TW201632630A - Desulfurizing method of molten iron and desulfurizing device of molten iron - Google Patents

Abstract

The invention provides a desulfurizing method of molten iron for stably improving the reaction efficiency of a desulfurizing agent and the molten iron. The desulfurizing method includes the following. An impeller 3 is immersed in the molten iron 5 housed in a reaction container 2, and the desulfurizing agent is added while the impeller rotates. The molten iron and the desulfurizing agent are stirred to desulfurize the molten iron. The desulfurization is carried out using a reaction container having an elliptical cross-section in a state where an angle between an axial centerline CL of the reaction container and an axis 3A of the impeller is 1.0 to 15.0 degrees.

Description

Fused iron desulfurization treatment method and molten iron desulfurization treatment device

The present invention relates to a method for desulfurizing molten iron and a device for desulfurizing a molten iron.

In recent years, there has been an increasing demand for steel grades of extremely low phosphorus and/or extremely low sulfur from the viewpoint of improving the material properties such as the high added value of steel or the expansion of the use of steel materials. In order to cope with this situation, in the steelmaking step of refining molten iron, it is necessary to melt the type of steel having extremely low phosphorus and/or extremely low sulfur without causing an increase in manufacturing cost or an increase in the amount of slag generated. Improve the reaction efficiency of the refining agent such as dephosphorization agent or desulfurizer and molten iron. In addition, in order to cope with the increase in demand for steel in recent years, it is also important to improve productivity and increase the speed of response.

As a technique for coping with these requirements, the desulfurization treatment method of the molten iron using the mechanically agitated desulfurization treatment apparatus has been widely used since the beginning. According to this technique, the impeller (also referred to as "rotating wing" or "stirring wing") is immersed in the molten iron and rotated, and the molten iron and the desulfurizing agent are strongly stirred, thereby being inexpensive even if used. The CaO (lime)-based desulfurizing agent (hereinafter referred to as "CaO-based desulfurizing agent") can also desulfurize the molten iron in a short time until the sulfur concentration is 0.002% by mass. 0.004% by mass of the low sulfur concentration range.

Further, the desulfurization treatment of the molten iron in the mechanically agitated desulfurization treatment apparatus using the CaO-based desulfurizing agent is such that the powdery or granular CaO-based desulfurizing agent added to the surface of the molten iron is immersed In the molten iron vortex formed by the rotation of the impeller, the contact interface area between the CaO-based desulfurizing agent and the molten iron is increased, and the reaction efficiency of the CaO-based desulfurizing agent is improved. At this time, the molten iron is stirred by the rotation of the impeller, and the sulfur in the molten iron is sequentially supplied to the reaction interface (the surface of the desulfurizing agent), thereby performing the desulfurization reaction. Generally, the reaction vessel containing the molten iron is a pan type having a circular cross section, and the movable impeller is inserted from the upper side of the vessel to a substantially center of the reaction vessel.

However, the increase in the demand for extremely low sulfur steel in recent years has gradually become difficult to cope with only by the prior art. Therefore, in the desulfurization treatment method of the molten iron in the mechanically agitated desulfurization treatment apparatus, as a technique for further improving the reaction efficiency of the CaO-based desulfurizing agent and further shortening the treatment time, it is proposed to spiral or move the movable impeller. Techniques such as eccentric insertion of the impeller and baffle placement in the reaction vessel.

For example, Patent Document 1 proposes a technique in which the thickness of the refractory to be applied to the bottom of the reaction vessel is such that the shape of the inner surface of the bottom of the reaction vessel containing the molten iron is not axisymmetric with respect to the central axis of the reaction vessel. By this, the eccentricity of the vortex formed by the rotation of the impeller is promoted to promote the entrapment of the CaO-based desulfurizing agent into the molten iron. Further, Patent Document 2 proposes a technique in which the insertion position of the impeller is deviated from the center of the reaction vessel, the vortex formed by the rotation of the impeller is eccentric, and the conveying gas and the powdery CaO-based desulfurizing agent are further Desulfurization treatment is carried out by blowing a formed vortex into a vortex formed, thereby achieving high reaction of the CaO-based desulfurizing agent effectiveness.

[Prior Art Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 2011-26696

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2011-42815

However, the prior art has room for improvement in the following aspects.

