Gas flow path, gas detection system

Abstract

To provide a gas flow path and a gas detection system that can condense a gaseous species to be detected in real time without occluding gas even when the concentration of the gaseous species to be detected is low.SOLUTION: A gas flow path (11) comprises: a filter (111) that selectively transmits gas; a cylindrical member (114) provided downstream of the filter (111), and having an opening area at a downstream end (112) narrower than an opening area at an upstream end (113); and a negative pressure generation device (pump 14) that is provided on the subsequent stage of the cylindrical member, and suctions gas having passed through the cylindrical member.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a gas flow path and a gas detection system.

Background Art

[0002] As methods for detecting gas species with relatively high concentrations, various methods are known. However, it is difficult to detect gas species with low concentrations that diffuse in the atmosphere. For example, an example of the detection limit concentration in a commercially available gas sensor for detecting a specific sulfur gas is on the order of ppm.

[0003] When the concentration of the gas species to be detected is lower than the detection limit concentration of the gas sensor, a method of concentrating the gas species is used. In this method, the gas species to be detected is occluded in a filter over a predetermined period, and then the gas species occluded in the filter is released from the filter. As a result, the gas species can be concentrated so that the concentration of the gas species is higher than the detection limit concentration of the gas sensor (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the conventional detection method, since the gas species to be detected is occluded in a filter over a predetermined period and then released from the filter, there is a problem that the gas species cannot be detected in real time.

[0006] One aspect of the present invention has been made in view of the above-mentioned problems, and its object is to provide a gas flow path and a gas detection system that can concentrate a gas species to be detected in real time without adsorbing gas, even when the concentration of the gas species to be detected is low. [Means for solving the problem]

[0007] To solve the above problems, the gas flow path according to embodiment 1 of the present invention comprises a filter that selectively permeates gas, a cylindrical member through which the gas that has permeated the filter passes, wherein the opening area at the downstream end is smaller than the opening area at the upstream end, and a negative pressure generating device provided downstream of the cylindrical member and for sucking in the gas that has passed through the cylindrical member.

[0008] According to the above configuration, the concentration of the target gas species contained in the gas can be increased by permeating through the cylindrical member. Therefore, this gas flow path can provide a gas flow path that can concentrate the target gas species in real time without adsorbing gas, even when the concentration of the target gas species is low.

[0009] The gas flow path according to embodiment 2 of the present invention, in addition to the configuration of the gas flow path according to embodiment 1, employs a configuration in which the cylindrical member has an internal space that smoothly tapers from the upstream end to the downstream end.

[0010] With the above configuration, when gas supplied from an upstream end with a large opening area is discharged from a downstream end with a small opening area, turbulence that may occur in the gas flow can be suppressed. Therefore, this gas flow path can concentrate the target gas species while reducing pressure loss in the gas.

[0011] The gas flow path according to embodiment 3 of the present invention is configured to further include, in addition to the configuration of the gas flow path according to embodiment 1 or 2, a coil arranged such that its axis is aligned with the axial direction of the cylindrical member and surrounds the cylindrical member.

[0012] By supplying a driving current to the coil, an electromagnetic field is generated around the coil. In particular, an electromagnetic field is generated near the coil's axis, aligned with the direction of that axis. With the above configuration, due to the interaction between the electromagnetic field generated by the coil and the type of gas, the gas supplied from the upstream end of the cylindrical member into the internal space of the cylindrical member flows toward the downstream end while swirling in a vortex. Therefore, this gas flow path can further reduce pressure loss in the gas.

[0013] The gas flow path according to embodiment 4 of the present invention is configured such that, in addition to the gas flow path configuration according to any one of embodiments 1 to 3, the cylindrical member is cylindrical, the coil is helical when viewed from the axial direction of the coil, and the cylindrical member and the coil are arranged coaxially.

[0014] With the above configuration, the gas flowing from the upstream end to the downstream end of the cylindrical member can be made to swirl more smoothly. Therefore, this gas flow path can further reduce pressure loss in the gas.

[0015] The gas flow path according to aspect 5 of the present invention, in addition to the configuration of the gas flow path according to any one of aspects 1 to 4, employs a configuration in which the filter is made of a metal-organic structure in which metal ions are crosslinked three-dimensionally and periodically by organic ligands, and the organic ligand has an acidic or basic functional group.

