JP2013190246A - Aerosol fine particle measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow a particle diameter distribution of fine particles in sample gas to be measured with one particle measuring device.SOLUTION: In a preferable embodiment, a sample gas flow path 2 is connected to one port of a three-way switch valve 7 and is connected to one of a main flow path 3 and a bypass flow path 4. The main flow path 3 distributes the sample gas to a particle growth flow path comprising a vapor saturation flow path 5 and a cooling concentration flow path 6, and to an adjustment flow path 8. The particle growth flow path supplies the sample gas with vapor in the vapor saturation flow path 5, allows fine particles in the sample gas to grow by cooling them in the cooling concentration flow path 6, and then guides the sample gas to a particle counter 12. The bypass flow path 4 is a particle non-growth flow path which guides the sample gas to the particle counter 12 without letting it pass the particle growth flow path.

Description

  The present invention relates to a measuring device for counting the number of particles in an aerosol containing nanometer-sized fine particles. The aerosol is in a state where solid or liquid fine particles are present in a relatively stable and floating state in the gas, and includes exhaust gas from automobiles, exhaust gas from factories, and the like.

  As a device that counts the number of particles, a particle sensor that measures the number concentration of particles by irradiating the particles with light and measuring the number of scattered light pulses, scattered light intensity, or transmitted light intensity at a specific scattering angle is known. (For example, refer to Patent Document 1). An apparatus such as a particle sensor can only measure particles having a particle size of a certain size (for example, several hundred nm) or more.

  A CPC (Condensing Particle Counter) is known as an apparatus capable of measuring fine particles having a diameter of several nanometers to several tens of nanometers. CPC uses particles as nuclei and condenses working fluid vapor such as water and butanol around it to increase the particle diameter, and irradiates these particles with light to measure the number of scattered light pulses at a specific scattering angle. .

JP 2006-275815 A

  The above-mentioned CPC measures fine particles that cannot be measured with the original size by growing them to a measurable size. The number of particles measured by CPC includes fine particles that can be measured by growing, as well as particles that have been measurable before they grow. That is, the measurement result only shows the number of fine particles having a particle diameter of a certain size or more after the growth, and the number of fine particles having a measurable size before the growth could not be measured. In other words, it has been impossible to measure the particle size distribution of the fine particles in the sample gas with the existing particle measuring apparatus.

  In view of the above, an object of the present invention is to make it possible to measure the particle size distribution of fine particles in a sample gas in one stage with one particle measuring device.

  An aerosol fine particle measuring apparatus according to the present invention includes a sample gas flow path for sucking an atmospheric pressure aerosol containing fine particles of nanometer size as a sample gas, a particle counter for counting the number of particles in the gas, and a sample gas flow path A particle growth channel that leads the sample gas from the sample gas to the particle counter by growing the particles in the sample gas by vapor, and the sample gas from the sample gas channel is counted without growing the particles in the sample gas. And a switching mechanism for switching the sample gas from the sample gas flow channel to either the particle growth flow channel or the particle non-growth flow channel.

  As a preferred embodiment, the particle non-growth channel is a channel provided separately from the particle growth channel so that the sample gas from the sample gas channel is guided to the particle counter without passing through the particle growth channel. An example can be given. In that case, the switching mechanism switches and connects the sample gas channel to either the particle growth channel or the particle non-growth channel.

  As another embodiment, an example in which the particle growth channel and the particle non-growth channel are formed of a common gas flow channel can be given. In that case, the apparatus is provided as a sheath gas that is provided between the sample gas flow path and the gas flow path and extracts a part of the sample gas, and a sheath gas containing saturated vapor by removing fine particles from the gas extracted by the splitter. A sheath gas flow path is further provided to join the sample gas flowing to the flow path. The switching mechanism is provided on the sheath gas channel and switches on / off of the gas flow in the sheath gas channel. When the switching mechanism is causing the gas to flow in the sheath gas flow path, the gas flow path cools and condenses the mixed gas of the sample gas and the sheath gas to grow the fine particles in the sample gas and guides them to the particle counter. When the particle growth flow path is configured and the switching mechanism blocks the gas flow in the sheath gas flow path, the gas flow path forms a particle non-growth flow path that directly guides the sample gas to the particle counter. That is, the gas distribution channel is switched to either the particle growth channel or the particle non-growth channel by switching the switching mechanism.

