Fluid form calcined petroleum coke for extra-high voltage direct current transmission grounding electrode and application of fluid form calcined petroleum coke

Abstract

The invention relates to the technical field of grounding electrode materials, in particular to fluid form calcined petroleum coke for an extra-high voltage direct current transmission grounding electrode and application of the fluid form calcined petroleum coke, and the fluid form calcined petroleum coke is prepared from the following raw materials in parts by weight: 80-90 parts of composite modified calcined petroleum coke and 5-10 parts of phenolic resin. After the calcined petroleum coke is subjected to plasma surface modification treatment, the microstructure of the surface of the calcined petroleum coke can be obviously changed, the specific surface area can be increased, and more conductive channels and contact points can be provided, so that the contact resistance is reduced, and the conductive efficiency is improved. The copper forms a good conductive network in the material, so that current is effectively conducted, the resistance of the grounding electrode is reduced, heat generated by the resistance is reduced, and the overall conductive performance is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of grounding electrode materials, and more specifically, to fluid-form calcined petroleum coke for UHVDC transmission grounding electrodes and its applications. Background Art

[0002] With the growth of global energy demand and the rapid development of renewable energy, ultra-high voltage direct current (UHVDC) transmission has become a key technology for long-distance and large-capacity power transmission. Compared with AC transmission, DC transmission has obvious advantages in reducing line losses and improving transmission efficiency, and at the same time helps to reduce the impact on the environment. To ensure the safe and stable operation of the power grid, UHVDC transmission systems have strict requirements for grounding electrodes, including good electrical conductivity, corrosion resistance, and long-term stability.

[0003] Traditional UHVDC transmission grounding electrodes use solid calcined petroleum coke as the conductive material. However, its powdery physical properties are prone to generate a large amount of dust during construction, resulting in serious environmental pollution and low visibility during operation. At the same time, the loose form is difficult to achieve uniform laying and compaction, with low construction efficiency and material waste. In view of this, we propose fluid-form calcined petroleum coke for UHVDC transmission grounding electrodes and its applications. Summary of the Invention

[0004] The purpose of the present invention is to provide fluid-form calcined petroleum coke for UHVDC transmission grounding electrodes to solve the problems in the above background art that traditional UHVDC transmission grounding electrodes use solid calcined petroleum coke as the conductive material, but its powdery physical properties are prone to generate a large amount of dust during construction, resulting in serious environmental pollution and low visibility during operation, and at the same time, the loose form is difficult to achieve uniform laying and compaction, with low construction efficiency and material waste.

[0005] To achieve the above purpose, on the one hand, the present invention provides fluid-form calcined petroleum coke for UHVDC transmission grounding electrodes, including the following raw materials: 80 - 90 parts by weight of composite modified calcined petroleum coke, and 5 - 10 parts by weight of phenolic resin; The composite modified calcined petroleum coke is prepared by first performing plasma surface modification on the calcined petroleum coke, then mixing it with a copper-based alumina composite material, and finally mixing it with titanium dioxide.

[0006] Preferably, the preparation method of the composite modified calcined petroleum coke is as follows: S1.1. Weigh the following raw materials in parts by weight respectively: 80 - 90 parts by weight of calcined petroleum coke, 5 - 10 parts by weight of copper powder, 3 - 5 parts by weight of alumina powder, 2 - 4 parts by weight of polyvinyl alcohol, 1 - 3 parts by weight of titanium dioxide nanoparticles, and 1 - 2 parts by weight of sodium polyacrylate; S1.2. Clean the calcined petroleum coke with a particle size of 20 - 80 mesh using anhydrous ethanol to remove surface impurities; after cleaning, place it in an oven at 60 - 100 °C and dry for 2 - 4 h; subject the dried calcined petroleum coke to plasma treatment; after the treatment is completed, naturally cool it to room temperature in argon to obtain plasma-treated calcined petroleum coke; S1.3. Put copper powder, alumina powder, and polyvinyl alcohol into a ball mill for grinding to form a copper-based alumina suspension; add the plasma-treated calcined petroleum coke to the copper-based alumina suspension, and at the same time, stir with a stirrer at a speed of 300 - 500 rpm for 1 - 2 h; conduct preliminary curing at room temperature, then place it in a high-temperature furnace and sinter under argon. The sintering temperature is raised to 800 - 1200 °C at a rate of 5 - 10 °C / min, and the sintering time is 1 - 5 h; after sintering is completed, naturally cool it to room temperature to obtain composite calcined petroleum coke; S1.4. Add titanium dioxide nanoparticles to acetone, then add sodium polyacrylate, and perform ultrasonic dispersion at a power of 200 - 300 W for 40 - 60 min to uniformly disperse it in the acetone solution to obtain a titanium dioxide suspension; grind the composite calcined petroleum coke into powder, add it to the titanium dioxide suspension, stir at a speed of 400 - 500 rpm, and perform ultrasonic treatment simultaneously to obtain a composite modified calcined petroleum coke in a fluid form.

[0007] Preferably, in S1.2, the plasma treatment is to put the dried calcined petroleum coke into a plasma reaction chamber, introduce nitrogen, turn on the plasma generator, set the power to 100 - 300 W, the pressure to 1 - 5 Pa, and the treatment time to 10 - 20 min.

