Specification
Title of invention: Level measuring device
Technical field
[0001]
　The present invention relates to 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, it is important to increase the acid feeding rate and shorten the time required for blowing when blowing a gas such as oxygen onto the slag surface. However, if the acid feeding rate is increased, not only sloping (a phenomenon in which formed slag overflows from the furnace opening) and spitting (a phenomenon in which slag is scattered by a flue) occur, which not only causes a decrease in yield, but also the furnace opening. In addition, there is a possibility that the metal or slag may adhere to the flue (hereinafter referred to as the exhaust hood) provided above the furnace opening of the converter, which may hinder the operation. 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]
　Therefore, for example, as shown in Patent Document 1, a method of measuring the bath surface level of the melt charged into the converter by using a radar type level meter using microwaves has been proposed. Here, when the slag is formed, the reflectance of microwaves is greatly reduced. Therefore, it is necessary to use an antenna having high directivity. Therefore, in Patent Document 1, the tip of the antenna is cut out and the directivity of the antenna is set to the furnace. A pair of antennas pointing toward the center of is used.
Prior art literature
Patent documents
[0004]
Patent Document 1: Japanese Unexamined Patent Publication No. 2016-180126
Outline of the invention
Problems to be solved by the invention
[0005]
　However, in the method shown in Patent Document 1, it is necessary to insert the tip of the antenna into the exhaust hood at the upper part of the converter in order to direct the directivity of the antenna toward the center of the furnace. Since the metal and slag are scattered in the exhaust hood during converter blowing (hereinafter, also simply referred to as blowing), these metal and slag also adhere to the tip of the antenna provided in the exhaust hood. However, it may interfere with the measurement of microwaves by the antenna. Therefore, in Patent Document 1, there is a risk that the slag surface during blowing cannot be accurately measured.
[0006]
　In addition, since various pipes and machines are arranged in the space above the converter and the exhaust hood, it is not possible to secure sufficient space for installing the antenna in the immediate vicinity of the converter and the exhaust hood, and as a result, In some cases, the antenna must be installed at a distance from the converter and exhaust hood. In such a case, the microwave from the antenna may be reflected by various obstacles above the converter, and the reflected microwave from the slag surface that you really want to detect cannot be detected, and the slag surface cannot be detected. There was a risk that the measurement could not be performed accurately.
[0007]
　The present invention has been made in view of the above problems, and an object of the present invention is to provide a level measuring device capable of measuring the slag surface during blowing more accurately than before by using microwaves. ..
Means to solve problems
[0008]
　The level measuring device of the present invention is a level measuring device for measuring the level of a slag surface inside a furnace, and is a hood opening of an exhaust hood provided above the furnace at a position facing the slag surface. And, a transmitting antenna provided above the hood opening and irradiating microwaves toward the inside of the furnace through the hood opening, and the transmitting antenna are separate and above the hood opening. A receiving antenna that receives reflected microwaves from the inside of the furnace through the hood opening, and antennas of the transmitting antenna and the receiving antenna provided at the tips of the transmitting antenna and the receiving antenna. A lens unit for increasing the gain and a level calculation unit for calculating the level of the slug surface from the reflected microwaves are provided, and the diameter of the transmitting antenna is larger than the diameter of the receiving antenna, and the diameter of the transmitting antenna is set. phi 1 and, when the diameter of the hood opening has a d, phi 1 meet> d / 2, having the structure.
Effect of the invention
[0009]
　According to the present invention, since the transmitting antenna and the receiving antenna are arranged above the hood opening and kept away from the slag surface in the furnace, it is possible to suppress the adhesion of bare metal and slag to the transmitting antenna and the receiving antenna. , The slag surface during blowing can be measured more accurately than before. Further, according to the present invention, by separating the transmitting antenna and the receiving antenna and making the diameter of the transmitting antenna larger than the diameter of the receiving antenna, unnecessary reflection at the time of level measurement of the slag surface can be suppressed. The slag surface during blowing can be measured more accurately than before. Further, according to the present invention, the S / N ratio at the time of level measurement of the slag surface can be improved by increasing the antenna gains of the transmitting antenna and the receiving antenna by the lens unit.
A brief description of the drawing
[0010]
FIG. 1 is a schematic view showing a configuration of a converter using the level measuring device of the present invention.
FIG. 2 is a schematic view for explaining the arrangement positions of the transmitting antenna and the receiving antenna.
[Fig. 3] It is a graph showing the relationship between the distance and the beam diameter.
FIG. 4 is a graph showing the relationship between the transmission antenna diameter and the irradiation area diameter.
[Fig. 5] Fig. 5 is a graph showing the relationship between the transmitting antenna diameter and the interference length.
FIG. 6 is a schematic view showing a level measuring device of Comparative Example 1 having the same transmitting antenna diameter and receiving antenna diameter.
FIG. 7 is a graph showing the relationship between distance and AD input.
FIG. 8 is a circuit diagram showing a circuit configuration of a level measuring device of Comparative Example 2 using a transmitting / receiving antenna.
FIG. 9 is a circuit diagram showing a circuit configuration of the level measuring device of the present invention.
FIG. 10 is a schematic diagram showing the configurations of a transmitting antenna and a receiving antenna of another embodiment.
FIG. 11 is a schematic view for explaining the arrangement positions of the transmitting antenna and the receiving antenna according to another embodiment.
FIG. 12 is a graph showing the relationship between the transmitting antenna diameter and the interference length in another embodiment.
Mode for carrying out the invention
[0011]
　 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.
[0012]
　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 form a component of the hot metal 2. Make adjustments 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 can measure 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.
[0013]
　In the processing 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, an end is provided near the furnace opening opened above the converter 1, and the portion is located above. An exhaust hood 5 extending to 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. Further, around the hood opening 6, an opening forming portion 7 extending upward is provided as a piping-like structure.
[0014]
　The opening forming portion 7 communicates the upper free space above the converter 1 with the inside of the furnace through the hood opening 6, for example, a sublance (not shown) and, if necessary, a hood opening 6. It can be inserted into the furnace via.
[0015]
　The hood opening 6 is an upper wall surface of the exhaust hood 5 and is opened at a position facing the slag surface 3 in the furnace, and a rod-shaped sublance inserted from above the opening forming portion 7 is a hood opening. It may be placed on the slug surface 3 through the portion 6.
[0016]
