One principle use
Submerged arc furnace is also called electric arc furnace or resistance electric furnace. It is mainly used to reduce raw materials such as smelting ores, carbonaceous reducing agents and solvents. It mainly produces ferrosilicon, ferromanganese, ferrochromium, tungsten, silicomanganese and other ferroalloys, which are important industrial raw materials in the metallurgical industry and calcium carbide and other chemical raw materials. Its working characteristic is to use carbonaceous or magnesia refractory materials as furnace lining, and use self-cultivating electrodes (electrode paste or airtight paste). The electrode is inserted into the furnace charge for submerged arc operation. It uses the energy and current of the electric arc to pass through the charge. The energy is generated by the charge resistance to smelt the metal. The charge is added one after another, and the iron slag is intermittently tapped. It is an industrial electric furnace that acts continuously.
Main categories and uses of submerged arc furnaces
| category | main ingreadient | manufactures | Reflecting temperature | Power consumption | ||
| 0℃ | KW*h/t | |||||
| Ferroalloy furnace | Ferrosilicon furnace | (45%) Ferrosilicon | Ferrosilicon,scrap iron, coke | Ferrosilicon | 1550-1770 | 2100-5500 |
| (75%) Ferrosilicon | 8000-11000 | |||||
| Ferromanganese furnace | Manganese ore, scrap iron, coke, lime | Ferromanganese | 1500-1400 | 2400-4000 | ||
| Ferrochrome furnace | Chrome ore, silica, coke | Ferrochrome | 1600-1750 | 3200-6000 | ||
| Tungsten furnace | Tungsten crystal ore, coke | Ferro Tungsten | 2400-2900 | 3000-5000 | ||
| Silicon chromium furnace | Ferrochromium, silica, coke | Silicon chromium alloy | 1600-1750 | 3500-6500 | ||
| Silico-manganese furnace | Manganese ore, silica, scrap iron, coke | Silicomanganese alloy | 1350-1400 | 3500-4000 | ||
| Steelmaking electric furnace | Iron ore, coke | pig iron | 1500-1600 | 1800-2500 | ||
| Calcium carbide furnace | Limestone, coke | Calcium carbide | 1900-2000 | 1900-3000 | ||
| Boron carbide furnace | Boron oxide, coke | Boron carbide | 1800-2500 | -20000 |
Industrial waste heat refers to the large amount of waste heat generated in the industrial production lines of steel, petrochemical, building materials, and non-ferrous metals. The waste heat power generation technology refers to the technology that uses the high-grade heat of the enterprise to recover and convert it into electric power for the enterprise’s own use. my country has always taken the use of waste heat power generation as one of the important measures to save energy and reduce consumption and realize cyclical development, and has given strong support. At present, the application field of waste heat power generation technology in my country is continuously expanding. However, in the fields of ferroalloy and calcium carbide, flue gas waste heat and other The waste heat comprehensive recovery power generation technology is still lacking.
A few days ago, the submerged arc furnace waste heat recovery and utilization technology program seminar was held in Beijing. Leaders and experts from the National Energy Office, the Central Iron and Steel Research Institute, the National Development and Reform Commission and various industry associations discussed the development by Xi’an Reach Energy Engineering Technology Co., Ltd. Waste heat power generation technology for ferroalloy, calcium carbide and other fields. The waste heat recovery power generation in ferroalloys, calcium carbide and other fields has been ignored because of its large volume and wide coverage. This technology fills this gap, improves the waste heat recovery rate and reduces the cost.
At present, energy conservation and emission reduction have become my country’s basic national policy, and the ferroalloy industry is a typical high-energy-consuming industry. The promotion of waste heat recovery power generation technology in this industry is conducive to reducing enterprise energy consumption and improving energy efficiency. Not long ago, the three national ministries and commissions issued a document to cancel the preferential electricity prices for high-energy-consuming enterprises, and the preferential electricity prices for the ferroalloy industry have been cancelled since October 20, 2007. In the case of increased electricity costs, the investment payback period of ferroalloy enterprises’ waste heat recovery power generation projects will be further shortened, and the technology will have better development prospects.
Fume collection and waste heat recovery 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. Before the 1950s, open fixed electric furnaces (figure 1a ferroalloy reduction electric furnaces) were generally used. With the improvement of environmental protection requirements and the progress of waste heat utilization technology, closed electric furnaces (figure 1b ferroalloy reduction electric furnaces) or short smoke were used for different products. Cover, semi-enclosed electric furnace (Figure 1c ferroalloy reduction electric furnace). The rotation of the furnace body can eliminate the suspended material, reduce the “thorn fire” of crusts, 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) generally ranged from a few hundred to ten thousand kVA before the 1950s, and then gradually developed to large-scale development. In the 1970s, the newly-built electric furnaces were generally 20,000 to 40,000 kVA, the largest enclosed 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 adjustable opening operation door under the hood to control the amount of air drawn and the temperature of the flue gas.
