JP6596041B2 - Fine particle collector - Google Patents

Description

  The present invention relates to a microparticle collection device for efficiently collecting microparticle materials contained in air.

  Particles floating in the atmosphere include not only pollen and dust, but also soot and organic compounds such as diesel exhaust emitted into the atmosphere. A microparticulate substance having a particle size of 2.5 μm or less, that is, a microparticle, is generally referred to as PM2.5 with respect to coarse particles having a large particle size such as pollen or dust. About 2.5% of PM2.5, that is, microparticulates are water-soluble inorganic substances, and the rest are soot and organic compounds such as diesel exhaust, and gas substances may become microparticles due to chemical reactions in the atmosphere. .

  It has been pointed out that such fine particles not only reach the nose and trachea, but also reach deep into the alveoli, causing respiratory and circulatory diseases and causing serious health problems. However, details of the cellular biochemical mechanism in the harmful expression of PM2.5 are not clear. The reason for this is that in addition to the complex assembly of microparticles made up of a wide variety of chemical components, there are a variety of cell types that should be tested and methods for analyzing the expression of effects, and further to cells. It is also difficult to prepare a large amount of microparticles for use in the exposure of the above. In other words, the difficulty of preparing a large amount of microparticles for use in exposure experiments is one major limitation in research.

  In response to this problem, for example, in the case of animal experiments, experiments are also conducted in which minute particles in the atmosphere are concentrated and exposed. However, this method is effective for exposure to actively breathing animals, but is not considered very effective for static in vitro cell experiments. This is because even if the particle size concentration in air is increased, the amount of particle exposure to cells does not necessarily increase linearly. Until now, after collecting microparticles, that is, PM2.5 particles once on a filter, the microparticles are often collected by mechanical vibration and used for exposure experiments. However, in this method, there remains a question as to whether the particles finally used for exposure can be regarded as truly microparticles, in particular whether the particle size distribution is the same, and the microparticles used for the experiment are The method to obtain becomes very complicated. For this reason, there is a strong demand for the development of a technique for simply collecting a large amount of microparticles necessary and sufficient for use in experiments for exposure to cells without using a filter.

  Patent Document 1 describes a dust separator that combines a fixed cyclone and a rotating cyclone to collect fine particles in exhaust gas generated from a combustor. Patent Document 2 describes an all-circular spiral cyclone that classifies dust of 10 μm or less and dust of more than 10 μm.

JP 2015-131265 A JP 2002-292308 A

  As described in Patent Document 1, a dust separator that combines a stationary cyclone and a rotating cyclone needs to drive the rotating cyclone with a motor, and an increase in size is inevitable. On the other hand, the all-circular spiral type cyclone described in Patent Document 2 has a small size that can be treated is about 16.7 L / min, and has a ceiling portion that is the same height as the upper part of the inlet of the cyclone in the introduction path. In order to avoid a large particle rising from the introduction path and a short path to the suction port. The dust that can be collected by the cyclone has a particle diameter of 1 to 10 μm, and finer dust than that cannot be collected.

  As described above, the particles contained in the atmosphere include fine particles having a particle size of 2.5 μm or less and coarse particles having a larger particle size. Virtual impactors have been developed to separate, or classify, particles contained in the atmosphere into fine particles and coarse particles. The virtual impactor is an inertia classification system that uses the inertial force of particles, and includes an acceleration nozzle and a collection nozzle that is disposed with a gap therebetween. The collection nozzle is provided in the top wall portion of the sizing cylinder arranged in the sizing container, and a side flow chamber is formed inside the sizing cylinder, and the outer surface of the sizing cylinder and the sizing A main flow chamber is formed between the containers. The fine particles are ejected from the acceleration nozzle and flow into the main flow chamber together with the atmosphere toward the main flow chamber. On the other hand, coarse particles flow into the secondary flow chamber from the collection nozzle by inertia force. Thereby, particles in the atmosphere are classified into fine particles and coarse particles.

  In order to classify the particles into fine particles and coarse particles using the inertial force of the particles, it has been found that the classification performance is greatly influenced by the inter-nozzle distance between the acceleration nozzle and the collection nozzle. As a result of various experiments, it has been found that the classification performance can be improved when the distance between the nozzles is set within a predetermined range. When the classification performance is improved, fine particles contained in the atmosphere can be efficiently collected.

  An object of the present invention is to make it possible to efficiently collect fine particles from particles contained in the atmosphere.

