JP2010025464A - Unit for measuring molten material surface level in vertical type furnace and measuring method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a unit for measuring a molten material surface level in a vertical type furnace allowing highly accurate measuring of the surface level of a molten material in the furnace and a measuring method therefor. <P>SOLUTION: At least four electrodes 21-24 are set in the vertical direction at a side of a furnace bottom part of the vertical type furnace. The upper most electrode 24 and the lower most electrode 21 out of the electrodes supply current as current supplying electrodes, and the electrodes other than the current supplying electrodes measure the electric potential difference as electric potential difference detecting electrodes. The surface level of the molten material is measured based on the measured electric potential difference or an electric resistance value calculated from the electric potential difference. A conductive refractory 11 is used at a portion where the electrodes are set in the vertical type furnace. The conductive refractory 11 is set to be in contact with molten metal accumulated at a lower part of the furnace and molten slag on a face of the furnace inner side, and on faces other than the face on the furnace inner side, the conductive refractory 11 covered by being in contact with a material having lower electric conductivity than itself. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to a vertical furnace melt level measuring device and a measuring method thereof, and more particularly to a vertical furnace melt in which a part of the refractory constituting the side portion of the furnace bottom is a conductive refractory. Regarding level measurement.

  In vertical furnaces such as blast furnaces and shaft furnaces, a melt is accumulated in the lower part of the furnace, and the melt is taken out intermittently or continuously from a spout attached to the lower part of the furnace. In a small vertical furnace such as a cupola (shaft furnace), there may be a problem that coke or the like is clogged around the tap outlet and the melt level rises. For this reason, it is necessary to monitor the melt level in the furnace during operation, but it is very difficult to observe directly. For this reason, a method for measuring the melt level indirectly from outside the furnace has been proposed.

  Since the lower part of the vertical furnace is often made of a conductive refractory (for example, carbon brick), an electric resistance type in-furnace melt level meter can be used. The electric resistance type melt level meter is equipped with a plurality of electrodes in the vertical direction on the outer surface of the refractory in the lower part of the furnace, and measures the electric resistance of the lower part of the furnace by the four-terminal method. Measure the increase and decrease of the melt level in the furnace from the change in value.

  For example, in the in-furnace melt level measurement method disclosed in Patent Document 1, a plurality of electrodes are provided at predetermined intervals in the height direction on the side surface of the blast furnace, and two of these electrodes are provided at the uppermost part and the lowermost part. Current is applied as an electrode for current application, and a potential difference between these electrodes is measured using an electrode other than the current application electrode as a voltage detection electrode. The melt level is grasped, and the melt level in the furnace can be known from the electric resistance value calculated from the potential difference measured by the voltage detection electrode among the plurality of electrodes. In addition, a sensitivity improves these electrodes by making it contact directly with the carbon brick which comprises a furnace lower part.

JP 2006-176849 A

  However, even in the in-furnace melt level measurement method disclosed in Patent Document 1 described above, when the conductive refractory is not electrically insulated from the furnace body, a material having low electrical conductivity due to an iron skin or the like. Therefore, there is a problem that the applied current flows into the furnace body and it is difficult to efficiently pass the current through the melt in the furnace, resulting in a decrease in measurement sensitivity.

  The present invention has been made in order to solve the above-mentioned problems, and a vertical furnace melt level measuring apparatus and a vertical furnace interior capable of measuring the level of the melt in the furnace with high accuracy. An object is to provide a melt level measurement method.

  In the vertical furnace melt level measuring apparatus according to the present invention, at least four or more electrodes are installed in the vertical direction on the side of the bottom of the vertical furnace, and the uppermost part and the lowermost part of the electrodes are arranged. Based on the measured potential difference or the electric resistance value calculated from the potential difference by supplying a current as the current supply electrode and measuring the potential difference using an electrode other than the current supply electrode as a potential difference detection electrode An in-furnace melt level measuring device for measuring the melt level in the furnace, using the conductive refractory at the site where the electrode of the vertical furnace is installed, and the conductive refractory on the inner surface of the furnace Is installed so as to be in contact with the molten metal and molten slag accumulated in the lower part of the furnace and in contact with a material lower than the electric conductivity of the conductive refractory except for the surface inside the furnace.

