Calcined anthracite coke (CAC) is a kind of recarburizer that uses as a carbon additive for steelmaking.
The calcined anthracite coke is an electrode material with low ash, low sulfur, low phosphorous, higher calorific value, and high compressive strength, which calcined in high temperature in electric furnaces, or calcining furnaces.
During the period of calcined anthracite coke manufacturing process, adding a suitable amount of carbon raiser can improve the physical and chemical properties, lower the specific resistance, and get better structural strength.
The traditional carbon raiser manufacturing process is easy to mix with new impurities. Impurity removal processes need to be added, which extends the production time and increases the production cost.
The Advantage of this new production method of carbon raiser
In order to solve the problem mentioned above, a new production method has been found. Through the graphitization treatment of the carbon raiser, the purity of the carbon raiser is improved, so as to improve the thermal and electrical conductivity of the carbon raiser.
The new manufacturing process of carbon additive
- The raw material mixing: The petroleum coke is first ground into a 300-mesh powder and then mixed evenly with a carbon-containing material. Then add asphalt and mix evenly to get mixed raw material.The mixed raw material comprises (By weight percentage) petroleum coke 15-25%, asphalt 1-3%, and carbon-containing material 60-80% (The mixing ratio of micropurified graphite and free carbon is 3:2).
- Pretreatment of raw material: Add water to the mixed raw material, and put it into a rotary granulator machine to granulate it.
- Surface treatment: Put the processed granules into the drum and rotate until the surface is smooth. Removal of protrusions and burrs can improve the uniformity of graphitization. This process takes 4-10 hours.
- Sieving: Separate the smooth surface granules, remove granules with a size greater than 8mm, crush them and repeat the surface treatment process until the size is less than or equal to 8mm.
- Drying: Put the Sieved particles into a vertical dryer. The drying temperature of the vertical dryer is 80℃-120℃, and the drying time is 60min-80min. Ensure that the water content of the material is 1% or less.
- Graphitization: Put the dried particles into a graphitization furnace, and calcined at 2300℃-2800℃ for 8-10 days.
- Packaging: Cool the calcined particles, and according to the particle size classification packaging. The sizes are 0-2mm, 2-5mm, and 5-8mm.
Four cases of the carbon additive manufacturing
| Case 1 | Case 2 | Case 3 | Case 4 | |
| 1. The raw material mixing | Petroleum coke 20%， carbon-containing material 78%， asphalt:2% | Petroleum coke 20%， carbon-containing material 78%， asphalt:2% | Petroleum coke 25% carbon-containing material 74%，asphalt:1% | Petroleum coke 23%， carbon-containing material 74%， asphalt3% |
| 2. Pretreatment of raw material | / | / | / | / |
| 3. Surface treatment | 5h | 5h | 8h | 10 |
| 4. Sieving | / | / | / | / |
| 5. Drying | / | / | / | / |
| 6. Graphitization | 2300℃, 10days | 2800℃, 10days | 2500℃, 10days | 2800℃, 10days |
| 7. Packaging | / | / | / | / |
The differences among the four cases of carbon additive manufacturing proces
Four cases are listed in the table, with some adjustments in raw material mixing ratio, surface treatment time, and graphitization treatment temperature.
The experimental results show that:
- The impurity removal rate is affected by graphitization calcination temperature. By increasing the calcination temperature to 2800, more than 90 % of impurities can be removed from the granules, and the purity of the carbon additive can be further improved.
- The surface treatment time affects the surface smoothness of the materials. If the treatment is too short, the surface of the material has burrs, materials are not uniformly heated during drying and graphitization, and affecting the quality of the carbon raiser.
- The content of the materials determined the specification of the product. The material ratio should be adjusted as required.
This new production method greatly improves the purity of carbon raiser products and reduces the production cost. This article provides several optimization cases on which technicians worldwide can adapt their best approach.