JPH08283830A - Method for restraining wearing of lining refractory for molten metal refining vessel - Google Patents

Abstract

PURPOSE: To execute sufficient preheating and heat-holding to a refractory even if the treating time is short by blowing and burning combustible gas from tuyeres and/or nozzles during the treatment without constructing a large scale installation and attaching/detaching time of burner, etc. CONSTITUTION: The combustible gas is introduced into the inner part of the molten metal refining vessel from the tuyeres 2 and/or the nozzles fitted to the vessel to execute the preheating or the heat holding of the lining refractory in the vessel. By this method, the wearing of the lining refractory caused by its thermal spalling is restrained and the service life of the refining vessel is drastically prolonged and the cost of furnace lining material can also be drastically reduced. When this method is applied to a molten metal refining vessel, particulary to a vacuum degassing vessel, wearing of the lining refractory caused by its thermal spalling can be restrained. By this method, the service life of the refining vessel is drastically prolonged, e.g. the cost of the furnace lining material in the secondary refining process of steelmaking can drastically be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molten metal refining vessel, and more particularly to a method for suppressing wear of refractory lining refractory lining in a vacuum degassing tank due to thermal shock and extending the life of the refining vessel to a large extent.

[0002]

2. Description of the Related Art In the current molten metal refining process,
The vacuum degassing tank is an indispensable facility for high-grade steel production. In particular, in recent years, various kinds of treatments for producing high purity steel and high cleanliness steel have been performed. As an example,
Examples include increasing the diameter of dipping pipes and circulating pipes (increasing the circulating flow) in order to improve the decarburization treatment speed of molten steel.

However, with the increase in diameter, the temperature in the container is remarkably lowered immediately after the end of the treatment, and at the start of the next treatment,
The hot molten steel came into contact with the cooled refractory, and a large thermal shock was applied to the refractory. For this reason, large cracks were generated in the refractory material, and in particular, the refractory material lined in the lower tank and the dip tube was worn, and the durability of the container was significantly reduced.

Conventionally, the following methods have been adopted to solve this problem. For example, JP-A-5-93
In Japanese Patent No. 219, a plurality of burners, which are inserted from the top of a vacuum degassing tank and have different capacities and lengths and which can be swung up and down freely, are used to burn the gas in the tank, and this combustion gas is immersed in a dipping pipe or special smoke. It discloses a method of forcibly exhausting air from the road to efficiently perform preheating and heat retention. In addition, JP-A-3-6
Japanese Patent No. 1311 discloses a method of preheating the inside of the RH vacuum degassing tank and the outside of the immersion tube to a high temperature using a special burner.

[0005]

However, when the treatment interval is short in the actual operation, it is difficult to install the forced exhaust device which is paired with the above-described vertically movable swivel burner in the immersion pipe in a short time. . Therefore, without forced exhaust, the upper tank of the vacuum degassing tank can be kept warm and preheated, but the lower tank and the immersion pipe cannot be sufficiently preheated and kept warm. Similarly, even with a method using a special burner, it is difficult to attach the burner to the dip tube in a short time, and it is difficult to perform sufficient heat retention between treatments. As described above, it is difficult to carry out heat retention sufficiently effectively by these methods.

By the way, FIG. 1 shows a tuyere attached to a vacuum degassing tank as an example of a molten metal refining vessel. For the tuyere, the Ar tuyere 1 attached to the dip tube and the OB tuyere (oxygen Blo) attached to the lower tank.
WinG) 2 has the former during operation, blowing Ar gas into the molten steel, is used to circulate the molten steel by using the principle of a bubble pump, the latter was the temperature in the main blowing O ₂ gas in the molten steel Used for promoting heat and decarburization.

The object of the present invention is to blow a combustible gas fluid from the tuyere between the treatments to burn the treatments without the need for constructing large-scale equipment or attaching and detaching a burner or the like. To provide sufficient preheating and heat retention for refractory materials. Then, a method for improving the durability of a vacuum degassing tank by suppressing the wear of a refractory lining refractory in a molten metal refining vessel, particularly a vacuum degassing tank due to thermal shock.

[0008]

[Means for Solving the Problems] As a result of intensive research on means for solving the above problems, the following has been found. That is, a flammable gas is introduced into the vessel from a tuyere attached to a molten metal refining vessel, and in the case of preheating, it is ignited by an igniter, and in the case of heat retention, an atmosphere of 600 ° C or more in the tank. Ignite spontaneously and burn gas at the same time. Then, the refractory lining of the container is preheated or heat-retained to suppress the wear of the refractory due to thermal shock, thereby extending the life of the refining container.

[0009]

By using the tuyere method of the present invention, even if the time between treatments is short, there is no need to attach or detach a burner or the like,
Preheating or heat retention can be efficiently performed.

In the present invention, the combustible gas fluid blown into the tuyere attached to the molten metal refining vessel is BFG or COG obtained in equipment such as a blast furnace or a converter.
Etc., LNG, or propane / propylene / ethylene /
CO, methane, petroleum mist, etc. may be used alone or in combination of two or more. In particular, COG and propane are preferable in terms of cost and the amount of heat obtained.

Further, when it is relatively easy to supply O ₂ gas such as Ar tuyere 1 attached to a dip tube,
The above-mentioned gas is introduced into the tuyere as it is, and the gas is burned to preheat or retain heat. However, as in the case of the OB tuyere 2 inside the vacuum degassing tank, when the O ₂ gas is thin and the combustion of the gas is difficult immediately after the treatment, the O ₂ gas or the air and the combustible gas are mixed. Apply.

