JP2003214997A - Capturing device for floating particulate matter in atmosphere and measuring method of particulate matter captured thereby - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a capturing device capable of efficiently capturing a floating particulate matter in the atmosphere, facilitating the observation of the captured particles with a microscope and the extraction and supply of independent particles to various analyzing equipments, and a method capable of measuring the particle size distribution of the floating particulate matter captured by the capturing device with high resolution in a wide particle size range. <P>SOLUTION: The atmospheric floating particulate matter sucked into a capturing vessel 1 is charged by a discharge electrode 3, and captured to a dust collecting electrode 4 having a conductive transparent film 4b formed at least one side of a transparent plate 4a such as glass plate, whereby the particle P can be simply observed and extracted. The space intensity distribution of the diffracted and scattered light obtained by irradiating the dust collecting electrode 4 with laser beam is measured, whereby the particle size distribution of the floating particulate matter P can be measured with high resolution in a wide particle size range on the basis of laser diffraction and scattering method. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for collecting suspended particulate matter existing in the atmosphere and a method for measuring the particle size distribution of suspended particulate matter collected by the collector.

[0002]

2. Description of the Related Art Among dust particles floating in the atmosphere, those having a particle size of 10 μm or less are called suspended particulate matter (SPM). This suspended particulate matter includes rolled up soil, but black smoke, unburned fuel, and sulfur compounds emitted by diesel vehicles account for a large proportion (35% in the Kanto region are from diesel vehicles). Is said to be more harmful. The particulate matter caused by the exhaust gas from this diesel vehicle is especially called DEP. Further, particles having a particle size of 2.5 μm or less, which are smaller, are called fine particulate matter (PM2.5), and investigations and studies have become popular in Europe and America. In the case of PM2.5, it is said that the cause of the emission is a higher proportion of exhaust gas from diesel vehicles.

Suspended particulate matter (S
PM) and fine particulate matter (PM2.5) shapes and the like, or to identify the chemical substances contained therein, collect these particulate matter from the atmosphere with a filter, Observe with a microscope or perform chemical analysis.

As a device for measuring the particle size distribution of suspended particulate matter (SPM) and fine particulate matter (PM2.5) in the atmosphere as described above, a device based on the cascade impactor system has been put into practical use. ing. The measuring device based on this cascade impactor method utilizes an impactor method in which particles are separated from the fluid by colliding the fluid with a collecting plate to suddenly change the direction of the flow, and the particle size is 50%. The impactors whose diameters were sequentially changed were connected in multiple stages in series, and the particle size of 50% collection efficiency in each stage was used as the representative diameter of each stage, and from the measurement result of the collection amount in each stage, This is for obtaining the particle size distribution.

[0005]

By the way, SPM and P
In the method of observing M2.5 with a microscope or collecting it with a filter so as to provide it to various chemical analyzers, it is extremely difficult to extract suspended particulate matter alone. The suspended particulate matter adhered to the surface will be observed, but in that case, the image of the particles becomes unclear in the background filter image,
There is a problem that it is difficult to observe. In addition, even when the collected suspended particulate matter is supplied to various chemical analysis instruments,
Since it is difficult to extract the suspended particulate matter from the filter alone, it is necessary to perform the analysis while attached to the filter depending on the device. In that case, for example, fluorescence X
In a line spectroscope or the like, it is difficult to irradiate only particles with X-rays, and there is a problem that analysis becomes substantially impossible.

Further, in the conventional measuring apparatus based on the cascade impactor system used for measuring the particle size distribution of suspended particulate matter, the upper limit of particle size measurement is limited to about 10 μm in principle. In addition to the problem, the particle size resolution is determined by the number of collecting plates, so that it is not possible to measure the particle size distribution with high resolution.

The present invention has been made in view of the above circumstances, and is an apparatus for collecting airborne particulate matter in the atmosphere, and the collected particles can be very easily observed with a microscope. In addition, it is very easy to determine the particle size distribution of the suspended particulate matter collected by the collection device and the collection device that can easily extract individual particles and provide them to various analytical instruments, and the particle size of 10 μm. It is an object of the present invention to provide a measuring method capable of measuring with a high resolution in a wider particle size range including the above.

[0008]

In order to achieve the above object, an airborne particulate matter trapping device of the present invention is a device for trapping airborne particulate matter. A collection container, a pump for sucking air into the collection container, a discharge electrode disposed in the collection container for generating unipolar ions to charge suspended particulate matter in the container, and the discharge electrode A dust collecting electrode that attracts and collects the floating particulate matter charged in the collection container by applying a potential difference to the dust collecting electrode, and the dust collecting electrode is a surface of the transparent plate facing at least the discharge electrode. It is characterized in that a transparent film made of a conductive material is formed on (1).

