JPH1171608A - Rerefining of molten iron - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently and effectively act a slag forming preventive agent by mixing a desiliconizing agent and the slag forming preventive agent and feeding the mixture to the falling stream of molten iron in a tilting trough and a torpedo car after the middle period of receiving of the molten iron. SOLUTION: The molten iron 1 from a blast furnace is received in the tilting trough 3 from a branch trough 2 and is then charged into the torpedo car 4. In the initial period of receiving, the desiliconizing agent 5 is fed via a lance 6 for the tilting trough 3 to at least the molten iron falling stream 1a from the branch trough 2 of the tilting trough 3, by which the molten iron is subjected to a desiliconization treatment. The desiliconizing agent 5 and the slag forming preventive agent 8 are mixed and the mixture is charged to the molten iron falling stream 1a and the molten iron falling stream 1b in the middle period of the receiving. More specifically, the desiliconizing agent 5 fed from a storage hopper 9 and the slag forming preventive agent 8 fed from a storage hopper 10 are mixed in a mixing hopper and the mixture is fed to the lance 6 for the tilting trough and a direct feeding lance 7. Air is projected as a carrier gas from both lances 6, 7 to the respective molten iron falling streams 1a, 1b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to
Particularly, the present invention relates to a method for advantageously performing a desiliconization treatment in a blast furnace cast floor.

[0002]

2. Description of the Related Art Generally, desiliconization in a blast furnace cast floor is performed by:
As disclosed in JP-A-63-176408, JP-B-62-32992, etc., in the process of once receiving hot metal from a branch gutter into a slanting gutter and charging the hot metal from the slanting gutter into a topped car, desiliconization is performed. The slag forming agent is introduced through a branch gutter or a tilting gutter, but as the amount of desiliconization increases, slag forming becomes more pronounced and the amount of received iron in topped cars decreases. Separately, it is common to throw into a torpedo car manually or with a throwing machine (see JP-A-5-287347).

[0003]

However, in the method of introducing the slag forming inhibitor into the torpedo car manually or by a charging machine, the effect of preventing the slag forming is poor, and the slag forming generated as a result of the slag forming does not allow the slag forming agent to receive the slag forming agent. Since the amount of pig iron is reduced and the amount of the desiliconizing agent is insufficient, an increase in the Si concentration in the steelmaking stage poses a problem.

[0004] A method has also been proposed in which a slag forming inhibitor is mixed with a desiliconizing agent and is poured into a slanting gutter. However, since the desiliconization reaction proceeds in the slanting gutter, the slag forming inhibitor is effectively used. Does not work.

Therefore, an object of the present invention is to propose an advantageous method of introducing a slag forming inhibitor in a desiliconization treatment, which solves the above problems.

[0006]

Means for Solving the Problems The inventors of the present invention have intensively studied means for solving the above-mentioned problems, and found that the introduction of a slag forming inhibitor after the middle stage of pig iron receiving in which slag forming occurs. The inventors have found that the present invention is effective and completed the present invention.

That is, according to the present invention, when the tapping of the blast furnace is once poured from a branch gutter into a slanting gutter and received by a tope car from the slanting gutter, at least after the middle stage of the pig ironing, the molten iron falls in the slanting gutter and the topped car. This is a pre-refining method for hot metal, which comprises mixing and adding a desiliconizing agent and a slag forming inhibitor to a stream.

Here, the mixing ratio of the desiliconizing agent and the slag forming inhibitor, and the ratio of the amounts of the desiliconizing agent and the slag forming inhibitor to the inclined pouring gutter and the topped car are adjusted in accordance with the amount of received iron in the toped car. In addition, it is advantageous to implement the desiliconizing agent and the forming inhibitor with compressed air.

