DC submerged arc furnace is the application of direct current to the smelting of the submerged arc furnace. Its main feature is the use of graphite electrodes or self-baking electrodes, and the bottom of the furnace is connected to one pole of the power supply, and the bottom of the furnace is both a conductor and a smelting crucible.
The main heat conduction mechanism of the DC electric furnace is direct and stable unidirectional convection. This heat transfer is superior to that of AC arcs in metallurgical processes. It has applications in the production of ferrochromium, ferrosilicon, silicon and ferromanganese in I industry.
Compared with the AC submerged arc furnace, the direct current submerged arc furnace has the advantages of simple structure (one electrode is commonly used in small and medium-sized direct current submerged arc furnaces, and the hood part is well sealed, which is convenient for maintenance and flue gas treatment), and the arc is stable (its flicker effect is only 50%~70% of the AC furnace), concentrated power, high thermal efficiency (the center temperature of the DC SAF electrode is high, the heat is concentrated, it is easy to bury the electrode deeply, and the bottom of the furnace is not easy to rise), high power factor (the natural power factor of the DC submerged arc furnace can be up to 0.94~0.96) and other characteristics. And it has the advantages of low smelting power consumption, low electrode consumption (electrode consumption is about 30% to 50% of AC furnace), low operating noise (noise during submerged arc operation is more than 20dB lower than AC submerged arc furnace), and high production efficiency.
Structural characteristics of once-through submerged arc furnace
The structure of DC SAF is basically similar to that of AC submerged arc furnace. The main electrical equipment includes rectifier transformer, rectifier cabinet, high and low voltage electrical equipment and electronic control system.
The main mechanical equipment includes single-phase self-baking electrode or graphite electrode, electrode holder, electrode lifting structure and electrode pressing and releasing device, semi-closed low smoke set, conductive furnace body, hydraulic system, water cooling system, feeding device and smoke exhaust system, etc. .
The self-baking electrode or graphite electrode used in the DC submerged arc furnace is connected with the negative electrode (cathode) of the rectifier, and the “bottom electrode” is connected with the positive electrode (anode) of the rectifier. Hollow electrodes are commonly used on the cathode to add cold fine powder to the end of the electrode to reduce the temperature of the arc zone at the end of the electrode, thereby further reducing the consumption of the electrode.
The special part of the structure of the DC submerged arc furnaces is the conductive bottom and the bottom anode, which are not only the melting crucible, but also an input end of the DC power supply.
The conductive furnace bottom should have good electrical conductivity to reduce power loss; good insulation to ensure safe production and high temperature in the reaction zone; uniform electrical distribution to make the temperature distribution of the smelting molten pool relatively close; long service life, to Reduce downtime maintenance and replacement manufacturing, and obtain higher economic benefits. Therefore, the conductive furnace bottom and its anode technology are the key to the design of the DC reduction furnace.
DC submerged arc furnace can be divided into single electrode, double electrode and three electrode electric furnace.
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