JP3334528B2 - Method and apparatus for measuring temperature of molten metal - Google Patents

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 such as hot metal in a blast furnace, and more particularly to a technique for measuring the temperature of molten metal flowing at high speed with high accuracy.

[0002]

2. Description of the Related Art In a blast furnace operation, iron ore, coke, and other auxiliary materials such as lime are filled in a furnace, and hot air is blown from a lower part of the furnace to burn coke, and the generated heat and a reducing gas generate iron ore. Is reduced to obtain hot metal. This hot metal is taken out together with the slag from a taphole provided in the lower part of the furnace, and this operation is usually called tapping. Since the filling in the furnace descends as the coke burns, raw materials and the like are charged from the upper part of the furnace to maintain an appropriate filling level.

In the operation of a blast furnace, it is important to perform a steady operation while maintaining various balances such as the material balance and the heat balance. In particular, the heat level in the furnace of a blast furnace reflects the conditions inside the furnace, such as the reaction conditions inside the furnace, and affects the consumption of coke, etc. It is very important from the viewpoint of early detection of waste and reduction of raw material costs.

[0004] Since the heat level of the blast furnace remarkably appears in the temperature of the generated hot metal, it is desired to accurately measure the temperature of the hot metal. Conventional techniques for measuring hot metal temperature in blast furnaces use immersion-type thermocouples or thermocouples with protective tubes.However, these methods immerse a thermocouple in hot metal stored in a slag removing device called a skinmer. Therefore, there is a problem that the measured temperature is considerably lower than the hot metal temperature near the taphole. This is because the hot metal in the skimmer requires several tens of minutes from the start of hot metal tapping until the temperature becomes stable, during which time a large amount of heat is taken away by the skinmer and the hot metal gutter.

Therefore, recently, as proposed by the present applicant, an attempt has been made to directly measure the hot metal temperature in the vicinity of the taphole using a radiation thermometer using an optical fiber. These techniques, for example, as disclosed in JP-A-7-243912 and JP-A-8-82553, insert the tip of an optical fiber into a hot metal stream jetting from a taphole,
The light incident from the tip is detected by the radiation thermometer at the other end,
It measures hot metal temperature. The optical fiber is covered with a metal tube to increase rigidity so that the optical fiber is not ejected by a high-speed hot metal flow at the time of insertion.

However, since the melting point of the metal tube, which is the coating material of the optical fiber, is lower than the temperature of the hot metal, the metal tube is damaged at the moment when the metal tube comes into contact with the outer surface of the hot metal flow, and the optical fiber is sufficiently inserted into the hot metal flow. And the immersion state was likely to be unstable. If the immersion state of the optical fiber is insufficient, the apparent emissivity becomes smaller than 1,
The reading of the radiation thermometer indicates a value lower than the true temperature, and
There has been a problem that the dispersion of the indicated values increases.

[0007]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a method and an apparatus for measuring the temperature of a molten metal capable of measuring the temperature with higher accuracy by judging the quality of the immersion state of the optical fiber. And

[0008]

According to the method for measuring the temperature of a molten metal according to the present invention, the tip of an optical fiber having a radiation thermometer connected to a base end is immersed in the molten metal, and the light is incident from the tip of the optical fiber. In the method of measuring the temperature of the molten metal by detecting light to be emitted, the light received through the optical fiber is divided into two lights having different wavelengths, and the indicated temperatures for the two lights are respectively measured by the radiation thermometer. When the immersion state of the tip of the optical fiber is good, the two indicated temperatures both indicate the true temperature and the difference between the two indicated temperatures is equal to or less than a predetermined threshold, and the immersion state of the tip of the optical fiber is determined. Is not good, the two indicated temperatures are lower than the true temperature, and the difference between the two indicated temperatures is equal to the predetermined threshold.
When the value exceeds the value, the indicated value when the difference between the two indicated temperatures is equal to or less than the predetermined threshold value is set as the true temperature. Further, the effective wavelength of one divided light is set in a range from 0.7 μm to 1.0 μm, and
The effective wavelengths of the two lights are in the range of 1.5 μm to 1.6 μm.