The fine particle collecting apparatus of the present invention includes a sizing container provided with an air introduction plate provided with a plurality of acceleration nozzles, an outer main flow chamber and an inner subflow chamber disposed in the sizing container. The sizing cylinder to be partitioned, provided on the top wall of the sizing cylinder facing the acceleration nozzle, and the main stream containing fine particles of the atmosphere that has passed through the acceleration nozzle is directed to the main flow chamber, while being coarse A virtual impactor having a plurality of collection nozzles for guiding a side flow containing particles to the side flow chamber, an inlet into which the main flow flows, and an atmosphere flowing in from the inlet to swirl the fine particles at the lower end. A cyclone for collecting microparticles, and a cyclone for collecting microparticles, comprising a conical cylinder part that is guided toward a particle dropping port, and an exhaust port that discharges the air that has risen inside the conical cylinder part to the outside Provided at the lower end of the A collecting container for storing the fine particles, and arranged at the upper end of the collecting container, the outer diameter of which is large from the upper part toward the lower part, and between the lower part and the inner peripheral surface of the collecting container. A conical body that forms a passage gap of the sub-flow, an inflow port into which the side flow flows, a conical cylinder unit that guides coarse particles toward the particle dropping port at the lower end by swirling the air flowing out from the inflow port, and A coarse particle collecting cyclone equipped with a discharge port for discharging the air that has risen inside the conical cylinder part to the outside, and a coarse particle received by the lower end of the coarse particle collecting cyclone and passed through the particle dropping port A collection container for containing particles, and the surface roughness of the inner peripheral surface of the conical cylinder part of the cyclone for collecting fine particles is 0.17 μm or less , and the discharge port of the acceleration nozzle and the The inter-nozzle distance between the collection nozzle and the inlet is 4.9 to 6 A 4mm, also to collect coarse particles.

The fine particle collecting apparatus according to the present invention includes a mounting ring in which a support member attached to the cone is provided at a central portion in the radial direction and a plurality of particle passage holes are provided at a radially outer peripheral portion. The upper end of the cone is abutted against the mounting ring, and the microparticles that have dropped the particle passage hole are guided to the space between the cone and the inner peripheral surface of the collection container. In the fine particle collecting apparatus of the present invention, the top wall of the sizing tube is circular, and the collecting nozzle is provided on the outer peripheral portion at the same radial position from the center of the top wall.

Fine particles having a particle size of 2.5 μm or less contained in the atmosphere are separated from the atmosphere by a cyclone, and the separated fine particles are collected in a collection container. When the surface roughness of the inner peripheral surface of the cyclone is 0.17 μm or less , it is possible to increase the collection rate of the fine particles by reducing the permeability of the fine particles that are transmitted through the cyclone from the exhaust port together with the atmosphere. Furthermore, if a cone is provided in the cyclone collection container for collecting fine particles , the fine particles collected in the collection container can be prevented from re-scattering into the cyclone, and the fine particles can be collected. Collection efficiency can be increased. Thereby, the microparticles contained in the atmosphere can be efficiently collected, and a large amount of microparticles can be obtained in a short time.

The atmosphere containing particles passes through the accelerating nozzle, the side flow containing coarse particles flows from the collection nozzle of the virtual impactor into the side flow chamber, and the main flow containing fine particles flows into the main flow chamber. The inter-nozzle distance between the accelerating nozzle and the collection nozzle is set to 4.9 to 6.4 mm, and the classification performance for distributing fine particles and coarse particles can be improved. Thereby, the microparticles contained in the atmosphere can be efficiently collected, and a large amount of microparticles can be obtained in a short time. Furthermore, coarse particles can also be efficiently collected.

It is a system configuration figure showing the collection device of the minute particles which is one embodiment. It is a perspective view which shows an example of the virtual impactor shown by FIG. It is a schematic sectional drawing of a virtual impactor. It is a partially notched front view which shows the modification of a virtual impactor. It is the sectional view on the AA line in FIG. It is sectional drawing which shows the up-and-down moving mechanism provided in the sizing container. FIG. 2 is a partially cutaway perspective view showing a cyclone for collecting fine particles, that is, a mainstream cyclone shown in FIG. 1. It is sectional drawing which shows the collection container provided in a 1st cyclone. It is a disassembled perspective view of a collection container. It is a characteristic diagram which shows the difference in the transmittance | permeability in the case of making the surface roughness of the inner peripheral surface of a cyclone different. It is a characteristic line figure which shows the difference in the transmittance | permeability about the case where a cone is not provided in the collection container, and the case where a cone is provided. Permeability for the case where the cone is not provided in the collection container without reducing the surface roughness of the inner peripheral surface of the cyclone and the case where the cone is provided in the collection container while reducing the surface roughness It is a characteristic diagram which shows the difference of these. It is the transmittance | permeability curve which shows the transmittance | permeability of the particle | grains in the cyclone for fine particle collection, and the inter-nozzle distance between the acceleration nozzle of a virtual impactor and a collection nozzle. It is the transmittance | permeability curve which shows the flow volume of the cyclone for coarse particle collection, and the transmittance | permeability of particle | grains. It is a graph which shows the measurement result of the chemical component of the powder collected by each of the cyclone for fine particle collection, and the cyclone for coarse particle collection. It is a graph which shows the ratio with respect to the coarse particle of the chemical component shown by FIG. 15 with respect to the coarse particle.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. A microparticle collection device 10 shown in FIG. 1 has a virtual impactor 11. The virtual impactor 11 divides the atmosphere containing particles into a fine particle substance having a particle size of 2.5 μm or less, that is, a main flow containing fine particles and a substream containing coarse particles having a larger particle size. A granulator. The mainstream is supplied to a mainstream, that is, a cyclone 13 for collecting fine particles through a mainstream guide pipe 12 including a hose and a pipe. The cyclone 13 separates fine particles contained in the mainstream atmosphere from the mainstream. In order to accommodate the separated fine particles, a collection container 14 is provided at the lower end of the cyclone 13.

