Specification
Title of the invention: Level measuring method and level measuring device
Technical field
[0001]
　The present invention relates to a level measuring method and a level measuring device for measuring the level of a slag surface inside a furnace.
Background technology
[0002]
　In order to improve productivity in the converter steelmaking process, the time required for converter blowing (hereinafter, simply referred to as blowing) is shortened by increasing the acid transfer rate when blowing a gas such as oxygen onto the slag surface. Is important. However, if the acid feeding rate is increased, the slag becomes easier to form, causing sloping (a phenomenon in which the formed slag overflows from the furnace opening) and spitting (a phenomenon in which the slag scatters due to the jet flow), resulting in a decrease in yield. In addition to inviting, there is a possibility that problems such as metal or slag adhering to the furnace opening or hood and hindering the operation may occur. Therefore, in order to improve productivity, it is important to measure the level of the contents of the converter and accurately grasp the forming behavior of slag, which is a sign of sloping, in real time.
[0003]
　Conventionally, as a level measuring device for a slag surface, as shown in Patent Document 1, a level measuring device using microwaves has been considered. Here, a large amount of hot metal and slag are scattered in the furnace during converter blowing, and hot metal and slag may adhere to the furnace mouth and the furnace wall in the furnace as bare metal. In the level measuring device, when the bare metal attached to the furnace wall is present in the microwave irradiation range, the reflected signal from the bare metal is received in addition to the reflected signal from the slag. Therefore, when the reflected signal intensity from the bare metal is larger than the reflected signal intensity from the slag, the position of the bare metal may be erroneously detected as the slag surface position (slag surface level).
[0004]
　In consideration of such a problem caused by bare metal, a level measuring device as shown in Patent Document 2 is also considered. Patent Document 2 discloses a method of obtaining a distance to a slag surface after removing as noise a signal that continuously exists without changing from the start of a blowing process. Further, in Patent Document 2, the difference between the reflected waveforms showing the relationship between the reflected intensity of the reflected wave and the reciprocating propagation time of the antenna and the slag surface is taken at a predetermined time interval, and such a reflected waveform is taken. The method of obtaining the distance is disclosed by using the signal having the largest absolute value of the difference or the difference as a signal from the slag surface.
Prior art literature
Patent documents
[0005]
Patent Document 1: Japanese Patent Application Laid-Open No. 2016-180126
Patent Document 2: Japanese Patent Application Laid-Open No. 2016-29212
Outline of the invention
Problems to be solved by the invention
[0006]
　However, in the method of judging the signal continuously existing from the start of the smelting process as noise, the bare metal newly attached to the furnace opening or the furnace wall during smelting cannot be judged as noise, and newly It is not possible to remove the reflected waves from the generated metal. In addition, the reflected signal from the slag surface may be blocked by the influence of dust generated in the furnace. In such a case, in the method of using the signal having the largest difference in the reflected waveforms or its absolute value as the signal from the slag surface, the intensity of the reflected wave may fluctuate greatly due to the influence of dust generated in the furnace. , The bare metal may be mistakenly judged as a slag surface. Therefore, Patent Document 2 has a problem that the level of the slag surface during blowing cannot be accurately measured.
[0007]
　Further, in Patent Document 2, when the reflectance of microwaves from the slag surface becomes extremely small due to the influence of dust generated in the furnace, the peak difference between the obtained reflected waveform and the previous reflected waveform also becomes small. Therefore, it becomes difficult to determine the peak. In addition, when the time variation of the intensity of the reflected wave due to the influence of dust is large, two peaks corresponding to the slag surface may appear in the waveform obtained by taking the absolute value of the difference of the reflected waveform. There is ambiguity as to whether to select the peak of. Therefore, Patent Document 2 has a problem that the level of the slag surface cannot be accurately measured during blowing in which dust is generated in the furnace.
[0008]
　The present invention has been made in view of the above problems, and provides a level measuring method and a level measuring device capable of measuring the slag surface during blowing more accurately than before by using microwaves. With the goal.
Means to solve problems
[0009]
　The level measurement method of the present invention is a level measurement method for measuring the level of the slag surface in the furnace by using microwaves, and irradiates the microwave toward the inside of the furnace to irradiate the inside of the slag surface or the inside of the furnace. The distance and signal strength to the slag surface or the bare metal in the furnace by the microwave irradiation receiving step of receiving the reflected microwaves from the bare metal adhering to the metal and the microwave and the reflected microwaves. The distance waveform signal generation step of generating the distance waveform signal showing the relationship between the above and the main peak in the distance waveform signal is used as a level measurement value indicating the time change of the distance to the slag surface or the metal in the furnace. A noise determination step of comparing the extraction step of extraction with the level measurement value and a past accumulation level measurement value to determine whether or not the level measurement value is noise, and the noise determination step of determining the noise. A level specifying step of removing the level measurement value and specifying the level of the slag surface in the furnace based on the level measurement value remaining without being removed is provided.
