Method for detecting height of melt, apparatus for detecting height of melt, and method for producing melt

Abstract

To provide a method and a device for detecting the height of a melt that can accurately detect the height of the melt inside a blast furnace. 【Solution means】The method for detecting the height of a melt according to the present invention is a method for detecting the height of a melt that detects the height of the melt inside a blast furnace, and includes a step of measuring vibrations at at least one position on the furnace wall at the lower part of the furnace of the blast furnace, a step of analyzing the frequency of the vibrations and calculating the vibration intensity of a frequency correlated with the vibrations generated by introducing gas into the inlet at the lower part of the furnace, and a step of detecting the height of the melt inside the blast furnace using a corrected vibration intensity obtained by removing the influence of the air flow rate of the gas introduced from the inlet and the physical properties of the packed bed existing in the lower part of the furnace from the vibration intensity of the frequency.

Description

Technical Field

[0001] The present invention relates to a method for detecting the height of a melt in a blast furnace, a device for detecting the height of a melt, and a method for producing a melt.

Background Art

[0002] As an example of a blast furnace whose interior cannot be directly visually inspected, a blast furnace in an ironmaking process can be cited. A blast furnace is a facility for producing pig iron by heating and reacting iron ore, which is a raw material for iron, and coke, which is a fuel, with a high-temperature gas. The melt of pig iron and slag produced in the blast furnace accumulates as a liquid pool at the bottom of the blast furnace and is discharged outside the furnace about once every three hours and supplied to the next process.

[0003] In the operation of a blast furnace, when there is a heat shortage in the blast furnace or a decrease in the particle size of the packed bed existing at the bottom of the blast furnace, the liquid flow resistance of the melt increases, and the discharge amount of the melt to the outside of the furnace may decrease. As a result, the liquid level height (melt height) of the melt rises, and furnace cooling or damage to the furnace body equipment may occur due to deterioration of the gas permeability in the blast furnace. In this case, it is feared that the operation of the blast furnace will ultimately be stopped, and the production volume of steel products will significantly decrease throughout the steelworks. Therefore, it is essential to always grasp the accumulation amount of the melt inside the blast furnace and detect blast furnace troubles at an early stage.

[0004] Against such a background, techniques for measuring the height of the melt inside a blast furnace and detecting excessive accumulation of the melt have been proposed. Specifically, Patent Document 1 describes a technique for calculating the melt height by taking two or more images of the discharge flow of the melt from the blast furnace to obtain the discharge rate of the melt and substituting the obtained discharge rate into an energy balance equation. Further, Patent Document 2 describes a technique for measuring the melt height from the wave height of the reflected echo by inputting elastic waves into the blast furnace. Further, Patent Document 3 describes a technique for measuring the vibration intensity of the furnace wall at the lower part of the blast furnace, analyzing the frequency of the vibration intensity, calculating the vibration intensity in a frequency band correlated with the variation of the height of the hot metal slag, and calculating the height of the hot metal slag using the calculated vibration intensity.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, since the technology described in Patent Document 1 utilizes the positive correlation between the discharge rate of the melt and the melt height, when the discharge rate decreases due to clogging of the discharge hole of the melt, an increase in the melt height cannot be detected. In addition, the visibility around the discharge hole of the melt is poor due to dust in the factory, and furthermore, the discharge flow may also spout violently, so there is a possibility that the image of the discharge flow cannot be accurately captured. On the other hand, in the technology described in Patent Document 2, since there are many factors that affect the reflection characteristics of elastic waves such as crack propagation and solidified matter of the melt in the furnace wall bricks constituting the blast furnace, there is a possibility that the melt height cannot be accurately measured. Also, in the technology described in Patent Document 3, since the height of the hot metal slag in an actual blast furnace is unknown, it is difficult to specify the frequency band correlated with the fluctuation of the hot metal slag height.

[0007] The present invention has been made in view of the above problems, and an object thereof is to provide a method and an apparatus for detecting the height of a melt that can accurately detect the height of the melt inside a blast furnace. Another object of the present invention is to provide a method for manufacturing a melt that can suppress the occurrence of operation troubles and manufacture the melt with good yield.

Means for Solving the Problems

[0008] The method for detecting the height of the melt according to the present invention is a method for detecting the height of the melt inside a blast furnace, comprising the steps of measuring vibrations at at least one position on the furnace wall at the lower part of the furnace, analyzing the frequency of the vibrations to calculate the vibration intensity of a frequency correlated with the vibrations generated by introducing gas into the inlet at the lower part of the furnace, and detecting the height of the melt inside the blast furnace using the corrected vibration intensity obtained by removing the influence of the air flow rate of the gas introduced from the inlet and the physical properties of the packed bed existing in the lower part of the furnace.