  An exhaust fan 16 is connected to the exhaust port of the cyclone 13 via an exhaust pipe 15 in order to discharge the atmosphere from which the fine particles have been separated to the outside. The exhaust fan 16 has an exhaust flow rate of about 1100 LPM, and the exhaust fan 16 causes the atmosphere of about 1100 liters per minute to flow through the cyclone 13. In order to detect the amount of air flowing through the exhaust pipe 15, a mass flow meter 17 is provided in the exhaust pipe 15. The air flowing through the mass flow meter 17 is cleaned by the filter 18.

  The side stream is supplied to the cyclone 23 for side stream, that is, for collecting coarse particles, by a side stream supply pipe 22 composed of a hose, a pipe or the like. The cyclone 23 separates coarse particles contained in the sidestream air from the sidestream. A collection container 24 is provided at the lower end of the cyclone 23 in order to collect the separated coarse particles. A vacuum pump 26 is connected to the exhaust port of the cyclone 23 via an exhaust pipe 25 in order to discharge the atmosphere from which coarse particles have been separated to the outside. The vacuum pump 26 has an exhaust flow rate of about 100 LPM, and about 100 liters of air flows per minute in the cyclone 23 by the vacuum pump 26. In order to detect the amount of air flowing through the exhaust pipe 25, the exhaust pipe 25 is provided with a mass flow meter 27. The air flowing through the mass flow meter 27 is cleaned by the filter 28.

  FIG. 2 is a perspective view showing an example of the virtual impactor shown in FIG. 1, and FIG. 3 is a schematic sectional view of the virtual impactor.

  The virtual impactor 11 includes a sizing container 31. The sizing container 31 includes a cylindrical portion 31a, an upper wall 31b, and a bottom wall portion 31c. An air introduction plate 32 is provided on the upper wall 31 b, and a plurality of acceleration nozzles 33 are provided on the air introduction plate 32. A cover 34 is provided above the sizing container 31 in order to prevent rainwater from entering the acceleration nozzle 33. The particles floating in the atmosphere flow into the cover 34 from the space 35 between the cover 34 and the outer periphery of the sizing container 31 together with the atmosphere.

  A sizing cylinder 36 is arranged inside the sizing container 31, and the sizing cylinder 36 divides the inside of the sizing container 31 into an outer main flow chamber 37 and an inner subflow chamber 38. Is done. The sizing cylinder 36 includes a cylindrical portion 36a, a ceiling wall portion 36b, and a conical portion 36c, and a subflow outlet 39 is provided at the lower end of the conical portion 36c. A plurality of collection nozzles 41 are provided on the circular ceiling wall 36 b so as to face the acceleration nozzle 33, and the inner diameter of the collection nozzle 41 is set slightly larger than the inner diameter of the acceleration nozzle 33. On the other hand, a mainstream outlet 42 is provided in the cylindrical portion 31 a of the sizing container 31. The inner diameter d of the acceleration nozzle 33 is 4.9 mm, and the inner diameter D of the collection nozzle 41 is 6.35 mm, which is about 1.3 times the inner diameter d.

  When the exhaust fan 16 and the vacuum pump 26 are operated, the atmosphere including particles is sucked and the atmosphere flows into the cover 34 from the space 35. When the exhaust fan 16 and the vacuum pump 26 have the above-described flow rates, the air inflow amount is about 1200 LPM, which is the total flow rate of both. The flow rate of the air sucked from the main flow chamber 37 to the outflow port 42 is about 10 times the flow rate of the air sucked from the sub flow chamber 38 to the outflow port 39. The air flowing into the cover 34 is accelerated by the air sucked by the acceleration nozzle 33 and flows into the sizing container 31. The inflowing atmosphere passes through the collection nozzle 41 facing the acceleration nozzle 33 and flows into the side flow chamber 38, and without changing the direction after passing through the acceleration nozzle 33 and heading toward the collection nozzle 41. The main flow is separated into the main flow chamber 37. Thus, the flow rate that flows through the collection nozzle 41, that is, the flow rate of the secondary flow is about 10% of the total flow rate, and a large amount of the main flow bypasses the collection nozzle 41 as compared with the secondary flow, and the outlet 42. Flowing into.

  The air flowing into the respective acceleration nozzles 33 from the cover 34 includes fine particles having a particle size of 2.5 μm or less and coarse particles having a larger particle size. In FIG. 3, the fine particles are denoted by reference numeral P <b> 1, the coarse particles are denoted by reference numeral P <b> 2, and the coarse particles P <b> 2 are schematically enlarged than the fine particles P <b> 1. Since the fine particles have a smaller inertia than the coarse particles, the fine particles remain in the main flow and flow into the main flow chamber 37 together with the main flow. On the other hand, coarse particles having a large inertial force enter the collection nozzle 41 along with the secondary flow and flow into the secondary flow chamber 38. Thus, the particles floating in the atmosphere are classified into fine particles and coarse particles by the virtual impactor 11 using the inertial force.

