JPH11326061A - Method and apparatus for measuring temperature of molten metal in furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and a device capable of measuring the accurate temperature of a molten bath in a furnace directly and instantaneously. SOLUTION: A double-tube tuyere 3 opened in a molten steel 2 is provided on the side wall of a blast furnace 1. At the time of a normal blast, the mixed gas of oxygen gas and nitrogen gas (inert gas) is introduced in an inner tube 3a, and the nitrogen gas for cooling the tip of the tuyere 3 is introduced in an outer tube 3b to maintain the blowing tuyere 3. At the time of temperature measurement, only the nitrogen gas (inert gas) is introduced in the inner tube 3a, the tip section of the tuyere 3 is photographed by a CCD camera 2 before a mushroom is generated from immediately after the introduced gas is switched (blast stop), and the temperature corresponding to the highest luminance in the obtained image is calculated by a temperature calculator 13 as the temperature of the molten steel 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for measuring the temperature of molten metal in a furnace through a tuyere of a metal smelting furnace such as a steelmaking converter, a smelting reduction furnace, a scrap melting furnace, and an electric furnace.

[0002]

2. Description of the Related Art For example, during oxygen gas blowing operation for about 20 minutes per charge in a steelmaking converter, a device called "sublance" for measuring the temperature of molten steel and collecting an analytical sample is generally used. It is a target. However, this apparatus is originally intended for non-continuous use, and furthermore, a waiting time of at least about 5 minutes is required to obtain an analysis result of a molten metal component based on a collected sample. is there. Therefore, there has been no other method but to predict the target end point based on only the temperature measurement result and the carbon content at one point during blowing, and to perform steelmaking control. Also, such "sublance" devices are bulky and require tall factory houses and significant expense to install.

[0003] The lack of continuous information on the temperature of molten steel, which dynamically changes during a short gas blowing operation, further increases the accuracy of the end point temperature at the end of the gas blowing operation and high-speed continuous casting. This is a major obstacle to achieving high efficiency by matching with the steel, and the development of a device that can continuously measure the temperature of molten steel is desired.

As a continuous temperature measuring method disclosed in Japanese Patent Application Laid-Open No. 60-61633, a method using an optical fiber provided in a tuyere-shaped thin tube has been attempted.
As such a temperature measuring means, an optical measuring device is usually applied. Therefore, in order to fully demonstrate the functions of these measuring devices, the front surface of the tuyere-shaped tubule inside the furnace is kept healthy so that the radiated light from the molten steel always reaches the detecting side of the measuring device. Must. Therefore, it is necessary to avoid a state in which the front surface of the tuyere-shaped thin tube is damaged.

As such tuyere-shaped thin tubes, single tubes of various materials or 2 tuyere originally developed as tuyere for refining are used.
A heavy pipe tuyere is used. However, the tuyere for this purpose is
In any case, since the cooling gas for protecting the tuyere including the detecting part of the measuring device from the heat of the molten steel is mainly flowed, solid matter (so-called mushroom) is formed from the molten steel on the front of the tuyere. Generated and winding gas passages,
Porous gas passages or complete blockage are likely to occur.
In this case, a so-called “field of sight loss” occurs, causing a decrease in measurement accuracy. In a severe case, information cannot be obtained at all from the molten steel side.

[0006]

In a conventional method of measuring the temperature of a molten metal by a normal non-contact thermometer provided in the tuyere, the shape change of the mushroom naturally generated at the tip of the front of the tuyere is limited. Since measurement accuracy is greatly affected, stable and accurate measurement is not possible. On the other hand, in order to form a mushroom having no lack of visual field, only gas blowing conditions in a direction in which the mushroom is not formed can be selected, so that the tuyere and a refractory around the tuyere are worn out. Therefore, in order to prevent the formation of mushrooms and to prevent the refractory from being worn at the tuyere, the flow rates of the oxygen gas and the cooling gas must be constantly varied, which is troublesome. .

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method and an apparatus for measuring the temperature of molten metal in a furnace, which can accurately measure the temperature of molten metal even at a tuyere having a lack of visual field. Aim.

Another object of the present invention is to ensure that even when the measurement field of view completely disappears, the measurement field of view can be secured again, for example, in a furnace in which the temperature that changes subtly at the end of blowing of a steelmaking converter can be accurately measured. An object of the present invention is to provide a method and an apparatus for measuring the temperature of a molten metal.

Still another object of the present invention is to provide a method and an apparatus for measuring the temperature of a molten metal in a furnace which can accurately measure the temperature of the molten metal in the furnace and can contribute to the improvement of the accuracy of the end point temperature. .

