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What is Ladle Refining Furnace?

ladle refining furnace

Ladle refining furnace refers to the equipment with the function of heating and refining of steel-making furnace. It is important metallurgical equipment used to refine the molten steel melted in the primary smelting furnace (electric arc furnace, open-hearth furnace, and converter), adjust the molten steel temperature, and buffer the process, so as to 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.

Ladle refining furnace’s main functions

1. Ladle refining furnace has the function of raising the temperature of molten steel and heat preservation. Liquid steel is heated by an electric arc to obtain new heat energy, which can not only add alloy and adjust composition, but also add slag during ladle refining, which is convenient for deep desulfurization and deoxidation of liquid steel. Moreover, the start pouring temperature of liquid steel required by continuous casting is guaranteed, which is conducive to the improvement of dry slab quality.

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 obtains a certain mixing function.

3. Vacuum degassing function. After the ladle is lifted into the vacuum tank, the steam jet pump is used for vacuum degassing, and argon is blown into the ladle bottom to stir the liquid steel, which can remove the hydrogen content and nitrogen content in the liquid steel, further reduce the oxygen content and sulfur content, and finally obtain the liquid steel with high purity and materials with superior performance.

For the whole enterprise, the application of the LF ladle refining furnace can at least increase the following benefits: speed up the production rhythm and improve the efficiency of the whole metallurgical production. Application: ladle refining furnace is widely used in industry, steel, metallurgy and other industries.

Dedusting of ladle refining furnace boiler

In the 21st century, due to the development of modern industry, new requirements are 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 refining, slag and alloy are added according to the process requirements, resulting in physical changes and chemical reactions, resulting in a large amount of flue gas and dust, causing pollution to the working environment and biological harm.

In order to make the refining furnace smoke exhaust and dust removal achieve ideal results, the maximum smoke exhaust volume, smoke composition, and smoke temperature shall be determined according to the molten steel refining process conditions and the overall design of the equipment 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 electric arc furnaces and converters, and now it is completed in a ladle refining furnace. Therefore, according to the smelting process requirements, the positive pressure is maintained in the furnace in order to make reduction slag. To control the positive pressure in the furnace, the flue gas is ejected from the electrode hole, charging port, furnace door and the joint between the furnace cover and the ladle.

In order to control the smelting atmosphere in the furnace and keep all parts free of smoke, one part is solved by using special structure in the equipment design, and the other part is to automatically adjust the smoke exhaust inside and outside the furnace through the action of water-cooled flap valve according to the pressure change in the furnace, so as to keep the pressure in the furnace basically within the range. The amount of flue gas in the ladle furnace is relatively less than that in the electric arc furnace and converter.

In the past, it was usually determined according to the amount of flue gas generated during the reduction period of the electric arc furnace. The exhaust gas of the electric arc furnace was mainly a combination of the exhaust gas inside and outside the furnace. Almost all refining furnaces use smoke exhaust outside the furnace, which does not affect the change of temperature in the furnace. At the same time, due to attracting external air, the flue gas temperature in the pipeline is low. The furnace cover is used for smoke exhaust.

Ladle refining furnaces’ flue gas properties

Flue gas temperature is important data for the design of ladle refining furnace flue gas purification. Especially when the purification equipment adopts bag-type dust collectors, due to the temperature resistance conditions of filter cloth, the flue gas temperature entering the bag-type dust collector should not be too high, which is generally 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 fan must also be increased.

As the structure adopts the integration of the electrode hole and the ladle mouth for smoke exhaust, it belongs to a way of smoke exhaust outside the furnace. Unlike the smoke exhaust system in the ladle me furnace, the water-cooled pipe and smoke cooling system are not used to ensure that the flue gas temperature entering the bag filter does not exceed the service temperature. If polyester flannelette is used, the flue gas temperature cannot exceed the service temperature. Therefore, generally, 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, it can meet the cooling requirements.

In order to prevent the flue gas temperature from rising instantaneously when the molten steel boils, so that the flue gas entering the bag is too high and the filter cloth will be burned out, therefore, the wild air valve and block valve are installed in the pipeline in the design. When the flue gas temperature in front of the dust collector exceeds, the wild air valve will be automatically opened and mixed with wild air, and the block valve can be closed at the same time to protect the bag from burning out.

The particle size of smoke and dust is fine. In the process of furnace smelting, the particle size of smoke and dust produced is very small, which is not easy to agglomerate, but has strong adhesion. The flue gas contains corrosive gas, which has strong corrosivity in the case of water. According to the analysis of the above smoke and dust characteristics and combined with the specific situation, the way of using bag filters is relatively common. Because of its high efficiency, stability, simple operation and management, the dust removal effect can fully meet the national emission standard. The working environment of field operators can be further changed through the collection of smoke and dust from three-electrode holes and the ladle mouth of the ladle refining furnace. The combination of electrode hole smoke exhaust and ladle mouth smoke exhaust is adopted, and the smoke temperature required for entering the bag filter can be reached without mixing wild wind. The analysis and calculation of the smoke exhaust characteristics of the furnace, provide a basis for the reasonable design of the structure of the dust removal cover and the selection of cloth bags, and can greatly reduce the motor power of the ladle furnace dust removal fan and improve the economic index of the equipment.

Operating procedures editing and broadcasting

1. Before work, check whether the interlocking protection device and travel switch of the ladle car are safe and reliable.

2. Check the vacuum system, oxygen blowing, hydrogen blowing, heat preservation, heating, feeding and other mechanical parts, and start the machine only after confirming that it is safe and reliable.

3. Check whether the sample spoon and sample mold are kept dry.

4. Check whether the station instruments used are easy to use.

5. Contact the power supply unit and vacuum control room as required.

6. Ring the bell or turn on other safety signals before driving.

7. Conduct high-voltage power transmission and vacuum degassing according to the procedure.

8. When starting the ladle car, the track must be checked and obstacles must be removed at any time.

9. It is forbidden to pass under the high-voltage line after power transmission.

10. When connecting and unloading pressure pipe joints, the valve must be closed before operation.

11. When using oxygen, it is strictly prohibited to hold hands in front of the card head and wear greasy gloves for operation.

12. After sampling, the remaining molten steel shall be poured into a dry place.

13. When releasing the vacuum, all personnel are not allowed to approach the air supply pipe orifice.

14. For inspection and maintenance, when it is necessary to board 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 his own key.

15. When lifting and changing electrodes, special personnel shall be assigned for command. The lifting ring and the hook shall be connected by steel wire rope. Close the hook safety. It is strictly prohibited to open the three phases at the same time and change them together.

16. Objects shall not be stacked on the furnace cover and bridge. It is strictly prohibited to throw objects up and down when working on the bridge.

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