JPH1136009A - Top-blown lance for refining and refining method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively restrain the spitting in a high speed blowing and to improve the refining yield by arranging an outside nozzle having larger inclination than an inside nozzle at the outside in the same direction of the inside nozzle and reducing molten drips flying out to a direction near the vertical direction. SOLUTION: In this lance 1, three inside nozzles 2 having the inclining angle θ1 are arranged as the circular state having the same distance from a lance center and three outside nozzle 3 having the inclining angle θ2 (>θ1 ) are arranged on the extension of the lines connecting the lance center with the inside nozzles 2, i.e., the same direction as the inside nozzle 2. Overlapping area of cavities according to the jet of the inside nozzle 2 and the jet of the outside nozzle 3 arranged in the same direction is made to <=50% of the cavity area according to the jet of the inside nozzle 2. It is desirable that the inclining angle θ1 of the inside nozzle 2 is made to 7-14 deg., and the inclining angle θ2 of the outside nozzle 3 is made to 10-25 deg.. Such operational trouble as the sticking of metal on a furnace opening hole part is avoided, and the productivity can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an upper blowing lance used for blowing a refining gas to a molten metal in a steelmaking converter, for example, and a refining method using the same.

[0002]

2. Description of the Related Art In a top-blown or top-bottom smelting furnace for molten metal, an oxidizing gas jet is sprayed from a top-blowing lance onto a molten metal bath, and carbon (C) in the molten metal is C +1/2 O ₂ =
It is removed by a decarburization reaction of CO and refined into a molten metal having a predetermined C content. When the oxidizing gas is blown, the molten metal bath is locally dented and a vigorous oxidation reaction occurs. This recess is called a cavity.

In recent years, the spread of hot metal pretreatment in the steelmaking process of the iron and steel industry has made it possible to reduce the amount of slag in the refining process of a converter, thereby reducing slopping (a phenomenon in which formed slag overflows from a furnace port). Accordingly, high-speed blowing is being pursued in order to improve the efficiency of the process.

However, in a converter, high-speed oxygen is blown upward by a lance, so when the amount of slag covering the molten steel is reduced, spitting (phenomenon in which molten steel is scattered by the upwardly blown jet) increases and the ground to the furnace port increases. Adhesion of gold and generation of dust are promoted, which causes troubles in operation and a problem of reduced yield.

In order to reduce spitting, it is effective to make the lance porous in order to disperse the energy when the oxygen jet collides with the steel bath surface. In a steelmaking converter, it is effective to use a porous lance. General. Usually, the nozzle of the multi-hole lance is arranged with an outward inclination angle θ with respect to the center axis of the lance. Is in the range of about 5 to 30 degrees. That is, when θ is close to 0 °, the meaning of porosity is lost, and when θ exceeds 30 °, the cavity approaches the inner wall of the converter, and the refractory may be significantly worn.

[0006] In the porous lance, the overlap of the cavities corresponding to the respective nozzles becomes a problem. That is, when the overlap of the cavities exceeds a certain level, a phenomenon in which the amount of spitting significantly increases is observed.

As a means for solving this problem, Japanese Patent Application Laid-Open
JP-A-165313 and JP-A-6-57320 disclose a method of determining a nozzle hole inclination angle so as to reduce the overlap of cavities.

[0008]

Problems to be Solved by the Invention
The method described in Japanese Patent Application Laid-Open No. 13-13813 is to widen the angle of the nozzle so as to reduce the overlap of the cavities. However, if the angle of the nozzle is made too wide, the secondary combustion rate of the CO gas generated in the decarburization reaction increases, so that the oxygen efficiency of the decarburization reaction in the final stage of blowing decreases significantly. That is, the yield decreases due to an increase in the total Fe (T.Fe) in the slag, and a problem such as an increase in wear of the refractory increases due to an increase in the blowing time.

