JP2000345228A - Top-blown lance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain the erosion of a lining refractory in a furnace and to achieve the soft blow of a top-blown oxygen gas jet by providing a nozzle composed of a circular shape cross sectional or a non-circular shape cross sectional contracting part, in which the gas flow becomes not less than the sound speed, and a non-circular shape cross sectional enlarging part which connects with the understream side of the contracting part and becomes less than the sound speed. SOLUTION: The cross sectional shape of the non-circular cross sectional contracting part and the enlarging part is anyone of an ellips, oblong circle, rectangle or isosceles triangle having <60 deg. apex angle or sector, and it is suitable to arrange so that the longitudinal direction of the cross sections in the contracting part and the enlarging part is aligned with the radius direction of a lance. In this nozzle, the oxygen gas jet flowing speed spouted from the lance is effectively attenuated before reaching the molten metal surface and the recessed depth formed on the molten metal surface is shallowed and the combustion of CO gas above the molten metal surface with the oxygen gas is sufficiently executed and the soft blow in the top-blown oxygen gas jet can be achieved.

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, and more particularly to an upper blowing lance used for oxygen blowing of molten iron in a converter, an iron bath type smelting reduction furnace, a converter type scrap melting furnace, and the like. Related to the structure.

[0002]

2. Description of the Related Art Recently, in the field of steelmaking, an ore raw material such as chromium ore and iron ore and a carbonaceous material such as coke are added to hot metal in a converter, and the ore is directly melted and reduced to obtain valuable metal in the ore. The technology for collecting waste has become widespread. In carrying out such smelting reduction of ore, a large amount of heating / reducing energy is usually required. Also, not limited to smelting reduction,
Even in a converter operation that performs general steelmaking using molten iron from a blast furnace, a large amount of ore and scrap may be supplied into the converter to perform heating, reduction, and melting. In order to perform such operations while maintaining a high productivity, it is necessary to supply a carbon material as an energy source and oxygen gas for burning the carbon material as quickly as possible.

Usually, the supply of oxygen gas to hot metal or molten steel (hereinafter, referred to as molten metal) held in a converter is performed by using an upper-blowing lance (a long cylindrical body) for the most part.
When the supply rate of oxygen gas is increased according to the above requirements,
There is a problem that the generation of dust increases. Since the increase in the generation rate of the dust causes a decrease in the yield of the molten steel to be manufactured and an increase in the cost of the subsequent dust treatment, the suppression of the dust generation rate is particularly important for performing the smelting reduction under a high productivity. .

[0004] By the way, it is considered that such dust is mainly caused by the CO gas bubbles generated by the decarburization reaction of the molten metal popping on the surface of the molten metal or by the direct evaporation of metal components from the molten metal. But
Both increase as the degree of collision between the oxygen gas jet blowing upward and the molten metal and the supply speed of the oxygen gas itself increase. As a measure for suppressing the generation of dust, it is effective to prevent the top-blown oxygen gas jet from directly colliding with the surface of the molten metal in the molten slag layer existing on the molten metal. Specifically, it is preferable to reduce the depth of the depression of the slag layer generated by the collision of the top-blown oxygen gas jet so that the depression does not reach the surface of the molten metal. That is, when the top-blown oxygen gas jet is so-called “soft blow”, the above condition is achieved.

[0005] It is known that the use of a soft blow of the top-blown oxygen gas jet improves the so-called "secondary combustion rate", and increases the rate of supplying thermal energy to the molten metal while reducing the rate of dust generation. This is extremely effective as a method for causing the above.

[0006] Here, the secondary combustion means that CO gas generated in the furnace by oxygen refining of molten iron is converted into C in the upper space in the furnace.
It means to burn to O ₂ , and the secondary combustion rate is (vol% CO ₂ ) / ｛(vol% CO) +
(Vol% CO ₂ )｝ × 100. In addition, said 2
The efficiency at which the heat generated at the next combustion rate becomes the sensible heat of the molten iron and slag is referred to as heat transfer efficiency.

Conventionally, in converter refining, in order to increase the secondary combustion rate in the furnace (to improve the heat supply capacity), the top-blown oxygen gas jet is soft blown by the following method. .

(1) Raise the tip position of the upper blowing lance (hereinafter referred to as the lance height).

(2) The nozzle of the top blow lance is made porous to disperse the top blow oxygen gas jet.

(3) The nozzle shape of the upper blow lance is made non-circular to promote the attenuation of the flow velocity of the upper blow oxygen gas jet.