　In addition to this configuration, the level measuring device 10 according to the present invention has an antenna installation portion 9 having an antenna installation opening 9a opened above the hood opening 6 into which the sublance is inserted. Depending on the type of process performed in the converter, either the antenna unit 10a or the sublance device is appropriately installed in the antenna installation unit 9 using a moving mechanism. When the antenna portion 10a is installed, microwaves are irradiated and received through the antenna installation opening 9a, but on the other hand, when the sublance device is installed, the antenna The sublance is inserted toward the slag surface and the molten steel through the installation opening 9a, the opening forming portion 7, and the hood opening 6. Therefore, the diameter of the antenna installation opening 9a, the diameter of the opening of the opening forming portion 7, and the diameter of the hood opening 6 are formed to have substantially the same size in order to facilitate the insertion of the sublance. Further, the openings of the antenna installation opening 9a, the hood opening 6, and the opening forming portion 7 are formed so that their center positions are aligned linearly in the vertical direction.
[0017]
　The level measuring device 10 arranges the antenna portion 10a in the antenna installation opening 9a of the antenna installation portion 9 when the sublance is not inserted in the hood opening 6. The level measuring device 10 has a level calculation unit 10b, and the level calculation unit 10b performs a calculation based on a received signal received based on a transmission signal transmitted from the antenna unit 10a toward the inside of the furnace. The height of the slag surface 3 can be calculated to measure the level of the slag surface 3. Here, the antenna installation opening 9a of the antenna installation portion 9 has a diameter substantially equal to the diameter d of the hood opening 6 (substantially the same diameter), and its central axis is the same as the central axis of the hood opening 6. It is placed on top.
[0018]
　The diameter d of the hood opening 6 prevents steam from the converter 1 and scattering of bare metal and slag from leaking to the outside of the exhaust hood 5, and various pipes and machines above the converter 1 and the exhaust hood 5 and the like. The sublance can be easily used within the allowable range from the arrangement of the above, and based on the antenna characteristics of the antenna portion 10a in the level measuring device 10, the wavelength of the microwave, the radar cross section of the slag surface 3, and the like. It is selected to the optimum size.
[0019]
　The antenna installation portion 9 has an antenna installation opening 9a at a predetermined height from the flange upper portion 7a at the uppermost portion of the opening formation portion 7 formed around the hood opening 6, and the antenna installation opening 9a The antenna portion 10a installed in the above is kept away from the hood opening 6. As a result, the antenna installation portion 9 can move the antenna portion 10a away from the slag surface 3 in the furnace, so that the bare metal and slag scattered from the slag surface 3 are difficult to reach the antenna portion 10a, and the bare metal and slag Can be prevented from adhering to the antenna portion 10a. Further, since the degree of freedom of distance can be increased, it is difficult to be bound by the arrangement of various pipes, machines, etc. above the converter 1 and the exhaust hood 5.
[0020]
　In the case of this embodiment, the antenna portion 10a is installed in the antenna installation portion 9, 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 O 4 ), and silicon dioxide (SiO 2 ). As a result, the heat insulating plate 14 can transmit and receive microwaves between the antenna portion 10a and the inside of the furnace, while reducing the heat from the inside of the furnace to prevent the antenna portion 10a from being damaged by the heat.
[0021]
　The antenna portion 10a is provided separately from the transmitting antenna 11 that irradiates microwaves toward the inside of the furnace through the hood opening 6 and the transmitting antenna 11, and reflects from the slag surface 3 in the furnace to hood. It includes a receiving antenna 12 that receives reflected microwaves that have passed through the opening 6. The frequency of the microwave radiated 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 microwave on the slag surface 3 is small. Is preferably 35 [GHz] or more and 85 [GHz] or less.
[0022]
　In addition to this configuration, the transmitting antenna 11 is formed to have a diameter larger than the diameter of the receiving antenna 12. The transmitting antenna 11 and the receiving antenna 12 are, for example, conical horn antennas, and the tip of the expanded diameter is directed toward the inside of the furnace, and the tip of the expanded diameter is adjacent to each other and arranged in the plane of the antenna installation opening 9a. It is installed. In the case of the present embodiment, the transmitting antenna 11 is formed so that the diameter at the tip of the enlarged diameter is larger than the diameter at the tip of the enlarged diameter of the receiving antenna 12. 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. The tips of the transmitting antenna 11 and the receiving antenna 12 are arranged over substantially the entire radial direction of the antenna installation opening 9a having substantially the same diameter as the hood opening 6.
[0023]
　Each of the transmitting antenna 11 and the receiving antenna 12 is 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.
[0024]
　Here, the level measuring device 10 can perform FM-CW type level measurement using microwaves. In this case, the width of the frequency modulation of the microwave irradiated in the furnace and the sweep period of the microwave are set to predetermined values ​​in advance. The frequency of the microwave (hereinafter, also simply referred to as the transmitted wave) emitted from the transmitting antenna 11 toward the inside of the furnace changes continuously and linearly with the passage of time.
[0025]
　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 (also called) is generated. As a result, a frequency difference Δf (Hz) corresponding to the separation distance is generated between the transmitted wave and the received wave at a certain time. When such a transmitted wave and a received 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.
[0026]
　The time delay Δt between the transmitted wave and the received wave corresponds to the time required for the microwave to be reflected from the transmitting antenna 11 on the slag surface 3 and returned to the receiving antenna 12. 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.
[0027]
　Therefore, in order to obtain the frequency of the beat signal composed of such a plurality of frequency components, the level calculation unit 10b performs a Fourier transform process based on the beat signal composed of the plurality of frequency components to generate a frequency spectrum signal. , The level of the slug surface 3 in the furnace can be specified based on the separation distance by generating a distance waveform in which the separation distance desired to be obtained from the frequency spectrum signal is given at the main peak.
[0028]
　By the way, as the distance from the antenna portion 10a (that is, from the antenna installation portion 9) to the hood opening 6 communicating with the inside of the furnace increases, the metal and slag scattered in the exhaust hood 5 become more scattered in the antenna portion 10a. And it becomes difficult to reach the heat insulating plate 14. Therefore, it is possible to prevent the bare metal and slag scattered in the exhaust hood 5 from adhering to the antenna portion 10a and the heat insulating plate 14, and it is possible to prevent the measurement of the slag surface 3 from being hindered.
[0029]
　On the other hand, as the distance from the antenna portion 10a to the hood opening 6 increases, the diameter of the transmitted wave emitted from the transmitting antenna 11 increases. When the transmitted wave spreads in this way, it hits the flange upper portion 7a on the upper portion of the opening forming portion 7 formed around the hood opening 6 before the transmitted wave reaches the inside of the furnace. As a result, unnecessary reflections other than the microwaves reflected by the slag surface 3 occur, which hinders the measurement of the slag surface 3.
[0030]
　Therefore, we examined the diameter of the transmitting antenna 11 (hereinafter, also referred to as the transmitting antenna diameter) that can suppress unnecessary reflection even when the distance from the antenna installation portion 9 to the hood opening 6 is large.
[0031]
　It is known that the microwave emitted from the transmitting antenna 11 provided with the lens portion 13 at the tip generally follows the propagation of the Gaussian beam as shown in the following equation.
[0032]
[Number 4]

