A low-cost, high-density graphitized carbon block and its preparation process

Abstract

This invention discloses a low-cost, high-density graphitized carbon block and its preparation process, which is prepared from the following raw materials: sponge coke with a particle size of 6-9 mm; sponge coke with a particle size of <0.5 mm; shot coke with a particle size of 0.5-6 mm; shot coke with a particle size of <0.5 mm; and coal tar pitch. The shot coke is calcined at 1300℃-1500℃ for 1-5 minutes and then at 1900℃-2200℃ for 1-5 minutes before being pulverized. This invention extensively utilizes shot coke, which is not used in the traditional production of graphitized cathode carbon blocks, thus solving the bottleneck in shot coke usage and reducing production costs. It employs an optimal particle size ratio of sponge coke and shot coke, as well as a mixing and molding process; combined with a unique calcination temperature rise curve, it achieves excellent strength, thermal conductivity, resistivity, sodium penetration expansion rate, and yield; making it highly suitable as a cathode material for electrolytic cells and fully meeting the needs of low-cost mass production in industrial applications.

Description

Technical Field

[0001] This invention relates to the field of graphite preparation, and more particularly to the preparation of graphitized cathode carbon blocks for aluminum electrolysis cells, specifically to a low-cost, high-density graphitized carbon block and its preparation process. Background Technology

[0002] Graphite cathode carbon blocks are mainly used in aluminum electrolysis cells as the cathode material. In the aluminum electrolysis industry, the electrolysis cell is a crucial piece of equipment for aluminum production, and the graphite cathode carbon block is one of its key components. The graphite cathode carbon block must possess good electrical conductivity to effectively transfer current and ensure the normal operation of the electrolysis cell. It must also have good chemical stability to resist the high temperatures, corrosion, and oxidation within the electrolysis cell, ensuring long-term stable operation. Furthermore, it must possess sufficient mechanical strength and wear resistance to withstand the impact and agitation of liquid aluminum in the electrolysis cell, maintaining a stable shape and structure over the long term. Petroleum coke, in contrast, can be classified into four types: needle coke, sponge coke, pellet coke, and powder coke.

[0003] Highly conductive graphitized carbon blocks are often produced using needle coke. Needle coke produces graphitized cathode carbon blocks with a higher degree of graphitization than ordinary calcined petroleum coke, thereby increasing the resistivity of the cathode block. The lowest resistivity of graphitized cathode carbon blocks produced using needle coke can reach 8 μΩ·m. However, the cost of graphitized cathode carbon blocks produced using needle coke is 4,000 yuan / ton higher than that produced using ordinary calcined petroleum coke, and the compressive strength decreases as the degree of graphitization increases.

[0004] Spherical coke, also known as pellet coke, is relatively hard, dense, and non-porous, existing as spherical molten masses. Its smooth exterior and inconsistent internal structure, coupled with a lack of surface pores, make it difficult for the binder to penetrate the coke during mixing with coal tar pitch, resulting in weak adhesion and internal defects. Furthermore, its high coefficient of thermal expansion and high sulfur content make it prone to thermal shock cracking during anode calcination. Therefore, petroleum coke used in graphitized electrode carbon blocks generally must be free of spherical coke. However, due to its low price, mastering the application technology of spherical coke in high-density, high-conductivity graphitized carbon blocks is of great significance for reducing production costs and enhancing market competitiveness for carbon enterprises.

[0005] Chinese patent application CN200910235983.6 discloses a carbon anode product obtained by calcining petroleum coke containing pellet coke at a calcination temperature of 1200℃. The product has a bulk density of 1.55 g / cm3, a compressive strength of 36.3 MPa, and a resistivity of 61.5 μΩ·m; however, these specifications clearly do not meet the requirements for cathode materials in electrolytic cells.

[0006] Chinese patent application CN202211128357.9 discloses a method for producing prebaked anodes using pellet coke as the main material, with the addition of anthracite and graphite. The method involves screening pellet coke fine powder with a particle size of less than 1 mm, mixing and kneading, shaping, calcining and then crushing into secondary material, and then starting the production of carbon blocks. This method has high requirements for raw materials, a complex process, and high costs; moreover, the specific parameters are unknown. Summary of the Invention

[0007] The purpose of this invention is to provide a low-cost, high-density graphitized carbon block and its preparation process, achieving high density, wear resistance, low resistivity, and low sodium permeation expansion rate while reducing production costs, making it suitable for industrial production. The technical solution adopted in this invention is as follows:

[0008] Low-cost, high-density graphitized carbon blocks are prepared from the following raw materials in parts by weight:

[0009] 30-34 parts sponge coke;

[0010] 63-72 parts of bullet char;

[0011] 18–22 parts coal tar pitch;

[0012] Before being pulverized, the pellets are calcined at 1300℃~1500℃ for 1~5 minutes and at 1900℃~2200℃ for 1~5 minutes.

