TWI638895B - Method for suppressing slag foaming - Google Patents

Abstract

The method for suppressing slag foaming according to the present invention is that after the molten iron treatment is performed by a converter, the molten slag is discharged from the converter at a speed of 3 tons or more per minute to the slag discharge pot, and after the discharge starts, the slag discharge ends. After the time point, the molten slag discharged from the above-mentioned converter from the top of the slag pot reaches the position in the slag pot, and continuously inputs 50.0 kg to 200 kg of water per minute and 50.0 kg to 200 kg per minute. A pulverized slag having a particle diameter of 5.0 mm to 30 mm.

Description

Method for suppressing slag foaming

FIELD OF THE INVENTION The present invention relates in particular to a method of suppressing foaming (foaming) of a slag discharged to a slag pot after the molten iron treatment in a slag pot.

BACKGROUND OF THE INVENTION In recent years, when refining molten iron to produce molten steel, the following method (multi-functional converter method) is performed, that is, after the molten iron dephosphorization treatment is performed by a converter, a part of the slag generated in the converter is discharged to the converter. The slag pot below it is subjected to decarburization treatment (see Patent Document 1). In this method, the mass ratio of CaO/SiO ₂ of the slag component (hereinafter referred to as alkalinity) is adjusted to 0.8 to 1.5 in the converter, thereby improving the viscosity of the slag and causing the slag to be foamed violently (from below) Soaking), whereby the slag discharge property is good.

Thus, in the steel making step, there is a case where FeO (iron oxide) in the slag reacts with C in the molten iron at the interface or FeO in the slag reacts with C in the granulated iron contained in the slag. Fine CO bubbles are generated and foaming occurs.

For example, when the slag is discharged from the converter to the slag pot, the slag and the granulated iron in the slag are vigorously stirred and mixed by the energy of the slag falling, and the FeO in the slag reacts with the C in the granulated iron rapidly. Produces fine CO bubbles. As a result, the slag is easily foamed immediately after being discharged to the slag pot. Further, even if the foaming is temporarily silenced, it is easy to continue foaming due to the slag discharged successively.

Therefore, in order to prevent the slag from overflowing from the slag pot and discharging the slag into the slag pot in a short time, it is necessary to suppress foaming in the slag pot or to cause blistering in the slag pot quickly. Quiet. For this reason, a technique for suppressing foaming or allowing the foam to be quickly calmed and the static state to continue is indispensable.

Further, in the case where the foaming suppressing effect in the slag pot is insufficient, in order to prevent the slag from overflowing from the slag pot, it is necessary to reduce the slag discharge speed or reduce the slag discharge amount. In this case, there is a problem that the cycle time of the converter is prolonged to cause a decrease in productivity, or the rephosphorization in the decarburization treatment after slag removal is increased, or a floating overflow occurs.

Further, the above-mentioned multiple phosphorus and floating can be suppressed by increasing the amount of CaO used in the decarburization blowing after slag discharge. However, in this case, the amount of slag generated with a high CaO concentration is increased, which is not only poor from the viewpoint of refining cost, but also poor from the viewpoint of slag treatment.

On the other hand, carbon powder is known to be effective as a foaming and sinking material. For example, Patent Document 2 discloses a method of cooling a foamed slag at a speed of 5 to 100 kg/min. Since carbon is hard to be wetted by the slag, if the carbon powder is blown into the foamed slag, the fine CO bubbles are promoted to each other and floated and separated by the carbon powder, so that the foaming is calmed.

Further, in Patent Document 3, as a method of suppressing slag foaming in a slag pot (slag pot), a method of spraying a spray-like water on the surface of a slag in a slag pot is disclosed. Foaming can be suppressed by cooling and solidifying the surface layer portion of the slag in the slag pot.

In order to calm the foaming in the slag pot, and to blow the toner toward the surface of the slag as in the method described in Patent Document 2, since the carbon powder has a small specific gravity and a small volume, it is difficult for the carbon powder to intrude. Inside the slag. As a result, the effect of the toner is only reflected on the surface side of the slag, and there is almost no effect in the case of severe foaming. Further, in order to blow the carbon powder into the slag, it is necessary to provide a complicated and expensive equipment such as a lifting device for blowing the lance in the vicinity of the slag pot.

