JP2001294918A - Method for measuring thickness of refractories in furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for precisely measuring the thickness of refrac tory bricks in a furnace from the outside of the furnace using ultrasonic wave. SOLUTION: A ultrasonic wave is transmitted from on the outside of the furnace toward the refractories in the inner part, and the detecting time of refractory signal from the inside surface of the refractory, is calculated with the variation with time of a specific frequency component decided with a material constituting the furnace surface to measure the thickness of the refractory.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of measuring the thickness of a refractory in a furnace having a multi-layered furnace wall of an industrial furnace, particularly a blast furnace, a converter, etc., from the outside of the furnace. .

[0002]

2. Description of the Related Art A blast furnace wall is usually made of steel, irregular refractory, and refractory brick from the outside. Since the refractory bricks at the bottom of the blast furnace are constantly exposed to the hot metal, the bricks gradually wear out during the operation of the blast furnace. For example, 200 when burning
The thickness of the refractory brick, which was 0 mm or more, may be reduced to about 300 mm at the time of stopping after about ten years. Accurately measuring the transition of the remaining thickness of refractory bricks during blast furnace operation is important to prevent blast furnace damage, such as the loss of iron shell due to hot metal and the outflow of hot metal, and to increase the life of blast furnace assets by grasping the life of the blast furnace. It is very important for effective use. For this reason,
Many techniques have been proposed for measuring the residual thickness of refractory bricks. For example, Japanese Patent Application Laid-Open No. 58-27002 discloses that an opening is formed in a part of a steel shell, and a metal rod is formed on a refractory brick or a stamp material which is an irregular type refractory embedded between the steel shell and the refractory brick. By directly connecting and hitting one end of the metal rod, efficiently generate elastic waves in the refractory brick,
A method has been proposed in which the time required for an elastic wave to reciprocate in a refractory brick is measured, and the thickness of the refractory is measured from the reciprocation time and the propagation speed of the elastic wave in the refractory brick. Furthermore, Japanese Unexamined Patent Publication No.
According to Japanese Patent Application Laid-Open No. 2-297710, the surface of the steel shell of a blast furnace is hit with a hammer, and the elastic wave generated by the hit propagates through the refractory brick, reflects on the inner end face of the refractory brick, and returns to the surface of the steel shell again. A method of measuring the thickness of the refractory brick from the reciprocating time and the propagation speed of the elastic wave in the refractory brick obtained in advance and the reciprocation time is disclosed.

[0003] The most popular method in recent years is
In this method, a thermometer is buried inside the brick to measure the heat flux transmitted from the core side to the steel shell side. In this method, around 100 thermometers are buried in the refractory brick around the entire circumference of the blast furnace side wall, and after measuring the heat flux, the position where the heat source of 1150 ° C., which is the pig iron solidification temperature, exists from the heat conduction equation. Is calculated and the remaining thickness of the refractory brick is estimated.

[0004]

However, the method disclosed in Japanese Patent Application Laid-Open No. 58-27002 discloses a method of opening a steel shell at a measuring point and hitting a metal rod brought into contact with a refractory brick by a blast furnace. There is a problem that only the thickness of the refractory brick at a specific location can be measured. Also, JP-A-62-297
The method disclosed in Japanese Patent Publication No.
In the case of a blast furnace having a multi-layered structure of refractory bricks, the reflection signal of the elastic wave transmitted from the outside of the steel shell is complicated, and it is difficult to extract only the reflection signal from the innermost end face of the refractory brick. In particular, if there are gaps between the refractory bricks or cracks in the refractory bricks, reflected signals will be generated there,
It takes skill to specify which of them is the reflected signal from the innermost end face of the refractory brick to be measured.

Further, the method for measuring the heat flux with the embedded thermometer has the following problems. That is, when calculating the refractory brick residual thickness from the heat flux, the refractory brick, the thermal conductivity of the stamp material, etc., is used, but since this thermal conductivity changes over time with the deterioration of the refractory brick, the stamp material, The difference between the thermal conductivity used when calculating the thickness and the actual thermal conductivity causes a thickness calculation error. When a heat insulating layer (crack portion) is present in the refractory brick, part of the heat flux is blocked by the heat insulating layer, and the thickness of the refractory brick is calculated to be larger than the actual value. Refractory brick management using such a thermometer is effective to constantly monitor the refractory brick erosion tendency using a large number of thermometers, but since it is embedded in the furnace wall and installed, it is necessary to change the measurement point Needs to install a new thermocouple.

An object of the present invention is to solve the above-mentioned problems of the prior art and to provide a method capable of accurately measuring the thickness of a refractory inside a furnace from outside the furnace.

