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

Abstract

To provide a method and an apparatus for measuring the molten material level in a blast furnace that 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 for each measurement position by performing a Fourier transform on the vibration frequency distribution, and a molten material level calculation step of calculating an inflection point of the distribution of the vibration intensity in the height direction of the furnace body and setting the position corresponding to the inflection point 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 melt level in a blast furnace, a measuring device for the melt level in a blast furnace, and an operation method for a blast furnace.

Background Art

[0002] In the ironmaking industry, since the blast furnace is located in the most upstream process, technology for stabilizing its operation is highly regarded. Ensuring good air permeability in the furnace is important for the stable operation of the blast furnace. One of the factors inhibiting air permeability in 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 in the furnace and can be a direct cause of 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 corrosion of the tuyere, and ultimately blockage of the tuyere and backflow of slag (a phenomenon where the melt flows backward from the tuyere). Therefore, in order to achieve stable operation of the blast furnace, it is necessary to reliably avoid the melt level reaching the tuyere level.

[0003] Against such a background, a method for evaluating the amount of melt retained in the furnace in terms of material balance from various operating conditions of the blast furnace has been proposed. 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 conditions, and comparing it with the actually discharged melt amount to estimate the amount of melt retained in the furnace. 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 with 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 the estimation error accumulates 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 existing state of these constituent materials. Accordingly, in the method described in Patent Document 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 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, so 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 is different 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. Taking the above into consideration, 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 associate 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 exert its effectiveness 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 molten material level in a blast furnace capable of accurately measuring the molten material level in the blast furnace regardless of the operating conditions of the blast furnace. Another object of the present invention is to provide an operating method for a blast furnace capable of stably performing an eco-friendly blast furnace operation.

Means for Solving the Problems

[0011] The method for measuring the molten material level in the 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 a Fourier transform on the vibration frequency distribution, and a molten material level calculation step of calculating an inflection point of the distribution of the vibration intensity in the height direction of the furnace body and setting the position corresponding to the inflection point as the position of the molten material level in the blast furnace.

[0012] The molten material level calculation step includes a step of classifying 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 at each measurement position, a step of constructing a first linear approximation formula and a second linear approximation formula showing the relationship between the height direction position of the furnace body and the vibration intensity from the first vibration intensity data and the second vibration intensity data at each measurement position, a step of calculating the distance between the intersection of the first linear approximation formula and the second linear approximation formula and the plot corresponding to the vibration intensity at the measurement position at each measurement position, and a step of setting the measurement position where the distance is minimized among all the measurement positions as the molten material level.

[0013] The vibration meter is preferably installed between the tapping hole level and the tuyere level of the furnace body.

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

[0015] The measuring device for the molten material 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, calculating the vibration intensity in the frequency range derived from the blast at each measurement position, calculating the inflection point of the distribution of the vibration intensity in the height direction of the furnace body, and an information processing device that sets the position corresponding to the inflection point as the position of the molten material level in the blast furnace.

[0016] The operation method of the blast furnace according to the present invention includes the step of operating the blast furnace according to the molten material level measured using the measuring method of the molten material level in the blast furnace according to the present invention.

Advantages of the Invention

[0017] According to the measuring method and measuring device for the molten material level in the blast furnace according to the present invention, the molten material level in the blast furnace can be accurately measured 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

[0018]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0019] Hereinafter, with reference to the drawings, a method for measuring the melt level in a blast furnace, a measuring device for 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.

[0020] 〔Configuration〕 First, with reference to FIG. 1, the configuration of a measuring device for the melt level in a blast furnace, which is an embodiment of the present invention, will be described.

[0021] FIG. 1 is a schematic cross-sectional view showing the configuration of a blast furnace to which a measuring device for 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 taphole 4 provided in the furnace body 2 below the tuyere 3. Further, the furnace bottom of the blast furnace 1 is composed of furnace bottom bricks 5 and furnace wall bricks 6, and the inner wall surface and the outer wall surface of the furnace wall bricks 6 are respectively covered with cooling sleeves 7 and steel sheets 8.

[0022] 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 a measuring device for the melt level in the blast furnace. Each vibration meter 9 is set at equal intervals along a straight line perpendicular to the circumferential tangent of the furnace body 2 and along the surface of the steel sheet 8 from the height position of the taphole 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.

[0023] 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 of each vibration meter 9 by performing a Fourier transform on the time-series data of the vibration values at the installation positions (measurement positions) of each vibration meter 9 generated by the data logger 10. Then, the information processing device 11 calculates the melt level in the blast furnace by executing the following method for measuring the melt level in the blast furnace using the calculated vibration intensity.

[0024] As a result of measurements on the actual machine, the vibration of the furnace body 2 has all vibration frequency bands. Among them, in particular, the vibration frequency band with a high peak value and a peak confirmed at all measurement positions is the frequency band of 700 to 900 Hz. It was confirmed that the vibration in the frequency band of 700 to 900 Hz has a general tendency to show high values at positions close to the tuyere 3. Therefore, it is considered to be vibration caused by the blast 23 from the tuyere 3 (blast-derived vibration). Therefore, in the present invention, the melt 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, the influence of the ground, etc., and there is no confirmation that it can be evaluated in the same frequency band in any blast furnace. For this reason, when the present invention is applied to other blast furnaces, it is desirable to analyze the basic vibration frequency band each time.

[0025] In the blast furnace 1 shown in FIG. 1, the iron ore 21 and coke 22 as raw materials are charged into the furnace body 2 in layers from the furnace top and are reduced by the blast (hot blast) 23 pumped from the tuyere 3 to become the melt 24. Then, the melt 24 is stored at the bottom of the furnace and is discharged as the tapping slag 25 from the tapping hole 4 by punching the tapping hole 4 every predetermined time. 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.

