JP5254915B2 - Suspended particulate matter generator - Google Patents

Description

  The present invention relates to a suspended particulate matter generator mainly used for confirming the operation of a concentration measuring device for particulate matter suspended in the air, and in particular, stabilizes suspended particulate matter-containing air containing microparticles of 2.5 μm or less. The present invention relates to a suspended particulate matter generator that can be obtained in this way.

  There are suspended particulate matter having various particle sizes in the atmosphere. The suspended particulate matter having a particle size of 10 μm or less is particularly toxic to humans because it is sucked and settled in the lung without being filtered by the respiratory tract when a person breathes. For this reason, the environmental standards related to air pollution based on the Pollution Control Basic Law stipulate that the suspended particulate matter in the atmosphere has a particle size of 10 μm or less. Conventionally, an apparatus for measuring the weight of suspended particulate matter having a particle size of 10 μm or less is commercially available according to this rule. In this specification, what is described as a suspended particulate matter is not limited to a particulate matter having a particle size of 10 μm or less, but is assumed to be a particulate matter suspended in the atmosphere.

  Airborne particulate matter may be abbreviated as coarse particles (hereinafter abbreviated as CP) and fine particles (hereinafter referred to as FP) with a particle size of about 2.5 μm as a boundary. Exist).

  CP contains naturally occurring things such as sea salt particles and dust derived from soil. FP, on the other hand, produces primary particles directly released into the atmosphere from sources such as dust and diesel vehicles emitted from factories, sulfur oxides (SOx), nitrogen oxides (NOx), and volatile organic compounds. There are secondary generated particles in which a gaseous substance such as (VOC) changes into a particulate substance in the atmosphere. Recently, as a result of epidemiological studies on the human body about the particle size of airborne particulate matter in urban areas, FP is thought to affect diseases such as cardiovascular disease, lung cancer and asthma even at low concentrations. Increased weight concentrations are believed to increase mortality.

Therefore, conventionally, a measuring apparatus has been developed that collects FP having a small particle diameter and measures the weight concentration of the collected FP (weight of FP contained in 1 m ² atmosphere). As an example of the measuring device, for example, there is a device that continuously measures FP contained in a certain amount of air. This measuring apparatus sucks the sample atmosphere containing FP, collects the FP contained in the sucked sample atmosphere on a tape filter, and measures the weight of the collected FP by the β-ray absorption method. By measuring the mass of FP in the atmosphere with the measurement device, it is possible to grasp the pollution state of the atmosphere and devise countermeasures. In addition to the β absorption method, TEOM (Tapered Element Oscillating Microbalance) and a light scattering method are also known.

  Since the measuring device is a very precise machine, regular inspection and maintenance are indispensable. Conventionally, in order to inspect and calibrate the operation of the measurement apparatus, for example, weight measurement is performed by a β-ray absorption method in a state where an equivalent film having a weight equal to a predetermined amount of FP is installed on a tape filter. Thereby, the operation of the weight measuring unit using the β-ray absorption method can be inspected, and the weight measuring unit can be calibrated as necessary. Calibration performed by installing an equivalent membrane on a filter is called static calibration.

  However, since the above static calibration is not performed in a state where the entire measuring apparatus is operated, the operation other than the weight measuring unit, for example, the operation of the suction pump, the tape filter moving mechanism, etc. is inspected and calibrated. I can't. Therefore, in order to inspect and calibrate (so-called dynamic calibration) the operation of the entire apparatus in a state where the entire measuring apparatus is in operation, it is desired to introduce an apparatus that stably supplies FP to the measuring apparatus.

  Note that Non-Patent Document 1 describes an ultrasonic sprayer. In this ultrasonic atomizer, a liquid supplied from a syringe pump into a chamber is vibrated by a piezoelectric crystal vibrator and discharged as an aerosol together with an air flow from an orifice. However, this ultrasonic atomizer can discharge 1 to 10 μm liquid particles, but it is difficult to stably discharge liquid particles having the same particle diameter over a long period of time. Also, with this ultrasonic atomizer, it is difficult to release fine particles of less than 1 μm. Furthermore, the entire apparatus becomes large, is not convenient to carry, and is difficult to use as a dynamic calibration apparatus by simply connecting to a continuous weight measuring apparatus for fine particulate matter on site.

