JPS63213615A - Desiliconizing method in molten iron trough with multi step - Google Patents

Abstract

PURPOSE:To attain sufficient desiliconizing effect in a trough by injecting desiliconizing agent into deep position at a charging position for the desiliconizing agent except the head step and collectively removing desiliconized slag at the downstream side from the above injection position of the finish step. CONSTITUTION:By arranging a diving weir 5 in an molten iron trough 3 and an over-flow weir 6 in a slag trough 4, the molten iron surface flowing charging position of desiliconizing agent in the head step is made to removal condition of the blast furnace slag and in there, the desiliconizing agent is charged on the above surface from a hopper 11. The desiliconizing agent is entrapped in the molten iron flow and desiliconizing reaction having good efficiency is advanced. At the above charging positions on and after second step, the injection is executed into the deep part of the molten iron through a lance 12 inserted as penetrating the desiliconized slag layer by desiliconized agent charged at the position before it and desiliconizing efficiency on the after the second step is improved. And, the over-flow weir 6b in the molten slag trough 3, desiliconized slag trough 9 and dividing weir 5b are arranged at the downstream side from the above charging position of the finish step and the siliconized slag is collectively removed from the trough 9, and the molten iron dives the diving weir 5b and flows down to the downstream side, to receive into a molten iron ladle, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a hot metal trough desiliconization method in which a desiliconizing agent is added to hot metal flowing in a hot metal trough of a blast furnace casthouse.

[Prior art] As a desiliconization treatment method for hot metal, a desiliconizing agent is added just as the hot metal is being poured into a ladle, and the energy under the molten pig iron is used to combine the desiliconizing agent and the hot metal. A method of increasing contact efficiency has been widely used, but in order to improve efficiency, a hot metal trough desiliconization method has been developed in which a desiliconizing agent is added to the hot metal flowing in the hot metal trough on the blast furnace casthouse. By the way, desiliconization of hot metal uses a desiliconization agent mainly composed of iron oxide, and 2Fe
This is a method of desiliconization by advancing the reaction represented by Ox + x [Si] - + 2Fe + x SiO
For example, as disclosed in Japanese Unexamined Patent Publication No. 130208/1984, there are two methods: (1) a method of injecting a desiliconizing agent onto the hot metal flowing on the hot metal trough and causing the desiliconizing agent to be entangled in the torrent of hot metal; A method in which the desiliconizing agent is sprayed by an air flow conveying means, and the spraying uses energy to aim for the above-mentioned entrainment effect of 0 or more. ■ A herrance is thrust into the hot metal flow, and the desiliconizing agent is transferred from the lance by a carrier gas to the hot metal. A method of injecting it into the body is being considered. In addition, when carrying out the above method, a step is provided in the hot metal trough to generate falling energy of the hot metal to promote the incorporation of the desiliconizing agent, or mechanical stirring is added at the position where the desiliconizing agent is introduced. A method has also been devised to increase the desiliconization efficiency.

However, in these conventional hot metal gutter desiliconization methods, the desiliconization reaction on the gutter does not necessarily proceed as fully as desired.
Since it is necessary to further desiliconize, the generated desiliconization slag is not discharged on the hot metal slag, but is flowed together with the hot metal into a mixing car or a hot metal ladle (hereinafter referred to as hot metal ladle).
It is customary to further advance the desiliconization reaction by utilizing the agitation generated by the falling energy (usually there is a considerable head difference of 1 to 3 m). Therefore, it was considered to be somewhat unavoidable that the following difficulties would arise. That is, the desiliconizing slag contains (1) iron oxide which is the main component of the desiliconizing agent, (2) CaO added to increase the activity of the iron oxide, and (2) 5102 produced by desiliconizing.
The basicity expressed by CaO/SiO2 is usually adjusted to a value of about 1.5 or less, and when such desiliconization slag is injected into a hot metal ladle with hot metal, there is a Residual desulfurization slag from the adhering precharge (when dephosphorization and desulfurization are continued in the hot metal ladle, desulfurization slag is removed as much as possible by a slag dragger, etc., but it is not completely removed, and a considerable amount of desulfurization remains) The slag remains attached to walls, etc.) becomes low basicity through contact with the desiliconization slag, and when it comes into contact with newly charged hot metal, resulfurization from the low basicity desulfurization slag occurs. , the amount of [Sl in the hot metal increases, and the desulfurization cost in the next step increases. In addition, if desiliconization slag with low basicity exists on the hot metal, it will be a hindrance to the molten 8A ladle dephosphorization in the next process as described above (it will reduce the basicity of the dephosphorization flux for which a high basicity is desired, and reduce the dephosphorization efficiency). However, even with these methods, the desiliconization slag cannot be completely removed.

