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

Abstract

Provided is a molten material height detection method with higher detection accuracy than conventional methods.　In the molten material height detection method for detecting the height of a molten material in a blast furnace, a vibration is measured at one or more positions of a furnace wall in a lower part of the blast furnace, the frequency of the vibration is analyzed to specify the vibration intensity of a frequency related to a vibration generated as a result of introducing gas to an inflow port of the lower part of the furnace, and the height of the molten material is detected using a corrected vibration intensity obtained by removing, from the intensity of the vibration of the specified frequency, the effect of the amount of Bosch gas generated by the introduction of the gas.

Description

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

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

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

[0003] In blast furnace operation, if the blast furnace is underheated or the particle size of the packed bed at the hearth of the blast furnace decreases, the resistance to the flow of molten material increases, which can reduce the amount of molten material discharged outside the furnace. As a result, the liquid level of the molten material rises, causing a decrease in the permeability of the gas inside the blast furnace, which can lead to furnace cooling and damage to the furnace equipment. This can ultimately lead to the shutdown of the blast furnace, which can lead to a significant drop in the production of steel products throughout the steelworks. Due to these concerns, it is essential to constantly monitor the amount of molten material accumulated inside the blast furnace and to detect blast furnace problems early.

[0004] There are technologies that measure the liquid level of molten material in a blast furnace to detect excessive accumulation of molten material. Patent Document 1 discloses a technology that takes two or more photographs of the molten material discharge flow from a blast furnace to determine the discharge rate, and then calculates the molten material height by substituting the discharge rate into an energy balance equation. Patent Document 2 discloses a technology that detects the height of molten metal and slag in a blast furnace from the vibration intensity of the furnace wall generated by introducing gas into an inlet at the bottom of the blast furnace. Patent Document 2 discloses that the frequency of the vibration intensity is analyzed to identify a frequency band that is correlated with fluctuations in the blast air volume, and the vibration intensity in the identified frequency band can be used to detect the height of molten metal and slag in a blast furnace.

[0005] JP 2017-160498 A Patent No. 7485247 A

[0006] The technology in Patent Document 1 utilizes the positive correlation between the discharge rate of the molten material and the height of the molten material, so it has the problem of not being able to detect an increase in the liquid level when the discharge rate of the molten material decreases due to clogging of the discharge hole. Visibility around the discharge hole is poor due to dust in the factory, and the molten material may violently eject from the discharge hole. In such cases, it is not possible to accurately capture the discharge flow surface, making it impossible to calculate the liquid level of the molten material.

[0007] In the technology of Patent Document 2, the influence of the gas blowing volume is removed from the vibration intensity to calculate the corrected vibration intensity. However, because the amount of gas produced by the reaction at the inlet end is not taken into account, there is a problem that the correction accuracy of the corrected vibration intensity is low, and the detection accuracy of the molten material height is also low. The present invention has been made in consideration of these circumstances, and its purpose is to provide a molten material height detection method, a molten material height detection device, and a molten material manufacturing method that have higher detection accuracy than conventional methods.

[0008] The gist of the present invention, which 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 frequencies of the vibrations to identify vibration intensities of frequencies correlated with vibrations generated by introducing gas into an inlet in the lower part of the furnace; and detecting the molten material height using corrected vibration intensities obtained by removing the influence of the amount of bosh gas generated by the introduction of the gas from the vibration intensities of the identified frequencies. [2] The molten material height detection method according to [1], in which the frequencies correlated with vibrations generated by introducing gas into the inlet are identified by confirming the correlation between vibration intensities of a frequency band having a predetermined width and the amount of bosh gas. [3] The molten material height detection method according to [1] or [2], in which, when the corrected vibration intensity reaches a maximum, the position at which the vibration of the corrected vibration intensity at the maximum is measured is detected as the molten material height in the blast furnace. [4] The method for detecting a smelt 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] The method for detecting a smelt height according to [1] or [2], wherein a correspondence relationship between the corrected vibration intensity and the smelt height is determined in advance, and the smelt height in the blast furnace is detected using the corrected vibration intensity obtained from the vibration measurement and the correspondence relationship. [6] The method for detecting a smelt height according to [5], wherein, in the height direction of the furnace wall in the lower part of the furnace, the vibration is measured at a position of 0.90 to 1.00, where the position of the upper end of the discharge hole is set to 0 and the position of the lower end of the inlet is set to 1. [7] A molten material height detection device for detecting the molten material 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 vibrations of the furnace wall; and a calculation device for performing frequency analysis of the vibrations measured by the vibration meters to identify vibration intensities of frequencies correlated with vibrations generated by introducing gas into an inlet in the lower part of the furnace, and detecting the molten material height using corrected vibration intensities obtained by removing the influence of the amount of Bosh gas generated by the introduction of the gas from the vibration intensities of the identified frequencies.[8] The molten material height detection device according to [7], which has two or more vibrometers, and the two or more vibrometers are installed at two or more different positions in the height direction of the furnace wall in the lower part of the furnace. [9] The molten material height detection device according to [7], which detects the molten material height using a correspondence relationship between the corrected vibration intensity and the molten material height.

