JP2813293B2 - Dust collector abnormality detection method and abnormality detection device - 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 detecting an abnormality of a dust collector.

[0002]

2. Description of the Related Art For example, in a steelworks, there are many places where dust is generated, such as a converter, and dust collectors are provided in various places to maintain a working environment. Recently, bag filters have been used from the viewpoint of dust collection performance. Often done. FIG. 11 shows an example of such a bag filter 35. Dust-containing gas 37 entering from a pipe 36 enters a dust collecting tank 39 through a damper 38 for adjusting the air volume. A large number of bugs 40 made of a cylindrical filter cloth are arranged in the dust collecting tank 39 via a suspension device 41, and the dust-containing gas 37 is filtered through each of the bugs 40, and is filtered. Only gas is exhausted to outlet 42.

[0003] Dust 43 accumulated on the inner surface of each bug 40
Is knocked down by applying vibration to the suspension device 41 or by reversely feeding the washing air from the outlet 42 side (backwashing). FIG. 12 is an overall configuration diagram of the dust collecting equipment. Usually, four to eight bag filters 35 shown in FIG. 11 are arranged side by side, and the dust-containing gas 37 is sent to each bag filter 35 by the blower 44, Are periodically switched between dust collection and backwashing by the entrance damper 45 and the exit damper 46. The dust-collected gas is sent to a chimney 48 through a pipeline 47, and an induction blower 49 is provided in the middle of the bag filter depending on the type of bag filter.

In the bag filter 35, each bug 40 in the dust collecting tank 39 may be broken by vibration. Once this breaks, a large amount of dust-containing gas 37 leaks out of it,
A large amount of dust is released from the chimney 48 into the atmosphere, which poses a serious problem for environmental protection. Therefore, the following countermeasures have been taken in steelworks. (1) A differential pressure gauge is provided before and after the bug 40 (for example, the pipe 36 and the outlet 42 in FIG. 11), and an abnormal change in the pressure value of the differential pressure gauge is caught to detect an abnormality of the dust collector (break of the bug 40). . (2) An optical dust densitometer is installed in the pipeline shown by B or C in FIG. 12, and abnormality of the dust collector is detected based on the value of the densitometer.

[0005]

However, in the detection method of the above (1), a differential pressure is generated only at the moment when the bug 40 is broken, and it is difficult to reliably detect the moment. There is a high risk of overlooking. Further, this detection method is useless when the breakage of the bug 40 is small and no differential pressure is generated.

On the other hand, the above method (2) does not cause such inconvenience, but the conventional optical dust densitometer directly analyzes the intensity of transmitted or scattered light incident from the light projector to determine the dust concentration. Because it is seeking, it reacts to the stationary dust. Therefore, if dust adheres to the window provided in the conduit and becomes dirty, an abnormality may be erroneously detected. Therefore, maintenance is troublesome, and it cannot be used for a long time with security.

In the case of an optical dust densitometer, the dust density is determined from the intensity of transmitted or scattered light, so that it is suitable for measuring the density in a low density range. The possible density range is small and the reliability is reduced in the high density range. Thus, the conventional optical dust densitometer is installed at the positions B and C in FIG. 12 where the density does not immediately rise even after the occurrence of the abnormality, and at the position A (immediately after the bag filter 35) where the concentration rapidly increases after the occurrence of the abnormality. Pipeline)
Could not be installed, so it was not possible to detect which of the bag filters 35 had an abnormality.

In view of such circumstances, the present invention provides a method and an apparatus for detecting an abnormality of a dust collector which can detect an abnormality of the dust collector stably even in a high concentration area without being affected by dirt on a window. The purpose is to do.

[0009]

In order to achieve the above object,
The present invention has taken the following technical measures. In other words, the invention according to claim 1 provides a dust-containing gas flowing through a pipe connected to the outlet side of a dust collector with a millimeter-wave band of 30 GHz or more at an angle that is not perpendicular to the flow direction of the dust-containing gas. Irradiate the electromagnetic wave, and while detecting the scattered wave scattered by the dust contained in the dust-containing gas, the electromagnetic wave and the amount of the Doppler shift of the scattered wave to obtain the frequency spectrum of the same shift amount, An abnormality of the dust collector is detected based on the frequency spectrum.