From this point of view, the applicant of the present application filed the Japanese Patent Publication No. 61-489.
As disclosed in Publication No. 1, a method was also attempted in which the desiliconizing slag was removed on a gutter to prevent the desiliconizing slag from getting mixed into the hot metal pot. However, with this method, the energy of the hot metal falling into the ladle is not utilized, and there is an undeniable tendency for the desiliconization to be insufficient.

[Problems to be Solved by the Invention] The present invention has been made with attention to the above-mentioned circumstances, and its purpose is to discharge and remove desiliconization slag on the hot metal sluice before entering the hot metal ladle. The object of the present invention is to provide a method for desiliconizing a hot metal trough that can obtain a sufficient desiliconization effect on the trough even in the case of a hot metal trough.

[Means for Solving the Problems] The configuration of the present invention that has achieved the above object includes introducing a desiliconizing agent into the hot metal flowing down on the hot metal gutter of the blast furnace casthouse at two or more different positions. This is a hot metal sluice multi-stage desiliconization method in which desiliconization is carried out in the second and subsequent stages, and the desiliconizing agent is injected deep into the hot metal sluice at the desiliconizing agent injection position in the second and subsequent stages, and the desiliconizing slag is injected into the final stage desiliconizing agent injection position. The key point is that the sludge is removed all at once on the downstream side.

[Function] In order to sufficiently progress the desiliconization of the hot metal trough, the present invention employs a multi-stage desiliconization method in which a desiliconizing agent is introduced into the hot metal flowing on the hot metal trough at two or more different positions to perform desiliconization. do. In this case, the surface of the hot metal flowing through the first desiliconizing agent injection position is after the blast furnace slag has been removed and there is no desiliconizing slag, so even if the desiliconizing agent is only introduced onto that surface. Direct contact with the hot metal is achieved immediately, and it is quickly drawn into the hot metal flow, allowing an efficient desiliconization reaction to proceed.
At the positions where the desiliconizing agent is introduced after the stage, the desiliconizing slag derived from the desiliconizing agent introduced at the previous position covers the hot metal surface. The purpose of multi-stage desiliconization cannot be achieved because the hot metal cannot be brought into direct contact with the hot metal and the amount that is drawn into the hot metal flow is also small. Therefore, in the present invention, a configuration is adopted in which the desiliconizing agent is injected into the deep part of the hot metal through a refractory lance inserted through the desiliconizing slag layer on the hot metal surface.
By increasing the desiliconization efficiency in the second and subsequent stages, [Si
They succeeded in reducing the amount of l to the target level. In order to efficiently proceed with the next dephosphorization process, the inventors of Naoki and others have set a goal after desiliconization [Sil content below rO, 15%], but conventional desiliconization on hot metal sluices alone cannot achieve this low level. It was not possible to secure the [Sil amount] of the level.

However, if the multi-stage desiliconization method of the present invention is adopted, the above target [Si
] Jt can be achieved reliably, and the next de-v4
Processing can be carried out efficiently and smoothly.