[10] The molten material height detection device according to [9], wherein, in the height direction of the furnace wall in the lower part of the furnace, when the upper end position of the discharge hole is set to 0 and the lower end position of the inlet is set to 1, the vibrometers are installed at positions 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 frequencies of the vibrations to identify vibration intensities at frequencies 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 corrected vibration intensities obtained by removing the influence of the amount of bosh gas generated by the introduction of the gas from the vibration intensities of the identified frequencies; and adjusting production conditions for the molten material so that the detected molten material height falls within a target molten material height range.

[12] A method for producing a molten material according to

[11] , wherein a correspondence relationship between the corrected vibration intensities and the molten material height is determined in advance, and the molten material height is detected using the correspondence relationship and the corrected vibration intensities obtained from the vibration measurements.

[0009] According to the present invention, the amount of Bosch gas generated by the introduction of gas is used to correct the vibration intensity of the specified frequency, so the vibration intensity can be corrected with higher accuracy than if the amount of gas blown is used. This increases the accuracy of vibration intensity correction, making it possible to detect the molten material height in a blast furnace with higher accuracy than in the past.

[0010] FIG. 1 is a partial cross-sectional schematic diagram of the lower part of a blast furnace. FIG. 2 is a partial cross-sectional schematic diagram showing the lower part of a blast furnace and a smelt height detection device according to the first embodiment. FIG. 3 is a graph showing the time progression of corrected vibration intensity. FIG. 4 is a flow chart illustrating a method for identifying frequencies correlated with vibrations generated by introducing gas. FIG. 5 is a graph showing vibration data and vibration intensity data obtained by FFT processing of the vibration data. FIG. 6 is a partial cross-sectional schematic diagram showing the lower part of a blast furnace and a smelt height detection device according to the second embodiment. FIG. 7 is a graph of a regression equation showing the correspondence relationship between corrected vibration intensity and smelt height. FIG. 8 is a schematic diagram showing the configuration of a vibrometer and its peripheral devices according to Example 1. FIG. 9 is a contour diagram showing the average value of the correlation coefficient between vibration intensity calculated from measurements taken by the vibrometer and the Bosh gas volume. FIG. 10 is a graph showing the regression line between the vibration intensity of the vibrometer and the Bosh gas volume. FIG. 11 is a graph showing the time progression of the smelt height and the time progression of corrected vibration intensity calculated from operational data. Fig. 12 is a graph showing a regression equation between corrected vibration intensity and molten material height, and Fig. 13 is a graph showing the correlation between detected and actually measured values ​​of molten material height.

[0011] First Embodiment A first embodiment of the present invention will be described below using a blast furnace, which is an example of a blast furnace, to illustrate an example of detecting the height of molten metal and slag 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 metal and slag (hereinafter, molten metal and slag 12) composed of pig iron and slag accumulates in the hearth of the blast furnace 10. The molten metal 12 is discharged from a discharge hole 14, generating a molten material flow 16. 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 the smelt height detection device 22 according to the first embodiment. The smelt height detection device 22 includes, for example, three vibrometers 24a to 24c and a computing device 26. The three vibrometers 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 vibrometers 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 by 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 identifies the vibration intensity of a frequency that is correlated with the vibration generated by introducing gas from the blower tuyere 20.

