Dust monitoring device

Abstract

Dust concentration of several tens of g / m³ 3 The present invention provides a dust sensor capable of reliably and easily measuring dust up to the high concentration range mentioned above. [Solution] The high-concentration dust sensor 10 is a sensor that measures the concentration of dust based on the strength of the signal of the amount of charge transfer generated when dust particles collide with or pass near the electrode portion 11, with an electrode portion 11 placed inside an induction duct 2 through which dust-containing air flows. The electrode portion 11 is an exposed electrode portion 12 that serves as a direct signal input for dust, and the periphery of this exposed electrode portion 12 is covered with an insulating electrode portion 13 as an insulating portion, with the tip of the exposed electrode portion 12 being flush with or slightly protruding from the tip of the insulating electrode portion 13.

Description

[Technical Field]

[0001] This invention relates to a dust concentration of, for example, several tens of g / m³. 3 This invention relates to a dust sensor for measuring dust concentrations up to the high concentration range described above, and a dust monitoring device equipped with the dust sensor. [Background technology]

[0002] Online dust meters (light scattering method, light transmission method, triboelectric method) specified by Japanese Industrial Standards (JIS) (JIS Z 8852, JIS B 7996, JIS B 7997-1, -2, -3) are generally suitable for low to medium concentrations of dust (0-1000 mg / m³). 3 It is used to measure dust concentrations that significantly exceed that level (for example, 30 g / m³). 3 It is considered difficult to automatically measure the above, and therefore, no product has been commercialized at present.

[0003] Conventionally, there is a high-concentration dust sensor, for example, described in Patent Document 1. This high-concentration dust sensor measures the dust concentration in a tunnel during excavation using a particulate detection sensor based on the light scattering method. This high-concentration dust sensor removes a portion of the dust (for example, relatively large diameter dust) in a primary dust removal space, then removes a portion of the dust (for example, relatively small diameter dust) again in a secondary dust removal space, and sets the dust concentration of the particulate-containing air to a low concentration (0-0.6 mg / m³) suitable for existing particulate detection sensors. 3 The particulate matter concentration is measured after reducing it to the following level. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Patent No. 7667576 [Overview of the project] [Problems that the invention aims to solve]

[0005] Incidentally, it is believed that one of the causes of fires and dust explosions in biomass power generation in recent years is that these dusts reach high concentrations (lower explosive limit), and for users, dust concentrations of several tens of g / m³ are considered to be high. 3 There is a need for a dust sensor capable of measuring such high concentrations of dust, and a monitoring device that has this dust sensor and can monitor it online.

[0006] Therefore, the present invention relates to a dust concentration of several tens of g / m³. 3 Dust that can reliably and easily measure up to the above high concentration range. monitoring device The purpose is to provide. [Means for solving the problem]

[0007] To achieve this objective, the method described in claim 1 invention This is a dust sensor in which an electrode is placed inside a duct through which air containing dust flows, and the concentration of the dust is measured based on the strength of the signal of the amount of charge transfer that occurs when dust particles collide with or pass near the electrode. Dust monitoring device equipped with And, The dust sensor The electrode portion is an exposed electrode portion that serves as a direct signal input for the dust, the periphery of the exposed electrode portion is covered with an insulating portion, and the tip of the exposed electrode portion is flush with the tip of the insulating portion or 0.1~5mm Outstanding Furthermore, the duct is provided with an air injection means for blowing away the dust adhering to the electrode portion by spraying air. It is characterized by having this feature.

[0008] Furthermore, the claim described in claim 2 invention The following is the claim described in claim 1. In addition to the configuration, the duct The system is characterized by the following features: an exhaust fan is connected to exhaust the air containing the dust inside the duct; the flow velocity of the air containing the dust inside the duct is measured by a flow meter; and the rotation speed of the exhaust fan is controlled by a fan controller based on the measurement result of the flow meter to keep the flow velocity of the air containing the dust constant.