In other words, in the method proposed in Patent Document 1, the height difference of the bottom of the reaction vessel provided by the height difference of the refractory material is reduced by the loss of the refractory material, and the effect cannot be maintained for a long period of time. In particular, when the cold iron source is preliminarily charged in the reaction vessel, the loss of the bottom refractory due to the pre-charged cold iron source is strong, and the tendency is large. Further, if the refractory for the bottom construction is thickened in order to maintain the height difference at the bottom of the reaction vessel for a long period of time, the molten iron accommodation capacity of the reaction container is lowered.

In the method proposed in Patent Document 2, since the eccentricity tolerance range of the movable impeller with respect to the center of the reaction vessel is narrow, it is difficult to adjust the positional relationship between the reaction vessel and the impeller, and a stable effect cannot be obtained. Further, when the insertion position of the impeller is deviated from the target, there is a case where the desulfurization treatment needs to be performed again, and the molten iron temperature is lowered or the productivity is lowered.

That is, from the viewpoint of stably improving the reaction efficiency of the CaO-based desulfurizing agent, there is still room for improvement in the prior art.

In view of the above problems, an object of the present invention is to provide a stable improvement A method for desulfurization of molten iron having a reaction efficiency between a desulfurizing agent and molten iron, and a desulfurization treatment device for molten iron.

The gist of the present invention for solving the above problems is as follows.

[1] A method for desulfurizing molten iron, which comprises immersing an impeller in a molten iron accommodated in a reaction vessel, and adding a desulfurizing agent while rotating the impeller, and the molten iron and the desulfurization The agent is subjected to a desulphurization treatment to desulfurize the molten iron, wherein a reaction vessel having an elliptical cross section is used as the reaction vessel, and the axial center line of the reaction vessel is The desulfurization treatment is performed in a state where the angle θ formed by the shaft of the impeller is set to 1.0 to 15.0 degrees.

[2] The method for desulfurizing molten iron according to [1], wherein the moving impeller is immersed in the molten iron by setting a shaft of the impeller to a vertical direction. The desulfurization treatment is performed by inclining the reaction vessel in a range in which the inclination angle α of the center line of the reaction vessel in the axial direction with respect to the vertical direction is 1.0 to 15.0 degrees.

[3] The method for desulfurizing molten iron according to [1], wherein the center line of the axial direction of the reaction vessel is fixed in a vertical direction, and the axis of the moving impeller is opposite to the vertical The desulfurization treatment is performed by inclining the moving impeller in a range in which the inclination angle β of the direction is 1.0 to 15.0 degrees.

[4] The method for desulfurizing molten iron according to any one of [1] to [3] wherein the cross section of the reaction vessel is a ratio of a short axis to a long axis (short axis/long axis) ) It is an elliptical shape of 0.70~0.95.

[5] A molten iron desulfurization treatment apparatus comprising: a reaction vessel having an elliptical cross section in which a molten iron is accommodated and a desulfurizing agent is added, and the molten iron is stirred, rotated, and stirred The molten iron and the moving impeller of the desulfurizing agent are disposed such that the angle θ formed by the axial center line of the reaction vessel and the axis of the moving impeller becomes 1.0 to 15.0 degrees. The impeller is described.

[6] The molten iron desulfurization treatment apparatus according to [5], wherein the moving impeller is provided in such a manner that its axis is in a vertical direction, and the reaction vessel is in a center line of its axial direction. The inclination angle α with respect to the vertical direction is set to be inclined in a range of 1.0 to 15.0 degrees.

[7] The molten iron desulfurization treatment apparatus according to [5], wherein the reaction vessel is disposed such that a center line of the axial direction thereof is fixed in a vertical direction, and the movable impeller is opposed to the shaft thereof The inclination angle β in the vertical direction is set to be inclined in a range of 1.0 to 15.0 degrees.

[8] The molten iron desulfurization treatment apparatus according to any one of [5] to [7] wherein the cross section of the reaction vessel is a ratio of a short axis to a long axis (short axis/long axis) ) is an elliptical shape of 0.70 to 0.95.

According to the method for desulfurizing molten iron of the present invention and the apparatus for desulfurizing the molten iron, the reaction efficiency of the desulfurizing agent and the molten iron can be stably improved.