[0016] When the organic ligand has an acidic functional group, the filter absorbs basic gas species and allows acidic gas species to pass through. Conversely, when the organic ligand has a basic functional group, the filter absorbs acidic gas species and allows basic gas species to pass through. With the above configuration, the filter can separate gas species according to the pore size of the metal-organic structure, as well as according to the polarity of the gas species. Therefore, this gas flow path can more effectively exclude gas species that are not the target of detection.

[0017] To solve the above problems, a gas detection system according to embodiment 6 of the present invention comprises a gas flow path described in any one of embodiments 1 to 5, a chamber provided downstream of the gas flow path, and a gas sensor housed in the chamber, wherein the negative pressure generating device is a pump provided downstream of the chamber for exhausting the gas flow path and the chamber.

[0018] According to the above configuration, the gas species to be detected can be concentrated in real time using a gas flow path according to one aspect of the present invention, and then the concentrated gas species to be detected can be detected in real time using a gas sensor installed downstream of the gas flow path.

[0019] The gas detection system according to embodiment 7 of the present invention further includes, in addition to the configuration of the gas detection system according to embodiment 6, a first pressure sensor and a second pressure sensor that detect a first pressure, which is the pressure inside the cylindrical member, and a second pressure, which is the pressure inside the chamber, respectively; a power supply that supplies a drive current to the coil; and a control unit that determines the drive current according to the difference between the first pressure and the second pressure.

[0020] According to the above configuration, the drive current of the coil is determined according to the difference between the first pressure and the second pressure, so the drive current can be set in such a way that the pressure loss in the gas is minimized.

[0021] The gas detection system according to embodiment 8 of the present invention employs a configuration in which, in addition to the configuration of the gas detection system according to embodiment 6 or 7, the control unit determines the drive current such that there is a positive correlation between the difference and the drive current.

[0022] A large difference between the first and second pressures means a large pressure loss in the gas. With the above configuration, the larger the difference between the first and second pressures, the stronger the vortex rotation generated in the gas can be. Therefore, the pressure loss in the gas can be appropriately reduced. [Effects of the Invention]

[0023] According to one aspect of the present invention, there can be provided a gas flow path and a gas detection system capable of concentrating a gas species to be detected in real time without adsorbing the gas even when the concentration of the gas species to be detected is low. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] [Figure 1] It is a block diagram of a gas detection system according to an embodiment of the present invention. MODE FOR CARRYING OUT THE INVENTION

[0025] (Configuration of Gas Detection System) The configuration of a gas detection system 10 according to an embodiment of the present invention will be described with reference to FIG. 1. FIG. 1 is a block diagram of the gas detection system. In FIG. 1, the white arrows indicate the direction in which the gas flows from upstream to downstream.

[0026] The gas detection system 10 is a system for detecting a gas. As shown in FIG. 1, the gas detection system 10 includes a gas flow path 11 according to one aspect of the present invention, a chamber 12 provided downstream of the gas flow path 11, and a gas sensor 13 housed in the chamber 12. According to such a configuration, the gas species to be detected is concentrated in real time using the gas flow path 11 according to one aspect of the present invention, and then the concentrated gas species to be detected can be detected in real time using the gas sensor 13 provided downstream of the gas flow path 11.

[0027] In this embodiment, the gas species to be detected in the gas detection system 10 is a sulfur-based gas. However, the gas that can be detected in the gas detection system 10 may be a gas that can be selectively permeated by the filter 111 described later. In this specification, "selective permeation" refers to using the properties of the gas to allow the gas species to be detected to pass through and to eliminate unwanted gases. Examples of gas properties that can be used include polarity and molecular weight. Furthermore, the gas that can be detected in the gas detection system 10 preferably contains polar molecules with a biased charge distribution, from the viewpoint of susceptibility to the influence of the electromagnetic field generated by the coil 116 described later. Examples of such polar molecules include ammonia, hydrogen sulfide, and ethanol.

[0028] (Gas flow path 11) The gas flow path 11 comprises a filter 111 that selectively allows gas to pass through, a cylindrical member 114 through which the gas that has passed through the filter 111 passes, the cylindrical member 114 having an opening area at its downstream end 112 that is smaller than the opening area at its upstream end 113, and a pump 14 located downstream of the chamber 12 that exhausts the gas flow path 11 and the chamber 12. The cylindrical member 114 is located downstream of the filter 111. In the gas flow path 11, the concentration of the target gas species contained in the gas can be increased by passing it through the cylindrical member 114. Therefore, even when the concentration of the target gas species is low, the gas flow path 11 can concentrate the target gas species in real time without adsorbing gas. The gas flow path 11 also further comprises an inlet 117. The gas flow path 11 draws in gas from the inlet 117. The gas flow path 11 may also further comprises a valve (not shown) at the downstream end of the filter 111. The valve prevents the filter 111 from entering the chamber 12. The pump 14 is an example of a negative pressure generating device and constitutes the end of the gas flow path 11. The negative pressure generating device is located downstream of the cylindrical member 114 and sucks in the gas that has passed through the cylindrical member 114. The specific configuration of the pump 14 will be described later.

