The electrode paste broken into pieces in advance is regularly added above the cylinder (500-1500mm in diameter) welded by steel plate. The electrode paste in the cylinder begins to soften and melt under the action of heat, and then the binder coal tar pitch is thermally decomposed to release volatile matter until it is roasted into carbonaceous electrode with good conductivity and high mechanical strength, Depending on the roasted electrode, the current (current density is generally 3 ~ sifcm2) is introduced into the ore thermal power furnace. Due to high temperature oxidation and chemical reaction of furnace charge, the lower end of the electrode is consumed continuously. Therefore, the whole electrode barrel should be lowered regularly, and the upper part of the electrode barrel should be connected with a new barrel timely and the electrode paste should be added.
The self baking process of electrode paste can be divided into three stages
(1) Soften and melt. The temperature of electrode paste rises to 150 ° C, which is plastic flow state, and its position is about 500mm above the conductive gripper( Coal tar pitch is pyrolyzed and volatiles are removed.
(2) The fully softened and semi flowing electrode paste flows along the cross section of the cylinder and fills the gap between the blocks. With the increasing temperature, the binder coal tar pitch in the electrode paste decomposes and escapes the volatile matter. After pyrolysis condensation reaction, the coal tar pitch gradually turns to the binder coke, and the temperature reaches 650-700 ℃ ° C. The position is close to the top of the conductive holder.
(3) Sintering stage. The coal tar pitch contained in the electrode paste is completely coked, the resistivity decreases continuously, and the mechanical strength increases gradually. Basically, the baking part is in the middle and lower part of the conductive gripper. At this time, the electrode paste is self baked and transformed into carbon electrode, and the temperature of the electrode itself reaches 800-900 ℃ ° C. Most of the current input into the furnace is in the middle and lower part of the conductive holder through the baked electrode.
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