William C. Hinds, Aerosol Technology Properties, Behavior, and Measurement of Airborne Particles Second Edition, (Canada) ), John Wiley & Sons, Inc., 1998

  The present invention has been made in view of such circumstances, and suspended particles that can stably obtain suspended particulate matter-containing air containing suspended particulate matter having an aerodynamic particle size of 2.5 μm or less. The purpose is to provide a particulate matter generator.

The first invention is an apparatus for generating a large number of suspended particulate matter,
A solution supply unit for supplying a solution having a particulate matter as a base of the suspended particulate matter as a solute;
A capillary-shaped first electrode to which a first potential is applied and which discharges the solution supplied from the solution supply unit as a droplet from a hole at the tip;
A second potential having a predetermined potential difference with respect to the first potential, a second potential having a structure in which the droplets containing the particulate matter are allowed to pass through the pores with a predetermined distance therebetween. Electrodes,
A voltage applying unit that generates the predetermined potential difference between the first electrode and the second electrode;
An air flow generator for generating an air flow from the first electrode toward the second electrode,
The droplet discharged from the first electrode is pulled by the second electrode due to the potential difference and flies, and the droplet in flight repeats fine separation while being dried by touching the air flow, and the fine separation Is repeated, and a large number of dispersed liquid droplets are generated. The large number of liquid droplets ride on the air flow and pass through the second electrode, and after the passage, the fine separation is repeated. A large number of suspended particulate matter is produced.

  According to the first invention, the solution in the first electrode is charged with the charge corresponding to the first electrode. The droplets discharged from the first electrode fly by being pulled by the second electrode due to the potential difference, and the droplets in flight are finely separated while being dried by touching the air flow. The principle of fine separation is due to the fact that the charge density on the droplet surface increases as the particle diameter decreases due to drying, and the droplet breaks up due to the repulsive force between the charges. By repeating the fine separation, a large number of dispersed droplets are generated, and the large number of droplets ride on the air flow and pass through the second electrode. A large number of droplets that have passed through the second electrode repeat the above-mentioned fine separation even after the passage, and a large number of dispersed particulate matters are generated by the repetition of the fine separation. This utilizes the principle of electrospray ionization (ESI). Thereby, suspended particulate matter-containing air containing solid particles having an aerodynamic particle size of approximately the same diameter of 2.5 μm or less can be obtained stably over a long period of time. It is also possible to stably obtain air containing fine particulate matter containing fine particulate matter having substantially the same diameter of 1 μm or less over a long period of time. The suspended particulate matter obtained in the present invention is not limited to a particulate matter of 2.5 μm or less, and may be a particulate matter exceeding 2.5 μm.

According to a second invention, in the first invention,
The apparatus further comprises a particle concentration measuring unit that detects optical characteristics of the suspended particulate matter during the flight of the suspended particulate matter and measures the particle concentration of the suspended particulate matter based on the optical characteristics. To do.

According to the second invention, the particle concentration of the suspended particulate matter that has passed through the second electrode is measured based on the optical characteristics of the suspended particulate matter. The “optical characteristics” referred to here are not particularly limited, and are, for example, light scattering characteristics and light absorption characteristics. The “particle concentration” referred to here is the number or weight of generated suspended particulate matter contained in air of unit volume (1 m ³ ). Since the particle size and density of the generated suspended particulate matter are constant, the number concentration and the weight concentration can be calculated. The particle concentration measurement unit, for example, calculates the number of generated suspended particulate matter based on the light scattering characteristics of the suspended particulate matter, and divides the weight obtained by weight conversion based on the calculated number by the volume of air. By doing so, the weight concentration can be calculated.

According to a third invention, in the second invention,
Feedback control of at least one of the solution supply amount of the solution supply unit and the air flow rate of the air flow generation unit based on the particle concentration of the suspended particulate matter measured by the particle concentration measurement unit; .

