Production process of prebaked anode carbon block

Abstract

The invention relates to the technical field of metallurgy, in particular to a production process of a prebaked anode carbon block, which comprises the following steps: pretreating raw materials, calcining petroleum coke, crushing and screening to obtain aggregate and powder, recovering electrolytic aluminum waste cathode carbon blocks, and roasting and regenerating to obtain regenerated materials and ingredients; 60-75 parts by weight of aggregate, 15-25 parts by weight of powder and 5-10 parts by weight of regenerated material are added into a blender mixer to be premixed for 10-20 minutes, a regenerated material deep purification process is established when petroleum coke and waste cathode carbon blocks are compounded by introducing a regenerated material synergistic treatment technology, the problem that metal impurities cannot be separated in a traditional process is effectively solved, and the production cost is reduced. The structure stability of the regenerated raw material in the prebaked anode formula is guaranteed, the conductivity of the anode is improved, meanwhile, the corrosion risk of an electrolytic bath caused by impurities is reduced, and the continuity of electrolytic aluminum production is further guaranteed.

Description

Technical Field

[0001] This invention relates to the field of metallurgical technology, specifically to the production process of prebaked anode carbon blocks. Background Technology

[0002] Metallurgy refers to the process and technology of extracting metals or metal compounds from minerals and processing them into metallic materials with certain properties using various processing methods.

[0003] As a core consumable component in the production of electrolytic aluminum, the physical and chemical properties of prebaked anode carbon blocks directly affect the current efficiency and energy consumption level of the electrolytic cell. This is a key aspect of anode production quality control. The traditional production process of prebaked anode carbon blocks involves multiple steps, including calcination, crushing, batching, kneading, molding, and baking. In actual production, optimizing the raw material formula, binder performance, and thermal control are the core elements to ensure anode quality.

[0004] Currently, due to the complex source of raw materials in the production of prebaked anode carbon blocks, conventional crushing processes cannot effectively separate iron impurities and electrolyte residues when using waste cathode carbon blocks from electrolytic aluminum for recycling. When the iron content in the recycled material exceeds the limit, it will lead to a decrease in the conductivity of the anode and accelerate the corrosion of the electrolytic cell.

[0005] Therefore, a production process for prebaked anode carbon blocks is proposed to solve the above problems. Summary of the Invention

[0006] The main objective of this invention is to provide a production process for prebaked anode carbon blocks to solve the problems mentioned in the background above.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a production process for prebaked anode carbon blocks, comprising the following steps: Step 1: Raw material pretreatment. After calcination, petroleum coke is crushed and screened to obtain aggregate and powder. At the same time, waste cathode carbon blocks from electrolytic aluminum are recycled and roasted to obtain recycled materials. Step 2: Ingredients: Add 60-75 parts by weight of aggregate, 15-25 parts by weight of powder and 5-10 parts by weight of recycled material into the mixer and premix for 10-20 minutes. Step 3: Mixing. Add 20-30 parts of composite binder to the premix and perform a gradient temperature mixing program in a vertical mixer. Step 4: Molding. After cooling the mixed material to 90-110℃, transfer it into the mold and use a double pressure curve vibration molding process. Step 5: Firing. Place the green blanks in a ring-shaped firing furnace and fire them for 48-72 hours according to the seven-temperature zone control curve. Step Six: Testing and Grading. The physicochemical properties of the roasted charcoal blocks are tested and then graded and packaged. The composite binder is composed of modified asphalt and coal tar in a mass ratio of 7:3-8:2, and the modified asphalt is subjected to pyrolysis polymerization treatment at 260-280℃, with the quinoline insoluble content controlled at 8-12%.

[0008] Preferably, in step one, the aggregate crushing adopts a four-stage crushing system, including a jaw crusher for coarse crushing to a particle size of less than 50 mm, a roller crusher for medium crushing to a particle size of less than 15 mm, a ball mill for fine crushing to a particle size of less than 5 mm, and finally, the aggregate is selected into four grades of aggregate by probability screening: 4-8 mm, 2-4 mm, 1-2 mm, and 0.5-1 mm, and the mass percentage of each particle size grade is 30±2%, 25±2%, 20±2%, and 15±2%, respectively; the preparation of recycled material includes: roasting the waste cathode carbon block at 800-850℃ for 2-3 hours to remove electrolyte, crushing it to 0.15-0.3 mm, and then removing iron with a magnetic separator to an iron content of less than 0.03 wt%.

[0009] Preferably, in step two, the aggregate is composed of four grades of particles: 4-8mm, 2-4mm, 1-2mm, and 0.5-1mm, in a mass ratio of 3:2.5:2:1.5. The powder is petroleum coke powder ground to D50=15-25μm by a ball mill. The recycled material is 200-mesh sieve material that has undergone iron removal treatment. Hot air at 80-90℃ is introduced during the premixing process to make the moisture content of the material less than 0.5%.

