WO2018146754A1 - Method for controlling slag foaming - Google Patents

Abstract

After processing molten pig iron in a converter furnace, molten slag is discharged from the converter furnace to a discharged slag pan at a rate of at least 3 tons per 1 minute. After starting said discharge until, or beyond, the time at which slag discharge is completed, 50.0 kg to 200 kg per 1 minute of water and 50.0 kg to 200 kg per 1 minute of crushed slag of 5.0 mm to 30 mm grain size are continuously charged from above the discharged slag pan to a position near the site where the molten slag discharged from the converter furnace arrives at the inside of the discharged slag pan.

Description

Slag forming suppression method

The present invention particularly relates to a method for suppressing the slag discharged to the slag pan after hot metal treatment from forming (foaming) in the slag pan.

In recent years, when producing molten steel by refining hot metal, after performing hot metal dephosphorization treatment in the converter, a part of the slag generated in the converter is placed in the waste ladle installed under the converter. A method (multifunctional converter method) of discharging and subsequently performing a decarburization process is performed (see Patent Document 1). In this method, the CaO / SiO ₂ mass ratio of the slag component (hereinafter referred to as basicity) is adjusted to 0.8 to 1.5 in the converter, and the viscosity of the slag is increased to cause the slag to foam vigorously (hereinafter referred to as “the slag”). ), The slag discharge performance is improved.

Thus, in the steelmaking process, FeO (iron oxide) in the slag reacts with C in the molten iron, or FeO in the slag reacts with C in the granular iron contained in the slag. A large amount of fine CO bubbles may be generated and form.

For example, when the slag is discharged from the converter to the slag pan, agitation and mixing occur vigorously between the slag and the granular iron in the slag due to the energy that the slag has dropped, and FeO in the slag and C in the granular iron It reacts rapidly and a large amount of fine CO bubbles are generated. As a result, it becomes easy to form slag rapidly immediately after being discharged to the discharge pan. Moreover, even if forming is once calmed, it is easy to form continuously by the slag discharged | emitted one after another.

Therefore, to prevent the slag from overflowing from the slag pan and to discharge such slag into the slag pan in a short time from the converter, the forming in the slag pan is suppressed or quickly settled down. It is necessary to. For this purpose, a technique for suppressing forming or quickly calming down and maintaining the calmed state is indispensable.

If the forming suppression effect in the slag pan is insufficient, it is necessary to reduce the slag speed or reduce the slag amount in order to avoid slag overflowing from the slag pan. is there. In this case, the cycle time of the converter is extended, resulting in a decrease in productivity, an increase in recovery in the decarburization process after exhausting, and a problem that slopping occurs.

In addition, said dephosphorization and slopping can be suppressed by increasing the amount of CaO used by decarburization blowing after exhausting. However, in this case, the amount of slag having a high CaO concentration is increased, which is not preferable from the viewpoint of not only the refining cost but also the slag treatment.

On the other hand, it is known that carbon powder is effective as a forming calming material. For example, Patent Document 2 discloses a calming method in which carbon powder is sprayed onto a forming slag at a rate of 5 to 100 kg / min. Since carbon is difficult to wet with slag, when carbon powder is blown into the forming slag, coalescence and floating separation of fine CO bubbles are promoted through the carbon powder, so that the forming is calmed down.

Patent Document 3 discloses a method of spraying sprayed water on the surface of the slag in the slag pan as a method for suppressing slag forming in the slag pan. It is said that forming can be suppressed by cooling and solidifying the slag surface layer in the slag pan.

When carbon powder is sprayed on the surface of the slag as in the method described in Patent Document 2 in order to calm the forming in the waste pan, the carbon powder penetrates into the slag because the carbon powder has a small specific gravity and a small volume. hard. As a result, the effect of the carbon powder appears only on the slag surface side, and has almost no effect under the condition of intense forming. In addition, in order to blow carbon powder into the slag, there is a problem that it is necessary to install complicated and expensive equipment such as an elevating device for a blowing lance in the vicinity of the waste pan.

In addition, as in the method described in Patent Document 3, sprayed water is sprayed on the slag surface in the slag pan to cool and solidify the slag surface in the slag pan to suppress forming. It is done. However, in a situation where slag is discharged from the converter one after another, stirring and mixing are vigorously caused by the slag falling flow, and the slag surface is continuously updated, so it is difficult to suppress forming.

Japanese Patent No. 2558292 JP-A-4-180507 JP-A-8-325619

In view of the above-mentioned problems, the present invention provides a slag forming suppression method that efficiently suppresses foaming without extending the slag discharge time when discharging slag from a converter to a waste ladle. With the goal.