[0013] As an optimization, low-cost, high-density graphitized carbon blocks are prepared from the following raw materials in parts by weight:

[0014] 7-9 parts of sponge coke with a particle size of 6-9 mm;

[0015] 23-25 ​​parts of sponge coke with a particle size <0.5mm;

[0016] 50–57 parts of shot coke with a particle size of 0.5–6 mm;

[0017] 13-15 parts of shot coke with a particle size <0.5mm;

[0018] 18–22 parts coal tar pitch;

[0019] The pretreatment of the pellet coke before pulverization is calcination at 1300℃~1500℃ for 1~5 minutes, and calcination at 1900℃~2200℃ for 1~5 minutes.

[0020] As an optimization, low-cost, high-density graphitized carbon blocks are prepared from the following raw materials in parts by weight:

[0021] 7-9 parts of sponge coke with a particle size of 6-9 mm;

[0022] 23-25 ​​parts of sponge coke with a particle size <0.5mm;

[0023] 7-9 parts of shot coke with a particle size of 4-6 mm;

[0024] 36-39 parts of shot coke with a particle size of 1-4 mm;

[0025] 7-9 parts of shot coke with a particle size of 0.5-1mm;

[0026] 13-15 parts of shot coke with a particle size <0.5mm;

[0027] 18-22 parts of coal tar pitch with a softening point of 105℃-115℃.

[0028] As an optimization, the low-cost, high-density graphitized carbon block is pretreated by calcining the pellet coke at 1300℃~1500℃ in a natural gas calcining furnace for 1~5 minutes, and then calcining it in a DC electric heating calcining furnace at 1900℃~2200℃ for 1~5 minutes.

[0029] As an optimization, the preparation process of low-cost, high-density graphitized carbon blocks includes the following steps:

[0030] The ingredients are mixed and kneaded; then vibrated in a vibration molding device and cooled in a water tank; finally, they are placed in a roasting furnace for roasting and graphitization in a graphitization furnace.

[0031] As an optimization, the preparation process of low-cost, high-density graphitized carbon blocks includes vibration molding, which involves vibrating for 130 to 170 seconds in a vibration molding device at a temperature of 165°C to 189°C and a vibration frequency of 16 to 40 Hz.

[0032] As an optimization, the preparation process of low-cost, high-density graphitized carbon blocks includes vibration molding, which involves vibrating for 90 seconds in a vibration molding device at a temperature of 178°C and a vibration frequency of 16–22 Hz; and then vibrating for 70 seconds in the vibration molding device at a temperature of 182°C and a vibration frequency of 25–40 Hz.

[0033] As an optimization, the preparation process of low-cost, high-density graphitized carbon blocks uses a calcination furnace with a calcination temperature of 1000℃~1100℃.

[0034] As an optimization, the preparation process of low-cost, high-density graphitized carbon blocks adopts a natural gas roasting furnace and roasts for 768 hours under air-isolated conditions.

[0035] Phase 1: 96 hours, temperature rises from 150℃ to 230℃;

[0036] Second stage: 48 hours, the temperature rises from 230℃ to 276℃;

[0037] The third stage: 48 hours, the temperature rises from 276℃ to 324℃;

[0038] Phase 4: 96 hours, the temperature rises from 324℃ to 431℃;

[0039] Fifth stage: 192 hours, the temperature rose from 431℃ to 606℃;

[0040] Phase 6: 252 hours, the temperature rises from 606℃ to 1078℃;

[0041] Phase 7: 36 hours, with the temperature maintained at 1078℃.

[0042] As an optimization, the preparation process of low-cost, high-density graphitized carbon blocks is described, wherein the heating curves of the first, second, third, fourth, and fifth stages are linear; and the heating curve of the sixth stage is: Y = 1169.365 - 3.17 * X + 0.00416 * X * X.

[0043] Y represents temperature; X represents time.

[0044] As an optimization, the low-cost, high-density graphitized carbon blocks are cooled from 1078℃ to 650℃ after the roasting process in the roasting furnace, with the cooling rate controlled at 4.2~4.8℃ / h.

