JP6870450B2 - Top-blown lance and converter blowing method using it - Google Patents

Description

The present invention relates to a top-blown lance for a converter used when decarburizing hot metal using a top-bottom blown converter type refining vessel, and a converter blowing method using the same.

Conventionally, a top-bottom blown converter type refining vessel has been widely used to remove carbon in hot metal produced in a blast furnace. In the decarburization process, hot metal is charged into a converter type refining vessel, and while stirring the hot metal by blowing a stirring gas from the bottom blowing tuyere, oxygen is blown up from the top blowing lance to remove carbon in the hot metal. Oxidize and remove. Further, in order to increase the productivity and reduce the cost of producing molten steel, it is possible to increase the flow rate of top-blown oxygen to perform high-speed smelting. However, if the oxygen flow rate is forcibly increased and blowing is performed, the amount of splashes such as bullion and the scattering distance increase, and a large amount of bullion adheres to the lance, the furnace body, the skirt, and the hood. (Hereinafter, spitting) causes troubles such as cooling water leakage. As a result, the non-operating time for removing the bullion and repairing the equipment increases, the productivity decreases, and the cost increases.

Therefore, in order to suppress such spitting, by rotating the top blow lance, the fire point where the jet ejected from the top blow lance collides with the hot metal bath surface is moved, and the momentum of the jet is transferred to the hot metal surface. Techniques have been proposed for widespread distribution. As a technique for performing blowing by rotating the top blowing lance, for example, Patent Documents 1 and 2 are disclosed.

Japanese Unexamined Patent Publication No. 62-130211 Japanese Unexamined Patent Publication No. 2016-74954

However, in order to rotate the top blown lance, it is necessary to change to equipment equipped with a motor, bearings, etc. that rotate the top blown lance body. Furthermore, from the viewpoint of maintenance, it cannot be easily performed because the top blow lance is a long object. Therefore, it is difficult to put the method of rotating the top-blown lance into practical use at present because it is difficult to overcome these equipment problems. Therefore, other than the method of rotating the top blowing lance, a method capable of speeding up decarburization while suppressing spitting while moving the fire point is desired.

In view of the above-mentioned problems, the present invention has a top-blown lance and a top-blown lance capable of continuously moving the fire point during blowing by a method other than rotating the lance in the top-bottom blown converter type refining vessel. It is an object of the present invention to provide a converter smelting method using it.

When the top blown lance is rotated around the center axis of the lance, the fire point moves in the circumferential direction around the center of the bath surface, but the fire point moves in the circumferential direction without rotating the top blown lance. In order to make it happen, it is necessary to change the injection direction of the jet. Here, in order to change the injection direction of the jet, a method of mechanically changing the direction of the nozzle at the tip of the top blowing lance can be considered, but in a situation where dust and bullion are scattered in a high temperature field in a converter. , It is very difficult to provide a mechanism to mechanically change the direction of the nozzle. Therefore, it is necessary to change the jet injection direction of the nozzle at the tip of the top blow lance without giving a mechanical change.

Therefore, the present inventors have found a top-blowing lance having a bifurcated nozzle in which two gas flow paths are united at a nozzle outlet, as shown in FIGS. 1 and 2, for example. Then, by controlling the gas flow rate ratio of the two flow paths of the upper blowing lance, the direction of the jet ejected from the upper blowing lance is adjusted, and a method of moving the fire point in the circumferential direction is found. It was.

