JP2007127427A - Collection device of fine particles and collection method of fine particles - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To collect an easily measurable number of fine particles on a collection plate by charging fine particles in a collection device of fine particles. <P>SOLUTION: A fine particle counter (LPC) 13 is provided on the inlet side of fine particles. Air is charged with the fine particles while counting the number of the fine particles by the LPC 13 to be collected on slide glass 20. If the count value of the fine particles counted by the fine particle counter 13 reaches a threshold value, a suction pump 23 is stopped to stop suctioning. By this constitution, a proper number of the fine particles can be collected on the slide glass 20. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a particulate collection device and a particulate collection method.

In order to analyze fine particles in the air, a sampling apparatus is conventionally known that collects fine particles floating in the air on a glass collecting plate and observes and analyzes the fine particles. (Patent Document 1) In this apparatus, a cylindrical hopper is provided and corona discharge is performed on a carrier gas to charge the fine particles, and the charged fine particles are collected in the cylindrical hopper.
JP 7-47299 A

  In recent years, damage due to asbestos has become a problem, and it is required to measure the number concentration of asbestos under various environments. However, in order to accurately measure the number of asbestos mixed in various fine particles, there is a drawback that it is difficult to count unless the asbestos is collected on a collecting plate.

  In the collection device disclosed in Patent Document 1, when observation and analysis of fine particles are performed after collection, shape analysis becomes difficult if a large number of fine particles are collected. Therefore, it is necessary to stop the collection after collecting an appropriate number of fine particles, but there is a drawback that it is difficult to determine the timing of this stop.

  The present invention has been made paying attention to such a conventional problem, and provides a particulate collection apparatus and a particulate collection method capable of easily collecting an appropriate number of particulates under various environments. The purpose is to provide.

  In order to solve this problem, the particulate collection device of the present invention is a particulate collection device that collects particulates floating in a gas, and counts the number of particulates in the gas taken in from the gas inlet. A fine particle counter, a corona discharge part provided on the outlet side of the fine particle counter via a duct, for charging fine particles in the gas, and a fine particle trap for collecting fine particles charged by the corona discharge part on a conductive glass. The gas is sucked from the inlet side of the fine particle counter so that the gas passes through the collecting portion, the fine particle counter, the corona discharge portion, and the fine particle collecting portion, and the gas passing through the fine particle collecting portion is discharged. A suction pump; and a pump control unit that stops the suction pump when the count value of the particulate counter reaches a threshold value after the operation starts.

  Here, the apparatus further includes a setting unit that is connected to the pump control unit and sets a concentration ratio between the fine particles to be measured and other fine particles, and the pump control unit has a large concentration ratio set by the setting unit. For example, the threshold value may be set to be small, and if the density ratio is small, the threshold value may be set to be large.

  In order to solve this problem, the fine particle collection method of the present invention is a fine particle collection method for collecting fine particles floating in a gas, and the number of fine particles in the gas taken in from the gas inlet by the fine particle counter. The particles in the gas after counting the number of particles are charged by a corona discharge unit, and the particles charged by the corona discharge are collected on a conductive glass, and the particle counter, the corona discharge unit and The gas is sucked from the inlet side of the fine particle counter so that the gas passes through the fine particle collecting portion, and the gas passing through the fine particle collecting portion is discharged. After the operation starts, the count value of the fine particle counter reaches the threshold value. In this case, the suction of the gas is stopped.

  Here, the concentration ratio between the fine particles to be measured and other fine particles is set, and the threshold value is set so that the threshold value is small if the set concentration ratio is large and the threshold value is large if the concentration ratio is small. Also good.

  According to the present invention having such a feature, it is possible to charge while counting the number of fine particles taken from the intake port and collect them. Therefore, by stopping suction after an appropriate number of fine particles have passed, the number of fine particles to be collected can be set to an appropriate number. Further, by setting the concentration ratio of the fine particles to be measured and the concentration ratio of the other fine particles, an effect that the threshold value can be appropriately set is obtained.

  The present invention is a block diagram showing a configuration of a particulate collection device according to an embodiment. In FIG. 1, the fine particle inlet 11 is provided with an impactor 12 having a T-shaped cross section as shown. The impactor 12 classifies the particle size of fine particles, and a laser fine particle counter (LPC) 13 is provided along the fine particle inlet 11. As will be described later, the LPC 13 irradiates the flow path of fine particles with laser light from a laser light source, and counts the number of particles having a predetermined particle diameter or more based on the scattered light.