[0009]

Next, the method of the present invention will be described in detail with reference to FIG. That is, after the hot metal 1 from the blast furnace is once received from the branch gutter 2 to the inclined gutter 3 and then charged into the torpedo car 4 from the inclined gutter 3, at least in the initial stage of the iron receiving, the desiliconizing agent 5 is at least inclined gutter. In FIG. 3, the molten metal falling flow 1a from the branch gutter 2 is introduced through a lance 6 for inclined gutter to perform a desiliconization treatment. In addition, if necessary, the desiliconizing agent 5
Can be further injected into the falling flow 1b of molten metal from the inclined pouring gutter 3 in the topped car 4 through the direct driving lance 7.

[0010] Thereafter, at the stage of the middle stage of receiving the hot metal, the desiliconizing agent 5 and the slag forming inhibitor 8 are mixed and charged into the hot metal falling flow 1a and the hot metal falling flow 1b.
It is important. Specifically, a predetermined amount of the desiliconizing agent 5 is cut out from the storage hopper 9 storing the desiliconizing agent 5, and a predetermined amount of the slag forming inhibitor 8 is separated from the storage hopper 10 storing the slag forming agent 8.
Are cut out and mixed by a mixing hopper 11, and from this mixing hopper 11, a desiliconizing agent 5 and a slag forming inhibitor 8 are sent to a lance 6 for tilting gutters and a direct lance 7,
From each lance, for example, air is used as a carrier gas and projected onto each falling stream.

According to the above-described steps, in the present invention,
At least after the middle stage of the pig iron receiving, the slag forming inhibitor 8 is mixed with the desiliconizing agent 5 and charged. However, in the early stage of the pig iron receiving, the Si concentration in the hot metal is high and the unreacted silicide decreases. This is because the amount of generated CO gas is small and the generation of slag forming is extremely small, so that slag forming does not become a problem. Of course, the slag forming inhibitor 8 can also be added in the initial stage of pig iron receiving. However, from the viewpoint of cost, the addition of the slag forming inhibitor 8 is performed at least after the middle stage of the pig iron receiving. That is, after the middle stage of the pig iron receiving, the reaction represented by the following formula (1) becomes active at the interface between the hot metal and the slag, so that the slag forming becomes remarkable. Therefore, it is essential to add a slag forming inhibitor after the middle stage of receiving pig iron.

[0012]

(Equation 1)

In addition, by simultaneously adding the desiliconizing agent and the forming inhibitor which were conventionally separately charged into the hot metal, the operation of inputting the desiliconizing agent and the forming inhibitor was performed manually, in particular. In order to make them lighter than in the case, and to enhance their charging effect, they are injected into both the hot metal falling stream 1a and the hot metal falling stream 1b.

Here, the storage hoppers 9 and 10
It is preferable to control the amount of each cut from the hopper 11 to adjust the mixing ratio of the desiliconizing agent 5 and the slag forming inhibitor 8 in the mixing hopper 11 in accordance with the amount of hot metal received by the topped car 4. That is, from the middle stage to the end stage of the pig iron receiving, the reaction according to the above formula (1) becomes active, and slag forming is apt to occur depending on the progress of the desiliconization. The change is advantageous and avoids slag forming by adding an appropriate amount of the slag forming inhibitor.

The mixing ratio of the desiliconizing agent and the slag forming inhibitor and the pouring position may be adjusted according to the amount of received iron (Ri) in the topped car. More specifically, as shown in Table 1, when the amount of received pig iron (Ri) at the completion of receiving pig iron is assumed to be 100%, mixing of the slag forming agent is started from the middle stage of receiving pig iron, and the amount is increased toward the end of the receiving period. It is required to effectively prevent the occurrence of slag forming by changing the distribution ratio between the gutter (1a) and the toped (1b).

[0016]

[Table 1]

Further, the supply amounts of the desiliconizing agent 5 and the slag forming inhibitor 8 from the mixing hopper 11 to the inclined lance 6 and the direct driving lance 7 are controlled to adjust the charging ratio between the two lances. Is preferred. Again,
For the same reason as described above, the charging ratio may be adjusted according to the amount of pig iron received by the topped car.