[0033]
　However, ω (x) indicates the beam radius at a position at a distance x from the antenna, ω 0 indicates the beam waist radius, and λ indicates the wavelength of the microwave. When applied to the microwave emitted from the transmitting antenna 11 , ω 0 corresponds to the beam radius at a distance of 0 from the transmitting antenna 11.
[0034]
　Next, as shown in FIG. 2, the diameter of the transmitting antenna 11 (hereinafter, also referred to as the transmitting antenna diameter) is set to φ 1 [m] (= 2ω 0 ), and the diameter of the flange upper portion 7a of the opening forming portion 7 from the transmitting antenna 11 is set. the irradiation region diameter of the transmitted wave in the distance r to the height position phi 3 [m] and (= 2 [omega), the irradiation region diameter phi with the number 4 3 calculating the irradiation region diameter phi 3 is used It changes depending on the microwave frequency f [Hz] and is expressed by the following equation. However, c is the speed of light [m / s].
[0035]
[Number 5]

[0036]
　Using the above equation 5, when the frequency of the microwave (transmitted wave) is 40 [GHz] and the transmitting antenna diameter φ 1 is 20 to 280 [mm], the irradiation region diameter φ 3 of the transmitted wave with respect to the distance r. As a result, the results shown in FIG. 3 were obtained.
[0037]
　As is clear from FIG. 3, the smaller the transmitting antenna diameter φ 1 is, the smaller the irradiation area diameter φ 3 at a short distance is, and the larger the transmitting antenna diameter φ 1 is, the larger the irradiation area diameter φ 3 at a short distance is. Become. However, as the from the transmitting antenna 11 away far (distance r increases), the trend is reversed, the transmission antenna diameter phi 1 the larger the irradiation area diameter phi 3 becomes smaller.
[0038]
　Therefore, since the general distance r from the tip of the transmitting antenna 11 to the height position of the flange upper portion 7a above the opening forming portion 7 is about 3 to 5 [m], the transmitting antenna 11 in such a general furnace at the position of 3 ~ 5 [m] apart flange upper portion 7a of the irradiation region diameter phi 3 optimal transmission antenna diameter phi for reducing the 1 revealed that the range is present.
[0039]
　Distance r = 4 irradiated region diameter phi in [m] 3 transmission antennas diameter phi 1 was calculated for to give the results shown in FIG. At a distance r = 4 [m], when the transmitting antenna diameter φ 1 is 195 [mm], the irradiation area diameter φ 3 becomes the smallest. The distance r = 3 in the case of [m], the transmitting antenna diameter phi 1 is 169 [mm] irradiation region diameter phi at 3 when the is minimized, the distance r = 5 [m], the transmitting antenna When the diameter φ 1 is 219 [mm], the irradiation area diameter φ 3 becomes the minimum. Therefore, it is desirable that the transmitting antenna diameter φ 1 is 169 to 219 [mm] when the distance r is 3 to 5 [m].
[0040]
　Then, if the diameter d of the hood opening 6 is definite constraints on the converter blowing equipment, as shown in FIG. 2, the transmitting antenna diameter phi 1 and the receiving antenna diameter phi 2 sum of and the diameter d It is desirable that the antenna dimensions are equal. As a result, the opening area of ​​the hood opening 6 can be effectively utilized, so that the transmission / reception efficiency of the transmitting antenna 11 and the receiving antenna 12 can be improved.
[0041]
　At this time, the transmission antenna diameter phi 1 center axis Z1 and the hood opening 6 of the transmission by the value antenna 11 (i.e., antenna installation openings 9a) horizontal distance of the central axis Z2 of the changes. As a result, the amount of interference between the upper flange 7a of the upper portion of the opening forming portion 7 communicating with the inside of the furnace and the transmitted wave from the transmitting antenna 11 also changes. Therefore, as shown in FIG. 2, the transmitting antenna diameter phi 1 and, in consideration of the change in the position of the center axis Z1, Z2, flange upper portion 7a and the irradiation region diameter phi 3 and interferes length (hereinafter, the interference Li = φ 3 / 2-φ 1/2 ( called length) was calculated.
[0042]
　The calculation result of the interference length Li at the distance r = 4 [m] is shown in FIG. As the transmitting antenna diameter φ 1 becomes larger, the irradiation area diameter φ 3 becomes smaller, and the central axis Z1 of the transmitting antenna 11 approaches the central axis Z2 of the hood opening 6, so that the interference length Li becomes smaller. ..
[0043]
　Here, as shown in FIG. 6 in which the corresponding portions with those in FIG. 1 are designated by the same reference numerals, as Comparative Example 1, a level measuring device having an antenna portion 100a in which the diameter of the transmitting antenna 111 and the diameter of the receiving antenna 112 are equal to each other. Consider 100. Here, in the level measuring device 100, as described above, the Fourier transform process is performed based on the beat signal obtained from the transmitted wave from the transmitting antenna 111 and the received wave at the receiving antenna 112, and the horizontal axis is the frequency ( A frequency spectrum signal with Hz) was generated.
[0044]
　Next, based on the obtained frequency spectrum signal, the horizontal axis is converted to the distance [m], and the vertical axis is the AD input [dB]. The waveform as shown in FIG. 7 (hereinafter, also referred to as “distance waveform”). ) Was generated. In this distance waveform, the position where the main peak is given at a distance of 18 to 25 [m] corresponds to the desired separation distance (distance from the antenna portion 100a to the slag surface 3).
[0045]
　When the transmitting antenna 111 and the receiving antenna 112 are separated, a minute transmission signal wraps around between the spatially divided transmitting antenna 111 and the receiving antenna 112. In FIG. 7, the position of the AD converter (not shown) in the level calculation unit 10b that generates the distance waveform is set without using the tips of the transmitting antenna 111 and the receiving antenna 112 as a reference (distance 0 [m]). The standard (distance 0 [m]) is used. Therefore, in FIG. 7, the peak showing the wraparound wave does not appear at a distance of 0 [m] on the horizontal axis, but appears at a distance of about 1 [m].
[0046]
　In FIG. 7, peaks appearing around a distance of 2 to 4 [m] on the horizontal axis indicate unnecessary reflection from the flange upper portion 7a of the upper portion of the opening forming portion 7.
[0047]
　In general, since a wraparound wave is inevitably generated, the sensitivity and the like are designed so that the necessary reflected microwave can be measured while the wraparound wave is generated in the circuit design of the antenna unit 100a. Therefore, if the size of the unwanted reflection can be made smaller than the size of the wraparound wave, the desired distance can be measured without any problem. Therefore, the size of the unwanted reflection should be made smaller than the size of the wraparound wave. is important.
[0048]
　As shown in FIG. 7, in the level measuring device 100 in which the diameter of the transmitting antenna 111 and the diameter of the receiving antenna 112 are equal, the result is that the magnitude of unnecessary reflection from the flange upper portion 7a and the magnitude of the wraparound wave are substantially equal. Obtained. Therefore, if the unnecessary reflection can be made smaller than the state of Comparative Example 1, the distance can be measured.
[0049]
　Since the unnecessary reflection shown in FIG. 7 is generated due to the presence of the interference length Li, it is considered that if the interference length Li is made smaller than in the case of FIG. 7, the unnecessary reflection is also reduced. Therefore, in order to suppress unnecessary reflection below the wraparound wave, the transmitting antenna diameter φ 1 is increased, that is, the transmitting antenna diameter φ 1 is made larger than the receiving antenna diameter φ 2 (φ 1 > d). / 2) is good.
[0050]
　Here, the reflectance of the slag surface 3 or the radar cross section of the slag surface 3 is greatly reduced when the slag is formed, and cannot be measured if the position of the formed slag surface 3 is more than a certain distance. Was clarified by the examination of the inventors. This point will be described below using a radar equation.
[0051]
　The radar reflection cross-sectional area is σ [m 2 ], the transmission output, which is the performance of the level measuring device 10, is P t [mW], the transmission antenna gain is G 1 , the reception antenna gain is G 2 , and 1 [in the environment above the furnace opening. Assuming that the transmittance of the microwave per [m] is T and the wavelength of the microwave is λ [m], the received signal strength Pr [mW] reflected by the slug surface 3 and returned to the receiving antenna 12 is as follows . Given by the number 6. Note that R here indicates the distance (separation distance) [m] from the receiving antenna 12 to the slag surface 3 when the slag surface 3 to be measured is formed. Further, since the distance between the transmitting antenna 11 and the receiving antenna 12 is sufficiently shorter than the separation distance R from the receiving antenna 12 to the slag surface 3, the separation distance from the transmitting antenna 11 to the slag surface 3 is also regarded as R. It doesn't matter.
[0052]
[Number 6]

