JP2007182624A - Continuous desiliconization method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To evenly and stably perform desiliconization and to improve efficiency of desiliconization. <P>SOLUTION: Desiliconization can be performed evenly and stably at an improved efficiency of desiliconization by controlling the relationship between the number of vanes 16 of an impeller 10, the relationship between the height b0 of the base of each impeller 16 and the height b1 of its top end, the relationship between the width d of each impeller 16 and the diameter or width of the passage of molten iron, the relationship between the depth Z of the molten iron flowing through the passage and the distance h1 from the top end of the impeller to the upper surface of the molten iron, and the relationship between the depth Z of the molten iron flowing the passage and the distance h2 from the lower end of the top end of the impeller to the bottom of the passage. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a continuous desiliconization method for continuously removing silicon in molten iron.

  The hot metal reduced and produced in the blast furnace is usually about 0.3 to 0.7% of silicon [Si], and about 4.3 to 4.6% of carbon [C], 0.09 to It contains about 0.13% phosphorus [P]. In order to refine this hot metal into steel, it is necessary to reduce carbon [C] and phosphorus [P] to a predetermined concentration. From the viewpoint of refining efficiency, however, silicon [Si] and sulfur are required prior to decarburization and dephosphorization. It is desirable to remove [S] to as low a concentration as possible (for example, silicon [Si] 0.25%). Therefore, conventionally, pretreatment such as desiliconization and desulfurization has been performed on the molten iron discharged from the blast furnace (for example, Patent Document 1 and Patent Document 2).

Patent Document 1 discloses a method of desulfurization treatment. A desulfurization agent is added to hot metal contained in a ladle, an impeller (stirring blade) is immersed in the hot metal, and the impeller is rotated to desulfurize. It is a method to do.
On the other hand, Patent Document 2 discloses a method of desiliconization treatment. A desiliconization reaction tank is provided in a hot metal flow path of a blast furnace casting floor, and a desiliconizing agent is added to the hot metal in a desiliconization conveyance tank. This is a method of desiliconization by stirring the hot metal with an impeller.
Japanese Patent Publication No.45-31053 JP 54-137420 A

As described above, in the desulfurization process and the desiliconization process, both processes are performed by stirring the hot metal with an impeller, whereas in the desulfurization process, the hot metal is stirred in a state where the hot metal is contained in the ladle. In the desiliconization process, unlike the desulfurization process, the hot metal continuously flowing in the hot metal flow path of the blast furnace casting is stirred.
Therefore, it is relatively easy to perform the desulfurization treatment by uniformly stirring the hot metal staying as in the desulfurization treatment of Patent Document 1, but the impeller that flows continuously as in Patent Document 2 is imperative. It is still difficult to carry out the desiliconization process by stirring, and there are problems that the desiliconization efficiency is lowered and that the desiliconization cannot be performed stably without variation.

  In view of the above problems, an object of the present invention is to provide a continuous desiliconization method capable of improving desiliconization efficiency and performing desiliconization stably without variation.

In order to achieve the above object, the present invention has taken the following measures.
That is, the technical means for solving the problems in the present invention include 3 to 6 blades of the impeller to be immersed and rotated in the molten iron, and the blades are expressed by the equations (1) and (2). In addition, the impeller is immersed in the hot metal so as to satisfy the expressions (3) and (4).
b0 ≧ b1 (1)
0.2 ≦ d / D ≦ 0.8 (2)
0 <h1 / Z ≦ 0.4 (3)
0 <h2 / Z ≦ 0.4 (4)
However,
d: Blade width (m)
D: Diameter or width (m) of hot metal flow path
b0: Height of the base of the blade (m)
b1: Height of blade tip (m)
Z: Depth of hot metal flowing in hot metal flow path (m)
h1: Distance from the upper end of the blade tip to the hot metal upper surface (m)
h2: Distance from the lower end of the blade tip to the bottom of the hot metal flow path (m)
The inventor verified the method of performing desiliconization stably from various angles while improving the desiliconization efficiency during the desiliconization process by uniformly stirring the hot metal flowing through the hot metal flow path of the blast furnace casting floor. .