According to a second aspect of the present invention, a dust concentration in a pipe corresponding to an area of a frequency spectrum obtained from a Doppler shift amount is obtained, and an abnormality of the dust collector is detected based on the value of the dust concentration. It is characterized by the following. Further, the invention according to claim 3 obtains an average flow velocity of dust particles in a pipeline corresponding to a frequency giving a peak value of a frequency spectrum obtained from the Doppler shift amount. An abnormality of the dust collector is detected based on the detected dust.

According to a fourth aspect of the present invention, there is provided a dust collector abnormality detecting apparatus for a millimeter wave band of 30 GHz or more at an angle which is not perpendicular to the flow direction of the dust-containing gas in a pipe leading to the outlet side of the dust collector. Irradiating means for irradiating electromagnetic waves, detecting means for detecting scattered waves in which the electromagnetic waves are scattered by dust contained in the dust-containing gas, a mixer for extracting a Doppler shift amount between the electromagnetic waves and the scattered waves, and the Doppler Measuring means for calculating a frequency spectrum of the shift amount and calculating an area of the frequency spectrum, a frequency giving a peak value of the spectrum, or both of them.

[0012]

[Function] The dust contained in the dust-containing gas has a diameter of about 0.1 μm.
The optical dust densitometer uses a light wave having a wavelength of about 0.5 μm to 1 μm, and mainly uses Mie scattering of this light wave. Thus, according to the concept of the conventional optical dust densitometer, if a wave having a long wavelength is used, it passes through the dust group, and scattering hardly occurs.

However, even after passing through the bag filter, 2
The dust content is about 0 to ³⁰ mg / m ³ , and the Mie scattering is sufficiently large. On the other hand, 5
For dust containing gas of about 00mg / m ³ ,
Since both the transmission and the light are saturated, and the window is easily stained, stable detection is difficult with the conventional optical densitometer.

Therefore, the present invention employs a Doppler radar using a millimeter wave having a wavelength of 10 mm or less as a device that passes through some window dirt due to dust adhesion and reacts only to flowing dust. I have. That is, in the millimeter wave region, the scattering by the particle group several orders of magnitude lower than that wavelength is also small, and it is difficult to detect the dust concentration in the related art simply by using the simple scattering or transmission, as shown in FIG. 1 (c). When the moving dust particles 6A are irradiated with the electromagnetic wave 4 in the millimeter wave band of 30 GHz or more at the irradiation angle θ, a very small amount of backscattered waves are generated.

[0015] Here, the order backscattered waves undergoing Doppler shift by the speed v of a particle 6A, resulting Doppler signal f _d by mixing (heterodyning) the original irradiated electromagnetic wave as shown by the following formula Can be f _d = 2 v · cos θ / λ (λ: oscillation wavelength) This Doppler signal f _d is several kHz or less, a frequency that is very small compared to the first oscillation frequency, and only a portion of this Doppler signal f _d can be selectively amplified. Therefore, a large signal can be obtained as a result. For example, λ = 5
mm, oscillation frequency 60 GHz, θ = 45 °, v = 20 m
In the case of / sec, f _d = 5.6 kHz.

[0016] The frequency spectrum of the Doppler signal f _d which depicts schematically is 2, the vertical axis represents the components of the Doppler frequency f _d of FIG. (Reflection intensity) and the horizontal axis represents Doppler frequency f _d is there. In FIG. 2, the maximum value f _max of the Doppler frequency f _d is close to the gas flow velocity, and the Doppler frequency f _o giving the peak value of the frequency spectrum is close to the average flow velocity of the particle group (dust). The reason is that it is considered that the number of particles at the average flow velocity is the largest, and the scattering by the particles is the largest.