  In the aerosol fine particle measuring apparatus of the present invention, the sample gas from the sample gas flow channel is used to grow the fine particles in the sample gas by vapor and lead to the particle counter, and the sample gas from the sample gas flow channel. A particle non-growth channel that leads the particle counter to the particle counter without growing fine particles in the sample gas, and a sample gas from the sample gas channel is switched to either the particle growth channel or the particle non-growth channel. Since the switching mechanism is provided, the switching mechanism of the switching mechanism can be switched between a mode for counting the fine particles grown in the sample gas and a mode for coefficient without growing the number of fine particles in the sample gas. . In the mode to count the fine particles in the grown sample gas, the fine particles that have a size larger than a certain value that can be counted by the particle counter are counted together with the fine particles that have grown to a size that can be counted by the particle counter. . On the other hand, in the mode in which the number of fine particles in the sample gas is multiplied without growing, only fine particles having a certain size or larger that can be counted by the particle counter from the beginning are counted. Therefore, a certain distribution of the size of the fine particles in the sample gas can be measured by measuring in the both modes under the same conditions for the same sample gas.

It is a schematic block diagram which shows a 1st Example. It is a schematic block diagram which shows 2nd Example.

(First embodiment)
FIG. 1 represents a first embodiment.
The sample gas flow path 2 sucks an atmospheric pressure aerosol containing nanometer-sized fine particles as a sample gas. The sample gas channel 2 is connected to one port of the three-way switching valve 7 and is connected to either the main channel 3 or the bypass channel 4. The main flow path 3 is a flow path for distributing the sample gas to the particle growth flow path including the vapor saturation flow path 5 and the cooling condensation flow path 6 and the adjustment flow path 8.

  The particle growth channel supplies the alcohol vapor to the sample gas in the vapor saturation channel 5 and cools the sample gas in the cooling condensation channel 6 to grow the fine particles in the sample gas. It is the flow path which leads to. The steam saturation channel 5 is a channel that heats butyl alcohol to about 40 ° C. to form steam, and supplies alcohol vapor to the sample gas flowing in the steam saturation channel 5. As the alcohol vapor adheres to the fine particles in the sample gas and condenses in the cooling condensation channel 6, the particle diameter of the fine particles grows. If the sample gas flow path 2 is connected to the main flow path 3 side by the three-way switching valve 7, particles having a size that cannot be counted by the particle counter 12 grow to a size that can be counted. To rise.

  On the other hand, the bypass channel 4 is a particle non-growth channel that guides the sample gas to the particle counter 12 without passing through the particle growth channel. If the sample gas flow path 2 is connected to the particle non-growth flow path side by the three-way switching valve 7, the fine particles in the sample gas are led to the particle counter 12 as they are without growing, from the beginning. Only fine particles of a size that can be counted by the particle counter 12 are counted.

  An example of the particle counter 12 is one that counts the number of particles in the aerosol passing through the particle counter 12 by irradiating a laser beam from a direction perpendicular to the aerosol flow and detecting the scattered light. it can.

  An exhaust pump 24 whose drive is controlled to exhaust at a predetermined flow rate is provided in the flow path 22 on the downstream side of the particle counter 12, and the adjustment flow path 8 is joined upstream of the exhaust pump 24. . In this embodiment, a filter 14 and a flow meter 18 are provided between the particle counter 12 and the exhaust pump 24. The filter 14 protects the orifice of the flow meter 18 from particle blockage. An example of the flow meter 18 measures the flow rate by detecting the pressure difference between the upstream side and the downstream side of the critical orifice. A filter 26 for protecting the indoor environment from dust generation from the pump is also provided on the downstream side of the exhaust pump 24. However, this filter 26 may not be provided as long as a general pump is used. A filter 16 and a flow rate adjustment valve 20 are provided on the adjustment flow path 8 to avoid a change in the flow rate of the flow path 8 due to a change in the throttle amount of the flow rate adjustment valve 20 due to the accumulation of particles. Yes. The exhaust pump 24 is feedback-controlled so that the measured value by the flow meter 18 becomes a predetermined constant value.

  The operation of this embodiment will be described. The three-way switching valve 7 is brought into a state in which the sample gas flow channel 2 is connected to the main flow channel 3, and an atmospheric aerosol containing nanometer-sized fine particles is sucked from the sample gas flow channel 2 as a sample gas. The suction of the sample gas is performed by driving the exhaust pump 24. A part of the sample gas is guided to the particle counter 12 through the particle growth channel composed of the vapor saturation channel 5 and the cooling condensation channel 6, and the remaining sample gas is passed through the adjustment channel 8 to the particle counter 12. To the downstream flow path and exhausted to the outside.