[0009] The frequency correlated with the vibrations generated by introducing gas into the inlet may be specified based on the correlation between the vibration intensity in a frequency band having a predetermined width and the air flow rate of the gas and the physical properties of the packed bed existing in the lower part of the furnace.

[0010] The physical properties of the packed bed may preferably include at least the particle size.

[0011] When the time transition of the corrected vibration intensity becomes a maximum or a minimum, it may be determined that the height of the melt inside the blast furnace is the position where the vibrations are being measured.

[0012] The vibrations may be measured at two or more different positions in the height direction of the furnace wall at the lower part of the furnace.

[0013] The correspondence between the corrected vibration intensity and the height of the melt may be obtained in advance, and the height of the melt inside the blast furnace may be detected using the corrected vibration intensity obtained from the measurement of the vibrations and the correspondence.

[0014] The molten material height detection device according to the present invention is a molten material height detection device for detecting the height of the molten material inside a blast furnace, which is provided on the furnace wall at the lower part of the blast furnace and measures at least one or more vibration meters for measuring the vibration of the furnace wall, and frequency-analyzes the vibration measured by the vibration meter to calculate the vibration intensity of a frequency correlated with the vibration generated by introducing gas into the inlet at the lower part of the furnace, calculates the vibration intensity of the air volume of the gas introduced from the inlet from the vibration intensity of the frequency, and uses the corrected vibration intensity obtained by removing the influence of the air volume of the gas introduced from the inlet and the physical properties of the packed bed existing in the lower part of the furnace to detect the height of the molten material in the blast furnace, and an arithmetic unit.

[0015] The method for producing a molten material according to the present invention is a method for producing a molten material using a blast furnace, which includes a step of measuring vibration at at least one or more positions on the furnace wall at the lower part of the blast furnace, a step of analyzing the frequency of the vibration to calculate the vibration intensity of a frequency correlated with the vibration generated by introducing gas into the inlet at the lower part of the furnace, a step of detecting the height of the molten material inside the blast furnace using the corrected vibration intensity obtained by removing the influence of the air volume of the gas introduced from the inlet and the physical properties of the packed bed existing in the lower part of the furnace from the vibration intensity of the frequency, and a step of adjusting the production conditions of the molten material so that the detected height of the molten material falls within the range of the target height of the molten material.

Advantages of the Invention

[0016] According to the molten material height detection method and detection device of the present invention, the height of the molten material inside the blast furnace can be accurately detected. Further, according to the method for producing a molten material of the present invention, the occurrence of operation troubles can be suppressed and the molten material can be produced with good yield.

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Mode for Carrying Out the Invention

[0018] Hereinafter, with reference to the drawings, a method and a device for detecting the molten material height according to the first and second embodiments of the present invention will be described.

[0019] 〔First Embodiment〕 First, with reference to FIGS. 1 to 5, a method and apparatus for detecting the height of a melt according to a first embodiment of the present invention will be described. This embodiment applies the present invention to the process of detecting the height of molten iron slag, which is a melt accumulated at the bottom of a blast furnace as an example of a smelting furnace.

[0020] FIG. 1 is a partial cross-sectional schematic view showing the configuration of the lower part of a blast furnace. As shown in FIG. 1, a melt (molten iron slag) 12 composed of pig iron and slag is accumulated in the lower part of the blast furnace 10. The melt 12 is discharged outside the furnace through a discharge hole 14, and a melt flow 16 is generated. Further, in the lower part of the blast furnace 10, a tuyere 20 for introducing gas 18 into the blast furnace 10 is provided. The tuyere 20 is an example of an inlet for introducing gas 18 into the blast furnace 10.

[0021] FIG. 2 is a partial cross-sectional schematic view showing the configuration of the lower part of a blast furnace and an apparatus for detecting the height of a melt according to a first embodiment of the present invention. As shown in FIG. 2, an apparatus 22 for detecting the height of a melt according to a second embodiment of the present invention includes three vibration meters 24a to 24c and an arithmetic unit 26. The three vibration meters 24a to 24c are provided at equal intervals in the height direction on the furnace wall between the discharge hole 14 and the tuyere 20, and measure the vibration of the furnace wall to generate vibration data. The vibration meters 24a to 24c are composed of, for example, piezoelectric elements.