[0010] Preferably, the preparation of the composite binder includes the following steps: coal tar is placed in a reactor and heated to 120-130°C for dehydration, then modified asphalt that has undergone pyrolysis and polymerization treatment is added, and the mixture is stirred and mixed at 150-200 r / min for 30-40 minutes under nitrogen protection, and then cooled to 90-100°C and kept warm for later use; the pyrolysis and polymerization treatment is: medium-temperature asphalt is bubbled with nitrogen at 260-280°C for 2-3 hours to make the toluene insoluble content reach 28-32%.

[0011] Preferably, the gradient heating and kneading program includes four stages of control: the first stage is kneading at a low speed of 20-30 r / min at 110-120℃ for 10-15 minutes; the second stage is heating up to 140-150℃ and kneading at 40-50 r / min for 20-30 minutes; the third stage is heating up to 170-180℃ and kneading at 50-60 r / min for 25-35 minutes; and the fourth stage is cooling down to 130-140℃ and kneading at 30-40 r / min for 15-20 minutes. The vacuum degree is maintained at -0.04 to -0.06 MPa throughout the kneading process.

[0012] Preferably, the dual-pressure curve vibration molding includes: a first stage of vibration at a pre-compression strength of 1-2 MPa and a vibration frequency of 25-30 Hz for 120-150 seconds; and a second stage of vibration at a main compressive strength of 3-4 MPa and a vibration frequency of 35-40 Hz for 180-220 seconds, with the vibration acceleration controlled at 3-5 g and the mold temperature maintained at 95-105 ℃. After demolding, the green body density reaches 1.75-1.82 g / cm³.

[0013] Preferably, the seven-zone temperature control curve is as follows: Zone 1: ambient temperature to 350℃, heating rate 25℃ / h, holding for 4h; Zone 2: 350-550℃, heating rate 15℃ / h, holding for 8h; Zone 3: 550-800℃, heating rate 20℃ / h, holding for 10h; Zone 4: 800-1050℃, heating rate 25℃ / h, holding for 12h; Zone 5: 1050-1150℃, heating rate 15℃ / h, holding for 15h; Zone 6: 1150-1250℃, heating rate 10℃ / h, holding for 18h; Zone 7: 1250-1100℃, cooling rate 20℃ / h, with protective gas introduced throughout to keep the oxygen content less than 0.5 vol.

[0014] Preferably, the waste gas generated during the roasting process is purified by a three-stage treatment system: the first stage uses a spray tower to neutralize hydrogen fluoride with a 20wt% sodium hydroxide solution; the second stage uses an activated carbon adsorption tower to remove benzo[a]pyrene; and the third stage uses an SCR denitrification device at 280-300℃ to improve the conversion rate of nitrogen oxides with a vanadium-titanium catalyst.

[0015] Preferably, the physicochemical performance testing in the detection and grading step includes: resistivity testing, measured using the four-probe method at a DC voltage of 500V, requiring a value less than 55μΩ·m; CO2 reactivity testing, requiring a weight loss rate of less than 8%; bulk density testing, determined by water immersion method, requiring a value greater than 1.58g / cm³; and internal defect testing: scanning with a 0.5MHz ultrasonic flaw detector, with a defect area of ​​less than 0.1%.

[0016] Preferably, the graded packaging is carried out according to the following rules: Grade A products have a resistivity of less than 50 μΩ·m, CO2 reactivity of less than 6%, bulk density of greater than 1.62 g / cm³ and no internal defects, and are packaged in vacuum moisture-proof packaging; Grade B products have a resistivity of 51-55 μΩ·m, CO2 reactivity of 6.1-8%, bulk density of 1.58-1.61 g / cm³ and defect area of ​​less than 0.05%, and are packaged in nitrogen-protected packaging; Grade C products exceed the Grade B standard but meet basic usage requirements, and are packaged in sealed plastic film packaging. All graded products are stored in stacks according to grade in the storage area, and the ambient humidity is controlled at less than 30%RH.

[0017] The present invention has the following beneficial effects: 1. In this invention, by introducing a recycled material co-processing technology, a deep purification process for recycled materials is established when compounding petroleum coke and waste cathode carbon blocks. This effectively solves the problem that traditional processes cannot separate metal impurities, ensures the structural stability of recycled raw materials in the prebaked anode formula, improves the conductivity of the anode, and reduces the risk of electrolytic cell corrosion caused by impurities, thereby further ensuring the continuity of electrolytic aluminum production.

[0018] 2. In this invention, by developing a gradient kneading and composite bonding system, the thermodynamic parameters are dynamically adjusted during the multi-stage temperature control and vacuum synergy operation in the kneading process to overcome the limitations of a single binder. This effectively overcomes the drawbacks of uncontrolled homogeneity of the paste, ensures the density balance of the green body during the complex vibration molding process, and makes the microcrystalline structure of the anode more compact after calcination. At the same time, it avoids crack defects caused by thermal stress concentration in traditional processes, and further extends the service life of the anode in the electrolytic cell.

