JPH04147021A - Radiation thermometer for molten iron - Google Patents

Abstract

PURPOSE:To enable highly-precise and continuous measurement of the temperature of molten iron by constructing a temperature measuring tube of an outer tube of zirconium boride ceramic and an inner tube of alumina ceramic provided inside the outer tube. CONSTITUTION:A temperature measuring tube 9 of a radiation thermometer B for molten iron is constructed of an outer tube 9A of zirconium boride ceramic and an inner tube 9B of alumina ceramic provided inside the outer tube. This temperature measuring tube 9 is connected to a connection tube 12 made of stainless steel, with a bolt 10 and an inorganic adhesive such as cement. When the temperature of the molten iron flowing through a pig iron gutter, the temperature measuring tube 9 is inserted into a hole of a pig iron gutter cover and heated preliminarily. Next, the thermometer B is lowered and then fixed to the pig iron gutter cover in a state wherein the fore end of the temperature measuring tube 9 is immersed in the molten iron. In a light- sensing element of a radiant temperature measuring unit, in this way, a radiant light emitted from the inside bottom of the temperature measuring tube 9 heated to the same temperature with that of the molten iron is sensed without being disturbed by a slag on the molten iron.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a radiation thermometer for molten iron, and particularly to a radiation thermometer for molten iron that can continuously measure the temperature of molten iron with high accuracy. .

[Conventional technology]

Automation of processes from pig iron production to steel production, and even more.

In order to achieve AI control, it is essential to continuously measure the temperature of molten iron such as hot metal or molten steel with high accuracy.

It is possible to use a radiation thermometer to measure the temperature of molten iron.6 However, as shown in Figure 3, when measuring the temperature of hot metal 1 with a radiation thermometer, the radiation thermometer 2 is simply installed in the tapping trough. If the cap of 3 is attached to <-4, the following problem will occur. That is, the emissivity of the hot metal 1 fluctuates due to suspended matter 5 such as slag on the hot metal 1 flowing in the tap duct 3, causing an error in the measured temperature.

Therefore, a radiation thermometer to solve the above problem was published in "Materials and Processes J Vo12 (19
89)-1446. Hereinafter, this will be referred to as a conventional radiation thermometer.

A conventional radiation thermometer will be explained with reference to the drawings.

FIG. 4 is a sectional view showing a situation in which hot metal temperature is measured using a conventional radiation thermometer. As shown in Figure 4,
The conventional radiation thermometer A includes a temperature measuring tube 6 whose tip is closed and which is immersed in the hot metal 1, and a light receiving section 7A that receives radiation light emitted from the inner surface of the tip of the temperature measuring tube 6, and detects the temperature of the hot metal 1. It consists of a radiation temperature measuring device 7 for measuring temperature.

As described later, the temperature measuring tube 6 is a connecting tube 8 made of stainless steel or the like.
It is connected to the light receiving section 7A of the radiation temperature measuring device 7 via. The temperature measuring tube 6 is made of zirconium boride ceramics that exhibits high corrosion resistance against the hot metal 1 at a high temperature.

The tip of the temperature measuring tube 6 is formed into a hemispherical shape. As will be described later, if the tip of the thermometer tube 6 is formed into a hemispherical shape, the apparent emissivity will be higher than if the tip of the thermometer tube 6 is formed into a flat shape, for example. is close to 1, and temperature measurement using synchrotron radiation can be performed more accurately.

[Problem to be solved by the invention]

However, the conventional radiation thermometer described above has the following problems. That is, as will be described later, zirconium boride ceramics can be heated to B20. The generation of gas causes errors in temperature measurements.

Therefore, an object of the present invention is to provide a radiation thermometer that can continuously measure the temperature of molten iron with high accuracy without generating B2O3 gas in a high-temperature atmosphere.

[Means to solve the problem]

The present invention includes a temperature measuring tube whose tip is closed in a hemispherical shape and is immersed in molten iron, and a light receiving section receives radiation light emitted from the inner surface of the tip of the temperature measuring tube to measure the temperature of the molten ore. A radiation thermometer for molten iron comprising a radiation temperature measuring device for measuring radiation temperature, the temperature measuring tube comprising an outer tube made of zirconium boride ceramics and an inner tube made of alumina ceramics provided inside the outer tube. It is characterized by the fact that it is

As for zirconium boride ceramics.

