Fluid-state calcined petroleum coke for UHVDC grounding electrodes and its application

Abstract

The present invention relates to the technical field of grounding electrode materials, and more specifically, to fluid-form calcined petroleum coke for ultra-high voltage direct current transmission grounding electrodes and its application. The fluid-form calcined petroleum coke comprises 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 calcined petroleum coke is subjected to plasma surface modification treatment, which significantly changes its surface microstructure, increases the specific surface area, and provides more conductive channels and contact points, thereby reducing contact resistance and improving conductive efficiency. Because copper forms a good conductive network within the material, it effectively conducts current, reduces the resistance of the grounding electrode, and reduces the heat generated by the resistance, thereby improving the overall conductive performance.

Description

Technical Field

[0001] The present invention relates to the technical field of grounding electrode materials, in particular to fluid-form calcined petroleum coke for ultra-high voltage direct current transmission grounding electrodes and applications thereof. 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, large-capacity power transmission. Compared with AC transmission, DC transmission has obvious advantages in reducing line losses and improving transmission efficiency, while also helping to reduce environmental impact. To ensure the safe and stable operation of the power grid, UHVDC transmission systems place strict requirements on grounding electrodes, including good conductivity, corrosion resistance, and long-term stability.

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

[0004] The purpose of the present invention is to provide fluid-form calcined petroleum coke for ultra-high voltage direct current transmission grounding electrodes, so as to solve the problems proposed in the above-mentioned background technology that traditional ultra-high voltage direct current transmission grounding electrodes use solid-state calcined petroleum coke as the conductive material, but its powdery physical properties easily generate a large amount of dust during construction, resulting in serious environmental pollution and low visibility during operation. At the same time, its loose form makes it difficult to achieve uniform laying and compaction, resulting in low construction efficiency and material waste.

[0005] To achieve the above object, the present invention provides, on the one hand, fluid-form calcined petroleum coke for ultra-high voltage direct current transmission grounding electrodes, comprising the following raw materials: 80-90 parts by weight of composite modified calcined petroleum coke, 5-10 parts by weight of phenolic resin;

[0006] 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.

[0007] Preferably, the preparation method of the composite modified calcined petroleum coke is as follows:

[0008] S1.1. Weigh the following raw materials in parts 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;

[0009] S1.2. Washing calcined petroleum coke having a particle size of 20-80 mesh with anhydrous ethanol to remove surface impurities; drying the calcined petroleum coke in an oven at 60-100°C for 2-4 hours; subjecting the dried calcined petroleum coke to plasma treatment; and cooling the calcined petroleum coke to room temperature in an argon atmosphere to obtain plasma-treated calcined petroleum coke.

[0010] S1.3. Grind copper powder, alumina powder, and polyvinyl alcohol in a ball mill to form a copper-based alumina suspension; add plasma-treated calcined petroleum coke to the copper-based alumina suspension while stirring at 300-500 rpm for 1-2 hours; perform preliminary curing at room temperature, then place in a high-temperature furnace and sinter under argon, raising the sintering temperature to 800-1200°C at a rate of 5-10°C / min for 1-5 hours; after sintering, naturally cool to room temperature to obtain a composite calcined petroleum coke;

[0011] 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 minutes to uniformly disperse them in the acetone solution to obtain a titanium dioxide suspension; grind the composite calcined petroleum coke into powder, add the powder to the titanium dioxide suspension, stir at a speed of 400-500 rpm, and perform ultrasonic treatment at the same time to obtain a composite modified calcined petroleum coke in a fluid form.

[0012] Preferably, in said S1.2, the plasma treatment is to place the dried calcined petroleum coke into a plasma reaction chamber, introduce nitrogen, turn on the plasma generator, set the power to 100-300W, the pressure to 1-5Pa, and the treatment time to 10-20min.

[0013] 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 transmission; 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 the coke particles to form a continuous metal conductive network, significantly reducing the contact resistance; and 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 the copper powder through physical adsorption or electrostatic action, and the copper network "bridges" the coke particles to form a three-dimensional conductive channel of "coke-copper-coke"; alumina stabilizes the dispersed system through the steric effect, avoiding the resistance bottleneck caused by local aggregation of copper or coke.

[0014] Preferably, the volume flow rate of the nitrogen gas introduced is 20-50 sccm.

[0015] Preferably, in said 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.

[0016] Preferably, in said S1.3, agate balls with a diameter of 5-10 mm are selected as grinding balls for the grinding process, 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.

[0017] Preferably, in said S1.4, the particle size of the titanium dioxide nanoparticles is 30-50 nm.

