JPH10152715A - Top-blown oxygen lance and converter blowing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a top-blown oxygen lance which can reduce iron loss without extending the blowing time, and a converter blowing method. SOLUTION: The top-blown lance 1 for refining molten metal is provided with one or more of round blowing holes 4 at the center part of tip part 3 of a nozzle 2 and one or more of annular blowing holes 5 surrounding these round blowing holes. This blowing method of the converter is executed by using this lance under condition, i.e., at the time of using Q1 for the sum of oxygen gas flow rate of the round blowing holes 4 and Q2 for the sum of the same gas flow rate of annular glowing holes 5, X=Q1/(Q1+Q2) is made to 0.1-0.9. Further, the above lance is used and the oxygen gas flow rates are independently controlled by separating the oxygen supplying systems of the round blowing holes 4 and the annular blowing holes 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a top blown oxygen lance for refining molten metal and a method for blowing a converter using the same.

[0002]

2. Description of the Related Art In a top-blowing or top-bottom-blowing converter for refining molten metal, a top-blown oxygen gas jet collides with a metal bath surface, for example, a molten iron bath surface, and its collision energy, or a fire point which is the collision surface. The so-called spitting phenomenon occurs in which the molten iron is scattered and scattered due to the energy generated by the CO gas generated in step (1). In addition, converter dust is generated from the above-mentioned fire point, and when this dust is classified into its causes, it is possible to reduce CO2 at the fire point due to evaporation of iron from a high-temperature fire point and decarburization reaction.
It is said that there are two types, one in which the scattered droplets become fine and become dusty due to volume expansion when gas is generated.

[0003] Various methods have been proposed to prevent a reduction in iron yield (iron loss) due to the above-mentioned spitting and dust.

For example, in Japanese Patent Application Laid-Open No. 60-165313, it is important to reduce the overlap of the jets from the nozzles on the molten iron bath surface. A method is disclosed in which the ratio of the diameter of the recessed cavity (cavity) to the minor axis of the overlapping portion is 0.2 or less.

In Japanese Patent Application Laid-Open No. 2-111809, the ratio between the depth and the diameter of the cavity is set to 2 or more,
A method for reducing the amount of dust generation is disclosed.

However, in these methods, the effects of spitting and reducing the amount of generated dust are unclear, and an improvement in iron yield cannot be obtained. The following ~ to solve this
Technology has been proposed.

Japanese Patent Application Laid-Open No. 7-305107 discloses “2-4
In a top lance for molten metal refining having 1 to 9 gas ejection holes composed of heavy pipes, at least a gas ejection hole in which the gas outlet of the inner pipe is located more deeply than the gas outlet of the outermost pipe. A single lance is shown.

[0008] Japanese Patent Application Laid-Open No. 8-13018 discloses that "oxygen for converter blowing has one or more strip-shaped or curved oxygen injection holes having a length-to-width ratio of 5 or more at the tip. Lance nozzle "is shown.

Japanese Patent Application Laid-Open No. H8-60219 states that "having two or more top-blowing nozzles, the shape of which is rectangular, elliptical, arc-shaped, or a combination thereof, Assuming that Y (m), the opening area is (w (m ² )), and W / Y is X, the distance between the nozzle tip and the steel bath surface is determined using an upper blowing lance where X is 30 or more and 300 or less. 10 G × X ^{0. 9}
A converter refining method with less dust generation of × Y ^0.1 or more and 30 × X ^0.9 × Y ^0.1 or less ”is shown.

[0010]

However, the above-mentioned prior arts have the following problems.

In the prior art top blow lance, the gas outlet of the inner tube needs to be located deeper than the gas outlet of the outer tube. Therefore, the lance structure, which has been complicated in the past, is further complicated, and difficulties in manufacturing occur. In the first place, this lance says, `` Since the throat diameter of the pipeline is not variable with conventional lances, it is necessary to change the secondary pressure of the lance to change the flow rate, and the linear flow rate decreases at the oxygen gas outlet. This is to prevent "doing". Therefore, there is no effect on spitting or reduction in the amount of dust generated, and there is no description in the above publication.

