JPS621814A - Method and apparatus for heating vacuum degassing device - Google Patents

Abstract

PURPOSE:To heat a degassing device for a blow-up type vacuum refining method with a simple installation without the wasteful loss of energy by using a burner provided to a degassing vessel and the waste combustion gas thereof to heat the above-mentioned vacuum degassing device. CONSTITUTION:A molten steel in a ladle 1 is lifted into the degassing vessel 4 above said ladle from an immersion pipe 2 in the lower part of the vessel and the molten steel is degassed under the reduced pressure. Fuel is supplied through a piping 6 to the burner 5 in the upper part of the vessel 4 and the O2-enriched air mixed with air and O2 from pipings 14, 15 is supplied into the burner so as to be burned by the burner prior to the above-mentioned treatment. The supply rates of the fuel, air and O2 are controlled by an O2 enriching control device 21, air to fuel ratio setter 10, a thermometer 3, arithmetic controller 22, etc., in accordance with the flow rates of the pipes 6, 14, 15 or the concn. of O2 in the pipe 20 or the temp. in the vessel 4. The inside of the pipe 20 or the temp. in the vessel 4. The inside of the vessel 4 is heated to a target temp. The waste combustion gas is discharged from the top end of the pipe 2 and therefore the need for heating from the pipe 2 is eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a heating method and apparatus for a vacuum degassing apparatus for out-of-furnace refining.

[Prior art]

In recent years, as technology related to the use of steel on the customer side has progressed, demands for reducing gas, nonmetallic inclusions, etc. in steel have increased, and the importance of vacuum degassing refining methods has increased. The expected effects of vacuum refining are decarburization, tax gas, and deoxidation.

Although there are various reasons such as the floating of inclusions, the basic functions of vacuum heating are circulation, stirring, and mixing. In the blow-up vacuum refining method (DLL method, RH method), which is the mainstream vacuum refining method, molten steel is sucked up from the pot into a degassing tank and degassed in the degassing tank, so a large stirring force is required. This is one of the characteristics, but accompanying this, a drop in the temperature of the molten steel during treatment is unavoidable. Therefore, 1. In order to reduce the temperature drop of molten steel during vacuum processing or prevent splash adhesion to the refractories in the tank, it is necessary to preheat the degassing tank before vacuum processing.

For this purpose, conventionally, the inside of the degassing tank was preheated to about 1050° C. by arc discharge using an electrode installed near the top of the tank before treatment.

However, in the above method, the temperature near the electrodes can be raised to a high temperature, but since there is almost no gas convection within the tank, the temperature near the immersion pipe installed at the bottom of the degassing tank is low, and if it is immersed in molten steel during processing, the immersion pipe may damage and a drop in molten steel temperature. Therefore, the immersion tube was preheated by burning fuel gas. As described above, the reality is that heating within the gas tank is performed using two systems of heating equipment, one for electrodes and one for fuel gas.

[Problem that the invention seeks to solve]

In the conventional method as described above, when electricity is stopped, the electrode rod for arc discharge is often damaged due to thermal stress (and must be replaced each time, so it cannot be used before, during, or after treatment. It has the disadvantage that it is necessary to keep the current on at all times, resulting in a lot of unnecessary power loss, and that the electrodes are consumed a lot, making it uneconomical.

In addition, there was a problem in that two systems of heating devices had to be installed in the vacuum degassing equipment.In addition to the above method, a burner was opened at the tip of the immersion tube and the fuel gas was combusted in the burner. There is also a method of heating the inside of the salt gas tank, but this method has the drawbacks that the tip of the immersion tube is severely damaged, and the burner is frequently clogged due to a large amount of metal falling from the degassing tank.

[Means for solving problems]

The present invention was made in view of the above circumstances, and its purpose is to install a burner at the top of a degassing tank, heat the tank by burning fuel from the burner, and remove the combustion exhaust gas. To provide a heating method and device for a vacuum degassing device, which has simpler equipment compared to conventional methods and devices and eliminates unnecessary energy loss by guiding the exhaust gas to the lower part of the degassing tank and discharging the exhaust gas from a immersion pipe. It is in.