[0010]

According to a first aspect of the present invention, there is provided a method for measuring a temperature of a molten metal in a furnace, wherein the temperature of the molten metal in the furnace is measured. Using a double tube tuyere, introducing an inert gas into one of the tubes of the double tube tuyere or a mixed gas of an inert gas and an oxygen gas having a concentration ratio to the inert gas of a predetermined value or less. At the same time, a tuyere cooling gas is introduced into the other tube of the double tube tuyere, an image of the melt side of the double tube tuyere is acquired, and the temperature of the molten metal is determined based on the acquired image. Is measured.

According to a second aspect of the present invention, there is provided a method for measuring a temperature of molten metal in a furnace according to the first aspect, wherein the oxygen is blown into the one pipe so that an inert gas and a concentration ratio of the inert gas to the inert gas are not less than a predetermined value. A gas mixture with a gas is introduced, and a gas for tuyere cooling is introduced into the other pipe.

According to a third aspect of the present invention, in the method for measuring the temperature of the molten metal in the furnace according to the first or second aspect, the temperature according to the highest luminance in the acquired image is measured as the temperature of the molten metal. I do.

According to a fourth aspect of the present invention, there is provided an apparatus for measuring the temperature of a molten metal in a furnace, which is provided in the refining furnace so as to open into the molten metal, A double tube tuyere having a second tube, and the first tube
Whether an inert gas is introduced or a mixed gas of an inert gas and an oxygen gas whose concentration ratio to the inert gas is equal to or less than a predetermined value, and an inert gas is supplied to the first pipe. Control means for switching and controlling a state of introducing a mixed gas of oxygen gas having a concentration ratio with respect to the inert gas equal to or more than a predetermined value; and means for introducing a tuyere cooling gas to the second pipe. A photographing means for photographing an image of the molten metal side of the double-tube tuyere, and a calculating means for calculating, as the temperature of the molten metal, a temperature according to a maximum luminance in an image photographed by the photographing means. I do.

According to a fifth aspect of the present invention, in the apparatus for measuring the temperature of the molten metal in the furnace, the photographing means is a CCD camera, and the calculating means is configured to calculate the brightness and the brightness in an image of the black body furnace photographed by the CCD camera. It is characterized by having information indicating a relationship with temperature.

At the tip of the tuyere during oxygen blowing, the temperature is high due to the oxidation reaction, so it is impossible to directly measure the temperature of the molten metal. However, attention was paid to the fact that no mushroom was present. Immediately after oxygen blowing is stopped, there is no mushroom, and as the tuyere tip cools, mushrooms are generated and the field of view narrows. It is.
Therefore, as the field of view gradually narrows, if the temperature inside the furnace is measured using a two-dimensional temperature distribution measuring instrument and the highest temperature in the obtained temperature distribution is adopted, the temperature of the mushroom will be the temperature of the molten metal. Therefore, the maximum temperature is the temperature of the molten metal.

Based on such knowledge, the present invention provides:
A double tube tuyere opening into the molten metal is provided on the side wall or bottom of a metal smelting furnace such as a smelting furnace, and usually, oxygen gas is mixed into one of the tubes (inner tube) and the other tube (outer tube) is opened. A gas for cooling the tuyere tip is introduced into the tube (tube) to maintain the blowing tuyere, and at the time of temperature measurement, an inert gas is introduced into one of the tubes (inner tube), and the mushroom is formed immediately after the introduction of the inert gas. Until the tuyere is generated, the tuyere tip is observed with a two-dimensional temperature distribution measuring instrument, and the highest temperature in the obtained two-dimensional temperature distribution is measured as the molten metal temperature. The gas introduced into one pipe (inner pipe) at the time of temperature measurement may be a mixed gas of an inert gas and a low-concentration oxygen gas narrowed to a concentration ratio that does not affect the measurement.

Further, the CC of visible light whose temperature has been calibrated in advance is
When the D camera is used as a temperature distribution measuring device, it is less susceptible to the emissivity of the molten metal and has higher measurement accuracy than a temperature distribution measuring device generally widely used in the infrared region.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the drawings showing the embodiments.

FIG. 1 is a schematic diagram showing an embodiment of a method for measuring a molten metal temperature according to the present invention, in other words, a configuration of a device for measuring a molten metal temperature according to the present invention. In the figure, reference numeral 1 denotes a molten steel furnace to which the temperature measurement according to the present invention is applied. The molten steel furnace 1 has a furnace wall 1a made of a refractory brick and a steel shell 1b outside the furnace wall 1a, and accommodates the molten steel 2 therein.

A furnace wall 1a and a steel shell 1
b, a double tube tuyere 3 is provided. The inner tube 3a of the double tube tuyere 3 is made of stainless steel having an inner diameter of 8 mm, the outer tube 3b of the double tube tuyere 3 is made of stainless steel having an inner diameter of 12 mm, and the inner tube 3a and the outer tube 3b are made of stainless steel. Each length is 700 mm.

