Preparation method of block carbon material and block carbon material

Abstract

The invention provides a preparation method of a block carbon material and the block carbon material.The method comprises the steps that A-type fibers are obtained, and the A-type fibers are formed by mixing polyacrylonitrile pre-oxidized fibers and a dispersing agent; carrying out first mixing on the A-type fiber and molten raw material asphalt to obtain B-type asphalt; carrying out second mixing on the green coke with gradient granularity; performing third mixing on the green coke after the second mixing and the type B asphalt to obtain a paste material; forming the paste to obtain a green body; and roasting the green body to obtain the block carbon material. The strength of the block carbon material is enhanced through a unique raw material combination and mixing mode.

Description

Technical Field

[0001] The present invention relates to the technical field of carbon materials, and in particular to a preparation method of a bulk carbon material and the bulk carbon material. Background Art

[0002] Due to its excellent performance, bulk carbon materials have been widely used in many fields. However, the strength of bulk carbon materials has always been a key factor affecting their performance. The cracks and fractures caused by insufficient strength of bulk carbon materials are one of the common factors affecting their normal production and use, which not only affects the quality of the product, but also increases the production cost. The same situation exists in bulk carbon materials prepared with green coke as coke raw material. Traditional methods to improve the strength of bulk carbon materials, such as formula optimization, kneading condition optimization, and molding condition optimization, are relatively mature and difficult to achieve significant improvements on the existing basis. Increasing strength by adding fiber materials is another way to improve the strength of bulk carbon materials, but the current problem is that the fiber materials are difficult to disperse evenly in the matrix, resulting in poor reinforcement effect. Therefore, how to effectively improve the strength of bulk carbon materials has become a technical problem that needs to be solved urgently in this field. Summary of the Invention

[0003] The present application provides a preparation method of a bulk carbon material and a bulk carbon material to solve the following technical problem: how to enhance the strength of a bulk carbon material prepared using green coke as a coke raw material.

[0004] In a first aspect, the present invention provides a method for preparing a bulk carbon material, comprising:

[0005] Obtaining A-type fibers, wherein the A-type fibers are formed by mixing pre-oxidized polyacrylonitrile fibers and a dispersant;

[0006] The type A fiber is first mixed with melted raw material asphalt to obtain type B asphalt;

[0007] subjecting the green coke having gradient particle size to a second mixing;

[0008] performing a third mixing of the green coke after the second mixing and the type B asphalt to obtain a paste;

[0009] shaping the paste to obtain a green body;

[0010] calcining the green body to obtain a bulk carbon material;

[0011] The green coke of gradient particle size includes: green coke fine powder with a particle size less than 0.075 mm, first green coke particles with a particle size of 0.075 mm-1 mm, and second green coke particles with a particle size greater than 1 mm.

[0012] Optionally, in the green coke with gradient particle size, the mass fraction of the green coke fine powder is 17%-24%, the mass fraction of the first green coke particles is 23%-36%, and the mass fraction of the second green coke particles is 40%-60%.

[0013] Optionally, the volatile matter content in the green coke is 3% to 10.5%, and the moisture content in the green coke is not greater than 0.5%.

[0014] Optionally, the weight ratio of the polyacrylonitrile pre-oxidized fiber to the dispersant is 1:(0.3-1.0), and / or the weight ratio of the polyacrylonitrile pre-oxidized fiber to the raw asphalt in the type B asphalt is (0.04-0.12):1,

[0015] Optionally, the length of the polyacrylonitrile pre-oxidized fiber is 2 mm to 7 mm, and / or,

[0016] The dispersant includes at least one of the following: oleic acid and dioctyl phthalate.

[0017] Optionally, the coking value of the raw asphalt is not less than 45%, and / or,

[0018] The raw asphalt includes at least one of the following: petroleum asphalt, coal asphalt, and / or

[0019] The raw material asphalt is contained in an amount of 0.14 to 0.18 parts by weight relative to 1 part by weight of the paste.

[0020] Optionally, the temperature of the first mixing satisfies: making the apparent viscosity of the raw asphalt between 200mPa·s and 800mPa·s, and / or,

[0021] The temperature of the third mixing satisfies: making the apparent viscosity of the raw asphalt between 300 mPa·s and 1500 mPa·s.

[0022] Optionally, the second mixing temperature is T1°C, and the third mixing temperature is T2°C, wherein 0≤T2-T1≤40.

[0023] Optionally, calcining the green body includes: calcining the green body in a first stage of heating, a second stage of heating, and a heat preservation stage;

[0024] The first stage of heating includes heating the green body from room temperature to 240°C to 260°C at a heating rate of 6°C / h to 20°C / h;

[0025] The second stage of heating includes: heating the green body from the end point temperature of the first stage of heating to 640° C. to 660° C. at a heating rate of 3° C. / h-15° C. / h;

[0026] The holding stage includes: heating the green body from the end temperature of the second stage heating to 1050°C to 1200°C at a heating rate of 5°C / h to 15°C / h, and keeping the green body at the end temperature of the holding stage for 10h to 80h.

[0027] In a second aspect, an embodiment of the present application provides a bulk carbon material prepared by any method described in the first aspect.