[0018] Preferably, in S1.4, the power of the ultrasonic treatment is 100-200 W, and the ultrasonic time is 30-40 min.

[0019] In another aspect, the present invention provides the use of the aforementioned fluid-form calcined petroleum coke for use in a UHVDC grounding electrode. The preparation method of the UHVDC grounding electrode is as follows:

[0020] S2.1. Weigh the following raw materials in parts by weight: 80-90 parts by weight of composite modified calcined petroleum coke and 5-10 parts by weight of phenolic resin;

[0021] S2.2. Place the composite modified calcined petroleum coke in a stirrer and stir at 100-200 rpm for 10-15 min. Slowly add the phenolic resin and increase the stirring speed to 300-500 rpm. Continue stirring for 10-20 min to obtain a mixture.

[0022] S2.3. Pour the mixed material into a mold, apply a pressure of 10-50 MPa to the mold, and maintain it for 5-10 minutes to form a grounding electrode body; place the grounding electrode body in a heating furnace, heat it to 150-200°C at a heating rate of 1-2°C / min and maintain it for 2-4 hours; heat it to 800-1200°C at a heating rate of 2-3°C / min and maintain it for 3-6 hours; after sintering, cool it naturally to room temperature to obtain a UHVDC grounding electrode.

[0023] Preferably, in S2.2, the phenolic resin is slowly added at a rate of 1-2 parts by weight per minute.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1. The fluid-form calcined petroleum coke used in the UHVDC grounding electrode and its application, after plasma surface modification treatment, can significantly change the microstructure of the calcined petroleum coke surface, increase the specific surface area, and provide more conductive channels and contact points, thereby reducing contact resistance and improving conductive efficiency. In addition, plasma treatment can introduce charges on the particle surface or change its surface energy, so that electrostatic repulsion or steric hindrance effect occurs between the particles, so that they can be more evenly dispersed during mixing, thereby ensuring uniformity.

[0026] 2. The UHVDC grounding electrode uses fluid-form calcined petroleum coke and its application, and the addition of copper-based alumina composite materials can significantly optimize the material's electrical conductivity. 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. DETAILED DESCRIPTION

[0027] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0028] The present invention provides fluid-form calcined petroleum coke for ultra-high voltage direct current transmission grounding electrodes, comprising the following raw materials: 80-90 parts by weight of composite modified calcined petroleum coke, 5-10 parts by weight of phenolic resin;

[0029] 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.

[0030] Example 1: Fluid-state calcined petroleum coke for UHVDC grounding electrodes and its application, comprising the following steps:

[0031] S2.1. Weigh the following raw materials in parts by weight: 80 parts by weight of composite modified calcined petroleum coke and 5 parts by weight of phenolic resin;

[0032] S2.2. The composite modified calcined petroleum coke was placed in a stirrer and stirred at 200 rpm for 15 min. A phenolic resin was added at a rate of 2 parts by weight per minute, and the stirring speed was increased to 500 rpm. The stirring was continued for 20 min to obtain a mixture.

[0033] S2.3. Pour the mixed material into a mold, apply a pressure of 30 MPa to the mold, and maintain it for 10 minutes to form a grounding electrode body; place the grounding electrode body in a heating furnace, heat it to 180°C at a heating rate of 2°C / min and maintain it for 4 hours; then heat it to 1000°C at a heating rate of 3°C / min and maintain it for 6 hours; after sintering, naturally cool it to room temperature to obtain a UHVDC grounding electrode.

[0034] The preparation method of composite modified calcined petroleum coke is as follows:

[0035] S1.1. Weigh the following raw materials in parts 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;

[0036] S1.2. Calcined petroleum coke having a particle size of 80 mesh was washed with anhydrous ethanol to remove surface impurities; after washing, the calcined petroleum coke was placed in an oven at 80°C for 4 hours; the dried calcined petroleum coke was placed in a plasma reaction chamber, nitrogen gas was introduced at a volume flow rate of 42 sccm, the plasma generator was turned on, the power was set to 200 W, the pressure was set to 3 Pa, and the treatment time was 20 minutes; after the treatment, the calcined petroleum coke was naturally cooled to room temperature in argon gas to obtain plasma-treated calcined petroleum coke;

[0037] S1.3. Copper powder with a particle size of 40 μm, alumina powder with a particle size of 20 μm, and polyvinyl alcohol are placed in a ball mill for grinding. Agate balls with a diameter of 8 mm are selected as grinding balls. The ball-to-material ratio is set to 8:1, the grinding speed is 300 rpm, and the grinding time is 6 h to form a copper-based alumina suspension; plasma-treated calcined petroleum coke is added to the copper-based alumina suspension, and the stirrer is stirred at a speed of 400 rpm for 2 h; preliminary solidification is carried out at room temperature, and then the mixture is placed in a high-temperature furnace and sintered under argon gas. The sintering temperature is increased to 1200°C at a rate of 6°C / min and the sintering time is 5 h; after sintering, the mixture is naturally cooled to room temperature to obtain a composite calcined petroleum coke;

[0038] 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 minutes 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 minutes to obtain a composite modified calcined petroleum coke in a fluid form.

