JP2003035655A - Method and equipment for measuring floating particulate material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and an equipment for measuring the particle size distribution of floating particulate material (SPM) or particulate material (PM2.5) in the atmosphere with high resolution over a wide particle size range including particle size of 10 μm and above. SOLUTION: Atmosphere is sucked by means of a pump 3 and supplied to a filter 1 where floating particulate material P in the atmosphere is captured and dispersed into liquid L which is then irradiated with laser light. Spatial intensity distribution of diffracted/scattered light thus obtained is measured and particle size distribution of floating particulate material P is determined from the measurements. Concentration of the floating particulate material P being dispersed into the liquid L is set at such a level as a laser diffraction/ scattering type particle size distribution measurement can be employed.

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 measuring the particle size distribution of suspended particulate matter existing in the atmosphere, and more particularly, to a method for measuring the particle size distribution of suspended particulate matter with high resolution over a wide particle size range. The present invention relates to a method and apparatus for measuring suspended particulate matter that can be originally measured.

[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
As a device for measuring the particle size distribution of PM and fine particulate matter (PM2.5), a device based on the cascade impactor system has been put into practical use. The measuring device based on the cascade impactor method uses an impactor method in which particles are separated from a fluid by colliding the fluid with a collecting plate to suddenly change the flow direction thereof.
Measuring the amount of trapping in each stage by connecting in series multiple impactors with varying particle size of% trapping efficiency in series and using the particle size of 50% trapping efficiency in each stage as the representative diameter of each stage. The particle size distribution in the fluid is determined from the results.

[0004]

By the way, SPM and P
In the measuring device based on the cascade impactor method used for the measurement of M2.5, there is a problem that the upper limit of the particle size measurement is limited to about 10 μm and the resolution of the particle size is trapped. Since it depends on the number of collecting plates, 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 the particle size distribution of suspended particulate matter (SPM) and fine particulate matter (PM2.5) in the atmosphere is more than that including a particle diameter of 10 μm or more. It is an object of the present invention to provide a method and apparatus for measuring suspended particulate matter that can be measured with a high resolution in a wide particle size range.

[0006]

In order to achieve the above object, the method for measuring suspended particulate matter of the present invention is a method for measuring suspended particulate matter contained in the atmosphere, wherein the atmosphere is pumped. By aspirating and supplying to the filter, the airborne particulate matter in the atmosphere is collected by the filter, and the suspended particulate matter collected by the filter is irradiated with laser light in a state of being dispersed in the liquid. It is characterized by measuring the spatial intensity distribution of the obtained diffracted / scattered light and determining the particle size distribution of the suspended particulate matter from the measurement result (claim 1).

The airborne particulate matter measuring apparatus of the present invention is an apparatus for measuring airborne particulate matter contained in the atmosphere using the above-described method of the present invention. A filter for collecting, a pump for sucking the air and supplying it to the filter, a dispersing means for dispersing the suspended particulate matter in the atmosphere captured by the filter in a liquid, and the suspended particulate matter Flow cell in which a liquid in which is dispersed flows, an irradiation optical system that irradiates the flow cell with laser light, and measurement optics that measures the spatial intensity distribution of the laser light diffracted / scattered by suspended particulate matter in the liquid The present invention is characterized by including a system and a calculation means for calculating a particle size distribution of suspended particulate matter dispersed in a liquid from the measured spatial intensity distribution of diffracted / scattered light (claim 2). .

Here, the pump referred to in each of the above claims refers to an air machine capable of sucking air and sending it by pressure, and more specifically, it is a compressor or a blower.

In the present invention, as the liquid used to disperse the suspended particulate matter collected by the filter, clean water such as distilled water or an organic solvent, or a dispersant such as a surfactant is added to these. The added one can be preferably used.

The present invention uses a particle size distribution measurement based on a laser diffraction / scattering method capable of measuring a particle size distribution with a high resolution in a wide particle size range, and a particle size distribution measurement of suspended particulate matter in the atmosphere. In addition to irradiating directly to the suspended particulate matter in the atmosphere with laser light in order to obtain diffracted / scattered light of sufficient intensity when irradiating with laser light, It is intended to achieve the intended purpose by efficiently collecting suspended particulate matter, dispersing it in a sufficient concentration, and irradiating it with laser light.