1‧‧‧Transportation tackle

1A‧‧‧Fused iron pot holder

2‧‧‧fused iron pot

3‧‧‧moving impeller

3A‧‧‧Moving wheel shaft

4‧‧‧ dust cover

5‧‧‧ molten iron

5A‧‧‧ molten iron bath surface at rest

5B‧‧‧ molten iron bath surface when mixing

6‧‧‧Tear shaft mount

7‧‧‧Tear

8‧‧‧ refractory layer

10‧‧‧Desulfurization treatment unit

C _L ‧‧‧ axial direction centerline melting iron

D _L ‧‧‧Inside diameter in the long axis direction

D _S ‧‧‧Inner diameter in the short axis direction

‧‧‧‧ tilt angle

1(A) is a schematic view of a mechanically agitated desulfurization treatment apparatus 10 according to an embodiment of the present invention, and FIG. 1(B) is a view showing a molten iron according to an embodiment of the present invention using the desulfurization treatment apparatus 10. A schematic view of the case of the desulfurization treatment method.

Fig. 2 is a schematic view showing a cross-sectional shape of the molten iron pan 2 shown in Figs. 1(A) to 1(B).

3 is a graph showing the relationship between the inclination angle α of the center line direction of the axial direction of the molten iron pan with respect to the vertical direction and the desulfurization rate.

The inventors have repeatedly studied the method of improving the reaction efficiency of the molten iron and the desulfurizing agent in the method of desulfurizing the molten iron in the mechanically agitated desulfurization treatment apparatus. As a result, it has been found that by using a reaction vessel having an elliptical cross section and performing desulfurization treatment in a state in which the axial center line of the reaction vessel is inclined with respect to the axis of the impeller, the vortex formed by the impeller may deviate from the reaction. The center of the container, thereby promoting the entrainment of the desulfurizing agent into the molten iron, thereby increasing the reaction efficiency of the desulfurizing agent.

The present invention has been completed based on the results of the research. Hereinafter, embodiments of the present invention will be specifically described with reference to the accompanying drawings.

1(A) to 1(B) show a case where the molten iron desulfurization treatment method according to an embodiment of the present invention is carried out by using the mechanically agitated desulfurization treatment apparatus 10 according to the embodiment of the present invention. Fig. 1(A) shows a state in which the movable impeller 3 is inserted in the vertical direction from the upper portion of the molten iron pan 2 as a reaction container which is housed in the transport car 1. Fig. 1(B) is a view showing an inclination angle ? of the axial center line line C _L of the molten iron pan 2 with respect to the vertical direction.

The molten iron pan 2 is provided with a trunnion 7 and a trunnion mount 6 on which the trunnion is attached. In the present embodiment, the upper end surface of the hood 1A of the transport trolley 1 is inclined with respect to the horizontal line, and the trunnion mount 6 of the lava pot 2 is carried on the inclined upper end surface. The lower end surface of the trunnion mount 6 is formed in such a manner that the molten iron pan 2 is erected parallel to the horizontal line. Thereby, the molten iron pan 2 is mounted on the transport pulley 1 at a predetermined inclination angle α with respect to the vertical direction.

The molten iron 5 is housed in the molten iron pot 2. The moving impeller 3 is driven by a motor (not shown), and rotates with the moving impeller shaft 3a as a rotating shaft. In the present embodiment, the movable impeller shaft 3A is placed in the vertical direction, and the impeller 3 is immersed in the molten iron 5, and the desulfurizing agent is added while rotating the impeller 3, and the state is performed in the state of FIG. 1(B). Desulfurization treatment. Thereby, the vortex formed by the movable impeller 3 is deviated from the center of the molten iron pot 2, and as a result, the desulfurizing agent is accelerated to be entangled in the molten iron 5, and the reaction efficiency of the desulfurizing agent is improved. Further, in Fig. 1(B), the line of the symbol 5A indicates the molten iron bath surface at rest, and the line of the symbol 5B indicates the molten iron bath surface at the time of stirring. In the desulfurization treatment, the molten iron pan 2 is protected by the dust collecting hood 4.

In FIG. 1 (B) said movable wheel 3 is positioned on the molten iron status 2 axial direction center line C _L, within the range of 0 to 0.25 when the dimensionless distance (r / r ₀₎ from the center line of Then, the vortex formed by the movable impeller 3 is deviated from the center of the molten iron pot 2, and as a result, the desulfurizing agent is promoted to be entangled in the molten iron 5, and the reaction efficiency of the desulfurizing agent is improved. Here, r represents the shortest distance _L of the movable iron melt with the center of the impeller 3 in the axial direction of the center line 2 C (m), r ₀ represents the radius of the molten iron (m). That is, it is shown that, by the present invention, in the case where the insertion position of the impeller is deviated from the target, it is not necessary to perform the desulfurization treatment again.