In the temperature measuring method according to the present invention, the tip of the optical fiber is immersed in a molten metal as an object to be measured, and the radiation incident from the tip of the optical fiber is divided into two lights having different wavelengths. The indicated temperatures for two different lights are determined by a radiation thermometer. At this time, when the immersion state of the tip of the optical fiber is good, the apparent emissivity is 1, so that the two indicated values are both true values and coincide. On the other hand, when the immersion state of the optical fiber tip is poor, the apparent emissivity is smaller than 1, so that the two indicated values are lower than the true temperature, and the two indicated values do not match. This is derived as follows. The relationship between the radiance L, the true temperature T0 (K), and the apparent temperature T is shown by a well-known Wien equation as a good approximation. ^{L = ε (c1 / λ 5} ) exp (-C2 / (λT0)) = (c1 / λ 5) exp (-C2 / (λT)) Here, c1, c2: constant, epsilon: emissivity, lambda: Wavelength. Thus, the temperature error dT caused by the emissivity error dε
Is given by dε / ε = −c2 dT / (λT ² ). That is, even though the apparent emissivity error is the same at two different wavelengths, the temperature reading error increases in proportion to the wavelength. From this, when the two indicated values match, the immersion state of the optical fiber tip is good,
When they do not match, it is possible to determine that they are defective, and by using only the indicated value when the two indicated values match, the accuracy of temperature measurement can be improved. In the present invention, the two indicated values match if the difference between the two indicated values is equal to or less than a predetermined threshold value.

In the temperature measuring device of the present invention used in the above-described temperature measuring method, the tip of an optical fiber having a radiation thermometer connected to the base end is immersed in molten metal, and the optical fiber is incident from the tip of the optical fiber. An apparatus for measuring the temperature of the molten metal by detecting light to be emitted, wherein means for dividing light received through the optical fiber into two lights having different wavelengths, and when the immersion state of the tip of the optical fiber is good. Each of the two indicated temperatures indicates a true temperature, and the difference between the two indicated temperatures is equal to or less than a predetermined threshold value, and when the immersion state of the tip of the optical fiber is poor, the two indicated temperatures are lower than the true temperature. The difference between the two indicated temperatures is the predetermined threshold.
Means for judging whether the optical fiber is immersed or not based on a difference between two temperature indication values of the two lights when the value exceeds the value .

[0011]

FIG. 1 is a block diagram of a temperature measuring device according to the present invention. In FIG. 1, reference numeral 1 denotes an optical fiber, the element wire of which is made of quartz glass or the like, and the outer periphery of the optical fiber 1 is covered with a metal tube such as stainless steel. Reference numeral 2 denotes a radiation thermometer connected to the base end of the optical fiber 1. The internal configuration of the radiation thermometer is different from that of the beam splitter 21 that divides the light guided by the optical fiber 1 into two lights. 0.7-1.0 μm, the other 1.5-1.6 μm
m) Two optical filters 22a and 22b and a photodiode (for example, S
i photodiode and InGaAs photodiode)
23a and 23b, temperature converters 24a and 24b for converting a light quantity signal into a temperature signal, peak hold units 25a and 25b for performing peak hold processing of a temperature signal waveform, and correcting the length accompanying the consumption of the optical fiber 1. Length corrector 26
a, 26b, and an immersion state determination unit 27 that determines the quality of the immersion state of the optical fiber 1 based on the difference between the two temperature indication values. In the figure, reference numeral 3 denotes a measuring roll, which detects the amount of fiber consumption from the supply amount of the optical fiber 1, and the signal is input to the length correctors 26a and 26b, respectively. Reference numeral 10 denotes a hot metal flow ejected from a tap hole of a blast furnace.

The optical fiber 1 coated with a metal tube is inserted perpendicularly to the flow direction of the hot metal flow 10 by a pinch roll (not shown). In this immersion state, light due to the heat radiation of the molten metal enters from the tip of the optical fiber 1 and is guided to the radiation thermometer 2. The radiated light guided through the optical fiber 1 is split into two lights by a beam splitter 21, and one of the lights is transmitted through an optical filter 22a having a transmission wavelength band of 0.7 μm to 1.0 μm. Diode 23
a and the other light has a transmission wavelength band of 1.5 μm
After passing through an optical filter 22b of 1.6 μm from
The light enters the nGaAs photodiode 23b. Then, after the light quantity signals are converted into temperature signals by the temperature converters 24a and 24b, peak hold processing is performed to read the temperature indicated values Ta and Tb, and the fiber length is corrected according to the fiber consumption. After that, the two indication values Ta and Tb are compared in the immersion state quality judgment unit 27, and the indication value T0 is adopted only when the error is within 2 ° C., for example. If the error exceeds 2 ° C, repeat the measurement.

