METHOD FOR DETECTING MELT HEIGHT, DEVICE FOR DETECTING MELT HEIGHT, AND MELT PRODUCTION METHOD

Abstract

A method for detecting a molten material height is provided that can easily identify a frequency at which the molten material height in a blast furnace can be detected, and that can detect the molten material height using the vibration intensity of that frequency. A molten material height detection method for detecting the molten material height in a blast furnace, comprising: measuring vibrations at one or more positions on the furnace wall in the lower part of the blast furnace; analyzing the vibration frequency 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; and detecting the molten material height in the blast furnace using a corrected vibration intensity that removes the influence of the amount of gas introduced from the inlet from the vibration intensity of the frequency.

Description

[Technical field]

[0001] The present invention relates to a molten material height detection method and device for detecting the molten material height inside a blast furnace, where the inside of the furnace cannot be directly observed, from the vibrations of the blast furnace, and a molten material height detection device and a molten material manufacturing method. [Background technology]

[0002] An example of a blast furnace where the inside of the furnace cannot be seen directly is the blast furnace in the steelmaking process. A blast furnace is a facility that uses high-temperature gas to heat and react the iron ore, the raw material for iron, and the coke, the fuel, to produce pig iron. The molten pig iron and slag produced in the blast furnace accumulate as a liquid pool at the bottom, and are discharged from the furnace approximately once every three hours to be supplied to the next process.

[0003] In blast furnace operation, if there is a heat shortage or the particle size of the packed bed at the bottom of the blast furnace decreases, the resistance to the passage of molten material increases, and the amount of molten material discharged outside the furnace may decrease. As a result, the liquid level of the molten material increases, causing the gas permeability inside the blast furnace to deteriorate, resulting in furnace cooling and damage to the furnace body equipment. This may ultimately lead to the blast furnace being forced to stop operating, and there is a concern that the production volume of steel products will decrease significantly throughout the steelworks. Due to these concerns, it is essential to constantly monitor the amount of molten material accumulated inside the blast furnace and detect blast furnace troubles early.

[0004] There is a technology that measures the liquid level of the molten material in a blast furnace to detect excessive accumulation. Patent Document 1 discloses a technology that takes two or more images of the discharge flow of the molten material from the blast furnace to determine the discharge speed, and calculates the molten material height by substituting the discharge speed into an energy balance equation. Patent Document 2 discloses a technology that inputs an elastic wave into the blast furnace and measures the molten material height from the wave height of the reflected echo. Patent Document 3 discloses a technology that measures the vibration intensity of the furnace wall at the bottom of the blast furnace, analyzes the frequency of the vibration intensity to calculate the vibration intensity of a frequency band that is correlated with the fluctuation of the molten metal and slag height, and calculates the height of the molten metal and slag in the blast furnace using the intensity of the calculated frequency band. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2017-160498 A [Patent Document 2] Japanese Patent Application Publication No. 10-185654 [Patent Document 3] International Publication No. 2022 / 201717 Summary of the Invention [Problem to be solved by the invention]

[0006] The technology of Patent Document 1 utilizes the positive correlation between the discharge speed of the molten material and the height of the molten material, so there is a problem that when the discharge speed of the molten material decreases due to clogging of the discharge hole, the rise in the liquid level cannot be detected. In addition, the visibility around the discharge hole is poor due to dust in the factory, and the molten material may violently erupt from the discharge hole. In such cases, there is a problem that the discharge flow surface cannot be accurately photographed, and the liquid level of the molten material cannot be calculated.

[0007] In the technology of Patent Document 2, it is predicted that there are many factors that affect the reflection characteristics of elastic waves, such as crack development in the furnace wall bricks that constitute the blast furnace and solidification of the molten material in the furnace, and there is a possibility that the molten material height cannot be measured accurately. In the technology of Patent Document 3, since the molten metal and slag height in an actual blast furnace is unknown, it is difficult to identify a frequency band that is correlated with the fluctuation of the molten metal and slag height. The present invention has been made in consideration of these circumstances, and its purpose is to provide a molten material height detection method and a molten material height detection device that can easily identify a frequency at which the molten material height in a blast furnace can be detected and that can detect the molten material height using the vibration intensity of the frequency. [Means for solving the problem]

