JP2018036224A - Level measurement method and level measurement device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a level measurement method and a level measurement device capable of improving an S/N ratio when a level of a slag surface is measured.SOLUTION: With a level measurement method of the present invention, even when a slag surface 3 becomes more than a prescribed level H and a state of the slag surface 3 changes, a processing gain at a time of Fourier transformation processing can be increased in accordance with the state of the slag surface 3 by radiating a microwave of a second sweeping period T2 that is longer that a first sweeping period T1 toward inside of a furnace, allowing an S/N ratio to be improved when the level of the slag surface 3 is measured.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a level measurement method and a level measurement device for measuring the level of a slag surface in a furnace.

  In converter blowing (hereinafter also simply referred to as blowing), a gas such as oxygen is blown onto the slag surface at a high speed and in a large amount, so that the slag surface flows and fluctuates at high speed. When the slag hatches as the blowing progresses, the slag is likely to form as the hatching is promoted, and slopping (a phenomenon in which the formed slag overflows from the furnace port) may occur. Therefore, in converter blowing, it is desired to measure the level of the slag surface in the converter more accurately in real time.

  Conventionally, as a method for measuring the level of a slag surface, as shown in Patent Document 1, a level measuring device using microwaves has been considered. In Patent Document 1, for example, both the slag surface and the lance side wall in the converter are irradiated with microwaves, and a so-called corner cube mirror is formed between the slag surface and the lance side wall to increase the reflectance of the microwave. Proposed. As another level measurement method, it has been proposed that the frequency of the microwave be 10 GHz or less in order to make it less susceptible to dust and the like (Patent Document 2).

JP2015-110817A JP-A-2006-29212

  However, in Patent Document 1, when the fluctuation speed of the slag surface is high, it is difficult to always form a corner cube mirror. With the fluctuation of the slag surface, the reflectance of the microwave is lowered and the S / N ratio is lowered. There was a problem that there was a risk that.

  On the other hand, as shown in Patent Document 2, when a microwave with a frequency of 10 GHz or less is used, the directivity of the microwave is low, so that unnecessary reflection from the structure in the converter increases, and S / There was a problem that the N ratio would decrease. In addition, since the slag surface during blowing is not a flat surface, if a low-frequency microwave with a large spread of the measurement wavefront is used, the S / N ratio is reduced due to the non-uniformity of the distance from the slag surface generated in the measurement wavefront. It will decline.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a level measurement method and a level measurement device that can improve the S / N ratio at the time of level measurement of the slag surface. .

  The level measurement method of the present invention is a level measurement method for measuring the level of a slag surface in a furnace using a microwave, and irradiates the microwave toward the inside of the furnace and reflects the reflected micro wave from the slag surface. By generating a beat signal from the microwave irradiation receiving step of receiving a wave, the microwave irradiated toward the furnace and the reflected microwave, and then executing a Fourier transform process based on the beat signal An operation processing step of generating a frequency spectrum signal and specifying a level of the slag surface in the furnace from the frequency spectrum signal, wherein the microwave irradiation receiving step is configured such that the slag surface is less than a predetermined level in the furnace. In this case, the microwave of the first sweep period is irradiated toward the inside of the furnace, the slag surface becomes equal to or higher than the predetermined level, and the state of the slag surface is With reduction, the microwave long second sweep period than the first sweep cycle and irradiating toward the furnace.

  The level measuring apparatus of the present invention is a level measuring apparatus that measures the level of a slag surface in a furnace using a microwave, irradiates the microwave toward the inside of the furnace, and reflects the microwave reflected from the slag surface. A microwave irradiation receiving unit for receiving a wave, a beat signal generating unit for generating a beat signal from the microwave irradiated toward the inside of the furnace and the reflected microwave, and a Fourier transform process based on the beat signal A frequency spectrum signal is generated by executing and an arithmetic processing unit that identifies a level of the slag surface in the furnace from the frequency spectrum signal, and the microwave irradiation receiving unit includes the slag in the furnace. When the surface is less than a predetermined level, a microwave having a first sweep period is irradiated toward the furnace, and the slag surface becomes equal to or higher than the predetermined level and the slurry is irradiated. The state of the surface is changed, the microwave long second sweep period than the first sweep cycle and irradiating toward the furnace.

  According to the present invention, even when the slag surface becomes a predetermined level or more and the state of the slag surface changes, by irradiating the microwave of the second sweep period longer than the first sweep period toward the inside of the furnace, After the state change of the slag surface, the processing gain at the time of Fourier transform processing can be increased, and thus the S / N ratio at the time of measuring the level of the slag surface can be improved.

It is the schematic which shows the structure of the converter using the level measuring method of this invention. 2A is a graph showing the relationship between the transmission wave and the reception wave, FIG. 2B is a graph showing the waveform of the transmission wave and the reception wave, FIG. 2C is a graph showing the waveform of the beat wave, and FIG. These are graphs showing a frequency spectrum signal in which a main peak appears. It is a graph with which it uses for description of an oversampling process gain. 4A and 4B are graphs for explaining the processing gain by FFT. It is a block diagram which shows the circuit structure of the level measuring apparatus of this invention. It is a flowchart which shows a level measurement process procedure. It is a flowchart which shows the level measurement process sequence by other embodiment. FIG. 8A is a simulation result in the first half of blowing when the sweep cycle is 10 (ms), and FIG. 8B is a simulation result in the first half of blowing when the sweep cycle is 1 (ms). FIG. 9A shows a simulation result in the second half of blowing when the sweep cycle is 10 (ms), and FIG. 9B shows a simulation result in the second half of blowing when the sweep cycle is 1 (ms).