[0022] The vibration data generated by the vibration meters 24a to 24c is output to and recorded by the arithmetic unit 26. The arithmetic unit 26 is composed of a general-purpose computer such as a personal computer including an arithmetic unit such as a CPU and a storage unit such as a memory. The arithmetic unit 26 performs frequency analysis on the vibration data acquired from the vibration meters 24a to 24c, and calculates the vibration intensity of a frequency correlated with the vibration generated by introducing gas from the tuyere 20.

[0023] The arithmetic unit 26 corrects the vibration intensity to the corrected vibration intensity using the following mathematical formula (1) in order to remove the influence of the air flow rate (introduction amount) of the gas and the particle size of the packed bed existing in the lower part of the furnace from the calculated vibration intensity. By correcting the vibration intensity to the corrected vibration intensity, the influence of fluctuations in the air flow rate of the gas and the particle size of the packed bed existing in the lower part of the furnace on the vibration intensity can be removed.

[0024] G 0 =G+(BV 0 -BV)×a+(DP 0 -DP)×b···(1)

[0025] In the above formula, G 0 (m / s 2 ) is the corrected vibration intensity, G (m / s 2 ) is the vibration intensity before correction, BV 0 (Nm 3 / min) is an arbitrary air flow rate of the gas, BV (Nm 3 / min) is the air flow rate of the gas at the time when the vibration data used as the calculation source of the vibration intensity G was measured, a is the slope of the regression line when the vibration intensity in the frequency band of the vibration due to the air flow is on the y-axis and the air flow rate is on the x-axis, DP 0 (m) is an arbitrary particle size of the packed bed in the lower part of the furnace, DP (m) is the average particle size of the packed bed in the lower part of the furnace at the time when the vibration data used as the calculation source of the vibration intensity G was measured, and b is the slope of the regression line when the vibration intensity in the frequency band of the vibration due to the air flow is on the y-axis and the average particle size of the packed bed in the lower part of the furnace is on the x-axis.

[0026] FIG. 3 is a graph showing the time change of the corrected vibration intensity. The horizontal axis in FIG. 3 represents time, and the vertical axis represents the corrected vibration intensity. As shown in FIG. 3, when the height of the melt 12 is lower than the installation heights of the vibration meters 24a to 24c, a positive correlation is obtained between the corrected vibration intensity and time. On the other hand, when the height of the melt 12 is higher than the installation heights of the vibration meters 24a to 24c, a negative correlation is obtained between the corrected vibration intensity and time. Therefore, for example, when the time change of the corrected vibration intensity shown in FIG. 3 is the corrected vibration intensity obtained from the vibration data generated by the vibration meter 24b, it can be determined that the height of the melt 12 at the time when the relationship between the corrected vibration intensity and time changes from a positive correlation to a negative correlation and reaches a maximum is the installation height of the vibration meter 24b.

[0027] The fact that the relationship between the corrected vibration intensity and time changes from a positive correlation to a negative correlation means that the vibration meter has detected the phenomenon of the liquid level of the melt rising. On the other hand, when the liquid level of the melt drops, the relationship between the corrected vibration intensity and time changes from a negative correlation to a positive correlation. Also in this case, the height of the melt 12 at the time when the relationship between the corrected vibration intensity and time changes from a negative correlation to a positive correlation and reaches a minimum is the installation height of the vibration meter.

[0028] The arithmetic unit 26 monitors the time change of the corrected vibration intensity obtained from the vibration data generated by the vibration meters 24a to 24c, and identifies the vibration meter in which the relationship between the corrected vibration intensity and time changes from a positive correlation to a negative correlation, or the vibration meter in which the relationship between the corrected vibration intensity and time changes from a negative correlation to a positive correlation. Then, when the arithmetic unit 26 identifies the vibration meter, it detects the height of the melt 12 assuming that the installation height of the identified vibration meter is the height of the melt 12.

[0029] Even when it is not possible to identify a vibration meter in which the relationship between the corrected vibration intensity and time has changed from a positive correlation to a negative correlation, or a vibration meter in which the relationship between the corrected vibration intensity and time has changed from a negative correlation to a positive correlation, if there are a vibration meter showing a positive correlation between the corrected vibration intensity and time and a vibration meter showing a negative correlation between the corrected vibration intensity and time, the arithmetic unit 26 detects the height of the molten metal 12 assuming that the height between the installation heights of these vibration meters is the height of the molten metal 12. In this way, the arithmetic unit 26 detects the height of the molten metal 12 in the blast furnace 10 from the vibration data generated by the vibration meters 24a to 24c.

