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

Abstract

Provided is a molten material height detection method with higher detection accuracy than conventional methods.　This molten material height detection method detects a molten material height in a blast furnace. In said method, vibrations are measured at one or more positions on a furnace wall in a lower part of the blast furnace; the vibration intensity of a frequency which is correlated with vibration generated by introducing a gas into an inlet in the lower part of the furnace is identified by analyzing the frequencies of the vibrations; and the height of the molten material is detected using corrected vibration intensities obtained by removing the influence of the wind speed of the gas in the inlet from the vibration intensities of the frequencies.

Description

Method for detecting molten material height, apparatus for detecting molten material height, and method for manufacturing molten material

[0001] The present invention relates to a method for detecting the height of molten material in a blast furnace where the inside of the furnace cannot be directly visually inspected, a device for detecting the height of molten material, and a method for manufacturing molten material.

[0002] One example of a blast furnace where the inside cannot be directly observed is the blast furnace in the steelmaking process. A blast furnace is a facility that produces pig iron by heating and reacting iron ore, the raw material for iron, and coke, the fuel, with high-temperature gas. The molten pig iron and slag produced in the blast furnace are accumulated in a liquid reservoir at the bottom and are discharged out of the furnace approximately once every three hours and supplied to the next process.

[0003] During blast furnace operation, insufficient heat in the furnace or a decrease in the particle size of the packed bed at the bottom of the furnace can increase the resistance to molten material flow, reducing the amount of molten material discharged from the furnace. As a result, the molten material level rises, leading to poor ventilation of the blast furnace gases, which can cause damage to furnace cooling and furnace equipment. Ultimately, this can force the blast furnace to shut down, raising concerns about a significant decrease in steel product production across the entire steelworks. For these reasons, it is essential to constantly monitor the amount of molten material accumulating in the blast furnace to detect blast furnace problems early.

[0004] Techniques exist for detecting excessive accumulation of molten material by measuring the liquid level of molten material inside a blast furnace. Patent Document 1 discloses a technique for calculating the molten material height by taking two or more photographs of the molten material discharge flow from the blast furnace to determine the discharge velocity and substituting the discharge velocity into an energy balance formula. Patent Document 2 discloses a technique for detecting the height of molten iron slag in a blast furnace from the vibration intensity of the furnace wall generated by introducing gas into the inlet at the bottom of the blast furnace. According to Patent Document 2, the frequency of the vibration intensity is analyzed to identify a frequency band correlated with fluctuations in the airflow rate, and the height of molten iron slag in the blast furnace can be detected using the vibration intensity in the identified frequency band.

[0005] Japanese Patent Publication No. 2017-160498, Japanese Patent Publication No. 7485247

[0006] The technology described in Patent Document 1 utilizes a positive correlation between the discharge rate of the molten material and the height of the molten material. However, it has the problem that it cannot detect a rise in the liquid level when the discharge rate of the molten material decreases due to a clogged discharge hole. Visibility around the discharge hole is poor due to dust in the factory, and furthermore, the molten material may be violently ejected from the discharge hole. In such cases, it is not possible to accurately photograph the discharge flow surface, and therefore it is not possible to calculate the liquid level of the molten material.

[0007] In the technology disclosed in Patent Document 2, the influence of the gas flow rate is removed from the vibration intensity when determining the corrected vibration intensity. However, the depth of the raceway formed at the tuyeres, which are the source of furnace vibration, is more greatly influenced by the gas velocity at the tuyeres than by the gas flow rate. For this reason, the technology disclosed in Patent Document 2, which corrects the vibration intensity using the gas flow rate, has the problem of low accuracy in correcting the vibration intensity and low accuracy in detecting the molten material height.

[0008] This invention has been made in view of these circumstances, and its purpose is to provide a method and apparatus for detecting molten material height with higher detection accuracy than conventional methods.