[0029] (Filter 111) The filter 111 is connected to the inlet 117 and selectively allows gases drawn in from the inlet 117 to pass through. In this embodiment, the filter 111 is made of a metal-organic framework (MOF) in which metal ions are crosslinked three-dimensionally and periodically by organic ligands, and the organic ligands have acidic functional groups. In this specification, the metal-organic framework is also called a porous coordination polymer (PCP). The filter 111 can separate permeable gas species by adjusting the pore size of the metal-organic framework. Furthermore, if the ligands have acidic functional groups, the filter 111 adsorbs basic gas species and allows acidic gas species to pass through. Therefore, the filter 111 allows sulfur-based gases, which are the target of detection, to pass through and adsorbs basic gas species that are not needed for detection. However, the organic ligands may also have basic functional groups. When the organic ligand has a basic functional group, the filter 111 absorbs acidic gas species and allows basic gas species to pass through. With this configuration, the filter 111 can separate gas species according to the pore size of the metal-organic structure, as well as according to the polarity of the gas species. Therefore, the gas channel 11 can more effectively exclude gas species that are not the target of detection. However, the filter 111 only needs to selectively allow the gas to be detected to pass through, and can be appropriately selected depending on the target gas species.

[0030] Furthermore, the gas species adsorbed by the filter 111 can be removed by the following method. Specifically, by stopping the operation of the gas sensor 13, the first pressure sensor 15 and the second pressure sensor 16, the power supply 17, and the control unit 18, and operating the pump 14, the temperature of the filter 111 can be increased to remove the adsorbed gas species. Therefore, the filter 111 can be reused without replacement, thereby reducing the effort and cost of replacing the filter 111.

[0031] (Cylindrical member 114) The cylindrical member 114 is provided downstream of the filter 111, and is a cylindrical member in which the opening area at the downstream end 112 is smaller than the opening area at the upstream end 113. The opening area at the downstream end 112 refers to the area of ​​the opening at the downstream end 112, and the opening area at the upstream end 113 refers to the area of ​​the opening at the upstream end 113. In this embodiment, both the openings at the downstream end 112 and the upstream end 113 are circular in shape. That is, in this embodiment, the cylindrical member 114 is cylindrical.

[0032] In this embodiment, the inner diameter of the cylindrical member 114 (the diameter of the internal space 115) is set to continuously decrease as it approaches the downstream end 112 from the upstream end 113. That is, in this embodiment, a tapered cylindrical member 114 is employed in which the internal space 115 smoothly narrows from the upstream end 113 to the downstream end 112. With this configuration, when gas supplied from the upstream end 113, which has a large opening area, is discharged from the downstream end 112, which has a small opening area, turbulence that may occur in the gas flow can be suppressed. Therefore, this gas flow path 11 can concentrate the gas species to be detected while reducing pressure loss in the gas.

[0033] (Coil 116) The gas flow path 11 further includes a coil 116 positioned so as to have its axis aligned with the axial direction of the cylindrical member 114 and to surround the cylindrical member 114. By supplying a drive current to the coil 116, an electromagnetic field is generated around the coil 116. In particular, an electromagnetic field is generated near the axis of the coil 116, aligned with the direction of that axis. The drive current is supplied by a power supply 17, which will be described later. With this configuration, due to the interaction between the electromagnetic field generated by the coil 116 and the type of gas, the gas supplied from the upstream end 113 of the cylindrical member 114 into the internal space 115 of the cylindrical member 114 flows toward the downstream end 112 while swirling in a vortex. Therefore, this gas flow path 11 can further reduce pressure loss in the gas.

[0034] In this embodiment, the coil 116 is helical when viewed from the axial direction of the coil 116, and the cylindrical member 114 and the coil 116 are arranged coaxially. With this configuration, the gas flowing from the upstream end 113 to the downstream end 112 of the cylindrical member 114 can be made to swirl more smoothly. Therefore, the gas flow path 11 can further reduce pressure loss in the gas.

