A method for preparing high-quality prebaked anodes from multi-source potential feedstock with high doping ratio

Abstract

This invention discloses a method for preparing high-quality prebaked anodes from high-dosage multi-source latent raw materials, comprising two main steps: synergistic pretreatment of latent raw materials and preparation of high-quality prebaked anodes. The synergistic pretreatment steps are as follows: S1: Raw material screening: Select at least one of low-grade calcined coke, electrolytic residue, and waste anodes as latent raw materials, establish a traceability ledger according to production area and type, and crush and screen to a particle size ≤3mm; S2: Magnetic separation for impurity removal: Feed the screened raw materials into a wet magnetic separator, control the magnetic field strength at 15000-25000GS and the feed rate at 0.5-1.2m³ / h to remove magnetic metal impurities. This method for preparing high-quality prebaked anodes from high-dosage multi-source latent raw materials improves the purity and stability of latent raw materials through synergistic pretreatment technology. Combined with high-dosage formula optimization and low-energy roasting process, it achieves a high latent raw material dosing ratio of 60%-70% while ensuring that the prebaked anode product meets the first-grade standard, significantly reducing production costs and energy consumption, and promoting the green and circular development of the industry.

Description

Technical Field

[0001] This invention relates to the field of prebaked anode production technology, specifically a method for preparing high-quality prebaked anodes from multi-source potential raw materials with high doping ratios. Background Technology

[0002] Prebaked anodes are a core consumable in electrolytic aluminum production, and their performance directly affects production efficiency, energy consumption, and aluminum quality. With the rapid growth in demand for high-purity aluminum from high-end fields such as new energy vehicles and aerospace, the market demand for high-quality prebaked anodes (bulk density ≥1.65g / cm³, resistivity ≤55μΩ・m) is growing at an average annual rate of 8% to 10%, but the market gap continues to widen.

[0003] The production of high-quality prebaked anodes is highly dependent on high-quality calcined coke (ash content ≤0.5%, sulfur content ≤3.5%). However, in recent years, this type of high-quality raw material has shown a trend of "scarcity, high price, and import dependence." In 2025, the average domestic price had risen to 4,000 yuan / ton, an increase of 40% compared to 2020. This has led to a rise in the proportion of raw material costs for anode manufacturers from 55% to 68%, severely squeezing profit margins. At the same time, the market generates more than 5 million tons of low-grade calcined coke, electrolytic residues, and waste anodes annually. Due to their high impurity content and poor component stability, 60% of these raw materials are sold at low prices or incinerated, causing serious resource waste and emissions of SO2 and NO. x Pollutants such as these exacerbate environmental pressures.

[0004] At present, some companies have tried to incorporate potential raw materials into production, but the blending ratio is generally ≤20%, and there are the following technical bottlenecks: (1) The pretreatment technology is simple, focusing on the removal of single impurities and not forming a synergistic treatment system. The raw material impurity removal rate is low and the composition fluctuates greatly, resulting in unstable performance of anode products and a pass rate of only 75% to 80%; (2) The formula design is unreasonable under high blending ratio, making it difficult to balance raw material cost and product performance, and problems such as anode cracking and increased resistivity are likely to occur; (3) The energy consumption of the roasting process is relatively high. The traditional roasting process consumes about 850 kWh / ton, and the raw material burn-off rate is high at high temperature, which further increases the production cost.

[0005] While some foreign companies have achieved a 30%–40% blending rate of potential raw materials, the high barriers to entry in core pretreatment technologies and the expensive equipment make them unsuitable for large-scale application by small and medium-sized enterprises in China. Therefore, developing a complete process technology that integrates "efficient impurity removal, high-ratio formulation optimization, and low-energy preparation" to achieve high-value conversion from "inferior raw materials to high-quality anodes" has become crucial for solving the industry's resource constraints and cost dilemmas. Summary of the Invention

[0006] The technical problem to be solved by this invention is to overcome the existing defects and provide a method for preparing high-quality prebaked anodes from multi-source latent raw materials with high doping ratio. By improving the purity and stability of latent raw materials through synergistic pretreatment technology, and combining high doping ratio formulation optimization and low-energy roasting process, a high doping ratio of 60% to 70% of latent raw materials can be achieved while ensuring that the prebaked anode products meet the first-grade standard. This significantly reduces production costs and energy consumption, promotes the green and circular development of the industry, and can effectively solve the problems in the background technology.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing high-quality prebaked anodes from multi-source latent raw materials with high doping ratios, comprising two main steps: synergistic pretreatment of latent raw materials and preparation of high-quality prebaked anodes. The synergistic pretreatment steps of the latent raw materials are as follows:

[0008] S1: Raw material screening: Select at least one of the following as potential raw materials: low-grade calcined coke, electrolytic residual electrode, and waste anode. Establish a traceability ledger according to the production area and type. After crushing and screening, the raw materials are ≤3mm in particle size.