[0053]
　If the received signal intensity Pr [mW] is greater than 10 times the minimum received power S min of the level measuring device 10, the reflected microwave can be measured by the level measuring device 10. Expressing this as an inequality, it becomes the following number 7.
[0054]
[Number 7]

[0055]
　Here, the transmitting antenna gain G 1 is determined by the opening area at the tip of the transmitting antenna 11, and the receiving antenna gain G 2 is determined by the opening area at the tip of the receiving antenna 12. For example, when a conical horn antenna is used, the antenna diameter (also called the aperture diameter) is φ n (n = 1 and 2, φ 1 indicates the transmitting antenna diameter, and φ 2 is the receiving antenna diameter. (Indicating) [m], and when the antenna gain G n (n = 1, 2, G 1 indicates the transmitting antenna gain, and G 2 indicates the receiving antenna gain), it is represented by the following equation 8. Can be done.
[0056]
[Number 8]

[0057]
　η is the aperture efficiency of the transmitting antenna 11 and the receiving antenna 12. Further, the aperture efficiency η is the same if the conical horn antenna has the same ratio of the aperture diameter and the length of the antenna, and here, the aperture efficiency η of the transmitting antenna 11 and the receiving antenna 12 is the same. The above-mentioned number 7 expressing the measurable condition of the reflected microwave can be expressed as the following number 9 by using the above-mentioned number 8.
[0058]
[Number 9]

