Method for measuring level of molten matter inside vertical furnace, and measuring device

Abstract

In this method for measuring the level of molten matter inside a vertical furnace: a plurality of measuring electrode groups each comprising at least four electrodes arrayed along the height direction of the vertical furnace are installed along the circumferential direction of the vertical furnace; in each of the measuring electrode groups, two electrodes at top and bottom are used as current-application electrodes to apply current, and at least two electrodes excluding the current-application electrodes are used as voltage-detection electrodes to measure voltage occurring across the voltage-detection electrodes; and the measured voltage or change in electrical resistance computed from this voltage is utilized to measure the molten matter level in the circumferential direction inside the vertical furnace. While current is being applied in a given measuring electrode group, current is not applied in the other measuring electrode groups.

Description

Method and device for measuring molten material level in a vertical furnace

[0001] The present invention relates to a method and an apparatus for measuring the level of a molten material in a vertical furnace.

[0002] A shaft furnace is a general term for a furnace in which raw materials are charged from the top and molten metal is discharged from the bottom. Among shaft furnaces, blast furnaces in the steel industry are located at the most upstream stage of steelworks, so technology to stabilize their operation is highly valued. Specifically, when the height of the molten iron and molten slag stored in the blast furnace (hereinafter referred to as the molten iron level) rises, the furnace condition becomes unstable and production may decrease. It has also been pointed out that the molten iron level varies around the blast furnace, making it necessary to measure local changes in the molten iron level. For this reason, measuring the molten iron level in a blast furnace has become an essential technology for stable operation. Against this background, Patent Document 1 proposes a method for measuring the molten iron level in a blast furnace. Specifically, in the method described in Patent Document 1, multiple measurement electrode groups, each consisting of at least four electrodes arranged linearly along the height direction of the blast furnace, are first installed around the circumferential direction of the blast furnace. Next, in each measurement electrode group, a current is applied to the top and bottom two electrodes as current application electrodes, and at least two electrodes other than the current application electrodes are used as voltage detection electrodes to measure the voltage generated between the voltage detection electrodes. The molten material level in the circumferential direction within the blast furnace is then measured using the measured voltage or a change in electrical resistance calculated from this voltage. In this method, the current is applied so that the rise and fall timings of the applied current are synchronized between the measurement electrode groups. Each measurement electrode group measures the molten material level in a limited range in the circumferential direction within the blast furnace.

[0003] JP 2010-138437 A

[0004] In the method described in Patent Document 1, when multiple measurement electrode groups are used to measure the molten material level simultaneously, the applied current may interfere with the measurement electrode groups, causing a current greater than expected to flow through the furnace body. As a result, a higher-than-expected voltage may be measured at the voltage detection electrode, reducing the accuracy of the molten material level measurement. Furthermore, it may become difficult to recognize differences in the voltage trends between the measurement electrode groups that should be measured.

[0005] The present invention has been made in consideration of the above-mentioned problems, and its purpose is to provide a method and device for measuring the molten material level in a vertical furnace, which is capable of accurately measuring the molten material level using each measurement electrode group, even when multiple measurement electrode groups are installed along the circumferential direction of the furnace to measure the molten material level.

[0006] The method for measuring the molten material level in a vertical furnace according to the present invention comprises installing a plurality of measurement electrode groups along the circumferential direction of the vertical furnace, each group consisting of at least four electrodes arranged along the height direction of the vertical furnace, applying a current to the two uppermost and lowermost electrodes in each measurement electrode group as current application electrodes, measuring the voltage generated between the voltage detection electrodes as at least two electrodes excluding the current application electrodes as voltage detection electrodes, and measuring the circumferential molten material level in the vertical furnace using the measured voltage or the change in electrical resistance calculated from the voltage, and while a current is being applied to one measurement electrode group, no current is applied to the other measurement electrode groups.