[0010]
　The level measuring device of the present invention is a level measuring device that measures the level of the slag surface in the furnace by using microwaves, and irradiates the microwave toward the inside of the furnace to irradiate the inside of the slag surface or the inside of the furnace. The relationship between the distance and the signal strength to the slag surface or the metal in the furnace is determined by the antenna unit that receives the reflected microwaves from the metal attached to the metal and the microwave and the reflected microwaves. Extraction of the distance waveform signal generator that generates the distance waveform signal shown and the main peak in the distance waveform signal as level measurement values ​​indicating the time change of the distance to the slag surface or the metal in the furnace. A noise determination unit that compares the unit, the level measurement value, and the past accumulation level measurement value to determine whether or not the level measurement value is noise, and the level measurement value determined to be noise. Is provided, and a level specifying unit for specifying the level of the slag surface in the furnace is provided based on the level measurement value remaining without being removed.
Effect of the invention
[0011]
　According to the present invention, it is possible to prevent the level of the slag surface in the furnace from being specified based on the erroneous level measurement value generated by the bare metal, so that the slag surface during blowing can be changed accordingly. Can also be measured accurately.
A brief description of the drawing
[0012]
FIG. 1 is a schematic view showing a configuration of a converter using the level measuring device of the present invention.
FIG. 2A is a graph showing the relationship between the transmitted wave and the received wave, FIG. 2B is a graph showing the waveforms of the transmitted wave and the received wave, and FIG. 2C is a graph showing the waveform of the beat wave. Yes, FIG. 2D is a graph showing a distance waveform signal in which the main peak appears.
FIG. 3 is a graph showing an example of a distance waveform signal.
[Fig. 4] Fig. 4 is a graph showing time-series changes in level measurement values ​​and a time average curve calculated based on level measurement values.
[Fig. 5] Fig. 5 is a block diagram showing a circuit configuration of a level calculation unit.
FIG. 6 is an enlarged graph of a part of the historical data shown in FIG.
FIG. 7A is a graph showing time-series changes in level measurement values, FIG. 7B is a graph used for explaining level measurement values ​​determined to be noise, and FIG. 7C is determination to be noise. It is a graph which provides the explanation when the level measurement value is removed.
FIG. 8 is a flowchart showing a level measurement processing procedure according to the present invention.
[Fig. 9] With respect to the historical data shown in FIG. 4, a level measurement value when the level measurement value actually determined to be noise is removed, and a time average curve calculated based on the remaining level measurement value. It is a graph showing.
Mode for carrying out the invention
[0013]
　 FIG. 1 is a schematic view showing the configuration of the level measuring device 10 of the present invention and the converter 1 in the converter steelmaking process in which the level measuring device 10 of the present invention is used.
[0014]
　In the converter steelmaking process, the hot metal 2 is charged inside the converter 1 (hereinafter, also simply referred to as the inside of the 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 formed on the surface of the melt as the treatment progresses. The level measuring device 10 according to the present invention measures the level of the slag surface 3 formed in the furnace in real time. In the present invention, the “slag surface” refers to the surface of 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 or a predetermined reference position.
[0015]
　In the process performed in the converter 1, steam, dust, etc. are generated. Therefore, in order to prevent the generated dust, etc. from being released to the external environment, the vicinity of the furnace opening opened above the converter 1 extends upward from the furnace opening. An exhaust hood 5 is provided. The exhaust hood 5 has a lance opening 6 for inserting the lance 4 into the converter 1 and a hood opening 6 above the furnace opening. An opening forming portion 7 extending upward is provided around the hood opening 6 as a piping-like structure.
[0016]
　The antenna portion 10a of the level measuring device 10 is arranged in the opening forming portion 7. In the case of this embodiment, the opening forming portion 7 is provided with an antenna portion 10a, and a heat insulating plate 14 is provided between the antenna portion 10a and the inside of the furnace. The heat insulating plate 14 is made of inorganic ceramics that can transmit microwaves , such as alumina (Al 2 O 3 ), silicon nitride (Si 3 N 4 ), and silicon dioxide (SiO 2 ). The heat insulating plate 14 can transmit and receive microwaves between the antenna portion 10a and the inside of the furnace, and can reduce the heat from the inside of the furnace to prevent the antenna portion 10a from being damaged by the heat.
[0017]
　The antenna portion 10a is provided separately from the transmitting antenna 11 that irradiates microwaves from the inside of the hood opening 6 toward the inside of the furnace and the transmitting antenna 11, and reflects from the slag surface 3 in the furnace to open the hood. It is provided with a receiving antenna 12 that receives reflected microwaves that have passed through the unit 6. The frequency of the microwaves irradiated toward the inside of the furnace is preferably more than 10 [GHz] and 90 [GHz] or less because the inside of the furnace is narrow and the reflectance of the microwaves on the slag surface 3 is small. Is preferably 35 [GHz] or more and 85 [GHz] or less.