[0014] The calculation device 26 corrects the vibration intensity to a corrected vibration intensity using the following formula (1) in order to remove the influence of the amount of Bosch gas generated at the tip of the blast tuyere 20 from the calculated vibration intensity. By correcting the vibration intensity to the corrected vibration intensity in this way, the influence of fluctuations in the amount of Bosch gas on the vibration intensity can be removed.

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

[0016] The bosh gas is a gas generated by a combustion reaction of the gas introduced from the blower tuyere 20. The amount of bosh gas is calculated using the following formula (2).

[0017] Bosh=BV×0.01×(X Ｎ２ +2X Ｏ２ +XBM Ｈ２ ) + α (2) In the above formula (2), BV is the air flow rate (Nm ３ / min). X Ｎ２ is the nitrogen content (volume%) in the air, and X Ｏ２ is the oxygen content (volume%) in the air, and XBMＨ２ is the hydrogen content (volume %) in the blast. α is the amount of gas from the injected fuel (Nm ３ / min).

[0018] The smelt height detection device 22 according to this embodiment detects the smelt height from the vibration of the furnace body of the blast furnace 10. The source of the vibration of the furnace body is the raceway formed at the tip of the blast tuyere 20. Since the vibration increases as the raceway volume increases, the amount of gas present in the raceway strongly affects the vibration intensity. For this reason, correcting the vibration intensity using the amount of bosh gas generated by the combustion reaction of gas at the tip of the blast tuyere 20 provides higher correction accuracy than using the flow rate of gas introduced through the blast tuyere 20. In this way, by using the corrected vibration intensity corrected with high correction accuracy, the height of the smelt 12 accumulated in the hearth of the blast furnace 10 can be detected with high accuracy. The bosh gas amount calculated by the above formula (2) may be further corrected using temperature and pressure.

[0019] FIG. 3 is a graph showing the time progression of the corrected vibration intensity. In FIG. 3, the horizontal axis represents time, and the vertical axis represents the corrected vibration intensity. The corrected vibration intensity exhibits 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 vibrometer. On the other hand, the corrected vibration intensity exhibits a negative correlation with the height of the molten material 12 when the height of the molten material 12 is higher than the installation height of the vibrometer. Therefore, for example, if the time progression of the corrected vibration intensity shown in FIG. 3 is the corrected vibration intensity calculated from the vibration data generated by the vibrometer 24b, the height of the molten material 12 at the time when the corrected vibration intensity changes from a positive correlation to a negative correlation and reaches its maximum is the installation height of the vibrometer 24b.

[0020] The change in the corrected vibration intensity from a positive correlation to a negative correlation is a result of the vibration meter capturing the phenomenon of the molten material level rising. On the other hand, when the molten material level at a position higher than the installation position of the vibration meter drops, the corrected vibration intensity also changes from a positive correlation to a negative correlation. In this case, too, 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.

[0021] 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, it determines that the installation height of the identified vibrometer is the height of the molten material 12 and detects the height of the molten material 12. On the other hand, even if it cannot identify a vibrometer whose correlation has changed from a positive correlation to a negative correlation, if there is a vibrometer whose correlation has changed from a positive correlation to a negative correlation, the computing device 26 determines that the height of the molten material 12 is between the installation heights of the vibrometers whose correlation has changed from a positive correlation to a negative correlation and detects the height of the molten material 12. 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.

[0022] Although the smelt height detection device 22 according to this embodiment has been described as having three vibrometers 24a to 24c, this is not limiting. The smelt height detection device 22 only needs to have at least one vibrometer. The height of the smelt 12 can be detected if the corrected vibration intensity calculated from the vibration data generated by this vibrometer changes from a positive correlation to a negative correlation. However, since the height of the smelt 12 is detected based on the installation height of the vibrometer as described above, the smelt height detection device 22 preferably has two or more vibrometers installed at different positions in the height direction of the lower part of the blast furnace 10. This allows the detection range for the height of the smelt 12 accumulated in the hearth of the blast furnace 10 to be expanded in the height direction of the blast furnace 10.

