JPH0694377A - Duct collecting method for ladle refining furnace - Google Patents

Abstract

PURPOSE:To effectively collect dusts of a ladle refining furnace without newly installing a separate dust collecting facility by refining by the furnace directly under a converter, and effectively utilizing a dust collecting facility attached to the converter to collect powder dusts of the furnace upon refining and to also serve it as a dust collector. CONSTITUTION:A ladle refining furnace 1 contains molten steel and slag 10 therein, and is placed on a conveying truck 12 to be conveyed. On the other hand, a waste gas recovery hood 3, a dust collecting duct 4, an operating deck 5, etc., are attached to a converter 2. In this case, the furnace 1 is refined directly under the converter 2. Powder dusts of the furnace 1 generated upon refining are collected by utilizing the hood 3 and the duct 4 attached to the converter 2. Thus, a period in which a load to be applied to a dust collecting facility of the converter 2 is small and a slag modifying process by the furnace 1 are lapped at timing to be operated, thereby eliminating installation of a new large- sized dust collecting facility.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dust collecting method for a ladle refining furnace.

[0002]

2. Description of the Related Art In recent years, demands for surface defects caused by inclusions of steel materials have become increasingly severe, and various cleaning techniques have been developed to meet such demands. As one of the techniques of this type, there is a technique based on the slag reforming method disclosed in Japanese Patent Publication No. 2-19168 and Japanese Patent Laid-Open No. 30711/1990. That is, this is a technique for purifying molten steel by subjecting a ladle refining furnace to steel, performing slag reforming treatment, and then performing vacuum treatment or the like. According to this method, it is necessary to mix a part of the slag into the ladle refining furnace at the time of steel reception to modify the slag.

However, since the slag reforming treatment involves the addition of flux and the like and stirring, it is unavoidable that significant smoke is generated. However, the actual time required for the slag reforming treatment is around 5 minutes as disclosed in, for example, Japanese Patent Laid-Open No. 2-30711. That is, generation of a large amount of dust in a short time is a characteristic of the slag reforming process by the ladle refining furnace. Therefore, the dust collection cannot be dealt with by the conventional dust collection equipment, and it is necessary to newly install a large dust collection equipment.

On the other hand, when the operating conditions of the exhaust gas recovery equipment and / or dust collecting equipment of the converter (hereinafter abbreviated as the dust collecting equipment of the converter) are investigated, after the tapping, the slag and the furnace body lining are
There are operations such as charging of raw materials, and even after the start of blowing acid, the molten steel temperature is low and the amount of exhaust gas is relatively small at the initial stage, that is, at the time when the decarburization rate rises with time. That is, about 5 to 10 minutes after tapping in the ladle refining furnace, the load on the dust collecting equipment of the converter is relatively small.

In addition, the dust collecting equipment of the converter is usually 1
Equipment having an exhaust gas treatment capacity of about 20,000 to 20,000 m ³ / min is installed. (Steel Manual 2
(3rd edition) p. 463, edited by Japan Iron and Steel Institute)

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the current state of the art as described above, and by effectively utilizing the dust collecting equipment of a converter, a new large dust collecting apparatus can be obtained. The object of the present invention is to provide a method for collecting dust in a ladle refining furnace that can perform sufficient dust collection without installing equipment.

[0007]

DISCLOSURE OF THE INVENTION According to the present invention, a ladle refining furnace is characterized in that refining by a ladle refining furnace is performed directly under a converter and dust is collected by using a dust collecting facility of the converter. It is a dust method.

[0008]

In the present invention, the time when the load on the dust collecting equipment of the converter is low and the slag reforming treatment by the ladle refining furnace are time-lapped and the operation place is changed. Since it was directly under the converter where the dust collection equipment of the furnace works,
It is not necessary to install new large-scale dust collection equipment.

The term "directly below the converter" as used herein means not only immediately below the converter but also within a range where the dust collecting action of the dust collecting equipment of the converter operates.

[0010]

EXAMPLE FIG. 1 is a vertical cross-sectional view showing a dust collection state during slag reforming treatment by Ar bubbling in Example 1, and FIG. 2 shows a dust collection state during slag reforming treatment by Ar bubbling in Comparative Example 1. FIG. 3 is a vertical sectional view, FIG. 3 is a plan view showing the arrangement of converters and ladle refining furnaces of Examples and Comparative Examples, and the measurement points of environmental dust concentration ,,, and FIG. It is a graph which shows the measured value of the environmental dust density in each measurement point of Comparative Examples 1 and 3.