[0039] Example 2: Fluid-state calcined petroleum coke for UHVDC grounding electrodes and its application, comprising the following steps:

[0040] S2.1. Weigh the following raw materials in parts by weight: 85 parts by weight of composite modified calcined petroleum coke and 5 parts by weight of phenolic resin;

[0041] S2.2. The composite modified calcined petroleum coke was placed in a stirrer and stirred at 200 rpm for 15 min. A phenolic resin was added at a rate of 2 parts by weight per minute, and the stirring speed was increased to 500 rpm. The stirring was continued for 20 min to obtain a mixture.

[0042] S2.3. Pour the mixed material into a mold, apply a pressure of 30 MPa to the mold, and maintain it for 10 minutes to form a grounding electrode body; place the grounding electrode body in a heating furnace, heat it to 180°C at a heating rate of 2°C / min and maintain it for 4 hours; then heat it to 1000°C at a heating rate of 3°C / min and maintain it for 6 hours; after sintering, naturally cool it to room temperature to obtain a UHVDC grounding electrode.

[0043] The preparation method of composite modified calcined petroleum coke is as follows:

[0044] S1.1. Weigh the following raw materials in parts 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;

[0045] S1.2. Calcined petroleum coke having a particle size of 80 mesh was washed with anhydrous ethanol to remove surface impurities; after washing, the calcined petroleum coke was placed in an oven at 80°C for 4 hours; the dried calcined petroleum coke was placed in a plasma reaction chamber, nitrogen gas was introduced at a volume flow rate of 42 sccm, the plasma generator was turned on, the power was set to 200 W, the pressure was set to 3 Pa, and the treatment time was 20 minutes; after the treatment, the calcined petroleum coke was naturally cooled to room temperature in argon gas to obtain plasma-treated calcined petroleum coke;

[0046] S1.3. Copper powder with a particle size of 40 μm, alumina powder with a particle size of 20 μm, and polyvinyl alcohol are placed in a ball mill for grinding. Agate balls with a diameter of 8 mm are selected as grinding balls. The ball-to-material ratio is set to 8:1, the grinding speed is 300 rpm, and the grinding time is 6 h to form a copper-based alumina suspension; plasma-treated calcined petroleum coke is added to the copper-based alumina suspension, and the stirrer is stirred at a speed of 400 rpm for 2 h; preliminary solidification is carried out at room temperature, and then the mixture is placed in a high-temperature furnace and sintered under argon gas. The sintering temperature is increased to 1200°C at a rate of 6°C / min and the sintering time is 5 h; after sintering, the mixture is naturally cooled to room temperature to obtain a composite calcined petroleum coke;

[0047] 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 minutes 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 minutes to obtain a composite modified calcined petroleum coke in a fluid form.

[0048] Example 3: Fluid-state calcined petroleum coke for UHVDC grounding electrodes and its application, comprising the following steps:

[0049] S2.1. Weigh the following raw materials in parts by weight: 90 parts by weight of composite modified calcined petroleum coke and 5 parts by weight of phenolic resin;

[0050] S2.2. The composite modified calcined petroleum coke was placed in a stirrer and stirred at 200 rpm for 15 min. A phenolic resin was added at a rate of 2 parts by weight per minute, and the stirring speed was increased to 500 rpm. The stirring was continued for 20 min to obtain a mixture.

[0051] S2.3. Pour the mixed material into a mold, apply a pressure of 30 MPa to the mold, and maintain it for 10 minutes to form a grounding electrode body; place the grounding electrode body in a heating furnace, heat it to 180°C at a heating rate of 2°C / min and maintain it for 4 hours; then heat it to 1000°C at a heating rate of 3°C / min and maintain it for 6 hours; after sintering, naturally cool it to room temperature to obtain a UHVDC grounding electrode.