In particular, regarding the above (3), many techniques have been proposed. That is, JP-A-61-143507
In order to obtain the effect of increasing the secondary combustion of CO, Japanese Patent Application Laid-Open No. H11-157556 discloses a converter having a non-circular opening having a ratio of a major axis to a minor axis of 1.2 or more and having at least two nozzles having the same shape.
A lance for promoting next combustion is disclosed. At this time, when the nozzle has three or four holes, the one having the major axis of each nozzle on the radius line of the lance is also shown, but these nozzle holes are uniform holes whose cross section does not change in the longitudinal direction. there were.

Japanese Patent Application Laid-Open No. Sho 62-44517 discloses that
Japanese Patent Application Laid-Open No. H8-60219 discloses a technique for recovering secondary combustion heat of CO gas by arranging a subsonic sub-nozzle having a band-shaped cross section surrounding the main nozzle. A converter refining technique using two or more nozzles and a nozzle having a rectangular shape, an elliptical shape, an arc shape, or a combination thereof is disclosed. These technologies relate to decarburization refining with high heat transfer efficiency, high secondary combustion rate, and low dust and high iron yield. It is described that the gas flowing out of the "outlet" has a large attenuation of the flow velocity of the gas immediately after the outflow, as compared with the gas flowing out of the circular hole. And, as an example, the arrangement of the nozzle openings is a two-letter shape in a plan view, a shape in which the majority circle and the small semicircle face each other, a shape in which a “C” character is arranged below the small semicircle, and a “two” shape. A nozzle having a shape in which an intermittent arc surrounds a character shape is illustrated. In these techniques, the nozzle hole was a uniform hole whose cross section did not change in the longitudinal direction.

[0013]

However, the increase in the lance height in the above (1) results in a low heat transfer efficiency of the heat generated in the secondary combustion, resulting in a rise in the temperature of the exhaust gas and a decrease in the refractory lining in the furnace. This results in increased erosion and is not preferred.
In addition, in the case of making the nozzle porous in the above (2), unless the inclination angle of the hole with respect to the vertical (hereinafter, referred to as the nozzle inclination angle) is increased to some extent, the oxygen gas jet dispersed and supplied from the multi-hole nozzle is reassembled. As a result, a sufficient soft blow effect cannot be obtained. On the other hand, when the nozzle inclination angle is increased, there is also a problem that the oxygen gas jet directly collides with the furnace wall and damages the refractory lining the furnace wall. Furthermore, regarding the non-circularization of the nozzle shape in (3), the effect of attenuating the flow velocity of the gas jet due to the mere non-circularization is just a step away. However, there is a problem in that the lance structure is complicated and durability is deteriorated accordingly.

In view of the above circumstances, the present invention suppresses the erosion of a refractory lining in a furnace by simply devising a conventional lance, and achieves a high secondary combustion rate and high deposition in a converter. It is an object of the present invention to provide an upper-blowing lance that can maintain the thermal efficiency, achieve a soft blow of the upper-blown oxygen gas jet, and suppress the dust generation rate during blowing.

[0015]

Means for Solving the Problems The inventor conducted intensive studies and experiments to achieve the above object, and completed the results as the present invention.

That is, according to the present invention, there is provided an oxygen top blowing lance used in a converter type refining furnace, wherein a reduced portion having a circular cross section or a non-circular cross section in which the gas flow is equal to or higher than the sonic speed is connected in series downstream of the reduced portion. Is provided at the tip thereof with an enlarged portion having a non-circular cross section that is lower than the speed of sound.

The oxygen blowing lance used in the converter type refining furnace is:
A gas that is used when refining by blowing oxygen gas from above onto hot metal or molten steel held in a furnace, and is formed by attaching a nozzle tip having one or more through holes to the tip of a long cylindrical body. It is a lance for upper blowing. The present invention is an improvement on the nozzle of such a lance, in which the nozzle hole is provided with a reduced portion having a circular or non-circular cross-sectional shape on the upstream side, and has a larger cross-sectional area than this reduced portion, and It is configured such that an enlarged portion having a non-circular shape is connected in series on the downstream side. The value obtained by dividing the gas flow rate by the cross-sectional area of the reduced portion is equal to or higher than the sonic speed, and the value obtained by dividing the gas flow rate by the cross-sectional area of the enlarged portion is lower than the sonic speed.