Specifically, a plurality of impellers having different numbers of impellers and blade widths are manufactured, and the impeller is immersed in the hot metal using the impeller (the distance h1 from the top of the blade tip to the top surface of the hot metal, An experiment for desiliconization was performed while changing the distance h2) from the lower end to the bottom of the hot metal flow path.
As a result of the experiment, the number of blades of the impeller to be immersed and rotated in the hot metal is 3 to 6, and the blades satisfy the formulas (1) and (2). By satisfying the formulas (3) and (4), the desiliconization efficiency can be improved and the desiliconization can be stably performed even when the molten metal flow continuously. I found it.

According to the present invention, desiliconization efficiency can be improved and desiliconization can be performed stably without variation.

First, an example of blast furnace equipment to which the continuous desiliconization method of the present invention is applied will be described. However, the continuous desiliconization method of the present invention is not applied only to this equipment.
As shown in FIGS. 1 to 3, a blast furnace casting bed 1 is provided around the blast furnace, and this blast furnace casting bed 1 has a hot metal 4 (hot metal flow path) through which hot metal discharged from the blast furnace 2 flows. Have.
A drainage 5 is branched in the middle of the feed 4, and a dive for guiding the molten iron slag 6 to flow in the waste 5 near the downstream of the branch portion of the feed 4. A weir 7 is provided.

In addition, a reaction tank 8 having a substantially circular shape in plan view is provided on the downstream side of the branch portion of the feed 4. A plurality of impellers 10 are arranged on the output 4. Specifically, an impeller 10 a (stirring blade) that stirs the hot metal flowing through the tap iron 4 is disposed in the reaction tank 8, or an impeller 10 b is disposed between the branched portion and the reaction tank 8. An addition device 12 for adding the desiliconizing agent 11 is provided in the vicinity of the impeller 10a or the impeller 10b.
Accordingly, the hot metal discharged from the blast furnace 2 flows from the upstream side to the downstream side of the hot metal 4, the slag 6 on the hot metal flows through the submergence weir 7 and flows to the exhaust 5, and the hot metal itself is a reaction tank. It will flow toward 8. And the desiliconization of the hot metal which flows continuously can be performed by rotating the impeller 10a or the impeller 10b immersed in the hot metal while adding the desiliconizing agent 11 to the hot metal with the addition device 12.

Next, the structure of the impeller used in the continuous desiliconization method will be described in detail.
As shown in FIGS. 3 and 4, the impeller 10 a or the impeller 10 b is made of a refractory or the like, and has a cylindrical or rod-shaped rotating shaft 15 and a plurality of blades 16 provided at the tip of the rotating shaft 15. is doing. Each blade 16 has a substantially rectangular shape projecting radially outward from the tip of the rotary shaft 15. The height b0 of the base part (joining part with the rotating shaft 15) of each blade | wing 16 is set so that it may become larger than the height b1 of the front-end | tip part (projection front-end | tip part) of the blade | wing 16. FIG.
That is, the heights b0 and b1 of the blades 16 of the impeller 10a or the impeller 10b are set so as to satisfy the formula (1).

b0 ≧ b1 (1)
In other words, as shown in FIGS. 5A to 5C, the impeller 10a or the impeller 10b is set so that the angle θ between the vertical wall 17 at the tip of the blade 16 and the horizontal wall 18 of the blade 16 is 90 ° or more. The blade 16 is configured. As shown in FIG. 5, the shape of the blade portion 16 of the impeller 10a or impeller 10b may be rectangular, trapezoidal, or arcuate (chamfered at the tip) as viewed from the side. Good.
The number of impellers 10a or 10b is set to 3-6. Specifically, in this embodiment, as shown in FIGS. 1 to 5 and FIG. 6A, the number of blades 16 is four. Each blade 16 is attached to the rotary shaft 15 at an equal angle with respect to the rotary shaft 15 corresponding to the number of blades 16. When the number of blades 16 is four, each blade 16 is attached to the rotary shaft 15 so that the arrangement angle between the blades 16 is approximately 90 °.

As shown in FIG. 6B, when the number of blades 16 is three, each blade 16 is attached to the rotating shaft 15 so that the arrangement angle between the blades 16 is approximately 120 °. Yes.
As shown in FIG. 6C, when the number of blades 16 is 6, each blade 16 is attached to the rotating shaft 15 so that the arrangement angle between the blades 16 is approximately 60 °.
Now, as shown in FIG. 4, the width d of the blade 16 is focused on the two blades 16 that are farthest apart from each other, and the protruding lengths (the length from the base of the blade 16 to the tip of the blade 16). In other words, that is, the sum of the projection length d1 of one blade 16 serving as a reference and the projection length d2 of the other blade 16 farthest from the blade 16, The width d is set so as to satisfy the formula (2).

