JPH04370722A - Furnace thermometer - Google Patents

Abstract

PURPOSE:To make it possible to conduct measurement of the temperature of an object of measurement in a noncontact, simple and accurate manner without being affected by stray light noise from the inner wall of a furnace, by a method wherein spectral radiation luminance is detected with at least one of measuring conditions varied, the temperature of the furnace wall is measured, the spectral radiation luminance is calculated and an operation is conducted so that the spectral emissivity defined beforehand be satisfied. CONSTITUTION:A spectral radiation luminance detector 2 for detecting spectral radiation luminance from a surface to be measured with at least one or more measuring conditions out of a wavelength, polarization and a measuring angle varied and converting it into two electric signals, a furnace wall temperature device 5 for measuring the temperature of a furnace wall, and an arithmetic device 3 which calculates two spectral radiation luminances from the two spectral radiation luminance signals and the temperature of the furnace wall detected by the furnace wall temperature device 5 and executes an operation satisfying a formula expressing the relation of emissivity which is defined beforehand and proper to an object of measurement, are provided.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is applicable to slab heating furnaces and C.I. A. P. The present invention relates to a radiation temperature measurement device that measures the surface temperature of a heated object such as a slab or thin plate being conveyed in an L heating furnace or the like with high accuracy without contacting the object and without adversely affecting the object.

0002

[Prior Art] Conventionally, temperature control of the slab inside the heating furnace, which has been generally carried out in slab heating furnaces, involves measuring the atmospheric temperature inside the furnace with a thermocouple in a protective tube, and estimating the temperature of the slab from this. Met.

[0003] On the other hand, it is possible to measure the surface temperature of an object inside a heating furnace in a non-contact manner using the radiation thermometry method. There is a method using a water-cooled shielding plate as disclosed in Japanese Patent Application Laid-Open No. 48-003680.

In addition, as in Japanese Patent Application Laid-open No. 55-155218, unknown stray light noise from the inner wall of the reactor is removed using a non-water-cooled shielding plate, while the influence of known stray light noise from the non-water-cooled shielding plate is removed. There is a method to measure the surface temperature of the slab by correcting the

[0005]

[Problem to be solved by the invention] With the above-mentioned method of measuring the temperature of the furnace atmosphere with a thermocouple in a protective tube and estimating the temperature of the slab, it is difficult to accurately estimate the temperature of the slab. There were also problems in managing energy costs, such as requiring longer baking times and setting higher temperatures.

[0006] Furthermore, the method using a water-cooled shielding plate as described in Japanese Patent Application Laid-Open No. 48-003680 is not applicable to measuring the temperature of an object that is stationary or transported at low speed, such as a slab in a heating furnace. Then, there was a problem that the water-cooled shielding plate cooled the object to be measured, which adversely affected the quality.

Furthermore, as in the above-mentioned Japanese Patent Application Laid-open No. 155218/1984, a non-water-cooled shielding plate is used to remove unknown stray light noise from the inner wall of the reactor, while eliminating known stray light noise from the non-water-cooled shielding plate. In the method of measuring the slab surface temperature by correcting the influence, the computation for correction is complicated, and the surface properties of the slab change due to the generation of scale, which increases the contribution rate of stray light noise from non-water-cooled shielding plates. There were problems such as a risk of measurement errors occurring if the temperature changed.

The object of the present invention is to provide a slab heating furnace and a C.I. A.
P. Provides a thermometer that can easily and accurately measure the surface temperature of an object to be measured transported in a furnace such as an L heating furnace without being affected by unknown stray light noise from the furnace inner wall without contact. It's about doing.

