JP4315348B2 - Gas replacement method, gas replacement apparatus, and analysis system - Google Patents

Description

  The present invention relates to a gas replacement method for replacing a sample gas containing fine particles with a replacement gas, a gas replacement device for implementing the gas replacement method, and an analysis system including the gas replacement device.

  In recent years, due to increasing interest in the living environment and the working environment, there has been a demand for improvements in technology for measuring the composition and concentration of fine particles present in the atmosphere. In industries that require high purity of raw material gas and atmospheric gas control in the manufacturing process, as represented by the semiconductor industry, analysis of raw material gas containing fine particles and atmospheric gas should be performed easily and with high accuracy. Is strongly desired.

  In addition to general gas chromatograph mass spectrometry (GC-MS method), inductively coupled plasma analysis (ICP method) and microwave plasma analysis (MIP method) can be used as analysis equipment for fine particles present in trace amounts in the sample gas. A method using a high-sensitivity analysis method is known. In the ICP method and the MIP method in which analysis is performed by detecting a signal change from plasma, a limited kind of gas such as argon gas, nitrogen gas and helium gas is used as the plasma gas, and the analysis sample is contained in the high-temperature plasma. The desired analysis is performed by introducing.

  In order to analyze fine particles present in a small amount in the sample gas with high accuracy, it is necessary to sufficiently eliminate gaseous contamination components in the sample gas. In particular, in order to realize high-sensitivity analysis using plasma, a large amount of fine particles contained in the analysis sample is plasma while maintaining a stable plasma without unnecessarily inducing changes in plasma temperature or electron density. Need to be introduced inside.

Therefore, in the fine particle classifier described in Patent Document 1, when the fine particles contained in the sample gas are charged and classified, the particulate contamination component in the sample gas is sufficiently eliminated, and the particles to be evaluated A state is formed in which the pollutant component floats in an atmosphere composed of a desired gas species.
In the sample introduction device described in Patent Document 2, a liquid sample is formed into droplets by an ultrasonic sprayer and heated to separate into sample components and solvent vapor, and a sample gas containing spray gas as a carrier gas. The sample gas is introduced into a tubular sealed filter made of a porous material having a pore diameter of 1 to 2 μm, and the solvent vapor is diffused outside the filter through the sealed filter and removed by the gas flowing outside the filter. The components are introduced into the plasma of the analyzer together with the carrier gas.
JP 2001-239181 A JP 7-500416

  However, the conventional fine particle classifier requires a device for charging the fine particles, a high voltage source for forming an electrostatic field, and the like, and thus has a problem of increasing the size and cost. In addition, when a sample is introduced into the plasma via a plasma torch made of quartz glass or the like using the above-described conventional sample introduction device using a sealed filter, the plasma may become unstable and the plasma torch may melt. There is a problem. The present invention aims to solve such problems of the prior art.