[0059]
　Here, first, a general level measuring device (described later) in which a transmission / reception antenna common to transmission / reception is installed above the furnace opening is set as Comparative Example 2, and Comparative Example 2 satisfies the measurable conditions shown in the above equation 9. Consider whether or not. In the level measuring device of Comparative Example 2, the minimum received power S min is about 10-8 [mW]. In the level measurement device of the comparative example 2, as a general parameter, the transmission output P t to 10 [mW], the wavelength λ of the microwave 6.67 [mm] (the frequency 45 [GHz]), the transmitting and receiving antennas The aperture efficiency η is 0.25, the microwave transmission T is 0.98, the radar reflection cross-sectional area σ of the slug surface is 10-4.3 [m 2 ], and the transmitting / receiving antenna when the slug surface 3 is formed. Assuming that the separation distance R from to the slug surface 3 is 25 [m] and the diameter φ of the transmitting / receiving antenna (since only the transmitting / receiving antenna is provided, φ = φ 1 = φ 2 ) is 250 [mm], the measurable conditions are shown. The above inequality of equation 9 is not satisfied. Therefore, this level measurement device, above-described transmission output P t , when the wavelength lambda, the aperture efficiency η and the like, constantly measuring the level of the slag surface 3 in the blowing is not possible.
[0060]
　Therefore, in order to constantly measure the level of the slag surface 3, it is necessary to increase the left side or decrease the right side of the above equation 9.
　First, the left side of the above number 9 will be examined. The parameters that can be changed on the left side include the antenna gain G n (Equation 8) and the transmission output P t . Here, the case where the transmission output Pt is increased will be examined with reference to FIG. FIG. 8 shows a circuit configuration of a level measuring device 101 as Comparative Example 2 in which a transmission / reception antenna 105 common to transmission / reception is installed above the furnace opening. As shown in FIG. 8, the level measuring device 101 as a comparative example amplifies the transmission signal transmitted from the oscillator 102 by the power amplifier 103, and then transmits the transmission signal to the transmission / reception antenna 105 via the circulator 104, and the transmission / reception antenna 105 Irradiate the inside of the furnace with microwaves.
[0061]
　In the level measuring device 101, when the reflected microwave from the inside of the furnace is received by the transmitting / receiving antenna 105, it is transmitted as a received signal to the low noise amplifier 106 via the circulator 104. The level measuring device 101 amplifies the received signal with the low noise amplifier 106, and the mixer 107 multiplies the received signal with the transmitted signal serving as the reference signal sent from the oscillator 102 to generate a beat signal. The level measuring device 101 amplifies the beat signal by the IF amplifier 108, executes an analog-to-digital conversion process by the AD converter 109, and sends the obtained signal to the personal computer (PC) 110. The personal computer (PC) 110 performs Fourier transform processing or the like on the signal received from the AD converter 109 to generate a distance waveform in which the distance (separation distance) from the transmission / reception antenna 105 to the slug surface 3 is given at the main peak. , The level of the slag surface 3 in the furnace can be specified based on the separation distance.
[0062]
　Here, the circulator 104 has an isolation characteristic. For example, when the isolation of the circulator 104 is 15 [dB], even if a transmission signal of 20 [dBm] is sent from the power amplifier 103 to the circulator 104, A signal wrapping around to the receiving side (low noise amplifier 106 side) is generated by 5 [dBm]. Level measuring device 101 provided with a circulator 104, the transmission output P t A larger, in the circulator 104, the signal sneaking from the sender directly receiving side is also increased.
[0063]
　At this time, since the operating region of the low noise amplifier 106 (maximum power capable of amplifying the signal) and the dynamic range of the AD converter 109 have an upper limit, distortion occurs in the signal portion exceeding the upper limit. Since the distorted signal has a high frequency component, it causes a large noise (broadband noise) in the measurement frequency (beat signal frequency) region. As a result, the minimum received power S min also increases according to the noise, and in the end, the inequality of the above equation 9 cannot be satisfied.
[0064]
　Next, the antenna gain Gn (Equation 8) on the left side of the above equation 9 will be examined. The diameter d of the hood opening 6 above the furnace opening needs to be limited to a size (for example, 600 [mm]) that does not affect the displacement of the exhaust hood 5. For example, if a transmitting / receiving antenna 105 having an opening size as large as possible is used with respect to the diameter d of the hood opening 6, the antenna diameter φ of the transmitting / receiving antenna 105 (since only the transmitting / receiving antenna 105 is provided, φ = φ 1 = φ 2 ) is given by d (diameter of the hood opening 6).
[0065]
　However, the diameter d of the hood opening 6 is set to 600 [mm], which is about twice the size of the equipment restriction, and the frequency of the transmission / reception antenna 105 is set to 45 [GHz], which is optimal for level measurement of the slag surface 3. In this case, the antenna gain G of the transmitting / receiving antenna 105 that can be installed according to the diameter d of the hood opening 6 is 104.9, which is almost the maximum. Therefore, it is impossible to increase the antenna gain G any further unless the diameter d of the hood opening 6 is increased. 10 4.9 even when using the transmission and reception antenna 105 with the antenna gain G, can not be measurable satisfy the above Equation 9, it is not possible to constantly measure the level of the slag surface 3.
[0066]