The present invention is as follows.
(1) A top-blowing lance provided with a nozzle portion having a plurality of ejection holes for ejecting gas on the tip surface.
The plurality of ejection holes are arranged at equal intervals in the circumferential direction on a circle concentric with the central axis of the lance.
Each of the plurality of ejection holes is an ejection hole shared by two nozzles having a circular cross section perpendicular to the central axis of the nozzles.
The two nozzles are a first nozzle and a second nozzle.
The intersection of a straight line in which the central axis of the first nozzle is projected on a plane perpendicular to the lance central axis and a straight line in which the central axis of the second nozzle is projected on a plane perpendicular to the lance central axis, and the plane. The angle of the straight line obtained by projecting the central axis of the first nozzle onto a plane perpendicular to the central axis of the lance with respect to the straight line passing through the intersection of the lance and the central axis of the lance is α. Let β be the angle of the central axis with the straight line projected on the plane perpendicular to the lance central axis.
In a plane parallel to the lance central axis and including the central axis of the first nozzle, a sharp angle formed by a straight line parallel to the lance central axis and the central axis of the first nozzle is defined as γ and the lance central axis. When the sharp angle formed by the straight line parallel to the lance central axis and the central axis of the second nozzle in a plane parallel to the center axis of the second nozzle is δ.
The conditions of γ = δ, 10 ° ≦ γ, δ ≦ 30 °, and (α + β) × sinγ ≧ 20 are satisfied, and the gas is separately transported to the first nozzle and the second nozzle. Top-blown lance characterized by the combined piping for.
Here, the unit of α, β, γ, and δ is “° (degree)”.
(2) The above-mentioned (1), wherein θ is 38 ° or less when the angle formed by the central axis of the first nozzle and the central axis of the second nozzle is θ. Top-blown lance.
(3) Further, the top-blown lance according to (1) or (2) above, wherein α = β.
(4) A converter blowing method in which blowing is performed using the top blowing lance according to any one of (1) to (3) above.
The ratio L / D of the fire point movement distance L and the fire point diameter D per second is set to 1.3 or more.
The feature is that the ratio of the gas flow rate between the oxygen gas flow rate A ejected from the first nozzle and the oxygen gas flow rate B ejected from the second nozzle: _RA = A / (A + B) is periodically changed. How to blow the converter .

According to the present invention, in the upper bottom blown converter type refining vessel, the fire point is continuously moved during blowing by a method other than rotating the lance to suppress the occurrence of spitting during high-speed blowing. can do.

It is a figure for demonstrating the shape of the nozzle at the tip of the top blowing lance which concerns on embodiment of this invention. It is a figure for demonstrating the flow path of the gas in the top blowing lance which concerns on embodiment of this invention. It is a figure for demonstrating the movement locus of a fire point when a jet is injected from a cylindrical tube A and a cylindrical tube B. It is a figure which shows the relationship between the angle θ formed by the cylindrical tube A and the cylindrical tube B, and the dynamic pressure fluctuation width. It is a figure which shows the result of the thickness of the bullion attached to the furnace mouth obtained in the decarburization smelting experiment when the frequency F was changed. The bullion attached to the furnace opening obtained in the decarburization smelting experiment when the ratio L / D of the fire point diameter D (mm) and the fire point movement distance L (mm / s) per second was changed. It is a figure which shows the result of the thickness of. The result of the thickness of the bullion attached to the furnace opening obtained in the decarburization smelting experiment when the ratio K / D of the fire point diameter D (mm) and the fire point movable distance K (mm) was changed was obtained. It is a figure which shows.

Hereinafter, the present invention will be described with reference to the drawings.
FIG. 1 is a diagram for explaining the shape of the nozzle at the tip of the top blowing lance according to the present embodiment. Hereinafter, the two nozzles (one set of nozzles) shown in FIG. 1 will be described as "cylindrical tube A" and "cylindrical tube B", respectively. When the top-blown gas is flowed, the top-blown gas is flowed from the gas flow path shown in FIG. 2 to the cylindrical tube A and the cylindrical tube B, but the total gas flow rate of the cylindrical tube A and the cylindrical tube B is kept constant. The direction of the jet can be changed by changing the flow rate ratio of the top-blown gas between the cylindrical tube A and the cylindrical tube B.