  In the vertical furnace melt level measuring apparatus according to the present invention, the electrical conductivity of the conductive refractory is larger than the electrical conductivity of the coke layer laminated above the upper surface of the molten slag in the vertical furnace. And it is a value smaller than the electric conductivity of the molten slag including coke of the molten slag layer.

  The vertical furnace melt level measuring device according to the present invention is provided with a temperature measuring device for measuring the temperature of the conductive refractory, and from the result of the temperature measuring device, the electric resistance value of the conductive refractory is calculated. The melt level is calculated by correcting the temperature change.

  In the method for measuring the melt level in the vertical furnace according to the present invention, at least four or more electrodes are installed in the vertical direction on the side of the bottom of the vertical furnace, and the uppermost part and the lowermost part of the electrodes are connected to each other. Based on the measured potential difference or the electric resistance value calculated from the potential difference by supplying a current as the current supply electrode and measuring the potential difference using an electrode other than the current supply electrode as a potential difference detection electrode A method for measuring an in-furnace melt level in a furnace, wherein a conductive refractory is used for a portion of the vertical furnace where the electrode is installed, and the conductive refractory is disposed on the inner surface of the furnace. Is installed so as to be in contact with the molten metal and the molten slag accumulated in the lower part of the furnace and in contact with a material lower than the electric conductivity of the conductive refractory except for the inner surface of the furnace.

  According to the present invention, a conductive refractory is used at a site where the electrode of the vertical furnace is installed, the conductive refractory is in contact with the molten metal and molten slag accumulated in the lower part of the furnace on the inner surface of the furnace, and The material other than the inner surface of the furnace is covered and covered with a material lower than the electrical conductivity of the conductive refractory, so that a material having a low electrical conductivity around the conductive refractory on which the electrode is installed ( (For example, a refractory with low electrical conductivity) is installed, so that the current applied to the conductive refractory does not sneak into the furnace body and can be efficiently flowed to the melt to perform highly sensitive measurement. It is possible. Further, by correcting a change in the electrical resistance of the conductive refractory due to the temperature, a more accurate measurement can be performed.

  An embodiment of the present invention will be described with reference to the drawings. In the present embodiment, description will be made assuming that the melt level is measured particularly in a small vertical furnace (such as a cupola).

  FIG. 1 is a schematic diagram of the in-furnace melt level measuring device according to the present embodiment, and FIG. 2 is an explanatory diagram when the conductive refractory of FIG. 1 is viewed from above. The conductive refractory 11 is exposed inside the furnace and is in direct contact with the melt 12 in the furnace during operation. Further, the bottom surface of the conductive refractory 11 is in contact with the hearth 13. In addition, four electrodes 21 to 24 are installed in the vertical direction outside the furnace of the conductive refractory 11, and the electrodes 21 and 24 installed at the bottom and the top are connected to a direct current via a cable 25. Connected to the source 26, current can be applied to the conductive refractory 11. In addition, two voltage detection electrodes 22 and 23 are installed between the current application electrodes 21 and 24, and the two voltage detection electrodes 22 and 23 are connected to a cable 27, respectively. The potential difference generated on the conductive refractory 11 by application is measured by the potential difference detection means 28. The measured potential difference is output from the potential difference detecting means 28, and is taken in and recorded in the PC 29, for example. As the melt level in the furnace changes, the current distribution of the applied current changes, so the potential difference also changes. At this time, since a large amount of current is distributed in the molten metal, the potential difference decreases as the melt level increases. The current supplied from the direct current source 26 to the current application electrodes 21 and 24 is measured by an ammeter 30 and output to the PC 29 for recording. Further, a thermometer 31 for measuring the temperature of the conductive refractory 11 is attached, and the output of the thermometer 31 is output to the PC 29 and used for correcting the electric resistance value of the conductive refractory 11.