[0019] 3. In this invention, by innovating multi-temperature zone dynamic roasting control, a key crystallization zone strengthening and orientation mechanism is established during the heat treatment of large-size green blanks. The microcrystal growth environment is optimized in real time to ensure the controllability of heat conduction processes in different dimensions. This makes the thermal expansion characteristics of the anode highly compatible with the electrolysis conditions. At the same time, it solves the problem of uneven crystallization in the traditional three-temperature zone process and further reduces the probability of anode breakage under extreme current loads. Detailed Implementation

[0020] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0021] The production process of prebaked anode carbon blocks includes the following steps: Step 1: Raw material pretreatment. After calcination, petroleum coke is crushed and screened to obtain aggregate and powder. At the same time, waste cathode carbon blocks from electrolytic aluminum are recycled and roasted to obtain recycled materials. Step 2: Ingredients: Add 60 parts by weight of aggregate, 15 parts by weight of powder and 5 parts by weight of recycled material into the mixer and premix for 10 minutes. Step 3: Mixing and kneading. Add 20 parts of composite binder to the premix and perform a gradient temperature kneading program in a vertical kneader. Step 4: Molding. After cooling the mixed material to 90°C, transfer it into the mold and use a double-pressure curve vibration molding process. Step 5: Firing. Place the green blanks in a ring-shaped firing furnace and fire them for 48 hours according to the seven-temperature zone control curve. Step Six: Testing and Grading. The physicochemical properties of the roasted charcoal blocks are tested and then graded and packaged. The composite binder is composed of modified asphalt and coal tar in a mass ratio of 7:3, and the modified asphalt is subjected to pyrolysis polymerization treatment at 260℃, with the quinoline insoluble content controlled at 8%. In step one, aggregate crushing employs a four-stage crushing system, including coarse crushing with a jaw crusher to a particle size less than 50mm, medium crushing with a roller crusher to a particle size less than 15mm, and fine crushing with a ball mill to a particle size less than 5mm. Finally, the aggregate is selected into four grades: 4mm, 2mm, 1mm, and 0.5mm, with each particle size grade having a mass percentage of 30±2%, 25±2%, 20±2%, and 15±2%, respectively. The recycled material preparation involves roasting waste cathode carbon blocks at 800℃ for 2-3 hours to remove electrolyte, crushing them to 0.15mm, and then removing iron using a magnetic separator to a metal content less than 0.03wt%. In step two, the aggregate consists of four particle sizes: 4mm, 2mm, 1mm, and 0.5mm, in a mass ratio of 3:2.5:2:1.5. The powder is petroleum coke powder ground to D50=15-25μm using a ball mill. The recycled material is 200-mesh sieve material that has undergone iron removal treatment. During the premixing process, 80℃ hot air is introduced to ensure that the moisture content of the material is less than 0.5%. The preparation of the composite binder includes the following steps: coal tar is placed in a reactor and heated to 120°C for dehydration, then modified asphalt that has undergone pyrolysis and polymerization treatment is added. The mixture is stirred and mixed at 