JP2008297590A - Method for pre-treating molten iron - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the occurrence of slopping caused by slag foaming in the pre-treatment of molten iron which performs in a torpedo car. <P>SOLUTION: While blowing solid oxygen source into the molten iron from the injection port at the tip end part of the lance by using an injection lance having gas injection port x on the side wall, (i) in the initial period of the treatment, the oxygen gas is injected into the stuck metal on the inside at the upper part of the torpedo car from the gas injecting port x in the injection lance to melt and remove the stuck metal, and (ii) on and after the middle period of the treatment, the gas injecting port x in the injection lance is positioned in the slag and nitrogen gas is injected into the slag from this gas injecting port x to perform the stirring of the slag. In this result, the staying of CO gas as the complex factor of the occurrence of the slopping in the slag layer and the upper part in the torpedo car is eliminated, thereby preventing the occurrence of the slopping. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a pretreatment method for hot metal held in a topped car.

As one of the hot metal pretreatment processes, a desiliconization / dephosphorization process is performed while injecting a solid oxygen source (iron oxide) from an injection lance into hot metal held in a topped car.
In such hot metal pretreatment, the injected solid oxygen source reacts with carbon in the hot metal to generate CO gas, which causes the formation of slag (top slag). A so-called slopping phenomenon popping out from the receiving port occurs, which hinders operation.
In order to suppress the occurrence of slopping during the hot metal pretreatment, it is effective to reduce the injection speed of the solid oxygen source. However, if the injection speed is reduced, the treatment time must be increased accordingly. This results in problems such as a decrease in productivity and a decrease in hot metal temperature.

As a method for suppressing slag forming in the processing vessel and preventing the occurrence of slopping, Patent Document 1 discloses that the side of the injection lance for blowing a solid oxygen source or the like toward the interface between the hot metal and the slag. A method has been proposed in which an opening is formed in the slag by blowing slag moving gas, and the CO gas in the hot metal is diffused into the air from the opening.
JP-A-2-290911

However, even if the method of Patent Document 1 is applied, the occurrence of slopping cannot be sufficiently suppressed.
Accordingly, an object of the present invention is to reliably prevent slapping from occurring due to slag forming in a hot metal pretreatment in which a solid oxygen source is blown into an hot metal held in a topped car through an injection lance to perform desiliconization and dephosphorization. It is to provide a method that can.

  The present inventors have investigated and examined in detail the cause of slopping, and as a result, (1) CO gas bubbles generated in the hot metal are trapped in the viscous slag and stay in the slag layer, The slag layer thickness is increased by slag forming. (2) Furthermore, the bullion attached to the inner surface (especially around the receiving port) of the upper part of the topped car serves as a barrier to prevent the emission of CO gas. It has been found that slapping occurs due to a complex factor of staying at the top. Therefore, in order to surely prevent the occurrence of slopping, (i) the treatment is performed with the bare metal adhering to the inner surface of the topped car being removed so that the CO gas does not stay on the toped car, (ii) It has been found that it is effective to sufficiently stir the slag layer to promote the emission of CO gas and prevent the CO gas from staying in the slag layer after the middle stage of the treatment when the slag layer thickness is increased.

The present invention has been made based on such findings, and the gist thereof is as follows.
[1] In a hot metal pretreatment method in which a solid oxygen source is blown into a hot metal held in a topped car through an injection lance to perform desiliconization and dephosphorization processing.
A hot metal preliminary treatment characterized in that an injection lance having a gas injection port (x) on its side is used and the following (i) and (ii) are performed while blowing a solid oxygen source into the hot metal from the injection port at the tip of the lance. Law.
(I) In the initial stage of the treatment, oxygen gas is sprayed from the gas injection port (x) of the injection lance to the attached metal at the upper inside of the topped car to dissolve and remove the attached metal.
(Ii) After the middle stage of the treatment, the gas injection port (x) of the injection lance is positioned in the slag, and nitrogen gas is injected into the slag from the gas injection port (x) to stir the slag.

[2] In the hot metal pretreatment method of [1] above, the top surface position of the slag in the topped car is measured before the start of the treatment, and the injection lance gas is used after the middle stage of the processing based on the measured top surface position of the slag. A hot metal preliminary treatment method, wherein the height of the injection lance is adjusted so that the injection port (x) is positioned in the slag.
[3] In the hot metal pretreatment method of [2] above, at the start of (ii), the height position of the gas injection port (x) of the injection lance is measured in advance by the height of the slag upper surface position before the treatment start. A hot metal pretreatment method characterized in that

  ADVANTAGE OF THE INVENTION According to this invention, generation | occurrence | production of the slopping by slag forming can be reliably prevented in the hot metal preliminary process which blows a solid oxygen source in the hot metal hold | maintained by the topped car through the injection lance, and performs a desiliconization-dephosphorization process. .

