Classification of ferroalloy electric furnace

The main equipment for smelting ferroalloys. Ferroalloy electric furnaces are divided into reduction electric furnaces and refining electric furnaces.

 Reduction electric furnace, also known as submerged arc electric furnace or submerged arc electric furnace, adopts the submerged arc operation in which the electrode is inserted into the charge. The reduction electric furnace is open, closed (or semi-closed), and the furnace body has various forms such as fixed and rotating.

The refining electric furnace is used for refining medium-carbon, low-carbon and micro-carbon iron alloys. The capacity of the electric furnace is generally 1500 ~ 6000 kVA, and it adopts open fixed or tilting with cover. The former is similar to a reduction electric furnace and can be equipped with continuous self-baking electrodes; the latter is similar to an electric arc steelmaking furnace and uses graphite or carbon electrodes.

Ferroalloy electric furnaces are divided into reduction electric furnaces and refining electric furnaces.

Reduction electric furnace

Also known as submerged arc electric furnace or submerged arc electric furnace,the electrodeis inserted into the furnace charge and the open fixed electric furnace is adopted. With the improvement of environmental protection requirements and the progress of waste heat utilization technology, closed electric furnaces or low smoke hoods are used for different products. Semi-closed electric furnace,the rotation of the furnace body can eliminate the suspended material, reduce the "stab fire" of the encrustation, make the cloth uniform, and expand the reaction zone to facilitate the smooth flow of the furnace.

Electric furnace capacity (referring to the capacity of electric furnace transformers in ferroalloy production, measured in kilovolt amperes, used to mark the capacity of electric furnaces) before the 1950s generally ranged from a few hundred to ten thousand kilovolt-amperes, and then gradually developed to large-scale. In the 1970s, the newly-built electric furnaces were generally 20,000 to 40,000 kVA, the largest closed furnace reached 75,000 kVA, and the largest semi-closed furnace reached 96,000 kVA.

Modern ferroalloy electric furnaces are generally circular furnace bodies equipped with three electrodes. Large-scale ferromanganese electric furnaces have rectangular multi-electrodes. Some large-scale ferrosilicon electric furnaces are equipped with a rotating mechanism, and the furnace body rotates in a horizontal direction or swings back and forth at a speed of 360° for 30 to 180 hours. The closed electric furnace is provided with a sealed furnace cover, and the semi-closed electric furnace is provided with an operating door with adjustable opening degree under the hood to control the amount of air drawn in and the temperature of the flue gas.

The electrode system widely uses continuous self-baking electrodes,the largest diametercan reach 2000 mm, and some are hollow. The continuous self-baking electrode is composed of a thin steel plate electrode shell and electrode paste. During operation, the electrode paste is self-baked by the heat generated when the current passes through and the conduction radiation of the furnace heat. As the electrode is consumed, the electrode shell should be welded section by section and filled with electrode paste.

The electrode holder is composed of a contact cheek plate (conductive copper tile), a copper tube, a holding ring and other components. Its function is to transmit current to the electrode and clamp the electrode at a certain height. It can also adjust the sintering of the electrode paste status. The electrode lifting and pressure release device hangs the whole electrode to adjust the electrode insertion depth.

The feeder line from the low-voltage side of the transformer to the electrode holder is generally called a short network, which is a section of a large cross-section conductor used to transport large currents into the furnace. Most of the secondary windingsof large electric furnace transformers complete the delta connection on the electrodes through short nets. The whole network is composed of hard bus wire harness, soft bus wire harness and copper pipe.

Refining electric furnace

Used for refining medium-carbon, low-carbon and micro-carbon iron alloys. The capacity of the electric furnace is generally 1500 ~ 6000 kVA, and it adopts open fixed or tilting with cover. The former is similar to a reduction electric furnace and can be equipped with continuous self-baking electrodes; the latter is similar to an electric arc steelmaking furnace and uses graphite or carbon electrodes.