[0030] This embodiment has three vibration meters 24a to 24c, but the number of vibration meters is not limited to this. The molten metal height detection device 22 only needs to have at least one vibration meter, and if there is a change from a positive correlation to a negative correlation in the relationship between the corrected vibration intensity obtained from the vibration data generated by this vibration meter and time, the height of the molten metal 12 can be detected. However, since the height of the molten metal 12 is detected based on the installation height of the vibration meter as described above, the molten metal height detection device 22 preferably has two or more vibration meters installed at different positions in the height direction at the lower part of the blast furnace 10. Thereby, the detection range of the height of the molten metal 12 in the lower part of the blast furnace 10 can be widened in the height direction.

[0031] FIG. 4 is a flowchart for explaining a method of identifying a frequency correlated with vibrations generated by introducing a gas. Using FIG. 4, a method of identifying a frequency correlated with vibrations generated by introducing a gas from the tuyere 20 will be explained. This frequency identification is preferably performed using the vibration meter 24a installed at the position closest to the tuyere 20, and is also preferably performed when the operation of the blast furnace 10 is stable. The time when the operation of the blast furnace 10 is stable means a time when the coke ratio in the blast furnace operation is within the target range and the variation in the air permeability in the blast furnace is low.

[0032] In this specific method, first, the vibrometer 24a measures the vibration at the lower part of the blast furnace 10 to generate vibration data (step S101). Next, the arithmetic unit 26 performs FFT processing on the vibration data to perform frequency analysis on the vibration data (step S102). The arithmetic unit 26 may perform overlap processing, smoothing processing, window function processing, etc. on the vibration data before executing the FFT processing as necessary.

[0033] FIG. 5 is a graph showing vibration data and vibration intensity data obtained by performing FFT processing on the vibration data. FIG. 5(a) shows the vibration data, and FIG. 5(b) shows the vibration intensity data obtained by performing FFT processing. In this way, the arithmetic unit 26 converts the vibration data shown in FIG. 5(a) into the vibration intensity data shown in FIG. 5(b) by performing FFT processing. The arithmetic unit 26 preferably calculates the vibration intensity at all frequencies using this vibration intensity data. For example, when the frequency band is 1000 to 1200 kHz, the arithmetic unit 26 sets the value obtained by adding and averaging the vibration intensities in the range of 1000 to 1200 kHz as the vibration intensity in the frequency band of 1000 to 1200 kHz.

[0034] Returning to FIG. 4. Next, if the arithmetic unit 26 has not acquired a plurality of pieces of this vibration intensity data under conditions where the gas blowing volume is changed (step S103: No), the gas blowing volume is changed (step S104), and the processes of step S101 and step S102 are repeatedly executed again. On the other hand, if a plurality of pieces of vibration intensity data have been acquired under conditions where the gas blowing volume is changed (step S103: Yes), the arithmetic unit 26 calculates the coefficient of determination (R 2 ) between the gas blowing volume and the vibration intensity at all frequencies (step S105).

[0035] After calculating the coefficient of determination (R 2 ) between the blowing volume and the vibration intensity at all frequencies, next, the arithmetic unit 26 identifies the frequency with the highest coefficient of determination among them as the frequency correlated with the vibration generated by introducing the gas (step S106). In this way, the arithmetic unit 26 preliminarily identifies the frequency correlated with the vibration generated by introducing the gas.

[0036] The identification of the frequency correlated with the vibration generated by introducing a gas may be performed using a plurality of vibration meters. For example, when using vibration meter 24a and vibration meter 24b, for these vibration meters, the coefficient of determination (R 2 ) between the air flow rate of the gas and the vibration intensity at all frequencies is calculated, and the coefficients of determination of vibration meter 24a and vibration meter 24b are averaged, and the frequency at which this average value becomes the highest may be identified.

[0037] Furthermore, when obtaining the coefficient of determination between the air flow rate and the vibration intensity, it is preferable to calculate the coefficient of determination (R 2 ) in consideration of a predetermined frequency width for each frequency. For example, the coefficient of determination may be calculated in consideration of a frequency width of ±25 Hz to ±300 Hz for each frequency. Also in this case, the coefficient of determination (R 2 ) at each frequency and for each frequency width corresponding to the frequency is confirmed, and the frequency and frequency width at which the coefficient of determination obtained by averaging these values becomes the largest may be identified as the frequency and frequency width correlated with the vibration generated by introducing the gas. By considering a predetermined frequency width for each frequency, the coefficient of determination becomes higher.