  A corona discharge unit 14 is provided on the outlet side of the LPC 13. The corona discharge part 14 has a spacer 16 made of an insulator in a cylinder 15 as shown in the figure, and an electrode 17 is held at the center thereof. The lower tip of the electrode 17 of this discharge part is formed as a needle 18. The duct guided from the outlet side of the LPC 13 is configured to pass through the vicinity of the electrode 17 and the needle 18 at the tip thereof. The periphery of the needle 18 is thin and the flow path is narrowed. As a result, corona discharge occurs in the vicinity of the needle 18 so that the fine particles passing through the duct are charged. The corona discharge charges the fine particles that have passed through the duct. A slide glass 20 is provided at a position facing the outflow port. The slide glass 20 has a conductive coating formed on one side by vapor deposition or the like, and collects charged fine particles on the surface. The slide glass 20 and the space above it constitute a fine particle collecting part 21 for collecting charged fine particles on the conductive glass.

  The high-voltage power supply unit 19 generates corona discharge by applying a high-voltage power supply to both ends of the electrode unit 17 and the slide glass 20. Here, the slide glass 20 is configured to be detachable so that it can be exchanged after collecting the fine particles.

  And the duct 22 is provided in the exit side of the particulate collection part 21 toward the exterior of a cylinder part, and also the suction pump 23 is provided. The suction pump 23 guides a gas containing fine particles from the outside through the fine particle inlet 11 and passes the gas through the LPC 13 and the corona discharge unit 14 to discharge the gas. The start and stop of the suction pump 23 are controlled by the pump control unit 24. The setting unit 25 inputs a signal to the pump control unit 24 in accordance with the state of fine particles in the measurement region. The pump control unit 24 stops the operation of the suction pump 23 when the count value obtained from the LPC 13 after starting the operation becomes a threshold value.

  Next, the configuration of the fine particle counter (LPC) 13 will be described with reference to FIG. The duct 31 from the impactor 12 described above is connected to the cylinder 31 of FIG. 2 as an inflow portion, and the tip of the duct 32 is narrowly configured as a nozzle. The discharge duct 33 is provided at a position facing the discharge duct 33. Then, as shown in the figure, a laser diode 34 is arranged in the upper part in the vertical direction, and the laser light is focused through the lens 35 to the tip side of the nozzle that is the measurement region. Here, the light passing through the measurement region as it is is blocked by the plate 36. Lenses 37 and 38 are provided below the cylinder 31. The lenses 37 and 38 are lenses that focus scattered light when fine particles pass through the measurement region. A photodiode 39 is disposed at this focusing position. The output of the photodiode 39 is guided to the waveform shaping unit 41 via the amplifier 40. The waveform shaping unit 41 shapes the input signal with a predetermined threshold, and its output is input to the counting unit 42. The counting unit 42 counts the number of particles passing through the ducts 32 and 33 by counting the number of pulses. The counter 42 is given a reset signal from the pump controller 24, and the count value is reset each time the reset signal is input.

  Here, the setting unit 25 and the pump control unit 24 will be further described. The setting unit 25 sets the ratio of the concentration of asbestos to be measured and the concentration of other fine particles when it is desired to measure the concentration ratio of surrounding fine particles to be measured, for example, the concentration of asbestos. The asbestos to be measured is assumed to have a length of 5 μm or more, a diameter of less than 3 μm, and a length to width ratio of 3 or more, for example. The concentration is expressed as the number per unit volume. It is necessary to measure the concentration of asbestos by measuring the number attached to the slide glass 20 with a microscope according to laws and regulations. Further, as extraction of only asbestos, there is known a method in which a filter is ashed using plasma and only asbestos is left, and an asbestos is extracted with a specific color for each type of asbestos by dyeing. In some cases, linear fine particles adhering to the slide glass are regarded as asbestos without using such a method. In any case, counting the number of asbestos is most easy when an appropriate number of fine particles are adhered on the slide glass, and it is difficult to measure whether the amount is too small or too large. Therefore, in the present invention, the stop timing of the suction pump is determined by the fine particle counter. In this case, a rough estimated value of the concentration ratio between the gas fine particles to be measured, here asbestos, and other fine particles is set by the setting unit 25 in advance.

