Molten material height detection method, molten material height detection device, and molten material production method

Abstract

This method for detecting the height of a molten material is for detecting the height of a molten material in a blast furnace, said method comprising: a step for measuring vibrations at at least one position of a furnace wall in a furnace lower part of the blast furnace; a step for analyzing the frequency of the vibrations and calculating the vibrational intensity of a frequency correlated with vibrations generated upon introduction of a gas into an inflow port of the furnace lower part; and a step for detecting the height of the molten material inside the blast furnace using a corrected vibrational intensity obtained by removing, from the vibrational intensity of the frequency, the influence of a blast amount of the gas introduced from the inflow port and a physical property of a filling layer which exists in the furnace lower part.

Description

MELT HEIGHT DETECTION METHOD, MELT HEIGHT DETECTION DEVICE, AND METHOD FOR MANUFACTURING MELT

[0001] The present invention relates to a molten material height detection method for detecting the molten material height inside a blast furnace, a molten material height detection device, and a molten material manufacturing method.

[0002] An example of a blast furnace whose interior cannot be directly inspected is the blast furnace used in the steelmaking process. A blast furnace is a facility that produces pig iron by heating iron ore, the raw material for iron, and coke, the fuel, with high-temperature gas, causing them to react. The molten pig iron and slag produced in the blast furnace accumulate as a liquid pool at the bottom of the furnace and are discharged from the furnace approximately once every three hours to be supplied to the next process.

[0003] During blast furnace operation, if the furnace experiences insufficient heat or the particle size of the packed bed at the bottom of the furnace decreases, the resistance to melt flow increases, which can reduce the amount of melt discharged outside the furnace. As a result, the melt level (melt height) rises, leading to a deterioration in gas permeability inside the blast furnace, which can lead to furnace cooling and damage to furnace equipment. In this case, the blast furnace may eventually be forced to shut down, raising concerns that this could significantly reduce the production of steel products throughout the steelworks. For this reason, it is essential to constantly monitor the amount of melt accumulated inside the blast furnace and detect blast furnace problems early.

[0004] In light of this background, technologies have been proposed for measuring the height of molten material inside a blast furnace and detecting excessive accumulation of molten material. Specifically, Patent Document 1 describes a technology in which two or more images of the molten material discharge flow from a blast furnace are captured to determine the molten material discharge rate, and the determined discharge rate is substituted into an energy balance equation to calculate the molten material height. Patent Document 2 describes a technology in which elastic waves are input into a blast furnace and the molten material height is measured from the wave height of the reflected echo. Patent Document 3 describes a technology in which the vibration intensity of a furnace wall in the lower part of a blast furnace is measured, the frequency of the vibration intensity is analyzed to calculate the vibration intensity in a frequency band correlated with fluctuations in the molten metal and slag height, and the calculated vibration intensity is used to calculate the molten metal and slag height.

[0005] JP 2017-160498 A JP 10-185654 A International Publication No. 2022 / 201717

[0006] However, since the technology described in Patent Document 1 utilizes a positive correlation between the discharge rate of the molten material and the molten material height, it is unable to detect an increase in the molten material height when the discharge rate decreases due to clogging of the molten material discharge hole. Furthermore, visibility around the molten material discharge hole is poor due to dust in the factory, and the discharge flow may also be violently ejected, making it difficult to accurately capture images of the discharge flow. On the other hand, the technology described in Patent Document 2 may be unable to accurately measure the molten material height because there are many factors that affect the reflection characteristics of elastic waves, such as crack propagation in the furnace wall bricks that make up the blast furnace and solidification of the molten material. Furthermore, the technology described in Patent Document 3 makes it difficult to identify a frequency band correlated with fluctuations in the molten material height because the actual molten metal and slag height in the blast furnace is unknown.

[0007] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a smelt height detection method and detection device capable of detecting the smelt height inside a blast furnace with high accuracy. Another object of the present invention is to provide a smelt manufacturing method capable of suppressing the occurrence of operational problems and manufacturing smelt with a high yield.

[0008] The smelt height detection method of the present invention is a method for detecting the smelt height inside a blast furnace, and includes the steps of measuring vibrations at at least one position on the furnace wall in the lower part of the blast furnace, analyzing the frequency of the vibrations and calculating the vibration intensity of a frequency that is correlated with the vibration generated by introducing gas into an inlet in the lower part of the furnace, and detecting the smelt height inside the blast furnace using a corrected vibration intensity that removes the effects of the blast volume 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.