A feature of the gas replacement method of the present invention is that a sample gas containing fine particles is caused to flow in a gas flow path surrounded by a porous partition wall, and the replacement gas is moved in a direction opposite to the flow direction of the sample gas around the porous partition wall. The sample gas is moved out of the gas flow path through the porous partition wall, and the replacement gas is moved through the porous partition wall by diffusion due to a partial pressure difference between the sample gas and the replacement gas. The gas is moved into the gas flow path, the replacement gas is allowed to flow out together with the fine particles from the outlet of the gas flow path, and the gas movement through the porous partition due to the internal and external pressure difference of the gas flow path is substantially performed by the porous partition. It is in the point to prevent. In this case, in order to prevent gas movement through the porous partition due to the pressure difference, it is preferable that each pore diameter of the porous partition is substantially 0.8 to 0.001 μm.
The inventors of the present invention use a conventional sample introduction device using a hermetic filter, and the plasma becomes unstable because the flow rate of the gas introduced into the plasma fluctuates. It has been found that this is due to the occurrence of gas movement through.
On the other hand, according to the present invention, the sample gas is porous by diffusion due to the partial pressure difference between the sample gas and the replacement gas, in other words, the concentration difference between the sample gas and the replacement gas inside and outside the gas flow path as a driving force. The replacement gas moves out of the gas flow path through the partition wall and moves into the gas flow path through the porous partition wall. In addition, the porous partition prevents gas movement through the porous partition due to the pressure difference between the inside and outside of the gas flow path. As a result, the amount of the sample gas that moves out of the gas flow path is substantially equal to the amount of the replacement gas that moves into the gas flow path, and most of the sample gas is replaced with the replacement gas in the gas flow path. It is possible to prevent fluctuations in the flow rate of the gas flowing out from the tank. At this time, the fine particles in the gas flow path are not permeated through or trapped in each hole if the diameter exceeds the pore diameter of the porous partition wall, and those below the pore diameter are also diffused by the gas. However, since the inertia force due to the flow of the diffusion gas is very slow, most of the fine particles flow out of the gas flow path together with the replacement gas. That is, the fine particles introduced into the gas flow path together with the sample gas can be supplied to the analyzer together with the replacement gas having substantially the same flow rate as the sample gas without deteriorating. As a result, the sample gas can be replaced with a gas suitable for the analyzer, and the analysis accuracy can be improved by preventing fluctuations in the flow rate of the gas introduced into the analyzer. In particular, when the analysis apparatus employs an analysis method using plasma, analysis with high sensitivity and high accuracy is possible while maintaining stable plasma without causing problems such as melting of the plasma torch. Furthermore, since the fine particles contained in the sample gas introduced into the gas flow channel are discharged from the gas flow channel with little loss and do not remain, a sample gas different from the previously introduced sample gas is later gasified. When introduced into the flow path, it can be prevented from being contaminated by the residual fine particles contained in the previous sample gas, and high sensitivity and high accuracy analysis of the different sample gas can be performed.

The gas replacement device of the present invention includes an inner tube and an outer tube that covers the inner tube, and the inner tube includes an inner inlet, an inner outlet, and an inner gas flow path between the inner inlet and the inner outlet. The outer tube includes an outer inlet, an outer outlet, and an outer gas flow path between the outer inlet and the outer outlet, and the inner inlet, the inner outlet, the outer inlet, and the outer The outlet is arranged so that the flow direction of the sample gas containing fine particles in the inner gas flow path and the flow direction of the replacement gas in the outer gas flow path are opposite to each other, and the outlet of the inner gas flow path in the inner pipe The portion covering at least a part moves the sample gas out of the inner gas flow path and moves the replacement gas into the inner gas flow path by diffusion due to a partial pressure difference between the sample gas and the replacement gas. Of porous partition walls, Each pore diameter of the porous partition wall is set so as to substantially prevent gas movement through the porous partition wall due to the difference between the pressure in the inner gas channel and the pressure in the outer gas channel. Features. It is preferable that each pore diameter of the porous partition wall is substantially 0.8 to 0.001 μm.
According to the gas replacement device of the present invention, the gas replacement method of the present invention can be implemented with a small and low-cost configuration.

  The analysis system of the present invention comprises the gas replacement device of the present invention and an analysis device for fine particles flowing out from the inner outlet of the gas replacement device. According to the analysis system of the present invention, analysis accuracy can be improved by preventing fluctuations in the flow rate of gas introduced into the analyzer.

  ADVANTAGE OF THE INVENTION According to this invention, it can contribute to analyzing the microparticles | fine-particles contained in sample gas easily and with high precision.

  A gas replacement device 1 shown in FIG. 1 has a double tube structure including an inner tube 2 that is a straight tube having a circular cross section and an outer tube 3 that is a straight tube having a circular cross section that covers the inner tube 2. Both ends of 2 protrude from the outer tube 3, and the vicinity of both ends of the outer tube 3 is gradually made smaller in diameter and joined to the outer periphery of the inner tube 2. The inner and outer tubes 2 and 3 do not have to be straight tubes and may be curved.