FIG. 3 is a diagram for explaining the movement locus of the fire point when the jet is injected from the cylindrical tube A and the cylindrical tube B.
For example, assuming that the gas flow ratio is cylindrical tube A: cylindrical tube B = 100: 0, the top-blown gas flows only in the cylindrical tube A, and the jet is ejected along the direction of the central axis of the cylindrical tube A. Further, assuming that the gas flow ratio is cylindrical tube A: cylindrical tube B = 0: 100, the top-blown gas flows only in the cylindrical tube B, and the jet is ejected along the direction of the central axis of the cylindrical tube B. By changing this flow rate ratio, as shown in FIG. 3, the traveling direction of the jet can be controlled between the central axis direction of the cylindrical tube A and the central axis direction of the cylindrical tube B.

Next, detailed conditions for the shape of the nozzle will be described. As shown in FIG. 1, the ejection holes of the cylindrical tube A and the cylindrical tube B are arranged concentrically with the central axis of the top blowing lance at equal intervals in the circumferential direction. The cylindrical tube A and the cylindrical tube B have a shape in which they are united while being tilted at twist angles α and β, respectively, and as shown in FIG. 1, they are orthogonal to the central axes of the cylindrical tube A and the cylindrical tube B, respectively. The cross section is circular, and the ejection hole, which is the outlet of the top blowing gas, is an ejection hole shared by the cylindrical tube A and the cylindrical tube B. Further, the united portion (overlapping portion) does not have a nozzle wall.

As shown in FIG. 1, when the plane perpendicular to the z-axis, which is the central axis of the top blowing lance, is the xy plane, the twist angles α and β are such that the central axes of the cylindrical tube A and the cylindrical tube B are set to the xy plane, respectively. The projected straight line represents the angle formed between the center of the ejection hole and the straight line (y-axis in FIG. 1) connecting the center of the ejection hole and the coordinate origin (center point of the top blowing nozzle) on the xy plane. The twist angles α and β determine the range in which the fire point is moved by controlling the gas flow rate ratio. The range of twist angles α and β will be described later.

Further, as shown in FIG. 1, the cylindrical tube A has a straight line passing through the center of the ejection hole of the cylindrical tube A and parallel to the central axis of the top blowing lance (z axis in FIG. 1) and the central axis of the cylindrical tube A. An acute angle of inclination γ is provided between the (0)-(0)'planes. Similarly, the cylindrical tube B is also provided with an acute angle of inclination δ. The (0)-(0)'plane is a plane including the central axis of the cylindrical tube A and parallel to the z-axis. The inclination angles γ and δ determine the distance from the position directly below the top blow lance to the fire point. The range of the inclination angles γ and δ will be described later.

In the examples shown in FIGS. 1 and 2, an example in which three sets of the cylindrical tube A and the cylindrical tube B are provided in the top blowing nozzle has been described, but the number of sets of the cylindrical tube A and the cylindrical tube B is particularly limited. However, in consideration of the labor and cost of manufacturing the nozzle and the gas flow path, it is preferable to use about 3 to 4 sets. Further, the gas flow path is not limited to the example shown in FIG.

Next, the ranges of the twist angles α and β and the inclination angles γ and δ will be described. In this embodiment, the nozzle diameter is smaller than the lance height H, so the nozzle diameter is ignored in the calculation. Further, the inclination angle γ of the cylindrical tube A and the inclination angle δ of the cylindrical tube B are set to be substantially the same angle, and the calculation is performed assuming that γ = δ in the calculation.

The inclination angles γ and δ are 10 ° or more and 30 ° or less. If the inclination angles γ and δ are less than 10 °, the jets may coalesce. Further, if the inclination angles γ and δ are more than 30 °, the jet will come too close to the furnace wall.

On the other hand, for the twist angles α and β, the upper limit and the lower limit can be defined by the sum of the twist angles (α + β), but the upper limit and the lower limit differ depending on the inclination angles γ and δ. Hereinafter, the ranges of the twist angles α and β will be described.