[0008] After plasma treatment, the specific surface area is increased, and more active sites (such as edge defects and oxygen-containing functional groups) are exposed, providing a low-resistance path for electron transport; at the same time, the graphitized carbon skeleton of the coke itself has basic conductivity; copper powder, as a highly conductive metal phase, fills the gaps between coke particles to form a continuous metal conductive network, significantly reducing the contact resistance; while alumina, as an insulating ceramic phase, is dispersed in the conductive network to prevent the agglomeration of coke particles and optimize the uniformity of the conductive path; the modified surface of the coke is tightly combined with copper powder through physical adsorption or electrostatic interaction, and the copper network "bridges" the coke particles to form a three-dimensional conductive channel of "coke - copper - coke"; alumina stabilizes the dispersion system through steric hindrance effects, avoiding resistance bottlenecks caused by local aggregation of copper or coke.

[0009] Preferably, the volume flow rate of the introduced nitrogen is 20 - 50 sccm.

[0010] Preferably, in S1.3, the particle size of the copper powder is 20 - 50 μm, and the particle size of the alumina powder is 10 - 30 μm.

[0011] Preferably, in S1.3, agate balls with a diameter of 5 - 10 mm are selected as the grinding balls for the grinding treatment, the ball-to-material ratio is set to 5 - 10:1, the grinding speed is 200 - 300 rpm, and the grinding time is 4 - 6 h.

[0012] Preferably, in S1.4, the particle size of the titanium dioxide nanoparticles is 30 - 50 nm.

[0013] Preferably, in S1.4, the power of the ultrasonic treatment is 100 - 200 W, and the ultrasonic time is 30 - 40 min.

[0014] On the other hand, the present invention provides the application of the fluidized - form calcined petroleum coke for the UHV DC transmission grounding electrode described above in the UHV DC transmission grounding electrode. The preparation method of the UHV DC transmission grounding electrode is as follows: S2.1: Weigh the following raw materials by weight: 80 - 90 parts by weight of the composite - modified calcined petroleum coke, and 5 - 10 parts by weight of the phenolic resin; S2.2: Put the composite - modified calcined petroleum coke into a stirrer, stir at a speed of 100 - 200 rpm for 10 - 15 min, slowly add the phenolic resin, and at the same time increase the stirring speed to 300 - 500 rpm, and continue to stir for 10 - 20 min to obtain a mixed material; S2.3: Pour the mixed material into a mold, apply a pressure of 10 - 50 MPa to the mold, and keep it for 5 - 10 min to form a grounding - electrode blank; put the grounding - electrode blank into a heating furnace, heat it at a heating rate of 1 - 2 °C / min to 150 - 200 °C and keep it for 2 - 4 h; heat it at a heating rate of 2 - 3 °C / min to 800 - 1200 °C and keep it for 3 - 6 h; after sintering is completed, naturally cool it to room temperature to obtain the UHV DC transmission grounding electrode.

[0015] Preferably, in S2.2, the speed of slowly adding the phenolic resin is 1 - 2 parts by weight per minute.

[0016] Compared with the prior art, the beneficial effects of the present invention: 1. In the fluid - shaped calcined petroleum coke for UHVDC transmission grounding electrodes and its application, after plasma surface modification, the microscopic structure of the surface of the calcined petroleum coke can be significantly changed, increasing the specific surface area, providing more conductive channels and contact points, thereby reducing the contact resistance and improving the conduction efficiency. In addition, plasma treatment can introduce charges on the particle surface or change its surface energy, generating electrostatic repulsion or steric hindrance effects between particles, so that they can be more evenly dispersed during mixing, thus ensuring uniformity.

[0017] 2. In the fluid - shaped calcined petroleum coke for UHVDC transmission grounding electrodes and its application, adding copper - based alumina composite materials can significantly optimize the electrical conductivity of the material. Copper forms a good conductive network inside the material, effectively conducting current, reducing the resistance of the grounding electrode, and reducing the accumulation of Joule heat caused by high resistance, thereby improving the overall electrical conductivity. Specific embodiments

[0018] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0019] The present invention provides a fluid - shaped calcined petroleum coke for UHVDC transmission grounding electrodes, including the following raw materials: 80 - 90 parts by weight of composite - modified calcined petroleum coke, 5 - 10 parts by weight of phenolic resin; The composite - modified calcined petroleum coke is prepared by first performing plasma surface modification on the calcined petroleum coke, then mixing it with copper - based alumina composite materials, and finally mixing it with titanium dioxide.

[0020] Example 1: The fluid - shaped calcined petroleum coke for UHVDC transmission grounding electrodes and its application, including the following steps: S2.1. Weigh the following raw materials by weight: 80 parts by weight of composite - modified calcined petroleum coke, 5 parts by weight of phenolic resin; S2.2. Put the composite - modified calcined petroleum coke into a stirrer, stir at a speed of 200 rpm for 15 min, add phenolic resin at a speed of 2 parts by weight per minute, and at the same time increase the stirring speed to 500 rpm and continue stirring for 20 min to obtain a mixed material; S2.3. Pour the mixed materials into a mold, apply a pressure of 30 MPa to the mold and maintain it for 10 min to form a grounding electrode green body; place the grounding electrode green body in a heating furnace, heat it to 180 °C at a heating rate of 2 °C / min and maintain it for 4 h; then heat it to 1000 °C at a heating rate of 3 °C / min and maintain it for 6 h; after sintering is completed, cool it naturally to room temperature to obtain a UHVDC transmission grounding electrode.