[0010] Furthermore, claims 3 The invention described in the claim 1In addition to the configuration described above, the air injection means is disposed obliquely downward on the upstream side in the flow direction of the air containing the dust with respect to the electrode portion in the duct.

[0011] Also, according to the invention described in claim 4 In addition to the configuration described in claim 1 The air injection means is provided with an air injection port at its tip, and a check valve is provided at the air injection port.

[0012] Also, according to the invention described in claim 5 In addition to the configuration described in any one of claims 1 to 4 The dust sensor measures the dust concentration in a high concentration range where the dust concentration is several tens of g / m 3 or more.

Advantages of the Invention

[0013] According to the invention described in claim 1, the electrode portion is an exposed electrode portion that serves as a direct signal input for dust, and this exposed electrode portion has an insulated electrode portion that is covered with an insulating portion and serves as an indirect signal input. The periphery of the exposed electrode portion is covered with an insulating portion, and the tip of the exposed electrode portion is flush with or 0.1~5mm protrudes from the tip of the insulating portion, thereby restricting the input signal of frictional static electricity, and making it possible to reliably and easily measure dust in a high concentration range where the dust concentration is several tens of g / m 3 or more. Furthermore, according to the invention described in claim 1, since an air injection means for blowing away dust adhering to the electrode is provided inside the duct, it is possible to measure the dust concentration with high accuracy at all times.

[0014] Also, according to the invention described in claim 2, the flow rate of the air containing dust in the duct is measured by a flow meter, and based on the measurement result of this flow meter, the rotational speed of the exhaust fan is controlled by a fan controller to control the flow rate of the air containing dust to be constant, thereby obtaining stable measurement results even in an environment with a high concentration range where the dust concentration is several tens of g / m 3 or more.

[0016] Furthermore, claims 3 According to the invention described above, the air injection means is positioned diagonally downward and upstream of the flow direction of the dust-containing air relative to the electrode portion in the duct, thereby minimizing the effects of pressure loss and flow velocity in the duct caused by the air injection means.

[0017] Furthermore, claims 4 According to the invention described above, the air injection means is provided with an air injection port at its tip, and a check valve is provided at this air injection port. This prevents dust in the duct from entering the piping of the air injection means even when the pressure inside the duct exceeds the air injection pressure of the air injection means.

[0018] Furthermore, claims 5 According to the invention described above, the dust sensor is used when the dust concentration is several tens of g / m³ 3 By measuring dust concentrations in the high-concentration range described above, it becomes possible to reliably measure dust concentrations in that range. [Brief explanation of the drawing]

[0019] [Figure 1] This is a schematic perspective view showing the installed state of one embodiment of the dust monitoring device according to the present invention. [Figure 2] This is a plan view showing one embodiment of a dust monitoring device according to the present invention. [Figure 3] This is a longitudinal cross-sectional view of Figure 2. [Figure 4] Figure 3 is a perspective view showing the dust sensor. [Figure 5] This is an explanatory diagram showing the flow of dust and the control system in one embodiment of the dust monitoring device according to the present invention. [Figure 6] This is a block diagram showing the control system of one embodiment of a dust monitoring device according to the present invention. [Modes for carrying out the invention]

[0020] Embodiments of the present invention will be described in detail below with reference to the drawings.

[0021] [An embodiment of a dust monitoring device] Figure 1 is a schematic perspective view showing one embodiment of the dust monitoring device according to the present invention. Figure 2 is a plan view showing one embodiment of the dust monitoring device according to the present invention. Figure 3 is a longitudinal cross-sectional view of Figure 2. Figure 4 is a perspective view showing the dust sensor of Figure 3.

[0022] In the following embodiment, the dust concentration is several tens of g / m³. 3 An example of applying a high-concentration dust sensor for measuring dust concentrations in the high-concentration range described above, and a high-concentration dust monitoring device for monitoring the dust concentration in the high-concentration range described above, will be explained. Therefore, in this embodiment, the dust concentration in the high-concentration range is defined as several tens of g / m³. 3 This refers to the dust concentration mentioned above.

