JP2000080419A - Smelting furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain wave motion on a molten metal bath surface without needing a large auxiliary facility and to reduce the erosion of a refractory by disposing a top-blown lance above a position apart from the node of a standing wave caused on the molten metal bath surface in a furnace by blowing wind from the top-blown lance. SOLUTION: In a smelting furnace 1 disposing a top-blown lance 2, the depth n2 (m) of a cavity formed on a molten metal bath surface caused by blowing wind from the top-blown lance 2 is obtd. by equations I and II, and a natural frequency fc (Hz) of the cavity is obtd. from this depth n2. Successively, the natural frequency (f) (Hz) of the standing wave formable on the molten metal bath surface. In this natural frequency (f), under assuming that the standing wave having the natural frequency (f) equal to 1/2 of the natural frequency fc causes on the bath surface, the top-blown lance 2 is disposed above a position apart from the node 6 of this standing wave. Then, in the equations, n1 is the depth (m) of slag, ρ1 is the density (kg/m3) of slag, ρ2 is the density (kg/m3) of crude copper and H is the height (m) of the top-blown lance from the molten metal bath surface, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a smelting furnace provided with a top blowing lance.

[0002]

2. Description of the Related Art In a smelting furnace, erosion of refractories constituting the furnace by a molten metal bath retained in the furnace is an important factor that governs the life of the furnace body. This erosion occurs locally and, depending on the operating conditions, significant erosion is observed, especially on bath-level refractories in contact with the bath surface. Therefore, by suppressing the erosion of the bath-level refractories and extending the furnace repair interval,
The economics of the smelting process can be significantly improved.
One of the main causes of erosion of bath-level refractories is the undulation of the molten metal bath surface. The wave of the bath not only accelerates the physical wear that causes the refractory structure to collapse,
It is also a factor that accelerates chemical erosion in that it reduces the concentration boundary layer at the refractory / slag interface and promotes mass transfer. Therefore, suppressing the wave of the bath surface is important in suppressing the erosion of the refractory.

[0003] As a smelting furnace capable of suppressing the wave motion of the bath surface in a conventional smelting furnace, for example, JP-A-9-176719 can be mentioned. In this smelting furnace, the angle θ between the gas blowing direction and the tangential direction of the inner circumferential circle of the side wall is 0 ° <θ <90 ° at an intermediate height position of the depth of the molten bath on the side wall in the furnace. A plurality of side-blowing tuyeres are provided, and the amount of gas to be blown in each side-blowing tuyere is periodically controlled so as to match the natural frequency of the molten metal bath.

[0004]

However, in this smelting furnace, it is difficult to control the amount of gas to be blown so as to coincide with the natural frequency of the molten metal bath, and ancillary facilities for controlling the amount of gas are large. And the life of the furnace is shortened due to tuyere wear.

The present invention has been made in view of the above-mentioned circumstances, and has as its object to provide a smelting furnace capable of suppressing a wave on a bath surface without requiring a large incidental facility.

[0006]

The present inventor has analyzed this wave for the purpose of suppressing the wear of refractory due to the wave of the molten metal bath surface generated by the blowing from the upper blowing lance. The generation of this wave is caused by the fact that the vertical vibration of the cavity generated by the blowing gas from the upper blowing lance excites the molten metal bath, and the natural frequency of the cavity is approximately 1 /
A standing wave with a frequency of 2 is generated on the bath surface ", and the eigenmode of the generated standing wave can be predicted. When the wave of the bath surface (in this case, the eigenmode of the standing wave) becomes predictable, it becomes possible to quantitatively examine the relationship between the smelting conditions and the characteristics of the wave (particularly, wave height).

[0007] In the standing wave, the amplitude is determined at each position on the bath surface. For example, the amplitude is zero at nodal points and there is no swaying, and at the antinode points a certain amount of amplitude. The largest swing in amplitude. That is, the points on the bath surface where the standing wave is formed are not equivalent in the standing wave. Therefore, even if the same amount of gas is blown from the upper blowing lance, it is presumed that the influence on the wave is different at different points on the bath surface, that is, the arrangement position of the upper blowing lance affects the generated wave. The inventor of the present invention has found that the wave height of the wave is reduced by disposing the upper blowing lance above a position away from the node of the standing wave.

The present invention for achieving the above object employs the following constitution. The smelting furnace according to claim 1 is a smelting furnace provided with an upper blowing lance, wherein a standing wave generated by blowing air from the upper blowing lance to a molten metal bath surface accommodated in the furnace. An upper blowing lance is disposed above a position away from the node.