[0007]

To achieve the above object, the present invention provides the following methods (1) to (4). (1) In a method of measuring the thickness of a refractory in a furnace radial direction in a heating furnace having a refractory on an innermost surface and a multi-layered wall made of another material outside the refractory, a method for measuring the thickness of the outermost wall An elastic wave is transmitted toward the inner refractory, a reflected signal from the innermost surface of the refractory is received on the outermost wall surface, and a reflected wave is detected from a time-series change of a specific frequency component of the reflected signal. The time is calculated, and the thickness of the refractory is measured from the propagation time remaining after subtracting the time required for the reciprocal propagation of the material other than the refractory from the reflection time from the elastic wave transmission start time to the reflected wave detection time. A method for measuring the thickness of a refractory in a furnace. (2) In the furnace refractory thickness measuring method according to the above (1), the specific frequency component is determined by a thickness in a furnace radial direction of a material constituting an outermost surface of the heating furnace and an elastic wave propagation velocity in the material. A method for measuring the thickness of a refractory in a furnace, wherein the determined frequency component is a repetition frequency value due to multiple reflection of an elastic wave in the material. (3) In the furnace refractory thickness measuring method according to the above (2), a wavelet transform is used as a signal processing method for obtaining a time series change of a specific frequency component of the reflected signal. Thickness measurement method. (4) In the furnace refractory thickness measuring method according to the above (3), as a means for judging a reflected signal from the innermost end face of the refractory, a peak of a waveform having an output of 0 as a boundary with respect to the reflected signal after the wavelet transform processing. And the valleys, the absolute value of the extreme value of the valley waveform starting from the valley waveform is calculated from the absolute values of the two peak waveforms before and after the valley waveform and the extreme values of the valley waveform. The trough waveform is also large, and furthermore, among the constituent materials of the furnace wall, the trough waveform which first appears beyond the time required for the reciprocating propagation of the elastic wave in the material located outside the refractory is called the refractory inner end face. A method for measuring the thickness of a refractory in a furnace, characterized in that the waveform is a reflection waveform from a furnace.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be specifically described below with reference to the drawings. FIG. 1 is a block diagram showing a method for measuring the thickness of a refractory according to the present invention. In a blast furnace having a multi-layered furnace wall, a stamp material 2 which is an amorphous refractory is provided inside an outermost steel shell 1, and a refractory brick 3 is further stacked inside. An elastic wave transmitter 4 and a receiver 5 are installed on the outermost steel surface 1a. A pulsar 6 for outputting an electric signal for generating an ultrasonic wave is connected to the transmitter 4, an amplifier 7 for amplifying a reflected signal detected by the receiver 5 is connected to the receiver 5, The reflected signal amplified by the amplifier 7 is recorded in the memory 10 via the A / D converter 9. At this time, the pulsar 6 is controlled by the control unit 8.
Is used as a trigger timing signal, and recording in the memory 10 is started at that timing. FIG. 2 shows an example of a reflected signal sampled by this method. In the graph shown in FIG. 2, the horizontal axis represents time and the vertical axis represents output, and the measured reflected signal S is shown.

[0009] As shown in FIG. 4, in steel shell 1 during the ultrasonic incident is outermost of the furnace wall transmitter 4 is in contact, multiple reflection wave R ₁ of the elastic wave is generated in its interior.
When the multiple reflection wave R ₁ is reflected by the steel shell 1 of the inner end face 1b, it continues to sequentially transmitted acoustic wave toward the furnace inside (in FIG. 4 P). In addition, as shown in FIG.
The elastic wave R ₃ transmitted to the inside of the refractory brick is reflected at the innermost end face 3 b of the refractory brick, and a multiple reflected wave R ₁ is again formed inside the steel shell 1 by the reflected signal reflected to the steel shell 1 of the outermost furnace wall. . This is the same phenomenon as a multiple reflection wave generated when an ultrasonic wave is incident.

At this time, the repetition frequency f (kHz) of the multiple reflection wave generated in the outermost furnace wall is the outermost material (steel 1).
Is calculated by the following equation from the thickness d ₁ (mm) in the furnace radial direction and the elastic wave propagation velocity v ₁ (m / sec) inside the material.

(Equation 1)

With respect to the reflection signal measured by the receiver 5, a time-series change of a frequency component having a repetition frequency f (kHz) calculated as a formula (1) as a center frequency is extracted. Wavelet transform is used as a means for extracting the time series change of the frequency component. For the specific calculation method of the wavelet transform, refer to the document Wavelet Understanding and Application (Benide
tto, JJ, Frazier, MW / Ed. Masaya Yamaguchi, Michio Yamada / Translated by Springer Verlag Tokyo).