[0023] As shown in Figure 1, for example, a factory or equipment building 6 is installed on the ground 5, and the inside of this building 6 is a high-concentration dust area, such as a dust collection area where a dust collector (not shown) is installed, or an area where a shot blasting system is installed. The high-concentration dust monitoring device 1 of this embodiment measures the dust concentration in the high-concentration area inside the building 6.

[0024] Specifically, the high-concentration dust monitoring device 1 is installed on the vertical wall 7 of the building 6 at a position above a height H1. This height H1 is approximately 2m above the ground 5. An intake pipe 8 is provided on the vertical wall 7 above this height H1 to draw in air containing high concentrations of dust from inside the building 6, and this intake pipe 8 is connected to the induction duct 2 of the high-concentration dust monitoring device 1 shown in Figures 1 to 3.

[0025] The induction duct 2 introduces air containing high concentrations of dust from the high-concentration dust area, which is drawn in from the intake pipe 8. Specifically, the induction duct 2 is formed in a hollow cylindrical shape, with its interior serving as a passage for air containing high concentrations of dust. One end is provided with an intake port 2a for drawing in air containing high concentrations of dust, and the other end is provided with an exhaust port 2b connected to the induction fan 3.

[0026] An induction fan 3 is connected to the induction duct 2 to act as an exhaust fan, drawing in air containing high concentrations of dust from the high-concentration dust area. An exhaust duct 4 is connected to the induction fan 3 to exhaust the air containing high concentrations of dust drawn in by the induction fan 3.

[0027] The exhaust duct 4, like the induction duct 2, is formed in a hollow cylindrical shape, with an intake port 4a at one end connected to the induction fan 3, and an exhaust port 4b at the other end for exhausting air containing high concentrations of dust. An exhaust pipe 9 is connected to the exhaust port 4b of this exhaust duct 4, and air with a high concentration of dust measured by the high-concentration dust monitoring device 1 is returned to the building 6 through this exhaust pipe 9. The exhaust pipe 9 is installed at a height H1 of the vertical wall 7.

[0028] figure 2 and figure 3 As shown, a high-concentration dust sensor 10 is installed in the induction duct 2 near the intake port 2a. This high-concentration dust sensor 10 has a housing portion 10a made from die-cast aluminum, and an electrode portion 11 is attached to this housing portion 10a via a stainless steel socket portion 10b. This electrode portion 11 is formed to a length of, for example, 28 mm and is positioned in the airflow passage of the induction duct 2 that contains high-concentration dust.

[0029] The high-concentration dust sensor 10 of this embodiment is capable of detecting dust concentrations of several tens of g / m³. 3 This sensor is capable of measuring high concentrations of dust. The high-concentration dust sensor 10 uses the movement of electric charge generated when dust particles collide with or pass near the electrode section 11 as a signal, and the measurement principle is that this amount of movement is proportional to the dust concentration. The high-concentration dust sensor 10 has a built-in preamplifier, and the electric charge movement signal obtained by the electrode section 11 is input to this preamplifier and amplified.

[0030] The electrode portion 11 of the high-concentration dust sensor 10 includes an exposed electrode portion 12 that provides direct signal input to the high-concentration dust sensor 10, and an insulated electrode portion 13 that covers the exposed electrode portion 12 and provides indirect signal input to the high-concentration dust sensor 10.

[0031] The exposed electrode portion 12 is, for example, made of stainless steel in the shape of a cylinder with a diameter of 5 mm. The insulated electrode portion 13 is, for example, formed from a cylindrical polyacetal (POM), PTFE (polytetrafluoroethylene), or ceramics, with a diameter of 15 mm. The tip portion 12a of the exposed electrode portion 12 is formed to be flush with the tip portion 13a of the insulated electrode portion 13, or to protrude by a small amount, 0.1 to 5 mm, preferably 2 mm, beyond the tip portion 13a of the insulated electrode portion 13.