A smelting furnace according to a second aspect is the smelting furnace according to the first aspect, wherein at least a node of the standing wave includes:
An upper blowing lance is arranged above a position where the outer circumference of a cavity formed on the molten metal bath surface by the blowing does not intersect.

The smelting furnace according to claim 3 is a smelting furnace provided with an upper blowing lance, wherein the smelting furnace is provided on the surface of the molten metal bath by the blowing from the upper blowing lance according to the following equation (5). The depth n ₂ (m) of the cavity to be formed is obtained, and the natural frequency f _c (Hz) of the cavity is obtained by substituting the depth of the cavity into the following equation (7). By the formula, the natural frequency f (Hz) of the standing wave that can be formed on the molten metal bath surface is obtained, and among the obtained natural frequencies f (Hz), the natural frequency f _c (Hz)
An upper blowing lance is provided above a position away from a node of a standing wave having a natural frequency f (Hz) equal to 1/2 of the above.

(Equation 5)

(Equation 6)

(Equation 7)

(Equation 8) Where n ₁ : slag depth (m) n ₂ : cavity depth (m) ρ ₁ : slag density (kg / m ³ ), ρ ₂ : blister copper density (kg / m ³ ), γ ₂ : γ = ^{_{gρ l (kg / s 2 m}} 2) H: distance from the molten metal bath surface of the top-blown lance (m) M: momentum transfer rate of blowing gas _{(N) β * = 125 f} c: the natural frequency of the cavity ( Hz) g: Gravitational acceleration b: 1.7 ≦ b ≦ 2.4 f: Natural frequency of standing wave that can be formed on the molten metal bath surface (Hz) j _mn : Bessel function J _m (x), x from 0 to positive The value of x when dJ _m (x) / dx = 0 at the n-th time when it is changed in the direction h: depth of the molten bath (m) R: radius of the molten bath (m)

[0011]

Embodiments of a smelting furnace according to the present invention will be described below with reference to the drawings.

In FIG. 1, reference numeral 1 denotes a smelting furnace. The smelting furnace 1 includes an upper blowing lance 2 for supplying gas into the furnace. The molten metal bath 3 stays below the upper blowing lance 2, and the upper blowing lance 2 is arranged in the furnace such that the distance from the lower end of the molten metal bath 3 to the bath surface 3 a is 4. I have. A bath line brick (refractory) 5 made of refractory bricks is in contact with the bath surface 3a of the molten metal bath 3 in the furnace.

FIG. 2 is a view taken along the line XX. The dashed line
FIG. 5 shows a standing wave node 6 of one of the standing waves that can be formed on the bath surface 3a of the molten metal bath 3 in the furnace. As shown in FIG. 2, the upper blowing lance 2 is disposed above a position away from the node 6.

The eigenmode of the generated standing wave can be theoretically predicted, and the position of the node 6 is uniquely determined except for the arbitrariness due to the symmetry of the molten metal bath 3. The theory of prediction of this standing wave and the water bath model experiment that verified it will be described in detail below.

FIG. 3 shows an apparatus used in a water bath model experiment. A flat-bottomed cylindrical container 11 having a diameter of 1.5 (m) is filled with water 12 having a depth of 40 (cm), and the inner diameter is 11.7 (mm) at a height of 30 (cm) from the still water surface.
Lances 13 and 13 are arranged. In order to measure the wave height (wave height) from the still water surface, a capacitive wave height meter 14 was arranged near the side wall. An amplifier 15, an A / D converter 16, and a computer 17 were arranged as a processing system for the output from the capacitive wavemeter 14.