[0052] The preparation method of composite modified calcined petroleum coke is as follows:

[0053] S1.1. Weigh the following raw materials in parts 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;

[0054] S1.2. Calcined petroleum coke having a particle size of 80 mesh was washed with anhydrous ethanol to remove surface impurities; after washing, the calcined petroleum coke was placed in an oven at 80°C for 4 hours; the dried calcined petroleum coke was placed in a plasma reaction chamber, nitrogen gas was introduced at a volume flow rate of 42 sccm, the plasma generator was turned on, the power was set to 200 W, the pressure was set to 3 Pa, and the treatment time was 20 minutes; after the treatment, the calcined petroleum coke was naturally cooled to room temperature in argon gas to obtain plasma-treated calcined petroleum coke;

[0055] S1.3. Copper powder with a particle size of 40 μm, alumina powder with a particle size of 20 μm, and polyvinyl alcohol are placed in a ball mill for grinding. Agate balls with a diameter of 8 mm are selected as grinding balls. The ball-to-material ratio is set to 8:1, the grinding speed is 300 rpm, and the grinding time is 6 h to form a copper-based alumina suspension; plasma-treated calcined petroleum coke is added to the copper-based alumina suspension, and the stirrer is stirred at a speed of 400 rpm for 2 h; preliminary solidification is carried out at room temperature, and then the mixture is placed in a high-temperature furnace and sintered under argon gas. The sintering temperature is increased to 1200°C at a rate of 6°C / min and the sintering time is 5 h; after sintering, the mixture is naturally cooled to room temperature to obtain a composite calcined petroleum coke;

[0056] 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 minutes 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 minutes to obtain a composite modified calcined petroleum coke in a fluid form.

[0057] Example 4: Fluid-state calcined petroleum coke for UHVDC grounding electrodes and its application, comprising the following steps:

[0058] S2.1. Weigh the following raw materials in parts by weight: 85 parts by weight of composite modified calcined petroleum coke and 8 parts by weight of phenolic resin;

[0059] S2.2. The composite modified calcined petroleum coke was placed in a stirrer and stirred at 200 rpm for 15 min. A phenolic resin was added at a rate of 2 parts by weight per minute, and the stirring speed was increased to 500 rpm. The stirring was continued for 20 min to obtain a mixture.

[0060] S2.3. Pour the mixed material into a mold, apply a pressure of 30 MPa to the mold, and maintain it for 10 minutes to form a grounding electrode body; place the grounding electrode body in a heating furnace, heat it to 180°C at a heating rate of 2°C / min and maintain it for 4 hours; then heat it to 1000°C at a heating rate of 3°C / min and maintain it for 6 hours; after sintering, naturally cool it to room temperature to obtain a UHVDC grounding electrode.

[0061] The preparation method of composite modified calcined petroleum coke is as follows:

[0062] S1.1. Weigh the following raw materials in parts 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;

[0063] S1.2. Calcined petroleum coke having a particle size of 80 mesh was washed with anhydrous ethanol to remove surface impurities; after washing, the calcined petroleum coke was placed in an oven at 80°C for 4 hours; the dried calcined petroleum coke was placed in a plasma reaction chamber, nitrogen gas was introduced at a volume flow rate of 25 sccm, and the plasma generator was turned on with a power setting of 200 W and a pressure of 3 Pa for a treatment time of 20 minutes; after the treatment, the calcined petroleum coke was naturally cooled to room temperature in argon to obtain plasma-treated calcined petroleum coke;

[0064] S1.3. Copper powder with a particle size of 40 μm, alumina powder with a particle size of 20 μm, and polyvinyl alcohol are placed in a ball mill for grinding. Agate balls with a diameter of 8 mm are selected as grinding balls. The ball-to-material ratio is set to 8:1, the grinding speed is 300 rpm, and the grinding time is 6 h to form a copper-based alumina suspension; plasma-treated calcined petroleum coke is added to the copper-based alumina suspension, and the stirrer is stirred at a speed of 400 rpm for 2 h; preliminary solidification is carried out at room temperature, and then the mixture is placed in a high-temperature furnace and sintered under argon gas. The sintering temperature is increased to 1200°C at a rate of 6°C / min and the sintering time is 5 h; after sintering, the mixture is naturally cooled to room temperature to obtain a composite calcined petroleum coke;

[0065] 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 minutes 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 minutes to obtain a composite modified calcined petroleum coke in a fluid form.

[0066] Example 5: Fluid-state calcined petroleum coke for UHVDC grounding electrodes and its application, comprising the following steps:

[0067] S2.1. Weigh the following raw materials in parts by weight: 85 parts by weight of composite modified calcined petroleum coke and 8 parts by weight of phenolic resin;

[0068] S2.2. The composite modified calcined petroleum coke was placed in a stirrer and stirred at 200 rpm for 15 min. A phenolic resin was added at a rate of 2 parts by weight per minute, and the stirring speed was increased to 500 rpm. The stirring was continued for 20 min to obtain a mixture.