On the other hand, in the method described in Japanese Patent Application Laid-Open No. Hei 6-57320, two types of nozzles having different inclination angles are alternately arranged on concentric circles to reduce the overlapping of the cavities. In this case, the above problem can be avoided because the oxygen jet from the nozzle having the smaller inclination angle hardly contributes to the secondary combustion of the CO gas.

However, according to the experimental results of the present inventors,
Even with the use of the lance described in JP-A-6-57320, the acid feed rate (flow rate) from the lance is still less than 3 tons of molten steel per ton.
It was found that the case of Nm ³ / min or more was not enough to suppress spitting. (Hereinafter, the oxygen flow rate per ton of molten steel is referred to as Nm ³ / min · ton) An object of the present invention is to perform spitting under high-speed blowing conditions in which the oxygen flow rate of the top blowing lance is ³ Nm ³ / min · ton or more. An object of the present invention is to provide an upper blowing lance for refining that can be effectively suppressed and a refining method using the same.

[0011]

The present inventors have studied lances of various shapes with the aim of reducing spitting, and as a result,
The following findings were obtained.

A. If the inclination angle of the outer nozzle is too large to avoid overlapping of the cavities, the secondary combustion of the CO gas increases, which causes a reduction in reaction efficiency and a problem of refractory wear. b. Of the molten steel droplets scattered by the jet, those that are problematic as metal adhesion to the furnace port or dust loss mainly scatter in a direction close to the vertical.

C. As the approach angle of the jet colliding with the steel bath surface becomes closer to the vertical, the number of droplets scattered in the direction closer to the vertical increases. As disclosed in Japanese Patent Application Laid-Open No. 6-57320, in a porous lance having nozzles of two kinds of inclination angles, the problematic scattering of molten steel droplets is mainly caused by nozzles having a small inclination angle. It is.

D. By arranging the outer nozzle having a larger inclination angle than the inner nozzle outside the same direction of the inner nozzle, it is possible to reduce the number of droplets that fly in a direction close to the vertical.

The present inventors have conceived a refining top blowing lance and a refining method using the same as shown in FIG. 1 based on the above findings. That is, the gist of the present invention is as follows (1) and (2).

(1) Three or more inner nozzles arranged on the circumference at an outward inclination angle θ ₁ and the same number of outer nozzles arranged at an outward inclination angle θ ₂ in the same direction as the inner nozzle. , Wherein θ ₂ is larger than θ ₁ .

(2) Using the upper blowing lance for refining as described in the above item (1), the overlapping area of the cavity formed by the jets of the inner nozzle and the outer nozzle arranged in the same direction is equal to the cavity formed by the jet of the inner nozzle. Area of 50
% Or less.

In the embodiment of the present invention, the nozzle inclination angle is preferably θ ₁ from 7 ° to 14 ° and θ ₂ from 10 ° to 10 °.
25 °, more preferably θ ₁ is 8 ° to 12 °, θ ₂ is 12 °
In the range of ° to 17 °.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors first examined the relationship between the direction of cavity overlap generated by two jets and spitting by a water model experiment.

FIG. 2 is a schematic view of a 1/20 scale water model experiment. Three types of A, B, and C were prepared for the lance 1, and experiments were respectively performed. The lance A assumes the lance (six holes) of the present invention, and the nozzles 2 and 3 are arranged at the tip of the lance 1 so as to open in the same direction. In the water model experiment, only one jetting direction was used, and the other direction (120 ° 240 ° direction) was blind. Angle of inclination of inner nozzle 2 θ ₁ = 10 °, outer nozzle 3
A tilt angle θ ₂ = 15 °.

The lance B corresponds to the technique disclosed in Japanese Patent Application Laid-Open No. 60-165313, and has six nozzles arranged on the circumference. Nozzle inclination angle θ is 15 °
It is. However, the lances used in the water model experiments only open in the 0 ° and 60 ° directions, and in other directions (120 °, 180 °, 240 °
° and 300 ° directions) were blind.