[0018]
　The transmitting antenna 11 and the receiving antenna 12 are, for example, conical horn antennas having the same diameter, and are arranged so that the opened tip of the enlarged diameter faces the inside of the furnace. The transmitting antenna 11 and the receiving antenna 12 are arranged in the opening forming portion 7 with the tips of the enlarged diameters adjacent to each other. In the case of the present embodiment, the total distance between the diameter of the tip of the transmitting antenna 11 and the diameter of the tip of the receiving antenna 12 is the same as the diameter d of the hood opening 6, and the tips of the transmitting antenna 11 and the receiving antenna 12 Are arranged over substantially the entire radial direction of the hood opening 6.
[0019]
　The transmitting antenna 11 and the receiving antenna 12 are provided with a lens portion 13 made of, for example, polytetrafluoroethylene (Teflon (registered trademark)) at each tip. The transmitting antenna 11 can increase the antenna gain of the transmitting antenna 11 by converging the microwave irradiating the slag surface 3 with the lens unit 13. Further, the receiving antenna 12 can increase the antenna gain of the receiving antenna 12 by converging the reflected microwaves from the slag surface 3 by the lens unit 13.
[0020]
　The level measuring device 10 has a level calculation unit 10b, and transmits the reflected microwaves received by the receiving antenna 12 from the inside of the furnace to the level calculation unit 10b. The level calculation unit 10b executes a predetermined arithmetic process based on the microwave transmitted from the transmitting antenna 11 toward the inside of the furnace and the reflected microwave received from the receiving antenna 12 from the inside of the furnace. Therefore, the height (level) of the slag surface 3 can be calculated and the level of the slag surface 3 can be measured.
[0021]
　
　First, the FM-CW method level measurement method using microwaves will be described. As shown in FIG. 2A, it is assumed that 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) when generating microwaves. .. The frequency of the microwave (hereinafter, also simply referred to as the transmitted wave) emitted toward the inside of the furnace changes continuously and linearly with the passage of time.
[0022]
　On the other hand, the reflected microwave (hereinafter, also simply referred to as a received wave) reflected by the slug surface 3 to be measured and received by the receiving antenna 12 is the distance from the receiving antenna 12 to the slag surface 3 (hereinafter, the separation distance). A delay Δt (seconds) proportional to (referred to as D) will occur. As a result, a frequency difference Δf (Hz) corresponding to the separation distance D is generated between the transmitted wave and the received wave at a certain time. As shown in FIGS. 2B and 2C, when such a transmitted wave and a received wave are mixed by a mixer, a difference frequency signal having a frequency component corresponding to Δf (hereinafter, also referred to as a beat wave or a beat signal) Become.
[0023]
　The time delay Δt between the transmitted wave and the received wave corresponds to the time required for the microwave to return from the transmitting antenna 11 to the receiving antenna 12 via the slag surface 3. The process of calculating the separation distance is equivalent to calculating the frequency of the beat signal (beat frequency Δf). Here, in an actual measurement environment, the beat signal (beat wave) generated by the mixer is often a composite wave in which a number of frequency components are mixed.
[0024]
　Therefore, in order to obtain the frequency of the beat signal composed of such a plurality of frequency components, a Fourier transform process is performed based on the beat signal composed of the plurality of frequency components to generate a frequency spectrum signal. Next, based on the frequency spectrum signal, a waveform signal as shown in FIG. 2D (hereinafter, also referred to as “distance waveform signal”) showing the relationship between the distance [m] and the signal intensity is generated. In the distance waveform signal, the horizontal axis is the distance [m] and the vertical axis is the signal intensity [dB], and the desired separation distance is given at the peak position.
[0025]
　By the way, during smelting, gas such as oxygen is blown from the lance 4 and argon gas or the like is blown from the tuyere of the furnace bottom (not shown in FIG. 1), so that hot metal or slag is blown into the furnace. Scatter a lot. When these scattered substances adhere to the furnace opening or the furnace wall inside the furnace, they grow as bare metal. Since the microwave emitted from the transmitting antenna 11 propagates in the space with a certain spread, it may be irradiated not only on the slag surface 3 but also on the bare metal adhering to the furnace opening and the furnace wall. As a result, when microwaves are reflected by the bare metal, the reflected microwaves reflected from both the slag surface 3 and the bare metal are detected. As a result, a plurality of peaks P1 and P2 may appear in the distance waveform signal obtained by Fourier transforming the beat wave, as shown in FIG. In such a case, for example, if it is determined that the main peak in the distance waveform signal corresponds to the level of the slag surface 3, the level of the slag surface 3 is not confused by the existence of a plurality of peaks. Can be identified.
[0026]
　However, at this time, depending on the degree of growth of the bare metal, the inclination of the slag surface 3 which is the reflecting surface, and the microwave reflectance of the slag surface 3, the reflected signal from the bare metal is higher than the reflected signal from the slag surface 3. May be larger. In such a case, the peak generated in the distance waveform signal by the reflected signal from the bare metal may be erroneously detected as the distance to the slag surface 3.
