Device for measuring electrode length of carbon electrode in electric resistance melting furnace and method for operating electric resistance melting furnace

Abstract

To more accurately measure the electrode length of a carbon electrode in an electric resistance melting furnace by detecting a molten liquid surface even if a metal guide pipe melts away.SOLUTION: A measuring device comprises: a guide pipe that is configured by connecting a plurality of metal guide pipe pieces and that is inserted so as to reach the lower end of a carbon electrode; and a distance meter that is mounted on the upper end of the guide pipe and that includes transmission / reception means for a microwave or millimeter wave, and a waveguide. The inner diameter of the guide pipe is greater than the inner diameter of the waveguide of the distance meter, the guide pipe and the distance meter are coupled via a tapered structure, which has a hollow that widens in a tapered shape from the waveguide toward the guide pipe, a microwave or millimeter wave is transmitted from the lower end of the guide pipe toward a molten liquid surface of a material to be melted, and a distance between the distance meter and the molten liquid surface is measured by receiving the microwave or millimeter wave reflected by the molten liquid surface.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a device for measuring the electrode length of carbon electrodes in an electric resistance melting furnace used for feeding and melting materials such as iron ore into the furnace, and also to a method for operating the electric resistance melting furnace. [Background technology]

[0002] An electric resistance melting furnace is used in which materials to be melted, such as iron ore, are put into the furnace, carbon electrodes are inserted into the piled materials to be melted, electricity is passed through the electrodes, the materials are melted, and the melted materials are collected. FIG. 12 is a schematic diagram showing an example of an electric resistance melting furnace, showing the case of melting iron ore. As shown in the figure, in an electric resistance melting furnace 100, carbon electrodes 101 are inserted into iron ore 102 piled up in the furnace, and current is passed through the carbon electrodes 101, and the iron ore 102 present between the electrodes is used as a resistor to melt the iron ore 102 by Joule heat. Power is supplied to the carbon electrodes 101 from a power source 110 via an electrode holder 180 attached to the carbon electrodes 101. As the melting progresses, three layers are formed in the bottom of the furnace: unmelted iron ore 102, molten slag layer 103, and molten iron layer 104, from top to bottom. The molten slag is collected from a slag discharge port 105, and the molten iron is collected from a steel tapping port 106.

[0003] In this case, an electrode lifting device 120 is used to raise and lower the carbon electrode 101 in the vertical direction in the figure while passing electricity through the carbon electrode 101. Therefore, it is necessary to detect the molten liquid level of the molten iron layer 104 to determine the electrode length of the carbon electrode 101 and control the raised and lowered position of the carbon electrode 101.

[0004] Therefore, in Patent Document 1, the applicant inserts a metal guide pipe into at least one carbon electrode, reaching the lower end of the carbon electrode, attaches a microwave or millimeter wave transceiver to the upper end of the guide pipe, transmits microwaves or millimeter waves from the transceiver through the inside of the guide pipe, receives the microwaves or millimeter waves reflected at the lower end of the guide pipe, detects the molten liquid level of the molten iron layer, and determines the electrode length of the carbon electrode from the distance from the transceiver to the molten liquid level. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 5671744 Summary of the Invention [Problem to be solved by the invention]

[0006] However, since the guide pipe is made of metal, if the material to be melted is a metal with a high melting point, such as iron ore, its lower end will melt away due to the high heat from the molten liquid surface. The inner wall of the carbon electrode will be exposed where the guide pipe has melted away, and the exposed carbon will absorb the microwaves and millimeter waves, resulting in a large attenuation of the transmission power and reception power. Therefore, there is a concern that the molten liquid surface will not be detected accurately, and the electrode length of the carbon electrode will not be measured accurately.

[0007] The present invention has been made in consideration of the above-mentioned circumstances, and has an object to more accurately detect the molten liquid level and more accurately measure the electrode length of the carbon electrode in an electric resistance melting furnace even if the metal guide pipe melts away. [Means for solving the problem]

[0008] In order to solve the above problems, the present invention provides the following (1) to (11) devices for measuring the electrode length of a carbon electrode in an electric resistance melting furnace.