[0028] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0029] The embodiments of the present application provide a method for preparing a bulk carbon material and a bulk carbon material. The strength of the bulk carbon material is enhanced by a unique raw material combination and mixing method. Type A fiber is made of a mixture of polyacrylonitrile pre-oxidized fiber and a dispersant. The polyacrylonitrile pre-oxidized fiber has excellent mechanical properties. After mixing with the dispersant, it can be evenly dispersed in the system, and finally forms a structure similar to a reinforcing phase in the bulk carbon material, dispersing stress, hindering crack propagation, and enhancing anti-destruction ability. Type A fiber is mixed with molten raw material asphalt to obtain type B asphalt. The asphalt and fiber are mixed in the molten state so that the two are tightly combined. After roasting, the fiber and the asphalt carbon formed by carbonization of the asphalt work synergistically to improve the strength of the material. The green coke with gradient particle size includes particles of different particle size ranges to form a filling system with a gradient structure. The multi-scale filling structure reduces internal defects and pores, improves density, and ensures the strength of the bulk carbon material. The entire preparation process rationally selects raw materials, controls particle size and mixing order, optimizes the internal structure, and makes the fiber reinforcing phase, asphalt carbon and coke filling particles work synergistically to effectively solve the problem of enhanced strength. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0031] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0032] Figure 1 A flow chart of a method for preparing a bulk carbon material provided in an embodiment of the present application. DETAILED DESCRIPTION

[0033] To make the purpose, technical solutions, and advantages of the embodiments of this application more clear, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0034] The range descriptions described in this article, such as numerical ranges, ratio ranges, etc., include all possible sub-ranges and single numerical values ​​within the range. For example, the range description of "1 to 6" or "1~6" covers all sub-ranges from 1 to 6 (such as 1 to 3, 2 to 5, etc.) and single numbers (such as 1, 2, 3, 4, 5, 6). Unless otherwise specified, the terms "including", "comprising", etc. used in this article mean "including but not limited to"; relational terms such as "first" and "second" are only used to distinguish different entities or operations, and do not imply an actual sequence or association relationship; "and / or" means that multiple situations can exist alone or at the same time; expressions such as "at least one", "multiple", and "at least one" refer to any combination of corresponding objects, including a combination of single or multiple objects. The proportional relationships involved in the article, such as mass ratios, molar ratios, etc., should be understood as the corresponding relationship between the first and second terms of the proportional formula in the order of description. The raw materials, reagents, instruments and equipment used in this article can be purchased on the market or prepared by existing methods.

[0035] Figure 1 A flow chart of a method for preparing a bulk carbon material provided in an embodiment of the present application.

[0036] See Figure 1 , the present application embodiment provides a method for preparing a bulk carbon material, comprising:

[0037] S1, obtaining type A fibers, wherein the type A fibers are formed by mixing pre-oxidized polyacrylonitrile fibers and a dispersant;

[0038] S2. performing a first mixing of the type A fiber and melted raw material asphalt to obtain type B asphalt;

[0039] S3, performing a second mixing on the green coke having gradient particle size;

[0040] S4, performing a third mixing of the green coke after the second mixing and the type B asphalt to obtain a paste;

[0041] S5, shaping the paste to obtain a green body;

[0042] S6, calcining the green body to obtain a bulk carbon material;

[0043] The green coke of gradient particle size includes: green coke fine powder with a particle size less than 0.075 mm, first green coke particles with a particle size of 0.075 mm-1 mm, and second green coke particles with a particle size greater than 1 mm.

[0044] Bulk carbon material: refers to carbonaceous materials with a certain shape and size, which generally have properties such as high mechanical strength, good conductivity and corrosion resistance. Polyacrylonitrile pre-oxidized fiber: The fiber obtained by pre-oxidation of polyacrylonitrile fiber has certain thermal stability and high strength, and can be used to enhance the performance of carbon materials. Dispersant: Used to improve the dispersion uniformity of fibers and other substances in a mixed system and prevent fiber agglomeration. Gradient particle size: refers to the particle size distribution of the material showing a gradual state from small to large or from large to small. Particles of different sizes play different roles in the material.

[0045] In this technical solution, by rationally selecting raw materials, controlling particle size and mixing sequence, and optimizing the internal structure, the fiber reinforcement phase, pitch carbon, and coke filling particles work synergistically to effectively solve the problem of enhanced strength and reduce the problem of cracks and breakage in the bulk carbon material during production and use. It should be noted that this preparation method can be combined with other material preparation technologies, such as adding other reinforcing phases or functional phases, to develop composite carbon materials with special properties. Exemplary:

[0046] The particle size of the green coke fine powder with a particle size of less than 0.075 mm can be: 0.01 mm (assuming the lower limit is 0.01 mm), 0.02 mm, 0.03 mm, 0.04 mm, 0.05 mm, 0.06 mm, 0.07 mm, 0.075 mm, etc.; the particle size of the first green coke particles with a particle size of 0.075 mm-1 mm can be: 0.075 mm, 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, The particle size of the second coke particles with a particle size greater than 1 mm can be: 0.6mm, 0.7mm, 0.8mm, 0.9mm, 1.0mm, etc.; the particle size of the second coke particles with a particle size greater than 1 mm can be: 1.1mm, 1.2mm, 1.3mm, 1.4mm, 1.5mm, 1.6mm, 1.7mm, 1.8mm, 1.9mm, 2.0mm, 2.5mm, 3.0mm, 3.5mm, 4.0mm, 4.5mm, 5.0mm (assuming the upper limit is 5.0mm), etc.