[0009] The gist of the present invention, which can solve the above problems, is as follows: [1] A method for detecting the height of molten material in a blast furnace, comprising: measuring vibration at one or more positions on the furnace wall in the lower part of the blast furnace; analyzing the frequency of the vibration to identify the vibration intensity of a frequency correlated with the vibration generated by introducing gas into the inlet in the lower part of the furnace; and detecting the height of the molten material using a corrected vibration intensity obtained by removing the effect of the wind speed of the gas at the inlet from the vibration intensity of the frequency. [2] The method for detecting the height of molten material according to [1], wherein the frequency correlated with the vibration generated by introducing the gas into the inlet is identified by confirming the correlation between the vibration intensity of a frequency band having a predetermined width and the wind speed of the gas. [3] The method for detecting the height of molten material according to [1] or [2], wherein when the corrected vibration intensity becomes maximum, the position where the vibration of the maximum corrected vibration intensity is being measured is detected to be the height of the molten material in the blast furnace. [4] A method for detecting the height of molten material 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 method for detecting the height of molten material according to [1] or [2], wherein the correspondence between the corrected vibration intensity and the height of molten material is determined in advance, and the height of molten material in the blast furnace is detected using the corrected vibration intensity obtained from the measurement of the vibration and the correspondence. [6] A device for detecting the height of molten material in a blast furnace, comprising: one or more vibration meters provided on the furnace wall in the lower part of the blast furnace for measuring the vibration of the furnace wall; and a calculation device that performs frequency analysis on the vibration measured by the vibration meters to identify vibration intensity at frequencies correlated with vibrations generated by introducing gas into the inlet in the lower part of the furnace, and detects the height of molten material using corrected vibration intensity obtained by removing the effect of the wind speed of the gas at the inlet from the vibration intensity at the frequencies. [7] The molten material height detection device according to [6], comprising two or more vibration meters, wherein the two or more vibration meters are provided at two or more different positions in the height direction of the furnace wall in the lower part of the furnace. [8] The molten material height detection device according to [6], wherein the calculation device detects the molten material height using the correspondence between the corrected vibration intensity and the molten material height.[9] A method for manufacturing a molten material using 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 frequency of the vibrations to identify vibration intensities of frequencies correlated with vibrations generated by introducing gas into the inlet in the lower part of the furnace; detecting the height of the molten material in the blast furnace using a corrected vibration intensity obtained by removing the effect of the wind speed of the gas at the inlet from the vibration intensities of the frequencies; and adjusting the manufacturing conditions of the molten material so that the detected height of the molten material falls within a range of a target height of the molten material.

[10] The method for manufacturing a molten material according to [9], wherein the correspondence between the corrected vibration intensity and the height of the molten material is determined in advance, and the height of the molten material is detected using the corrected vibration intensity obtained from the measurement of the vibrations and the correspondence.

[0010] According to the present invention, since the gas velocity at the inlet is used to correct the vibration intensity at a specified frequency, the vibration intensity can be corrected with higher accuracy than when using the gas flow rate. As a result, the molten material height in the blast furnace can be detected using the corrected vibration intensity with high accuracy, making it possible to detect the molten material height in the blast furnace with higher accuracy than in conventional methods.

[0011] Figure 1 is a schematic partial cross-sectional view of the lower part of a blast furnace. Figure 2 is a schematic partial cross-sectional view showing the lower part of a blast furnace and a molten height detection device according to the first embodiment. Figure 3 is a graph showing the time course of corrected vibration intensity. Figure 4 is a flowchart explaining a method for identifying frequencies correlated with vibrations generated by introducing gas. Figure 5 is a graph showing vibration data and vibration intensity data obtained by processing the vibration data with FFT. Figure 6 is a schematic partial cross-sectional view showing the lower part of a blast furnace and a molten height detection device according to the second embodiment. Figure 7 is a graph of a regression equation showing the correspondence between corrected vibration intensity and molten height. Figure 8 is a schematic diagram showing the configuration of the vibration meter and its peripheral equipment in Example 1. Figure 9 is a contour plot showing the average value of the correlation coefficient between vibration intensity calculated from the vibration meter's measurements and the gas velocity at the blower tuyere. Figure 10 is a graph showing the regression line between vibration intensity from the vibration meter and the gas velocity at the blower tuyere. Figure 11 is a graph showing the time course of molten height and corrected vibration intensity obtained from operational data. Figure 12 is a graph showing the regression equation between corrected vibration intensity and molten material height. Figure 13 is a graph showing the correlation between detected and measured values ​​of molten material height.

[0012] [First Embodiment] Hereinafter, the 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 iron slag, which is molten material accumulated at the bottom of the blast furnace. Figure 1 is a schematic partial cross-sectional view of the lower part of a blast furnace 10. Molten iron slag (hereinafter referred to as "molten material 12"), which is composed of pig iron and slag, is accumulated at the bottom of the blast furnace 10. The molten material 12 is discharged from the discharge hole 14, and a molten material flow 16 is generated. A tuyere 20 for introducing gas 18 is provided at the lower part of the blast furnace 10. The tuyere 20 is an example of an inlet for introducing gas 18 into the furnace.

[0013] Figure 2 is a schematic partial cross-sectional view showing the lower part of the blast furnace 10 and the molten material height detection device 22 according to the first embodiment. The molten material height detection device 22 includes, for example, three vibration meters 24a to 24c and a calculation device 26. The three vibration meters 24a to 24c are installed on the furnace wall at equal intervals in the height direction between the discharge hole 14 and the air blower nozzle 20, and measure the vibration of the furnace wall to generate vibration data. The vibration meters 24a to 24c are, for example, piezoelectric elements.

[0014] The vibration data generated by the vibration meters 24a to 24c is output to and recorded by the computing device 26. The computing device 26 is a general-purpose computer such as a personal computer, which has a computing unit such as a CPU and a storage unit such as memory. The computing device 26 performs frequency analysis on the vibration data acquired from the vibration meters 24a to 24c and identifies the vibration intensity of frequencies that are correlated with the vibrations generated by introducing gas from the air blower nozzle 20.

