Method for measuring level of molten material in furnace of blast furnace, device for measuring level of molten material in furnace of blast furnace, and method for operating blast furnace

Abstract

A method for measuring a molten material level in a blast furnace according to the present invention includes: a measurement step of measuring a vibration frequency distribution in a height direction of a furnace body of the blast furnace by using a plurality of vibration meters arranged at predetermined intervals along the height direction of the furnace body; a vibration intensity calculation step of calculating a vibration intensity in a frequency range due to blast at each of measurement positions by performing Fourier transform on the vibration frequency distribution; and a molten material level calculation step of calculating a point of discontinuity of a change in the vibration intensity in the height direction of the furnace body and determining a position corresponding to the point of discontinuity as the molten material level in the blast furnace.

Description

Field

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

[0002] In the iron and steel industry, a blast furnace is located in the most upstream process, and thus a technique for stabilizing the operation of the blast furnace is regarded as important. It is important to ensure good air permeability in the furnace for stable operation of the blast furnace. One of the factors inhibiting the air permeability in the furnace is an increase in liquid surface level of molten iron and molten slag (hereinafter, both are collectively referred to as molten material) accumulated in the packed bed in the lower part of the furnace. An increase in the liquid surface level of the molten material (hereinafter, abbreviated as molten material level) may cause a narrowing of a gas flow path in the furnace and may directly cause an increase in blast pressure. In addition, in the case where the molten material level reaches a blast tuyere level, erosion of the blast tuyere, and eventually, serious troubles such as clogging of the blast tuyere and slag return (a phenomenon in which the molten material flows back from the blast tuyere) may be caused. For this reason, in order to achieve a stable operation of the blast furnace, it should be surely avoided that the molten material level reaches the blast tuyere level.

[0003] From such a background, a method for evaluating the amount of the molten material accumulated in the furnace on the basis of the material balance from various operating parameters of the blast furnace has been proposed. Specifically, Patent Literature 1 describes a method for estimating an amount of a molten material accumulated in a furnace by obtaining a theoretical amount of the molten material discharged from the blast furnace using an actual volume value of a charge in the furnace and a theoretical volume value calculated from the operating parameters, and comparing the theoretical amount with the amount of the molten material actually discharged. In addition, Patent Literature 2 describes a method for estimating a molten material level in a furnace by solving variables measured by a plurality of strain gauges installed in the furnace body by giving parameters representing properties of constituent materials of the blast furnace including the molten material level to a general equation for continuous ambient strain.

[0004] In addition, Patent Literature 3 describes a method using so-called Bernoulli's principle in which a discharge speed of a molten material is calculated from a discharge distance, a discharge angle, and a discharge height of the molten material discharged from a taphole of a blast furnace, and a molten material level in the furnace is estimated using the discharge speed. The estimation accuracy of the present method depends on the calculation accuracy of the discharge speed of the molten material discharged from the taphole, and in the same method, the discharge speed is estimated by performing image analysis on an image captured by a camera. In addition, Patent Literature 4 describes a method in which vibration intensity of a furnace wall in a lower part of a furnace is measured and a molten material level in the furnace is estimated on the basis of a correspondence relationship between the vibration intensity of a specific frequency band obtained in advance and the molten material level.Citation ListPatent Literature

[0005] Patent Literature 1: JP 2002-302709 A Patent Literature 2: JP 2015-528905 A Patent Literature 3: JP 7056813 B1 Patent Literature 4: WO 2022 / 201717 A SummaryTechnical Problem

[0006] However, the method described in Patent Literature 1 does not consider porosity of a packed bed in a lower part of the furnace and a shape of a solidified layer. Therefore, even if the amount of the molten material accumulated in the furnace can be estimated, there remains a problem in estimating a liquid surface level of the molten material, which is important for the stable operation of the blast furnace. In addition, since it is affected by various weighing errors, there is a concern that estimation errors accumulate in a blast furnace process in which a large mass is handled, and the estimation accuracy deteriorates over time.