[0009] (1) A device for measuring the electrode length of a carbon electrode in an electric resistance melting furnace in which a material to be melted is piled up in the furnace and a current is passed through the carbon electrode, the device comprising: a guide pipe formed by connecting a plurality of metal guide pipe pieces and inserted so as to reach a lower end of the carbon electrode; a range finder attached to the upper end of the guide pipe and including a microwave or millimeter wave transmitting / receiving means and a waveguide; In addition to providing The inner diameter of the guide pipe is larger than the inner diameter of the waveguide of the range finder, and the guide pipe and the range finder are connected via a tapered structure having a cavity tapered from the waveguide toward the guide pipe, An electrode length measuring device for a carbon electrode in an electric resistance melting furnace, which transmits the microwaves or millimeter waves from the lower end of the guide pipe toward the molten liquid surface of the material to be melted, receives the microwaves or millimeter waves reflected by the molten liquid surface, and measures the distance between the distance meter and the molten liquid surface. (2) The electrode length measuring device for a carbon electrode in an electric resistance melting furnace as described in (1), in which the guide pipe pieces are connected to each other with a threaded socket. (3) A device for measuring the electrode length of a carbon electrode in an electric resistance melting furnace described in (1), in which the guide pipe pieces are connected to each other by a taper union having an outer shape in which two tapered surfaces extending continuously from the central part, which is the maximum diameter, to both ends are formed. (4) A device for measuring the electrode length of a carbon electrode in an electric resistance melting furnace as described in (1), in which the connection between the tapered structure and the guide pipe is closed with a member made of a material through which the microwaves or millimeter waves are transmitted. (5) A device for measuring the electrode length of a carbon electrode in an electric resistance melting furnace described in (1), which supplies an inert gas to the guide pipe to increase the internal pressure, and when the internal pressure suddenly rises, determines that the guide pipe is blocked, and increases the supply of the inert gas to remove the blocked portion. (6) A device for measuring the electrode length of a carbon electrode in an electric resistance melting furnace described in (1), in which a metal plate having holes with an opening diameter that does not allow microwaves or millimeter waves to penetrate, or a wire mesh with openings that does not allow microwaves or millimeter waves to penetrate, is attached to the inert gas supply port to the guide pipe. (7) An apparatus for measuring the electrode length of a carbon electrode in an electric resistance melting furnace as described in (1), in which the microwaves or millimeter waves are circularly polarized and transmitted toward the molten liquid surface. (8) The device for measuring the electrode length of a carbon electrode in an electric resistance melting furnace according to (1), further comprising a measurement mode for measuring the electrode length of the carbon electrode multiple times and calculating the average value. (9) An apparatus for measuring the electrode length of a carbon electrode in an electric resistance melting furnace as described in (1), comprising a measurement mode for measuring the electrode length of the carbon electrode multiple times and averaging either or both of the obtained received beat waveform and a distance spectrum waveform obtained by FFT processing of the received beat waveform. (10) The device for measuring the electrode length of a carbon electrode in an electric resistance melting furnace according to (1), wherein the guide pipe is made of stainless steel. (11) An apparatus for measuring the electrode length of a carbon electrode in an electric resistance melting furnace as described in (1), which observes reflected signals appearing at equal distances on the guide pipe.

[0010] In order to solve the above problems, the present invention provides the following operating method (12).

[0011] (12) A method for operating an electric resistance melting furnace, comprising inserting a carbon electrode suspended in the furnace into a material to be melted piled up in the furnace and passing an electric current through the carbon electrode to melt the material, The distance (L1) from the distance meter to the molten liquid surface is obtained by the electrode length measuring device of the carbon electrode according to any one of (1) to (11), a second distance meter is disposed above the distance meter, a distance (L2) between the second distance meter and the distance meter is measured, and the distance (L2) is added to the determined distance (L1) to determine a distance (L3) from the second distance meter to the melt surface; A method for operating an electric resistance melting furnace, characterized in that the hanging position of the carbon electrode is controlled based on the distance (L3).

[0012] In the following description, the "device for measuring the electrode length of a carbon electrode in an electric resistance melting furnace" will also be referred to simply as the "measuring device." Effect of the Invention

[0013] According to the measuring device of the present invention, even if the metal guide pipe melts away, the molten liquid level can be detected and the electrode length of the carbon electrode can be measured more accurately.