The present invention is a hot metal pretreatment method in which a solid oxygen source is blown through an injection lance into hot metal held in a topped car to perform desiliconization and dephosphorization treatment. In the initial stage of the treatment, desiliconization treatment is mainly performed, After the middle period, the dephosphorization process is mainly performed. Although there is no special restriction | limiting in the solid oxygen source to be used, Usually, iron oxide containing powders, such as an iron ore powder, a sintered powder, a mill scale, are used.
In the present invention, an injection lance having an injection port for powder (+ carrier gas) injection at the tip and a gas injection port x at the side (in the middle of the longitudinal direction) is used. Then, the following (i) and (ii) are performed while blowing a solid oxygen source into the hot metal.
(I) In the initial stage of the treatment, oxygen gas is sprayed from the gas injection port x of the injection lance to the attached metal on the inside of the toped car, and this attached metal is dissolved and removed.
(Ii) In the middle of the process, the gas injection port x of the injection lance is positioned in the slag, and the slag is stirred by injecting nitrogen gas into the slag from the gas injection port x.

Hereinafter, an embodiment of the present invention will be described with reference to FIGS.
In these drawings, 1 is a topped car, 10 is its receiving port, 2 is an injection lance, 3 is hot metal, and 4 is a slag layer. The injection lance 2 has an injection port 20 for injecting a powder (+ carrier gas) such as a solid oxygen source at the tip, and a gas injection port for injecting a gas to the side (in the middle of the longitudinal direction). x. Powder (+ carrier gas) or gas is supplied to the injection port 20 and the gas injection port x through supply lines 6a and 6b in the lance.
Here, FIG. 4 shows the transition of the amount of CO gas generated by the reaction between the solid oxygen source and the carbon in the hot metal in the hot metal pretreatment in which the solid oxygen source is blown into the hot metal through an injection lance to perform desiliconization and dephosphorization. The amount of CO gas generation is very small at the initial stage of the treatment mainly involving desiliconization, but the amount of CO gas generation increases rapidly from the middle stage of the treatment mainly involving dephosphorization treatment. .

  FIG. 1 shows the processing status of the initial stage of the processing (mainly the stage where desiliconization is performed), and the adherence metal 5 generated by the previous charge protrudes downward inside the topped car 1. Is generated. The inventors of the present invention are one of the complex factors that cause slopping that the adhering metal 5 serves as a barrier to prevent the diffusion of CO gas and the CO gas stays in the upper part of the topped car. I found out. Therefore, in the present invention, at the initial stage of the treatment, the injection lance 2 is positioned so that the gas injection port x faces the adhesion metal 5, and a solid oxygen source (+ carrier such as air) is fed from the injection port 20 into the hot metal. Gas) is blown in, and oxygen gas is directly injected from the gas injection port x onto the adhesion metal 5 to dissolve and remove the adhesion metal 5.

As oxygen gas injected from the gas injection port x, oxygen-containing gas may be used in addition to pure oxygen gas.
The supply amount of the oxygen gas is not particularly limited as long as the attached metal 5 can be dissolved and removed, but is generally preferably about 15 to 20 m ³ / min. When the supply amount of oxygen gas exceeds 20 m ³ / min, there is a concern about the influence on the refractory.
The supply line 6b of the gas injection port x can selectively supply oxygen gas and nitrogen gas, and oxygen gas is supplied in the processing stage of FIG.
In FIG. 1, the line indicated by α is the upper surface level of the slag before the start of processing, and in the initial stage of this processing, a slight amount of slag forming has occurred, but a large retention of CO gas that causes slopping has occurred. Absent.

FIG. 2 shows the treatment status of the stage after the middle stage of the treatment (mainly the stage where dephosphorization treatment is performed). At this stage, the gas injection port x of the injection lance 2 is positioned in the slag layer 4. While blowing a solid oxygen source (+ carrier gas such as air) from the injection port 20 into the molten iron, nitrogen gas is injected into the slag layer 4 from the gas injection port x to stir the slag.
Here, when shifting from the processing stage of FIG. 1 to the processing stage of FIG. 2, the height of the injection lance 2 is adjusted so that the gas injection port x is always located in the slag layer 4 during the processing of FIG. 2. For this reason, the slag upper surface position in the topped car 1 is measured before the start of processing, and the injection lance 2 is always positioned in the slag based on the measured slag upper surface position. It is preferable to perform height adjustment of 2.
The upper surface position of the slag layer 4 before the start of the processing can be measured with a microwave level meter 7 from above the receiving port 10 of the topped car 1 as shown in FIG. 3, for example. The measurement of the upper surface position of the slag layer 4 may be performed by other methods.