  4 is a partially cutaway front view showing a modified example of the virtual impactor, and FIG. 5 is a cross-sectional view taken along line AA in FIG.

  The air introduction plate 32 is mounted on the sizing container 31 so as to be movable up and down, and the distance between the acceleration nozzle 33 and the collection nozzle 41 is adjusted by adjusting the vertical position of the air introduction plate 32. be able to. In order to move the air introduction plate 32 up and down, the sorting container 31 is provided with a vertical movement mechanism 43. As shown in FIG. 5, the air introduction plate 32 is provided with 20 acceleration nozzles 33, facing each acceleration nozzle 33, the top wall portion 36 b of the sizing tube 36 has Twenty collection nozzles 41 are provided. In FIG. 4, one collection nozzle 41 is shown. As shown in FIG. 5, a plurality of arc-shaped communication holes 40 are provided on the outer periphery of the air introduction plate 32, and the fine particles flow into the main flow chamber 37 from the communication holes 40 together with the main flow.

  Since each collection nozzle 41 faces the acceleration nozzle 33, the collection nozzle 41 shown in FIG. 4 is the center of the atmosphere introduction plate 32, that is, the center of the top wall portion 36b, as shown in FIG. Are provided at the same radius at a predetermined interval in the circumferential direction. In FIG. 4, one of the 20 collection nozzles 41 is shown. Thus, if each collection nozzle 41 is provided in the same radius position, the flow velocity of the side flow which flows into each collection nozzle 41 will be on substantially the same conditions. Thereby, even if a large amount of air is supplied into the sizing container 31, only the coarse particles flow into the respective collection nozzles 41, and the sizing accuracy between the fine particles and the coarse particles is improved while improving the sizing efficiency. Can be increased. Note that the number of the acceleration nozzles 33 and the collection nozzles 41 provided to face the acceleration nozzles 33 is not limited to 20 as long as it is plural, and can be set to an arbitrary number according to the capacity of the sizing treatment.

  FIG. 6 is a cross-sectional view showing a vertical movement mechanism 43 for moving the air introduction plate 32 up and down. The vertical movement mechanism 43 has a cylindrical support base 44 attached to the sizing container 31, and a vertical movement cylinder 45 provided with an air introduction plate 32 is mounted in the support base 44 so as to be movable up and down. . A guide pin 46 is attached to the vertical moving cylinder 45, and the guide pin 46 passes through a long hole 47 provided in the support base 44 so as to extend in the vertical direction. The vertical moving cylinder 45 extends in the vertical direction of the long hole 47. The length of the stroke range is driven up and down. The cover 34 is attached to the flange portion 45b of the vertical moving cylinder 45 by a plurality of support pieces 34a.

  A male screw 45 a is provided on the outer peripheral surface of the vertical moving cylinder 45, and an adjustment ring 48 is rotatably provided between the upper end surface of the support base 44 and the flange portion 45 b of the vertical moving cylinder 45. Knurls are engraved on the outer peripheral surface of the adjustment ring 48, and the adjustment ring 48 is a knurled ring. The adjustment ring 48 is provided with a female screw 48a screwed to the male screw 45a. When the adjustment ring 48 is rotated to move the vertical moving cylinder 45 up and down, an acceleration nozzle provided on the atmosphere introduction plate 32 is provided. 33 and the gap S between the collection nozzle 41 provided on the top wall portion 36b of the sizing tube 36, that is, the inter-nozzle distance S between the discharge port of the acceleration nozzle 33 and the inlet of the collection nozzle 41. Can be adjusted.

  A fixing screw 49 a for fixing the vertical moving cylinder 45 to the support base 44 is provided on the support base 44, and a fixing screw 49 b for fixing the adjustment ring 48 to the vertical movement cylinder 45 is provided on the adjustment ring 48. Yes.

  In order to adjust the distance between the accelerating nozzle 33 and the collection nozzle 41, that is, the dimension of the inter-nozzle distance S, the cover 34 is removed and the fixing screws 49a and 49b are loosened. This is done by rotating 48. FIG. 6 shows a state where the right half of the vertical moving cylinder 45 is set at the lower limit position. When the adjustment ring 48 is rotated to bring the upper surface of the adjustment ring 48 into contact with the flange portion 45b and the vertical moving cylinder 45 is pushed in to bring the lower surface of the adjustment ring 48 into contact with the upper surface of the support base 44, the inter-nozzle distance S is obtained. In FIG. 6, the minimum value is indicated by Smim. This minimum value Smin is 0.4 mm.

  Under this state, when the adjustment ring 48 is rotated in the clockwise direction when seen from the plane, the vertical moving cylinder 45 is driven upward with respect to the support base 44. At this time, the guide pin 46 moves upward while being guided by the long hole 47. When the adjustment ring 48 is rotated once, the vertical moving cylinder 45 is raised by 1.5 mm. When the adjustment ring 48 is rotated eight times, the up-and-down moving cylinder 45 is in the ascending limit position. FIG. 6 shows a state where the left half of the vertical moving cylinder 45 is in the ascending limit position. The inter-nozzle distance S at this time is the maximum value indicated by Smax in FIG. This maximum value Smax is 12.4 mm.