  Next, the operation of this embodiment will be described. The particulate collection device shown in FIG. 1 is arranged at the measurement site. Here, a concentration ratio between the target fine particles, for example, asbestos fine particles and other fine particles is set in advance. For example, if the concentration ratio is 1:10, the concentration ratio is set in the setting unit 25. The pump control unit 24 sets a threshold value corresponding to this. Here, when the density ratio is smaller than 1:10, for example, 1: 100, the threshold is set large, and when the density ratio is large, the threshold is set small. Then, a reset signal is sent to the counter 42 to reset the count value, and the operation of the suction pump 23 is started. The gas to be measured, here the air, passes through the duct via the impactor 12 from the fine particle inlet 11 and flows into the LPC 13 shown in FIG. In the LPC 13, as described above, the number of fine particles is counted by the counting unit 42. The fine particles are guided to the corona discharge unit 14 through the discharge duct 33 and discharged, and the fine particles are collected in the collection region of the slide glass 20 for measurement.

Now, when the count value from the counting unit 42 reaches a predetermined threshold, the pump control unit 24 stops the operation of the suction pump 23. The amount of atmospheric suction is determined by the operating time of the suction pump 23. Then, the slide glass 20 is taken out, and asbestos is extracted as it is or by the means described above, and the number thereof is measured with a microscope. The number obtained is divided by the suction amount (m ³ ) to obtain the number concentration of asbestos per unit volume.

  Here, since the threshold value is set on the slide glass 20 according to the concentration set by the setting unit, the number of fine particles containing asbestos is not too small or too large, and measurement can be easily performed. it can.

  Here, the laser particle counter having the configuration shown in FIG. 2 is used to focus forward scattered light, but various particle counters can be used as long as the number of particles can be counted.

  In the above-described embodiment, the impactor is provided on the fine particle inlet side for classification, but the impactor is not necessarily used.

  Further, in the above-described embodiment, asbestos is described as the fine particles to be measured, but the present invention can be applied to other fine particles.

  If there is no single particle in the gas or if it is not necessary to select and count a specific particle, it is not necessary to set a concentration ratio by the setting unit and set a threshold value accordingly. It can be used to stop pump suction when a suitable number of particulates have been collected.

It is a block diagram which shows the whole structure of the particulate collection apparatus by this invention. It is a block diagram which shows the fine particle counter of this Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Fine particle inlet 12 Impactor 13 Laser particle counter 14 Corona discharge part 15 Cylinder 16 Spacer 17 Electrode 18 Needle 19 High voltage power supply part 20 Slide glass 21 Fine particle collection part 22 Duct 23 Suction pump 24 Pump control part 25 Setting part

Claims (4)

A fine particle collecting device for collecting fine particles floating in a gas,
A particle counter for counting the number of particles in the gas taken in from the gas inlet;
A corona discharge part that is provided on the outlet side of the particulate counter via a duct and charges particulates in the gas;
A fine particle collecting part for collecting fine particles charged by the corona discharge part on a conductive glass;
A suction pump that sucks the gas from the inlet side of the particle counter and discharges the gas that has passed through the particle collector so that the gas passes through the particle counter, the corona discharge unit, and the particle collecting unit;
A particulate collection device, comprising: a pump control unit that stops the suction pump when the count value of the particulate counter reaches a threshold value after the start of operation. A setting unit that is connected to the pump control unit and sets a concentration ratio between the fine particles to be measured and the other fine particles;
2. The particulate trap according to claim 1, wherein the pump control unit sets the threshold value so that the threshold value decreases when the concentration ratio set by the setting unit is large, and the threshold value increases when the concentration ratio is small. Collector. A method for collecting fine particles floating in a gas,
Count the number of fine particles in the gas taken in from the gas inlet by the fine particle counter,
Charge the fine particles in the gas after counting the number of fine particles by the corona discharge part,
Collecting fine particles charged by the corona discharge on conductive glass,
As the gas passes through the fine particle counter, the corona discharge part and the fine particle collection part, the gas is sucked from the inlet side of the fine particle counter to discharge the gas that has passed through the fine particle collection part,
A fine particle collecting method, comprising: stopping gas suction when the count value of the fine particle counter reaches a threshold value after the start of operation. Set the concentration ratio between the fine particles to be measured and other fine particles,
4. The method for collecting fine particles according to claim 3, wherein the threshold value is set to be small if the set concentration ratio is large, and to be large if the concentration ratio is small.

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