[0007] The device for measuring the melt level in a vertical furnace according to the present invention comprises a plurality of measurement electrode groups each consisting of at least four electrodes arranged along the height direction of the vertical furnace, the measurement electrode groups being installed along the circumferential direction of the vertical furnace, and applying a current to the two uppermost and lowermost electrodes in each measurement electrode group as current application electrodes, and measuring the voltage generated between the voltage detection electrodes as at least two electrodes excluding the current application electrodes as voltage detection electrodes, and using the measured voltage or the change in electrical resistance calculated from the voltage to measure the melt level in the circumferential direction inside the vertical furnace, and while a current is being applied to one measurement electrode group, no current is applied to the other measurement electrode groups.

[0008] The current signal to be applied to the current application electrodes may be a square wave signal or a pseudo-random signal.

[0009] The measurement electrode group to which no current is applied may be a measurement electrode group that exists within a predetermined distance from the measurement electrode group to which a current is applied.

[0010] The predetermined distance may be determined by current distribution analysis.

[0011] A current may be applied to the measurement electrodes located at a distance greater than the predetermined distance, simultaneously with the measurement electrodes to which the current is being applied.

[0012] According to the method and device for measuring the molten material level in a vertical furnace of the present invention, even when the molten material level is measured by installing multiple measurement electrode groups along the circumferential direction of the furnace, the molten material level can be measured accurately by each measurement electrode group.

[0013] FIG. 1 is a schematic diagram showing the overall configuration of a device for measuring the level of a molten material in a vertical furnace according to one embodiment of the present invention. FIG. 2 is a diagram for explaining overdetection of voltage due to current interference. FIG. 3 is a diagram showing an example of a current distribution analysis result. FIG. 4 is a diagram showing the installation positions of measurement electrode groups in an example. FIG. 5 is a diagram showing the timing of current application to each measurement electrode group in an example. FIG. 6 is a diagram showing an example of a detected voltage waveform in an example. FIG. 7 is a diagram showing changes in electrical resistance when the current control of the present invention is performed and when it is not performed.

[0014] Hereinafter, a method and device for measuring the molten material level in a vertical furnace according to one embodiment of the present invention will be described with reference to the drawings.

[0015] [Overall Configuration] First, with reference to FIG. 1, the overall configuration of a device for measuring the level of a molten material in a vertical furnace, which is one embodiment of the present invention, will be described.

[0016] Fig. 1 is a schematic diagram showing the overall configuration of a device for measuring the level of a molten material in a shaft furnace according to one embodiment of the present invention. In this embodiment, the present invention is applied to a blast furnace, which is a type of shaft furnace, and Fig. 1 shows the furnace body 1 of the blast furnace in an expanded state. In Fig. 1, reference numeral 1a denotes a furnace throat, and reference numeral 1b denotes a taphole.

[0017] As shown in FIG. 1 , one embodiment of the present invention, a device for measuring the level of a molten material in a vertical furnace, includes a group of measurement electrodes, each consisting of at least four electrodes arranged linearly along the height of the furnace body 1, at each of a plurality of measurement positions set around the circumferential direction of the furnace body 1. In this embodiment, the measurement electrode group includes current application electrodes 10a, 10b and voltage detection electrodes 11a, 11b, each of which is provided at each measurement position. Each electrode is installed so that its tip contacts the outer furnace surface of the carbon bricks that form the lower part of the furnace body 1. Each electrode is installed so that the line L formed by the multiple electrodes installed at each measurement position is parallel to the line L formed by the multiple electrodes installed at other measurement positions, and the installation heights of the electrodes are uniform between the measurement positions. Details of the installation positions of the current application electrodes 10a, 10b and the voltage detection electrodes 11a, 11b will be described later.

[0018] In this embodiment, a current generator 12 is connected to the current applying electrodes 10a, 10b, and a recording device 13 is connected to the voltage detecting electrodes 11a, 11b. The recording device 13 is configured, for example, with an A / D converter and an information processing device such as a computer. When measuring the molten material level in the furnace at each measurement position, a signal generating device 21 connected to the current generator 12 outputs a square wave signal or a pseudo-random signal. This allows signals with consistent time changes to be applied to the current applying electrodes 10a, 10b at each measurement position.