Further, in order to spray the water on the surface of the slag in the slag pot, the surface of the slag in the slag pot is cooled and solidified to suppress foaming, as in the method described in Patent Document 3. However, in the case where the slag is successively discharged from the converter, stirring and mixing are vigorously generated by the slag falling flow, and the surface of the slag is continuously renewed, so that it is difficult to suppress foaming. [ Prior Technical Literature ] [ Patent Literature ]

[Patent Document 1] Japanese Patent Publication No. 2582692 [Patent Document 2] Japanese Laid-Open Patent Publication No. 4-180507 [Patent Document 3] Japanese Laid-Open Patent Publication No. 8-325619

SUMMARY OF THE INVENTION Problems to be Solved by the Invention In view of the foregoing problems, an object of the present invention is to provide a method for suppressing slag foaming, which can efficiently and efficiently discharge slag from a converter to a slag pot without extending the slag discharge time. Suppresses foaming. Means to solve the problem

As a result of the inventors' research, the inventors have found out that the above problem can be solved by using a simple apparatus to put low-cost and easily available water and pulverized slag as a foaming suppressing material into a slag discharging pot, thereby completing the present invention. . The invention is as set forth below. (1) A method for suppressing slag foaming, characterized in that after the molten iron treatment by a converter, the molten slag is discharged from the converter to a slag pot at a rate of more than 3 tons per minute, and after the start of the discharge Until the end of the slag discharge time, the molten slag discharged from the above-mentioned slag pot reaches the vicinity of the slag pot in the vicinity of the slag pot, and continuously inputs 50.0 kg to 200 kg of water per minute and 50.0 per minute. A crushing slag having a particle diameter of 5.0 mm to 30 mm of kg to 200 kg. (2) The method of suppressing slag foaming according to (1), wherein the pulverized slag is one or more selected from the group consisting of a slag slag, a molten iron dephosphorization slag, a converter slag, and a slag. [Effects of the Invention]

According to the present invention, it is possible to efficiently suppress foaming without discharging the slag discharge time when the slag is discharged from the rotary kiln to the slag discharge pot.

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 foaming in the slag pot 2. The example shown in Fig. 1 shows an example in which the molten slag is discharged from the converter 1 to the slag pot 2 in the multi-function converter method. First, after performing the dephosphorization treatment, the converter 1 is tilted while leaving the molten iron in the converter 1, and discharged from the furnace opening 3 of the converter 1 to the slag pot 2 disposed below the converter 1, for example, 12t~ 14t molten slag. At this time, from the beginning of the slag discharge to the time after the slag discharge end time, the water is supplied from the pipe 4 provided above the slag discharge pot 2, and is discharged from the chute (not shown) provided above the slag discharge pot 2. Crushed slag. At this time, the molten slag flow discharged from the converter 1 reaches the position in the slag pot 2, and water and pulverized slag are introduced. Further, the position where the molten slag flow reaches the slag discharge pot 2 means that the molten slag flow reaches the surface of the molten slag in the slag discharge pot 2, and the water and the pulverized slag must be thrown to the surface of the molten slag near the arrival position to flow vigorously. Within the scope. The above range refers to a region surrounded by one of the circumferences of the slag flow at the position where the molten slag flow reaches. Thereby, the foaming of the molten slag in the slag pot 2 is suppressed. In the experiment described later, the discharge time of the molten slag was set to about 3 minutes. Further, the quality of the molten slag in the slag discharge can be measured by a weighing machine attached to a moving trolley provided with the slag pot 2, but the quality of the molten slag can be estimated based on the operating conditions and actual performance. Among them, the mass of the pulverized slag from the above-mentioned chute is subtracted and calculated.

Further, it is preferred that the pulverized slag is contaminated with water in advance, and it is preferred that the pulverized slag is contained in water beforehand. The reason for this is that the above method more reliably mixes water and pulverized slag into the foaming slag. Further, when the diameter of the pipe 4 is relatively large, water and pulverized slag may be supplied together from the pipe 4. In the example shown in Fig. 1, an example in which water and pulverized slag are introduced from the pipe 4 is shown. In this case, the diameter of the pipe 4 may be such a degree that the pulverized slag does not clog in the pipe.