[0015] The calculation unit 26 corrects the vibration intensity to a corrected vibration intensity using the following equation (1) in order to remove the effect of the air velocity of the gas introduced from the air blower nozzle 20 from the identified vibration intensity. By correcting the vibration intensity to a corrected vibration intensity in this way, the effect of fluctuations in the air velocity of the gas introduced from the air blower nozzle 20 on the vibration intensity can be eliminated.

[0016] G ０ = G + (Vtuy ０ -Vtuy) × a ... (1) In the above equation (1), G ０ This is the corrected vibration intensity (m / sec). ２ ) is the vibration intensity before correction (m / sec). ２ ) is. Vtuy ０ is the air velocity (m / sec) at a reference arbitrary air tuyere 20. Vtuy is the air velocity (m / sec) at the air tuyere 20 at the time the vibration data used to calculate G was measured. a is the slope of the regression line when the vibration intensity at frequencies correlated with the vibration due to airflow is on the y-axis and the air velocity at the air tuyere 20 is on the x-axis.

[0017] The airflow velocity at the air blower nozzle 20 is the flow velocity of the gas introduced from the air blower nozzle 20. The airflow velocity of the gas introduced from the air blower nozzle 20 is calculated using the following equation (2).

[0018] Vtuy = (BV / 60) × (BT / 273.15) × [1 / (BP × Stuy)] ... (2) In equation (2) above, Vtuy is the air velocity (m / sec) at the air tuyere 20. BV is the airflow rate (Nm ３ ( / min). BT is the air temperature (K). BP is the air pressure (atm). Stüy is the total cross-sectional area (m²) of the air nozzle 20. ２ )

[0019] In the molten material height detection device 22 according to this embodiment, the molten material height is detected from the vibration of the blast furnace 10. The source of the furnace body vibration is the raceway formed at the tip of the blower nozzle 20. As the raceway depth increases, the vibration increases, so the amount of gas present in the raceway strongly affects the vibration intensity.

[0020] On the other hand, the influence on the raceway depth is dominated by the gas velocity at the tuyere 20 rather than the airflow rate. Therefore, correcting the vibration intensity using the gas velocity at the tuyere 20 yields higher correction accuracy than using the gas flow rate introduced from the tuyere 20. By using the corrected vibration intensity corrected with high accuracy in this way, the height of the molten material 12 accumulated at the bottom of the blast furnace 10 can be detected with high precision.

[0021] Figure 3 is a graph showing the time course of the corrected vibration intensity. In Figure 3, the horizontal axis represents time, and the vertical axis represents the corrected vibration intensity. The corrected vibration intensity has a positive correlation with the height of the molten material 12 when the height of the molten material 12 is lower than the installation height of the vibration meter. On the other hand, a negative correlation is obtained when the height of the molten material 12 is higher than the installation height of the vibration meter. Therefore, for example, if the time course of the corrected vibration intensity shown in Figure 3 is the corrected vibration intensity obtained from vibration data generated by the vibration meter 24b, the corrected vibration intensity changes from a positive correlation to a negative correlation, and the height of the molten material 12 at the time of maximum correlation is equal to the installation height of the vibration meter 24b.

[0022] The change from a positive correlation to a negative correlation in the corrected vibration intensity indicates that the vibration meter has detected a rise in the molten material's liquid level. Conversely, if the molten material's liquid level, located higher than the vibration meter's installation position, drops, the corrected vibration intensity also changes from a positive correlation to a negative correlation. In this case as well, the height of the molten material 12 at the time when the corrected vibration intensity changes from a positive correlation to a negative correlation and reaches its maximum becomes the installation height of the vibration meter.

[0023] The calculation unit 26 monitors the time progression of the corrected vibration intensity obtained from the vibration data generated by the vibration meters 24a to 24c, and identifies the vibration meter whose corrected vibration intensity has changed from a positive correlation to a negative correlation. Once the calculation unit 26 identifies a vibration meter, it detects the height of the molten material 12 by assuming that the installation height of the identified vibration meter is the height of the molten material 12. On the other hand, even if it is not possible to identify a vibration meter whose correlation has changed from a positive to a negative correlation, if there are vibration meters showing a positive correlation and vibration meters showing a negative correlation, the calculation unit 26 detects the height of the molten material 12 by assuming that the space between the installation heights of those vibration meters is the height of the molten material 12. In this way, the calculation unit 26 detects the height of the molten material 12 in the blast furnace 10 from the vibration data generated by the vibration meters 24a to 24c.