[0008] The gist of the present invention that can solve the above problems is as follows. [1] A molten material height detection method for detecting a molten material height in a blast furnace, comprising: measuring vibrations at one or more positions on a furnace wall in a lower part of the blast furnace; analyzing the frequency of the vibrations to calculate a vibration intensity of a frequency correlated with vibrations generated by introducing gas into an inlet in the lower part of the furnace; and detecting the molten material height using a corrected vibration intensity obtained by removing the influence of the amount of gas introduced from the inlet from the vibration intensity of the frequency. [2] The method for detecting the height of a molten material described in [1], wherein a frequency correlated with the vibration generated by introducing gas into the inlet is identified by confirming the correlation between the vibration intensity of a frequency band having a predetermined width and the volume of the gas blown. [3] A molten material height detection method according to [1] or [2], in which, when the time progression of the corrected vibration intensity becomes a maximum or minimum, it is detected that the molten material height in the blast furnace is the position where the vibration is being measured. [4] A method for detecting a molten material height according to any one of [1] to [3], 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. [5] A smelt height detection method according to [1] or [2], in which a correspondence relationship between the corrected vibration intensity and the smelt height is determined in advance, and the smelt height in a blast furnace is detected using the corrected vibration intensity obtained from the vibration measurement and the correspondence relationship. [6] A method for detecting the height of a molten material described in [5], in which the vibration is measured at a position of 0.90 or more and 1.00 or less in the height direction of the furnace wall at the lower part of the furnace, where the upper end position of the discharge hole is 0 and the lower end position of the inlet is 1. [7] A smelt height detection device for detecting a smelt height in a blast furnace, comprising: one or more vibration meters provided on a furnace wall in the lower part of the blast furnace for measuring vibration of the furnace wall; and a calculation device for performing frequency analysis of the vibrations measured by the vibration meters to calculate vibration intensity of a frequency correlated with vibration generated by introducing gas into an inlet in the lower part of the furnace, and detecting the smelt height using a corrected vibration intensity that removes the influence of the amount of gas introduced from the inlet from the vibration intensity. [8] A molten material height detection device as described in [7], comprising two or more vibration meters, the two or more vibration meters being provided at two or more different positions in the height direction of the furnace wall in the lower part of the furnace. [9] The melt height detection device according to [7], wherein the calculation device detects the melt height using a correspondence relationship between the corrected vibration intensity and the melt height.

[10] The molten material height detection device described in [9], wherein, in the height direction of the furnace wall at the lower part of the furnace, when the upper end position of the discharge hole is 0 and the lower end position of the inlet is 1, the vibration meter is provided at a position between 0.90 and 1.00.

[11] A method for producing a molten material using a blast furnace, comprising: measuring vibrations at one or more positions on a furnace wall in a lower part of the blast furnace; analyzing the frequency of the vibrations to calculate a vibration intensity of a frequency correlated with vibrations generated by introducing gas into an inlet in the lower part of the furnace; detecting a molten material height in the blast furnace using a corrected vibration intensity obtained by removing the influence of the amount of gas introduced from the inlet from the vibration intensity of the frequency; and adjusting production conditions for the molten material so that the detected molten material height is within a range of a target molten material height.

[12] The method for producing a molten material described in

[11] , further comprising determining a correspondence relationship between the corrected vibration intensity and the molten material height in advance, and detecting the molten material height using the corrected vibration intensity obtained by measuring the vibration and the correspondence relationship. Effect of the Invention

[0009] According to the present invention, the frequency of vibration intensity at which the molten material height in a blast furnace can be detected is obtained by identifying a frequency that is correlated with the vibration generated by introducing gas into the inlet of the blast furnace, so that the frequency of vibration intensity at which the molten material height in a blast furnace can be detected can be easily identified. Then, the molten material height in a blast furnace, whose interior cannot be directly observed with the naked eye, can be detected with high accuracy by using a corrected vibration intensity that removes the influence of the amount of gas blown into the inlet from the vibration intensity of the identified frequency. [Brief description of the drawings]