FIG. 3 shows the result of frequency components extracted from the reflection signal S shown in FIG. 2 with the repetition frequency f (kHz) as the center frequency. In the graph of FIG. 3, the horizontal axis represents time, and the vertical axis represents output, and the reflected signal A after wavelet transform processing is performed. The signal processing by the wavelet transform has advantages that the time error after the processing is small and the phase of the reflected signal is not changed as compared with the processing result by the band pass filter or the like.

The following method is used as a method for determining the reflected wave from the innermost part of the refractory brick from the reflected signal with respect to the time-series change signal of the frequency component extracted by the frequency component extracting process. The procedure for determining the reflected signal will be described with reference to FIGS. FIG. 7 is an enlarged view of a part of the reflected signal after the signal processing of FIG. The waveform signal shown in FIG. 7 is divided into a peak waveform which is a positive output including zero with 0 as a threshold and a valley waveform which is a negative output ((1) to (1) in FIG. 7).
7), odd numbers are trough waveforms, even numbers are peak waveforms). The absolute value of the extreme value of the valley waveform to be determined is two waveforms before the valley waveform and four absolute values after the valley waveform.
If it is larger than the absolute value of each extreme value of the valley waveform and the peak waveform of the waveform, it is determined as a reflected wave. As a specific example, when the determination method is applied to the valley waveform (7) in FIG.
The absolute value of the extreme value of (7) is larger than the absolute value of the extreme values of (5) and (6) of the previous two waveforms and (8), (9), (10) and (11) of the last four waveforms Thus, the reflected wave is determined. Similarly, the valley waveform (1
3) is also determined to be a reflected wave by comparing the absolute values of the extreme values. Thus, (7) and (13) of the valley waveform shown by the solid line in FIG. 8 are determined. The time of the fall start point of the determined valley waveform is set as the reflected wave detection time of the measured waveform.

[0014] Of the reflected wave detection times determined by the above method, the reflected wave detection time is determined by the time when the elastic wave reciprocates through the steel shell 1 and the stamp material 2 that pass through to the refractory brick 3 to be measured. The time that first appears after the time t (msec) required is determined as the detection time of the reflected wave from the inner end face 3b of the refractory brick. Since the stamp material 2 is not eroded in the normal blast furnace operation, the thickness d of the steel
₁ (mm) and the thickness d ₂ (mm) of the stamp material 2 are known from the drawing dimensions, and the elastic wave propagation velocity v ₁ (m / sec) in the steel shell 1 and the stamp material 2 The time t (msec) can be calculated by the following equation using the elastic wave propagation velocity v ₂ (m / sec) at

(Equation 2)

When the waveform signal of FIG. 3 is determined by using this determination method, the vertical line in FIG. 3 is determined. Than this,
The detection time T (msec) of the reflection signal from the innermost end face 3b of the refractory brick is obtained from the start time of the elastic wave incidence, and the remaining thickness L (mm) of the refractory brick can be calculated by the following equation.

(Equation 3)

That is, from the time T (msec) required for transmitting the elastic wave from the outermost surface to receiving the reflected signal from the inner surface 3b of the refractory brick at the outermost surface, the refractory brick to be measured is obtained. Iron skin that penetrates up to 3
After subtracting the time t (msec) required for the elastic wave to reciprocate propagate through the stamp material 2, the refractory brick is obtained by using the elastic wave propagation velocity V (m / sec) in the refractory brick 3 determined in advance. The remaining thickness L (mm) can be calculated.

[0017]

FIG. 1 shows an embodiment of the present invention. The in-furnace refractory thickness measuring apparatus of this embodiment measures the thickness of a refractory brick lined inside a blast furnace whose surface is covered with an iron shell. In the furnace which we measured this time, the first layer from the surface was steel skin, thickness 60mm, sound speed 5980m / se
c, the second layer is a stamp material having a thickness of 100 mm and a sound speed of 16
The third layer is a refractory brick to be measured and has a sound speed of 3000 m / sec.

A transmitter 4 is provided on the steel surface 1a via a couplant.
And the receiver 5 are installed. Using ultrasonic waves for elastic waves,
A voltage step pulse of 500 V is input from the pulsar 6 to the transmitter 4 and generated. Receiving frequency characteristic is 20kHz ~
The reflected signal was measured at the receiver 5 at 500 kHz. 5MHz sampling frequency, 8000 memory data points
The measurement range was 1.6 msec. FIG. 2 shows an example of a reflected signal sampled by this method. In the graph shown in FIG. 2, the horizontal axis represents time, and the vertical axis represents output, and the measured reflected signal S
Is shown.

The reflection signal is subjected to a frequency extraction process using a wavelet transform. The analyzing wavelet ψ (t) used for the wavelet transform uses a general Mexican hat function. The Mexican hat function ψ (t) is represented by the following equation, and the shape is shown in FIG.