The inner pipe 3a is connected to an oxygen gas source 5 and a nitrogen gas source 6 via a switch 4 for switching the type of the introduced gas. A gas controller 7 for controlling the flow rate of the oxygen gas to be introduced is provided between the switch 4 and the oxygen gas source 5, and similarly, the gas is introduced between the switch 4 and the nitrogen gas source 6. A gas controller 8 for controlling the flow rate of the nitrogen gas is provided. By the switching operation of the switch 4, the gas introduced into the inner pipe 3a can be changed to only a mixed gas of oxygen gas and nitrogen gas and nitrogen gas. On the other hand, the outer pipe 3b is connected to a nitrogen gas source 10 via a gas controller 9 for controlling a flow rate of a gas to be introduced. With this configuration, a mixed gas of oxygen gas and nitrogen gas or only nitrogen gas is introduced into the inner tube 3a, and nitrogen gas for tuyere cooling is always introduced into the outer tube 3b.

An observation box 11 having an observation window 11a for photographing at the open end outside the furnace is connected to the inner tube 3a. A monochrome CCD camera 12 as a two-dimensional temperature distribution measuring device is provided in the observation box 11. CC
The D camera 12 captures light emitted from the molten steel 2 in the molten steel furnace 1 at the tip of the double tube tuyere 3 through the double tube tuyere 3 (inner tube 3a) and the observation window 10a. 2 of molten steel 2
A dimensional image is obtained, and the obtained image is output to the temperature calculator 13.

The temperature calculator 13 has a brightness / temperature conversion table showing the relationship between brightness and temperature in an image obtained by photographing the inside of the black body furnace with the CCD camera 12. Then, the temperature calculator 13 detects the maximum luminance in the input image, calculates a temperature corresponding to the detected maximum luminance with reference to the luminance / temperature conversion table, and displays the calculation result on the display 14. Output to The display 14 displays the calculated temperature.

Next, the operation will be described. Normally, when the oxygen blowing is performed to cause the decarbonization reaction, the switch 4 is switched to the side communicating with the oxygen gas source 5 to introduce the mixed gas of the oxygen gas and the nitrogen gas into the inner pipe 3a and the outer pipe 3
A nitrogen gas for tuyere cooling is introduced into b, and gas is blown. At this time, the gas controllers 7, 8, 9
The flow rate of oxygen gas to the inner pipe 3a is controlled to 30 Nm ³ / H, the flow rate of nitrogen gas is controlled to 30 Nm ³ / H, and the flow rate of nitrogen gas to the outer pipe 3b is controlled to 15 Nm ³ / H. During the oxygen blowing, the temperature of the molten steel 2 cannot be directly measured because the tip of the double tube tuyere 3 is in a high temperature state due to the oxidation reaction.

After stopping the oxygen blowing, the molten steel 2
Is carried out. Immediately after the oxygen blowing is stopped, no mushroom is generated at the tip of the double tube tuyere 3. First, the switch 4 is switched to the side not communicating with the oxygen gas source 5 so that only the nitrogen gas can be introduced into the inner pipe 3a. Then, while introducing nitrogen gas into the inner tube 3a,
A nitrogen gas for tuyere cooling is introduced into the outer tube 3b. On this occasion,
The gas control device 8,9, for example, the flow rate of the nitrogen gas into the inner tube 3a is 30 Nm ³ / H, the flow rate of the nitrogen gas into the outer tube 3b are respectively controlled to 15 Nm ³ / H.

The light radiated from the molten steel 2 at the tip of the double tube tuyere 3 is reflected by the double tube tuyere 3 (inner tube 3a) and the observation window 1.
The light enters the CCD camera 12 provided in the observation box 11 via 1a, and the molten steel 2 is imaged by the CCD camera 12. The obtained two-dimensional image data is output to the temperature calculator 13 as digital data.

The temperature calculator 13 detects the maximum luminance level in the input image data, and refers to a luminance / temperature conversion table prepared in advance to obtain the maximum luminance level.
A temperature corresponding to the detected luminance level is calculated. Since the temperature of the mushroom is lower than the temperature of molten steel 2,
The highest temperature in the obtained two-dimensional temperature distribution corresponds to the temperature of the molten steel 2.

The temperature calculated in this way is output to the display 14, and the result is displayed on the display 14.
As described above, the temperature of the molten steel 2 can be measured directly and instantaneously.

In the above example, the double tube tuyere 3 is provided on the side wall of the molten steel furnace 1, but the double tube tuyere 3 may be formed on the bottom wall of the molten steel furnace 1.

In the above example, the inner pipe 3a
Although nitrogen gas is introduced into the inner tube 3a, another inert gas such as Ar gas which does not react with the molten steel 2 may be introduced into the inner tube 3a. When reducing the concentration of oxygen gas to a concentration ratio that does not affect temperature measurement during temperature measurement, a mixed gas of an inert gas such as nitrogen gas and oxygen gas is introduced into the inner tube 3a. However, it is possible to measure the temperature of molten steel 2.