[0047] In some embodiments, in the green coke having gradient particle size, the mass fraction of the green coke fines is 17%-24%, the mass fraction of the first green coke particles is 23%-36%, and the mass fraction of the second green coke particles is 40%-60%.

[0048] Mass fraction: refers to the ratio of the mass of a component to the total mass of the mixture, used to describe the proportion of the component in the mixture.

[0049] By specifying the mass fraction range of coke particles of different particle sizes in the coke with gradient particle size, the coke particle size that meets this condition contains coke particles of different particle size ranges, forming a filling system with a gradient structure. The multi-scale filling structure is conducive to reducing internal defects and pores in the bulk carbon material, improving density and enhancing strength. It should be noted that in actual applications, fine-tuning can be made within this mass fraction range according to different application scenarios and performance requirements to further optimize the performance of the material. For example:

[0050] The mass fraction of green coke fine powder can be: 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, etc.; the mass fraction of the first green coke particles can be: 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, etc.; the mass fraction of the second green coke particles can be: 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58, 59%, 60%, etc.

[0051] In some embodiments, the volatile matter content in the green coke is 3% to 10.5%, and the moisture content in the green coke is no more than 0.5%.

[0052] Volatile matter: refers to the mass fraction of volatile substances produced by the decomposition of materials under specific conditions. Moisture: refers to the mass fraction of water contained in the material.

[0053] Tests have shown that when the volatile content in green coke exceeds 10.5%, the plasticity of the paste deteriorates, affecting the molding effect and performance of the green body. It should be noted that in actual production, the quality of the paste and the final carbon material can be ensured by testing and controlling the volatile content and moisture content in the green coke, depending on the source of the raw materials and the preparation process. For example:

[0054] The content of volatile matter in green coke can be: 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, 10.5%, etc.; the content of water in green coke can be: 0.1% (assuming the lower limit is 0.1%), 0.2%, 0.3%, 0.4%, 0.5%, etc.

[0055] In some embodiments, the weight ratio of the polyacrylonitrile pre-oxidized fiber to the dispersant is 1:(0.3-1.0), and / or,

[0056] The weight ratio of the polyacrylonitrile pre-oxidized fiber in the B-type asphalt to the raw asphalt is (0.04-0.12):1.

[0057] Polyacrylonitrile pre-oxidized fiber: A pre-oxidized polyacrylonitrile fiber with high thermal stability and mechanical strength, suitable for reinforcing carbon materials. Dispersant: Used to improve the dispersion uniformity of the fiber in the mixed system, prevent fiber agglomeration, and enhance the overall performance of the material.

[0058] Controlling the weight ratio of polyacrylonitrile pre-oxidized fiber to dispersant to 1: (0.3-1.0) can ensure the dispersion effect of polyacrylonitrile pre-oxidized fiber in asphalt, and will not introduce too much dispersant into the asphalt, resulting in excessive volatiles produced during the roasting process, affecting indicators such as the volume density of the roasted block. Controlling the weight ratio of polyacrylonitrile pre-oxidized fiber to raw asphalt in type B asphalt to (0.04-0.12): 1 can avoid using too little polyacrylonitrile pre-oxidized fiber, which affects its effect on improving the strength of the bulk carbon material; and avoid using too much polyacrylonitrile pre-oxidized fiber, which causes poor dispersion or affects the fluidity of type B asphalt. It should be noted that in actual production, fine-tuning can be made within this weight ratio range according to different application scenarios and performance requirements to further optimize the performance of the material. Exemplary:

[0059] The weight ratio of polyacrylonitrile pre-oxidized fiber to dispersant can be: 1:0.3, 1:0.4, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1.0, etc.; the weight ratio of polyacrylonitrile pre-oxidized fiber to raw asphalt in type B asphalt can be: 0.04:1, 0.05:1, 0.06:1, 0.07:1, 0.08:1, 0.09:1, 0.10:1, 0.11:1, 0.12:1, etc.

[0060] In some embodiments, the length of the polyacrylonitrile pre-oxidized fiber is 2 mm to 7 mm, and / or,

[0061] The dispersant includes at least one of the following: oleic acid and dioctyl phthalate.

[0062] Length of polyacrylonitrile pre-oxidized fibers: Fiber length has a significant impact on the material's reinforcement and processing properties. Type of dispersant: Different dispersants have different chemical properties and dispersing effects. Choosing the right dispersant can improve fiber dispersibility.

[0063] Controlling the length of the polyacrylonitrile pre-oxidized fiber within the range of 2mm-7mm can play a connecting and reinforcing role in the bulk carbon material, but it is not too long, which causes mutual entanglement during use and affects fiber dispersion. At the same time, selecting a suitable dispersant (such as oleic acid, dioctyl phthalate, etc.) can ensure the dispersion effect, and these dispersants are low in cost and high in safety. It should be noted that in actual production, according to different application scenarios and performance requirements, a suitable fiber length can be selected within this length range, and a suitable dispersant can be selected according to the properties of the raw materials and the preparation process to further optimize the performance of the material. Exemplary:

[0064] The length of polyacrylonitrile pre-oxidized fiber can be: 2mm, 3mm, 4mm, 5mm, 6mm, 7mm, etc.