For example, FIGS. 1 and 2 are a schematic plan view and a schematic sectional view showing an embodiment of the present invention, and hot metal is tapped through a hot metal sluice 3 extending from a tap hole 2 of a blast furnace 1. A slag drain 4 is branched in the middle of the hot metal trough 3, and the blast furnace slag is separated in this part. That is, at the branch part, a submerged weir 5 is provided on the hot metal trough 3 side, and an overflow weir 6 is provided on the slag trough 4 side.
The blast furnace slag with low specific gravity is transferred to the submerged weir 5.
The slag is dammed up and guided from the overflow weir 6 to the slag culvert 4 direction, and the hot metal with a high specific gravity passes under the submerged weir 5 and flows to the downstream side of the slag 3. Immediately downstream of the submerged weir 5, a desiliconizing agent charging hopper 11 is arranged to charge the desiliconizing agent, and the first stage of desiliconizing treatment is performed downstream of the charging position.

In this case, a stepped portion 8 is provided on the downstream side of the hopper 11 as shown in the figure.
If a falling flow is provided to disturb the hot metal flow and promote entrainment of the desiliconizing agent, the first stage of desiliconization can be efficiently carried out. For the same purpose, the desiliconizing reaction can be carried out by immersing an agitator immediately downstream of the hopper 11, or by using a desiliconizing agent blowing device instead of the hopper 11 to inject the desiliconizing agent deep into the hot metal flow. It is also effective to promote this.

[S] in the hot metal achieved by the first stage desiliconization process described above.
i]ffi varies depending on the amount of Sil in hot metal and the amount of desiliconizing agent added, but before treatment [Si]ffi after treatment when the Sil amount exceeds 0.4% is at most Approximately 0.15 to 0.2%, before treatment [Sil amount 0.5
% after treatment [Sil amount becomes even higher and 0
．． This decreases to only about 2 to 0.25%, and cannot satisfy the above-mentioned requirement of "target [Sil amount 0.15% or less"] before the dephosphorization treatment. Therefore, in the present invention, a second stage of desiliconization is performed further downstream. However, since the surface of the hot metal that has completed the first stage desiliconization is covered with desiliconization slag, even if the desiliconization agent is added from above, it will not mix with the hot metal and the purpose cannot be achieved. Therefore, in the second stage desiliconization, as shown in Figures 1 and 2, the lance 12 is inserted so as to penetrate the desiliconization slag layer, and the desiliconization agent is injected deep into the hot metal. The amount of [Sil in the hot metal is reduced to 0.15].
% or less to the target value. A desiliconizing slag trough 9 is branched downstream from the second stage desiliconizing position, and a submerged weir 5b is provided on the hot metal trough 3 side to dam the desiliconizing slag with low specific gravity, and the desiliconizing slag is Silica slag gutter 9
The hot metal is separated in the direction of the desiliconization slag gutter 9 through an overflow weir 6b provided at the branching part of the slag, and the hot metal passes through the submerged weir 5b and flows downstream to be received into a hot metal ladle, a pig iron mixing car, etc.

With this method, the second desiliconization step removes [[
It is now possible to reduce the amount of Sil to 0.15% or less, and the desiliconization slag is reliably removed before it reaches the hot metal pot, etc., so there is no need to reduce the dephosphorization efficiency due to insufficient desiliconization or remove the desiliconization slag. Problems such as resulfurization and dephosphorization failure caused by lowering the basicity of the residual desulfurization slag due to the contamination of the desulfurization slag are solved at once.

FIG. 3.4 is a schematic vertical sectional view showing other embodiments of the present invention, each of which shows a three-stage desiliconization method, in which the desiliconizing agent is fed from a common desiliconizing agent supply source 13 in the first stage desiliconizing method. The desiliconizing agent is sprayed onto the surface using a lance 12a.

Figure 3 shows the lance 12 for injecting the desiliconizing agent.
Two units of molten pig iron are immersed in a common pool in the hot metal sluice 3 along the flow direction, and desiliconization is carried out in three stages.

