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

Abstract

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 of which consists of at least four electrodes arranged along the height direction of the vertical furnace, applying a current to the top and bottom two electrodes in each measurement electrode group as current application electrodes, measuring the voltage generated between the voltage detection electrodes using 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 this voltage, wherein while a current is being applied to a certain measurement electrode group, no current is applied to the other measurement electrode groups.

Description

[Technical field]

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

[0002] A shaft furnace is a general term for a furnace in which raw materials are charged from the top and molten metal is taken out from the bottom of the furnace. Among shaft furnaces, the blast furnace in the steel industry is located at the most upstream process of a steelworks, so technology for stabilizing its operation is important. Specifically, when the height of the molten pig iron and molten slag stored in the blast furnace (hereinafter, the molten level) rises, the furnace condition becomes unstable and production may decrease. In addition, it has been pointed out that there is a deviation in the molten level in the circumferential direction of the blast furnace, and it is necessary to measure the local change in the molten level as well. For this reason, measuring the molten level in a blast furnace is an essential technology for stable operation. In light of this background, Patent Document 1 proposes a method for measuring the molten level in a blast furnace. Specifically, in the method described in Patent Document 1, first, a plurality of measurement electrode groups consisting of at least four electrodes arranged in a straight line along the height direction of the blast furnace are installed along 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 in 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 timing of the rise and fall of the applied current is consistent between the measurement electrode groups. Each measurement electrode group measures the molten material level in a limited range in the circumferential direction in the blast furnace. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2010-138437 A Summary of the Invention [Problem to be solved by the invention]

[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 each other between the measurement electrode groups, causing a current greater than expected to flow through the furnace body. As a result, a higher voltage than expected may be measured at the voltage detection electrode, reducing the measurement accuracy of the molten material level. In addition, it may become difficult to recognize the difference 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 object 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. [Means for solving the problem]

[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 top and bottom two electrodes in each measurement electrode group as current application electrodes, measuring the voltage generated between the voltage detection electrodes using 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, wherein while a current is being applied to a certain measurement electrode group, no current is applied to the other measurement electrode groups.

[0007] The device for measuring the molten material level in a vertical furnace according to the present invention includes a measurement electrode group consisting of at least four electrodes arranged along the height direction of the vertical furnace and installed in multiple locations along the circumferential 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 a current, and at least two electrodes excluding the current application electrodes are used as voltage detection electrodes to measure the voltage generated between the voltage detection electrodes, and the device measures the molten material level in the circumferential direction of 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 a certain measurement electrode group, no current is applied to the other measurement electrode groups.

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

[0009] The measurement electrodes to which no current is applied may be those that are present within a predetermined distance from the measurement electrodes 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 present at a position that is spaced apart from the predetermined distance at the same time as the measurement electrodes to which the current is being applied. Effect of the Invention

[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. [Brief description of the drawings]

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

[0014] Hereinafter, a method and device for measuring a 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 structure] First, with reference to FIG. 1, 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 will be described.

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

[0017] As shown in FIG. 1, the measuring device for measuring the molten material level in a vertical furnace according to one embodiment of the present invention includes a group of measuring electrodes, each consisting of at least four electrodes arranged linearly along the height direction of the furnace body 1, at each of a plurality of measuring positions set in the circumferential direction of the furnace body 1. In this embodiment, current application electrodes 10a, 10b and voltage detection electrodes 11a, 11b are provided at each measuring position as the group of measuring electrodes. Each electrode is installed so that its tip contacts the outer furnace surface of the carbon brick constituting the lower part of the furnace body 1. Each electrode is installed so that the straight line L formed by the multiple electrodes installed at each measuring position is parallel to the straight line L formed by the multiple electrodes installed at other measuring positions, and the installation heights of the electrodes are uniform between the measuring 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 composed of, for example, 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 makes it possible to apply signals with the same time change to the current applying electrodes 10a, 10b at each measurement position.