  Thus, the value of the inter-nozzle distance S can be set in any of the range of 0.4 to 12.4 mm. When the inter-nozzle distance S is set, the vertical moving cylinder 45 is fixed to the support base 44 by the fixing screw 49a, and the adjustment ring 48 is fixed to the vertical moving cylinder 45 by the fixing screw 49b. When the virtual impactor 11 is used, the cover 34 is attached to the vertical moving cylinder 45.

  7 is a partially cutaway perspective view showing the cyclone 13 for collecting fine particles, that is, the mainstream shown in FIG. 1, and FIG. 8 is a cross section showing the collection container 14 provided in the cyclone 13 for the mainstream. FIG. 9 is an exploded perspective view of the collection container 14.

  As shown in FIG. 7, the cyclone 13 includes a conical cylinder portion 51 whose inner diameter gradually decreases toward the lower end portion, and a cylindrical portion 52 is provided above the conical cylinder portion 51. An end wall portion 53 is provided at the upper end of the. The cylindrical portion 52 is provided with an inflow port 54 into which a mainstream atmosphere including fine particles that has been sized by the virtual impactor 11 flows. As shown in FIG. 1, the main flow guide pipe 12 is connected to the inflow port 54. A particle drop port 55 is provided at the lower end of the conical cylinder part 51, and the air flowing into the cyclone 13 from the inlet 54 is the inner peripheral surface of the cyclone 13 including the cylindrical part 52 and the conical cylinder part 51. 56 flows toward the particle dropping port 55 at the lower end portion of the conical cylinder portion 51 while turning along 56. The microparticles contained in the mainstream atmosphere receive centrifugal force by the swirling flow, are guided to the inner peripheral surface of the cyclone 13, and fall and collect while swirling to the particle dropping port 55.

  On the other hand, the atmosphere in which the fine particles are separated by reaching the lower end of the conical cylinder part 51 rises in the cyclone 13. In order to discharge the raised atmosphere to the outside, an exhaust port 57 is provided in the end wall portion 53, and the exhaust pipe 15 shown in FIG. 1 is connected to the exhaust port 57. The main stream is sucked and supplied into the cyclone 13 by the exhaust fan 16, and the atmosphere from which the fine particles are separated and removed is exhausted to the outside of the collection device 10.

  The basic structure of the substream cyclone 23 is substantially the same as that of the mainstream cyclone 13. However, since the substream has a smaller flow rate than the mainstream, the cyclone 23 is smaller than the cyclone 13. is there. Similarly to the cyclone 13, the cyclone 23 also has a conical cylinder part, and the conical cylinder part swirls the air flowing out from the side flow chamber to guide coarse particles toward the particle dropping port at the lower end. Further, the cyclone 23 is provided with an inflow port through which air containing coarse particles flows and an exhaust port through which the air rising inside the conical cylinder part is discharged to the outside. At the lower end portion of the cyclone 23, a collection container 24 for storing coarse particles that have passed through the particle dropping port is provided.

  As shown in FIGS. 8 and 9, the collection container 14 for storing fine particles is attached to the conical cylinder part 51 by a joint member 61 that is attached to the lower end part of the conical cylinder part 51 to form the particle dropping port 55. It is done. An attachment ring 62 is inserted into the joint member 61, and the attachment ring 62 is abutted and sandwiched between the upper end surface of the collection container 14 and the joint member 61. Inside the collection container 14, a cone 63 is disposed on the upper end side of the collection container 14. The cone 63 has an outer peripheral surface 64 whose outer diameter increases from the upper part toward the lower part, and a bar-like support member 65 is mounted on the upper part. The support member 65 is located at the center in the radial direction of the mounting ring 62. It is attached. The support member 65 is detachably attached to the cone 63. By exchanging the support member 65, the distance between the upper end surface of the cone 63 and the mounting ring 62, that is, the installation height of the cone 63 is obtained. h can be changed. The cone 63 may be made of sheet metal as long as it has a conical outer peripheral surface 64.

  As shown in FIG. 9, a plurality of particle passage holes 66 are provided on the outer peripheral portion in the radial direction of the mounting ring 62, and the fine particles that have reached the particle dropping hole 55 pass through the particle passage hole 66 and are outer periphery. It falls toward the surface 64. A passage gap 67 is formed between the lower part of the cone 63 and the inner peripheral surface of the collection container 14, and the fine particles that have fallen into the collection container 14 from the particle drop port 55 through the particle passage hole 66. Passes through the space 68 between the outer peripheral surface of the cone 63 and the inner peripheral surface of the collection container 14 and falls from the passage gap 67 to the bottom of the collection container 14.