First, the upper limit of the sum of twist angles was obtained from the results of the following computational fluid dynamics analysis. By the following numerical fluid analysis, the behavior of the jet when oxygen gas was flowed from a nozzle having a shape in which the cylindrical tube A and the cylindrical tube B overlap at the outlet was confirmed. Regarding the shapes of the cylindrical tube A and the cylindrical tube B, a straight nozzle having a diameter of 8.0 mm is used, the twist angles α and β are in the range of 5 to 60 °, and the inclination angles γ and δ are 10 to 30 °. did. Computational fluid analysis is performed by unsteady analysis using a k-ε turbulent flow model, and as a boundary condition, the total flow rate of oxygen gas in the cylindrical tube A and the cylindrical tube B is ^{constant at 12.0 Nm 3} / min and flows through the cylindrical tube A. The ratio _RA was increased from 0.0 to 1.0 and then decreased to 0.0 continuously and periodically. _{Increasing RA} from 0.0 to 1.0 and then decreasing it to 0.0 was defined as one cycle, and its frequency was kept constant at 3 Hz.

After 5 seconds after the start of flowing oxygen gas, the flow settled in a constant pattern, and then the dynamic pressure distribution on the surface perpendicular to the lance axis 500 mm from the tip of the nozzle was measured. The location of the maximum dynamic pressure is the fire point under the condition of the lance height H = 500 mm when oxygen is blown onto the hot metal, and the dynamic pressure can be regarded as the dynamic pressure of the fire point. The results are shown in Table 1 and FIG. 4 below. In the numerical fluid analysis, α = β and γ = δ.

Here, θ represents the acute angle formed by the central axes of the cylindrical tube A and the cylindrical tube B, and the dynamic pressure fluctuation width is | instantaneous dynamic pressure value-average dynamic pressure value | / average dynamic pressure value × 100. And said. As a result of the analysis, the fire point position in the lance conditions height H = 500 mm in any of the conditions, by varying the ratio R _A to flow periodically oxygen gas in the cylindrical tube A at 3Hz, circumferentially 3Hz I was able to confirm that I could move to. However, it was also confirmed that the stability of the fire point dynamic pressure differs depending on the conditions.

If the fire point dynamic pressure is not stable, it may cause secondary combustion of an unstable jet, resulting in local melting damage of the refractory. As shown in Table 1, the greater the magnitude of the angles α, β, γ, and δ, the greater the instability of the jet, which is due to the angle θ formed by the central axes of the cylindrical tube A and the cylindrical tube B. It is presumed that the larger the angle, the greater the turbulence of the gas at the overlapping points of the cylindrical tube A and the cylindrical tube B of the oxygen gas. Assuming that the dynamic pressure fluctuation range from the allowable average dynamic pressure is 5%, it was confirmed that θ can be allowed up to 38 ° as shown in FIG. Note that θ can be defined by the following equation (1) in relation to α, β, and γ when γ = δ.
θ = 2 × arctan (tan ((α + β) / 2) ・ sin (arctan (tanγ ・ cos ((α + β) / 2))))
... (1)

Since θ is preferably 38 ° or less as described above, the preferable upper limit of the sum of twist angles (α + β) is defined by the condition that the right side of the equation (1) is 38 ° or less in relation to the inclination angle γ. Will be done.

Next, the lower limit of the sum of twist angles (α + β) will be described. As shown in FIG. 3, when the sum of the twist angles (α + β) is small, the fire point movable distance K becomes small. The fire point movable distance K can be calculated by the following equation (2). Further, the diameter D of the fire point is calculated by the following equation (3), where φ is the spread half-width of the jet.
K = 2π × H × tanγ × (α + β) / 360 ・ ・ ・ (2)
D = 2H / cosγ × tanφ ・ ・ ・ (3)

Here, in order to suppress spitting, it is necessary that the entire range of fire points does not overlap due to movement. That is, as can be seen from the experimental results shown in FIG. 7, which will be described later, the ratio of the fire point movable distance K (mm) to the fire point diameter (mm) needs to be 1.0 or more. That is, the condition of the following equation (4) is calculated from the condition of K / D ≧ 1.0 and the above equations (2) and (3), assuming that the jet spread half-width φ = 10 °.
(Α + β) × sinγ ≧ 20 ・ ・ ・ (4)

Since it is necessary to satisfy the condition of the equation (4) in order to suppress the spitting as described above, the lower limit of the sum of the twist angles (α + β) is determined by the equation (4) in relation to the inclination angle γ. Defined. Further, the twist angles α and β are preferably the same angles from the viewpoint of manufacturing cost. When the twist angles α and β are the same, it is preferable that α and β ≧ 5 ° in relation to the spread angle of the jet.