That is, in the laser diffraction / scattering type particle size distribution measuring apparatus, generally, the spatial intensity distribution of the diffracted / scattered light obtained by irradiating the measured particle group in the dispersed state with laser light is measured. By utilizing that the light intensity distribution is based on Mie's scattering theory or Fraunhofer's diffraction theory, the measured particles can be calculated from the measurement results of the spatial intensity distribution of diffracted / scattered light by Mie's scattering theory or Fraunhofer's diffraction theory. Determine the particle size distribution of the group. According to this laser diffraction / scattering type particle size distribution measuring apparatus, by setting the concentration of the measured particle group in the medium for dispersing the measured particle group in an appropriate range, the particle size distribution with high resolution in a wide particle size range can be obtained. Can be asked.

However, even if an attempt is made to measure the diffracted / scattered light by directly irradiating the suspended particulate matter in the atmosphere with a laser beam, the particle size distribution will be reduced because the concentration of the suspended particulate matter in the atmosphere is too low. Not enough diffracted / scattered light to obtain.

Therefore, in the present invention, the air is sucked by the pump and supplied to the filter, whereby the suspended particulate matter contained in the atmosphere is collected by the filter, and the collected suspended particulate matter is collected. A substance is dispersed in a liquid within a concentration range suitable for laser diffraction / scattering particle size distribution measurement, and laser light is irradiated to measure the spatial intensity distribution of diffracted / scattered light. As a result, the particle size distribution of suspended particulate matter can be determined with high resolution in a wide particle size range equivalent to that of ordinary laser diffraction / scattering particle size distribution measurement, that is, in a wide particle size range from submicron order to more than 10 μm. You can ask.

Further, according to the present invention, the air is sucked by the pump and supplied to the filter, so that the suspended particulate matter contained in the air is collected by the filter. The amount of air supplied to the filter can be easily grasped according to the time, and by appropriately selecting the filter (for example, a membrane filter, etc.), the suspended particulate matter in the air supplied from the pump can be hardly leaked. Therefore, it is possible to easily collect the amount of the suspended particulate matter existing in the atmosphere for each particle size.

[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 configuration diagram of an embodiment of the present invention, and is a diagram in which a schematic diagram showing an optical configuration and a piping configuration and a block diagram showing an electrical configuration are shown together.

The filter 1 is a membrane filter having a submicron pore size in this example, and is held inside a filter holding member 2 comprising a base 21 and a lid 22 which is detachable from the base 21. The inside of the filter holding member 2 is partitioned vertically. The base 21 and the lid 22 of the filter holding member 2 have large diameter portions 21a and 22a for holding the filter 1 and a small diameter opening portion 2 respectively.
It has a funnel-like shape with 1b and 22b, the opening 21b of the base 21 communicates with the suction port of the pump (compression compressor) 3, and the opening 22b of the lid 22 has It is open to the atmosphere and forms an inlet for the atmosphere.

In the above structure, when the pump 3 is driven, the atmosphere is sucked into the inside of the filter holding member 2 through the opening 22b, and after passing through the filter 1, the opening 21 is opened.
It is sucked into the suction port of the pump 3 via b. At this time,
The suspended particulate matter P existing in the atmosphere is almost entirely collected when passing through the filter 1 using a membrane filter having a pore size of submicron order.

The suspended particulate matter P collected by the filter 1
Is poured into and dispersed in a dispersion tank 41 containing a liquid medium L made of, for example, distilled water or an organic solvent, or a liquid in which a dispersant such as a surfactant is added. Dispersion tank 4
1 is equipped with a stirrer 42 and an ultrasonic oscillator 43, and when the suspended particulate matter P collected in the filter 1 is separated and input into the dispersion tank 41, the suspended particulate matter P is attached to the filter 1. If the adhesion is weak, filter 1 to dispersion tank 4
1 is washed away by an appropriate method, or when the adherence of the suspended particulate matter P to the filter 1 is strong, the ultrasonic vibrator 43 is immersed in the dispersion tank 41 while the ultrasonic transducer 43 is being immersed. A method of separating from the filter 1 by ultrasonic cleaning by driving can be adopted.

