Method for measuring melt level in blast furnace, device for measuring melt level in blast furnace, and method for operating blast furnace

Abstract

A method for measuring the level of a melt in 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 using a plurality of vibrometers disposed at predetermined intervals in the height direction of the furnace body; a vibration intensity calculation step in which the vibration intensity of the frequency range originating from the blowing air at each measurement position is calculated by Fourier transform of the vibration frequency distribution; and a melt level calculation step for calculating a discontinuity point of the change in the vibration intensity in the height direction of the furnace body, and using a position corresponding to the discontinuity point as the position of the melt level in the blast furnace.

Description

Technical Field

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

[0002] In the ironmaking industry, the blast furnace is located at the most upstream process, so the stabilization technology of its operation is considered to be very important. For the stable operation of the blast furnace, it is important to ensure good air permeability in the furnace. As one of the factors hindering the air permeability in the furnace, the rise in the liquid level of molten iron and molten slag (hereinafter, both are collectively referred to as melt) retained in the filling layer at the bottom of the furnace can be cited. The rise in the liquid level of the melt (hereinafter referred to as the melt level) may cause the gas flow path in the furnace to narrow, becoming a direct cause of the increase in the air supply pressure. In addition, when the melt level reaches the height of the air supply tuyere, it may become the cause of major faults such as melting loss of the air supply tuyere, or even blockage of the air supply tuyere, slag reflux (the phenomenon of melt reflux from the air supply tuyere). Therefore, in order to achieve stable operation of the blast furnace, the melt level should be reliably prevented from reaching the height of the air supply tuyere.

[0003] Against this backdrop, a method has been proposed for performing a material balance evaluation of the amount of melt remaining in a blast furnace based on various operating specifications. Specifically, Patent Document 1 describes a method for estimating the amount of melt remaining in the furnace by using the actual volume of the material charged to the furnace and a theoretical volume calculated based on the operating specifications to determine the theoretical amount of melt discharged from the blast furnace, and then comparing this amount with the actual amount of melt discharged. Furthermore, Patent Document 2 describes a method for estimating the melt level in the furnace by substituting parameters representing the properties of the blast furnace's constituent materials, including the melt level, into a general equation related to continuous circumferential strain to solve for variables measured by multiple strain gauges installed in the furnace body.

[0004] Patent Document 3 describes a method utilizing the so-called Bernoulli theorem, which calculates the discharge velocity of the molten material from the taphole of a blast furnace based on the discharge distance, discharge angle, and discharge height of the molten material, and uses this discharge velocity to infer the molten liquid level within the furnace. The accuracy of this method's inference depends on the accuracy of the calculation of the discharge velocity of the molten material from the taphole. In this method, the discharge velocity is estimated through image analysis of images captured by a camera. Furthermore, Patent Document 4 describes a method for measuring the vibration intensity of the furnace wall at the bottom of the furnace and inferring the molten liquid level within the furnace based on a previously determined relationship between the vibration intensity in a specific frequency band and the molten liquid level.

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2002-302709

[0006] Patent Document 2: Japanese Patent Application No. 2015-528905

[0007] Patent Document 3: Japanese Patent No. 7056813

[0008] Patent Document 4: International Publication No. 2022 / 201717

[0009] However, the method described in Patent Document 1 does not consider the porosity of the filling layer below the furnace or the shape of the solidified layer. Therefore, even if the amount of melt remaining in the furnace can be estimated, estimating the melt level, which is crucial for stable blast furnace operation, remains problematic. Furthermore, due to the influence of various weighing errors, there is a concern that estimation errors may accumulate in blast furnace processes involving high mass production, leading to a decrease in estimation accuracy over time.