  When the melt level increases, the potential difference between the voltage detection electrodes 22 and 23 or the electrical resistance calculated from the potential difference decreases. Further, in the shaft furnace, since the level can be estimated from the level of the tap water, the pressure in the furnace, and the density of each melt, it is possible to calibrate the relationship between the level and the voltage during steady operation.

  At this time, when the conductive refractory 11 is in direct contact with the refractory or material constituting the furnace body, and the refractory or material is smaller than the electrical resistance of the conductive refractory 11, the current constitutes the furnace body. As a result, the current does not flow to the molten metal or molten slag inside the furnace, and the change in potential difference due to the level change of the molten material is reduced, so that the measurement sensitivity is lowered. For this reason, in this embodiment, the right and left side surfaces, the top surface, the bottom surface, and the back surface of the conductive refractory 11 are insulated and refractory except for the periphery of the conductive refractory 11, that is, the surface in contact with the melt inside the furnace. (In other words, the conductive refractory 11 is inserted into the insulated refractory 14 on the bottom side of the furnace with the portion facing the furnace inside exposed in the furnace.) ing.). Thereby, it can suppress that an electric current flows into the refractory material and material which comprise a furnace body, and can implement | achieve highly sensitive measurement. At this time, the electrical conductivity of the insulating refractory 14 installed around the conductive refractory 11 is preferably 1/100 or less of the electrical conductivity of the conductive refractory 11 in order to suppress current inflow. .

Next, the electrical conductivity of the conductive refractory 11 will be described.
FIG. 3 is a characteristic diagram showing the relationship between the electrical conductivity and sensitivity of the conductive refractory 11. As indicated by the solid line in FIG. 3, the smaller the electrical conductivity of the conductive refractory 11, the easier the current flows in the furnace, and thus the sensitivity (S / N) is considered to be improved. That is, the upper limit of the electrical conductivity of the conductive refractory 11 may be considered as the upper limit of a value at which the applied current flows through the conductive refractory 11 to the molten slag in the furnace. Specifically, the electrical conductivity of the conductive refractory 11 may be lower than the electrical conductivity of the molten slag. Usually, it is known that the electric conductivity of molten slag is about 10 ³ (1 / Ωm). However, in the molten slag in the furnace, coke with high electrical conductivity (the electrical conductivity per coke grain is about 3 × 10 ⁴ (1 / Ωm)) is piled up. Therefore, it is considered that the apparent electrical conductivity of the molten slag layer is higher than 10 ³ (1 / Ωm), and the apparent electrical conductivity of the molten slag is estimated to be about 10 ⁴ (1 / Ωm). It is. For this reason, unless the electrical conductivity of the conductive refractory 11 is lower than the electrical conductivity of the molten slag, the current flows only to the conductive refractory (inside the brick) 11 and the sensitivity is also lowered. End up. Specifically, it may be smaller than 10 ⁴ (1 / Ωm).

On the other hand, the lower limit of the electrical conductivity of the conductive refractory 11 is considered as follows. As described above, although the sensitivity is improved as the electrical conductivity of the conductive refractory 11 is lowered, among the cokes stacked in the furnace, the melt in the furnace (molten steel, molten slag, etc.) The portion above the upper surface of the metal is in direct contact with the conductive refractory 11 so that a current flows directly through the coke. In this case, if an electric current flows in the upper part of the laminated coke, a measurement error of the melt level is caused. The conductivity may be larger than the apparent electrical conductivity of the laminated coke. The electric conductivity per coke grain is about 3 × 10 ⁴ (1 / Ωm), but when it is laminated and in contact with each other, a contact resistance is generated between the particles. For this reason, it is considered that the apparent electrical conductivity when coke is laminated is smaller than the electrical conductivity per grain and is about 10 ² (1 / Ωm). When the electrical conductivity of the conductive refractory 11 becomes 10 ² (1 / Ωm) or less, a current flows through the coke, and the measured value varies depending on the contact state between the coke and the conductive refractory 11. Conceivable. Therefore, the electrical conductivity of the conductive refractory 11 needs to be larger than 10 ² (1 / Ωm).

