JP2020100889A - Desulfurization process of molten iron - Google Patents

Abstract

To provide a molten iron desulfurization process for stably desulfurizing the molten iron even when the temperature of the molten iron is changed.SOLUTION: Molten iron is desulfurized by charging a desulfurization refining agent to the molten iron and performing a mechanical stirring desulfurization treatment. The desulfurization refining agent is charged to the molten iron so that a liquid phase ratio η(%) calculated by the following expression is within a range from 15% to 30%, and that the content of CaO in the desulfurization refining agent is 70% or more by mass, where a content of CaO in the desulfurization refining agent is (CaO%), a content of MgO is (MgO%), a content of SiO2 is (SiO2%), a content of FeO is (FeO%), a content of Al2O3 is (Al2O3%) in a mass ratio, and a temperature of the molten iron is T(°C). η=-0.20×((CaO%)+(MgO%))+0.15×((SiO2%)+(FeO%))+1.34×(Al2O3%)+0.026×T-11.71SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to a hot metal desulfurization method for desulfurizing hot metal by introducing a desulfurization refining agent into hot metal and performing mechanical stirring type desulfurization treatment.

Usually, the hot metal discharged from the blast furnace contains about several percent of carbon and sulfur, so the sulfur is removed from the hot metal (desulfurization) before the hot metal is charged into the converter and decarburized. There is a need to.
As a desulfurization method of hot metal, there are a powder blowing method in which a powder of a desulfurizing agent is blown into hot metal, and a mechanical stirring desulfurization treatment method (KR method) in which a desulfurizing refining agent is added to hot metal and mechanically stirred. Especially, recently, mechanical stirring type desulfurization treatment method has been widely used.

As a desulfurization refining agent used in this mechanical stirring type desulfurization treatment method, one having characteristics such as high desulfurization ability and being easily caught in hot metal by mechanical stirring is required.
Therefore, for example, Patent Documents 1 and 2 propose a desulfurization refining agent suitable for a mechanical stirring type desulfurization treatment method.

Patent Document 1 proposes a desulfurization refining agent in which the amount of granular iron, the FeO concentration, and the CaO concentration are specified. In addition, in this patent document 1, the steelmaking slag is mix|blended with quick lime and it is supposed that the composition of the said desulfurization refining agent is adjusted.
Further, Patent Document 2 proposes a material containing metal Al and Al nitride, the content of which is defined according to the hot metal temperature.

JP 2008-138253A JP, 2005-218392, A

By the way, even when using the desulfurization refining agent described in the above-mentioned patent document 1, when the temperature of the hot metal is low, a sufficient desulfurization effect may not be obtained.
Here, in the desulfurizing and refining agent described in Patent Document 2, the composition of the desulfurizing and refining agent is defined in consideration of the temperature of the hot metal, but in the desulfurizing and refining agent of this Patent Document 2, it occurs in aluminum refining. It is a mixture of dross (aluminum dross) that is used, and the cost of using the desulfurizing agent is high, and since the aluminum content is high, the liquid phase ratio may become excessive, and it may not be possible to obtain a sufficient desulfurizing effect. It was

The present invention has been made in view of the above-mentioned circumstances, and provides a desulfurization method of hot metal capable of efficiently and stably performing desulfurization of hot metal even when the temperature of the hot metal changes. With the goal.

In order to solve the above problems, as a result of intensive studies by the present inventors, when performing mechanical stirring type desulfurization treatment, by controlling the liquid phase ratio of the desulfurization refining agent to be within a certain range, the hot metal We have found that it is possible to efficiently and stably perform desulfurization.

The present invention is made based on the above findings, the desulfurization method of the hot metal according to the present invention, the desulfurization refining agent is added to the hot metal, by performing mechanical stirring type desulfurization treatment, desulfurization of the hot metal a hot metal desulfurization process of performing, in a mass ratio, the content of CaO in desulfurization refining agent (CaO%), the content of MgO (MgO%), the content of _{SiO 2} (SiO _2%), the content of FeO and (FeO%), the content of _{Al 2 O 3 (Al 2 O} 3%), in the case where the temperature of the molten iron was T (° C.), the liquid phase ratio calculated by the following formula The desulfurization refining agent was added to the hot metal under the condition that η (%) was in the range of 15% or more and 30% or less and the content of CaO in the desulfurization refining agent was 70% or more by mass ratio. The feature is to throw in.
η=−0.20×((CaO%)+(MgO%))+0.15×((SiO ₂ %)+(FeO%))+1.34×(Al ₂ O ₃ %)+0.026×T -11.71

According to the hot metal desulfurization method of this configuration, the content of CaO in the desulfurization refining agent is adjusted so that the liquid phase ratio η(%) of the desulfurization refining agent calculated from the above formula is 15% or more and 30% or less. (CaO%), the content of MgO (MgO%), the content of SiO _{2 (SiO 2%),} the content of FeO (FeO%), adjusting the content of _Al 2 _{O 3} and _{(Al 2 O} 3%) By doing so, the desulfurization treatment of the hot metal can be stably performed. Further, since the temperature of the hot metal is taken into consideration in the above formula, the desulfurization treatment can be stably performed even when the temperature condition of the hot metal changes.
Furthermore, in the present invention, since the content of CaO in the desulfurization refining agent is 70% or more by mass ratio, the desulfurization ability of the desulfurization refining agent is ensured and the hot metal desulfurization can be efficiently performed. ..