[0032] Therefore, the exposed electrode portion 12, which receives a direct signal input to the high-concentration dust sensor 10, has a significantly smaller surface area than the insulated electrode portion 13, which receives an indirect signal input to the high-concentration dust sensor 10, thereby severely limiting the input signal to the preamplifier. As a result, when the dust concentration reaches several tens of g / m³, 3 This makes it possible to measure dust at the above high concentrations.

[0033] Meanwhile, a flow meter 15 is installed near the exhaust port 2b of the induction duct 2. This flow meter 15 measures the flow velocity of the air containing high concentrations of dust circulating inside the induction duct 2.

[0034] As shown in Figure 3, an air injection unit 16 is provided inside the induction duct 2 as an air injection means. This air injection unit 16 blows air onto the dust adhering to the electrode portion 11 of the high-concentration dust sensor 10 to blow it away. This air injection unit 16 is positioned diagonally downward and upstream of the electrode portion 11 of the high-concentration dust sensor 10 in the direction of air flow containing high-concentration dust. By positioning the air injection unit 16 in this way, the effects of pressure loss and flow velocity within the induction duct 2 caused by the air injection unit 16 can be minimized.

[0035] The air injection unit 16 is equipped with an air injection port 17 at its tip, and a check valve 18 is provided at this air injection port 17. As a result, even if the pressure inside the induction duct 2 exceeds the air injection pressure of the air injection unit 16, the check valve 18 will close, preventing air containing a high concentration of dust from the induction duct 2 from entering the air injection unit 16.

[0036] Next, the control system of the high-concentration dust monitoring device 1 of this embodiment will be described based on Figures 5 and 6. Figure 5 is an explanatory diagram showing the dust flow and control system in one embodiment of the dust monitoring device according to the present invention. Figure 6 is a block diagram showing the control system in one embodiment of the dust monitoring device according to the present invention.

[0037] As shown in Figures 5 and 6, air containing high concentrations of dust generated in the high-concentration dust area inside building 6 is drawn to the normal area of ​​the outdoor vertical wall 7, where the dust concentration is measured through a sensor unit 20 (described later). After this air containing high concentrations of dust, whose dust concentration has been measured, is returned to, for example, the high-concentration dust area inside building 6.

[0038] In the normal area, a sensor unit 20 is provided, which includes a high-concentration dust sensor 10, a flow meter 15, an induction fan 3, and an air injection unit 16. The high-concentration dust sensor 10 of this sensor unit 20 measures the high-concentration dust drawn into the induction duct 2, and the flow velocity of the air containing the high-concentration dust is measured by the flow meter 15 and exhausted into the exhaust duct 4.

[0039] The sensor unit 20 is electrically connected to the control unit 21. The control unit 21 is installed at a height H2 of the vertical wall 7, as shown in Figure 1. This height H2 is set to, for example, the eye level of a worker of average height. Inside the control unit 21 are a fan controller 22, a sensor-dedicated converter 23, and an AC / DC converter 24. AC voltage is applied to the sensor-dedicated converter 23 and the AC / DC converter 24 from an AC power supply 25. The AC voltage applied from the AC power supply 25 is applied directly to the sensor-dedicated converter 23, while the fan controller 22 is supplied with a DC current that has been converted to a DC current via the AC / DC converter 24. The sensor-dedicated converter 23 further amplifies the signal measured by the high-concentration dust sensor 10, and this signal is output to the control unit 26, which will be described later.

[0040] The flow velocity of the air containing high concentrations of dust in the induction duct 2 is measured by the flowmeter 15, and a signal indicating the measurement result from the flowmeter 15 is output to the fan controller 22 as shown in Figure 6. The fan controller 22 controls the flow velocity of the air containing high concentrations of dust circulating in the induction duct 2 to be constant by outputting a control signal that controls the rotation speed (rpm) of the induction fan 3 based on the signal indicating the measurement result.