In the experimental apparatus having the above-described configuration, the change in the wave height of the bath surface with time is measured by the capacitance type wave height meter 14. The temporal change is an irregular vertical wave, and the irregular wave is subjected to a fast Fourier transform (FFT) by the computer 17 and is decomposed into a sum of sinusoidal waves to obtain a frequency spectrum. The frequency spectrum obtained by the experiment has one peak frequency which is significantly higher than the others. If only the air blowing amount is changed without changing the arrangement of the upper blowing lance, the frequency at which this peak appears in the frequency spectrum and its height (peak height) change. A change in the peak height indicates an increase or decrease in the wave height, and a change in the frequency at which the peak is located indicates that the manner of swaying of the bath has changed. FIG. 4B is a graph showing the relationship between the amount of air flow and the peak height. The plot in the figure can be classified into three stages with the transition boundary where the wave attenuates.
The peak height increases stepwise with an increase in the air volume, and the peak height once decreases at the boundary of each step. The gradual increase in peak height is in good agreement with the visual observation of wave height. The frequency of each corresponding peak for the same spectrum as in FIG. 4B is plotted in FIG. It can be seen that the peaks belonging to the three stages are located at the same frequency. The broken line in the figure indicates the above equation (8) (IGCurrie: FundamentalMechanics of Fl
uids 2 / e., (1993), 201, McGraw-Hill. The above (8)
The waveform of the bath calculated based on the natural frequency obtained by the equation was in good agreement with the way the bath swayed visually. Therefore, the wave on the bath surface generated by the upper blowing lance can be approximately regarded as a standing wave due to the natural vibration of the bath surface.

Next, the origin of the standing wave will be described. It is known that when a liquid storage tank having an arbitrary shape is vibrated in the vertical direction, the bath surface shakes at a frequency of about 1/2 of the vibration frequency. Therefore, we consider the wave generated on the molten metal bath surface to be an equivalent phenomenon. "The vertical vibration of the cavity formed by the blowing gas from the top blowing lance excites the bath, and it is about 1/2 of the natural frequency of the cavity. A standing wave with a frequency of で is generated on the bath surface. ' The vertical time-average position of the oscillating cavity is defined as a stable equilibrium position, and the cavity is regarded as a mass point of mass that balances buoyancy at this stable equilibrium position. At this time, when buoyancy is considered as a restoring force for the deviation of the cavity depth n ₂ (m) at the stable equilibrium position, the vertical vibration of the cavity can be regarded as a simple vibration of the mass point. Therefore, vertical motion equation of the simple harmonic oscillation, as paraboloid release rotate a cavity shape, Solving this equation of motion approximates, said representing the natural frequency f _c of the cavity (7) is obtained . From this equation (7), it can be seen that f _c is determined only by the cavity depth n ₂ . However,
Cavity depth and n _2, Banks et al. Equation shown below (J. Fluid. Mech., 15 , 13~34, (1963)) to beta _* = 125
Was determined.

(Equation 9) Where n ₂ : cavity depth (m) γ: γ = gρ ₀ (kg / s ² m ² ) ρ ₀ : bath density (kg / m ³ ), (the same symbol as above means the same physical quantity Shown.)

FIG. 5 shows the relationship between the minimum cavity depth n ₀ at which generation of each natural vibration is observed and the natural frequency of a standing wave when air is blown by a single top blowing lance. In the area surrounded by the two curves in the figure, in equation (7), b is similar to that of Ito et al. (Iron and steel, 55, 1164-1175), and 1.7 ≦ b
It represents a range of 1/2 of the curves of natural frequency f _c of the cavity when changing between ≦ 2.4. The plot in the figure and the area surrounded by the two curves are in good agreement,
It was proved that the wave on the bath surface generated by the blowing gas from the top lance vibrated at half the natural frequency of the cavity. It was also confirmed that this vibration rule was satisfied when two lances were blown or when a heavy liquid (CH ₂ Br ₂ ) was used as a bath. Thus, it has been clarified that the phenomenon that the standing wave is generated on the bath surface by the blowing gas of the upper blowing lance can be explained by a model that is caused by the vibration of the cavity formed by the blowing gas.

Although all of the above experiments were discussed based on experimental data in a single liquid phase bath, the actual furnace was slag-blended copper.
Since it is a liquid phase bath, the cavity depth cannot be expressed by the above equation (9). Therefore, the inventors obtained a formula for estimating the cavity depth in the two liquid phase bath by the momentum balance formula of the blown gas, and obtained the formulas (1) and (2) (the formulas (5) and (6)). ) Got.