[0012] The prior art publication states that "oxygen jets spouted from a strip-shaped oxygen jet have greater jet velocity attenuation than oxygen jets spouted from a conventional circular jet or the like. Therefore, by using the lance nozzle of the present invention, it becomes possible to obtain a low oxygen jet flow velocity on the molten steel surface at the same oxygen supply speed and the same lance nozzle height as the conventional lance nozzle. Here, if the ratio of the length to the width is less than 5, the above-mentioned effects cannot be obtained remarkably. " However, for example, as shown in FIG. 1 (c) of the official gazette, also in the case where a strip-shaped ejection hole is arranged around a conventional circular ejection hole, attention is paid only to the ratio between the length and width of the strip-shaped ejection hole. The relative relationship between the strip-shaped orifice and the central orifice (eg, flow ratio)
Is not clear at all.

[0013] In the refining method of the prior art, a strip-shaped ejection hole is formed in the same manner as in the prior art, despite the use of an upper blowing lance composed of only strip-shaped ejection holes and having only a plurality of strip-shaped ejection holes. The relationship between comrades is not clear. In addition, since blowing is performed using only the strip-shaped ejection holes, a predetermined acid feed rate cannot be obtained, and the blowing time becomes longer.

An object of the present invention is to clarify the optimum conditions for suppressing the amount of spitting and dust generation, which have not been sufficiently defined in the past, between the oxygen gas discharge holes, so that the blowing efficiency is not reduced. Another object of the present invention is to provide a top blown oxygen lance for refining molten iron having a circular jet hole and an annular jet hole surrounding the circular jet hole, which can reduce iron loss, and a method for blowing a converter using the same.

[0015]

The gist of the present invention is as follows.
(1) Top-blown oxygen lance and its use (2), (3)
Blowing method of converter.

(1) At least one circular jet hole at the center of the tip of the nozzle, and one or more annular jet holes surrounding the circular jet hole. Blowing oxygen lance.

(2) A method for blowing a converter using an upper-blown oxygen lance as described in (1) above, wherein the sum of the oxygen gas flow rates of the circular orifices is Q1 and the sum of the same gas flow rates of the annular orifices is Q2. Wherein X = Q1 / (Q1 + Q2) is set to 0.1 to 0.9.

(3) A method for blowing a converter using an upper-blown oxygen lance as described in (1) above, wherein the oxygen supply system for the circular orifice and the annular orifice is separated and the oxygen gas flow rate is independently controlled. A blowing method for a converter, characterized in that:

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS With reference to FIG. 1, an example of the configuration of an upper-blown oxygen lance for refining molten metal of the present invention will be described.

FIG. 1 is an external view of a main part showing the outline thereof. The example shown in FIG. 1 is an upper-blowing oxygen lance 1 for converter blowing, in which three circular ejection holes 4 are provided at the center of a tip portion 3 of a nozzle 2, and these circular ejection holes 4 are surrounded. It has one annular ejection hole 5 on the outside. This annular ejection hole 5 is actually recognized as an annular slit in appearance. The cooling method and the structure for it are the same as before,
The illustration is omitted.

The number of the circular ejection holes 4 is one or more, and a desirable upper limit thereof is six. The number of the annular ejection holes 5 is also one or more, and a desirable upper limit thereof is three. When a plurality of annular ejection holes 5 are provided, they are provided so that the centers of the respective annular ejection holes coincide with each other.

The shape of each of the jet holes 4 and 5 may be either a straight type or a Laval type with a divergent shape. Therefore, the angles of the oxygen gas jets jetted from the jet holes 4 and 5 are all equal. Not limited.

The provision of at least one circular orifice at the center and one or more annular orifices surrounding the circular orifice is to secure the amount of acid supply only with the strip or annular orifice. This is because the blowing time of the converter is prolonged due to the inability to perform the heat treatment, and the productivity is lowered. Also,
This is because, in the case of only the annular orifice, a region where the pressure is reduced is generated at the center thereof, causing a problem of adhesion of the scattered iron particles, and in a worst case, a water leakage accident due to erosion of the lance may occur. . On the other hand, with only circular vents,
As described in connection with the related art, it is not possible to suppress a reduction in iron yield (iron loss) due to spitting and dust.
Therefore, it is an essential condition to provide one or more circular ejection holes and one or more annular ejection holes at the same time.