[0038] Thus, the melt height detection method and detection device according to the first embodiment of the present invention detect the height of the melt 12 using the vibration intensity of the frequency correlated with the vibration generated by introducing a gas from the air supply port 20. The frequency correlated with the vibration generated by introducing a gas into the inlet of the blast furnace can be easily identified by acquiring vibration data with the air flow rate changed, so the frequency of the vibration intensity that can detect the melt height of the blast furnace can be easily identified. Then, using the corrected vibration intensity obtained by removing the influence of the air flow rate of the gas introduced from the inlet and the average particle diameter of the packed bed in the lower part of the furnace from the vibration intensity of the identified frequency, the melt height inside the blast furnace that cannot be directly visually observed can be detected with high accuracy.

[0039] Further, it is preferable to adjust the production conditions of the melt so that the height of the melt detected in this way falls within the range of the target melt height in the blast furnace. For example, when the melt height is likely to be higher than the target range, the production conditions of the melt may be adjusted by reducing the charging amount of the raw material or increasing the discharge amount of the melt. Also, when the melt height is likely to be lower than the target range, the production conditions of the melt may be adjusted by increasing the charging amount of the raw material or reducing the discharge amount of the melt. By adjusting the production conditions of the melt in this way so that it falls within the range of the target melt height, for example, in a blast furnace, an excessive rise in the melt level surface can be suppressed, and the melt can be produced with good yield while suppressing furnace cooling due to deteriorated air permeability and damage to the furnace body equipment.

[0040] 〔Second Embodiment〕 Next, with reference to FIGS. 6 and 7, a method and apparatus for detecting the height of a melt according to a second embodiment of the present invention will be described. This embodiment applies the present invention to the process of detecting the height of molten iron slag, which is a melt accumulated at the bottom of a blast furnace as an example of a blast furnace.

[0041] FIG. 6 is a partial cross-sectional schematic view showing the configuration of the lower part of a blast furnace and a melt height detection apparatus according to the second embodiment. As shown in FIG. 6, a melt height detection apparatus 30 according to the second embodiment of the present invention includes one vibration meter 32 and an arithmetic unit 34. In FIG. 6, the same components as those in FIG. 2 are denoted by the same reference numerals, and the description thereof is omitted.

[0042] The vibration meter 32 measures the vibration of the furnace wall at the lower part of the blast furnace 10 and generates vibration data. The vibration meter 32 is constituted by, for example, a piezoelectric element.

[0043] The vibration data generated by the vibrometer 32 is output to and recorded by the arithmetic unit 34. The arithmetic unit 34 is composed of a general-purpose computer such as a personal computer including an arithmetic unit such as a CPU and a storage unit such as a memory. The arithmetic unit 34 performs frequency analysis on the vibration data acquired from the vibrometer 32 and calculates the vibration intensity of a frequency correlated with the vibration generated by introducing gas from the air supply port 20. The arithmetic unit 34 corrects the vibration intensity to the corrected vibration intensity using the above formula (1) in order to remove the influence of the gas flow rate and the particle size of the packed bed existing in the lower part of the furnace from the calculated vibration intensity.

[0044] Figure 7 is a graph showing the relationship between the corrected vibration intensity and the molten material height. The horizontal axis of Figure 7 is the corrected vibration intensity (m / s 2 ), and the vertical axis is the height (m) of the molten material. In the arithmetic unit 34, a regression equation showing the correspondence between the corrected vibration intensity and the height of the molten material 12 as shown in Figure 7 is obtained in advance and stored. The regression equation showing the correspondence between the corrected vibration intensity and the height of the molten material 12 is preferably created using operation data for as long a period as possible.

[0045] When the arithmetic unit 34 calculates the corrected vibration intensity, it reads out the data of the regression equation showing the correspondence between the corrected vibration intensity and the height of the molten material shown in Figure 7, and detects the height of the molten material 12 using the regression equation and the calculated corrected vibration intensity. In this way, the molten material height detection device 30 detects the height of the molten material 12 in the blast furnace 10.

[0046] As described above, the method and apparatus for detecting the height of the melt, which are the second embodiment of the present invention, detect the height of the melt 12 using the vibration intensity of a frequency correlated with the vibration generated by introducing gas from the blower tuyere 20. Since the frequency correlated with the vibration generated by introducing gas into the inlet of the blast furnace can be easily specified by acquiring vibration data with different air volumes, the frequency of the vibration intensity capable of detecting the height of the melt in the blast furnace can be easily specified. Then, by using the corrected vibration intensity obtained by removing the influence of the air volume of the gas introduced from the inlet and the particle size of the packed bed existing in the lower part of the furnace from the vibration intensity of the specified frequency and the above regression equation, the height of the melt inside the blast furnace that cannot be directly visually observed can be detected with high accuracy.