Next, suitable conditions for decarburization using a top-blown lance equipped with a nozzle having the shape described above will be described. Further, in order to investigate a suitable range of frequencies for controlling the gas flow rate ratio of the cylindrical tube A and the cylindrical tube B by the above method, a decarburization experiment of hot metal after dephosphorization was carried out using a test converter. .. In the decarburization experiment of hot metal after dephosphorization, a gas flow rate ratio control method suitable for reducing spitting during high-speed blowing by the above method was also investigated.

[Hot metal decarburization experiment]
First, 2.0 tons of hot metal is charged into a converter, 10.0 kg of quicklime with a maximum particle size of 20 mm and 2.5 kg of silica stone are added, and then oxygen is blown onto the hot metal from a top-blown lance to decarburize the hot metal. And conducted an experiment to investigate the amount of bullion scattering. The CaO concentration in the massive lime was 92%.
The hot metal has a temperature of 1300 ° C., [% C] = 3.5% by mass, [% Si] = 0.01% by mass, [% Mn] = 0.10% by mass, [% P] = 0.02% by mass. , [% S] = 0.001% by mass, 2.0t was charged into the converter. The bath depth was 385 mm.

The top-blown lance was decarburized using a general normal lance and a lance having a bifurcated nozzle of the present embodiment, and the degree of bullion scattering was evaluated based on the thickness of the bullion adhering to the furnace opening. ..
As the normal lance, a straight nozzle having an inclination angle of 20 ° and a diameter of 8.0 mm was used in which three holes were arranged at equal intervals on the same circumference. On the other hand, the top-blowing lance having a bifurcated nozzle of the present embodiment is composed of two cylindrical tubes A and a cylindrical tube B having a diameter of 8.0 mm at the nozzle portion, and has a twist angle α of the cylindrical tube A and a cylindrical tube B. The twist angle β of the cylinder tube A was the same 45 °, and the inclination angle γ of the cylindrical tube A and the inclination angle δ of the cylindrical tube B were the same 20 °. That is, three sets of bifurcated nozzles having an angle θ formed by the cylindrical tube A and the cylindrical tube B of 28.0 ° were arranged on the same circumference at equal intervals.

The top-blown oxygen flow rate was ^{constant at 12.0 Nm 3} / min, and the blowing time was 6.0 min. The height H of the lance was fixed at 500 mm. Further, stirring with bottom blowing gas was also performed to stir the hot metal, and the bottom blowing was made into four tuyere, and Ar gas was flowed from each bottom blowing tuyere at 0.2 Nm ³ / min during decarburization blowing.

When the top-blowing lance having a bifurcated nozzle of the present embodiment is used, the total flow rate of oxygen gas is ^{constant at 12.0 Nm 3} / min, and it flows through the cylindrical tube A of the cylindrical tube A and the cylindrical tube B. The ratio _RA was increased from 0.0 to 1.0 and then decreased to 0.0 continuously and periodically. _{Increasing RA} from 0.0 to 1.0 and then decreasing it to 0.0 was defined as one cycle, and its frequency was kept constant at 0.1-10 Hz. FIG. 5 shows the result of the thickness of the bare metal adhering to the furnace opening obtained in the decarburization smelting experiment when the frequency F was changed. The numerical values on the vertical axis shown in FIG. 5 represent the ratio when the thickness of the attached bullion is 1.0 under the condition of using the normal lance, and for other results, this normal lance is used. Comparison and evaluation were performed by dividing by the measured value of the conditions used.