In addition, FIG. 1(A) to FIG. 1(B) show a state in which the molten iron pan 2 having an elliptical cross section is inclined toward the long axis side with the short axis of the ellipse as the center of rotation. However, in the present invention, the major axis of the ellipse may be the center of rotation and may be inclined toward the short axis side.

Fig. 2 is a schematic view showing a cross-sectional shape of the molten iron pan 2 shown in Figs. 1(A) to 1(B). The symbol 8 shown in Fig. 2 is a refractory layer on the side wall of the molten iron pan, D _L is an inner diameter in the long axis direction of the side wall refractory layer having an elliptical cross section, and D _S is a side wall refractory having an elliptical cross section. The inner diameter of the layer in the short axis direction. Further, the structure of the molten iron itself is not particularly limited, and it is preferable that the bottom surface of the molten iron pan has a substantially flat surface and a wall surface is attached to the bottom surface so as to be substantially perpendicular to the bottom surface, as shown in Fig. 1(B).

Table 1 shows an example of the specifications of the mechanically agitated desulfurization treatment apparatus shown in Figs. 1(A) to 1(B) and the conditions of the desulfurization treatment when the mechanically agitated desulfurization treatment apparatus is used.

Under the specifications of the desulfurization treatment apparatus and the desulfurization treatment conditions shown in Table 1, the inclination direction of the molten iron pan 2 is set to the long axis side or the short axis side of the elliptical shape, and the inclination angle α of the molten iron pan 2 is Various changes were made in the range of 0 to 20.0 degrees, and the molten iron 5 was subjected to a desulfurization treatment test using a desulfurizing agent, and the desulfurization rate at this time was measured. The movable impeller 3 is inserted in the vertical direction. As the desulfurizing agent, a CaO-CaF ₂ -based desulfurizing agent formulated with 10% by mass of fluorite (CaF ₂ ) was used, and the amount of the desulfurizing agent used was constant at 6.0 kg / molten iron - ton throughout the test.

Here, the desulfurization rate is defined by the following formula (1).

Desulfurization rate (%) = {(sulfur concentration (% by mass) in molten iron before treatment) - (sulfur concentration (% by mass) in molten iron after treatment)} × 100 / (concentration of sulfur in molten iron before treatment (% by mass) ))...(1)

When the unit consumption of the desulfurizing agent used is the same, that is, under the condition that the amount of the desulfurizing agent per ton of molten iron is the same, the higher the desulfurization rate, indicating the reaction of the desulfurizing agent with the molten iron. The higher the efficiency.

3 is a view showing a relationship between a case where the molten iron pan is inclined toward the long axis side of the elliptical shape and a case where it is inclined toward the short axis side, and shows a relationship between the inclination angle α of the molten iron pan and the desulfurization rate.

As shown in FIG. 3, it is understood that the inclination direction is the long axis side or the short axis side of the elliptical shape, and if the inclination angle α is approximately 10.0 degrees, the inclination is as follows. When the angle α is increased and the desulfurization rate is increased, when the inclination angle α is 3.0 degrees or more, the desulfurization rate is 90% or more, and when the inclination angle α is 6.0 degrees or more, the desulfurization rate is 95% or more. Further, in the case where the oblique direction is the elliptical shape on the long axis side and the case of the short axis side, there is no difference in the desulfurization rate, and it is confirmed that the oblique direction has no influence on the desulfurization rate. Further, by visually observing the vortex of the molten iron bath surface 5B formed in the desulfurization treatment, it was confirmed that when the inclination angle α is increased, the vortex formed around the impeller is deviated from the center of the molten iron pan, and the promotion is performed. The added desulfurizing agent is entrained in the molten iron.

On the other hand, it is understood that when the inclination angle α exceeds approximately 10.0 degrees, the desulfurization rate starts to decrease, and when the inclination angle α exceeds 15.0 degrees, the desulfurization rate is equal to the case where the molten iron pan is erected (α=0 degrees) or It is below. The reason for this is that the swirling flow of the molten iron is suppressed by the side wall surface of the molten iron pan.