[0024] In this embodiment, the molten material height detection device 22 is shown as having three vibration meters 24a to 24c, but it is not limited to this. The molten material height detection device 22 only needs to have at least one vibration meter, and if there is a change from a positive correlation to a negative correlation in the corrected vibration intensity obtained from the vibration data generated by this vibration meter, the height of the molten material 12 can be detected. However, as described above, since the height of the molten material 12 is detected by the installation height of the vibration meter, it is preferable that the molten material height detection device 22 has two or more vibration meters 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 accumulated at the bottom of the blast furnace 10 in the height direction of the blast furnace 10.

[0025] Figure 4 is a flowchart illustrating a method for identifying frequencies correlated with vibrations generated by introducing gas. Using Figure 4, we will explain how to identify frequencies correlated with vibrations generated by introducing gas from the vent nozzle 20. This frequency identification is preferably performed using a vibration meter 24a installed closest to the vent nozzle 20, and is preferably performed during a period when the operation of the blast furnace 10 is stable. A 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 the target range and the fluctuation in the permeability inside the blast furnace 10 is low.

[0026] First, vibration data is generated by measuring the vibration of the lower part of the blast furnace 10 with a vibration meter 24a (step S101). The vibration data is subjected to FFT processing to perform frequency analysis (step S102). Overlap processing, smoothing processing, and window function processing may be performed on the vibration data before FFT processing as needed.

[0027] Figure 5 is a graph showing vibration data and vibration intensity data obtained by processing the vibration data using FFT. Figure 5(a) shows the vibration data, and Figure 5(b) shows the vibration intensity data. Thus, the vibration data shown in Figure 5(a) is processed using FFT to convert it into the vibration intensity data shown in Figure 5(b). It is preferable to use this vibration intensity data to calculate the vibration intensity at all frequencies.

[0028] The vibration intensity may be defined as 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 frequency 1100 Hz will be the arithmetic mean of the vibration intensities of each frequency present in the range of 1000 to 1200 Hz. The interval between frequencies present in the frequency band can be arbitrarily set by FFT processing of the vibration data. For example, if the sampling frequency of the vibration meter is 10000 Hz and the recording length is 10 seconds, the frequency interval will be 3.3 Hz.

[0029] Again, referring to FIG. 4, if a plurality of vibration intensity data have not been acquired under conditions where the wind speed of the gas at the air supply port 20 is changed (step S103: No), the wind speed of the gas at the air supply port 20 is changed (step S104). Then, the processes of steps S101 and S102 are repeatedly performed again. On the other hand, if a plurality of vibration intensity data have been acquired under conditions where the wind speed of the gas at the air supply port 20 is changed (step S103: Yes), the correlation coefficient (R) between the wind speed and the vibration intensity of the gas at the air supply port 20 at all frequencies is calculated (step S105).

[0030] After calculating the correlation coefficient between the wind speed and the vibration intensity of the gas at the air supply port 20 at all frequencies, the frequency with the largest correlation coefficient among them is specified as the frequency correlated with the vibration generated by introducing the gas (step S106). In this way, the frequency correlated with the vibration generated by introducing the gas is specified in advance.

[0031] The specification of the frequency correlated with the vibration generated by introducing the gas may be performed using a plurality of vibration meters. For example, when using the vibration meter 24a and the vibration meter 24b, the correlation coefficient between the wind speed and the vibration intensity of the gas at the air supply port 20 at all frequencies is calculated for these vibration meters. Then, the correlation coefficients of the vibration meter 24a and the vibration meter 24b that are calculated are averaged, and the frequency with the largest average value may be specified.

[0032] Furthermore, when obtaining the correlation coefficient between the wind speed and the vibration intensity of the gas at the air supply port 20, it is preferable to calculate the correlation coefficient in consideration of a predetermined frequency width for each frequency. For example, the correlation coefficient may be calculated in consideration of a frequency width of ±25 Hz to ±300 Hz for each frequency. Also in this case, the correlation coefficients at each frequency and each frequency width corresponding to the frequency are confirmed, and the frequency at which the average value of these correlation coefficients becomes the largest may be specified as the frequency correlated with the vibration generated by introducing the gas. In this way, by considering a predetermined frequency width for each frequency, the difference in the correlation coefficients at each frequency becomes large, and it becomes easier to specify the frequency with a large correlation coefficient.

[0033] As described above, the molten material height detection method and detection device according to the first embodiment detect the height of the molten material 12 using vibration intensity at a frequency correlated with the vibrations generated by introducing gas from the inlet of the blast furnace. The frequency correlated with the vibrations generated by introducing gas from the inlet of the blast furnace can be easily identified by acquiring vibration data with varying gas velocity at the blower nozzle 20, so that the frequency of vibration intensity capable of detecting the molten material height in the blast furnace can be easily identified. Then, using the corrected vibration intensity obtained by removing the effect of gas velocity at the blower nozzle 20 from the vibration intensity at the identified frequency, the molten material height in a blast furnace, which cannot be directly observed, can be detected with high accuracy.