[0023] Fig. 4 is a flow chart illustrating a method for identifying a frequency correlated with vibrations generated by introducing gas. A method for identifying a frequency correlated with vibrations generated by introducing gas through the blast tuyere 20 will be described with reference to Fig. 4. This frequency identification is preferably performed using a vibration meter 24a installed closest to the blast tuyere 20, and is preferably performed during a period when operation of the blast furnace 10 is stable. A period when operation of the blast furnace 10 is stable means a period when the coke rate in blast furnace operation is within a target range and fluctuations in permeability within the blast furnace 10 are low.

[0024] First, the vibration meter 24a measures the vibration of the lower part of the blast furnace 10 to generate vibration data (step S101). The vibration data is subjected to FFT processing (step S102) to perform frequency analysis of the vibration data. If necessary, overlap processing, smoothing processing, or window function processing may be performed on the vibration data before FFT processing.

[0025] 5A and 5B are graphs showing vibration data and vibration intensity data obtained by FFT processing of the vibration data. Fig. 5A shows the vibration data, and Fig. 5B shows the vibration intensity data. Thus, the vibration data shown in Fig. 5A is converted into the vibration intensity data shown in Fig. 5B by FFT processing. It is preferable to use this vibration intensity data to calculate vibration intensity at all frequencies.

[0026] 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 average of the vibration intensity of each frequency between 1000 and 1200 Hz. The interval between frequencies in the frequency band is set arbitrarily by FFT processing of the vibration data. For example, if the sampling frequency of the vibrometer is 10,000 Hz and the recording length is 10 seconds, the frequency interval will be 3.3 Hz.

[0027] 4 again. If the vibration intensity data has not been acquired multiple times under conditions with different Bosch gas amounts (step S103: No), the Bosch gas amount is changed (step S104), and the processes of steps S101 and S102 are repeated. On the other hand, if the vibration intensity data has been acquired multiple times under conditions with different Bosch gas amounts (step S103: Yes), the correlation coefficient (R) between the Bosch gas amount and the vibration intensity at all frequencies is calculated (step S105).

[0028] After calculating the correlation coefficients between the Bosch gas amount and the vibration intensity at all frequencies, the frequency with the largest correlation coefficient 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.

[0029] The frequency correlated with the vibration caused by the introduction of the gas may be identified using multiple vibrometers. For example, when using the vibrometers 24a and 24b, the correlation coefficients between the amount of Bosch gas and the vibration intensity at all frequencies are calculated for these vibrometers, and the correlation coefficients of the vibrometers 24a and 24b are averaged to identify the frequency at which this average value is greatest.

[0030] Furthermore, when calculating the correlation coefficient between the Bosch gas amount and the vibration intensity, it is preferable to calculate the correlation coefficient taking into account a predetermined frequency width for each frequency. For example, the correlation coefficient may be calculated taking into account a frequency width of ±25 Hz to ±300 Hz for each frequency. Even 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 is greatest is identified as the frequency correlated with the vibrations generated by introducing gas. In this way, by taking into account a predetermined frequency width for each frequency, the difference in the correlation coefficients at each frequency becomes larger, making it easier to identify frequencies with large correlation coefficients.

[0031] 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 the vibration intensity of a frequency correlated with the vibration generated by introducing gas into the inlet of the blast furnace. The frequency correlated with the vibration generated by introducing gas into the inlet of the blast furnace can be easily identified by acquiring vibration data obtained by changing the amount of bosh gas. Therefore, it is easy to identify the frequency of the vibration intensity at which the molten material height in the blast furnace can be detected. Then, the corrected vibration intensity, which removes the influence of the bosh gas amount from the vibration intensity of the identified frequency, can be used to accurately detect the molten material height in a blast furnace, where the interior of the furnace cannot be directly observed.

[0032] In particular, by using the amount of Bosch gas generated by the introduction of gas to correct the vibration intensity of the specified frequency, the corrected vibration intensity can be corrected with higher accuracy than by using the amount of gas blown. By using the corrected vibration intensity corrected with high correction accuracy in this way, the molten material height in the blast furnace can be detected with higher accuracy than before.