In the above lance, the cross-sectional shape of the reduced portion and the enlarged portion of the non-circular cross section is any one of an ellipse, an ellipse, a rectangle, an isosceles triangle having a vertex angle of less than 60 °, or a sector shape. It is preferable that the longitudinal direction of the cross section of the reduced portion and the enlarged portion is aligned with the radial direction of the lance. That is, when the cross-sectional shape of the reduced portion and the enlarged portion is an ellipse or an ellipse, its major axis direction, when it is a rectangle, its long side direction, and when it is an isosceles triangle and a sector, its apex angle is 2 or the like. The lance lines are arranged such that the direction of the shunting line coincides with the radial direction of the lance cylinder.

Further, in the present invention, it is preferable that a concave groove corresponding to the radial direction of the lance is formed on the upper end surface of the enlarged portion. Thereby, the length of the enlarged portion in the longitudinal direction of the nozzle can be reduced.

According to the present invention, the velocity of the oxygen gas jet jetted from the lance is effectively attenuated before reaching the surface of the molten metal, so that the depth of the depression formed on the surface of the molten metal is reduced. As a result, the combustion of the CO gas above the surface of the molten metal by the oxygen gas is sufficiently performed, and the soft blow of the oxygen gas jet blows upward without increasing the lance height or enlarging the nozzle inclination. Therefore, dust generation can be suppressed under a high secondary combustion rate and a high heat transfer efficiency. Further, since the adjacent jets are separated from each other, the contact area between the jet and the atmosphere is increased, and the above effect is further improved.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the circumstances that led to the invention.

In order to achieve the soft blow of the oxygen gas jet blown by means other than increasing the lance height or increasing the nozzle inclination angle, it is necessary to design the nozzle in consideration of the following two points.

(A) The discharge velocity of the gas at the nozzle outlet is reduced.

(B) Increase the attenuation of the gas jet flow velocity until the gas jet ejected from the nozzle reaches the bath surface.

With respect to the above (a), the reduction of the gas discharge flow rate at the nozzle outlet is a value obtained by dividing the supplied oxygen gas flow rate by the nozzle cross-sectional area. By taking the cross-sectional area as large as possible,
Achieved. However, the change in the static pressure of the gas between the nozzle inlet and the outlet when the apparent gas discharge flow rate becomes the sonic speed is as small as 1 kgf / cm ² at the maximum, and it is possible to avoid the molten metal splashing into the nozzle hole. No, it may cause damage to the lance. Therefore, (a) is difficult to be put to practical use.

In order to solve this problem, a rapidly expanding nozzle has been developed. It is configured by connecting a reduction section in the upstream side and an expansion section in the downstream side in one nozzle in series. In this rapidly expanding nozzle,
By setting the apparent gas discharge flow rate at the contraction section to be equal to or higher than the sonic speed and setting the discharge flow rate at the enlargement section to be lower than the sonic velocity to increase the cross-sectional area of the enlargement section as much as possible, the static pressure of gas is maintained high up to the contraction section, While avoiding the splash of molten metal into
It is possible to reduce the gas discharge flow rate.

Meanwhile, the velocity of the gas jet that has been jetted into the space is attenuated while being swept by surrounding gas. Therefore, the above (b) can be achieved by providing a means for increasing the amount of entrained ambient gas. Therefore, it is necessary to design the shape of the gas jet so that the contact area between the gas jet and the surrounding gas is as large as possible.

For example, regarding a gas jet ejected from a single hole, the side area of the gas jet per unit geometrical gas flow rate is smallest when the cross-sectional shape is circular, and as the cross-sectional shape deviates from the circular shape. To increase. Therefore, it is desirable that the cross-sectional shape of the nozzle that determines the shape of the gas jet be non-circular.

Further, when the gas jet from a single hole and the gas jet from a plurality of holes are compared with each other in terms of the geometrical side area per unit gas flow rate, as long as the gas jets from a plurality of holes exist independently, Since the above-mentioned side area increases as the number of holes increases, it is desirable in principle to make the surface porous. On the other hand, as described above, when the nozzle is made porous, it is necessary to avoid re-aggregation of the gas jet. As a method of this, there is an increase in the circumferential direction interval of the nozzles in addition to the increase in the nozzle inclination angle. However, the increase in the nozzle interval must be performed while securing a cooling water channel within a predetermined lance outer cylinder diameter range, and there is a limit as long as a circular nozzle cross-sectional shape is employed. Therefore, if the longitudinal direction of the nozzle having a non-circular (elongated) cross section is laid out so as to coincide with the radial direction of the lance outer cylinder, the circumferential interval of the nozzle can be increased.