[0041] The sensor-dedicated converter 23 of the control unit 21 is electrically connected to the control unit 26, which serves as a control means. This control unit 26 includes a determination unit 27 and a timer 28. The determination unit 27 determines whether the signal of the high concentration of dust captured by the sensor-dedicated converter 23 exceeds a preset threshold. This threshold is set, for example, to the concentration before it reaches a high concentration state (lower explosive limit).

[0042] The control unit 26 outputs a signal indicating a high concentration of dust to the display unit 30, and the high concentration of dust is displayed in the dust amount display unit 31 within the display unit 30. As shown in Figure 1, the control unit 26 and the display unit 30 are arranged at a height H2 of the vertical wall 7, similar to the control unit 21. When the determination unit 27 determines that the signal for the high concentration of dust exceeds a preset threshold, the alarm display unit 32 displays an alarm. Specifically, the alarm display unit 32 displays an image to that effect on a display unit such as a display, lights up or flashes an indicator such as a lamp or LED to indicate an abnormal condition, or emits a sound from an audio generator such as a horn, bell, or buzzer to indicate an alarm. Therefore, the alarm display of the alarm display unit 32 in this embodiment includes image display or alarm display.

[0043] The control unit 26 has a timer 28 as described above, and outputs an operation signal to the air injection unit 16 at a preset time interval, for example, once every few minutes. The air injection unit 16 receives this operation signal and operates by injecting air once every few minutes to blow away dust adhering to the electrode unit 11.

[0044] Next, the operation of the high-concentration dust sensor 10 of this embodiment will be explained.

[0045] As shown in Figure 4, the high-concentration dust sensor 10 limits the input signal to the preamplifier through the structure of the electrode section 11, which is optimally designed to include an exposed electrode section 12 that receives a direct signal input and an insulated electrode section 13 covered by an insulating section that generates an indirect signal input. Here, the input signal of triboelectric static electricity is affected by the width of the surface area of ​​the electrode section 11. In this embodiment, this phenomenon is utilized, and the input signal is reduced by intentionally configuring the electrode section 11 to have a narrow surface area.

[0046] Specifically, the diameter of the exposed electrode portion 12 is set to, for example, 5 mm, the length of the insulated electrode portion 13 is set to, for example, 26 mm and the diameter to 15 mm, and the tip portion 12a of the exposed electrode portion 12 is formed to protrude only 2 mm more than the tip portion 13a of the insulated electrode portion 13. By making the surface area of ​​the exposed electrode portion 12 as small as possible compared to the surface area of ​​the insulated electrode portion 13, the input signal to the preamplifier is significantly limited. As a result, in this embodiment, the dust concentration is several tens of g / m³. 3 This makes it possible to measure dust concentrations in the high-concentration range described above.

[0047] As mentioned above, the input signal of triboelectric static electricity is affected by the surface area of ​​the electrode. In this embodiment, this phenomenon is utilized, and the input signal is made extremely small by intentionally forming the exposed electrode portion 12 to have a narrow surface area.

[0048] Furthermore, in this embodiment, by reducing the diameter of the exposed electrode portion 12, it becomes possible to form a thicker insulating portion of the insulated electrode portion 13, thereby keeping the input signal from the insulated electrode portion 13, which is an indirect input signal, to a minimum.

[0049] Next, the operation of the high-concentration dust monitoring device 1 of this embodiment will be explained.

[0050] By driving the induced draft fan 3, air containing high concentrations of dust is drawn from the high-concentration dust area inside building 6 through the intake pipe 8 and the intake port 2a of the induced draft duct 2 into the normal area. This air then flows through the flow path of the induced draft duct 2, passes through the exhaust port 2b and the induced draft fan 3, flows through the intake port 4a of the exhaust draft duct 4, and is exhausted from the exhaust port 4b through the exhaust pipe 9 back into the high-concentration dust area inside building 6.

[0051] The electrode section 11 of the high-concentration dust sensor 10 is installed in the flow passage of the induction duct 2, along with a flow meter 15 and an air injection section 16.