The dispersion tank 41 has a circulation pipe 4 at the bottom thereof.
4, one end of which communicates with the circulation pipe 44, which communicates with the inlet of the flow cell 51 of the laser diffraction / scattering particle size distribution measuring device 50 through the circulation pump 45, and further from the outlet of the flow cell 51. It opens up to above 41. A discharge valve 41a for discharging the contents is provided at the bottom of the dispersion tank 41.

By driving the stirrer 42 and the ultrasonic vibrator 43 in a state where the suspended particulate matter P is put into the medium solution L in the dispersion tank 41, the suspended particulate matter P is transferred into the medium solution L. Air bubbles contained in the liquid medium L are removed while being dispersed uniformly.

The medium L and the suspended particulate matter P dispersed therein flow in the flow cell 51 through the circulation pipe 44 by the drive of the circulation pump 45, and then the dispersion tank 41.
Returned inside.

Laser diffraction / scattering type particle size distribution measuring device 50
Is a flow cell 51, an irradiation optical system 52 that irradiates the flow cell 51 with laser light, and a measurement optical system 53 that measures the spatial intensity distribution of the diffracted / scattered light of the laser light from the irradiation optical system 52. And a data sampling circuit 54 for sampling the output of the measurement optical system 53,
And a computer 55 for calculating the particle size distribution of the particle group contained in the liquid medium L using the spatial intensity distribution data of the diffracted / scattered light sampled by the data sampling circuit 54.

The irradiation optical system 52 is composed of a laser light source 52a, a condenser lens 52b, a spatial filter 52c, and a collimator lens 52d, and irradiates the flow cell 51 with the laser light output from the laser light source 52a as a parallel light flux. The laser light applied to the flow cell 51 is diffracted and scattered by the suspended particulate matter P in the liquid medium L flowing inside the flow cell 51. The spatial intensity distribution of the diffracted / scattered light is measured by the measurement optical system 53.

The measurement optical system 53 is a condenser lens 53 arranged on the optical axis of the irradiation optical system 52 with the flow cell 51 interposed therebetween.
a and the ring detector 53b, the front wide-angle scattered light sensor group 53c arranged outside thereof, and the flow cell 5
It is configured by side / back scattered light sensor groups 53d arranged on the side and the rear of the No. 1 (on the side of the irradiation optical system 52). The ring detector 53b 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 53a. It is possible to detect the intensity distribution of the diffracted / scattered light within the predetermined front angle. Therefore, by the measurement optical system 53 including these sensor groups, the spatial intensity distribution of the diffracted / scattered light by the suspended particulate matter P dispersed in the liquid medium L in the flow cell 51 extends from the front minute angle to the rear. It is measured in a wide range.

The light intensity detection signal for each diffraction / scattering angle by the above measurement optical system 53 is a data sampling circuit 54 having respective amplifiers and AD converters.
Is amplified, digitized, and taken into the computer 55 as spatial intensity distribution data of diffracted / scattered light.

The computer 55 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 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.

In the above configuration, the total amount of the air supplied to the filter 1 can be grasped from the flow rate of the pump 3 per unit time and its driving time, and the total amount of the air supplied to the filter 1 can be set appropriately. Accordingly, when the suspended particulate matter P collected by the filter 1 is dispersed in the medium liquid L in the dispersion tank 41, the concentration of the suspended particulate matter P in the medium solution L is measured by the measurement optical system 53. Therefore, the spatial intensity distribution of the diffracted / scattered light can be sufficiently measured.

According to the measurement of the particle size distribution by the laser diffraction / scattering type particle size distribution measuring device 50, the particle size distribution can be measured with a high resolution in a wide particle size range from the submicron order to over 10 μm.

As described above, a predetermined amount of air is supplied to the filter 1 to collect the suspended particulate matter P, and the collected suspended particulate matter P is introduced into the medium liquid L in the dispersion tank 41. After the laser light is dispersed and irradiated, the spatial intensity distribution of the diffracted / scattered light is measured to obtain the particle size distribution, the discharge valve 41a is opened to discharge the internal liquid, and a new clean liquid medium L is obtained. After being injected into the dispersion tank 41, the suspended particulate matter P collected in the same manner as above using the new filter 1 is dispersed in the medium L, and the space for the next diffraction / scattered light is dispersed. By repeating the operation of starting the intensity distribution measurement operation at regular intervals, it is possible to continuously monitor the state of suspended particulate matter in the atmosphere.

