Submerged arc furnace process is that the submerged arc furnace is intermittently fed into the furnace through the feeding device, the stoking machine maintains the material surface, the liquid alloy flows into the ladle and other containers, and then transported to the mold for pouring, and the finished product is formed after cooling. The iron slag is discharged intermittently through the slag outlet.
Main equipment of submerged arc furnace
The submerged arc furnace process equipment is mainly composed of furnace body, furnace cover, short net, water cooling system, smoke exhaust system, dust removal system, waste heat treatment system, electrode shell, electrode pressing and lifting system, loading and unloading system, controller, burn-through device , hydraulic system, submerged arc furnace transformer and various electrical equipment and other components.
The electric furnace body consists of a furnace shell and a refractory lining.
The furnace shell is composed of furnace bottom plate, furnace wall plate, hoop and rib plate. The furnace shell adopts a circular structure, the side plate of the furnace shell adopts a thick steel plate, and the support is a channel steel framed on concrete.
The lining of the electric furnace uses high alumina, magnesia, and carbon refractory materials;
First-grade magnesia bricks and magnesia materials are used near the furnace outlet, combined with refractory materials such as carbonaceous silica bricks.
Furnace shell requirements: The strength should be able to meet the severe expansion of the furnace lining caused by heating, adapt to the requirements of thermal expansion and cooling of the furnace lining, and strive to save materials and facilitate manufacturing.
A tap hole is integrated on the furnace shell.
The furnace cover of the sealed furnace is built with refractory bricks and refractory materials with water-cooled steel beams as the skeleton.
The three electrode holes on the top of the furnace cover mainly allow the three-phase electrode holder to pass through the furnace, and use insulating materials to insulate the electrode holder from the furnace cover.
There are 9 thermometer sockets on the furnace cover, which are inserted into the refractory bricks with protective tubes. Insert the thermometer into the protective tube to measure the temperature of the furnace steam in the furnace cover.
The function of the fume hood is to close the furnace mouth, block the radiant heat, collect the flue gas produced during the smelting reaction, and improve the operating environment.
The fume hood is composed of cover plate, side wall, furnace door, fume hood skeleton and so on. The fume hood is a hexagonal shape formed by welding steel plates and profiles. Sit on the operating platform through the hood skeleton.
Flue gas outlet pipe
The function of the flue gas outlet pipe is to rely on the natural pressure difference or the fan of the dust collector to form a negative pressure in the low fume hood, so as to discharge the smoke outward.
Each electric furnace is provided with 2 flues, and the flues are made of steel plates and profiles. The flue is composed of a lower water cooling section, a flue pipe section, a bell valve and a flue hanging.
The water-cooled section at the lower part of the flue is seated on the beam ring of the short smoke hood, and it is cooled by water.
The smoke pipe section is divided into several sections, which lead directly to the outside of the house. There is a bell valve on the flue opening outside the roof, and the bell valve is used to close the flue.
The bell valve is opened and closed by the flue oil cylinder. When the dust collector needs to be connected, the bell valve is closed, and the flue gas is sent to the dust collector through the three-way under the action of the fan.
The electrode holder is the core equipment of the submerged arc furnace. It is composed of a conductive device, a holding device, a pressing and releasing device, a lifting device, a holding cylinder and an electrode shell.
The electrode holder mainly uses the holding device to make the copper tile stick to the motor shell under suitable pressure to ensure that the large current from the short network passes through the collector ring or the collector support of the electrodeless electric ring, and the electric copper tube passes through the copper wire. watts to the electrodes.
Hold the barrel
The holding cylinder is one of the important components in the holding system. The holding cylinder, also known as the electrode outer cylinder, is used to suspend the electrode holder and the electrode, and can lift the electrode during operation.
Traditional conductive devices generally include slip rings, conductive copper pipes and copper tiles.
The collector ring mainly plays the role of equalizing the voltage, collecting the current, and then distributing it to the conductive copper tube, so that the current of each copper tile on each electrode is basically equal, and the copper tile sends the electrical energy to the main components of the electrode.