[0014] Furthermore, according to the operating method of the present invention, even if the metal guide pipe melts away, the electrode length of the carbon electrode can be measured more accurately, so that the raising and lowering of the carbon electrode can be controlled more accurately, enabling efficient and stable operation. [Brief description of the drawings]

[0015] [Figure 1] FIG. 1 is a cross-sectional view showing a schematic configuration of an embodiment of a measuring device according to the present invention, taken along the axis of a carbon electrode. [Diagram 2] FIG. 2 is an enlarged view showing the threaded socket. [Diagram 3] FIG. 3 is an enlarged view showing the taper structure and the plug member. [Figure 4] 4(A) is a partial enlarged view of part A in FIG. 1, FIG. 4(B) is a partial enlarged view of part B in FIG. 1, and FIG. 4(C) is a partial enlarged view of part C in FIG. [Diagram 5] FIG. 5(A) is a cross-sectional view showing a taper union, and FIG. 5(B) is a plan view seen from the AA direction in FIG. 5(A). [Figure 6] FIG. 6(A) is a side view showing a set screw, and FIG. 6(B) is a plan view seen from the direction BB in FIG. 6(A). [Figure 7] FIG. 7 is a schematic diagram showing the rotation direction of the electric field during transmission and reception when circularly polarized microwaves or millimeter waves are used. [Figure 8] FIG. 8 is a chart showing the results of the verification result 1. [Figure 9] FIG. 9 is a chart showing the results of verification result 2. [Figure 10] FIG. 10 is a chart showing the results of verification result 3. [Figure 11] FIG. 11 is a diagram for explaining the method of operating the electric resistance melting furnace of the present invention. [Figure 12]FIG. 12 is a schematic diagram showing an example of an electric resistance melting furnace. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] The present invention will now be described in detail with reference to the drawings.

[0017] As shown in Fig. 12, in an electric resistance melting furnace, multiple carbon electrodes are inserted into the material to be melted, such as iron ore, and electricity is passed through the carbon electrodes to melt the material. In the present invention, at least one carbon electrode functions as a "measurement device for the electrode length of the carbon electrodes."

[0018] [Measuring equipment] 1 is a cross-sectional view showing a schematic configuration of the measuring device of the present invention along the axis of a carbon electrode. As shown in the figure, the measuring device 1 has a normal carbon electrode 10, a metal guide pipe 20 that reaches the lower end of the carbon electrode 10, and a range finder 30 attached to the upper end of the guide pipe 20.

[0019] The carbon electrode 10 is configured by housing an electrode body 18 inside an electrode case (metal cover) 15 made of a metal cylinder. The electrode body 18 of the carbon electrode 10 is divided into an electrode baking section 18a, a coal tar melting section 18b, and an electrode material section 18c, in that order from the side closest to the molten liquid surface 200 of the material to be melted. When the material to be melted is melted, the side of the electrode baking section 18a that contacts or faces the molten liquid surface 200 (hereinafter referred to as the "lower end") is consumed. To compensate for this consumption, a mixture of carbon mass and coal tar pitch, which is the electrode material, is poured from the opening at the upper end of the electrode case 15. The electrode case 15 is configured by connecting multiple electrode case pieces (metal cover pieces) 16 into one piece, and since the lower end is consumed during melting, a new electrode case piece (metal cover piece) 16b is added on top of the lower electrode case piece (metal cover piece) 16a. The reference numeral 17 denotes the joint of the electrode case pieces 16.

[0020] The guide pipe 20 is made up of multiple guide pipe pieces 21 connected together using joints 22, and since the lower end is consumed when melted, similar to the carbon electrode 10, a new guide pipe piece 21b is added onto the lower guide pipe piece 21a using the joint 22. When adding the guide pipe piece 21, a guide pipe clamp 25 is used to separate the tapered structure 40 and the guide pipe 20, which will be described later, and then reconnect them.

[0021] The joint 22 (see Fig. 1) is preferably a threaded socket 70 as shown in Fig. 2. The threaded socket 70 has a thread groove 71 formed on its inner peripheral surface, and accordingly, thread grooves 23 are formed on the outer peripheral surface of both ends of the guide pipe piece 21 so as to engage with the thread groove 71 of the threaded socket 70. By using the threaded socket 70, the guide pipe piece 21 can be reliably connected, and linearity can be achieved when multiple guide pipe pieces 21 are connected.

[0022] The electrode case piece 16 of the carbon electrode 10, the guide pipe piece 21 of the guide pipe 20, and the joint 22 are preferably made of a metal with a higher melting point. As such a metal, for example, SUS304 can be preferably used because it is inexpensive, has excellent workability and environmental resistance, and does not rust. SUS304 suppresses the decrease in propagation loss due to deterioration of the quality of the material, enabling stable measurement.

[0023] Incidentally, the waveguide 35 and tapered structure 40 described below are also preferably made of SUS304.

