JPH10185654A - Method of detecting liquid level of furnace-melted matter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of detecting liquid level in which the level of a furnace-melted matter can be stably detected over a long period of time without being influenced by the gain fluctuation of a transmitting and receiving system resulted from the contact force of an elastic wave transmitting element and receiving element to the furnace wall and others. SOLUTION: When an elastic wave transmitting element 11 and an elastic wave receiving element 12 are set on a furnace outer wall whose circumference is covered with a refractory, and an elastic wave is emitted from the elastic wave transmitting element 11 into a furnace 100 to detect the liquid level of a furnace melted matter 101 on the basis of the received signal obtained from the elastic wave receiving element 12 by the emission of the elastic wave, the surface wave propagating the furnace outer wall surface and the reflected echo by the furnace inner wall are received by the elastic wave receiving element 12, the wave height of the reflected echo is corrected on the basis of the wave height of the surface wave, and the level is detected on the basis of the wave height of the corrected reflected echo.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting a liquid level of a melt in a blast furnace or another furnace. Hereinafter, for convenience of explanation, a method of detecting the liquid level of the hot metal in the blast furnace will be described as an example.

[0002]

2. Description of the Related Art In the operation of a blast furnace, the liquid level of hot metal at a bottom sump (hereinafter simply referred to as "hot metal level") is used.
It is extremely important to improve the operation efficiency. In particular, if the hot metal level rises above the allowable level, it may lead to instability of the furnace condition, such as an increase in tuyere blowing pressure, and sometimes lead to troubles such as poor tapping / slagging and backflow of the slag. Loss. For this reason, detecting the level of hot metal is an indispensable task from the viewpoint of monitoring furnace operation.

As a method for detecting the level of hot metal in a blast furnace, for example, Japanese Patent Laid-Open Publication No. Sho 52-127354 discloses a method in which a plurality of ultrasonic probes for vertical flaw detection are arranged on a furnace wall in the height direction. There is disclosed an apparatus in which the level of hot metal in a furnace is detected by comparing the levels of reflected ultrasonic waves received by each probe.

Further, the present applicant also radiates an elastic wave from the outer wall of the furnace to receive a reflected wave from the inner wall of the furnace, and the wave height of the received reflected wave and the reflected wave in the height direction of the furnace. Has already been developed that calculates the hot metal level of the molten metal in the furnace based on the wave receiving position, the correspondence between the wave height of the reflected wave and the molten liquid level in the furnace set in advance. (Japanese Patent Application No. 7-304565).

[0005]

However, according to various studies by the present inventors, according to the method for measuring the hot metal level in a furnace using an elastic wave such as an ultrasonic wave as described above, It has been found that there are points to be improved as follows. That is, in the hot metal level measurement method described above,
The basis for determining the presence or absence of hot metal, or for calculating the hot metal level, is the wave height of the reflected echo on the inner wall of the furnace in the received waveform, and its detection method is as follows. The maximum value or the maximum value of the absolute value is detected.

Here, in general, a piezoelectric element is used for transmitting and receiving an elastic wave of an ultrasonic probe or the like, and the piezoelectric efficiency (electric-acoustic conversion coefficient) of the piezoelectric element is affected by stress and temperature. It is known to receive. For this reason, if an ultrasonic probe is installed in a blast furnace or the like for a long period of time, an external force due to thermal expansion of the furnace wall refractory may act on the probe, and a temperature change of the furnace wall outer surface may cause the external force. The temperature of the probe itself changes, causing an error in the wave height of the reflected echo to be detected.

[0007] As a method of solving such a problem,
For example, by simultaneously monitoring the temperature and stress on the installation surface of the ultrasonic probe, a gain correction value calculated from the monitored amount and the sensitivity calibration relationship of the probe created in advance,
It is conceivable to correct the wave height of the reflected echo. However, in this case, it is necessary to add measurement means for each factor that affects the gain variation of the probe, and it is necessary to obtain in advance the sensitivity calibration relationship of the probe corresponding to those measured values. Not only complicates the equipment configuration,
A problem arises in that the post-correction processing is also complicated.

As another solution, as is known in the field of ultrasonic flaw detection, a reference hole is previously formed in a medium, and the echo height to be detected is corrected based on the echo height of the reference hole. It is possible. According to this method,
This has the advantage that the overall gain related to ultrasonic transmission and reception can be easily corrected.On the other hand, however, since a reference hole is made in the medium in advance, the strength of the furnace wall may be impaired. When the thickness is reduced, it becomes difficult to distinguish the echo from the reference hole and the echo from the inner wall surface, or it becomes inapplicable after melting to the furnace wall position, etc. Will be.