In the processing stage of FIG. 2, for example, if the height position of the gas injection port x is set to the height of “slag upper surface position before the start of processing”, the gas injection port is formed in the slag layer 4 whose layer thickness has increased by slag forming. x can always be placed, and the slag layer 4 can be reliably stirred.
Although there is no special restriction | limiting in the supply amount of nitrogen gas, Generally 5-7Nm < ³ > / min grade is preferable.
As described above, the CO gas in the slag layer 4 can be appropriately released (degassed) from the slag layer by stirring the slag layer 4 after the middle stage of the process in which the generation amount of the CO gas rapidly increases. .

The switching timing from the processing stage of FIG. 1 (mainly the stage where desiliconization is performed) to the processing stage of FIG. 2 (mainly the stage where dephosphorization is performed) is, for example, from the hot metal component and oxygen supply amount before processing The concentration in the molten iron Si is calculated and determined based on this Si concentration.
Further, in both the processing stage of FIG. 1 and the processing stage of FIG. 2, gaseous oxygen may be blown into the hot metal together with the solid oxygen source. As this gaseous oxygen source, oxygen-containing gas may be used in addition to pure oxygen gas. In addition, when gaseous oxygen is blown from the same injection lance as the solid oxygen source, there is a risk of ignition if both come into contact with each other in the lance, so they are supplied by separate supply systems in the lance and mixed and blown at the tip of the lance. It is preferable to make it.
Further, mainly in the processing stage of FIG. 2, a CaO source such as quick lime, limestone, and slaked lime is supplied as a refining agent (dephosphorizing agent). This CaO source is, for example, from the same injection lance as the solid oxygen source. It can be added to the hot metal by any method, such as a method of blowing into the hot metal, a method of blowing into the hot metal from another lance or a method of spraying on the hot metal bath surface, and a method of placing it on top.

FIG. 5 shows a comparison between the conventional method (FIG. 5 (A)) and the method of the present invention (FIG. 5 (B)) regarding the solid oxygen source and the gas supply mode.
In the method of the present invention, by combining the operation at the initial stage of the process shown in FIG. 1 and the operation after the middle stage of the process shown in FIG. 2, the CO gas slag layer and It is possible to effectively eliminate stagnation at the upper part in the topped car, and as a result, it is possible to reliably prevent the occurrence of slopping during processing without lowering the injection speed.

The hot metal was desiliconized and dephosphorized using a topped car (a hot metal treatment amount of 250 t). In this desiliconization-dephosphorization treatment, necessary solids and gases were supplied through an injection lance. The hot metal components and hot metal temperature at each refining stage are as follows.
(1) Before desiliconization treatment-Hot metal component Si: 0.2 mass%, P: 0.150 mass%
-Hot metal temperature 1360 ° C
(2) After desiliconization and before dephosphorization · Hot metal component Si: 0.01 mass%, P: 0.150 mass%
-Hot metal temperature 1350 ° C
(3) After dephosphorization-Hot metal component Si: 0.01 mass%, P: 0.050 mass%
-Hot metal temperature 1250 ° C

[Invention Example]
Using an injection lance having a gas injection port x on the side as shown in FIGS. 1 and 2, desiliconization treatment (initial stage of treatment) and dephosphorization treatment (after the middle stage of treatment) are performed as follows according to the conditions of the present invention. I went.
(A) Desiliconization treatment As shown in FIG. 1, oxygen gas is injected at a supply rate of 15 Nm ³ / min from the gas injection port x of the injection lance to the adhering metal on the inside of the topped car throughout the entire period of the treatment. The adhered metal was dissolved and removed. Similarly, a solid oxygen source (iron ore powder) + carrier gas (air) was blown into the hot metal from the injection port 20 of the injection lance, and oxygen gas supplied from another supply system of the lance was blown into the hot metal. Each supply amount and processing time are as follows.
・ Supply amount Solid oxygen source: 30 Nm ³ / min (gaseous oxygen equivalent)
Carrier gas: 7 Nm ³ / min
Oxygen gas: 15 Nm ³ / min
・ Processing time: 15 minutes