  The inner tube 2 of the gas replacement device 1 has an inner inlet 2a formed at one end, an inner outlet 2b formed at the other end, and an inner gas flow path 2c between the inner inlet 2a and the inner outlet 2b. From the inner inlet 2a, the sample gas G1 containing fine particles and the liquid sample that becomes the sample gas G1 containing fine particles by evaporation are formed into droplets by a sprayer. The fine particles contained in the sample gas G1 are solid substances including, for example, metals such as iron powder, metal compounds such as oxides and sulfides, organic substances such as ceramics and polymer compounds, and the like. is there.

  The outer tube 3 includes an outer inlet 3a formed on the peripheral wall near one end for introducing the replacement gas G2, an outer outlet 3b formed on the peripheral wall near the other end, and an outer inlet 3a and an outer outlet 3b. The outer gas flow path 3c. In the inner inlet 2a, the inner outlet 2b, the outer inlet 3a, and the outer outlet 3b, the flow direction of the sample gas G1 in the inner gas flow path 2c and the flow direction of the replacement gas G2 in the outer gas flow path 3c are opposite to each other. Is arranged.

  The portion between both ends of the peripheral wall covering the inner gas flow path 2c in the inner pipe 2 moves the sample gas G1 out of the inner gas flow path 2c by diffusion due to the partial pressure difference between the sample gas G1 and the replacement gas G2, and the replacement gas G2 It is comprised by the porous partition 2A for moving in the inner side gas flow path 2c. Each pore diameter of the porous partition wall 2A is set so as to prevent gas movement through the porous partition wall 2A due to the difference between the pressure in the inner gas channel 2c and the pressure in the outer gas channel 3c, and is substantially 0.8 μm. It is set to -0.001 micrometer. Each pore diameter is set to 0.001 μm or more, preferably 0.002 μm or more, more preferably 0.02 μm or more in order to prevent the replacement efficiency of the gases G1 and G2 from being reduced and the apparatus to be enlarged. In order to prevent fine particles permeating through each hole or being trapped in each hole to reduce analysis accuracy or causing gas movement due to a pressure difference, it is 0.8 μm or less, preferably 0.5 μm or less, More preferably, it is 0.2 μm or less. In the porous partition wall 2A, the diameter of a small number of holes that does not affect the function and effect of the present invention may be outside the range of 0.8 μm to 0.001 μm. What is necessary is just 8 micrometers-0.001 micrometer. The porosity of the porous partition wall 2A is not particularly limited, but is preferably 40% to 80% from the viewpoint of gas replacement efficiency and mechanical strength. The material of the porous partition wall 2A is not particularly limited as long as it is a porous material meeting the above conditions, and glass such as quartz glass, ceramics, and the like are preferable. For example, shirasu porous glass (SPG) can be used. The portions 2B and 2C in the vicinity of both ends of the inner tube 2 are smoothly joined to the porous partition wall 2A with the same inner and outer diameters. The entire peripheral wall that covers the inner gas flow path 2c may be the porous partition wall 2A, and the portion that covers at least a part of the inner gas flow path 2c may be the porous partition wall 2A.

  The materials of the portions 2B, 2C near the both ends of the inner tube 2 and the outer tube 3 are not particularly limited, and may be composed of a plurality of different materials. Ease of processing and easy heating of the sample gas G1 introduced into the inner tube 2 From the viewpoints of heat resistance and heat resistance, for example, metal, ceramic, and glass are preferable, and glass such as ceramic and quartz glass is preferable.

  You may add a heating means (illustration omitted) to the gas displacement apparatus 1 as needed. The heating means is not particularly limited, and can be constituted by, for example, a belt-like heater wound around the outer tube 3 or an infrared lamp disposed around the outer tube 3. In this case, the temperature in the inner and outer tubes 2 and 3 is controlled. A temperature sensor for controlling the heating means according to the temperature sensor and the detected temperature may be provided.