[0009] S2: Magnetic separation for impurity removal: The screened raw material is fed into a wet magnetic separator, and the magnetic field strength is controlled at 15000-25000GS and the feeding rate is 0.5~1.2m³ / h to remove magnetic metal impurities.

[0010] S3: Acid washing and purification: Mix the magnetically separated raw material with acid solution at a solid-liquid ratio of 1:3 to 1:5. The acid solution is a mixture of hydrochloric acid and sulfuric acid with a concentration of 10% to 15%. Stir and react at 50 to 70°C for 60 to 90 minutes to remove non-magnetic metal impurities.

[0011] S4: Co-desulfurization: First, place the acid-washed raw material in a high-temperature desulfurization reactor and treat it at 500-600℃ under a nitrogen atmosphere for 2-3 hours. Then, introduce a reaction system containing desulfurization microbial liquid, control the temperature at 30-35℃ and the pH value at 6.5-7.5, and react for 12-16 hours to reduce the sulfur content of the raw material to below 1.5%.

[0012] S5: Homogenization treatment: The desulfurized raw materials are fed into a twin-screw integrated homogenizer and mixed for 30 to 45 minutes to ensure that the fluctuation range of raw material composition is ≤5% and to obtain qualified pre-treated raw materials.

[0013] The steps for preparing the high-quality prebaked anode are as follows:

[0014] S6: Formula ingredients: By mass percentage, take 60% to 70% of the qualified raw materials pretreated in step S5, 25% to 35% of the high-quality calcined coke, and 8% to 10% of the binder. The binder is a composite binder of modified coal tar pitch and petroleum pitch, with a softening point of 100 to 110°C.

[0015] S7: Ingredient mixing: Put the above raw materials into a continuous mixer, dry mix at room temperature for 15-20 minutes, then add the binder, heat to 100-120℃ and wet mix for 30-40 minutes to obtain a uniform paste.

[0016] S8: Molding process: The paste is fed into an automatic molding machine, and the molding pressure is controlled at 30-35MPa and the holding time is 3-5min to produce a green body with a bulk density ≥1.55g / cm³.

[0017] S9: Firing treatment: The green body is sent into the firing furnace and a segmented heating process is adopted: the heating rate from room temperature to 300℃ is 3~5℃ / h, the heating rate from 300 to 800℃ is 6~8℃ / h, the heating rate from 800 to 1150℃ is 5~6℃ / h, and the temperature is held at 1100~1150℃ for 8~10h. Nitrogen gas is introduced for protection during the firing process, and the nitrogen flow rate is 0.8~1.2m³ / h.

[0018] S10: Cooling the finished product: After calcination, the product is naturally cooled to room temperature to obtain a high-quality prebaked anode product.

[0019] As a preferred embodiment of the present invention, in step S2, the spacing between the magnetic rods of the wet magnetic separator is 20-30 mm, and the uniformity error of the magnetic field strength on the surface of the magnetic rods is ≤ ±5%.

[0020] In a preferred embodiment of the present invention, the volume ratio of hydrochloric acid to sulfuric acid in step S3 is 2:1.

[0021] As a preferred embodiment of the present invention, the desulfurization microorganism in step S4 is a composite strain of Thiobacillus ferrooxidans and Thiobacillus acidophilus, and the inoculation amount is 3% to 5% of the raw material mass.

[0022] As a preferred embodiment of the present invention, in step S5, the total removal rate of metal impurities in the pretreated qualified raw materials is ≥80%, wherein the removal rates of impurities for Fe, Ni, and V are ≥85%, 82%, and 78%, respectively, and the stability of the raw materials reaches more than 90% of that of high-quality calcined coke.

[0023] In a preferred embodiment of the present invention, the mass ratio of modified coal tar pitch to petroleum pitch in step S6 is 3:1.