  A slight swirling flow may occur at the upper end of the collection container 14 due to the swirling flow that reaches the particle dropping port 55 while swirling along the inner peripheral surface of the conical cylinder portion 51. Even if the generated swirling flow rises, the conical body 63 suppresses the generation of swirling flow in the gas in the bottom of the collection container 14. Thereby, it is possible to reliably prevent the microparticles collected at the bottom of the collection container 14 from flowing back toward the cyclone 13 and to increase the collection efficiency of the microparticles.

  The atmosphere discharged from the exhaust port 57 of the cyclone 13 includes fine particles that are not collected in the collection container 14 and permeate the cyclone. When the transmittance, which is the ratio of fine particles that permeate the cyclone 13, is reduced, the collection rate by the cyclone 13 can be increased. The fine particles are separated from the air flow and collected by the centrifugal force applied to the turning fine particles in the vicinity of the inner peripheral surface 56. Therefore, it was estimated that the centrifugal force applied to the fine particles swirling in the cyclone 13 is related to the surface roughness of the inner peripheral surface 56 of the cyclone 13. It was considered that reducing the surface roughness of the inner peripheral surface 56, that is, reducing the centrifugal force of the microparticles, the experiment was conducted on the relationship between the surface roughness and the transmittance of the microparticles. Further, the fine particles collected in the collection container 14 from the cyclone 13 are sucked into the atmosphere returning to the exhaust port 57 after being swirled by the swirling flow in the cyclone 13, and re-scattered. The scattering prevention technique was examined, and the transmittance was measured when the cone 63 for preventing re-scattering was provided in the collection container 14 and when it was not provided.

  FIG. 10 is a characteristic diagram showing the difference in transmittance when the surface roughness of the inner peripheral surface 56 of the cyclone is made different. FIG. 10 shows the relationship between the particle size (Dp) of fine particles and the transmittance when the surface roughness Ra of the inner peripheral surface 56 is made different. In addition, the cone 63 is not provided in the collection container 14 used for each experiment. In FIG. 10, Comparative Example A1 shows the case where the surface roughness Ra of the inner peripheral surface 56 is 5.1 μm, Example B1 shows the case where the surface roughness Ra of the inner peripheral surface 56 is 0.17 μm, Example B2 shows the case where the surface roughness Ra is 0.08 μm. Regardless of the surface roughness, when the particle size increases, the transmittance decreases and the collection efficiency increases. As shown in FIG. 10, the transmittance of particles having a particle size of 0.1 μm is 76% in the case of Comparative Example A1 having a surface roughness Ra of 5.1 μm, whereas the surface roughness Ra is In the case of 0.08 μm, it was 69%, and an improvement in the collection efficiency of 10% was observed. Moreover, even when the surface roughness Ra is 0.17 μm, high collection efficiency is obtained, but the collection efficiency is enhanced by reducing the surface roughness Ra. Therefore, according to experiments, it was confirmed that the surface roughness Ra is 0.17 μm or less, and preferably 0.08 μm or less, whereby the collection efficiency can be further improved. If it is 0.20 micrometer or less, it is thought that the same collection efficiency can be obtained.

  FIG. 11 is a characteristic diagram showing the difference in transmittance between when the collection container is not provided with a cone and when the cone is provided. In FIG. 11, Comparative Example A2 is a case where the cone 63 is not installed in the collection container 14, Example B3 is a case where the installation height h of the cone 63 is 10 mm, and Example B4 is a cone. This is a case where the installation height h of the body 63 is 0 mm. The surface roughness Ra of the inner peripheral surface of the cyclone 13 used in each experiment is 5.1 μm. The installation height h indicates the distance between the attachment ring 62 and the upper surface of the cone 63, as shown in FIG. As shown in Examples B3 and B4 in FIG. 11, it was possible to reduce the transmittance when the cone 63 was not installed, compared with the case where the cone 63 was not installed. Further, it has been found that when the installation height h is 0 mm and the cone 63 is brought closer to the cyclone 13, the transmittance is further reduced. When the installation height h is lengthened, the volume of the space 68 above the cone 63 is increased, and the atmosphere above the collection container 14 rises while swirling and suppresses fine particles from re-scattering into the cyclone 13. It is thought that this is because the effect to do has been reduced. Therefore, the collection effect can be enhanced by setting the installation height h to zero.

  FIG. 12 shows a case where the cone is not provided in the collection container without reducing the surface roughness of the inner peripheral surface of the cyclone, and a case where the cone is provided in the collection container while reducing the surface roughness. It is a characteristic line figure which shows the difference in the transmittance | permeability about. In FIG. 12, Comparative Example A3 shows the case where the inner surface 56 has a surface roughness Ra of 5.1 μm and no cone 63 is provided, and Example B5 has a surface roughness Ra of 0.08 μm. The case where the installation height h of the cone 63 is 0 mm is shown. As shown in FIG. 12, when the cone 63 is installed and the surface roughness Ra of the inner peripheral surface 56 is 0.08 μm, the synergistic effect of the reduction of the surface roughness and the installation of the cone results in the comparative example A3. It has been found that the transmittance is clearly reduced as compared with the above and the collection efficiency can be increased.

