METHOD FOR MEASURING MOLTEN MATERIAL LEVEL IN A BLAST FURNACE, MEASURING DEVICE FOR MOLTEN MATERIAL LEVEL IN A BLAST FURNACE, AND METHOD FOR OPERATING A BLAST FURNACE

Abstract

A method for measuring the level of a molten material in the furnace of a blast furnace according to the present invention comprises: a measurement step for measuring a vibration frequency distribution in the height direction of a furnace body of the blast furnace by using a plurality of vibration meters arranged at a predetermined interval along the height direction of the furnace body; a vibration intensity calculation step for calculating the vibration intensity in a frequency range derived from blast at each measurement position by performing Fourier transformation on the vibration frequency distribution; and a molten material level calculation step for calculating a point of discontinuity in changes in the vibration intensity in the height direction of the furnace body, and determining a position corresponding to the point of discontinuity as the position of the level of the molten material in the furnace of the blast furnace.

Description

[Technical Field]

[0001] The present invention relates to a method for measuring a molten material level in a blast furnace, a device for measuring a molten material level in a blast furnace, and a method for operating a blast furnace. [Background technology]

[0002] In the steelmaking industry, blast furnaces are located at the most upstream stage, and therefore technologies for stabilizing their operation are highly valued. Ensuring good permeability within the furnace is crucial for stable blast furnace operation. One of the factors impairing permeability within the furnace is the rise in the liquid level of molten pig iron and molten slag (hereinafter collectively referred to as the molten material) remaining in the packed bed at the bottom of the furnace. A rise in the liquid level of the molten material (hereinafter abbreviated as the molten material level) can narrow the gas flow path within the furnace and directly cause an increase in blast pressure. Furthermore, if the molten material level reaches the blast tuyere level, it can cause serious problems such as blast tuyere melting, blockage of the blast tuyere, and slag backflow (a phenomenon in which molten material flows back from the blast tuyere). Therefore, to achieve stable blast furnace operation, it is essential to ensure that the molten material level does not reach the blast tuyere level.

[0003] Against this background, a method has been proposed for evaluating the amount of molten material remaining in a blast furnace based on material balance from various operational parameters of the furnace. Specifically, Patent Document 1 describes a method for estimating the amount of molten material remaining in the furnace by calculating the theoretical amount of molten material to be discharged from the blast furnace using the actual volume value of the charge material in the furnace and a theoretical volume value calculated from the operational parameters, and comparing this with the amount of molten material actually discharged. Furthermore, Patent Document 2 describes a method for estimating the molten material level in a furnace by solving variables measured by multiple strain gauges installed in the furnace body by providing parameters representing the properties of the constituent materials of the blast furnace, including the molten material level, to a general equation for continuous ambient strain.

[0004] Furthermore, Patent Document 3 describes a method utilizing the so-called Bernoulli's theorem, in which the discharge rate of the molten material discharged from the taphole of a blast furnace is calculated from the discharge distance, discharge angle, and discharge height, and the molten material level in the furnace is estimated using this. The accuracy of this method depends on the accuracy of the calculation of the discharge rate of the molten material discharged from the taphole, and this method estimates the discharge rate by image analysis of images taken with a camera. Furthermore, Patent Document 4 describes a method for measuring the vibration intensity of the furnace wall in the lower part of the furnace and estimating the molten material level in the furnace from the correspondence relationship between the vibration intensity in a specific frequency band obtained in advance and the molten material level. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-302709 [Patent Document 2] Special Publication No. 2015-528905 [Patent Document 3] Patent No. 7056813 [Patent Document 4] International Publication No. 2022 / 201717 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the method described in Patent Document 1 does not take into account the void ratio of the packed bed in the lower part of the furnace or the shape of the solidified layer. Therefore, even if it is possible to estimate the amount of molten material remaining in the furnace, there remains a problem in estimating the liquid level of the molten material, which is important for stable operation of the blast furnace. In addition, because it is affected by various weighing errors, there is a concern that estimation errors will accumulate in blast furnace processes that handle large masses, and estimation accuracy will decrease over time.