Further, as described below, if the cross-sectional shape of the reduced portion is also made non-circular, adjacent jets can be separated, and the contact area between the jet and the atmosphere can be further increased. As a result, the combustion of CO gas on the molten metal surface is further promoted.

Summarizing the above, it is inferred that the following three requirements should be satisfied to obtain the desired soft blow conditions.

1) A rapidly expanding nozzle is employed to reduce the gas discharge flow rate while avoiding molten metal splashing into the nozzle hole.

2) The shape of the enlarged portion of the nozzle is made non-circular (elongated), and its longitudinal direction is arranged so as to coincide with the radial direction of the lance outer cylinder.

3) The shape of the nozzle reduction portion is also made non-circular (elongated) to improve separation of adjacent jets and promote secondary combustion.

The present inventors have developed a software based on the above preliminary study.
Confirm the effect of blow blow and separation of adjacent jets
Therefore, in the three cold model experiments,
The flow velocity distribution was measured. In all experiments,
The gas used was nitrogen, and the gas jet was
Spouted vertically (downward). Gas flow rate is 5Nm ^Three
/ Min, about 600 mm from the tip of the nozzle tip
The radial distribution of the vertical component of the gas jet velocity
It was measured. (Cold model experiment 1) First, the above 1) and 2)
Fig. 1 shows the nozzle tip of the top-blowing lance used to check the terms.
4 to 4 schematically. The nozzle chip shown in FIGS.
Each of the nozzles 1 is a rapidly expanding nozzle. In addition, FIG.
The nozzle hole of the tip 1 has a reduced portion 2 having a circular cross section.
And an enlarged section 3 having an oval cross section connected in series.
However, the nozzle holes of the nozzle tip 1 in FIG.
And a circular reduction unit 2 and an enlargement unit 3 connected to each other. What
Note that the nozzle tip 1 shown in FIGS.
The diameter and the cross-sectional area of the enlarged portion 3 must be equal.
Is being measured. The nozzle tip 1 shown in FIG. 3 and FIG.
It is a straight nozzle and the opening 4 of the nozzle hole in FIG.
Has a diameter equal to the diameter of the enlarged portion 3 of FIG.
The diameter of the opening 4 of the nozzle hole is reduced in FIGS.
Equal to the diameter of 2. Nozzle tip shown in FIGS. 1 to 4
The number of nozzle holes is 6 in each case.
The central axis of the hole is inclined by 15 ° with respect to the lance axis.

FIG. 5 shows a flow velocity distribution when each of the nozzle tips shown in FIGS. 1 to 4 is used. The maximum value of the flow velocity is shown in FIG.
The nozzle tip of FIG.
Next, the nozzle tips of FIGS. 2 and 3 shown by curves 22 and 23 are comparable. Note that the curves 22 and 23 overlap in FIG. Further, in the nozzle tip of FIG. 4 indicated by the curve 24, the flow velocity was the largest. The decrease in the flow velocity maximum from the curve 24 to the curve 23 in FIG. 5 is due to a decrease in the gas discharge velocity at the nozzle outlet due to an increase in the nozzle cross-sectional area. In addition, the fact that the maximum values of the flow velocities of the curves 22 and 23 in FIG. 5 are substantially the same means that the jet characteristics of the rapidly expanding nozzle shown in FIG. 2 are substantially equal to the straight nozzle having the same diameter as the diameter of the expanding portion. Means Further, the decrease in the flow velocity maximum from the curve 22 to the curve 21 in FIG. 5 is caused by an increase in the side area of the gas jet due to the non-circular cross-sectional shape of the enlarged portion.

Focusing on the radial distribution of the flow velocity distribution, in the nozzle tip of FIG. 1, as shown by a curve 21 in FIG.
There is a flow velocity peak corresponding to the plurality of nozzle holes, and the spread is large. On the other hand, in the nozzle tips shown in FIGS. 2, 3 and 4, as shown by curves 22, 23 and 24, respectively, the peak of the flow velocity exists on the center axis of the lance,
It can be seen that the spread is smaller than the curve 21 for the nozzle tip shown in FIG. This result indicates that in the case of the nozzle tip shown in FIG. 1, coalescence of a plurality of jets did not occur, and the lance having this nozzle tip was used as the upper blowing lance according to the present invention.