Here, in the hot metal desulfurization method of the present invention, the desulfurization refining agent is a mixture of CaO and secondary refining slag, and the mixing ratio of the CaO and the secondary refining slag is changed according to the temperature of the hot metal. The liquid phase ratio η may be controlled by adjustment.
In this case, the desulfurization refining agent is a mixture of CaO that is unlikely to be in the liquid phase at low temperatures and secondary refining slag that is likely to be in the liquid phase at low temperatures, and the liquid phase ratio η is controlled by the mixing ratio of these, Even if the temperature condition of the hot metal changes, the desulfurization treatment can be stably performed.
By preliminarily measuring the composition of the secondary refining slag, it becomes possible to adjust the composition of the desulfurization refining agent so as to satisfy the above formula.

As described above, according to the present invention, it is possible to provide a hot metal desulfurization method capable of efficiently and stably performing the desulfurization of hot metal even when the temperature of the hot metal changes.

It is explanatory drawing which shows an example of the mechanical stirring type desulfurization processing apparatus which implements the desulfurization method of the hot metal which concerns on embodiment of this invention. It is a flowchart of the manufacturing method of the secondary refining slag used in the desulfurization method of the hot metal which concerns on embodiment of this invention. It is a graph which shows the relationship between the hot metal temperature and the S removal rate in an Example. 4 is a graph showing the results of FIG. 3 stratified by the hot metal temperature. It is a graph which shows the relationship between the hot metal temperature and the liquid phase rate in an Example. It is a graph which shows the relationship between the liquid phase rate and the S removal rate in an example.

Hereinafter, a method for desulfurizing hot metal that is an embodiment of the present invention will be described with reference to the accompanying drawings. The present invention is not limited to the embodiments below.

The hot metal desulfurization method according to the present embodiment removes sulfur from the hot metal tapped from the blast furnace.
First, an example of a mechanical stirring type desulfurization treatment apparatus for carrying out the hot metal desulfurization method of the present embodiment will be described with reference to FIG.

As shown in FIG. 1, the mechanical stirring type desulfurization treatment apparatus 10 includes a ladle support portion 11 for supporting a molten pig ladle 5 in which the molten pig iron 1 is stored, and a molten pig iron 1 for the molten pig iron ladle 5 supported by the ladle support portion 11. And a desulfurization refining agent charging means 30 for adding a desulfurization refining agent to the hot metal 1 of the hot metal ladle 5 supported by the pan supporting portion 11.

As shown in FIG. 1, the stirring means 20 includes a frame 21 arranged above the hot metal ladle 5 supported by the ladle supporting portion 11, an impeller 22 arranged to be movable up and down on the frame 21, and an impeller. An elevating means 23 for elevating and lowering 22 and a rotation drive part 24 for rotating the impeller 22 are provided.

As shown in FIG. 1, the desulfurization refining agent charging means 30 includes a CaO hopper 31 in which CaO is stored, a secondary refining slag hopper 32 in which secondary refining slag is stored, and CaO supplied from these CaO hoppers 31. And a mixing hopper 33 for mixing the secondary refining slag supplied from the secondary refining slag hopper 32, and a charging shooter 34 for charging the desulfurization refining agent from the mixing hopper 33 to the hot metal ladle 5.
An adjusting valve 35 for adjusting the amount of CaO supplied is provided between the CaO hopper 31 and the mixing hopper 33, and a secondary refining slag is provided between the secondary refining slag hopper 32 and the mixing hopper 33. An adjusting valve 36 for adjusting the supply amount of is provided.

Here, in the mechanical agitation type desulfurization treatment apparatus 10 described above, the hot metal ladle 5 is placed on the pan support portion 11, and the desulfurizing and refining agent is added to the hot metal 1 by the desulfurizing and refining agent feeding means 30. Then, the impeller 22 is lowered by the elevating means 23 to be inserted into the hot metal ladle 5 and the impeller 22 is rotated by the rotation drive unit 24 to mechanically stir the hot metal 1.
As a result, the desulfurization refining agent is caught inside the hot metal 1, the desulfurization refining agent reacts with the hot metal 1, and the sulfur in the hot metal 1 is removed.