[0010] [Figure 1]FIG. 1 is a schematic partial cross-sectional view of a lower part of a blast furnace 10. As shown in FIG. [Diagram 2] FIG. 2 is a partial cross-sectional schematic diagram showing the lower part of the blast furnace 10 and a molten material height detection device 22 according to the first embodiment. [Diagram 3] FIG. 3 is a graph showing the change over time in the corrected vibration strength. [Figure 4] FIG. 4 is a flow diagram illustrating a method for identifying a frequency correlated with vibrations generated by introducing a gas. [Diagram 5] FIG. 5 is a graph showing vibration data and vibration intensity data obtained by subjecting the vibration data to FTT processing. [Figure 6] FIG. 6 is a partial cross-sectional schematic diagram showing a lower part of a blast furnace 10 and a molten material height detection device 30 according to a second embodiment. [Figure 7] FIG. 7 is a graph showing the relationship between corrected vibration intensity and melt height. [Figure 8] FIG. 8 is a schematic diagram showing the configuration of the vibrometer of the first embodiment and its peripheral devices. [Figure 9] FIG. 9 is a contour diagram showing the coefficient of determination (R2) between the vibration intensity and the airflow volume calculated from the measurements of the vibration meters 24a and 24b. [Figure 10] FIG. 10 is a graph showing the relationship between the vibration intensity of the vibration meters 24a to 24c and the airflow rate. [Figure 11] FIG. 11 is a graph showing the time course of the molten height and the time course of the corrected vibration intensity obtained from the operational data. [Figure 12] FIG. 12 is a graph showing a regression equation between corrected vibration intensity and melt height. [Figure 13] FIG. 13 is a graph showing the relationship between the detected value of the molten material height calculated from the corrected vibration intensity and the actual value of the molten material height obtained from the operational data. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] [First embodiment] Hereinafter, a first embodiment of the present invention will be described using a blast furnace, which is an example of a blast furnace, and an example of detecting the height of molten pig iron and slag, which is a molten material accumulated in the hearth of the blast furnace. FIG. 1 is a partial cross-sectional schematic diagram of a lower part of a blast furnace 10. Molten pig iron and slag (hereinafter, the molten pig iron and slag will be referred to as "molten material 12") are accumulated in the lower part of the blast furnace 10. The molten material 12 is discharged from a discharge hole 14, and a molten material flow 16 is generated. In addition, a blast tuyere 20 for introducing a gas 18 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 furnace.

[0012] 2 is a partial cross-sectional schematic diagram showing the lower part of the blast furnace 10 and a smelt height detection device 22 according to the first embodiment. The smelt height detection device 22 has, for example, three vibration meters 24a to 24c and a computing device 26. The three vibration meters 24a to 24c are provided on the furnace wall between the discharge hole 14 and the blast tuyere 20 at equal intervals in the height direction, and measure the vibration of the furnace wall to generate vibration data. The vibration meters 24a to 24c are, for example, piezoelectric elements.

[0013] The vibration data generated by the vibration meters 24a to 24c is output to and recorded in the calculation device 26. The calculation device 26 is a general-purpose computer such as a personal computer having 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 correlated with the vibration generated by introducing gas from the blower tuyere 20.

[0014] In order to remove the influence of the airflow rate from the calculated vibration strength, the calculation device 26 corrects the vibration strength to a corrected vibration strength using the following formula (1). By correcting the vibration strength to the corrected vibration strength in this manner, the influence of fluctuations in the airflow rate on the vibration strength can be removed.

[0015] G 0 =G+(BV 0 -BV) × a (1) In the above formula (1), G 0 is the corrected vibration intensity (m / s 2) and G is the vibration intensity before correction (m / s 2 ) and BV 0 is the standard airflow rate (Nm 3 / min), and BV is the airflow (Nm 3 / min), and a is the slope of the regression line when the vibration intensity of the frequency correlated with the vibration caused by air blowing is on the y-axis and the air blowing volume is on the x-axis.