　Therefore, the present inventors have studied a method of reducing the minimum received power (sensitivity of the level measuring device 10), that is, reducing the right side of the above equation 9. In the level measuring device 10 according to the present invention, by separating the conventional transmission / reception antenna 105 into a transmission-only transmission antenna 11 and a reception-only reception antenna 12, the circulator 104 is omitted, which causes noise. The wraparound of the transmitted signal to the receiving side in the circuit has been reduced. Here, FIG. 9 shows a circuit configuration of the level measuring device 10 of the present invention in which the transmitting antenna 11 and the receiving antenna 12 are separately provided.
[0067]
　As shown in FIG. 9, in the level measuring device 10, after the transmission signal generated by the oscillator 22 is amplified by the power amplifier 23, this is transmitted to the transmitting antenna 11 and the transmitting antenna 11 irradiates the inside of the furnace with microwaves. .. When the level measuring device 10 receives the reflected microwave from the inside of the furnace by the receiving antenna 12, it sends it to the low noise amplifier 26 as a reception signal, amplifies the received signal by the low noise amplifier 26, and then receives the reception by the mixer 27. A beat signal is generated by multiplying the signal and the transmission signal which is the reference signal sent from the oscillator 22.
[0068]
　The level measuring device 10 amplifies the beat signal by the IF amplifier 28, executes an analog-to-digital conversion process by the AD converter 29, and sends the obtained signal to the personal computer (PC) 30. The personal computer (PC) 30 executes a Fourier transform process or the like on the signal received from the AD converter 29 to generate a distance waveform in which the distance (separation distance) from the receiving antenna 12 to the slag surface 3 is given at the main peak. Therefore, the level of the slag surface 3 in the furnace can be specified based on the separation distance.
[0069]
　As described above, since the level measuring device 10 is not provided with the circulator 104, the transmission signal in the circulator 104 does not wrap around. On the other hand, the isolation between the spatially divided transmitting antenna 11 and the receiving antenna 12 is about 30 [dB]. However, the transmission / reception isolation is improved from 15 [dB] to 30 [dB] when the transmission / reception antenna 105 is used, and the wraparound of the transmission signal is reduced to −20 [dBm]. As a result, it is possible to prevent the occurrence of signal distortion in the low noise amplifier 26 and the AD converter 29.
[0070]
　If there is no distortion, the beat frequency generated by the wraparound signal is limited to the low frequency region, so that it can be distinguished from the beat frequency based on the reflected microwaves from the inside of the furnace. In the level measuring device 10, it is possible to remove noise generated in a low frequency region by a wraparound signal by using a high-pass filter (not shown), and the wraparound signal generated in the receiving antenna 12 is used for level measurement of the slag surface 3. Does not affect. At this time, the minimum received power S min of the level measuring device 10 is 10-14 [mW].
[0071]
　For example, in the level measuring device 10, if the bit rate of the AD converter 29 that performs analog-digital conversion processing of the amplified beat signal is 24 [bit], the dynamic range is 146 [dB]. Since the intensity of the spatial wraparound signal from the transmitting antenna 11 to the receiving antenna 12 is -20 [dBm], if the dynamic range for AD conversion processing so as not to distort this is set as the upper limit, it is -164 [dBm]. ] Will be captured. Furthermore, if the sampling frequency is 2 [MHz], k B TaB (k B : Boltzmann constant, Ta: temperature, B: bandwidth) band noise given by the Ta = 300 -110 in [K] [dBm] By performing FFT at 2048 points, the minimum received power S min is reduced by 30 [dB], and the minimum received power S min is improved to 10-14 [mW] (= −140 [dBm]).
[0072]
　When the transmitting antenna 11 and the receiving antenna 12 are provided separately, the transmitting antenna diameter φ 1 and the receiving antenna diameter φ 2 are φ 1 + φ using the diameter d of the hood opening 6 as shown in FIG. It can be expressed as 2 = d. Therefore, compared with the case of using the transmission and reception common reception antenna 105 (φ = d), the antenna gain G n is 10 3 reduced to about. However, the antenna gain G n be is reduced, if the maximum the distance R between 25 [m], when computing the received signal strength, 10 -11 [mW], and the minimum reception power S min is 10 - Since it is sufficiently larger than 10 times 14 [mW], the level of the slag surface 3 can always be measured.
[0073]
　From the above, when the antenna is installed above the hood opening 6 where the size of the opening is restricted, in the conventional way of thinking, in order to increase the antenna gain, the maximum antenna size is within the diameter d of the hood opening 6. One transmission / reception antenna 105 common to transmission / reception is arranged so as to have dimensions. On the other hand, in the level measuring device 10 of the present invention, a separate transmitting antenna 11 and receiving antenna 12 are provided. As a result, the level measuring device 10 eliminates the need for the circulator 104, which is conventionally required by using the transmission / reception antenna 105, suppresses the wraparound of the transmission signal, and reduces the noise. Level measurement with a high N ratio becomes possible.
[0074]
　However, as described above, when the transmitting antenna 11 and the receiving antenna 12 are separated, the transmitting antenna diameter φ 1 and the receiving antenna diameter φ 2 are φ 1 + φ 2 with the diameter d of the hood opening 6. = d, i.e., phi 2 = d-phi 1 relation (FIG. 2). That is, since the improvement of sensitivity and the antenna gain Gn are in a trade-off relationship, there may be a condition of diameter d in which the S / N ratio is larger when the transmission / reception antenna 105 common to transmission / reception is used. Therefore, the condition of the diameter d in which the transmitting antenna 11 and the receiving antenna 12 are better arranged than the transmitting and receiving antenna 105 is examined.
[0075]
　In the case of Comparative Example 2 using the transmission / reception antenna 105 common to transmission / reception, the minimum reception power S min is 10-8 [mW], and the antenna diameter φ is d. Therefore, the measurable conditions for the transmission / reception antenna 105 common to transmission / reception are as follows from the above number 9 to the following number 10.
[0076]
[Number 10]