[0065] In some embodiments, the coking value of the raw pitch is not less than 45%, and / or,

[0066] The raw asphalt includes at least one of the following: petroleum asphalt, coal asphalt, and / or

[0067] The raw material asphalt is contained in an amount of 0.14 to 0.18 parts by weight relative to 1 part by weight of the paste.

[0068] The coking value of raw asphalt refers to the proportion of coke converted from asphalt at a certain temperature.

[0069] Controlling the coking value of the raw asphalt to be no less than 45% can ensure that the raw asphalt has sufficient carbon-forming ability during the roasting process, thereby reducing the porosity of the bulk carbon material and improving the mechanical strength and conductivity of the material. Relative to 1 part by weight of the paste, the raw asphalt is 0.14 parts by weight to 0.18 parts by weight, which can ensure that the paste has good plasticity; and avoid excessive asphalt, which causes excessive burn-out rate during roasting and deterioration of indicators such as the volume density and strength of the roasted block. It should be noted that in actual production, the appropriate type of raw asphalt can be selected according to different application scenarios and performance requirements, and adjusted within the range of the coking value and dosage to further optimize the performance of the material. Exemplary:

[0070] The coking value of raw asphalt can be: 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60% (assuming the upper limit is 60%), etc.; relative to 1 weight part of paste, the weight part of raw asphalt can be: 0.14, 0.15, 0.16, 0.17, 0.18, etc.

[0071] In some embodiments, the temperature of the first mixing satisfies: making the apparent viscosity of the raw asphalt between 200 mPa·s and 800 mPa·s, and / or,

[0072] The temperature of the third mixing satisfies: making the apparent viscosity of the raw asphalt between 300 mPa·s and 1500 mPa·s.

[0073] Mixing temperature: refers to the temperature controlled during the mixing process, which has a significant impact on the mixing uniformity and performance of the material. Apparent viscosity: The ratio of shear stress to shear rate of Newtonian or non-Newtonian fluids, usually used to characterize the fluidity of the material.

[0074] Controlling the temperature of the first mixing so that the apparent viscosity of the raw asphalt is between 200mPa·s and 800mPa·s can ensure that the asphalt has a lower viscosity, which is conducive to the dispersion of the fibers, and does not require excessively high temperature conditions to avoid asphalt aging. Controlling the temperature of the third mixing so that the apparent viscosity of the raw asphalt is between 300mPa·s and 1500mPa·s can ensure that the asphalt has good fluidity during the third mixing, which is conducive to the wetting and penetration of the asphalt into the coke particles and ensures the mixing effect. It should be noted that in actual production, the apparent viscosity of the raw asphalt can be adjusted by controlling the mixing temperature according to the different raw material properties and preparation processes so that it is within this viscosity range to further optimize the quality and performance of the paste. Exemplary:

[0075] The apparent viscosity corresponding to the temperature of the first mixing may be: 200mPa·s, 300mPa·s, 400mPa·s, 500mPa·s, 600mPa·s, 700mPa·s, 800mPa·s, etc.; the apparent viscosity corresponding to the temperature of the third mixing may be: 300mPa·s, 400mPa·s, 500mPa·s, 600mPa·s, 700mPa·s, 800mPa·s, 900mPa·s, 1000mPa·s, 1100mPa·s, 1200mPa·s, 1300mPa·s, 1400mPa·s, 1500mPa·s, etc.

[0076] In some embodiments, the second mixing temperature is T1° C., and the third mixing temperature is T2° C., wherein 0≤T2-T1≤40.

[0077] Mixing temperature difference: refers to the temperature difference between the second and third mixing. Controlling the temperature of the second mixing to T1°C and the temperature of the third mixing to T2°C, and 0≤T2-T1≤40°C, can ensure that the mixed coke has a suitable temperature after the second mixing, creating favorable conditions for the third mixing. It should be noted that in actual production, the mixing temperature can be adjusted according to different raw material properties and preparation processes to further optimize the quality and performance of the paste. Example:

[0078] T 2- T1 can be: 0, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, etc.

[0079] In some embodiments, calcining the green body comprises: calcining the green body in a first stage of heating, a second stage of heating, and a heat preservation stage;

[0080] The first stage of heating includes heating the green body from room temperature to 240°C to 260°C at a heating rate of 6°C / h to 20°C / h;

[0081] The second stage of heating includes: heating the green body from the end point temperature of the first stage of heating to 640° C. to 660° C. at a heating rate of 3° C. / h-15° C. / h;

[0082] The holding stage includes: heating the green body from the end temperature of the second stage heating to 1050°C to 1200°C at a heating rate of 5°C / h to 15°C / h, and keeping the green body at the end temperature of the holding stage for 10h to 80h.

[0083] The green body is subjected to a first stage of heating, a second stage of heating, and a heat preservation stage of roasting. This roasting temperature curve can not only avoid too fast heating, which leads to a high roasting loss rate and even cracks in the roasted block, but also ensure the indicators of the roasted block, and also has a certain roasting efficiency, avoiding a long roasting cycle and excessive energy consumption. It should be noted that in actual production, the roasting temperature curve can be adjusted according to different raw material properties and preparation processes to keep it within this temperature range and time range to further optimize the performance of the carbon material. Exemplary:

[0084] The heating rate range of the first stage of heating is: 6℃ / h~20℃ / h, which can be 6℃ / h, 7℃ / h, 8℃ / h, 9℃ / h, 10℃ / h, 11℃ / h, 12℃ / h, 13℃ / h, 14℃ / h, 15℃ / h, 16℃ / h, 17℃ / h, 18℃ / h, 19℃ / h, 20℃ / h, etc. The temperature range of the first stage of heating is: from room temperature to 240℃~260℃, which can be 240℃, 245℃, 250℃, 255℃, 260℃, etc.

