The submerged electric arc furnace principle (heating principle) is: not only uses the heat generated by the resistance of the charge when the current passes through the charge but also uses the heat generated by the arc between the electrode and the charge. Therefore, it is also called an arc resistance furnace.
The submerged arc furnace is made of ore with high resistivity as raw material, and the lower part of the electrode is generally buried in the charge during the working process.
The submerged arc furnace is composed of a power supply system such as a submerged arc furnace transformer, high current conductor (short net), electrode, electric furnace body, cooling system, feeding system, discharging system, dust removal system, etc.
According to the production of different ferroalloy products, the secondary voltage of the furnace transformer should be reasonably adjusted. The feeder line from the low-voltage side of the transformer to the electrode holder is generally called a short grid, which consists of hard busbars, soft busbars, and copper tubes. The layout of the three-phase transformer and the short grid can be divided into positive triangles or inverted triangles.
Design and installation of the length of the conductive busbar should be reduced as much as possible, that is, the transformer should be as close as possible to the submerged arc furnace. The transformer of the large electric furnace can also be composed of three single-phase transformers, and most of the secondary windings complete the delta connection on the electrodes through the short net.
Submerged Electric Arc Furnace Working Principle
The electrode system is the core component of the submerged arc furnace equipment, which consists of electrodes and their holders, lifting mechanisms, and pressing and releasing devices.
Due to the high temperature of the reaction zone in the furnace, the electrode material used must be able to carry a large current and at the same time withstand high temperature, so it is mostly a carbon material electrode. Commonly used electrodes are graphite electrodes, carbon electrodes, and self-baking electrodes.
The self-baking electrode is filled with electrode paste in the iron shell, and the electrode paste is self-baking by the heat generated when the current passes through and the conduction radiation of the furnace heat.
With the consumption of the electrode, the electrode shell should be welded section by section accordingly, and the shell should be filled with electrode paste.
The electrode holder is composed of conductive copper tiles, copper tubes, electrode clamping devices, protective sleeves, cooling water channels, and hanging parts. The sintered state of the paste. The electrode lifting and pressing device hang the whole electrode to adjust the electrode insertion depth. According to the gripping method of the gripper to the electrode, it can be divided into a pressure ring gripper, an electrode combination gripper, and a conical ring gripper.
The electric furnace body consists of a furnace shell, a furnace cover, and a refractory lining. The furnace lining has carbon lining and magnesia lining. In order to prolong the life of the furnace lining, the submerged arc furnace began to use the water-cooled furnace lining, that is, the furnace is built with low thermal resistance refractory materials and equipped with cooling facilities (water cooling furnace wall and strong air cooling furnace bottom).
The cooling system cools the components (including short nets, pressure rings, protective sleeves, furnace shells, fume hoods, and chimneys) that work under high-temperature conditions by passing cooling water through the water separator.
The feeding system adopts a vibrating conveying feeding truck to transport the prepared charge to the feeding port of the submerged arc furnace, or an automatic feeding and batching system are used for remote control. The discharge system includes an opening machine, ladle, etc., among which the opening machine has various forms such as mechanical type, hydraulic type, burn-through device, and so on. The dust removal system generally uses a bag filter.
Submerged Electric Arc Furnace Operation Procedure Principle
The feeding system is intermittently fed into the furnace, and the pounding machine maintains the material surface. The electrode is inserted into the charge for submerged arc operation, and the metal is melted by the energy of the arc and the resistance heat generated when the current passes through the charge.
Molten metal and slag accumulate in the bottom of the furnace and are periodically discharged separately through the tap hole. The molten metal is transported to the mold for pouring, and after cooling, it is processed by finishing and crushing, and the product is put into the finished product warehouse.