Method for measuring molten material level in blast furnace, measuring apparatus for molten material level in blast furnace, and operation method of blast furnace

Abstract

Provided are a method and a device for measuring the molten material level in a blast furnace, which can accurately measure the molten material level in the blast furnace regardless of the operating conditions of the blast furnace. 【Solution means】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 derived from the blast using Fourier transform of the vibration frequency distribution; a numerical analysis step of calculating the maximum vibration intensity distribution in the lower part of the blast furnace including the furnace body steel skin, the in-furnace filling layer, the hearth bricks, and the solidified layer of the in-furnace molten material using a numerical analysis model with the molten material level and the blast volume in the blast furnace as variables; and a molten material level calculation step of calculating the molten material level at which the difference between the vibration intensity calculated in the vibration intensity calculation step and the maximum vibration intensity distribution calculated in the numerical analysis step is minimized, and setting the calculated molten material level as the position of the molten material level in the blast furnace.

Description

Technical Field

[0001] The present invention relates to a method for measuring the level of a melt in a blast furnace, a device for measuring the level of a melt in a blast furnace, and an operation method for a blast furnace.

Background Art

[0002] In the iron and steel industry, since the blast furnace is located in the most upstream process, technology for stabilizing its operation is highly regarded. Ensuring good air permeability inside the blast furnace is important for stable operation of the blast furnace. One of the factors inhibiting air permeability inside the furnace is the rise in the liquid level of hot metal and molten slag (hereinafter, both are collectively referred to as melt) retained in the packed bed at the lower part of the furnace. The rise in the liquid level of the melt (hereinafter abbreviated as the melt level) causes narrowing of the gas flow path inside the furnace and can directly cause an increase in the blowing pressure. In addition, when the melt level reaches the level of the tuyere, it can cause serious problems such as melting loss of the tuyere, and ultimately blockage of the tuyere and backflow of slag (a phenomenon where the melt flows backward from the tuyere). For this reason, in order to achieve stable operation of the blast furnace, it is necessary to reliably avoid the melt level reaching the level of the tuyere.

[0003] Against such a background, a method has been proposed for evaluating the amount of melt retained in the furnace in terms of material balance from various operating specifications of the blast furnace. Specifically, Patent Document 1 describes a method of obtaining the theoretical melt amount discharged from the blast furnace using the actual volume value of the charged material in the furnace and the theoretical volume value calculated from the operating specifications, and estimating the amount of melt retained in the furnace by comparing it with the actually discharged melt amount. Further, Patent Document 2 describes a method of estimating the melt level in the furnace by solving variables measured by a plurality of strain gauges installed on the furnace body using a general equation for continuous circumferential strain and giving parameters representing the properties of the constituent materials of the blast furnace including the melt level.

[0004] In addition, Patent Document 3 describes a method using Bernoulli's theorem that calculates the discharge velocity of the melt discharged from the taphole of a blast furnace from the discharge distance, discharge angle, and discharge height of the melt, and uses this to estimate the melt level in the furnace. The estimation accuracy of this method depends on the calculation accuracy of the discharge velocity of the melt discharged from the taphole, and in this method, the discharge velocity is estimated by image analysis of an image taken by a camera. Further, Patent Document 4 describes a method of measuring the vibration intensity of the furnace wall at the lower part of the furnace and estimating the melt level in the furnace from the correspondence between the vibration intensity in a specific frequency band obtained in advance and the melt level.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, the method described in Patent Document 1 does not consider the porosity of the packed bed or the shape of the solidified layer at the lower part of the furnace. Therefore, even if the amount of melt remaining in the furnace can be estimated, there are still problems in estimating the melt level, which is important for the stable operation of the blast furnace. In addition, since it is affected by various weighing errors, there is also a concern that estimation errors accumulate in the blast furnace process with a large mass to be handled, and the estimation accuracy decreases over time.

[0007] In addition, the method described in Patent Document 2 has the following problems. It is known that in the lower part of the furnace, in addition to the iron skin on the surface of the blast furnace and the cooling stave, there are refractory bricks and a solidified layer formed by the cooling and solidification of the molten material in the furnace. The refractory bricks deteriorate over time due to abrasion and thermal stress, and the existence range of the solidified layer changes daily according to the thermal conditions in the lower part of the furnace. Therefore, it is extremely difficult to grasp the existence state of these constituent materials. Consequently, in the method described in Patent Document 2, it is practically impossible to exclude unknown parameters other than the molten material level representing the constituent materials of the blast furnace from the general equation, and thus it is hard to say that the accuracy of the molten material level estimated from the general equation is satisfactory.