However, if the number of circular ejection holes at the center exceeds six, the cooling structure of the nozzle portion becomes complicated, and the possibility of water leakage due to a decrease in cooling capacity increases. If the number of annular ejection holes exceeds three, the cooling structure of the nozzle part becomes complicated, the cooling water passage becomes extremely narrow, and the possibility of water leakage due to a decrease in cooling capacity increases as described above.

The former is disposed inside the latter at the relative position of the circular orifice and the annular orifice, because the molten iron droplet generated by the gas jet injected from the circular orifice or the evaporation fume at the gas spraying ignition point Is caused to be caught in the gas ejected from the annular ejection hole, and again landed on the molten iron or the slag. When there are a plurality of annular ejection holes, it is possible to obtain an effect that liquid iron droplets or evaporation fumes not captured by the gas jet injected from the inner annular ejection hole can be captured.

In the method of the present invention, first, hot metal carried from a blast furnace or the like by a topped car or the like, or after performing hot metal treatment such as desiliconization, dephosphorization, desulfurization, etc., is charged into a top-blowing or top-bottom-blowing converter. I do. Thereafter, an upper-blowing oxygen lance configured as shown in FIG. 1 is lowered into the furnace from above the furnace port, and oxygen blowing is performed. When the present invention is applied to a top-bottom blow converter and a cooling gas such as oxygen gas, CO ₂ gas, inert gas, or propane or a mixed gas thereof is used as the bottom blow gas, conditions such as gas type and flow rate are not limited.

Here, regardless of the top-blowing or top-bottom-blowing converter, as the blowing condition of the top-blown oxygen gas, the sum of the oxygen gas flow rate of the circular orifice and the sum of the oxygen gas flow rate of the annular orifice are Q1. Assuming that Q2, the range of X = Q1 / (Q1 + Q2)
0.1 to 0.9.

The reason for limiting the range of X as described above is as follows.

When X is less than 0.1, the flow rate of oxygen gas from the central circular ejection hole is small, and the problem of spitting and increase in the amount of generated dust is small. However, since the flow rate of oxygen gas from the annular ejection hole becomes large, the amount of spitting and dust generated due to this increases. On the other hand, when X exceeds 0.9, the flow rate of oxygen gas from the central circular orifice is large, and the problems of spitting and the increase in the amount of generated dust due to the flow cannot be ignored. In addition, since the oxygen gas flow rate from the annular orifice is relatively small, spitting and dust generated by the gas jet from the circular orifice in the center are involved and the efficiency of landing on the molten iron or slag again decreases. I do.

Regarding the above-mentioned optimum conditions of X, the results obtained by a survey using a 5-ton top-bottom blow test converter (inner diameter: about 1.3 m) will be described. In this test, the amount of hot metal charged was 4.4 tons, and slag was removed as much as possible before charging, and blowing was performed under slagless or less slag conditions. Table 1 shows the typical composition of the hot metal. The top blown oxygen lance used had three circular ejection holes at the center and one annular ejection hole on the outer periphery surrounding these, similarly to the configuration shown in FIG. At this time, the condition of the bottom blown gas is as follows:
The total gas flow from the four tuyeres was 2 Nm ³ / min.

[0031]

[Table 1]

The hot metal temperature at the start of blowing is 1200 to 12
30 ℃, oxygen gas flow rate per unit time is 12Nm ³ / mi
n was fixed. That is, the total flow rate of Q1 and Q2 is
X was adjusted by changing the ratio between Q1 and Q2 while keeping the value constant at 12 Nm ³ / min.

In the middle of the blowing, a sampler equipped with 10 iron cases in the height direction was inserted into the furnace for 1 minute to collect the scattered iron. Dust was collected from the exhaust duct during blowing. These results are shown in FIG. 2 and FIG.