The desiliconizing agent and the slag forming inhibitor can be charged by using compressed air as a carrier gas.
Recommended. That is, by transporting with compressed and pressurized air and driving the desiliconizing agent and the slag forming inhibitor into the hot metal, the so-called blasting effect (implantation depth by projection) is improved, and particularly, the slag forming prevention is prevented. The effect can be enhanced. here,
The carrier gas, the increase the blasting effect is required air pressurized to at least 5.0 kg / cm ² or so,
On the other hand, the upper limit of the pressure is about 9.0 kg / cm ² . The higher the pressure of air, the better. However, if the pressure is too high, damage to the refractory lining of the inclined gutter becomes large, which may hinder the continuation of the desiliconization treatment. Preferred air pressurization is 7.0 ~
The pressure is about 8.0 kg / cm ² .

In addition, as a desiliconizing agent, in addition to FeO, Fe ₂ O ₃
In an ironworks, mill scale generated in a rolling mill or the like, dust collected in a steelmaking factory, sintered dust obtained in a sintering factory, or the like can also be used. Further, as the slag forming inhibitor, aluminum slag, coal powder, coke powder and the like can be used.

[0020]

EXAMPLE In the desiliconization treatment of the blast furnace cast floor shown in FIG. 1, a slag forming inhibitor was introduced according to the conditions shown in Table 2. Here, FeO, specifically, sinter dust, collected dust, and mill scale were used as the desiliconizing agent, while aluminum slag and coke powder were used as the slag forming inhibitor. Table 2 also shows the results of an investigation on the desiliconization efficiency, the effect of preventing slag forming, and the cost in each operation. In Table 2, when the desiliconizing agent and the slag forming inhibitor were mixed and charged, and the mixing ratio was adjusted (Invention Example 2, Comparative Examples 3 and 4), the mixing ratio shown in Table 3 was used. .

The desiliconization efficiency is evaluated by the ratio of the oxygen consumed in the desiliconization reaction to the oxygen in the desiliconization agent added.
The effect of preventing slag foaming was evaluated based on the change in the toped free board value after the addition of the forming inhibitor.

[0022]

[Table 2]

[0023]

[Table 3]

From Table 2, it can be seen that when a desiliconizing agent and a slag forming inhibitor are mixed and introduced into the falling flow of hot metal in a downspout gutter and a topped car according to the present invention, the desiliconizing efficiency is high and the slag forming preventing effect is obtained. It turns out that it is also excellent. Particularly, Invention Example 2 in which the mixing ratio of the desiliconizing agent and the slag forming inhibitor was adjusted.
Can advantageously use a slag forming inhibitor and is also excellent in cost.

[0025]

According to the present invention, a slag forming inhibitor is introduced at an appropriate time and in an appropriate step.
The added slag forming inhibitor can be effectively applied without waste, and an excellent slag forming prevention effect can be obtained at low cost. In particular, by changing the mixing ratio of the desiliconizing agent and the slag forming inhibitor, and further changing the charging ratio in the inclined gutter and the tope car, the waste of the desiliconizing agent and the slag forming agent is reduced. Can be avoided.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a desiliconization treatment of a blast furnace cast floor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Hot metal 2 Branch gutter 3 Inclined gutter 4 Topped car 5 Desiliconizer 6 Lance for inclined gutter 7 Direct driving lance 8 Slag forming inhibitor

Claims (4)

[Claims] When the tapping from a blast furnace is once poured from a branch gutter into a slanting gutter and received by a tope car from the slanting gutter, at least after the middle stage of the pig ironing, the falling flow of hot metal in the slanting gutter and the topped car is removed. A method for preliminarily refining hot metal, comprising mixing and adding a silicic acid and a slag forming inhibitor. 2. The method according to claim 1, wherein the mixing ratio of the desiliconizing agent and the slag forming inhibitor is adjusted in accordance with the amount of received iron in the topped car. 3. The hot metal according to claim 1, wherein the ratio between the amounts of the desiliconizing agent and the slag forming inhibitor in the inclined gutter and the topped car is adjusted in accordance with the amount of received iron in the topped car. Pre-refining method. 4. The method for preliminarily refining hot metal according to claim 1, wherein the desiliconizing agent and the forming inhibitor are charged with compressed air.