150 r / min for 30 minutes under nitrogen protection, and then cooled to 90°C and kept warm for later use. The pyrolysis and polymerization treatment involves bubbling the medium-temperature asphalt with nitrogen at 260°C for 2 hours to achieve a toluene-insoluble content of 28%. The gradient temperature kneading program includes four stages of control: the first stage is kneading at 20 r / min at 110℃ for 10 minutes; the second stage is heating up to 140℃ and kneading at 40 r / min for 20 minutes; the third stage is heating up to 170℃ and kneading at 50 r / min for 25 minutes; and the fourth stage is cooling down to 130℃ and kneading at 30 r / min for 15 minutes. The vacuum degree is maintained at -0.04 MPa throughout the kneading process. The dual-pressure curve vibration molding process includes: the first stage is vibration for 120 seconds at a pre-compression strength of 1MPa and a vibration frequency of 25Hz; the second stage is vibration for 180 seconds at a main compressive strength of 3MPa and a vibration frequency of 35Hz. The vibration acceleration is controlled at 3g, the mold temperature is maintained at 95℃, and the density of the green blank after demolding reaches 1.75g / cm³. The specific temperature control curves for the seven temperature zones are as follows: Zone 1: ambient temperature to 350℃, heating rate 25℃ / h, hold for 4 hours; Zone 2: 350℃, heating rate 15℃ / h, hold for 8 hours; Zone 3: 550℃, heating rate 20℃ / h, hold for 10 hours; Zone 4: 800℃, heating rate 25℃ / h, hold for 12 hours; Zone 5: 1050℃, heating rate 15℃ / h, hold for 15 hours; Zone 6: 1150℃, heating rate 10℃ / h, hold for 18 hours; Zone 7: 1250℃, cooling rate 20℃ / h. Protective gas is circulated throughout the process to maintain an oxygen content of less than 0.5 vol%. The exhaust gas generated during the roasting process is purified by a three-stage treatment system: the first stage uses a spray tower to neutralize hydrogen fluoride with a 20wt% sodium hydroxide solution; the second stage uses an activated carbon adsorption tower to remove benzo[a]pyrene; and the third stage uses an SCR denitrification device at 280℃ to improve the conversion rate of nitrogen oxides with a vanadium-titanium catalyst. The physicochemical performance tests in the grading and testing process include: resistivity testing, measured using the four-probe method at 500V DC, with a requirement of less than 55μΩ·m; CO2 reactivity testing, with a weight loss rate of less than 8%; bulk density testing, determined by water immersion method, with a requirement of greater than 1.58g / cm³; and internal defect testing: scanning with a 0.5MHz ultrasonic flaw detector, with a defect area of ​​less than 0.1%. Graded packaging shall be carried out according to the following rules: Grade A products have a resistivity of less than 50 μΩ·m, CO2 reactivity of less than 6%, bulk density of greater than 1.62 g / cm³ and no internal defects, and shall be packaged in vacuum moisture-proof packaging; Grade B products have a resistivity of 51 μΩ·m, CO2 reactivity of 6.1%, bulk density of 1.58 g / cm³ and defect area of ​​less than 0.05%, and shall be packaged in nitrogen-protected packaging; Grade C products exceed the Grade B standard but meet the basic usage requirements, and shall be packaged in sealed plastic film packaging. All graded products shall be stored in stacks according to grade in the storage area, and the ambient humidity shall be controlled at less than 30%RH.