[0034] In particular, by using the airflow velocity at the air tuyere 20 to correct the vibration intensity at a specific frequency, the corrected vibration intensity can be corrected with higher accuracy than by using the airflow rate. By using the corrected vibration intensity corrected with such high accuracy, the height of the molten material in the blast furnace can be detected with higher accuracy than before.

[0035] It is preferable to manufacture the molten material by adjusting the manufacturing conditions so that the molten material height detected in this manner falls within the range of the target molten material height in the blast furnace. For example, if the molten material height is likely to exceed the target range, the manufacturing conditions can be adjusted by reducing the amount of raw materials charged or increasing the amount of molten material discharged. If the molten material height is likely to fall below the target range, the manufacturing conditions can be adjusted by increasing the amount of raw materials charged or decreasing the amount of molten material discharged. By adjusting the manufacturing conditions of the molten material in this way so that it falls within the range of the target molten material height, for example, in a blast furnace, excessive rise in the liquid level of the molten material can be suppressed, and the molten material can be manufactured while suppressing furnace cooling due to poor permeability and damage to the furnace body equipment.

[0036] [Second Embodiment] Next, similar to the first embodiment, the second embodiment of the present invention will be described using an example of detecting the height of the melt 12 accumulated at the bottom of the furnace of the blast furnace 10, which is an example of a smelting furnace. FIG. 6 is a schematic partial cross-sectional view showing the lower part of the blast furnace 10 and the melt height detection device 30 according to the second embodiment. The melt height detection device 30 includes one vibration meter 32 and an arithmetic unit 34. In the example shown in FIG. 6, the same components as those in FIG. 2 are given the same reference numerals, and the description thereof is omitted.

[0037] The vibration meter 32 measures the vibration of the furnace wall in the lower part of the furnace to create vibration data. The vibration meter 32 is, for example, a piezoelectric element.

[0038] The vibration data generated by the vibration meter 32 is output to and recorded by the arithmetic unit 34. The arithmetic unit 34 is also a general-purpose computer such as a personal computer having an arithmetic unit such as a CPU and a storage unit such as a memory. The arithmetic unit 34 performs frequency analysis on the vibration data acquired from the vibration meter 32 and calculates the vibration intensity of a frequency correlated with the vibration generated by introducing gas from the tuyere 20. The arithmetic unit 34 corrects the vibration intensity to the corrected vibration intensity using the above formula (1) in order to remove the influence of the gas wind speed at the tuyere 20 from the calculated vibration intensity.

[0039] FIG. 7 is a graph of a regression equation showing the correspondence between the corrected vibration intensity and the melt height. In FIG. 7, the horizontal axis is the corrected vibration intensity (m / sec ２ ), and the vertical axis is the height of the melt (m). In the arithmetic unit 34, a regression equation showing the correspondence between the corrected vibration intensity and the height of the melt 12 as shown in FIG. 7 is obtained in advance and stored. The regression equation showing the correspondence between the corrected vibration intensity and the height of the melt 12 is preferably created using operation data for as long a period as possible.

[0040] When the arithmetic unit 34 calculates the corrected vibration intensity, it reads out the regression equation showing the correspondence between the corrected vibration intensity and the height of the melt shown in FIG. 7, and uses the regression equation and the calculated corrected vibration intensity to detect the height of the melt 12. In this way, the melt height detection device 30 according to the second embodiment detects the height of the melt 12 accumulated at the bottom of the blast furnace 10.

[0041] The vibration meter 32 is preferably installed in a position close to the blower tuyere 20. This makes it easier for the vibration meter 32 to detect vibrations caused by the blower. In the height direction of the furnace wall at the bottom of the blast furnace 10, if the upper end position of the discharge hole 14 is set to 0 and the lower end position of the blower tuyere 20 is set to 1, the vibration meter 32 is preferably installed at a position between 0.90 and 1.00. It is more preferable that the vibration meter 32 be installed at a position between 0.95 and 1.00, and even more preferable that it be installed at 1.00. If the vibration meter 32 is installed at a position higher than the lower end position of the blower tuyere 20, the vibration measured by the vibration meter 32 will be affected by vibrations caused by the descent of raw materials inside the blast furnace, which is undesirable.

[0042] As described above, in the molten material height detection method and detection device according to the second embodiment, the height of the molten material 12 is detected using vibration intensity at a frequency correlated with the vibrations generated by introducing gas from the blower tuyere 20. The frequency correlated with the vibrations generated by introducing gas into the inlet of the blast furnace can be easily identified by acquiring vibration data with varying gas velocity at the blower tuyere 20, so the frequency of vibration intensity that can detect the molten material height in the blast furnace can be easily identified. Then, by using the corrected vibration intensity obtained by removing the effect of gas velocity at the blower tuyere 20 from the vibration intensity at the identified frequency and the above regression equation, the molten material height of a blast furnace, which cannot be directly observed, can be detected with high accuracy.

