TWI638683B - Inertial impactor with a wetted impaction plate to prevent particle loading effect - Google Patents

Abstract

The invention discloses an inertial impactor with a wet impact surface, which can prevent the particle loading effect. The structure is composed of an upper case, an impact part and a lower case. The upper casing has a gas inlet and a circular nozzle connected to the gas inlet. The impact part has an impact well, and the lower part of the impact well is an impact surface. The nozzle is positioned directly above the center of the impact surface. The center of the impact surface has a liquid input port. The liquid is continuously or intermittently introduced to form a wet impact surface and remove particulate accumulation. At the same time, the liquid is discharged from the liquid discharge path on the impact surface. Monitoring device.

Description

Inertial impactor with wet impact surface protection against particulate loading effects

The invention relates to a particle impactor, in particular to a particle impactor which can reduce the influence of particle loading effect.

With the advent of more and more nano products, nano particles may escape or be released during the manufacturing and use process. Many research results show that the nanometer particles inhaled by the human body can affect health, and in order to assess the health hazards of nanometer particles in the workplace to relevant practitioners, nanometer particles of different particle sizes are collected and subjected to subsequent component analysis necessary.

A particle impactor is a conventional particle collection device. When the airflow passes through the nozzle, it hits the impact plate downwards. Because the gas cannot penetrate the impact plate, the airflow makes a 90-degree turn, so it is larger than a specific aerodynamic particle size ( (Or interception particle size) particles that cannot be moved with the airflow streamline are collected by the impact plate; conversely, particles smaller than a specific aerodynamic particle diameter leave the impact surface with the airflow streamline to the downstream particle sampling device or Particle monitoring equipment.

However, as the sampling time increases, particle mound or particle deposits will gradually form on the impact plate below the nozzle, causing subsequent collected particles to hit the previously accumulated particles instead of the impact surface, which may make it smaller than a specific Particles with aerodynamic particle size are collected, resulting in a reduction in the interceptor diameter of the impactor, making the particle sampling or monitoring concentration downstream of the impactor underestimated.

In view of this, it is an object of the present invention to provide an inertial impactor with a wet impact surface that can prevent the particle loading effect. Through continuous or intermittent introduction of liquid from the center of the impact plate to remove the accumulation of particles, and the impact surface is wetted with liquid to prevent the particles from rebounding, so the fixed interception diameter of the impactor and accurate particle sampling or monitoring concentration can be maintained.

The particle impactor includes an upper case, an impact portion, and a lower case. The upper casing has a gas inlet and a circular nozzle connected to the gas inlet. The impact part has an impact well. The lower part of the impact well is the impact surface. The nozzle is located directly above the center of the impact surface. A liquid input port is provided below the center of the impact surface. The liquid is continuously or intermittently introduced to form a wet impact surface. The particulate accumulation is removed while the liquid is discharged through the liquid discharge path on the impact surface. Its lower housing has a gas outlet channel that can be connected to a particle sampling device or monitoring equipment.

In this embodiment, the air enters the impact well sequentially through the gas inlet and the circular nozzle. The particles in the sampling gas that are larger than the specific aerodynamic particle size are wetted by the impact surface because the particles have sufficient inertia and cannot move with the airflow. Collected, particles smaller than a specific aerodynamic particle size will leave the impactor and be collected to the sampling device or monitoring equipment. By using the present invention to continuously or intermittently introduce liquid to wet the impact surface, it is possible to prevent particles from rebounding and remove the accumulation of particles. The liquid is discharged from the discharge path, and the air is discharged to the sampling device or monitoring equipment through the downstream gas outlet. The invention can maintain a fixed interception diameter of the impactor and accurately sample or monitor the concentration.

Additional features and advantages of the present invention will be explained in the following description to make it more obvious, or can be learned through the practice of the present invention. Other objects and advantages of the present invention will be achieved and achieved from the scope of this specification and its patent application and the structure described in the attached drawings.

1‧‧‧ Particle Impactor

11‧‧‧ Upper case

12‧‧‧Impact

13‧‧‧ lower case

111‧‧‧Gas inlet

112‧‧‧Nozzle

113‧‧‧ Outer shell

120‧‧‧ Impact well

121‧‧‧ impact surface

122‧‧‧Liquid input path

123‧‧‧Liquid discharge path

124‧‧‧ filter paper

125‧‧‧ porous metal sheet

131‧‧‧Gas outlet

1211‧‧‧Groove

1221‧‧‧Input port

1231‧‧‧Exit

FIG. 1 is a cross-sectional view of an embodiment of the particle impactor of the present invention.

FIG. 2 is a measurement diagram of the present invention and the conventional particle impactor.

FIG. 3A is a particle deposition diagram of a conventional particle impactor.

FIG. 3B is a particle deposition diagram of the particle impactor of the present invention.

