Requirements for electrodes of submerged arc furnace
Taking electric energy as the main heat source, mining reduction electric furnace (submerged arc furnace), reducing ore with carbon as reductant, and producing deoxidizer and alloying agent required by iron and steel industry is the process of ferroalloy production in submerged arc furnace. The high temperature and heat energy required for the production of ferroalloys are usually converted after the electric energy is sent into the furnace through the self baking electrode. Self baking electrode is the basic condition and premise of smelting ferroalloy in submerged arc furnace.
In view of the continuous operation of high-temperature production, the submerged arc furnace usually operates continuously for several years. Therefore, the self baking electrode of the electric furnace is required to be able to transmit power continuously. The quality, performance, roasting technology and conditions of electrode paste should meet the technical requirements of production.
2.1 preparation process of self baking electrode
The self baking electrode is made of anthracite, coke, asphalt and coke as raw materials, mixed according to a certain proportion of particle size, stirred and kneaded at an appropriate temperature, pressed into shape and cooled into paste. When in use, small pieces of electrode paste are loaded into the electrode shell of the submerged arc furnace. In the production process, it is self sintered and coking by relying on the Joule heat generated when the current passes through and the heat conduction in the furnace. The electrode can be continuously shaped while being used, connected and sintered, and different diameters are configured according to the capacity of the electric furnace. Self baking electrode is widely used in ferroalloy production because of its simple process and low cost.
2.2 raw materials for preparing electrode paste
The raw materials for making electrode paste are composed of solid carbon materials and bonding materials. The quality of electrode paste is related to the raw material formula and preparation process. Solid materials include calcined anthracite, metallurgical coke, petroleum coke and graphite electrode debris. Anthracite is dense with high carbon content, which can improve the thermal stability, conductivity and mechanical strength of the electrode; The binder of electrode paste includes asphalt and refined tar. Tar is added to adjust the softening point. During the sintering process of electrode paste, the binder decomposes and removes volatiles, and then turns into coke for coking, which makes the electrode line into a rigid whole. The formula of electrode paste should consider the proportion of various solid materials, particle size composition, softening point and addition amount of binder.
2.3 classification and performance of electrode paste
Electrode paste can be divided into standard paste and sealed paste due to different uses. The former is mostly used in semi closed submerged arc furnace; The latter is often used in closed electric furnaces and large capacity semi closed electric furnaces because of its low roasting temperature and easy sintering. Most of the solid materials in the standard paste are anthracite and metallurgical coke, while the solid materials in the closed paste need a large amount of graphite chips and petroleum coke. The binder in the standard paste is mostly medium temperature asphalt, while the binder in the sealed paste uses a lot of tar and more graphite chips. Special sealed electrode paste, which is favored by ferronickel smelting enterprises in submerged arc furnace, has significantly increased the amount of tar and graphite chips. The high price of graphite chips and tar is the main reason for the high price of sealed paste, especially super dense paste.