[0045] Compared with the prior art, the beneficial effects of the present invention are:

[0046] This invention relates to low-cost, high-density graphitized carbon blocks and their preparation process. It makes extensive use of shot coke, which is not used in the production of traditional graphitized cathode carbon blocks, thus solving the bottleneck of shot coke usage and reducing production costs.

[0047] This invention performs two short-time calcination treatments at different temperatures on the bullet coke, which completes the pretreatment of impurities and morphology within the bullet coke. During the roasting process, it can form a reinforced interfacial carbon mesh layer with the coked pitch, resulting in tighter adhesion, reduced internal defects, and the low-cost short-time calcination treatment has no significant impact on production costs.

[0048] This invention employs the optimal particle size ratio of sponge coke and pellet coke, as well as a mixed molding process; combined with a unique roasting temperature curve, it further reduces the occurrence of cracks during roasting; the final graphitized carbon block has a dense internal structure, achieving excellent strength, thermal conductivity, and resistivity.

[0049] The addition of shot coke in this invention further improves the wear resistance of the graphitized carbon block and achieves a good sodium penetration expansion rate. The low-cost, high-density graphitized carbon block of this invention is very suitable for use as a cathode material in electrolytic cells and can fully meet the needs of low-cost mass production in industrial applications. Attached Figure Description

[0050] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, illustrate exemplary embodiments of the invention and, together with their description, serve to explain the invention and do not constitute an undue limitation thereof. In the drawings:

[0051] Figure 1 The above are the temperature rise curves for Embodiment 3 and Comparative Example 6 of the present invention. Detailed Implementation

[0052] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0053] Example 1: The following materials were selected by weight: 7 parts sponge coke with a particle size of 6-9 mm; 23 parts sponge coke with a particle size <0.5 mm; 7 parts shot coke with a particle size of 4-6 mm; 36 parts shot coke with a particle size of 1-4 mm; 7 parts shot coke with a particle size of 0.5-1 mm; 13 parts shot coke with a particle size <0.5 mm; and 18 parts coal tar pitch. After mixing the dry materials, tar pitch was added and kneaded. Then, the mixture was vibrated and shaped in a vibration molding device; then placed in a roasting furnace for roasting; and finally, it was graphitized in a graphitization furnace.

[0054] The pellets are fed into a natural gas calcining furnace at 1300℃~1500℃ for 1~5 minutes via a transmission device, then calcined in a DC electric heating calcining furnace at 1900℃~2200℃ for 1~5 minutes, and then crushed into the required particle size.

[0055] Among them, coal tar pitch with a softening point of 105℃~115℃, sulfur content ≤2%, ash content ≤0.3%, and sulfur content ≤0.3% is selected.

[0056] The vibration forming process requires vibration for 95 seconds at a temperature of 165℃ and a vibration frequency of 16–22Hz in a vibration forming device; then, vibration for 75 seconds at a temperature of 176℃ and a vibration frequency of 25–40Hz in the same device. The formed blank is then placed in a water tank to cool. The blank is 3000–3500mm long, 800–1000mm wide, and 1400–1600mm high.

[0057] Among them, the roasting furnace adopts a natural gas ring roasting furnace, with 7 to 9 furnace chambers in the heating state, the roasting temperature is 1000℃ to 1100℃, and the roasting is carried out for 768 hours under the condition of excluding air.

[0058] Phase 1: 96 hours, with the temperature linearly increasing from 145℃ to 225℃;

[0059] Second stage: 48 hours, the temperature linearly increases from 225℃ to 271℃;

[0060] The third stage: 48 hours, the temperature linearly increased from 271℃ to 319℃;

[0061] Fourth stage: 96 hours, the temperature linearly increases from 319℃ to 425℃;

[0062] Fifth stage: 192 hours, the temperature linearly increased from 425℃ to 601℃;

[0063] Phase 6: 252 hours, the temperature rises from 606℃ to 1073℃;

[0064] Phase 7: 36 hours, with the temperature maintained at 1073℃.

[0065] The sixth stage heating curve is: Y = 1164.365 - 3.17 * X + 0.00416 * X * X; Y is temperature; X is time, and the value of X ranges from 480 to 732.

[0066] After the roasting process, the temperature was reduced from 1073℃ to 650℃, with the cooling rate controlled at 4.2~4.8℃ / h.