That is, in one embodiment of the present invention, based on the results shown in Figure 3, with a cross-sectional elliptical shape of reaction vessel as the reaction vessel, is accommodated in the axial direction of the molten iron reaction vessel with respect to the center line C _L The inclination angle α in the vertical direction is in the range of 1.0 to 15.0 degrees, preferably in the range of 2.5 to 15.0 degrees, the reaction vessel is inclined, and the impeller is immersed in the molten iron from the vertical direction, and in this state, The impeller is rotated to perform desulfurization treatment on the molten iron.

At this time, the inclination direction of the reaction container may be either one of the major axis side or the minor axis side of the elliptical shape. Moreover, as shown in FIG. 3, in terms of obtaining a high desulfurization rate of 95% or more, the inclination angle α is particularly preferably in the range of 6.0 to 13.0 degrees.

The reaction vessel may have any shape as long as the cross section of the refractory layer 8 of the side wall is elliptical, and preferably the ratio of the short axis to the major axis of the ellipse (short axis/long axis) D _S /D _L is 0.70 to 0.95. Elliptical shape. If the ratio (short axis/long axis) is less than 0.70, in order to secure the molten iron capacity of the reaction container, it is necessary to increase the long axis and it is difficult to perform in the range of the installed equipment. On the other hand, when the ratio (short axis/long axis) exceeds 0.95, the agitation form of the molten iron becomes a form similar to that of a circular reaction container, and it becomes difficult to increase the reaction efficiency of the desulfurizing agent and the molten iron to Target value.

The present invention necessitates the use of a reaction vessel having an elliptical cross section as a reaction vessel. The reason for this is that in the reaction vessel having an elliptical cross section, since the symmetry of the flow in the bath formed around the impeller is broken, the stirring of the molten iron is obtained as compared with the reaction vessel having a circular cross section. promote.

Further, as the desulfurizing agent to be used, a CaO-based desulfurizing agent having a CaO content of more than 50% by mass is preferable. However, quicklime (CaO), hydrated lime (Ca(OH) ₂ ), limestone (CaCO ₃ ), calcined dolomite (MgO.CaO), etc. may be used alone, or aluminum oxide (Al may be mixed therein). ₂ O ₃ ) or fluorite (CaF ₂ ).

The means for tilting the reaction container and mounting it on the transport carriage is not limited to FIG. 1(A) to FIG. 1(B), and can be tilted by any means.

As another embodiment of the desulfurization treatment apparatus of the present invention, the center line of the axial direction of the reaction vessel may be fixed in the vertical direction and disposed, and the inclination angle of the shaft of the impeller with respect to the vertical direction β may be It is set to be tilted within a range of 1.0 to 15.0 degrees. The desulfurization treatment device can also be used to fix the center line of the axial direction of the reaction vessel in the vertical direction, and the inclination angle β of the axis of the movable impeller with respect to the vertical direction becomes 1.0 to 15.0 degrees. Desulfurization treatment is carried out by tilting. In this case, the vortex formed by the impeller will also deviate from the reaction vessel. At the center, the result is that the desulfurizing agent is entrained in the molten iron, and the reaction efficiency of the desulfurizing agent is improved. In other words, in the present invention, it is important to carry out the desulfurization treatment in a state where the angle θ between the axial center line of the reaction container and the axis of the moving impeller is 1.0 to 15.0 degrees.

Example

Under the specifications of the mechanically agitated desulfurization treatment apparatus and the desulfurization treatment conditions shown in Fig. 1(A) to Fig. 1(B) and Table 1, the standards are each counted at the following nine levels. Desulfurization treatment test of molten iron in charge, investigation of sulfur concentration of molten iron before and after desulfurization treatment: existing conditions without tilting the molten iron pan (conventional example); making the inclination angle α relative to the long axis direction of the elliptical shape . The short-axis direction is changed to three levels of conditions of 1.0 degrees, 7.0 degrees, and 15.0 degrees (invention example); and the inclination angle α is relative to the long-axis direction of the elliptical shape. The short axis direction was set to a condition of 17.0 degrees (Comparative Example). Further, for a part of the conditions, the installation position of the impeller is changed in such a manner that the dimensionless distance (r/r ₀ ) becomes three levels of ₀ , 0.25, and _0.3 , and the desulfurization treatment test of the molten iron of several ten charges is performed. , investigate the sulfur concentration of molten iron before and after desulfurization treatment. In the test, the moving impeller was inserted in the vertical direction. Further, as the CaO-based desulfurizing agent, a CaO-CaF ₂ -based desulfurizing agent prepared by disposing 10% by mass of fluorite was used. The test conditions and survey results are shown in Table 2. In addition, in Table 2, the "average value of the sulfur concentration in the molten iron" means the average value of all the charges in each example, and the "maximum value of the sulfur concentration in the molten iron" means that all the charges in each example are in the charge. The sulfur concentration of the charge which exhibits the maximum sulfur concentration, and the ratio of the "sulphur concentration in the molten iron after the treatment exceeds 0.010% by mass" means the sulfur concentration in the molten iron after treatment in all the charges in each of the examples. The ratio of the charge exceeding 0.010% by mass.

