JP7277744B2 - Hot Diagnosis Method for Refractories - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for diagnosing a refractory while it is hot, and more particularly to a technique for diagnosing the remaining dimension of a refractory lined inside a container at a high temperature.

In steel smelting vessels, the inner surface of the steel shell is lined with refractories that can withstand high temperatures. Decreasing. If the operation is continued without noticing abnormal wear of the refractory or reduction of the remaining size, the refractory may completely disappear, the steel shell may be melted and ruptured, and the molten metal and slag contained in it may leak out. Therefore, it is necessary to repair or replace refractories at appropriate timing.

In particular, the vacuum degassing equipment used in iron and steel refining is divided into an upper tank, a lower tank, and a immersion pipe. Of these, the refractory lining the lower tank, in which the molten steel is refluxed, is particularly severely damaged. However, since the vacuum degassing apparatus is a closed container, there are few locations where the refractory can be visually inspected under high temperatures immediately after treatment, and it can be said that hot diagnosis of the refractory is particularly difficult.

To solve the above problems, the following methods have been proposed for diagnosing the remaining dimensions and conditions of refractories. For example, Patent Document 1 and Patent Document 2 propose a method of measuring the residual size of refractories in a refining vessel using a fixed profile meter. There is a problem that cannot be measured when In the case of equipment with small openings such as vacuum degassing equipment, blind spots are likely to occur due to adhesion of bare metal inside the tank. It is difficult.

Patent Documents 3 and 4 propose a method of inspecting by inserting a camera or a laser profile meter from an immersion pipe at the bottom of the vacuum degassing equipment. However, in this method, since the measuring equipment is inserted inside the lower tank in a high-temperature atmosphere, there is a problem that the life of the measuring equipment is shortened due to the heat load. In addition, since the laser profile meter is inserted into the tank by combining a number of driving devices, there is a problem that the position of the laser profile meter itself has a large error, and the accuracy of the measured data is low. Furthermore, there is also the problem that the frequency of inspection is limited because it takes time to move the measuring equipment and the vacuum degassing tank itself.

On the other hand, Patent Literature 5 and Patent Literature 6 propose a method of measuring the internal temperature of the refractory and the temperature of the shell to indirectly grasp the remaining size of the refractory in the tank. However, this method has the problem that the accuracy of the predicted remaining dimension is low because the temperature varies depending on the number of times the lower tank is used and the operating conditions such as treatment time and treatment interval.

JP-A-60-138407 JP 2007-291435 A JP 2006-299314 A JP-A-1-145514 JP 2010-281515 A JP 2013-147714 A

The present invention has been made in view of the above problems. It is an object of the present invention to provide a hot diagnostic method for refractories that can accurately grasp the

The gist of the present invention is the following configuration.
(1) Using one or more laser profile meters installed outside the container lined with the refractory on the inner surface of the steel shell, irradiating the container with a laser to measure the profile of the refractory, calculating the remaining dimension A of the refractory based on the profile; measuring the surface temperature of at least the steel shell from the outside of the container at the same time as measuring the profile; and calculating a remaining dimension B, wherein if the profile is measurable, the remaining dimension A is the remaining dimension of the refractory, and both the profile and the surface temperature are measurable. In this case, the difference between the remaining dimension A and the remaining dimension B calculated based on each is recorded as a correction value, and if the profile is not measurable and the surface temperature is measurable, A method for hot diagnostics of a refractory, wherein the residual dimension of the refractory is calculated by correcting the residual dimension B using the most recent correction value.

(2) The method for hot diagnosis of a refractory according to (1), wherein in the step of calculating the remaining dimension B, the surface temperature of the refractory is measured in addition to the surface temperature of the steel shell. .

(3) The vessel is a vacuum degassing device used in steel refining, and the laser profile meter is arranged above the furnace outside the vacuum degassing device, and the inside of the vacuum degassing device is measured from the top opening of the vacuum degassing device. The method for hot diagnosis of a refractory according to (1) or (2), characterized in that the laser is directed toward.