  By the way, the electrical resistance of the conductive refractory 11 generally has temperature dependency. When the melt starts to accumulate after the operation is started, the temperature of the conductive refractory 11 also rises. Further, when the melt in the furnace is discharged at the end of the operation, the temperature of the conductive refractory 11 decreases. Since it is considered that the electrical resistance also changes due to such a temperature change of the conductive refractory 11, in order to measure with higher sensitivity, the melt level measuring device while measuring the temperature of the conductive refractory 11 with the thermometer 31. Correct the measured value. As shown in the following equation (1), the electric resistivity ρ (T, T, T) at a certain time t during operation is based on the electric resistance value ρ0 (T0,0) with respect to the temperature T0 at the start of operation. The ratio t) is multiplied by the measured value Vdata to correct it.

  At this time, by selecting the conductive refractory 11 having a high thermal conductivity, the temperature change in the furnace is transmitted to the conductive refractory 11 in a short time, and the temperature distribution becomes steady. On the other hand, if the insulating refractory installed around the conductive refractory 11 is lower than the thermal conductivity of the conductive refractory 11, fluctuations in the conductive refractory temperature due to changes in the temperature outside the furnace are greatly suppressed. Therefore, the temperature distribution of the conductive refractory 11 does not change. With such a configuration, stable measurement is possible.

  In addition, when the conductive refractory 11 is integrated, stable measurement can be performed. This is because, when the divided and blocked conductive refractories 11 are stacked in the height direction, it is considered that the contact state between the conductive refractory blocks changes due to heat and the current distribution becomes unstable.

In the above description, an example in which two voltage detection electrodes 22 and 23 are provided has been described, but the number thereof may be any number of three or more.
Further, the current supplied to the conductive refractory 11 is not limited to direct current, and may be alternating current.

An embodiment of the present invention will be described. A present Example is an example of the melt level measuring apparatus in the shaft furnace for manufacturing cast iron. A manhole for furnace repair is installed on the side of the shaft furnace bottom, and it is closed with refractory during operation. A part of this refractory was used as a conductive refractory, and an insulating refractory was installed around it. The inside of the furnace of conductive refractory should be in direct contact with the melt. The conductive refractory used in this example had an electric conductivity of 2.9 × 10 ⁴ (1 / Ωm).

Figure 4 shows the data when 10 ^-8 (1 / Ωm) insulating brick is installed around the conductive refractory. The melt level obtained by the melt level measuring device in the operation of the shaft furnace The time transition of is shown. The melt level increases with the start of operation and becomes constant when the molten slag begins to flow out of the dredging. In addition, when the operation is completed, when the operation of discharging the melt is performed in order to discharge the melt in the furnace, the melting level decreases in a short time. From the characteristics of FIG. 4, it can be seen that the change in the melt level in the series of operations as described above can be captured with sufficient sensitivity. When the melt level rises, the output of the melt level measuring device decreases, so the vertical axis in FIG. Moreover, the same display is performed also about the data which shows transition of the melting level mentioned later.

On the other hand, FIG. 5 shows a level measurement result when the conductive refractory 11 is installed in direct contact with the furnace body without installing the insulating refractory 14. Originally, the sensitivity of the level change to be measured becomes very small, and it can be seen that sufficient sensitivity to the level change cannot be obtained.
Furthermore, the temperature transition of the conductive refractory 11 is shown in FIG. Moreover, the temperature dependence of the electrical resistance of this conductive refractory 11 is shown in FIG. When the data of FIG. 4 is corrected by the temperature of the insulating brick, it is as shown in FIG. Since there is no melt in the furnace immediately before the start of operation and immediately after the end of operation, the output of the melt level measuring device (measured potential difference or electrical resistance) should be the same value, but at the start of operation and at the end of operation. However, since the temperature in the furnace is different, the output in the data in FIG. 4 is different, but as a result of the temperature correction, the output value at the start of operation and the output value at the end of operation are the same. In addition, the temperature of the conductive refractory was measured by attaching a thermocouple directly to the conductive refractory, and sequentially corrected.