[0024] The range finder 30 is equipped with a microwave or millimeter wave transmitting / receiving means (not shown), and is connected to the upper end of the guide pipe 20 via a tapered structure 40. As shown in Figures 1 and 3, the inner diameter of the guide pipe 20 is larger than the inner diameter of the waveguide 35 of the range finder 30, and the tapered structure 40 is a member having a tapered cavity 41 that expands from the tip of the waveguide 35 of the range finder 30 toward the upper end of the guide pipe 20. The tapered structure 40 is connected to the guide pipe 20 by, for example, a threaded socket 70.

[0025] The above-mentioned guide pipe 20, waveguide 35 and tapered structure 40 may also have a square cross section in addition to a circular cross section.

[0026] Microwaves and millimeter waves can be effectively propagated through the guide pipe 20 and further through the portion where the guide pipe 20 has melted off (exposed surface 12, described below), allowing for more accurate measurement of the electrode length of the carbon electrode 10. However, it is preferable that the inner diameter of the guide pipe 20 is larger than the inner diameter of the waveguide 35, but this may lead to an increase in costs if the guide pipe 20 becomes too thick. Specifically, when a millimeter wave of 79 GHz is used and the inner diameter of the waveguide 35 is φ2.8 mm, it is preferable that the inner diameter of the guide pipe 20 is φ35.0 to 38.0 mm, which is a dozen times larger. In the case of a carbon electrode that is not a self-baking type, a circular hole drilled directly to the lower end of the carbon electrode is used as a substitute for the guide pipe 20 to measure the electrode length.

[0027] 3, it is preferable to close the connection between the tapered structure 40 and the guide pipe 20 with a plug member 50 made of a material that transmits the detection wave, such as a fluororesin. The plug member 50 protects the internal components of the rangefinder 30, such as the transmitting and receiving means, because the internal components are exposed to high heat from the molten liquid surface 200 and dust from inside the furnace can enter through the guide pipe 20.

[0028] The detection wave is a microwave or millimeter wave, but a higher frequency is preferable, and a millimeter wave is more preferable.

[0029] In the measuring device 1 configured in this manner, the lower end of the carbon electrode 10 is worn away, and at the lower end portion of the guide pipe 20, part of the guide pipe 20 and the joint 22 melt away due to the high heat from the molten liquid surface 200, exposing the interface with the carbon electrode 10. For example, Figure 4(A) shows an enlarged view of part A in Figure 1, Figure 4(B) shows an enlarged view of part B in Figure 1, and Figure 4(C) shows an enlarged view of part C in Figure 1. Figure 4(A) shows the part where the guide pipe 20 has begun to melt away and the boundary with the carbon electrode 10 is beginning to appear, Figure 4(B) shows the part where the fitting 22 has melted away, and Figure 4(C) shows the part where the guide pipe 20 has melted away.

[0030] As shown in FIG. 4(A), the cross-sectional shape changes at the beginning of the melting of the guide pipe 20, but since the inner diameter of the guide pipe 20 is sufficiently larger than the wall thickness of the guide pipe 20, it can be said that this does not substantially affect the measurement. In Fig. 4(A), the guide pipe 20 melts down and the cross-sectional shape changes to a stepped portion, but the steps do not have to be at the same horizontal position over the entire circumference of the inner diameter, and may be different in the vertical direction in the figure. As shown in the figure, in a portion closer to the molten liquid level 200 than the lower half of part A, the guide pipe 20 and the joint 22 melt down, and the boundary surface with the carbon electrode 10 is exposed as shown by reference numeral 12.

[0031] In the following description, the portion where the guide pipe 20 and the joint 22 have melted off and the carbon electrode 10 is exposed will be referred to as the "exposed surface 12."

[0032] Normally, when microwaves or millimeter waves propagate through a carbon tube, the wall has low electrical conductivity, resulting in large propagation losses and absorption of transmitted and received signals. Because exposed surface 12 is made of carbon, microwaves and millimeter waves are significantly attenuated while propagating through exposed surface 12. However, as described above, by making the inner diameter of guide pipe 20 larger than the inner diameter of waveguide 35 and minimizing excitation of unnecessary higher-order modes other than the circular TE11 mode that constitutes the circularly polarized wave and maintaining propagation mainly in the circular TE11 mode, it is possible to reduce propagation losses and deterioration of distance measurement accuracy.