[0067] Among them, the graphitization process is carried out in a graphitization furnace, which is a linear series graphitization furnace. The power supply curve when power is supplied is as follows: initial power 4000kW.

[0068] In the first stage, the power was linearly increased to 5100kW, taking 2 hours;

[0069] In the second stage, the power was linearly increased to 6400kW in 3.8 hours;

[0070] In the third stage, the power was linearly increased to 6900kW in 1.9 hours;

[0071] In the fourth stage, the power was linearly increased to 8000kW in 4.2 hours;

[0072] In the fifth stage, the power was increased to the maximum power of 16,000 kW, which took 3.0141 hours;

[0073] In the sixth stage, maintain the maximum power of 16,000 kW for 3.8 hours.

[0074] The power transmission curve for the fifth stage is: Y = 8000 - 156.2*X + 149.7*X*X + 259.7*X*X*X

[0075] Y represents the power transmitted; X represents the time, with a value ranging from 0 to 3.0141.

[0076] Example 2: The following materials were selected by weight: 9 parts sponge coke with a particle size of 6-9 mm; 25 parts sponge coke with a particle size <0.5 mm; 9 parts shot coke with a particle size of 4-6 mm; 39 parts shot coke with a particle size of 1-4 mm; 9 parts shot coke with a particle size of 0.5-1 mm; 15 parts shot coke with a particle size <0.5 mm; and 22 parts coal tar pitch. After mixing the dry materials, tar pitch was added and kneaded. Then, the mixture was vibrated and shaped in a vibration molding device. Finally, it was placed in a roasting furnace for roasting and then graphitized in a graphitization furnace.

[0077] The pellets are fed into a natural gas calcining furnace at 1300℃~1500℃ for 1~5 minutes via a transmission device, then calcined in a DC electric heating calcining furnace at 1900℃~2200℃ for 1~5 minutes, and then crushed into the required particle size.

[0078] Among them, coal tar pitch with a softening point of 105℃~115℃, sulfur content ≤2%, ash content ≤0.3%, and sulfur content ≤0.3% is selected.

[0079] The vibration forming process requires vibration for 70 seconds at a temperature of 183℃ and a vibration frequency of 16–22Hz in a vibration forming device; then, vibration for 60 seconds at a temperature of 189℃ and a vibration frequency of 25–40Hz in the same device. The formed blank is then placed in a water tank to cool. The blank is 3000–3500mm long, 800–1000mm wide, and 1400–1600mm high.

[0080] Among them, the roasting furnace adopts a natural gas ring roasting furnace, with 7 to 9 furnace chambers in the heating state, the roasting temperature is 1000℃ to 1100℃, and the roasting is carried out for 768 hours under the condition of excluding air.

[0081] Phase 1: 96 hours, with the temperature linearly increasing from 155℃ to 235℃;

[0082] Second stage: 48 hours, the temperature linearly increases from 235℃ to 281℃;

[0083] The third stage: 48 hours, the temperature linearly increased from 281℃ to 329℃;

[0084] Fourth stage: 96 hours, the temperature linearly increases from 329℃ to 436℃;

[0085] Fifth stage: 192 hours, the temperature linearly increased from 436℃ to 611℃;

[0086] Phase 6: 252 hours, the temperature rises from 611℃ to 1083℃;

[0087] Phase 7: 36 hours, with the temperature maintained at 1083℃.

[0088] The sixth stage heating curve is: Y = 1174.365 - 3.17 * X + 0.00416 * X * X; Y is temperature; X is time.

[0089] After the roasting process, the temperature was reduced from 1083℃ to 650℃, with the cooling rate controlled at 4.2~4.8℃ / h.

[0090] Among them, the graphitization process is carried out in a graphitization furnace, which is a linear series graphitization furnace. The power supply curve when power is supplied is as follows: initial power 4200kW.

[0091] In the first stage, the power was linearly increased to 5400kW in 2.5 hours;

[0092] In the second stage, the power was linearly increased to 6600kW in 4.2 hours;

[0093] In the third stage, the power was linearly increased to 7100kW in 2.2 hours;

[0094] In the fourth stage, the power was linearly increased to 8200kW in 4.7 hours;

[0095] In the fifth stage, the power was increased to the maximum power of 16,000 kW, which took 2.9883 hours;

[0096] In the sixth stage, maintain the maximum power of 16000kW for 4.2 hours.

[0097] The power transmission curve for the fifth stage is: Y = 8200 - 156.2*X + 149.7*X*X + 259.7*X*X*X

[0098] Y represents the power transmitted; X represents the time.

