Ladle furnace metallurgy means that the ladle refining furnace is used to refine the molten steel melted in the primary smelting furnace (electric arc furnace, open hearth furnace and converter), adjust the temperature of molten steel, buffer the process, and meet the requirements of continuous casting and continuous rolling. A ladle furnace is one of the main pieces of equipment for refining outside the furnace.
Main Functions of Ladle Furnace
1. Make the molten steel temperature rise and keep warm. The molten steel is heated by an electric arc to obtain new heat energy, which can not only add alloy and adjust composition during ladle furnace metallurgy, but also add slag to facilitate deep desulfurization and deoxidation of molten steel. Moreover, the opening temperature of molten steel required by continuous casting can be guaranteed, which is beneficial to the improvement of the quality of the dry cast slab.
2. Argon stirring function. Argon is blown into the molten steel through the permeable brick installed at the bottom of the ladle, and the molten steel has a certain stirring function.
3. Vacuum degassing function. After the ladle is hoisted into the vacuum tank, the steam jet pump is used for vacuum degassing, and the molten steel is stirred by blowing argon at the bottom of the ladle, which can remove the hydrogen content and nitrogen content in the molten steel, and further reduce the oxygen content and sulfur content. Finally, a higher purity molten steel and a material with superior performance are obtained.
For the whole enterprise, the application of a ladle refining furnace can at least increase the following benefits: speed up the production rhythm and improve the overall ladle furnace metallurgy production efficiency. Application areas: Ladle refining furnaces are widely used in industry, steel, metallurgy and other industries.
Dedusting of Refining Furnace
In recent years, due to the development of modern industry, new requirements have been put forward for the quality of steel. Therefore, ladle refining furnaces are almost equipped with converters and electric arc furnaces. In the process of molten steel ladle furnace metallurgy, slag and alloy are added according to the process requirements, so physical changes and chemical reactions occur, resulting in a large amount of flue gas and dust, causing pollution to the working environment and harm to organisms.
In order to make the exhaust gas and dust removal of the refining furnace reach a better effect, the maximum exhaust gas volume, flue gas composition and flue gas temperature shall be determined in the overall design of the equipment according to the conditions of the molten steel refining process. As the basis for pipeline design and dust collector selection. Refining conditions and formation and control of flue gas. Generally speaking, the reduction period is carried out in the electric arc furnace and converter, and now it is completed in the refining furnace.
Therefore, according to the smelting process requirements, the furnace shall be kept at a positive pressure so as to make reducing slag. To control the positive pressure in the furnace, the flue gas is ejected from the electrode hole, the charging port, the furnace door, and the junction of the furnace cover and the ladle. In order to control the smelting atmosphere in the furnace and keep all parts free from smoke, one part is solved by using a special structure in the equipment design, and the other part is to automatically adjust the exhaust gas inside and outside the furnace through the action of water-cooled flap valve according to the pressure change in the furnace, so that the pressure in the furnace is basically kept within the range.
Compared with the electric arc furnace and converter, the flue gas volume of the refining furnace is relatively small. In the past, it was mainly determined by the amount of flue gas generated during the reduction period of the electric arc furnace. However, the exhaust gas of the electric arc furnace is mainly combined with the exhaust gas inside and outside the furnace. However, almost all refining furnaces use exhaust gas outside the furnace, which does not affect the temperature change in the furnace. At the same time, the flue gas temperature in the pipeline is low due to the external air. The furnace cover exhausts smoke.
Nature of Flue Gas
The temperature of flue gas is important data for the design of flue gas purification of refining furnaces, especially when the bag-type dust collector is used as the purification equipment, the temperature of flue gas entering the bag-type dust collector should not be too high due to the temperature resistance of filter cloth. Generally, it is cooled by mixing cold air. If the temperature is too high, the mixed wild air volume is large, and the capacity of the dust collector and the fan must also be increased.
Since the electrode hole and the ladle mouth are integrated into the structure, it belongs to a way of smoke exhaust outside the furnace. Unlike the smoke exhaust system inside the furnace, the water-cooled pipe and the smoke cooling system are not used to ensure that the temperature of the flue gas entering the bag filter does not exceed the service temperature. If polyester fiber flannel is used, the temperature of the flue gas cannot exceed the service temperature.
Therefore, in general, the exhaust pipe from the exhaust hood to the front of the dust collector is used for heat dissipation and cooling, and no other measures are adopted. Under normal conditions, the cooling requirements can be met. In order to prevent the temperature of the flue gas from rising instantaneously when the molten steel is boiling, and the flue gas entering the bag is too high to burn the filter cloth, a wild air valve and a cut-off valve are installed in the pipeline during the design. When the flue gas temperature in front of the dust collector exceeds, the wild air valve is automatically opened to add the wild air, and the cut-off valve can be closed at the same time to protect the bag from burning.
The dust particle size is fine. During the ladle furnace metallurgy process, the dust particle size produced is small, which is not easy to agglomerate, but has strong adhesion. The dust particles in the soot are high. The concentration of smoke and dust is high. After the slag is added, at the initial stage when the ladle is just covered and the arc is sent, at the later stage when the slag is melted and heated. The flue gas is corrosive. The flue gas contains gas, which will be strongly corrosive in the case of water.
According to the above analysis of smoke and dust characteristics, combined with specific conditions, the way of adopting a bag-type dust collector is relatively common. Because of its high efficiency, stability, simple operation and management, the dust removal effect can fully meet the national emission standards. The working environment of on-site operators can be further changed by collecting the dust from the three electrode holes of the ladle refining furnace and the ladle mouth. The combination of electrode hole smoke exhaust and ladle mouth smoke exhaust can achieve the required smoke temperature for entering the bag filter without mixing wild wind. Through the analysis and calculation of the smoke exhaust characteristics of the ladle furnace metallurgy, the basis is provided for the rational design of the structure of the dust cover and the selection of the cloth bag, which can greatly reduce the motor power of the furnace dust removal fan and improve the economic index of the equipment.
Operating Procedures
Before work, check whether the interlocking protection device and travel switch of the ladle car are safe and reliable.
Check the vacuum system, oxygen blowing, hydrogen blowing, thermal insulation, heating, feeding and other mechanical parts, and start the machine only after it is confirmed to be safe and reliable.
- Check whether the sample spoon and sample mold are kept dry.
- Check whether the station tools used are easy to use.
- Contact the power supply unit and vacuum control room as required.
- Ring the bell or turn on other safety signals before starting.
- Conduct high-voltage power transmission and vacuum degassing according to the procedure.
- When the ladle car is started, the track must be checked and obstacles must be removed at any time.
- It is forbidden to pass under the high-voltage line after power transmission.
- When connecting and unloading the pressure pipe joint, the valve must be closed before operation.
- When using oxygen, it is strictly prohibited to hold it in front of the chuck and wear greasy gloves for operation.
- After sampling, the remaining molten steel shall be poured into a dry place.
- When the vacuum is removed, all personnel are not allowed to approach the air supply pipe orifice.
- For inspection and maintenance, when it is necessary to mount the heating bridge for operation, the high-voltage key must be pulled out, the high-voltage power supply must be cut off, and the operator shall bring the key with him.
- Special personnel shall be assigned to direct the lifting and replacement of electrodes. The lifting ring and the hook shall be connected with steel wire rope, and the hook safety shall be closed. It is strictly prohibited to open the three phases at the same time for lifting and replacement.
- Objects shall not be stacked on the furnace cover and bridge. It is prohibited to throw objects up and down when working on the bridge.
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