[0085] The heating rate range of the second stage heating is: 3℃ / h~15℃ / h, which can be 3℃ / h, 5℃ / h, 7℃ / h, 9℃ / h, 11℃ / h, 13℃ / h, 15℃ / h, etc.; the temperature range of the second stage heating is: from the end temperature of the first stage to 640℃~660℃, which can be 640℃, 645℃, 650℃, 655℃, 660℃, etc.

[0086] The heating rate range of the insulation stage is: 5℃ / h~15℃ / h, which can be 5℃ / h, 7℃ / h, 9℃ / h, 11℃ / h, 13℃ / h, 15℃ / h, etc.; the temperature range of the insulation stage is: from the end temperature of the second stage to 1050℃~1200℃, which can be increased to 1050℃, 1075℃, 1100℃, 1125℃, 1150℃, 1200℃, etc.; the insulation time range of the insulation stage is: 10h~80h, which can be 10h, 20h, 30h, 40h, 50h, 60h, 70h, 80h, etc.

[0087] In a second aspect, an embodiment of the present application provides a bulk carbon material prepared by any method described in the first aspect.

[0088] The bulk carbon material is prepared based on the above method. The specific steps of the preparation method can refer to the above embodiment. Since the bulk carbon material adopts part or all of the technical solutions of the above embodiment, it at least has all the beneficial effects brought by the technical solutions of the above embodiment, which will not be repeated here.

[0089] The present application will be further described below in conjunction with specific examples. It should be understood that these examples are intended to illustrate the present application only and are not intended to limit the scope of the present application. The experimental methods in the following examples where specific conditions are not specified are generally measured according to industry standards. If there are no corresponding industry standards, then the methods are carried out according to general international standards, conventional conditions, or the conditions recommended by the manufacturer.

[0090] Example 1

[0091] Using oleic acid as a dispersant, polyacrylonitrile pre-oxidized fibers with a length of 3 mm were mixed with the dispersant at a weight ratio of 1:0.5 to obtain type A fibers.

[0092] Coal tar pitch L1, with a coking value of 56.3%, was used as the raw pitch. After melting, the raw pitch was maintained at 175°C, and its apparent viscosity at 175°C was 577 mPa·s. Type A fiber was added to the melted raw pitch, with a weight ratio of pre-oxidized polyacrylonitrile fiber to raw pitch of 0.08:1. The type A fiber and raw pitch were first mixed at 175°C to produce type B pitch.

[0093] The green coke with volatile matter of 8.81% and moisture of 0.22% is prepared according to the following particle sizes: by mass percentage, fine powder less than 0.075mm accounts for 21%, particles of 0.075mm-1mm account for 26%, particles of 1mm-3mm account for 27%, and particles of 3mm-6mm account for 26%.

[0094] The batched green coke was mixed for a second time at 140°C, followed by the addition of Type B asphalt and a third mixing process at 170°C to produce a paste. One part by weight of the paste contained 0.165 parts by weight of the raw asphalt. The apparent viscosity of the raw asphalt at the third mixing temperature of 170°C was 769 mPa·s.

[0095] The paste was shaped to obtain a green body with a bulk density of 1.29 g·cm -3 , compressive strength 31MPa.

[0096] The green body was calcined according to the following temperature profile: from room temperature to 250°C at a heating rate of 10°C / h, then to 650°C at a heating rate of 3°C / h, then to 1200°C at a heating rate of 10°C / h, and then held at 1200°C for 10 hours. After cooling, a calcined bulk carbon material was obtained.

[0097] The bulk density of the calcined carbon material is 1.63 g·cm -3 , compressive strength 67MPa.

[0098] Example 2

[0099] Using dioctyl phthalate as a dispersant, polyacrylonitrile pre-oxidized fibers with a length of 4 mm were mixed with the dispersant in a weight ratio of 1:1 to obtain type A fibers.

[0100] Coal tar pitch L2, with a coking value of 58.6%, was used as the raw pitch. After melting, the raw pitch was maintained at 180°C, and its apparent viscosity at 180°C was 685 mPa·s. Type A fiber was added to the melted raw pitch, with a weight ratio of pre-oxidized polyacrylonitrile fiber to raw pitch of 0.1:1. The type A fiber and raw pitch were first mixed at 180°C to produce type B pitch.

[0101] The green coke with volatile matter of 10.39% and moisture of 0.31% is prepared according to the following particle sizes: in terms of mass percentage, fine powder less than 0.075mm accounts for 19%, particles of 0.075mm-1mm account for 25%, particles of 1mm-2mm account for 32%, and particles of 2mm-4mm account for 24%.

[0102] The batched green coke was mixed for a second time at 145°C, followed by the addition of Type B pitch and a third mixing process at 170°C to produce a paste. One part by weight of the paste contained 0.175 parts by weight of the raw pitch. The apparent viscosity of the raw pitch at the third mixing temperature of 170°C was 1478 mPa·s.