  Fine particles in the sample gas grow by passing through the particle growth flow path consisting of the vapor saturation flow path 5 and the cooling condensation flow path 6, and therefore, fine particles having a particle size of nm order that cannot be counted by the particle counter 12 are counted. Fine particles having a particle size on the order of 100 nm that can be counted by the counter 12 are guided to the particle counter 12 and counted.

  Next, the three-way switching valve 7 is switched to a state in which the sample gas flow path 2 is connected to the bypass flow path 4 so that the sample gas is guided to the particle counter 12 without passing through the particle growth flow path. In this measurement, the exhaust pump 24 is adjusted based on the measured value of the flow meter 18 so that the sample gas is guided to the particle counter 12 at the same flow rate as that in the measurement performed through the particle growth channel. In this measurement, fine particles having an outer shape on the order of nm are not counted, and only fine particles having a particle diameter of 100 nm order or more are counted by the particle counter 12.

  For example, assuming that the particle counter 12 can only count fine particles having a particle diameter of 100 nm or more, first, in the measurement of the sample gas that has passed through the particle growth flow path, By passing through the particle growth channel, the total number of fine particles grown to have a particle diameter of 100 nm or more is counted. In the measurement of the sample gas that does not pass through the particle growth channel, only the number of fine particles having a particle diameter of 100 nm or more is counted. Therefore, the number of fine particles grown up to a particle diameter of 100 nm or more through the particle growth channel can be derived from the difference between these count values. Therefore, the particle size distribution of the fine particles in the sample gas can be measured by performing the above two types of measurements. Specifically, in this case, the number of particles having a particle diameter smaller than that with a particle diameter of 100 nm as a boundary, the number of particles having a particle diameter of 100 nm or more, and the total number of both are obtained. Can do.

(Second embodiment)
FIG. 2 represents a second embodiment.
An atmospheric pressure aerosol containing nanometer-sized fine particles is sucked from the sample gas channel 2 as a sample gas. A splitter 30 is provided at the tip of the sample gas flow path 2. The splitter 30 separates the sample gas into a gas flowing through the aerosol flow capillary 32 and a remaining gas.

  The aerosol flow capillary 32 allows a part of the sample gas separated by the splitter 30 to flow as an aerosol flow. The remainder of the sample gas separated by the splitter 30 flows into the sheath gas flow path 34.

  The sheath gas channel 34 is provided with a filter 38 such as a HEPA (High Efficiency Particulate Air Filter) filter that removes particles in the sample gas. A flow path opening / closing valve 36 as a switching mechanism is provided on the upstream side of the filter 38 in the sheath gas flow path 34. A vapor saturation flow path 40 is provided to make the gas from the sheath gas flow path into a saturated vapor state sheath gas and merge with the aerosol flow flowing out of the aerosol flow capillary 32. The steam saturation flow path 40 heats butyl alcohol to about 40 ° C. to form steam, and the flow path opening / closing valve 36 is opened so that the sheath gas flows through the alcohol vapor and the sheath gas saturated with alcohol vapor Become.

  A cooling condensing channel 6 is provided for cooling the combined gas of the aerosol flow from the aerosol flow capillary 4 and the sheath gas from the saturator 14 to grow the fine particles in the aerosol flow by the vapor of the sheath gas. The combined gas is guided to the cooling condensing flow path 6 and cooled to about 10 ° C., so that the surroundings of the aerosol flow are cooled in a state of being wrapped with a sheath gas saturated with alcohol vapor, and the alcohol vapor is converted into fine particles in the aerosol. Will grow and grow as the particle size grows.

  On the other hand, when the flow path opening / closing valve 36 is closed, the sheath gas is not supplied to the aerosol flow from the aerosol flow capillary 32, and the fine particles in the aerosol flow do not grow in the cooling condensation flow path 6. That is, the cooling condensation channel 6 constitutes a particle growth channel when the channel opening / closing valve 36 is opened, and the cooling condensation channel 6 serves as a particle non-growth channel when the channel opening / closing valve 36 is closed. Configure.

  A particle counter 12 is provided to count the number of particles in the gas that has passed through the cooling condensation channel 6. The counter 12 is the same as that shown in FIG.