As shown in Table 2, in the example of the present invention, it was confirmed that the average value of the sulfur concentration in the molten iron after the desulfurization treatment was stabilized and reduced to less than 0.010% by mass. It can be confirmed that by applying the present invention, the reaction efficiency of the desulfurizing agent can be stably improved.

[Industrial availability]

According to the method for desulfurizing the molten iron of the present invention and the apparatus for desulfurizing the molten iron, the reaction efficiency of the desulfurizing agent and the molten iron can be stably improved.

1‧‧‧Transportation tackle

1A‧‧‧Fused iron pot holder

2‧‧‧fused iron pot

3‧‧‧moving impeller

3A‧‧‧Moving wheel shaft

4‧‧‧ dust cover

5‧‧‧ molten iron

5A‧‧‧ molten iron bath surface at rest

5B‧‧‧ molten iron bath surface when mixing

6‧‧‧Tear shaft mount

7‧‧‧Tear

10‧‧‧Desulfurization treatment unit

C _L ‧‧‧ axial direction centerline melting iron

‧‧‧‧ tilt angle

Claims (8)

A method for desulfurizing molten iron by immersing an impeller in a molten iron accommodated in a reaction vessel, and adding a desulfurizing agent while rotating the impeller, and performing the molten iron and the desulfurizing agent a method of desulfurizing the molten iron by stirring, wherein the molten iron desulfurization treatment method is characterized in that, as the reaction vessel, a reaction vessel having an elliptical cross section is used, and the reaction vessel is The desulfurization treatment is performed in a state where the angle θ between the axial center line and the shaft of the moving impeller is 1.0 to 15.0 degrees. The method for desulfurizing molten iron according to claim 1, wherein the moving impeller is immersed in the molten iron in a vertical direction of the moving impeller, and the reaction is performed in the molten iron. The desulfurization treatment is performed by inclining the reaction vessel in a range in which the inclination angle α of the center line of the container in the axial direction with respect to the vertical direction is 1.0 to 15.0 degrees. The method for desulfurizing molten iron according to claim 1, wherein the center line of the axial direction of the reaction vessel is fixed in a vertical direction, and the axis of the moving impeller is opposite to a vertical direction. The desulfurization treatment is performed by inclining the movable impeller in a range in which the inclination angle β is 1.0 to 15.0 degrees. The method for desulfurizing molten iron according to any one of claims 1 to 3, wherein the cross section of the reaction vessel is a ratio of a short axis to a long axis (short axis/long axis) An elliptical shape of 0.70 to 0.95. A desulfurization treatment device for molten iron, characterized in that it has a molten iron And adding a reaction vessel having an elliptical cross section in a desulfurizing agent; and a moving impeller immersed in the molten iron to rotate to stir the molten iron and the desulfurizing agent, and in the reaction vessel The reaction vessel and the impeller are provided such that the angle θ between the center line in the axial direction and the shaft of the impeller becomes 1.0 to 15.0 degrees. The molten iron desulfurization treatment apparatus according to claim 5, wherein the movable impeller is disposed in such a manner that its axis is in a vertical direction, and the reaction vessel is opposite to a center line of the axial direction thereof. The inclination angle α in the vertical direction is set to be inclined in a range of 1.0 to 15.0 degrees. The desulfurization treatment apparatus according to claim 5, wherein the reaction vessel is disposed such that a center line of the axial direction thereof is fixed in a vertical direction, and the movable impeller is axially opposite to the vertical direction thereof. The inclination angle β is set to be inclined in a range of 1.0 to 15.0 degrees. The molten iron desulfurization treatment apparatus according to any one of claims 5 to 7, wherein the cross section of the reaction vessel is a ratio of a short axis to a long axis (short axis/long axis) An elliptical shape of 0.70 to 0.95.