According to the present invention, by installing the profile meter outside the furnace, the heat load on the profile meter is reduced and the measurement accuracy is improved. Furthermore, by measuring the shell temperature at the same time as the profile measurement, and recording the difference between the accurate remaining dimension from the profile and the estimated remaining dimension from the shell temperature as a correction value, blind spots due to adhesion of bare metal etc. can be recorded. Even if the profile cannot be measured due to the deformation, the correct residual dimension can be grasped by correcting the predicted residual dimension based on the steel shell temperature.

It is a figure which shows the structure of the lower tank refractory of RH equipment. It is a figure which shows the RH equipment external appearance and an example of a profile meter installation. It is a graph which shows the frequency|count of use of RH equipment, and a lower tank refractory residual dimension transition. It is a graph which shows the lower tank refractory residual dimension measurement example in a prior art.

FIG. 1 is a view showing the wall structure (RH lower tank side wall) of a container to which the hot diagnosis method for refractories according to the embodiment of the present invention is applied. In the illustrated example, the container 1 has a wall structure in which the inner surface of the steel shell 2 is lined with a refractory 4 via a back heat insulating material 3, and the refractory 4 is a permanent refractory 4A on the steel shell side and an inner and wear refractories 4B.

In this embodiment, one or more laser profile meters installed outside the container 1 are used to measure the residual dimension (remaining dimension A) of the wear refractory. A laser profile meter measures the profile of the wear refractory and the profile of at least a portion of the steel skin. If the positional relationship between the shell shape and the wear refractory is known from a design drawing or the like, the residual dimension of the wear refractory can be calculated from the above-described profile measurement results with the shell profile as a reference. Here, the laser profile meter is installed at a position where it is possible to observe the portion where the wear of the refractory is severe and the residual dimension needs to be measured. Even if it is difficult to fix the device in such a position due to equipment constraints, the travel time is much shorter than when a laser profilometer is inserted into the container, for example. In addition, since the residual dimension value of the wear refractory measured by the laser profile meter is calculated based on the steel shell profile each time, it can be measured with good accuracy even if the laser profile meter is not fixedly installed.

On the other hand, in the prediction of remaining dimension by temperature measurement, the temperature of the steel shell or the back of the refractory is measured using a radiation thermometer, thermocouple, optical fiber, etc., and the temperature inside the tank and the physical properties of the refractory are used to The residual dimension of the wear refractory is calculated using Equation 1 representing the heat flux Q of the multi-layer flat plate below.

Here, _t1 is the temperature of the working surface of the wear refractory [K], _t2 is the temperature of the back of the wear refractory and the working surface of the permanent refractory [K], and _t3 is the temperature of the back of the permanent refractory and the back insulation working surface [K]. K], t ₄ is the temperature of the back of the back insulation material and the steel shell [K], t ₅ is the temperature of the atmosphere [K], h _a is the heat transfer coefficient between the steel shell and the atmosphere [W / mK ² ], λ ₁ is Thermal conductivity of wear refractory [W/mK], λ ₂ is thermal conductivity of permanent refractory [W/mK], λ ₃ is thermal conductivity of back insulation [W/mK], l ₁ is wear refractory The thickness of the object [mm], _l2 is the thickness of the permanent refractory [mm], and _l3 is the thickness of the back refractory [mm].

For temperature measurement, for example, referring to Patent Document 5 (Japanese Patent Application Laid-Open No. 2010-281515) and Patent Document 6 (Japanese Patent Application Laid-Open No. 2013-147714), in order to suppress temperature variations due to the influence of cooling, etc. , the measurement is performed after a certain amount of time has passed. In addition, if there is a difference between the residual dimension of the wear refractory obtained by profile measurement and the residual dimension of the wear refractory calculated from temperature measurement (predicted residual dimension), the difference between the two residual dimensions is recorded as a correction value. . The correction value is recorded each time the profile is measured. For example, if the profile measurement is difficult due to the influence of bare metal adhesion, the correction value calculated at the time of the most recent profile measurement is added or subtracted to the predicted residual dimension to obtain the predicted residual dimension. It is possible to improve the accuracy of

The results of applying the present invention to a vacuum degassing facility (RH) will be described below. The lower tank 8 of the RH equipment according to this embodiment shown in FIG. 2 has a wall structure composed of the steel shell 2, the heat insulating material 3, the permanent refractory 4A and the wear refractory 4B as shown in FIG. In the RH facility, one molten steel ladle is subjected to refining for 20 to 40 minutes, which is 1 ch (charge).

