KR100816790B1 - Improvement of Skimming Efficiency for De-[S] Slag in Hot Metal Pretreatment - Google Patents

Abstract

The present invention relates to a method for improving the excretion efficiency of high-density sulfur (S) -containing desulfurization slag generated during the pre-treatment desulfurization process in the steelmaking process, in particular, of the desulfurization slag for effectively disposing the desulfurization slag incorporated in the charging ladle It is an object of the present invention to provide a method for improving exclusion efficiency.

As described above, the method for improving the excretion efficiency of the desulfurization slag according to the present invention is obtained by drawing a molten iron onto the charging ladle in the TLC, and then, at a certain point, a predetermined amount of converter slag having a particle size distribution in the charging ladle is inputted to the upper desulfurization slag. Not only does the upper slag be easily removed by increasing the basicity, melting point, and viscosity according to the reaction of the converter slag, but also the ease of solidification and excretion of the liquid desulfurization slag, and even when the reaction does not proceed, By allowing the desulfurized slag to exist between the molten iron and the molten iron, it is easy to dispose of the liquid desulfurized slag, thereby increasing the excretion efficiency of the desulfurized slag and reducing the degree of abdominal sulfur.

Steelmaking process, molten iron, desulfurization slag, excretion efficiency, charging ladle, converter, double sulfur, desulfurization agent, TLC

Description

 Improving Efficiency of De- [S] Slag in Hot Metal Pretreatment

1 is a schematic view showing a conventional molten iron desulfurization slag treatment process and exclusion state

Figure 2 is a schematic diagram showing the molten iron desulfurization slag treatment process and exclusion state according to the present invention

<Description of the symbols for the main parts of the drawings>

10: TLC (Torpedo Ladle Car) 20: Charging Ladle

30: exhaust device 40: slag port

50: converter 60: skimmer

70: liquid desulfurization slag 80: solid desulfurization slag

90: converter slag 100: molten iron

The present invention relates to a method for improving the excretion efficiency of high-density sulfur (S) -containing desulfurization slag generated during the pre-treatment desulfurization process in the steelmaking process, more specifically Torpedo Ladle Car (hereinafter referred to as "TLC") ), Desulfurization of molten iron by blowing deliming agent in quicklime system (hereinafter referred to as "CaO system") or calcium carbide system (hereinafter referred to as "CaC2 system"), and then desulfurizing molten iron in the loading ladle. Inevitably, a high concentration of sulfur-containing desulfurization slag is also incorporated into the charging ladle. If the entrained desulfurization slag is poorly contained, sulfur is desulfurized from the desulfurization slag into the molten steel during the refining of the converter. In extreme cases, agitation occurs, and in order to solve this problem, it is necessary to effectively exclude the desulfurization slag incorporated in the charging ladle. It relates to improving the efficiency of desulfurization slag excluded method.

In general, the desulfurization treatment is carried out in the molten iron state. The reason is that when a large amount of carbon (C), silicon (Si), and manganese (Mn) is present, the activity coefficient of sulfur is increased, so that the desulfurization reaction takes place effectively. This is because about 5 times the desulfurization agent should be used to obtain the desulfurization degree.

Meanwhile, as the desulfurization agent, CaO-based or CaC2-based is used. In the case of CaO-based, 7-10 (kg / TP) is used depending on the sulfur concentration before desulfurization, and 4-6 (kg / TP) in the case of CaC2-based. Doing.

In general, steel mills perform desulfurization treatment in TLC (Torpedo Ladle Car), which is a transport vessel, for efficient process flow, and desulfurization is performed by blowing CaO-based and CaC2-based desulfurization agents into a molten iron to meet a desired sulfur concentration.

The desulfurized molten iron is transferred to the molten iron preparation site through the TLC 10 as shown in FIG. 1, and is then embarked on the charging ladle 20, which is a container for charging the molten iron in the furnace 50. In this drawing process, not only the molten iron but also a part of the desulfurization slag 70 and 80 are mixed together and introduced into the charging ladle 20 from the inlet of the upper part of the TLC 10. Desulfurization slag on the order of 9 to 13 (kg / TP) is incorporated into the charging ladle.