[0021] The preparation method of the composite modified calcined petroleum coke is as follows: S1.1. Weigh the following raw materials by weight: 80 parts by weight of calcined petroleum coke, 5 parts by weight of copper powder, 3 parts by weight of alumina powder, 2 parts by weight of polyvinyl alcohol, 1 part by weight of titanium dioxide nanoparticles, and 1 part by weight of sodium polyacrylate; S1.2. Wash the calcined petroleum coke with a particle size of 80 mesh with absolute ethanol to remove surface impurities; after washing, place it in an oven at 80 °C and dry it for 4 h; put the dried calcined petroleum coke into a plasma reaction chamber, introduce nitrogen at a volume flow rate of 42 sccm, turn on the plasma generator, set the power to 200 W, the pressure to 3 Pa, and the treatment time to 20 min; after the treatment is completed, cool it naturally to room temperature in argon to obtain plasma-treated calcined petroleum coke; S1.3. Put copper powder with a particle size of 40 μm, alumina powder with a particle size of 20 μm, and polyvinyl alcohol into a ball mill for grinding. Select agate balls with a diameter of 8 mm as grinding balls, set the ball-to-material ratio to 8:1, the grinding speed to 300 rpm, and the grinding time to 6 h to form a copper-based alumina suspension; add the plasma-treated calcined petroleum coke to the copper-based alumina suspension, and at the same time, stir with a stirrer at a speed of 400 rpm for 2 h; perform preliminary curing at room temperature, and then put it into a high-temperature furnace and sinter it under argon. The sintering temperature is raised to 1200 °C at a rate of 6 °C / min, and the sintering time is 5 h; after sintering is completed, cool it naturally to room temperature to obtain composite calcined petroleum coke; S1.4. Add titanium dioxide nanoparticles with a particle size of 40 nm to acetone, then add sodium polyacrylate, and perform ultrasonic dispersion at a power of 200 W for 40 min to make it evenly dispersed in the acetone solution to obtain a titanium dioxide suspension; grind the composite calcined petroleum coke into powder, add it to the titanium dioxide suspension, stir at a speed of 500 rpm, and at the same time perform ultrasonic treatment at a power of 200 W for 40 min to obtain a composite modified calcined petroleum coke in a fluid form.

[0022] Example 2: A fluid-form calcined petroleum coke for UHVDC transmission grounding electrodes and its application, including the following steps: S2.1. Weigh the following raw materials by weight: 85 parts by weight of composite modified calcined petroleum coke and 5 parts by weight of phenolic resin; S2.2. Put the composite modified calcined petroleum coke into a stirrer, stir at a speed of 200 rpm for 15 min, add phenolic resin at a speed of 2 parts by weight per minute, and at the same time increase the stirring speed to 500 rpm and continue stirring for 20 min to obtain a mixed material; S2.3. Pour the mixed material into a mold, apply a pressure of 30 MPa to the mold and keep it for 10 min to form a grounding electrode blank; put the grounding electrode blank into a heating furnace, heat it to 180 °C at a heating rate of 2 °C / min and keep it for 4 h; then heat it to 1000 °C at a heating rate of 3 °C / min and keep it for 6 h; after sintering is completed, cool it naturally to room temperature to obtain a UHVDC transmission grounding electrode.

[0023] The preparation method of the composite modified calcined petroleum coke is as follows: S1.1. Weigh the following raw materials by weight: 80 parts by weight of calcined petroleum coke, 5 parts by weight of copper powder, 3 parts by weight of alumina powder, 2 parts by weight of polyvinyl alcohol, 1 part by weight of titanium dioxide nanoparticles, and 1 part by weight of sodium polyacrylate; S1.2. Wash the calcined petroleum coke with a particle size of 80 mesh with absolute ethanol to remove surface impurities; after washing, put it into an oven at 80 °C and dry it for 4 h; put the dried calcined petroleum coke into a plasma reaction chamber, introduce nitrogen at a volume flow rate of 42 sccm, turn on the plasma generator, set the power to 200 W, the pressure to 3 Pa, and the treatment time to 20 min; after the treatment is completed, cool it naturally to room temperature in argon to obtain plasma-treated calcined petroleum coke; S1.3. Put copper powder with a particle size of 40 μm, alumina powder with a particle size of 20 μm and polyvinyl alcohol into a ball mill for grinding. Select agate balls with a diameter of 8 mm as grinding balls, set the ball-to-material ratio to 8:1, the grinding speed to 300 rpm, and the grinding time to 6 h to form a copper-based alumina suspension; add the plasma-treated calcined petroleum coke to the copper-based alumina suspension, and at the same time stir with a stirrer at a speed of 400 rpm for 2 h; perform preliminary curing at room temperature, and then put it into a high-temperature furnace and sinter it under argon. The sintering temperature rises to 1200 °C at a rate of 6 °C / min, and the sintering time is 5 h; after sintering is completed, cool it naturally to room temperature to obtain composite calcined petroleum coke; S1.4. Add titanium dioxide nanoparticles with a particle size of 40 nm to acetone, then add sodium polyacrylate, and perform ultrasonic dispersion at a power of 200 W for 40 min to uniformly disperse them in the acetone solution, obtaining a titanium dioxide suspension; grind the composite calcined petroleum coke into powder, add it to the titanium dioxide suspension, stir at a speed of 500 rpm, and simultaneously perform ultrasonic treatment at a power of 200 W for 40 min to obtain a composite modified calcined petroleum coke in a fluid form.

[0024] Example 3: Fluid-form calcined petroleum coke for UHVDC transmission grounding electrodes and its application, including the following steps: S2.1. Weigh the following raw materials by weight: 90 parts by weight of composite modified calcined petroleum coke and 5 parts by weight of phenolic resin; S2.2. Put the composite modified calcined petroleum coke into a stirrer, stir at a speed of 200 rpm for 15 min, add phenolic resin at a rate of 2 parts by weight per minute, and at the same time increase the stirring speed to 500 rpm and continue stirring for 20 min to obtain a mixed material; S2.3. Pour the mixed material into a mold, apply a pressure of 30 MPa to the mold and keep it for 10 min to form a grounding electrode blank; put the grounding electrode blank into a heating furnace, heat it to 180 °C at a heating rate of 2 °C / min and keep it for 4 h; then heat it to 1000 °C at a heating rate of 3 °C / min and keep it for 6 h; after sintering is completed, cool it naturally to room temperature to obtain a UHVDC transmission grounding electrode.