[0069] S2.3. Pour the mixed material into a mold, apply a pressure of 30 MPa to the mold, and maintain it for 10 minutes to form a grounding electrode body; place the grounding electrode body in a heating furnace, heat it to 180°C at a heating rate of 2°C / min and maintain it for 4 hours; then heat it to 1000°C at a heating rate of 3°C / min and maintain it for 6 hours; after sintering, naturally cool it to room temperature to obtain a UHVDC grounding electrode.

[0070] The preparation method of composite modified calcined petroleum coke is as follows:

[0071] S1.1. Weigh the following raw materials in parts 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;

[0072] S1.2. Calcined petroleum coke having a particle size of 80 mesh was washed with anhydrous ethanol to remove surface impurities; after washing, the calcined petroleum coke was placed in an oven at 80°C for 4 hours; the dried calcined petroleum coke was placed in a plasma reaction chamber, nitrogen gas was introduced at a volume flow rate of 34 sccm, and the plasma generator was turned on with a power setting of 200 W and a pressure of 3 Pa for a treatment time of 20 minutes; after the treatment, the calcined petroleum coke was naturally cooled to room temperature in argon to obtain plasma-treated calcined petroleum coke;

[0073] S1.3. Copper powder with a particle size of 40 μm, alumina powder with a particle size of 20 μm, and polyvinyl alcohol are placed in a ball mill for grinding. Agate balls with a diameter of 8 mm are selected as grinding balls. The ball-to-material ratio is set to 8:1, the grinding speed is 300 rpm, and the grinding time is 6 h to form a copper-based alumina suspension; plasma-treated calcined petroleum coke is added to the copper-based alumina suspension, and the stirrer is stirred at a speed of 400 rpm for 2 h; preliminary solidification is carried out at room temperature, and then the mixture is placed in a high-temperature furnace and sintered under argon gas. The sintering temperature is increased to 1200°C at a rate of 6°C / min and the sintering time is 5 h; after sintering, the mixture is naturally cooled to room temperature to obtain a composite calcined petroleum coke;

[0074] 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 minutes 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 minutes to obtain a composite modified calcined petroleum coke in a fluid form.

[0075] Example 6: Fluid-state calcined petroleum coke for UHVDC grounding electrodes and its application, comprising the following steps:

[0076] S2.1. Weigh the following raw materials in parts by weight: 85 parts by weight of composite modified calcined petroleum coke and 8 parts by weight of phenolic resin;

[0077] S2.2. The composite modified calcined petroleum coke was placed in a stirrer and stirred at 200 rpm for 15 min. A phenolic resin was added at a rate of 2 parts by weight per minute, and the stirring speed was increased to 500 rpm. The stirring was continued for 20 min to obtain a mixture.

[0078] S2.3. Pour the mixed material into a mold, apply a pressure of 30 MPa to the mold, and maintain it for 10 minutes to form a grounding electrode body; place the grounding electrode body in a heating furnace, heat it to 180°C at a heating rate of 2°C / min and maintain it for 4 hours; then heat it to 1000°C at a heating rate of 3°C / min and maintain it for 6 hours; after sintering, naturally cool it to room temperature to obtain a UHVDC grounding electrode.

[0079] The preparation method of composite modified calcined petroleum coke is as follows:

[0080] S1.1. Weigh the following raw materials in parts 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;

[0081] S1.2. Calcined petroleum coke having a particle size of 80 mesh was washed with anhydrous ethanol to remove surface impurities; after washing, the calcined petroleum coke was placed in an oven at 80°C for 4 hours; the dried calcined petroleum coke was placed in a plasma reaction chamber, nitrogen gas was introduced at a volume flow rate of 42 sccm, the plasma generator was turned on, the power was set to 200 W, the pressure was set to 3 Pa, and the treatment time was 20 minutes; after the treatment, the calcined petroleum coke was naturally cooled to room temperature in argon gas to obtain plasma-treated calcined petroleum coke;

[0082] S1.3. Copper powder with a particle size of 40 μm, alumina powder with a particle size of 20 μm, and polyvinyl alcohol are placed in a ball mill for grinding. Agate balls with a diameter of 8 mm are selected as grinding balls. The ball-to-material ratio is set to 8:1, the grinding speed is 300 rpm, and the grinding time is 6 h to form a copper-based alumina suspension; plasma-treated calcined petroleum coke is added to the copper-based alumina suspension, and the stirrer is stirred at a speed of 400 rpm for 2 h; preliminary solidification is carried out at room temperature, and then the mixture is placed in a high-temperature furnace and sintered under argon gas. The sintering temperature is increased to 1200°C at a rate of 6°C / min and the sintering time is 5 h; after sintering, the mixture is naturally cooled to room temperature to obtain a composite calcined petroleum coke;

[0083] 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 minutes 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 minutes to obtain a composite modified calcined petroleum coke in a fluid form.