[0022] Implementation 2: The production process of prebaked anode carbon blocks includes the following steps: Step 1: Raw material pretreatment. After calcination, petroleum coke is crushed and screened to obtain aggregate and powder. At the same time, waste cathode carbon blocks from electrolytic aluminum are recycled and roasted to obtain recycled materials. Step 2: Ingredients: Add 70 parts by weight of aggregate, 20 parts by weight of powder and 7 parts by weight of recycled material into the mixer and premix for 15 minutes. Step 3: Mixing and kneading. Add 25 parts of composite binder to the premix and perform a gradient temperature kneading program in a vertical kneader. Step 4: Molding. After cooling the mixed material to 100°C, transfer it into the mold and use a double-pressure curve vibration molding process. Step 5: Firing. Place the green blanks in a ring-shaped firing furnace and fire them for 60 hours according to the seven-temperature zone control curve. Step Six: Testing and Grading. The physicochemical properties of the roasted charcoal blocks are tested and then graded and packaged. The composite binder is composed of modified asphalt and coal tar in a mass ratio of 7:3, and the modified asphalt is subjected to pyrolysis polymerization treatment at 270℃, with the quinoline insoluble content controlled at 10%. In step one, the aggregate crushing adopts a four-stage crushing system, including a jaw crusher for coarse crushing to a particle size of less than 50 mm, a roller crusher for medium crushing to a particle size of less than 15 mm, and a ball mill for fine crushing to a particle size of less than 5 mm. Finally, it is sorted into four grades of aggregate by probability screening: 6 mm, 3 mm, 1.5 mm, and 0.8 mm, with the mass percentage of each particle size grade being 30±2%, 25±2%, 20±2%, and 15±2%, respectively. The preparation of recycled material includes roasting the waste cathode carbon block at 820℃ for 2.5 hours to remove electrolyte, crushing it to 0.2 mm, and then removing iron with a magnetic separator to an iron content of less than 0.03 wt%. In step two, the aggregate in the batching consists of four particle sizes: 6mm, 2.5mm, 1.5mm, and 0.8mm, in a mass ratio of 3:2.5:2:1.5. The powder is petroleum coke powder ground to D50=15-25μm using a ball mill. The recycled material is sieve material that has undergone iron removal treatment. During the premixing process, hot air at 85℃ is introduced to ensure that the moisture content of the material is less than 0.5%. The preparation of the composite binder includes the following steps: coal tar is placed in a reactor and heated to 125°C for dehydration, then modified asphalt that has undergone pyrolysis and polymerization treatment is added. The mixture is stirred and mixed at 170 r / min for 35 minutes under nitrogen protection, and then cooled to 95°C and kept warm for later use. The pyrolysis and polymerization treatment involves bubbling the medium-temperature asphalt with nitrogen at 270°C for 2.5 hours to achieve a toluene-insoluble content of 30%. The gradient temperature kneading program includes four stages of control: the first stage is kneading at 115℃ at a low speed of 25r / min for 13 minutes; the second stage is to raise the temperature to 145℃ and increase the speed to 45r / min for 25 minutes; the third stage is to raise the temperature to 175℃ and maintain the speed of 55r / min for 30 minutes; and the fourth stage is to cool down to 135℃ and knead at 35r / min for 17 minutes. The vacuum degree is maintained at -0.05MPa throughout the kneading process. The dual-pressure curve vibration molding process includes: the first stage is vibration for 130 seconds at a pre-compression strength of 1.5MPa and a vibration frequency of 27Hz; the second stage is vibration for 200 seconds at a main compressive strength of 3.5MPa and a vibration frequency of 37Hz. The vibration acceleration is controlled at 4g, the mold temperature is maintained at 100℃, and the green body density after demolding reaches 1.8g / cm³. The specific temperature control curves for the seven temperature zones are as follows: Zone 1: ambient temperature to 350℃, heating rate 25℃ / h, hold for 4 hours; Zone 2: 450℃, heating rate 15℃ / h, hold for 8 hours; Zone 3: 650℃, heating rate 20℃ / h, hold for 10 hours; Zone 4: 900℃, heating rate 25℃ / h, hold for 12 hours; Zone 5: 1110℃, heating rate 15℃ / h, hold for 15 hours; Zone 6: 1200℃, heating rate 10℃ / h, hold for 18 hours; Zone 7: 1200℃, cooling rate 20℃ / h. Protective gas is circulated throughout to maintain an oxygen content of less than 0.5 vol%. The exhaust gas generated during the roasting process is purified by a three-stage treatment system: the first stage uses a spray tower to neutralize hydrogen fluoride with a 20wt% sodium hydroxide solution; the second stage uses an activated carbon adsorption tower to remove benzo[a]pyrene; and the third stage uses an SCR denitrification device at 290℃ to improve the conversion rate of nitrogen oxides with a vanadium-titanium catalyst. The physicochemical performance tests in the grading and testing process include: resistivity testing, measured using the four-probe method at 500V DC, with a requirement of less than 55μΩ·m; CO2 reactivity testing, with a weight loss rate of less than 8%; bulk density testing, determined by water immersion method, with a requirement of greater than 1.58g / cm³; and internal defect testing: scanning with a 0.5MHz ultrasonic flaw detector, with a defect area of ​​less than 0.1%. Graded packaging shall be carried out according to the following rules: Grade A products have a resistivity of less than 50 μΩ·m, CO2 reactivity of less than 6%, bulk density of greater than 1.62 g / cm³ and no internal defects, and shall be packaged in vacuum moisture-proof packaging; Grade B products have a resistivity of 53 μΩ·m, CO2 reactivity of 7%, bulk density of 1.6 g / cm³ and defect area of ​​less than 0.05%, and shall be packaged in nitrogen-protected packaging; Grade C products exceed the Grade B standard but meet the basic usage requirements, and shall be packaged in sealed plastic film packaging. All graded products shall be stored in stacks according to grade in the storage area, and the ambient humidity shall be controlled at less than 30%RH.