[0025] The preparation method of the composite modified calcined petroleum coke is as follows: S1.1. Weigh the following raw materials by weight: 80 parts by weight of calcined petroleum coke, 5 parts by weight of copper powder, 3 parts by weight of alumina powder, 2 parts by weight of polyvinyl alcohol, 1 part by weight of titanium dioxide nanoparticles, and 1 part by weight of sodium polyacrylate; S1.2. Wash the calcined petroleum coke with a particle size of 80 mesh with absolute ethanol to remove surface impurities; after washing, put it into an oven at 80 °C and dry it for 4 h; put the dried calcined petroleum coke into a plasma reaction chamber, introduce nitrogen at a volume flow rate of 42 sccm, turn on the plasma generator, set the power to 200 W, the pressure to 3 Pa, and the treatment time to 20 min; after the treatment is completed, cool it naturally to room temperature in argon to obtain the plasma-treated calcined petroleum coke; S1.3. Put copper powder with a particle size of 40 μm, alumina powder with a particle size of 20 μm, and polyvinyl alcohol into a ball mill for grinding. Select agate balls with a diameter of 8 mm as grinding balls, set the ball-to-material ratio to 8:1, the grinding speed to 300 rpm, and the grinding time to 6 h to form a copper-based alumina suspension; add the plasma-treated calcined petroleum coke to the copper-based alumina suspension, and at the same time, stir with a stirrer at a speed of 400 rpm for 2 h; conduct preliminary curing at room temperature, then put it into a high-temperature furnace and sinter under argon. The sintering temperature is raised to 1200 °C at a rate of 6 °C / min, and the sintering time is 5 h; after sintering is completed, cool it naturally to room temperature to obtain the composite calcined petroleum coke; S1.4. Add titanium dioxide nanoparticles with a particle size of 40 nm to acetone, then add sodium polyacrylate, and perform ultrasonic dispersion at a power of 200 W for 40 min to make it evenly dispersed in the acetone solution to obtain a titanium dioxide suspension; grind the composite calcined petroleum coke into powder, add it to the titanium dioxide suspension, stir at a speed of 500 rpm, and at the same time perform ultrasonic treatment at a power of 200 W for 40 min to obtain a fluid-form composite modified calcined petroleum coke.

[0026] Example 4: Fluid-form calcined petroleum coke for UHVDC transmission grounding electrode and its application, including the following steps: S2.1. Weigh the following raw materials by weight: 85 parts by weight of composite modified calcined petroleum coke, 8 parts by weight of phenolic resin; S2.2. Put the composite modified calcined petroleum coke into a stirrer, stir at a speed of 200 rpm for 15 min, add phenolic resin at a speed of 2 parts by weight per minute, and at the same time increase the stirring speed to 500 rpm and continue stirring for 20 min to obtain a mixed material; S2.3. Pour the mixed material into a mold, apply a pressure of 30 MPa to the mold and keep it for 10 min to form a grounding electrode blank; put the grounding electrode blank into a heating furnace, heat it to 180 °C at a heating rate of 2 °C / min and keep it for 4 h; then heat it to 1000 °C at a heating rate of 3 °C / min and keep it for 6 h; after sintering is completed, cool it naturally to room temperature to obtain the UHVDC transmission grounding electrode.

[0027] The preparation method of the composite modified calcined petroleum coke is as follows: S1.1. Weigh the following raw materials by weight: 85 parts by weight of calcined petroleum coke, 8 parts by weight of copper powder, 4 parts by weight of alumina powder, 3 parts by weight of polyvinyl alcohol, 2 parts by weight of titanium dioxide nanoparticles, 1.5 parts by weight of sodium polyacrylate; S1.2. Clean the calcined petroleum coke with a particle size of 80 mesh using absolute ethanol to remove surface impurities; after cleaning, place it in an oven at 80 °C and dry for 4 h; put the dried calcined petroleum coke into the plasma reaction chamber, introduce nitrogen at a volume flow rate of 25 sccm, turn on the plasma generator, set the power to 200 W, the pressure to 3 Pa, and the treatment time to 20 min; after the treatment is completed, let it cool naturally to room temperature in argon to obtain the plasma-treated calcined petroleum coke; S1.3. Put copper powder with a particle size of 40 μm, alumina powder with a particle size of 20 μm, and polyvinyl alcohol into a ball mill for grinding. Select agate balls with a diameter of 8 mm as grinding balls, set the ball-to-material ratio to 8:1, the grinding speed to 300 rpm, and the grinding time to 6 h to form a copper-based alumina suspension; add the plasma-treated calcined petroleum coke to the copper-based alumina suspension, and at the same time, stir with a stirrer at a speed of 400 rpm for 2 h; perform preliminary curing at room temperature, then put it into a high-temperature furnace and sinter under argon. The sintering temperature is raised to 1200 °C at a rate of 6 °C / min, and the sintering time is 5 h; after sintering is completed, let it cool naturally to room temperature to obtain the composite calcined petroleum coke; S1.4. Add titanium dioxide nanoparticles with a particle size of 40 nm to acetone, then add sodium polyacrylate, and perform ultrasonic dispersion at a power of 200 W for 40 min to make it uniformly dispersed in the acetone solution to obtain a titanium dioxide suspension; grind the composite calcined petroleum coke into powder, add it to the titanium dioxide suspension, stir at a speed of 500 rpm, and at the same time perform ultrasonic treatment at a power of 200 W for 40 min to obtain the composite modified calcined petroleum coke in a fluid form.