The copper tile is cast with red copper, and there is a cooling water pipe inside. The allowable current density of the copper tile and the electrode contact surface is in the range of 0.9~2.5A/cm2.
The height of the copper tile is approximately equal to the electrode diameter, and the number of copper tiles can be calculated according to the current of each phase electrode.
The electrode sintering belt is the weak link of the entire electrode strength. The holding force of the copper tile to the electrode is 0.05~0.15MPa, and the contact pressure comes from the electrode holder.
Electrodes with combined holders help improve electrode sintering.
Electrode lifting device
The electrode lifting device can change the electrode position by lifting and lowering the electrode, adjust the electrode arc length to adjust the resistance, and achieve the purpose of adjusting the current size.
The electrode lift speed varies with the furnace power. Generally, when the electrode diameter is greater than 1m, the electrode lifting speed is 0.2~0.5m/min, and when it is less than 1m, it is 0.4~0.8m/min. The electrode lifting stroke is 2.1~2.6m.
Short net system for submerged arc furnace process
A short network is a device that transmits low-voltage, high-current electrical energy. In order to enable it to effectively input the energy taken from the grid into the SAF, considering the configuration of a reasonable short grid structure, selecting an appropriate short grid current density has a great effect on obtaining good power operation indicators and saving non-ferrous metal consumption. economic significance.
The main function of the short network is to transmit large current, so the reactance and resistance in the short network account for a large proportion of the entire line, which is enough to determine the electrical characteristics of the entire equipment. Therefore, the following basic requirements must be met:
(1) There is sufficient current carrying capacity.
(2) Reduce the short-circuit resistance as much as possible.
(3) The inductive reactance value of the short network should be small enough.
(4) It has good insulation and mechanical strength.
Short network compensation
70% of the reactance of the SAF system is generated by the short network system. For this reason, the natural power factor of the submerged arc furnace is difficult to reach above 0.85. The natural power factor of most furnaces is between 0.7 and 0.8. The lower power factor not only reduces the efficiency of the transformer, consumes a lot of useless work and wastes a lot of power, but also imposes extra power fines by the power department.
Due to the manual control of the electrodes and the stacking process, the power imbalance between the three phases increases, and the highest unbalance can reach more than 20%, which leads to low smelting efficiency and high electricity bills. Unbalanced power grid has become an effective means to reduce energy consumption and improve smelting efficiency.
High voltage power supply system
The high-voltage power supply system consists of high-voltage incoming line isolating switches and voltage transformers, high-voltage vacuum circuit breakers and current transformers, zinc oxide arresters and resistance-capacitance absorption protection devices, which constitute high-voltage incoming line cabinets, vacuum switch cabinets, oxidation arresters and resistance-capacitance protection cabinets .
The high-voltage power supply system can provide the main power supply to the electric furnace, and can perform short-circuit protection of the main circuit. An overvoltage absorption device is set in the high-voltage circuit to absorb the operating overvoltage and surge voltage to protect the transformer.
The zinc oxide arrester is used for lightning protection, and the incoming line disconnect switch is convenient for debugging and maintenance.
Cooling water system
The water supply system sends the water to the high platform, and then the water cooling system cools the short net, water-cooled hood, water-cooled chimney, pressure ring, copper tile, water-cooled large jacket, etc. through the water distributor.
The other way sends water into the strong oil water cooling device of the transformer to cool the transformer.
Main spare parts
1) Refractory materials for building furnaces;
2) Electrode paste;
3) Transformer rails and fasteners;
4) Hydraulic medium;
5) Copper tile;
6) Water cooling cable;
The above is the knowledge about the submerged arc furnace process. I believe we all know better. For more professional information about smelting furnace equipment, please pay more attention to the news on our website.
If you have any other questions, or need submerged arc furnaces, electric arc furnaces, ladle refining furnaces and other melting furnaces, please feel free to contact us at Hani Metallurgy.