(Equation 4)

The target steel skin is 60 mm thick and has a sound speed of 598.
From equation (1), the repetition frequency f ≒ 49.8 kHz from 0 m / sec
Becomes FIG. 3 shows the result of extracting frequency components with this frequency f as the center frequency. FIG. 3 shows the reflected signal A after performing the wavelet transform processing with the horizontal axis representing time and the vertical axis representing output.

Next, the determination method will be described. Due to the general structure of the blast furnace, the phase of the reflected signal from the steel shell end face 1b and the refractory brick end face 3b is inverted with respect to the incident signal. In addition, a normal reception waveform forms an attenuation wave. The reflected signal is determined using these two characteristics. Specifically, the determination is performed on the reflection signal based on the output value and the output direction parameter.

The reflection time T is determined by applying the above-described determination method to the extracted frequency components. A reflection time T = 0.56 msec is obtained from the determined reflected wave detection time. The reflection time T = 0.56 msec and the sound speed value of the refractory brick previously measured as 3000 m / sec, and the round trip time t of the steel shell and stamp material t = 0.0201 + 0.
When the thickness of the refractory brick is calculated from Equation 3 using 1212 = 0.1413 msec, the residual thickness of the refractory brick L ≒ 628.1
mm is obtained.

[0023]

By using the method for measuring the thickness of a refractory in a furnace according to the present invention, the thickness of the innermost refractory for determining the life of the blast furnace can be measured from the outermost surface of the furnace. An unspecified portion can be measured by the above-described effect, and the reflected wave determination method of the present invention does not require any skill to specify a reflected signal, so that the reflected signal can be easily handled. INDUSTRIAL APPLICABILITY The present invention is effective in refractory residual thickness management, and can accurately estimate the life of a furnace, and as a result, can predict the time of furnace repair.

[Brief description of the drawings]

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

FIG. 2 is a measurement waveform graph obtained by measuring a blast furnace wall using the present apparatus.

FIG. 3 is a processed waveform graph after performing a wavelet transform process on a measured waveform.

FIG. 4 is an explanatory diagram of multiple reflected waves in a steel shell.

FIG. 5 is an explanatory diagram of generation of an iron skin multiple wave by a brick reflected wave.

FIG. 6: Mexican hat used for wavelet transform
(Mexican hat) A graph showing the shape of the function.

FIG. 7 is a graph illustrating a method of determining a reflected wave.

FIG. 8 is a graph illustrating a method of determining a reflected wave.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 steel 2 stamp material 3 refractory brick 4 transmitter 5 receiver 6 pulsar 7 amplifier 8 measuring device control unit 9 A / D conversion unit 10 memory 11 frequency separation processing unit 12 thickness calculation unit 13 display S reflection signal A signal processing Reflection signal after T Reflection time of elastic wave from refractory end face 3b

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Hiroyuki Tanaka 20-1 Shintomi, Futtsu-shi, Chiba F-term in the Technology Development Division of Nippon Steel Corporation (reference) 2F068 AA28 BB14 BB29 CC00 FF13 FF25 KK14 QQ00 2G047 AA08 BA03 BC02 BC18 EA10 4K002 CA01 4K015 KA07

Claims (4)

[Claims] 1. A method for measuring the thickness of a refractory in a heating furnace having a refractory on an innermost surface and a multi-layered wall made of another material on the outer side, the method comprising: The elastic wave is transmitted toward the refractory, the reflected signal from the innermost surface of the refractory is received on the outermost wall surface, and the reflected wave detection time is determined from the time-series change of a specific frequency component of the reflected signal. Calculate and measure the thickness of the refractory from the propagation time remaining after subtracting the time required for the reciprocal propagation of the material other than the refractory from the reflection time from the elastic wave transmission start time to the reflected wave detection time. Characteristic method for measuring refractory thickness in furnace. 2. As a specific frequency component, a repetition frequency value by multiple reflection of an elastic wave in the material, which is determined by a thickness of a material constituting an outermost surface of the heating furnace and a propagation speed of the elastic wave in the material. 2. The method for measuring the thickness of a refractory in a furnace according to claim 1, wherein the frequency component is the following. 3. The method according to claim 2, wherein a wavelet transform is used as a signal processing method for obtaining a time-series change of a specific frequency component in the reflected signal. 4. As a means for determining a reflected signal from the innermost end face of the refractory, the reflected signal after the wavelet transform processing is divided into peaks and valleys with an output of 0 as a boundary. The valley waveform whose absolute value of the extreme value of the valley waveform is larger than the absolute values of the extreme values of the two peaks and the four valley waveforms before and after the valley waveform starting from the waveform, is a valley waveform. The valley waveform which first appears in the material located outside the refractory material out of the refractory material beyond the time required for the reciprocating propagation of the elastic wave is a reflection waveform from the refractory inner end face. 3. The method for measuring refractory thickness in a furnace according to 3.