[0033] It is preferable to adjust the melt production conditions so that the melt height detected in this manner falls within a target melt height range in the blast furnace. For example, if the melt height is likely to be higher than the target range, the melt production conditions can be adjusted to reduce the amount of raw material charged or increase the amount of melt discharged. If the melt height is likely to be lower than the target range, the melt production conditions can be adjusted to increase the amount of raw material charged or decrease the amount of melt discharged. By adjusting the melt production conditions in this way so that the melt height falls within the target melt height range, for example, in a blast furnace, excessive rise in the melt level can be suppressed, and melt can be produced while suppressing furnace cooling and damage to furnace body equipment due to poor permeability.

[0034] Second Embodiment Next, a second embodiment of the present invention will be described using an example in which a blast furnace 10, which is an example of a blast furnace, is used to detect the height of molten material 12 accumulated in the hearth of the blast furnace 10, as in the first embodiment. Fig. 6 is a partial cross-sectional schematic diagram showing the 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 computing device 34. In the example shown in Fig. 6, the same components as those in Fig. 2 are designated by the same reference numerals, and their description will be omitted.

[0035] The vibrometer 32 measures the vibration of the furnace wall in the lower part of the furnace to generate vibration data. The vibrometer 32 is, for example, a piezoelectric element.

[0036] 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 acquired 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 amount of Bosch gas from the calculated vibration intensity, the calculation device 34 corrects the vibration intensity to a corrected vibration intensity using the above formula (1).

[0037] 7 is a graph of a regression equation showing the correspondence relationship between the corrected vibration intensity and the melt height. In FIG. 7, the horizontal axis represents the corrected vibration intensity (m / s ２ ) and the vertical axis represents the height (m) of the molten material. A regression equation showing the correspondence relationship between the corrected vibration intensity and the height of the molten material 12 as shown in Figure 7 is calculated in advance and stored in the computing device 34. It is preferable to create the regression equation showing the correspondence relationship between the corrected vibration intensity and the height of the molten material 12 using operational data from as long a period as possible.

[0038] 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 Figure 7, and detects the height of the molten material 12 using the regression equation and the calculated corrected vibration intensity. In this way, the molten material height detection device 30 according to the second embodiment detects the height of the molten material 12 accumulated in the hearth portion of the blast furnace 10.

[0039] 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, if the upper end position of the discharge hole 14 is set to 0.00 and the lower end position of the blast tuyere 20 is set to 1.00, the vibration meter 32 is preferably installed at a position between 0.90 and 1.00. The vibration meter 32 is more preferably installed at a position between 0.95 and 1.00, and even more preferably at 1.00. It is not preferable to install the vibration meter 32 at a position higher than the lower end position of the blast tuyere 20, because the vibrations measured by the vibration meter 32 will be affected by vibrations caused by the descent of raw materials inside the blast furnace.

[0040] As described above, the molten material height detection method and detection device according to the second embodiment also detect the height of the molten material 12 using the vibration intensity of a frequency correlated with the vibration generated by introducing gas through the blast tuyere 20. The frequency correlated with the vibration generated by introducing gas into the inlet of the blast furnace can be easily identified by acquiring vibration data obtained by varying the amount of bosh gas. This makes it easy to identify the frequency of the vibration intensity at which the molten material height in the blast furnace can be detected. Then, by using the above regression equation and a corrected vibration intensity obtained by removing the influence of the bosh gas amount from the vibration intensity of the identified frequency, the molten material height in a molten steel furnace, where the furnace interior cannot be directly observed, can be detected with high accuracy.

[0041] In the second embodiment, the vibration intensity of the specified frequency is corrected using the amount of Bosch gas generated by the introduction of gas, thereby enabling correction to the corrected vibration intensity with higher accuracy than using the amount of gas blown. By using the corrected vibration intensity corrected with high accuracy in this way, the molten material height in the blast furnace can be detected with higher accuracy than in the past.

[0042] [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 hearth of a large blast furnace is detected. In this example, a molten material height detection device configured with two vibration meters provided at different positions in the height direction is used. The installation heights of the vibration meters 24a and 24b from the hearth, and the heights of the blast tuyere 20 and the discharge hole 14 are shown in Table 1 below.