The damping effect of the gas jet increases as the ratio of the major axis length to the minor axis length of the cross-section of the enlarged portion increases. However, if the value is designed to be 2 or more, the production of the nozzle tip can be improved. And the effect can be enjoyed within a practical range.

Incidentally, in order to fully enjoy the effect of reducing the flow velocity of the nozzle exit by the rapidly expanding nozzle, it is desirable to appropriately design the length of the enlarged portion in the nozzle longitudinal direction according to the diameter of the reduced portion. According to the examination, it has been found that the length of the suddenly enlarged portion should be at least four times the diameter of the reduced portion and should be as long as possible. However, there is a limit to the length of the enlarged portion that can be manufactured in a practical range, and there may be a case where the effect of reducing the flow velocity by the rapidly expanding nozzle cannot be sufficiently obtained due to a problem in manufacturing the nozzle.

Therefore, the inventor studied a countermeasure in another cold model experiment similar to the above in order to solve this problem. (Cold Model Experiment 2) The nozzle tip of the upper blowing lance used here is schematically shown in FIGS.

The nozzle tip 1 shown in FIG. 7 is a rapid enlargement nozzle in which a reduced section 2 having a circular cross section and an enlarged section 3 having an oval cross section are arranged in series. It has a concave groove 5 having a triangular cross section in the direction. In addition,
The length of the enlarged portion 3 in the nozzle longitudinal direction (hereinafter, simply referred to as length) is 2.5 times the diameter of the reduced portion 2. The nozzle tip 1 shown in FIG. 8 has the same shape as the nozzle tip 1 of FIG. 7 except that the concave groove 5 is not provided, and corresponds to the above-described upper lance according to the present invention. Nozzle tip 1 shown in FIG.
Has no groove 5 and the length of the enlarged portion 3 is 5.0 times the diameter of the reduced portion 2 and the length of the enlarged portion 3 is long.

FIG. 10 shows a flow velocity distribution when each of the nozzle tips shown in FIGS. 7 to 9 is used. The maximum value of the flow velocity is as small as that of the nozzle tips of FIGS. 7 and 9 shown by curves 25 and 27 in FIG. 10 (curves 25 and 27 are overlapped in FIG. 10), and FIG. Nozzle tip increased in size. This result indicates that, in the nozzle tip of FIG. 8, the length of the enlarged portion 3 is not sufficient, and the gas ejected from the reduced portion 2 is ejected from the nozzle before completely expanding in the enlarged portion 3. ing. On the other hand, in the nozzle tip of FIG. 7, the maximum value of the flow velocity is as small as that of the nozzle tip of FIG. By providing the groove 5, even when the length of the enlarged portion is short, it is possible to enjoy the effect of reducing the flow velocity by the suddenly enlarged nozzle. Therefore, when the concave groove 5 is provided on the upper end surface of the enlarged portion 3 of the nozzle of the above-described upper blowing lance according to the present invention, the effect of the present invention is further enhanced. And the upper blowing lance.

Here, as in the present invention, the elongated enlarged portion 3 is used.
In the nozzle having the above, the gas is likely to be incompletely expanded in the longitudinal direction, so the concave groove 5 needs to be provided in the longitudinal direction. The optimum shape of the concave groove 5 varies depending on the diameter of the reduced portion 2 and the shape (cross-sectional shape, cross-sectional area, length) of the enlarged portion 3, but the vertical cross-sectional shape generally has an apex angle of 60 ° or less. It is effective to set the width (the length of the base) to be at least 1/4 of the diameter of the reduced portion 2 and less than the diameter. (Cold model experiment 3) Next, the nozzle tip of the upper blowing lance used for confirming the above item 3) is shown in FIG.
1 to 13 are schematically shown. The nozzle tip shown in FIG. 11 is a rapid enlargement nozzle in which a reduced portion 2 having an oval cross section and an enlarged portion 3 having an oval cross section similar to the reduced portion 2 are arranged in series. The nozzle tip shown in FIG. 12 is a rapid enlargement nozzle in which a reduced section 2 having a circular cross section and an enlarged section 3 having an oval cross section are arranged in series, and the nozzle tip according to the present invention shown in FIG. It has basically the same structure. The nozzle tip shown in FIG. 13 is a rapid enlargement nozzle in which a reduced portion 2 and an enlarged portion 3 having a circular cross section are arranged in series, and has the same structure as the nozzle tip shown in FIG.