In the RH equipment as described above, as shown in FIG. The refractory profile was measured to determine the residual dimension. However, as shown in FIG. 2, if the base metal 10 adheres to the upper tank 7, the refractory material in the lower tank 8 is positioned in a blind spot, making profile measurement impossible.

On the other hand, as shown in FIG. 2, at the same time as the profile measurement, the temperature of the iron shell in the lower tank 8 and the temperature of the working surface of the wear refractory were measured using a radiation thermometer 12 (AD5616 manufactured by A&D). Minutes later, ie, at the same timing as the profile measurement, each charge was performed. Regarding the temperature measurement part, since the part located at the level of the molten steel recirculation in the third to fifth stages of the side wall refractory of the lower tank 8 has the smallest remaining refractory, was measured. In addition, the operating surface temperature of the wear refractory was measured by using a radiation thermometer on the side wall refractory within a range visible from the immersion tube 9 and substituted into Equation (1). If it is not possible to measure the temperature of the working surface of the refractory, by unifying the measurement timing and applying the result of the most recent measurement to the temperature of the working surface, it is possible to measure the refractory residue while maintaining accuracy only by measuring the temperature of the steel shell. dimensions can be calculated. Measured values for thermal conductivity of wear refractory, permanent refractory, and heat insulating material (wear refractory: 12 [W/mK] permanent refractory: 1.2 [M/mK] heat insulating material: 0.03 [W/ mK]) was substituted, and the thickness of the permanent refractory and insulation was assumed unchanged from the time of construction. For the atmospheric temperature, the actual measurement value of the outside air temperature was substituted, and the remaining size of the wear was calculated using Equation 1. Further, when the profile measurement was performed every 10 charges, the difference between the calculated predicted residual dimension and the profile measurement result was recorded as a correction value.

Figure 3 shows changes in the number of times of use and remaining refractory size. Let residual dimension A be the profile measurement dimension, and residual dimension B be the predicted residual dimension from the temperature measurement. The remaining dimensions were indexed with 100 as the initial value of the profile measurement dimensions. Both the remaining dimension A and the remaining dimension B show a situation in which the remaining dimension of the refractory decreases as the number of uses increases. By installing the laser profile meter 11 outside the furnace as described above, the measurement time can be shortened, and measurement can be performed at much shorter intervals than before without production loss. However, in the measurements of 90ch, 100ch, 190ch, 200ch, 310ch, 320ch, and 390ch, as shown in FIG. (a value greatly deviating from the previous measured value), and the profile could not be measured.

On the other hand, the residual dimension B calculated from the temperature measurement result can be calculated even if the profile measurement cannot be performed as described above, but the deviation is large compared to the residual dimension A calculated from the profile measurement. This is because the remaining dimension B is calculated from the steady-state heat transfer calculation, but the physical property values of the refractory at the time of temperature measurement do not necessarily match the actual values measured in advance, and the physical property values themselves have been repeatedly used. This is thought to be due to the fact that it changes each time it receives a heat load.

Therefore, in this embodiment, as described above, the residual dimension A obtained by profile measurement is used as a basic control value for the residual dimension of the lining refractory, while both the residual dimension A obtained by profile measurement and the residual dimension B obtained by temperature measurement are used. is obtained, the difference (residual dimension A - residual dimension B) is recorded as a correction value, and if the profile is not measurable and therefore residual dimension A cannot be obtained, residual dimension B is the most recent Correction is performed using the correction value, that is, (remaining size B + most recent correction value) is set as the control value for the remaining size of the refractory lining. Specifically, in FIG. 3, profile measurement was possible with 80 ch, for example, and the correction value represented by the index was 11. In the next 90ch, profile measurement was not possible due to metal adhesion, but temperature measurement could be performed without problems, so (90ch remaining dimension A) = (80ch remaining dimension B) + (80ch correction value 11 ).