[0043]

[0044] FIG. 8 is a schematic diagram showing the configuration of a vibrometer and its peripheral devices according to Example 1. In FIG. 8, the same components as those in FIG. 2 are assigned the same reference numerals, and their description will be omitted. Amplifiers 40a and 40b were connected to the vibrometers 24a and 24b, respectively, to amplify the vibration data. The vibration data amplified by the amplifiers 40a and 40b was stored in data loggers 42a and 42b. The vibration data stored in the data loggers 42a and 42b was processed using the computing device 26. The vibration measurement conditions were a sampling frequency of 10,000 Hz and a recording length of 10 seconds, assuming the vibration frequency due to the air blowing measured in a blast furnace. Under these conditions, the vibration of the furnace wall was measured every three minutes for four days, and vibration data for that period was obtained.

[0045] In this example, prior to FFT analysis, the vibration data underwent overlap processing, smoothing processing, and window function processing. In the overlap processing, the raw vibration data was divided into 3 / 10 of the recording length, and processed so that half of the data overlapped. Each divided frame was smoothed using a Gaussian filter. In the window function processing, a Hanning window was applied. After processing the divided frames in this way, FFT analysis was performed, and the average value of the vibration intensity calculated by FFT analysis of all divided frames was used.

[0046] After performing the 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 and 24b. In order to evaluate the vibration intensity of all these frequencies, the vibration frequency was divided into a reference vibration frequency f and a frequency width Δf. 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 taking into account the frequency width Δf, 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.

[0047] In this way, the vibration intensity at each frequency was calculated, and then the correlation coefficient between the vibration intensity and the amount of Bosh gas was calculated. In Example 1, the correlation coefficient was calculated using the vibration data of the vibrometer 24a measured on the day when the height of the molten material was the lowest during the four-day measurement period.

[0048] 9 is a contour diagram showing the average value of the correlation coefficient between the vibration intensity and the Bosch gas amount calculated from the measurements of the vibration meter 24a. In Example 1, the R between the vibration intensity and the Bosch gas amount was largest when f = 1300 Hz and Δf = 275 Hz. Therefore, f ± Δf = 1300 ± 275 Hz was identified as the frequency correlated with the vibration generated by introducing gas.

[0049] Next, the vibration intensity was corrected for the bosh gas amount by determining the regression line to be used in the above formula (1) using the vibration intensity and the bosh gas amount for two days out of the four days for which the vibration data was measured, when the amount of accumulated molten material at the furnace bottom was small.

[0050] 10A and 10B are graphs showing the regression line between the vibration intensity of the vibration meters 24a and 24b and the amount of Bosh gas. FIG. 10A shows the graph and regression line of the vibration meter 24a, and FIG. 10B shows the graph and regression line of the vibration meter 24b. The horizontal axis of these graphs represents the amount of Bosh gas (Nm ３ / min), and the vertical axis is the vibration intensity (m / s ２ By substituting the slopes of these regression lines into the above equation (1), the following equations (3) and (4) were calculated to correct the vibration intensity to a corrected vibration intensity.

[0051] G ０ =G+(Bosh−Bosh ０ ) x 2.1 x 10 －３ ...(3)

[0052] G ０ =G+(Bosh−Bosh ０ ) x 0.8 x 10 －３ ...(4)

[0053] The corrected vibration intensity, which was free from the influence of the Bosh gas amount, was calculated using the above formulas (3) and (4).The calculated corrected vibration intensity was used to detect the melt height.