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

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

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

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

[0013] It is preferable to determine in advance the correspondence relationship between the corrected vibration intensity and the molten material height, and then use the corrected vibration intensity obtained from the vibration measurement and the correspondence relationship to detect the molten material height inside the blast furnace.

[0014] The smelt height detection device of the present invention is a smelt height detection device that detects the smelt height inside a blast furnace, and includes at least one vibration meter installed on the furnace wall in the lower part of the blast furnace and measuring the vibration of the furnace wall, and a calculation device that performs frequency analysis of the vibrations measured by the vibration meter to calculate the vibration intensity of a frequency correlated with the vibration generated by introducing gas into an inlet in the lower part of the furnace, calculates the vibration intensity of the gas blast volume introduced from the inlet from the vibration intensity of the frequency, and detects the smelt height in the blast furnace using a corrected vibration intensity that removes the effects of the gas blast volume 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.

[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, and includes the steps of measuring vibrations at at least one position on the furnace wall in the lower part of the blast furnace, analyzing the frequency of the vibrations and calculating the vibration intensity of a frequency correlated with the vibration generated by introducing gas into an inlet in the lower part of the furnace, detecting the molten material height inside the blast furnace using a corrected vibration intensity obtained by removing the effects of the gas flow rate 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, and adjusting the production conditions for the molten material so that the detected molten material height is within a target molten material height range.

[0016] The smelt height detection method and detection device according to the present invention can detect the smelt height inside a blast furnace with high accuracy. Also, the smelt production method according to the present invention can suppress the occurrence of operational problems and produce smelt with high yield.

[0017] FIG. 1 is a partial cross-sectional schematic diagram showing the configuration of the lower part of a blast furnace. FIG. 2 is a partial cross-sectional schematic diagram showing the configuration of the lower part of a blast furnace and a smelt height detection device according to a first embodiment of the present invention. FIG. 3 is a graph showing the time progression of corrected vibration intensity. FIG. 4 is a flowchart showing a method for identifying frequencies correlated with vibrations generated by introducing gas. FIG. 5 is a graph showing vibration data and vibration intensity data obtained by FFT processing of the vibration data. FIG. 6 is a partial cross-sectional schematic diagram showing the configuration of the lower part of a blast furnace and a smelt height detection device according to a second embodiment of the present invention. FIG. 7 is a graph showing the relationship between corrected vibration intensity and smelt height. FIG. 8 is a schematic diagram showing the configuration of a vibrometer and its peripheral equipment according to Example 1. FIG. 9 is a contour diagram showing the coefficient of determination between vibration intensity and blast volume calculated from measurements taken by the vibrometer. FIG. 10 is a graph showing the relationship between vibration intensity measured by the vibrometer and blast volume. FIG. 11 is a graph showing the relationship between vibration intensity measured by the vibrometer and particle size of the packed bed in the lower furnace. FIG. 12 is a graph showing the time progression of smelt height and corrected vibration intensity determined from operational data. Fig. 13 is a graph showing a regression equation between corrected vibration intensity and molten material height. Fig. 14 is a graph showing the relationship between the detected value of molten material height calculated from corrected vibration intensity and the actual value of molten material height obtained from operational data.

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

[0019] First, a molten material height detection method and detection device according to a first embodiment of the present invention will be described with reference to Figures 1 to 5. In this embodiment, the present invention is applied to a process for detecting the height of molten metal or slag, which is a molten material accumulated at the bottom of a blast furnace, which is an example of a blast furnace.

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

[0021] Figure 2 is a partial cross-sectional schematic diagram showing the configuration of the lower part of a blast furnace and a smelt height detection device according to a first embodiment of the present invention. As shown in Figure 2, a smelt height detection device 22 according to a second embodiment of the present invention includes three vibrometers 24a to 24c and a computing device 26. The three vibrometers 24a to 24c are installed at equal intervals in the height direction on the furnace wall between the discharge hole 14 and the blast tuyere 20, and measure the vibration of the furnace wall to generate vibration data. The vibrometers 24a to 24c are configured, for example, with piezoelectric elements.