[0019] When measuring the molten metal level simultaneously using measurement electrode groups at multiple measurement positions, interference between the applied currents of the measurement electrode groups at different measurement positions can generate a larger current than expected, as shown in FIG. 2 , resulting in a detected voltage (voltage signal Vb) higher than the expected voltage (voltage signal Va). In one aspect, whether or not interference between applied currents occurs depends on the spacing between the measurement electrode groups. Here, interference between applied currents refers to the leakage of currents from other measurement electrode groups. When the spacing between the measurement electrode groups is shorter than a specific value, a voltage higher than the expected voltage is detected due to the leakage of currents from other measurement electrode groups. The spacing between the measurement electrode groups at which interference between applied currents occurs can be derived by current distribution analysis using the electrical resistances and dimensions of the molten iron, molten slag, and carbon bricks as inputs. FIG. 3 shows an example of the current distribution analysis results. In the current distribution analysis, the current density in the carbon brick is calculated when a current is passed through the measurement electrode groups installed at the measurement positions. FIG. 3 shows the results of mapping the magnitude of current density on a top view of a vertical furnace, with areas closer to black indicating higher current density. As shown in FIG. 3 , in the current distribution analysis, the current density was found to be high within a ±15° range around the measurement position of a measurement electrode group through which current was passed. That is, when the distance between the measurement positions is less than ±15°, the current passed through adjacent measurement electrode groups bypasses the carbon brick and flows into the adjacent measurement electrode group. Therefore, in this embodiment, when the measurement positions of any two pairs of measurement electrode groups are shorter than the distance between the measurement electrode groups at which applied currents interfere with each other, as determined by the current distribution analysis, the signal switching device 22 installed between the current generator 12 and the signal generating device 21 shifts the timing of outputting signals to the current generator 12 between the measurement positions, so that while a signal is being output to one measurement position, a signal is not being output to the other measurement positions. That is, while a current is being applied to one measurement electrode group, current is not being applied to the other measurement electrode groups. This prevents over-detection of voltage and enables the molten material level to be measured accurately at each measurement position even when the molten material level is measured at multiple measurement positions along the circumferential direction of the furnace.Here, since current does not flow around in measurement electrodes located at measurement positions farther apart than the distance at which interference between applied currents occurs, current may be applied simultaneously to measurement electrodes to which current is being applied, thereby shortening the time required for measurements at all measurement electrode groups, shortening the time interval between molten material level measurements, and enabling more precise management of the molten material level.

[0020] Each current generator 12 applies a current to the current application electrodes 10a, 10b in accordance with a square wave signal or pseudorandom signal output from the signal switching device 22, thereby causing a current to flow through the furnace body 1. The recording device 13 then measures and records the voltage generated between the voltage detection electrodes 11a, 11b. At this time, the recording device 13 also records the current applied by the current generator 12 as a reference signal along with the voltage. The recording device 13 then calculates the molten material level in the blast furnace based on the recorded voltage value or the change in electrical resistance between the voltage detection electrodes 11a, 11b calculated from this voltage value. It is believed that the molten material level may vary locally in the lower part of the furnace body 1 due to factors such as differences in viscosity between the molten iron and slag and uneven distribution of coke in the center of the furnace. Such deviations in the molten material level may have an adverse effect on the furnace conditions. In contrast, this embodiment makes it possible to detect deviations in the molten material level increase or decrease in the circumferential direction of the furnace body 1. For example, if the molten material level rises excessively locally, the molten material level can be made uniform in the circumferential direction by opening the tap hole 1b near the measurement position where the molten material level rises and tapping the molten material.