[0010] In addition, the method described in Patent Document 2 has the following problems. It is known that in addition to the iron sheet and cooling staves on the surface of the blast furnace, there are also refractory bricks and a solidified layer formed by the cooling and solidification of the molten material in the furnace in the lower part of the furnace. Moreover, refractory bricks deteriorate over the years due to wear and thermal stress, and the range of the solidified layer varies daily depending on the thermal conditions in the lower part of the furnace. Therefore, it is extremely difficult to grasp the existence status of these constituent materials. Therefore, in the method described in Patent Document 2, it is essentially impossible to exclude unknown parameters other than the melt level representing the constituent materials of the blast furnace from the general equation. Therefore, it is difficult to say that the accuracy of the melt level inferred from the general equation can be met.

[0011] In addition, in the method described in patent document 3, since a large amount of dust is generated as the high-temperature melt is discharged during the tapping operation, the possibility of being able to use a camera to clearly capture the discharge behavior of the melt is low. In addition, the generation of opening errors represented by transverse holes is unavoidable during the tapping operation, which also contributes to the reduction in the frequency of inferred discharge behavior of the melt. In addition, due to this, the shape of the opening is different each time the iron is tapped, so it is difficult to quantify the friction force on the path from the furnace to the discharge port. In summary, in the method described in patent document 3, it can be said that it is extremely difficult to measure the melt level with high precision.

[0012] Furthermore, the method described in Patent Document 4 presents the following problems. The actual vibration intensity of the furnace body is significantly affected by fluctuations in the air flow above the melt level, as well as changes in the shape of structures such as the furnace filling, furnace bottom bricks, and the solidified layer. Therefore, in blast furnace processes where operating conditions fluctuate constantly, a one-to-one correlation between the vibration intensity of the furnace body and the melt level cannot be established. Consequently, the method described in Patent Document 4 is effective only under extremely ideal conditions, where furnace conditions other than the melt level are stable. Long-term, stable melt level measurement is difficult. Summary of the Invention

[0013] The present invention has been developed to address the aforementioned issues, and its purpose is to provide a method and device for measuring the melt level in a blast furnace that can accurately measure the melt level in the blast furnace regardless of the blast furnace's operating conditions. Furthermore, another object of the present invention is to provide a blast furnace operating method that enables stable and environmentally friendly blast furnace operation.

[0014] The method for measuring the melt level in a blast furnace involved in the present invention includes: a measuring step, using a plurality of vibrometers arranged at predetermined intervals along the height direction of the furnace body of the blast furnace to measure the vibration frequency distribution in the height direction of the furnace body; a vibration intensity calculating step, by performing Fourier transform on the above-mentioned vibration frequency distribution, calculating the vibration intensity of the frequency range originating from the air supply at each measuring position; and a melt level calculating step, calculating the discontinuity point of the change in the vibration intensity in the height direction of the furnace body, and taking the position corresponding to the discontinuity point as the position of the melt level in the blast furnace.

[0015] The melt level calculation step preferably includes: a step of classifying, at each of the measurement positions, 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; a step of constructing, at each of the measurement positions, a first linear approximation and a second linear approximation representing the relationship between the height position of the furnace body and the vibration intensity based on the first vibration intensity data and the second vibration intensity data, respectively; a step of calculating, at each of the measurement positions, the difference in vibration intensity between the first linear approximation and the second linear approximation at the measurement position as a discontinuity; and a step of determining, among all the measurement positions, the measurement position at which the discontinuity is largest as the melt level.

[0016] The vibration meter is preferably arranged between the height of the tap hole and the height of the tuyere of the furnace.

[0017] The frequency range of the air supply is preferably within the range of 700 to 900 Hz.

[0018] The device for measuring the melt level in a blast furnace according to the present invention comprises: 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; and an information processing device for calculating the vibration intensity of the frequency range originating from the air supply at each measurement position by performing Fourier transform on the vibration frequency distribution, calculating the discontinuity point of the change in the vibration intensity in the height direction of the furnace body, and taking the position corresponding to the discontinuity point as the position of the melt level in the blast furnace.

[0019] The blast furnace operating method according to the present invention includes the step of operating the blast furnace according to the melt level measured by the melt level measuring method in the blast furnace according to the present invention.

