JPH07258715A - Method for restraining foaming of converter slag - Google Patents

Abstract

PURPOSE:To prevent the flowing-out of slag from the furnace opening of a converter by spreading granular materials having the specific grain diameter and composition on the slag surface in the converter with compressed air. CONSTITUTION:The granular material to be spread is used the one having substantial 5-20mm grain diameter and 5-20wt.% total C and 40-60wt.% SiO2. this granular material is filled into e.g. shiftable inversed-conical shaped hopper. Further, a double structural pipe with ejector mechanism is fitted to the upper part of the hopper, and the granular material is spread on the slag surface in the converter by jetting force of the compressed air in the inner pipe. By this method, the danger work can be eliminated.

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for suppressing the formation of slag by injecting a granular calming material on the surface of slag in a converter.

2. Description of the Related Art During refining of a converter, in the slag generation process,
The phenomenon of slag expanding and flowing out of the furnace is called forming. In order to prevent the occurrence of this forming, it is necessary to prevent excessive slag formation, but this is a phenomenon that occurs not a little in order to promote the P removal. Forming causes troubles in terms of operation and quality, such as a large temperature drop during tapping due to the occurrence of it, and slag that has flowed out enters the ladle. Therefore, forming needs to be calmed down at an early stage. As a technique for calming the forming of slag that covers the upper surface of molten steel in a converter, a method is generally used in which a lump material containing carbon as a main component or a lump material containing carbon and converter slag is charged from a furnace hopper. . For example, Japanese Patent Publication No. 57-39291 discloses that
Impurities such as pulp sludge, Al ₂ O ₃ and SiO ₂ are 3
The main component is 0% or less of industrial waste, and 30 to 50% of a small particle substance obtained by crushing a slag is mixed, and a small amount of an olefin polymer is further added to form a kneaded product having a particle size of 20 to 80.
A slag soothing agent for a converter which is molded and solidified into a granular or lumpy material having a size of mm is described. Further, the publication describes that when the sedative is put on the slag when the converter is tilted, there is a rapid sedative effect. Also, JP-A-57-16
Japanese Patent No. 1017 discloses a method of suppressing foaming of slag by introducing a molded body having a refractory material of 30 to 70%, a pulp sludge of 20% or less, an organic material of 20% or less and a binder of 30% or less into a converter. Have been described. The object of the above two inventions relates to a method of charging a soothing material mainly into a converter from a hopper or the like on a converter furnace. Therefore, the size thereof is relatively large and a certain amount of binder is provided from the viewpoint of strength compensation. The feature is that it is pelletized by adding a substance that becomes. Further, Japanese Patent Publication No. 63-61368 describes a slag foaming-preventing material containing an oxidizing material composed of light metal powder, carbonaceous powder and sodium nitrate for the purpose of suppressing foaming of slag on the hot metal. This is intended for the hot metal treatment process, and lowers the viscosity of the slag surface by utilizing the heat generated by the oxidation reaction of metal or the like. Further, the shape thereof is similarly briquetted into pellets of 30 to 50 mm. In addition, there is no effective method for forming that occurs during tapping, and the tilting of the converter again to the original position and addition of the above-mentioned calming material from the furnace hopper, or a worker The actual situation is to throw in raw wood of various sizes to calm the forming. Here, in the former case, the decrease in productivity due to the delay in tapping becomes a problem. Regarding the latter, the charging work is at the time when the tilting of the furnace progresses after the middle of tapping, and the method using raw wood has a long forming sedation time, and slag scattering from the inside of the furnace occurs In order to ensure safety, it was not possible to add sufficient soothing material, and the quality problems associated with the decrease in molten steel temperature and the outflow of slag from the converter furnace mouth to the ladle were issues to be solved. In the tapping operation of the converter,
A furnace heat shield is installed for the safety of workers. However, it is difficult to form a completely sealed structure in view of the current work form. Therefore, it is impossible to add a sufficient sedative material because there is a risk of the operator being burned by the scattered slag against the occurrence of forming during tapping.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for calming slag foaming early even during tapping operation of a converter. Is.

The present invention has a particle size of 5 to 2
A method for suppressing foaming of a converter slag, which comprises spraying a granular material of 0 mm, the main components of which are Total C; 5 to 20 wt% and SiO ₂ ; 40 to 60 wt% on the surface of the slag in the converter with compressed air. It is a summary. The following method is relatively simple and recommended for spraying. Granular soothing material (diameter 5 to 20 mm) is filled in a movable conical hopper as shown in FIG. A pipe with a double pipe structure having an ejector mechanism is attached to the upper part of the pipe, and the pressure air (7 to 15 Kg / c) of the inner pipe is attached.
It is a method of injecting the granular calming material from the inside of the hopper into the suction furnace by the injection force of m ² ). Further, it is preferable that the nozzle diameter and the amount / pressure of the blown gas are appropriately suppressed so that the injection surface of the above-described calming material is ¼ or more of the total slag surface.

