Electrode Carbon Paste is a Soderberg paste processed from a mix of a specific fraction of Calcined Petroleum Coke (CPC) and / or Electrically Calcined Anthracite Coal (ECA), impregnated with selective Coal Tar Pitch Binder at a definite temperature.

It is used in submerged Arc Furnaces for production of various Ferro Alloys and Calcium Carbide.

Manufacturing Process

The first step in the manufacture of Electrode Carbon Paste is screening the Calcined Petroleum Coke (CPC) and / or (ECA) to different fractions and pulverizing 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 150ºC 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 mould box and cast into blocks 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 temperature 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 or percentage of coke fines. 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 with out breakages.

A Typical Characteristics of CPC based Carbon Electrode Paste is as follows

Green Paste

Volatile Matter 15% Max
Fixed Carbon 84% Min
Ash 1.0% Max
Plasticity 45 - 55%
Apparent Density 1.55 gms/cc Min
Binder Content 22 - 24%

Baked Paste at 1000deg Centigrade

Apparent Density 1.35 gms/cc Min
Electrical Resistivity 90 ohm-meter Max
Compressive Strength 150 Kg/cm2 Min
Porosity 35% Max