[0077]
　On the other hand, when the transmitting antenna 11 and the receiving antenna 12 having separated transmission and reception are used, the minimum received power S min is 10-14 [mW]. Therefore, the measurable conditions for the transmitting antenna 11 and the receiving antenna 12 that separate the transmission and reception are as shown in the above equation 9 to the following equation 11. However, the transmitting antenna diameter φ 1 and the receiving antenna diameter φ 2 are preferably equal to or larger than the wavelength of the microwave to be used , and φ 1 ≧ λ and φ 2 = d−φ 1 ≧ λ, that is, λ ≦ φ 1 ≦. It is preferable to satisfy d-λ.
[0078]
[Number 11]

[0079]
　Therefore, when the transmitting antenna 11 and the receiving antenna 12 having separated transmission and reception are used, the condition of the diameter d at which the S / N ratio is the highest is expressed as the following equation 12 by combining the above equations 10 and 11. Can be done. As described above, R indicates the distance (separation distance) from the receiving antenna 12 to the slug surface 3 when the slug surface 3 to be measured is formed, and λ indicates the wavelength of the microwave. P t indicates the transmission output [mW] of the microwave in the level measuring device 10, σ indicates the radar cross section of the slag surface 3, T indicates the transmittance of the microwave around 1 [m], and η is. The aperture efficiency of the receiving antenna 12 is shown. However, λ ≤ φ 1 ≤ d−λ.
[0080]
[Number 12]

[0081]
　 In the
　above configuration, in the level measuring device 10, a receiving antenna 12 is provided separately from the transmitting antenna 11, and a lens unit for increasing each antenna gain at each tip of the transmitting antenna 11 and the receiving antenna 12 13 are provided respectively. Thus, the level measuring device 10, the lens unit 13 transmitting antenna gain G of the transmitting antennas 11 1 and the receiving antenna gain G of the receiving antenna 12 2 and is increased, the S / N ratio at the time of the level measurement of the slag surface 3 Can be improved.
[0082]
　Further, in the level measuring device 10, an opening forming portion 7 for forming a hood opening 6 for communicating the upper free space and the inside of the furnace is provided in the exhaust hood 5, and an antenna installing portion 9 is provided above the hood opening 6. The antenna installation portion 9 is provided so that both the transmitting antenna 11 and the receiving antenna 12 are arranged above the hood opening 6. In the level measuring device 10, by providing the transmitting antenna 11 and the receiving antenna 12 separately, the transmission signal does not wrap around directly to the receiving side in the circuit, and noise generated by the wraparound signal can be prevented.
[0083]
　In the level measuring device 10, since the transmitting antenna 11 and the receiving antenna 12 are arranged above the hood opening 6 and kept away from the slag surface 3 in the furnace, the metal or slag adheres to the transmitting antenna 11 and the receiving antenna 12. Can be suppressed, and the measurement of the slag surface 3 during blowing can be performed more accurately than before.
[0084]
　Furthermore, the level measuring device 10, the diameter φ of the transmitting antennas 11 1 a diameter φ of the receiving antenna 12 2 and more, and the transmitting antenna 11 and receiving antenna 12 are adjacent to arranged the hood opening 6 above With the configuration, unnecessary reflection can be suppressed at the time of level measurement of the slag surface 3, and the measurement of the slag surface 3 during blowing can be performed more accurately than before.
[0085]
　Further, in the level measuring device 10, the diameter d of the hood opening 6 is optimally adjusted to improve the S / N ratio in consideration of the antenna characteristics of the transmitting antenna 11 and the receiving antenna 12 and the characteristics of the slag surface 3. By selecting the above, even if both the transmitting antenna 11 and the receiving antenna 12 are arranged, the S / N ratio at the time of level measurement of the slag surface 3 can be improved.
[0086]
　Specifically, by making the diameter d satisfy the condition represented by the above equation 12, even if both the transmitting antenna 11 and the receiving antenna 12 are arranged above the hood opening 6, the slag surface 3 It is possible to improve the S / N ratio at the time of level measurement.
[0087]
　 In the
　above-described embodiment, the case where one transmitting antenna 11 and one receiving antenna 12 are arranged above the hood opening 6 has been described, but the present invention is not limited to this. As shown in 10 and 11, two or more receiving antennas 32 may be provided around one transmitting antenna 31, and these may be arranged above the hood opening 6.
[0088]
　For example, as shown in FIG. 10, a plurality of receiving antennas 32 are arranged at equal intervals in the antenna installation opening 9a so as to surround the transmitting antenna 31. In the antenna installation opening 9a, the peripheral edges of the receiving antennas 32 are arranged so as to be in contact with the peripheral edges of the transmitting antenna 31. Further, as shown in FIG. 11, in the antenna installation opening 9a, the transmitting antenna 31 is arranged so that the central axis Z1 of the transmitting antenna 31 and the central axis Z2 of the hood opening 6 are arranged on the same axis. It is arranged. Accordingly, the diameter d of the hood opening 6, the diameter phi of the transmit antenna 31 1 , the diameter phi of the receiving antenna 32 2 is, d = phi 1 + 2 [phi 2 have a relationship.
[0089]
　In this case, the interference length Li is expressed as Li = φ 3 / 2-d / 2. The interference length Li when d = 300 [mm] is shown in FIG. When the interference length Li is 0 or less, the irradiation region and the flange upper portion 7a do not interfere with each other. When the distance r from the transmitting antenna 31 to the height position of the flange upper portion 7a of the opening forming portion 7 is 4 [m] and d = 300 [mm], the diameter φ 1 of the transmitting antenna 31 is 148 to 282. When it is [mm], the interference length Li is 0 or less. Summarizing such conditions, Li = φ 3 / 2-d / 2 ≦ 0, and φ 3 ≦ d. Therefore, from the above equation 5, it can be expressed as the following equation.
[0090]
[Number 13]