It is preferable that ZrB is contained in an amount of 66 wt% or more, for example, ZrB: 70-95 tzt%, Si
C: 1 to 15 wt%, BN: 0 to 29 wt%, bulk specific gravity =
3-6, bending strength: 10 kg/am" or more, thermal expansion coefficient 26 x 10-@/"C, thermal shock resistance (ΔT) 250-
A material having a composition and characteristics such as 1000° C. can be used.

Of these, SiC is added as an auxiliary agent to promote the sintering of zirconium boride ceramics, and B
N is added to zirconium boride ceramics to impart thermal shock resistance. For example, if the amount of addition of these subcomponents is small, the effect of adding BN less than 4 wt% will not be obtained, but in order to ensure corrosion resistance against molten iron and slag, it is preferable to have a large amount of ZrB.

Materials that do not contain BN have low thermal shock resistance and require sufficient preheating, but have excellent durability.

If the inner bottom (inner surface of the tip) of the temperature measuring tube is formed into a spherical shape (1, for example, a hemisphere), the apparent emissivity of the bottom of the temperature measuring tube will be closer to 1 than in the case of a temperature measuring tube with a flat bottom. Temperature measurement using synchrotron radiation can be performed more accurately.

For example, when L = 200 In, the apparent emissivity of a thermometer tube with a flat inner bottom is 0.94, but under the same conditions, L/
By setting R=10 and using a hemispherical inner bottom, the apparent emissivity increases to 0.9'76.

However, L is the immersion depth of the temperature measuring tube, and R is the inner radius of the temperature measuring tube.

In addition, if the tip of the temperature measuring tube is formed into a spherical shape with approximately uniform wall thickness, when heating or cooling the tip of the temperature measuring tube,
This is preferable because there is no place where stress concentration occurs in the wall of the temperature measuring tube, and the temperature measuring tube is less likely to be damaged by thermal stress.

By placing a connecting tube made of stainless steel or other material between the radiation temperature measuring device and the zirconium boride ceramic temperature measuring tube, the expensive zirconium boride temperature measuring tube can be shortened to the necessary and minimum length. By adjusting the length of the connecting tube, it is also possible to adjust the position of the tip of the temperature measuring tube for temperature measurement. This connecting tube is sealed at the connection part between it and the temperature measuring tube. This function prevents the radiation from being blocked by fumes, etc., and from contaminating the light receiving part of the radiation temperature measuring device.

In order to make the apparent emissivity of the inner bottom of the temperature measuring tube even closer to 1, the depth L from the molten metal surface of the inner bottom of the temperature measuring tube immersed in the molten metal should be changed by the inner radius R of the temperature measuring tube. It is preferably 10 times or more and 30 times or less. The inner bottom is formed into a hemispherical shape, and the L/R ratio is 1.
When greater than 0.

The apparent emissivity is usually 0.97 or higher, and L/R is 1.
5, the apparent emissivity is usually 0.99, which is close to that of a black body.
It becomes 9. The reason why it is preferable that the inner length of the temperature measuring tube immersed in the molten metal is 30 times or less the inner radius R is because no useful effect can be obtained even if the tube is immersed deeper. However, if the molten metal surface fluctuates up and down, it is better to make L a little larger to account for this fluctuation.

In order to ensure L/R of 10 or more, the total length of the temperature measuring tube is preferably 20 times R or more, including the length required for the connection with the connecting tube and the amount for the rise and fall of the molten metal surface. Further, since there is no advantage in making the length too long, it is sufficient to make the length R 700 times or less.

When the inner tube made of alumina ceramics is arranged as in the present invention, it is sufficient that the relationship between R and L is satisfied for the inner tube.

The inner radius R of the temperature measuring tube is, for example, when the distance between the light receiving part of the radiation temperature measuring device and the inner bottom of the temperature measuring tube is 1000 m, in order to ensure a sufficient viewing angle and measure the temperature with good accuracy. 3m
It is preferable that the number is m or more. However, there is no advantage to increasing R too much, and when using a commercially available radiation temperature measuring device, 3
0+m+ is sufficient.