[0008] In addition, in the method described in Patent Document 3, during the tapping operation, a large amount of dust is generated along with the discharge of the high-temperature molten material. Therefore, it is less likely to be able to clearly photograph the discharge behavior of the molten material using a camera. Furthermore, in the tapping operation, the occurrence of opening errors typified by horizontal holes cannot be avoided, which also contributes to the decrease in the estimation frequency of the discharge behavior of the molten material. Also, since the opening shape varies for each tapping, it is difficult to quantify the frictional force received by the molten material in the path from the furnace interior to the discharge port. Considering the above, it can be said that it is extremely difficult to measure the molten material level with high accuracy in the method described in Patent Document 3.

[0009] In addition, the method described in Patent Document 4 has the following problems. The vibration intensity of the actual furnace body is strongly affected by fluctuations in the blast volume above the molten material level and changes in the shape of structures such as the furnace charge, the bottom bricks, and the solidified layer in the furnace. Therefore, in the blast furnace process where the operating conditions change every moment, it is impossible to directly link the correlation between the vibration intensity of the furnace body and the molten material level on a one-to-one basis. For this reason, the method described in Patent Document 4 can only be effective in an extremely ideal situation where the furnace conditions other than the molten material level are in a steady state, and it is difficult to measure the molten material level in a long-term and stable manner.

[0010] The present invention has been made to solve the above problems, and an object thereof is to provide a method and an apparatus for measuring the level of molten material in a blast furnace capable of accurately measuring the level of molten material in the blast furnace 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 capable of stably performing an eco-friendly blast furnace operation.

Means for Solving the Problems

[0011] The method for measuring the level of molten material 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 derived from the blast by performing Fourier transform on the vibration frequency distribution; a numerical analysis step of calculating the maximum vibration intensity distribution in the lower part of the blast furnace including the furnace body steel skin, the in-furnace packed bed, the hearth bricks, and the solidified layer of the molten material in the furnace using a numerical analysis model with the level of molten material and the blast volume in the blast furnace as variables; and a molten material level calculation step of calculating the molten material level at which the difference between the vibration intensity calculated in the vibration intensity calculation step and the maximum vibration intensity distribution calculated in the numerical analysis step is minimized, and setting the calculated molten material level as the position of the molten material level in the blast furnace.

[0012] The vibration meter may be installed between the tapping hole level and the tuyere level of the furnace body.

[0013] The frequency range derived from the blast is preferably within the range of 700 to 900 Hz.

[0014] The measuring device for the melt level in the blast furnace according to the present invention includes a plurality of vibration meters 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, and by performing Fourier transform on the vibration frequency distribution, the vibration intensity in the frequency range derived from the blast is calculated at each measurement position, and using a numerical analysis model with the melt level and the blast volume in the blast furnace as variables, the maximum vibration intensity distribution in the lower part of the blast furnace including the furnace body steel skin, the in-furnace filling layer, the hearth bricks, and the solidified layer of the in-furnace melt is calculated, and the melt level at which the difference between the vibration intensity and the maximum vibration intensity distribution is minimized is calculated, and an information processing device that sets the calculated melt level as the position of the melt level in the blast furnace.

[0015] The operation method of the blast furnace according to the present invention includes a step of operating the blast furnace according to the melt level measured using the method for measuring the melt level in the blast furnace according to the present invention.

Effect of the Invention

[0016] According to the method and device for measuring the melt level in the blast furnace according to the present invention, the melt level in the blast furnace can be measured with high accuracy regardless of the operating conditions of the blast furnace. Further, according to the operation method of the blast furnace according to the present invention, an eco-friendly blast furnace operation can be stably performed.

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

BEST MODE FOR CARRYING OUT THE INVENTION

[0018] Hereinafter, with reference to the drawings, a method for measuring the melt level in a blast furnace, a device for measuring the melt level in a blast furnace, and an operation method for a blast furnace, which are embodiments of the present invention, will be described.