[0007] Furthermore, the method described in Patent Document 2 has the following problems. It is known that in the lower furnace, in addition to the steel shell and cooling staves on the surface of the blast furnace, refractory bricks and a solidified layer formed by the cooled and solidified molten material in the furnace are present. Refractory bricks deteriorate over time due to wear and thermal stress, and the extent of the solidified layer changes daily depending on the thermal conditions in the lower furnace. This makes it extremely difficult to grasp the state of these constituent materials. Therefore, with the method described in Patent Document 2, it is virtually impossible to exclude unknown parameters other than the molten material level, which represents the constituent materials of the blast furnace, from the general equation. Therefore, the accuracy of the molten material level estimated from the general equation is not satisfactory.

[0008] Furthermore, with the method described in Patent Document 3, a large amount of dust is generated during the tapping operation due to the discharge of high-temperature molten material, making it unlikely that a clear image of the molten material's discharge behavior can be captured using a camera. Furthermore, tapping operations inevitably involve opening errors, such as with horizontal holes, which also contributes to a decrease in the frequency of estimating the molten material's discharge behavior. Furthermore, because the shape of the opening varies for each tap, it is difficult to quantify the frictional force that the molten material experiences along its path from the furnace to the discharge port. Taking all of these factors into consideration, it can be said that the method described in Patent Document 3 makes it extremely difficult to accurately measure the molten material level.

[0009] Furthermore, the method described in Patent Document 4 has the following problems: The vibration intensity of an actual furnace body is more strongly affected by fluctuations in the blast rate and changes in the shape of furnace fillers and structures such as hearth bricks and the solidified layer than the molten material level. For this reason, in a blast furnace process where the operating conditions change from moment to moment, it is impossible to establish a one-to-one correlation between the vibration intensity of the furnace body and the molten material level. For this reason, the method described in Patent Document 4 is effective only under extremely ideal conditions where the conditions inside the furnace other than the molten material level are steady, making it difficult to measure the molten material level stably over the long term.

[0010] The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a method and device for measuring the molten material level in a blast furnace that can measure the molten material level in the blast furnace with high accuracy regardless of the operating conditions of the blast furnace. Another object of the present invention is to provide a method for operating a blast furnace that can perform stable, eco-friendly blast furnace operation. [Means for solving the problem]

[0011] The method for measuring the molten material level in a blast furnace according to the present invention includes a measurement step of measuring the vibration frequency distribution in the height direction of the furnace body using a plurality of vibration meters arranged at predetermined intervals along the height direction of the furnace body of the blast furnace, a vibration intensity calculation step of calculating the vibration intensity in the frequency range caused by the air blowing at each measurement position by Fourier transforming the vibration frequency distribution, and a molten material level calculation step of calculating discontinuities in the change in vibration intensity in the height direction of the furnace body and setting the position corresponding to the discontinuity as the position of the molten material level in the blast furnace.

[0012] The molten material level calculation step preferably includes the steps of: classifying vibration intensity data at each measurement position into first vibration intensity data at a measurement position higher than the measurement position and second vibration intensity data at a measurement position lower than the measurement position; constructing a first linear approximation equation and a second linear approximation equation at each measurement position from the first vibration intensity data and the second vibration intensity data, respectively, which indicate the relationship between the vertical position of the furnace body and vibration intensity; calculating the difference in vibration intensity at the measurement positions of the first linear approximation equation and the second linear approximation equation as a discontinuity at each measurement position; and determining the measurement position among all measurement positions where the discontinuity is maximum as the molten material level.

[0013] The vibration meter may be installed between the taphole level and the tuyere level of the furnace body.

[0014] The frequency range derived from the air blowing is preferably within the range of 700 to 900 Hz.

[0015] The device for measuring the molten material level in a blast furnace according to the present invention comprises a plurality of vibration meters arranged at predetermined intervals along the height direction of the blast furnace body, which measure the vibration frequency distribution in the height direction of the furnace body, and an information processing device which calculates the vibration intensity in the frequency range caused by the air blowing at each measurement position by Fourier transforming the vibration frequency distribution, calculates discontinuities in the change in vibration intensity in the height direction of the furnace body, and regards the positions corresponding to the discontinuities as the position of the molten material level in the blast furnace.