<Configuration of Converter Using Level Measurement Method of the Present Invention>
FIG. 1 is a schematic view showing a configuration of a converter 1 used in a converter steelmaking process. In the converter steelmaking process, the hot metal 2 is charged into the converter 1 (hereinafter also simply referred to as “furnace”), and a gas such as oxygen is blown into the hot metal 2 from the lance 4 to adjust the components of the hot metal 2. To produce molten steel. Slag is generated on the surface of the melt as the treatment proceeds. The level measuring method according to the present invention can measure the level of the slag surface 3 formed in the furnace in this way in real time. In the present invention, the “slag surface” refers to the surface of the molten slag exposed to the outside in the furnace. The “level” of the slag surface 3 refers to the height of the slag surface 3 in the furnace as viewed from the bottom of the furnace and a predetermined reference position.

  In the process performed in the converter 1, steam, dust, and the like are generated. Therefore, a hood 5 is provided near the furnace port of the converter 1 in order not to release the generated dust and the like to the external environment. The hood 5 is formed with an opening for inserting the lance 4 into the converter 1 and an opening where the antenna 6 used in the level measuring method according to the present invention is disposed. The antenna 6 disposed above the furnace port of the converter 1 can irradiate the microwave toward the inside of the furnace and can receive the reflected microwave reflected from the slag surface 3 in the furnace. In the level measurement method according to the present invention, the level of the slag surface 3 can be measured by using the microwave irradiated toward the furnace and the reflected microwave reflected from the slag surface 3.

  Here, in the converter 1, for example, a cylindrical lance 4 is inserted into the furnace, and the tip of the lance is positioned at a predetermined level H in the furnace. In the converter 1, by blowing a gas such as oxygen from the tip of the lance to the slag surface 3 in the furnace, the molten slag contains bubbles, and foaming occurs in which the slag and the molten iron 2 expand in volume. In the lance 4, for example, when slag forming proceeds, the tip of the lance is immersed in the slag or the molten iron 2, and gas is directly injected into the slag from the tip of the lance in this state.

  Here, the period before the tip of the lance is immersed in the slag is the first half of the blowing, and the period after the tip of the lance is immersed in the slag is the latter half of the blowing. In the first half of the blowing, the gas injected from the tip of the lance is the slag surface 3 Therefore, the slag surface 3 is vigorously stirred and the fluctuation speed of the slag surface 3 becomes relatively fast. On the other hand, in the second half of the blowing, the tip of the lance is immersed in the slag or in the hot metal 2 and gas is injected into the slag around the tip of the lance. Become slow.

  As described above, in the converter 1, the state of the slag surface 3 changes around the predetermined level H, and the fluctuation speed of the slag surface 3 changes. The level measurement method of the present invention is described later in “Level measurement method of the present invention”. Based on “Summary of No.”, the S / N ratio at the time of level measurement of the slag surface 3 can be improved even after the state change of the slag surface 3 during blowing.

<Outline of Level Measuring Method of the Present Invention>
Here, first, an FM-CW level measurement method using a microwave will be described. As shown in FIG. 2A, when generating a microwave, the frequency modulation width of the oscillator controlled by the frequency sweeper is set to F (Hz), and the sweep period is set to T (seconds). . The frequency of microwaves (hereinafter also simply referred to as transmission waves) irradiated into the furnace changes continuously and linearly with time.

  On the other hand, a reflected microwave (hereinafter simply referred to as a received wave) that is reflected by the slag surface 3 that is the measurement object and received by the antenna 6 is a distance from the antenna 6 to the slag surface 3 (hereinafter referred to as a separation distance D). A delay Δt (seconds) proportional to the frequency of As a result, there is a frequency difference Δf (Hz) corresponding to the separation distance D between the transmission wave and the reception wave at the same time. When such a transmission wave and a reception wave are mixed by the mixer, a difference frequency signal having a frequency component corresponding to Δf (hereinafter also referred to as a beat wave or a beat signal) is obtained.

  The time delay Δt between the transmission wave and the reception wave corresponds to the time required for the microwave to reciprocate between the antenna 6 and the slag surface 3. Further, since the propagation speed of the microwave is the speed of light c, the time delay Δt can be expressed by the following formula [1]. On the other hand, the relationship represented by the following formula [2] is established between the frequency (beat frequency) Δf of the beat signal and the time delay Δt. Therefore, it can be understood that the separation distance D can be calculated by the following equation [3] by using the equations [1] and [2]. As is apparent from Equation [3], the process of calculating the separation distance D is equivalent to calculating the beat signal frequency (beat frequency Δf) shown in FIG. 2C.