[0052] The frictional electrostatic method applied in this embodiment cannot obtain a signal without a flow of air containing a high concentration of dust, which is a fluid. Furthermore, the signal obtained is affected by changes in the flow velocity of the air containing the high concentration of dust, so the flow velocity must be kept constant.

[0053] On the other hand, when the dust concentration becomes high, a certain flow rate is required to ensure that the dust flows through the induction duct 2 without settling. Since the applicable range differs depending on the type of dust, the flow rate of air containing high concentrations of dust must be controllable as needed.

[0054] Therefore, in this embodiment, the flow velocity of the air containing high-concentration dust in the induction duct 2 is constantly measured by the flowmeter 15, and a signal indicating the flow velocity is output to the fan controller 22. By feeding back the control signal from this fan controller 22 to the induction fan 3, the rotation speed of the induction fan 3 is controlled, and the flow velocity in the induction duct 2 is always kept constant. As a result, even in a high-concentration dust environment, it is possible to stably measure the dust concentration regardless of the type of dust.

[0055] Furthermore, when measuring the amount of dust in a high-concentration dust environment, it is anticipated that the adhesion of high-concentration dust to the electrode section 11 will be a problem. In this embodiment, an air injection section 16 is provided to solve this problem.

[0056] The control unit 26 outputs an operation signal to the air injection unit 16 at a preset interval, such as once every few minutes. This operation signal activates the air injection unit 16, causing it to inject air from the air nozzle 17 to blow away dust adhering to the electrode unit 11.

[0057] Here, the air nozzle 17 of the air injection unit 16 is positioned diagonally within the induction duct from upstream of the high-concentration dust sensor 10. This effectively removes dust from the electrode unit 11 and minimizes the effects of pressure loss and flow velocity within the induction duct 2 caused by the installation of the air injection unit 16.

[0058] Furthermore, if the pressure inside the induction duct 2 exceeds the pressure of the air flowing through the piping of the air injection unit 16, air containing a high concentration of dust may flow into the piping of the air injection unit 16, potentially clogging the piping.

[0059] Therefore, in this embodiment, a check valve 18 is provided at the air injection port 17 to prevent dust in the induction duct 2 from flowing back into the piping of the air injection unit 16, even if the pressure in the induction duct 2 exceeds the air injection pressure.

[0060] Thus, according to this embodiment, the electrode portion 11 has an exposed electrode portion 12 that receives a direct signal input of dust, and an insulated electrode portion 13 that receives an indirect signal input by covering the exposed electrode portion 12 with an insulating portion. The tip portion 12a of the exposed electrode portion 12 is formed to protrude slightly more than the tip portion 13a of the insulated electrode portion 13, thereby limiting the input signal of triboelectric static electricity, and reducing the dust concentration to several tens of g / m³. 3 This makes it possible to reliably and easily measure dust up to the high concentration ranges mentioned above.

[0061] Furthermore, according to this embodiment, the flow velocity of the dust-containing air in the induction duct 2 is measured by the flowmeter 15, and the rotation speed of the induction fan 3 is controlled by the fan controller 22 based on the measurement result of the flowmeter 15 to keep the flow velocity of the air containing high concentration of dust constant, thereby reducing the dust concentration to several tens of g / m³. 3 Stable measurement results can be obtained even in environments with the high concentrations mentioned above.

[0062] Furthermore, according to this embodiment, since an air injection unit 16 is provided inside the induction duct 2 to blow away dust adhering to the electrode unit 11 by spraying air, it is possible to measure the dust concentration with high accuracy at all times.

[0063] Furthermore, according to this embodiment, the air injection unit 16 is positioned diagonally downward and upstream of the electrode unit 11 in the induction duct 2 in the direction of air flow containing dust, thereby minimizing the effects of the air injection unit 16 on pressure loss and flow velocity within the induction duct 2.

[0064] Furthermore, according to this embodiment, the air injection unit 16 is provided with an air injection port 17 at its tip, and a check valve 18 is provided at this air injection port 17. This prevents dust from entering the piping of the air injection unit 16 even when the pressure inside the induction duct 2 exceeds the air injection pressure of the air injection unit 16.