1 to 3, 1 is a ladle refining furnace, 2 is a converter,
3 is an exhaust gas recovery hood attached to the converter, 4 is a dust collecting duct of the converter connected to a dust collector, 5 is a working deck of the converter, 6 is a trunnion shaft of the converter, 7 is a converter operating room, and 8 is an embodiment. The dotted line indicates the position of the ladle refining furnace (immediately below the converter), and 9 indicates the position of the ladle refining furnace of the comparative example (Ar bubbling field) by the dotted line. Also, 10 is molten steel in the ladle refining furnace,
The slag, 11 is dust generated in the ladle refining furnace, and 12 is a ladle carrier truck. The Ar bubbling equipment is not shown.

After tapping the steel from the converter into the ladle refining furnace, slag reforming treatment was carried out. Aluminum ash was used as the slag modifier, and 1 kg was added per 5 kg of slag. In each of Examples 1 and 2, the treatment was performed while operating the dust collecting equipment of the converter. The presence / absence of the slag reforming treatment, the location of the slag reforming treatment and the presence / absence of Ar bubbling at this time are summarized in Table 1 as Examples 1 and 2 and Comparative Examples 1 and 2. The Ar bubbling alley is about 17m from directly under the converter.
Located in a remote location.

Table 1 also shows the measurement results of the environmental dust concentration at each measuring point near the converter at this time.

[0014]

[Table 1]

As shown in FIG. 3, the measurement point is the farthest measurement point from the converter, and is a position approximately 9 m from directly below the converter. From FIG. 4, in the case of Comparative Example 1 in which the slag reforming treatment was performed while Ar bubbling in the Ar bubbling field, the maximum value of the environmental dust concentration reached 22.25 mg / m ³ at the measurement point, while the converter Ar bubbling directly below, and
In Example 1 in which the slag reforming treatment was carried out while operating the dust collecting equipment of the converter, the maximum value of the environmental dust concentration decreased to 0.82 mg / m ³ at the measurement point. It can be seen that the environmental dust concentration is almost the same as that of Comparative Example 3 in which the bubbling treatment is not performed.

In Comparative Example 3, the slag reforming treatment was performed using Ar.
Normal ladle molten steel treatment without bubbling treatment Ar
The results of the measurement performed at the bubbling alley are also shown in order to clarify the effect of the present invention. In addition, in Example 1, the method of performing the slag reforming treatment on the steel receiving trolley equipped with the Ar supply hose and the ladle bottom blowing bubbling device disclosed in Japanese Utility Model Publication No. 58-2528 was adopted and the treatment cycle was changed. I tried to shorten it.

Further, Example 2 is an example in which the slag reforming treatment by mechanical stirring was carried out directly under the converter while operating the dust collecting equipment of the converter without Ar bubbling, and Comparative Example 2
In the Ar bubbling field, the environmental dust concentration is significantly lower than the environmental dust concentration when the slag reforming treatment is performed by mechanical stirring without Ar bubbling. That is, the maximum environmental dust concentration of Comparative Example 2 was 21.75 mg / m 2 at the measurement point.
^On the other hand, in Example 2, the maximum value of the environmental dust concentration reaches 0.80 mg / m ³ at the measurement point.

As is clear from the above results, the effects of the present invention are exhibited regardless of the stirring device. The effect of the present invention can be further improved by using a known sealing facility such as an air curtain or a conventional existing small dust collecting facility. Further, the dust collecting method of the present invention can be applied not only to the slag reforming treatment but also to the treatment by the ladle refining furnace that generates a large amount of dust in a short time.

[0019]

According to the dust collecting method of the ladle refining furnace of the present invention, since the dust collecting equipment of the converter can be effectively used, it is possible to sufficiently collect dust without installing new dust collecting equipment. The dust effect can be obtained.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing a dust collecting state during a slag reforming process by Ar bubbling in Example 1.

FIG. 2 is a vertical cross-sectional view showing a dust collecting state during a slag reforming treatment by Ar bubbling in Comparative Example 1.

FIG. 3 is a plan view showing the arrangement of converters and ladle refining furnaces of Examples and Comparative Examples, and the positions of measurement points for environmental dust concentration.

FIG. 4 is a graph showing measured values of environmental dust concentration at each measurement point in Example 1 and Comparative Examples 1 and 3.

[Explanation of symbols]

 1 ladle refining furnace 2 converter 3 exhaust gas recovery hood of converter 4 converter dust collection duct 5 converter working deck 6 converter trunnion shaft 7 converter operating room 8 position of ladle refining furnace of example ( Directly below the converter) 9 Position of ladle refining furnace of comparative example (Ar bubbling field) 10 Molten steel, slag 11 Dust of ladle refining furnace 12 Ladle carrier

Claims (1)

[Claims] [Claim 1] The refining by a ladle refining furnace is performed directly under the converter,
A method for collecting dust in a ladle refining furnace, comprising collecting dust using an exhaust gas recovery facility and / or a dust collecting facility attached to the converter.