[0007] In addition, the method described in Patent Literature 2 has the following problems. It is known that a refractory brick and a solidified layer in which a molten material in the furnace is cooled and solidified are present in the lower part of the furnace in addition to an iron shell and a cooling stave on a surface of the blast furnace. Then, the refractory brick deteriorates over time due to wear and thermal stress, and a range where the solidified layer exists changes daily according to thermal conditions of the lower part of the furnace. Therefore, it is extremely difficult to grasp a state of existence of these constituent materials. Therefore, in the method described in Patent Literature 2, it is substantially impossible to exclude unknown parameters other than the molten material level representing the constituent materials of the blast furnace from the general equation, and therefore, the accuracy of the molten material level estimated from the general equation is also far from satisfactory.

[0008] In addition, in the method described in Patent Literature 3, since a large amount of dust is generated along with discharge of a high-temperature molten material during tapping work, there is a low possibility that a clear discharge behavior of the molten material can be captured using a camera. In addition, the occurrence of an opening mistake represented by a lateral hole cannot be avoided in the tapping work, and this is also a cause contributing to a decrease in estimation frequency of the discharge behavior of the molten material. Furthermore, in association with this, since the opening shape is different for each tapping, it is difficult to quantify a frictional force received by the molten material in a path from the inside of the furnace to a discharge port. From the above, it can be said that it is extremely difficult to measure the molten material level with high accuracy by the method described in Patent Literature 3.

[0009] In addition, the method described in Patent Literature 4 has the following problems. Vibration intensity of the actual furnace body is affected by variations in blast amount and changes in the shape of structures such as a furnace packing material, a furnace bottom brick, and the solidified layer more strongly than the molten material level. For this reason, in the blast furnace process in which the operational situation changes from moment to moment, it is impossible to establish the correlation between the vibration intensity of the furnace body and the molten material level on a one-to-one basis. Therefore, the method described in Patent Literature 4 is effective only in an extremely ideal situation in which the conditions in the furnace other than the molten material level are in a steady state, and long-term and stable measurement of the molten material level is difficult.

[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 a device for measuring a molten material level in a blast furnace capable of accurately measuring the molten material level in the blast furnace regardless of operation conditions of the blast furnace. In addition, another object of the present invention is to provide a blast furnace operation method in which eco-friendly blast furnace operation can be performed stably.Solution to Problem

[0011] A method for measuring a molten material level in a blast furnace according to the present invention includes: a measurement step of measuring a vibration frequency distribution in a height direction of a furnace body of the blast furnace by using a plurality of vibration meters arranged at predetermined intervals along the height direction of the furnace body; a vibration intensity calculation step of calculating a vibration intensity in a frequency range due to blast at each of measurement positions by performing Fourier transform on the vibration frequency distribution; and a molten material level calculation step of calculating a point of discontinuity of a change in the vibration intensity in the height direction of the furnace body and determining a position corresponding to the point of discontinuity as the molten material level in the blast furnace.

[0012] The molten material level calculation step may include: a step of classifying vibration intensity data at each of the measurement positions 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 approximate expression and a second linear approximate expression indicating from the first vibration intensity data and the second vibration intensity data, respectively, a relationship between a height direction position and the vibration intensity of the furnace body at each of the measurement positions; a step of calculating, at each of the measurement positions, a difference between the vibration intensities at the measurement position of the first linear approximate expression and the second linear approximate expression as a discontinuity; and a step of determining the measurement position at which the discontinuity is maximized among all the measurement positions as the molten material level.

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

[0014] The frequency range due to the blast may be in a range of 700 to 900 Hz.

[0015] A device for measuring a molten material level in a blast furnace according to the present invention includes: a plurality of vibration meters arranged at predetermined intervals along a height direction of a furnace body of the blast furnace and configured to measure a vibration frequency distribution in the height direction of the furnace body; and an information processing device configured to calculate a vibration intensity in a frequency range due to blast at each of measurement positions by performing Fourier transform on the vibration frequency distribution, calculate a point of discontinuity of a change in the vibration intensity in the height direction of the furnace body and determine a position corresponding to the point of discontinuity as the molten material level in the blast furnace.