[0054] 11A and 11B are graphs showing the time course of the molten material height and the time course of the corrected vibration intensity obtained from the operational data. FIG. 11A is a graph showing the time course of the molten material height obtained from the operational data, with the horizontal axis representing time and the vertical axis representing the molten material height (m). FIGS. 11B and 11C are graphs showing the time course of the corrected vibration intensity measured by the vibration meters 24a and 24b, with the horizontal axis representing time and the vertical axis representing the corrected vibration intensity (m / s ２ )

[0055] As shown in Figure 11, the corrected vibration intensity value for vibration meter 24b began to decrease around 18:30 on April 19, while the corrected vibration intensity value for vibration meter 24a continued to increase. Therefore, it can be seen that the molten material height reached the position of vibration meter 24b at 18:30 on April 19. From 18:30 to 23:59 on April 19, the molten material height was between 2.0 and 2.6 m, between vibration meter 24a and 24b. The molten material height values ​​estimated and calculated at the same time showed an increase from approximately 0.0 m to 2.0 m between 12:00 and 23:59 on April 19. Thus, the molten material height detected from the vibration intensity and the molten material height estimated and calculated from the operational data were nearly identical, confirming that the molten material height can be detected using the method of Example 1.

[0056] [Example 2] Next, Example 2 will be described, in which it was confirmed that the melt height can be detected using a single vibration meter. In Example 2, the same capacity as Example 1 was used, but the melt height was 5000 m ３ The molten material height of the large blast furnace was detected using vibration data from the vibration meter 24a. The vibration data acquired from the vibration meter 24a was subjected to overlap processing, smoothing processing, and window function processing, as in Example 1, and then FFT analysis.

[0057] The frequency correlated with the vibration caused by the air blowing was set to f±Δf=1300±275 Hz, the same as in Example 1. The vibration intensity of this frequency from 0:00 to 23:59 on April 19th was corrected using the following formula (3) to calculate the corrected vibration intensity. The height of the molten material accumulated in the hearth of the blast furnace was calculated using the operation data obtained from the blast furnace from 0:00 to 23:59 on April 19th and the following formula (5).

[0058] G ０ =G+(Bosh−Bosh ０ ) x 2.1 x 10 －３ ...(3)

[0059] h=(Wi / ρi+Ws / ρs) / (ε×Sb)...(5)

[0060] In the above formula (5), h is the melt height (m), Wi is the weight of the molten pig iron at the hearth (kg), and ρi is the density of the molten pig iron (kg / m ３ ), Ws is the weight of the molten slag at the hearth (kg), 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 ２ ) where (-) means dimensionless.

[0061] The weights of the molten pig iron and molten slag at the hearth were calculated by adding the amounts of pig iron and slag obtained in each tapping operation and subtracting the amounts of pig iron and slag produced by the amounts of tapped pig iron and slag, respectively, and correcting for 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.

[0062] Using the molten material height calculated in this way, a regression equation showing the correspondence relationship between the corrected vibration intensity and the molten material height was obtained. As a comparative example, a corrected vibration intensity corrected by the gas blowing volume disclosed in Patent Document 2 was obtained, and a regression equation showing the correspondence relationship between the corrected vibration intensity and the molten material height was obtained.

[0063] 12 is a graph showing a regression equation between corrected vibration intensity and melt height. The horizontal axis of FIG. 12 is the corrected vibration intensity (m / s ２ ) and the vertical axis is the height of the molten material (m). The graph shown in Figure 12(a) is a regression equation showing the correspondence relationship between the corrected vibration intensity corrected by the amount of Bosh gas and the height of the molten material, and this regression equation is the following equation (6). The graph shown in Figure 12(b) is a regression equation showing the correspondence relationship between the corrected vibration intensity corrected by the amount of gas blown and the height of the molten material, and this regression equation is the following equation (7).

[0064] h = G ０ ×0.875-15.9...(6) h=G０ × 0.813 - 15.5 (7) In the above formulas (6) and (7), h is the height (m) of the molten material accumulated at the bottom of the furnace, and G ０ is the corrected vibration intensity (m / s ２ )

[0065] The detected value of the height of the smelt accumulated in the hearth of the blast furnace was calculated using the above formula (6) and the corrected vibration intensity corrected by the amount of bosh gas (Example). Similarly, the detected value of the height of the smelt accumulated in the hearth of the blast furnace was calculated using the above formula (7) and the corrected vibration intensity corrected by the amount of gas blown (Comparative Example). The actual measured value of the height of the smelt accumulated in the hearth of the blast furnace was calculated using the above formula (5) and operational data. Then, the correlation between the detected value and the actual measured value of the calculated smelt height was confirmed in the Example and Comparative Example.