As a result of extensive studies, the present inventor has found that the above problem can be solved by introducing water and crushed slag, which are inexpensive and easily available, with simple equipment into the slag pan as a forming inhibitor. Completed the invention. The present invention is listed below.
(1) After the hot metal treatment is performed in the converter, the molten slag is discharged from the converter to the discharge pan at a rate of 3 tons or more per minute, and after the discharge starts until the end of the discharge. The molten slag discharged from the converter from 50.0 kg to 200 kg per minute of water from above the drain pan and 50.0 kg to 200 kg of crushed slag having a particle size of 5.0 mm to 30 mm per minute. Continues to be introduced to the vicinity of the position where it reaches the inside of the slag pan.
(2) The slag forming according to (1), wherein the crushed slag is at least one selected from the group consisting of desiliconized slag, hot metal dephosphorized slag, converter slag, and ladle slag. Suppression method.

According to the present invention, when slag is discharged from the converter to the discharge pan, the slag discharge time is not extended and the forming can be efficiently suppressed.

FIG. 1 is a diagram for explaining a method of suppressing slag forming in the slag pan.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a view for explaining a method of suppressing slag forming in the slagging pan 2.
The example shown in FIG. 1 shows an example in which molten slag is discharged from the converter 1 to the discharge pan 2 in the multi-function converter method. First, after the dephosphorization treatment, the converter 1 is tilted while the hot metal remains in the converter 1, and melted from the furnace port 3 of the converter 1 to the slag pan 2 installed below the converter 1. Slag is discharged, for example, 12t to 14t. At that time, from immediately after the start of sewage to after the end of sewage, water is introduced from the pipe 4 installed above the sewage pan 2 and crushed from a chute (not shown) installed above the sewage pan 2. Add crushing slag. At this time, water and crushed slag are thrown into the vicinity of the position where the molten slag flow discharged from the converter 1 reaches the slag pan 2. The position where the molten slag flow reaches the inside of the slag pan 2 is a position where the molten slag flow reaches the surface of the molten slag in the sewage pan 2, and the water and the crushed slag are in the vicinity of the reached position. It is necessary to put the molten slag surface in a range where the surface of the slag is flowing vigorously. The range is an area surrounded by a circumference 1 m away from the outer circumference of the slag flow at the position where the molten slag flow arrives. As a result, the formation of molten slag in the waste pan 2 is suppressed. In the experiment described below, the molten slag was discharged for about 3 minutes. In addition, although the mass of the molten slag in waste can be measured with the weighing machine attached to the mobile trolley which installs the waste pan 2, the mass of molten slag may be estimated from operation conditions and results. . However, the mass of the crushed slag introduced from the chute is subtracted and calculated.

In addition, it is preferable to wet the crushed slag with water in advance, and it is more preferable to keep it hydrated. This is because the water and the crushed slag can be more reliably involved in the forming slag. Further, when the diameter of the pipe 4 is relatively large, water and crushed slag may be supplied together from the pipe 4. In the example shown in FIG. 1, an example is shown in which water and crushed slag are put together from a pipe 4. In this case, the diameter of the pipe 4 only needs to be large enough to prevent crushing slag from being blocked in the pipe.

Next, from the time when the molten slag starts to be discharged from the converter 1 to the waste pan 2 and after the end of the waste, the water and the crushed slag are introduced near the position where the molten slag reaches the waste pan 2. The mechanism which can suppress the forming of the molten slag in the waste pan 2 will be described in detail.

The molten slag discharged from the converter 1 to the waste pan 2 has, for example, a CaO / SiO ₂ mass ratio (basicity) of 0.8 to 2.0 and an FeO concentration of 10 to 40 mass%. . In the initial stage of sewage, the molten slag is struck against the bottom of the sewage pan 2, so that the molten slag is vigorously stirred and the fine CO bubbles inside the molten slag are combined and floated. Moreover, since the discharged | emitted molten slag is rapidly cooled by contacting with the bottom of the discharge pan 2, the solid-phase rate of molten slag rises. Since water and crushed slag are introduced from above the slag pan 2 in a state where the solid phase ratio of the molten slag is increased in this way, the molten slag discharged from the converter 1 is further rapidly cooled by vaporization of moisture. As a result, the solid phase ratio of the molten slag is further increased, and the forming is further remarkably suppressed.

In addition, although the solid phase rate of the bottom side of the waste pan 2 and the surface layer of the molten slag is increased, forming is temporarily suppressed, but the molten slag in the waste pan 2 is discharged from the converter 1 one after another. When it comes into contact with the molten slag and melts again, it begins to form. On the other hand, since the crushed slag that is introduced together with water destroys the solidified surface layer of the molten slag in the slag pan 2, water enters the molten slag in the slag pan 2 and is cooled to further form. Can be suppressed.