[0047] [Example 1] Next, Example 1 in which the height of the melt accumulated in the lower part of a large blast furnace with a capacity of 5000 m 3 will be described for the purpose of confirming the validity of the present invention. In this example, an apparatus having the same configuration as the melt height detection apparatus 22 shown in FIG. 2 was used. The vibration meters 24a to 24c were installed at equal intervals between the blower tuyere 20 and the discharge hole 14 provided in the lower part of the blast furnace 10. Table 1 below shows the installation height of the vibration meters 24a to 24c from the furnace bottom, the height of the blower tuyere 20, and the height of the discharge hole 14.

[0048]

Table 1

[0049] FIG. 8 is a schematic diagram showing the configuration of the vibration meter of Example 1 and its peripheral devices. In FIG. 8, the same components as those in FIG. 2 are denoted by the same reference numerals, and the description thereof is omitted. In this embodiment, amplifiers 40a to 40c for amplifying vibration data are connected to each of the vibration meters 24a to 24c. Then, the vibration data amplified by the amplifiers 40a to 40c is stored by data loggers 42a to 42c. Then, the vibration data stored in the data loggers 42a to 42c is processed using the arithmetic unit 26. The conditions for measuring vibration were assumed to be the vibration frequency derived from the blast measured in the blast furnace, the sampling frequency was set to 10000 (Hz), and the recording length was set to 10 (sec). The vibration of the furnace wall was measured every 3 minutes for 4 days under these conditions, and the vibration data for the period was acquired.

[0050] In this embodiment, before the FFT analysis, the vibration data was subjected to overlap processing, smoothing processing, and window function processing. In the overlap processing, the raw data of the vibration data was divided by a size of 3 / 10 with respect to the recording length, and half of them were processed so as to overlap. Also, each divided frame was leveled using a Gaussian filter. In the window function processing, a Hanning window was applied. After processing the divided frames in this way, the FFT analysis was performed, and the average value of the vibration intensities calculated by performing the FFT analysis on all the divided frames was used.

[0051] After performing the FFT analysis, the vibration intensities in all frequency bands were calculated. In Example 1, vibrations having frequencies of 5000 Hz or less were measured by the vibration meters 24a to 24c. To evaluate the vibration intensities of all these frequencies, the frequency of the vibration was considered in terms of a reference vibration frequency f (Hz) and a frequency width Δf (Hz). That is, the average value of the vibration intensities of f±Δf was taken as the vibration intensity of f±Δf (Hz), f was changed in 50 (Hz) increments from 300 (Hz) to 4700 (Hz), and Δf was changed in 25 (Hz) increments from 25 (Hz) to 300 (Hz) to define the frequency band of f±Δf (Hz).

[0052] In this way, after calculating the vibration intensity at each frequency, the coefficient of determination (R 2 ) between the vibration intensity and the air flow rate was calculated. In Example 1, the coefficient of determination (R 2 ) was calculated using the vibration data of the vibration meters 24a and 24b measured on the day with the lowest height of the melt during the 4-day measurement period.

[0053] FIG. 9 is a contour diagram showing the values of the coefficient of determination (R 2 ) between the vibration intensity calculated from the measured values of the vibration meters 24a and 24b and the air flow rate. FIG. 9(a) is the contour diagram of the vibration meter 24a, and FIG. 9(b) is the contour diagram of the vibration meter 24b. In Example 1, the R 2 in the vibration frequency band of f = 1400 (Hz) and Δf = 250 (Hz) was the highest. Therefore, f ± Δf = 1400 ± 250 (Hz) was set as the frequency correlated with the vibration generated by introducing the gas.

[0054] Next, the air flow rate of the vibration intensity and the correction of the particle size of the lower furnace packing layer were performed. The correction was performed using the vibration intensity, the air flow rate, and the particle size of the lower furnace packing layer on two days with a small accumulation amount of the melt in the lower furnace during the 4 days when the vibration data was measured, and the equation of the regression line used in the above formula (1) was obtained.

[0055] FIG. 10 is a graph showing the relationship between the vibration intensity of the vibration meters 24a to 24c and the air flow rate. FIG. 10(a) shows the graph and the regression line of the vibration meter 24a, FIG. 10(b) shows the graph and the regression line of the vibration meter 24b, and FIG. 10(c) shows the graph and the regression line of the vibration meter 24c. The horizontal axis of these graphs is the air flow rate of the gas (Nm 3 / min), and the vertical axis is the vibration intensity (m / s 2 ). FIG. 11 is a graph showing the relationship between the vibration intensity of the vibration meters 24a to 24c and the particle size of the lower furnace packing layer. FIG. 11(a) shows the graph and the regression line of the vibration meter 24a, FIG. 11(b) shows the graph and the regression line of the vibration meter 24b, and FIG. 11(c) shows the graph and the regression line of the vibration meter 24c. The horizontal axis of these graphs is the particle size of the lower furnace packing layer (m), and the vertical axis is the vibration intensity (m / s 2) That is. By substituting the slopes of these regression lines into the above formula (1), the following formulas (2), (3), and (4) were calculated.