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

[0023] The computing device 26 corrects the vibration intensity to a corrected vibration intensity using the following formula (1) to remove the effects of the gas blowing rate (introduction rate) and the particle size of the packed bed present in the lower part of the furnace from the calculated vibration intensity. By correcting the vibration intensity to the corrected vibration intensity, the effects of fluctuations in the gas blowing rate and the particle size of the packed bed present 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 the arbitrary gas flow rate, BV (Nm ３ / min) is the volume of gas blown at the time when the vibration data used to calculate the vibration intensity G was measured, a is the slope of the regression line when the vibration intensity of the frequency band of vibration caused by the blown air is on the y-axis and the volume of blown air is on the x-axis, and DP ０ (m) is an arbitrary particle diameter in the packed bed at the lower part of the furnace, DP(m) is the average particle diameter in the packed bed at the lower part of the furnace at the time when the vibration data from which the vibration intensity G is calculated is measured, and b is the slope of the regression line when the vibration intensity in the frequency band of the vibration caused by the air blowing is plotted on the y-axis and the average particle diameter in the packed bed at the lower part of the furnace is plotted on the x-axis.

[0026] FIG. 3 is a graph showing the time progression of the corrected vibration intensity. The horizontal axis of FIG. 3 represents time, and the vertical axis represents the corrected vibration intensity. As shown in FIG. 3, when the height of the molten material 12 is lower than the installation height of the vibrometers 24a to 24c, a positive correlation is obtained between the corrected vibration intensity and time. On the other hand, when the height of the molten material 12 is higher than the installation height of the vibrometers 24a to 24c, a negative correlation is obtained between the corrected vibration intensity and time. Therefore, for example, if the time progression of the corrected vibration intensity shown in FIG. 3 is the corrected vibration intensity calculated from the vibration data generated by the vibrometer 24b, the height of the molten material 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 can be determined to be the installation height of the vibrometer 24b.

[0027] The change in the relationship between corrected vibration intensity and time from a positive correlation to a negative correlation means that the vibration meter has detected the phenomenon of the molten material level rising. On the other hand, when the molten material level falls, the relationship between corrected vibration intensity and time changes from a negative correlation to a positive correlation. In this case, too, the height of the molten material 12 at the time when the relationship between 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 computing device 26 monitors the time transition of the corrected vibration intensity obtained from the vibration data generated by the vibrometers 24 a to 24 c, and identifies a vibrometer in which the relationship between the corrected vibration intensity and time has changed from a positive correlation to a negative correlation, or a vibrometer in which the relationship between the corrected vibration intensity and time has changed from a negative correlation to a positive correlation. Then, upon identifying a vibrometer, the computing device 26 determines that the installation height of the identified vibrometer is the height of the molten material 12 and detects the height of the molten material 12.

[0029] On the other hand, even if it is not possible to identify a vibrometer in which the correlation between the corrected vibration intensity and time has changed from a positive correlation to a negative correlation, or a vibrometer in which the correlation between the corrected vibration intensity and time has changed from a negative correlation to a positive correlation, if there is a vibrometer in which the correlation between the corrected vibration intensity and time is positive and a vibrometer in which the correlation between the corrected vibration intensity and time is negative, the computing device 26 detects the height of the molten material 12 by determining that the height is between the installation heights of those vibrometers. In this way, the computing device 26 detects the height of the molten material 12 in the blast furnace 10 from the vibration data generated by the vibrometers 24a to 24c.

[0030] Although this embodiment includes three vibrometers 24a to 24c, the number of vibrometers is not limited to this. The smelt height detection device 22 only needs to include at least one vibrometer, and the height of the smelt 12 can be detected if the relationship between the corrected vibration intensity obtained from the vibration data generated by this vibrometer and time changes from a positive correlation to a negative correlation. However, since the height of the smelt 12 is detected based on the installation height of the vibrometer as described above, it is preferable that the smelt height detection device 22 include two or more vibrometers installed at different positions in the vertical direction of the lower part of the blast furnace 10. This allows the detection range for the height of the smelt 12 in the lower part of the blast furnace 10 to be expanded in the vertical direction.

[0031] 4 is a flowchart illustrating a method for identifying a frequency correlated with vibrations generated by introducing gas. A method for identifying a frequency correlated with vibrations generated by introducing gas through the blast tuyere 20 will be described with reference to FIG. 4. This frequency identification is preferably performed using a vibration meter 24a installed closest to the blast tuyere 20, and is preferably performed during a period when operation of the blast furnace 10 is stable. A period when operation of the blast furnace 10 is stable means a period when the coke rate in blast furnace operation is within a target range and fluctuations in permeability within the blast furnace are low.