[0016] FIG. 3 is a graph showing the time transition of the corrected vibration intensity. In FIG. 3, the horizontal axis is time, and the vertical axis is corrected vibration intensity. The corrected vibration intensity has a positive correlation with the height of the melt 12 when the height of the melt 12 is lower than the installation height of the vibration meter. On the other hand, the corrected vibration intensity has a negative correlation with the melt height when the height of the melt 12 is higher than the installation height of the vibration meter. Therefore, for example, if the time transition 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, the height of the melt 12 at the time when the corrected vibration intensity changes from a positive correlation to a negative correlation and becomes a maximum is the installation height of the vibration meter 24b.

[0017] The change in the corrected vibration intensity from positive to negative correlation is the result of the vibration meter capturing the phenomenon of the liquid level of the molten material rising. On the other hand, when the liquid level of the molten material, which is located higher than the installation position of the vibration meter, falls, the corrected vibration intensity also changes from positive to negative correlation. In this case, too, the height of the molten material 12 at the time when the corrected vibration intensity changes from positive to negative correlation and reaches its maximum is the installation height of the vibration meter.

[0018] The computing device 26 monitors the time transition of the corrected vibration intensity obtained from the vibration data generated by the vibrometers 24a to 24c, and identifies a vibrometer whose corrected vibration intensity has changed from a positive correlation to a negative correlation. When the computing device 26 identifies a vibrometer, the computing device 26 detects the height of the molten material 12 assuming that the installation height of the identified vibrometer is the height of the molten material 12. On the other hand, even if the computing device 26 cannot identify a vibrometer whose corrected vibration intensity has changed from a positive correlation to a negative correlation, if there is a vibrometer whose corrected vibration intensity shows a positive correlation and a vibrometer whose corrected vibration intensity shows a negative correlation, the computing device 26 detects the height of the molten material 12 assuming that the height is between the installation heights of the 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.

[0019] The molten material height detection device 22 according to the present embodiment has three vibrometers 24a to 24c, but is not limited thereto. The molten material height detection device 22 only needs to have at least one vibrometer, and the height of the molten material 12 can be detected if the corrected vibration intensity obtained from the vibration data generated by this vibrometer changes from a positive correlation to a negative correlation. However, since the height of the molten material 12 is detected depending on the installation height of the vibrometer as described above, it is preferable that the molten material height detection device 22 has two or more vibrometers installed at different positions in the height direction of the lower part of the blast furnace 10. This makes it possible to expand the detection range of the height of the molten material 12 in the lower part of the blast furnace 10 in the height direction.

[0020] FIG. 4 is a flow diagram for explaining a method for identifying a frequency correlated with vibrations caused by introducing gas. A method for identifying a frequency correlated with vibrations caused by introducing gas from the blast tuyere 20 will be explained with reference to FIG. 4. This frequency is preferably identified using a vibration meter 24a installed at a position closest to the blast tuyere 20, and is preferably identified during a period when the operation of the blast furnace 10 is stable. The period when the operation of the blast furnace 10 is stable means a period when the coke ratio in the blast furnace operation is within a target range and the fluctuation in the permeability inside the blast furnace is low.

[0021] First, the vibration meter 24a measures the vibration of the lower part of the blast furnace 10 to generate vibration data (step S101). FFT processing (step S102) is performed on the vibration data to perform frequency analysis of the vibration data. Note that overlap processing, smoothing processing, and window function processing may be performed on the vibration data before FFT processing as necessary.

[0022] 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. In this way, the vibration data shown in Fig. 5(a) is converted into the vibration intensity data shown in Fig. 5(b) by FFT processing. It is preferable to use this vibration intensity data to calculate the vibration intensity at all frequencies.

[0023] The vibration intensity may be the vibration intensity in a frequency band having a predetermined width around the target frequency. For example, if the predetermined width is ±100 Hz, the vibration intensity at a frequency of 1100 Hz is the arithmetic mean value of the vibration intensity of each frequency present in the range of 1000 to 1200 Hz. The interval between frequencies present in the frequency band is arbitrarily set by FFT processing of the vibration data. For example, if the sampling frequency of the vibrometer is 10000 Hz and the recording length is 10 sec, the frequency interval is 3.3 Hz.