The wall thickness of the thermometer tube is also related to the durability of the thermometer tube, so
A thickness of 1II11 or more is required, preferably 4II
I11 or higher. However, if the wall thickness is too large, the thermal shock resistance may deteriorate, so it is preferably 15IIIl or less.

Temperature-measuring tubes usually suffer severe erosion at the surface of the hot water, and their lifespan is determined by the rate of erosion at the surface of the hot water.

In order to extend the life of the temperature measuring tube, that is, the radiation thermometer, it is effective to provide a ring-shaped protector in this area. As for the material C of the protector, various refractories that are used for molten iron specimens can be used, but zirconium boride can be used because it is durable without being too thick and can be used in narrow spaces. It is advantageous to use refractory or ceramic protectors. The ring-shaped protector can be fixed to the thermometer tube with an inorganic adhesive, but if the hot water level moves up and down, it is preferable to use it while floating on the hot water surface.

In this case, a ring-shaped protector is fitted onto the thermometer tube, suspended by a wire, and immersed in molten iron.

If a sealing material made of ceramic fiber such as alumina silica is wrapped around a temperature measuring tube and a ring-shaped protector is fitted around the outer circumference and immersed in molten iron, the wire and sealing material will melt and the ring-shaped protector will melt. becomes suspended on the surface of the water.

The inner diameter of the connecting tube is preferably equal to or larger than the inner diameter of the temperature measuring tube so as not to narrow the field of view of the inner bottom of the temperature measuring tube from the light receiving part of the radiation temperature measuring device. In addition, it is preferable to use a connecting tube that is equal to or longer than a normal temperature measuring tube.
In most cases, a total length of 2,500 m is sufficient when the temperature measuring tube and the connecting tube are connected.

The surface of zirconium boride ceramics is 1500m
At a high temperature of about
rB2+ 50□-+ 22rO2+ 28203
The reaction generates a fume of B2O3. This fume will float for several hours, for example, until the inner surface of the zirconium boride ceramic thermometer tube is covered with ZrO□. When this fume floats in the temperature measuring tube, the temperature measured by the radiation thermometer will be 20 to 40 degrees Celsius.
It gets lower.

This invention is based on this B20. eliminate the influence of Huyum,
In order to obtain accurate temperature measurements, the temperature measuring tube has a double structure of an outer tube made of zirconium boride ceramics and an inner tube made of alumina ceramics.

Oxide ceramics are resistant to oxidizing atmospheres and do not generate fumes when oxidized. Examples of oxide ceramics that can be used include zirconia ceramics, magnesia ceramics, and alumina ceramics, which have high melting points. Quality ceramics are commercially available in various sizes for use in protection tubes, and because they do not react with zirconium boride ceramics at operating temperatures, they are suitable as materials for the inner tubes constituting thermometer tubes.

Radiation temperature measuring instruments that use monochromatic synchrotron radiation are less affected by scattered light from the surroundings and gases in the atmosphere.

This is convenient for performing accurate temperature measurements.

In addition, as a radiation temperature measuring device, in addition to one that measures temperature by the intensity of radiation light of a single wavelength, it is also possible to use a dichroic temperature measuring device that measures temperature from the intensity ratio of radiation light of two wavelengths. .

〔Example〕

Hereinafter, the radiation thermometer for molten iron of the present invention will be explained in more detail using an example in which the temperature of molten pig iron flowing in a blast furnace gutter is measured.

FIG. 1 is a partially cutaway sectional view of the radiation thermometer for molten iron of the present invention.

In Fig. 1, the radiation thermometer B for molten iron has a connecting tube 1 made of stainless steel or the like connected to the light receiving part of the radiation temperature measuring device (not shown).
2, a temperature measuring tube 9 whose tip is closed in a spherical shape is attached.

The temperature measuring tube 9 has an outer tube 9A made of zirconium boride ceramics, which will be described later, and 99 wt% or more of A1 on the inside of the outer tube 9A.
It has a structure in which an inner tube 9B made of alumina ceramics □O1 is arranged. In FIG. 1, the temperature measuring tube 9 has a length of 400 mm, an outer diameter of 45 mm, and an inner diameter of 35 mm, and the inner tube 9B has a total length of 395 m.