[0019] Here, when the molten material level is measured simultaneously using a plurality of measurement electrode groups at different measurement positions, the applied currents of the measurement electrode groups at different measurement positions may interfere with each other, as shown in FIG. 2, and a voltage (voltage signal Vb) higher than the expected voltage (voltage signal Va) may be detected. In one embodiment, the occurrence of interference between the applied currents depends on the size of the interval between the measurement electrode groups. Here, the interference between the applied currents refers to the current of the other measurement electrode groups being leaked, and when the interval between the measurement electrode groups is shorter than a specific value, a voltage higher than the expected voltage is detected due to the current of the other measurement electrode groups being leaked. The interval between the measurement electrode groups at which interference between the applied currents occurs can be derived by a current distribution analysis using the electrical resistances and dimensions of the molten pig iron, molten slag, and carbon bricks as inputs. FIG. 3 is a diagram showing an example of the current distribution analysis result. 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 the current density on a top view of a vertical furnace, and the closer to black the area, the higher the current density. As shown in FIG. 3, in the current distribution analysis, the current density is high within a range of ±15° centered on a measurement position of a measurement electrode group through which a current flows. That is, when the interval between the measurement positions is smaller than ±15°, the current flowing through the adjacent measurement electrode groups flows around the carbon bricks into the adjacent measurement electrode group. For this reason, in this embodiment, when the measurement positions of any two sets of measurement electrode groups are shorter than the interval between the measurement electrode groups at which the applied currents interfere with each other, which is derived 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 a signal to the current generator 12 between the measurement positions, so that while a signal is being output to a certain measurement position, a signal is not output to other measurement positions. That is, while a current is being applied to a certain measurement electrode group, a current is not applied to other measurement electrode groups. This prevents overdetection 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 there is no current leakage in the measurement electrode group located at a measurement position farther away than the distance at which interference occurs between the applied currents, the measurement may be performed by applying a current simultaneously to the measurement electrode group to which the current is being applied. This shortens the time required for measurements by all the measurement electrode groups, shortens the time interval between molten material level measurements, and enables more precise management of the molten material level.

[0020] Each current generator 12 applies a current to the current application electrodes 10a, 10b according to a square wave signal or a pseudo-random signal output from the signal switching device 22, and causes 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 together with the voltage. Thereafter, the recording device 13 calculates the molten material level in the blast furnace based on the recorded voltage value or the change in the electrical resistance between the voltage detection electrodes 11a, 11b calculated from this voltage value. In the lower part of the furnace body 1, it is considered that the molten material level may differ locally due to factors such as the difference in viscosity between the molten iron and slag and the uneven distribution of coke in the center of the furnace. Such deviations in the molten material level may have an impact on the furnace condition. In contrast, according to this embodiment, it is possible to find the deviation in the increase and decrease in the molten material level in the circumferential direction of the furnace body 1. For example, if the smelt level has risen excessively locally, the smelt level in the circumferential direction can be made uniform by opening the tap hole 1b near the measurement position that indicates an increase in the smelt level and tapping the smelt.

[0021] When the signal output from the signal switching device 22 is a square wave signal, the voltage value recorded in the recording device 13 is divided by the current value (the absolute value of the current is constant) corresponding to each time range to calculate the electrical resistance value between the voltage detection electrodes 11a, 11b. On the other hand, when 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 by two values, 0 and 1, but continues to take that value within the time of the clock frequency. For this reason, if the 0 of the pseudo-random signal corresponds to -1 and the 1 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 value between the voltage detection electrodes 11a, 11b can be calculated by dividing the obtained voltage value by the amplitude A of the current value.

[0022] [Electrode installation position] Next, the positions at which current application electrodes 10a, 10b and voltage detection electrodes 11a, 11b are disposed will be described in detail.

[0023] As shown in FIG. 1, the current application electrodes 10a and 10b are installed one above and one below the tap hole 1b. When measuring the slag level, the level of the molten iron in the furnace is considered to change only by a few tens of centimeters above the tap hole 1b. Therefore, of the two electrodes installed above the tap hole 1b, the lower electrode is installed at a position where it is always above the level of the molten iron. The electrodes installed at the other measurement positions are set to have the same spacing and installation positions. This is to make it easier to compare the increase and decrease in the molten iron level at each measurement position. It is known that the measurement value is not significantly affected even if the electrode installation positions are shifted by a few tens of centimeters in the vertical direction, so it is desirable to match the electrode installation positions with a difference of within a few 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] In order to obtain comparable electrical resistance at each measurement position, it is necessary to align the number of carbon brick tiers (the number of carbon bricks stacked from the hearth) that the electrodes at the same position at each measurement position contact. This is because the joints of carbon bricks are conductive, but are coated with cement that has a higher electrical resistance than carbon bricks. In addition, it is ideal to install the four electrodes in a straight line, but they may be shifted in the circumferential direction depending on the installation conditions of the auxiliary equipment of the blast furnace. However, the shortest flow path of the applied current must be within a range that does not penetrate the joints of the carbon bricks in the left and right direction. In practice, the allowable vertical and circumferential deviations of these installation positions can be determined from the design drawings of the blast furnace to be measured. In addition, by installing each electrode so that the straight lines formed by the installation positions of the electrodes at one measurement position are parallel, it is also easy to compare the measured electrical resistance values. EXAMPLES