When the dust concentration is increased, the level of the frequency spectrum is increased as shown by the phantom line in FIG. 2, and the dust concentration of the dust-containing gas to be measured is estimated from the area of the frequency spectrum. You can do it. That is, when the relationship between the existence probability and velocity distribution of dust dust containing gas (concentration) expressed as schematically FIG. 3 (a), the frequency spectrum of the Doppler signal f _d obtained when the Fig. 3 ( As shown in b), the two are almost similar. This is a millimeter wave backscatter receiving Doppler shift by each particle, the frequency component (reflection intensity of the Doppler signal f _d corresponding to the portion received much backscatter as particle density of a certain speed is high ) Becomes larger.

Accordingly, dust-containing gas streams having various dust concentrations are artificially created, and each of the dust-containing gas streams is obliquely irradiated with a millimeter wave having a certain frequency, and the Doppler signal f _{d at} that time is emitted.
The frequency spectrum of each is obtained by experiments, and if the correspondence between the dust concentration and the area of the frequency spectrum is understood, the area of the frequency spectrum obtained by irradiating any dust-containing gas with millimeter waves can be obtained. The dust concentration of the dust-containing gas can be estimated.

As described above, the feature of the method of the present invention is that an electromagnetic wave in the millimeter wave band which is obliquely applied to a dust-containing gas flow,
Since the dust concentration and the average flow velocity of the dust particles are estimated from the frequency spectrum of the Doppler shift with the scattered waves of the electromagnetic wave dust particles, the moving particle group is detected as a result larger and stopped. Particles are not detected, and as a result, even if some dust adheres to the front of the horn antenna corresponding to the conventional optical dust densitometer, it is possible to detect the abnormality of the dust collector with little effect. is there.

On the other hand, in the method of the present invention, dust density and the like are estimated on the basis of scattered waves of millimeter waves that actually occur only slightly, so that high sensitivity in a low density region cannot be expected. As shown in the experimental example, there is an advantage that it is possible to reliably measure an ultra-high concentration such as 15 g / m ³ in a high concentration region.

[0021]

Embodiments of the present invention will be described below with reference to the drawings. FIGS. 1A and 1B show an abnormality detection device 1 for implementing the method of the present invention. This abnormality detection device 1
Irradiation means 5 for irradiating an electromagnetic wave 4 in a millimeter wave band of 30 GHz or more at an angle that is not perpendicular to the flow direction of the dust-containing gas 3 in a pipe 2 leading to the outlet side of the dust collector; Detecting means 8 for detecting scattered waves 7 scattered by dust 6 contained in dust-containing gas 3;
And a mixer 9 for taking out a Doppler shift amount between the scattered wave 7, the value of the frequency, or both gives a peak value f _o of the area S or the spectrum of the frequency spectrum in search of the frequency spectrum of the Doppler shift amount And a signal processing circuit (measuring means) 10 for calculating.

The irradiating means 5 is adapted to control the electromagnetic wave 4 in the millimeter wave band.
An oscillation unit 11 that oscillates the electromagnetic wave 4, a waveguide 12 that transmits the electromagnetic wave 4, and a horn antenna 13 that radiates the electromagnetic wave 4 into the pipe 2. It is provided in the connected branch pipe 14. The waveguide 12 having the antenna 13 at its tip is inserted through a cover plate 15 for covering the branch pipe 14, and the oscillation unit 11 is provided at an outer end of the waveguide 12.

The oscillation unit 11 has a circuit configuration shown by a broken line in FIG. That is, the electromagnetic wave 4 generated by the gun oscillator 16 driven only by the AC power supply reaches the circulator 18 via the isolator 17, and a part of the electromagnetic wave 4 is converted by the circulator 18 into the mixer 9.
And the rest is radiated to the space from the antenna 13 through the waveguide 12.