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

[0033] FIG. 5 is a graph showing vibration data and vibration intensity data obtained by FFT processing of the vibration data. FIG. 5(a) shows the vibration data, and FIG. 5(b) shows the vibration intensity data obtained by FFT processing. In this manner, the arithmetic unit 26 converts the vibration data shown in FIG. 5(a) into the vibration intensity data shown in FIG. 5(b) by FFT processing. It is preferable that the arithmetic unit 26 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 calculates the arithmetic mean of the vibration intensities in the 1000 to 1200 kHz frequency band as the vibration intensity in the 1000 to 1200 kHz frequency band.

[0034] Returning to Fig. 4 , next, if the calculation device 26 has not acquired a plurality of pieces of vibration intensity data under conditions in which the amount of gas blown has been changed (step S103: No), the calculation device 26 changes the amount of gas blown (step S104) and repeats the processes of steps S101 and S102 again. On the other hand, if the calculation device 26 has acquired a plurality of pieces of vibration intensity data under conditions in which the amount of gas blown has been changed (step S103: Yes), the calculation device 26 calculates the coefficient of determination (R２ ) is calculated (step S105).

[0035] The coefficient of determination (R ２ ) is calculated, the calculation device 26 then 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 calculation device 26 identifies in advance the frequency correlated with the vibration generated by introducing the gas.

[0036] The frequency correlated with the vibration caused by the introduction of the gas may be identified using a plurality of vibration meters. For example, when the vibration meters 24a and 24b are used, the coefficient of determination (R ２ ) and average the coefficients of determination of the vibrometers 24a and 24b, and identify the frequency at which this average value is highest.

[0037] Furthermore, when determining the coefficient of determination between the airflow rate and the vibration intensity, the coefficient of determination (R ２ For example, the coefficient of determination may be calculated by taking into account a frequency range of ±25 Hz to ±300 Hz for each frequency. In this case, the coefficient of determination (R ２ ) and identify the frequency and frequency range where the coefficient of determination obtained by averaging these values ​​is the largest as the frequency and frequency range correlated with the vibration generated by introducing the gas. By considering a predetermined frequency range for each frequency, the coefficient of determination becomes high.

[0038] As described above, the molten material height detection method and detection device according to the first embodiment of the present invention detects the height of the molten material 12 using the vibration intensity of a frequency correlated with the vibration generated by introducing gas through the blast tuyere 20. The frequency correlated with the vibration generated by introducing gas into the inlet of the blast furnace can be easily identified by acquiring vibration data obtained by changing the blast rate, so that the frequency of the vibration intensity at which the molten material height in the blast furnace can be detected can be easily identified. Then, the molten material height inside the blast furnace, which cannot be directly observed with the naked eye, can be detected with high accuracy using a corrected vibration intensity obtained by removing the influence of the blast rate of the gas introduced through the inlet and the average particle size of the packed bed in the lower part of the furnace from the vibration intensity of the identified frequency.

[0039] It is also preferable to adjust the melt production conditions so that the melt height detected in this manner falls within a target melt height range in the blast furnace. For example, if the melt height is likely to be higher than the target range, the melt production conditions can be adjusted to reduce the amount of raw material charged or increase the amount of melt discharged. If the melt height is likely to be lower than the target range, the melt production conditions can be adjusted to increase the amount of raw material charged or decrease the amount of melt discharged. By adjusting the melt production conditions in this way so that the melt height falls within the target melt height range, for example, in a blast furnace, excessive rise in the melt level can be suppressed, and melt can be produced with a high yield while suppressing furnace cooling and damage to furnace equipment due to poor permeability.

[0040] Second Embodiment Next, a molten material height detection method and detection device according to a second embodiment of the present invention will be described with reference to Figures 6 and 7. In this embodiment, the present invention is applied to a process for detecting the height of molten metal and slag, which is molten material accumulated at the bottom of a blast furnace, which is an example of a blast furnace.

[0041] Figure 6 is a partial cross-sectional schematic diagram showing the configuration of the lower part of a blast furnace and a smelt height detection device according to a second embodiment. As shown in Figure 6, a smelt height detection device 30 according to the second embodiment of the present invention includes one vibration meter 32 and a computing device 34. In Figure 6, the same components as those in Figure 2 are designated by the same reference numerals, and their description will be omitted.