[0028] Example 5: Fluid-form calcined petroleum coke for UHVDC transmission grounding electrodes and its application, including the following steps: S2.1. Weigh the following raw materials by weight: 85 parts by weight of composite modified calcined petroleum coke, 8 parts by weight of phenolic resin; S2.2. Put the composite modified calcined petroleum coke into a stirrer, stir at a speed of 200 rpm for 15 min, add phenolic resin at a speed of 2 parts by weight per minute, and at the same time increase the stirring speed to 500 rpm and continue stirring for 20 min to obtain a mixed material; S2.3. Pour the mixed material into a mold, apply a pressure of 30 MPa to the mold and keep it for 10 min to form a grounding electrode blank; put the grounding electrode blank into a heating furnace, heat it to 180 °C at a heating rate of 2 °C / min and keep it for 4 h; then heat it to 1000 °C at a heating rate of 3 °C / min and keep it for 6 h; after sintering is completed, let it cool naturally to room temperature to obtain the UHVDC transmission grounding electrode.

[0029] The preparation method of the composite modified calcined petroleum coke is as follows: S1.1: Weigh the following raw materials by weight: 85 parts by weight of calcined petroleum coke, 8 parts by weight of copper powder, 4 parts by weight of alumina powder, 3 parts by weight of polyvinyl alcohol, 2 parts by weight of titanium dioxide nanoparticles, and 1.5 parts by weight of sodium polyacrylate; S1.2: Wash the calcined petroleum coke with a particle size of 80 mesh with absolute ethanol to remove surface impurities; after washing, put it into an oven at 80 °C and dry it for 4 h; put the dried calcined petroleum coke into a plasma reaction chamber, introduce nitrogen at a volume flow rate of 34 sccm, turn on the plasma generator, set the power to 200 W, the pressure to 3 Pa, and the treatment time to 20 min; after the treatment is completed, let it cool naturally to room temperature in argon to obtain the plasma-treated calcined petroleum coke; S1.3: Put the copper powder with a particle size of 40 μm, the alumina powder with a particle size of 20 μm, and polyvinyl alcohol into a ball mill for grinding. Select agate balls with a diameter of 8 mm as grinding balls, set the ball-to-material ratio to 8:1, the grinding speed to 300 rpm, and the grinding time to 6 h to form a copper-based alumina suspension; add the plasma-treated calcined petroleum coke to the copper-based alumina suspension, and at the same time, stir with a stirrer at a speed of 400 rpm for 2 h; perform preliminary curing at room temperature, and then put it into a high-temperature furnace and sinter it under argon. The sintering temperature is raised to 1200 °C at a rate of 6 °C / min, and the sintering time is 5 h; after the sintering is completed, let it cool naturally to room temperature to obtain the composite calcined petroleum coke; S1.4: Add the titanium dioxide nanoparticles with a particle size of 40 nm to acetone, then add sodium polyacrylate, and perform ultrasonic dispersion at a power of 200 W for 40 min to make it uniformly dispersed in the acetone solution to obtain a titanium dioxide suspension; grind the composite calcined petroleum coke into powder, add it to the titanium dioxide suspension, stir at a speed of 500 rpm, and at the same time perform ultrasonic treatment at a power of 200 W for 40 min to obtain the composite modified calcined petroleum coke in a fluid form.

[0030] Example 6: Fluid-form calcined petroleum coke for UHVDC transmission grounding electrodes and its application, including the following steps: S2.1: Weigh the following raw materials by weight: 85 parts by weight of composite modified calcined petroleum coke, 8 parts by weight of phenolic resin; S2.2: Put the composite modified calcined petroleum coke into a stirrer and stir at a speed of 200 rpm for 15 min. Add phenolic resin at a speed of 2 parts by weight per minute, and at the same time increase the stirring speed to 500 rpm and continue stirring for 20 min to obtain a mixed material; S2.3. Pour the mixed materials into the mold, apply a pressure of 30 MPa to the mold, and maintain it for 10 min to form a grounding electrode blank. Place the grounding electrode blank in a heating furnace, heat it to 180 °C at a heating rate of 2 °C / min and maintain it for 4 h. Then heat it to 1000 °C at a heating rate of 3 °C / min and maintain it for 6 h. After sintering is completed, cool it naturally to room temperature to obtain a UHVDC transmission grounding electrode.