The heating method of the vacuum degassing apparatus according to the present invention is to suck up the molten metal in the pot through the immersion pipe at the lower part of the degassing tank above it into the degassing tank, and treating the molten metal with salt gas under reduced pressure. A heating method for a vacuum degassing device is characterized in that a heating combustion burner is provided at the top of the degassing tank, and the burner heats the inside of the tank by combustion, and the combustion exhaust gas is discharged from the immersion pipe. .

〔Example〕

Hereinafter, the present invention will be explained based on drawings showing embodiments thereof. The drawing is a schematic diagram of the apparatus of the present invention, and 4 in the drawing indicates a salt gas tank. The gas tank 4 is provided at its lower part with a dip pipe 2 for sucking up molten steel from the ladle 1, which is indicated by a two-dot broken line. Further, a side wall of the salt gas tank 4 is partially opened, and a burner 5 having a double pipe structure whose tip is positioned inside the degassing tank 4 is attached thereto.

The tip of the oxygen-enriched air pipe 20 is open in the outer tube of the burner 5, and the base end of the oxygen-enriched air pipe 20 is open to the air pipe 1.
4 and oxygen pipe 15, and the air pipe 1
The base end side of the oxygen pipe 15 is connected to an air source (not shown), and the base end side of the oxygen pipe 15 is connected to an oxygen source (not shown).

An oxygen concentration output meter 19 is provided in the middle of the oxygen enriched air pipe 20 to measure the oxygen concentration, and this output signal is input to the oxygen enrichment control device 21. In the oxygen enrichment control device 21, the oxygen concentration is set based on the theoretical value of the amount of oxygen to maintain the temperature inside the tank at the target value, and the oxygen enrichment control device 2
1, an oxygen amount instruction signal is transmitted to the oxygen flow rate indicating regulator 18, and a controlled oxygen concentration signal is transmitted to the arithmetic controller 22.

In the middle of the air piping 14, a flow meter 12 is installed in order from the air source side.
, an air supply N adjustment valve 13 is attached, the flow rate of the air sent from the air source is adjusted by the valve 13, and the flow rate is sent to the meter by a flow meter 12.

The output of the flow meter 12 is given to the air flow rate indicating regulator 11, and the air flow rate indicating regulator 11, based on the air amount signal from the air-fuel ratio setting device 10 and the output signal of the flow meter 12, The opening degree of the valve 13 is adjusted to control the amount of air supplied.

In the middle of the oxygen pipe 15, a flow meter 17 is installed in order from the oxygen source side.
．． An oxygen supply 1 ftm adjustment valve 16 is attached, and the flow rate of oxygen sent from the oxygen source is adjusted by the valve 16, and the flow rate is measured by a flow meter 17.

The output of the flow meter 17 is given to an oxygen flow rate indicating regulator 18, and the oxygen flow rate indicating regulator 18 receives the output signal based on the oxygen amount signal from the oxygen enrichment control device 21 and the output signal of the flow meter 17. , valve 1 to control the amount of oxygen supplied.
Adjust the opening degree of 6.

The tip of the fuel pipe 6 is open in the inner pipe of the burner 5.
The base end of the fuel pipe 6 is connected to a fuel source (not shown). A flow meter 7 is installed in the middle of the fuel pipe 6 in order from the fuel source side.
．． A fuel supply amount adjustment valve 9 is attached, and the flow rate of fuel sent from a fuel source, such as COG gas, is adjusted by the valve 9.

The flow rate is measured by a flow meter 7, and the output signal of the flow meter 7 is input to a fuel flow rate indicating regulator 8. In the fuel flow rate indicator 8, the fuel amount is set based on the theoretical value of the fuel amount to maintain the tank internal temperature at the target value, and the fuel flow rate indicator 8 sends a controlled fuel signal to the air-fuel ratio setting device 10. is transmitted. Further, the fuel flow rate indicating regulator 8 adjusts the opening degree of the valve 9 in order to control the amount of fuel supplied.