Hereinafter, the measurement results of the present invention will be described. FIG. 2 is a graph showing changes in measured values when the temperature of molten steel 2 is continuously measured in the present invention. FIG.
Is a graph showing a change in measured value when the temperature of the molten steel 2 is continuously measured in a conventional example as a comparative example (temperature measurement by a normal monochromatic radiation thermometer provided in a tuyere).

In the measuring method according to the present invention, the temperature is higher than 2000 ° C. due to the oxidation reaction during the oxygen blowing, and the measured value does not reflect the temperature of the molten steel 2. During the mushroom generation period, a measurement value consistent with the sampling temperature measurement value is obtained. When the same temperature measurement test was performed 20 times, it was found that the error from the sampling temperature measurement value was within ± 10 ° C.

On the other hand, in the measuring method according to the conventional example, the measured value decreases after stopping the oxygen blowing, and no measured value reflecting the temperature of the molten steel 2 is obtained. This is because mushrooms grow from the periphery of the tuyere with the cooling of the tuyere tip, causing a lack of visual field, and only a part of the radiation from the molten steel 2 reaches the monochromatic radiation thermometer. Responsible.

Further, the relationship between the measured temperature value according to the present invention and the actual sampling measured temperature value was examined using a certain test furnace. The result is shown in FIG. Even when compared with the sampling temperature measured experimentally immediately before the stop of the blowing, the error remains within ± 10 ° C. and the variation is small. This indicates that the method according to the present invention can measure the temperature without being affected by the change in the visual field area of the emitted light from the molten steel 2.

[0035]

As described above, according to the present invention, the accurate temperature of the molten metal in the furnace can be measured directly and instantaneously. Therefore, the present invention has excellent effects, for example, it is possible to stably perform the blowing and improve the hit ratio of the end point temperature, which can contribute to the reduction of the refining cost.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an embodiment of a molten metal temperature measuring method according to the present invention (a configuration of a molten metal temperature measuring device according to the present invention).

FIG. 2 is a graph showing a change in measured temperature value of molten steel continuously measured in the present invention.

FIG. 3 is a graph showing a change in temperature measured value of molten steel continuously measured in a conventional example.

FIG. 4 is a graph showing measurement accuracy of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Molten steel furnace 2 Molten steel 3 Double tube tuyere 3a Inner tube 3b Outer tube 4 Switching device 5 Oxygen gas source 6,10 Nitrogen gas source 12 CCD camera 13 Temperature calculator 14 Display

Claims (5)

[Claims] 1. A method for measuring the temperature of a molten metal in a refining furnace, wherein a double-tube tuyere provided in the refining furnace so as to be opened in the molten metal is used. Introducing an inert gas or introducing a mixed gas of an inert gas and an oxygen gas having a concentration ratio of the inert gas to a predetermined value or less, and cooling the tuyere to the other tube of the double tube tuyere. A temperature of the molten metal in the furnace, wherein a temperature of the molten metal is measured based on the acquired image. 2. During oxygen blowing, a mixed gas of an inert gas and an oxygen gas having a concentration ratio of the inert gas to a predetermined value or more is introduced into the one pipe, and a tuyere is introduced into the other pipe. The method for measuring the temperature of molten metal in a furnace according to claim 1, wherein a gas for cooling is introduced. 3. The method for measuring the temperature of a molten metal in a furnace according to claim 1, wherein a temperature corresponding to the highest luminance in the acquired image is measured as the temperature of the molten metal. 4. An apparatus for measuring the temperature of a molten metal in a refining furnace, wherein the double-hole tuyere is provided in the refining furnace so as to be open in the molten metal, and has a first pipe and a second pipe. A state in which an inert gas is introduced into the first pipe, or a mixed gas of an inert gas and an oxygen gas having a concentration ratio to the inert gas of a predetermined value or less is introduced; 1
Control means for switching and controlling the state of introducing a mixed gas of an inert gas and an oxygen gas having a concentration ratio to the inert gas equal to or higher than a predetermined value to the pipe; and a tuyere cooling pipe in the second pipe. Means for introducing a gas, photographing means for photographing an image of the molten metal side of the double-tube tuyere, and calculating means for calculating, as the temperature of the molten metal, a temperature corresponding to a maximum luminance in an image photographed by the photographing means. And a temperature measuring device for the molten metal in the furnace. 5. The apparatus according to claim 4, wherein said photographing means is a CCD camera, and said calculating means has information indicating a relationship between luminance and temperature in an image of a black body furnace photographed by said CCD camera. Temperature measuring device for molten metal in furnace.