[0065] Furthermore, according to this embodiment, the high-concentration dust sensor 10 is used when the dust concentration is several tens of g / m³. 3 By measuring dust concentrations in the high-concentration range described above, it becomes possible to reliably measure dust concentrations in that range.

[0066] [Other embodiments] Although one embodiment of the invention has been described, this embodiment is presented as an example and is not intended to limit the scope of the invention. This embodiment can be carried out in various other forms, and various omissions, substitutions, modifications, and combinations can be made without departing from the spirit of the invention. This embodiment and its variations are included in the scope and spirit of the invention, as well as in the claims and their equivalents.

[0067] For example, in the embodiment described above, the high-concentration dust sensor 10 detects that the dust concentration is several tens of g / m³. 3 The above examples illustrate how to measure dust concentrations in the high-concentration range, but this is not limited to such high-concentration ranges; it also applies to low to medium concentration dust (0-1000 mg / m³).3 It is also possible to measure the concentration of ).

[0068] Furthermore, in the above embodiment, an example was described in which the tip portion 12a of the exposed electrode portion 12 protrudes only 0 to 5 mm, preferably 2 mm, from the tip portion 13a of the insulated electrode portion 13. However, the length is not limited to this, and can be appropriately set according to, for example, the particle size and type of dust. In short, it is sufficient to make it protrude only slightly to reduce the surface area of ​​the exposed electrode portion 12. [Explanation of Symbols]

[0069] 1 High concentration dust monitoring device (dust monitoring device) 2. Induction duct (duct) 2a Intake 2b Exhaust port 3. Induced draft fan (exhaust fan) 4 Exhaust duct 4a Air intake 4b Exhaust port 5 Ground 6 buildings 7 Vertical wall 8. Intake pipe 9 Exhaust pipe 10. High-concentration dust sensor (dust sensor) 10a Housing section 10b Socket section 11 Electrode part 12 Exposed electrode part 12a Tip 13. Insulated electrode section (insulating section) 13a Tip 15 Current meter 16. Air injection unit (air injection means) 17 Air nozzles 18. Check valve 20 Sensor Units 21 Control Unit 22 Fan Controller 23 Sensor-specific converter 24 AC / DC Converters 25 AC power supply 26 Control Unit (Control Means) 27 Judgment section 28 Timer 30 Display section 31 Dust amount display section 32 Alarm display section

Claims

1. A dust monitoring device comprising a dust sensor that measures the concentration of dust based on the strength of a signal representing the amount of charge transfer generated when dust particles collide with or pass near the electrode, wherein an electrode is placed inside a duct through which dust-containing air flows, The electrode portion of the dust sensor is an exposed electrode portion that receives a direct signal input of the dust, the periphery of the exposed electrode portion is covered with an insulating portion, and the tip of the exposed electrode portion is flush with the tip of the insulating portion or protrudes by 0.1 to 5 mm. A dust monitoring device characterized in that an air injection means is provided inside the duct for blowing away the dust adhering to the electrode part by spraying air.

2. An exhaust fan is connected to the duct for exhausting the air containing the dust, The flow velocity of the air containing the dust in the duct is measured by a flow meter. The dust monitoring device according to claim 1, characterized in that the rotation speed of the exhaust fan is controlled by a fan controller based on the measurement results of the flow meter to keep the flow velocity of the dust-containing air constant.

3. The dust monitoring device according to claim 1, characterized in that the air injection means is disposed diagonally downward and upstream of the flow direction of the air containing the dust with respect to the electrode portion in the duct.

4. The dust monitoring device according to claim 1, characterized in that the air injection means is provided with an air injection port at its tip and a check valve is provided at the air injection port.

5. The dust monitoring device according to any one of claims 1 to 4, characterized in that the dust sensor measures the dust concentration in a high-concentration range where the dust concentration is several tens of g / m³ or more.

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