[0026] 〔Measurement method〕 Next, with reference to FIGS. 2 and 3, a method for measuring the melt level in the blast furnace in one embodiment of the present invention will be described.

[0027] Figure 2 shows the result of plotting the vibration intensity derived from the blast, measured by a plurality of vibration meters 9, against the height of the relative measurement position of the vibration meter 9 with respect to the melt level (vibration meter height based on the liquid surface) when the melt level was changed using a cold model simulating the lower part of the blast furnace 1. As shown in Figure 2, it can be seen that the vibration intensity derived from the blast has an inflection point at the surface layer of the melt. Also, this experiment includes the results of multiple cases in which factors that can vary in an actual blast furnace, such as the physical properties of the melt, the blast volume, the particle size of the packed particles, and the particle size distribution of the packed particles, were simulated and given. However, none of the cases deviated from the trend shown in Figure 2. Furthermore, 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 hearth bricks, and the installation status of the furnace body, the same trend as shown in Figure 2 was confirmed.

[0028] From the above, it is considered that the variation in vibration intensity having an inflection point at the surface layer of the melt is an event that can be uniformly confirmed under all operating conditions. Therefore, if the most inflectional measurement point of the vibration intensity in the height direction of the furnace body can be calculated, since the melt level exists near that measurement point, the melt level in the blast furnace can be accurately measured regardless of the operating conditions of the blast furnace. Also, by this, an increase in the melt level can be detected early, and by preventing an increase in the reduction material ratio caused by an increase in the ventilation resistance due to the increase in the melt level, an eco-friendly blast furnace operation can be stably performed. The technical idea of the present invention is based on the above logic.

[0029] FIG. 3 is a diagram showing an outline of a method for measuring the level of a melt in a blast furnace, which is an embodiment of the present invention. In the method for measuring the level of a melt in a blast furnace, which is an embodiment of the present invention, first, vibration meters 9 installed at equal intervals at a plurality of locations on a line perpendicular to the circumferential tangent of the furnace body 2 from the tapping hole 4 to the height position of the tuyere 3 are used to measure the vibration intensity in the frequency band derived from the blast. In this embodiment, it is assumed that n (≧2) vibration meters 9 are installed. Next, the information processing device 11 classifies the vibration intensity data into first vibration intensity data at a measurement position higher than the measurement position and second vibration intensity data at a measurement position lower than the measurement position at each measurement position (vibration measurement point) i (=1 to n). Next, the information processing device 11 constructs a first linear approximation formula and a second linear approximation formula showing the relationship between the height direction position of the furnace body 2 and the vibration intensity from the first vibration intensity data and the second vibration intensity data at each measurement position i, respectively. Next, as shown in FIG. 3, the information processing device 11 calculates the distance between the plot corresponding to the vibration intensity at the measurement position i of the intersection of the two linear approximation formulas at each measurement position i. And finally, the information processing device 11 sets the measurement position i at which the shortest distance is calculated among the distances calculated for the n measurement positions as the melt level.

Example

[0030] In this example, the capacity is about 5000 m 3In a large blast furnace, pulverized coal was blown from the tuyere using normal charged 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 taphole 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 197 (kg / t), the reductant ratio was 530 (kg / t), the tapping volume was 9900 (t / d), and the tapping temperature was 1510 (°C). In Example 2, the coke ratio was 329 (kg / t), the pulverized coal ratio was 205 (kg / t), the reductant ratio was 534 (kg / t), the tapping volume was 9830 (t / d), and the tapping temperature was 1514 (°C). Fig. 4 shows the time change of the measured values of the molten material level from the initial stage to the final stage of tapping. As shown in Fig. 4, in both Examples 1 and 2, the molten material level finally reached approximately the same level as the taphole level. From this, it was confirmed that according to the present invention, the molten material level can be measured with high accuracy.

[0031] 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, other embodiments, examples, and operation techniques made by those skilled in the art based on this embodiment are all included in the scope of the present invention.

Explanation of Reference Numerals

[0032] 1 Blast furnace 2 Furnace body 3 Tuyere, Blowing tuyere 4 Taphole 5 Bottom bricks 6 Wall bricks 7 Cooling sleeve 8 Steel sheet 9 Vibration meter 10 Data logger 11 Information processing device 21 Iron ore 22 Coke 23 Blowing 24 Molten material 25 Tapping slag

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 molten material level calculation step of calculating an inflection point of the distribution of vibration intensity in the height direction of the furnace body and setting a position corresponding to the inflection point 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 melt level calculation step includes: 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; At each of the measurement positions, a first linear approximation equation and a second linear approximation equation showing a relationship between the height direction position of the furnace body and the vibration intensity are constructed from the first vibration intensity data and the second vibration intensity data, respectively; calculating, for each of the measurement positions, a distance between an intersection of the first linear approximation formula and the second linear approximation formula and a plot corresponding to the vibration intensity at the measurement position; determining the measurement position at which the distance is smallest among all measurement positions as the melt level; The method for measuring a smelt level in a blast furnace according to claim 1, comprising:

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

4. 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.

5. 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 the vibration intensity in the frequency range caused by the blowing air at each measurement position by performing a Fourier transform on the vibration frequency distribution, calculates an inflection point of the distribution of the vibration intensity in the height direction of the furnace body, and sets the position corresponding to the inflection point as the position of the molten material level in the blast furnace; A device for measuring the molten material level in a blast furnace.

6. 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.

Images