The lance C corresponds to the technique disclosed in Japanese Patent Application Laid-Open No. 6-57320, in which six nozzles having two kinds of inclination angles are arranged on the circumference. Nozzle tilt angle is 10 °
And 15 °. However, the lance used in the experiment was 0
Open only in ° and 60 ° directions, and in other directions (120 °, 180 °, 240
° and 300 ° directions) were blind. The lance height is 135 mm for each of the lances A, B and C. The gas used is compressed air.

In the water model test, the probe 10 for measuring the dynamic pressure is arranged downward at a height of 300 mm from the water surface, the dynamic pressure of the splash 8 is measured by the dynamic pressure sensor 11, and those having a certain threshold or more are discriminated. The number was counted by the counter 12. The probe 10 was scanned in the horizontal plane at the above-mentioned height, and the distribution of the splashed splash was measured.

FIG. 3 shows the distribution of the splash in the water model experiment. FIG. 7A corresponds to the lance A, FIG. 7B corresponds to the lance B, and FIG. In the figure, the count number immediately above the center of the overlap between the two cavities is taken as one count, and the count number at each point is indexed, and an equal count line 9 of 0.8 count or more is drawn.

As can be seen from the figure, in the case of the lance A, the cocoon-shaped scattering distribution is long in the circumferential direction from the center of the lance, and in the case of the lance B, the gourd is long in the radial direction when viewed from the center of the lance. In the case of a lance with a scattering distribution, the lance has a gourd shape inclined with respect to the radial direction. The reason is presumed to be that the splash generated and scattered from the overlapping portion of the cavity is pushed back to the jet, but can be scattered freely because the jet wall is thin in the direction of the intersection. Further, since the jet is inclined and enters the steel bath surface, the equal count line is shifted outward (in a direction away from the lance) from the center of the cavity overlap.

Comparing FIGS. 7A, 7B and 7C, the amount of splash reaching the vicinity of point C which is the center of the lance is as follows.
It can be seen that (a) is less than (b) and (c).
That is, it can be seen that the A-type lance according to the present invention can also reduce the amount of spitting scattered in the furnace port direction in the converter from the B and C-type lances.

Next, the present inventors examined the arrangement of the cavities formed by the inner nozzle and the outer nozzle. The amount was investigated.

FIG. 1 is a schematic view showing a main part of the tip of the upper blowing lance of the present invention, taking a 6-hole lance as an example. FIG. 1 (a) is a longitudinal sectional view, and FIG. It is a top view. In the lance 1, three inner nozzles 2 having an inclination angle θ ₁ are arranged concentrically, and three outer nozzles 3 having an inclination angle θ ₂ (> θ ₁ ).
Are arranged on an extension of a line connecting the center of the lance 1 and the inner nozzle 2, that is, in the same direction as the inner nozzle 2. Here, the distances between the centers of the outlets of the inner nozzle 2 and the outer nozzle 3 and the lance axis are r ₁ and r ₂ , and the throat diameter of the nozzle is d.
Let _t1 , _dt2 , and the outlet diameter of the nozzle be _de1 , _de2 .

FIG. 4 shows the spread of the jet.
It is a longitudinal cross-sectional view which shows typically the positional relationship of the cavity 5 or 6 formed on the molten metal bath surface 4 by the nozzle 2 or 3.

FIG. 5 is an explanatory view showing the overlap of the inner cavity 5 and the outer cavity 6 corresponding to the inner nozzle 2 and the outer nozzle 3 arranged in the same direction on the molten metal bath surface 4. Note that the cavity overlapping area is considered by a projection onto a plane as shown in FIG.

As shown in FIG. 4, the jet ejected from the inner nozzle 2 or the outer nozzle 3 at supersonic speed has a length X
_There is a supersonic core 7 of _c , which then develops into a complete turbulent flow through the transition region and spreads at a spreading angle of 2φ = about 20 °. Here, the supersonic core length _Xc is calculated by the following empirical formula (1).

[0032]

(Equation 1)

Here, P ₀ is the pressure before the lance (kgf / c
m ^2), d _e is the nozzle outlet diameter (mm). When the lance tip lance showing the distance to the molten metal bath level height H ₀ of the (mm), from the positional relationship shown in FIG. 4, the cavity diameter D _i shown in the following formula (2) is formed. Distance R _i between the center and the lance center just below C of the cavity can be calculated by the following equation (3).