[0099] Example 3: The following materials were selected by weight: 8.4 parts sponge coke with a particle size of 6-9 mm; 24 parts sponge coke with a particle size <0.5 mm; 8.4 parts shot coke with a particle size of 4-6 mm; 36.5 parts shot coke with a particle size of 1-4 mm; 8.8 parts shot coke with a particle size of 0.5-1 mm; 14.2 parts shot coke with a particle size <0.5 mm (the purity of the above particle sizes is not less than 85%); and 19.5 parts coal tar pitch. The dry materials, including sponge coke and shot coke, were mixed, and then pitch was added for kneading. The mixture was then vibrated and shaped in a vibration molding device; then placed in a roasting furnace for roasting; and finally, it was graphitized in a graphitization furnace.

[0100] The pellet coke is fed into a high-temperature calcining furnace via a transmission device, calcined at 1300℃~1500℃ for 2~3 minutes, calcined at 1900℃~2200℃ for 2~3 minutes, and then crushed into the required particle size.

[0101] Among them, coal tar pitch with a softening point of 105℃~115℃, sulfur content ≤2%, ash content ≤0.3%, and sulfur content ≤0.3% is selected.

[0102] The vibration forming process requires vibration for 90 seconds at a temperature of 178℃ and a vibration frequency of 16–22Hz in a vibration forming device; then, vibration for 70 seconds at a temperature of 182℃ and a vibration frequency of 25–40Hz in the same device. The formed blank is then placed in a water tank to cool. The blank is 3000–3500mm long, 800–1000mm wide, and 1400–1600mm high.

[0103] The preheated billet to 150°C is placed in a calcining furnace for calcination. A natural gas ring calcining furnace is used, with 8 furnace chambers in the heating state. The calcination temperature is 1000°C to 1100°C, and the calcination lasts for 768 hours under air-isolated conditions.

[0104] Phase 1: 96 hours, temperature rises from 150℃ to 230℃;

[0105] Second stage: 48 hours, the temperature rises from 230℃ to 276℃;

[0106] The third stage: 48 hours, the temperature rises from 276℃ to 324℃;

[0107] Phase 4: 96 hours, the temperature rises from 324℃ to 431℃;

[0108] Fifth stage: 192 hours, the temperature rose from 431℃ to 606℃;

[0109] Phase 6: 252 hours, the temperature rises from 606℃ to 1078℃;

[0110] Phase 7: 36 hours, with the temperature maintained at 1078℃.

[0111] The heating curve for the sixth stage is: Y = 1169.365 - 3.17 * X + 0.00416 * X * X; Y is temperature; X is time.

[0112] After the roasting process, the temperature was reduced from 1078℃ to 650℃, with the cooling rate controlled at 4.2~4.8℃ / h.

[0113] Among them, the graphitization process is carried out in a graphitization furnace, which is a linear series graphitization furnace. The power supply curve when power is supplied is as follows: initial power 4154kW.

[0114] In the first stage, the power was linearly increased to 5332kW in 2.5 hours;

[0115] In the second stage, the power was linearly increased to 6473kW, taking 4 hours;

[0116] In the third stage, the power was linearly increased to 6994kW, taking 2 hours;

[0117] In the fourth stage, the power was linearly increased to 8110kW in 4.5 hours;

[0118] In the fifth stage, the power was increased to the maximum power of 16,000 kW, which took 3 hours;

[0119] In the sixth stage, maintain the maximum power of 16,000 kW for 4 hours.

[0120] The power transmission curve for the fifth stage is: Y = 8110 - 156.2*X + 149.7*X*X + 259.7*X*X*X

[0121] Y represents the power transmitted; X represents the time.

[0122] Example 4: The following materials were selected by weight: 8 parts of sponge coke with a particle size of 6-9 mm; 24 parts of sponge coke with a particle size <0.5 mm; 54 parts of shot coke with a particle size of 0.5-6 mm; 14 parts of shot coke with a particle size <0.5 mm; 20 parts of coal tar pitch (the purity of the above particle sizes is not less than 85%); and 19.5 parts of coal tar pitch. After mixing the dry materials, tar pitch was added and kneaded; then, the mixture was vibrated and shaped in a vibration molding device; then, it was placed in a roasting furnace for roasting; finally, it was graphitized in a graphitization furnace.