  In the gas replacement by the gas replacement device 1, the sample gas G1 containing fine particles from the inner inlet 2a and the liquid sample that becomes the sample gas G1 containing fine particles by evaporation are introduced into the inner tube 2 as droplets by a sprayer. The inner gas flow path 2c surrounded by the porous partition wall 2A is caused to flow, the replacement gas G2 is caused to flow into the outer tube 3 from the outer inlet 3a, and the sample gas G1 flows in the outer gas flow path 3c around the porous partition wall 2A. This is done by flowing in the opposite direction. Thereby, due to the diffusion due to the partial pressure difference between the sample gas G1 and the replacement gas G2, in other words, the concentration difference between the sample gas G1 and the replacement gas G2 inside and outside the inner gas flow path 2c is used as a driving force to increase the sample gas G1. The portion is moved out of the inner gas channel 2c through the porous partition wall 2A, and a part of the replacement gas G2 is moved into the inner gas channel 2c through the porous partition wall 2A. In the inner gas flow path 2c, the concentration of the sample gas G1 gradually decreases and the concentration of the replacement gas G2 gradually increases as it goes from the inner inlet 2a to the inner outlet 2b. In the outer gas flow path 3c, the concentration of the replacement gas G2 gradually increases. As it goes to 3b, the concentration of the replacement gas G2 gradually decreases and the concentration of the sample gas G1 gradually increases. As a result, the replacement gas G2 is discharged as an analysis gas G3 from the inner outlet 2b together with the fine particles and a small amount of the sample gas G1 and supplied to the analyzer, and the sample gas G1 and the replacement gas G2 are discharged from the outer outlet 3b as the exhaust gas G4. Can be made. At this time, gas movement through the porous partition wall 2A due to a pressure difference between the inner gas channel 2c and the outer gas channel 3c, that is, a difference between the inner and outer pressures of the inner gas channel 2c can be substantially prevented by the porous partition wall 2A. Therefore, by appropriately setting each pore diameter, porosity, thickness, tube diameter, length, shape, inner diameter and shape of the outer tube 4, the flow rate of the sample gas G1 and the replacement gas G2, etc. of the porous partition wall 2A, The sample gas G1 flowing out from the outlet 2b can be reduced to a limit amount or less that does not adversely affect the analysis in the analyzer.

  According to the gas replacement device 1, the amount of the sample gas G1 that moves outside the inner gas flow path 2c and the amount of the replacement gas G2 that moves into the inner gas flow path 2c are substantially equal to each other in the inner gas flow path 2c. Most of the sample gas G1 is replaced with the replacement gas G2, and the flow rate of the analysis gas G3 flowing out from the inner outlet 2b can be prevented from fluctuating. At this time, as for the fine particles in the inner gas flow path 2c, those whose diameter exceeds the pore diameter of the porous partition wall 2A are not transmitted through or trapped in each hole, and those smaller than the pore diameter are also gas. Since the diffusion speed is slower and the inertial force due to the flow of the diffusion gas is very weak, most of the fine particles flow out from the inner outlet 2b together with the replacement gas G2 without moving to the outer gas flow path 3c. Therefore, the fine particles introduced into the inner gas flow path 2c together with the sample gas G1 can be supplied to the analyzer together with the replacement gas G2 having substantially the same flow rate as the sample gas G1 without deteriorating. As a result, the sample gas G1 can be replaced with a gas suitable for the analyzer, and the analysis accuracy can be improved by preventing fluctuations in the flow rate of the gas introduced into the analyzer. In particular, when the analysis apparatus employs an analysis method using plasma, analysis with high sensitivity and high accuracy is possible while maintaining stable plasma without causing problems such as melting of the plasma torch. Furthermore, the fine particles contained in the sample gas G1 introduced into the inner pipe 2 are discharged from the inner outlet 2b together with the replacement gas G2 and hardly remain in the inner pipe 2 with almost no loss. When a sample gas different from the sample gas G1 is introduced into the inner tube 2 later, it can be prevented from being contaminated by the residual fine particles contained in the previous sample gas G1, and the high sensitivity and high accuracy of the different sample gas can be prevented. Analysis is also possible.

  The analysis system A shown in FIG. 2 is used when the sample to be analyzed is a gas body and the sample gas G1 itself. The gas replacement device 1 and an inductively coupled plasma mass spectrometer (ICP-MS) 100 are used. And a sprayer 101. The analysis apparatus 100 is a known apparatus having a plasma torch 100a for forming a plasma P for high sensitivity analysis, and a gas similar to the plasma gas G5 such as argon gas introduced into the plasma torch 100a is replaced with a replacement gas. It can be G2. The plasma torch 100 a is connected to the inner outlet 2 b of the gas replacement device 1 via the sprayer 101. The atomizer 101 is a well-known one, and the inside thereof is decompressed by the flow of the carrier gas G6 to introduce the analysis gas G3 into the plasma torch 100a.

  The analysis system A ′ shown in FIG. 3 is used when the sample to be analyzed is a liquid, and includes the gas replacement device 1, the inductively coupled plasma mass spectrometer 100, and the nebulizer 101 similar to the analysis system A described above. The difference from the analysis system A is that the plasma torch 100a is directly connected to the inner outlet 2b of the gas displacement device 1, the inner inlet 2a of the gas displacement device 1 is connected to the nebulizer 101, and the nebulizer 101 is supplied liquid sample. L1 is introduced into the inner tube 2 from the inner inlet 2a of the gas displacement device 1 as a droplet together with the carrier gas G6 which is a spray gas. In this case, the gas replacement device 1 includes the heating unit, so that the liquid sample L1 in a droplet form can be quickly evaporated to obtain the sample gas G1 containing fine particles. Others are the same as those of the analysis system A, and the same parts are denoted by the same reference numerals.

  In addition, the kind of analyzer is not specifically limited, For example, a gas chromatograph mass spectrometer (GC-MS), an inductively coupled plasma emission spectrometer (ICP-AES), an inductively coupled plasma mass spectrometer (ICP-MS), a microwave, for example A plasma emission analyzer (MIP-AES) or the like may be used as the analyzer. Further, when the sample to be analyzed is a gas body, the gas displacement device 1 may be directly connected to the analyzer without using the nebulizer 101.

An evaluation experiment of gas replacement property, flow rate stability, and metal fine particle recovery rate was performed using the gas replacement device 1 according to the embodiment shown in FIG. 1, and a commercially available solvent removal device was used for the flow rate stability and metal fine particle recovery rate. A comparison experiment with the case of using was performed.
The material of the porous partition wall 2A of the gas replacement device 1 of the example used for the experiment is shirasu porous glass, each pore diameter is 0.2 μm, the porosity is 70%, the wall thickness is 0.7 mm, the outer diameter is 10 mm, long The inner tube 2 is made of quartz glass and the inner diameter of the outer tube 3 is 16 mm.
The solvent removal apparatus of the comparative example used for the comparative experiment corresponds to that of the conventional patent document 2, manufactured by Setac Technologies, and the product name is U-6000AT ⁺ ULTRASONIC NEBULIZER. Instead, a sealed filter is provided, and the sealed filter is made of a straight tubular microporous PTFE (polytetrafluoroethylene) film.