[0024] As a preferred embodiment of the present invention, the energy consumption of the roasting process in step S9 is ≤720kWh / ton.

[0025] As a preferred technical solution of the present invention, the roasting furnace in step S9 is an energy-saving roasting furnace containing a segmented temperature control system, a nitrogen circulation system and a waste heat recovery system. The nitrogen circulation system realizes closed-loop recycling of nitrogen, and the waste heat recovered by the waste heat recovery system is used for the raw material pretreatment and preheating process in steps 1-5, with a waste heat utilization rate of ≥60%.

[0026] Compared with the prior art, the beneficial effects of the present invention are: (1) It is the first to create a technical system that combines multi-stage pretreatment of "magnetic separation-acid washing-homogenization" with high temperature-microbial synergistic desulfurization, breaking through the limitations of traditional single pretreatment technology, realizing the efficient synergistic removal of magnetic impurities, non-magnetic impurities and sulfur in potential raw materials, with a total removal rate of metal impurities in raw materials ≥80%, sulfur content reduced to below 1.5%, and component fluctuation range ≤5%, providing a stable raw material basis for high doping ratio applications of 60% to 70%; (2) It optimizes the design of high doping ratio formula, using 60% to 70% of qualified pretreated raw materials with high-quality calcined coke and composite binder, combined with precise molding and segmented roasting process, to solve the problem of anode performance fluctuation under high doping ratio, and the product conforms to YS / T 285-2012 The first-grade product standard has core indicators of volume density ≥1.65g / cm³, compressive strength ≥25MPa, resistivity ≤55μΩ・m, and pass rate ≥95%; (3) adopting an energy-saving roasting furnace with segmented temperature control, nitrogen circulation and waste heat recovery system, combined with segmented heating process, to achieve roasting energy consumption ≤720kWh / ton, which is ≥15% lower than the traditional process. At the same time, the nitrogen circulation utilization rate is ≥90% and the waste heat utilization rate is ≥60%, which significantly reduces production costs and environmental pressure; (4) the whole process technology solution can digest a large amount of low-grade calcined coke, electrolytic residual electrode and other potential raw materials, promote resource recycling, reduce solid waste emissions and dependence on imported high-quality raw materials, provide the industry with a replicable high-value utilization example, and has significant economic benefits and ecological value. Attached Figure Description

[0027] Figure 1 This is a process flow diagram of the method of the present invention. Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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 skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] Example 1

[0030] like Figure 1This invention provides a technical solution: a method for preparing high-quality prebaked anodes from high-doping multi-source potential raw materials, comprising the following steps:

[0031] S1: Raw material screening: Low-grade calcined coke from North China and electrolytic residue from an aluminum plant were selected as potential raw materials and mixed at a 1:1 ratio. A traceability ledger was established, and the raw materials were crushed and screened to a particle size of ≤3mm.

[0032] S2: Magnetic separation for impurity removal: A wet magnetic separator is used with a magnetic field strength of 20000GS, a feeding rate of 0.8m³ / h, and a magnetic rod spacing of 25mm to remove magnetic metal impurities;

[0033] S3: Acid washing and purification: Solid-liquid ratio 1:4, acid solution is a mixture of 12% hydrochloric acid and sulfuric acid, the volume ratio of hydrochloric acid to sulfuric acid is 2:1, stir and react at 60℃ for 75 min, wash with water until neutral;

[0034] S4: Synergistic desulfurization: High-temperature desulfurization temperature 550℃, nitrogen atmosphere treatment for 2.5h, microbial inoculum amount

[0035] At 4%, under conditions of 32℃ and pH 7.0, the reaction time was 14 hours, and the sulfur content decreased to 1.3%.

[0036] S5: Homogenization treatment: Mixed in a twin-spiral homogenizer for 40 minutes, with a composition fluctuation range of 4.2%. The total removal rate of metal impurities in the raw material after pretreatment was 83%, and the removal rates of Fe, Ni, and V were 87%, 84%, and 80%, respectively.