[0023] Implementation 3: The production process of prebaked anode carbon blocks includes the following steps: Step 1: Raw material pretreatment. After calcination, petroleum coke is crushed and screened to obtain aggregate and powder. At the same time, waste cathode carbon blocks from electrolytic aluminum are recycled and roasted to obtain recycled materials. Step 2: Ingredients: Add 75 parts by weight of aggregate, 25 parts by weight of powder and 10 parts by weight of recycled material into the mixer and premix for 20 minutes. Step 3: Mixing and kneading. Add 30 parts of composite binder to the premix and perform a gradient temperature kneading program in a vertical kneader. Step 4: Molding. After cooling the mixed material to 110°C, transfer it into the mold and use a double-pressure curve vibration molding process. Step 5: Firing. Place the green blanks in a ring-shaped firing furnace and fire them for 72 hours according to the seven-temperature zone control curve. Step Six: Testing and Grading. The physicochemical properties of the roasted charcoal blocks are tested and then graded and packaged. The composite binder is composed of modified asphalt and coal tar in a mass ratio of 8:2, and the modified asphalt is subjected to pyrolysis polymerization treatment at 280℃, with the quinoline insoluble content controlled at 12%. In step one, the aggregate crushing adopts a four-stage crushing system, including a jaw crusher for coarse crushing to a particle size of less than 50 mm, a roller crusher for medium crushing to a particle size of less than 15 mm, and a ball mill for fine crushing to a particle size of less than 5 mm. Finally, it is selected into four grades of aggregate by probability screening: 8 mm, 4 mm, 2 mm, and 1 mm, with the mass percentage of each particle size grade being 30±2%, 25±2%, 20±2%, and 15±2%, respectively. The preparation of recycled material includes roasting the waste cathode carbon blocks at 850℃ for 3 hours to remove electrolyte, crushing them to 0.3 mm, and then removing iron with a magnetic separator to an iron content of less than 0.03 wt%. In step two, the aggregate consists of four particle sizes: 8mm, 4mm, 2mm, and 1mm, in a mass ratio of 3:2.5:2:1.5. The powder is petroleum coke powder ground to D50=15-25μm using a ball mill. The recycled material is 200-mesh sieve material that has undergone iron removal treatment. During the premixing process, 90℃ hot air is introduced to ensure that the moisture content of the material is less than 0.5%. The preparation of the composite binder includes the following steps: coal tar is placed in a reactor and heated to 130°C for dehydration, then modified asphalt that has undergone pyrolysis and polymerization treatment is added. The mixture is stirred and mixed at 200 r / min for 40 minutes under nitrogen protection, and then cooled to 100°C and kept warm for later use. The pyrolysis and polymerization treatment involves bubbling medium-temperature asphalt with nitrogen at 280°C for 3 hours to achieve a toluene-insoluble content of 32%. The gradient temperature kneading program includes four stages of control: the first stage is kneading at 30 r / min at 120℃ for 15 minutes; the second stage is heating up to 150℃ and kneading at 50 r / min for 30 minutes; the third stage is heating up to 180℃ and kneading at 60 r / min for 35 minutes; and the fourth stage is cooling down to 140℃ and kneading at 40 r / min for 20 minutes. The vacuum degree is maintained at -0.06 MPa throughout the kneading process. The dual-pressure curve vibration molding process includes: the first stage is a vibration at a pre-compression strength of 2MPa and a vibration frequency of 30Hz for 150 seconds; the second stage is a vibration at a main compressive strength of 4MPa and a vibration frequency of 40Hz for 220 seconds. The vibration acceleration is controlled at 5g, the mold temperature is maintained at 105℃, and the green body density after demolding reaches 1.82g / cm³. The specific temperature control curves for the seven zones are as follows: Zone 1: ambient temperature to 350℃, heating rate 25℃ / h, hold for 4 hours; Zone 2: 550℃, heating rate 15℃ / h, hold for 8 hours; Zone 3: 800℃, heating rate 20℃ / h, hold for 10 hours; Zone 4: 1050℃, heating rate 25℃ / h, hold for 12 hours; Zone 5: 1150℃, heating rate 15℃ / h, hold for 15 hours; Zone 6: 1250℃, heating rate 10℃ / h, hold for 18 hours; Zone 7: 1100℃, cooling rate 20℃ / h. Protective gas is circulated throughout to maintain an oxygen content of less than 0.5 vol%. The exhaust gas generated during the roasting process is purified by a three-stage treatment system: the first stage uses a spray tower to neutralize hydrogen fluoride with a 20wt% sodium hydroxide solution; the second stage uses an activated carbon adsorption tower to remove benzo[a]pyrene; and the third stage uses an SCR denitrification device at 300℃ to improve the conversion rate of nitrogen oxides with a vanadium-titanium catalyst. The physicochemical performance tests in the grading and testing process include: resistivity testing, measured using the four-probe method at 500V DC, with a requirement of less than 55μΩ·m; CO2 reactivity testing, with a weight loss rate of less than 8%; bulk density testing, determined by water immersion method, with a requirement of greater than 1.58g / cm³; and internal defect testing: scanning with a 0.5MHz ultrasonic flaw detector, with a defect area of ​​less than 0.1%. Graded packaging shall be carried out according to the following rules: Grade A products have a resistivity of less than 50 μΩ·m, CO2 reactivity of less than 6%, bulk density of greater than 1.62 g / cm³ and no internal defects, and shall be packaged in vacuum moisture-proof packaging; Grade B products have a resistivity of 55 μΩ·m, CO2 reactivity of 8%, bulk density of 1.61 g / cm³ and defect area of ​​less than 0.05%, and shall be packaged in nitrogen-protected packaging; Grade C products exceed the Grade B standard but meet the basic usage requirements, and shall be packaged in sealed plastic film packaging. All graded products shall be stored in stacks according to grade in the storage area, and the ambient humidity shall be controlled at less than 30%RH.