[0084] Example 7: Fluid-state calcined petroleum coke for UHVDC grounding electrodes and its application, comprising the following steps:

[0085] S2.1. Weigh the following raw materials in parts by weight: 85 parts by weight of composite modified calcined petroleum coke and 8 parts by weight of phenolic resin;

[0086] S2.2. The composite modified calcined petroleum coke was placed in a stirrer and stirred at 200 rpm for 15 min. A phenolic resin was added at a rate of 2 parts by weight per minute, and the stirring speed was increased to 500 rpm. The stirring was continued for 20 min to obtain a mixture.

[0087] S2.3. Pour the mixed material into a mold, apply a pressure of 30 MPa to the mold, and maintain it for 10 minutes to form a grounding electrode body; place the grounding electrode body in a heating furnace, heat it to 180°C at a heating rate of 2°C / min and maintain it for 4 hours; then heat it to 1000°C at a heating rate of 3°C / min and maintain it for 6 hours; after sintering, naturally cool it to room temperature to obtain a UHVDC grounding electrode.

[0088] The preparation method of composite modified calcined petroleum coke is as follows:

[0089] S1.1. Weigh the following raw materials in parts 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;

[0090] S1.2. Calcined petroleum coke having a particle size of 80 mesh was washed with anhydrous ethanol to remove surface impurities; after washing, the calcined petroleum coke was placed in an oven at 80°C for 4 hours; the dried calcined petroleum coke was placed in a plasma reaction chamber, nitrogen gas was introduced at a volume flow rate of 50 sccm, and the plasma generator was turned on with a power setting of 200 W and a pressure of 3 Pa for a treatment time of 20 minutes; after the treatment, the calcined petroleum coke was naturally cooled to room temperature in argon to obtain plasma-treated calcined petroleum coke;

[0091] S1.3. Copper powder with a particle size of 40 μm, alumina powder with a particle size of 20 μm, and polyvinyl alcohol are placed in a ball mill for grinding. Agate balls with a diameter of 8 mm are selected as grinding balls. The ball-to-material ratio is set to 8:1, the grinding speed is 300 rpm, and the grinding time is 6 h to form a copper-based alumina suspension; plasma-treated calcined petroleum coke is added to the copper-based alumina suspension, and the stirrer is stirred at a speed of 400 rpm for 2 h; preliminary solidification is carried out at room temperature, and then the mixture is placed in a high-temperature furnace and sintered under argon gas. The sintering temperature is increased to 1200°C at a rate of 6°C / min and the sintering time is 5 h; after sintering, the mixture is naturally cooled to room temperature to obtain a composite calcined petroleum coke;

[0092] 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 minutes 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 minutes to obtain a composite modified calcined petroleum coke in a fluid form.

[0093] Comparative Example 1: The method of Example 6 was adopted, but the composite modified calcined petroleum coke was not used, and the calcined petroleum coke was directly used to prepare the UHVDC grounding electrode.

[0094] Comparative Example 2: The method of Example 6 was adopted to remove the copper powder in the preparation method of the composite modified calcined petroleum coke.

[0095] Comparative Example 3: The method of Example 6 was adopted to remove the alumina powder in the preparation method of the composite modified calcined petroleum coke.

[0096] The present invention prepares a UHVDC grounding electrode by composite modified calcined petroleum coke, wherein the performance index inspection items and inspection standards of the UHVDC grounding electrode are as follows:

[0097] According to GB / T 3048.2-2007 "Test methods for electrical properties of wires and cables - Part 2: Resistivity test for metallic materials", connect the two ends of the sample to the two terminals of a double-arm bridge using the four-wire method. Without connecting the sample, adjust the bridge to a balanced state to ensure that the initial reading is zero. After connecting the sample, adjust the bridge until it reaches balance again and read the resistance value. Repeat the measurement for the same sample at least three times, and take the average value as the final result. The resistivity should meet the design requirements, and a low resistivity is usually required to ensure good conductivity.