The present invention has been made in view of such a problem, and is not affected by gain fluctuation of a transmission / reception system due to a contact force between an elastic wave transmitter and a receiver against a furnace wall and the like. Another object of the present invention is to provide a liquid level detection method capable of stably detecting the liquid level of a melt in a furnace over a long period of time.

[0010]

In order to achieve the above object, the present invention provides an elastic wave transmitter and an elastic wave receiver provided on an outer wall of a furnace covered with a refractory. Radiating an elastic wave toward the inside of the furnace, and detecting the liquid level of the melt in the furnace based on a reception signal obtained from the elastic wave receiver by radiating the elastic wave, the elastic wave receiver A surface wave propagating on the outer wall of the furnace and a reflected echo on the inner wall of the furnace are received, and the wave height of the reflected echo is corrected based on the wave height of the surface wave, and the liquid level is corrected based on the corrected wave height of the reflected echo. Is detected.

In a preferred embodiment of the present invention, the wave height of the reflection echo is divided by the wave height of the surface wave for correction.

In another preferred embodiment of the present invention, the received signal is amplified so that the wave height of the surface wave becomes a predetermined value, and the wave height of the reflected echo is corrected.

According to still another preferred embodiment of the present invention, when the received signal is amplified so that the wave height of the surface wave becomes a predetermined value and the wave height of the reflected echo is corrected, When the wave height of the surface wave exceeds the maximum amplified voltage, the received signal is amplified so that the wave height of the surface wave becomes the maximum amplified voltage for a predetermined time, and the wave height of the reflected echo is corrected.

[0014]

FIG. 1 is a diagram for explaining the principle of the present invention. As shown in FIG. 1, an elastic wave transmitter 2 and an elastic wave receiver 3 are attached to an outer wall of a furnace 1 made of a solid medium, and a pulse voltage is transmitted to the transmitter 2 to generate an elastic wave (longitudinal wave transmission wave) inside the furnace. For example, when an ultrasonic wave is radiated, the receiver 3 has a surface acoustic wave traveling along the wall surface in addition to a reflected echo (longitudinal wave reflected wave) which travels vertically in the medium and is reflected on the reflecting surface. And the output voltage waveform is as shown in FIG.

In the output voltage waveform shown in FIG. 2, the peak height Ve of the reflected echo and the peak height Vs of the surface wave are represented by Vp, the transmission (applied) pulse voltage applied to the transmitter 2, and the electric potential of the transmitter 2 in FIG. The acoustic conversion coefficient is G ₁ , the gain of the reflection propagation path is D ₁ , the reflectivity on the inner wall of the furnace wall is r, the electro-acoustic conversion coefficient of the receiver 3 is G ₂ , and the output signal of the receiver 3 is processed. the gain of the acoustic measuring instruments (not shown) a, when the gain of the surface wave propagation path and D _2, expressed by _{Ve = VpG 1 D 1 rG 2} a Vs = VpG 1 D 2 G 2 a.

Here, the transmitter 2 and the receiver 3 are connected to the furnace 1
, The gain D _{1 of the} reflection propagation path
And the gain D ₂ of the surface wave propagation path can be regarded as a constant. Therefore, for example, the wave height V of the reflected echo
divided by height Vs of the surface wave e, take their ratio becomes _{Ve / Vs = r (D 1} / D 2), the amount proportional only to the reflectance r in the furnace wall inner surface . That is, by taking the ratio between Ve and Vs in the same reception waveform, the transmission pulse voltage Vp, the electro-acoustic conversion coefficient G _{1 of} the transmitter 2, and the electro-acoustic conversion coefficient G of the receiver 3 are obtained.
_{Even if 2} fluctuates, a measurement result related only to the reflectance r on the inner surface of the furnace wall can be obtained without being affected by them.

Further, instead of performing the above division, when the gain A of the ultrasonic measuring device is adjusted so that the wave height Vs of the surface wave becomes a predetermined value Vso, A = Vso / (VpG ₁ D ₂ G ₂ ) Therefore, the wave height Ve 'of the reflected echo after changing the gain
Is

(Equation 1) Becomes Therefore, as in the case of the above division, V
Unaffected by fluctuations in p, G ₁ and G ₂ , r
Can obtain measurement results related only to.

When the gain A of the ultrasonic measuring device is adjusted so that the wave height Vs of the surface wave becomes the predetermined value Vso, Vs is already the maximum amplified voltage in the ultrasonic measuring device, that is, Vso. Is greater than Vs
Is amplified to Vso for a predetermined time to correct Ve. In this way, similarly, Vp, G ₁ and G
_The measurement result related only to r can be obtained without being affected by the fluctuation of ₂ .