  Here, in an actual measurement environment, the beat signal (beat wave) generated by the mixer is rarely a sine wave as shown in FIG. 2C, and a composite wave in which several frequency components are mixed together. There are many cases. Therefore, when obtaining the frequency of the beat signal composed of such a plurality of frequency components, digital signal processing described later is performed.

  Specifically, after performing a Fourier transform process based on a beat signal composed of a plurality of frequency components to generate a frequency spectrum signal having the horizontal axis as a frequency (Hz), the horizontal axis is further expressed by the above equation [3]. A waveform as shown in FIG. 2D (hereinafter also referred to as “distance waveform”) is generated by converting into distance (m) and having the vertical axis as intensity. In this distance waveform, the position of the horizontal axis that gives the main peak corresponds to the desired separation distance D. In the level measurement method, the level of the slag surface 3 in the furnace can be specified based on the separation distance D thus obtained.

  As described above, in actual operation, oxygen is blown from the lance 4 to the slag surface 3 at a high speed and in a large amount. Therefore, the slag surface 3 as a measurement surface also flows and fluctuates at a high speed. When the sweep period T is longer than the fluctuation period of the slag surface, the distance to the microwave reflection surface varies during one measurement. Then, as is clear from the following equation [4] obtained by substituting equation [1] into equation [2], the beat frequency has a frequency distribution centered on the frequency Δf corresponding to the separation distance D. become. This is because the peak intensity at the measurement distance is lowered in the distance waveform obtained by Fourier transform processing using the beat signal and the horizontal axis is converted into the distance, and the S / N ratio of the measurement is lowered. It will be.

  By the way, when the verification test which measures the reflectance of the microwave of frequency 2.45 (GHz) about CaO contained in slag, changing temperature from 25 degreeC to 1200 degreeC was performed, reflection of the microwave of CaO was carried out. The rate was found to decrease with increasing temperature.

  Moreover, about the powder which contains about 28% of CaO, after measuring a dielectric constant by the cavity resonator perturbation method, the obtained dielectric constant is converted into a reflectance, and the frequency is in the range of 1 (GHz) to 10 (GHz). When the reflectance at 25 ° C. was measured, it was found that the reflectance of CaO hardly changed in the frequency range.

  Such a state is estimated to be the same up to about 90 (GHz), and therefore it is considered that the behavior of the reflectance of CaO does not change in the range of 1 (GHz) to 90 (GHz). Therefore, if the temperature of the slag rises and hatching is promoted in the second half of the blowing, the microwave reflectivity in the slag decreases, the power of the microwave reflected on the antenna 6 decreases, and the level of the slag surface 3 It became clear that the S / N ratio at the time of measurement decreased.

  Therefore, in the level measurement method of the present invention, the microwave sweep cycle T is defined, and the microwave sweep cycle T is set according to the level (height position) of the slag surface during the level measurement of the slag surface 3. By changing it, the S / N ratio during blowing was always maintained at a high level. The specific method will be described below.

  If the fluctuation of the slag surface 3 during the microwave sweep period T (one period) is equal to or less than the wavelength λ of the microwave, the fluctuation of the slag surface 3 is The level measurement of the slag surface 3 is hardly affected. Therefore, in the first half of the blowing when the slag surface 3 is less than the predetermined level H, if the sweeping period T of the microwave is the first sweeping period T1 and the fluctuation speed of the slag surface 3 is v1, if T1 × v1 ≦ λ is satisfied, The S / N ratio decrease at the time of level measurement of the slag surface 3 can be suppressed. Therefore, in the first half of blowing, the microwave sweep cycle T is set to the first sweep cycle T1 that satisfies T1 ≦ λ / v1, and the microwave of the first sweep cycle T1 is irradiated toward the slag surface 3.

  In the second half of blowing, the tip of the lance is immersed in the slag, and the fluctuation speed of the slag surface 3 becomes slower than the first half of blowing. Therefore, in the second half of blowing, assuming that the fluctuation speed of the slag surface 3 is v2 (v2 <v1) and the microwave sweep period T is the second sweep period T2, T2 × v2 ≦ λ is set as in the first half of blowing. If it satisfies, the S / N ratio decrease at the time of level measurement of the slag surface 3 can be suppressed. In the second half of blowing, as described above, the fluctuation speed v2 of the slag surface 3 becomes slower than the first half of blowing, so that the second sweep period T2 of the microwave is made longer than the first sweep period T1 of the first half of blowing. be able to.

  Therefore, in the second half of blowing, the microwave sweep cycle T is set to the second sweep cycle T2 that satisfies the conditions of T2 ≦ λ / v2 and T1 <T2, and the microwave of the second sweep cycle T2 is set to the slag surface 3. Irradiate toward.

  In the second half of the blowing, as described above, it was confirmed that the microwave reflectivity decreased on the slag surface 3 as compared with the first half of the blowing, as the slag temperature increased. By making this longer than the first sweep period T1 in the first half of blowing, the S / N ratio can be improved during signal processing performed when measuring the level of the slag surface 3, as will be described later. As a result, in the second half of blowing, the S / N ratio decrease caused by the decrease in the microwave reflectivity at the slag surface 3 due to the increase in the slag temperature is improved by signal processing performed when the level of the slag surface 3 is measured. Can be made. Hereinafter, this point will be described.