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

[0017] According to the method and the device for measuring the molten material level in the blast furnace of the present invention, the molten material level in the blast furnace can be measured with high accuracy regardless of operation conditions of the blast furnace. In addition, according to the blast furnace operation method of the present invention, eco-friendly blast furnace operation can be performed stably.Brief Description of Drawings

[0018] [FIG. 1] FIG. 1 is a schematic cross-sectional view illustrating a configuration of a blast furnace to which a device for measuring a molten material level in the blast furnace according to an embodiment of the present invention is applied. [FIG. 2] FIG. 2 is a diagram illustrating a result of plotting vibration intensities due to blast with respect to the height of a measurement position relative to a molten material level, the vibration intensities being measured by a plurality of vibration meters when the molten material level is changed. [FIG. 3] FIG. 3 is a view illustrating an overview of a method for measuring a molten material level in the blast furnace according to the embodiment of the present invention is applied. [FIG. 4] FIG. 4 is a diagram illustrating a time-dependent change of a measurement value of the molten material level from an initial stage to an end stage of tapping. Description of Embodiments

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

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

[0021] FIG. 1 is a schematic cross-sectional view illustrating a configuration of the blast furnace to which the device for measuring the molten material level in the blast furnace according to the embodiment of the present invention is applied. As illustrated in FIG. 1, a blast furnace 1 according to the embodiment of the present invention includes a furnace body 2 having a substantially cylindrical shape, a blast tuyere (hereinafter, abbreviated as tuyere) 3 provided below the furnace body 2, and a taphole 4 provided in the furnace body 2 below the tuyere 3. Further, a furnace bottom portion of the blast furnace 1 is constituted by a furnace bottom brick 5 and a furnace wall brick 6, and an inner wall surface and an outer wall surface of the furnace wall brick 6 are covered with a cooling sleeve 7 and an iron shell 8, respectively.

[0022] In addition, the blast furnace 1 according to the embodiment of the present invention includes a plurality of vibration meters 9, a data logger 10, and an information processing device 11 as the device for measuring the molten material level in the blast furnace. The vibration meters 9 are perpendicular to a tangent in the circumferential direction of the furnace body 2 and are set at equal intervals along a straight line along the surface of the iron shell 8 from the height position of the taphole 4 to the height position of the tuyere 3. Each vibration meter 9 measures a 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.

[0023] The data logger 10 converts the current value measured by each vibration meter 9 into the 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 installation position of each vibration meter 9 by performing Fourier transform on time-dependent data of the vibration value 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 described below using the calculated vibration intensity.

[0024] As a result of measurement with an actual machine, it has been confirmed that the vibration of the furnace body 2 has all vibration frequency bands, and the vibration frequency band having a particularly high peak value and a peak confirmed at all the measurement positions is the frequency band of 700 to 900 Hz. Since it was confirmed that there is a rough tendency that the vibration in the frequency band of 700 to 900 Hz shows a high value at a position close to the tuyere 3, it is considered that the vibration is caused by a blast 23 from the tuyere 3 (vibration due to blast). 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 vibration due to blast. Note that there is a possibility that the frequency band in which the vibration due to blast is confirmed varies depending on the shape of the furnace body 2, the ground influence, and the like, and there is no proof that the evaluation can be performed in every blast furnace with this frequency band. Therefore, when the present invention is developed for another blast furnace, it is desirable that basic analysis for the vibration frequency band is performed each time.