(B) Dephosphorization treatment As shown in FIG. 2, the gas injection port x of the injection lance is positioned in the slag throughout the entire period of the treatment (the slag upper surface position immediately before the start of the dephosphorization treatment). The slag was stirred by injecting nitrogen gas into the slag at a supply rate of 5 Nm ³ / min. Similarly, a solid oxygen source (iron ore powder) + carrier gas (air) is blown into the hot metal from the injection lance 20 of the injection lance, and oxygen gas + CaO (dephosphorizing agent) is supplied from another supply system of the lance. Was blown into the hot metal. Each supply amount and processing time are as follows.
・ Supply amount Solid oxygen source: 50 Nm ³ / min (gaseous oxygen equivalent)
Carrier gas: 7 Nm ³ / min
Oxygen gas: 20 Nm ³ / min
CaO: 2-3t / ch
-Treatment time: 15 minutes As a result of appropriately suppressing slag forming in the dephosphorization treatment, high-speed treatment became possible, and the dephosphorization treatment was completed in 15 minutes. Moreover, the frequency of occurrence of slopping could be suppressed to about 20 to 30% of the conventional method.

[Comparative example (conventional method)]
Using an injection lance conventionally used, desiliconization treatment and dephosphorization treatment were performed as follows.
(A) Desiliconization treatment Throughout the treatment period, a solid oxygen source (iron ore powder) + carrier gas (air) was blown into the hot metal from the injection port at the tip of the injection lance. Each supply amount and processing time are as follows.
・ Supply amount Solid oxygen source: 30 Nm ³ / min (gaseous oxygen equivalent)
Carrier gas: 7 Nm ³ / min
・ Processing time: 15 minutes

(B) Dephosphorization treatment Throughout the treatment period, a solid oxygen source (iron ore powder) + carrier gas (air) was blown into the hot metal from the injection lance injection port. Further, CaO as a dephosphorizing agent was placed on top. Each supply amount and processing time are as follows.
・ Supply amount Solid oxygen source: 50 Nm ³ / min (gaseous oxygen equivalent)
Carrier gas: 7 Nm ³ / min
CaO: 2-3t / ch
-Treatment time: 20 minutes Since slag forming was required to be suppressed in the dephosphorization process, high-speed treatment was not possible, and the dephosphorization process took 20 minutes.

Explanatory drawing which shows the processing condition of the initial stage of processing in the present invention Explanatory drawing which shows the processing status of the stage after the middle stage of processing in the present invention Explanatory drawing which shows an example of the measuring method of the slag upper surface position before a process start in this invention Graph showing the transition of the amount of CO gas generated by the reaction between the solid oxygen source and the carbon in the hot metal in the hot metal pretreatment in which a solid oxygen source is blown into the hot metal to perform desiliconization and dephosphorization. Drawing comparing the conventional method (Figure (A)) and the method of the present invention (Figure (B)) for solid oxygen source and gas supply mode

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Topped car 2 Injection lance 3 Hot metal 4 Slag layer 5 Adhesive metal 6a, 6b Supply line 7 Microwave level meter 10 Receiving port 20 Injection port x Gas injection port

Claims (3)

In the hot metal pretreatment method in which a solid oxygen source is blown into the hot metal held in the topped car through an injection lance to perform desiliconization and dephosphorization treatment,
A hot metal preliminary treatment characterized in that an injection lance having a gas injection port (x) on its side is used and the following (i) and (ii) are performed while blowing a solid oxygen source into the hot metal from the injection port at the tip of the lance. Law.
(I) In the initial stage of the treatment, oxygen gas is sprayed from the gas injection port (x) of the injection lance to the attached metal at the upper inside of the topped car to dissolve and remove the attached metal.
(Ii) After the middle stage of the treatment, the gas injection port (x) of the injection lance is positioned in the slag, and nitrogen gas is injected into the slag from the gas injection port (x) to stir the slag.   Before the start of processing, the top surface position of the slag in the topped car is measured, and based on the measured top surface position of the slag, the gas injection port (x) of the injection lance is positioned in the slag after the middle of the processing. The hot metal preliminary treatment method according to claim 1, wherein the height of the injection lance is adjusted.   The hot metal according to claim 2, wherein at the start of (ii), the height position of the gas injection port (x) of the injection lance is set to the height of the upper surface position of the slag before the start of processing, which is measured in advance. Pretreatment method.

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