[0031] The preparation method of the composite modified calcined petroleum coke is as follows: S1.1. Weigh the following raw materials by weight: 85 parts by weight of calcined petroleum coke, 8 parts by weight of copper powder, 4 parts by weight of alumina powder, 3 parts by weight of polyvinyl alcohol, 2 parts by weight of titanium dioxide nanoparticles, and 1.5 parts by weight of sodium polyacrylate. S1.2. Wash the calcined petroleum coke with a particle size of 80 mesh with absolute ethanol to remove surface impurities. After washing, place it in an oven at 80 °C and dry it for 4 h. Put the dried calcined petroleum coke into a plasma reaction chamber, introduce nitrogen at a volume flow rate of 42 sccm, turn on the plasma generator, set the power to 200 W, the pressure to 3 Pa, and the treatment time to 20 min. After the treatment is completed, let it cool naturally to room temperature in argon to obtain plasma-treated calcined petroleum coke. S1.3. Put the copper powder with a particle size of 40 μm, the alumina powder with a particle size of 20 μm, and polyvinyl alcohol into a ball mill for grinding. Select agate balls with a diameter of 8 mm as grinding balls, set the ball-to-material ratio to 8:1, the grinding speed to 300 rpm, and the grinding time to 6 h to form a copper-based alumina suspension. Add the plasma-treated calcined petroleum coke to the copper-based alumina suspension, and at the same time, stir with a stirrer at a speed of 400 rpm for 2 h. Conduct preliminary curing at room temperature, and then put it into a high-temperature furnace and sinter it under argon. The sintering temperature rises to 1200 °C at a rate of 6 °C / min, and the sintering time is 5 h. After sintering is completed, cool it naturally to room temperature to obtain composite calcined petroleum coke. S1.4. Add the titanium dioxide nanoparticles with a particle size of 40 nm to acetone, then add sodium polyacrylate, and perform ultrasonic dispersion at a power of 200 W for 40 min to make it evenly dispersed in the acetone solution to obtain a titanium dioxide suspension. Grind the composite calcined petroleum coke into powder, add it to the titanium dioxide suspension, stir at a speed of 500 rpm, and at the same time perform ultrasonic treatment at a power of 200 W for 40 min to obtain a composite modified calcined petroleum coke in a fluid form.

[0032] Example 7: A fluid-form calcined petroleum coke for UHVDC transmission grounding electrodes and its application, including the following steps: S2.1. Weigh the following raw materials by weight parts respectively: 85 weight parts of composite modified calcined petroleum coke and 8 weight parts of phenolic resin; S2.2. Put the composite modified calcined petroleum coke into a stirrer, stir at a speed of 200 rpm for 15 min, add phenolic resin at a speed of 2 weight parts per minute, and at the same time increase the stirring speed to 500 rpm and continue stirring for 20 min to obtain a mixed material; S2.3. Pour the mixed material into a mold, apply a pressure of 30 MPa to the mold and keep it for 10 min to form a grounding electrode blank; put the grounding electrode blank into a heating furnace, heat it to 180 °C at a heating rate of 2 °C / min and keep it for 4 h; then heat it to 1000 °C at a heating rate of 3 °C / min and keep it for 6 h; after sintering is completed, cool it naturally to room temperature to obtain a UHVDC transmission grounding electrode.

[0033] The preparation method of the composite modified calcined petroleum coke is as follows: S1.1. Weigh the following raw materials by weight parts respectively: 85 weight parts of calcined petroleum coke, 8 weight parts of copper powder, 4 weight parts of alumina powder, 3 weight parts of polyvinyl alcohol, 2 weight parts of titanium dioxide nanoparticles, and 1.5 weight parts of sodium polyacrylate; S1.2. Wash the calcined petroleum coke with a particle size of 80 mesh with absolute ethanol to remove surface impurities; after washing, put it into an oven at 80 °C and dry it for 4 h; put the dried calcined petroleum coke into a plasma reaction chamber, introduce nitrogen at a volume flow rate of 50 sccm, turn on the plasma generator, set the power to 200 W, the pressure to 3 Pa, and the treatment time to 20 min; after the treatment is completed, cool it naturally to room temperature in argon to obtain plasma-treated calcined petroleum coke; S1.3. Put copper powder with a particle size of 40 μm, alumina powder with a particle size of 20 μm and polyvinyl alcohol into a ball mill for grinding treatment, select agate balls with a diameter of 8 mm as grinding balls, set the ball-to-material ratio to 8:1, the grinding speed to 300 rpm, and the grinding time to 6 h to form a copper-based alumina suspension; add the plasma-treated calcined petroleum coke to the copper-based alumina suspension, and at the same time stir with a stirrer at a speed of 400 rpm for 2 h; carry out preliminary curing at room temperature, and then put it into a high-temperature furnace and sinter it under argon. The sintering temperature rises to 1200 °C at a rate of 6 °C / min, and the sintering time is 5 h; after sintering is completed, cool it naturally to room temperature to obtain composite calcined petroleum coke; S1.4. Add titanium dioxide nanoparticles with a particle size of 40 nm to acetone, then add sodium polyacrylate, and perform ultrasonic dispersion at a power of 200 W for 40 min to uniformly disperse them in the acetone solution to obtain a titanium dioxide suspension; grind the composite calcined petroleum coke into powder, add it to the titanium dioxide suspension, stir at a speed of 500 rpm, and simultaneously perform ultrasonic treatment at a power of 200 W for 40 min to obtain a composite modified calcined petroleum coke in a fluid form.

[0034] Comparative Example 1: Using the method of Example 6, without using the composite modified calcined petroleum coke, directly use the calcined petroleum coke to prepare the UHVDC transmission grounding electrode.

[0035] Comparative Example 2: Using the method of Example 6, in the preparation method of the composite modified calcined petroleum coke, remove the copper powder.

[0036] Comparative Example 3: Using the method of Example 6, in the preparation method of the composite modified calcined petroleum coke, remove the alumina powder.

[0037] The UHVDC transmission grounding electrode prepared by the present invention through the composite modified calcined petroleum coke, wherein, the performance index inspection items and inspection standards of the UHVDC transmission grounding electrode are as follows: According to the standard of GB / T 3048.2 - 2007 "Test Methods for Electrical Properties of Electric Wires and Cables - Part 2: Test for Resistivity of Metallic Materials", connect the two ends of the sample to the two terminals of the double - arm bridge respectively, and use the four - wire method for connection; in the case of not connecting the sample, adjust the bridge to the balanced state to ensure that the initial reading is zero. After connecting the sample, adjust the bridge until it reaches the balanced state again, and read the resistance value; repeat the measurement of the same sample at least three times, and take the average value as the final result; the resistivity should meet the design requirements, and usually a low resistivity is required to ensure good conductivity.