Since the mixed slag has a high concentration of sulfur, most of the sulfur moves to the molten steel during refining of the converter 50, which is the next process, unless the disposal process, which is a process of removing the slag floating on the surface of the molten iron after completion of the molten iron, is carried out. In the steelmaking process, desulfurization slag is treated as an essential work to prevent the abdominal phenomena and gaps, since the sulfur phenomenon occurs when sulfur concentration becomes very high. have.

However, the above-mentioned mixed slag does not exist in a uniform state, but a part in contact with the air exists in a solid state (hereinafter referred to as "solid desulfurization slag 80"), and a part in contact with a molten iron is in a liquid state. (Hereinafter referred to as "liquid desulfurization slag 70"). At this time, it is difficult to accurately measure each sulfur concentration, but qualitatively, since the sulfur concentration in the liquid desulfurization slag 70 exists in a much higher state, only the solid desulfurization slag 80 present in the upper portion during the desulfurization slag treatment is disposed. When it is removed, there is still a problem that the abdominal phenomenon occurs because the removal of the liquid desulfurization slag 70 containing a much higher sulfur concentration is not made.

Typically, the excretion treatment is classified into unexposed, medium excreted for about 5 minutes, and complete excretion for about 10 minutes, depending on the treatment time, even if the complete excretion is present in the liquid desulfurization slag 70. Due to the double phenomena of about 0.005 ~ 0.01% of the molten sulfur concentration in the charging ladle 20 occurs.                         

Meanwhile, as a method for solving the above problem, a part of the silica (SiO 2) -based material, which is generally called a flocculant, is partially injected into the upper portion of the charging ladle 20, and the discharge is performed by an exhauster called a skimmer 60. It is a discharging method that gives the desulfurized slag a sticky glassy property to agglomerate slag existing in the upper part of the charging ladle when moving the discharging machine. Although the effect is partially recognized, a flocculant is expensive and a large amount of the dispersing agent is added. Dust is generated, and the ratio of sulfur / sulfur to be balanced by silica addition is lowered, so there is a possibility of double sulfur in the molten iron by the addition itself. A further problem is that slag adheres to the exhauster, so that the frequent replacement of the exhauster and the weight of the exhauster are increased. Due to the decrease in the exclusion rate has a disadvantage that the exclusion efficiency is lowered.

In addition, the slag discharging device for the ladle devised by the present invention to reduce the working time of the post-process by effectively disposing the solid desulfurization slag 80 and the liquid desulfurization slag 70 (application number 20-1996-046535) However, the invention is excellent in the effect, but the current exhaustor due to the increase in weight due to the change in the shape of the exhaustor is insufficient as its exhaustion efficiency is lowered, the upper portion for reinforcement of liquid desulfurization slag Blowing device has the disadvantage of being supplemented additionally because it is not currently available due to frequent damage due to thermal shock.

In the accompanying drawings, reference numeral 30 denotes a discharging device, and 40 denotes a slag port.

 The present invention has been made to improve the above-mentioned conventional problems, and among the desulfurization slag generated during the pretreatment desulfurization during steelmaking process, in particular, easy to dispose of the liquid desulfurization slag, thereby reducing the sulfur in the converter process that is a post process The purpose of the present invention is to provide a method for improving the excretion efficiency of molten iron desulfurization slag that can prevent and further reduce the sulfur dislocation caused by abdominal sulfur.

As a means for achieving the above object, the method of improving the excretion efficiency of the molten iron desulfurization slag of the present invention is a converter slag having a particle size distribution of a certain size in the charging ladle at some point after the molten iron is wired to the charging ladle in TLC By adding a certain amount, the basicity, melting point, and viscosity according to the reaction of the upper desulfurization slag and converter slag to increase the slag not only easily, but also to give solidification and ease of liquid desulfurization slag, and also does not proceed the reaction If not, the high specific gravity converter slag may be present between the liquid desulfurization slag and the molten iron to facilitate the exclusion of the liquid desulfurization slag, thereby increasing the excretion efficiency of the desulfurization slag and thereby reducing the degree of abdominal sulfur.