[0020] The method and device for measuring the melt level in a blast furnace according to the present invention can accurately measure the melt level in the blast furnace regardless of the blast furnace operating conditions. Furthermore, the blast furnace operating method according to the present invention enables stable and environmentally friendly blast furnace operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a schematic cross-sectional view showing the structure of a blast furnace to which a device for measuring the melt level in a blast furnace according to one embodiment of the present invention is applied.

[0022] Figure 2 This is a graph showing the results of plotting the vibration intensity due to air blowing measured by a plurality of vibration meters when the melt level is changed, against the relative height of the measurement position with respect to the melt level.

[0023] Figure 3 This is a diagram showing an outline of a method for measuring the melt level in a blast furnace according to one embodiment of the present invention.

[0024] Figure 4 This is a graph showing the temporal change in the measured value of the melt level from the initial stage to the final stage of tapping. DETAILED DESCRIPTION

[0025] Hereinafter, a method for measuring the melt level in a blast furnace, an apparatus for measuring the melt level in a blast furnace, and a blast furnace operating method according to one embodiment of the present invention will be described with reference to the accompanying drawings.

[0026] 〔structure〕

[0027] First, refer to Figure 1 , the structure of a device for measuring the melt level in a blast furnace according to one embodiment of the present invention will be described.

[0028] Figure 11 is a schematic cross-sectional view showing the structure of a blast furnace to which a device for measuring the melt level in a blast furnace according to one embodiment of the present invention is applied. Figure 1 As shown, a blast furnace 1 as one embodiment of the present invention includes a generally cylindrical furnace body 2, an air supply tuyere (hereinafter referred to as a tuyere) 3 provided below the furnace body 2, and a taphole 4 provided in the furnace body 2 below the tuyere 3. The bottom of the blast furnace 1 is composed of furnace bottom bricks 5 and furnace wall bricks 6, and the inner and outer wall surfaces of the furnace wall bricks 6 are covered with a cooling sleeve 7 and iron sheet 8, respectively.

[0029] Furthermore, a blast furnace 1, as 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 melt level within the blast furnace. Each vibration meter 9 is positioned perpendicular to a tangent to the circumference of the furnace body 2, extending from the height of the tap hole 4 to the height of the tuyere 3, and is positioned at equal intervals along a straight line extending along the surface of the iron sheet 8. Each vibration meter 9 measures the vibration value of the furnace body 2 as a current value and outputs an electrical signal representing the measured current value to the data logger 10.

[0030] The data logger 10 converts the current value measured by each vibration meter 9 into a vibration value based on the electrical signal output from each vibration meter 9. The information processing device 11 calculates the vibration intensity of the furnace body 2 at the location where each vibration meter 9 is installed by performing a Fourier transform on the time-varying vibration value data at the location where each vibration meter 9 is installed (measurement location), generated by the data logger 10. The information processing device 11 then calculates the melt level within the blast furnace by using the calculated vibration intensity to execute the following method for measuring the melt level within the blast furnace.

[0031] The results of the measurements in the actual equipment confirmed that the vibration of the furnace body 2 has all vibration frequency bands, among which the peak value is particularly high and the vibration frequency band in which the peak value is confirmed at all measurement positions is the frequency band of 700 to 900 Hz. Since it has been confirmed that the vibration in the frequency band of 700 to 900 Hz has a general trend of showing high values ​​at a position close to the tuyere 3, it is considered to be the vibration caused by the air supply 23 from the tuyere 3 (vibration derived from the air supply). Therefore, in the present invention, the vibration intensity confirmed in the frequency range of 700 to 900 Hz corresponding to the vibration derived from the air supply is used to measure the melt level. However, there is a possibility that the frequency band in which the vibration derived from the air supply is confirmed to vary depending on the shape of the furnace body 2, the influence of the foundation, etc., and there is no conclusive evidence that any blast furnace can be evaluated in the same frequency band. Therefore, it is expected that each time the present invention is deployed in other blast furnaces, a basic vibration frequency band analysis will be performed.