Under the condition that the top-blown lance of the present embodiment is used, the thickness of the bare metal adhering to the furnace mouth is reduced by increasing the frequency of the gas flow rate ratio control, and by setting it to 0.5 Hz or more, it is compared with the normal lance. The thickness of the bullion has been reduced by half. It is probable that this is because the high-speed jet collided with the hot metal and the bullion was scattered, but the momentum of the jet was dispersed to the hot metal by the movement of the fire point, and the scattering of the bullion was suppressed. ..

However, the effect of reducing spitting is not determined only by the frequency of gas flow rate ratio control, but is considered to depend on the lance shape and blowing conditions. Therefore, first, it was decided to evaluate by the ratio L / D of the fire point diameter D (mm) and the fire point movement distance L (mm / s) per second. As described above, γ = δ, and the fire point diameter D (mm) is obtained by the above-mentioned equation (3). Further, the fire point movement distance L (mm / s) per second is calculated by using the fire point movement distance K (mm) shown in the equation (2) and the gas flow rate control frequency F (Hz) as follows. It is calculated by the formula (5).
L = 2 × K × F ・ ・ ・ (5)

FIG. 6 shows the result of re-evaluating the result of FIG. 5 by L / D. As shown in FIG. 6, L / D ≥ 1.3 (1 / s), that is, if the fire point moves 1.3 times the diameter in 1 second, the thickness of the bullion is half that of the normal lance. It turned out to be.

However, even if L / D ≥ 1.3 (1 / s), if the condition of the top blowing nozzle does not satisfy the above equation (4), the fire point hardly moves and moves at high speed in a narrow range. It means that the spinning cannot be suppressed. Therefore, the same experiment was conducted by fixing D and L / D and changing K / D. At that time, the twist angle and frequency were changed so that the L / D was 2.0 (1 / s), and the other conditions were the same as in the previous experiment. The result is shown in FIG. As shown in FIG. 7, it was confirmed that the amount of bare metal was reduced by setting the ratio of the fire point movable distance K (mm) to the fire point diameter D (mm) to 1.0 or more. That is, it was confirmed that the nozzle of the top blow lance needs to satisfy the condition of the equation (4).

Next, the present invention will be further described based on Examples, but the conditions in the Examples are one conditional example adopted for confirming the feasibility and effect of the present invention, and the present invention is the same. It is not limited to the conditional example. The present invention can adopt various conditions as long as the gist of the present invention is not deviated and the object of the present invention is achieved.

In a 300t / heat top-bottom blown converter, decarburization of hot metal after dephosphorization was performed, and the effect of the present invention was confirmed. First, a total of 290 to 300 tons of hot metal and scrap after dephosphorization are charged into a converter, and 3.0 to 4.0 tons of quicklime with a maximum particle size of 30 mm and 0. After adding 8 to 1.2t, MgO brick scrap 0.2 to 0.3t, and iron ore 1.5 to 2.0t, 1800Nm ³ / min from the top blowing lance installed about 3000mm above the hot metal bath surface. Oxygen was sprayed onto the hot metal at the above, and the blowing time was adjusted so that the [% C] after the treatment was 0.04% by mass. The evaluation was performed with an average iron yield of 10 Ch that meets the above conditions. The iron yield was determined from the weight ratio of the iron content in the molten steel in the ladle after smelting to the iron content in the hot metal and scrap charged into the converter before smelting.

(Comparative Example 1)
First, an experiment was conducted using a 4-hole normal lance in which nozzles having a throat diameter of 80 mm and a nozzle inclination angle of 20 ° were arranged at equal intervals on the same circumference as the top blow lance. In this experiment, the height H of the lance was kept constant at 3000 mm from the surface of the still metal of the hot metal. As a result of the experiment, it was observed that the scale of the splash generated during the smelting was large and the spitting frequently flowed out from the furnace mouth to the outside of the furnace. The average iron yield (%) of 10 Ch when this normal lance was used was calculated, and the comparison with other conditions was performed using this as a reference.