FIG. 4 is another actual measurement diagram of the present invention and the conventional particle impactor.

FIG. 5 is a cross-sectional view of another embodiment of the particle impactor of the present invention.

In the following, a plurality of embodiments of the present invention will be disclosed by means of drawings and text descriptions. For the sake of clear description, many practical details will be described in the following description. It should be understood, however, that these practical details should not be used to limit the invention. In addition, in order to simplify the drawings, some conventional structures and elements will be drawn in a simple and schematic manner in the drawings.

Referring to FIG. 1, the particle impactor 1 includes an upper case 11, an impact portion 12, and a lower case 13 connected to each other. The upper casing 11 preferably has a gas inlet 111, a nozzle 112 connected to the gas inlet 111, and an outer casing 113 extending downward from the upper casing 11. The gas inlet 111 is used to receive outside air. The impact portion 12 is covered inside the outer casing 113 and has an impact well 120, and the cavity surrounded by the impact portion 12 corresponds to the nozzle 112. Below the impact well 120, there is an impact surface 121. The impact surface 121 is provided with a liquid input path 122 and a liquid discharge path 123. Air enters the gas inlet 111 and enters the impact portion 12 through the nozzle 112. The liquid input path 122 forms an input port 1221 at a center position of the impact surface 121. The input port 1221 is preferably provided corresponding to the position of the nozzle 112. The liquid discharge path 123 has a discharge port 1231. The discharge port 1231 is preferably formed on the edge of the impact surface 121. The lower case 13 is connected to the impact portion 12 Connected with a gas outlet 131.

According to this design, air can enter the impact portion 12 through the gas inlet 111 and the nozzle 112 in this order. Particles larger than a specific aerodynamic particle size in the air are collected by the wet impact surface 121. In detail, after the air enters the impact portion 12, it cannot penetrate the impact surface, so that the air flow is discharged from the gas outlet 131 as the internal space of the impactor 1 turns. Therefore, particles larger than a specific aerodynamic particle size in the air cannot be collected by the wet impact surface 121 as the airflow streamlines move.

In this embodiment, if PM _{2.5 is taken} as an example, particles with an aerodynamic particle size larger than 2.5 μm in the air will be collected by the wet impact surface 121. In other embodiments, the present invention can be made into impactors with different interception particle sizes. If a PM ₁₀ particle impactor is taken as an example, particles with an aerodynamic diameter greater than 10 μm will be collected by the wet impact surface 121. Taking PM _0.1 as an example, particles with an aerodynamic diameter greater than 0.1 μm will be collected by the wet impact surface 121, and so on.

However, in order to prevent particles from accumulating on the wet impact surface 121, the interception diameter of the inertial impactor is affected. In this embodiment, this situation can be avoided by using a wet impact surface or placing a wet filter paper on the impact surface, and washing the wet surface or the surface of the wet filter paper 124 by continuously or intermittently introducing liquid. Specifically, the wet impact surface 121 is used or a wet filter paper 124 is provided on the wet impact surface. In this embodiment, the filter paper 124 is a glass fiber filter paper, but not limited thereto. The purpose is to keep the impact surface wet and improve the impactor particle removal efficiency. The liquid input path 122 (relative to the other end of the input port 1221) may be externally connected to a pump (not shown), and the liquid is injected through the pump. The liquid discharge path 123 (relative to the other end of the discharge port 1231) can also be connected to a pump (not shown) for drawing out liquid.

Through the continuous uninterrupted or intermittent injection of liquid, the impact surface or the filter paper 124 can be soaked, and a uniformly distributed water film can be formed on the wet impact surface 121 or the surface of the wet filter paper 124. When air enters the impact part 12, particles with an aerodynamic particle size larger than 2.5 μm will be collected by the wet impact surface 121 or wet filter paper, and particles with an aerodynamic particle size smaller than 2.5 μm will enter the lower casing 13 with the airflow and pass through the gas The outlet 131 is discharged. Since the impact surface and the surface of the filter paper 124 have a water film, that is, the liquid is injected and extracted by the pump, the water film on the surface of the wet impact surface 121 and the wet filter 124 is in a continuous flow state, which can reduce the accumulation of particles in the wet Impact surface or wet filter 124 surface. In addition, the continuously flowing liquid can also be used for cleaning the surface of the filter paper 124 without additional cleaning.

In this embodiment, the injected liquid system uses deionized water. If the pump connected to the liquid outlet 123 is matched with other chemical analysis instruments (for example, the online real-time gas-water solution ion automatic monitoring system, but not limited to this), it can also target the discharged deionized water (particles collected by filter paper Will dissolve in) for chemical analysis of particles.

In this embodiment, there is a preset distance between the discharge port 1231 and the input port 1221, that is, the distance from the center of the impact surface 121 to the edge. However, in other embodiments, the pitch can be designed by oneself without any particular limitation.