[0056] G 0 = G + (BV - BV 0 ) × 2.00 × 10 -3 + (DP - DP 0 ) × 3.91 × 10 -3 ···(2)

[0057] G 0 = G + (BV - BV 0 ) × 1.72 × 10 -3 + (DP - DP 0 ) × 4.12 × 10 -3 ···(3)

[0058] G 0 = G + (BV - BV 0 ) × 1.04 × 10 -3 + (DP - DP 0 ) × 3.78 × 10 -3 ···(4)

[0059] Using the above formulas (2) to (4), the corrected vibration intensity from which the influence of the air volume and the particle size of the lower furnace packing layer was removed was calculated. Then, the melt height was detected using the calculated corrected vibration intensity.

[0060] Figure 12 is a graph showing the time change of the melt height and the time change of the corrected vibration intensity obtained from the operation data. Figure 12(a) is a graph showing the time change of the melt height obtained from the operation data, where the horizontal axis is time and the vertical axis is the melt height (m). Figures 12(b) to (d) are graphs showing the time change of the corrected vibration intensity of the vibration meters 24a to 24c, where the horizontal axis is time and the vertical axis is the corrected vibration intensity (m / s 2 ).

[0061] As shown in Fig. 12, in the vibrometer 24c, the value of the corrected vibration intensity has been decreasing since 16:30 on August 3, while in the vibrometers 24a and 24b, it has been continuously increasing. Therefore, it can be seen that from 16:30 to 23:59 on August 3, the molten material height exists between 4.8 and 5.2 (m), which is between the vibrometers 24b and 24c. Looking at the value of the molten material height estimated and calculated at the same time, it has been rising from about 4.4 (m) to 5.2 (m) from 16:30 to 23:59 on April 19. Thus, the molten material height detected from the vibration intensity and the value of the molten material height estimated and calculated from the operation data are almost the same, and it was confirmed that the molten material height can be detected by the method of Example 1.

[0062] [Example 2] Next, Example 2 in which it was confirmed that the molten material height can be detected using a single vibrometer will be described. In Example 2, the molten material height of a large blast furnace with the same capacity of 5000 m 3 was detected using the vibration data of the vibrometer 24a. The vibration data obtained from the vibrometer 24a was subjected to FFT analysis after overlapping processing, smoothing processing, and window function processing in the same manner as in Example 1.

[0063] The frequency correlated with the vibration due to the blast was set to f±Δf = 1400±250 (Hz) in the same manner as in Example 1. The vibration intensity at this frequency from 0:00 to 23:59 on August 3 was corrected using the above formula (2) to calculate the corrected vibration intensity. Also, the molten material height in the blast furnace was calculated using the operation data obtained in the blast furnace from 0:00 to 23:59 on August 3 and the following formula (5).

[0064] h=(Wi / ρi+Ws / ρs) / (ε×Sb)···(5)

[0065] In the above formula (5), h is the molten material height (m), Wi (kg) is the weight of the hot metal at the furnace bottom, ρi (kg / m 3 ) is the hot metal density, Ws (kg) is the weight of the molten slag at the furnace bottom, ρs (kg / m 3 ) is the molten slag density, ε (-) is the porosity of the furnace bottom, Sb (m 3) is the cross-sectional area of the furnace bottom. The weights of the molten iron and molten slag at the furnace bottom were obtained by adding the values obtained by subtracting the amount of iron production and slag production obtained for each tapping operation from the amount of iron production and slag production, and correcting for the error of the weighing machine of the actual machine. In Example 2, the density of the molten iron was 6800 (kg / m 3 ), the density of the molten slag was 2650 (kg / m 3 ), and the porosity of the furnace bottom was 0.35. Using the corrected vibration intensity and the height of the melt thus calculated, a regression equation showing the relationship between the corrected vibration intensity and the height of the melt was obtained.

[0066] Figure 13 is a graph showing the regression equation between the corrected vibration intensity and the height of the melt. The horizontal axis in Figure 13 is the corrected vibration intensity (m / s 2 ), and the vertical axis is the height of the melt (m). The regression equation shown in Figure 13 becomes a calibration curve for detecting the height of the melt from the corrected vibration intensity. The regression equation obtained from the graph of Figure 13 was the following mathematical formula (6).