0.2 ≦ d / D ≦ 0.8 (2)
However,
D: Diameter or width (m) of hot metal flow path
Specifically, as shown in FIG. 6A, when the number of blades 16 is four, the protrusion length d1 of the first blade 16a and the protrusion length d2 of the second blade 16b The total is the width d of the blade 16.
As shown in FIG. 6B, when the number of blades 16 is three, the total of the projection length d1 of the first blade 16a and the projection length d2 of the second blade 16c is The width is d.

As shown in FIG. 6C, when the number of blades 16 is six, for example, the sum of the protruding length d1 of the first blade 16a and the protruding length d2 of the fourth blade 16d is The width d of the blade 16 is set.
In formula (2), the diameter of the hot metal flow path (outlet 4), that is, the diameter of the reaction tank 8, is applied to the impeller 10a disposed in the reaction tank 8. Moreover, D of Formula (2) is the width | variety of the hot metal flow path (outlet 4) with respect to the impeller 10b arrange | positioned between the reaction tank 8 and a branch part (width in the linear part of a hot metal flow path). Applies.

Therefore, the width d of the blade 16 of the impeller 10a or the impeller 10b is changed according to the location of the impellers 10a and 10b.
Although the configuration of the impeller is as described above, efficient continuous desiliconization treatment can be performed by using the impeller configured in this way as described below. Hereinafter, the continuous desiliconization method will be described.
First, when hot metal is fed from the brewing port of the blast furnace 2 to the hot metal 4, the desiliconizing agent 11 is added to the hot metal flowing through the hot metal 4 using the adding device 12. At this time, the impellers 10a and 10b configured as described above are immersed and rotated in the hot metal so as to satisfy the expressions (3) and (4), and the hot metal and the desiliconizing agent are mixed.

0 <h1 / Z ≦ 0.4 (3)
0 <h2 / Z ≦ 0.4 (4)
However,
Z: Depth of hot metal flowing in hot metal flow path (m)
h1: Distance from the upper end of the tip of the blade 16 to the upper surface of the hot metal (m)
h2: Distance (m) from the lower end of the tip of the blade 16 to the bottom of the hot metal flow path
When impeller 10 is immersed in hot metal, the relational expression h1 / Z + h2 / Z + b1 / Z = 1.0 is satisfied, and blade 16 is set so as to satisfy this expression, Expression (3), and Expression (4). The height b1 is set.

The hot metal that has been subjected to the silicon removal treatment is charged into a chaotic car (topie car) that flows downstream and transports the hot metal.
By doing in this way, while desiliconization efficiency improves, desiliconization can be performed stably without variation.

  Hereinafter, the impeller 10 was manufactured so that the number of blades 16 was 3 to 6 and the expressions (1) and (2) were satisfied, and the silicon removal treatment was performed using the impeller 10 and the expression (1 ), A comparative example in which an impeller 10 that does not satisfy the formula (2) is manufactured and desiliconization processing is performed using the impeller 10 will be described as an example. The implementation conditions are as shown in Table 1.

Silicon [Si] in the hot metal reacts with oxygen [O] in the desiliconizing agent 11 and is removed from the hot metal as (SiO ₂ ) according to the reaction formula of Si + 2O = SiO ₂ . The desiliconization oxygen efficiency shown by Formula (5) was used as an index showing whether the desiliconization agent 11 added to the hot metal contributed to the desiliconization reaction efficiently.
The desiliconization oxygen efficiency indicates the ratio of the oxygen content used for the oxidation of Si in the hot metal to the oxygen content in the desiliconization agent 11.

Table 2 and FIGS. 7 to 10 summarize the desiliconization oxygen efficiency when the desiliconization process is performed using a plurality of impellers 10. Hereinafter, the results shown in Table 2 and FIGS. 7 to 10 will be described.
In addition, “樋” in the column of the stirring position in Table 2 indicates a straight portion of the output 4, and “circular reaction vessel” indicates that the reaction vessel 8 is used.
In actual operation, the maximum basic unit of the desiliconizing agent that can be charged is 60 kg / ton due to the restrictions of the molten iron passing speed and the desiliconizing agent charging speed, and when the desiliconizing oxygen efficiency is less than 60%, When the maximum silicon [Si] is as high as about 0.7 mass%, the silicon [Si] after the majority treatment
Will exceed 0.25 mass%. Therefore, it is necessary to ensure the desiliconization oxygen efficiency of 60% or more.