[0021] If the signal output from the signal switching device 22 is a rectangular wave signal, the electrical resistance between the voltage detection electrodes 11a and 11b can be calculated by dividing the voltage value recorded in the recording device 13 by the current value (the absolute value of the current is constant) corresponding to each time range. On the other hand, if the signal output from the signal switching device 22 is a pseudo-random signal, the cross-correlation between the reference signal and the voltage signal is calculated, and the maximum value (correlation maximum) of the cross-correlation waveform is detected and used as the voltage value. Here, the pseudo-random signal is a signal expressed as two values, 0 and 1, but continues to maintain that value within the time of the clock frequency. Therefore, if the pseudo-random signal's 0 corresponds to -1 and 1 corresponds to +1, and the amplitude of the current value is A, the current value changes from -A to +A in the same pattern as the pseudo-random signal. Therefore, the electrical resistance between the voltage detection electrodes 11a and 11b can be calculated by dividing the obtained voltage value by the amplitude A of the current value.

[0022] [Positions of Electrodes] Next, the positions of the current application electrodes 10a, 10b and the voltage detection electrodes 11a, 11b will be described in detail.

[0023] As shown in FIG. 1 , current application electrodes 10a and 10b are installed one above the taphole 1b and one above the taphole 1b. Since the molten iron level in the furnace is expected to change only a few tens of centimeters above the taphole 1b when measuring the slag level, the lower electrode of the two electrodes installed above the taphole 1b is positioned so that it is always above the molten iron level. The electrodes installed at other measurement positions are positioned with the same spacing and installation positions. This is to facilitate comparison of the increases and decreases in the molten iron level at each measurement position. Since it has been found that a vertical deviation of several tens of centimeters does not significantly affect the measured values, it is desirable to match the electrode installation positions to within a difference of several tens of centimeters. The positive and negative electrodes of the current application electrodes 10a and 10b and the voltage detection electrodes 11a and 11b are arranged in the same order at all measurement positions.

[0024] To obtain comparable electrical resistance at each measurement point, it is necessary to align the number of carbon brick layers (the number of carbon bricks stacked from the hearth) between electrodes at the same measurement point. This is because the joints between carbon bricks are conductive but coated with cement, which has higher electrical resistance than the carbon bricks. Ideally, the four electrodes should be installed in a straight line, but they may be circumferentially offset depending on the installation conditions of the blast furnace's auxiliary equipment. However, the shortest path of the applied current must not penetrate the lateral joints of the carbon bricks. The allowable vertical and circumferential offsets of these installation positions can be determined from the design drawings of the blast furnace to be measured. Furthermore, installing each electrode so that the lines formed by the electrode installation positions at one measurement point are parallel also facilitates comparison of measured electrical resistance values.

[0025] In this example, the volume is 5000 m ３ The molten metal level in a blast furnace with four tapholes installed circumferentially was measured using a current switching device. Specifically, because the molten metal level can be calculated from the material balance, the measurement was performed to detect the slag level. As shown in Figure 4, the molten metal level was measured at a total of four locations, and measurement electrodes were installed near the four tapholes 1b to measure the molten metal level. A pseudo-random signal with a code length of 127 and a clock frequency of 6 Hz was supplied to the current application electrodes of each measurement electrode group with a time-series synchronization. A current value of 3 A was applied to each current application electrode of each measurement electrode group in sequence using a current switching device, as shown in Figure 5.

[0026] The distance between the current application electrodes in each measurement electrode group was 6 m, and the top voltage detection electrode was installed 1 m below the top current application electrode. The bottom voltage detection electrode was installed 1 m below the top voltage detection electrode. At this height, it was assumed that the voltage detection electrodes would always be above the molten iron level. Each electrode was installed in a straight line along the height direction of the blast furnace. However, two voltage detection electrodes at one measurement position were installed approximately 200 mm to the right of the straight line due to the presence of piping for auxiliary equipment. The cross section of the carbon bricks that make up the furnace body was 600 mm square, and the shortest current flow path did not penetrate the joints. The tip of each electrode was in contact with the exposed surface of the carbon brick. The electrodes at all measurement positions were installed at the same height.