The theory of the wave motion of the bath surface generated by the blowing gas of the top blowing lance, which has been discussed so far, was applied to the Naoshima Smelter Mitsubishi continuous copper process C furnace, and the validity of the model was verified. FIG. 6 is a diagram showing prediction of standing wave generation in the C furnace. Calculate the natural frequency of the bath assuming a flat-bottom cylindrical shape with an inner diameter of 8.05 (m) and a depth of 1.0 (m) for three types of normal vibration modes and their harmonics, and form a horizontal band for each vibration order displayed. In addition, 1/2 of the natural frequency of the cavity of each depth calculated by the above equation (7) is shown in a downward-sloping band shape. The gas temperature at the outlet of the upper blowing lance is assumed to be 20 to 100 (° C), and 56.1 (Nm
_The depth of a cavity formed in a bath with a slag layer thickness of 15 (cm) when blowing air at ₃ / min) is calculated to be 21 to 23 (cm). When the predicted range of the cavity depth is superimposed on a vertical band in the figure, it is predicted from the intersection of these three types of bands that the third harmonic is generated in the actual furnace. You. The third harmonic group occupies a frequency of 0.71 to 0.79 (Hz). On the other hand, slag overflow was observed in the furnace, and the frequency of the standing wave in the furnace was calculated from the period of the pulsating flow. The observation was based on the recorded video images. As a result, it was found that the average period of the pulsating flow was 1.38 (sec) (average value of 22 times), and the frequency of the standing wave was 0.72 (Hz).
This value was within the range of the predicted value shown above, and it was confirmed that the above theory can be applied to an actual furnace.

As described above, the eigenmode of the standing wave generated on the bath surface by the blowing gas of the upper blowing lance can be theoretically predicted. When the wave of the bath surface (in this case, the eigenmode of the standing wave) can be predicted, the relationship between the smelting conditions and the characteristics of the wave (particularly, wave height) can be quantitatively examined. As described above, the larger the wave height of the wave generated on the bath surface, the greater the wear of the refractory of the furnace body. Therefore, it is important to reduce the wave height. Therefore, the present inventor
Next, the wave height of the wave that can be approximated by the standing wave and the parameters closely related were investigated. By manipulating the parameters, the wave height is reduced.

In the standing wave, the amplitude is determined at each position on the bath surface. For example, the amplitude is zero at nodal points and there is no shaking, and the amplitude at the antinodes is a certain maximum. The value fluctuates the most. Thus, since each point on the bath surface where the standing wave is formed is not equivalent, the arrangement of the upper blowing lance that blows gas directly to the bath surface may have a great effect on the generated standing wave. Inferred.
Then, the inventor examined the relationship between the arrangement position of the upper blowing lance and the wave height.

In a flat-bottomed cylindrical container having a diameter of 1.5 (m), a depth of 40 (cm)
In a water bath filled with water of 30 cm in height from the still water surface
The arrangement of the upper blowing lance 13 of 11.7 (mm) is shown in FIG.
(B) As shown in (c), when both are arranged above the joint 6, one is arranged above the joint 6, and the other is arranged at a position apart from above the joint 6. In the three cases where both are arranged at positions away from above the node 6, the gas flow rate is controlled using two upper blowing lances, and a concentric node as shown in FIG. The relationship between the position of the upper blowing lance 13 and the wave height of the wave was examined so as to generate a wave. FIG. 8 shows the result. In FIG. 8, the vertical axis represents the wave height, and the horizontal axis represents the gas flow rate from the single upper blowing lance. From this experimental example, it was found that even when the number of upper blowing lances was the same, the wave height was lower when the number of upper blowing lances arranged above the node was smaller.

FIG. 9 shows a case where a single upper-blowing lance is used under the same conditions as in the above experiment. A standing wave (second-order harmonic) having a node as shown by a broken line in FIG. In the figure, a is a case where the upper blowing lance is arranged above the diameter of the node, and b is 15 mm perpendicular to the diameter.
(cm) This is a case in which the upper blowing lance is arranged above the distant position. FIG. 10 shows the result of examining the relationship between the amount of air blown and the wave height of the wave with respect to the arrangement position of the upper blowing lance in FIG. 9. From this experimental example, it was verified that the wave height was lower when the upper blowing lance was disposed above a position away from the node.

Next, the effect of the wave height on the arrangement position of the upper blowing lance in the actual furnace was examined. As shown in FIG.
1.5 (m) diameter, 20 (c) depth lined with castable refractories
On top of the molten blister copper bath m), eight top blowing lances 2 were arranged in two ways at a height of 15 cm from the static bath surface. That is, FIG.
11A shows a case where the antenna is arranged above the node 6 and the vicinity of the node 6, and FIG. Then, air was blown so as to generate a standing wave having a node 6 as shown in the figure. The erosion depth of the refractory after blowing for 300 hours was 5 (mm) in the case of FIG.
In the case of 1 (b), it was 3 (mm). In the actual furnace, it has been proved that the erosion is smaller when the upper blowing lance 2 is disposed at a position farther from the node 6.