When the separation distance D is obtained, it is necessary to digitally process the beat signal. In order to digitally process the beat signal, the beat signal of the analog signal is converted from analog to digital (A / D conversion). Although the A / D conversion data are discretely sampled, the sampling frequency F _s, in order to prevent aliasing, it is necessary to at least twice the beat frequency Delta] f. At this time, the maximum beat frequency (the maximum value of the beat frequency Δf corresponding to the maximum value of the assumed separation distance D) determined by the equation [4] is B (Hz), and Fourier transform (fast Fourier transform: FFT) Assuming that the number of sampling points when performing M is M, the degree of improvement in the S / N ratio can be expressed by the following equation [5].

As shown in FIG. 3, the first term in the equation [5] is that the maximum frequency on the horizontal axis when FFT is performed increases as F _s increases, so that the noise power is constant. noise by increasing the F _s are averaged to wideband, noise amount in the target frequency is represents to be a relatively small, called oversampling processing gain. For example, as shown in FIG. 3, at the sampling frequency F _s ′ (= 2F _s ) where the sampling frequency F _s is doubled, the noise level is halved compared to the case of F _s , and the S / N ratio (FIG. Among them, it is simply expressed as S / N).

On the other hand, as shown in FIGS. 4A and 4B, the second term in the equation [5] has a large sampling point number M because the frequency domain interval of the discretized horizontal axis after FFT is F _s / M. The smaller the bandwidth Bw (= 1 / M) of one FFT bin, the smaller the band noise given by “Boltzmann constant × temperature × bandwidth” (W), while the reflection from the slag. Since the signal appears at the position of the beat frequency Δf, which is a single frequency, the narrower the FFT bin, the higher the peak intensity, and this is called the FFT processing gain.

For example, as shown in FIG. 4B, in the sampling point number M ′ (= 2M) obtained by doubling the sampling point M, the band noise becomes smaller and the S / N ratio becomes smaller than in the case of M shown in FIG. 4A. improves. Here, since the number M of sampling points is given by M = T × F _s (T is a sweep cycle (seconds) and F _s is a sampling frequency (Hz)), Equation [5] is rewritten as Equation [6] below. be able to.

Therefore, from the above formula [6], if the sampling frequency F _s is constant, the number of sampling points M is increased by lengthening the sweep period T, the improvement of S / N ratio due to the processing gain of the FFT becomes larger Yes. Therefore, as described above, in the second half of blowing, the second sweep period T2 of the microwave is made longer than the first sweep period T1 of the first half of blowing, thereby performing signal processing performed at the time of measuring the level of the slag surface 3. In this case, the S / N ratio can be improved. Thus, in the latter half of the blowing, the microwave reflectivity on the slag surface 3 decreases as the slag temperature rises compared to the first half of the blowing, but the S / N ratio decrease caused by the reduction in the microwave reflectivity is reduced. This can be improved by signal processing performed when the level of the slag surface 3 is measured.

<About level measuring device>
Next, a level measuring apparatus that executes signal processing according to the above-described “Outline of Level Measuring Method of the Present Invention” will be described below. As shown in FIG. 5, the level measuring apparatus 10 includes an antenna 6 (FIG. 1), a microwave irradiation receiving unit 11 including an oscillator, a frequency sweeper, and the like, and the antenna of the microwave irradiation receiving unit 11. The separation distance D from 6 to the slag surface 3 in the converter 1 can be measured, and the level of the slag surface 3 can be specified from the separation distance D.

  The microwave irradiation receiver 11 is a micro in which the frequency (Hz) changes in a sawtooth shape from the minimum frequency f1 to the maximum frequency f2 at the first sweep period T1 (seconds) during the first half of the blowing when the slag surface 3 is less than the predetermined level H. A wave is irradiated from the antenna 6 toward the furnace as a transmission wave (FIG. 2A). The microwave irradiation receiving unit 11 thereby receives the reflected microwave reflected from the slag surface 3 in the furnace by the antenna 6 as a received wave (FIG. 2A).

  Here, the first sweep period T1 satisfies the condition of T1 ≦ λ / v1, where the wavelength of the microwave is λ (mm) and the fluctuation speed of the slag surface 3 in the first half of blowing is v1 (m / s). For the fluctuation speed v1 (m / s) of the slag surface 3, for example, numerical values (average speed, maximum speed, etc.) determined based on analysis of past operation data, experimental data, etc. are applied, but in addition, measurement is performed in real time. A numerical value calculated based on the level displacement of the slag surface 3 may be used. λ may be the wavelength of the microwave at the center frequency of the sweep, expressed as λ = c / [(f1 + f2) / 2] (mm) (c is the speed of light).

  For example, when it is obtained from the analysis result that the maximum value of the fluctuation speed of the slag surface 3 in the first half of the blowing in the converter 1 is about 5 (m / s), the fluctuation speed v1 of the slag surface 3 Is 5 (m / s) which is the maximum speed. At this time, in the case of a microwave having a frequency of 10 to 90 (GHz), when the wavelength is about 3.3 to 30 (mm), the first sweep period T1 in the first half of blowing is 0.67 to It may be set to 6 (ms) or less.