[0016] A method for operating a blast furnace according to the present invention includes a step of operating the blast furnace according to the smelt level measured using the method for measuring the smelt level in a blast furnace according to the present invention. [Effects of the Invention]

[0017] According to the method and device for measuring the molten material level in a blast furnace of the present invention, the molten material level in a blast furnace can be measured with high accuracy regardless of the operating conditions of the blast furnace. Furthermore, according to the method for operating a blast furnace of the present invention, it is possible to stably perform eco-friendly blast furnace operation. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a schematic cross-sectional view showing the configuration of a blast furnace to which a device for measuring the level of molten material inside a blast furnace according to one embodiment of the present invention is applied. [Figure 2] FIG. 2 shows the results of plotting the strength of the airflow-induced vibration measured by multiple vibration meters when the melt level was changed against the height of the measurement position relative to the melt level. [Figure 3] FIG. 3 is a diagram showing an outline of a method for measuring the molten material level in a blast furnace according to one embodiment of the present invention. [Figure 4] FIG. 4 is a graph showing the time variation of the measured value of the molten material level from the early stage to the end of tapping. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, a method for measuring a molten material level in a blast furnace, a device for measuring a molten material level in a blast furnace, and a method for operating a blast furnace according to one embodiment of the present invention will be described with reference to the drawings.

[0020] 〔composition〕 First, with reference to FIG. 1, the configuration of a device for measuring the level of molten material in a blast furnace according to one embodiment of the present invention will be described.

[0021] Fig. 1 is a schematic cross-sectional view showing the configuration of a blast furnace to which a device for measuring the level of molten material inside a blast furnace according to one embodiment of the present invention is applied. As shown in Fig. 1, a blast furnace 1 according to one embodiment of the present invention includes a substantially cylindrical furnace body 2, a blast tuyere (hereinafter abbreviated as tuyere) 3 provided below the furnace body 2, and a tap hole 4 provided in the furnace body 2 below the tuyere 3. The hearth of the blast furnace 1 is composed of hearth bricks 5 and hearth bricks 6, and the inner and outer wall surfaces of the hearth bricks 6 are covered with a cooling sleeve 7 and a steel shell 8, respectively.

[0022] Furthermore, the blast furnace 1, which is one embodiment of the present invention, is equipped with a plurality of vibration meters 9, a data logger 10, and an information processing device 11 as devices for measuring the molten material level inside the blast furnace. Each vibration meter 9 is set at equal intervals along a straight line that is perpendicular to a tangent in the circumferential direction of the furnace body 2 and that follows the surface of the steel shell 8, from the height position of the tap hole 4 to the height position of the tuyere 3. Each vibration meter 9 measures the vibration value of the furnace body 2 as a current value and outputs an electric signal indicating the measured current value to the data logger 10.

[0023] The data logger 10 converts the current values ​​measured by each vibration meter 9 into vibration values ​​based on the electrical signals output from each vibration meter 9. The information processing device 11 calculates the vibration intensity of the furnace body 2 at the installation position of each vibration meter 9 by performing a Fourier transform on the time-lapse data of the vibration values ​​at the installation position (measurement position) of each vibration meter 9 generated by the data logger 10. Then, the information processing device 11 calculates the molten material level in the blast furnace by executing the method for measuring the molten material level in the blast furnace shown below using the calculated vibration intensity.

[0024] Measurements using an actual furnace revealed that the vibration of the furnace body 2 spans a wide range of vibration frequencies, with the highest peaks observed at all measurement positions in the 700-900 Hz frequency band. It was also confirmed that vibrations in the 700-900 Hz frequency band tended to exhibit higher values ​​near the tuyere 3, suggesting that the vibrations were caused by the blast 23 from the tuyere 3 (blast-induced vibrations). Therefore, in the present invention, the molten material level was measured using vibration intensity observed in the 700-900 Hz frequency range, which corresponds to blast-induced vibrations. However, the frequency band in which blast-induced vibrations are observed may vary depending on the shape of the furnace body 2, the influence of the ground, and other factors, and there is no certainty that this frequency band can be used to evaluate all blast furnaces in the same way. Therefore, when applying the present invention to other blast furnaces, it is desirable to analyze the basic vibration frequency bands each time.