[0066] 13A and 13B are graphs showing the correlation between the detected value and the actual measurement value of the molten material height. Fig. 13A is a graph showing the correlation between the detected value and the actual measurement value of the molten material height detected using the corrected vibration intensity corrected by the amount of Bosch gas. Fig. 13B is a graph showing the correlation between the detected value and the actual measurement value of the molten material height detected using the corrected vibration intensity corrected by the amount of blown gas.

[0067] As shown in Fig. 13(a), the correlation coefficient between the detected value of the molten material height detected using the corrected vibration intensity corrected by the Bosh gas volume and the actual measurement value was 0.723. On the other hand, as shown in Fig. 13(b), the correlation coefficient between the detected value of the molten material height detected using the corrected vibration intensity corrected by the gas blowing volume and the actual measurement value was 0.691.

[0068] Thus, it was confirmed that the correlation between the detected value of the smelt height detected using the corrected vibration intensity corrected for the bosh gas volume and the actual measurement value is stronger than the correlation between the detected value of the smelt height detected using the corrected vibration intensity corrected for the gas blast volume and the actual measurement value. These results confirm that by detecting the smelt height using the corrected vibration intensity corrected for the bosh gas volume, it is possible to detect the smelt height in a blast furnace with higher accuracy than the conventional method of detecting the smelt height using the corrected vibration intensity corrected for the gas blast volume.

[0069] REFERENCE SIGNS LIST 10 Blast furnace 12 Melt 14 Discharge hole 16 Melt flow 18 Gas 20 Blast tuyeres 22 Melt height detection device 24a to 24c Vibration meters 26 Calculation device 30 Melt height detection device 32 Vibration meters 34 Calculation device 40a, 40b Amplifiers 42a, 42b Data loggers

Claims

1. A method for detecting the height of a molten material 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 frequency of the vibrations to identify the vibration intensity of a frequency that is correlated with vibrations generated by introducing gas into an inlet in the lower part of the furnace; and detecting the height of the molten material using a corrected vibration intensity that removes the influence of the amount of bosh gas generated by the introduction of the gas from the vibration intensity of the identified frequency.

2. The method for detecting the height of a molten material 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 amount of Bosch gas.

3. A method for detecting the height of a molten material according to claim 1 or claim 2, wherein when the corrected vibration intensity reaches a maximum, the position where the vibration of the corrected vibration intensity that has reached a maximum is measured is detected as the height of the molten material in the blast furnace.

4. A method for detecting the height of a 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 a molten material height according to claim 1 or claim 2, wherein a correspondence relationship between the corrected vibration intensity and the molten material height is determined in advance, and the molten material 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 according to claim 5, wherein the vibration is measured at a position between 0.90 and 1.00 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 height of a 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 to measure vibrations of the furnace wall; and a computing device that performs frequency analysis of the vibrations measured by the vibration meters to identify vibration intensities of frequencies correlated with vibrations generated by introducing gas into an inlet in the lower part of the furnace, and detects the molten material height using corrected vibration intensities obtained by removing the influence of the amount of Bosch gas generated by the introduction of the gas from the vibration intensities of the identified frequencies.

8. A molten material height detection device as described in claim 7, comprising two or more of the 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 molten material height detection device according to claim 7, wherein the calculation device detects the molten material height using a correspondence relationship between the corrected vibration intensity and the molten material height.

10. A molten material height detection device as described in claim 9, wherein the vibration meter is installed at a position between 0.90 and 1.00 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.

11. A method for producing 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 the vibration intensity of a frequency correlated with the vibration generated by introducing gas into an inlet in the lower part of the furnace; detecting the molten material height in the blast furnace using a corrected vibration intensity obtained by removing the influence of the amount of bosh gas generated by the introduction of the gas from the vibration intensity of the identified frequency; and adjusting the production conditions for the molten material so that the detected molten material height is within a target molten material height range.

12. The method for producing a molten material according to claim 11, wherein a correspondence relationship between the corrected vibration intensity and the molten material height is determined in advance, and the molten material height is detected using the correspondence relationship and the corrected vibration intensity obtained from the vibration measurement.

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