(Comparative Example 2)
In this experiment, a top-blown lance having a bifurcated nozzle was used as the top-blown lance. The top-blown lance used in the experiment consists of two cylindrical tubes A and a cylindrical tube B having a diameter of 80 mm at the nozzle portion, and the twist angle α of the cylindrical tube A and the twist angle β of the cylindrical tube B are the same at 25 °. , The inclination angle γ of the cylindrical tube A, and the inclination angle δ of the cylindrical tube B are the same 20 °, and the angle θ formed by the cylindrical tube A and the cylindrical tube B is 16.6 °. The lances are evenly spaced on the circumference.

As the oxygen gas total flow rate constant, of a cylindrical tube A and the cylindrical tube B, continuously that the ratio R _A to be supplied to the cylindrical tube A was increased from 0.0 to 1.0, is then decreases to 0.0 And it was done periodically. _{Increasing RA} from 0.0 to 1.0 and then decreasing it to 0.0 was defined as one cycle, and its frequency F was kept constant at 1.0 Hz. The height H of the lance was kept constant at 3000 mm from the surface of the still metal of the hot metal. From the above conditions, the L / D was 1.7 (1 / s), but the K / D was 0.8, and as a result of the calculation, the condition was (α + β) × sinγ = 17.1.

As a result of the experiment, since the shape of the top-blown lance did not meet the condition of Eq. (4), the scale of splash generation during blowing was not small, and the frequency of spitting flowing out of the furnace opening was high. It was about the same as that of Comparative Example 1. From this, as a result of calculating the average iron yield (%) of 10 Ch, no change was observed with respect to the average iron yield (%) when the normal lance was used in Comparative Example 1. On the other hand, since the angle θ formed by the cylindrical tube A and the cylindrical tube B was 16.6 ° and 38 ° or less, the dynamic pressure fluctuation range was small, and the influence that could occur due to the disturbance of the jet such as large melting damage of the refractory. There was no such thing.

(Comparative Example 3 )
In this experiment, a lance with a bifurcated nozzle was used as the top blow lance. The top-blown lance used in the experiment consists of two cylindrical tubes A and a cylindrical tube B having a diameter of 80 mm at the nozzle portion, and the twist angle α of the cylindrical tube A and the twist angle β of the cylindrical tube B are the same at 45 °. , The inclination angle γ of the cylindrical tube A, and the inclination angle δ of the cylindrical tube B are the same, and the angle θ between the cylindrical tube A and the cylindrical tube B is 28.0 °. The lances are evenly spaced on the circumference.

As the oxygen gas total flow rate constant, of a cylindrical tube A and the cylindrical tube B, continuously that the ratio R _A to be supplied to the cylindrical tube A was increased from 0.0 to 1.0, is then decreases to 0.0 And it was done periodically. _{Increasing RA} from 0.0 to 1.0 and then decreasing it to 0.0 was defined as one cycle, and its frequency was kept constant at 0.25 Hz. The height H of the lance was kept constant at 3000 mm from the surface of the still metal of the hot metal. The K / D was 1.5 and the condition was (α + β) × sinγ = 30.8, but from the above conditions, the L / D was 0.76 (1 / s).

As a result of the experiment, since the L / D was not 1.3 or more, the scale of splash generation during blowing was not small, and the frequency of spitting flowing out from the furnace mouth to the outside of the furnace was about the same as that of Comparative Example 1. Met. From this, as a result of calculating the average iron yield (%) of 10 Ch, no change was observed with respect to the average iron yield (%) when the normal lance was used in Comparative Example 1. On the other hand, since the angle θ formed by the cylindrical tube A and the cylindrical tube B was 28.0 ° and 38 ° or less, the dynamic pressure fluctuation range was small, and the influence that could occur due to the disturbance of the jet such as large melting damage of the refractory. There was no such thing.