  The microwave irradiation receiving unit 11 guides the microwaves and reflected microwaves irradiated toward the inside of the furnace to the beat signal generation unit 12, and causes the beat signal generation unit 12 to generate a beat signal (FIG. 2C). When the arithmetic processing unit 13 receives the beat signal from the beat signal generation unit 12, it converts the beat signal from analog to digital and then Fourier-transforms the beat signal to generate a frequency spectrum signal having the horizontal axis as the frequency (Hz).

In the case of this embodiment, in accordance with the above-described “Outline of Level Measurement Method of the Present Invention”, the arithmetic processing unit 13 has a maximum sampling frequency F _{s to} be measured when analog-to-digital conversion of a beat signal in order to prevent aliasing. The beat frequency Δf corresponding to the separation distance D is fixed to a value more than twice.

  The arithmetic processing unit 13 further converts the horizontal axis into the distance (m) by the above equation [3], generates a distance waveform (FIG. 2D) with the vertical axis as the intensity, and calculates the main peak position in the distance waveform. The separation distance D is set, and this is transmitted to the sweep cycle switching unit 14 as separation distance data.

  The sweep cycle switching unit 14 has a memory that stores in advance a predetermined level H at which the state of the slag surface 3 changes, and the level of the slag surface 3 becomes equal to or higher than the predetermined level H from the separation distance D based on the separation distance data. It is determined whether or not. When the sweep cycle switching unit 14 determines that the level of the slag surface 3 has become equal to or higher than the predetermined level H, the sweep cycle switching unit 14 recognizes that the temperature of the slag surface 3 has shifted to the latter half of blowing and generates a sweep cycle switching signal. It is sent to the microwave irradiation receiver 11. Based on the sweep cycle switching signal, the microwave irradiation receiving unit 11 switches the sweep cycle of the microwave radiated into the furnace from the first sweep cycle T1 to the second sweep cycle T2, and the second sweep Irradiation with microwaves of period T2 is directed toward the inside of the furnace.

  Here, the second sweep period T2 satisfies the condition of T2 ≦ λ / v2, where the wavelength of the microwave is λ (mm) and the fluctuation speed of the slag surface 3 in the latter half of blowing is v2 (m / s). At this time, the fluctuation speed v2 of the slag surface 3 in the latter half of the blowing is slower than the fluctuation speed v1 of the slag surface 3 in the first half of the blowing, so that T1 <T2. As the fluctuation speed v2 (m / s) of the slag surface 3, for example, numerical values (average speed, maximum speed, etc.) determined based on analysis of past operation data, experimental data, etc. are applied. The numerical value calculated based on the level displacement of the slag surface 3 measured in step 1 may be used.

  For example, when it is obtained from the analysis result that the maximum value of the fluctuation speed of the slag surface 3 in the second half of blowing is about 0.5 (m / s), the fluctuation speed v2 of the slag surface 3 is maximized. The speed is 0.5 (m / s). At this time, in the case of a microwave having a frequency of 10 to 90 (GHz), when the wavelength is about 3.3 to 30 (mm), the second sweep period T2 in the latter half of blowing is 6.7 to It may be 60 (ms) or less.

  Regarding the first sweep cycle T1 and the second sweep cycle T2, the condition of T1 <T2 is satisfied, but it is desirable that T1 <T2 ≦ 10 (ms), and it is desirable that T2 = 10 × T1. Thereby, in both the first half of blowing and the second half of blowing, it becomes possible to further improve the S / N ratio.

  Next, level measurement processing executed by the level measuring apparatus 10 will be briefly described using the flowchart shown in FIG. Here, an example in which the microwave sweep period T is changed according to the level of the slag surface 3 will be described. As shown in FIG. 6, the level measuring device 10 enters from the start step of the routine RT1 and proceeds to step SP1, where the microwave of the first sweep period T1 is generated by the microwave irradiation receiver 11, and this is generated in the furnace. Then, the light is guided to the beat signal generator 12 and the process proceeds to the next step SP2.

  In step SP2, the microwave irradiation receiving unit 11 receives the reflected microwave from the furnace, guides it to the beat signal generation unit 12, and proceeds to the next step SP3. In step SP3, the beat signal generation unit 12 generates a beat signal from the microwave and the reflected microwave, sends this to the arithmetic processing unit 13, and proceeds to the next step SP4.

  In step SP4, the arithmetic processing unit 13 generates a frequency spectrum signal by performing Fourier transform or the like on the beat signal, and proceeds to the next step SP5. In step SP5, the arithmetic processing unit 13 specifies the level of the slag surface 3 in the furnace based on the frequency spectrum signal, and sends this to the sweep cycle switching unit 14 as separation distance data, and goes to the next step SP6. Move.

  In step SP6, the sweep cycle switching unit 14 determines whether or not the level of the slag surface 3 is a predetermined level H set in advance based on the separation distance data. If a negative result is obtained here, this means that the level of the slag surface 3 is less than the predetermined level H, and the level measuring apparatus 10 executes the loop of steps SP1 to SP6 described above, and performs microwave irradiation. The receiving unit 11 continues to irradiate the microwave of the first sweep period T1 toward the furnace.