[0091]
　However, the diameter phi of the receiving antenna 32 2 is, (d-phi 1 is given by) Such conditions, (d-phi 1 is a) / 2 ≧ λ. The diameter φ of transmitting antennas 31 1 also needs to have a size of more than the wavelength of the microwave. Therefore, when the above conditions are also combined, it can be expressed as λ ≤ φ 1 ≤ d-2 λ.
[0092]
　Further, the condition that the inequality of the above equation 13 has a solution is the same as the condition that the following equation 14 has one or more solutions.
[0093]
[Number 14]

[0094]
　In Equation 14, phi 1 and considering that, c, r, f, d are both positive values, phi 1 2 replaces the the? ', Transforming the equation 14, the equation 15 below ..
[0095]
[Number 15]

[0096]
　The condition having one or more solutions in the above equation 15 is represented by the following equation 16, and the equation 16 can be expressed as the equation 17. The diameter d of the hood opening 6 must satisfy the conditions of the above number 13 and the following number 17. The same effect as that of the above-described embodiment can be obtained in other embodiments having the above-described configuration.
[0097]
[Number 16]

[0098]
[Number 17]

[0099]
　In the above-described embodiment, the case where the converter 1 used in the converter steelmaking process is applied as the furnace has been described, but the present invention is not limited to this, for example, in addition to the melt reduction furnace, a non-ferrous metal refining process. It can also be applied to various other furnaces such as the furnace used in the above. Examples of the non-ferrous metal refining process include a copper smelting process.
[0100]
　Further, in the above-described embodiment, the case where the diameter of the antenna installation opening 9a of the antenna installation portion 9 is selected to be substantially the same as the diameter d of the hood opening 6 has been described, but the present invention is limited to this. However, the diameter of the antenna installation opening 9a of the antenna installation portion 9 may be of various sizes as long as it is equal to or larger than the diameter d of the hood opening 6 (diameter of the antenna installation opening 9a ≥ diameter of the hood opening 6). d).
Code description
[0101]
　1 converter (furnace)
　3 slag surface
　5 exhaust hood
　6 hood opening
　7 opening forming part
　7a flange upper part
　9 antenna installation part
　9a antenna installation opening
　10 level measuring device
　10b level calculation part
　11 transmitting antenna
　12 receiving antenna
The scope of the claims
[Claim 1]
　In a level measuring device for measuring the level of a slug surface inside a furnace,
　a hood opening opened at a position facing the slug surface of an exhaust hood provided above the furnace and an upper portion of the
　hood opening. A
　transmitting antenna that is provided in the above and irradiates a microwave toward the inside of the furnace through the hood opening, and a transmitting antenna that is separate from the transmitting antenna and is provided above the hood opening. A receiving antenna that receives reflected microwaves from the inside of the furnace via the above, a
　lens unit provided at each tip of the transmitting antenna and the receiving antenna, and increasing the antenna gain of the transmitting antenna and the receiving antenna, and the
　above. from the reflected microwave, and a level calculator for calculating the level of the slag surface
with a
　diameter of said transmitting antennas is greater than the diameter of the receiving antenna,
　the diameter of the transmitting antenna phi 1 and the hood opening when the diameter was d, phi 1 meet> d / 2, the level measuring device.
[Claim 2]
　In a level measuring device for measuring the level of a slug surface inside a furnace,
　a hood opening opened at a position facing the slug surface of an exhaust hood provided above the furnace and
　around the hood opening. The 　hood, which is formed in the above and extends upwardly through the inside of the furnace,
　an antenna installation portion provided above the opening formation portion, and an
antenna installation portion. An antenna installation opening having substantially the same diameter as the opening,
　a transmitting antenna provided in the antenna installation opening and irradiating microwaves toward the inside of the furnace, and the
　transmitting antenna are installed separately from the transmitting antenna. A receiving antenna provided in the opening for receiving reflected microwaves from the inside of the furnace, and a
　lens portion provided at each tip of the transmitting antenna and the receiving antenna to increase the antenna gain of the transmitting antenna and the receiving antenna. If,
　from the reflected microwave, and a level calculator for calculating the level of the slag surface
with a
　diameter of said transmitting antennas is greater than the diameter of the receiving antenna,
　the diameter of the transmitting antenna phi 1 and, A level measuring device that satisfies φ 1 > d / 2 when the diameter of the hood opening is d .
[Claim 3]
　The second aspect of the present invention, wherein the distance from the tip of the transmitting antenna to the height position of the opening forming portion is 3 to 5 [m], and
　the diameter of the transmitting antenna is 169 to 219 [mm]. Level measuring device.
[Claim 4]
　Assuming that the diameter of the transmitting antenna is φ 1 [m], the diameter of the receiving antenna is d−φ 1 [m], and
　the diameter d [m] of the hood opening is expressed by the following equation. The level measuring device according to any one of claims 2 or 3, which satisfies the conditions.
[Equation 1]

　However, λ ≤ φ 1 ≤ d−λ, and
　R indicates the distance [m] from the receiving antenna to the slug surface when the slug surface to be measured is formed. λ indicates the wavelength [m] of the microwave , P t indicates the transmission output [mW] of the microwave, σ indicates the radar cross section of the slug surface, and T indicates the said in the vicinity of 1 [m]. The microwave transmission rate is indicated, and η indicates the aperture efficiency of the receiving antenna.
[Claim 5]
　The central axis of the transmitting antenna and the central axis of the hood opening are arranged on the same axis,
　and two or more receiving antennas are arranged around the transmitting antenna, claim 2 or 3. The level measuring device according to any one item.
[Claim 6]
　The level measuring device according to claim 5, wherein the diameter d of the hood opening satisfies the condition represented by the following formula.
[ 　Equation 2]

[

Equation 3] , c indicates the speed of light [m / s], and r indicates the distance [m] from the transmitting antenna to the height position of the upper part of the flange of the opening forming portion. f indicates the frequency [Hz] of the microwave.