  According to the third invention, if the particle concentration of the generated suspended particulate matter is too larger than the predetermined particle concentration, at least one of the solution supply amount and the air flow rate is reduced, and the generated suspended particulate matter If the particle concentration is too smaller than a predetermined particle concentration, feedback control can be performed to increase at least one of the solution supply amount and the air flow rate. By this feedback control, the particle concentration of the suspended particulate matter can be adjusted to a predetermined particle concentration.

According to a fourth invention, in the first invention,
A device for collecting the suspended particulate matter in the atmosphere and measuring the weight concentration of the collected suspended particulate matter and confirming the operation of the measuring device, and configured to be connectable to the measuring device. It is characterized by being.

  According to the fourth invention, in order to inspect and calibrate (so-called dynamic calibration) the operation of the entire measuring device while the entire mass measuring device of the FP is operated, the FP is stably supplied to the measuring device. can do.

According to a fifth invention, in the first invention,
The suspended particulate material is magnesium sulfate.

  According to the fifth aspect of the invention, it is possible to stably generate a relatively large amount of suspended particulate matter for a long time, compared to the case of using other materials.

  According to the present invention, suspended particulate matter-containing air containing a solid particulate matter having an aerodynamic particle size of 2.5 μm or less can be obtained stably.

The figure which shows the structure of the microparticulate matter generator based on 1st Embodiment of this invention. The figure which shows the variation of the 2nd electrode in FIG. The figure which shows the number of the microparticulate matter which changes according to the electric potential difference between a 1st electrode and a 2nd electrode. Diagram showing the number of microparticulates that change with the type of solute The figure which shows the structure of the microparticulate matter generator based on 2nd Embodiment of this invention.

(First embodiment)
Hereinafter, a suspended particulate matter generator according to a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a configuration of a suspended particulate matter generator according to the first embodiment. FIG. 2 is a diagram showing a variation of the second electrode in FIG.

  The suspended particulate matter generator 1 (hereinafter abbreviated as the generator 1) according to the first embodiment is a device that generates a large number of fine particulate matter. In the present specification, “floating particulate matter” includes coarse particulate matter (hereinafter abbreviated as CP) and fine particulate matter (hereinafter referred to as FP) with a particle diameter of about 2.5 μm as a boundary. May be abbreviated). “Microparticulate material” means microparticles of 2.5 μm or less, in particular 1 μm or less.

  The generator 1 includes a solution supply unit 2, a first electrode 3, a second electrode 4, a voltage application unit 5, and an air flow generation unit 6.

The solution supply unit 2 supplies the first electrode 3 with a solution containing particulate matter (for example, fine particulate matter) as a solute. The solution supply unit 2 includes a liquid feed pump 12, and the supply amount (L / min) of the solution can be adjusted by adjusting the rotation speed of the liquid feed pump 12. Type of particulate matter as a solute is not particularly limited, but is preferably, for example, be a magnesium sulfate (MgSO _4). The particulate material may be another material, for example, calcium nitrate (Ca (NO ₃ ) ₂ ) or sodium chloride (NaCl). Although it does not specifically limit also about a solvent, For example, water and ethanol can be mixed in the ratio of 1: 1. By mixing ethanol, the solvent is dried to facilitate solid particles.

The first electrode 3 is a needle-shaped electrode to which the first potential V ₁ is applied and discharges the solution supplied from the solution supply unit 2 from the tip hole 13 as a droplet. The first electrode 3 is made of, for example, metal.

The second electrode 4 is given a second potential V ₂ having a predetermined potential difference V _S with respect to the first potential V ₁ . The second electrode 4 is disposed to face the hole 13 at a predetermined interval, and has a gap 18 or a hole 14 through which a fine particulate matter riding on an air flow can pass. The second electrode 4 is made of, for example, metal.

  Although the form of the 2nd electrode 4 is not specifically limited, For example, it can be set as either form shown by FIG. 2 (A)-(E). The second electrode 4 shown in FIG. 2A is composed of two rod-like portions 19 provided in parallel with each other with a gap 18 therebetween. The width of the gap 18 is, for example, about 5 to 15 mm, but is not particularly limited.

  The second electrode 4 shown in FIG. 2B is a metal disk-like portion 50 having a hole portion 14 formed in the center portion. The hole 14 shown in FIG. 2B has a circular shape, but may be any of a triangular shape, a quadrangular shape, and a polygonal shape having five or more corners instead. The diameter of the hole 14 is, for example, 15 mm, but is not limited to this value.