  On the other hand, if a positive result is obtained in step SP6, this means that slag forming has progressed and the level of the slag surface 3 has become equal to or higher than the predetermined level H. At this time, the level measuring device 10 Control goes to step SP7. In step SP7, the sweep cycle switching unit 14 determines whether or not the level of the slag surface 3 is a preset stop level based on the separation distance data. If a negative result is obtained here, this means that the level of the slag surface 3 is equal to or higher than the predetermined level H and lower than the stop level, the process proceeds to the next step SP8, and the sweep cycle switching unit 14 performs the sweep. A period switching signal is sent to the microwave irradiation receiver 11.

  In step SP8, the microwave irradiation receiving unit 11 sets the sweep period of the microwave irradiated into the furnace to the second sweep period T2 longer than the first sweep period T1 based on the sweep period switching signal. Switching is started, and the microwave of the second sweep period T2 starts to be irradiated into the furnace, and the process proceeds to the next step SP2. As a result, the level measuring apparatus 10 has the above-described steps SP8, SP2, SP3, and SP4 as long as the level of the slag surface 3 is equal to or higher than the predetermined level H and lower than the stop level (that is, as long as a positive result is obtained in step SP7). , SP5, SP6, and SP7 are executed, and the microwave irradiation receiver 11 continuously irradiates the microwave of the second sweep period T2 into the furnace.

  On the other hand, if an affirmative result is obtained in step SP7, this means that the level of the slag surface 3 has reached the stop level. At this time, the level measuring device 10 causes the slag surface 3 to reach the stop level. A notification for notifying the arrival is made, the process proceeds to the next step SP9, and the level measurement process described above is terminated.

  In the above configuration, in the level measurement method, when the slag surface 3 is less than the predetermined level H in the furnace, the microwave of the first sweep cycle T1 is irradiated toward the furnace, and the slag surface 3 is equal to or higher than the predetermined level H. When the state of the slag surface 3 changes, a sweep cycle switching step of irradiating the microwave of the second sweep cycle T2 longer than the first sweep cycle T1 into the furnace is performed.

  As described above, in the level measurement method, even when the slag surface 3 becomes equal to or higher than the predetermined level H and the state of the slag surface 3 changes, the microwave having the second sweep period T2 longer than the first sweep period T1 is placed in the furnace. By irradiating the slag surface 3, the processing gain at the time of Fourier transform processing can be increased after the state of the slag surface 3 changes, and thus the S / N ratio at the time of level measurement of the slag surface 3 can be improved.

  In particular, in the converter steelmaking process in the converter 1, when the slag temperature rises from the first half of the blowing to the second half of the blowing, the microwave reflectance on the slag surface 3 decreases accordingly. . In the level measurement method, when the second half of the blowing process, where the microwave reflectivity is likely to drop, is entered, the S / N ratio drop caused by the drop in the microwave reflectivity is switched to the microwave of the second sweep period T2. Can be made.

<Other embodiments>
In the above-described embodiment, the case where the converter 1 used for the converter steelmaking process is applied has been described. However, the present invention is not limited to this, for example, a furnace used for a nonferrous metal refining process in addition to a smelting reduction furnace. It can also be applied to various other furnaces. An example of the nonferrous metal refining process is a copper smelting process.

  In the above-described embodiment, the case where the height position of the lance tip of the lance 4 is set to the predetermined level as the predetermined level that serves as a guide for switching the sweep cycle has been described. A position located above or below the tip with respect to the tip, and various other height positions may be set as the predetermined level.

<Level measurement processing according to another embodiment>
In the above-described embodiment, as shown in FIG. 6, the level of the slag surface 3 is measured by microwaves, and the microwave sweep period T is changed according to the measured level of the slag surface 3. However, the present invention is not limited to this, and the level of the slag surface 3 is estimated over time, and the level of the slag surface 3 becomes a predetermined level when a predetermined time elapses. It may be changed.

  In this case, it is assumed that the slag surface 3 is less than the predetermined level H in the furnace until the predetermined time elapses in advance, and continues to irradiate the microwave of the first sweep period T1 toward the furnace. When the predetermined time has elapsed, assuming that the slag surface 3 reaches the predetermined level H, the microwave is switched to the microwave of the second sweep period T2, and the microwave is irradiated toward the inside of the furnace.

  In this embodiment, for example, the sweep cycle switching unit 14 includes a timer, and changes the microwave sweep cycle T according to the measurement time of the timer. Next, a level measurement process for switching the microwave sweep period T as the timer elapses will be described below with reference to the flowchart shown in FIG. In this case, as shown in FIG. 7, the level measuring apparatus 10 enters from the start step of the routine RT21, moves to step SP21, starts measurement by the timer provided in the sweep cycle switching unit 14, and then proceeds to the next step SP22. Move.

  In step SP22, the sweep cycle switching unit 14 determines whether or not the measurement time of the timer has passed the first predetermined time. The first predetermined time is set in advance with reference to a predetermined level H in the furnace. Here, the first predetermined time corresponds to, for example, a time when the level of the slag surface 3 becomes higher than the tip of the lance as the blowing progresses, and can be set as appropriate with a time margin.