An oxygen concentration signal is transmitted from the oxygen enrichment control device 21 to the arithmetic controller 22, and the arithmetic controller 22 receives the fuel.

The supply amount of air and #I element is calculated, and the calculated signal is transmitted to the air-fuel ratio setting device 10. The air-to-fuel volume ratio is set in the air-fuel ratio setter 10, and an air amount signal is transmitted to the air flow rate indicator controller 11 based on the set value.

Further, numeral 3 indicates a thermometer provided in the gas tank 4.

When controlling the supply amount of fuel, air, and oxygen based on the temperature inside the gas tank 4, the temperature signal from the thermometer 3 is transmitted to the arithmetic controller 22, and the arithmetic controller 22, based on the temperature signal, Calculates the supply amount of fuel, air, and oxygen and controls each supply amount.

In the apparatus of the present invention as described above, prior to degassing, valves 9, 13, and 16 are opened to supply fuel and oxygen-enriched air to burner 5 for combustion. Then, the inside of the tank is heated to the target temperature value based on the control system as described above. Further, at this time, the combustion exhaust gas is discharged from the tip of the immersion pipe 2. Heating from the dip tube 2 is therefore unnecessary.

On the other hand, the pressure inside the degassing tank 4 is always positive and there is no intruding air, so the temperature inside the tank does not drop. Further, in the burner 5, since the fuel is combusted by adding oxygen-rich air to the fuel, it is possible to bring the inside of the tank to a desired high temperature.

[Effects] Next, the effects of the present invention will be explained for the cases where the conventional electrode heating method and the heating method of the present invention are used in the DH method.

The i-shield ring coefficient of f4 steel is 34 times/charge (1 charge 2
The experiment was conducted under conditions where the inner diameter of the immersion tube was 450 nm and the length was 1400 mm. The power of the conventional electrode heating method is 33
7 -. Further, the fuel in the heating method of the present invention is C
OG gas, further increase the oxygen enrichment concentration to 35%, and COG
Supply amount of gas and oxygen respectively COG gas-12ONm37
H, O2 = 72Nm3/ll. A comparison of the results of both methods is shown in the table below.

As can be seen from the table, in the conventional electrode heating method, the furnace bottom temperature was 1300°C and the immersion tube temperature was 540°C, with a temperature difference of 760°C, but in the heating method of the present invention, the furnace bottom temperature was 1300°C.
360℃, the immersion tube temperature is 990℃, the temperature difference is 370℃.
℃, and the difference between the furnace bottom temperature and the immersion tube temperature was less than half that of the conventional method. In addition, the temperature drop of molten steel is conventionally 30 to 40℃.
However, in the present invention, the temperature was 15 to 25°C, and the temperature could be suppressed by about 15°C.

Therefore, by the method according to the present invention, the temperature in the tank can be made high and uniform, and the temperature drop in the molten steel can be suppressed to a small scale.

Furthermore, according to the present invention, there is no need for dedicated heating of the tip of the immersion tube, and there is no need for power loss and electrode wear due to arc discharge during and after degassing treatment.
Energy saving compared to conventional technology.

It is possible to save resources.

[Brief explanation of drawings]

The drawings are schematic diagrams showing embodiments of the present invention.

Claims (1)

[Scope of Claims] 1. A vacuum degassing device that sucks up molten metal in a ladle into a degassing tank from an immersion pipe at the bottom of a degassing tank above it, and degasses the molten metal under reduced pressure. In the heating method, a heating combustion burner is provided in the upper part of the degassing tank, and the inside of the tank is heated by combustion by the burner, and the combustion exhaust gas is discharged from the immersion pipe. Method. 2. In a heating method for a vacuum degassing device, in which molten metal in a pot is sucked up into a degassing tank from a dip pipe at the bottom of a degassing tank above it, and the molten metal is degassed under reduced pressure. A heating burner installed at the top of the tank, piping for supplying fuel, air, and oxygen to the burner, the flow rate of the piping, the oxygen concentration mixed with the air and supplied to the burner, or the degassing 1. A heating device comprising: an arithmetic controller that controls the supply of fuel, air, and oxygen based on the temperature inside the tank.