[0123] The pellet coke is fed into a high-temperature calcining kiln via a transmission device, calcined at 1300℃~1500℃ for 1~5 minutes, calcined at 1900℃~2200℃ for 1~5 minutes, and then crushed into the required particle size.

[0124] Among them, coal tar pitch with a softening point of 105℃~115℃, sulfur content ≤2%, ash content ≤0.3%, and sulfur content ≤0.3% is selected.

[0125] The vibration forming process requires vibration for 90 seconds at a temperature of 178℃ and a vibration frequency of 16–22Hz, and for 70 seconds at a temperature of 182℃ and a vibration frequency of 25–40Hz. The formed blank is then placed in a water tank to cool. The blank is 3000–3500mm long, 800–1000mm wide, and 1400–1600mm high.

[0126] The preheated billet to 150°C is placed in a calcining furnace for calcination. A natural gas ring calcining furnace is used, with 8 furnace chambers in the heating state. The calcination temperature is 1000°C to 1100°C, and the calcination lasts for 768 hours under air-isolated conditions.

[0127] Phase 1: 96 hours, temperature rises from 150℃ to 230℃;

[0128] Second stage: 48 hours, the temperature rises from 230℃ to 276℃;

[0129] The third stage: 48 hours, the temperature rises from 276℃ to 324℃;

[0130] Phase 4: 96 hours, the temperature rises from 324℃ to 431℃;

[0131] Fifth stage: 192 hours, the temperature rose from 431℃ to 606℃;

[0132] Phase 6: 252 hours, the temperature rises from 606℃ to 1078℃;

[0133] Phase 7: 36 hours, with the temperature maintained at 1078℃.

[0134] The heating curve for the sixth stage is: Y = 1169.365 - 3.17 * X + 0.00416 * X * X; Y is temperature; X is time.

[0135] After the roasting process, the temperature was reduced from 1078℃ to 650℃, with the cooling rate controlled at 4.2~4.8℃ / h.

[0136] Among them, the graphitization process is carried out in a graphitization furnace, which is a linear series graphitization furnace. The power supply curve when power is supplied is as follows: initial power 4154kW.

[0137] In the first stage, the power was linearly increased to 5332kW in 2.5 hours;

[0138] In the second stage, the power was linearly increased to 6473kW, taking 4 hours;

[0139] In the third stage, the power was linearly increased to 6994kW, taking 2 hours;

[0140] In the fourth stage, the power was linearly increased to 8110kW in 4.5 hours;

[0141] In the fifth stage, the power was increased to the maximum power of 16,000 kW, which took 3 hours;

[0142] In the sixth stage, maintain the maximum power of 16,000 kW for 4 hours.

[0143] The power transmission curve for the fifth stage is: Y = 8110 - 156.2*X + 149.7*X*X + 259.7*X*X*X

[0144] Y represents the power transmitted; X represents the time.

[0145] Comparative Example 1: The production formula and process of graphitized carbon blocks are the same as those of Example 3. The pellet coke used in Comparative Example 1 is fed into a high-temperature calcining kiln through a transmission device, calcined at 1300℃~1500℃ for 5~10 minutes, and then crushed into the required particle size.

[0146] Comparative Example 2: The production formula and process of graphitized carbon blocks are the same as those of Example 3. The pellet coke used in Comparative Example 2 is fed into a high-temperature calcining kiln through a transmission device, calcined at 1900℃~2200℃ for 5~10 minutes, and then crushed into the required particle size.

[0147] Comparative Example 3: The production formula and process of graphitized carbon blocks are the same as those of Example 4. The pellet coke used in Comparative Example 3 is fed into a high-temperature calcining kiln through a transmission device, calcined at 1300℃~1500℃ for 5~10 minutes, and then crushed into the required particle size.

[0148] Comparative Example 4: The production process of graphitized carbon blocks is the same as in Example 3. The formula for Comparative Example 4, selected by weight, is: 24.3 parts sponge coke; 78 parts shot coke; and 19.5 parts coal tar pitch. Specifically, 6.3 parts are sponge coke with a particle size of 6–9 mm; 18 parts are sponge coke with a particle size <0.5 mm; 9.65 parts are shot coke with a particle size of 4–6 mm; 42 parts are shot coke with a particle size of 1–4 mm; 10 parts are shot coke with a particle size of 0.5–1 mm; and 16.35 parts are shot coke with a particle size <0.5 mm (the purity of the above particle sizes is not less than 85%). The final product is coal tar pitch with a softening point of 105℃–115℃, sulfur content ≤2%, ash content ≤0.3%, and sulfur content ≤0.3%.