It should be noted that, in order to enhance the drainage effect, the impact surface 121 may be designed to have an inclined angle, but not limited thereto. Specifically, the impact surface 121 is inclined downward (in the direction of gravity) from the center of the impact surface 121.

Please refer to the actual measurement diagrams of FIGS. 2, 3A and 3B, which are data and photos of particle accumulation on the wet impact surface after sampling for 17 consecutive days. The well impactor Ninety-Six (WINS) in Fig. 2 and Fig. 3A are the actual measurement diagrams of the impact surface of the filter with 1 mL of silicone oil dripped. On filter paper, the particle sampling error increases as the sampling time increases. The invention of FIG. 2 and FIG. 3B are According to the actual measurement chart of the wet impact surface of the particle impactor of the present invention, it can be seen that there is almost no deviation in particle collection and no particle accumulation occurs.

Please refer to FIG. 4 again, which is a graph showing the change of the cut diameter of WINS and the particle impactor of the present invention under different particle loads. As shown in the figure, under different particle loads, the interception diameter of the particle impactor of the present invention does not decrease as the particle load increases, indicating that the interception diameter of the impactor can be maintained, and the interception diameters of the other particle impactors follow Particle load increases and decreases, indicating that the impactor is affected by particle accumulation.

In other embodiments, an oil body such as silicone oil may be used as the liquid to be injected, but not limited thereto. The difference is that if the oil body is used for injection, its viscosity is greater than that of deionized water, and the volatilization time is longer than that of deionized water. Therefore, there is no need for continuous injection to have the wet impact surface 121 and the filter paper 124 and maintain the effect of having an oil film thereon. However, in order to avoid the accumulation of particles for a long time, it is still necessary to intermittently inject the oil body and flush out the particles that may have accumulated.

In another embodiment of the present invention, as shown in FIG. 5, the groove 1211 can be opened downward (toward the gas outlet) on the wet impact surface 121, and the porous metal sheet 125 can be placed in the groove 1211. A filter, such as a glass fiber filter, is disposed above the porous metal sheet 125. In this embodiment, the surface of the filter paper 124 and the impact surface 121 may be at the same horizontal plane, but not limited thereto. The porous metal sheet 125 can be used for chemical analysis after sampling. The rest of the structure and the flow mechanism of the particles and liquid are the same as those of the previous embodiment, and will not be repeated here.

The PM _2.5 inertial impactor of the present invention is only an embodiment, and can also be applied to inertial impactors with different intercepting diameters, such as PM ₁₀ , PM _1.0 , PM _0.25 , PM _0.1 inertial impactors, which can also be designed to target different Particle sampler is used in combination. For example, by designing a multi-stage impactor with PM ₁₀ , PM _2.5, and PM _0.1 connected in series from top to bottom, particles of different particle sizes can be collected for analysis.

Compared with the prior art, the particle impactor of the present invention can continuously or intermittently introduce liquid to flush the wet impact surface or the accumulation of particles on the wet filter paper, which can effectively reduce the problem of the reduction of the interception diameter caused by the accumulation of particles, and can be used for a long time. Maintains the interceptor diameter of the impactor and reduces particle sampling errors.

Claims (9)

A particle impactor for collecting particles with a specific aerodynamic particle size in the air includes: an upper casing having a gas inlet, a nozzle connected to the gas inlet, and an outer shell; an impact portion, and The shell connection setting includes: an impact well, the cavity surrounded by the impact well corresponds to the nozzle; an impact surface is located at the bottom of the impact well, and has a filter paper thereon, the impact surface has An inclination angle; a liquid input path that forms an input port on the impact surface; and a liquid discharge path that forms a row of outlets on the impact surface; wherein a pre-set between the discharge port and the input port A gap is set, and the liquid entering from the input port is discharged from the discharge port through the filter paper; and a lower case is connected to the impact part and has a gas outlet, wherein the air enters through the gas inlet and the nozzle in order The impact part, and the particles in the air that are larger than a specific aerodynamic particle size are collected by the impact surface, and then the air is discharged through the gas outlet. The particulate impactor according to claim 1, wherein the filter paper is a glass fiber filter paper. The particle impactor according to claim 1, wherein the input port is disposed at the center of the impact surface. The particle impactor according to claim 3, wherein the discharge port is provided at an edge of the impact surface. According to the particle impactor described in claim 1, the at least part of the particles are flushed by the liquid injected from the liquid input path and discharged through the liquid discharge path. The particulate impactor according to claim 5, wherein the liquid system is continuously injected deionized water. The particulate impactor according to claim 5, wherein the liquid system is an intermittently injected oil body. The particle impactor according to claim 1, wherein the impact surface has a groove, the groove has a porous metal sheet therein, and the filter paper is placed on the porous metal sheet. The particle impactor according to claim 3, wherein the nozzle is disposed corresponding to the center of the impact surface.