into a kneader, then add 14 parts of modified coal tar pitch, knead at 165°C for 20 min to obtain a paste. Put the paste into a mold and press it into shape under a pressure of 480 KN to obtain a green anode.

[0085] Anode baking: The prepared anode is cooled to room temperature, and then placed in a baking furnace for baking. It is heated from room temperature to 250°C at a heating rate of 4°C / h; heated to 650°C at a heating rate of 3°C / h; heated to 950°C at a heating rate of 3°C / h; heated to 1150°C at a heating rate of 4°C / h; kept at a temperature of 1150°C for 50 h; after baking, it is cooled slowly. After the temperature drops to 200 - 300°C, the anode carbon block is taken out of the furnace, and the pre-baked anode is obtained.

[0086] Example 4

[0087] This example provides a preparation method of carbon anodes for aluminum, including the following steps:

[0088] Modification of coal tar pitch: Take 98 parts of coal tar pitch and put it into a reaction kettle, heat up and keep the temperature at 180°C, then add 2 parts of carbon black, turn on the stirring paddle, set the rotation speed to 350 r / min, and set the stirring time to 90 min. After stirring, the required coal tar pitch is obtained.

[0089] Raw material dry materials: Weigh 29 parts of calcined petroleum coke with a particle size of 8 mm to 5 mm, 17 parts of calcined petroleum coke with a particle size of 5 mm to 2 mm, 22 parts of calcined petroleum coke with a particle size of 2 mm to 1 mm, and 32 parts of fine powder calcined petroleum coke with a particle size ≤ 0.3 mm, and put them into a mixer to mix evenly.

[0090] Anode preparation: Put 84 parts of dry materials into a kneader, then add 6 parts of carbon black modified coal tar pitch and 10 parts of aluminum fluoride modified pitch, and knead at 170 °C for 20 min to obtain a paste. Put the paste into a mold and press it into shape under a pressure of 500 KN to obtain a green anode.

[0091] Anode baking: Cool the prepared anode to room temperature, then place the anode in a baking furnace for baking. Heat from room temperature to 250 °C at a heating rate of 3 °C / h; heat to 650 °C at a heating rate of 3 °C / h; heat to 950 °C at a heating rate of 4 °C / h; heat to 1150 °C at a heating rate of 5 °C / h; keep the temperature at 1150 °C for 48 h; after baking, cool down slowly. After the temperature drops to 200 - 300 °C, take out the anode carbon block, and the pre-baked anode is obtained.

[0092] Example 5

[0093] This example provides a preparation method of carbon anodes for aluminum production, including the following steps:

[0094] Modification of coal tar pitch: Take 98 parts of coal tar pitch, put it into a reaction kettle, heat up and keep the temperature at 165 °C, then add 1 part of p-methylbenzaldehyde and 1 part of chlorobenzene compound, turn on the stirring paddle, set the rotation speed to 390 r / min, and set the stirring time to 75 min. After stirring ends, the required coal tar pitch is obtained.

[0095] Raw material dry materials: Weigh 28 parts of calcined petroleum coke with a particle size of 8 mm to 5 mm, 18 parts of calcined petroleum coke with a particle size of 5 mm to 2 mm, 19 parts of calcined petroleum coke with a particle size of 2 mm to 1 mm, and 35 parts of fine powder calcined petroleum coke with a particle size ≤ 0.3 mm, and put them into a mixer to mix evenly.

[0096] Anode preparation: Put 86 parts of dry materials into a kneader, then add 14 parts of modified coal tar pitch, and knead at 175 °C for 15 min to obtain a paste. Put the paste into a mold and press it into shape under a pressure of 400 KN to obtain a green anode.

[0097] Anode baking: The prepared anode is cooled to room temperature, and then the anode is placed in a baking furnace for baking. It is heated from room temperature to 250°C at a heating rate of 5°C / h; heated to 650°C at a heating rate of 2°C / h; heated to 950°C at a heating rate of 5°C / h; heated to 1150°C at a heating rate of 4°C / h; and held at 1150°C for 55 h. After baking, it is cooled slowly. After the temperature drops to 200 - 300°C, the anode carbon block is taken out of the furnace, and the pre-baked anode is obtained.

[0098] Comparative Example 1

[0099] The difference between this comparative example and Example 1 is that the coal tar pitch is not modified and is directly used as the binder for the anode carbon block.