[0038] Use the ammeter - voltmeter method for measurement. The distance between the remote grounding point and the DC grounding electrode is at least 10 times the distance between the two farthest ends of the DC grounding electrode body, and the number of measurement points is not less than 3. Calculate the grounding resistance through the formula; a low grounding resistance can effectively reduce the voltage drop caused by the fault current passing through the grounding device, thereby reducing the electric shock risk.

[0039] Through the above - mentioned standards, test the UHVDC transmission grounding electrodes prepared in the above - mentioned Examples 1 - 7 and Comparative Examples 1 - 3, and the obtained data are shown in Table 1: Table 1 Performance data of the UHVDC transmission grounding electrodes in Examples 1 - 7 and Comparative Examples 1 - 3 It can be seen from the comparison of Examples 1-3 that: when other components remain unchanged, only when the proportion of the composite modified calcined petroleum coke gradually increases, the resistivity and grounding resistance of the UHVDC transmission grounding electrode gradually decrease. Thus, it can be known that as the proportion of the composite modified calcined petroleum coke increases, a better conductive path is formed in the grounding electrode material; after the calcined petroleum coke is modified, its internal structure changes, such as the degree of graphitization increases, and electron conduction becomes easier, thereby reducing the resistivity of the material; in addition, the synergistic conduction effect between the composite modified calcined petroleum coke and other additive components (such as conductive components like copper-based alumina composites) enhances as its proportion increases; this material can better connect with other conductive components, reducing the resistance bottleneck in the conductive channels, further optimizing the overall conductive network, and effectively reducing the resistivity and grounding resistance of the grounding electrode; the interaction between the composite modified calcined petroleum coke and the binder (such as phenolic resin) and the reinforcing phase (such as alumina) enhances as its proportion increases. The modified groups on the surface of the calcined petroleum coke form stronger chemical bonding with the binder molecules, and the conductive carbon black generated by its pyrolysis fills the pores, further reducing the grounding resistance.

[0040] Furthermore, it can be seen from Examples 4-7 that: when the mass ratio of the nitrogen gas volume flow rate to the calcined petroleum coke in the composite modified calcined petroleum coke gradually increases, the resistivity and grounding resistance of the UHVDC transmission grounding electrode gradually decrease, but when the mass ratio of the nitrogen gas volume flow rate to the calcined petroleum coke reaches a certain value, the resistivity and grounding resistance of the UHVDC transmission grounding electrode gradually increase. Thus, it can be known that as the mass ratio of the nitrogen gas volume flow rate increases, both the resistivity and grounding resistance of the UHVDC transmission grounding electrode are improved, but excessive increase will increase the resistivity and grounding resistance of the UHVDC transmission grounding electrode; Specifically, the nitrogen atoms in the nitrogen gas combine with the active sites on the coke surface, which can introduce nitrogen-containing functional groups. These functional groups will change the electronic structure of the coke, increase the degree of electron delocalization, thereby improving the conductivity of the material, reducing the resistivity, and ultimately resulting in a decrease in the grounding resistance; a higher nitrogen gas volume flow rate helps the calcined petroleum coke to be more evenly distributed during the formation process, reducing the agglomeration phenomenon, enabling the conductive components inside the material to form a better conductive network, which is beneficial to reducing the resistance.

[0041] Comparing Example 6 with Comparative Example 1, it can be seen that when directly using the calcined petroleum coke without using the composite modified calcined petroleum coke, the resistivity and grounding resistance of the UHVDC transmission grounding electrode increase significantly.

[0042] Taking Example 6 as the optimal example and combining it with Comparative Example 2, it can be known that in the preparation method of the composite modified calcined petroleum coke, when the copper powder is removed, the resistivity and grounding resistance of the UHVDC transmission grounding electrode increase significantly; In the composite modified calcined petroleum coke, copper powder, as an important conductive component, can provide an efficient conductive path. When the copper powder is removed, the grounding electrode material mainly relies on the calcined petroleum coke itself and other minor conductive components to conduct current, thereby increasing the resistivity. In the composite modified material, the copper powder can fill the gaps between the calcined petroleum coke particles and other additives, making the contact between them closer. When the copper powder is absent, the resistance at these contact points increases, resulting in an increase in the resistivity and grounding resistance of the entire grounding electrode material.

[0043] Example 6 is taken as the optimal example. Combining with Comparative Example 3, it can be seen that in the preparation method of the composite modified calcined petroleum coke, when the alumina powder is removed, the resistivity and grounding resistance of the UHVDC transmission grounding electrode increase significantly. The alumina powder plays a filling role in the gaps between the calcined petroleum coke particles, making the contact between the particles closer, thus facilitating the conduction of electrons between the particles. When the alumina powder is removed, the gaps between the particles increase, and the path of electron transmission becomes discontinuous, resulting in an increase in resistivity and a significant increase in the grounding resistance. In addition, in the composite modified material, there is a synergistic conductive effect between the alumina, the calcined petroleum coke, and the copper powder, which can promote the transfer of electrons between different conductive phases and improve the conductive performance by adjusting the electronic state at the interface. Once the alumina powder is removed, this synergistic conductive mechanism is destroyed, and the overall conductive performance of the material decreases, with the resistivity and grounding resistance increasing.

[0044] The above shows and describes the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. The above embodiments and the descriptions in the specification are only preferred examples of the present invention and are not used to limit the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents.