[0035] (Chamber 12) Chamber 12 is located downstream of the gas passage 11. Chamber 12 is connected to the downstream end 112 of the cylindrical member 114 and is provided with a supply port (not shown) for receiving gas from the gas passage 11 and an exhaust port (not shown) for exhausting gas to the pump 14.

[0036] (Gas sensor 13) The gas sensor 13 is housed in the chamber 12. In this embodiment, the gas sensor 13 is a gas sensor capable of detecting sulfur-based gases. However, the gas sensor 13 can be any gas sensor capable of detecting the target gas species, and for example, semiconductor type, electrochemical type, and quartz crystal type gas sensors can be used.

[0037] (Pump 14) In this embodiment, a pump 14 is used as a negative pressure generating device. The pump 14 is located downstream of the chamber 12 and exhausts the gas passage 11 and the chamber 12. In this embodiment, the type of pump 14 can be any pump capable of exhausting the gas passage 11 and the chamber 12, and can be appropriately selected depending on the exhaust capacity. For example, a diaphragm pump, rotary pump, oil diffusion pump, and turbomolecular pump can be used. By exhausting the gas passage 11 and the chamber 12, the pump 14 makes the pressure inside the gas passage 11 and the chamber 12 lower than atmospheric pressure (i.e., negative pressure).

[0038] The gas detection system 10 of this embodiment further comprises a first pressure sensor 15 and a second pressure sensor 16, a power supply 17, and a control unit 18. The first pressure sensor 15 and the second pressure sensor 16 can each detect the first pressure, which is the pressure inside the cylindrical member 114, and the second pressure, which is the pressure inside the chamber 12. With this configuration, the drive current of the coil 116 is determined according to the difference between the first pressure and the second pressure, so that the drive current can be determined in such a way that the pressure loss in the gas is minimized.

[0039] (First pressure sensor 15 and second pressure sensor 16) The first pressure sensor 15 is housed in a cylindrical member 114 and detects a first pressure, which is the pressure inside the cylindrical member 114, and supplies first pressure information representing the first pressure to the control unit 18. The second pressure sensor 16 is housed in a chamber 12 and detects a second pressure, which is the pressure inside the chamber 12, and supplies second pressure information representing the second pressure to the control unit 18. The types of the first pressure sensor 15 and the second pressure sensor 16 can be any sensors capable of measuring negative pressure, and can be appropriately selected by those skilled in the art.

[0040] (power supply 17) The power supply 17 is configured to supply a drive current to the coil 116. The power supply 17 acquires a control signal generated by the control unit 18 (described later) and supplies a drive current to the coil 116 based on the control signal. The power supply 17 is preferably a DC constant current source. However, the power supply 17 is not limited to this, and is only required to be configured to supply a drive current to the coil 116 that is capable of generating the desired electromagnetic field.

[0041] (Control Unit 18) The control unit 18 is configured to determine the drive current according to the difference between the first pressure and the second pressure. The control unit 18 acquires first pressure information supplied from the first pressure sensor 15 and second pressure information supplied from the second pressure sensor 16. Then, the control unit 18 calculates the difference between the first pressure and the second pressure and determines the drive current according to the difference. Here, the control unit 18 refers to a predetermined correlation between the difference and the drive current and determines the drive current corresponding to the difference based on that correlation. Preferably, the correlation is defined so that there is a positive correlation between the difference and the drive current. The correlation may be represented by a lookup table or by a function (e.g., a linear function). Furthermore, the control unit 18 supplies a control signal to the power supply 17 to control the power supply 17 so that the power supply 17 supplies the determined drive current to the coil 116. Some or all of the functions of the control unit 18 may be implemented by hardware such as an integrated circuit (IC chip) or by software. In this embodiment, the control unit 18 is implemented by software. In this case, each function of the control unit 18 is implemented, for example, by a computer that executes instructions for a software program.

[0042] (Operation) Next, the operation of the gas detection system 10 according to this embodiment, which is configured with the above-described components, will be explained below.

[0043] First, the pump 14 is activated to evacuate the gas passage 11 and chamber 12, so that the gas to be inhaled and detected does not mix with the existing gas in the gas passage 11 and chamber 12.