[0149] Comparative Example 5: The production process of graphitized carbon blocks is the same as in Example 3. The formula for Comparative Example 5 is as follows (by weight): 40.5 parts sponge coke; 59.8 parts shot coke; and 19.5 parts coal tar pitch. Specifically, 10.5 parts are sponge coke with a particle size of 6–9 mm; 30 parts are sponge coke with a particle size <0.5 mm; 7.4 parts are shot coke with a particle size of 4–6 mm; 32.15 parts are shot coke with a particle size of 1–4 mm; 7.75 parts are shot coke with a particle size of 0.5–1 mm; and 12.5 parts are shot coke with a particle size <0.5 mm (the purity of the above particle sizes is not less than 85%). The final product is coal tar pitch with a softening point of 105℃–115℃, sulfur content ≤2%, ash content ≤0.3%, and sulfur content ≤0.3%.

[0150] Comparative Example 6: The production formula and process of graphitized carbon blocks are the same as those of Example 3. The difference in Comparative Example 6 is that the roasting process in the roasting furnace adopts the original temperature curve of 768 hours of roasting.

[0151] Phase 1: 96 hours, with the temperature linearly increasing from 100℃ to 400℃;

[0152] Second stage: 48 hours, the temperature is linearly increased from 400℃ to 412℃;

[0153] The third stage: 48 hours, the temperature linearly increases from 412℃ to 612℃;

[0154] Fourth stage: 96 hours, the temperature linearly increases from 612℃ to 812℃;

[0155] Fifth stage: 192 hours, the temperature linearly increased from 812℃ to 1012℃;

[0156] Stage 6: 252 hours, the temperature linearly increases from 1012℃ to 1052℃;

[0157] Phase 7: 36 hours, with the temperature maintained at 1052℃.

[0158] Comparative Example 7: The production formula and process of graphitized carbon blocks are the same as those of Example 3. The difference in Comparative Example 7 is that the vibration molding process requires vibration for 90 seconds in a vibration molding device at a temperature of 158°C and a vibration frequency of 16-22Hz; and vibration for 70 seconds in a vibration molding device at a temperature of 162°C and a vibration frequency of 25-40Hz. Then the molded blank is placed in a water tank to cool down.

[0159] Comparative Example 8: The production formula and process of graphitized carbon blocks are the same as those of Example 3. The difference in Comparative Example 8 is that after the calcination process, the temperature is reduced from 1078℃ to 650℃, and the cooling rate is controlled at 30-40℃ / h.

[0160] The bulk density, resistivity, flexural strength, compressive strength, porosity, sodium permeation expansion rate, thermal conductivity, and crack failure rate of the final graphitized carbon blocks in Examples 1-4 and Comparative Examples 1-8 were measured. The results are shown in Table 1.

[0161]

[0162] As shown in Table 1, in Examples 1-4, the graphitized carbon blocks exhibited better performance in terms of bulk density, resistivity, flexural strength, compressive strength, porosity, sodium permeation expansion rate, thermal conductivity, and crack failure rate compared to Comparative Examples 1-8, fully meeting the requirements for use as cathode materials in electrolytic cells.

[0163] Comparative Examples 1 and 2 used the same formulation and process as Example 3, while Comparative Example 3 used the same formulation and process as Example 4. However, due to the different pellet coke calcination processes used in Comparative Examples 1 and 3, the final graphitized carbon block indicators of Comparative Examples 1 and 3 were significantly lower than those of Examples 3 and 4. Among them, Comparative Example 2 had a higher pellet coke calcination cost, but the final graphitized carbon block indicators were still significantly lower than those of the preferred Example 3. Through Examples 1 to 4 and Comparative Examples 1 to 3, it was found that small-scale adjustments to the formulation had a limited impact on the final graphitized carbon block indicators; however, different pellet coke calcination processes had a significant impact on the graphitized carbon block indicators; and longer calcination times and higher temperatures did not necessarily lead to better results.

[0164] Compared to Example 3, Comparative Example 4 increased the amount of shot coke, and Comparative Example 5 increased the amount of sponge coke; however, the final bulk density of the carbon blocks decreased, and the crack rate increased. In fact, excessively high or low shot coke content ratios can affect the mechanical strength, bulk density, conductivity, and crack rate of graphite electrodes, thereby affecting the service life of the electrodes.