As described above, from the received waveform received by the elastic wave receiver 3, the peak height Ve /
After obtaining Vs or Ve ', the liquid level of the melt in the furnace is calculated based on Vs or Ve'. For example, in the liquid level measurement method according to the above-mentioned proposal of the present applicant, the relationship between the wave height V of the reflected echo to be observed and the liquid level L of the molten material in the furnace depends on the installation height of the transceiver. h

(Equation 2) Which is transformed using the inverse function G (x) of F (x)

(Equation 3) , The liquid level L can be calculated from the detected peak height V of the reflected echo. Therefore, instead of this peak height V, the corrected peak height Ve / Vs of the reflected echo or Ve ′ is used.

(Equation 4) The liquid level can be calculated based on In addition,
The present invention can be widely applied to a method of detecting a liquid level based on the wave height of a reflected echo, in addition to the above calculation method.

[0020]

FIG. 3 is a diagram showing a configuration of an example of an apparatus for implementing a method for detecting a liquid level of a melt in a furnace according to the present invention. In FIG. 3, reference numeral 100 denotes a furnace made of a refractory material;
Is an in-furnace melt, 11 is an elastic wave transmitter, 12 is an elastic wave receiver, 13 is an elastic wave measuring instrument, 14 is a reflection echo detection circuit,
Reference numeral 15 denotes a surface wave detection circuit, 16 denotes a division circuit, 17 denotes an operation circuit, and 18 denotes a display device.

The elastic wave transmitter 11 and the receiver 12 make use of the electro-acoustic conversion effect of a piezoelectric material, and are preferably commercially available at low cost for transmitting and receiving elastic waves of several tens kHz to 200 kHz. Use the one that is The elastic wave transmitter 11 and the receiver 12 are preferably attached in close contact with the brick surface of the furnace wall via an appropriate elastic wave coupling material.

The elastic wave measuring device 13 applies a high voltage signal to the elastic wave transmitter 11 at time intervals according to the liquid level monitoring frequency to excite the elastic wave, and the elastic wave receiver 11 converts the electric signal into an electric signal. The converted received elastic wave signal is amplified to a voltage signal within an appropriate range, for example, several hundred mV to several V, and supplied to the reflection echo detection circuit 14 and the surface wave detection circuit 15 at the subsequent stage.

The reflected echo detecting circuit 14 and the surface wave detecting circuit 15 detect the wave height of the reflected echo on the inner wall of the furnace wall and the wave height of the surface wave propagating on the outer wall of the furnace, respectively, from the output waveform of the elastic wave measuring device 13. The gate circuit, the absolute value circuit, the peak detection circuit, etc. used in general elastic wave measurement are combined, and the gate circuit reflects the reflected wave on the inner wall of the furnace wall and the surface that propagates on the outer wall of the furnace. It is configured to extract a wave and detect a peak of its absolute value.

The division circuit 16 includes a reflection echo detection circuit 14
Ve / V based on the peak height Ve of the reflected echo detected in step S1 and the peak height Vs of the surface wave detected in the surface wave detection circuit 15.
s is calculated to correct the peak height Ve of the reflected echo. Further, the arithmetic circuit 17 calculates the liquid level L of the in-furnace melt 101 by, for example, the above equation (1) based on the corrected reflected echo peak height Ve / Vs calculated by the division circuit 16. And display the calculation result on the display device 18 at the subsequent stage.

The reflection echo detection circuit 14, the surface wave detection circuit 15, the division circuit 16 and the operation circuit 17 can be realized by analog elements.
By digitizing all subsequent data, it is also possible to adopt a configuration in which arithmetic processing using an arithmetic circuit such as a microprocessor is substituted.

Hereinafter, the operation of this embodiment will be described. In this embodiment, while the liquid level of the in-furnace melt 101 is substantially constant, an elastic wave is transmitted from the elastic wave transmitter 11 and thereby, based on a reception waveform obtained from the elastic wave receiver 12, The peak Ve of the reflected echo and the peak Vs of the surface wave were detected by the reflection echo detection circuit 14 and the surface wave detection circuit 15, respectively, and the detection results shown in FIG. 4 were obtained. Here, in the first half of the period during which the measurement was performed, the temperature rise due to abnormal cooling of the attachment portion of the elastic wave transmitter 11 and the receiver 12 of the furnace 100, and in the second half, electric work was performed nearby. The random fluctuation of the power supply voltage caused by the peaks Ve and Vs
It appears that the detection error appears.