Further, the filter 1 is used in each measurement operation.
Assuming that the total amount of the atmosphere supplied to the air is constant, the absolute intensity of the diffracted / scattered light obtained in each measurement is correlated with the concentration of the suspended particulate matter P in the atmosphere. It is possible to monitor the time-dependent change in the concentration of the suspended particulate matter P.

Furthermore, if calibration is performed using standard particles of which the number contained in the unit volume of the liquid medium L is known, the suspended particulate matter P dispersed in the liquid medium L is collected. From the total amount of air required for this purpose and the absolute intensity of the diffracted / scattered light obtained at that time, the particle size distribution of suspended particulate matter P contained in the unit volume of the atmosphere and the number of particles of each particle size You can also calculate the relationship with.

Although a membrane filter is used as the filter 1 in the above embodiments, the present invention is not limited to this, and a filter using glass fiber, for example, can be used. Can be any filter as long as it can separate and collect particles exceeding 10 μm from the submicron order contained in the supplied atmosphere.

Further, the filter holding member 2 for holding the filter 1 is not limited to the structure used in the above-described embodiment, and the sucked air can be guided to the filter 1 completely. Of course, any structure can be used.

[0034]

As described above, according to the present invention, the air is supplied to the filter by the pump, the suspended particulate matter contained in the atmosphere is collected by the filter, and the collected suspended particles are collected. The laser light is irradiated in the state that the particulate matter is dispersed in the medium liquid at an appropriate concentration, and the spatial intensity distribution of the diffracted / scattered light by the suspended particulate matter of the laser light is measured. Since the particle size distribution of suspended particulate matter is obtained based on the principle of laser diffraction / scattering particle size distribution measurement, the particle size resolution can be greatly improved compared to the conventional particle size distribution measurement using a cascade impactor. At the same time, the particle size distribution in the particle size range of 10 μm or more can be measured.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention, in which a schematic diagram showing an optical configuration and a pipe configuration and a block diagram showing an electrical configuration are shown together.

[Explanation of symbols]

1 filter 2 Filter holding member 21 Base 22 Lid 21a, 22a Large diameter part 21b, 22b openings 3 pumps 41 dispersion tank 42 Stirrer 43 Ultrasonic transducer 44 Circulation piping 45 Circulation pump 50 Laser Diffraction / Scattering Particle Size Analyzer 51 flow cell 52 Irradiation optical system 53 Measuring optical system 54 Data sampling circuit 55 Computer L medium P Suspended particulate matter

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 2G052 AA01 AA04 AA05 AC02 AD02                       AD29 AD46 BA05 BA14 CA02                       CA03 CA04 CA12 EA03 FD09                       GA11

Claims (2)

[Claims] 1. A method for measuring suspended particulate matter contained in the atmosphere, the method comprising collecting the suspended particulate matter in the atmosphere by sucking the atmosphere with a pump and supplying the same to a filter. , The spatial intensity distribution of the diffracted / scattered light obtained by irradiating the laser light with the suspended particulate matter collected by the filter dispersed in the liquid is measured, and from the measurement results, the particle size of the suspended particulate matter is measured. A method for measuring suspended particulate matter, characterized by obtaining a distribution. 2. An apparatus for measuring suspended particulate matter contained in the atmosphere, comprising: a filter for collecting suspended particulate matter in the atmosphere; and a pump for sucking the atmosphere and supplying it to the filter. A dispersion means for dispersing the suspended particulate matter collected in the filter in a liquid, a flow cell in which the liquid in which the suspended particulate matter is dispersed, and a irradiation optical system for irradiating the flow cell with laser light And the measuring optical system for measuring the spatial intensity distribution of the diffracted / scattered light of the laser light by the suspended particulate matter in the liquid, and the measured spatial intensity distribution of the diffracted / scattered light dispersed in the liquid An apparatus for measuring suspended particulate matter, comprising an arithmetic means for calculating a particle size distribution of suspended particulate matter.