[0032] exist Figure 1In the blast furnace 1 shown, raw materials, iron ore 21 and coke 22, are loaded into the furnace body 2 in layers from the furnace top and reduced by blast (hot air) 23, which is pressure-fed from the tuyere 3, to form a melt 24. The melt 24 then accumulates at the furnace bottom and is discharged from the taphole 4 as iron and slag 25 by perforating the taphole 4 at predetermined intervals. A device for measuring the melt level in a blast furnace, which is one embodiment of the present invention, measures the liquid level of the melt 24 at the bottom of the furnace as the melt level.

[0033] [Measurement method]

[0034] Next, refer to Figure 2 、 Figure 3 , a method for measuring the melt level in a blast furnace according to one embodiment of the present invention will be described.

[0035] Figure 2 The results are plotted when the molten metal level is changed using a cold model simulating the lower part of the blast furnace 1 and the vibration intensity due to the blown air measured by the plurality of vibration meters 9 is plotted against the height of the relative measurement position of the vibration meter 9 relative to the molten metal level (the height of the vibration meter based on the liquid surface). Figure 2 As shown in the figure, it can be seen that the vibration intensity caused by the air supply varies discontinuously on the surface of the molten material. In addition, this experiment includes the results of multiple cases by simulating factors that may vary in actual blast furnaces, such as the physical properties of the molten material, the air supply volume, the filling particle size, and the particle size distribution of the filling particles. However, in no case does it overturn the Figure 2 Furthermore, even in experiments simulating vibrations during raw material charging, changes in the total weight of the furnace filling due to changes in the ratio of reduced materials in the blast furnace, structural changes due to age-related degradation of the furnace bottom bricks due to wear, and the installation conditions of the furnace body, which are considered to be factors of interfering vibration fluctuations, the same trend was confirmed. Figure 2 The trend shown.

[0036] In summary, it can be considered that the discontinuous change in the vibration intensity of the surface layer of the melt is a phenomenon that is uniformly confirmed under all operating conditions. Therefore, if the discontinuous point of the change in the vibration intensity in the height direction of the furnace body can be calculated, then since the liquid surface of the melt exists near the discontinuous point, the melt level in the blast furnace can be measured with high precision regardless of the operating conditions of the blast furnace. In addition, by detecting the rise in the melt level in advance, the increase in the reduced material ratio caused by the increase in ventilation resistance due to the rise in the melt level can be prevented before it occurs, thereby enabling stable and environmentally friendly blast furnace operation. The technical concept of the present invention is based on the above logic.

[0037] Figure 3: is a diagram showing an overview of a method for measuring the molten material level in a blast furnace as one embodiment of the present invention. In the method for measuring the molten material level in a blast furnace as one embodiment of the present invention, first, the vibration intensity of the frequency band originating from the air supply is measured using vibration meters 9 that are arranged at equal intervals at multiple locations on a line perpendicular to a tangent to the circumference of the furnace body 2 at height positions from the iron outlet 4 to the tuyere 3. In this embodiment, it is assumed that n (≥2) vibration meters 9 are provided. Next, the information processing device 11 classifies the vibration intensity data at each measurement position (vibration measurement point) i (=1 to n) into first vibration intensity data for a measurement position higher than the measurement position and second vibration intensity data for a measurement position lower than the measurement position. Next, the information processing device 11 constructs a first linear approximation and a second linear approximation representing the relationship between the height direction position of the furnace body 2 and the vibration intensity based on the first vibration intensity data and the second vibration intensity data at each measurement position i. Next, as Figure 3 As shown in FIG. 1 , the information processing device 11 calculates the difference in vibration intensity at each measurement position i using the two linear approximations as the discontinuity Δe(i). Finally, the information processing device 11 calculates the maximum value max[Δe(i)] among the discontinuities Δe(i) at each measurement position i. i = 1，n The measured position i is used as the melt level.