[0025] In a blast furnace 1 shown in Figure 1, raw materials, iron ore 21 and coke 22, are charged in layers into a furnace body 2 from the furnace top and reduced by blast (hot air) 23 sent under pressure from tuyere 3 to form molten material 24. The molten material 24 is then stored in the furnace bottom and is discharged as tapping slag 25 from a tap hole 4 that is drilled at predetermined intervals. An apparatus for measuring the molten material level in a blast furnace, which is one embodiment of the present invention, measures the liquid level of the molten material 24 in the lower part of the furnace as the molten material level.

[0026] [Measurement method] Next, a method for measuring the molten material level in a blast furnace according to one embodiment of the present invention will be described with reference to FIGS.

[0027] Figure 2 shows the blast-induced vibration intensity measured by multiple vibration meters 9 when the molten material level was changed using a cold model simulating the lower part of a blast furnace 1. The vibration intensity was plotted against the relative height of the measurement position of the vibration meters 9 relative to the molten material level (vibration meter height relative to the liquid level). As shown in Figure 2, the blast-induced vibration intensity varied discontinuously at the surface of the molten material. This experiment also included results for multiple cases simulating factors that may vary in an actual blast furnace, such as the physical properties of the molten material, the blast rate, the packing particle size, and the packing particle size distribution. None of these cases overturned the trend shown in Figure 2. Furthermore, the trend shown in Figure 2 was also confirmed in experiments simulating factors that are thought to be caused by external disturbances, such as vibration during raw material charging, changes in the total weight of the furnace charge due to changes in the blast furnace reducing agent ratio, structural changes due to aging deterioration of the hearth bricks due to wear, and the installation conditions of the furnace body.

[0028] From the above, it is believed that discontinuous fluctuations in vibration intensity at the surface layer of the molten material are a phenomenon that is consistently observed under all operating conditions. Therefore, if the discontinuous point in the change in vibration intensity along the furnace body height can be calculated, the molten material level in the blast furnace can be measured with high accuracy regardless of the blast furnace operating conditions, because the molten material liquid surface is located near that discontinuous point. Furthermore, this allows for early detection of a rise in the molten material level and prevents an increase in the reducing agent rate caused by an increase in the air flow resistance due to the rise in the molten material level, thereby enabling stable, eco-friendly blast furnace operation. The technical concept of the present invention is based on the above logic.

[0029] FIG. 3 is a diagram illustrating an overview of a method for measuring the molten material level in a blast furnace according to one embodiment of the present invention. In this method for measuring the molten material level in a blast furnace according to one embodiment of the present invention, first, vibration intensity in a frequency band originating from the blast is measured using vibration meters 9 installed at equal intervals at multiple locations on a line perpendicular to a tangent line in the circumferential direction of the furnace body 2 from the tap hole 4 to the height of the tuyere 3. In this embodiment, n (≧2) vibration meters 9 are installed. Next, at each measurement position (vibration measurement point) i (=1 to n), the information processing device 11 classifies the vibration intensity data into first vibration intensity data at a measurement position higher than the measurement position and second vibration intensity data at a measurement position lower than the measurement position. Next, at each measurement position i, the information processing device 11 constructs a first linear approximation formula and a second linear approximation formula, respectively, that indicate the relationship between the vertical position of the furnace body 2 and the vibration intensity, from the first vibration intensity data and the second vibration intensity data. Next, as shown in FIG. 3, the information processing device 11 calculates the vibration intensity difference at each measurement position i between the two linear approximations as a discontinuity Δe(i). Finally, the information processing device 11 calculates the maximum value max[Δe(i)] among the n discontinuities Δe(i). i=1,n The measurement position i where [Example]