  The second electrode 4 shown in FIG. 2C includes a ring-shaped portion 40 and a mesh-shaped portion 42 attached to the ring-shaped portion 40 so as to be positioned at the opening 41 of the ring-shaped portion 40. For example, as shown in FIG. 2C, the mesh portion 42 can have a structure in which four metal wires 43 are combined in a mesh shape. The hole 14 is a square region surrounded by four metal wires 43. The inner diameter of the ring-shaped portion 40 is, for example, 60 mm, and the outer diameter is, for example, 76 mm, but is not limited to these values. Moreover, although the space | interval of the parallel wire 43 which comprises the mesh-shaped part 42 is 15 mm, for example, it is not limited to this value.

  The second electrode 4 shown in FIG. 2 (D) includes a ring-shaped portion 40 and a radial portion 44 attached to the ring-shaped portion 40 so as to be positioned in the opening 41 of the ring-shaped portion 40. For example, as shown in FIG. 2D, the radial portion 44 may have a structure in which a linear metal wire 46 is combined with each vertex of a hexagonal metal wire 45. Instead of the hexagonal metal wire 45, a polygonal wire having a triangular shape, a quadrangular shape, a pentagonal shape, or a heptagonal angle or more may be provided. Regardless of which polygonal shape is employed, a linear wire is combined at each vertex. The hole 14 is a region surrounded by a hexagonal metal wire 45 in the example shown in FIG.

  The second electrode 4 shown in FIG. 2 (E) includes a ring-shaped portion 40 and a radial portion 47 attached to the ring-shaped portion 40 so as to be positioned at the opening 41 of the ring-shaped portion 40. For example, as shown in FIG. 2E, the radial portion 47 can have a structure in which four linear wires 49 are combined around a circular metal wire 48. In addition, the number of the linear wire 49 is not limited to four, For example, two, three, or five or more may be sufficient. 2E is thicker than the linear wire 46 shown in FIG. 2D, but is as thin as FIG. 2D. It may be. The hole 14 is an area surrounded by a hexagonal metal wire 45 in the example shown in FIG. The inner diameter of the circular metal wire 48 is, for example, 15 mm, but is not limited to this value.

The voltage application unit 5 generates a predetermined potential difference V _S between the first electrode 3 and the second electrode 4. For example, an arbitrary potential of, for example, 5 to 7 volts is applied to the first electrode 3 with respect to the second electrode 4. Conversely, any potential between 5 and 7 volts, for example, may be applied to the second electrode 4 with respect to the first electrode 3.

The first electrode 3 and the second electrode 4 are accommodated in the first flow pipe 7. The first flow pipe 7 is connected to the second flow pipe 8, and the second flow pipe 8 is connected to the third flow pipe 9. The second flow pipe 8 is thinner than the first flow pipe 7 and the third flow pipe 9. The third flow pipe 9 is connected to an FP mass measuring device (not shown). The third flow pipe 9 is provided with a flow rate sensor 10. The flow sensor 10 measures the amount of air (L / min) flowing through the third flow pipe 9. The flow sensor 10 is connected to the CPU 11. The CPU 11 controls the applied voltage of the voltage application unit 5, the solution supply amount (L / min) of the solution supply unit 2, and the air flow rate of the air flow generation unit 6 based on the flow rate data input from the flow sensor 10. The distance between the tip of the first electrode 3 and the second electrode 4 is, for example, about 1 cm.

  The air flow generation unit 6 generates an air flow from the first electrode 3 toward the second electrode 4. The air flow is preferably an air flow that is as dry as possible by means of drying. The airflow generation part 6 can be comprised with a ventilation fan, for example. The air flow is preferably clean air obtained by removing air outside the apparatus with a particulate removal filter. The rotational speed of the blower fan is controlled so that the amount of air flowing through the third circulation pipe 9 is, for example, 20 L / min.