The gun oscillator 16 of this embodiment has an oscillation frequency of 59.5 GHz (λ = about 5 mm) and an oscillation output of 1 mW. The opening of the branch pipe 14 is preferably closed with a transparent plate 15 made of ceramic or plastic for preventing dust 6 from entering. Further, in FIG. 1B, the reason why the waveguide unit 12 is elongated and the oscillator unit 11 is kept away from the branch pipe 14 is that when the dust-containing gas 3 is at a high temperature, the heat is not directly transmitted to the oscillator unit 11. That's why.

The detecting means 8 includes the horn antenna 13,
The electromagnetic wave 4, which is composed of the waveguide 12 and the circulator 18 and is obliquely irradiated on the dust-containing gas 3 by the antenna 13, is back-scattered by the dust particles 6 </ b> A, and the scattered wave 7 is again transmitted to the antenna 13 and the waveguide 13. Return to circulator 18 through tube 12. Further, the circulator 18 mixer (mixer) 9 is connected, the mixer 9 mixes the scattered wave 4 of the electromagnetic wave 4 and the frequency f + f _d of the same oscillation frequency f as that first irradiation, the frequency of the difference f _d is extracted as the Doppler shift amount.

[0026] The Doppler signal f _d As described above is at most a few kHz, for can be amplified in the usual simple amplifier 20, the above-mentioned mixer 9 is connected to a known amplifier 20, further to the amplifier 20 the Signal processing circuit 1
0 is connected. Therefore, the Doppler signal f _d extracted by the mixer 9 is amplified by the amplifier 20 and input to the signal processing circuit 10.

The signal processing circuit 10 obtains the frequency spectrum of the Doppler shift amount, and calculates the area of the frequency spectrum and the frequency giving the peak value of the spectrum. That is, the peak frequency f shown in FIG.
The position of _o is determined to be the median value of the dust particle group A (which is actually close to the average flow velocity of the particle group), and the dust concentration is specified from the area of the frequency spectrum.

In specifying the dust concentration, it is necessary to previously understand the correspondence between the dust concentration and the area of the frequency spectrum by an experiment as described above. Although it is preferable to use a computer for the signal processing, as shown in FIG. 4, the frequency spectrum is divided and components for each frequency band are integrated by an integrator 22 through a band-pass filter 21 to obtain a total sum thereof. A simple integrating circuit, such as calculating the area of the entire spectrum, can also be employed.

On the other hand, as shown in FIG. 6, if the branch pipe 14 is connected to the bent portion 23 of the pipe 2, the electromagnetic wave 4 can be irradiated directly in front of the dust-containing gas 3, and the irradiation angle shown in FIG. Since θ can be set to 0 °, a larger Doppler signal f _d can be obtained. Also, as shown in FIG. 5, the cover plate 15 of the branch pipe 14 is covered with a bottomed cylindrical nonmetallic case 24 that transmits the electromagnetic wave 4 in the millimeter wave band, so that the horn antenna 13 and the waveguide 12 can be covered. Dust can be prevented from adhering. (Experimental Example) An experiment was conducted to test the validity of the method of the present invention using a test machine 26 shown in FIG.

The tester 26 has a first pipe 28 for flowing a dust-containing gas 27 and a second pipe 29 connected upstream of the first pipe 28. Is blower 30
Are connected, and an anemometer 31 is provided in the second pipe line 29. On the upstream side of the first pipe 28, a blower 30
A dust feeder 33 with a measuring device for feeding the dust 32 into the air from the air is provided.
By supplying a constant amount of dust under a constant air flow according to 3, the dust concentration in the first conduit 28 can be artificially set.

The above-described abnormality detecting device 1 of the present invention is provided upstream of the first pipeline 28.
The method according to the invention was carried out under each dust concentration set to a certain value. The result is shown in FIG.
(A), (b) and FIGS. 9 (c), (d). As is clear from these figures, when the dust concentration is increased, the antenna gain (reflection intensity) of the millimeter wave is also increased.

FIG. 10 plots the relationship between the area of the frequency spectrum and the dust density in each of these figures. From FIG. 10, the dust density can be estimated based on the area of the frequency spectrum.