[0165] Comparative Example 6 used the original temperature curve for 768 hours of roasting; compared with Example 3, the temperature curve of Comparative Example 6 could not be better controlled at the stage of semi-coke structure decomposition, large-scale generation of hydrogen and carbon monoxide, and gradual formation of coke by polycondensation reaction, resulting in a higher rate of crack failure and lower density.

[0166] Comparative Example 7 used different parameters in the forming stage of the vibration forming device. However, the parameter adjustment caused the coal tar pitch to coat and adhere to the coke pellets, which in turn adversely affected the various properties of the subsequent graphitized carbon blocks. Comparative Example 8 adopted a faster cooling rate after the roasting stage. Due to the faster cooling rate, for large-sized graphitized carbon block blanks, the surface and interior of the blanks did not shrink in a uniform way, generating internal stress and causing cracks.

Claims

1. A low-cost, high-density graphitized carbon block, characterized in that, It is prepared from the following parts by weight of raw materials: 7-9 parts of sponge coke with a particle size of 6-9 mm; 23-25 ​​parts of sponge coke with a particle size <0.5mm; 50–57 parts of shot coke with a particle size of 0.5–6 mm; 13-15 parts of shot coke with a particle size <0.5mm; 18–22 parts coal tar pitch; The pretreatment of the pellet coke before pulverization is calcination at 1300℃~1500℃ for 1~5 minutes, and calcination at 1900℃~2200℃ for 1~5 minutes; The preparation process of the low-cost, high-density graphitized carbon block includes the following steps: mixing ingredients and kneading; vibrating and molding in a vibration molding device and cooling in a water tank; roasting in a calcination furnace; and graphitizing in a graphitization furnace. The vibration molding process includes vibrating for 130 to 170 seconds in a vibration molding device at a temperature of 165℃ to 189℃ and a vibration frequency of 16 to 40Hz.

2. The low-cost, high-density graphitized carbon block according to claim 1, characterized in that, It is prepared from the following parts by weight of raw materials: 7-9 parts of sponge coke with a particle size of 6-9 mm; 23-25 ​​parts of sponge coke with a particle size <0.5mm; 7-9 parts of shot coke with a particle size of 4-6 mm; 36-39 parts of shot coke with a particle size of 1-4 mm; 7-9 parts of shot coke with a particle size of 0.5-1mm; 13-15 parts of shot coke with a particle size <0.5mm; 18-22 parts of coal tar pitch with a softening point of 105℃-115℃.

3. The low-cost, high-density graphitized carbon block according to claim 2, characterized in that, The pretreatment of the pellet coke before pulverization is to calcine it in a natural gas calcining furnace at 1300℃~1500℃ for 1~5 minutes, and then calcine it in a DC electric heating calcining furnace at 1900℃~2200℃ for 1~5 minutes.

4. A process for preparing low-cost, high-density graphitized carbon blocks according to any one of claims 1 to 3, characterized in that, The process includes the following steps: mixing ingredients and kneading; vibrating and molding in a vibration molding device and cooling in a water tank; roasting in a roasting furnace; and graphitizing in a graphitization furnace. The vibration molding process includes vibrating for 90 seconds in a vibration molding device at a temperature of 178°C and a vibration frequency of 16–22 Hz; and then vibrating for 70 seconds in the vibration molding device at a temperature of 182°C and a vibration frequency of 25–40 Hz.

5. The preparation process of low-cost, high-density graphitized carbon blocks according to claim 4, characterized in that, The roasting temperature in the roasting furnace is 1000℃~1100℃.

6. The preparation process of low-cost, high-density graphitized carbon blocks according to claim 5, characterized in that, A natural gas roasting furnace was used, and the roasting was carried out for 768 hours under air-isolated conditions. Phase 1: 96 hours, temperature rises from 150℃ to 230℃; Second stage: 48 hours, the temperature rises from 230℃ to 276℃; The third stage: 48 hours, the temperature rises from 276℃ to 324℃; Phase 4: 96 hours, the temperature rises from 324℃ to 431℃; Fifth stage: 192 hours, the temperature rose from 431℃ to 606℃; Phase 6: 252 hours, the temperature rises from 606℃ to 1078℃; Phase 7: 36 hours, with the temperature maintained at 1078℃.

7. The preparation process of low-cost, high-density graphitized carbon blocks according to claim 6, characterized in that, After the roasting in the roasting furnace is completed, the temperature is reduced from 1078℃ to 650℃, and the cooling rate is controlled at 4.2~4.8℃ / h.

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