Next, operation | movement of the generator 1 is demonstrated.
First, a solution is supplied from the solution supply unit 2 to the first electrode 3. Next, the droplet discharged from the first electrode 3 is pulled by the second electrode 4 by the potential difference and flies. The droplets in flight repeat the fine separation while being dried by touching the air flow, and by the repetition of the fine separation, a large number of droplets are dispersed under normal pressure. The large number of droplets ride on the air flow and pass through the gap 18 or the hole 14. The large number of droplets repeats fine separation even after passing through the gap 18 or the hole 14, and a large number of dispersed suspended particulate matters are generated by repeating the fine separation. The principle of fine separation is due to the fact that the charge density on the droplet surface increases as the particle diameter decreases due to drying, and the droplet breaks up due to the repulsive force between the charges. By repeating the fine separation, a large number of fine particulate substances dispersed under normal pressure are generated. Thereby, according to the generator 1, the suspended particulate matter-containing air containing the suspended particulate matter having substantially the same diameter of 2.5 μm or less, particularly 1 μm or less, can be stably obtained over a long period of time. The above is the main operation of the generator 1.

FIG. 3 is a diagram showing the relationship between the applied voltage of the voltage application unit 5 and the concentration of the generated fine particulate matter. As shown in FIG. 3, when the applied voltage (potential difference) is 6.0 to 6.5 kV, the concentration of the microparticulate substance becomes maximum. Therefore, it can be seen that the applied voltage (potential difference) is preferably 6.0 to 6.5 kV.
In addition, the concentration measurement uses an air flow rate of 20 L / min, a solution obtained by dissolving magnesium sulfate at a concentration of 0.1% in a solvent obtained by mixing water and ethanol at 1: 1, and the solution flow rate is 10 μL / min. It was performed under the conditions.

FIG. 4 is a diagram showing the relationship between the kind of solute and the concentration of the generated fine particulate matter. As shown in FIG. 4, when the solute is magnesium sulfate, the concentration of microparticulate matter is maximized. Therefore, it turns out that magnesium sulfate is preferable as a solute.
In addition, the concentration measurement uses an air flow rate of 20 L / min, a solution obtained by dissolving magnesium sulfate at a concentration of 0.1% in a solvent obtained by mixing water and ethanol at 1: 1, and the solution flow rate is 10 μL / min. The test was performed under the condition of a linear type of 0.475.

The generator 1 is a measuring device for confirming and calibrating the operation of a measuring device that collects and collects suspended particulate matter (for example, fine particulate matter) in the atmosphere and measures the weight concentration of the suspended particulate matter. Is a device for supplying suspended particulate matter to the measuring device, and is configured to be connectable to the measuring device. The “weight concentration of the suspended particulate matter” referred to here is the weight of the suspended particulate matter contained in the unit volume (1 m ³ ) of the atmosphere.

  Therefore, according to the generator 1, in order to inspect and calibrate (so-called dynamic calibration) the operation of the entire measurement apparatus in the state in which the entire apparatus for measuring the concentration of suspended particulate matter is operated, For example, a fine particulate material having a particle size of 2.5 μm or less can be stably supplied to the measurement apparatus.

(Second Embodiment)
A second embodiment of the present invention will be described with reference to the drawings.
FIG. 5 is a diagram illustrating a configuration of the suspended particulate matter generation device according to the second embodiment. In addition, about the structure similar to 1st Embodiment, the same referential mark as FIG. 1 is attached | subjected and the description is abbreviate | omitted.

  The difference between the suspended particulate matter generating device 15 (hereinafter referred to as the generating device 15) according to the second embodiment and the first embodiment is that the particle concentration measuring unit 16 is further provided. This is the same as in the first embodiment.

The particle concentration calculation unit 16 detects the optical characteristics of the suspended particulate matter that has passed through the gap 18 or the hole portion 14, and based on the optical characteristics, the number concentration of the suspended particulate matter that has passed through the gap 18 or the pore portion 14 and Calculate the weight concentration. The “optical characteristics” referred to here are not particularly limited, and are, for example, light scattering characteristics and light absorption characteristics. Further, the “particle concentration” referred to here is the number (number concentration) or weight (weight concentration) of the generated suspended particulate matter contained in air of unit volume (1 m ³ ). Since the particle size and density of the generated suspended particulate matter are constant, the number concentration and the weight concentration can be calculated. The particle concentration measurement unit 16 calculates the number concentration and the weight concentration of the suspended particulate matter based on the optical data output from the optical detection unit 17 provided in the second flow pipe 8. For example, the particle concentration measurement unit 16 calculates the number of generated suspended particulate matter based on the light scattering characteristics or light absorption characteristics of the suspended particulate matter, and calculates the weight obtained by weight conversion based on the calculated number. By dividing by the volume flow rate of air, the weight concentration can be calculated.

