JP6930193B2 - Desulfurization method of hot metal - Google Patents

Description

The present invention relates to a method for desulfurizing hot metal in a steelmaking process.

The hot metal discharged from the blast furnace is desulfurized as a hot metal pretreatment before the dephosphorization and decarburization treatment by the converter. Since it is desirable to suppress the residual S in the refining process as much as possible in order to produce high quality steel, various desulfurization methods have been developed in order to further reduce S.

Patent Document 1 discloses a technique for adjusting the stirring force at the time of adding a desulfurizing material to make it easier for the newly added desulfurizing material to come into contact with slag in a desulfurization method in which a desulfurizing material is added to a hot metal a plurality of times and stirred. ing. As a result, agglomeration due to direct contact of the desulfurizing material with the surface of the hot metal is avoided, and the reaction efficiency of the desulfurizing material is improved.

Japanese Patent No. 4844679

According to the desulfurization method of Patent Document 1, it is possible to reduce S in the hot metal, but when the slag after the desulfurization treatment is discharged, the slag that cannot be completely discharged remains in the hot metal pot. Since this slag is poured into the converter together with the hot metal, desulfurization occurs by oxidative refining in the converter, and the S concentration of the molten steel after the converter refining is higher than the S concentration of the hot metal at the time of charging the converter. It gets higher. That is, the S of the slag brought into the converter contributed to the increase of the S in the molten steel.

The present invention has been made in view of the above circumstances, and an object of the present invention is to reduce S brought into a converter and reduce S in molten steel after refining.

The present invention is a method for desulfurizing hot metal, which solves the above problems. When the hot metal in a container is desulfurized a plurality of times, the waste is discharged after the first desulfurization treatment and again after the second desulfurization treatment. When the amount of desulfurization material used in the first desulfurization treatment and the amount of desulfurization material used in the second desulfurization treatment are determined by discharging the waste, 0.3 ≤ in the first desulfurization treatment. Desulfurization material basic unit / (desulfurization material basic unit during the first desulfurization treatment + desulfurization material basic unit during the second desulfurization treatment) ≤ 0.9 , and the amount of desulfurization material is adjusted so as to satisfy the formula. It is characterized in that the first desulfurization treatment and the second desulfurization treatment are performed once determined.

It is possible to reduce the S brought into the converter and reduce the S in the molten steel after refining.

It is a figure which shows the schematic structure of the steelmaking equipment which concerns on embodiment of this invention. It is a figure which shows the flow of the desulfurization method of the hot metal which concerns on embodiment of this invention. It is a figure which shows the S concentration of hot metal and slag when desulfurization treatment is carried out only once. It is a figure which shows the S concentration of hot metal and slag when the desulfurization treatment is carried out twice, and the slag is carried out between the first and second desulfurization treatments. It is a figure which shows the fluctuation of the converter input S concentration by the difference between the desulfurization material basic unit at the time of the 1st desulfurization treatment and the desulfurization material basic unit at the time of the 2nd desulfurization treatment.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the present specification and the drawings, elements having substantially the same functional configuration are designated by the same reference numerals, so that duplicate description will be omitted.

In this embodiment, the hot metal M is desulfurized using the steelmaking equipment 1 shown in FIG. The flow from the hot metal output from the blast furnace 2 to the hot metal charging into the converter 5 is roughly as shown in FIG.

First, the hot metal M ejected from the blast furnace 2 is charged into the torpedo car 3 and transported to the converter refining facility. During this period, the first desulfurization treatment is carried out on the hot metal M in the torpedo car. The method of the first desulfurization treatment is not particularly limited, and for example, a method of injecting a desulfurization material into hot metal is adopted. This desulfurization treatment reduces S in the hot metal and instead increases S in the slag. In addition, slag (pre-slag) may be carried out before the first desulfurization treatment.

Then, the slag in the torpedo car is discharged. That is, the slag whose S concentration has increased is once discharged before the hot metal M is put into the converter charging pot 4. Since it is difficult for a slag slag discharger (not shown) to discharge all slag due to its structure, a certain amount of slag usually remains in the torpedo car 3 at the time of slag removal. Also in this embodiment, a certain amount of slag remains inside the torpedo car 3 after the slag is discharged. Since this slag contains S removed from the hot metal M, the S concentration is higher than that of the slag at the time of tapping.

Next, the hot metal M in the torpedo car is put into the converter pot 4. At this time, the slag in the torpedo car is also poured into the converter pot 4. That is, S in the slag after the first desulfurization treatment is brought into the converter charging pot 4.

Subsequently, the converter loading pot 4 is placed on a transport carriage and transported toward the converter 5. During this period, the hot metal M of the converter charging pot 4 is subjected to a second desulfurization treatment. The method of the second desulfurization treatment is not particularly limited, and for example, a desulfurization method using a KR desulfurization facility is adopted. By the second desulfurization treatment, S in the hot metal is further reduced, and the hot metal M has an S concentration suitable for charging into a converter.