FIG. 14 shows a radial flow velocity distribution when each of the nozzle tips shown in FIGS. 11 to 13 is used. The maximum value of the flow velocity is determined by the nozzle tip (FIG. 11) indicated by the curve 28 in FIG.
Nozzle tip), and slightly increased by the nozzle tip shown by the curve 29 (nozzle tip in FIG. 12).
The value increased with the nozzle tip indicated by 0 (the nozzle tip in FIG. 13). FIG. 15 shows a flow velocity distribution between two adjacent holes when these nozzle tips are used. The maximum value of the flow velocity was in the same order as shown in FIG.
However, in the case of the nozzle tip of FIG. 11 shown by curve 28, the jet between two adjacent holes is largely separated.
As a result, when the nozzle tip of FIG. 11 is used, the contact area between the jet and the atmosphere increases, and the jet flow velocity is lower than when another nozzle tip is used.
Due to this effect, the combustion of CO gas by oxygen on the molten metal surface is sufficiently performed, and the height of the lance is increased,
Alternatively, it is expected that the soft blowing of the top-blown oxygen gas jet can be achieved without increasing the nozzle tilt angle, and that the suppression of dust generation can be brought about under a high secondary combustion rate and a high heat transfer efficiency. Therefore, the nozzle tip of FIG. 11 is also added to the nozzle tip of the upper blowing lance according to the present invention.

Further, under the same conditions as in the above three cold model experiments, the cross-sectional shape of the enlarged portion 3 is not an ellipse but an ellipse as shown in FIGS. 6 (a), 6 (b), 6 (c) and 6 (d). An attempt was also made for a shape 6, a rectangle 7, an isosceles triangle 8, or a sector 9. As a result, in each of the experiments, the same effect as in the case of the above-described elliptical shape was obtained, so that the non-circular shape corresponding to the nozzle tips of FIGS. 1, 7 and 11 according to the present invention described above was obtained. These shapes are also added to the cross-sectional shape. Of course, also in this case, a concave groove 5 is provided on the upper end surface of the enlarged portion 3 or the sectional shape of the reduced portion 2 is changed as shown in FIG.
As shown in FIG.

[0046]

EXAMPLES (Example 1) The operation of smelting reduction blowing of chrome ore was performed in a 5-ton scale top and bottom blown converter, and the generation rate of dust and the amount of wear of the furnace wall refractories were investigated. In addition, the above-mentioned cold model experiments 1 and 2
Under the geometrical similarity to the nozzle tip used in the above, the nozzle tip having a nozzle tip designed to have the same apparent gas discharge flow rate was used interchangeably.

The operation was performed according to the following procedure. After charging the molten pig iron having a chemical composition shown in Table 1 to the converter, first bottom-blown feather nitrogen gas through the opening 5.0 nm ³ / min, and the top-blown through lances pure oxygen gas 15 Nm ³ / min While blowing, lump coke and quicklime and silica as a slag-making material were put into the furnace from a shooter provided on the furnace, and heat was raised and slag was formed. During the blowing period, the melt temperature was 1550 ° C,
Until the amount of molten slag reaches 100 kg / t, about 2
0 minutes. Then, continuously, the lump coke was fed from the on-furnace shooter at a rate of 19 kg / min, and the lumped chromium ore was placed at 2 kg so that the molten metal temperature became 1550 ° C. ± 20 ° C.
/ Min to 25 kg / min. Lumpy lime was added from the on-furnace shooter so that the slag basicity was 2.0.

Table 2 shows the composition of the chromium ore used.
During the operation, the temperature of the molten metal was measured using a so-called sub-lance, and based on the measured values, the charging speed of the chromium ore was adjusted as described above, and the temperature of the molten metal was 1550 ° C. ±
The temperature was set to 20 ° C. The addition of chromium ore was performed for about 60 minutes, and thereafter, a finish reduction for reducing and recovering chromium remaining in the slag without adding chromium ore was performed at a melt temperature of 1550 ° C to 1600 ° C for about 10 minutes. The dust generation rate was determined by measuring the dust concentration in the exhaust gas in the flue.

Table 3 shows an example using a lance according to the present invention and a comparative example using a lance of another type, showing an index of dust generation rate during operation, a refractory wear index, and a productivity index (unit). Index of chromium ore usage per hour).
The lance used in Comparative Examples 1 and 2 was the nozzle tip shown in FIG. 4 described above, the lance used in Comparative Example 3 was the nozzle tip shown in FIG. 2, and the lances used in Invention Examples 1 and 2 were:
Each is geometrically similar to the nozzle tip shown in FIG. The nozzle tip used in Invention Example 3 has a concave groove 5 on the upper end surface of the enlarged portion 3 shown in FIG.
Is 40% shorter than that of FIG. Further, the lance height shown in Table 3 is the distance from the surface of the molten metal to the tip of the upper blowing lance, and the velocity index of dust generation is:
This is a relative comparison, with the dust generation speed of Comparative Example 1 being 100. Further, the refractory wear index and the productivity index are comparatively shown by setting the value of Comparative Example 1 to 1.0.