[Number of impeller blades]
As shown in Table 2 and FIG. 7, when the number of blades 16 was less than 3 and the number of blades 16 was small, the desiliconization oxygen efficiency was less than 60% (Comparative Examples 12 and 13). This is presumably because the number of blades 16 is small, and thus the ability (stirring ability) to entrain the desiliconizing agent 11 in the hot metal when the impeller 10 is rotated is lowered.
On the other hand, when the number of blades 16 is more than 6, the desiliconization oxygen efficiency is less than 60% (Comparative Example 14). This is because the number of blades 16 is too large, so that when the impeller 10 is rotated, the slag 6 generated by the desiliconization reaction easily adheres to the blades 16 and the slag 6 clings to the blades 16 to form a dumpling. It is thought that the cause is that it hardens. Even if the impeller 10 is rotated with the dumpling-like slag 6 attached, the stirring force is weak, and therefore the reaction efficiency is deteriorated.

Therefore, the number of blades 16 is preferably 3 to 6 so that the stirring ability can be increased and the slag 6 is difficult to cling, and in this way, the desiliconization oxygen efficiency can be 60% or more. did it.
[Relationship between blade width and hot metal diameter or width]
As shown in Table 2 and FIG. 8, when the relationship between the width of the blade 16 and the diameter or width of the hot metal flow path is d / D <0.2, the desiliconization oxygen efficiency was less than 60% (comparison) Examples 19, 20).
This means that when the impeller 10 is immersed, the immersion width (width d) of the impeller 10 is smaller than the diameter and width of the hot metal flow path. Even if the impeller 10 is rotated, the vicinity of the impeller 10 is not affected. It is considered that the stirring force can be given only to a part of the flowing hot metal, and the sufficient stirring force cannot be given to the hot metal flowing away from the impeller 10.

That is, the hot metal flowing on the side of the side wall 4a forming the feed 4 passes through a place away from the blades 16 of the impeller 10 and is therefore not stirred much. The hot metal which is not given sufficient stirring force flows from the upstream to the downstream as it is and is not sufficiently mixed with the desiliconizing agent 11.
On the other hand, when the relationship between the width of the blade 16 and the diameter or width of the hot metal channel is d / D> 0.8, the desiliconization oxygen efficiency was less than 60% (Comparative Examples 15 and 16).
This means that when the impeller 10 is immersed, the immersion width (width d) of the impeller 10 is too large with respect to the diameter and width of the hot metal flow path. The vortex for drawing in the hot metal could not be generated on the surface of the hot metal, and the reaction efficiency was deteriorated.

Therefore, the relationship between the width d of the blade 16 and the diameter or width of the hot metal flow path is as shown in the expression (2) in which the width d of the blade 16 is not too large and too small with respect to the diameter or width of the hot metal flow path. In this way, the desiliconization oxygen efficiency was able to be 60% or more.
[About the depth of the hot metal and the distance from the upper end of the blade tip to the upper surface of the hot metal]
As shown in Table 2 and FIG. 9, the upper end of the tip of the blade 16 is flush with the hot metal upper surface, that is, the relationship between the depth of the hot metal and the distance from the upper end of the tip of the blade 16 to the upper surface of the hot metal is h1. When / Z = 0, the desiliconization oxygen efficiency was less than 60% (Comparative Examples 14, 15, and 21).

Even if the impeller 10 is rotated, the upper end of the tip of the blade 16 only rotates the upper surface (bath surface) of the hot metal, that is, the interface between the desiliconizing agent 11 and the hot metal bath surface. It is considered that the reason is that the agent 11 cannot be sufficiently entrained in the hot metal.
On the other hand, when the relationship between the depth of the hot metal and the distance from the upper end of the tip of the blade 16 to the upper surface of the hot metal is h1 / Z> 0.4, the desiliconization oxygen efficiency was less than 60% (Comparative Example 20). .
Even if the impeller 10 is deeply submerged with respect to the hot metal and the impeller 10 is rotated, only a part of the hot metal flowing in the vicinity of the impeller 10 can be agitated, and flows above the vane 16. It is thought that this is because sufficient stirring power cannot be applied to hot metal. The hot metal flowing above the blades 16 flows from the upstream to the downstream as it is, and is not sufficiently mixed with the desiliconizing agent 11.