Hereinafter, an example of the present invention will be described in detail with reference to the accompanying drawings.

After the molten iron 100 is wired to the charging ladle 20 in the TLC 10, the converter slag 90 having a particle size distribution of 2 to 5 mm in the charging ladle 20 is 1.5 to about 40 to 60% of the time. By adding 3 (kg / TP), the basicity, melting point, and viscosity according to the reaction of the upper desulfurization slag and converter slag 90 are respectively increased to easily exclude the upper slag, and the solidification of the liquid desulfurization slag 70 and ease of disassembly. Also, even if the reaction does not proceed, a high specific gravity converter slag 90 is present between the interface between the liquid desulfurization slag 70 and the molten iron 100 to facilitate the discharging of the liquid desulfurization slag, thereby desulfurization. Increasing the slag discharge efficiency and at the same time reducing the degree of abdominal pain.

The converter slag 90 is typically made of 35 to 45% CaO, 10 to 15% SiO2, 15 to 20% T.Fe, 0.035 to 0.045% S, the molten iron 100 to the charging ladle 20 When the converter slag 90 is introduced before starting the ship, a foaming phenomenon in which the slag blows like a bubble due to the reaction between the silicon oxide (Si) in the molten iron and the molten iron is generated, and the slag overflows the charging ladle. This becomes impossible. However, if about 30% of the time has elapsed after entering the molten iron 100, since the forming phenomenon is significantly reduced, it is preferable to input at 40% after leaving the ship. In this case, the uniform mixing or reaction of the input slag 90 and the desulfurization slag does not proceed so that the converter slag is present on the desulfurization slag. Accordingly, since the discharge efficiency of the liquid slag is greatly reduced, the input time of the converter slag is preferably 40 to 60%.

On the other hand, in the method of improving the excretion efficiency of molten iron desulfurization slag of the present invention, the reason for limiting the particle size distribution (particle size distribution of 2 to 5mm) of the converter slag 90 introduced into the charging ladle 20 is as follows. .

Typically generated converter slag 90 has a particle size distribution from the differential to about 10mm, separately from the converter slag 90 in the molten state by spraying the air (Air) in the amorphous state 2 ~ There is a wind-blast slag which has a particle size distribution of 4 mm and is present in a spherical shape. As a result of the input of the converter slag, less than 2 mm has a problem of generating a large amount of dust during input. In addition, there is a problem that a considerable amount cannot be introduced into the charging ladle through the hood, the particle size larger than 4mm is so large that the particle size is too large enough to separate the interface between the molten iron 100 and the desulfurization slag in the charging ladle 20 The problem occurs because it does not limit the granularity of 2 ~ 4mm. Here, the converter slag 90 having a particle size distribution of 2 to 4 mm is preferably a wind slag.

As a result of the operation at the site, the input amount of converter slag 90 was not enough when 400 kg was injected based on the 300 ton molten metal. Therefore, the molten iron slag was observed after the exclusion. However, excessive decrease in temperature occurred in the molten iron with an average temperature decrease of 8 degrees or more, and the preferred converter slag input amount was 1.5-3 (kg / TP). In addition, although the converter slag 90 was introduced into the charging ladle by using a crane (not shown) for transporting the charging ladle 20 in a further test, the charging ladle 20 is preferable. In this waiting state, it is preferable to feed naturally through a hopper (not shown) that stores the converter slag 90 or the like.

Hereinafter, the method of improving the exhaust efficiency of the molten iron desulfurization slag of the present invention described above in detail as follows.

(Example)

In order to compare the conventional method for discharging the desulfurization slag mixed in the charging ladle after the desulfurization treatment and the discharging method according to the present invention, the TLC 10 and the charging ladle 20 having a capacity of 300 tons are used in the actual process. After the desulfurization treatment was carried out using the molten iron in the charging ladle was compared the molten sulfur concentration at the end of the converter (50).

For the accuracy of the experiment, the sulfur concentration of the molten iron before desulfurization was 0.2 ~ 0.25% molten iron and CaO-based desulfurization agent was used as the desulfurization agent. In addition, the sulfur concentration of the molten iron after the desulfurization treatment was compared using a molten iron of 0.003%.