  The 50% cut-off diameter was dp = 0.19 μm in Comparative Example A3 and dp = 0.15 μm in Example B5. Therefore, if the surface roughness Ra is reduced to 0.17 μm or less and the cone 63 is installed in the collection container 14, it is possible to greatly improve the effect of collecting fine particles by the cyclone 13. There was found. Thus, if a large amount of PM2.5, which is a microparticle, can be collected, it is considered that there is a relationship with toxicity evaluation of cell / biological exposure experiments using microparticles and the toxicity of microparticles. It is possible to advance the hazard assessment of fine particles such as measurement of chemical composition and specific surface area. In particular, when the amount of air supplied to the virtual impactor 11 is increased as compared with the conventional case, a large amount of fine particles can be collected in a short time.

  As shown in FIG. 6, the inter-nozzle distance S of the virtual impactor 11 can be adjusted in the range of 0.4 to 12.4 mm. Therefore, the transmissivity, that is, the classification performance, which is the ratio of particles permeating toward the mainstream without changing the inter-nozzle distance S and flowing into the mainstream, that is, the particles contained in the mainstream, that is, the collecting nozzle 41 was measured. FIG. 13 shows the measurement results, and is a transmittance curve showing the inter-nozzle distance S between the acceleration nozzle 33 and the collection nozzle 41 of the virtual impactor 11 and the transmittance of particles flowing in the mainstream.

  As shown in FIG. 13, when the inter-nozzle distance S is set to 10 mm, it is considered that a large amount of coarse particles having a particle size (Dp) of 2.5 μm or more are mixed in the mainstream. On the other hand, when the inter-nozzle distance S is set to 1.0 mm, the mixing rate of fine particles having a particle size of 2.5 μm or less into the main flow is reduced, and a large amount of fine particles are mixed in the substream. it is conceivable that.

  On the other hand, when the inter-nozzle distance S is 1.9 mm, the 50% particle size is 2.1 μm, and the mixing rate of coarse particles having a particle size of 2.5 μm or more can be reduced. The transmittance of fine particles having a particle size of 2.5 μm or less can be increased as compared with the case where the inter-nozzle distance S is 1.0 mm.

  Furthermore, when the inter-nozzle distance S is 4.9 mm, the 50% particle size is 2.5 μm, and the slope defined by the ratio of the 20% particle size to the 80% particle size is 1.4. there were. The transmittance of fine particles having a particle size of 2.5 μm or less can be increased as compared with the case where the inter-nozzle distance S is set to 1.9 mm, and the transmittance of coarse particles having a particle size of 2.5 μm or more is reduced. Can do.

  When the inter-nozzle distance S is 7.9 mm, the 50% particle size is 2.8, and the transmittance of fine particles having a particle size of 2.5 μm or less is set to 4.9 mm. The value was close to the case. However, the amount of coarse particles having a particle size of 2.5 μm or more was larger than when the inter-nozzle distance S was 4.9 mm.

  As shown in FIG. 13, when the inter-nozzle distance S is in the range of 1.9 to 7.9 mm, it is considered sufficient for practical classification performance as the virtual impactor 11. More preferably, as described above, when the inter-nozzle distance S is 4.9 mm, the particle size can be reduced to 2.5 μm by 50%, and the transmittance of particles larger than 2.5 μm is drastically reduced. Therefore, it was found that the amount of coarse particles contained in the main stream can be reduced, and the inter-nozzle distance S is preferably 4.9 mm. When the inter-nozzle distance S was set to 3.4 mm and 6.4 mm, the transmittance was almost the same as when 4.9 mm.

  Therefore, in order to improve the classification performance of the virtual impactor 11 and reduce the amount of coarse particles mixed into the mainstream so that the mainstream does not include coarse particles, the inter-nozzle distance S is set to 1.9 to The range is 7.9 mm, preferably 3.4 mm to 6.4 mm. More preferably, it has been found that the inter-nozzle distance S is preferably 4.9 mm.

  When the classification performance of the virtual impactor 11 is increased and the transmittance of the microparticles discharged to the outside of the cyclone 13 is reduced, combined with the improvement of the classification performance, the cyclone 13 further increases the collection rate of the microparticles. Can be increased.

  FIG. 14 is a transmittance curve showing the flow rate and particle transmittance of the cyclone 23 for collecting coarse particles.

  As described above, air flows through the cyclone 23 at a flow rate of 100 liters per minute (LPM). As shown in FIG. 14, this flow rate was changed to 50 LPM, 75 LPM, and 100 LPM, and the transmittance in the cyclone 23 for collecting coarse particles was measured. When the flow rate was 50 LPM, the particle size for 50% was about 1.0 μm. When the flow rate was increased to 75 LPM and 100 LPM, the 50% particle size was reduced, the 50% particle size at 100 LPM was about 0.68 μm, and the collection efficiency of particles having a particle size of 1 μm was 95%.

  Due to the classification performance of the virtual impactor 11, most of the particles having a particle size of 1 μm or less are considered to flow into the cyclone 13 for collecting fine particles. Therefore, the cyclone 23 for collecting coarse particles collects particles having a particle size of 1 μm or more. If it can be collected, it is considered to have sufficient performance. Therefore, it was confirmed that the coarse particles flowing into the secondary flow side can be sufficiently collected by setting the flow rate to 100 LPM.