[0027]
　FIG. 4 shows historical data in which the main peak appearing in the distance waveform signal is extracted each time a distance waveform signal is obtained and this time change is plotted in time series (hereinafter, “level measurement”). Also called "value"). S1 in FIG. 4 shows a time average curve calculated based on these level measurement values. As shown in FIG. 4, the measured values ​​at each level, which should indicate the distance to the slag surface 3, vary. From this, if it is simply determined that the main peak indicates the level of the slag surface 3, the position of the main peak includes both the reflection from the slag surface 3 and the reflection from the bare metal. It can be seen that the peak due to the reflection from the bare metal is erroneously detected as a level measurement value indicating the level of the slag surface 3 in the furnace.
[0028]
　Further, the time average curve S1 showing the time average of the distance to the slag surface 3 is also affected by the erroneous detection of the main peak generated in the distance waveform signal due to the reflected signal from the bare metal as the level measurement value, resulting in an error. Will be included a lot.
[0029]
　Therefore, the present inventors distinguish between the two signals even when the reflected signal from the bare metal and the reflected signal from the slag surface 3 are both received by the antenna unit 10a, and the reflected signal from the bare metal is used. We diligently studied the method of removing the reflected signal. As a result, it became clear that the level measurement values ​​indicating the molten steel surface and the slag surface vibrate at high speed, while the level measurement values ​​indicating the bare metal appear at almost the same height position. I came up with a method to identify the reflected signal of the metal and remove the reflected signal from the bare metal. Hereinafter, a level measurement method for obtaining an accurate level measurement value by removing the reflected signal from the bare metal will be described in detail using the level calculation unit 10b shown in FIG.
[0030]
　
　FIG. 5 is a block diagram showing a circuit configuration of the level calculation unit 10b. As shown in FIG. 5, the level calculation unit 10b has a control unit 20 having a microcomputer configuration including a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), and the like (not shown). .. The level calculation unit 10b includes a storage unit 21 in which various information is stored, a display unit 22, a signal processing unit 23 connected to the antenna unit 10a, a distance waveform signal generation unit 24, an extraction unit 25, and noise determination. The unit 26 and the level specifying unit 27 are connected to the control unit 20 via the bus B.
[0031]
　The control unit 20 comprehensively controls various functions in the level calculation unit 10b by loading and starting up various programs such as a basic program stored in the ROM and a level measurement processing program in the RAM, which will be described later. Execute the level measurement process. The signal processing unit 23 transmits microwaves to the transmitting antenna 11 and the distance waveform signal generation unit 24. The signal processing unit 23 irradiates the inside of the furnace with microwaves from the transmitting antenna 11, receives the reflected microwaves received by the receiving antenna 12, and sends the reflected microwaves to the distance waveform signal generation unit 24.
[0032]
　The distance waveform signal generation unit 24 has a beat signal generation unit 29 and a Fourier transform processing unit 30. The beat signal generation unit 29 mixes the microwave which is the transmission wave and the reflected microwave which is the reception wave by the mixer to generate a beat signal (difference frequency signal), and sends this to the Fourier transform processing unit 30. The Fourier transform processing unit 30 performs Fourier transform processing on the beat signal to generate a frequency spectrum signal. Further, the Fourier transform processing unit 30 generates a distance waveform signal as shown in FIG. 2D, which shows the relationship between the distance [m] and the signal intensity, based on the frequency spectrum signal, and sends the distance waveform signal to the extraction unit 25.
[0033]
　During blowing, the distance waveform signal generation unit 24 uses microwaves and reflected microwaves to generate a distance waveform signal indicating the relationship between the distance and the signal strength to the slag surface 3 or the bare metal in the furnace at predetermined time intervals. Will be generated by. Each time the extraction unit 25 receives the distance waveform signal, the extraction unit 25 extracts the main peak appearing in the distance waveform signal as a level measurement value, and sends this to the storage unit 21, the noise determination unit 26, and the level identification unit 27, respectively. To do. In this case, the extraction unit 25 identifies the highest peak that appears within a predetermined distance range (for example, 10 to 20 [m]) in the distance waveform signal as the main peak, and determines this as the level measurement value.
[0034]
　When the storage unit 21 receives the level measurement value from the extraction unit 25, the storage unit 21 stores the level measurement value as a past accumulation level measurement value in chronological order (storage process). As a result, as shown in FIG. 4, the storage unit 21 has historical data (that is, distance and time) in which all the level measurement values ​​obtained during the blowing are arranged in chronological order as the past accumulation level measurement values. Data showing the relationship) is generated.
[0035]
　Here, FIG. 6 is a graph in which the area from 350 seconds to 500 seconds of the historical data shown in FIG. 4 is enlarged. It is presumed that the bare metal adhering to the furnace wall and the like is not easily affected by oxygen blown from the lance 4 and argon gas blown from the tuyere of the furnace bottom. Therefore, the plots (level measurement values) appearing at substantially the same height position in the regions ER1, ER2, and ER3 shown in FIG. 6 are level measurement values ​​calculated by erroneously detecting the reflected signal from the bare metal. Can be guessed.