However, the reflection echo height Ve and the surface wave height Vs detected by the reflection echo detection circuit 14 and the surface wave detection circuit 15, respectively, are supplied to a division circuit 16 to divide Ve by Vs. When the wave height of the reflected echo is corrected, as shown in FIG. 5, a corrected wave height (Ve / Vs) of the reflected echo which changes substantially in the same manner as the actual level of the melt 101 in the furnace is obtained. When the liquid level was calculated by the calculation circuit 17 based on this,
The liquid level of the in-furnace melt 101 could be accurately and stably detected without being affected by the temperature rise of the elastic wave transmitter 11 and the receiver 12 and random fluctuation of the power supply voltage.

It should be noted that the present invention is not limited to the above-described embodiment, but can be variously modified or changed. For example, in FIG. 3, a gain adjustment circuit is provided instead of the division circuit 16, and the reflection detected by the reflection echo detection circuit 14 is set so that the wave height of the surface wave detected by the surface wave detection circuit 15 becomes a predetermined value. The wave height of the echo may be amplified and corrected, and the arithmetic circuit 17 may detect the liquid level based on the amplified and corrected wave height of the reflected echo. Further, in this case, when the wave height of the surface wave detected by the surface wave detection circuit 15 exceeds the maximum amplified voltage in the gain adjustment circuit, the wave height of the surface wave becomes the maximum amplified voltage for a predetermined time. So that the reflection echo detection circuit 14
It is also possible to amplify and correct the wave height of the reflected echo detected in step (a), and to detect the liquid level in the arithmetic circuit 17 based on the amplified wave height of the reflected echo.

[0029]

According to the present invention, the wave height of the reflected echo, which is the basis for measuring the liquid level of the melt in the furnace, is corrected based on the wave height of the surface wave component in the same received wave. Therefore, the liquid level can be stably measured over a long period of time without being affected by an error due to a voltage fluctuation of a transmission pulse or a gain fluctuation of an elastic wave transmitting / receiving system due to temperature, stress, or the like. Therefore, not only can the melting furnace such as a blast furnace be operated stably, but also if the wave height of the surface wave is abnormally large or small, it is regarded as an abnormality of the measuring device and an alarm is issued. It can be used, and the operational reliability of the measuring device can be increased.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining the principle of the present invention.

FIG. 2 is a diagram showing an example of a reception waveform obtained from the elastic wave receiver shown in FIG.

FIG. 3 is a diagram showing a configuration of an example of an apparatus for performing a method for detecting a liquid level in a furnace melt according to the present invention.

FIG. 4 is a diagram showing detection results of an example of the height of a reflected echo and the height of a surface wave in the reflected echo detection circuit and the surface wave detection circuit shown in FIG.

5 is a diagram showing an example of the wave height of a corrected reflected echo obtained from the division circuit shown in FIG. 3;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Furnace 2 Elastic wave transmitter 3 Elastic wave receiver 100 Furnace 101 Furnace melt 11 Elastic wave transmitter 12 Elastic wave receiver 13 Elastic wave measuring instrument 14 Reflection echo detection circuit 15 Surface wave detection circuit 16 Division circuit 17 Operation circuit 18 Display device

Claims (4)

[Claims] 1. An elastic wave transmitter and an elastic wave receiver are installed on a furnace outer wall whose periphery is covered with a refractory, and an elastic wave is radiated from the elastic wave transmitter toward the inside of the furnace. In detecting the liquid level of the in-furnace melt based on the reception signal obtained from the elastic wave receiver by the radiation of, the surface acoustic wave propagating on the furnace outer wall surface by the elastic wave receiver and the reflected echo on the furnace inner wall are Receiving, correcting the wave height of the reflected echo based on the wave height of the surface wave, and detecting the liquid surface level based on the wave height of the corrected reflected echo, Level detection method. 2. The liquid level detection method according to claim 1, wherein a wave height of the reflected echo is corrected by dividing the wave height of the reflected echo by a wave height of the surface wave. . 3. The liquid level detection method according to claim 1, wherein the reception signal is amplified so that the wave height of the surface wave becomes a predetermined value, and the wave height of the reflection echo is corrected. A method for detecting the liquid level of the melt in the furnace. 4. The liquid level detecting method according to claim 3, wherein when the wave height of the surface wave exceeds a maximum amplified voltage,
A method for detecting a liquid level of a melt in a furnace, comprising: amplifying the received signal so that the wave height of the surface wave becomes the maximum amplified voltage for a predetermined time; and correcting the wave height of the reflected echo.