Comparison between Comparative Example 1 and Comparative Example 2 in Table 3 shows that
In Comparative Example 2, since the lance height was increased to make the soft blow, the dust generation rate was lower than in Comparative Example 1. However, the amount of wear of refractories increases significantly, and the amount of chromium ore used does not increase so much, so that the effect of improving productivity is not large. In Comparative Example 3, a lance having a circular rapidly expanding nozzle was used. However, compared to Comparative Example 1 in which the lance height was the same, the effects of lowering the dust generation rate and improving the productivity were recognized. Can be However, refractory erosion tends to increase slightly.

In contrast to the above comparative example, in the invention example 1 using the lance having the non-circular suddenly expanding portion, the refractory wear index increases slightly at the same lance height as the comparison example 1, but the chromium Ore usage is increasing and dust generation rates are decreasing significantly. In Invention Example 2 in which the lance height was further reduced,
Compared with Comparative Example 1, the refractory wear index also decreased, the chromium ore usage increased, and the dust generation rate decreased. In other words, as a result of achieving a soft blow even at a low lance height and increasing the secondary combustion rate and the heating efficiency, the heat input to the molten metal increases without increasing the load on the converter refractory, and the chromium A large amount of ore can be smelted and reduced.
In addition, the length of the enlarged portion 3 in Inventive Example 3 is shorter than that of Inventive Example 2, but almost the same results are obtained.

[0052]

[Table 1]

[0053]

[Table 2]

[0054]

[Table 3]

(Example 2) Using a top blown lance having a geometric similarity to the nozzle tip used in the cold model experiment 3, a 5-ton scale top-bottom blower was used in the same manner as in (Example 1). The operation of smelting reduction blowing of the chrome ore was performed, and the generation rate of dust and the amount of wear of the furnace wall refractories were investigated.

Evaluation of operating conditions, procedures, and survey results
As in the case of (Example 1), the chemical compositions of hot metal and chromium ore charged in the converter are as shown in Tables 1 and 2.

Table 4 shows the index of the dust generation rate during operation.
The refractory wear index and productivity index (index of chromium ore usage per unit time) are shown.

Comparison between Comparative Example 4 and Comparative Example 6 in Table 4 shows that
Inventive Example 4 uses a lance having an oval rapid expansion nozzle in both the reduction section 2 and the expansion section 3, so that the effects of reducing the dust generation rate and improving the productivity are recognized, and the refractory wear index is the same. is there. Also, the use of chromium ore is increasing and the rate of dust generation is decreasing. Further, in Invention Example 5 in which the lance height was reduced, the refractory wear index was also reduced (the use amount of chromium ore was increased and the dust generation rate was decreased) as compared with Comparative Examples 4, 5, and 6. In other words, soft blow was achieved even at a low lance height, and as a result of the increase in the secondary combustion rate and the heat transfer efficiency, the amount of heat input to the molten metal increased, and a large amount of chromium ore could be melted and reduced. Moreover, erosion of the converter refractory can be reduced.

Although the above-mentioned invention examples and comparative examples both relate to the smelting reduction of chromium ore, the top blowing lance according to the present invention uses iron ore, manganese ore, nickel ore, and other carbon reductions. It is also possible to apply effectively to possible ores and their agglomerated ores, pre-reduced ores and the like. Also, such as scrap in converter refining,
It goes without saying that the use of the cold iron source is also effective.

[0060]

[Table 4]

[0061]

As described above, according to the present invention, the rate of dust generation can be greatly increased while maintaining the secondary combustion rate and the heat transfer efficiency at a high level and without increasing the refractory lining of the converter. Could be lowered. Further, the productivity of molten steel could be improved without lowering the yield and increasing the cost of dust treatment thereafter.

[Brief description of the drawings]

1A and 1B show a nozzle tip according to an embodiment of the present invention, wherein FIG. 1A is a sectional view and FIG. 1B is a longitudinal sectional view.

FIG. 2 shows a conventional example of a rapidly expanding nozzle tip, and FIG.
Is a sectional view, and (b) is a longitudinal sectional view.