[0030] In this example, the capacity is approximately 5000 m 3 In a large blast furnace, pulverized coal was injected through the tuyere using normal charging materials. The vibration of the furnace body was measured using vibration meters installed at equal intervals on a line perpendicular to the tangent line of the circumferential direction of the furnace body from the tap hole level (height 2 m) to the tuyere level, and the molten material level in the blast furnace was measured. Table 1 shows the operating conditions for Examples 1 and 2. Figure 4 shows the time change in the measured molten material level from the beginning to the end of tapping. As shown in Figure 4, in both Examples 1 and 2, the molten material level ultimately reached the same level as the tap hole level. This confirmed that the present invention can measure the molten material level with high accuracy.

[0031] [Table 1]

[0032] Although the present invention has been described above as an embodiment, the present invention is not limited to the descriptions and drawings that form part of the disclosure of the present invention. In other words, other embodiments, examples, and operational techniques that can be made by those skilled in the art based on the present invention are all included in the scope of the present invention. [Industrial Applicability]

[0033] According to the present invention, it is possible to provide a method and an apparatus for measuring the molten material level in a blast furnace, which are capable of measuring the molten material level in the blast furnace with high accuracy regardless of the operating conditions of the blast furnace. Furthermore, according to the present invention, it is possible to provide a method for operating a blast furnace, which is capable of stably performing eco-friendly blast furnace operation. [Explanation of symbols]

[0034] 1 blast furnace 2 Furnace body 3 Blowout tuyere, tuyere 4 Taphole 5 hearth bricks 6 Furnace wall bricks 7 Cooling sleeve 8 Ironhide 9 Vibration meter 10 Data Logger 11 Information processing equipment 21 Iron Ore 22 Coke 23 Ventilation 24 Melt 25 Casting slag

Claims

1. a measuring step of measuring a vibration frequency distribution in the height direction of the furnace body using a plurality of vibrometers arranged at predetermined intervals along the height direction of the furnace body of the blast furnace; a vibration intensity calculation step of calculating the vibration intensity in a frequency range caused by air blowing at each measurement position by performing a Fourier transform on the vibration frequency distribution; A molten material level calculation step of calculating a discontinuous point in the change in vibration intensity in the height direction of the furnace body and determining the position corresponding to the discontinuous point as the position of the molten material level in the blast furnace; Including, The vibration meter is installed between the tap hole level and the tuyere level of the furnace body, The frequency range from the air blowing is within the range of 700 to 900 Hz. A method for measuring the molten material level inside a blast furnace.

2. The melt level calculation step includes: classifying vibration intensity data at each measurement position into first vibration intensity data at a measurement position higher than the measurement position and second vibration intensity data at a measurement position lower than the measurement position; At each of the measurement positions, a first linear approximation formula and a second linear approximation formula are constructed from the first vibration intensity data and the second vibration intensity data, respectively, which represent the relationship between the height direction position of the furnace body and the vibration intensity; calculating a vibration intensity difference between the first linear approximation formula and the second linear approximation formula at each measurement position as a discontinuity; determining the measurement position at which the discontinuity is greatest among all measurement positions as the melt level; 2. The method for measuring the melt level in a blast furnace according to claim 1, comprising:

3. a plurality of vibrometers arranged at predetermined intervals along the height direction of the furnace body of the blast furnace, for measuring the vibration frequency distribution in the height direction of the furnace body; An information processing device that calculates the vibration intensity in the frequency range caused by the air blowing at each measurement position by performing a Fourier transform on the vibration frequency distribution, calculates a discontinuity point in the change in the vibration intensity in the height direction of the furnace body, and determines the position corresponding to the discontinuity point as the position of the molten material level in the blast furnace; Equipped with The vibration meter is installed between the tap hole level and the tuyere level of the furnace body, The frequency range from the air blowing is within the range of 700 to 900 Hz. A device for measuring the molten material level inside a blast furnace.

4. A method for operating a blast furnace, comprising the step of operating the blast furnace according to a smelt level measured using the method for measuring a smelt level in a blast furnace according to claim 1 or 2.

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