[0024] Referring again to FIG. 4, if the vibration intensity data has not been acquired multiple times under conditions with different airflow rates (step S103: No), the airflow rate is changed (step S104), and the processes of steps S101 and S102 are repeated again. On the other hand, if the vibration intensity data has been acquired multiple times under conditions with different airflow rates (step S103: Yes), the coefficient of determination (R 2 ) is calculated (step S105).

[0025] The coefficient of determination (R 2), the frequency with the largest coefficient of determination is identified as the frequency correlated with the vibration caused by the introduction of gas (step S106). In this way, the frequency correlated with the vibration caused by the introduction of gas is identified in advance.

[0026] In addition, 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 meter 24a and the vibration meter 24b are used, the coefficient of determination (R 2 ) and average the coefficients of determination of the vibration meters 24a and 24b, and identify the frequency at which this average value is largest.

[0027] Furthermore, when calculating the coefficient of determination between the airflow rate and 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 at which the average value of these coefficients of determination is the largest as the frequency correlated with the vibration caused by the introduction of gas. In this way, by considering a predetermined frequency width for each frequency, the difference in the coefficients of determination at each frequency becomes large, making it easier to identify the frequency with a large coefficient of determination.

[0028] In this way, in the molten material height detection method and detection device according to the first embodiment, the height of the molten material 12 is detected using the vibration intensity of a frequency correlated with the vibration generated by introducing gas from 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 with different blast volumes, 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 in a blast furnace, whose interior cannot be directly observed with the naked eye, can be detected with high accuracy using a corrected vibration intensity that removes the influence of the blast volume of the gas introduced from the inlet from the vibration intensity of the identified frequency.

[0029] It is also preferable to adjust the melt production conditions so that the melt height detected in this way falls within a range of the target melt height in the blast furnace. For example, if the melt height is likely to be higher than the target range, the melt production conditions may 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 may be adjusted to increase the amount of raw material charged or decrease the amount of melt discharged. In this way, by adjusting the melt production conditions so that the melt height falls within the target melt height range, for example, in a blast furnace, an excessive rise in the melt level is suppressed, and the melt can be produced while suppressing furnace cooling and damage to furnace body equipment due to deterioration of permeability.

[0030] [Second embodiment] Next, a second embodiment of the present invention will be described using an example of detecting the height of molten material 12 accumulated in the hearth of a blast furnace 10, which is an example of a blast furnace, in the same manner as in the first embodiment. FIG. 6 is a partial cross-sectional schematic diagram showing a lower part of the blast furnace 10 and a molten material height detection device 30 according to the second embodiment. The molten material height detection device 30 has one vibration meter 32 and a calculation device 34. In the example shown in FIG. 6, the same components as those in FIG. 2 are given the same reference numbers, and their description will be omitted.

[0031] The vibration meter 32 measures the vibration of the furnace wall at the bottom of the furnace to generate vibration data. The vibration meter 32 is, for example, a piezoelectric element.

[0032] The vibration data generated by the vibration meter 32 is output to and recorded by the calculation device 34. The calculation device 34 is also a general-purpose computer such as a personal computer having 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 obtained from the vibration meter 32, and calculates the vibration intensity of a frequency correlated with the vibration generated by introducing gas from the blower tuyere 20. In order to remove the influence of the blowing volume from the calculated vibration intensity, the calculation device 34 corrects the vibration intensity to a corrected vibration intensity using the above formula (1).

[0033] FIG. 7 is a graph showing the relationship between the corrected vibration intensity and the melt height. In FIG. 7, the horizontal axis 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 Fig. 7 is determined 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 operation data from as long a period as possible.

[0034] After calculating the corrected vibration intensity, the calculation device 34 reads out the regression equation showing the correspondence relationship between the corrected vibration intensity and the height of the molten material shown in Fig. 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 according to the second embodiment detects the height of the molten material 12 in the blast furnace 10.