Further, FIG. 4 shows an example in which two pools are formed in the hot metal trough 3 and injection lances 12 for second-stage desiliconization and third-stage desiliconization are immersed in each. In either example, the desiliconizing slag produced is separated and removed from the hot metal on the downstream side of the desiliconizing agent injection position in the final stage in the same manner as in the example shown in FIG. 1.2. If the desiliconization treatment is performed in three or four or more stages in this way, the amount of [Sil] in the hot metal can be further reduced. This is extremely effective if you want to make a steel type with a target of .

[Example] The following experiment was conducted using hot metal trough desiliconization equipment as shown in FIG.

Comparative Example 1 One-stage desiliconization was performed by omitting the injection of the desiliconizing agent from the injection lance 12, and only by dropping the desiliconizing agent from the step portion 8 and stirring, and examining the hot metal components at a predetermined position. Ta.

Comparative Example 2 One-stage desiliconization was performed by omitting the introduction of the desiliconizing agent from the hopper 11 and only injecting the desiliconizing agent from the injection lance 12, and the hot metal components at predetermined positions were examined.

The first stage of desiliconization is performed by injecting a desiliconizing agent from the hopper 11, and the second stage is by injecting a desiliconizing agent from the injection lance 12.
Step-by-step desiliconization was performed continuously, and the hot metal components at predetermined locations were investigated.

The amount of desiliconizing agent used in each experimental example and the hot metal components before and after desiliconization are shown in Table 1 below, and the [Si
Figure 5 shows the changes in the amount of l.

As is clear from the results shown in Table 1 and Figure 5, in both conventional one-stage desiliconization methods (Comparative Examples 1 and 2) Although it is not possible to reduce rO to 15% or less, according to the present invention, the initial Sil content of blast furnace hot metal [Sil content is about 0.3 to 0.4% as well as those exceeding 0.5%] However, the amount of Sil can be reduced to 0.15% or less by two-stage desiliconization.

[Effects of the Invention] The present invention is configured as described above, and its effects are summarized as follows.

(1) Since the amount of [Sil] in the hot metal can be reduced to 0.15% or less only by desiliconization of two or more stages of hot metal sluices, the efficiency of subsequent dephosphorization processing can be increased.

(2) Since the second and subsequent stages of desiliconization are carried out by injection of the desiliconizing agent, no desiliconizing agent is wasted, and an excellent desiliconizing effect can be obtained even with a relatively small amount of desiliconizing agent. can.

(3) Since the desiliconizing slag is almost completely removed on the hot metal gutter, there is no need to remove the desiliconizing slag in a hot metal pot, etc., and there is no need to remove the desiliconizing slag due to the contamination of the desiliconizing slag. Problems such as deterioration do not occur at all.

[Brief explanation of the drawing]

Figures 1 to 4 show examples of the present invention, with Figure 1 being a schematic plan view, Figures 2 to 4 being a schematic longitudinal cross-sectional view, and Figure 5 showing the progress of desiliconization in a desiliconization experiment. It is a graph showing a comparison between the sampling position and the sampling position. 1...Blast furnace 2...Tapping hole 3...Hot metal trough 4...Slag slag 5.5b...Submerging i
6, 6b...Overflow base 8...Step part
9... Desiliconization slag gutter 11... Hopper

Claims (1)

[Claims] This is a hot metal trough multi-stage desiliconization method in which desiliconization is performed by injecting a desiliconizing agent into the hot metal flowing down on the gutter of a blast furnace casthouse at two or more different positions, and the desiliconizing agent is introduced in the second and subsequent stages. A multi-stage desiliconization method using a hot metal sluice, characterized in that a desiliconizing agent is injected into the deep part of the hot metal sluice, and the desiliconizing slag is discharged all at once downstream from the position where the desiliconizing agent is introduced in the final stage.