[0103] The paste was shaped to obtain a green body with a bulk density of 1.30 g·cm -3 , compressive strength 33MPa.

[0104] The green body was calcined according to the following temperature profile: from room temperature to 250°C at a heating rate of 15°C / h, then to 650°C at a heating rate of 15°C / h, then to 1080°C at a heating rate of 5°C / h, and then held at 1080°C for 70 hours. After cooling, a calcined bulk carbon material was obtained.

[0105] The bulk density of the calcined carbon material is 1.60 g·cm -3 , compressive strength 71MPa.

[0106] Example 3

[0107] Oleic acid and dioctyl phthalate were mixed in a weight ratio of 1:1 and used as a dispersant. Polyacrylonitrile pre-oxidized fibers with a length of 6 mm were mixed with the dispersant in a weight ratio of 1:0.7 to obtain type A fibers.

[0108] Coal tar pitch and petroleum asphalt were mixed in a 1:1 weight ratio to produce asphalt L3 with a coking value of 52.1%. L3 was used as the raw asphalt. After melting, the raw asphalt was maintained at 170°C, and its apparent viscosity at 170°C was 483 mPa·s. Type A fiber was added to the melted raw asphalt, with the weight ratio of pre-oxidized polyacrylonitrile fiber to raw asphalt being 0.06:1. The type A fiber and raw asphalt were first mixed at 170°C to produce type B asphalt.

[0109] The green coke with volatile matter of 7.32% and moisture of 0.46% is prepared according to the following particle size: in terms of mass percentage, fine powder less than 0.075mm accounts for 17%, particles of 0.075mm-1mm account for 23%, particles of 1mm-2mm account for 31%, and particles of 2mm-4mm account for 29%.

[0110] The batched green coke was mixed for a second time at 170°C, followed by the addition of Type B asphalt and a third mixing process at 175°C to produce a paste. One part by weight of the paste contained 0.142 parts by weight of the raw asphalt. The apparent viscosity of the raw asphalt at the third mixing temperature of 175°C was 647 mPa·s.

[0111] The paste was shaped to obtain a green body with a bulk density of 1.29 g·cm -3 , compressive strength 29MPa.

[0112] The green body was calcined according to the following temperature profile: from room temperature to 250°C at a heating rate of 6°C / h, then to 650°C at a heating rate of 9°C / h, and then to 1150°C at a heating rate of 15°C / h, where it was held at 1150°C for 40 hours. After cooling, a calcined bulk carbon material was obtained.

[0113] The bulk density of the calcined carbon material is 1.58 g·cm -3 , compressive strength 63MPa.

[0114] Example 4

[0115] Using dioctyl phthalate as a dispersant, polyacrylonitrile pre-oxidized fibers with a length of 5 mm were mixed with the dispersant at a weight ratio of 1:0.5 to obtain type A fibers.

[0116] Petroleum asphalt L4 with a coking value of 49.8% was used as the raw asphalt. After melting, the raw asphalt was maintained at 170°C, and its apparent viscosity at 170°C was 436 mPa·s. Type A fiber was added to the melted raw asphalt, with a weight ratio of pre-oxidized polyacrylonitrile fiber to raw asphalt of 0.09:1. The type A fiber and raw asphalt were first mixed at 170°C to produce type B asphalt.

[0117] The green coke with volatile matter of 5.97% and moisture of 0.29% is prepared according to the following particle size: in terms of mass percentage, fine powder less than 0.075mm accounts for 22%, particles of 0.075mm-1mm account for 33%, particles of 1mm-3mm account for 20%, and particles of 3mm-6mm account for 25%.

[0118] The batched green coke was mixed for a second time at 135°C, followed by the addition of Type B asphalt and a third mixing process at 165°C to produce a paste. One part by weight of the paste contained 0.158 parts by weight of the raw asphalt. The apparent viscosity of the raw asphalt at the third mixing temperature of 165°C was 584 mPa·s.

[0119] The paste was shaped to obtain a green body with a bulk density of 1.29 g·cm -3 , compressive strength 31MPa.

[0120] The green body was calcined according to the following temperature profile: from room temperature to 250°C at a heating rate of 20°C / h, then to 650°C at a heating rate of 12°C / h, and then to 1130°C at a heating rate of 8°C / h, where it was held at 1130°C for 50 hours. After cooling, a calcined bulk carbon material was obtained.

[0121] The bulk density of the calcined carbon material is 1.61 g·cm -3 , compressive strength 67MPa.

[0122] Example 5

[0123] Oleic acid and dioctyl phthalate were mixed in a weight ratio of 1:2 and used as a dispersant. Polyacrylonitrile pre-oxidized fibers with a length of 7 mm were mixed with the dispersant in a weight ratio of 1:0.3 to obtain type A fibers.

[0124] Petroleum pitch L5 with a coking value of 45.7% was used as the raw pitch. After melting, the raw pitch was maintained at 180°C, and its apparent viscosity at 180°C was 210 mPa·s. Type A fiber was added to the melted raw pitch, with a weight ratio of pre-oxidized polyacrylonitrile fiber to raw pitch of 0.04:1. The type A fiber and raw pitch were first mixed at 180°C to produce type B pitch.