[0024] Comparative Example 1: The difference between this comparative example and Example 1 is that no recycled material was added during the preparation of this comparative example.

[0025] Comparative Example 2 differs from Example 2 in that the comparative example did not undergo pyrolysis polymerization during the preparation of the composite adhesive.

[0026] Comparative Example 3 differs from Example 3 in that the gradient heating process is eliminated in this comparative example, and a constant temperature of 150°C is used for kneading.

[0027] Comparative Example 4 differs from Example 3 in that it uses a traditional three-temperature zone curve during calcination.

[0028] The prebaked anode carbon blocks prepared in Examples 1-3 and Comparative Examples 1-4 were subjected to performance tests. The test items and test methods are as follows: Resistivity test: The four-probe method is used to measure the resistivity under a DC voltage of 500V. The stable resistance value is recorded and the volume resistivity is calculated. The test standard is GB / T1410-2006. CO2 reactivity test: According to ISO12989-1 standard, the sample is placed in a 950℃ reaction furnace and CO2 gas is introduced. After 120 minutes, the mass loss rate is calculated. Bulk density test: determined by water immersion method. After drying and weighing the sample, it is immersed in distilled water, removed and the surface moisture is wiped off to calculate the density increment. Test standard GB / T24529-2009. Compressive strength test: The test was conducted using a universal testing machine in accordance with GB / T1431-2009 "Method for Determination of Compressive Strength of Carbon Materials".

[0029] The prebaked anode carbon blocks prepared in Examples 1-3 and Comparative Examples 1-4: The prebaked anode carbon blocks prepared using processes 1-3 exhibit significantly superior performance compared to those prepared using processes 1-4 in Comparative Examples. This demonstrates that by introducing recycled material co-processing technology and establishing a deep purification process for recycled materials during the compounding of petroleum coke and waste cathode carbon blocks, the problem of separating metallic impurities that traditional processes cannot solve is effectively addressed. This ensures the structural stability of the recycled raw materials in the prebaked anode formulation, thereby improving the anode's conductivity and reducing the risk of electrolytic cell corrosion caused by impurities. This further guarantees the continuity of electrolytic aluminum production. Furthermore, by developing a gradient kneading and composite bonding system, and by dynamically adjusting thermodynamic parameters during multi-stage temperature control and vacuum co-operation in the kneading process, the performance can be significantly improved. Breaking the limitations of single binders, this method effectively overcomes the drawbacks of uncontrolled paste homogeneity, ensuring density uniformity of the green body during complex vibration molding processes. This results in a denser microcrystalline structure of the anode after calcination, while avoiding crack defects caused by thermal stress concentration in traditional processes. This further extends the service life of the anode in the electrolytic cell. Through innovative multi-temperature zone dynamic calcination control, a key crystallization zone strengthening and orientation mechanism is established during the heat treatment of large-size green bodies. The microcrystalline growth environment is optimized in real time, ensuring the controllability of heat conduction processes in different dimensions. This makes the thermal expansion characteristics of the anode highly compatible with the electrolytic conditions, while solving the problem of uneven crystallization in traditional three-temperature zone processes, further reducing the probability of anode fracture under extreme current loads.

[0030] The prebaked anode carbon blocks prepared by the process of this invention not only have good anode conductivity, density uniformity and controllability, but also indicate that the production process of prebaked anode carbon blocks provided by this invention has a broader market prospect and is more suitable for promotion.

[0031] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A production process based on prebaked anode carbon blocks, characterized in that, Includes the following steps: Step 1: Raw material pretreatment. After calcination, petroleum coke is crushed and screened to obtain aggregate and powder. At the same time, waste cathode carbon blocks from electrolytic aluminum are recycled and roasted to obtain recycled materials. Step 2: Ingredients: Add 60-75 parts by weight of aggregate, 15-25 parts by weight of powder and 5-10 parts by weight of recycled material into the mixer and premix for 10-20 minutes. Step 3: Mixing. Add 20-30 parts of composite binder to the premix and perform a gradient temperature mixing program in a vertical mixer. Step 4: Molding. After cooling the mixed material to 90-110℃, transfer it into the mold and use a double pressure curve vibration molding process. Step 5: Firing. Place the green blanks in a ring-shaped firing furnace and fire them for 48-72 hours according to the seven-temperature zone control curve. Step Six: Testing and Grading. The physicochemical properties of the roasted charcoal blocks are tested and then graded and packaged. The composite binder is composed of modified asphalt and coal tar in a mass ratio of 7:3-8:2, and the modified asphalt is subjected to pyrolysis polymerization treatment at 260-280℃, with the quinoline insoluble content controlled at 8-12%.

2. The production process of prebaked anode carbon blocks according to claim 1, characterized in that, In step one, the aggregate crushing adopts a four-stage crushing system, including a jaw crusher for coarse crushing to a particle size of less than 50 mm, a roller crusher for medium crushing to a particle size of less than 15 mm, and a ball mill for fine crushing to a particle size of less than 5 mm. Finally, it is selected into four grades of aggregate by probability screening: 4-8 mm, 2-4 mm, 1-2 mm, and 0.5-1 mm, with the mass percentage of each particle size grade being 30±2%, 25±2%, 20±2%, and 15±2%, respectively. The preparation of recycled material includes roasting the waste cathode carbon block at 800-850℃ for 2-3 hours to remove electrolyte, crushing it to 0.15-0.3 mm, and then removing iron with a magnetic separator to an iron content of less than 0.03 wt%.