[Function] The slag foaming phenomenon is caused by bubbles in the slag layer.
It is difficult to get caught and get out of the slag while passing.
It is a phenomenon that pushes up the entire slag layer. In extreme cases
Is a sloping pin where slag and molten steel scatter as bubbles break.
Trigger a phenomenon. As bubbles, C generated by the reaction
Blow for O air bubbles (FeO + C → CO) and agitation of molten steel
Entrapped inert gas bubbles etc. are involved. Slag formin
The factors that influence the
And physical properties of slag (viscosity and surface tension)
The amount of bubbles (= gas amount) is increased.
As the forming gas increases,
Ming subsides. Also, the smaller the bubble size, the more
Warming becomes more intense. On the other hand, as for
However, high viscosity, high surface tension slag, etc. will not form.
It is said to be easy. From the above, the slag in the present invention
The following is a detailed description of the warming and sedative effect. (1) Effect of granular soothing material The main components of the granular soothing material are C and SiO.₂And soothing material
The local site in the supplied slag is C and FeO in the slag.
CO gas is generated by the reaction of. Also SiO ₂Addition of
Depending on the basicity (CaO / SiO₂) Of the slag
Viscosity decreases. Here, the decrease in the viscosity of the slag and the gas
Slag foaming is suppressed by balancing the amount
Calm down. However, the surface tension in the slag does not change much
No, its impact is small. Effect of particle size Based on the above concept, the present inventors
The slag forming effect was investigated using the wood. In Figure 1
The relationship between the particle size of the soothing material of the present invention and the amount of soothing slag foaming
Indicates the person in charge. As a result of the investigation, the optimum particle size is 5 to 20 mm
I found that. If particle size is less than 5 mm, calm
Most of the material floats on the upper surface of the slag, so the sedative effect is small.
If the particle size exceeds 20 mm, the reaction time will be long.
It turned out that a sufficient effect could not be obtained. (2) Effect of injection with compressed air As described above, when the gas amount exceeds a certain amount, forming occurs.
Is calmed down, the amount of gas generated by the reaction + blowing
Gas in the area where the total amount of entrapped air calms the forming
It has become the amount. The specific effect in this case is the so-called
It is a degassing action. Also, during air slag
FeO is Fe₂O₃Is oxidized to. Temperature associated with this reaction
As the temperature increases, the viscosity of the slag decreases and the forming is suppressed.
The effect of calming can be considered. Based on this idea
The authors used a simple ejector type injector to slag
The warming effect was investigated. Fig. 2 shows the sedative material of the present invention.
Slag foam at the time of charging and spraying with compressed air
The amount of sedation is shown. The effect of injection is clear from FIG.
As this is blown into the mechanism and slag mentioned above
This is probably because the reaction efficiency was improved. (3) Effect of injection area Figure 3 shows the injection area ratio (injection area / total slag area) and sedation
Shows the relationship between. From Figure 3, the injection area ratio has been increased to 1/4 or more.
It has been found that effective sedation can be achieved by
It

EXAMPLE An example in which the above apparatus is applied to actual operation is shown below.
In the converter operation in which the molten steel amount was 270 tons, the blow stop [C] = 0.15%, and the blow stop temperature = 1660 ° C., in-furnace forming occurred during tapping. The in-furnace monitoring ITV (Fig. 4A) installed there confirmed the forming state in the furnace, and the amount of compressed air was 2500 Nm ³ from this device (B part of the converter bottom B and Fig. 4 ceiling part C). / in h, C; 5 to 20 wt%, SiO _2; 40~60 wt%, Al ₂ O _3; 15~
A granular (5 to 20 mm in diameter) forming and quenching material containing 25% by weight was charged into the furnace at a rate of 120 kg / min for 0.2 minutes. The injection area ratio was 0.33. as a result,
Forming at the early stage of tapping could be suppressed in advance (settling amount of forming: 800 mm). In addition, at this time, since this device is operated remotely for the slag scattering from the furnace opening, the worker was able to work safely without being exposed to the risk of burns. The temperature decrease at the time of tapping at this time was reduced by about 5 ° C. as compared with the conventional forming of the steel type.

By applying the present invention, forming at the initial stage of tapping of the converter can be suppressed in advance and slag outflow from the converter furnace opening can be prevented. Also, during the middle and final stages of tapping, it is possible for workers to put in sedative materials one after another while watching the inside of the furnace with a monitoring camera in a safe place away from the dangerous furnace area, eliminating dangerous work. In addition, the manual work of one or two persons can be omitted by the present invention. Further, by applying the present invention, the temperature drop at the time of tapping due to the occurrence of forming can be reduced, and the life of the refractory in the converter can be extended. In addition, since slag can be prevented from flowing out into the ladle, quality problems can be eliminated.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between a particle size of a soothing material and a slag foaming soothing amount.

FIG. 2 is a diagram showing a slag foaming sedation amount when a sedative material is thrown by hand and when sprayed by compressed air.

FIG. 3 is a diagram showing a relationship between an injection area ratio of a soothing material and a soothing time.

FIG. 4 is a diagram illustrating an embodiment of the present invention.

FIG. 5 is a diagram illustrating another embodiment of the present invention.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroshi Terashima 12 Nakamachi, Muroran City, Hokkaido Nippon Steel Corporation Stock Muroran Works

Claims (1)

[Claims] 1. The particle size is 5 to 20 mm, and the main component is T
A method for suppressing foaming of a converter slag, which comprises spraying a granular substance containing 5% by weight to 20% by weight of total C and 40% to 60% by weight of SiO _{2 on the} surface of slag in the converter with compressed air.