[0098] The ammeter-voltmeter method is used for measurement. The distance between the remote grounding point and the DC grounding electrode must be at least 10 times the distance between the farthest two ends of the DC grounding electrode body, and there must be no less than 3 measuring points. The grounding resistance is calculated using the formula. Low grounding resistance can effectively reduce the voltage drop caused by the fault current passing through the grounding device, thereby reducing the risk of electric shock.

[0099] The UHVDC grounding electrodes prepared in Examples 1-7 and Comparative Examples 1-3 were tested using the above standards, and the obtained data are shown in Table 1:

[0100] Table 1 Performance data of UHVDC grounding electrodes of Examples 1-7 and Comparative Examples 1-3

[0101]

[0102] By comparing Examples 1-3, it can be seen that, with other components remaining unchanged, only when the proportion of composite modified calcined petroleum coke gradually increases, the resistivity and grounding resistance of the UHVDC grounding electrode gradually decrease. This shows that as the proportion of composite modified calcined petroleum coke increases, a better conductive path is formed in the grounding electrode material. After the calcined petroleum coke is modified, the internal structure changes, for example, the degree of graphitization is improved, electron conduction is easier, thereby reducing the resistivity of the material. In addition, the synergistic conductive effect between the composite modified calcined petroleum coke and other added components (such as conductive components such as copper-based alumina composite materials) increases with the increase of their proportion. This material can better connect with other conductive components, reduce the resistance bottleneck in the conductive path, further optimize the overall conductive network, and effectively reduce 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) increases with the increase of their proportion. The modified groups on the surface of the calcined petroleum coke form stronger chemical bonds with the binder molecules, and the conductive carbon black generated by its pyrolysis fills the pores, further reducing the grounding resistance.

[0103] Furthermore, Examples 4-7 show that when the nitrogen volume flow rate to calcined petroleum coke mass ratio in the composite modified calcined petroleum coke gradually increases, the resistivity and grounding resistance of the UHVDC grounding electrode gradually decrease. However, when the nitrogen volume flow rate to calcined petroleum coke mass ratio reaches a certain value, the resistivity and grounding resistance of the UHVDC grounding electrode gradually increase. Therefore, it can be seen that as the nitrogen volume flow rate mass ratio increases, the resistivity and grounding resistance of the UHVDC grounding electrode are improved, but an excessive increase will increase the resistivity and grounding resistance of the UHVDC grounding electrode.

[0104] Specifically, the nitrogen atoms in nitrogen combine with the active sites on the surface of coke to introduce nitrogen-containing functional groups. These functional groups will change the electronic structure of the coke and increase the degree of electron delocalization, thereby improving the conductivity of the material, reducing resistivity, and ultimately leading to a reduction in ground resistance; a higher nitrogen volume flow rate helps to distribute the calcined petroleum coke more evenly during the formation process, reduce agglomeration, and enable the conductive components inside the material to form a better conductive network, which is beneficial to reducing resistance.

[0105] Comparing Example 6 with Comparative Example 1, it can be seen that when calcined petroleum coke is used directly without using composite modified calcined petroleum coke, the resistivity and grounding resistance of the UHVDC grounding electrode are significantly improved.

[0106] Taking Example 6 as the optimal example and combining it with Comparative Example 2, it can be seen that in the preparation method of composite modified calcined petroleum coke, when the copper powder is removed, the resistivity and grounding resistance of the UHVDC grounding electrode are significantly improved;

[0107] 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 small amounts of conductive components to conduct current, thereby increasing the resistivity. In the composite modified material, 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 does not exist, the resistance of these contact points increases, resulting in an increase in the resistivity and grounding resistance of the entire grounding electrode material.

[0108] Example 6 is the best example, and in combination with Comparative Example 3, it can be seen that in the preparation method of composite modified calcined petroleum coke, when the alumina powder is removed, the resistivity and grounding resistance of the UHVDC grounding electrode are significantly improved;

[0109] Alumina powder fills the gaps between calcined petroleum coke particles, making the contact between the particles closer, which is beneficial to the conduction of electrons between the particles. When the alumina powder is removed, the gaps between the particles increase, and the electron transmission path becomes discontinuous, resulting in an increase in resistivity and a significant increase in grounding resistance. In addition, in the composite modified material, there is a synergistic conductive effect between alumina, calcined petroleum coke and copper powder, which can promote the transfer of electrons between different conductive phases and improve the conductive properties by adjusting the electronic state of the interface. Once the alumina powder is removed, this synergistic conductive mechanism is destroyed, the overall conductive properties of the material decrease, and the resistivity and grounding resistance increase.

[0110] 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 to the above embodiments. The above embodiments and descriptions are merely preferred examples of the present invention and are not intended to limit the present invention. Various changes and improvements may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and improvements fall within the scope of the present invention. The scope of protection claimed in the present invention is defined by the appended claims and their equivalents.

