How is electrode paste used in a mine electric furnace and how is its self baking process carried out?

At present, self baking electrode paste is mainly used for ore heating furnaces. The electrode paste that has been broken into pieces beforehand is regularly added above a cylinder welded from a steel plate with a diameter of 500-1500mm. The electrode paste inside the cylinder begins to soften and melt under the action of heat, and then the binder coal tar is thermally decomposed to release volatile substances. It is roasted into a carbon electrode with good conductivity and high mechanical strength. The current (current density is generally 3-8A/cm2) is introduced into the ore heating furnace by relying on the roasted electrode. Due to high-temperature oxidation and participation in chemical reactions of furnace materials, the lower end of the electrode is constantly consumed. Therefore, the entire electrode cylinder should be regularly lowered, and a new cylinder should be timely connected to the upper part of the electrode cylinder and electrode paste should be replenished.

The self roasting process of electrode paste in a mine electric furnace can be divided into three stages:
(1) Softening and melting. The temperature of the electrode paste rises to around 150 ℃, indicating a plastic flow state, located approximately 500mm above the conductive gripper.
(2) Pyrolysis of coal tar pitch and removal of volatile matter. The electrode paste, which is fully softened and in a semi flowing state, flows along the cross-section of the cylinder and fills the gaps between the material blocks. As the temperature continues to rise, the binder coal tar in the electrode paste decomposes and escapes volatile matter. After thermal decomposition and condensation reaction, the coal tar gradually transforms into adhesive coke. At this time, the temperature reaches 650-700 ℃, located near the top of the conductive gripper.
(3) Sintering stage. The coal tar pitch contained in the electrode paste is completely carbonized. The electrical resistivity continuously decreases, and the mechanical strength gradually increases. Basically, the calcination is completed in the middle and lower parts of the conductive gripper. At this time, the electrode paste self calcines and transforms into a carbon electrode. The humidity of the electrode itself reaches 800-900 ℃. Most of the input current into the furnace is introduced through the calcined electrode in the middle and lower parts of the conductive gripper.
Understanding the roasting process of electrode paste in a submerged arc furnace is of great help in the selection of electrode paste materials, as well as the amount and operation of electrode paste addition.