[0034]

(Equation 2)

[0035]

(Equation 3)

Here, i is the nozzle number, in this case,
1 and 2 corresponding to nozzles 2 and 3, respectively. Cavity weight
Area ratio S_rExceeds 50%, spitting loss
Increase significantly. Therefore, in the present invention, this S_rIs 50% or less
Nozzle inclination angle θ ₁, Θ_TwoIs determined. S_r
The lower limit of is not particularly limited, and may be 0%.

In the positional relationship shown in FIG. 5, the center of the cavity 5 corresponding to the inner nozzle 2 and the inner cavity 5
And the straight line connecting the intersection point of overlap of the outer cavity 6 an angle and gamma (rad), and the overlapping areas of the two cavities, the ratio S _r (overlapping area ratio of the cavity) to the area of the inner cavity 5 by the following equation ( 4).

[0038]

(Equation 4)

Here, γ is expressed by the following equation (5).

[0040]

(Equation 5)

An example in which the lance of the present invention is applied to a top-bottom blowing converter process will be described. In the lance of the present invention, an outer nozzle having a larger inclination angle than the inner nozzle is arranged in the same direction as the inner nozzle in order to suppress scattering of the molten steel droplet in a direction nearly vertical. As shown in Examples described later, the cavity corresponding to the two nozzles, spitting as the overlapping area ratio S _r is small is reduced.

[0042] However, if too large an inclination angle of the outer nozzle in order to reduce the overlapping area ratio S _r of the cavity, the secondary combustion of CO gas generated is promoted, lowering the yield with a decrease in reaction efficiency Problems and refractory wear.

If the lance height H ₀ is reduced, the cavity can be formed near the center of the steel bath surface. Will be shortened. Also, if the lance height H ₀ is too large, the spread of the jet becomes large, and similarly to the case where the inclination angle of the outer nozzle is made too large,
Problems such as secondary combustion of CO gas and wear of refractories occur.

In order to avoid the above problems relating to the outer nozzle, for example, in a converter having an inner diameter of 6 m, when blowing at 270 ton / ch and an acid feed rate of 60,000 Nm ³ / hr, the appropriate range of lance conditions is as follows. It is as follows.

Θ ₂ ≦ 20 ° 2 m ≦ H ₀ ≦ 3 m where θ ₂ is the inclination angle of the outer nozzle and H ₀ is the lance height.

The lance of the present invention is optimally used in a top-bottom blow converter process, but is not limited to this and can also be applied to a steelmaking process using a top-blown lance. Other AOD
It is applicable to any process using a top-blown refining lance, such as a furnace or a copper refining furnace.

[0047]

[Example] In a top and bottom blown converter with a molten steel amount of 270 ton / ch,
Low carbon steel was melted using the upper blowing lance of the present invention, and the amount of spitting loss was investigated. At that time, the amount of wear of the refractory on the furnace wall was also investigated.

The blowing is all a Resusuragu blowing with dephosphorizing pig iron, top-blown oxygen flow rate 60,000Nm ³ / hr, was blown 2000 Nm ³ / hr of CO ₂ as a bottom-blown gas. The lance had 6 holes in both the example and the comparative example, and the throat diameter of the nozzle was φ46 mm for both the inner nozzle and the outer nozzle.

The outlet position of the nozzle of the present invention is the inner nozzle,
The outer nozzles are each distanced from the center of the lance r ₁ = 160
mm, r ₂ = 240 mm, concentric with the outer nozzle and the same orientation as the inner nozzle.

The lances of Comparative Examples 1 and 2 are disclosed in JP-A-6-57.
No. 320 discloses nozzles having two kinds of inclination angles alternately arranged on the same circumference, and the circumference radius is r = 240 mm. In Comparative Examples 3 and 4 and Example, 2
A lance having nozzles of various inclination angles arranged in the same direction was used.