[0033] Therefore, as shown by the symbol M in Fig. 1, the microwaves and millimeter waves from the transmitting / receiving means of the range finder 30 propagate through the waveguide 35, the cavity 41 of the tapered structure 40, and the guide pipe 20, and further propagate well through the exposed surface 12 without significant attenuation, and are transmitted from the lower end of the guide pipe 20 to the melt level 200. Then, the microwaves are reflected by the melt level 200 and are received by the transmitting / receiving means of the range finder 30 along the reverse path, and the melt level 200 is detected. Then, the distance from the range finder 30 to the melt level 200, i.e., the electrode length of the carbon electrode 10, is obtained from the time difference between the transmission and reception. Conventionally, microwaves and millimeter waves were significantly attenuated by the exposed surface 12, but in the measuring device 1 of the present invention, the attenuation by the exposed surface 12 is suppressed, so that the melt level 200 can be detected more accurately and the electrode length of the carbon electrode 10 can be obtained.

[0034] As described above, the detection wave propagates well through the exposed surface 12 with low attenuation, but in order to improve the propagation, it is also preferable to use a taper union 80 as the joint 22 shown in Fig. 5. Fig. 5(A) is a cross-sectional view of the taper union 80, and Fig. 5(B) is a plan view seen from the AA direction in Fig. 5(A). As shown in Fig. 5(A), the taper union 80 is formed in a cylindrical shape with a predetermined width and a central portion 81 having the maximum outer diameter, and two tapered surfaces 82 are formed that extend continuously from the central portion 81 to both ends, and the entirety of the taper union 80 has an approximately barrel-shaped outer shape.

[0035] Furthermore, a stepped stopper 83 with the same width as the wall thickness of the guide pipe piece 21 protrudes in an annular shape from the inner peripheral surface of the longitudinal center of the taper union 80, and the guide pipe piece 21 is inserted so that its end abuts against the stopper 83. Here, since the stopper 83 has the same thickness as the guide pipe piece 21, there is no hindrance to the propagation of microwaves or millimeter waves.

[0036] Additionally, it is preferable that the longitudinal dimensions H1 and H2 of the central portion 81 and the tapered surfaces 82 of the tapered union 80 are equal to or greater than the wavelength of microwaves or millimeter waves, respectively. The length H2 of the two tapered surfaces 82 may be the same or different.

[0037] The maximum outer diameter D of the tapered union 80 is preferably set to a dimension that does not generate higher-order modes of microwaves or millimeter waves.

[0038] Furthermore, as shown in Fig. 5(B), a central portion 81 of the taper union 80 has a plurality of screw holes 85 formed at equal intervals along the circumferential direction, penetrating through to the inner circumferential surface for mounting set screws 90 shown in Fig. 6. Fig. 6(A) is a side view showing the set screws 90, and Fig. 6(B) is a plan view seen from the direction BB in Fig. 6(A).

[0039] The set screw 90 has a longitudinal length L that is longer than the thickness of the central portion 81 of the taper union 80, and has a thread 91 formed on its outer circumferential surface that engages with the threads of the screw hole 85 of the taper union 80. Also, a hexagonal hole 95 is formed on one end face. The set screw 90 is made of the same material as the taper union 80 and the guide pipe piece 21.

[0040] To connect the guide pipe piece 21 with such a taper union 80 and set screw 90, the guide pipe piece 21 is inserted until it abuts against the stopper 83 of the taper union 80, and then the set screw 90 is attached to the threaded hole 85 of the taper union 80 and screwed in until the end face of the set screw 90 reaches the outer circumferential surface of the guide pipe piece 21 to fix the guide pipe piece 21. Thereafter, the portion of the set screw 90 protruding from the threaded hole 85 of the taper union 80 is cut off with a sander or the like, and the outer circumferential surface of the taper union 80 is processed so that there are no irregularities.

[0041] By using the taper union 80 as the joint 22, the step portion 12a is eliminated on the exposed surface 12 shown in FIG. 4(B), and the reflection of microwaves and millimeter waves due to the step portion 12a is eliminated.

[0042] The measuring device 1 is configured as described above, but various modifications are possible. For example, as shown in FIG. 1, it is preferable to supply nitrogen gas (N2) or an inert gas between the tapered structure 40 of the guide pipe 20 and the distance meter 30 to increase the internal pressure of the guide pipe 20. Since the lower end of the guide pipe 20 is open, molten metal may flow in, and the internal pressure of the guide pipe 20 is increased to prevent the inflow of molten metal. In addition, the lower end of the guide pipe 20 may melt and block the guide pipe 20, causing the internal pressure of the guide pipe 20 to suddenly rise. When a sudden rise in the internal pressure is detected, the supply of nitrogen gas or inert gas may be increased to remove any clogging (clogging material) in the guide pipe 20. The internal pressure is adjusted by a pressure regulator 60. Reference numeral 61 denotes a pressure gauge.