[0038] Example

[0039] In this embodiment, the capacity is about 5000m 3 In a large blast furnace of this type, conventional raw materials were charged, pulverized coal was blown in through the tuyere, and vibration meters were placed at equal intervals from the taphole level (2 m) to the tuyere level on a line perpendicular to the circumferential tangent of the furnace body to measure the vibration of the furnace body and the melt level within the blast furnace. Table 1 shows the operating conditions for Examples 1 and 2. Figure 4 Indicates the time variation of the measured value of the melt level from the beginning to the end of tapping. Figure 4 As shown, the molten liquid level eventually became approximately the same as the tap hole height in both Examples 1 and 2. Therefore, it was confirmed that the molten liquid level can be measured with high accuracy according to the present invention.

[0040] [Table 1]

[0041] Table 1

[0042] Example 1 Example 2 Coke rate (kg / t) 350 320 Pulverized coal ratio (kg / t) 248 243 Reducing material ratio (kg / t) 598 563 Iron output (t / d) 9798 9744 Iron tapping temperature (℃) 1542 1540

[0043] While the embodiments of the invention developed by the present inventors have been described above, the present invention is not limited to the description and drawings that constitute part of the disclosure of the present invention shown in these embodiments. In other words, other embodiments, examples, and application technologies developed by those skilled in the art based on these embodiments are all within the scope of the present invention.

[0044] Industrial applicability

[0045] According to the present invention, a method and device for measuring the melt level in a blast furnace can be provided, which can accurately measure the melt level in the blast furnace regardless of the blast furnace operating conditions. Furthermore, according to the present invention, a method for operating a blast furnace can be provided, which can stably and environmentally friendly operate the blast furnace.

[0046] Description of Reference Numerals

[0047] 1… blast furnace; 2… furnace body; 3… air vents and tuyere; 4… tapping hole; 5… furnace bottom bricks; 6… furnace wall bricks; 7… cooling sleeve; 8… iron sheet; 9… vibration meter; 10… data recorder; 11… information processing device; 21… iron ore; 22… coke; 23… air vents; 24… melt; 25… tapping and slag.

Claims

1. A method for measuring the melt level in a blast furnace, characterized in that: include: 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 of the frequency range originating from the blown air at each measurement position by performing Fourier transform on the vibration frequency distribution; and The melt level calculation step calculates a discontinuity point of change in vibration intensity in the height direction of the furnace body, and defines a position corresponding to the discontinuity point as a position of the melt level in the blast furnace.

2. The method for measuring the melt level in a blast furnace according to claim 1, wherein: The melt level calculation step comprises: a step of classifying the 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; A step of constructing a first linear approximation and a second linear approximation expressing the relationship between the height direction position of the furnace body and the vibration intensity based on the first vibration intensity data and the second vibration intensity data at each of the measurement positions; a step of calculating, at each of the measurement positions, a difference in vibration intensity between the first linear approximation and the second linear approximation at the measurement position as a discontinuity; and The measurement position where the discontinuity is the largest among all the measurement positions is taken as the step of the melt level.

3. The method for measuring the melt level in a blast furnace according to claim 1 or 2, wherein: The vibration meter is arranged between the height of the tap hole and the height of the tuyere of the furnace body.

4. The method for measuring the melt level in a blast furnace according to claim 1 or 2, wherein: The frequency range of the air supply is within the range of 700 to 900 Hz.

5. A device for measuring the level of melt in a blast furnace, characterized in that: have: a plurality of vibrometers arranged at predetermined intervals along the height direction of the furnace body of the blast furnace to measure a vibration frequency distribution in the height direction of the furnace body; and The information processing device calculates the vibration intensity of the frequency range originating from the air supply at each measurement position by performing Fourier transform on the vibration frequency distribution, calculates the discontinuity point of the change in the vibration intensity in the height direction of the furnace body, and uses the position corresponding to the discontinuity point as the position of the melt level in the blast furnace.

6. A method for operating a blast furnace, characterized in that: The method comprises the step of operating the blast furnace according to the melt level measured by the method for measuring the melt level in a blast furnace according to claim 1 or 2.

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