[0019] 〔Configuration〕 First, with reference to FIG. 1, the configuration of a device for measuring the melt level in a blast furnace, which is an embodiment of the present invention, will be described.

[0020] FIG. 1 is a schematic cross-sectional view showing the configuration of a blast furnace to which a device for measuring the melt level in a blast furnace according to an embodiment of the present invention is applied. As shown in FIG. 1, a blast furnace 1 according to an embodiment of the present invention includes a substantially cylindrical furnace body 2, a tuyere (hereinafter abbreviated as tuyere) 3 provided below the furnace body 2, and a tapping hole 4 provided in the furnace body 2 below the tuyere 3. Further, the furnace bottom of the blast furnace 1 is composed of hearth bricks 5 and wall bricks 6, and the inner wall surface and the outer wall surface of the wall bricks 6 are respectively covered with cooling sleeves 7 and steel sheets 8.

[0021] In addition, the blast furnace 1 according to an embodiment of the present invention includes a plurality of vibration meters 9, a data logger 10, and an information processing device 11 as measuring devices for 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 the circumferential tangent of the furnace body 2 and along the surface of the steel skin 8 from the height position of the tapping 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 electrical signal indicating the measured current value to the data logger 10.

[0022] The data logger 10 converts the current value measured by each vibration meter 9 based on the electrical signal output from each vibration meter 9 into a vibration value. The information processing device 11 calculates the vibration intensity of the furnace body 2 at the installation position (measurement position) of each vibration meter 9 by performing a Fourier transform on the time-series data of the vibration value at the installation position of each vibration meter 9 generated by the data logger 10. Then, the information processing device 11 calculates the molten material level inside the blast furnace by executing the following method for measuring the molten material level inside the blast furnace using the calculated vibration intensity.

[0023] As a result of measurements on the actual machine, it was confirmed that the vibration of the furnace body 2 has all vibration frequency bands, and in particular, the vibration with a particularly high peak value and a peak confirmed at all measurement positions is in the frequency band of 700 to 900 Hz. Since it was confirmed that the vibration in the frequency band of 700 to 900 Hz has a general tendency to show a high value at a position close to the tuyere 3, it is considered to be a vibration caused by the blast 23 from the tuyere 3 (blast-derived vibration). Therefore, in the present invention, the molten material level is measured using the vibration intensity confirmed in the frequency range of 700 to 900 Hz corresponding to the blast-derived vibration. However, the frequency band in which the blast-derived vibration is confirmed may change depending on the shape of the furnace body 2, ground influence, etc., and there is no confirmation that this frequency band can be evaluated in the same way for every blast furnace. For this reason, when deploying the present invention to other blast furnaces, it is desirable to analyze the basic vibration frequency band each time.

[0024] In the blast furnace 1 shown in Fig. 1, iron ore 21 and coke 22 as raw materials are charged into the furnace body 2 in layers from the top of the furnace, and are reduced by the blowing air (hot air) 23 pumped from the tuyere 3 to become a melt 24. Then, the melt 24 is stored at the bottom of the furnace, and is discharged as tapping slag 25 from the tapping hole 4 by punching the tapping hole 4 at predetermined time intervals. The measuring device for the melt level in the blast furnace in one embodiment of the present invention measures the liquid level of the melt 24 in the lower part of the furnace as the melt level.

[0025] 〔Measuring method〕 Next, with reference to Figs. 2 to 5, the measuring method for the melt level in the blast furnace in one embodiment of the present invention will be described.

[0026] In the measuring method for the melt level in the blast furnace in one embodiment of the present invention, first, the information processing device 11 measures the vibration intensity in the height direction perpendicular to the tangent in the circumferential direction of the furnace body 2, and estimates the maximum vibration intensity distribution of the furnace body 2 by executing a numerical analysis model related to vibration. Although the melt level and the blowing rate are required as input information for the numerical analysis model related to vibration, in this embodiment, the former is treated as a variable for fitting the measured data and the numerical analysis results of the vibration intensity distribution, and the latter sequentially captures the operation data of the blast furnace. Thereby, the melt level can be obtained by fitting the measured data and the numerical analysis results of the vibration intensity distribution.