If consecutive profile measurements are not possible, the most recent or previously obtained correction value is continued to be used. For example, in FIG. 3, the remaining dimension A of 100ch could not be measured following 90ch, but the temperature measurement could be performed without any problem, so (100ch remaining dimension A) = (90ch remaining dimension B) + (80ch remaining dimension B) Correction value 11). If the profile measurement becomes possible by removing the bare metal adhering to the inside of the tank (for example, 110ch), the residual dimension A obtained by the profile measurement is used as the residual dimension of the lining refractory without performing the above correction. In addition to setting it as a control value, the difference between the remaining dimension A and the remaining dimension B obtained by temperature measurement (remaining dimension A - remaining dimension B) is recorded as a new correction value.

As a comparative example, the residual dimension of the refractory was measured by a conventional method of inserting a profile meter from a dip tube in the same RH facility as that of the example, and the results were compared with the results of the example. FIG. 4 shows changes in the number of times of use and remaining dimensions of the refractory in the comparative example. In the case of the comparative example, it takes time to move the profile meter directly under the tank for measurement, and the operation is interrupted during this time. Measurements can be performed less frequently than (every 10 charges). In addition, in the process of inserting and measuring the profile meter into the tank using many driving devices, the positional accuracy of the profile meter is degraded, and as a result, the accuracy of the measurement results is also degraded.

Table 1 shows the result of verifying the remaining dimension accuracy for a plurality of lower tanks in the examples and comparative examples as described above. In each example, when calculating the error between the hot measurement value after the treatment and the actual measurement value measured in the furnace after that, the error from the actual measurement value is 25% or more in the comparative example (conventional technology). While there is about 40%, in the present invention, it is suppressed to 4% or less, and accuracy is greatly improved.

By applying the present invention, the residual size of the refractory in the tank was accurately grasped, and the trouble of perforation of the refractory in the lower tank was reduced from 4 times/year to 0 times/year. In addition, the tank can be replaced after the refractories have been safely used up, and the cost of the refractories can be reduced.

DESCRIPTION OF SYMBOLS 1... Container, 2... Steel skin, 3... Back heat insulating material, 4A... Permanent refractory material, 4B... Wear refractory material, 5... OB lance insertion hole, 6... Canopy, 7... Upper tank, 8... Lower tank, 9 ... immersion tube, 10 ... base metal, 11 ... laser profile meter, 12 ... radiation thermometer.

Claims (3)

Using one or more laser profile meters installed on the outside of a container lined with a refractory on the inner surface of a steel shell, a laser is irradiated into the container to measure the profile of the refractory, and the profile is measured. a step of calculating the remaining dimension A of the refractory based on
At the same time as measuring the profile, measuring the surface temperature of at least the steel shell from the outside of the container, and calculating the residual dimension B of the refractory based on the surface temperature,
If the profile is measurable, the remaining dimension A is the remaining dimension of the refractory;
When both the profile and the surface temperature are measurable, the difference between the residual dimension A and the residual dimension B calculated based on each is recorded as a correction value,
When the profile is not measurable and the surface temperature is measurable, the remaining dimension of the refractory is calculated by correcting the remaining dimension B using the most recent correction value. , Hot Diagnosis Method for Refractories. The method for hot diagnosis of a refractory according to claim 1, wherein in the step of calculating the remaining dimension B, the surface temperature of the refractory is measured in addition to the surface temperature of the steel shell. The vessel is a vacuum degassing device used in steel smelting,
The laser profile meter is installed above the furnace outside the vacuum degassing device and irradiates a laser from a furnace top opening toward the inside of the vacuum degassing device. 2. The hot diagnosis method for the refractory according to 2.

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