The method for measuring suspended particulate matter in the atmosphere according to the present invention is a method for measuring the particle size distribution of suspended particulate matter collected by the collector according to claim 1. After collecting airborne particulate matter on the surface of the dust electrode, irradiate the dust collecting electrode with laser light, and the spatial intensity of diffracted / scattered light by the airborne particulate matter adhering to the surface. It is characterized by measuring the distribution and calculating the particle size distribution of the suspended particulate matter from the measurement result (claim 2).

The airborne particulate matter trapping apparatus of the present invention electrically charges the suspended particulate matter in the atmosphere, and charges the charged suspended particulate matter into a transparent material such as a glass plate or a transparent plastic plate. The desired object is achieved by collecting by utilizing the potential difference on the surface of the dust collecting electrode formed by coating the plate with a film made of a conductive material.

That is, in the device for collecting suspended particulate matter in the atmosphere of the present invention, the atmosphere is injected into a collection container by a pump, and a single electrode is generated by a discharge electrode arranged in the collection container. Then, the suspended particulate matter contained in the atmosphere is charged. This charged suspended particulate matter
In the collection container, it goes to the dust collecting electrode to which a potential difference is applied with respect to the discharge electrode and is collected on the dust collecting electrode. As the dust collecting electrode, a transparent plate made of a conductive material is formed on at least the surface facing the discharge electrode of a transparent plate such as a glass plate or a transparent plastic plate to form a flat surface of the transparent plate. The suspended particulate matter is placed on the top, and it becomes possible to observe a clear particle image without observing the background image by observing with a microscope as it is. In addition, since it becomes possible to extract particles alone, chemical analysis using various analytical instruments such as a fluorescent X-ray analyzer becomes easy. Further, since the dust collecting electrode has a transparent film made of a conductive material formed on the surface of the transparent plate, it is possible to collect a relatively large amount of charged suspended particulate matter by connecting to a ground potential, for example. Since the electric potential can be always kept constant, efficient collection becomes possible.

On the other hand, in the method for measuring suspended particulate matter in the air according to the present invention, the trapped state of the suspended particles by the trapper of the invention according to claim 1 is determined by a laser diffraction / scattering method. This is done by using the fact that the condition required for the measured particle group by measurement is satisfied.

That is, it is known that the particle size distribution measurement based on the laser diffraction / scattering method can measure the particle size distribution in a wide particle size range with high resolution.
In particle size distribution measurement based on this laser diffraction / scattering method, diffraction /
The spatial intensity distribution of scattered light is measured, and the particle size distribution of the particle group is calculated. When measuring the diffracted / scattered light in this particle size distribution measuring method, it is a condition that the particles to be measured are in a dispersed state and that diffracted / scattered light with sufficient intensity can be obtained. The suspended particulate matter collected on the dust collecting electrode of the collecting device of the invention according to claim 1 is randomly dispersed on the electrode, and the dust collecting electrode is the surface of a transparent plate such as a glass plate. A transparent film made of a conductive material is formed on the surface of the dust collecting electrode, and the potential can be kept constant to efficiently collect the suspended particulate matter. (Concentration) can be arbitrarily set by appropriately setting the collection time,
Moreover, the dust collecting electrode is a transparent plate.

Therefore, by collecting the suspended particulate matter in the air at an appropriate concentration on the dust collecting electrode in the invention according to claim 1, the suspended particulate matter is directly attached to the dust collecting electrode. By irradiating with laser light, sufficient diffracted / scattered light sufficient to calculate the particle size distribution of the particle group can be obtained, and it is easy to obtain high resolution in a wide particle size range from submicron order to over 10 μm. The particle size distribution of suspended particulate matter can be determined.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram showing a configuration of an embodiment of a collection device of the present invention, and FIG. 2 is a schematic sectional view showing the structure of the dust collecting electrode 2.

The collection container 1 provided with a lid 1a that can be opened and closed is provided with an air inlet 1b and a communication port 1c to a suction port of a pump (collection compressor) 2 and the lid 1a. By driving the pump 2 in the closed state, the atmosphere is sucked into the collection container 1 through the inflow port 1b.

In the collection container 1, a discharge electrode 3 is provided on the upper part thereof.
Is provided, and the dust collecting electrode 4 is arranged below the discharge electrode so as to face the discharge electrode. A high voltage from the high voltage power source 5 is applied to the discharge electrode 3, whereby the air in the vicinity of the discharge electrode 3 is ionized and monopolar ions are generated.