[0025] In the blast furnace 1 illustrated in FIG. 1, an iron ore 21 and a coke 22, which are raw materials, are charged in layers into the furnace body 2 from the top of the furnace, and are reduced by the blast (hot air) 23 pressure-fed from the tuyere 3 to become a molten material 24. Then, the molten material 24 is stored in the furnace bottom portion, and is discharged from the taphole 4 as the tapped molten iron slag 25 by boring the taphole 4 every predetermined time. The device for measuring the molten material level in the blast furnace according to the embodiment of the present invention measures a liquid surface level of the molten material 24 in the lower part of the furnace as the molten material level.[Measurement Method]

[0026] Next, the method for measuring the molten material level in the blast furnace according to the embodiment of the present invention will be described with reference to FIGS. 2 and 3.

[0027] FIG. 2 illustrates a result of plotting vibration intensities due to blast with respect to the height of the measurement position of the vibration meter 9 relative to the molten material level (height of the vibration meter with respect to the liquid surface), the vibration intensities being measured by the plurality of vibration meters 9 when the molten material level is changed by using a cold model in which the lower part of the blast furnace 1 is simulated. As illustrated in FIG. 2, it can be seen that the vibration intensity due to blast changes discontinuously in the surface layer of the molten material. In addition, this experiment included results obtained in a plurality of cases where simulation is performed in consideration of factors that can fluctuate in an actual blast furnace, such as physical properties of the molten material, a blast amount, a packed particle diameter, and particle size distribution of the packed particles, but none of the cases reversed the tendency illustrated in FIG. 2. Furthermore, also in an experiment in which simulation was performed in consideration of factors of vibration fluctuation that are assumed to occur due to disturbance, such as vibration at the time of raw material charging, a change in the total weight of the furnace packing material due to a change in the reducing agent ratio of the blast furnace, a structural change due to aging due to wear of the furnace bottom brick, and an installation situation of the furnace body, the tendency illustrated in FIG. 2 has been similarly confirmed.

[0028] From the above, it is considered that the discontinuous variation in the vibration intensity on the surface of the molten material is an event that is uniformly confirmed under all operational conditions. Therefore, if a point of discontinuity of the change in the vibration intensity in the height direction of the furnace body can be calculated, since the liquid level of the molten material exists in the vicinity of the point of discontinuity, the molten material level in the blast furnace can be accurately measured regardless of operation conditions of the blast furnace. In addition, with this method, by detecting an increase in the molten material level at an early stage and preventing an increase in reducing agent ratio caused by an increase in ventilation resistance due to an increase in the molten material level, it is possible to stably perform eco-friendly blast furnace operation. The technical idea of the present invention is based on the above logic.

[0029] FIG. 3 is a view illustrating an overview of the method for measuring the molten material level in the blast furnace according to the embodiment of the present invention is applied. In the method for measuring the molten material level in the blast furnace according to the embodiment of the present invention, first, the vibration intensity of the frequency band due to the blast is measured using the vibration meters 9 installed at equal intervals at a plurality of positions on a line perpendicular to a tangent in a circumferential direction of the furnace body 2 from the height position of the taphole 4 to the height position of the tuyere 3. In the present embodiment, it is assumed that n (≥ 2) vibration meters 9 are installed. Next, the information processing device 11 classifies vibration intensity data at each measurement position (vibration measurement point) i (= 1 to n) 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, the information processing device 11 constructs a first linear approximate expression and a second linear approximate expression indicating a relationship between the height direction position and the vibration intensity of the furnace body 2 from the first vibration intensity data and the second vibration intensity data, respectively, at each measurement position i. Next, as illustrated in FIG. 3, the information processing device 11 calculates, at each measurement position i, a difference between the vibration intensities at the measurement position i of the two linear approximate expressions as a discontinuity Δe(i). Finally, the information processing device 11 determines the measurement position i indicating the maximum value max [Δe(i)] i=1 , n among the discontinuities Δe(i) at n points as the molten material level.[Examples]