[0125] The green coke with volatile matter of 3.10% and moisture of 0.35% is prepared according to the following particle size: in terms of mass percentage, fine powder less than 0.075mm accounts for 24%, particles of 0.075mm-1mm account for 35%, particles of 1mm-3mm account for 25%, and particles of 3mm-6mm account for 16%.

[0126] The batched green coke was mixed for a second time at 160°C, followed by the addition of Type B asphalt and a third mixing process at 170°C to produce a paste. One part by weight of the paste contained 0.15 parts by weight of the raw asphalt. The apparent viscosity of the raw asphalt at the third mixing temperature of 170°C was 311 mPa·s.

[0127] The paste was shaped to obtain a green body with a bulk density of 1.30 g·cm -3 , compressive strength 27MPa.

[0128] The green body was calcined according to the following temperature profile: from room temperature to 250°C at a heating rate of 12°C / h, then to 650°C at a heating rate of 6°C / h, and then to 1055°C at a heating rate of 12°C / h, where it was held at 1055°C for 80 hours. After cooling, a calcined bulk carbon material was obtained.

[0129] The bulk density of the calcined carbon material is 1.60 g·cm -3 , compressive strength 60MPa.

[0130] Example 6

[0131] Using oleic acid as a dispersant, polyacrylonitrile pre-oxidized fibers with a length of 2 mm were mixed with the dispersant at a weight ratio of 1:0.8 to obtain type A fibers.

[0132] Coal tar pitch L6 with a coking value of 50.9% was used as the raw pitch. After melting, the raw pitch was maintained at 160°C, and its apparent viscosity at 160°C was 786 mPa·s. Type A fiber was added to the melted raw pitch, with a weight ratio of pre-oxidized polyacrylonitrile fiber to raw pitch of 0.12:1. The type A fiber and raw pitch were first mixed at 160°C to produce type B pitch.

[0133] The green coke with volatile matter of 9.21% and moisture of 0.26% is prepared according to the following particle sizes: in terms of mass percentage, fine powder less than 0.075mm accounts for 22%, particles of 0.075mm-1mm account for 30%, particles of 1mm-3mm account for 25%, and particles of 3mm-6mm account for 23%.

[0134] The batched green coke was mixed for a second time at 155°C, followed by the addition of Type B asphalt and a third mixing process at 155°C to produce a paste. One part by weight of the paste contained 0.178 parts by weight of the raw asphalt. The apparent viscosity of the raw asphalt at the third mixing temperature of 155°C was 1065 mPa·s.

[0135] The paste was shaped to obtain a green body with a bulk density of 1.30 g·cm -3 , compressive strength 34MPa.

[0136] The green body was calcined according to the following temperature profile: from room temperature to 250°C at a heating rate of 17°C / h, then to 650°C at a heating rate of 10°C / h, and then to 1180°C at a heating rate of 9°C / h, where it was held at 1180°C for 20 hours. After cooling, a calcined bulk carbon material was obtained.

[0137] The bulk density of the calcined carbon material is 1.59 g·cm -3 , compressive strength 73MPa.

[0138] Comparative Example 1

[0139] This comparative example is a comparative example of Example 1. Except that polyacrylonitrile pre-oxidized fiber and dispersant are not used, type A fiber is not prepared, and type B asphalt is not prepared, all other conditions are the same as in Example 1. When preparing the paste, raw asphalt is used instead of type B asphalt. For every 1 part by weight of the paste, the raw asphalt corresponds to 0.165 parts by weight, the same as in Example 1.

[0140] The bulk density of the prepared green body is 1.29 g·cm -3 , compressive strength 23MPa; calcined block bulk density 1.63g·cm -3 , compressive strength 53MPa.

[0141] Comparative Example 2

[0142] This comparative example is a comparative example of Example 2. Except that polyacrylonitrile pre-oxidized fiber and dispersant are not used, type A fiber is not prepared, and type B asphalt is not prepared, all other conditions are the same as in Example 2. When preparing the paste, raw asphalt is used instead of type B asphalt. For every 1 part by weight of the paste, the raw asphalt is also 0.175 parts by weight, the same as in Example 2.

[0143] The bulk density of the prepared green body is 1.30 g·cm -3 , compressive strength 23MPa; calcined block bulk density 1.61g·cm -3 , compressive strength 52MPa.

[0144] Comparative Example 3

[0145] This comparative example is a comparative example of Example 3. Except that polyacrylonitrile pre-oxidized fiber and dispersant are not used, type A fiber is not prepared, and type B asphalt is not prepared, all other conditions are the same as in Example 3. When preparing the paste, raw asphalt is used instead of type B asphalt. For every 1 part by weight of the paste, the raw asphalt corresponds to 0.142 parts by weight, the same as in Example 3.

[0146] The bulk density of the prepared green body is 1.29 g·cm -3 , compressive strength 22MPa; calcined block bulk density 1.58g·cm -3 , compressive strength 50MPa.

[0147] Comparative Example 4

[0148] This comparative example is a comparison to Example 4, except that no dispersant was used, Type A fiber was not prepared, and Type B pitch was not prepared. Polyacrylonitrile pre-oxidized fiber was mixed with green coke under the same mixing conditions as in the second mixing step in Example 4. Raw pitch was then added and mixed under the same mixing conditions as in the third mixing step in Example 4. All other conditions were the same as in Example 4. When preparing the paste, raw pitch was used instead of Type B pitch, with 1 part by weight of paste corresponding to 0.158 parts by weight of raw pitch.