[0036]
　On the other hand, the slag surface 3 is affected by oxygen blown from the lance 4 and gas such as argon blown from the tuyere of the furnace bottom, and is long while vibrating finely in a range of about ± 500 [mm] in a short time. The height fluctuates as a whole with the cycle. Therefore, the plot (level measurement value) showing fine vibration with a short period other than the regions ER1, ER2, and ER3 shown in FIG. 6 is a level measurement value calculated by detecting the reflected signal from the slag surface 3. Can be guessed.
[0037]
　The level calculation unit 10b determines the difference between the level measurement value calculated by detecting the reflected signal from the slag surface 3 and the level measurement value calculated by erroneously detecting the reflection signal from the bare metal. It is used to remove the reflected signal from the bare metal. Each time the noise determination unit 26 shown in FIG. 5 receives a level measurement value from the extraction unit 25, the noise determination unit erroneously detects a reflected signal from the bare metal by using the past accumulated level measurement value. It is determined whether or not the level measurement value (hereinafter, also referred to as noise) is calculated.
[0038]
　In the case of this embodiment, the noise determination unit 26 has a comparison unit 31 and a determination unit 32. Each time the comparison unit 31 receives the level measurement value from the extraction unit 25, the comparison unit 31 reads out the accumulation level measurement value within the determination range from the history data stored in the storage unit 21. In the case of this embodiment, as the determination range, for example, when the nth level measurement value from the start of blowing is received from the extraction unit 25, among the past accumulation level measurement values ​​stored in the storage unit 21. The determination range is 10 accumulated level measurement values ​​from n-1 times to n-10 times stored immediately before the nth level measurement value.
[0039]
　The comparison unit 31 compares a plurality of accumulated level measurement values ​​within the determination range with the latest level measurement value received from the extraction unit 25. The comparison unit 31 indicates whether or not any of the accumulated level measured values ​​within the determination range has an accumulated level measured value in which the absolute value of the difference from the latest level measured value is equal to or less than a predetermined value. Is generated and sent to the determination unit 32.
[0040]
　In the case of this embodiment, the comparison unit 31 may select, for example, one of the accumulated level measured values ​​in the determination range whose absolute value of the difference from the level measured value to be determined is equal to or less than a predetermined value. When it is detected, the comparison process is terminated, but the present invention is not limited to this. The comparison unit 31 may compare the level measurement value to be determined with all the accumulation level measurement values ​​within the determination range.
[0041]
　Regarding the regulation of "below the specified value" which is the judgment standard of the absolute value of the difference between the level measurement value and the accumulation level measurement value, and the judgment range, the size of the furnace and the bare metal obtained from the past operation data are incorrect. An appropriate value may be selected for each furnace according to the frequency of detection, the growth rate of the bare metal, the reflectance of the slag surface 3, the distance resolution of the level measuring device 10, and the like. For example, when the FMCW type level measuring device 10 is used as in the present embodiment, the microwave frequency bandwidth is set to F [Hz] for the absolute value of the difference between the level measured value and the accumulated level measured value. If the speed of light is c [m / s], it is preferable that the resolution is about the resolution of the level measuring device 10 determined by c / 2F. That is, it is desirable to generate a comparison result of whether or not the absolute value of the difference between the level measurement value and the accumulation level measurement value is c / 2F or less.
[0042]
　Further, for example, as a comparison result of whether or not the absolute value of the difference between the level measurement value and the accumulation level measurement value is equal to or less than a predetermined value, the absolute value of the distance difference between the level measurement value and the accumulation level measurement value is 30. A comparison result of whether or not it is [mm] or less may be generated.
[0043]
　A method for determining such a level measurement value will be described below using historical data as shown in FIG. 7A. Here, attention is paid to the level measurement value d 11 in the historical data . When the comparison unit 31 receives the nth level measurement value d 11 from the extraction unit 25 as the latest level measurement value, the comparison unit 31 stores the historical data stored in the storage unit 21 immediately before the level measurement value d 11. ten accumulation level measurements d to n-10 times from been n-1 times 10 ~ d 1 sequentially read. Comparing unit 31, the accumulation level measurement d in read determination range 10 ~ d 1 and, level measurement value d 11 Yuki sequentially comparing the accumulation level measurement value d 10 ~ d 1 in the level A comparison result is generated indicating whether or not there are accumulated level measured values ​​d 10 to d 1 in which the absolute value of the difference from the measured value d 11 is equal to or less than a predetermined value .