[0100] Specifically, this comparative example provides a method for preparing an anode using traditional coal tar pitch, including the following steps:

[0101] Raw material dry materials: Weigh 28 parts of calcined petroleum coke with a particle size of 8 mm - 5 mm, 18 parts of calcined petroleum coke with a particle size of 5 mm - 2 mm, 19 parts of calcined petroleum coke with a particle size of 2 mm - 1 mm, and 35 parts of fine powder calcined petroleum coke with a particle size ≤ 0.3 mm, and put them into a mixer to mix evenly.

[0102] Anode preparation: Put 86 parts of the dry materials into a kneader, then add 14 parts of traditional coal tar pitch, and knead at 175°C for 15 min to obtain a paste. Put the paste into a mold and press it into shape under a pressure of 400 KN to obtain a green anode.

[0103] Anode baking: The prepared anode is cooled to room temperature, and then the anode is placed in a baking furnace for baking. It is heated from room temperature to 250°C at a heating rate of 5°C / h; heated to 650°C at a heating rate of 2°C / h; heated to 950°C at a heating rate of 5°C / h; heated to 1150°C at a heating rate of 4°C / h; and held at 1150°C for 55 h. After baking, it is cooled slowly. After the temperature drops to 200 - 300°C, the anode carbon block is taken out of the furnace, and the pre-baked anode is obtained.

[0104] Comparative Example 2

[0105] The difference between this comparative example and Example 1 is that the mass ratio of coal tar pitch to the modifier is 98:8.

[0106] Specifically, this comparative example provides a method for preparing an aluminum-carbon anode, including the following steps:

[0107] Modification of coal tar pitch: Take 98 parts of coal tar pitch and 8 parts of carbon black, put them into a reaction kettle, heat up to 180°C, turn on the stirring paddle, set the rotation speed to 350 r / min, set the stirring time to 90 min, and the required coal tar pitch is obtained after stirring ends.

[0108] Raw material dry materials: Weigh 29 parts of calcined petroleum coke with a particle size of 8 mm to 5 mm, 17 parts of calcined petroleum coke with a particle size of 5 mm to 2 mm, 22 parts of calcined petroleum coke with a particle size of 2 mm to 1 mm, and 32 parts of fine powder calcined petroleum coke with a particle size ≤ 0.3 mm, and put them into a mixer to mix evenly.

[0109] Anode preparation: Put 85 parts of the dry materials into a kneader, then add 15 parts of carbon black modified coal tar pitch, and knead at 170 °C for 20 min to obtain a paste. Put the paste into a mold and press it into shape under a pressure of 500 KN to obtain a green anode.

[0110] Anode baking: The prepared anode is cooled to room temperature, and then the anode is placed in a baking furnace for baking. It is heated from room temperature to 250 °C at a heating rate of 3 °C / h; heated to 650 °C at a heating rate of 3 °C / h; heated to 950 °C at a heating rate of 4 °C / h; heated to 1150 °C at a heating rate of 5 °C / h; keep it at 1150 °C for 48 h; after baking, cool it slowly. After the temperature drops to 200 - 300 °C, the anode carbon block is taken out of the furnace to obtain a pre-baked anode.

[0111] Comparative Example 3

[0112] The difference between this comparative example and Example 1 is that the mass ratio of coal tar pitch to the modifier is 99.5:0.5.

[0113] Specifically, this comparative example provides a preparation method of carbon anodes for aluminum, including the following steps:

[0114] Coal tar pitch modification: Take 99.5 parts of coal tar pitch and 0.5 parts of aluminum fluoride and put them into a reaction kettle, heat up to 175 °C, turn on the stirring paddle, set the rotation speed to 340 r / min, set the stirring time to 75 min, and the required coal tar pitch is obtained after stirring ends.

[0115] Raw material dry materials: Weigh 25 parts of calcined petroleum coke with a particle size of 8 mm to 5 mm, 21 parts of calcined petroleum coke with a particle size of 5 mm to 2 mm, 18 parts of calcined petroleum coke with a particle size of 2 mm to 1 mm, and 36 parts of fine powder calcined petroleum coke with a particle size ≤ 0.3 mm, and put them into a mixer to mix evenly.

[0116] Anode preparation: Put 86 parts of the dry materials into a kneader, then add 14 parts of the modified coal tar pitch, and knead at 165 °C for 20 min to obtain a paste. Put the paste into a mold and press it into shape under a pressure of 480 KN to obtain a green anode.