[0042] The vibrometer 32 generates vibration data by measuring the vibration of the furnace wall at the bottom of the blast furnace 10. The vibrometer 32 is configured by, for example, a piezoelectric element.

[0043] The vibration data generated by the vibration meter 32 is output to and recorded by the calculation device 34. The calculation device 34 is configured by a general-purpose computer such as a personal computer including a calculation unit such as a CPU and a storage unit such as a memory. The calculation device 34 performs frequency analysis on the vibration data acquired from the vibration meter 32 and calculates the vibration intensity of a frequency correlated with the vibration generated by introducing gas from the blast tuyere 20. In order to remove the influence of the gas blast rate and the particle size of the packed bed present in the lower part of the furnace from the calculated vibration intensity, the calculation device 34 corrects the vibration intensity to a corrected vibration intensity using the above formula (1).

[0044] 7 is a graph showing the relationship between the corrected vibration intensity and the melt height. The horizontal axis of FIG. 7 is the corrected vibration intensity (m / s ２ ), and the vertical axis represents the height (m) of the molten material. A regression equation showing the correspondence relationship between the corrected vibration intensity and the height of the molten material 12 as shown in Figure 7 is calculated in advance and stored in the computing device 34. It is preferable to create the regression equation showing the correspondence relationship between the corrected vibration intensity and the height of the molten material 12 using operational data from as long a period as possible.

[0045] After calculating the corrected vibration intensity, the calculation device 34 reads out data of the regression equation showing the correspondence relationship 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 molten material height detection method and detection device according to the second embodiment of the present invention detects the height of the molten material 12 using the vibration intensity of a frequency correlated with the vibration generated by introducing gas through the blast tuyere 20. The frequency correlated with the vibration generated by introducing gas into the inlet of the blast furnace can be easily identified by acquiring vibration data obtained by changing the blast flow rate, so the frequency of the vibration intensity at which the molten material height in the blast furnace can be detected can be easily identified. Then, by using the above-mentioned regression equation and a corrected vibration intensity obtained by removing the effects of the blast flow rate of the gas introduced through the inlet and the particle size of the packed bed present in the lower part of the furnace from the vibration intensity of the identified frequency, the molten material height inside the blast furnace, which cannot be directly observed with the naked eye, can be detected with high accuracy.

[0047] [Example 1] Next, in order to confirm the validity of the present invention, ３ This example describes Example 1, in which the height of molten material accumulated in the lower part of a large blast furnace was detected. In this example, a device having the same configuration as the molten material height detection device 22 shown in Figure 2 was used. Vibration meters 24a to 24c were installed at equal intervals between the blast tuyere 20 and the discharge hole 14 provided in the lower part of the blast furnace 10. The installation heights of the vibration meters 24a to 24c from the hearth, the heights of the blast tuyere 20, and the discharge hole 14 are shown in Table 1 below.

[0048]

[0049] FIG. 8 is a schematic diagram showing the configuration of a vibrometer and its peripheral devices according to Example 1. In FIG. 8, the same components as those in FIG. 2 are assigned the same reference numerals, and their description will be omitted. In this example, amplifiers 40a to 40c were connected to the vibrometers 24a to 24c to amplify the vibration data. The vibration data amplified by the amplifiers 40a to 40c was then stored in data loggers 42a to 42c. The vibration data stored in the data loggers 42a to 42c was then processed using the computing device 26. The vibration measurement conditions were a sampling frequency of 10,000 Hz and a recording length of 10 seconds, assuming the vibration frequency due to the air blowing measured in a blast furnace. Under these conditions, the vibration of the furnace wall was measured every three minutes for four days, and vibration data for that period was obtained.

[0050] In this example, prior to FFT analysis, the vibration data underwent overlap processing, smoothing processing, and window function processing. In the overlap processing, the raw vibration data was divided into 3 / 10 of the recording length, and processed so that half of the data overlapped. Furthermore, each divided frame was subjected to smoothing processing using a Gaussian filter. Furthermore, a Hanning window was applied in the window function processing. After processing the divided frames in this manner, FFT analysis was performed on all divided frames, and the average value of the vibration intensity calculated by FFT analysis was used.