[0043] In the second embodiment as well, by using the airflow velocity at the air blower nozzle 20 to correct the vibration intensity at a specified frequency, the corrected vibration intensity can be corrected with higher accuracy than by using the airflow rate. In this way, by using the corrected vibration intensity corrected with high accuracy, the height of the molten material in the blast furnace can be detected with higher accuracy than in the conventional method.

[0044] [Example 1] Next, in order to confirm the validity of the present invention, a volume of 5000 m was used. ３This document describes Example 1, which describes the detection of the molten material height accumulated at the bottom of a large blast furnace. In this example, a molten material height detection device was used, which had two vibration meters installed at different positions in the height direction. The installation heights of the vibration meters 24a and 24b from the furnace bottom, and the heights of the air vent 20 and the discharge hole 14 are shown in Table 1 below.

[0045]

[0046] Figure 8 is a schematic diagram showing the configuration of the vibration meter and its peripheral equipment in Example 1. In Figure 8, the same reference numerals are used for components identical to those in Figure 2, and their explanations are omitted. Amplifiers 40a and 40b were connected to each vibration meter 24a and 24b to amplify the vibration data. The vibration data amplified by amplifiers 40a and 40b was stored in data loggers 42a and 42b. The vibration data stored in data loggers 42a and 42b was processed using a computing device 26. The conditions for measuring vibration were set to a sampling frequency of 10,000 Hz and a recording length of 10 seconds, assuming the vibration frequency originating from the blast furnace. Under these conditions, the vibration of the furnace wall was measured every 3 minutes for approximately 2 days, and vibration data for that period was acquired.

[0047] In this embodiment, before FFT analysis, the vibration data was subjected to overlapping, smoothing, and windowing. In the overlapping process, the raw vibration data was divided into segments of 3 / 10 of the recording length, and half of these segments were processed to overlap. Each segment was then smoothed using a Gaussian filter. A Hanning window was applied for the windowing process. After processing the segmented frames in this way, FFT analysis was performed, and the average vibration intensity calculated by performing FFT analysis on all segmented frames was used.

[0048] After performing FFT analysis, the vibration intensity for all frequency bands was calculated. In Example 1, vibrations with frequencies below 5000 Hz were measured by vibration meters 24a and 24b. To evaluate the vibration intensity for all frequencies, the frequency of the vibration was considered separately as a reference vibration frequency f (Hz) and a frequency bandwidth Δf (Hz). That is, the average value of the vibration intensity in the frequency band f ± Δf (Hz) was taken as the vibration intensity, and f was varied in 50 Hz increments from 300 Hz to 4700 Hz, while Δf was varied in 25 Hz increments from 25 Hz to 300 Hz.

[0049] In this manner, after calculating the vibration intensity at each frequency, the correlation coefficient between the vibration intensity and the gas velocity at the air vent nozzle 20 was calculated. In Example 1, the correlation coefficient was calculated using the vibration data from the vibrometer 24a measured on the day with the lowest molten material height during the two-day measurement period.

[0050] Figure 9 is a contour plot showing the average correlation coefficient between vibration intensity calculated from the measurements of the vibration meter 24a and the airflow velocity of the gas at the air vent 20. In Example 1, the correlation coefficient was largest in the vibration frequency band f = 1050 Hz and Δf = 300 Hz. Therefore, f ± Δf = 1050 ± 300 Hz was identified as the frequency correlated with the vibration generated by introducing gas.

[0051] Next, the vibration intensity was corrected using the gas velocity at the blower tuyere 20 to calculate the corrected vibration intensity. For the correction, the vibration intensity and gas velocity at the blower tuyere 20 were used for the two days out of the two days on which vibration data was measured, and the equation of the regression line used in equation (1) above was determined.

[0052] Figure 10 is a graph showing the regression line between the vibration intensity of vibration meters 24a and 24b and the airflow velocity of the gas at the air tuyere 20. Figure 10(a) shows the graph and regression line for vibration meter 24a, and Figure 10(b) shows the graph and regression line for vibration meter 24b. The horizontal axis of these graphs represents the airflow velocity (m / sec) at the air tuyere 20, and the vertical axis represents the vibration intensity (m / sec) ２ ) . By substituting the slopes of these regression lines into equation (1) above, we calculated equations (3) and (4) below, which correct the vibration intensity to the corrected vibration intensity.

[0053] G ０ = G + (Vtuy ０ -Vtuy)×0.23...(3)

[0054] G ０ = G + (Vtuy ０ -Vtuy)×0.18...(4)

[0055] In equations (3) and (4) above, G ０ G, Vtuy ０ And Vtuy are the same as in equation (1) above. Using equations (3) and (4) above, the corrected vibration intensity was calculated to remove the effect of the air velocity at the air blower nozzle 20. The molten material height was detected using the calculated corrected vibration intensity.