Then, in the hot metal desulfurization method of the present embodiment, the composition of the desulfurization refining agent to be added is adjusted according to the temperature of the hot metal 1.
Specifically, the mass ratio, the content of CaO in desulfurization refining agent (CaO%), the content of MgO (MgO%), the content of SiO _{2 (SiO 2%),} the content of FeO (FeO%), the content of _Al 2 _{O 3} and _{(Al 2 O} 3%), in the case where the temperature of the molten iron was T (° C.), the liquid phase ratio calculated by the following equation eta (%) is The desulfurization refining agent is added to the hot metal 1 under the condition that the content of CaO in the desulfurization refining agent is 70% or more in the range of 15% or more and 30% or less.
η=−0.20×((CaO%)+(MgO%))+0.15×((SiO ₂ %)+(FeO%))+1.34×(Al ₂ O ₃ %)+0.026×T -11.71

That is, in the present embodiment, the content of CaO (CaO%), the content of MgO (MgO%), and SiO in the desulfurizing and refining agent are based on the above formula in accordance with the temperature T (° C.) of the hot metal 1. ₂ content (SiO ₂ %), FeO content (FeO%), Al ₂ O ₃ content (Al ₂ O ₃ %) are adjusted to control the liquid phase rate η (%) of the desulfurization refining agent. Is doing.

Below, in the desulfurization method of the hot metal which is the present embodiment, the liquid phase ratio η (%) calculated by the above formula and the CaO content will be explained as to the reasons specified above.

(Liquid phase rate η)
When the liquid phase ratio η of the desulfurization refining agent is less than 15%, the liquid phase is insufficient, and the desulfurization refining agent cannot be sufficiently included in the hot metal 1 and the desulfurization effect by the desulfurization refining agent is insufficient. There is a risk of becoming. On the other hand, when the liquid phase ratio η of the desulfurization refining agent exceeds 30%, the liquid phase becomes excessive and the entrained liquid phase desulfurization refining agent agglomerates and becomes coarse, resulting in a small reaction area. Therefore, the desulfurization effect of the desulfurization refining agent may be insufficient.
Therefore, in the present embodiment, the liquid phase ratio η of the desulfurization refining agent is set within the range of 15% or more and 30% or less.
The lower limit of the liquid phase rate η of the desulfurization refining agent is preferably 21% or more. On the other hand, the upper limit of the liquid phase ratio η of the desulfurization refining agent is preferably 28% or less.

(CaO content)
CaO contained in the desulfurization refining agent can remove sulfur from the hot metal 1 by reacting sulfur (S) and carbon (C) in the hot metal 1 as shown in the following formula.
2(CaO)+2[S]+[C]→2(CaS)+CO ₂ (g)
Here, when the content of CaO in the desulfurization refining agent is less than 70% by mass, the desulfurization ability of the desulfurization refining agent may be insufficient, and sulfur may not be efficiently removed from the hot metal 1.
Therefore, in the present embodiment, the content of CaO in the desulfurization refining agent is set to 70% or more.

And in this embodiment, as shown in FIG. 1, the composition of the desulfurization refining agent is adjusted by adjusting the compounding ratio of CaO and secondary refining slag. That is, the composition of the desulfurization refining agent is adjusted by adjusting the opening degree of the adjustment valve 35 for adjusting the supply amount of CaO and the opening degree of the adjustment valve 36 for adjusting the supply amount of the secondary refining slag. There is.
Here, the manufacturing process of the secondary refining slag used in this embodiment will be described with reference to FIG.

The secondary refined slag raw ore generated in the secondary refining process is separated by the primary magnetic separator, and the magnetically adsorbed (primary magnetic adhering material) is stored in the metal hopper and is not magnetically adhering (primary non-magnetic adhering material). Stored in the ball hopper.
The unmagnetized material is crushed by a crusher, separated by a secondary magnetic separator, and the magnetized material (secondary magnetic material) is mixed with the primary magnetic material and is not magnetized (secondary unmagnetic material). Becomes a ballast. The above-mentioned ballast is used as a raw material for cement, for example.
Then, the primary magnetic material and the secondary magnetic material are crushed by a crusher to be the secondary refining slag used in the present embodiment. The average particle size of the secondary refining slag is, for example, in the range of 0.1 mm or more and 3.0 mm or less.

Since the secondary refining slag is a magnetic substance magnetized by the magnetic separator as described above, it is supposed to contain metallic Fe.
Here, the secondary refining slag has a large content of metallic Fe and is not suitable as a cement raw material.
In this embodiment, the secondary refining slag that is not suitable as a cement raw material is reused as a part of the desulfurization refining agent.