Next, the following mechanism will be described in detail: from the start of the converter 1 to the slag pot 2, after discharging the molten slag to the point after the end of the slag discharge, the water is poured into the slag pot 2 and the slag is poured into the slag pot 2, Thereby, foaming of the molten slag in the slag pot 2 can be suppressed.

The molten slag discharged from the converter 1 to the slag pot 2 has a mass ratio (basicity) of, for example, CaO/SiO ₂ of 0.8 to 2.0, and a FeO concentration of 10% by mass to 40% by mass. At the initial stage of slag discharge, the molten slag impinges on the bottom of the slag pot 2, so that the molten slag is strongly stirred to melt the fine CO bubbles inside the slag and float up and separate. Further, the discharged molten slag is rapidly cooled by being brought into contact with the bottom of the slag pot 2, so that the solid phase ratio of the molten slag is increased. When the solid phase ratio of the molten slag is increased, water is poured from the slag pot 2 and the slag is pulverized. Therefore, the molten slag discharged from the converter 1 is further cooled by the vaporization of moisture, and the molten slag is solidified. The phase rate is further increased, and foaming is more significantly suppressed.

Further, the solid phase ratio of the bottom side of the slag pot 2 and the surface layer of the molten slag is increased to temporarily suppress the foaming, but if the molten slag in the slag pot 2 is in contact with the molten slag successively discharged from the converter 1, When it melts, it starts to foam. On the other hand, the pulverized slag which is put together with the water destroys the solidified surface layer portion of the molten slag in the slag pot 2, so that the water enters the inside of the molten slag in the slag pot 2 and is cooled, thereby further suppressing bubble.

Thereafter, a slag heap is produced in the slag pot 2, and the molten slag is successively discharged from the converter 1 to the slag pile. Then, the molten slag discharged from the converter 1 reaches the vicinity of the position in the slag pot 2, and the water and the pulverized slag are continuously supplied, and the water and the pulverized slag are mixed into the molten slag to exhibit the same effect as the initial stage of slag discharge. By continuously pouring water and pulverizing the slag in the initial stage of self-slagging, the water and the pulverized slag are mixed into the molten slag, and the molten slag discharged from the converter 1 is sequentially cooled to increase the solid phase ratio of the molten slag. Thereby, the foaming of the slag pile in the slag pot 2 can be suppressed. In order to surely enjoy this effect, it is necessary to continuously supply water and pulverize the slag at least until the end of the slag discharge. In order to more reliably enjoy the effect, it is preferable to continue to input water and pulverize the slag after the slag discharge end time. If the input continuation time after the slag discharge time point is too long, the cost is not good in terms of time and cost, and the molten slag does not need to be completely solidified. Therefore, it is preferably within 20 seconds.

Here, when only water is supplied, the range in which it can infiltrate into the molten slag is limited, and the foaming suppression effect is also limited. When the slag is not put into the slag, the surrounding molten slag is rapidly cooled to form a solidified shell when the water is vaporized, and most of the water vapor generated by the vaporization is blown upward. Thereby, the cooling range of the molten slag is narrowed. On the other hand, when the pulverized slag is charged together with the water, the pulverized slag physically destroys the solidified shell of the slag generated by the vaporization of water, so that the pulverized slag and the water can be invaded from the portion where the solidified shell is broken. In the molten slag, the molten slag can be cooled in a larger range to increase the solid phase ratio, and foaming can be efficiently suppressed.

Second, describe the better conditions. In the following, the following conditions are studied and the desired condition range is described. The condition range is that after the molten iron treatment in the converter, the molten slag of 3 tons or more is discharged to the slag pot for 1 minute, and is put into the 1 minute. 30.0kg to 250kg of water and 30.0kg to 250kg of pulverized slag having a particle diameter of 1.0mm to 50mm per minute.

First, from the viewpoint of not extending the operation time of the converter, the speed at which the molten slag is discharged to the slag pot having an internal volume of 30 m ³ to 70 m ³ is set to be 3 tons or more per minute. It should be 4 tons or more. Further, the upper limit is not particularly limited, but the faster the speed, the stronger the momentum of the molten slag that falls, and the easier it is to fly out of the slag pot. Therefore, it is preferably set to 6 tons or less per minute. More preferably 5 tons or less.