The lance height was kept constant at 2.7 m under all conditions. Table 1 shows the spitting loss and the state of wear of the furnace wall refractories by the lances of the examples and comparative examples.

[0052]

[Table 1]

In Table 1, the overlapping area ratio S of the cavity is shown.
_r is calculated by the above equation (5). The spitting loss is expressed in terms of% by weight with respect to Comparative Example 1, and the wear of the furnace wall refractory is a relative comparison based on Comparative Example 1.

As is clear from Table 1, the combination of the two types of nozzle inclination angles is the same, and these arrangements are arranged on the same circumference (Comparative Examples 1 and 2). Comparing the arrangements (Examples 1 and 4 of the present invention), the latter showed a smaller spitting loss despite the larger overlapping area ratio.

Also, comparing a lance in which nozzles of two kinds of inclination angles are arranged in the same direction and in which the inclination angle θ ₁ of the inner nozzle is the same, the inclination angle θ ₂ of the outer nozzle becomes larger. Accordingly, the overlapping area ratio of the cavities was reduced, and the amount of spitting loss was reduced. Further, the lance inclination angle theta ₂ is at least 18 ° of the outer nozzle, wear of the furnace wall refractories was the degree to which has been slightly worse not a operational problems.

FIG. 6 shows the spitting loss amounts of the lances (Comparative Examples 3, 4 and Example of the present invention) in which nozzles of two kinds of inclination angles are arranged in the same direction, arranged by the overlapping area ratio of the cavities. As is clear from the figure, the spitting loss amount largely depends on the overlapping area ratio of the cavities. When the overlapping area ratio of the cavities exceeds 50%, the spitting loss amount is larger than that in Comparative Example 1.

From the above, it was found that it is necessary to determine the nozzle inclination angle so that the lance in which two types of nozzles having different angles are arranged in the same direction has a cavity overlapping area ratio of 50% or less.

[0058]

EFFECT OF THE INVENTION In the refining process in which a refining gas is blown onto the surface of a molten metal bath, spitting can be greatly reduced by using the lance of the present invention without adversely affecting refractory wear. As a result, improvement of the smelting yield and avoidance of operation troubles such as the adhesion of furnace slab metal are achieved, and the productivity can be improved.

[Brief description of the drawings]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing a tip portion of an upper blowing lance of the present invention taking a 6-hole lance as an example, and FIG.
(b) is an AA plan view.

FIG. 2 is a schematic diagram of a water model experiment for examining splash due to interference between two cavities.

FIG. 3 is an explanatory diagram showing a distribution of splash. Same figure
(a) shows the case of the present invention, FIG. (b) shows the case where nozzles with the same inclination angle are arranged on the same circumference, and FIG. (c) shows the case where nozzles with two inclination angles are arranged on the same circumference. The following shows the case.

FIG. 4 is a schematic vertical sectional view showing a positional relationship of a cavity by an upper blowing lance of the present invention.

FIG. 5 is an explanatory view showing overlapping of cavities by a lance according to the present invention.

FIG. 6 is a graph showing the relationship between the overlapping area ratio of cavities and the amount of spitting loss.

[Explanation of symbols]

 Reference Signs List 1 lance 7 supersonic core 2 inner nozzle 8 splash 3 outer nozzle 9 equal count line 4 molten metal bath surface 10 probe 5 inner cavity 11 dynamic pressure sensor 6 outer cavity 12 counter

Claims (2)

[Claims] _1. Three or more inner nozzles arranged on the circumference at an outward inclination angle θ ₁ and the same number of outer nozzles arranged at an outward inclination angle θ ₂ in the same direction as the inner nozzle. An upper blowing lance for refining, wherein θ ₂ is larger than θ ₁ . 2. An overlapping area of a cavity formed by a jet of an inner nozzle and a jet of an outer nozzle arranged in the same direction using an upper blowing lance for refining according to claim 1, wherein an area of a cavity formed by a jet of the inner nozzle is reduced. Refining method characterized by being 50% or less.