[0051] After performing the FFT analysis, the vibration intensity for all frequency bands was calculated. In Example 1, vibrations with frequencies of 5000 Hz or less were measured using the vibration meters 24a to 24c. In order to evaluate the vibration intensity for all of these frequencies, the vibration frequency was divided into a reference vibration frequency f (Hz) and a frequency width Δf (Hz). That is, the average value of the vibration intensity for f±Δf was defined as the vibration intensity for f±Δf (Hz), and f was varied from 300 (Hz) to 4700 (Hz) in 50 (Hz) increments, and Δf was varied from 25 (Hz) to 300 (Hz) in 25 (Hz) increments to define the frequency band for f±Δf (Hz).

[0052] After calculating the vibration intensity at each frequency in this way, the coefficient of determination (R ２ In Example 1, the coefficient of determination (R ２ ) was calculated.

[0053] FIG. 9 shows the coefficient of determination (R ２ 9A is a contour diagram of the vibration meter 24a, and FIG. 9B is a contour diagram of the vibration meter 24b. In Example 1, the R ２ Therefore, f±Δf=1400±250 (Hz) was set as the frequency correlated with the vibration generated by introducing the gas.

[0054] Next, the vibration intensity was corrected for the airflow rate and the particle size of the packed layer in the lower part of the furnace by determining the regression line for the equation (1) using the vibration intensity, airflow rate, and particle size of the packed layer in the lower part of the furnace for two days out of the four days for which vibration data was measured, when the amount of accumulated molten material in the lower part of the furnace was small.

[0055] 10A and 10B are graphs showing the relationship between the vibration intensity of the vibration meters 24a to 24c and the airflow rate. FIG. 10A shows the graph and regression line of the vibration meter 24a, FIG. 10B shows the graph and regression line of the vibration meter 24b, and FIG. 10C shows the graph and regression line of the vibration meter 24c. The horizontal axis of these graphs represents the airflow rate (Nm ３ / min), the vertical axis is vibration intensity (m / s ２ ) are graphs showing the relationship between the vibration intensity of the vibration meters 24a to 24c and the particle size of the packed bed at the bottom of the furnace. FIG. 11(a) shows the graph and regression line of the vibration meter 24a, FIG. 11(b) shows the graph and regression line of the vibration meter 24b, and FIG. 11(c) shows the graph and regression line of the vibration meter 24c. The horizontal axis of these graphs represents the particle size (m) of the packed bed at the bottom of the furnace, and the vertical axis represents the vibration intensity (m / s ２ ) The slopes of these regression lines were substituted into the above formula (1) to calculate the following formulas (2), (3), and (4).

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

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

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

[0059] The corrected vibration intensity was calculated by using the above formulas (2) to (4), eliminating the influence of the blast rate and the particle size of the packed bed in the lower part of the furnace.The calculated corrected vibration intensity was then used to detect the melt height.

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

[0061] 12 shows that the corrected vibration intensity value for vibration meter 24c began to decrease from 16:30 on August 3, while it continued to increase for vibration meters 24a and 24b. Therefore, from 16:30 to 23:59 on August 3, the molten material height was between 4.8 and 5.2 m, between vibration meters 24b and 24c. Looking at the estimated molten material height values ​​calculated at the same time, it rose from approximately 4.4 m to 5.2 m between 16:30 and 23:59 on April 19. Thus, the molten material height detected from the vibration intensity and the molten material height estimated from the operational data were nearly identical, confirming that the molten material height could be detected using the method of Example 1.

[0062] Example 2 Next, Example 2 will be described, in which it was confirmed that the melt height can be detected using a single vibration meter. In Example 2, the same capacity as Example 1 was used, but the melt height was 5000 m ３ The molten material height of the large blast furnace was detected using vibration data from the vibration meter 24a. As in Example 1, the vibration data acquired from the vibration meter 24a was subjected to overlap processing, smoothing processing, and window function processing, and then FFT analysis.

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

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

[0065] In the above formula (5), h is the melt height (m), Wi (kg) is the weight of the hot metal at the hearth, and ρi (kg / m ３ ) is the density of the hot metal, Ws (kg) is the weight of the molten slag at the hearth, ρs (kg / m ３ ) is the density of the molten slag, ε(-) is the hearth void ratio, Sb(m ３ ) is the cross-sectional area of ​​the hearth. The weights of the molten pig iron and molten slag at the hearth were calculated by adding the amounts of pig iron and slag obtained at each tapping operation and subtracting the amounts of pig iron and slag produced by the amounts of tapped pig iron and slag, and correcting for the error of the weighing machine in the actual machine. In Example 2, the density of the molten pig iron was 6800 (kg / m ３ ), the molten slag density is 2650 (kg / m ３ ), and the hearth void ratio was set to 0.35. Using the corrected vibration intensity and molten material height calculated in this way, a regression equation showing the correspondence relationship between the corrected vibration intensity and the molten material height was obtained.