  The CPU 11 feedback-controls at least one of the solution supply amount of the solution supply unit 2 and the air flow rate of the airflow generation unit 6 based on the number calculated by the number calculation unit 16.

  According to the generator 15, the particle concentration of the suspended particulate matter that has passed through the gap 18 or the hole 14 is calculated based on the optical characteristics of the suspended particulate matter.

  Moreover, according to the generator 15, if the particle concentration of the generated suspended particulate matter is too larger than a predetermined particle concentration, at least one of the solution supply amount and the air flow rate is reduced, and the generated suspended particulate matter is generated. If the particle concentration is less than a predetermined particle concentration, feedback control can be performed to increase at least one of the solution supply amount and the air flow rate. By this feedback control, the particle concentration of the generated fine particulate matter can be adjusted to a predetermined particle concentration.

  INDUSTRIAL APPLICABILITY The present invention is particularly applicable to a microparticulate material generator that can stably obtain microparticle-containing air containing solid microparticles of 2.5 μm or less over a long period of time.

DESCRIPTION OF SYMBOLS 1,15 Microparticulate matter generator 2 Solution supply part 3 1st electrode 4 2nd electrode 40 Ring-shaped part 41 Opening part 42 Mesh-like part 43,46,49 Linear metal wire 44,47 Radial part 45 Hexagonal shape Metal wire material 48 Circular metal wire material 50 Disc-shaped portion 5 Voltage application portion 6 Air flow generation portion 7 First flow tube 8 Second flow tube 9 Third flow tube 10 Flow rate sensor 11 CPU
DESCRIPTION OF SYMBOLS 12 Flow pump 13 Hole 14 Hole 16 Particle concentration measurement part 17 Optical detection part 18 Gap 19 Rod-shaped part

Claims (5)

An apparatus for generating a large number of suspended particulate matter,
A solution supply unit for supplying a solution having a particulate matter which is a basis of the suspended particulate matter as a solute;
A capillary-shaped first electrode to which a first potential is applied and which discharges the solution supplied from the solution supply unit as a droplet from a hole at the tip;
A second electric potential having a predetermined electric potential difference with respect to the first electric potential, a second electric potential having a predetermined interval with respect to the hole, and a second structure having a structure that allows a droplet containing the particulate matter to pass therethrough. Electrodes,
A voltage application unit that generates the predetermined potential difference between the first electrode and the second electrode;
An air flow generation unit that generates an air flow from the first electrode toward the second electrode,
The droplet discharged from the first electrode is pulled by the second electrode due to the potential difference and flies, and the droplet in flight repeats fine separation while being dried by touching the air flow, and the fine separation Is repeated, and a large number of dispersed liquid droplets are generated. The large number of liquid droplets ride on the air flow and pass through the second electrode, and after the passage, the fine separation is repeated. A suspended particulate matter generating device characterized in that a large number of suspended particulate matter is produced.   The apparatus further comprises a particle concentration measurement unit that detects optical characteristics of the suspended particulate matter during the flight of the suspended particulate matter and measures the particle concentration of the suspended particulate matter based on the optical characteristics. The suspended particulate matter generator according to claim 1.   Feedback control of at least one of the solution supply amount of the solution supply unit and the air flow rate of the airflow generation unit based on the particle concentration of the suspended particulate matter measured by the particle concentration measurement unit The suspended particulate matter generator according to claim 2.   It is a device for collecting the suspended particulate matter in the atmosphere and measuring the operation of the measuring device for measuring the weight concentration of the collected suspended particulate matter, and is configured to be connectable to the measuring device. The suspended particulate matter generator according to claim 1, wherein   The suspended particulate matter generator according to claim 1, wherein the suspended particulate matter is magnesium sulfate.

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