[0067] h = G 0 × 0.6953 - 18.486 ··· (6)

[0068] In the above mathematical formula (6), G 0 is the corrected vibration intensity (m / s 2 ). The height of the melt was detected using this mathematical formula (6). In the detection of the height of the melt, the height of the melt was calculated using the corrected vibration intensity at four points near 0:00 of 8 / 3 and the above mathematical formula (6). Also, in the detection of the actual value of the height of the melt, the height of the melt was calculated using the four operating data at the same time and the above mathematical formula (5).

[0069] Figure 14 is a graph showing the relationship between the detected value of the height of the melt calculated from the corrected vibration intensity and the actual value of the height of the melt obtained from the operating data. The horizontal axis in Figure 14 is the detected value of the height of the melt calculated from the corrected vibration intensity (m), and the vertical axis is the actual value of the height of the melt (m). As shown in Figure 14, the detected value of the height of the melt obtained from the regression equation of mathematical formula (6) and the actual value of the height of the melt obtained from the operating data were almost the same. From this result, it was confirmed that the height of the melt can be detected by the method of Example 2.

Explanation of Symbols

[0070] 10 Blast furnace 12 Melt 14 Discharge hole 16 Melt flow 18 Gas 20 Tuyere 22 Melt height detection device 24a~24c Vibrometer 26 Arithmetic unit 30 Melt height detection device 32 Vibrometer 40a~40c Amplifier 42a~42c Data logger

Claims

1. A method for detecting a molten material height inside a blast furnace, comprising: Measuring vibrations at at least one or more positions on a furnace wall in a lower part of the blast furnace; A step of analyzing a frequency of the vibration and calculating a vibration intensity of a frequency correlated with a vibration generated by introducing a gas into an inlet of the lower part of the furnace; Detecting the molten material height inside the blast furnace using a corrected vibration intensity obtained by removing the influence of the amount of gas introduced from the inlet and the physical properties of the packed bed present in the lower part of the furnace from the vibration intensity of the frequency; 4. A method for detecting a melt height comprising:

2. 2. The method for detecting the height of a molten material according to claim 1, wherein a frequency correlated with vibrations generated by introducing gas into the inlet is identified based on a correlation between vibration intensity in a frequency band having a predetermined width, the amount of gas blown, and physical properties of a packed bed present in the lower part of the furnace.

3. The method for detecting a melt height according to claim 1 , wherein the physical properties of the packed bed include at least a grain size.

4. 2. The method for detecting a smelt height according to claim 1, further comprising the step of determining, when the time transition of the corrected vibration intensity becomes a maximum or a minimum, that the smelt height inside the blast furnace is at a position where the vibration is being measured.

5. The method for detecting a molten material height according to claim 1 , wherein the vibration is measured at two or more different positions in a height direction of a furnace wall in the lower part of the furnace.

6. A correspondence relationship between the corrected vibration intensity and the molten material height is obtained in advance, The method for detecting a smelt height according to claim 1, further comprising the step of detecting a smelt height inside a blast furnace using a corrected vibration intensity obtained from the vibration measurement and the correspondence relationship.

7. A molten material height detection device for detecting a molten material height inside a blast furnace, At least one vibration meter is provided on a furnace wall in a lower part of the blast furnace to measure vibration of the furnace wall; a calculation device that performs frequency analysis on the vibrations measured by the vibration meter to calculate a vibration intensity of a frequency that is correlated with the vibration generated by introducing gas into the inlet at the lower part of the furnace, calculates the vibration intensity of the amount of gas introduced from the inlet from the vibration intensity of the frequency, and detects the molten material height of the blast furnace using a corrected vibration intensity obtained by removing the effects of the amount of gas introduced from the inlet and the physical properties of the packed bed present in the lower part of the furnace from the vibration intensity of the frequency; 1. A melt height detection device comprising:

8. A method for producing a molten material using a blast furnace, comprising the steps of: Measuring vibrations at at least one or more positions on a furnace wall in a lower part of the blast furnace; A step of analyzing a frequency of the vibration and calculating a vibration intensity of a frequency correlated with a vibration generated by introducing a gas into an inlet of the lower part of the furnace; Detecting the molten material height inside the blast furnace using a corrected vibration intensity obtained by removing the influence of the amount of gas introduced from the inlet and the physical properties of the packed bed present in the lower part of the furnace from the vibration intensity of the frequency; adjusting the melt production conditions so that the detected melt height is within a range of a target melt height; A method for producing a melt, comprising:

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