[0044] Next, since the pump 14 is still running and the gas flow path 11 and chamber 12 remain under negative pressure, the gas to be detected can be drawn in through the inlet 117. The drawn-in gas is selectively passed through the filter 111 and then flows into the cylindrical member 114 surrounded by the coil 116.

[0045] At that time, the coil 116 surrounding the cylindrical member 114 is supplied with a drive current determined by the control unit 18 based on the pressure information detected by the first pressure sensor 15 and the second pressure sensor 16 from the power supply 17, thereby generating an electromagnetic field around the cylindrical member 114.

[0046] Due to the interaction between the generated electromagnetic field and the gas flowing into the cylindrical member 114, the gas, which is trying to flow down due to the negative pressure of the pump 14, flows more smoothly toward the downstream end 112 while swirling in a vortex that reduces pressure loss.

[0047] The type of gas that flows into the chamber 12 from the downstream end 112 is detected by a gas sensor 13 installed inside the chamber 12.

[0048] The gas that has been detected by the gas sensor 13 is exhausted by the pump 14 connected to the chamber 12.

[0049] (effect) Based on the above, the gas detection system 10 allows for the real-time concentration of sulfurous gases to be detected using a gas flow path 11 according to one aspect of the present invention, and then the real-time detection of the concentrated sulfurous gases using a gas sensor 13 located downstream of the gas flow path 11. Therefore, for example, by detecting low concentrations of sulfurous gases originating from agricultural products, the maturity and spoilage status of agricultural products can be determined in real time. This enables efficient cultivation, distribution, and storage of agricultural products, leading to a reduction in agricultural product losses.

[0050] [Additional Notes] The present invention is not limited to the embodiments described above, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention. [Explanation of symbols]

[0051] 10 Gas detection system 11 Gas flow path 111 Filter 112 Downstream end 113 Upstream end 114 Cylindrical member 115 Interior space 116 coils 117 Inlet 12 Chambers 13 Gas Sensor 14 pumps 15. First pressure sensor 16. Second pressure sensor 17 Power supply 18 Control Unit

Claims

1. A filter that selectively allows gas to pass through, A cylindrical member through which the gas that has passed through the filter passes, wherein the opening area at the downstream end is smaller than the opening area at the upstream end, A negative pressure generating device is provided downstream of the cylindrical member and sucks in the gas that has passed through the cylindrical member, The device comprises a coil positioned such that its axis is aligned with the axial direction of the cylindrical member and surrounds the cylindrical member. A gas flow path characterized by the following features.

2. The cylindrical member has an internal space that tapers smoothly from the upstream end to the downstream end. The gas flow path according to feature 1.

3. A filter that selectively permeates gas, A cylindrical member through which the gas that has passed through the filter passes, wherein the opening area at the downstream end is smaller than the opening area at the upstream end, A negative pressure generating device is provided downstream of the cylindrical member and sucks in the gas that has passed through the cylindrical member, The system includes a heating unit that raises the temperature of the filter to remove the gas adsorbed on the filter. A gas flow path characterized by the following features.

4. The shape of the tubular member is cylindrical, The coil is helical when viewed from a plan view in the axial direction of the coil. The cylindrical member and the coil are arranged coaxially. The gas flow path according to feature 1.

5. A filter that selectively permeates gas, A cylindrical member through which the gas that has passed through the filter passes, wherein the opening area at the downstream end is smaller than the opening area at the upstream end, The system includes a negative pressure generating device provided downstream of the cylindrical member, which sucks in the gas that has passed through the cylindrical member. gas passage, The aforementioned filter consists of a metal-organic structure in which metal ions are cross-linked three-dimensionally and periodically by organic ligands. The aforementioned organic ligand has an acidic or basic functional group. A gas flow path characterized by the following features.

6. The gas flow path described in claim 1, A chamber provided downstream of the aforementioned gas flow path, The chamber comprises a gas sensor, The negative pressure generating device is located downstream of the chamber and is a pump that exhausts the gas passage and the chamber. A gas detection system characterized by the following features.

7. A first pressure sensor and a second pressure sensor each detect a first pressure, which is the pressure inside the cylindrical member, and a second pressure, which is the pressure inside the chamber. A power supply that supplies drive current to the aforementioned coil, The system further comprises a control unit that determines the drive current according to the difference between the first pressure and the second pressure. The gas detection system according to claim 6, characterized in that it is as described above.

8. The control unit determines the drive current such that there is a positive correlation between the difference and the drive current. The gas detection system according to claim 7, characterized in that it is as described above.

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