  An exhaust pump 46 whose drive is controlled to exhaust at a predetermined flow rate is provided downstream of the particle counter 12. In this embodiment, a flow meter 44 is provided between the particle counter 12 and the exhaust pump 46. An example of the flow meter 44 measures the flow rate by detecting the pressure difference between the upstream side and the downstream side of the critical orifice. In this embodiment, the exhaust pump is controlled so that the flow rate of the sample gas flowing through the aerosol flow capillary 32 is equal when the flow path opening / closing valve 36 is opened and closed.

  In this embodiment, as an example of the operation, in the state where the flow path opening / closing valve 36 is opened, the splitter 30 has an aerosol flow and a sheath gas flow in which the sample gas sucked from the sample gas flow path 2 flows through the aerosol flow capillary 32. The gas is diverted to the sheath gas flowing through the passage 34. Particles in the sample gas guided to the sheath gas flow path 34 are removed by the filter 38, and the gas not containing the particle component is saturated as a sheath gas by the alcohol vapor through the vapor saturation flow path 40 and flows through the aerosol flow capillary 32. Then, it joins the aerosol flow and is guided to the cooling condensing flow path 6. The combined gas of the sheath gas and the aerosol flow capillary passes through the cooling condensation channel 6 so that the fine particles in the aerosol flow grow so as to increase the particle diameter, and the fine particles having a certain particle diameter or more are counted by the particle counter 12. The

  In a state where the flow path opening / closing valve 36 is closed, the sample gas sucked from the sample gas flow path 2 is not diverted by the splitter 30 and no gas flows through the sheath gas flow path 34. Therefore, the sheath gas from the sheath gas flow path 34 is not supplied to the aerosol flow that has flowed through the aerosol flow capillary 32, and the fine particles in the aerosol flow are not grown in the cooling condensing flow path 6 and remain in the same size. Guided to the counter 12.

  Accordingly, if the flow rate of the aerosol flow flowing through the aerosol flow capillary 32 is the same in each of the opened state and the closed state of the flow path opening / closing valve 36 and the number of particles is counted, the same as in the first embodiment. In addition, the particle size distribution of the fine particles in the sample gas can be measured.

  The present invention can be used for environmental measurement for automobile exhaust gas, factory exhaust gas, and the like.

2 Sample gas flow path 3 Main flow path 4 Bypass flow path 5,40 Steam saturation flow path 6 Cooling condensation flow path 7 Three-way switching valve 8 Adjustment flow path 12 Particle counter 14, 16, 26, 38 Filter 18, 44 Flow meter 24, 46 Exhaust pump 30 Splitter 32 Aerosol flow capillary 34 Sheath gas flow path 36 Flow path opening / closing valve

Claims (3)

A sample gas flow path for inhaling atmospheric pressure aerosol containing nanometer-sized fine particles as a sample gas;
A particle counter for counting the number of particles in the gas;
A particle growth channel that guides the sample gas from the sample gas channel to the particle counter by growing fine particles in the sample gas by vapor;
A particle non-growth flow path that guides the sample gas from the sample gas flow path to the particle counter without growing fine particles in the sample gas;
An aerosol fine particle measuring apparatus comprising: a switching mechanism that switches and guides the sample gas from the sample gas channel to either the particle growth channel or the particle non-growth channel. The particle non-growth channel is a channel separately provided from the particle growth channel so that the sample gas from the sample gas channel is guided to the particle counter without passing through the particle growth channel,
The aerosol fine particle measuring apparatus according to claim 1, wherein the switching mechanism switches and connects the sample gas flow channel to either the particle growth flow channel or the particle non-growth flow channel. The particle growth channel and the particle non-growth channel consist of a common gas flow channel,
The gas flow as a splitter provided between the sample gas flow channel and the gas flow flow channel to extract a part of the sample gas, and a sheath gas containing saturated vapor by removing fine particles from the gas extracted by the splitter A sheath gas flow path for joining the sample gas flowing through the flow path,
The switching mechanism is provided on the sheath gas flow path to switch on / off of gas flow in the sheath gas flow path,
The gas flow channel grows fine particles in the sample gas by cooling and condensing a mixed gas of the sample gas and the sheath gas when the switching mechanism is circulating the gas in the sheath gas flow channel, thereby counting particles. A particle non-growth channel that guides the sample gas directly to the particle counter when the switching mechanism blocks the gas flow in the sheath gas channel. The aerosol fine particle measuring apparatus according to claim 1.

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