After that, the slag of the converter charging pot 4 is discharged. As described above, since the slag slag discharger (not shown) has a limited amount of slag discharge due to its structure, a certain amount of slag remains in the converter charging pot after slag removal. This slag contains S of the slag brought in from the torpedo car 3 and S removed from the hot metal M by the second desulfurization treatment. After the slag is discharged, the hot metal M of the converter charging pot 4 is charged into the converter 5, and the converter refining is started.

In the conventional desulfurization method in which the desulfurizing material is added to the hot metal M multiple times, the second desulfurization treatment is started without slag slag after the first desulfurization treatment, so that the slag after the second desulfurization treatment is started. Occasionally, the slag contains S for two desulfurization treatments. For this reason, slag having a high S concentration remains in the pot after the slag after the second desulfurization treatment is carried out. On the other hand, according to the desulfurization method of the present embodiment, since the slag (first slag) is once performed between the first desulfurization treatment and the second desulfurization treatment, the first desulfurization treatment is performed. A certain amount of S removed from the hot metal M is discharged before starting the second desulfurization treatment. As a result, when the second slag after the second desulfurization treatment is carried out (second slag), the S concentration of the slag remaining in the pot is lower than when the first slag is not carried out. It becomes the concentration.

In the present embodiment as well, as in the conventional case, when the hot metal M is charged from the converter charging pot 4 to the converter 5, the slag moves together with the hot metal M and S is brought into the converter. Then, since the S concentration of the slag remaining in the converter charging pot 4 is lower than that in the conventional case, the amount of S brought into the converter 5 is reduced as a result. This makes it possible to reduce S in the molten steel after the steel is discharged.

In the present embodiment, the first desulfurization treatment is carried out in the torpedo car 3, and the second desulfurization treatment is carried out in the converter charging pot 4, but in which container the desulfurization treatment is carried out is particularly important. The desulfurization treatment may be carried out by transferring the hot metal M to another container without limitation. Further, the number of desulfurization treatments is not limited to two, and may be a plurality of times. Further, the desulfurization treatment may be carried out a plurality of times in the same container. However, if the desulfurization treatment is carried out a plurality of times in the same container, the distribution will be stagnant, so it is preferable to carry out the desulfurization treatment in different containers. In particular, since the torpedo car 3 and the converter charging pot 4 are usually used for transporting the hot metal M from the blast furnace 2 to the converter 5, the first desulfurization treatment is performed from the viewpoint of suppressing a decrease in productivity. Is preferably carried out in the torpedo car 3, and the second desulfurization treatment is carried out in the converter charging pot 4.

Further, in carrying out the first desulfurization process and the second desulfurization process, the relationship between the first time the desulfurization treatment of desulfurizing material intensity and desulfurizing material per unit of time the second desulfurization process, 0.3 It is preferable that ≤ 0.9 is satisfied with the desulfurization material basic unit during the first desulfurization treatment / (desulfurization material basic unit during the first desulfurization treatment + desulfurization material basic unit during the second desulfurization treatment). Thereby, S of the slag remaining in the converter charging pot 4 can be further reduced. If the value of the desulfurization material basic unit during the first desulfurization treatment / (the desulfurization material basic unit during the first desulfurization treatment + the desulfurization material basic unit during the second desulfurization treatment) is smaller than 0.3, 1 Since the amount of slag after the second desulfurization treatment is small, it becomes difficult to perform the slag removal work, and there is a possibility that the slag cannot be sufficiently discharged. As a result, a large amount of S in the slag may remain. On the other hand, when the above value is larger than 0.9, the amount of slag after the second desulfurization treatment is small, and similarly, sufficient slag removal work cannot be performed, and a large amount of S in the slag may remain. The preferable lower limit of the desulfurization material basic unit during the first desulfurization treatment / (the desulfurization material basic unit during the first desulfurization treatment + the desulfurization material basic unit during the second desulfurization treatment) is 0.5. Further, the preferable upper limit value of the desulfurization material basic unit at the time of the first desulfurization treatment / (the desulfurization material basic unit at the time of the first desulfurization treatment + the desulfurization material basic unit at the time of the second desulfurization treatment) is 0.8.

Although the embodiments of the present invention have been described above, the present invention is not limited to such examples. It is clear that a person skilled in the art can come up with various modifications or modifications within the scope of the technical idea described in the claims, and of course, the technical scope of the present invention also includes them. It is understood that it belongs to.

A simulation of the desulfurization treatment was carried out, and the S concentration of hot metal and slag in the process from the start of the desulfurization treatment to the slag slag discharge was calculated. In this example, a simulation was carried out assuming two desulfurization methods, a desulfurization method as a comparative example of the present invention and a desulfurization method according to the present invention. The desulfurization method of the comparative example is a method in which the desulfurization treatment is performed only once and then the slag is discharged. Further, in the desulfurization method according to the present invention, the desulfurization treatment is carried out twice in total, the slag is carried out between the first desulfurization treatment and the second desulfurization treatment, and the desulfurization treatment is carried out again after the second desulfurization treatment. It is a method of desulfurization.

