Application and Advantage Analysis of Graphitized Petroleum Coke in the Aluminum Electrolysis Industry
I. Application of Graphitized Petroleum Coke in Cathode Blocks and Anode Paste
1. Cathode Block Production
Graphitized petroleum coke is the core raw material for manufacturing graphitized cathode carbon blocks. After high-temperature graphitization treatment at approximately 3000°C, its carbon purity exceeds 98%, and true density increases significantly, forming a highly ordered graphite crystal structure. This structure endows cathode blocks with the following properties:
- Enhanced sodium erosion resistance: The high-purity graphitized structure effectively resists sodium penetration during aluminum electrolysis, extending cathode service life.
- Improved electrical conductivity: Graphitization reduces resistivity substantially, lowering the cell bottom voltage drop and reducing aluminum production energy consumption by approximately 5%–10%.
- Optimized thermal stability: Low volume expansion at high temperatures minimizes cracking risks caused by thermal stress.
2. Anode Paste Preparation
In anode paste, graphitized petroleum coke primarily serves as a carbon additive and conductive framework material, with the following effects:
- Enhanced electrical conductivity: The graphitized structure promotes uniform current distribution, reducing anode overvoltage.
- Improved oxidation resistance: Low sulfur content (typically <0.06%) minimizes gas-induced cracking during reactions with CO₂, reducing anode consumption per ton of steel (e.g., a 12% reduction in a specific enterprise’s application).
- Optimized pore structure: Graphitization reduces the porosity of pitch coke, increasing anode density and mechanical strength.
II. Key Advantages of Graphitized Petroleum Coke Over Calcined Petroleum Coke
| Performance Metric | Graphitized Petroleum Coke | Calcined Petroleum Coke |
|---|---|---|
| Sulfur content | 0.03%–0.06% (low-sulfur type) | ~0.5% (standard type) |
| Absorption rate | 90%–95% | 80%–90% |
| Graphitization degree | Highly graphitized (true density ≥2.18 g/cm³) | Partially graphitized (true density 1.8–2.0 g/cm³) |
| Impurity content | Ash ≤0.15%, volatile matter <0.5% | Ash 0.3%–0.8%, volatile matter 0.7%–1.5% |
| Thermal expansion coefficient | Low (needle coke type) | High (sponge coke type) |
| Application scenarios | High-power graphite electrodes, specialty carbon products | Standard prebaked anodes, industrial silicon electrodes |
Specific Advantages:
1. Electrochemical Performance Optimization
- The resistivity of graphitized petroleum coke is 30%–50% lower than that of calcined coke, significantly reducing electrolysis cell energy consumption. For example, in 750 mm needle coke electrodes, conductivity exceeds that of standard coke by threefold, improving steelmaking efficiency to 25 minutes per furnace.
- Low sulfur content reduces reactions between anodes and fluoride-containing electrolytes, minimizing gas-induced swelling and extending anode lifespan.
2. Mechanical Property Enhancement
- Graphitization increases material hardness and thermal shock resistance. In high-temperature aluminum electrolysis environments, the thermal expansion coefficient of graphitized cathode blocks is 30% lower than that of calcined coke, reducing structural damage from temperature fluctuations.
- Elevated true density (≥2.18 g/cm³) enhances material compactness, minimizing aluminum liquid penetration and sodium erosion.
3. Environmental and Economic Benefits
- Reduced sulfur content lowers SO₂ emissions, meeting environmental regulations. For instance, an aluminum plant using low-sulfur graphitized coke reduced SO₂ emissions per ton of aluminum by 15%.
- Despite higher costs (approximately 1.5–2 times that of calcined coke), the extended lifespan and lower energy consumption offset initial investments. For example, cathode block lifespan increased from 5 to 8 years, reducing overall costs by 20%.
III. Application Cases and Data Support
- Aluminum Electrolysis Industry: Globally, 70% of calcined coke is used for aluminum electrolysis anodes, but high-end markets (e.g., graphitized cathodes) are increasingly adopting graphitized coke. One enterprise reduced anode consumption from 420 kg/t-Al to 370 kg/t-Al after adopting graphitized cathodes, saving RMB 200 million annually.
- Steel Industry: 750 mm needle coke electrodes carrying 100,000 A currents achieved steelmaking efficiency of 25 minutes per furnace, with conductivity three times higher than standard coke.
- Energy Storage Sector: Asphalt-modified calcined coke improved hard carbon anode cycle life by 400 cycles, gaining traction in sodium-ion battery markets.
IV. Conclusion
Graphitized petroleum coke, through high-temperature graphitization, demonstrates superior purity, electrical conductivity, and thermal stability compared to calcined petroleum coke, making it ideal for high-end aluminum electrolysis cathode blocks and specialty anode paste production. Despite higher costs, its extended lifespan, energy efficiency, and environmental benefits position it as a critical material for upgrading the aluminum industry. Future advancements in graphitization technology (e.g., ultra-high-temperature treatment at 3000°C) will further expand its applications into nuclear-grade graphite, lithium-ion battery anodes, and other cutting-edge fields.
Post time: Sep-22-2025