  If a negative result is obtained in step SP22, this indicates that the time measured by the timer has not passed the first predetermined time, that is, the level of the slag surface 3 is less than the predetermined level H. At this time, the sweep cycle switching unit 14 proceeds to the next step SP23. In step SP23, the level measuring apparatus 10 generates the microwave having the first sweep period T1 by the microwave irradiation receiving unit 11, irradiates the microwave toward the furnace, and also guides it to the beat signal generating unit 12. Then, the process proceeds to the next step SP25.

  In step SP25, the microwave irradiation receiver 11 receives the reflected microwave from the furnace, guides it to the beat signal generator 12, and proceeds to the next step SP26. In step SP26, the beat signal generation unit 12 generates a beat signal from the microwave and the reflected microwave, sends this to the arithmetic processing unit 13, and proceeds to the next step SP27.

  In step SP27, the arithmetic processing unit 13 generates a frequency spectrum signal by performing Fourier transform or the like on the beat signal, and proceeds to the next step SP28. In step SP28, the arithmetic processing unit 13 specifies the level of the slag surface 3 in the furnace based on the frequency spectrum signal, and proceeds to the next step SP29.

  In step SP29, the sweep cycle switching unit 14 determines whether or not the measurement time of the timer has passed the second predetermined time. Here, the second predetermined time is set to a time longer than the first predetermined time of step SP22, which corresponds to the time for which the progress of the blowing is completed. It can be set appropriately. If a negative result is obtained in step SP29, the process returns to step SP22, and the above-described processing is continued until a positive result is obtained in step SP22, and microwaves of the first sweep period T1 are continuously irradiated into the furnace.

  On the other hand, if a positive result is obtained in step SP22, this means that the measurement time of the timer has passed the first predetermined time, that is, the level of the slag surface 3 has become equal to or higher than the predetermined level H. At this time, the sweep cycle switching unit 14 proceeds to the next step SP24. In step SP24, the level measuring apparatus 10 switches the microwave sweep cycle to the second sweep cycle T2, generates the microwave of the second sweep cycle T2 by the microwave irradiation receiver 11, and directs the microwave into the furnace. And is also guided to the beat signal generation unit 12, and proceeds to the next step SP25.

  The level measuring apparatus 10 repeats the above-described steps SP24, SP25, SP26, SP27, SP28, SP29, and SP22 until a positive result is obtained in step SP29, and directs the microwave of the second sweep period T2 into the furnace. Continue to irradiate. On the other hand, when an affirmative response is obtained in step SP29, this indicates that the timer measurement time has passed the second predetermined time, that is, the level of the slag surface 3 has reached the stop level. Then, the process proceeds to step SP30, and the level measurement process described above is terminated.

  In the first level measurement process shown in FIG. 6, the case where both the switching of the sweep cycle and the end of the level measurement process are determined by the level (height) of the slag surface 3 measured by the microwave will be described. However, the present invention is not limited to this, only the switching of the sweep cycle is determined according to the time from the start of blowing as in the level measurement process of FIG. 7, or only the end of the level measurement process, You may judge according to the time from the start of blowing like the level measurement process of FIG.

  Even in the level measurement method using the measurement time of the timer as described above, the microwave of the second sweep period T2 is directed into the furnace according to the state change of the slag surface 3 as in the above-described embodiment. Therefore, after the state of the slag surface 3 is changed, the processing gain at the time of Fourier transform processing can be increased, and thus the S / N ratio at the time of level measurement of the slag surface 3 can be improved.

  In the steel converter, when the level of the slag surface is less than the tip of the lance (first half of blowing), the following simulation was performed to see how the S / N ratio changes depending on the sweep cycle T. In the simulation of the first half of blowing, the separation distance (distance between the antenna and the slag surface) D was 5 (m), the fluctuation speed of the slag surface was 5 (m / s), and the reflectance of the microwave on the slag surface was 10%. .

  Under these conditions, a beat wave with a microwave sweep period T of 10 (ms) is generated by numerical analysis, and this is Fourier transformed. From the obtained results, the horizontal axis is converted into distance. Generated distance waveform. As a result, a result as shown in FIG. 8A was obtained. Also, under the same conditions, a beat wave with a microwave sweep period T of 1 (ms) is generated by numerical analysis, this is Fourier transformed, and the horizontal axis is converted to distance from the obtained result. Generated distance waveform. As a result, a result as shown in FIG. 8B was obtained.

  As shown in FIG. 8A, when the sweep cycle T is 10 (ms), the fluctuation speed of the slag surface is fast, and the separation distance D changes during the sweep, so that the distance waveform spreads in the horizontal axis direction. As a result, the S / N ratio decreased to 7.4 (dB). The S / N ratio is a ratio between the peak signal intensity and the average noise level expressed in dB. On the other hand, when the sweep cycle T is shortened to 1 (ms), a sufficient S / N ratio (= 9.7 (dB)) can be obtained with a sharp peak as shown in FIG. 8B. It could be confirmed.