[0037] S6: Formula and ingredients: 65% pretreated qualified raw materials, 30% high-quality calcined coke, 9% composite binder, wherein modified coal tar pitch: petroleum pitch = 3:1, softening point 105℃;

[0038] S7: Ingredient mixing: Dry mix at room temperature for 18 min, wet mix at 110℃ for 35 min;

[0039] S8: Molding process: molding pressure 32MPa, holding time 4min, green bulk density 1.58g / cm³;

[0040] S9: Calcination treatment: Energy-saving calcining furnace with segmented heating: heating rate from room temperature to 300℃ is 4℃ / h, heating rate from 300 to 800℃ is 7℃ / h, heating rate from 800 to 1150℃ is 5.5℃ / h, holding at 1120℃ for 9h, nitrogen flow rate is 1.0m³ / h.

[0041] S10: Cooling the finished product: Naturally cool to room temperature, test product performance: bulk density 1.68g / cm³, compressive strength 27MPa, resistivity 52μΩ・m, air permeability 8.5×10⁻¹²m², pass rate 96.3%, calcination energy consumption 705kWh / ton.

[0042] Example 2

[0043] S1: Raw material screening: Low-grade calcined coke and waste anodes from East China are mixed at a ratio of 2:1 as potential raw materials, and crushed and screened to a particle size of ≤3mm.

[0044] S2: Magnetic separation for impurity removal: magnetic field strength 18000GS, feed rate 1.0m³ / h, magnetic bar spacing 22mm;

[0045] S3 pickling and purification: solid-liquid ratio 1:3.5, acid solution is a mixture of 14% hydrochloric acid and sulfuric acid, the volume ratio of hydrochloric acid to sulfuric acid is 2:1, stir and react at 55℃ for 80 min;

[0046] S4: Synergistic desulfurization: High-temperature desulfurization at 580℃ for 2 hours, with a microbial inoculum of 3.5%, followed by a reaction at 33℃ and pH 6.8 for 15 hours, resulting in a sulfur content reduction to 1.2%;

[0047] S5: Homogenization treatment: mixing time 38 min, composition fluctuation range 3.8%, total removal rate of metal impurities 85%;

[0048] S6: Formula and ingredients: 68% pretreated qualified raw materials, 27% high-quality calcined coke, and 8.5% composite binder;

[0049] S7: Ingredient mixing: Dry mix at room temperature for 16 min, wet mix at 115℃ for 32 min;

[0050] S8: Molding process: molding pressure 34MPa, holding time 3.5min, green bulk density is 1.60g / cm³;

[0051] S9: Calcination treatment: Segmented heating rate: The heating rate from room temperature to 300℃ is 3.5℃ / h, the heating rate from 300 to 800℃ is 7.5℃ / h, the heating rate from 800 to 1150℃ is 5.2℃ / h, and the temperature is held at 1140℃ for 8.5h.

[0052] S10: Cooled finished product: Product performance: Bulk density 1.70g / cm³, compressive strength 28MPa, resistivity 50μΩ・m, air permeability 7.8×10⁻¹²m², pass rate 97.1%, calcination energy consumption 698kWh / ton.

[0053] Comparative example (existing process)

[0054] The prebaked anode was prepared using 85% high-quality calcined coke and 15% binder through traditional kneading, molding and calcination processes. The calcination energy consumption was 860 kWh / ton. The product had a bulk density of 1.66 g / cm³, a compressive strength of 26 MPa and a resistivity of 54 μΩ·m. The raw material cost was 32% higher than that of Example 1 of this invention.

[0055] The comparison shows that, under the premise of significantly increasing the proportion of potential raw materials (60% to 70%), the product performance of this invention is better than that of traditional processes, and the energy consumption is reduced by more than 15% and the raw material cost is significantly reduced, which has significant technical advantages and application value.

[0056] The parts of the invention not described in detail are prior art. 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 method for preparing high-quality prebaked anodes from multi-source potential raw materials with high doping ratios, characterized in that: The process includes two main steps: co-treatment of latent raw materials and preparation of high-quality prebaked anodes. The steps of the co-treatment of latent raw materials are as follows: S1: Raw material screening: Select at least one of the following as potential raw materials: low-grade calcined coke, electrolytic residual electrode, and waste anode. Establish a traceability ledger according to the production area and type. After crushing and screening, the raw materials are ≤3mm in particle size. S2: Magnetic separation for impurity removal: The screened raw material is fed into a wet magnetic separator, and the magnetic field strength is controlled at 15000-25000GS and the feeding rate is 0.5~1.2m³ / h to remove magnetic metal impurities. S3: Acid washing and purification: Mix the magnetically separated raw material with acid solution at a solid-liquid ratio of 1:3 to 1:

5. The acid solution is a mixture of hydrochloric acid and sulfuric acid with a concentration of 10% to 15%. Stir and react at 50 to 70°C for 60 to 90 minutes to remove non-magnetic metal impurities. S4: Co-desulfurization: First, place the acid-washed raw material in a high-temperature desulfurization reactor and treat it at 500-600℃ under a nitrogen atmosphere for 2-3 hours. Then, introduce a reaction system containing desulfurization microbial liquid, control the temperature at 30-35℃ and the pH value at 6.5-7.5, and react for 12-16 hours to reduce the sulfur content of the raw material to below 1.5%. S5: Homogenization treatment: The desulfurized raw materials are fed into a twin-screw integrated homogenizer and mixed for 30 to 45 minutes to ensure that the fluctuation range of raw material composition is ≤5% and to obtain qualified pre-treated raw materials. The steps for preparing the high-quality prebaked anode are as follows: S6: Formula ingredients: By mass percentage, take 60% to 70% of the qualified raw materials pretreated in step S5, 25% to 35% of the high-quality calcined coke, and 8% to 10% of the binder. The binder is a composite binder of modified coal tar pitch and petroleum pitch, with a softening point of 100 to 110°C. S7: Ingredient mixing: Put the above raw materials into a continuous mixer, dry mix at room temperature for 15-20 minutes, then add the binder, heat to 100-120℃ and wet mix for 30-40 minutes to obtain a uniform paste. S8: Molding process: The paste is fed into an automatic molding machine, and the molding pressure is controlled at 30-35MPa and the holding time is 3-5min to produce a green body with a bulk density ≥1.55g / cm³. S9: Firing treatment: The green body is sent into the firing furnace and a segmented heating process is adopted: the heating rate from room temperature to 300℃ is 3~5℃ / h, the heating rate from 300 to 800℃ is 6~8℃ / h, the heating rate from 800 to 1150℃ is 5~6℃ / h, and the temperature is held at 1100~1150℃ for 8~10h. Nitrogen gas is introduced for protection during the firing process, and the nitrogen flow rate is 0.8~1.2m³ / h. S10: Cooling the finished product: After calcination, the product is naturally cooled to room temperature to obtain a high-quality prebaked anode product.

2. The method for preparing high-quality prebaked anodes from high-doping multi-source latent raw materials according to claim 1, characterized in that: In step S2, the spacing between the magnetic rods of the wet magnetic separator is 20-30 mm, and the uniformity error of the magnetic field strength on the surface of the magnetic rods is ≤ ±5%.

3. The method for preparing high-quality prebaked anodes from high-doping multi-source latent raw materials according to claim 1, characterized in that: In step S3, the volume ratio of hydrochloric acid to sulfuric acid is 2:

1.

4. The method for preparing high-quality prebaked anodes from high-doping multi-source latent raw materials according to claim 1, characterized in that: In step S4, the desulfurization microorganisms are a composite strain of *Thiobacillus ferrooxidans* and *Thiobacillus acidophilus*, and the inoculation amount is 3% to 5% of the raw material mass.

5. The method for preparing high-quality prebaked anodes from high-doping multi-source latent raw materials according to claim 1, characterized in that: In step S5, the total removal rate of metal impurities in the pretreated qualified raw materials is ≥80%, of which the removal rates of Fe, Ni, and V impurities are ≥85%, 82%, and 78%, respectively, and the stability of the raw materials reaches more than 90% of that of high-quality calcined coke.

6. The method for preparing high-quality prebaked anodes from high-doping multi-source latent raw materials according to claim 1, characterized in that: In step S6, the mass ratio of modified coal tar pitch to petroleum pitch is 3:

1.

7. The method for preparing high-quality prebaked anodes from high-doping multi-source latent raw materials according to claim 1, characterized in that: The energy consumption of the roasting process in step S9 is ≤720kWh / ton.

8. The method for preparing high-quality prebaked anodes from high-doping multi-source latent raw materials according to claim 1, characterized in that: In step S9, the roasting furnace is an energy-saving roasting furnace containing a segmented temperature control system, a nitrogen circulation system, and a waste heat recovery system. The nitrogen circulation system realizes closed-loop recycling of nitrogen, and the waste heat recovered by the waste heat recovery system is used for the raw material pretreatment and preheating process in steps 1-5, with a waste heat utilization rate of ≥60%.

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