[0009]

[Means for Solving the Problems] In order to achieve the above object, the present invention detects spectral radiance from a surface to be measured by changing at least one measurement condition among wavelength, polarization, and measurement angle. A spectral radiance detector for converting into two electrical signals, a furnace wall temperature device for measuring the furnace wall temperature, and a furnace wall temperature detected by the two spectral radiance signals and the furnace wall temperature device. Calculate the following spectral radiance, Lx=εxLbλx(T)+(1-εx)Lb
λx(Ts) Ly=εyLbλy(T)+(1
-εy) Lbλy(Ts) (where, Lbλx(T) is the blackbody spectral radiance at temperature T and wavelength λx, Lbλy(T) is the blackbody spectral radiance at temperature T and wavelength λy, and εx and εy are the surface of the object to be measured. , T is the surface temperature of the object to be measured,
(Ts is the furnace wall temperature) A calculation device is provided which executes calculations satisfying εy=f(εx), which is a predefined expression representing the relationship between emissivity specific to the object to be measured.

[0010] In addition, in order to prevent deterioration of the S/N ratio and to prevent inaccurate calculation of stray light noise brightness, the light collecting surface of the spectral radiance detector and the measurement point of the furnace wall temperature measuring device are is an optical object with respect to the normal line set at the center of the measurement field of view of the object to be measured of the spectral emissivity luminance detector, and the angle formed between the normal line and the measurement direction of the spectral radiance detector is 45
It is arranged within the range of 70 degrees.

[0011]

[Operation] According to the above-described means, the spectral radiance from the surface to be measured is detected by changing at least one of the measurement conditions of wavelength, polarization, and measurement angle, and the spectral radiance is detected by the spectral radiance detector. On the other hand, the furnace wall temperature is measured by a furnace wall temperature device, and from the two obtained spectral radiance signals and the detected furnace wall temperature, the direct thermal spectral radiance component from the surface of the object to be measured is determined. The spectral radiances of Lx and Ly, which are composed of stray light noise components in the measurement field of view, are calculated, and the arithmetic device performs calculations so that the predefined spectral emissivity εy=f(εx) satisfies a predetermined condition. Therefore, it is possible to easily and accurately measure the temperature of an object to be measured whose emissivity changes as it is transported inside the heating furnace without being affected by stray light noise from the furnace inner wall. .

Further, the spectral radiance detector and the furnace wall temperature measuring device are optically symmetrical to the normal line erected on the slab surface, and the angle between the normal line and the measurement direction of the spectral radiance detector is By arranging it within the range of 45° to 70°, the brightness of stray light noise when exceeding 70° is prevented from becoming larger than the spectral radiance from the surface of the object to be measured. Stray light noise incident on the detector at temperatures below 10°C limits the increase in the proportion of radiance from areas other than the reactor wall portion that is optically symmetrical to the normal to the measurement point. Therefore, it is possible to prevent deterioration of the S/N ratio and prevent inaccurate calculation of stray light noise brightness.

[0013]

Embodiment 1 FIG. 1 is a front view showing an embodiment of a furnace thermometer according to the present invention. Here, an example is shown in which it is applied to temperature measurement of a slab inside a heating furnace.

Before explaining the embodiment shown in FIG. 1, the principle of the furnace temperature of the present invention will be explained.

Two types of spectral radiance Lx and Ly from the surface of the object to be measured in the heating furnace, which differ in at least one condition among wavelength, polarization, and measurement angle, are expressed by the following equations.

Lx=εxLbλx(T)+(1−εx)Lb
λx(Ts) (1) Ly=εyL
bλy(T)+(1-εy)Lbλy(Ts)
(2) The first term on the right side of equations (1) and (2) is the direct thermal spectral radiance component from the object to be measured, and the second term is the stray light noise in the measurement field of view.

This stray light noise is mainly emitted from the part of the furnace wall that uses the field of view of the spectral radiance detector as a reflective surface and is above the detector and the optical object, so it is necessary to measure the furnace wall temperature of this part by some method. and the spectral radiation εx of the surface of the object to be measured
, εy are given, the noise term in the second term on the right side of equations (1) and (2) can be calculated.

[0018] Furthermore, it is possible to blacken the surface corresponding to the reactor wall surface in the direction symmetrical to the field of view of the detector and the optical axis, or to actively control cooling, or to use both means at the same time (
1) Reduce the stray light noise term in the second term on the right side of equation (2) to reduce the S/N
Of course, it is also possible to improve the temperature measurement accuracy by improving the ratio.