After that, a slag pool is generated in the slag pan 2, and molten slag is discharged from the converter 1 to the slag pool one after another. Then, water and crushed slag are continuously introduced to the vicinity of the position where the molten slag discharged from the converter 1 reaches the inside of the slagging pan 2, and the water and crushed slag are entrained in the molten slag, which is the same as the initial stage of sewage Such an effect is exhibited. In this way, water and crushed slag are continuously introduced from the initial stage of sewage, so that water and crushed slag are entrained in the molten slag, and the molten slag discharged from the converter 1 is sequentially cooled to obtain molten slag. By increasing the solid phase ratio, the formation of the slag pool in the slag pan 2 can be suppressed. In order to enjoy this effect with certainty, it is necessary to continue to add water and crushing slag at least until the end of the evacuation. It is preferable to continue. The charging duration after the end of evacuation is not preferable in terms of time and cost even if it is too long, and it is not necessary to completely solidify the molten slag. .

Here, if only water is added, the range that can enter the molten slag is limited, and the forming suppression effect is also limited. When the crushed slag is not added, when the water is vaporized, the surrounding molten slag is rapidly cooled to form a solidified shell, and most of the water vapor generated by the vaporization is blown upward. This narrows the cooling range of the molten slag. On the other hand, when crushed slag is added together with water, the crushed slag physically breaks the solidified shell of the slag generated by the vaporization of water, so water enters the molten slag from the portion where the solidified shell is broken into the molten slag. The molten slag can be cooled in a wider range to increase the solid phase ratio, and forming can be efficiently suppressed.

Next, further preferred conditions will be described. After the hot metal treatment in the converter, 3 tons or more of molten slag is discharged into a ladle for 1 minute, and water is crushed slag with a particle size of 30.0 kg to 250 kg and a particle size of 1.0 mm to 50 mm per minute. Consideration is made in the condition range where 30.0 kg to 250 kg is charged per minute, and the desirable condition range obtained will be described.

First, the speed of discharging the molten slag to a discharge slag pot having an internal volume of 30 m ³ ~ 70m ³ shall be more than 3 tons per minute from the viewpoint of not extending the operating time of the converter. Preferably it is 4 tons or more. Moreover, although it does not specifically limit about an upper limit, Since the momentum of the molten slag which falls will increase and it will become easy to jump out of a waste pan, it is preferable to set it as 6 tons or less per minute. More preferably, it is 5 tons or less.

Next, when the particle size range of the crushed slag was changed under the condition that 50.0 kg to 200 kg of water per minute and 50.0 kg to 200 kg of crushed slag were charged per minute, The particle size was found to be 5.0 mm to 30 mm. With crushed slag having a particle size of less than 5.0 mm, the solidified shell of molten slag generated by rapid cooling by vaporization of water cannot be destroyed.

On the other hand, since crushed slag with a particle size exceeding 30 mm is too heavy, even if it is introduced near the position where the molten slag flow discharged from the converter reaches the waste pan, it has the kinetic energy of the molten slag that has fallen. Even so, the crushed slag is not very dispersed in the slag pan. Note that the crushed slag to be added may contain crushed slag having a particle size of less than 5.0 mm and greater than 30 mm, and at least 50.0 kg to 200 kg of crushed slag having a particle size of 5.0 mm to 30 mm is charged per minute. do it. More preferably, the particle size of the crushed slag is 8.0 mm to 20 mm, more preferably 10 mm to 15 mm. The input amount of crushed slag will be described later.

Next, under the condition that 50.0 kg to 200 kg of crushed slag having a particle size of 5.0 mm to 30 mm was added in an amount of 50.0 kg to 200 kg per minute, the water amount was changed to 50.0 kg to 200 kg per minute. It turned out that an effect is acquired by doing. Moreover, it turned out that this tendency is the same also when the crushed slag is supplied 50.0 kg per minute and when 200 kg is added. If the amount of water per minute is less than 50.0 kg, the molten slag discharged from the converter cannot be cooled sequentially, forming becomes intense from the middle of the waste and overflows from the upper end of the waste pan. On the other hand, even if the amount of water per minute is 200 kg or more, the formation of molten slag in the slag pan is sufficiently suppressed, so the effect is saturated and water is wasted. The amount of water is preferably 70 kg to 150 kg per minute, more preferably 100 kg to 120 kg.