[0043] 3, a metallic inert gas intake member 65 having a large number of fine holes 63 may be attached to the inlet 62 for nitrogen gas or inert gas into the guide pipe 20. Although not shown, the inert gas intake member 65 may be a wire mesh. The opening diameter of the fine holes 63 is set to a diameter that prevents microwaves and millimeter waves from entering and allows the inert gas to flow easily, for example, about φ1.5 mm in the case of a millimeter wave of 79 GHz. The mesh size of the wire mesh is also set to a similar size. The inert gas intake member 65 can prevent the microwaves and millimeter waves from leaking from the inlet 62.

[0044] It is also preferable to use circularly polarized microwaves or millimeter waves M'. As shown in Fig. 7, the range finder 30 includes a receiving circuit 31, a transmitting circuit 32, and a circular polarizer 33. The receiving circuit 31 receives a linearly polarized wave with a different electric field direction from the linearly polarized wave transmitted from the transmitting circuit 32. By utilizing this characteristic, the receiving circuit 31 and the transmitting circuit 32 are separated, and the circular polarizer 33 is interposed between them and the waveguide 35, thereby improving the accuracy of signal processing.

[0045] On the right side of Fig. 7, the direction of the electric field of the detection wave M' in each part of the measurement device 1 is indicated by arrows. The receiving circuit 31 and the transmitting circuit 32 both receive or transmit linearly polarized waves in which the electric field direction faces in one direction. When a circularly polarized received signal in which the electric field direction rotates in the opposite direction passes through the circular polarization generator 33, the effect of the circular polarization generator 33 causes the signal to become linearly polarized with an electric field direction different from that of the transmitted wave.

[0046] Then, a circularly polarized wave generator 33 transmits microwaves or millimeter waves M whose electric field direction is rotated in one direction (clockwise in the figure) from the transmission circuit 32. O ' is sent to the tapered structure 40 through the waveguide 35, and propagates through the guide pipe 20 and further through the exposed surface 12 of the carbon electrode 10 while remaining a right-handed rotating electric field, and is transmitted toward the molten liquid surface 200.

[0047] Microwaves and millimeter waves with circular polarization (right-handed or positive circular polarization) in which the electric field rotates clockwise relative to the direction of propagation O ' is a left-handed circularly polarized (negative circularly polarized) microwave or millimeter wave M that, when reflected by the melt surface 200, rotates in the left-handed direction relative to the propagation direction of the microwave or millimeter wave. r The left-handed electric field is then sent to the range finder 30 via the exposed surface 12 of the carbon electrode 10, the guide pipe 20, the tapered structure 40, and the waveguide 35, and travels backward through the circular polarized wave generator 33. At that time, the circular polarized wave generator 33 converts the wave into a linearly polarized wave with an electric field direction different from that of the transmitted linearly polarized wave, and the wave is received by the receiving circuit 31.

[0048] In this way, by using circularly polarized microwaves or millimeter waves M', the receiving circuit 31 receives the microwaves or millimeter waves M from the transmitting circuit 32. O Microwaves and millimeter waves M' have different electric fields. r Since only the transmitted wave and the received wave are received, the measurement accuracy can be greatly improved since the transmitted wave and the received wave can be almost completely separated.

[0049] In addition, in order to lower the noise level and increase the SNR, the measurement is repeated multiple times (N times) and the average value is calculated, thereby making it possible to lower the floor noise power by 1 / N.

[0050] Alternatively, the floor noise power can be reduced by 1 / N by performing multiple measurements and averaging either or both of the received beat waveform and the distance spectrum waveform obtained by FFT processing of the received beat waveform.

[0051] (Verification result 1) In imitation of the measuring device 1 in Fig. 1, six SUS304 pipes with a total length of 2 m were connected as guide pipe pieces to create a SUS304 guide pipe with a total length of 12 m. An iron plate representing the molten surface of the molten iron layer was then used to cover the opening at one end of the SUS304 guide pipe, and millimeter waves were transmitted from the waveguide of the range finder attached to the other end to measure the signal strength at each distance. The results are shown in Fig. 8.

[0052] In the chart shown in the figure, the peaks in the signal strength are due to minute reflections at the joints of the SUS304 pipe. These peaks appear regularly every 2 m, and an equivalent peak appears at a distance of 12 m, indicating that the millimeter waves propagate throughout the entire length of the SUS304 guide pipe.

[0053] In addition, because it is possible to detect peaks every 2 m, which correspond to the joints in the guide pipe pieces, by observing the peaks that appear at equal distances and the fixed reflections that appear at a distance, it is possible to estimate the locations of blockages within the guide pipe or locations where guide pipe pieces have become dislodged.