If the spectral emissivity of the object to be measured changes due to oxidation or the like, the relationship between the emissivities is determined in advance and approximated by equation (3).

εy=f(εx)

(3) Spectral radiance (L
x, Ly) and the furnace wall temperature Ts on the detector field of view and optical object
εx, εy, and T can be calculated by substituting Equations (1) and (2) into Equations (1), (2), and (3) and solving them simultaneously.

In equations (1) and (2), if the measurement conditions, wavelength, polarization, and measurement angle of the spectral radiances Lx and Ly are all equal, then equations (1) and (2) become exactly the same and are not independent of each other.

[0022] Furthermore, equation (3) is εy=εx

(3) Therefore, the temperature and emissivity of the object to be measured cannot be calculated. Therefore, equation (3) holds εy≠εx and εy=f(εx), which results in (1)(
2) The measurement conditions (wavelength,
The spectral radiances Lx and Ly are measured by the detector while changing at least one measurement condition among (polarization, measurement angle). However, Lx, Ly: Spectral radiance (
W・sr−1・m−2) Lbλx(T): Blackbody spectral radiance at temperature T and wavelength λx (
W・sr−1・m−2) Lbλy(T): Blackbody spectral radiance at temperature T and wavelength λy (
W・sr−1・m−2) εx, εy: Spectral emissivity T of the surface of the object to be measured
: Surface temperature of measured object (K)T
s: Furnace wall temperature
(K) The detector and the furnace wall thermometer are placed within the range of 45° to 70° with respect to the normal to the slab surface. Within this range, the brightness of the stray light noise incident on the detector can be estimated with high accuracy, so the second right-hand side of equations (1) and (2) above
Since the noise term in the term can be calculated accurately, accurate temperature measurement can be performed with less error. However, the installation angle is 70°
If it exceeds , the brightness of the stray light noise incident on the detector will be much larger than the spectral radiance from the surface of the object to be measured, so measure the stray light noise source temperature with a furnace wall thermometer and correct the amount of stray light noise. However, the S/N ratio deteriorates and accurate temperature measurement becomes difficult. Also, if the installation angle is less than 45°,
Stray light noise incident on the detector is caused by a large proportion of radiance coming from areas other than the optically targeted furnace wall normal to the measurement point.If there is a temperature distribution on the furnace wall, the furnace wall temperature measured by the furnace wall thermometer and the stray light noise source temperature no longer match. For this reason, the calculation of the stray light noise brightness becomes inaccurate, causing an error in the temperature measurement result.

In this way, the present invention optimally selects the conditions for the two spectral radiances (wavelength, polarization, and measurement angle) to be detected, thereby controlling the temperature of the object to be measured in the heating furnace, where the emissivity changes, by minimizing stray light noise. It becomes possible to remove the influence from measurement.

Next, the configuration of the embodiment shown in FIG. 1 will be explained.

The spectral radiance from the surface of the slab 1 is measured by the detector 2 through a measurement window in the wall 4 of the heating furnace soaking zone. This measurement is carried out by 4
This is done from a 5° angle.

The radiance collected by the light receiving lens of the detector 2 passes through a band pass filter (0.9 μm),
The light is divided into S and P polarization components by a polarizer, focused on a detection element (silicon element), photoelectrically converted, and then transmitted to the arithmetic unit 3 as luminance signals Lx and Ly.

The furnace wall temperature Ts is measured by a furnace wall thermometer (thermocouple) 5 installed at the center of the furnace wall above the optical object in the measurement field. The calculation device 3 calculates the luminance signals Lx, Ly and the furnace wall temperature T.
Substituting s into equations (1) and (2) above, we get (1) (2) (3
) equations are used to calculate εx, εy, and T.

FIG. 2 shows the results of measuring the slab surface using the furnace thermometer of the present invention. The figure shows the measurement results of a conventional furnace thermometer for comparison.