[0044]
　In this case, as shown in FIG. 7A, the level measurement value d 11 as the judgment target is at almost the same height position as the accumulation level measurement values ​​d 9 , d 8 , d 7 , and d 2 within the judgment range. , These accumulated level measured values ​​d 9 , d 8 , d 7 , d 2 are judged to have an absolute value of difference from the level measured value d 11 equal to or less than a predetermined value. The comparison unit 31 generates, for example, a comparison result in which the accumulation level measurement value d 9 in which the absolute value of the difference from the level measurement value d 11 is equal to or less than a predetermined value exists, and sends this to the determination unit 32. In this way, each time the comparison unit 31 receives the level measurement value from the extraction unit 25, whether or not there is an accumulation level measurement value within the determination range in which the absolute value of the difference from the level measurement value is equal to or less than a predetermined value. The comparison result of is generated.
[0045]
　With respect to the historical data shown in FIG. 7A, each time the comparison unit 31 receives the level measurement value from the extraction unit 25, the determination as described above is performed, and as shown in FIG. 7B, a white circle (“◯”) The level measurement values ​​d 7 , d 8 , d 9 , d 10 , d 11 , d 16 , and d 17 indicated by ()) are within the respective judgment ranges, respectively, and the level measurement values ​​d 7 , d 8 , d 9 , d 10 , D 11 , d 16 and d 17 are compared with the existence of an accumulation level measurement value in which the absolute value of the difference is equal to or less than a predetermined value. For example, the level measured value d 10 shown in FIG. 7B has an accumulated level measured value d 4 in which the absolute value of the difference from the level measured value d 10 is equal to or less than a predetermined value within the determination range, and the level measured value d 16 is within the determination range, the level measurement value d 16 absolute value of the difference between the accumulation level measurement value d becomes equal to or less than the predetermined value 10 to obtain a comparison result between there.
[0046]
　When the determination unit 32 receives from the comparison unit 31 a comparison result that the accumulated level measurement value in which the absolute value of the difference from the level measurement value d 11 to be determined is equal to or less than a predetermined value exists within the determination range, this level measurement is performed. Assuming that the value d 11 continues to appear at approximately the same height position as the past accumulation level measurements d 2 , d 7 , d 8 , d 9 , the level measurement value d 11 is taken from the bare metal. It is determined that the noise is calculated by erroneously detecting the reflected signal. The determination unit 32 sends this determination result to the level identification unit 27.
[0047]
　On the other hand, when the determination unit 32 receives from the comparison unit 31 a comparison result that the accumulated level measurement value in which the absolute value of the difference from the level measurement value to be determined is equal to or less than a predetermined value does not exist within the determination range, the latest value is obtained. Assuming that the level measurement value of is based on the slag surface 3 whose height fluctuates as a whole over a long period, it is determined that the level measurement value is calculated by detecting the reflected signal from the slag surface 3. Then, the determination unit 32 sends this determination result to the level identification unit 27.
[0048]
　The level specifying unit 27 shown in FIG. 5 has a removing unit 34 and a level output unit 35. The removing unit 34 receives the latest level measurement value from the extraction unit 25, and also receives the determination result for the latest level measurement value from the determination unit 32. When, for example, the removing unit 34 receives the determination result that the latest level measurement value is noise, the removing unit 34 removes the latest level measurement value determined to be noise. On the other hand, when the removing unit 34 receives the determination result that the latest level measurement value is not noise, the removal unit 34 sends the level measurement value that is not determined to be noise to the level output unit 35.
[0049]
　Here, FIG. 7C, historical level measurement value d which is determined as noise in the data of FIG. 7B 7 , d 8 , d 9 , d 10 , d 11 , d 16 , d 17 was removed by the level specifying unit 27 The later historical data is shown. As shown in FIG. 7C, the level output unit 35 outputs only the level measurement value that is not determined to be noise and is not removed as the level measurement result indicating the level of the slag surface 3 in the furnace.
[0050]
　As a result, the level output unit 35 can present a level measurement value obtained by removing most of the reflected signal from the bare metal, and a time average curve showing a time average of the distance to the slag surface 3 based on these level measurement values. S2 can be generated. The time average curve S2 thus obtained shows the level of the slag surface 3 in the furnace more accurately because most of the noise generated by the reflected signal from the bare metal is removed. It becomes a thing.
[0051]
　Among the historical data becomes determination reference level measurements as noise level measurement values d by the reflected signal from the first bullion 2 , d 4 without is removed, as it is from the level output section 35 It will be output. However, the level output unit 35, by outputting a time average curve S2, the level measurement value d which have not been removed as noise 2 , d 4 can reduce the influence of. Further, even if the level measurement value due to the reflected signal from the slag surface 3 is erroneously removed as noise, the level output unit 35 can reduce the influence by outputting the time average curve S2.
[0052]
　As described above, the level measurement value generated by the reflected signal from the slag surface 3 may also be erroneously determined as noise and several points may be removed. However, since the measurement cycle by transmitting and receiving microwaves is generally as high as 100 [ms] or less, there is no problem even if several level measurement values ​​generated by the reflected signal from the slag surface 3 are lost. Accurate level measurement of the slag surface 3 can be performed.