[0027] The numerical analysis model related to vibration will be described. The numerical analysis model related to vibration is a physical model for estimating the maximum vibration intensity distribution in the lower part of the furnace composed of the furnace body steel skin area, the in-furnace packed bed area, the bottom bricks of the furnace, and the solidified layer of the melt in the furnace. Fig. 2 shows the calculation flow of the numerical analysis model related to vibration. As shown in Fig. 2, when executing the numerical analysis model related to vibration, first, the mesh conditions necessary for setting the calculation grid, the analysis time step, and the density and Young's modulus as the physical properties of the steel skin and the packed bed are set. In addition, the blowing rate to the blast furnace 1 considered as the vibration source is input as the operating specifications (step S1).

[0028] Next, as shown in FIG. 3, the information processing apparatus 11 includes one of tuyeres 3 installed at a plurality of locations in the circumferential direction of the central axis of the furnace body 2 and the furnace body 2 within the lower part of the blast furnace 1 composed of the furnace body skin area, the in-furnace filling layer area, the hearth bricks, and the solidified layer of the in-furnace melt, and divides a two-dimensional axisymmetric region 31 of a cross-section perpendicular to the furnace bottom into a plurality of element regions 32 to set a calculation grid (step S2). In this model, each element region 32 is connected by a spring 33 and a dashpot 34, and the acceleration applied to a certain element region 32 propagates to the surrounding element regions 32 through the spring 33 and the dashpot 34. The spring 33 represents a restoring force that describes the vibration phenomenon, and the dashpot 34 represents a damping force by which vibration energy is lost due to various energy conversions during the propagation of vibration. Also, in this model, considering the liquid level (melt level) L of the melt, for the element region 32 having a center of gravity below the liquid level L, a buoyancy force and a resistance force due to the melt are applied to its movement.

[0029] Returning to FIG. 2, next, the information processing apparatus 11 calculates the spring constant k of each element region 32 using the following mathematical formula (1) (step S3). In the mathematical formula (1), E is the Young's modulus, A is the cross-sectional area of the element region 32 in the direction perpendicular to the spring 33, and L is the length of the element region 32 in the same direction as the spring 33. In this embodiment, since the numerical analysis model is a two-dimensional analysis model, A is set to the square of the length of the element region 32 perpendicular to the spring 33. Also, since the spring constant k as the material property of each element region 32 is obtained, the average value of the spring constants k of the two element regions 32 to be joined is given as the spring constant of the spring 33 joining the two element regions 32.

[0030]

Number

[0031] Next, the information processing apparatus 11 calculates the viscosity coefficient c of each element region 32 using the following mathematical formula (2) (step S4). In the mathematical formula (2), m represents the mass of each element region 32. The volume of each element region 32 was given as the product of A and L. Also, since the viscosity coefficient c is obtained as a material property of each element region 32, the average value of the viscosity coefficients c of the two element regions 32 to be joined was given as the viscosity coefficient of the dashpot 34 joining the element regions 32.

[0032]

Number

[0033] Next, the information processing apparatus 11 formulates the vibration equation based on the vibration engineering theory for each element region 32 as shown in the following mathematical formula (3) using the processing results of steps S2 and S3 (step S5). In the mathematical formula (3), x is the displacement of each element region 32, t is time, C d represents the liquid resistance force, and F represents the buoyancy force and the blowing external force. Also, as shown in FIG. 3, the radial position of the two-dimensional region 31 is represented by the subscript I, and the height direction position is represented by the subscript J.

[0034]

Number

[0035] The above mathematical formula (3) is an equation based on Newton's equation of motion. On the left side, the inertial force of each element region 32 is considered, and on the right side, the restoring force, damping force, liquid resistance force, and buoyancy force and blowing external force acting on each element region 32 are considered. Also, the restoring force is formulated under the assumption that it is proportional to the magnitude of the displacement of each element region 32, and the damping force is proportional to the velocity of each element region 32. Also, the liquid resistance force C d is calculated from the Kozeny-Carman equation, and the blowing external force is calculated as the product of the pressure loss in front of the orifice calculated by the Ergun equation and the surface area of the raceway calculated from the depth estimation equation of the raceway.