[0025] In this embodiment, the volume is 5000 m 3 The molten metal level in a blast furnace with four tap holes installed in the circumferential direction was measured using a current switch. In detail, the measurement was performed for the purpose of detecting the slag level, since the molten metal level can be calculated from the material balance. As shown in Fig. 4, the molten metal level was measured at four positions in total, and the molten metal level was measured by installing measurement electrodes near the four tap holes 1b. Then, 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 the same time change, and the measurement was performed. The current value was set to 3 A, and a current was applied to the current application electrodes of each measurement electrode group in sequence using a current switching device as shown in Fig. 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 is assumed that the voltage detection electrodes are always above the level of the molten iron. 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 about 200 mm to the right of the straight line due to the presence of piping for ancillary equipment. The cross section of the carbon bricks that make up the furnace body is 600 mm square, and the shortest flow path of the current does not penetrate the joints. The tip of each electrode was in contact with the surface of the exposed 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. No overdetection of voltage was observed in the detected voltage waveform, and it was confirmed that the voltage was measured as expected. In addition, FIG. 7(a) and (b) show the change in electrical resistance when the current control of the present invention is performed and when it is not performed. As shown in FIG. 7(a), when the current control of the present invention is not performed, the amount of current flowing increases, and as a result, the absolute value of the electrical resistance becomes large and the amplitude becomes small, thereby weakening the tendency of the change in electrical resistance. In contrast, as shown in FIG. 7(b), when the current control of the present invention is performed, the amount of current flowing is the expected value, so the absolute value of the electrical resistance becomes small and the amplitude becomes large, and the tendency of the change in electrical resistance can be clearly confirmed. As a result, it was confirmed that according to the present invention, even when the molten material level is measured at multiple measurement positions along the circumferential direction of the blast furnace, the molten material level can be accurately measured at each measurement position.

[0028] Although the embodiments of the present invention have been described above, the present invention is not limited by the descriptions and drawings that form part of the disclosure of the present invention according to the present embodiments. In other words, other embodiments, examples, and operation techniques, etc., made by those skilled in the art based on the present embodiments are all included in the scope of the present invention. [Industrial Applicability]

[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 measuring the molten material level with high accuracy 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. [Explanation of symbols]

[0030] 1 Furnace body 1a Furnace mouth 1b Tap hole 10a,10b Current application electrode 11a, 11b Voltage detection electrodes 12 Current Generator 13 Recording Devices 21 Signal Generator 22 Signal switching device

Claims

1. A method for measuring a molten material level in a vertical furnace, comprising: 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; measuring a voltage generated between the voltage detection electrodes as at least two electrodes excluding the current application electrodes as voltage detection electrodes; and measuring the molten material level in the circumferential direction of the vertical furnace using the measured voltage or a change in electrical resistance calculated from the measured voltage, A method for measuring the molten material level in a vertical furnace, in which while a current is applied to a group of measurement electrodes, no current is applied to other groups of measurement electrodes.

2. 2. The method for measuring a 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 said current applying electrode.

3. 3. The method for measuring the molten material level in a vertical furnace according to claim 1, wherein the measurement electrode group to which no current is applied is a measurement electrode group located within a predetermined distance from the measurement electrode group to which current is applied.

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

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

6. A method for measuring the molten material level in a vertical furnace as described in Claim 4, wherein a current is applied to a group of measurement electrodes located at a position further away than the specified distance at the same time as the group of measurement electrodes to which the current is being applied.

7. A device for measuring a molten material level in a vertical furnace, comprising a plurality of measurement electrode groups each consisting of at least four electrodes arranged along the height direction of the vertical furnace and installed along the circumferential direction of the vertical furnace, wherein in each measurement electrode group, the top and bottom two electrodes are used as current application electrodes to apply a current, and at least two electrodes other than the current application electrodes are used as voltage detection electrodes to measure a voltage generated between the voltage detection electrodes, and the molten material level in the circumferential direction inside the vertical furnace is measured using the measured voltage or a change in electrical resistance calculated from the voltage, 1. An apparatus for measuring a molten material level in a vertical furnace, characterized in that while a current is applied to one group of measurement electrodes, no current is applied to other groups of measurement electrodes.

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

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