[0026]

As described above in detail, according to the smelting furnace according to the present invention, the smelting furnace according to the present invention rises above the position distant from the node of the standing wave generated on the molten metal bath surface by the blowing from the upper blowing lance. Since the blowing lance is provided, it is possible to obtain an effect that the wave of the molten metal bath surface can be suppressed without requiring a large incidental facility. As a result, it is possible to reduce the erosion of the bus line brick (refractory), and to obtain the effect of extending the life of the furnace.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing one embodiment of a smelting furnace according to the present invention.

FIG. 2 is a view taken along line XX in FIG.

FIG. 3 is a schematic configuration diagram of an apparatus used in a water bath model experiment.

FIG. 4A is a graph showing a relationship between an amount of air blown and a peak frequency of a frequency spectrum of a generated wave. (B)
It is a graph which shows the relationship between the amount of ventilation and the peak height in the peak frequency of a frequency spectrum.

FIG. 5 is a diagram showing the minimum cavity depth observed at each natural frequency. The two curves show half the natural frequency of the cavity.

FIG. 6 is a diagram for predicting an eigenmode of a standing wave generated in the Naoshima Smelter C furnace.

FIG. 7 is a view showing an arrangement position of two upper blowing lances. (A) When both are arranged above the node, (b) 1
The case where the book is arranged above the node and the other is arranged above the position away from the node, and (c) the case where both books are arranged above the position away from the node.

8 is a graph showing the relationship between the amount of air blown and the wave height of a standing wave generated for each arrangement of the upper blowing lances in FIG. 7;

FIG. 9 is a view showing an arrangement position of one upper blowing lance.

FIG. 10 shows each arrangement of the upper blowing lance in FIG.
It is a graph which shows the relationship between the amount of ventilation and the wave height of the standing wave which generate | occur | produces.

FIG. 11 is a diagram showing the arrangement positions of eight upper blowing lances. (A) When placed above a knot and near the knot,
(B) when all are arranged above the position away from the node,
It is.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Smelting furnace 2 Top blowing lance 3 Molten bath 6 Node (of standing wave) 13 Top blowing lance

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Naoki Horihata 1-297 Kitabukuro-cho, Omiya-shi, Saitama F-term in Mitsubishi Materials Corporation Research Laboratory (reference) 4K001 AA09 DA01 GB03

Claims (3)

[Claims] 1. A smelting furnace provided with an upper blowing lance, wherein the smelting furnace is located at a position distant from a node of a standing wave generated by blowing air from the upper blowing lance on a surface of a molten metal bath accommodated in the furnace. A smelting furnace having an upper blow lance disposed above. 2. The smelting furnace according to claim 1, wherein at least a node of the standing wave does not cross an outer periphery of a cavity formed on a molten metal bath surface by the blowing air. A smelting furnace provided with a blowing lance. 3. A smelting furnace provided with an upper blowing lance, wherein a depth n of a cavity formed on a molten metal bath surface due to air blowing from the upper blowing lance according to the following equation (1). ₂ (m)
Is obtained, and the natural frequency f _c (Hz) of the cavity is obtained by substituting the cavity depth into the following equation (3). The standing wave that can be formed on the molten metal bath surface is obtained by the following equation (4). The natural frequency f (Hz) of the obtained natural frequency f (Hz)
Of, and characterized in that arranged on the lance above a position away from the node of the standing wave having the natural frequency f _c (Hz) 1/2 to equal the natural frequency f (Hz) Smelting furnace. (Equation 1) (Equation 2) (Equation 3) (Equation 4) Where n ₁ : slag depth (m) n ₂ : cavity depth (m) ρ ₁ : slag density (kg / m ³ ), ρ ₂ : blister copper density (kg / m ³ ), γ ₂ : γ _{2 ^{= gρ l (kg / s 2}} m 2) g: gravitational acceleration H: the distance from the molten metal bath surface of the top-blown lance (m) M: momentum transfer rate of blowing gas _{(N) β * = 125 f} c: cavity B: 1.7 ≤ b ≤ 2.4 f: Natural frequency of standing wave that can be formed on the molten metal bath surface (Hz) j _mn : Bessel function J _m (x), x from 0 The value of x when dJ _m (x) / dx = 0 at the n-th time when changed in the direction of h: Depth of molten bath (m) R: Radius of molten bath (m)