[0030] In this example, in a large blast furnace having a capacity of about 5000 m 3< , pulverized coal was blown from a tuyere using an ordinary charged raw material, vibration of the furnace body was measured using vibration meters installed at equal intervals on a line perpendicular to a tangent in a circumferential direction of the furnace body from a taphole level (height position 2 m) to a tuyere level, and a molten material level in the blast furnace was measured. Table 1 illustrates operation conditions of Example 1 and Example 2. A time-dependent change of a measurement value of the molten material level from an initial stage to an end stage of tapping is illustrated in FIG. 4. As illustrated in FIG. 4, in both Examples 1 and 2, the molten material level is finally about the same as the taphole level. From this, according to the present invention, it was confirmed that the molten material level can be measured with high accuracy.[Table 1]

[0031] Table 1Example 1Example 2Coke ratio (kg / t)350320Pulverized coal ratio (kg / t)248243Reducing agent ratio (kg / t)598563Tapped molten iron amount (t / d)97989744Tapped molten iron temperature (°C)15421540

[0032] Although the embodiments to which the invention made by the present inventors is applied have been described above, the present invention is not limited by the description and drawings constituting a part of the disclosure of the present invention according to the present embodiments. That is, other embodiments, examples, operation techniques, and the like made by those skilled in the art based on the present embodiment 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 a device for measuring a molten material level in a blast furnace capable of accurately measuring the molten material level in the blast furnace regardless of operation conditions of the blast furnace. In addition, according to the present invention, it is possible to provide a blast furnace operation method in which eco-friendly blast furnace operation can be performed stably.Reference Signs List

[0034] 1BLAST FURNACE 2FURNACE BODY 3BLAST TUYERE, TUYERE 4TAPHOLE 5FURNACE BOTTOM BRICK 6FURNACE WALL BRICK 7COOLING SLEEVE 8IRON SHELL 9VIBRATION METER 10DATA LOGGER 11INFORMATION PROCESSING DEVICE 21IRON ORE 22COKE 23BLAST 24MOLTEN MATERIAL 25TAPPED MOLTEN IRON SLAG

Claims

1. A method for measuring a molten material level in a blast furnace, the method comprising: a measurement step of measuring a vibration frequency distribution in a height direction of a furnace body of the blast furnace by using a plurality of vibration meters arranged at predetermined intervals along the height direction of the furnace body; a vibration intensity calculation step of calculating a vibration intensity in a frequency range due to blast at each of measurement positions by performing Fourier transform on the vibration frequency distribution; and a molten material level calculation step of calculating a point of discontinuity of a change in the vibration intensity in the height direction of the furnace body and determining a position corresponding to the point of discontinuity as the molten material level in the blast furnace.

2. The method for measuring the molten material level in the blast furnace according to claim 1, wherein the molten material level calculation step includes: a step of classifying vibration intensity data at each of the measurement positions 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 approximate expression and a second linear approximate expression indicating from the first vibration intensity data and the second vibration intensity data, respectively, a relationship between a height direction position and the vibration intensity of the furnace body at each of the measurement positions; a step of calculating, at each of the measurement positions, a difference between the vibration intensities at the measurement position of the first linear approximate expression and the second linear approximate expression as a discontinuity; and a step of determining the measurement position at which the discontinuity is maximized among all the measurement positions as the molten material level.

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

4. The method for measuring the molten material level in the blast furnace according to claim 1 or 2, wherein the frequency range due to the blast is in a range of 700 to 900 Hz.

5. A device for measuring a molten material level in a blast furnace, the device comprising: a plurality of vibration meters arranged at predetermined intervals along a height direction of a furnace body of the blast furnace and configured to measure a vibration frequency distribution in the height direction of the furnace body; and an information processing device configured to calculate a vibration intensity in a frequency range due to blast at each of measurement positions by performing Fourier transform on the vibration frequency distribution, calculate a point of discontinuity of a change in the vibration intensity in the height direction of the furnace body and determine a position corresponding to the point of discontinuity as the molten material level in the blast furnace.

6. A blast furnace operation method comprising a step of operating a blast furnace according to a molten material level measured by using the method for measuring the molten material level in the blast furnace according to claim 1 or 2.

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