[0036] It is known that the general solution of the differential equation of the above formula (3) is expressed by the following formula (4). Here, a represents the maximum acceleration of each element region 32, i represents the imaginary unit, and ω represents the vibration frequency.

[0037]

Number

[0038] Therefore, substituting formula (4) into formula (3) and arranging for the maximum acceleration a, the following formula (5) is obtained.

[0039]

Number

[0040] The above formula (5) is an equation regarding the maximum acceleration of the element region 32 represented by the coordinates (I, J) of interest and the four surrounding element regions 32. Setting up the above formula (5) for all element regions 32 results in a system of simultaneous equations regarding the maximum acceleration a of all element regions 32. By solving this using the BiCG-Stab method, the maximum acceleration a of each element region 32 can be calculated. Therefore, the information processing device 11 calculates the maximum acceleration a of each element region 32, and substitutes the calculated maximum acceleration a into formula (4) to calculate the maximum vibration intensity distribution of the furnace body 2 (step S6). Then, the information processing device 11 repeatedly executes this process until the maximum vibration intensity distribution of the furnace body 2 reaches a steady state (step S7). In this embodiment, as the vibration frequency ω, 800 Hz, which is the average value of the actually measured vibration frequencies from 700 to 900 Hz due to the air flow, is set.

[0041] As described above, based on the vibration engineering theory, the maximum vibration intensity distribution in the lower part of the furnace, which is composed of the furnace body iron skin area, the furnace interior filling layer area, the furnace bottom bricks, and the solidified layer of the molten material in the furnace, can be estimated. However, the molten material level remains as an unknown parameter. Since the ranges where the liquid resistance and buoyancy in Equation (3) act change depending on the setting of the molten material level, the molten material level also affects the calculation result of the maximum vibration intensity distribution. Therefore, next, the information processing device 11 determines the molten material level with the molten material level as a variable so that the error between the vibration intensity distribution measured multiple times in the height direction of the furnace body 2 and the maximum vibration intensity distribution estimated by this numerical analysis model is minimized. Thereby, the molten material level in the blast furnace can be accurately measured regardless of the operating conditions of the blast furnace. Further, by detecting an increase in the molten material level at an early stage and preventing an increase in the reduction material ratio caused by an increase in the ventilation resistance due to the increase in the molten material level, an eco-friendly blast furnace operation can be stably performed.

[0042] Fig. 4 shows an analysis example of the two-dimensional vibration model. As shown in Fig. 4, it is possible to confirm that the blowing vibration generated in the raceway space, where the coke burns violently in front of the tuyere 3 and is constrained and swirled by the blowing pressure, gradually dissipates energy and attenuates as it propagates to the surroundings. Further, in the analysis example shown in Fig. 4, it was assumed that the molten material surface exists in the region of 2 / 3 of the distance from the furnace bottom to the tuyere 3, and it was possible to confirm that the vibration intensity attenuates discontinuously at that interface. On the other hand, Fig. 5 shows the vibration intensity derived from blowing measured by a plurality of vibration meters 9 when the molten material level was changed using a cold model simulating the lower part of the blast furnace 1, plotted against the height of the relative measurement position of the vibration meter 9 with respect to the molten material level (vibration meter height based on the liquid level). As shown in Fig. 5, the vibration intensity derived from blowing has an inflection point at the surface layer of the molten material, and this result was qualitatively consistent with the prediction result of the numerical analysis model shown in Fig. 4. Further, this experiment includes the results of a plurality of cases in which factors that can vary in an actual blast furnace, such as the physical properties of the molten material, the blowing rate, the filling particle diameter, and the particle size distribution of the filling particles, were simulated. However, none of the cases deviated from the trend shown in Fig. 5. Furthermore, even in experiments simulating vibration variation factors that are considered to occur randomly, such as vibrations during raw material charging, changes in the total weight of the in-furnace filling due to fluctuations in the blast furnace reduction material ratio, structural changes due to aging deterioration caused by wear of the furnace bottom bricks, and the installation status of the furnace body, the same trend as shown in Fig. 5 was confirmed. From the above, it is considered that the variation in the vibration intensity having an inflection point on the molten material surface confirmed in Fig. 5 is an event that can be uniformly confirmed under all operating conditions.