Therefore, the relationship between the depth of the hot metal and the distance from the upper end of the tip of the blade 16 to the upper surface of the hot metal is preferably expressed by the equation (3) in which the impeller 10 does not float and sink too much with respect to the hot metal. By doing so, the desiliconization oxygen efficiency could be increased to 60% or more.
[About the depth of the hot metal and the distance from the lower end of the tip of the blade to the bottom of the hot metal flow path]
As shown in Table 2 and FIG. 10, the lower end of the tip of the blade 16 is in contact with the bottom of the hot metal flow path. That is, when h2 / Z = 0, the bottom of the hot metal flow path and the blades 16 are in contact with each other, and the operation itself is not realized.

On the other hand, the blade 16 of the impeller 10 is separated from the bottom of the hot metal flow path, and the relationship between the depth of the hot metal and the distance from the lower end of the tip of the blade 16 to the bottom of the hot metal flow path is set to h2 / Z> 0.4. In some cases, the silicon removal oxygen efficiency was less than 60% (Comparative Examples 13, 21, 22).
This is because the blades 16 of the impeller 10 are not submerged with respect to the hot metal, so that only a part of the hot metal flowing in the vicinity of the impeller 10 can be stirred. Is considered to be caused by the inability to provide sufficient stirring force. The hot metal flowing under the blades 16 flows from the upstream to the downstream as it is, and mixing with the desiliconizing agent 11 is not sufficiently performed.

Therefore, the relationship between the depth of the hot metal and the distance from the lower end of the tip of the blade 16 to the bottom of the hot metal flow path is preferably expressed by the equation (4) in which the impeller 10 does not float and sink too much with respect to the hot metal. In this way, the desiliconization oxygen efficiency could be increased to 60% or more.
As described above, the number of the blades 16 of the impeller 10 is set to 3 to 6, and the blades satisfy the expressions (1) and (2). When the impeller 10 is desiliconized, the expression (3 ), Soaking in the hot metal so as to satisfy the formula (4) and rotating, the desiliconization efficiency can be improved and the desiliconization can be performed stably without variation.

  The present invention is not limited to the above embodiment. In the above embodiment, the hot metal is stirred with one impeller 10 to perform the desiliconization process. However, a plurality of impellers 10 may be provided in the tub 4 (the straight portion of the tub 4) or in the reaction tank 8.

  The present invention can be used in a method for continuously refining hot metal discharged from a blast furnace.

FIG. 1 is a schematic plan view of a blast furnace casting floor in a blast furnace facility. FIG. 2 is a schematic side view of a blast furnace casting floor. FIG. 3 is a perspective view of the hot metal supply path and the impeller. FIG. 4 is an immersion diagram showing an impeller immersion state. FIG. 5 is a schematic diagram of impeller blades. FIG. 6 is a layout diagram for explaining the layout of the blades. FIG. 7 is a diagram summarizing the relationship between the number of blades and the desiliconization oxygen efficiency. FIG. 8 is a graph summarizing the relationship between d / D and desiliconization oxygen efficiency. FIG. 9 is a graph summarizing the relationship between h1 / Z and desiliconization oxygen efficiency. FIG. 10 is a graph summarizing the relationship between h2 / Z and desiliconization oxygen efficiency.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Blast furnace casting floor 2 Blast furnace 4 Outlet 5 Exhaust 8 Reaction tank 10 Impeller 12 Adder

Claims (1)

Add desiliconizing agent to the hot metal flowing in the hot metal flow path of the blast furnace casting floor, mix the hot metal and desiliconizing agent by rotating the impeller immersed in the hot metal, and continuously remove the silicon in the hot metal In the continuous desiliconization method,
The number of blades of the impeller to be immersed and rotated in the hot metal is set to 3 to 6, and the blades satisfy the formulas (1) and (2). , A continuous desiliconization method characterized by immersing in hot metal so as to satisfy Equation (4).
b0 ≧ b1 (1)
0.2 ≦ d / D ≦ 0.8 (2)
0 <h1 / Z ≦ 0.4 (3)
0 <h2 / Z ≦ 0.4 (4)
However,
b0: Height of the base of the blade (m)
b1: Height of blade tip (m)
d: Blade width (m)
D: Diameter or width (m) of hot metal flow path
Z: Depth of hot metal flowing in hot metal flow path (m)
h1: Distance from the upper end of the blade tip to the hot metal upper surface (m)
h2: Distance from the lower end of the blade tip to the bottom of the hot metal flow path (m)

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