Next, when 50.0 kg to 200 kg of water was added per minute and the particle size of the crushed slag was changed to 5.0 mm to 30 mm, the speed of crushed slag was changed. It was found that an effect can be obtained by adding 0.0 kg to 200 kg. It was also found that this tendency was the same when 50.0 kg of water was added per minute and when 200 kg of water was added. If the amount of crushed slag per minute is less than 50.0 kg, the range in which the solidified shell of slag generated by rapid vaporization of water can be broken by crushed slag is limited, and the cooling range of molten slag becomes narrower. End up. As a result, the forming becomes intense from the middle of the drainage and overflows from the upper end of the drainage pan. On the other hand, even if the amount of crushed slag per minute exceeds 200 kg, the formation of molten slag in the waste pan is sufficiently suppressed, so the effect is saturated and the crushed slag is wasted. Preferably, the crushed slag is 70 kg to 150 kg per minute, more preferably 100 kg to 120 kg.

Moreover, as a kind of crushing slag, any of converter slag, desiliconization slag, hot metal dephosphorization slag, ladle slag (ingot slag) may be sufficient. This is because the above-described strength and specific gravity are required to break down the slag solidified shell generated when water is vaporized. The representative composition of the slag is shown in Table 1.

Converter slag is slag discharged from the furnace after decarburization and blowing in the converter, and the basicity is generally about 3 to 5. The desiliconized slag is slag having a high SiO ₂ concentration that is produced when iron oxide or oxygen gas is added to the hot metal to oxidize [Si] in the hot metal. The hot metal dephosphorization slag is a slag in which CaO, iron oxide and oxygen gas are added to oxidize [P] in the hot metal to (P ₂ O ₅ ) and take it in. The ladle slag is a slag having a high concentration of Al ₂ O ₃ remaining in the ladle after discharging the molten steel to the continuous casting machine.

Next, the present invention will be further described based on examples, but the conditions in the examples are one example of conditions adopted for confirming the feasibility and effects of the present invention. It is not limited to the example conditions. The present invention can adopt various conditions as long as the object of the present invention is achieved without departing from the gist of the present invention.

[Example 1]
After the hot metal dephosphorization process by the multi-functional converter method, the converter is tilted while the hot metal remains in the converter, and the furnace furnace port is placed at the discharge pan with a volume of 50 m ³ installed below the furnace body. From about 14 tons of molten slag having a basicity of about 1 was discharged over about 3 minutes. In addition, when discharging molten slag, from immediately after the start of sewage to the end of sewage, 100 kg of water per minute is introduced from the pipe, and at the same time, converter slag having a composition shown in Table 1 of 200 kg per minute (particle size 5 (0.0 mm to 30 mm) was introduced from the chute. At this time, water and the converter slag were continuously supplied to the vicinity of the position where the molten slag flow discharged from the converter reached the inside of the waste pan. In addition, the mass of the molten slag during the slag was not measured with a weighing machine attached to the moving carriage where the slag pan was installed, but was estimated from the operating conditions and results. However, the mass of the crushed slag introduced from the chute was subtracted.
As a result, the molten slag discharged from the converter into the slag pan did not form much and did not overflow from the slag pan.

[Comparative Example 1]
After the hot metal dephosphorization process by the multi-functional converter method, the converter is tilted with the hot metal left in the converter, and the volume installed below the furnace body is moved to the discharge pan of 50 m ³ from the converter furnace port. About 14 t of molten slag having a basicity of about 1 was discharged over about 3 minutes. In addition, when discharging molten slag, from immediately after the start of sewage to the end of sewage, 40.0 kg of water per minute is introduced from the piping and at the same time, 300 kg per minute of converter slag (grains) shown in Table 1 A diameter of 5.0 mm to 30 mm) was introduced from the chute. At this time, water and the converter slag were continuously supplied to the vicinity of the position where the molten slag flow discharged from the converter reached the inside of the waste pan. In addition, the mass of the molten slag during evacuation was estimated from the operating conditions and results. However, the mass of the converter slag introduced from the chute was subtracted.
As a result, from the time when 1.5 minutes passed after the start of evacuation from the converter into the slag pan, the molten slag in the slag pan formed violently and overflowed from the slag pan.

According to the present invention, when slag is discharged from the converter to the discharge pan, the slag discharge time is not extended and the forming can be efficiently suppressed.

Claims (2)

After the hot metal treatment is performed in the converter, the molten slag is discharged from the converter to the discharge pan at a rate of 3 tons or more per minute, and after the start of the discharge until the end of the discharge. From the top of the pot, 50.0 kg to 200 kg of water per minute and 50.0 kg to 200 kg of crushed slag with a particle size of 5.0 mm to 30 mm per minute, and the molten slag discharged from the converter is discharged A method for suppressing slag forming, characterized in that the slag continues to be introduced near the position where it reaches the inside of the pot. The slag forming suppression method according to claim 1, wherein the crushed slag is at least one selected from the group consisting of desiliconized slag, hot metal dephosphorized slag, converter slag, and ladle slag.

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