FIG. 2 is a diagram showing the amount of scattered iron, that is, the effect of X on the amount of scattered iron.

This is the result of dimensionalizing the amount of iron scattered in the furnace collected during the blowing with a value of X = 0.1 and arranging it in X. As can be seen from FIG. 2, the amount of iron scattered in the furnace can be suppressed when X is in the range of 0.1 to 0.9.

FIG. 3 is a diagram showing the influence of X on the amount of dust collected, that is, the amount of dust generated.

This is a result of dimensionalizing the amount of dust collected during blowing with a value of X = 0.1 and arranging it with X. As can be seen from FIG. 3, the amount of dust generated can be suppressed when X is in the range of 0.1 to 0.9.

In carrying out the method of the present invention, when designing and manufacturing the nozzle portion, when there are a plurality of circular ejection holes, the oxygen gas flow rate Q1 is evenly distributed to each of the circular ejection holes. When there are a plurality of annular ejection holes, care is taken so that the oxygen gas flow rate Q2 is equal to or smaller with respect to each annular ejection hole.

In the method of the present invention, as shown in FIGS. 2 and 3, X may be changed in the range of 0.1 to 0.9 depending on spitting and dust generation conditions during blowing, or a certain constant value may be used. May be fixed. However, when the supply system of oxygen gas is the same at the entrance and inside of the lance, it is not easy to realize such a method freely. Therefore, the lance structure is a multiple tube, and the oxygen supply system is separated for the circular orifice and the annular orifice on the entrance side and inside of the lance.
It is desirable to control each of them independently.

[0040]

[Example] 250 tons of hot metal having the composition shown in Table 2 (temperature: 1250
1300 ° C.) was charged into an upper-bottom blower, and an oxygen gas of 1000 Nm ³ / min under the conditions of X shown in Table 3 was used as a top blown oxygen lance (center: circular ejection hole 3) as shown in FIG. Pieces, outside: one annular ejection hole, lance height: about 3 m, oxygen gas flow rate: the above independent control), and iron yield loss was compared. The bottom gas condition at this time was Ar gas type, and the total gas flow rate from the four tuyeres was 50 Nm ³ / min.

[0041]

[Table 2]

[0042]

[Table 3]

For each condition of X shown in Table 3, 50
The blowing over the charge was performed to calculate the yield loss amount, and the change amount with respect to the base method No. 15 of the conventional method, that is, X = 1 (Q2 = 0) was obtained. The results are shown in Table 3.

As shown in Table 3, when X was in the range of 0.1 to 0.9, a large improvement in yield loss was observed. on the other hand,
There was no effect under conditions outside this range. At this time, the blowing time did not change much.

[0045]

According to the present invention, it is possible to reduce iron loss without extending the blowing time of the converter.

[Brief description of the drawings]

FIG. 1 is an external view of a main part schematically showing a configuration example of a top-blown oxygen lance of the present invention.

FIG. 2 is a diagram showing the influence of X on the amount of scattering iron (scattering amount).

FIG. 3 is a diagram showing an influence of X on a dust collection amount (generation amount).

[Explanation of symbols]

1: Top blow oxygen lance, 2: Nozzle, 3: Tip,
4: Circular orifice, 5: Annular orifice

Claims (3)

[Claims] 1. An upper blow for molten metal refining, comprising: at least one circular blow hole at the center of the tip of the nozzle; and at least one annular blow hole surrounding the circular blow hole. Oxygen lance. 2. The method of claim 1, wherein the sum of the oxygen gas flow rates of the circular jet holes is Q1, and the sum of the oxygen gas flow rates of the annular jet holes is Q2. Wherein X = Q1 / (Q1 + Q2) is set to 0.1 to 0.9. 3. A method for blowing a converter using an upper-blown oxygen lance according to claim 1, wherein the oxygen supply system for the circular orifice and the annular orifice is separated and the oxygen gas flow rate is independently controlled. A blowing method for a converter, characterized in that: