JP5495978B2 - Gas particle measurement system - Google Patents

Description

  The present invention relates to a gas particle measurement system that measures particles floating in a gas other than air.

In the electronic device industry such as semiconductors, etching, film formation, and cleaning are often repeated in the device production process, and the gas used in these operations is required to maintain high cleanliness. As a means for managing gas, a particle measuring instrument that accurately detects particles floating in the gas is desired. Here, the gas is a gas other than air. In general, a particle counter that measures the number of particles floating in the air is called an air particle counter, and a gas counter is a gas particle counter. Among the air particle counters, the light scattering air particle counter is used for clean room management.

  In order to measure the particles in the gas, because the particle counter in the air adjusted in the air can not be used due to differences in gas density, refractive index, viscosity, etc., use the gas to be measured, The sample air supply must be adjusted for the gas. In addition, adjustment of the light receiving unit and calibration of the indicated value of the flow meter are also required. In addition, it is essential to adjust the light source unit for each gas even in the laser cavity. Similarly, maintenance must be performed using the gas to be measured.

Also, particle management in corrosive, toxic and reactive gas requires a structure that is highly leaky and does not leave impurities, so use an aerodynamic nozzle to introduce sample air into the particle detection area. In addition, it is known to use a dedicated gas particle counter in which a particle detection region is configured by a sealed transparent flow path (flow cell). Here, the sample air is air containing particles to be measured.

In addition, as a technique for measuring the number of particles in a reactive gas such as hydrogen, the reactive gas is diluted with an inert gas while maintaining the number of particles contained in the reactive gas such as hydrogen as it is. Discloses a technique for measuring the number of particles in a reactive gas using a diffusion dilution device that is inactivated to such an extent that it does not react with alcohol vapors (see, for example, Patent Document 1).

JP-A-5-264432

However, the gas particle counter using the flow cell uses the gas to be measured for each gas, and it is not necessary to adjust the supply unit and the light receiving unit, but use the open cavity method. Therefore, in order to obtain an irradiation intensity equivalent to that in the cavity of the laser used in the air particle counter, a light source with a higher irradiation intensity is required. Alternatively, it is necessary to reduce the sample flow rate in order to increase the energy density of the irradiation light. For these reasons, gas particle counters using flow cells are much more expensive than light scattering airborne particle counters.

Further, in the invention described in Patent Document 1, a reactive gas such as hydrogen that can ensure safety even with dilution of about 97% is diluted with an inert gas, and particles are measured in the diluted gas. Some devices can be dangerous. In addition, depending on the degree of dilution, the measurement accuracy may be lowered depending on the particle counter used.

  The present invention has been made in view of such problems of the prior art, and the object of the present invention is to measure particles in a gas with an air particle counter without reducing accuracy. It is intended to provide a gas particle measurement system that can be used.

In order to solve the above-mentioned problem, the invention according to claim 1 is a gas particle measurement system for measuring particles suspended in a gas other than air, and includes a sample gas and air to be measured via a porous partition wall. A gas air replacement unit that replaces the sample gas with air by diffusion due to a partial pressure difference, an air particle counter that measures particles in the air replaced by the gas air replacement unit, and a sample gas of the gas air replacement unit A differential pressure gauge that measures the differential pressure between the inlet and the air inlet, and a valve that controls the air flow rate to the air inlet, the flow rate of the sample gas is controlled by a flow rate controller provided in the particle counter in the air. , based on the measured value of the differential pressure gauge according to the flow rate of the sample gas, it is shall adjust the pressure in the air inlet in the valve.

The invention according to claim 2 is the gas in the particle measuring system according to claim 1, upstream of the sample gas inlet of the gas air displacement unit, guides select the sample gas or air to the sample gas inlet A switching valve is provided.

The invention according to claim 3 is an in-gas particle measurement system for measuring particles suspended in a gas other than air , wherein the sample gas is dispersed by diffusion due to a partial pressure difference between the sample gas and the intermediate gas through a porous partition wall. A two-stage replacement section that replaces the intermediate gas with the intermediate gas, and a two-stage replacement section that replaces the intermediate gas replaced with the first-stage replacement section with air through a porous partition wall by diffusion due to a partial pressure difference between the intermediate gas and air. An air particle counter for measuring particles in the air replaced by a stage replacement unit, a differential pressure gauge for measuring a differential pressure between a sample gas inlet and an intermediate gas inlet of the first stage replacement unit, and the two-stage replacement unit A differential pressure gauge for measuring a differential pressure between the sample intermediate gas inlet and the air inlet, an intermediate gas valve for controlling an intermediate gas flow rate to the intermediate gas inlet, and an air flow rate to the air inlet Equipped with air valve, sample gas flow rate And the flow rate of the sample intermediate gas is controlled by a flow rate controller provided in the air particle counter, and based on the measured value of the differential pressure gauge provided in the one-stage replacement unit according to the flow rate of the sample gas, The pressure is adjusted by the intermediate gas valve, and the pressure at the air inlet is adjusted by the air valve based on the measured value of the differential pressure gauge provided in the two-stage replacement unit according to the flow rate of the sample intermediate gas. It is.

According to a fourth aspect of the present invention, in the gas particle measurement system according to the third aspect , a sample gas or an intermediate gas is selected and introduced to the sample gas inlet upstream of the sample gas inlet of the one-stage replacement unit. a switching valve, upstream of the sample intermediate gas inlet of the two-stage replacement unit, provided with a switching valve that selects the sample intermediate gas or air leads to the sample intermediate gas inlet.

The invention according to claim 5 is the gas particle measurement system according to claim 3 or 4 , wherein the sample gas is a special gas and the intermediate gas is an inert gas.

According to a sixth aspect of the present invention, in the gas particle measurement system according to any one of the third to fifth aspects, the intermediate gas is helium.

According to claim 7 invention is provided in claim 1 gas particle measurement system according to claim 6, the gas air displacement unit inside the air particle counter.

The invention according to claim 8, in gas particle measurement system according to any one of claims 1 to 7, wherein the air in the particle counter is an optical scattering airborne particle counter or condensation particle counter is there.

The invention according to claim 9, in claim 1 or gas particle measurement system according to claim 7, wherein the air in the particle counter is provided with a specific particle diameter valve function by electrical mobility classifier .

The invention according to claim 10, in claim 1 or gas particle measurement system according to claim 9, the number of particles measured value when the air particle counter suctions a predetermined reference air flow rate And a processing unit for converting the sample gas flow rate sucked into the gas / air replacement unit into the number concentration.

The invention according to claim 11 is the gas particle measurement system according to any one of claims 1 to 10, the outer tube and the connecting pipe of the gas air displacement unit is made of stainless steel.

According to the present invention, it is not necessary to perform operations such as adjustment of the rectification state by an aerodynamic nozzle or the like, adjustment of an optical system such as a laser, or focus adjustment of a light receiving system for each gas to be measured. An air particle counter can be used as it is. Similarly, maintenance can be performed with air without using the gas to be measured. Moreover, each adjustment work becomes easy compared with the case where gas is used. In addition, the manufacturing cost is lower than when gas is used, such as not using a flow cell. Furthermore, even if there are a plurality of types of gases to be measured, a dedicated particle counter is not required for each gas, so that the equipment cost can be reduced and management is facilitated.

  In addition, if a differential pressure gauge for measuring the differential pressure between the sample gas inlet and the air inlet of the gas / air replacement unit is provided, the differential pressure between the sample gas inlet and the air inlet is adjusted to a predetermined value, When replacing the air, the gas replacement efficiency can be maintained and the particles in the sample gas can be efficiently moved into the sample air without damaging the particles.

When the gas-air replacement unit is a two-stage type consisting of a single-stage replacement unit and a two-stage replacement unit, a differential pressure gauge that measures the differential pressure between the sample gas inlet and the intermediate gas inlet of the first-stage replacement unit, and a two-stage replacement unit If a differential pressure gauge that measures the differential pressure between the intermediate gas inlet and the air inlet is provided, the differential pressure between the sample gas inlet and the intermediate gas inlet is adjusted to a predetermined value to replace the sample gas and the intermediate gas. In this case, the gas replacement efficiency is maintained and the particles in the sample gas are efficiently moved into the intermediate gas without damaging the particles, and then the differential pressure between the intermediate gas inlet and the air inlet is adjusted to a predetermined value. When the air is replaced, the gas replacement efficiency can be maintained and the particles in the intermediate gas can be efficiently moved into the air without damaging the particles.

  In addition, if a switching valve that selects the sample gas or air and leads it to the sample gas inlet is provided upstream of the sample gas inlet of the gas / air replacement unit, cleaning is performed by flowing the air through the gas / air replacement unit. When the sample gas is changed, the influence of the previous sample gas can be eliminated.

  When the gas / air replacement unit is a two-stage type consisting of a single-stage replacement unit and a two-stage replacement unit, a sample gas or an intermediate gas (or air) is selected upstream of the sample gas inlet of the single-stage replacement unit. If a switching valve that leads to the inlet and a switching valve that selects the intermediate gas or air and leads it to the intermediate gas inlet upstream of the intermediate gas inlet of the two-stage replacement unit are provided, the intermediate gas (or air) is one stage. When the sample gas is changed by flowing air through the two-stage replacement unit in the replacement unit, the influence of the previous sample gas can be eliminated.

  In addition, if the outer tube and connecting tube of the gas / air replacement part are made of stainless steel, there is no need for welding or other processes compared to quartz glass, which lowers manufacturing costs and also allows for installation work, transportation, and installation on site. At times, the possibility of damage to the outer tube can be reduced.

The block diagram of 1st Embodiment of the particle | grain measurement system in gas which concerns on this invention Cross section of gas air replacement part Configuration of light scattering airborne particle counter Configuration diagram of second embodiment of gas particle measurement system according to the present invention

  As shown in FIG. 1, the first embodiment of the gas particle measurement system according to the present invention is replaced with a gas / air replacement unit 1 that replaces a sample gas to be measured with air, and a gas / air replacement unit 1. An air particle counter 2 for measuring particles in the air, valves 3, 4, 5, 6 for introducing sample gas and air under predetermined conditions, flow meters 7, 8, 9, and differential pressure gauge 10 And a switching valve 12 and the like. Reference numeral 13 denotes a filter for maintaining the cleanliness of the air supplied to the gas / air replacement unit 1 at a desired level. In addition, the minimum configuration of the gas particle measurement system can be configured by providing the gas air replacement unit 1, the air particle counter 2, the valve 3, the flow meter 7, and the filter 13.

The gas air replacement unit 1 can also be provided inside the air particle counter 2. As a replacement method in the gas-air replacement unit 1, there is known a method of replacing a sample gas with air by diffusion due to a partial pressure difference between the sample gas and air through a porous partition wall (for example, Japanese Patent Application Laid-Open No. 2006-170659). No. publication).

  As shown in FIG. 2, the gas-air replacement unit 1 to which this method is applied connects an inner tube 1a formed of a porous partition wall, an outer tube 1b surrounding the inner tube 1a, and an inner tube 1a and an outer tube 1b. Connecting pipe 1c to be used. The outer tube 1b and the connecting tube 1c are made of stainless steel, and the inner tube 1a is made of quartz glass or ceramics. By fixing the inner pipe 1a and the connecting pipe 1c and the connecting pipe 1c and the outer pipe 1b with a resin material or the like, it is possible to prevent leakage of gas or air. The resin material is not limited as long as it is selected according to the type of the sample gas, and it is difficult for gas to leak and foreign substances including particles are difficult to adhere.

According to this method, a sample gas (for example, carbon dioxide) containing particles to be measured flows into the inner tube 1a from the sample gas inlet A, and air as a replacement gas passes from the air inlet B to the inner tube 1a. It flows into the passage 1d formed by the outer tube 1b. Then, the flow of the sample gas and air is reversed, and the sample gas is replaced with air while increasing the efficiency of diffusion due to the partial pressure difference between the sample gas and air via the porous partition. Particles in the sample gas pass through the inner pipe 1a as they are, flow out of the sample air exhaust port D together with the substituted air, and flow into the air particle counter 2. The sample gas includes air and is discharged from the sample gas exhaust port C.

In order to use the air particle counter 2 without newly adjusting, the substitution rate from carbon dioxide to air is about 99% or more, and the passage rate at which particles in carbon dioxide pass through the gas-air substitution unit 1. Is preferably at least 95% or more. Here, the amount of air flowing in from the air inlet B is adjusted by the valve 3 depending on the type of the sample gas. The smaller the molecular weight (density) of the sample gas, the higher the substitution rate.

In the measurement by the particle counter in air, the sample air flow rate is generally 0.3 liter / minute to 30 liter / minute. In order to cope with this sample air flow rate, the number of gas air replacement sections 1 is not limited to one, and a plurality of gas air replacement sections 1 can be provided in parallel.

Here, the case where the light scattering type air particle counter 20 is used as the air particle counter 2 for measuring particles in the air will be described. As shown in FIG. 3, the light scattering airborne particle counter 20 includes a sample air supply unit 21, a light source unit 22, a light receiving unit 23, and a signal processing unit 24. The electric signal from the light receiving unit 23 is processed by the signal processing unit 24, and the measurement result of the particles is displayed or output to a printer or the like.

  The sample air supply unit 21 rectifies the sample air in the particle detection region 27 by using the aerodynamic nozzles 25 and 26 and the flow rate adjustment unit (not shown). The flow rate adjusting unit is provided with a flow rate measuring device. Sample air passes from the aerodynamic nozzle 25 through the particle detection region 27 and into the aerodynamic nozzle 26. Clean air circulates around.

The light source unit 22 includes a laser element 28 such as a solid-state laser and a resonance mirror 29. The light source unit 22 is an open cavity type in order to obtain a high light energy density, and includes a particle detection region 27 serving as a rectified sample air passage. The surroundings are filled with air. For example, when the particle size is as small as about 0.1 μm, the open cavity method is adopted, but when the particle size is large, the open cavity method is not particularly required.

  Whether or not to adopt the open cavity method is selected depending on the detection sensitivity of the particles. Here, in the open cavity system, an optical path L1 of high light energy is formed between the laser element 28 and the resonator mirror 29 by resonance of light, and a particle detection region 27 is provided in the optical path L1, so that high light energy can be obtained. This is a method of irradiating particles in the air.

The light receiving unit 23 receives the scattered light L <b> 2 of the particles in the particle detection region 27 by the photoelectric conversion element 31 through the lens 30. The photoelectric conversion element 31 converts it into an electric signal S1 according to the intensity of light and sends it to the signal processing unit 24.

  A measurement procedure according to the first embodiment of the gas particle measurement system according to the present invention configured as described above will be described. First, an air flow path is set. The valves 3 and 4 are opened, the switching valve 12 is operated, the inlet F is communicated with the sample inlet A, air is introduced from the sample gas inlet A, and the valve 3 and the flow meter 7 are connected. The air is introduced from the air inlet B to the gas air replacement unit 1. The air flows into the gas-air replacement unit 1 through the filter 13 so as not to affect the particle measurement.

Next, a flow path for the sample gas (for example, carbon dioxide) is set. The valve 4 is closed, the valve 6 is opened, the switching valve 12 is operated to connect the inlet E to the sample gas inlet A of the gas air replacement unit 1, and the sample gas is supplied from the sample gas inlet A to the gas. It leads to the air replacement part 1. The flow rate of the sample gas is controlled by a flow rate controller provided in the air particle counter 2 (for example, the light scattering air particle counter 20).

  Next, the flow rates of the sample gas and air are adjusted. In order to efficiently replace the sample gas and air, the pressure at the sample gas inlet A of the gas / air replacement unit 1 into which the sample gas flows and the pressure at the air inlet B of the gas / air replacement unit 1 into which air flows in are obtained. So that the pressure difference between the sample gas inlet A and the air inlet B is measured by the differential pressure gauge 10 and adjusted by the valve 5. Here, if the amount of the sample gas exhausted by the flow meter 9 is sufficient and the pressure of the sample gas inlet A is almost atmospheric pressure, this adjustment is unnecessary.

In the light scattering type airborne particle counter 20, normally, when the pressure on the sample gas side is higher than the atmospheric pressure, the particles are measured while releasing the sample gas from the flow meter 9 in order to obtain a substantially atmospheric pressure.

Regarding the adjustment of the valve 5 and the differential pressure gauge 10, for example, the valve 5 may be automatically controlled based on a measured value of the differential pressure gauge 10 based on a predetermined condition, or the sample gas flow of the gas air replacement unit 1 may be controlled. A differential pressure gauge may be provided between the inlet A and the sample gas outlet C. A pressure gauge (not shown) may be provided instead of the differential pressure gauge. For example, it is provided at the sample gas exhaust port C.

  Next, the sample gas whose flow rate is adjusted is replaced with air in the gas-air replacement unit 1. Further, the particles in the sample gas are included in the air as they are. The particles are introduced to the sample air outlet D together with the air.

  Next, the sample air flowing out from the sample air exhaust port D of the gas air replacement unit 1 is measured by the air particle counter 2. Further, the substituted sample gas is mixed with air, and is discharged from the sample gas exhaust port C of the gas air replacement unit 1 through the valve 5. If the sample gas is harmful, a detoxifying device for removing the sample gas is provided downstream of the valve 5.

  Next, the gas-air replacement unit 1 and the like are washed as appropriate. The switching valve 12 is operated to make the inlet F communicate with the sample gas inlet A of the gas / air replacement unit 1, and the valves 3 and 4 are opened. Then, the air / air replacement unit 1 is cleaned by flowing air from the sample gas inlet A and the air inlet B into the gas / air replacement unit 1 under the desired conditions such as the air flow rate and pressure. Since this cleaning operation is premised on the use of a plurality of sample gases, it is performed to eliminate the influence of the previous sample gas when the sample gas is changed. A switching valve (not shown) may be provided between the sample air exhaust port D and the in-air particle coefficient device 2 to provide a path for discharging without passing through the in-air particle coefficient device 2.

  Next, the second embodiment of the gas particle measurement system according to the present invention is a two-stage system in which the gas-air replacement unit is composed of a single-stage replacement unit 41 and a two-stage replacement unit 42, as shown in FIG. This is employed when the desired replacement rate cannot be increased by the one-stage system, or when the sample gas is replaced with an intermediate gas and then replaced with air.

In the second embodiment, a one-stage replacement unit 41 that replaces a sample gas to be measured with an intermediate gas, a two-stage replacement unit 42 that replaces the intermediate gas with air, and the air replaced with the two-stage replacement unit 42 A particle counter 2 for measuring particles in the air, valves 43, 44, 45, 46, 47, 48, 49 for guiding sample gas / intermediate gas / air under predetermined conditions, and flow meters 50, 51, 52, 53, 54, differential pressure gauges 55, 56, switching valves 57, 58, and the like. 59 is a filter for maintaining the cleanliness of the supplied air at a desired level in the first-stage replacement section 41 and 60 in the second-stage replacement section 42. The minimum configuration of the gas particle measurement system provided with the two-stage replacement unit includes a one-stage replacement unit 41, a two-stage replacement unit 42, an air particle counter 2, valves 43 and 47, flow meters 50 and 53, and It can be configured by providing filters 59 and 60.

  In the case of the two-stage type, it is desirable to use an intermediate gas having a small molecular weight (density) in the one-stage replacement unit 41. For example, helium, which is an inert gas, may be used as the intermediate gas.

Ozone, which is the sample gas, flows from the sample gas inlet K of the first stage replacement unit 41 through the switching valve 57, and helium flows from the intermediate gas inlet L of the first stage replacement unit 41. Subsequently, helium flowing out from the sample intermediate gas exhaust port N of the first stage replacement unit 41 flows from the sample intermediate gas inlet R of the second stage replacement unit 42 through the switching valve 58, and air flows in the second stage replacement unit 42. By flowing in from the air inlet S, helium is replaced with air, and air containing particles (sample air) may flow into the air particle counter 2 from the sample air exhaust port U.

What is necessary is just to comprise piping other than the 1st stage replacement part 41 and the 2nd stage replacement part 42 similarly to 1st Embodiment shown in FIG. Sample gases for which such two-stage replacement is effective include special gases such as ozone, special material gases, toxic gases, flammable gases, and oxygen that is dangerous at high concentrations. There are 39 types of special material gases used in semiconductor manufacturing and the like. The toxic gas is carbon monoxide or the like, and the combustible gas is hydrogen or the like. Further, it is desirable to use an inert gas as the intermediate gas. Examples of the inert gas include nitrogen, carbon dioxide, helium, and argon.

  A measurement procedure according to the second embodiment of the gas particle measurement system according to the present invention configured as described above will be described. First, an air flow path is set. The valve 47 is opened, the valve 48 is closed, and air is guided from the air inlet S to the two-stage replacement portion 42 via the valve 47 and the flow meter 53. The air flows into the two-stage replacement unit 42 through the filter 60 so as not to affect the particle measurement.

  Next, a flow path for the intermediate gas is set. The valves 43 and 44 are opened, the switching valve 57 is operated, the inlet Q is communicated with the sample gas inlet K, the intermediate gas is guided from the sample gas inlet K, and the valve 43 and the flow meter 50 are connected. Through the intermediate gas inlet L to the first stage replacement section 41. Further, the switching valve 58 is operated to connect the inlet V with the sample intermediate gas inlet R of the two-stage replacement unit 42. The order of setting the air flow path and the intermediate gas flow path is not limited.

Next, a flow path for the sample gas is set. The valve 44 is closed, the valve 46 is opened, and the switching valve 57 is operated so that the inlet P is communicated with the sample gas inlet K of the first stage replacement unit 41, and the sample gas is replaced one stage from the sample gas inlet K. Guide to section 41. The flow rate of the sample gas and the flow rate of the sample intermediate gas are controlled by a flow rate controller provided in the air particle counter 2 (for example, the light scattering air particle counter 20). Here, the sample intermediate gas is an intermediate gas containing particles to be measured.

  Next, the flow rates of the sample gas, intermediate gas, and air are adjusted. In order to efficiently replace the sample gas and the intermediate gas, the pressure at the sample gas inlet K of the first-stage replacement unit 41 into which the sample gas flows and the intermediate gas inlet L of the first-stage replacement unit 41 into which the sample gas flows in. The pressure difference between the sample gas inlet K and the intermediate gas inlet L is measured by the differential pressure gauge 55 and adjusted by the valve 45 so that the pressures are approximately the same. Here, if the amount of the sample gas exhausted by the flow meter 52 is sufficient and the pressure of the sample gas inlet K is almost atmospheric pressure, this adjustment is unnecessary.

  In addition, in order to efficiently replace the sample intermediate gas and air, the pressure in the sample intermediate gas inlet R of the two-stage replacement unit 42 into which the sample intermediate gas flows and the air in the two-stage replacement unit 42 into which air flows in. The pressure difference between the sample intermediate gas inlet R and the air inlet S is measured by the differential pressure gauge 56 and adjusted by the valve 49 so that the pressure at the inlet S becomes approximately the same.

  Next, the sample gas whose flow rate has been adjusted is replaced with the intermediate gas in the one-stage replacement unit 41. Further, the particles in the sample gas are included in the intermediate gas as they are. The particles are guided together with the intermediate gas to the sample intermediate gas outlet N.

  Next, the sample intermediate gas that has flowed from the sample intermediate gas exhaust port N through the switching valve 58 into the sample intermediate gas inlet R of the two-stage replacement unit 42 flows into the air flowing from the air inlet S in the two-stage replacement unit 42. Is replaced by Further, the particles in the sample intermediate gas are included in the air as they are. The particles are guided to the sample air outlet U together with air.

  Next, the sample air flowing out from the sample air exhaust port U of the two-stage replacement unit 42 is measured by the air particle counter 2. In addition, the sample gas replaced by the first-stage replacement unit 41 is mixed with the intermediate gas and is discharged from the sample gas exhaust port M through the valve 45. Further, the intermediate gas replaced by the two-stage replacement unit 42 is mixed with air and is discharged from the sample intermediate gas exhaust port T through the valve 49. If the sample gas is harmful, a detoxification device for removing the sample gas is provided downstream of the valve 45.

  Next, the first-stage replacement unit 41, the second-stage replacement unit 42, and the like are washed appropriately. The switching valve 57 is operated to make the inlet Q communicate with the sample gas inlet K of the first stage replacement unit 41, and the valve 43 and the valve 44 are opened. Then, the inside of the first stage replacement unit 41 is cleaned by flowing the intermediate gas into the first stage replacement unit 41 from the sample gas inlet K and the intermediate gas inlet L under the desired conditions such as the flow rate and pressure of the intermediate gas. In addition, you may wash | clean using air instead of intermediate gas as needed.

Further, the switching valve 58 is operated so that the inlet W communicates with the sample intermediate gas inlet R of the two-stage replacement portion 42, and the valves 47 and 48 are opened. Then, the inside of the two-stage replacement section 42 is cleaned by flowing air from the sample intermediate gas inlet R and the air inlet S into the two-stage replacement section 42 under the desired conditions such as the air flow rate and pressure. Since these cleaning operations are premised on the use of a plurality of sample gases, they are performed to eliminate the influence of the previous sample gas when the sample gas is changed. In addition, a switching valve (not shown) may be provided between the sample air exhaust port U of the two-stage replacement unit 42 and the air particle counter 2, and a discharge path may be provided without passing through the air particle counter 2. .

  As the air particle counter 2, an electric mobility classifier (DMA: Differential Mobility Analyzer) and an air particle counter may be combined. DMA is also commonly used for airborne particles. DMA is a device that classifies only particles having a predetermined mobility by controlling an applied voltage.

Clean air (sheath air) is essential for DMA. When introducing gas as a sample, if the same gas is cleaned and used as sheath air, in principle it will work, but it requires more than ten times the sample gas flow rate, and the cost must be high because it must be very clean. It is not practical to introduce a sample other than air into DMA.

  Further, as the air particle counter 2, a DMA and a condensation particle counter (CPC) may be combined. This combination is called a scanning mobility particle sizer (SMPS) and is often used. CPC is a method in which vaporized alcohol, water, or the like is condensed into particles so that particle detection by the light scattering method can be applied to even smaller particles. Since the alcohol is detected by condensing it into particles, the actual particle size information is lost.

  Further, the particle counter 2 in the air can be provided with a processing unit that converts the measured particle number when the predetermined sample air flow rate is sucked into the number concentration converted from the gas flow rate sucked into the gas air replacement unit 1. . Movement by molecular diffusion is basically based on the balance of mass transfer amount (mass flux) per unit time. In the present invention, there are portions that actually depend on the pressure gradient, such as making the gas flows face each other, but the basic principle is based on molecular diffusion, and the diffusion rate of molecules is inversely proportional to the molecular weight (mass) to the 1/2 power. . That is, when the microparticle meter in the air sucks a predetermined sample air flow rate as air, the suction (volume) flow rate of the sample gas before replacement varies depending on the type of gas.

If you want to obtain the particle number concentration equivalent to the air volume even if the gas type is different, you can use the displayed value of the air particle meter as it is, but find the number concentration as the number of particles per volume of the original sample gas. In this case, it is necessary to convert the volume for each gas type.
A processing unit for calculating the flow meter and the sample gas volume is provided in the fine particle meter in the air, the sample air volume is obtained by the flow meter, and the sample gas volume is calculated by the processing unit using the obtained sample air volume.

According to the present invention, operations such as adjustment of a rectification state using an aerodynamic nozzle, adjustment of an optical system such as a laser, and focus adjustment of a light receiving system are performed with air without using a gas to be measured. It is possible to provide a gas particle measurement system that does not require a dedicated particle counter for each gas even when there are a plurality of types of gases to be measured.

DESCRIPTION OF SYMBOLS 1 ... Gas air replacement part, 2 ... Particle counter in air, 3, 4, 5, 6, 43, 44, 45, 46, 47, 48, 49 ... Valve, 7, 8, 9, 50, 51, 52 , 53, 54 ... flow meter, 10, 55, 56 ... differential pressure gauge, 12, 57, 58 ... switching valve, 13, 59, 60 ... filter, 20 ... light scattering airborne particle counter, 41 ... one-stage replacement unit 42, two-stage replacement part, A, K, sample gas inlet, B, S, air inlet, C, M, sample gas outlet, D, U, sample air outlet, L, intermediate gas inlet, N, T: Sample intermediate gas exhaust port, R: Sample intermediate gas inlet.

Claims (11)

A gas particle measurement system that measures particles suspended in a gas other than air, and replaces the sample gas with air by diffusion due to the partial pressure difference between the sample gas to be measured and the air through the porous partition wall. An air replacement unit, an air particle counter for measuring particles in the air replaced by the gas air replacement unit, and a differential pressure gauge for measuring a differential pressure between the sample gas inlet and the air inlet of the gas air replacement unit And a valve for controlling the air flow rate to the air inlet, the flow rate of the sample gas is controlled by a flow rate controller provided in the particle counter in the air, and the measured value of the differential pressure gauge according to the flow rate of the sample gas the basis, the gas in the particle measuring system characterized that you adjust the pressure at the valve in the air inlet. 2. The gas particle measurement system according to claim 1 , wherein a switching valve is provided upstream of a sample gas inlet of the gas-air replacement unit to select a sample gas or air and guide the sample gas or air to the sample gas inlet. Gas particle measurement system. A gas particle measurement system that measures particles suspended in a gas other than air, and replaces the sample gas with the intermediate gas by diffusion due to the partial pressure difference between the sample gas and the intermediate gas through the porous partition. A two-stage replacement section that replaces the intermediate gas replaced by the first-stage replacement section with air through a porous partition wall by diffusion due to a partial pressure difference between the intermediate gas and air, and an air replaced by the two-stage replacement section A particle counter for measuring particles in the air, a differential pressure gauge for measuring a differential pressure between the sample gas inlet and the intermediate gas inlet of the first stage replacement unit, and a sample intermediate gas inlet and the air of the second stage replacement unit A differential pressure gauge for measuring the differential pressure at the inlet, an intermediate gas valve for controlling the intermediate gas flow rate to the intermediate gas inlet, and an air valve for controlling the air flow rate to the air inlet, Flow rate and sample intermediate gas flow rate The intermediate gas valve is configured to control the pressure at the intermediate gas inlet based on the measured value of the differential pressure gauge provided in the one-stage replacement unit according to the flow rate of the sample gas, controlled by a flow rate controller provided in the air particle counter. And adjusting the pressure at the air inlet with the air valve based on the measured value of the differential pressure gauge provided in the two-stage replacement unit according to the flow rate of the sample intermediate gas. Measuring system. 4. The gas particle measurement system according to claim 3 , wherein a switching valve for selecting a sample gas or an intermediate gas and leading the sample gas or the intermediate gas to the sample gas inlet upstream of the sample gas inlet of the first stage replacement unit, and the two-stage replacement. upstream of the sample intermediate gas inlet parts, the gas in the particle measuring system and providing a change-over valve to select a sample intermediate gas or air leads to the sample intermediate gas inlet. 5. The gas particle measurement system according to claim 3 , wherein the sample gas is a special gas and the intermediate gas is an inert gas. In claims 3 to gas particle measurement system according to claim 5, gas particle measurement system, wherein the intermediate gas is helium. In claims 1 to gas particle measurement system according to claim 6, the gas in the particle measuring system, characterized in that it comprises the gas air displacement unit inside the air particle counter. In claims 1 to gas particle measurement system according to claim 7, gas that the air particle counter, characterized in that a light scattering airborne particle counter or condensation particle counter Particle measurement system. In claims 1 to gas particle measurement system according to claim 7, wherein the air in the particle counter is a gas in the particles, characterized in that it comprises a particle diameter valve by function by electrical mobility classifier Measuring system. Suction in claims 1 to gas particle measurement system according to claim 9, the number of particles measured value when the air particle counter suctions a predetermined reference air flow rate, the gas air displacement unit A gas particle measurement system comprising a processing unit that converts a sample gas flow rate into a number concentration. In claims 1 to gas particle measurement system according to claim 10, the gas in the particle measuring system, characterized in that the outer pipe and the connecting pipe of the gas air displacement unit is made of stainless steel.

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