[0053]
　Here, the storage unit 21 stores all the level measurement values ​​extracted by the extraction unit 25, and the noise determination unit 26 uses all these level measurement values ​​as past accumulation level measurement values ​​for extraction. It is determined whether or not the level measurement value obtained in unit 25 is noise generated by the reflected signal from the bare metal. That is, the level measurement value determined as noise is not output from the level output unit 35, but is included in the determination range in the determination process by the noise determination unit 26. In this way, the noise determination unit 26 includes the level measurement value determined as noise in the determination range and determines whether or not the latest level measurement value is noise, so that the level measurement value is more accurate. Noise can be determined.
[0054]
　The level measurement value after the determination process output from the level output unit 35 and the time average curve S2 obtained from these level measurement values ​​are sent to the display unit 22 and displayed on the display unit 22. As a result, the operator can recognize the level of the slag surface 3 in the furnace in real time based on the time-series change of the level measurement value displayed on the display unit 22 and the time average curve S2.
[0055]
　Further, in Patent Document 2, the level of the slag surface 3 is specified by taking a difference with respect to the distance waveform signal indicating the relationship between the distance and the signal strength and detecting the signal having the largest difference or the absolute value of the difference. There is a problem that the microwave reflectance of the slag surface 3 is extremely small, the distance waveform signal fluctuates greatly due to noise, and the intensity decreases due to dust in the furnace. Further, it is difficult to measure the correct slag surface because the intensity is further reduced by taking the difference. However, in the above configuration according to the present embodiment, the slag is not processed by the distance waveform signal itself. By converting to a level measurement value indicating the relationship between the distance to the surface 3 or the bare metal and the signal strength and processing, the dependence on the signal strength can be eliminated, and even if the difference is taken, the signal becomes small. It is possible to avoid problems such as being buried in noise.
[0056]
　
　Next, the above-mentioned level measurement process executed by the level measurement device 10 will be briefly described with reference to the flowchart shown in FIG. As shown in FIG. 8, the level measuring device 10 generates microwaves in the signal processing unit 23 in step SP1, irradiates the microwaves from the transmitting antenna 11 toward the inside of the furnace, and uses the microwaves as transmission signals. It is sent to the beat signal generation unit 29, and the process proceeds to the next step SP2.
[0057]
　In step SP2, the receiving antenna 12 receives the reflected microwave from the inside of the furnace, sends it as a received signal to the beat signal generation unit 29 via the signal processing unit 23, and moves to the next step SP3. In step SP3, the beat signal generation unit 29 generates a beat signal from the microwave that is the transmission signal and the reflected microwave that is the reception signal, sends the beat signal to the Fourier transform processing unit 30, and moves to the next step SP4. ..
[0058]
　In step SP4, the Fourier transform processing unit 30 generates a frequency spectrum signal by performing a Fourier transform or the like on the beat signal. Next, in step SP4, the Fourier transform processing unit 30 generates a distance waveform signal indicating the relationship between the distance and the signal strength to the slag surface 3 or the bare metal in the furnace based on the frequency spectrum signal, and generates a distance waveform signal. It is sent to the extraction unit 25, and the process proceeds to the next step SP5.
[0059]
　In step SP5, the extraction unit 25 extracts the main peak generated in the distance waveform signal as a level measurement value indicating the time change of the distance to the slag surface 3 or the bare metal, and extracts this as a level measurement value indicating the time change of the distance to the slag surface 3 or the bare metal, and extracts this as the storage unit 21 and the noise determination unit. It is sent to 26 and the level specifying unit 27, and the process proceeds to the next step SP6. In step SP6, the storage unit 21 stores the level measurement values ​​as the accumulation level measurement values, generates historical data in which the past accumulation level measurement values ​​are arranged in chronological order, and moves to the next step SP7.
[0060]
　In step SP7, the noise determination unit 26 reads the accumulated level measurement value within the preset determination range from the storage unit 21, and the absolute value of the difference from the level measurement value is equal to or less than a predetermined value (for example, the absolute value of the distance difference). Is 30 [mm] or less, or c / 2F or less), and it is determined whether or not the accumulated level measured value exists within the determination range (whether or not it is close to the accumulated level measured value). If a negative result is obtained in step SP7, this means that the accumulated level measurement value whose absolute value of the difference from the level measurement value is less than or equal to the predetermined value does not exist within the judgment range, that is, the level measurement value is the bare metal. It is shown that the noise is not generated by the reflected signal from, and at this time, the noise determination unit 26 sends the determination result to the level identification unit 27 and moves to the next step SP8.
[0061]
　On the other hand, when an affirmative result is obtained in step SP7, this means that the accumulated level measurement value whose absolute value of the difference from the level measurement value is equal to or less than a predetermined value exists within the determination range, that is, the level measurement value. Indicates that the noise is generated by the reflected signal from the bare metal. At this time, the noise determination unit 26 sends the determination result to the level identification unit 27 and moves to the next step SP9. In step SP9, the level specifying unit 27 removes the level measurement value determined to be noise, and moves to the next step SP8.
