Carbon Electrode Paste
Electrode Carbon Paste is a Soderberge paste processed from a mix of a specific fraction and / or Electrically Calcined Anthracite Coal – ECA, impregnated with selective Coal Tar Pitch. It is used in submerged Arc Furnaces for production of Ferro Alloys and Calcium Carbide.
Manufacturing Process
The first step in the manufacture of Electrode Carbon Paste is crushing and screening the Calcined Petroleum Coke (CPC) and / or Electrically Calcined Anthracite (ECA) to different fractions and milling and storing it separately. Following this, pre-determined quantities of different fractions are weighed and transferred to a Sigma Mixer which is heated to about 160oC by thermic fluid. The required quantity of binder is also weighed separately and added to the mixer. The mixing is continued for a pre-determined period known as the mixing cycle. At the end of the mixing cycle, the mixed material is dumped on the mold box and cast into blocks for shipment. Sometimes the blocks are crushed and screened to required size of customers and packed in bags for shipment.
Quality Specification
At the customer’s end the paste is fed in the upper part of the electrode. As the paste moves downwards in the electrode it softens and melts forming the shape of the electrode casing. Flowability of Carbon Paste is essential for proper operation of the electrode. It is important that the paste flows at a reasonable temperate and fills the casing of the Electrode, maintaining a consistent mixture of components. The paste then gets baked to a solid mass as it moves down and is capable of passing the required current to the furnace charge. The plasticity of Paste, the measure of its Flowability is controlled in the mixer by adjusting the Binder content. The lower baked part of the electrode is the final Electrode Product. The physical properties of this paste are of vital importance to ensure proper electrode operation without breakages.
A Typical Characteristics of CPC base Carbon Electrode Paste is as follows
| GREEN PASTE: | BAKED PASTE AT 1000o C | ||
| Volatile Matter | 15% max | Apparent Density | 1.35 gms/cc min. |
| Fixed Carbon | 84% min | Electrical Resistivity | 90 ohm M max |
| Ash | 1.0 % max | Compressive Strength | 200 kg/cm2 min. |
| Plasticity | 30 – 40% | Porosity | 35% max. |
| Apparent Density | 1.55 gms/cc min. | ||
| Binder Content | 22 – 25% | ||
A Typical Characteristics of ECA base Carbon Electrode Paste is as follows
| GREEN PASTE: | BAKED PASTE AT 1000o C | ||
| Volatile Matter | 13% max | Apparent Density | 1.38 gms/cc min. |
| Ash | 5.0 % max | Electrical Resistivity | 70 ohm M max |
| Plasticity | 30 – 40% | Compressive Strength | 235 kg/cm2 min. |
| Apparent Density | 1.55 gms/cc min. | ||
| Binder Content | 20 – 22% | ||