Next, when the amount of the input water is 50.0 kg to 200 kg per minute and the amount of the pulverized slag is 50.0 kg to 200 kg per minute, the particle size range of the pulverized slag is changed, and as a result, it is understood that the particle size of the pulverized slag obtained is 5.0mm ~ 30mm. The pulverized slag having a particle diameter of less than 5.0 mm cannot break the solidified shell formed by the rapid cooling of the molten slag by vaporization of water.

On the other hand, the pulverized slag having a particle diameter of more than 30 mm is excessively heavy. Therefore, even if the molten slag flow discharged from the converter reaches the position near the slag pot, the kinetic energy of the molten slag which falls can not cause the slag to be crushed. Dispersed in the slag pot. Further, the pulverized slag to be charged may include pulverized slag having a particle diameter of less than 5.0 mm and more than 30 mm, and it is sufficient to supply at least 50.0 kg to 200 kg of pulverized slag having a particle diameter of 5.0 mm to 30 mm per minute. The particle size of the pulverized slag is preferably 8.0 mm to 20 mm, and more preferably 10 mm to 15 mm. The input amount of the pulverized slag will be described below.

Then, when the pulverized slag having a particle diameter of 5.0 mm to 30 mm is charged in an amount of 50.0 kg to 200 kg per minute, the water input speed is changed. As a result, it is understood that the amount of water is 50.0 kg to 200 kg per minute. Get results. In addition, it is understood that this tendency is the same when 50.0 kg of pulverized slag is charged per minute and when 200 kg of pulverized slag is charged. If the amount of water per minute is less than 50.0 kg, the molten slag discharged from the converter cannot be completely cooled in order, and the foaming is intensified from the middle of the slag discharge, and the upper end of the slag pot overflows. On the other hand, even if the amount of water per minute is 200 kg or more, since the foaming of the molten slag in the slag pot is sufficiently suppressed, the effect is saturated and water is wasted. The amount of water is preferably from 70 kg to 150 kg per 1 minute, more preferably from 100 kg to 120 kg.

Then, when the input water is 50.0 kg to 200 kg per minute and the particle size of the pulverized slag is 5.0 mm to 30 mm, the input speed of the pulverized slag is changed. As a result, it is found that 50.0 kg to 200 kg is charged per minute. The slag is pulverized to obtain an effect. Further, it is understood that this tendency is the same when 50.0 kg of water is charged per minute and when 200 kg of water is charged. When the amount of the pulverized slag per minute is less than 50.0 kg, the range of the solidified shell formed by the rapid cooling of the slag by the pulverization of the slag can be limited, so that the cooling range of the molten slag is narrowed. As a result, foaming is intensified from the middle of the slag discharge and overflows from the upper end of the slag pot. On the other hand, even if the amount of the pulverized slag per one minute exceeds 200 kg, the foaming of the molten slag in the slag pot is sufficiently suppressed, so that the effect is saturated and the pulverized slag is wasted. The pulverized slag is preferably from 70 kg to 150 kg per 1 minute, more preferably from 100 kg to 120 kg.

Further, the type of the pulverized slag may be any one of a converter slag, a slag slag, a molten iron dephosphorization slag, and a slag slag (agglomerated slag). The reason for this is that the strength and specific gravity of the degree of destruction of the solidified shell of the slag generated when the water is vaporized is required. Further, the representative composition of the above slag is shown in Table 1.