Under the same conditions as above, after the complete exclusion (10 min exclusion) using the conventional exclusion method, converter refining was carried out by inputting the same subsidiary materials without the use of scrap metal. Was investigated. And in the method of discharging according to the present invention, when the molten iron 100 in the charging ladle 20 in the TLC (10) at 500% of the starting point after the input of the converter wind slag 500kg, the remaining molten iron was embarked, and then After complete exclusion in the same manner, the same converter refining was carried out to investigate the concentration of sulfur in the molten steel.

In addition, 10Ch was carried out by the conventional method in terms of accuracy of the experiment, and compared with the degree of duplex by carrying out 10Ch by the method according to the present invention is shown in [Table 1] below, wherein the sulfur is The difference between the concentration of sulfur in the converter end molten steel and the concentration of sulfur in the molten iron in the charging ladle (sulfur concentration in the converter end molten steel-the sulfur concentration in the molten iron in the charging ladle).

 division  Prior art  The present invention  Converter slag input  0kg  500 Kg  Sulfur concentration in molten iron-A  0.0033%  0.0032%  Converter Concentration Sulfur Concentration in Molten Steel-B  0.0082%  0.0054%  Double sulfur amount (B-A)  0.0059%  0.0022%  result  standard  66% reduction

[Table 1] is a comparison of the degree of abdominal sulfur by the conventional method and the method of improving the excretion efficiency of molten iron desulfurization slag of the present invention, as shown in the table by the present invention increases the excretion efficiency of the desulfurization slag in the charging ladle As a result, 66% of the reduction in sulfur content was achieved.

Through the above experiment, the following effects could be expected when the converter slag was added according to the present invention.

First, increase in basicity, melting point and viscosity.

Second, the mixing and dilution effect.

Third, liquid desulfurization slag and molten iron separation effect due to specific gravity difference (specific gravity: converter slug> desulfurization slug).

First, the basicity of the converter slag (CaO / SiO2 ratio) is an average level of 3, the sulfur concentration in the molten iron can be further lowered due to the high basicity compared to the molten slag 2 ~ 2.5 level, and also the FeO and molten iron in the converter slag Due to some reaction with Si in the FeO concentration is lowered, high melting point and high viscosity is made, the slag excretion efficiency is increased.

Secondly, desulfurization slag of about 9 ~ 13 (kg / TP) and high sulfur concentration desulfurization slag, which are usually mixed with charging ladle, are charged by converting converter slag with sulfur concentration of 0.035 ~ 0.045%. There is a dilution effect of lowering the overall sulfur concentration, which means that it is possible to reduce the sulfur concentration in the molten iron in the equilibrium reaction.

Third, when the reaction of desulfurization slag and converter slag by the first and second is insufficient, even if it is not mixed and diluted, the specific gravity of converter slag is greater than that of desulfurization slag, so that liquid desulfurization slag does not exist on the molten iron. Converter slag is present (shown in FIG. 2). Therefore, it is easy to exclude the liquid desulfurization slag.

As described above, by the method of improving the excretion efficiency of the molten iron desulfurization slag of the present invention to put the converter slag in the process of drawing the molten iron to the charging ladle in the TLC to facilitate the exclusion of the desulfurization slag, in particular of the liquid desulfurization slag Exclusion may be facilitated, and thus, sulfur may be prevented in the converter process, which is a post-process, and further, sulfur separation due to the sulfur may be reduced.

Claims (2)

After the molten iron is drawn to the charging ladle 20 in the TLC 10, the converter slag 90 having a particle size distribution of 2 to 4 mm in the charging ladle 20 is 1.5 to 3 (kg) at 40 to 60% of the time. / TP) to increase the basicity, melting point and viscosity according to the reaction of the upper desulfurization slag and converter slag 90, the high specific gravity converter slag 90 of the liquid desulfurization slag 70 and the molten iron 100 Method for improving the exhaust efficiency of molten iron desulfurization slag characterized in that it exists between the interfaces. The method of claim 1, wherein the converter slag (90) uses a wind-breaking slag.

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