The prerequisites for the simulation are as follows.
Hot metal S concentration at blast furnace hot metal = 0.02%
Slag S concentration at blast furnace tapping = 0.30%
Slag amount at the time of tapping = 3.3 kg / t
Desulfurization material input amount = 10 kg / t (In the case of the desulfurization method according to the present invention: Desulfurization material input amount during the first desulfurization treatment = 5 kg / t, Desulfurization material input amount during the second desulfurization treatment = 5 kg / t)
Residual slag after slag = 3 kg / t
-Ln (after desulfurization hot metal S concentration / desulfurization before the molten pig iron S concentration) / desulfurization material consumption per unit = 0.3
Hot metal S concentration at the time of charging in the converter = 0.001%

FIG. 3 shows the S concentrations of hot metal and slag when the desulfurization method of the comparative example was carried out. Further, FIG. 4 shows the S concentrations of hot metal and slag when the desulfurization method according to the present invention is carried out. The S concentration of slag is calculated by converting the amount of slag into the amount of hot metal, and is calculated from S in the slag and the amount of hot metal.

As shown in FIG. 3, in the desulfurization method of the comparative example, the total of the S concentration of the hot metal after the slag and the S concentration of the slag was 60 ppm. On the other hand, as shown in FIG. 4, according to the desulfurization method according to the present invention, the total of the S concentration of the hot metal and the S concentration of the slag after the second slag was 50 ppm. In any of the desulfurization methods, there is no difference in the S concentration of the final hot metal after the desulfurization treatment, but there is a difference in the S concentration of the slag. This is because in the desulfurization method of the comparative example, the slag at the time of slag contains all the S removed in the desulfurization process, so that the S concentration of the slag remaining in the pot after the slag increases. be. Further, for example, even in the desulfurization method in which the desulfurization material is charged into the hot metal in two steps, if the slag is not discharged between the first desulfurization treatment and the second desulfurization treatment, the slag at the time of drainage The S concentration is similarly high.

On the other hand, in the desulfurization method according to the present invention, since the slag is discharged once between the first desulfurization treatment and the second desulfurization treatment, the slag after the discharge after the second desulfurization treatment is carried out. The S concentration is relatively low. Therefore, according to the desulfurization method according to the present invention, the S concentration of slag before charging into the converter can be reduced, and the S brought into the converter can be reduced.

In the desulfurization method of the present invention, the first desulfurizing material per unit of time of the desulfurization process was performed the same simulation as that of Example 1 by changing the second desulfurizing material per unit of time desulfurization process. The converter input S concentration at that time (that is, the total S concentration of hot metal and slag at the time of final slag) was calculated. The result is shown in FIG.

If the first desulfurizing material per unit of time of the desulfurization process too small as shown in FIG. 5, or if too large, reduction of the converter input S concentration was small. According to the results of FIG. 5, in the practice of the desulfurization process of the present invention, 0.3 ≦ first desulfurization when processing desulfurizing material intensity / (first desulfurizing material per unit of time desulfurized +2 preferably satisfies the desulfurizing material intensity) ≦ 0.9 at times th desulfurization treatment. As a result, the converter input S concentration can be significantly reduced. Further, in order to further reduce the converter input S concentration, first desulfurization treatment time of the desulfurizing material intensity / (first desulfurization treatment time of the desulfurizing material intensity +2 th desulfurizing material per unit of time desulfurized ) Is preferably 0.5 or more and 0.8 or less.

The present invention can be applied to the desulfurization treatment of hot metal.

1 Steelmaking equipment 2 Blast furnace 3 Torpedo car 4 converter loading pot 5 converter M hot metal

Claims (2)

When the desulfurization treatment of the hot metal in the container is performed a plurality of times, the slag is discharged after the first desulfurization treatment, and the slag is discharged again after the second desulfurization treatment.
When determining the amount of the desulfurizing material used in the first desulfurization treatment and the amount of the desulfurizing material used in the second desulfurization treatment, 0.3 ≦ the desulfurization material basic unit in the first desulfurization treatment / (The basic unit of the desulfurizing material at the time of the first desulfurization treatment + the basic unit of the desulfurizing material at the time of the second desulfurization treatment) Using the formula of ≤0.9, the amount of the desulfurizing material was determined so as to satisfy the formula. A method for desulfurizing hot metal, which comprises the desulfurization treatment of 1 and the second desulfurization treatment. The method for desulfurizing hot metal according to claim 1, wherein the first desulfurization treatment is performed by a torpedo car and the second desulfurization treatment is performed by a converter charging pot.

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