FIG. 3 shows a conventional straight nozzle tip,
(A) is a sectional view, and (b) is a longitudinal sectional view.

FIG. 4 shows a conventional straight nozzle tip,
(A) is a sectional view, and (b) is a longitudinal sectional view.

FIG. 5 is a diagram showing a vertical component distribution of a gas jet flow velocity obtained in a cold model experiment 1 using various lances.

6A and 6B are diagrams showing a nozzle tip cross section of an example of the invention having an enlarged section cross section other than an oval, wherein FIG. 6A is a cross section of an enlarged section having an elliptical shape, and FIG. In the case of a rectangle, (c) shows the case where the cross-sectional shape of the enlarged portion is an isosceles triangle, and (d) shows the case where the cross-sectional shape of the enlarged portion is a sector.

FIGS. 7A and 7B show a nozzle tip of the invention example having a concave groove on an upper end surface of an enlarged portion, wherein FIG. 7A is a cross-sectional view, FIG. 7B is a vertical cross-sectional view, and FIG. FIG.

8A and 8B show a conventional sharply enlarged nozzle tip without a groove and having a length of an enlarged portion shorter than that of FIG. 7, wherein FIG. 8A is a sectional view and FIG. 8B is a longitudinal sectional view.

9A and 9B show a conventional sharply enlarged nozzle tip without a groove and having a length of an enlarged portion longer than that of FIG. 7, wherein FIG. 9A is a sectional view and FIG. 9B is a longitudinal sectional view.

FIG. 10 is a diagram showing a vertical component distribution of a gas jet flow velocity obtained in a cold model experiment 2 using the nozzle tips of FIGS.

11A and 11B show a nozzle tip of an example of the present invention used in the cold model experiment 3, in which FIG. 11A is a cross-sectional view, FIG. 11B is a vertical cross-sectional view, and FIG. .

FIG. 12 shows a nozzle tip basically similar to FIG. 1,
(A) is a cross-sectional view, (b) is a vertical cross-sectional view, and (c) is a view taken along the line BB of (a).

FIGS. 13A and 13B show a nozzle tip of a comparative example basically similar to FIG. 3, wherein FIG. 13A is a sectional view and FIG. 13B is a longitudinal sectional view.

FIG. 14: Cold model experiment 3 using various lances
FIG. 5 is a diagram showing a vertical component distribution of a radial gas jet flow velocity obtained in FIG.

FIG. 15 is a diagram showing a distribution of a vertical component of a gas jet flow velocity between two adjacent holes obtained in a cold model experiment 3.

16A and 16B are views showing a nozzle tip cross section of an example of the invention having a reduced section cross section other than an ellipse, where FIG. 16A is an ellipse, FIG. 16B is a rectangle, and FIG. 16C is an isosceles triangle. Is the case.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Nozzle tip (nozzle) 2 Reduction part 3 Enlargement part 4 Opening part 5 Concave groove 6 Oval shape 7 Rectangle 8 Isosceles triangle 9 Fan shape

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yukio Takahashi 1 Kawasaki-cho, Chuo-ku, Chiba City, Chiba Prefecture Inside the Technical Research Institute of Kawasaki Steel Corp. (72) Inventor Shuji Takeuchi 1 Kawasaki-cho, Chuo-ku, Chiba City, Chiba Prefecture Kawasaki (72) Inventor Kenichi Sorimachi 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba F-term (reference) 4K002 AC05 AD02 BF01 BF03

Claims (3)

[Claims] 1. An oxygen top-blowing lance used in a converter type refining furnace, wherein a reduced portion having a circular or non-circular cross-section in which a gas flow is equal to or higher than a sonic speed is connected in series downstream of the reduced portion, and the gas flow is determined to be lower than a sonic speed. An upper blowing lance, characterized in that a nozzle comprising an enlarged portion having a non-circular cross section is provided at the tip. 2. The cross-sectional shape of the reduced portion and the enlarged portion of the non-circular cross section is an ellipse, an ellipse, a rectangle, or a vertex angle of 60.
2. The upper blowing lance according to claim 1, wherein the shape is any one of an isosceles triangle and a sector of less than 0 °, and a longitudinal direction of a cross section of the enlarged portion is arranged to coincide with a radial direction of the lance. 3. The lance according to claim 2, wherein a groove is formed on an upper end surface of the enlarged portion so as to coincide with a radial direction of the lance.
Top blow lance described.