(Gas replacement)
Nitrous oxide was introduced as a sample gas into the gas replacement device 1 of the example, nitrogen gas was introduced as a replacement gas, and the concentration of nitrous oxide contained in the analysis gas was measured by gas chromatography (GC-TCD). . FIG. 4 shows the measurement results when the flow rate of the sample gas is changed in the range of 100 to 500 mL / min and the flow rate of the replacement gas is changed in the range of 1 to 2 L / min.
As shown in FIG. 4, as the flow rate of the sample gas increases, the nitrous oxide concentration decreases as the flow rate of the replacement gas increases. However, if the flow rate of the sample gas is 250 mL / min or less, the nitrous oxide is used regardless of the flow rate of the replacement gas. The concentration drops to 0.02% or less. Thus, according to the gas replacement device 1 of the present invention, it can be confirmed that excellent gas replacement performance is achieved without increasing the flow rate of the replacement gas in a practical range.

(Flow rate stability)
Nitrogen gas is introduced as the sample gas and the replacement gas into the gas replacement device 1 of the example and the solvent removal device of the comparative example, the flow rate of the sample gas is fixed to 500 mL / min, and the flow rate of the replacement gas is set to 500 to 2000 mL / min. FIG. 5 shows the measurement result of the flow rate of the analysis gas when the range is changed.
From FIG. 5, in the solvent removal apparatus of the comparative example, the flow rate of the analysis gas greatly changes in the range of 360 to 800 mL / min in accordance with the change of the flow rate of the replacement gas, whereas the gas replacement apparatus 1 of the example. The flow rate of the analysis gas was constant at the introduced flow rate of 500 mL / min even when the flow rate of the replacement gas changed. Thereby, according to the gas replacement apparatus 1 of an Example, even if the flow volume of substitution gas fluctuates, it can confirm that the flow volume of analysis gas is stabilized without being influenced.

(Metal fine particle recovery rate)
After the gas flow paths of the gas displacement device 1 of the example and the solvent removal device of the comparative example were heated to 160 ° C., the sample gas and the replacement gas were introduced. The sample gas was prepared by diluting a 5 ppm Fe standard solution prepared by diluting a metal standard solution manufactured by SPEX with an ultrasonic sprayer (heating unit temperature: 140 ° C., cooling unit temperature: −5 ° C.) provided in the solvent removal apparatus of the comparative example. What was formed by atomizing and spraying argon gas as a carrier gas was used. Argon gas was used as the replacement gas. Thereafter, the Fe content contained in the sample gas = α, the Fe content contained in the analysis gas flowing out from the gas replacement device 1 of the embodiment = β, and the analysis gas flowing out from the solvent removal device of the comparative example. The total amount of Fe content = γ was collected on a PTFE filter having a pore size of 0.1 μm, dissolved in a methanol nitric acid solution, and then measured by inductively coupled plasma emission spectrometry.
When the flow rate of the sample gas is fixed to 500 mL / min and the flow rate of the replacement gas is changed in the range of 500 to 2000 mL / min, the Fe recovery rate (%) by the gas replacement device 1 of the example = 100 × β FIG. 6 shows the calculation result of Fe content recovery rate (%) = 100 × γ / α using the solvent removal apparatus of Comparative Example.
From FIG. 6, in the solvent removal apparatus of Comparative Example 1, the metal fine particle recovery rate is greatly affected by the flow rate of the replacement gas, and when the replacement gas flow rate is equal to the analysis gas flow rate from FIG. It can be confirmed that the fine particle recovery rate remains at 75.3%. On the other hand, according to the gas replacement apparatus 1 of the example, the metal fine particle recovery rate is 99.8%, and it can be confirmed that the flow rate of the replacement gas is not affected.

  If the flow rate of the replacement gas is increased in order to increase the metal fine particle recovery rate in the solvent removal apparatus of Comparative Example 1, the flow rate of the analysis gas increases as shown in FIG. It is necessary to strictly control the flow rate of the replacement gas and its fluctuation. On the other hand, according to the gas replacement apparatus 1 of the embodiment, even if the flow rate of the replacement gas varies, the metal particulate recovery rate is not affected, and most of the metal particulates contained in the sample gas are not impaired. It can be supplied to the analyzer, and the flow rate of the analysis gas introduced into the analyzer is not changed. Therefore, when an analysis apparatus using plasma is used, a good plasma state can be maintained and high-precision analysis can be performed.