In this embodiment, a thermocouple is used to measure the temperature of the conductive refractory, but this thermocouple is installed between the voltage detection electrode 22 and the voltage detection electrode 23. The position where the thermocouple is installed is a height at which the melt does not reach during steady operation, so that the change in electrical resistance of the conductive refractory 11 can be directly measured. The temperature change of the electrical resistance can be corrected.
Further, in this example, an insulating refractory having a low thermal conductivity was installed outside the furnace to cut off from the outside air. When the measurement is performed in such a configuration, it becomes easy to keep the temperature distribution of the conductive refractory constant, and temperature correction can be easily performed.

1 is a schematic diagram of a vertical furnace melting level measuring apparatus according to an embodiment of the present invention. It is explanatory drawing which showed the structure of the conductive refractory installed in the side part of the bottom part in a furnace, and the surrounding insulation refractory. It is the characteristic view which showed the relationship between a conductive refractory and a sensitivity (S / N). In the Example of this invention, it is a graph which shows the time transition of the output of a melt level measuring apparatus. It is a graph which shows the time transition of the output of the melt level measuring device shown as a comparative example (when not implementing this invention). It is a graph which shows the temperature change during operation of the conductive refractory used for the example of the present invention. It is a graph which shows the relationship between the temperature of an electrically conductive refractory used for the Example of this invention, and an electrical resistance. It is a graph which shows the result of having performed the temperature correction of FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 Conductive refractory, 12 Melt, 13 Hearth, 14 Insulation refractory, 21, 24 Current application electrode, 22, 23 Voltage detection electrode, 25, 27 Cable, 26 DC current source, 28 Potential difference detection means, 29 PC, 30 Ammeter 31 Thermometer.

Claims (4)

At least four or more electrodes are installed in the vertical direction on the side of the bottom of the vertical furnace, and current is supplied using the uppermost and lowermost electrodes as current supply electrodes. Other than the current supply electrodes An in-furnace melt level measuring device for measuring the melt level in the furnace based on the measured potential difference or the electric resistance value calculated from the potential difference by measuring the potential difference using the electrode of There,
Using a conductive refractory at the site where the electrode of the vertical furnace is installed,
The conductive refractory is covered on the inner surface of the furnace in contact with the molten metal and molten slag accumulated in the lower part of the furnace, and on the surface other than the inner surface of the furnace, in contact with a material lower than the electric conductivity of the conductive refractory A vertical furnace melt level measuring device, characterized in that it is installed as described above.   The electric conductivity of the conductive refractory is larger than the electric conductivity of the coke layer laminated above the upper surface of the molten slag in the vertical furnace, and the electric conductivity of the molten slag including the coke of the molten slag layer. The apparatus for measuring a melt level in a vertical furnace according to claim 1, characterized in that the value is smaller than the rate.   Installing a temperature measuring device for measuring the temperature of the conductive refractory, and calculating a melt level value by correcting a temperature change of the electric resistance value of the conductive refractory from the result of the temperature measuring device; The vertical furnace melt level measuring device according to claim 1 or 2, characterized in that At least four or more electrodes are installed in the vertical direction on the side of the bottom of the vertical furnace, and current is supplied using the uppermost and lowermost electrodes as current supply electrodes. Other than the current supply electrodes In-furnace melt level measurement method for measuring the melt level in the furnace based on the measured potential difference or the value of electric resistance calculated from the potential difference There,
Using a conductive refractory for the part of the vertical furnace where the electrodes are installed,
The conductive refractory is covered on the inner surface of the furnace in contact with the molten metal and molten slag accumulated in the lower part of the furnace, and on the surface other than the inner surface of the furnace, in contact with a material lower than the electric conductivity of the conductive refractory A method for measuring the melt level in a vertical furnace characterized by being installed as described above.

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