The electrode system widely uses continuous electrode paste sintered self-baked electrodes, the largest diameter can reach 2000 mm, and some are hollow. The continuous self-baking electrode is composed of a thin steel plate electrode shell and an 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 the electrode paste shall be filled into the shell. The electrode holder is composed of a contact cheek (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 state. The electrode lifting and pressure release device hangs the entire electrode to adjust the electrode insertion depth. Rongxin Carbon Electrode Paste Hermetic Paste is a self-baking electrode material widely used by alloy plants. The production of electrode paste is an activity with simple technology but complex process. Therefore, for the production of various raw materials in the control room, the production of Rongxin electrode paste closed paste is automatically controlled by the central computer, and the ratio of raw materials The error can reach 0.2%, so the quality of the finished electrode paste is very stable.
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 windings of large electric furnace transformers complete the delta connection on the electrodes through short nets. The entire network is composed of hard bus harnesses, soft bus harnesses and copper pipes.
Refining electric furnace is used for refining medium-carbon, low-carbon and micro-carbon ferroalloys. The capacity of the electric furnace is generally 1500～6000 kVA, and it adopts open fixed or tilting mode 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 Furnace Gas Purification A large amount of coal gas is produced during the production process of ferroalloy reduction electric furnace. When producing with an open electric furnace, the coal gas burns into flue gas when it encounters air, which is large and dusty. It is difficult to purify and is not conducive to energy recovery. It will pollute the environment for a long time, cause public hazards and cause energy loss. Since the 1970s, in order to protect the environment and save energy, ferroalloy reduction electric furnaces have gradually changed from open electric furnaces to closed or semi-closed electric furnaces. A closed electric furnace is used for smelting ferromanganese, ferrochrome and other ferroalloys, and a semi-closed electric furnace is used for smelting ferroalloys (ferrosilicon, metallic silicon, etc.) that require surface operation.
The closed electric furnace is equipped with a sealed furnace cover and an explosion venting device, and the produced gas is led out in an unburned state, and then introduced into the gas purification facility for purification and recovery. The gas generation process is continuous and stable, and the gas volume is only 1 to 2% of the flue gas volume of the open electric furnace. Therefore, the gas purification equipment is small, the combination is simple, and the purification* is convenient. Gas purification generally adopts wet process. Coal gas contains CO, H□, CH□ and other effective fuel components that account for about 80% of the gas volume, mainly CO, with a calorific value of 2100-2400 kcal/standard meter □.
In order to control the flue gas of the ferrosilicon electric furnace, the high fume hood of the open electric furnace was changed to a low fume hood at first, and later developed into a semi-enclosed electric furnace. The development process is shown in Figure 2 for the development process of flue gas treatment of open ferroalloy electric furnace.
It can control the amount of flue gas to facilitate purification and heat recovery. When the waste heat boiler is installed, the recovered heat can reach 30% of the total energy consumption of the electric furnace or 65% of the total power consumption. For example, it can recover about 20% of the electric energy for power generation. The flue gas purification generally adopts a dry process.
Two structural characteristics
Submerged arc furnace is a kind of industrial electric furnace that consumes huge power. Mainly consists of furnace shell, furnace cover, furnace lining, short net, water cooling system, smoke exhaust system, dust removal system, electrode shell, electrode pressure release and lifting system, loading and unloading system, controller, burning through device, hydraulic system, submerged arc furnace Transformers and various electrical equipment, etc.
The submerged arc furnace is divided into three layers
The first layer is composed of furnace shell, furnace lining, tapping system, burn-through device, etc.
Second floor
(1) Furnace cover. Most modern human-shaped submerged arc furnaces adopt a closed type with a sealed furnace cover. Adopting this structure can collect the exhaust gas (mainly carbon monoxide) produced in production and comprehensively utilize it, and can reduce the heat loss of the circuit, lower the temperature of the upper part of the electrode, and improve the operating conditions.
(2) Electrode holder. Most submerged arc furnaces are powered by three-phase power and are arranged in the middle of the furnace in a symmetrical position of a regular triangle. Large-scale submerged arc furnaces generally use electrode materials mixed with anthracite, coke and pitch kerosene, and self-grown electrodes burned during the working process of the electric furnace.
(3) Short network
(4) Copper tiles
(5) Electrode shell
(6) Cutting system
(7) Stove machine
(8) Smoke exhaust system
(9) Water cooling system
(10) Submerged arc furnace transformer
(11) Operating system
the third floor
(1) Hydraulic system
(2) Electrode pressure release device
(3) Electrode lifting system
(4) Steel platform
(5) Hopper and circular distributing vehicle
Other accessories; skew bridge feeding system, electronic batching system, etc.
Three various technical parameters
| Transformer capacity (KVA) | 12500 | 16,500 |
| Shell diameter (mm) | 7800 | 8000 |
| Furnace shell height (mm) | 4300 | 4200 |
| Hearth diameter (mm) | 6200 | 6400 |
| Furnace depth (mm) | 2200 | 1900 |
| Diameter of polar center circle (mm) | 2800±100 | 2800-3000 |
| Electrode diameter (mm) | 1050 | 1100 |
| Electrode current density (A/cm 2 ) | 5.95 | 6.15 |