  Using the gas displacement device of the example and the solvent removal device of the comparative example, the metal fine particle recovery rate was similarly evaluated for each standard solution of Cd, Co, Cr, Mn, Mo, Ni, Pb, Ti, and Zn. The same results were obtained as for the above Fe standard solution.

  In addition, this invention is not limited to the said embodiment and Example at all.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to implement | achieve real-time highly accurate analysis in a use point easily regarding the environmental analysis of a living environment or a working environment, and the impurity analysis in various industrial raw materials.

Sectional drawing which shows the whole structure of the gas replacement apparatus which concerns on embodiment of this invention Configuration explanatory diagram of an analysis system according to an embodiment of the present invention Structure explanatory drawing of the analysis system which concerns on different embodiment of this invention The figure which shows the relationship between the nitrous oxide density | concentration contained in the sample gas flow volume, substitution gas flow volume, and analysis gas for evaluating the gas substitution property in the gas substitution apparatus of the Example of this invention. The figure which shows the relationship between the sample gas flow rate, substitution gas flow rate, and analysis gas flow rate for evaluating the flow rate stability in the gas displacement device of the embodiment of the present invention and the solvent removal device of the comparative example. The figure which shows the relationship between the displacement gas flow rate in the gas displacement apparatus of the Example of this invention, and the solvent removal apparatus of a comparative example, and a metal particulate collection rate.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Gas displacement apparatus 2 Inner pipe | tube 2A Porous partition 2a Inner inlet 2b Inner outlet 2c Inner gas flow path 3 Outer pipe 3a Outer inlet 3b Outer outlet 3c Outer gas path 100 Analyzer A, A 'analysis system

Claims (5)

Flowing a sample gas containing fine particles in a gas flow path surrounded by a porous partition;
The replacement gas is caused to flow in the direction opposite to the flow direction of the sample gas around the porous partition wall, and the sample gas is passed through the porous partition wall by diffusion due to a partial pressure difference between the sample gas and the replacement gas. Moving the gas out of the gas flow path and moving the replacement gas into the gas flow path through the porous partition;
Let the replacement gas flow out together with the fine particles from the outlet of the gas flow path;
A gas replacement method for substantially preventing gas movement through the porous partition due to a pressure difference between the inside and outside of the gas flow path by the porous partition. 2. The gas replacement method according to claim 1, wherein each pore diameter of the porous partition wall is substantially 0.8 to 0.001 μm in order to prevent gas movement through the porous partition wall due to the pressure difference. An inner pipe,
An outer tube covering the inner tube,
The inner tube has an inner inlet, an inner outlet, and an inner gas flow path between the inner inlet and the inner outlet,
The outer tube has an outer inlet, an outer outlet, and an outer gas flow path between the outer inlet and the outer outlet;
The inner inlet, the inner outlet, the outer inlet, and the outer outlet are arranged so that the flow direction of the sample gas containing fine particles in the inner gas flow path is opposite to the flow direction of the replacement gas in the outer gas flow path. And
The portion of the inner tube that covers at least a part of the inner gas flow path moves the sample gas out of the inner gas flow path by diffusion due to a partial pressure difference between the sample gas and the replacement gas, and causes the replacement gas to flow. The porous partition wall is configured to move into the inner gas channel, and each pore diameter of the porous partition wall is determined by the difference between the pressure in the inner gas channel and the pressure in the outer gas channel. A gas displacement device that is set to substantially prevent gas movement through the. The gas replacement device according to claim 3, wherein each pore diameter of the porous partition wall is substantially 0.8 to 0.001 μm. A gas replacement device according to claim 3 or 4,
An analysis system comprising: an analysis device for fine particles flowing out from an inner outlet of the gas replacement device.

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