Claims

1. Fluid-state calcined petroleum coke for UHVDC grounding electrodes, characterized in that: The method comprises 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 subjecting the calcined petroleum coke to plasma surface modification, then mixing it with a copper-based alumina composite material, and finally mixing it with titanium dioxide; The preparation method of the composite modified calcined petroleum coke is as follows: S1.

1. Weigh the following raw materials in parts 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 anhydrous ethanol to remove surface impurities; After cleaning, the calcined petroleum coke is placed in an oven at 60-100°C for 2-4 hours; the calcined petroleum coke after drying is subjected to plasma treatment; after the treatment is completed, the calcined petroleum coke is naturally cooled to room temperature in argon gas to obtain plasma-treated calcined petroleum coke; S1.

3. Grind copper powder, alumina powder, and polyvinyl alcohol in a ball mill to form a copper-based alumina suspension; add plasma-treated calcined petroleum coke to the copper-based alumina suspension while stirring at 300-500 rpm for 1-2 hours; perform preliminary curing at room temperature, then place in a high-temperature furnace and sinter under argon, raising the sintering temperature to 800-1200°C at a rate of 5-10°C / min for 1-5 hours; after sintering, naturally cool to room temperature to obtain a composite calcined petroleum coke; S1.

4. Add titanium dioxide nanoparticles to acetone, then add sodium polyacrylate, and ultrasonically disperse the particles at a power of 200-300 W for 40-60 min to uniformly disperse the particles in the acetone solution to obtain a titanium dioxide suspension. The composite calcined petroleum coke is ground into powder, added into a titanium dioxide suspension, stirred at a speed of 400-500 rpm, and simultaneously subjected to ultrasonic treatment to obtain a fluid-shaped composite modified calcined petroleum coke.

2. The fluid-form calcined petroleum coke for UHVDC grounding electrode according to claim 1, characterized in that: In said S1.2, the plasma treatment is to place the dried calcined petroleum coke into a plasma reaction chamber, introduce nitrogen, turn on the plasma generator, set the power to 100-300W, the pressure to 1-5Pa, and the treatment time to 10-20min.

3. The fluid-form calcined petroleum coke for UHVDC grounding electrode according to claim 2, characterized in that: The volume flow rate of the nitrogen gas introduced is 20-50 sccm.

4. The fluid-form calcined petroleum coke for UHVDC grounding electrode according to claim 1, characterized in that: In the above S1.3, the particle size of the copper powder is 20-50 μm, and the particle size of the aluminum oxide powder is 10-30 μm.

5. The fluid-form calcined petroleum coke for UHVDC grounding electrode according to claim 1, characterized in that: In the S1.3, agate balls with a diameter of 5-10 mm are selected as grinding balls for the grinding process, 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.

6. The fluid-form calcined petroleum coke for UHVDC grounding electrode according to claim 1, characterized in that: In the above-mentioned S1.4, the particle size of the titanium dioxide nanoparticles is 30-50 nm.

7. The fluid-form calcined petroleum coke for UHVDC grounding electrode according to claim 1, characterized in that: In the above-mentioned S1.4, the power of ultrasonic treatment is 100-200 W, and the ultrasonic treatment time is 30-40 min.

8. A use of the fluid-form calcined petroleum coke for a UHVDC grounding electrode according to any one of claims 1 to 7 in a UHVDC grounding electrode, comprising the preparation of a UHVDC grounding electrode, characterized in that: The preparation method of the UHVDC grounding electrode is as follows: S2.

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

2. Place the composite modified calcined petroleum coke in a stirrer and stir at 100-200 rpm for 10-15 min. Slowly add the phenolic resin and increase the stirring speed to 300-500 rpm. Continue stirring for 10-20 min to obtain a mixture. S2.

3. Pour the mixed material into a mold, apply a pressure of 10-50 MPa to the mold, and maintain it for 5-10 minutes to form a grounding electrode body; place the grounding electrode body in a heating furnace, heat it to 150-200°C at a heating rate of 1-2°C / min and maintain it for 2-4 hours; heat it to 800-1200°C at a heating rate of 2-3°C / min and maintain it for 3-6 hours; after sintering, cool it naturally to room temperature to obtain a UHVDC grounding electrode.

9. The use of the fluid-form calcined petroleum coke for UHVDC grounding electrodes according to claim 8 is characterized in that: In the above S2.2, the phenolic resin is slowly added at a speed of 1-2 parts by weight per minute.

Images