  FIG. 15 is a graph showing the measurement results of the chemical components of the powder collected by the cyclone 13 for collecting fine particles and the cyclone 23 for collecting coarse particles. FIG. 16 is a graph showing a ratio of the chemical components shown in FIG. 15 to the coarse particles, and shows a value obtained by dividing the weight of the coarse particles by the weight of the fine particles.

Comparing the chemical composition of the particles collected by each cyclone, Na ⁺ , Ca ²⁺ , Si, Fe, etc., which are considered to exist mainly on the coarse side in the atmosphere, are collected by the cyclone 23 for collecting coarse particles. It was contained in a large proportion in the collected particles. On the other hand, EC (elemental carbon), Cu, Zn, Pb, etc., which are considered to exist mainly as fine particles in the atmosphere, are contained in a large proportion in the particles collected by the cyclone 13 for collecting fine particles. It was.

  Therefore, the apparatus provided with the virtual impactor 11 and the cyclones 13 and 23 can collect fine particles and coarse particles having a characteristic composition by the cyclones 13 and 23, respectively. By collecting the coarse particles using the cyclone 23, it can be used for a harmful investigation on the living body due to the coarse particles in the atmosphere. Apart from fine particles, coarse particles such as yellow sand are also known to cause inflammation in the living body, and by conducting exposure experiments by collecting coarse particles and fine particles at the same time, biological harm caused by particles in the atmosphere It becomes possible to elucidate the mechanism that expresses sex in detail.

  The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the invention.

DESCRIPTION OF SYMBOLS 10 Collection apparatus 11 Virtual impactor 13 Cyclone 14 Collection container 16 Exhaust fan 23 Cyclone 24 Collection container 26 Vacuum pump 31 Sizing container 32 Atmospheric introduction plate 33 Acceleration nozzle 34 Cover 36 Sizing cylinder 37 Main flow chamber 38 Secondary flow chamber 39 Outlet 41 Collection nozzle 42 Outlet 43 Vertical movement mechanism 44 Support base 45 Vertical movement cylinder 45a Male thread 45b Flange part 46 Guide pin 47 Long hole 48 Adjustment ring 48a Female thread 49a, 49b Fixing screw 51 Conical cylinder part 52 Cylindrical part 54 Inlet port 55 Particle drop port 56 Inner peripheral surface 57 Exhaust port 63 Cone 64 Outer peripheral surface

Claims (3)

A sizing container provided with an air introduction plate provided with a plurality of acceleration nozzles, a sizing cylinder disposed in the sizing container and partitioned into an outer main flow chamber and an inner subflow chamber, the sizing tube A main stream that is provided on the top wall of the body so as to face the accelerating nozzle and directs the main flow containing fine particles out of the air that has passed through the accelerating nozzle to the main flow chamber, while a sub flow containing coarse particles is transferred to the sub flow chamber. A virtual impactor with multiple collection nozzles to guide,
The inlet into which the main flow flows in, the conical cylinder part that swirls the air flowing in from the inlet and guides the microparticles toward the particle dropping port at the lower end, and the atmosphere that has risen inside the conical cylinder part to the outside A cyclone for collecting fine particles with an exhaust port for discharging to the
A collection container that is provided at the lower end of the cyclone for collecting fine particles, and that contains the fine particles that have passed through the particle dropping port,
A cone that is arranged at the upper end of the collection container, has a large outer diameter from the upper part toward the lower part, and forms a passage for passing microparticles between the lower part and the inner peripheral surface of the collection container;
An inlet through which the side stream flows, a conical cylinder section that swirls the air flowing out from the inlet and guides coarse particles toward a particle dropping port at a lower end, and an atmosphere that rises inside the conical cylinder section. A cyclone for collecting coarse particles with a discharge port for discharging to the outside,
A collection container that receives the coarse particles received by the lower end of the cyclone for collecting the coarse particles and that has passed through the particle dropping port ;
The surface roughness of the inner peripheral surface of the conical cylinder part of the cyclone for collecting microparticles is 0.17 μm or less ,
The inter-nozzle distance between the discharge port of the acceleration nozzle and the inlet of the collection nozzle is 4.9 to 6.4 mm, and the fine particle collection device collects coarse particles . 2. The apparatus for collecting fine particles according to claim 1 , wherein a support member attached to the cone is provided at a central portion in the radial direction, and a mounting ring in which a plurality of particle passage holes are provided at a radially outer peripheral portion is provided. Provided at the drop port, the upper end of the cone is abutted against the mounting ring, and guides the microparticles that have dropped the particle passage hole into the space between the cone and the inner peripheral surface of the collection container. , Microparticle collection device. 3. The apparatus for collecting fine particles according to claim 1 , wherein the top wall of the sizing tube is circular, and the collection nozzle is provided on an outer peripheral portion at the same radial position from the center of the top wall. , Microparticle collection device.

Images