[0033]

As described above, according to the present invention,
From the frequency spectrum of the Doppler shift amount of the electromagnetic wave in the millimeter-wave band irradiated obliquely to the dust-containing gas flow and the scattered wave of this electromagnetic wave by the dust particles, the dust concentration and the average flow velocity of the dust particles are obtained. Since the abnormality of the dust collector is detected based on this, it is possible to stably detect the abnormality of the dust collector even in a high concentration region without being affected by the contamination of the window.

Also, since the dust concentration can be specified even in a high concentration area, the detection device can be installed at the outlet of each bag filter, which cannot be installed with the conventional optical dust densitometer, and which bag filter has an abnormality is determined. Can be grasped immediately.

[Brief description of the drawings]

1A is a circuit configuration diagram of an abnormality detection device, FIG. 1B is a cross-sectional view of the device, and FIG. 1C is an explanatory diagram showing a scattering model of electromagnetic waves.

FIG. 2 is a graph showing a frequency spectrum of Doppler shift.

3A is a graph showing the relationship between the speed of dust particles and their probability of occurrence (concentration), and FIG. 3B is a graph showing the frequency spectrum of Doppler shift.

FIG. 4 is a circuit configuration diagram of a Doppler shift amount integration circuit.

FIG. 5 is a sectional view showing a modification of the abnormality detection device.

FIG. 6 is a cross-sectional view showing another modification of the abnormality detection device.

FIG. 7 is an overall configuration diagram of a testing machine.

FIG. 8 is a frequency spectrum of a Doppler frequency obtained in an experiment.

FIG. 9 is a frequency spectrum of a Doppler frequency obtained in an experiment.

FIG. 10 is a graph showing the relationship between the dust concentration and the area of the frequency spectrum obtained in the experiment.

FIG. 11 is a sectional view of a bag filter.

FIG. 12 is an overall configuration diagram of a dust collecting facility.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Abnormality detection apparatus 2 Pipeline 3 Dust-containing gas 4 Electromagnetic wave 5 Irradiation means 6 Dust 6A Dust particles 7 Scattered waves 9 Mixer 10 Measuring means (signal processing circuit)

Claims (4)

(57) [Claims] A dust-containing gas (3) flowing through a pipe (2) connected to an outlet side of a dust collector has a millimeter of 30 GHz or more at an angle that is not perpendicular to the flow direction of the dust-containing gas (3). Irradiating an electromagnetic wave (4) in a wave band, the electromagnetic wave (4) detects a scattered wave (7) scattered by dust (6) contained in the dust-containing gas (3), and detects the electromagnetic wave (4). A Doppler shift amount between the scattered wave and the scattered wave (7) is obtained to obtain a frequency spectrum of the same shift amount, and an abnormality of the dust collector is detected based on the frequency spectrum. 2. The method according to claim 1, wherein a dust concentration in the pipeline corresponding to an area of the frequency spectrum obtained from the Doppler shift amount is obtained, and an abnormality of the dust collector is detected based on the value of the dust concentration. Item 2. The abnormality detection method for a dust collector according to Item 1. 3. An average flow velocity of the dust particles (6A) in the pipe (2) corresponding to the frequency giving the peak value of the frequency spectrum obtained from the Doppler shift amount, and an average flow velocity of the dust particles (6A) The abnormality detection method for a dust collector according to claim 1, wherein the abnormality of the dust collector is detected based on the value of (i). 4. An angle of 30 G which is not perpendicular to the flow direction of the dust-containing gas in the conduit (2) leading to the outlet side of the dust collector.
An irradiating means (5) for irradiating an electromagnetic wave (4) in a millimeter band of not less than Hz, and a scattered wave (7) in which the electromagnetic wave (4) is scattered by dust (6) contained in the dust-containing gas (3).
(8), a mixer (9) for extracting a Doppler shift amount between the electromagnetic wave (4) and the scattered wave (7), and a frequency spectrum of the Doppler shift amount to obtain an area of the frequency spectrum. Or a measuring means (10) for calculating a frequency giving a peak value of the spectrum or both of them, the abnormality detecting device for a dust collector.