[0056] Figure 11 is a graph showing the time course of molten material height and corrected vibration intensity obtained from operational data. Figure 11(a) is a graph showing the time course of molten material height obtained from operational data, with the horizontal axis representing time and the vertical axis representing molten material height (m). Figures 11(b) and (c) are graphs showing the time course of corrected vibration intensity from vibration meters 24a and 24b, with the horizontal axis representing time and the vertical axis representing corrected vibration intensity (m / sec). ２ )

[0057] As shown in Figure 11, the corrected vibration intensity value on vibration meter 24b decreased from around 3:00 on July 8, but it continued to increase on vibration meter 24a. From this result, it can be seen that from around 3:00 on July 8 to 12:00, the molten material height was between 3.3 and 3.8 (m), which is between vibration meters 24a and 24b. Looking at the estimated molten material height value calculated at the same time, it rose from approximately 2.5 m to 3.8 m from 12:00 on July 7 to 12:00 on July 8. Thus, the molten material height detected from vibration intensity and the molten material height estimated from operation data are in close agreement, confirming that the molten material height can be detected by the method of Example 1.

[0058] [Example 2] Next, Example 2 will be described, in which it was confirmed that the molten material height can be detected using a single vibration meter. In Example 2, the same volume as in Example 1 is 5000 m ３The molten material height of the large blast furnace was detected using vibration data from a vibrometer 24a. The vibration data acquired from the vibrometer 24a was subjected to overlap processing, smoothing processing, and window function processing, as in Example 1, and then analyzed using FFT.

[0059] The frequency correlated with the vibration caused by the airflow was set to f ± Δf = 1050 ± 300 Hz, the same as in Example 1. Similar to Example 1, the corrected vibration intensity was calculated using equation (3) below. The molten material height in the blast furnace was calculated using the operating data obtained in the blast furnace in June 2022 and equation (5) below. The height of the molten material accumulated at the bottom of the blast furnace from 0:00 to 23:59 on April 19th was calculated.

[0060] G ０ = G + (Vtuy ０ -Vtuy)×0.23...(3)

[0061] h=(Wi / ρi+Ws / ρs) / (ε×Sb)...(5)

[0062] In equation (5) above, h is the height of the molten material (m), Wi is the weight of the molten iron at the bottom of the furnace (kg), and ρi is the density of the molten iron (kg / m³). ３ ) is the weight of the molten slag at the bottom of the furnace (kg). ρs is the density of the molten slag (kg / m³). ３ ) is the furnace bottom porosity (-). Sb is the furnace bottom cross-sectional area (m ２ ) (-) means dimensionless.

[0063] The weights of the molten iron at the bottom of the furnace and the molten slag at the bottom of the furnace were determined by adding the values ​​obtained by subtracting the amount of iron produced and slag produced from the amount of iron produced and slag produced from the amount of iron produced and slag produced for each tapping operation, and then correcting for the error of the actual weighing machine. In Example 2, the molten iron density was 6800 kg / m³. ３ The molten slag density was set to 2650 kg / m³. ３ The furnace bottom porosity was set to 0.33.

[0064] Using the molten material height calculated in this manner, a regression equation showing the correspondence between the corrected vibration intensity and the molten material height was obtained. As a comparative example, the corrected vibration intensity corrected by the gas airflow rate disclosed in Patent Document 2 was determined, and a regression equation showing the correspondence between the corrected vibration intensity and the molten material height was obtained.

[0065] Figure 12 is a graph showing the regression equation between corrected vibration intensity and molten material height. The horizontal axis of Figure 12 represents corrected vibration intensity (m / sec). ２ ) and the vertical axis is the molten material height (m). The graph shown in Figure 12(a) is a regression equation showing the correspondence between the corrected vibration intensity corrected by the gas velocity at the air blower nozzle 20 and the molten material height, and this regression equation is given by equation (6) below. The graph shown in Figure 12(b) is a regression equation showing the correspondence between the corrected vibration intensity corrected by the gas airflow rate and the molten material height, and this regression equation is given by equation (7) below.

[0066] h = G ０ ×0.312-6.2354...(6) h=G ０ × 0.281 - 7.4305 ... (7) In equations (6) and (7) above, h is the height of the molten material (m). G ０ This is the corrected vibration intensity (m / sec). ２ )

[0067] The detected value of the molten material height accumulated at the bottom of the blast furnace was calculated using equation (6) above and the corrected vibration intensity corrected by the gas velocity at the air vent 20 (Example of Invention). Similarly, the detected value of the molten material height accumulated at the bottom of the blast furnace was calculated using equation (7) above and the corrected vibration intensity corrected by the gas airflow rate (Comparative Example). The measured value of the molten material height accumulated at the bottom of the blast furnace was calculated using equation (5) above and operational data. Then, the correlation between the detected value and the measured value of the molten material height in the Example of Invention and the Comparative Example was confirmed using the calculated detected value and the measured value.