It has an outer diameter of 32 m and an inner diameter of 28 nm. The temperature measuring tube 9 is
It is connected to a stainless steel connecting pipe 12 via a bolt 10 and an inorganic adhesive 11 such as cement, and the total length of the connection is 2000 on.

Zirconium boride ceramic thermometer tube used for testing 9
The material has a composition of 296 wt% ZrB and 4 wt% SiC. As a radiation temperature measuring device.

Model IR-R5T-65 manufactured by Chino Co., Ltd.
5 was used.

This radiation temperature measuring device uses 5 ilicon cells.
0.65μ sensor and interference film filter are used.
1000-160 depending on the intensity of monochromatic radiation with a wavelength of m
It can measure temperatures in the temperature range of 0°C at 1000°C with a resolution of within 1°C.

Since the radiation thermometer B was also used for high-temperature molten iron, the radiation thermometer was protected by being housed in a cooling box that was cooled by supplying air. In order to measure the temperature of the hot metal flowing in the tap duct with this molten iron radiation thermometer B, insert the temperature measuring tube 9 of the molten iron radiation thermometer B into the hole provided in the tap duct cover. The thermometer tube 9 is preheated for about 40 minutes while the tip of the tube 9 is held above the hot metal. With this preheating method, the temperature at the tip of the thermometer tube 9 reaches approximately 1000°C, and the thermal shock when the thermometer tube 9 is immersed in the hot metal is reduced, and the slag floating on the hot metal It is possible to reduce the phenomenon in which the temperature measuring tube 9 comes into contact with the immersed temperature measuring tube 9, is cooled, and adheres to the tube wall. Lower the radiation thermometer B and touch the tip of the thermometer tube 9 by about 2
The radiation thermometer B is immersed in 1011IIl hot metal and fixed to the tap-hole cover. Thus, in the light receiving part of the radiation temperature measuring instrument.

Radiant light emitted from the inner bottom of the thermometer tube 9, which has reached the same temperature as the hot metal, reaches the hot metal without being disturbed by slabs floating on the hot metal or by fumes generated from the hot metal.

Using this radiation thermometer B for molten iron, the temperature of the hot metal flowing through the hot metal gutter was measured over nine tappings.

During this time, the temperature of the hot metal was simultaneously measured 84 times using a disposable thermocouple thermometer, and the correlation between the temperature values and the temperature measurements of the radiation thermometer for molten iron of the present invention is shown in FIG. In Figure 2, each point indicates the correspondence between the temperature measured using a disposable thermocouple thermometer and the temperature measured using the radiation thermometer for molten iron according to the present invention. It is a regression line.

From this result, it was confirmed that when using the radiation thermometer for molten iron of the present invention, temperature can be measured with good accuracy of standard deviation of about 2°C.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to continuously perform highly accurate and stable temperature measurements by eliminating the influence of slag floating on molten iron such as hot metal or molten steel on measured values. . As a result, we have automated the process from pig iron making to steel making, and also improved the temperature of molten iron, which is an essential value for AI control.
Accurate and continuous measurement values can now be stably obtained.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway sectional view of a radiation thermometer for molten iron according to the present invention, and FIG. A graph showing the results of temperature measurement, FIG. 3 is a cross-sectional view showing the measurement status of hot metal temperature by a radiation thermometer without a temperature measuring tube,
FIG. 4 is a cross-sectional view showing how hot metal temperature is measured by a conventional radiation thermometer. In the drawings, A--Conventional radiation thermometer, B-- Radiation thermometer of the present invention, 1-- Hot metal, 2-- Radiation thermometer, 3-
...Tapping trough, 5.--Floating objects, 7.--Radiation temperature measuring device, 9-.-Temperature measuring tube, 11.-Adhesive, 4-..Cover 6.--Temperature measuring tube , 8-connecting pipe, 10...bolt, 12-connecting pipe.

Claims (1)

[Claims] (1) Measure the temperature of the molten iron by using a temperature measuring tube whose tip is immersed in molten iron and whose tip is closed in a hemispherical shape, and by receiving radiation light emitted from the inner surface of the tip of the temperature measuring tube into a light receiving section. In the radiation thermometer for molten iron, the temperature measuring tube is composed of an outer tube made of zirconium boride ceramics and an inner tube made of alumina ceramics provided inside the outer tube. A radiation thermometer for molten iron.