[0013]

EXAMPLES The results measured using the above temperature measuring device are shown below. FIG. 2 shows an example of a temperature waveform when an optical fiber is inserted into a high-speed hot metal stream from a taphole for about 1 second and measured, and FIG. 2A shows a case where the immersion state is good.
(B) shows a case where the immersion state is poor. In FIG. 7A, both waveforms coincide at the peak of the temperature waveform (point P), and it can be seen that a favorable immersion state is realized. on the other hand,
(B) In the figure, there is no place where both waveforms coincide, and it can be seen that the immersion state was not good.

FIG. 3 shows the measurement results of the hot metal temperature.
As can be seen, the error between the two temperature readings is 2 ° C.
For those determined that a good immersion state was realized within (circle ○), the variation was as small as about 8 ° C in width,
Sufficient accuracy has been obtained. On the other hand, when the error between the two temperature indication values exceeded 2 ° C. and the immersion state was determined to be poor (×
With respect to the mark (), the indicated value is generally low and the variation is large. In addition, the ones marked with ▲ show the results of the skinmmer thermocouple measurement. For the measurement several tens of meters downstream from the taphole,
The temperature is about 15 ° C. lower than the measurement result of the method of the present invention.

[0015]

As described above, according to the present invention, the light guided through the optical fiber is divided into two lights having different wavelengths, and the optical fiber is immersed based on the error of the temperature indicating value for each light. By judging the quality of the state and setting the indicated value when the error is equal to or less than a predetermined threshold value to the true temperature, the temperature of the high-speed flowing molten metal can be measured with high accuracy.

[Brief description of the drawings]

FIG. 1 is a block diagram of a temperature measuring device according to the present invention.

FIG. 2 is a waveform diagram of the hot metal temperature when the immersion state of the optical fiber is good and bad.

FIG. 3 is a view showing a measurement result of hot metal temperature.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Optical fiber 2 Radiation thermometer 10 Hot metal flow 21 Beam splitter 22a, 22b Optical filter 23a, 23b Photodiode 24a, 24b Temperature converter 25a, 25b Peak hold unit 26a, 26b Length corrector 27 Immersion state good / bad judgment device

Continuing from the front page Examiner Ayako Yokoi (56) References JP-A-7-324983 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01J 5/00-5/62

Claims (2)

(57) [Claims] 1. A method for measuring the temperature of a molten metal by immersing a distal end of an optical fiber having a radiation thermometer at a base end into a molten metal and detecting light incident from the distal end of the optical fiber. Dividing the light received through the optical fiber into two lights having different wavelengths; obtaining the indicated temperatures for the two lights by the radiation thermometer; and 2 when the immersion state of the tip of the optical fiber is good.
Each of the two indicated temperatures indicates the true temperature , the difference between the two indicated temperatures is equal to or less than a predetermined threshold value, and when the immersion state of the tip of the optical fiber is poor, the two indicated temperatures indicate values lower than the true temperature. The difference between the two indicated temperatures is the predetermined threshold
A method for measuring the temperature of a molten metal, wherein when the difference is exceeded , the indicated value when the difference between the two indicated temperatures is equal to or less than the predetermined threshold value is the true temperature. 2. An apparatus for measuring the temperature of a molten metal by immersing a distal end of an optical fiber having a radiation thermometer connected to a base end in molten metal and detecting light incident from the distal end of the optical fiber. Means for splitting light received through the optical fiber into two lights having different wavelengths; and 2 when the immersion state of the tip of the optical fiber is good.
Each of the two indicated temperatures indicates the true temperature , the difference between the two indicated temperatures is equal to or less than a predetermined threshold value, and when the immersion state of the tip of the optical fiber is poor, the two indicated temperatures indicate values lower than the true temperature. The difference between the two indicated temperatures is the predetermined threshold
Means for judging whether the optical fiber is immersed or not based on a difference between two temperature indication values of the two lights when the temperature is exceeded .