[0035] The vibration meter 32 is preferably installed at a position close to the blast tuyere 20. This makes it easier for the vibration meter 32 to detect vibrations caused by the blast. In the height direction of the furnace wall at the lower part of the blast furnace 10, when the upper end position of the discharge hole 14 is 0 and the lower end position of the blast tuyere 20 is 1, the vibration meter 32 is preferably installed at a position of 0.90 to 1.00, more preferably at a position of 0.95 to 1.00, and even more preferably at the position of 1.00. If the vibration meter 32 is installed at a position higher than the lower end position of the blast tuyere 20, the vibration measured by the vibration meter 32 is affected by the vibration caused by the descent of the raw materials in the blast furnace, which is not preferable.

[0036] As described above, in the smelt height detection method and detection device according to the second embodiment, the height of the smelt 12 is detected using the vibration intensity of a frequency correlated with the vibration generated by introducing gas from 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 with different blast volumes, so that the frequency of the vibration intensity at which the smelt height in the blast furnace can be detected can be easily identified. Then, by using the above regression equation and a corrected vibration intensity that removes the influence of the blast volume of the gas introduced from the inlet from the vibration intensity of the identified frequency, the smelt height in a blast furnace, whose interior cannot be directly observed, can be detected with high accuracy. EXAMPLES

[0037] [Example 1] Next, in order to confirm the validity of the present invention, 3 Example 1 will be described, 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 Fig. 2 was used. The 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 bottom, and the heights of the blast tuyere and the discharge hole are shown in Table 1 below.

[0038] [Table 1]

[0039] FIG. 8 is a schematic diagram showing the configuration of the vibration meter and its peripheral devices of the first embodiment. In FIG. 8, the same components as those in FIG. 2 are given the same reference numbers, and the description thereof will be omitted. Amplifiers 40a to 40c for amplifying vibration data were connected to the vibration meters 24a to 24c. The vibration data amplified by the amplifiers 40a to 40c was stored in the data loggers 42a to 42c. The vibration data stored in the data loggers 42a to 42c was processed using the arithmetic unit 26. The conditions for measuring vibration were a sampling frequency of 10000Hz and a recording length of 10sec, assuming the vibration frequency derived from the air blowing measured in a blast furnace. Under these conditions, the vibration of the furnace wall was measured every 3 minutes for 4 days, and vibration data for that period was obtained.

[0040] 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 vibration data was divided into 3 / 10 of the recording length, and half of the data was processed so as to overlap. Each divided frame was subjected to smoothing processing using a Gaussian filter. In addition, a Hanning window was applied in the window function processing. After processing the divided frames in this way, an FFT analysis was performed and the average value of the vibration intensity calculated by FFT analyzing all the divided frames was used.

[0041] After performing FFT analysis, the vibration intensity of all frequencies was calculated. At this time, the frequency interval was 3.3 Hz. In Example 1, vibrations having frequencies of 5000 Hz or less were measured by the vibration meters 24a to 24c. In order to evaluate the vibration intensity of all these frequencies, the frequency of the vibration was divided into a reference vibration frequency f (Hz) and a frequency width Δf (Hz). That is, the average value of the vibration intensity of each frequency included in the frequency band f±Δf was taken as the vibration intensity of the reference vibration frequency f (Hz) considering the frequency width Δf (Hz), and f was changed from 300 Hz to 4700 Hz in 50 Hz increments, and Δf was changed from 25 Hz to 300 Hz in 25 Hz increments.

[0042] In this way, after calculating the vibration intensity at each frequency, the coefficient of determination (R 2 In Example 1, the coefficient of determination (R 2 ) was calculated.

[0043] FIG. 9 shows the coefficient of determination (R 2 9(a) is a contour diagram of the vibration meter 24a, and FIG. 9(b) is a contour diagram of the vibration meter 24b. In the first embodiment, R 2 Therefore, taking into account Δf = 250 Hz, f = 1400 Hz was set as the frequency correlated with the vibration generated by introducing gas.

[0044] Next, the vibration intensity was corrected for the airflow volume by calculating the regression line for the above formula (1) using the vibration intensity and airflow volume 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.

[0045] FIG. 10 is a graph showing the relationship between the vibration intensity of the vibration meters 24a to 24c and the airflow rate. FIG. 10(a) shows the graph of the vibration meter 24a and the regression line, FIG. 10(b) shows the graph of the vibration meter 24b and the regression line, and FIG. 10(c) shows the graph of the vibration meter 24c and the regression line. The horizontal axis of these graphs represents the airflow rate (Nm 3 / min, and the vertical axis is 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) to (4) for correcting the vibration intensity to a corrected vibration intensity.