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

[0067] h = G ０ ×0.6953-18.486...(6)

[0068] In the above formula (6), G ０ is the corrected vibration intensity (m / s ２) The melt height was detected using this formula (6). In detecting the melt height, the melt height was calculated using the corrected vibration intensity at four points around midnight on August 3rd and the formula (6) above. In detecting the actual value of the melt height, the calculation was performed using the operational data at four points at the same time and the formula (5) above.

[0069] 14 is a graph showing the relationship between the detected melt height value calculated from the corrected vibration intensity and the actual melt height value obtained from operational data. The horizontal axis of FIG. 14 represents the detected melt height value (m) calculated from the corrected vibration intensity, and the vertical axis represents the actual melt height value (m). As shown in FIG. 14, the detected melt height value obtained from the regression equation of Equation (6) and the actual melt height value obtained from operational data were almost identical. This result confirmed that the melt height can be detected by the method of Example 2.

[0070] According to the present invention, it is possible to provide a smelt height detection method and detection device capable of detecting the smelt height inside a blast furnace with high accuracy. Also, according to the present invention, it is possible to provide a smelt manufacturing method capable of suppressing the occurrence of operational problems and manufacturing smelt with a high yield.

[0071] REFERENCE SIGNS LIST 10 Blast furnace 12 Melt 14 Discharge hole 16 Melt flow 18 Gas 20 Blast tuyeres 22 Melt height detection device 24a to 24c Vibration meters 26 Calculation device 30 Melt height detection device 32 Vibration meters 40a to 40c Amplifiers 42a to 42c Data loggers S Molten steel

Claims

1. A method for detecting the height of a molten material inside a blast furnace, comprising the steps of: measuring vibrations at at least one position on the furnace wall in the lower part of the blast furnace; analyzing the frequency of the vibrations to calculate the vibration intensity of a frequency that is correlated with the vibration generated by introducing gas into an inlet in the lower part of the furnace; and detecting the height of a molten material inside the blast furnace using a corrected vibration intensity obtained by removing the effects of the blast volume 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.

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

3. The method for detecting the height of a molten material according to claim 1 or 2, wherein the physical properties of the packed bed include at least particle size.

4. A method for detecting the height of a molten material according to any one of claims 1 to 3, wherein when the time progression of the corrected vibration intensity becomes a maximum or minimum, it is determined that the height of the molten material inside the blast furnace is the position where the vibration is being measured.

5. A method for detecting the height of a molten material according to any one of claims 1 to 4, wherein the vibration is measured at two or more different positions in the height direction of the furnace wall in the lower part of the furnace.

6. A method for detecting a molten material height according to any one of claims 1 to 5, wherein a correspondence relationship between the corrected vibration intensity and the molten material height is determined in advance, and the molten material height inside the blast furnace is detected using the corrected vibration intensity obtained from the vibration measurement and the correspondence relationship.

7. A molten material height detection device for detecting the height of a molten material inside a blast furnace, comprising: at least one vibration meter attached to a furnace wall in the lower part of the blast furnace to measure vibrations of the furnace wall; and a computing device that performs frequency analysis of the vibrations measured by the vibration meter to calculate vibration intensity of a frequency correlated with vibrations generated by introducing gas into an inlet in the lower part of the furnace, calculates the vibration intensity of the gas blast volume introduced from the inlet from the vibration intensity of the frequency, and detects the molten material height in the blast furnace using corrected vibration intensity obtained by removing the effects of the gas blast volume 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.

8. A method for producing a molten material using a blast furnace, comprising the steps of: measuring vibrations at at least one position on the furnace wall in the lower part of the blast furnace; analyzing the frequency of the vibrations to calculate the vibration intensity of a frequency correlated with the vibration generated by introducing gas into an inlet in the lower part of the furnace; detecting the molten material height inside the blast furnace using a corrected vibration intensity obtained by removing the effects of the gas flow rate 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; and adjusting the production conditions for the molten material so that the detected molten material height is within a target molten material height range.

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