On the other hand, the dust collecting electrode 4 is, as shown in FIG.
A transparent film 4b made of a conductive material is formed on one surface of a transparent glass plate 4a. The conductive transparent film 4b is connected to the ground potential 6, and the conductive transparent film 4b is applied to the discharge electrode 3. It is arranged in the collection container 1 so as to face the upper surface. As a material of the conductive transparent film 4b, a known conductive material such as ITO or SnO2 can be used. Further, instead of the glass plate 4a, a transparent plastic such as an acrylic resin plate can be used.

In the above structure, when a high voltage is applied to the discharge electrode 3 while driving the pump 2, the unipolar ions generated by the ionization of the surrounding air ionize the conductive transparent film 4b.
Moves toward the dust collecting electrode 4 side due to the potential difference between and and contacts the floating particulate matter P in the atmosphere sucked into the collection container 1 in the process to charge it. The charged suspended particulate matter P is also collected in a state of being randomly dispersed on the upper surface of the dust collecting electrode 4 due to the potential difference between the discharge electrode 3 and the conductive transparent film 4b. At this time, since the conductive transparent film 4b on the upper surface of the dust collecting electrode 4 is grounded, the potential does not change even if a relatively large amount of the suspended particulate matter P is collected, and the efficiency is high. The suspended particulate matter P can be collected.

By collecting the suspended particulate matter P in the atmosphere on the dust collecting electrode 4 composed of the glass plate 4a and the conductive transparent film 4b as described above, the laser diffraction / scattering particle size distribution measurement shown below is carried out. By using the device, the particle size distribution can be measured very easily with a high resolution in a wide particle size range.

FIG. 3 is a diagram showing an example of the apparatus configuration for measuring the particle size distribution, and is a diagram showing both a schematic diagram showing the optical configuration and a block diagram showing the electrical configuration.

Laser diffraction / scattering type particle size distribution measuring device 20
Is an irradiation optical system 21 for irradiating a laser beam parallel to the measured particle group, a measurement optical system 22 for measuring the spatial intensity distribution of the diffracted / scattered light by the measured particle group, and the measurement optical system 22. The data sampling circuit 23 for sampling the output, and the computer 24 for calculating the particle size distribution of the measured particle group using the spatial intensity distribution data of the diffracted / scattered light sampled by the data sampling circuit 23 are mainly configured. There is.

The suspended particulate matter P collected on the surface of the dust collection electrode 4 by the collection device of FIG. 1 remains in contact with the irradiation optical system 21 while being attached to the surface of the dust collection electrode 4. The measurement optical systems 22 are arranged upright so as to be orthogonal to the optical axis thereof.

The irradiation optical system 21 is composed of a laser light source 21a, a condenser lens 22b, a spatial filter 22c and a collimator lens 23d, and the laser light output from the laser light source 21a is attached to the dust collecting electrode 4 as a parallel light flux. The suspended particulate matter P present is irradiated. This dust collecting electrode 4
The laser light applied to the laser beam is diffracted and scattered by the suspended particulate matter P attached to the surface of the laser beam. The spatial intensity distribution of the diffracted / scattered light is measured by the measurement optical system 22.

The measuring optical system 22 includes a condenser lens 22a and a ring detector 22b, a front wide-angle scattered light sensor group 22c arranged outside thereof, and side and rear sides of the dust collecting electrode 4 (on the side of the irradiation optical system 21). ) Is arranged by the side / back scattered light sensor group 22d. The ring detector 22b is an optical sensor array in which optical sensors having ring-shaped, ½ ring-shaped, or ¼ ring-shaped light-receiving surfaces having different radii are concentrically arranged, and are condensed by a condenser lens 22a. The spatial intensity distribution of the diffracted / scattered light within the predetermined front angle can be detected. Therefore, the measurement optical system 22 including these sensor groups
Thus, the spatial intensity distribution of the diffracted / scattered light by the suspended particle group P that is randomly dispersed and attached on the dust collecting electrode 4 is
It is measured in a wide range from the front minute angle to the rear.

The light intensity detection signal for each diffraction / scattering angle by the above measurement optical system 22 is a data sampling circuit 23 having respective amplifiers and AD converters.
Is amplified, digitized, and taken into the computer 24 as spatial intensity distribution data of diffracted / scattered light.

The computer 24 uses the spatial intensity distribution of the diffracted / scattered light to calculate the laser light by a calculation method based on Mie's scattering theory and Fraunhofer's diffraction theory, which are known in the laser diffraction / scattering particle size distribution measurement. Calculate the particle size distribution of the suspended particulate matter that is the cause of the diffracted and scattered particles.