[0027] FIG. 6 shows an example of a detected voltage waveform at a measurement position. The detected voltage waveform did not show any overdetection of voltage, confirming that the expected voltage was measured. Furthermore, FIGS. 7(a) and (b) show the change in electrical resistance when the current control of the present invention was implemented and when it was not implemented. As shown in FIG. 7(a), when the current control of the present invention was not implemented, the amount of current flowing increased, resulting in a larger absolute value of electrical resistance and a smaller amplitude, thereby weakening the trend of change in electrical resistance. In contrast, as shown in FIG. 7(b), when the current control of the present invention was implemented, the amount of current flowing was the expected value, resulting in a smaller absolute value of electrical resistance and a larger amplitude, allowing the trend of change in electrical resistance to be clearly confirmed. This confirms that the present invention enables accurate measurement of the molten material level at each measurement position, even when measuring the molten material level at multiple measurement positions along the circumferential direction of the blast furnace.

[0028] Although the present invention has been described above as an embodiment, the present invention is not limited to the descriptions and drawings that form part of the disclosure of the present invention. In other words, other embodiments, examples, and operational techniques that can be made by those skilled in the art based on the present invention are all included in the scope of the present invention.

[0029] According to the present invention, it is possible to provide a method and device for measuring the molten material level in a vertical furnace, which is capable of accurately measuring the molten material level using each measurement electrode group, even when measuring the molten material level by installing multiple measurement electrode groups along the circumferential direction of the furnace.

[0030] REFERENCE SIGNS LIST 1 furnace body 1a furnace throat 1b tap hole 10a, 10b current application electrodes 11a, 11b voltage detection electrodes 12 current generator 13 recording device 21 signal generator 22 signal switching device

Claims

1. A method for measuring the molten material level in a vertical furnace, which comprises installing a plurality of measurement electrode groups along the circumferential direction of the vertical furnace, each group consisting of at least four electrodes arranged along the height direction of the vertical furnace, applying a current to the top and bottom two electrodes of each measurement electrode group as current application electrodes, and measuring the voltage generated between the voltage detection electrodes as at least two electrodes excluding the current application electrodes as voltage detection electrodes, and using the measured voltage or the change in electrical resistance calculated from the voltage to measure the molten material level in the circumferential direction inside the vertical furnace, wherein while a current is being applied to one measurement electrode group, no current is being applied to the other measurement electrode groups.

2. A method for measuring the molten material level in a vertical furnace according to claim 1, wherein a square wave signal or a pseudo-random signal is used as the current signal applied to the current application electrode.

3. A method for measuring the molten material level in a vertical furnace as described in claim 1 or 2, wherein the group of measurement electrodes to which no current is applied is a group of measurement electrodes located within a predetermined distance from the group of measurement electrodes to which current is applied.

4. The method for measuring the molten material level in a vertical furnace according to claim 3, wherein the predetermined distance is determined by current distribution analysis.

5. A method for measuring the molten material level in a vertical furnace as described in claim 3 or 4, wherein a current is applied to the measurement electrode group located at a position more than the specified distance away at the same time as the measurement electrode group to which the current is being applied.

6. A device for measuring the molten material level in a vertical furnace, which is provided with a plurality of measurement electrode groups each consisting of at least four electrodes arranged along the height direction of the vertical furnace, and in each measurement electrode group, the top and bottom two electrodes are used as current application electrodes to apply current, and at least two electrodes other than the current application electrodes are used as voltage detection electrodes to measure the voltage generated between the voltage detection electrodes, and measures the molten material level in the circumferential direction inside the vertical furnace using the measured voltage or the change in electrical resistance calculated from the voltage, characterized in that while current is being applied to one measurement electrode group, no current is applied to the other measurement electrode groups.

7. The apparatus for measuring the level of a molten material in a vertical furnace according to claim 6, wherein a square wave signal or a pseudo-random signal is used as the current signal applied to said current application electrode.

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