  Next, in the steel converter, when the level of the slag surface is equal to or higher than the tip of the lance (the second half of blowing), a simulation was also performed on how the S / N ratio changes due to the difference in the sweep cycle T. In the simulation of the second half of blowing, the separation distance D was 4 (m), the fluctuation speed of the slag surface was 0.5 (m / s), and the microwave reflectance on the slag surface was 6%.

  Under these conditions, a beat wave with a microwave sweep period T of 1 (ms) is generated by numerical analysis, and this is Fourier transformed. From the obtained results, the horizontal axis is converted into distance. Generated distance waveform. As a result, a result as shown in FIG. 9A was obtained. Also, under the same conditions, a beat wave with a microwave sweep period T of 10 (ms) is generated by numerical analysis, this is Fourier transformed, and the horizontal axis is converted to distance from the obtained result. Generated distance waveform. As a result, a result as shown in FIG. 9B was obtained.

  As shown in FIG. 9A, when the sweep cycle T was set to 1 (ms), the S / N ratio decreased to 7.6 (dB) with the decrease in the reflectance of the microwave on the slag surface. However, as shown in FIG. 9B, it was confirmed that when the sweep cycle T was increased to 10 (ms), a sufficient S / N ratio (= 14.1 (dB)) was obtained with a sharp peak. . Theoretically, if the sweep period T is increased 10 times, the S / N ratio should be improved by 10 (dB), and the S / N ratio in FIG. 9B should be 17.6 (dB). However, the simulation result shows an improvement of 6.5 (dB). This is presumed that the random noise is not completely random, so that the ideal characteristics were not obtained.

DESCRIPTION OF SYMBOLS 1 Converter 3 Slag surface 10 Level measuring device 11 Microwave irradiation receiving part 12 Beat signal generation part 13 Arithmetic processing part 14 Sweep period switching part

Claims (7)

A level measurement method for measuring the level of a slag surface in a furnace using a microwave,
A microwave irradiation receiving step of irradiating the microwave into the furnace and receiving a reflected microwave from the slag surface;
After generating the beat signal by the microwave and the reflected microwave irradiated toward the furnace, a frequency spectrum signal is generated by executing a Fourier transform process based on the beat signal, and the frequency spectrum signal And an arithmetic processing step for specifying the level of the slag surface in the furnace,
The microwave irradiation receiving step includes
When the slag surface is less than a predetermined level in the furnace, the microwave of the first sweep period is irradiated toward the furnace, and when the slag surface becomes the predetermined level or more and the state of the slag surface changes, A level measurement method characterized by irradiating the inside of the furnace with a microwave having a second sweep period longer than the first sweep period. The microwave irradiation receiving step includes
The first sweep cycle is T1, the second sweep cycle is T2, the wavelength of the microwave is λ, the fluctuation speed of the slag surface when the slag surface is less than the predetermined level is v1, and the slag surface is the predetermined When the fluctuation speed of the slag surface at the level or higher is v2 (v2 <v1),
When the slag surface is less than the predetermined level, the condition of T1 ≦ λ / v1 is satisfied,
2. The level measurement method according to claim 1, wherein when the slag surface is equal to or higher than the predetermined level, a microwave satisfying a condition of T2 ≦ λ / v2 is irradiated. The microwave irradiation receiving step includes
The microwave of the first sweep cycle is switched to the microwave of the second sweep cycle when the level of the slag surface measured based on the microwave reaches the predetermined level. The level measuring method according to 1 or 2. The microwave irradiation receiving step includes
3. The microwave of the first sweep cycle is switched to the microwave of the second sweep cycle on the assumption that the level of the slag surface becomes the predetermined level when a predetermined time has elapsed. 4. Level measurement method. The furnace is a converter;
The level measurement method according to any one of claims 1 to 4, wherein the predetermined level is set based on a tip of a lance provided in the converter. A level measuring device that measures the level of a slag surface in a furnace using a microwave,
A microwave irradiation receiving unit that irradiates the microwave toward the inside of the furnace and receives a reflected microwave from the slag surface;
A beat signal generating unit that generates a beat signal by the microwave and the reflected microwave irradiated toward the furnace;
A frequency spectrum signal is generated by executing a Fourier transform process based on the beat signal, and an arithmetic processing unit that identifies the level of the slag surface in the furnace from the frequency spectrum signal,
The microwave irradiation receiver is
When the slag surface is less than a predetermined level in the furnace, the microwave of the first sweep period is irradiated toward the furnace, and when the slag surface becomes the predetermined level or more and the state of the slag surface changes, A level measuring apparatus that irradiates a microwave having a second sweep period longer than the first sweep period toward the inside of the furnace. The microwave irradiation receiver is
The first sweep cycle is T1, the second sweep cycle is T2, the wavelength of the microwave is λ, the fluctuation speed of the slag surface when the slag surface is less than the predetermined level is v1, and the slag surface is the predetermined When the fluctuation speed of the slag surface at the level or higher is v2 (v2 <v1),
When the slag surface is less than the predetermined level, the condition of T1 ≦ λ / v1 is satisfied,
The level measurement apparatus according to claim 6, wherein when the slag surface is equal to or higher than the predetermined level, microwaves that satisfy a condition of T2 ≦ λ / v2 are irradiated.

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