(Example 1)
In this experiment, a lance with a bifurcated nozzle was used as the top blow lance. The top-blown lance used in the experiment consists of two cylindrical tubes A and a cylindrical tube B having a diameter of 80 mm at the nozzle portion, and the twist angle α of the cylindrical tube A and the twist angle β of the cylindrical tube B are the same at 45 °. , The inclination angle γ of the cylindrical tube A, and the inclination angle δ of the cylindrical tube B are the same, and the angle θ between the cylindrical tube A and the cylindrical tube B is 28.0 °. The lances are evenly spaced on the circumference.

As the oxygen gas total flow rate constant, of a cylindrical tube A and the cylindrical tube B, continuously that the ratio R _A to be supplied to the cylindrical tube A was increased from 0.0 to 1.0, is then decreases to 0.0 And it was done periodically. _{Increasing RA} from 0.0 to 1.0 and then decreasing it to 0.0 was defined as one cycle, and its frequency was kept constant at 1.0 Hz. The height H of the lance was kept constant at 3000 mm from the surface of the still metal of the hot metal. From the above conditions, L / D was 3.1 (1 / s), K / D was 1.5, and (α + β) × sinγ = 30.8.

As a result of the experiment, the scale of splash generation during smelting was small, and the frequency of spitting flowing out from the furnace opening to the outside of the furnace was reduced as compared with Comparative Example 1. From this, as a result of calculating the average iron yield (%) of 10 Ch in this example, it increased by 0.13% with respect to the average iron yield (%) when the normal lance was used in Comparative Example 1. .. Further, since the angle θ formed by the cylindrical tube A and the cylindrical tube B was 28.0 ° and 38 ° or less, the dynamic pressure fluctuation range was small, and the influence that could occur due to the disturbance of the jet such as large melting damage of the refractory. There was no such thing.

Claims (4)

A top-blowing lance equipped with a nozzle portion having a plurality of ejection holes for ejecting gas on the tip surface.
The plurality of ejection holes are arranged at equal intervals in the circumferential direction on a circle concentric with the central axis of the lance.
Each of the plurality of ejection holes is an ejection hole shared by two nozzles having a circular cross section perpendicular to the central axis of the nozzles.
The two nozzles are a first nozzle and a second nozzle.
The intersection of a straight line in which the central axis of the first nozzle is projected on a plane perpendicular to the lance central axis and a straight line in which the central axis of the second nozzle is projected on a plane perpendicular to the lance central axis, and the plane. The angle of the straight line obtained by projecting the central axis of the first nozzle onto a plane perpendicular to the central axis of the lance with respect to the straight line passing through the intersection of the lance and the central axis of the lance is α. Let β be the angle of the central axis with the straight line projected on the plane perpendicular to the lance central axis.
In a plane parallel to the lance central axis and including the central axis of the first nozzle, a sharp angle formed by a straight line parallel to the lance central axis and the central axis of the first nozzle is defined as γ and the lance central axis. When the sharp angle formed by the straight line parallel to the lance central axis and the central axis of the second nozzle in a plane parallel to the center axis of the second nozzle is δ.
The conditions of γ = δ, 10 ° ≦ γ, δ ≦ 30 °, and (α + β) × sinγ ≧ 20 are satisfied, and the gas is separately transported to the first nozzle and the second nozzle. Top-blown lance characterized by the combined piping for.
Here, the unit of α, β, γ, and δ is “° (degree)”. The top-blowing lance according to claim 1, wherein θ is 38 ° or less when the angle formed by the central axis of the first nozzle and the central axis of the second nozzle is θ. Further, the top-blown lance according to claim 1 or 2, wherein α = β. A converter blowing method for blowing using the top blowing lance according to any one of claims 1 to 3.
The ratio L / D of the fire point movement distance L and the fire point diameter D per second is set to 1.3 or more.
The feature is that the ratio of the gas flow rate between the oxygen gas flow rate A ejected from the first nozzle and the oxygen gas flow rate B ejected from the second nozzle: _RA = A / (A + B) is periodically changed. How to blow the converter.

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