According to the measurement of the particle size distribution by the laser diffraction / scattering type particle size distribution measuring device 20, it is possible to measure the particle size distribution with a high resolution in a wide particle size range from the submicron order to over 10 μm, and the dust collection. The particle size distribution of the suspended particulate matter P in the atmosphere can be immediately measured with high accuracy simply by setting the amount of the suspended particulate matter P on the electrode 4 to such an extent that sufficient diffraction / scattered light intensity can be obtained. .

Further, the suspended particulate matter P collected by the collecting device shown in FIG. 1 is a dust collecting electrode 4 which is a transparent flat plate.
Since it adheres to the upper surface in a dispersed state, it can be observed with a microscope as it is. In that case, a clear particle image can be obtained without being affected by the background image. In addition, the suspended particulate matter P collected on the surface of the dust collecting electrode 4 in a dispersed state.
The particles can be easily extracted by themselves, and since each particle is exposed on the surface of the flat plate-shaped dust collecting electrode 4, it is possible to directly irradiate electromagnetic waves such as X-rays and light. Therefore, it becomes possible to easily carry out chemical analysis using various analytical instruments as compared with the case of collecting with a filter.

In the apparatus configuration shown in FIG. 3, when the suspended particulate matter P adhering to the surface of the dust collecting electrode 4 may drop, another adhering surface is covered with another glass plate or the like. It is also possible to irradiate with laser light.

[0031]

As described above, according to the airborne particulate matter trapping apparatus of the present invention, the airborne particulate matter is charged to form a conductive transparent film on the surface of the transparent plate. Since it collects on the dust collecting electrode which is a transparent flat plate that is formed, a clear particle image can be obtained without being affected by the background image when observed with a microscope, and it is necessary to extract only suspended particulate matter. Since it is easy to carry out, it becomes possible to carry out chemical analysis using various analytical instruments which cannot be used for collection by a conventional filter. Moreover, by connecting the conductive transparent film of the dust collecting electrode to, for example, the ground potential, the potential of the dust collecting electrode does not change even if a relatively large amount of charged suspended particulate matter is collected. The suspended particulate matter can be collected with high efficiency.

Further, by collecting the suspended particulate matter in the atmosphere by the above-mentioned collecting device, laser diffraction
Using a scattering type particle size distribution measuring device, the spatial intensity distribution of the diffracted / scattered light is measured by directly irradiating the suspended particulate matter collected and attached on the dust collecting electrode with laser light. It becomes possible to measure from sub-micron order to 10 by the particle size distribution measurement based on this laser diffraction / scattering method.
High-resolution particle size distribution measurement is possible in a wide particle size range exceeding μm.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing the configuration of an embodiment of a device for collecting airborne particulate matter of the present invention.

FIG. 2 is a schematic cross-sectional view showing the structure of a dust collection electrode 4 in the embodiment of FIG.

FIG. 3 is a diagram showing a device configuration example used in the embodiment of the method for measuring airborne particulate matter of the present invention, in which a schematic diagram showing an optical configuration and a block diagram showing an electrical configuration are shown together. FIG.

[Explanation of symbols]

1 Collection container 2 pumps 3 discharge electrodes 4 Dust collecting electrode 4a glass plate 4b Conductive transparent film 5 high voltage power supply 6 Ground potential 20 Laser diffraction / scattering particle size distribution analyzer 21 Irradiation optical system 22 Measuring optical system 23 Data sampling circuit 24 computer P Suspended particulate matter

Claims (2)

[Claims] 1. An apparatus for collecting suspended particulate matter in the atmosphere, comprising: a collection container, a pump for sucking the atmosphere into the collection container, and a monopolar ion disposed in the collection container. And a discharge electrode that charges the suspended particulate matter in the container, and a dust collection that attracts and collects the charged suspended particulate matter in the collection vessel by applying a potential difference to the discharge electrode. This dust collecting electrode is characterized in that a transparent film made of a conductive material is formed on at least the surface of the transparent plate facing the discharge electrode to collect airborne particulate matter. apparatus. 2. A method for measuring the particle size distribution of suspended particulate matter collected by the collection device according to claim 1.
After collecting the suspended particulate matter in the atmosphere on the surface of the dust collecting electrode, irradiating the dust collecting electrode with a laser beam, and diffracted / scattered light by the suspended particulate matter adhering to the surface A method for measuring suspended particulate matter in the atmosphere, which comprises measuring a spatial intensity distribution and calculating a particle size distribution of suspended particulate matter from the measurement result.