As a result, the preheating or heat retention of the lower tank and the dipping tube, which has been difficult by the conventional method, can be performed sufficiently efficiently. In particular, when the OB tuyere 2 inside the vacuum degassing tank is used for preheating, the tuyere position coincides with the contact position of the molten steel during actual operation, and in order to perform heat retention / preheating, It is in a very convenient position. Therefore, a preferable effect can be obtained as compared with the conventional preheating or heat retaining method or the preheating or heat retaining method in another refining vessel.

However, in order to prevent an accident such as a gas leak, it is necessary to supply O ₂ gas to the tuyere so as to completely burn the combustible gas. For example, in the case of propane gas, the ratio of propane gas to O ₂ gas should be 1: 5. Further, the OB tuyere, which has a high temperature around the tuyere, has a double tube structure, and it is necessary to flow a cooling gas in order to protect the tuyere. for that reason,
The outer pipe for cooling mainly covers the inner pipe for sending gas, and therefore, the cross-sectional area of the outer pipe is small and the flow rate of gas can be small. Therefore, combustion gas should flow in the outer tube and O ₂ gas or air should flow in the inner tube.

On the other hand, in order to prevent the temperature of the lining bricks in the tank from decreasing during operation, a means for preventing air from entering the tank is generally taken. For example, an operation such as closing the exhaust cutoff valve (damper) 3 shown in FIG. 1 is performed. However, in the present invention, especially when O ₂ gas cannot be supplied,
In order to assist combustion of gas in the tank, it is preferable to control the opening / closing of the exhaust cutoff valve. At that time, in order to avoid thermal shock to the refractory material, the surface temperature of the refractory material during preheating and heat retention must be kept at 800 ° C. or higher. By these operations, preheating or heat retention by the method of the present invention can be effectively performed.

Further, in the case of preheating, in the case of preheating, the flammable gas is ignited by setting a heater type or spark type ignition electrode in the vicinity of the tuyere and / or the nozzle and igniting it by an ignition device including its power source. On the other hand, in the case of heat retention, the inside of the tank is spontaneously ignited in an atmosphere of 600 ° C. or higher immediately after the treatment. Thereby, in the present invention, preheating or heat retention can be performed safely and effectively.

By using the heat retention method of the present invention, it is possible to suppress wear due to thermal shock, thermal spalling, and structural spalling of refractory lining refractory in a molten metal refining vessel, especially in a vacuum degassing tank.
The life of the vacuum degassing tank can be dramatically improved.

[0017]

Embodiments of the present invention will be described in detail below with reference to FIGS.

<Embodiment 1> As shown in FIG.
The present invention was applied to the Ar tuyere 1 of the molten steel ascending side immersion pipe attached to the 00 t / ch RH vacuum degassing tank. Immediately after the treatment, a total of 20 Nm ³ / hr was applied to 12 Ar tuyeres.
COG was flowed to burn these gases to preheat and retain the refractory in the tank. At this time, the exhaust cutoff valve (damper) was half-opened, and a hanging sand seal was attached to the immersion pipe on the molten steel descending side.

As a result, the surface temperature of the refractory material on the side wall of the lower tank was close to 900 ° C., which was about 200 ° C. higher than that of the conventional one, 15 minutes after the end of the treatment. Further, the large cracks generated in the lining refractory after use, particularly in the lining refractory near the dip pipe, were reduced, and the life of the tank could be extended to an average of 25% per furnace cost compared to the conventional case.

Example 2 The present invention was applied to the OB tuyere 2 of the RH vacuum degassing tank of Example 1 as shown in FIG.
The two OB tuyere 2 attached to this tank have a double pipe structure. Immediately after completion of the treatment, propane gas is flown to these _two outer pipes and O ₂ gas is flown to the inner pipe to burn these gases. Then, the refractory in the tank was preheated and kept warm. At this time, the exhaust cutoff valve (damper) was closed. Further, the flow rate of propane gas is 100 Nm ³ / hr in total, and in consideration of safety, the ratio of propane gas and O ₂ gas is set so that the gas completely burns.
It was set to 1: 5.

As a result, the surface temperature of the refractory material on the side wall of the lower tank was close to 1000 ° C., which was about 300 ° C. higher than the conventional temperature, 15 minutes after the end of the treatment. Further, the large cracks generated in the lining refractory after use, especially in the lining refractory near the dip pipe, were drastically reduced, and the life of the tank could be extended by 38% on average per furnace cost compared to the conventional case.

[0022]

When the present invention is applied to a molten metal refining vessel, particularly a vacuum degassing tank, it is possible to suppress wear of a refractory lining due to heat spalling. As a result, the life of the refining vessel can be greatly extended, and for example, the cost of the furnace material in the secondary refining process for steelmaking can be greatly reduced.

[Brief description of drawings]

FIG. 1 is a diagram schematically showing an RH type vacuum degassing tank.

FIG. 2 is a diagram schematically showing an example of an embodiment of the present invention (applied to Ar tuyere).

FIG. 3 is a diagram showing an outline of an embodiment example of the present invention (applied to OB tuyere).

[Explanation of symbols]

 1 ... Ar tuyere 2 ... OB tuyere 3 ... Exhaust cutoff valve

Claims (1)

[Claims] 1. A method of preheating and / or keeping heat of a refractory lining a container by introducing a flammable gas into the container through a tuyere and / or a nozzle attached to a molten metal refining container to burn the gas. And a method for suppressing wear of refractory linings for molten metal refining vessels.