[0068] Figure 13 is a graph showing the correlation between the detected value and the measured value of the molten material height. Figure 13(a) is a graph showing the correlation between the detected value and the measured value of the molten material height, which is detected using the corrected vibration intensity corrected by the gas velocity at the air blower nozzle 20. Figure 13(b) is a graph showing the correlation between the detected value and the measured value of the molten material height, which is detected using the corrected vibration intensity corrected by the gas airflow rate.

[0069] As shown in Figure 13(a), the correlation coefficient between the detected value of the molten material height, which was detected using the corrected vibration intensity corrected by the gas velocity at the air tuyere 20, and the measured value was 0.7505. On the other hand, as shown in Figure 13(b), the correlation coefficient between the detected value of the molten material height, which was detected using the corrected vibration intensity corrected by the gas airflow rate, and the measured value was 0.4458.

[0070] Thus, the correlation coefficient between the detected value of molten material height, which was detected using the corrected vibration intensity corrected by the gas velocity at the tuyere 20, and the measured value was greater than the correlation coefficient between the detected value of molten material height, which was detected using the corrected vibration intensity corrected by the gas flow rate, and the measured value. This confirmed that the correlation between the detected value of molten material height, which was detected using the corrected vibration intensity corrected by the gas velocity at the tuyere 20, and the measured value is stronger than the correlation between the detected value of molten material height, which was detected using the corrected vibration intensity corrected by the gas flow rate, and the measured value. From these results, it was confirmed that detecting the molten material height using the corrected vibration intensity corrected by the gas velocity at the tuyere 20 allows for detection of the molten material height in a blast furnace with higher accuracy than the conventional method using the corrected vibration intensity corrected by the gas flow rate.

[0071] 10 Blast furnace 12 Molten material 14 Discharge port 16 Molten material flow 18 Gas 20 Air blower nozzle 22 Molten material height detection device 24a-24c Vibration meter 26 Calculation unit 30 Molten material height detection device 32 Vibration meter 34 Calculation unit 40a, 40b Amplifier 42a, 42b Data logger

Claims

1. A method for detecting the height of molten material in a blast furnace, comprising: measuring vibration at one or more positions on the furnace wall in the lower part of the blast furnace; analyzing the frequency of the vibration to identify the vibration intensity at a frequency correlated with the vibration generated by introducing gas into the inlet in the lower part of the furnace; and detecting the height of the molten material using a corrected vibration intensity obtained by removing the effect of the wind speed of the gas at the inlet from the vibration intensity at the frequency.

2. The method for detecting the height of molten material according to claim 1, wherein the frequency correlated with the vibration generated by introducing the gas into the inlet is determined by confirming the correlation between the vibration intensity in a frequency band having a predetermined width and the wind speed of the gas.

3. The method for detecting the height of molten material according to claim 1 or 2, wherein when the corrected vibration intensity reaches its maximum, the position where the vibration of the maximum corrected vibration intensity is being measured is detected to be the height of the molten material in the blast furnace.

4. A method for detecting the height of molten material according to any one of claims 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 method for detecting the height of molten material according to claim 1 or 2, wherein the correspondence between the corrected vibration intensity and the height of the molten material is determined in advance, and the height of the molten material in the blast furnace is detected using the corrected vibration intensity obtained from the measurement of the vibration and the correspondence.

6. A device for detecting the height of molten material in a blast furnace, comprising: one or more vibration meters provided on the furnace wall at the lower part of the blast furnace for measuring vibrations of the furnace wall; and a calculation device that performs frequency analysis on the vibrations measured by the vibration meters to identify vibration intensities at frequencies correlated with vibrations generated by introducing gas into the inlet at the lower part of the furnace, and detects the molten material height using corrected vibration intensities obtained by removing the effect of the wind speed of the gas at the inlet from the vibration intensities at those frequencies.

7. The molten material height detection device according to claim 6, comprising two or more vibration meters, wherein the two or more vibration meters are provided at two or more different positions in the height direction of the furnace wall in the lower part of the furnace.

8. The molten material height detection device according to claim 6, wherein the calculation device detects the molten material height using the correspondence between the corrected vibration intensity and the molten material height.

9. A method for manufacturing a molten material using 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 frequency of the vibrations to identify vibration intensities of frequencies correlated with vibrations generated by introducing gas into the inlet in the lower part of the furnace; detecting the height of the molten material in the blast furnace using a corrected vibration intensity obtained by removing the effect of the wind speed of the gas at the inlet from the vibration intensities of the frequencies; and adjusting the manufacturing conditions of the molten material so that the detected height of the molten material falls within a range of a target height of the molten material.

10. A method for manufacturing a molten material according to claim 9, wherein the correspondence between the corrected vibration intensity and the molten material height is determined in advance, and the molten material height is detected using the corrected vibration intensity obtained from the measurement of the vibration and the correspondence.

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