[0054] (Verification result 2) A carbon pipe with the same diameter and total length of 2 m was connected to one end of a SUS304 guide pipe equivalent to that in verification result 1, and the opening of the carbon pipe was covered with an iron plate. The carbon pipe corresponds to the exposed surface 12 of the carbon electrode 10 in the measurement device 1 in Figure 1. Then, millimeter waves were transmitted from the waveguide of a range finder attached to the other end of the SUS guide pipe, and the signal strength was measured for each distance. The results are shown in Figure 9.

[0055] In the chart shown, as in verification result 1, peaks appear every 2 m, corresponding to the SUS304 guide pipe. Also, a peak appears at a distance of 12 m, which is the joint between the SUS304 guide pipe and the carbon pipe. Furthermore, a peak appears at a distance of 14 m, which is caused by the iron plate blocking the carbon pipe, and it can be seen that the millimeter waves are also propagating through the carbon pipe.

[0056] (Verification result 3) As in verification result 2, a carbon pipe was connected to a SUS304 guide pipe, and an iron plate was placed 1m away from the opening of the carbon pipe. Then, millimeter waves were transmitted from the waveguide of a range finder attached to the other end of the SUS304 guide pipe, and the signal strength was measured for each distance. The results are shown in Figure 10.

[0057] In the chart shown in the figure, as in the verification result 2, peaks appear every 2 m corresponding to the SUS304 guide pipe and the carbon pipe. In addition, a peak appears at a position 15 m away, 1 m from the carbon pipe, and it can be seen that the millimeter wave propagates through the carbon pipe and even through the air. This shows that stable measurement is possible by propagating through the exposed surface 12 even from the bottom end where the guide pipe 20 has melted off.

[0058] In the above verification results, peaks due to the joints of the SUS304 guide pipe pieces are observed, so by counting the number of peaks in the measurement device 1, the number of guide pipe pieces 21 and the total length of the guide pipe 20 can be determined. In addition, since peaks of the reflected wave appear every 2 m, the position of the joints can be measured without correction. This shows that the signal velocity (group velocity) of the circular TE11 mode is almost equal to the speed of light (speed of plane waves). In other words, it shows that the inner diameter of the guide pipe 20 is sufficiently large compared to the inner diameter of the waveguide 35.

[0059] [Operation method] The present invention also relates to a method for operating an electric resistance melting furnace using the above-mentioned measuring device 1. First, as shown in Fig. 11, the measuring device 1 is used to measure the distance (L1) of the guide pipe 20, i.e., the electrode length of the carbon electrode 10, from a distance meter 30.

[0060] Also, for example, a plate-shaped position measuring member 38 is attached to the range finder 30, and a second range finder 210 is placed above the range finder 30 to measure the separation distance (L2) between the second range finder 210 and the range finder 30. A general microwave or millimeter wave range finder can be used as the second range finder 210, which transmits microwaves or millimeter waves from an antenna 220 toward the position measuring member 38, receives the microwaves or millimeter waves reflected by the position measuring member 38, and determines the separation distance (L2) from the time difference.

[0061] Then, the distance (L1) and the separation distance (L2) are added together to determine the distance (L3), and the hanging position of the carbon electrode 10 is controlled based on a distance signal of the distance (L3).

[0062] Since the carbon electrode 10 is consumed by melting and gradually shortens, it is necessary to gradually lower the carbon electrode 10 accordingly. Therefore, as described above, the second distance meter 210 is fixed to a place whose height does not change, such as the ceiling of the furnace equipment, as a reference position, and the hanging position of the carbon electrode 10 can be controlled by knowing the distance (L3) from this reference position to the bottom end of the carbon electrode 10.

[0063] This will enable more stable operations. [Explanation of symbols]

[0064] 1. Measuring equipment 10 Carbon Electrode 12 Exposed surface 12a Step part 15 Electrode case (metal cover) 16, 16a, 16b Electrode case piece (metal cover piece) 18 Electrode body 18a Electrode baking section 18b Coal tar melting section 18c Electrode material section 20 Guide pipe 21, 21a, 21b Guide pipe piece 22 Joint (Joint) 23,71 Thread groove 25 Guide pipe clamp 30 Rangefinder 31 Receiving circuit 32 Transmitting circuit 33 Circularly polarized wave generator 35 Waveguide 38 Position measuring components 40 Tapered Structure 41 Cavity 50 Pry parts 60 Pressure Regulator 62 Intake 63 Pore 65 Inert gas intake member 70 Threaded Socket 80 Taper union 81 Central part 82 Tapered surface 83 Stopper 85 screw hole 90 Set screw 91 Screw 95 hexagonal hole 120 Electrode lifting device 200 Melt surface 210 Second Rangefinder 220 Antenna