3. The production process of prebaked anode carbon blocks according to claim 1, characterized in that, In step two, the aggregate is composed of four particle sizes: 4-8mm, 2-4mm, 1-2mm, and 0.5-1mm, in a mass ratio of 3:2.5:2:1.

5. The powder is petroleum coke powder ground to D50=15-25μm using a ball mill. The recycled material is 200-mesh sieve material that has undergone iron removal treatment. During the premixing process, hot air at 80-90℃ is introduced to make the moisture content of the material less than 0.5%.

4. The production process of prebaked anode carbon blocks according to claim 1, characterized in that, The preparation of the composite adhesive includes the following steps: Coal tar is placed in a reactor and heated to 120-130℃ for dehydration. Modified asphalt that has undergone pyrolysis and polymerization treatment is then added. The mixture is stirred and mixed at 150-200 r / min for 30-40 minutes under nitrogen protection. The mixture is then cooled to 90-100℃ and kept warm for later use. The pyrolysis and polymerization treatment involves bubbling medium-temperature asphalt with nitrogen at 260-280℃ for 2-3 hours to achieve a toluene-insoluble content of 28-32%.

5. The production process of prebaked anode carbon blocks according to claim 1, characterized in that, The gradient heating and kneading program includes four stages of control: the first stage is kneading at a low speed of 20-30 r / min at 110-120℃ for 10-15 minutes; the second stage is heating up to 140-150℃ and kneading at 40-50 r / min for 20-30 minutes; the third stage is heating up to 170-180℃ and kneading at 50-60 r / min for 25-35 minutes; and the fourth stage is cooling down to 130-140℃ and kneading at 30-40 r / min for 15-20 minutes. The vacuum degree is maintained at -0.04 to -0.06 MPa throughout the kneading process.

6. The production process of prebaked anode carbon blocks according to claim 1, characterized in that, The dual-pressure curve vibration molding process includes: a first stage of vibration at a pre-compression strength of 1-2 MPa and a vibration frequency of 25-30 Hz for 120-150 seconds; and a second stage of vibration at a main compressive strength of 3-4 MPa and a vibration frequency of 35-40 Hz for 180-220 seconds, with the vibration acceleration controlled at 3-5 g and the mold temperature maintained at 95-105 ℃. After demolding, the green body density reaches 1.75-1.82 g / cm³.

7. The production process of prebaked anode carbon blocks according to claim 1, characterized in that, The specific temperature control curves for the seven temperature zones are as follows: Zone 1: ambient temperature to 350℃, heating rate 25℃ / h, holding for 4h; Zone 2: 350-550℃, heating rate 15℃ / h, holding for 8h; Zone 3: 550-800℃, heating rate 20℃ / h, holding for 10h; Zone 4: 800-1050℃, heating rate 25℃ / h, holding for 12h; Zone 5: 1050-1150℃, heating rate 15℃ / h, holding for 15h; Zone 6: 1150-1250℃, heating rate 10℃ / h, holding for 18h; Zone 7: 1250-1100℃, cooling rate 20℃ / h. A protective gas is introduced throughout the process to ensure an oxygen content of less than 0.5 vol.

8. The production process of prebaked anode carbon blocks according to claim 1, characterized in that, The waste gas generated during the roasting process is purified by a three-stage treatment system: the first stage uses a spray tower to neutralize hydrogen fluoride with a 20wt% sodium hydroxide solution; the second stage uses an activated carbon adsorption tower to remove benzo[a]pyrene; and the third stage uses an SCR denitrification device at 280-300℃ to improve the conversion rate of nitrogen oxides with a vanadium-titanium catalyst.

9. The production process of prebaked anode carbon blocks according to claim 1, characterized in that, The physicochemical performance tests in the detection and grading steps include: resistivity testing, measured using the four-probe method at a DC voltage of 500V, requiring a value less than 55μΩ·m; CO2 reactivity testing, requiring a weight loss rate of less than 8%; bulk density testing, determined by water immersion method, requiring a value greater than 1.58g / cm³; and internal defect testing: scanning with a 0.5MHz ultrasonic flaw detector, with a defect area of ​​less than 0.1%.

10. The production process of prebaked anode carbon blocks according to claim 1, characterized in that, The graded packaging shall be carried out in accordance with the following rules: Grade A products have a resistivity of less than 50 μΩ·m, CO2 reactivity of less than 6%, bulk density of greater than 1.62 g / cm³ and no internal defects, and shall be packaged in vacuum moisture-proof packaging; Grade B products have a resistivity of 51-55 μΩ·m, CO2 reactivity of 6.1-8%, bulk density of 1.58-1.61 g / cm³ and defect area of ​​less than 0.05%, and shall be packaged in nitrogen-protected packaging; Grade C products exceed the Grade B standard but meet the basic usage requirements, and shall be packaged in sealed plastic film packaging. All graded products shall be stored in stacks according to grade in the storage area, and the ambient humidity shall be controlled at less than 30%RH.