[0062]
　In step SP8, the level specifying unit 27 uses the remaining level measured values ​​excluding the removed level measured values ​​and the time average curve S2 calculated from these remaining level measured values ​​as the level of the slag surface 3 in the furnace. Is displayed on the display unit 22 as a level measurement result that can identify the above-mentioned level measurement processing procedure.
[0063]
　 In the
　above configuration, the level measuring device 10 irradiates the inside of the furnace with microwaves, receives the reflected microwaves from the slag surface 3 (microwave irradiation receiving step), and these microwaves and The reflected microwave is used to generate a distance waveform signal indicating the relationship between the distance and the signal strength to the slag surface 3 or the bare metal in the furnace (distance waveform signal generation step). Each time the distance waveform signal is obtained, the level measuring device 10 extracts the main peak in the distance waveform signal as a level measurement value indicating the relationship between the distance and the signal strength to the slag surface 3 or the bare metal ( Extraction process). The level measuring device 10 compares the latest level measured value with the past accumulated level measured value within the determination range, and determines whether or not the level measured value is noise (noise determination step).
[0064]
　Here, the level measurement value obtained from the reflected signal from the bare metal adhering to the furnace opening or the furnace wall has a small distance fluctuation per unit time, while the level measurement obtained from the reflected signal from the slag surface 3 As for the value, the distance changes periodically, and the period of distance fluctuation is high. From this, if there is an accumulation level measurement value in which the absolute value of the difference from the level measurement value to be determined is equal to or less than a predetermined value among the past accumulation level measurement values ​​used as the determination range, the level measurement is performed. As for the value, it can be said that the distance fluctuation per unit time is small, so the level measurement value is judged as noise.
[0065]
　The level measuring device 10 removes the level measured value determined to be noise, and specifies the level of the slag surface 3 in the furnace based only on the level measured value remaining without being removed (level specifying step). As a result, the level measuring device 10 can prevent the level of the slag surface 3 in the furnace from being specified based on the erroneous level measured value generated by the bare metal, so that the slag being blown is slag. The surface 3 can be measured more accurately than before.
[0066]
　Further, in Patent Document 2, the level of the slag surface 3 is specified by taking a difference from the distance waveform signal showing the relationship between the distance and the signal strength and detecting the signal having the largest difference or the absolute value of the difference. However, there is a problem that the microwave reflectance of the slag surface 3 is extremely small, the distance waveform signal fluctuates greatly due to noise, and the intensity decreases due to dust in the furnace. Further, it is difficult to measure the correct slag surface because the intensity is further reduced by taking the difference. However, in the above configuration according to the present embodiment, the slag is not processed by the distance waveform signal itself. By converting to a level measurement value indicating the relationship between the distance to the surface 3 or the bare metal and the signal strength and processing, the dependence on the signal strength can be eliminated, and even if the difference is taken, the signal becomes small. It is possible to avoid problems such as being buried in noise.
[0067]
　In this embodiment, two antennas, a transmitting antenna 11 and a receiving antenna 12, are used, and the transmitting antenna 11 and the receiving antenna 12 are arranged in the opening formed by the hood opening 6. In this way, when the two antennas of the transmitting antenna 11 and the receiving antenna 12 are arranged in the hood opening 6, the center of the hood opening 6 and the center of the transmitting antenna 11 are deviated from each other. For this reason, the microwave from the transmitting antenna 11 is likely to hit the metal other than the slag surface 3, and noise is likely to be generated.
[0068]
　Further, as described above, when the two antennas of the transmitting antenna 11 and the receiving antenna 12 are arranged in the hood opening 6, the amount of the receiving antenna 12 provided is larger than that when a single transmitting / receiving antenna is used. The transmission area of ​​the transmission antenna 11 becomes small. Therefore, it is desirable to improve the sensitivity by increasing the output from the transmitting antenna 11 or lowering the noise floor inside the circuit. However, as the sensitivity is increased, noise due to bare metal other than the slag surface 3 is also generated. It becomes easy to occur.
[0069]
　However, in the level measuring device 10, even if the two antennas of the transmitting antenna 11 and the receiving antenna 12 are arranged in the hood opening 6, the level of the slag surface 3 is specified from the erroneous level measurement value generated by the bare metal or the like. Since it is possible to suppress the slag surface 3 being blown, the slag surface 3 during blowing can be accurately measured.
[0070]
　 In
　the above-described embodiment, as the determination range of the accumulated level measurement value to be compared with the latest nth level measurement value, it is stored up to immediately before the nth level measurement value of the determination target. In addition, 10 accumulation level measured values ​​from n-1 times to n-10 times were set as the determination range, but the present invention is not limited to this. For example, nm 1 time to nm 2 times (m 1 and m 2 are integers other than 0 and m 1