[0117] Anode baking: The prepared anode is cooled to room temperature, and then the anode is placed in a baking furnace for baking. It is heated from room temperature to 250°C at a heating rate of 4°C / h; heated to 650°C at a heating rate of 3°C / h; heated to 950°C at a heating rate of 3°C / h; heated to 1150°C at a heating rate of 4°C / h; and held at 1150°C for 50 h. After baking, it is cooled slowly. After the temperature drops to 200 - 300°C, the anode carbon block is taken out of the furnace, and the pre-baked anode is obtained.

[0118] The performance of the anode carbon blocks obtained in Examples 1 - 5 and Comparative Examples 1 - 3 was measured, and the results are shown in Table 1.

[0119] Table 1 Performance of the anode carbon blocks obtained in Examples 1 - 5 and Comparative Examples 1 - 3

[0120]

[0121]

[0122] As can be seen from Table 1, the bulk density of the pre-baked anodes in Examples 1 - 5 is ≥1.57 g / cm 3 , the resistivity is 55.4 μΩ·m - 56.8 μΩ·m, the ash content is 0.28% - 0.31%, and the air reaction residual rate is ≥67%. Using modified coal tar pitch instead of traditional coal tar pitch as the binder to prepare the pre-baked anode can effectively increase the coking value of coal tar pitch, improve the quality of the anode, and provide guarantee for the production of high-quality anodes.

[0123] In addition, one or more technical solutions in the embodiments of the present application at least further have the following technical effects or advantages:

[0124] In the embodiments of the present application, modifying coal tar pitch can effectively solve the problem of low coking value of coal tar pitch used in anodes, improve the properties of anodes such as strength, antioxidant property, and compactness, greatly improve the anode quality, and meet the usage requirements of electrolytic aluminum enterprises for anodes.

[0125] 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 will conform to the broadest scope consistent with the principles and novel features claimed herein.

Claims

1. A preparation method of modified coal tar pitch, the method comprising: heating the coal tar pitch to a set temperature; adding a modifier to the coal tar pitch at the set temperature to obtain a mixture; the mass ratio of the coal tar pitch to the modifier being (95-99):(1-5); and stirring the mixture at the set temperature for a set time to polymerize light components and short-chain components in the coal tar pitch to form long-chain macromolecules, thereby obtaining modified coal tar pitch.

2. The method according to claim 1, characterized in that, The modifier includes one or more of a copper-containing compound, carbon black, petroleum asphalt, sulfur compound, boron-containing compound, p-methylbenzaldehyde, fluorine-containing compound, chlorobenzene compound, and hexahydroxymethylmelamine hexamethyl ether.

3. The method according to claim 2, wherein The copper-containing compound includes one or more of copper sulfate, copper hydroxide, and copper bromide; The sulfur compound includes one or more of sulfur trioxide, sodium sulfite, and copper sulfide; The boron-containing compound includes one or more of boric acid and borate; The fluorine-containing compound includes one or more of aluminum fluoride, sodium fluoride, and sulfur hexafluoride; The chlorobenzene compound includes one or more of chlorobenzene and dichlorobenzene; 4. The method according to claim 1, wherein The set temperature is 150°C to 180°C.

5. The method according to claim 1, characterized in that, The set time is 60 min to 120 min.

6. A modified coal tar pitch prepared by the method according to any one of claims 1 to 5, the modified coal tar pitch being a thermoplastic pitch.

7. A pre-baked anode, the pre-baked anode comprising: The modified coal tar pitch according to claim 6 and calcined petroleum coke; the mass ratio of the modified coal tar pitch to the calcined petroleum coke being (13-16):(84-87).

8. The pre-baked anode according to claim 7, wherein, The calcined petroleum coke is composed of aggregate calcined petroleum coke and fine powder calcined petroleum coke, and the mass ratio of the aggregate calcined petroleum coke to the fine powder calcined petroleum coke is (55-75):(25-45).

9. The pre-baked anode according to claim 7, wherein The particle size distribution of the aggregate calcined petroleum coke includes coarse coke of 8 mm to 5 mm, medium coke of 5 mm to 2 mm, and fine coke of 2 mm to 1 mm, and the mass ratio of the coarse coke, the medium coke, and the fine coke is (25-29):(17-21):(17-22).

10. The prebaked anode according to claim 7, characterized in that, The pre-baked anode meets the following properties: bulk density ≥ 1.57 g / cm 3 , resistivity is 55.4 μΩ·m to 56.8 μΩ·m, ash content is 0.28% to 0.31%, and the air reaction residual rate ≥ 67%.

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