As is clear from FIG. 2, in the present invention, even if the furnace wall temperature and the emissivity of the slab change, the temperature measurement error is smaller than that of the conventional furnace thermometer, and the temperature measurement error is smaller than that of the conventional furnace temperature meter. It can be seen that the temperature accuracy is good.

[0030] Such a temperature measurement system is expected to be applied to many areas such as slab heating furnaces and high brightness annealing furnaces in the steel industry alone, as well as furnace interiors in the non-ferrous metal manufacturing industry, ceramic manufacturing industry, electronic material manufacturing industry, etc. If you also consider its application to temperature measurement, the effects of improved product quality, operational management, energy savings, etc. will be immeasurable.

[0031]

[Embodiment 2] This embodiment has the same structure as the previous embodiment, and its application and measurement angle are also the same as those of the previous embodiment, but polarization by a polarizer is not performed. That is, the radiance collected by the light receiving lens of the detector 2 passes through a band pass filter (0.9 μm, 0.65 μm), is divided into each wavelength component, and is focused on a detection element (silicon element) to be photoelectronically transmitted. It is converted and transmitted to the arithmetic unit 3 as luminance signals Lx and Ly.

The furnace wall temperature Ts is measured by a furnace wall thermometer (thermocouple) 5 installed on the furnace wall above the optical object in the measurement field. The arithmetic unit 3 substitutes the luminance signals Lx, Ly and the furnace wall temperature Ts into the above-mentioned equations (1) and (2), and combines equations (1), (2), and (3) to calculate εx, εy, and T. .

As a result of applying the furnace thermometer of the present invention, it was found that the measurement accuracy of the present invention was better as in Example 1.

[0034]

Embodiment 3 FIG. 3 is a front view showing a third embodiment of the present invention. This embodiment is characterized in that the radiance from the surface of the slab 1 is measured by a detector 2 and a detector 6 installed at two locations on the wall of the heating furnace soaking zone. The measurement angle in this case is that the detector 2
is measured from an angle of 45°, and the detector 6 is measured from an angle of 70°.

The radiance collected by the light-receiving lens of the detector passes through a band-pass filter (0.9 μm) and is focused on a detection element (silicon element), where it is photoelectrically converted and sent to the arithmetic unit 3 as luminance signals Lx and Ly. transmitted to. Furnace wall temperature T
s is measured at two locations with a furnace wall thermometer (thermocouple) 5 installed at the center of the furnace wall above the optical object in the measurement field of view.

The arithmetic unit 3 substitutes the luminance signals Lx, Ly and the furnace wall temperature Ts into the above-mentioned equations (1) and (2).
Equations (3) are combined to calculate εx, εy, and T.

As a result of applying the furnace thermometer of the present invention, it was found that the measurement accuracy of the present invention was better as in Example 1.

[0038]

[Embodiment 4] This embodiment has the same structure as the above-mentioned embodiment 3, and its application and measurement angle are also the same as those of the above-mentioned embodiment, but the feature is that processing is performed using a polarizer. That is, the radiance collected by the light receiving lens of each detector is divided into S and P polarization components by a polarizer. The detector 2 uses a P polarization component, and the detector 6 uses a detection element (silicon element), performs photoelectric conversion, and outputs it as a luminance signal. The luminance signal from detector 2 is
x, the luminance signal from the detector 6 is transmitted to the arithmetic unit 3 as Ly.

The furnace wall temperature Ts is determined by a furnace wall thermometer (thermocouple) installed at the center of the furnace wall above the optical object in the measurement field of each detector.
5, measurements were taken at two locations. The arithmetic unit 3 receives the luminance signal Lx,
εx, εy, and T are calculated by substituting Ly and the furnace wall temperature Ts into the above-mentioned equations (1), (2), and combining equations (1), (2), and (3).

As a result of applying the furnace thermometer of the present invention, it was found that the measurement accuracy of the present invention was better as in Example 1.