Claims

1. 1. A device for measuring the electrode length of a carbon electrode in an electric resistance melting furnace in which a carbon electrode suspended in a furnace is inserted into a material to be melted piled up in the furnace and a current is passed through the carbon electrode to melt the material, comprising: a guide pipe formed by connecting a plurality of metal guide pipe pieces and inserted so as to reach a lower end of the carbon electrode; a range finder attached to the upper end of the guide pipe and including a microwave or millimeter wave transmitting / receiving means and a waveguide; In addition to providing The inner diameter of the guide pipe is larger than the inner diameter of the waveguide of the range finder, and the guide pipe and the range finder are connected via a tapered structure having a cavity tapered from the waveguide toward the guide pipe, An electrode length measuring device for a carbon electrode in an electric resistance melting furnace, which transmits the microwaves or millimeter waves from the lower end of the guide pipe toward the molten liquid surface of the material to be melted, receives the microwaves or millimeter waves reflected by the molten liquid surface, and measures the distance between the distance meter and the molten liquid surface.

2. 2. The device for measuring the electrode length of a carbon electrode in an electric resistance melting furnace according to claim 1, wherein the guide pipe pieces are connected to each other by a threaded socket.

3. 2. The device for measuring the electrode length of a carbon electrode in an electric resistance melting furnace as described in claim 1, wherein the guide pipe pieces are connected to each other by a taper union having an outer shape in which two tapered surfaces extending continuously from a central portion having a maximum diameter to both ends are formed.

4. 2. The device for measuring the electrode length of a carbon electrode in an electric resistance melting furnace as described in claim 1, wherein the connection portion between the tapered structure and the guide pipe is closed with a member made of a material through which the microwaves or millimeter waves are transmitted.

5. An inert gas is supplied to the guide pipe to increase the internal pressure, and when the internal pressure suddenly increases, it is determined that the guide pipe is blocked, and the amount of the inert gas supplied is increased.

2. The device for measuring the electrode length of a carbon electrode in an electric resistance melting furnace according to claim 1, wherein the blocking portion is removed.

6. 2. The device for measuring the electrode length of a carbon electrode in an electric resistance melting furnace according to claim 1, wherein a metal plate having holes with an opening diameter that does not allow microwaves or millimeter waves to penetrate, or a wire mesh with openings that does not allow microwaves or millimeter waves to penetrate, is attached to the inert gas supply port to the guide pipe.

7. 2. The device for measuring the electrode length of a carbon electrode in an electric resistance melting furnace according to claim 1, wherein the microwaves or millimeter waves are circularly polarized and transmitted toward the molten liquid surface.

8. 2. The device for measuring the electrode length of a carbon electrode in an electric resistance melting furnace according to claim 1, further comprising a measurement mode for measuring the electrode length of the carbon electrode multiple times and calculating an average value of the measured electrode lengths.

9. 2. The device for measuring the electrode length of a carbon electrode in an electric resistance melting furnace according to claim 1, further comprising a measurement mode for measuring the electrode length of the carbon electrode multiple times and averaging either or both of the obtained received beat waveform and a distance spectrum waveform obtained by subjecting the received beat waveform to FFT processing.

10. 2. The device for measuring the electrode length of a carbon electrode in an electric resistance melting furnace according to claim 1, wherein the guide pipe is made of SUS.

11. 2. The device for measuring the electrode length of a carbon electrode in an electric resistance melting furnace according to claim 1, wherein reflected signals appearing at equal distances on the guide pipe are observed.

12. A method for operating an electric resistance melting furnace, comprising inserting a carbon electrode suspended in the furnace into a material to be melted that has been piled up in the furnace, and passing an electric current through the carbon electrode to melt the material to be melted, comprising the steps of: The electrode length measuring device according to any one of claims 1 to 11 is used to measure the distance (L1) from the distance meter to the molten liquid surface, a second distance meter is disposed above the distance meter, a distance (L2) between the second distance meter and the distance meter is measured, and the distance (L2) is added to the determined distance (L1) to determine a distance (L3) from the second distance meter to the melt surface; A method for operating an electric resistance melting furnace, comprising controlling the hanging position of a carbon electrode based on the distance (L3).

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