[0046] G 0 =G+(BV-BV 0 )×2.00×10 -3 (2)

[0047] G 0 =G+(BV-BV 0 )×1.72×10 -3 (3)

[0048] G 0 =G+(BV-BV 0 )×1.04×10 -3 (4)

[0049] The corrected vibration intensity was calculated by removing the influence of the air flow rate using the above formulas (2) to (4). The calculated corrected vibration intensity was used to detect the molten material height.

[0050] FIG. 11 is a graph showing the time progression of the molten height and the time progression of the corrected vibration intensity obtained from the operational data. FIG. 11(a) is a graph showing the time progression of the molten height obtained from the operational data, with the horizontal axis representing time and the vertical axis representing the molten height (m). FIG. 11(b) to (d) are graphs showing the time progression 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 ).

[0051] As shown in FIG. 11, the corrected vibration intensity value for the vibration meter 24c has been decreasing since 16:30 on 4 / 19, but continues to increase for the vibration meters 24a and 24b. Therefore, it can be seen that the molten material height is between 4.8 and 5.2 m between the vibration meters 24b and 24c from 16:30 to 23:59 on 4 / 19. Looking at the molten material height value estimated and calculated at the same time, it rose from about 4.4 m to 5.2 m from 16:30 to 23:59 on 4 / 19. In this way, the molten material height detected from the vibration intensity and the molten material height value 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.

[0052] [Example 2] Next, a second embodiment will be described, in which it was confirmed that the melt height can be detected using a single vibration meter. In the second embodiment, the same capacity as in the first embodiment was 5000m 3The molten material height of the large blast furnace was detected using vibration data from the vibration meter 24a. The vibration data acquired from the vibration meter 24a was subjected to overlap processing, smoothing processing, and window function processing in the same manner as in Example 1, and then FFT analysis was performed.

[0053] The frequency correlated with the vibration caused by the air blowing was set to f=1400Hz considering Δf=250Hz as in Example 1. The vibration intensity of the frequency from 00:00 to 23:59 on 4 / 19 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 00:00 to 23:59 on 4 / 19 and the following formula (5).

[0054] h=(Wi / ρi+Ws / ρs) / (ε×Sb)···(5)

[0055] In the above formula (5), h is the height of the molten material (m), Wi is the weight of the molten iron at the hearth (kg), and ρi is the density of the molten iron (kg / m 3 ), Ws is the weight of the molten slag at the hearth (kg), and ρs is the density of the molten slag (kg / m 3 ), ε is the hearth void ratio (-), and Sb is the hearth cross-sectional area (m 3 ). (-) means dimensionless.

[0056] The weights of the molten pig iron and molten slag in the hearth were calculated by adding up the amounts of pig iron and slag obtained in each tapping operation and subtracting the amounts of pig iron and slag produced by the amounts of tapping operation, and correcting the error of the weighing machine in the actual machine. 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 the molten material height calculated in this manner, a regression equation showing the correspondence relationship between the corrected vibration intensity and the molten material height was obtained.

[0057] FIG. 12 is a graph showing a regression equation between corrected vibration intensity and molten height. In FIG. 12, the horizontal axis is the corrected vibration intensity (m / s 2) and the vertical axis is the melt height (m). The regression equation shown in Figure 12 is the calibration curve for detecting the melt height from the corrected vibration intensity. The regression equation obtained from the graph in Figure 12 is the following equation (6).

[0058] h=G 0 ×0.6953-18.486···(6)

[0059] In the above formula (6), G 0 is the corrected vibration intensity (m / s 2 ) The molten material height was detected using this formula (6). The molten material height was calculated using the corrected vibration intensity at four points around midnight on August 31st and the above formula (6). The actual molten material height was calculated using the operational data at four points for the same time and the above formula (5).