According to the hot metal desulfurization method of the present embodiment configured as described above, the liquid phase ratio η (%) calculated from the above equation is within a range of 15% or more and 30% or less, the content of CaO in desulfurization refining agent (CaO%), the content of MgO (MgO%), the content of SiO _{2 (SiO 2%),} the content of FeO (FeO%), the content of _Al 2 _{O 3} ( Since Al ₂ O ₃ %) is adjusted, the desulfurization treatment of the hot metal 1 can be stably performed.
Further, since the temperature of the hot metal 1 is taken into consideration in the above formula, the desulfurization treatment can be stably performed even when the temperature condition of the hot metal 1 changes.
Further, since the content of CaO in the desulfurization refining agent is 70% or more by mass ratio, the desulfurization ability of the desulfurization refining agent is ensured and the desulfurization of the hot metal 1 can be efficiently performed.

Further, in the present embodiment, a mixture of CaO and secondary refining slag is used as the desulfurization refining agent, and the liquid phase ratio η of the desulfurization refining agent is adjusted by adjusting the mixing ratio of CaO and the secondary refining slag. Since the control is performed, the desulfurization treatment can be stably performed even when the temperature condition of the hot metal 1 changes.
Further, in the present embodiment, the composition of the secondary refining slag is measured in advance, and the composition of the desulfurization refining agent is adjusted so as to satisfy the above formula, so that the composition of the desulfurization refining agent is relatively easy. Can be adjusted.
Moreover, since the secondary refining slag that cannot be used as a cement raw material is reused as a desulfurization refining agent, it is possible to reduce the use cost of the desulfurization refining agent.

Although the method for desulfurizing hot metal which is the embodiment of the present invention has been specifically described above, the present invention is not limited to this and can be appropriately modified without departing from the technical idea of the invention.
For example, although the present embodiment has been described as being performed by the mechanical stirring desulfurization treatment device 10 shown in FIG. 1, the present invention is not limited to this, and is applied to a mechanical stirring desulfurization treatment device having another configuration. Good.

Below, the results of experiments conducted to confirm the effects of the present invention will be described.

Desulfurization treatment of hot metal was performed using a desulfurization refining agent in which the mixing ratio of the secondary refining slag was changed. At this time, the relationship between the hot metal temperature and the S removal rate was confirmed. The S-elimination rate was calculated by the following formula. The results are shown in Figure 3.
Desulfurization rate (%)=(amount of sulfur before treatment−amount of sulfur after treatment)/(amount of sulfur before treatment)×100
As shown in FIG. 3, it is confirmed that the S removal rate in the hot metal greatly varies as the hot metal temperature decreases.

Therefore, the hot metal temperature is stratified into three levels of (a) 1300±20°C, (b) 1350±20°C, and (c) 1400±20°C, and the mixing ratio of the secondary refining slag and the de-S ratio are determined. Confirmed the relationship. The result is shown in FIG.
As shown in FIG. 4, it is confirmed that the blending ratio of the secondary refining slag having a high S removal rate varies depending on the hot metal temperature.

Therefore, the liquid phase ratio η was calculated from the composition of the desulfurization refining agent in which the mixing ratio of the secondary refining slag was changed and the hot metal temperature by the above formula. Then, the relationship between the hot metal temperature and the liquid phase ratio η is shown in FIG. Further, FIG. 6 shows the relationship between the liquid phase ratio η and the S removal rate.
As shown in FIG. 6, it is confirmed that the S removal rate stably increases when the liquid phase rate is within the range of 15% or more and 30% or less.

From the above, it was confirmed that the present invention can provide a hot metal desulfurization method capable of efficiently and stably performing hot metal desulfurization even when the temperature of the hot metal changes.

Claims (2)

A method for desulfurizing hot metal, in which a desulfurization refining agent is added to the hot metal and mechanical desulfurization treatment is performed to desulfurize the hot metal.
The mass ratio, the content of CaO in the desulfurization refining agent (CaO%), the content of MgO (MgO%), the content of SiO _{2 (SiO 2%),} the content of FeO (FeO%) , Al ₂ O ₃ content is (Al ₂ O ₃ %), and the hot metal temperature is T (° C.),
A condition that the liquid phase ratio η (%) calculated by the following formula is in the range of 15% or more and 30% or less, and the content of CaO in the desulfurization refining agent is 70% or more by mass ratio. 2. A method for desulfurizing hot metal, characterized in that the desulfurization refining agent is added to the hot metal.
η=−0.20×((CaO%)+(MgO%))+0.15×((SiO ₂ %)+(FeO%))+1.34×(Al ₂ O ₃ %)+0.026×T -11.71 The desulfurization refining agent is a mixture of CaO and secondary refining slag, and controls the liquid phase ratio η by adjusting the mixing ratio of CaO and the secondary refining slag according to the temperature of the hot metal. The method for desulfurizing hot metal according to claim 1, wherein

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