【Table 1】  <TABLE border="1" borderColor="#000000" width="85%"><TBODY><tr><td> Table 1 Representative composition of crushed slag (% by mass) </td></tr> <tr><td> variety</td><td> CaO </td><td> SiO₂</td><td> t.Fe </td><td> Al< Sub>2</sub>O₃</td></tr><tr><td> converter slag</td><td> 45 </td><td> 12 </ Td><td> 15 </td><td> 1 </td></tr><tr><td> 脱炉炉</td><td> 20 </td><td> 45 </td ><td> 8 </td><td> 4 </td></tr><tr><td> molten iron dephosphorization slag</td><td> 30 </td><td> 30 </ Td><td> 15 </td><td> 2 </td></tr><tr><td> pouring slag </td><td> 45 </td><td> 10 </td ><td> 8 </td><td> 15 </td></tr></TBODY></TABLE>

The converter slag is a slag discharged from the furnace after decarburization and blowing by a converter, and the alkalinity is generally about 3 to 5. The slag is a slag having a high concentration of SiO ₂ formed when iron oxide or oxygen is added to the molten iron to oxidize [Si] in the molten iron. The molten iron dephosphorization furnace slag is added with CaO or iron oxide, oxygen to oxidize [P] in the molten iron to (P ₂ O ₅ ) and is doped with P ₂ O ₅ slag. The ladle slag is a slag having a high concentration of Al ₂ O ₃ remaining in the ladle after the molten steel is discharged to the continuous casting machine. [Examples]

Next, the present invention will be further described based on examples, and the conditions in the examples are a conditional example employed to confirm the workability and effects of the present invention, and the present invention is not limited to the one condition example. 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 molten iron dephosphorization treatment was carried out by the multi-function converter method, the converter was tilted while the molten iron was kept in the converter, and the volume of the converter furnace mouth was set to be 50 m ³ below the furnace body. The slag pot takes about 3 minutes to discharge about 14 tons of molten slag having a basicity of about 1. In addition, when the molten slag is discharged, 100 kg of water is supplied from the piping every 1 minute from the start of slag discharge, and 200 kg of the converter slag having the composition shown in Table 1 is injected from the chute every minute. 5.0mm ~ 30mm). At this time, the molten slag flow discharged from the converter into the slag pot is continuously supplied with water and converter slag. Further, the quality of the molten slag in the slag discharge is not measured by a weighing machine attached to a moving trolley provided with a slag pot, but is estimated based on the operating conditions and actual performance. Among them, the mass of the pulverized slag input from the above chute is subtracted. As a result, the molten slag discharged from the converter to the slag pot does not foam much, but does not overflow from the slag pot.

[Comparative Example 1] After the molten iron dephosphorization treatment was carried out by the multi-function converter method, the converter was tilted while the molten iron was kept in the converter, and the volume of the converter furnace mouth was set to be 50 m ³ below the furnace body. The slag pot takes about 3 minutes to discharge about 14 tons of molten slag having a basicity of about 1. In addition, when the molten slag is discharged, 40.0 kg of water is supplied from the piping immediately after the slag discharge to the end of the slag discharge, and 300 kg of the converter slag having the composition shown in Table 1 is injected from the chute every minute. The diameter is 5.0mm to 30mm). At this time, the molten slag flow discharged from the converter into the slag pot is continuously supplied with water and converter slag. Furthermore, the quality of the molten slag in the slag is estimated based on the operating conditions and actual performance. Among them, the mass of the converter slag input from the above chute is subtracted. As a result, from 1.5 minutes after the start of the slag discharging from the converter to the slag pot, the molten slag in the slag pot is vigorously foamed and overflows from the slag pot. [Industrial availability]

According to the present invention, it is possible to efficiently suppress foaming without discharging the slag discharge time when the slag is discharged from the rotary kiln to the slag discharge pot.

1... converter 2... slag pot 3... furnace mouth 4... piping

Fig. 1 is a view for explaining a method of suppressing slag foaming in a slag pot.

Claims (2)

A method for suppressing slag foaming, characterized in that: after the molten iron treatment by a converter, the molten slag is discharged from the converter at a speed of more than 3 tons per minute to the slag discharge pot, and after the discharge is started, the slag discharge is performed. After the end time point, the molten slag discharged from the above-mentioned converter from the top of the slag pot reaches the position in the slag pot, and continuously inputs 50.0 kg to 200 kg of water per minute and 50.0 kg to 200 kg per minute. The pulverized slag having a particle diameter of 5.0 mm to 30 mm. The method of inhibiting slag foaming according to claim 1, wherein the pulverized slag is one or more selected from the group consisting of a slag slag, a molten iron dephosphorization slag, a converter slag, and a slag.