[0041]

[Example 5] This example has the same configuration as Example 3, and its application and measurement angle are also the same as in the example above, but the wavelengths used when condensing light with two detectors are limited. The place has its characteristics.

The radiance collected by the light receiving lens of each detector is filtered through a bandpass filter (0.9μm, 0.65μm).
m) and is divided into each wavelength component, and the detector 2 detects the component with a wavelength of 0.9 μm, and the detector 6 detects the component with a wavelength of 0.65 μm.
The component m is focused on a detection element (silicon element), photoelectrically converted, and output as a luminance signal. The luminance signal from the detector 2 is transmitted to the arithmetic unit 3 as Lx, and the luminance signal from the detector 6 as Ly.

The furnace wall temperature Ts is determined by a furnace wall thermometer (thermocouple) installed at the center of the furnace wall above the optical object in the measurement field of each detector.
5, measurements were taken at two locations. The arithmetic unit 3 receives the luminance signal Lx,
εx, εy, and T are calculated by substituting Ly and the furnace wall temperature Ts into the above-mentioned equations (1), (2), and combining equations (1), (2), and (3).

As a result of applying the furnace thermometer of the present invention, it was found that the measurement accuracy of the present invention was better as in Example 1.

[0045]

[Embodiment 6] This embodiment has the configuration of Embodiment 3, but
The feature is that the measurement is performed using only the detector 2. Its purpose is to measure the temperature of the slab inside the heating furnace, similar to the above embodiments. In this case, the radiance from the surface of the slab 1 is measured by the detector 2 through a measurement window on the wall of the heating furnace soaking zone. Moreover, the measurement angle is 45° with respect to the normal line erected on the slab surface.

The radiance collected by the light receiving lens of the detector is divided into S and P polarization components by a polarizer, and then passed through a band pass filter (0.9 μm, 0.65 μm).
m), is separated into each wavelength component, and is sent to a detection element (
The light is focused on a silicon element) and photoelectrically converted into luminance signals Lx,L.
It is transmitted to the arithmetic unit 3 as y.

The furnace wall temperature Ts is measured by a furnace wall thermometer (thermocouple) 5 installed at the center of the furnace wall above the optical object in the measurement field. The calculation device 3 calculates the luminance signals Lx, Ly and the furnace wall temperature Ts.
Substituting into equations (1) and (2) above, we get (1), (2), and (3).
εx, εy, and T are calculated using simultaneous equations.

As a result of applying the furnace thermometer of the present invention, it was found that the measurement accuracy of the present invention was better as in Example 1.

[0049]

[Embodiment 7] This embodiment is characterized in that it is a combination of Embodiments 3 and 4, and the radiance from the surface of the slab 1 is measured by the detector 2 installed on the wall of the heating furnace and soaking zone. It is measured by the detector 6. The measurement angle is such that the detector 2 measures from an angle of 45° and the detector 6 measures from an angle of 70° with respect to the normal line erected on the slab surface.

The radiance collected by the light receiving lens of each detector is filtered through a band pass filter (0.9 μm, 0.65 μm).
m), and after being separated into each wavelength component, the polarized light is separated into S and P polarized components by a polarizer and sent to the detector 2.
is an S-polarized light component with a wavelength of 0.65 μm, and the detector 6 focuses the P-polarized light component with a wavelength of 0.9 μm onto a detection element (silicon element), photoelectrically converts it, and outputs it as a luminance signal. The luminance signal from the detector 2 is transmitted to the arithmetic unit 3 as Lx, and the luminance signal from the detector 6 as Ly.

The furnace wall temperature Ts is determined by a furnace wall thermometer (thermocouple) installed at the center of the furnace wall above the optical object in the measurement field of each detector.
5, measurements were taken at two locations. The arithmetic unit 3 receives the luminance signal Lx,
εx, εy, and T are calculated by substituting Ly and the furnace wall temperature Ts into the above-mentioned equations (1), (2), and combining equations (1), (2), and (3).