[0060] Fig. 13 is a graph showing the relationship between the detected value of the molten material height calculated from the corrected vibration intensity and the actual value of the molten material height calculated from the operational data. In Fig. 13, the horizontal axis represents the detected value of the molten material height (m) calculated from the corrected vibration intensity, and the vertical axis represents the actual value of the molten material height (m). As shown in Fig. 13, the detected value of the molten material height calculated from the regression equation (6) and the actual value of the molten material height calculated from the operational data were almost the same. From this result, it was confirmed that the molten material height can be detected by the method of Example 2. [Explanation of symbols]

[0061] 10 blast furnace 12 Melt 14 Discharge hole 16 Melt flow 18 Gas 20 Blow hole 22 Melt height detection device 24a~24c Vibration meter 26 Arithmetic unit 30 Melt height detection device 32 Vibration meter 40a~40c amplifier 42a~42c Data logger

Claims

1. A method for detecting a smelt height in a blast furnace, comprising: measuring vibrations at one or more positions on a furnace wall in a lower portion of the blast furnace; Analyzing the frequency of the vibration to calculate a vibration intensity of a frequency correlated with vibration generated by introducing a gas into the inlet of the lower part of the furnace; The molten material height detection method includes detecting the molten material height using a corrected vibration intensity obtained by removing an effect of an amount of gas blown through the inlet from the vibration intensity of the frequency.

2. 2. The molten material height detection method according to claim 1, wherein the frequency correlated with the vibration generated by introducing gas into the inlet is identified by checking the correlation between the vibration intensity of a frequency band having a predetermined width and the volume of the gas blown.

3. 3. The method for detecting a smelt height according to claim 1, further comprising the step of detecting, when the time transition of the corrected vibration intensity becomes a maximum, the smelt height in the blast furnace is detected as being at a position where the vibration is being measured.

4. 3. 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.

5. A correspondence relationship between the corrected vibration intensity and the molten material height is obtained in advance, 3. The method for detecting a smelt height according to claim 1, further comprising the step of detecting a smelt height in a blast furnace using a corrected vibration intensity obtained from the vibration measurement and said correspondence relationship.

6. 6. The method for detecting a molten material height according to claim 5, wherein the vibration is measured at a position of 0.90 or more and 1.00 or less in the height direction of the furnace wall in the lower part of the furnace, where the upper end position of the discharge hole is 0 and the lower end position of the inlet is 1.

7. A molten material height detection device for detecting the molten material height of a blast furnace, One or more vibration meters are 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 vibration measured by the vibration meter, calculates a vibration intensity of a frequency that is correlated with the vibration generated by introducing a gas into the inlet at the lower part of the furnace, and detects the height of the molten material using a corrected vibration intensity obtained by removing the influence of the amount of gas introduced from the inlet from the vibration intensity of the frequency; A melt height detection device having a

8. Two or more of the vibration meters are provided, 8. The molten material height detection device according to claim 7, wherein the two or more vibration meters are provided at two or more different positions in a height direction of the furnace wall in the lower part of the furnace.

9. The melt height detection device according to claim 7 , wherein the calculation device detects the melt height using a correspondence relationship between the corrected vibration intensity and the melt height.

10. The molten material height detection device according to claim 9, wherein, in the height direction of the furnace wall in the lower part of the furnace, the upper end position of the discharge hole is set to 0 and the lower end position of the inlet is set to 1, and the vibration meter is provided at a position of 0.90 or more and 1.00 or less.

11. A method for producing a molten material using a blast furnace, comprising the steps of: measuring vibrations at one or more positions on a furnace wall in a lower portion of the blast furnace; Analyzing the frequency of the vibration to calculate a vibration intensity of a frequency correlated with vibration generated by introducing a gas into the inlet of the lower part of the furnace; Detecting the molten material height of the blast furnace using a corrected vibration intensity obtained by removing the influence of the amount of gas introduced from the inlet from the vibration intensity of the frequency; A method for producing a melt, comprising adjusting production conditions for the melt so that the detected melt height falls within a range of a target melt height.

12. A correspondence relationship between the corrected vibration intensity and the molten material height is obtained in advance, The method for producing a melt according to claim 11, further comprising the step of detecting the melt height using a corrected vibration intensity obtained from the vibration measurement and the correspondence relationship.