[0149] The bulk density of the prepared green body is 1.28 g·cm -3 , compressive strength 25MPa; calcined block bulk density 1.59g·cm -3 , compressive strength 55MPa.

[0150] Table 1 Part of the process parameters and bulk carbon material indicators of the examples and comparative examples

[0151]

[0152] Based on the results of Examples 1-6 and Comparative Examples 1-4, the preparation method of the present invention has a significant effect in enhancing the strength of bulk carbon materials. The details are as follows:

[0153] In this example, Type A fibers were successfully prepared by treating pre-oxidized polyacrylonitrile fibers with a dispersant. These fibers were then mixed with the raw pitch to form Type B pitch. This treatment ensured uniform distribution of the fibers within the pitch, forming a uniform reinforcement network during carbonization. Experimental data showed that the green and calcined compressive strengths of Examples 1 to 6 were significantly higher than those of the comparative examples, demonstrating that uniform fiber dispersion plays a key role in improving material strength.

[0154] Comparative Examples 1 to 3 did not use pre-oxidized polyacrylonitrile fibers or a dispersant, thus failing to form an effective reinforcement network. Comparative Example 4, while using pre-oxidized polyacrylonitrile fibers, lacked a dispersant, resulting in poor fiber dispersion and a weak reinforcement effect. Experimental data showed that the compressive strength of both the green and calcined bodies of the comparative examples was lower than that of the examples, demonstrating that uniform fiber dispersion is a key factor in improving material strength.

[0155] The foregoing is merely a list of specific embodiments of the present application, intended to enable those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application is not limited to the embodiments shown herein, but is intended to conform to the broadest scope consistent with the principles and novel features of the present application.

Claims

1. A method for preparing a bulk carbon material, comprising: Obtaining A-type fibers, wherein the A-type fibers are formed by mixing pre-oxidized polyacrylonitrile fibers and a dispersant; The type A fiber is first mixed with melted raw material asphalt to obtain type B asphalt; subjecting the green coke having gradient particle size to a second mixing; performing a third mixing of the green coke after the second mixing and the type B asphalt to obtain a paste; shaping the paste to obtain a green body; calcining the green body to obtain a bulk carbon material; The green coke with gradient particle size includes: green coke fine powder with a particle size less than 0.075 mm, first green coke particles with a particle size of 0.075 mm-1 mm, and second green coke particles with a particle size greater than 1 mm.

2. The method for preparing a bulk carbon material according to claim 1, wherein: In the green coke with gradient particle size, the mass fraction of the green coke fine powder is 17%-24%, the mass fraction of the first green coke particles is 23%-36%, and the mass fraction of the second green coke particles is 40%-60%.

3. The method for preparing a bulk carbon material according to claim 1, wherein: The content of volatile matter in the green coke is 3% to 10.5%, and the content of water in the green coke is no more than 0.5%.

4. The method for preparing a bulk carbon material according to claim 1, wherein: The weight ratio of the polyacrylonitrile pre-oxidized fiber in the A-type fiber to the dispersant is 1:(0.3-1.0), and / or, The weight ratio of the polyacrylonitrile pre-oxidized fiber in the B-type asphalt to the raw asphalt is (0.04-0.12):

1.

5. The method for preparing a bulk carbon material according to claim 1, wherein: The length of the polyacrylonitrile pre-oxidized fiber is 2 mm to 7 mm, and / or The dispersant includes at least one of the following: oleic acid and dioctyl phthalate.

6. The method for preparing a bulk carbon material according to claim 1, characterized in that: The coking value of the raw pitch is not less than 45%, and / or The raw asphalt includes at least one of the following: petroleum asphalt, coal asphalt, and / or The raw material asphalt is contained in an amount of 0.14 to 0.18 parts by weight relative to 1 part by weight of the paste.

7. The method for preparing a bulk carbon material according to claim 1, characterized in that: The temperature of the first mixing satisfies: making the apparent viscosity of the raw asphalt between 200 mPa·s and 800 mPa·s, and / or, The temperature of the third mixing satisfies: making the apparent viscosity of the raw asphalt between 300 mPa·s and 1500 mPa·s.

8. The method for preparing a bulk carbon material according to claim 1, wherein: The second mixing temperature is T1° C., and the third mixing temperature is T2° C., wherein 0≤T2-T1≤40.

9. The method for preparing a bulk carbon material according to claim 1, wherein: The calcining of the green body comprises: calcining the green body in a first stage of heating, a second stage of heating and a heat preservation stage; The first stage of heating includes heating the green body from room temperature to 240°C to 260°C at a heating rate of 6°C / h to 20°C / h; The second stage of heating includes: heating the green body from the end point temperature of the first stage of heating to 640° C. to 660° C. at a heating rate of 3° C. / h-15° C. / h; The holding stage includes: heating the green body from the end temperature of the second stage heating to 1050°C to 1200°C at a heating rate of 5°C / h to 15°C / h, and keeping the green body at the end temperature of the holding stage for 10h to 80h.

10. A bulk carbon material prepared by the method according to any one of claims 1 to 9.

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