As a result of applying the furnace thermometer of the present invention, it was found that the measurement accuracy of the present invention was better as in Example 1.

As described above, in the present invention, the stray light noise is corrected and the temperature of the object in the furnace can be measured by correcting the stray light noise and the variation in the emissivity of the object to be measured. It is possible to measure with high accuracy as shown in Figure 2 compared to methods without this method.

[0054]

[Effects of the Invention] Since the present invention is constructed as described above, it achieves the following effects.

[0055] In the furnace thermometer of claim 1, the wavelength;
A spectral radiance detector for detecting spectral radiance from the surface to be measured and converting it into two electrical signals by changing at least one measurement condition among polarization and measurement angle, and for measuring furnace wall temperature. The following spectral radiance is calculated from the furnace wall temperature device detected by the furnace wall temperature device, the two spectral radiance signals, and the furnace wall temperature detected by the furnace wall temperature device, Lx=εxLbλx(T)+(1−εx)Lb
λx(Ts) Ly=εyLbλy(T)+(1
-εy) Lbλy(Ts) (where, Lbλx(T) is the blackbody spectral radiance at temperature T and wavelength λx, Lbλy(T) is the blackbody spectral radiance at temperature T and wavelength λy, and εx and εy are the surface of the object to be measured. , T is the surface temperature of the object to be measured,
Ts is the furnace wall temperature) Since the heating furnace It becomes possible to easily and accurately measure the temperature of an object to be measured whose emissivity changes while being transported within the furnace without being affected by stray light noise from the inner wall of the furnace.

In the furnace thermometer according to the second aspect, the light collecting surface of the spectral radiance detector and the measurement point of the furnace wall temperature measuring device are located within the measurement field of view of the object to be measured of the spectral radiance detector. It is an optical object with respect to the normal line set at the center, and the angle formed between the normal line and the measurement direction of the spectral radiance detector is 45° to 7°.
Since it is arranged within the range of 0°, it is possible to prevent deterioration of the S/N ratio and prevent inaccurate calculation of stray light noise brightness.

[Brief explanation of the drawing]

FIG. 1 is a front view showing an embodiment of a furnace thermometer according to the present invention.

FIG. 2 is a characteristic diagram showing the relationship between furnace wall temperature change and measurement error when the slab temperature in the heating furnace is measured using the furnace temperature meter of the present invention and the conventional furnace temperature meter.

FIG. 3 is a front view showing another configuration diagram of the furnace thermometer according to the present invention.

[Explanation of symbols]

1 Slab 2 Detector 3 Arithmetic device 4 Heating furnace soaking zone furnace wall 5　Furnace wall thermometer

Claims (2)

[Claims] 1. A spectral radiance detector for detecting spectral radiance from a surface to be measured and converting it into two electrical signals by changing at least one measurement condition among wavelength, polarization, and measurement angle; A furnace wall temperature device is used to measure the furnace wall temperature, and the following spectral radiance is calculated from the two spectral radiance signals and the furnace wall temperature detected by the furnace wall temperature device, and Lx=εxLbλx(T)+ (1-εx)Lb
λx(Ts) Ly=εyLbλy(T)+(1
-εy) Lbλy(Ts) (Lbλx(T) is the blackbody spectral radiance at temperature T and wavelength λx, Lbλy(T)
are temperature T, blackbody spectral radiance at wavelength λx, εx and εy
is the spectral emissivity of the surface of the object to be measured, T is the surface temperature of the object to be measured, and Ts is the furnace wall temperature. An in-furnace thermometer characterized by comprising: an arithmetic device that executes an arithmetic operation that satisfies the requirements. 2. The light condensing surface of the spectral radiance detector and the measurement point of the furnace wall temperature measuring device are aligned with respect to a normal line set at the center of the measurement field of view of the object to be measured of the spectral radiance detector. The furnace thermometer according to claim 1, which is an optical object and is arranged so that the angle between the normal line and the measurement direction of the spectral radiance detector is within a range of 45° to 70°.