Example

[0043] In this example, the capacity is approximately 5000 m 3In a large blast furnace, pulverized coal was blown from the tuyere using normal charging materials, and the vibration of the furnace body was measured using vibration meters installed at equal intervals on a line perpendicular to the circumferential tangent of the furnace body from the tapping hole level (height position 2 m) to the tuyere level, and the molten material level in the blast furnace was measured. In Example 1, the coke ratio was 333 (kg / t), the pulverized coal ratio was 207 (kg / t), the reducing agent ratio was 540 (kg / t), the tapping amount was 10,000 (t / d), and the tapping temperature was 1495 (°C). In Example 2, the coke ratio was 335 (kg / t), the pulverized coal ratio was 198 (kg / t), the reducing agent ratio was 533 (kg / t), the tapping amount was 9950 (t / d), and the tapping temperature was 1500 (°C). The time change of the measured values of the molten material level from the initial stage to the final stage of tapping is shown in FIG. 6. Also, FIG. 7 shows the result of fitting the vibration intensity measured in the actual machine and the maximum vibration intensity estimated by the numerical analysis model with the molten material level. As shown in FIG. 6, in both Examples 1 and 2, the molten material level finally reached about the same level as the tapping hole level. From this, it was confirmed that according to the present invention, the molten material level can be measured with high accuracy. Also, as shown in FIG. 7(a), at the initial stage of tapping, the difference between the actual value and the estimated value was minimized by setting the molten material level to about 4.0 m. Also, as shown in FIG. 7(b), at the final stage of tapping, the difference between the actual value and the estimated value was minimized by setting the remaining slag level to 2.0 m.

[0044] As described above, the embodiments to which the invention made by the present inventors is applied have been described, but the present invention is not limited by the description and drawings that form a part of the disclosure of the present invention according to this embodiment. That is, all other embodiments, examples, and operation techniques made by those skilled in the art based on this embodiment are included in the scope of the present invention.

Explanation of Signs

[0045] 1 Blast furnace 2 Furnace body 3 Tuyere, blowing tuyere 4 Tapping hole 5 Bottom bricks of the furnace 6 Wall bricks of the furnace 7 Cooling sleeve 8 Steel sheet 9 Vibration meter 10 Data logger 11 Information processing device 21 Iron ore 22 Coke 23 Blowing 24 Melt 25 Tapping slag 31 Two-dimensional region 32 Element region 33 Spring 34 Dashpot

Claims

1. A measuring step of measuring a 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 a vibration intensity in a frequency range caused by blowing air at each measurement position by performing a Fourier transform on the vibration frequency distribution; A numerical analysis step of calculating a maximum vibration intensity distribution of a lower part of a blast furnace including a furnace shell, a furnace packed layer, hearth bricks, and a solidified layer of molten material in the furnace, using a numerical analysis model with a molten material level and a blast volume in the blast furnace as variables; A molten material level calculation step of calculating the molten material level at which the difference between the vibration intensity calculated in the vibration intensity calculation step and the maximum vibration intensity distribution calculated in the numerical analysis step is minimized, and the calculated molten material level is set as the position of the molten material level in the blast furnace; A method for measuring the molten level in a blast furnace, comprising:

2. The method for measuring a molten material level in a blast furnace according to claim 1, wherein the vibration meter is installed between a tap hole level and a tuyere level of the furnace body.

3. The method for measuring a molten material level in a blast furnace according to claim 1 or 2, wherein the frequency range derived from the air blowing is within the range of 700 to 900 Hz.

4. A plurality of vibration meters arranged at predetermined intervals along the height direction of the blast furnace body to measure the vibration frequency distribution in the height direction of the furnace body; an information processing device that calculates vibration intensity in a frequency range due to air blowing at each measurement position by performing a Fourier transform on the vibration frequency distribution, calculates a maximum vibration intensity distribution in a lower part of the blast furnace including the furnace body shell, the furnace packed layer, the hearth bricks, and the solidified layer of the molten material in the furnace using a numerical analysis model with the molten material level in the blast furnace and the air blowing volume as variables, calculates the molten material level at which the difference between the vibration intensity and the maximum vibration intensity distribution is minimized, and sets the calculated molten material level as the position of the molten material level in the blast furnace; A device for measuring the molten material level in a blast furnace.

5. 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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