Claims

1. The fluidized calcined petroleum coke for the grounding electrode of UHVDC transmission is characterized in that, It includes the following raw materials: 80 - 90 parts by weight of composite modified calcined petroleum coke and 5 - 10 parts by weight of phenolic resin; The composite modified calcined petroleum coke is prepared by first performing plasma surface modification on the calcined petroleum coke, then mixing it with a copper - based alumina composite material, and finally mixing it with titanium dioxide.

2. The fluidized calcined petroleum coke for the grounding electrode of UHVDC transmission line according to claim 1, characterized in that, The preparation method of the composite modified calcined petroleum coke is as follows: S1.1: Weigh the following raw materials by weight: 80 - 90 parts by weight of calcined petroleum coke, 5 - 10 parts by weight of copper powder, 3 - 5 parts by weight of alumina powder, 2 - 4 parts by weight of polyvinyl alcohol, 1 - 3 parts by weight of titanium dioxide nanoparticles, and 1 - 2 parts by weight of sodium polyacrylate; S1.2: Wash the calcined petroleum coke with a particle size of 20 - 80 mesh with absolute ethanol to remove surface impurities; After washing, put it into an oven at 60 - 100 °C and dry it for 2 - 4 h; after drying, perform plasma treatment on the calcined petroleum coke; after the treatment is completed, naturally cool it to room temperature in argon to obtain the plasma - treated calcined petroleum coke; S1.3: Put the copper powder, alumina powder, and polyvinyl alcohol into a ball mill for grinding to form a copper - based alumina suspension; add the plasma - treated calcined petroleum coke to the copper - based alumina suspension, and at the same time, stir with a stirrer at a speed of 300 - 500 rpm for 1 - 2 h; perform preliminary curing at room temperature, then put it into a high - temperature furnace and sinter it under argon. The sintering temperature is raised to 800 - 1200 °C at a rate of 5 - 10 °C / min, and the sintering time is 1 - 5 h; after sintering is completed, naturally cool it to room temperature to obtain the composite calcined petroleum coke; S1.4: Add the titanium dioxide nanoparticles to acetone, then add sodium polyacrylate, and perform ultrasonic dispersion at a power of 200 - 300 W for 40 - 60 min to make it evenly dispersed in the acetone solution to obtain a titanium dioxide suspension; Grind the composite calcined petroleum coke into powder, add it to the titanium dioxide suspension, stir at a speed of 400 - 500 rpm, and at the same time perform ultrasonic treatment to obtain the composite modified calcined petroleum coke in a fluid form.

3. The fluidized calcined petroleum coke for the grounding electrode of UHV DC transmission is characterized in that, as described in claim 2, In S1.2, the plasma treatment is to put the dried calcined petroleum coke into a plasma reaction chamber, introduce nitrogen, turn on the plasma generator, set the power to 100 - 300 W, the pressure to 1 - 5 Pa, and the treatment time to 10 - 20 min.

4. The fluidized calcined petroleum coke for the grounding electrode of UHV DC transmission according to claim 3, characterized in that, The volume flow rate of the introduced nitrogen is 20 - 50 sccm.

5. The fluidized calcined petroleum coke for the grounding electrode of UHVDC transmission according to claim 2, characterized in that In S1.3, the particle size of the copper powder is 20 - 50 μm, and the particle size of the alumina powder is 10 - 30 μm.

6. The fluidized calcined petroleum coke for the grounding electrode of UHVDC transmission line according to claim 2, wherein In S1.3, the grinding treatment selects agate balls with a diameter of 5 - 10 mm as grinding balls, sets the ball - to - material ratio to 5 - 10:1, the grinding speed to 200 - 300 rpm, and the grinding time to 4 - 6 h.

7. The fluidized calcined petroleum coke for the grounding electrode of UHV DC transmission according to claim 2, characterized in that, In S1.4, the particle size of the titanium dioxide nanoparticles is 30 - 50 nm.

8. The fluidized calcined petroleum coke for the grounding electrode of UHV DC transmission according to claim 2, wherein, In S1.4, the power of the ultrasonic treatment is 100 - 200 W, and the ultrasonic time is 30 - 40 min.

9. Application of fluid - form calcined petroleum coke for UHV DC transmission grounding electrode described in any one of claims 1 - 8 in the UHV DC transmission grounding electrode, including the preparation of the UHV DC transmission grounding electrode, characterized in that, The preparation method of the UHVDC transmission grounding electrode is as follows: S2.

1. Weigh the following raw materials by weight parts respectively: 80 - 90 weight parts of composite modified calcined petroleum coke, 5 - 10 weight parts of phenolic resin; S2.

2. Put the composite modified calcined petroleum coke into a stirrer, stir at a speed of 100 - 200 rpm for 10 - 15 min, slowly add the phenolic resin, and at the same time increase the stirring speed to 300 - 500 rpm, and continue to stir for 10 - 20 min to obtain a mixed material; S2.

3. Pour the mixed material into a mold, apply a pressure of 10 - 50 MPa to the mold and keep it for 5 - 10 min to form a grounding electrode blank; put the grounding electrode blank into a heating furnace, heat it to 150 - 200 °C at a heating rate of 1 - 2 °C / min and keep it for 2 - 4 h; heat it to 800 - 1200 °C at a heating rate of 2 - 3 °C / min and keep it for 3 - 6 h; after sintering is completed, cool it naturally to room temperature to obtain a UHVDC transmission grounding electrode.

10. Use of fluidized calcined petroleum coke for UHVDC transmission grounding electrodes according to claim 9 in UHVDC transmission grounding electrodes, characterized in that, In the above S2.2, the speed of slowly adding the phenolic resin is 1 - 2 weight parts per minute.

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