JP2000097909A - Dust monitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a dust monitor which can reduce the costs for purchasing a flow velocity sensor and for setup man-hours, and little in error in measurement while preventing a probe from being deformed when the probe is set horizontally at a high-temperature flow passage. SOLUTION: In the dust monitor, a probe 1 is inserted into a gas flowing a flow passage, a frictional electricity generated when dusts included in the gas collide with the surface of the probe 1 is detected, and the concentration change of dusts in the gas is detected. In this case, a means for measuring a flow velocity of the gas is added to the probe 1. Moreover, a material of the probe 1 is a conductive ceramic, or an insulating ceramic which is covered with a conductive metal thereover.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dust monitor for detecting a change in the amount of dust contained in a gas, and more particularly to a dust monitor in which a flow rate measuring means is added to a flow forming the dust monitor.

[0002]

2. Description of the Related Art Conventionally, an optical type is used as a means for measuring the amount of dust (particles) in a flue (chimney) of a thermal power plant, a dust collecting device in a cement plant, a powder transferring device, and the like. Have been. However, in the optical system, since light is transmitted and received through a transparent window, there is a problem such as a short maintenance cycle for maintaining the transparency of the window.

[0003] In recent years, gas (air) has been used as an alternative.
A method has been developed in which a probe having conductivity is inserted into the flow path of the probe to detect static electricity generated when particles (dust) contained in gas collide with the probe, and the probe 1 and the converter 2 shown in FIG. A dust monitor 10 is commercially available.

[0004]

In such a probe system, a constant flow rate is required as a measurement condition.
Output correction according to the change in flow velocity is required. for that reason,
As shown in FIG. 6, the dust monitor 10 attached to the flow path 11
Is provided near (upstream or downstream), and the output of the current monitor 12 is used to correct the output of the dust monitor 10. I was

[0005] However, the provision of a separate current meter increases the cost due to the purchase of the current meter and the number of installation steps, and also requires consideration of the installation location. When the probe is installed in a flue or the like, for example, it is required to have oxidation resistance as well as conductivity because it becomes a high-temperature, oxidizing atmosphere, and a special metal such as an expensive superalloy, Hastelloy, or Inconel is used as a material for the probe. Needed.

Further, when the probe is mounted horizontally on a vertical flue, if the temperature of the gas is high (hundreds of degrees), permanent deformation due to heat and its own weight occurs, making it impossible to remove the dust monitor or causing errors in the output. There was a problem that occurred. SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and provides a dust monitor which can suppress the cost increase by separately installing a current meter and reduce a measurement error when a probe is horizontally mounted in a high-temperature gas. With the goal.

[0007]

In order to achieve the above object, according to the present invention, a probe is inserted into a gas flowing through a flow path, and dust contained in the gas is removed from the surface of the probe. In a dust monitor for detecting a change in the concentration of dust in a gas by detecting triboelectricity generated by colliding with a gas, a flow velocity measuring means for measuring a gas flow velocity is added to the probe.

According to a second aspect of the present invention, in the dust monitor according to the first aspect, the flow velocity is measured by detecting a deflection of the probe caused by the Karman vortex. According to a third aspect of the present invention, in the dust monitor according to the second aspect, the deflection is detected by a strain detecting element provided near the base of the probe.

According to a fourth aspect of the present invention, in the dust monitor according to the second aspect, the flow rate measurement is performed by detecting a pressure change around the probe caused by the Karman vortex. According to a fifth aspect of the present invention, in the dust monitor according to the fourth aspect, the pressure change is detected by a pressure-sensitive element or a pressure sensor provided in the middle of the probe.

According to a sixth aspect of the present invention, in the dust monitor according to the fifth aspect, the pressure sensitive elements are provided on two opposing surfaces to detect a differential pressure. In claim 7, the probe is inserted into the gas flowing through the flow path, and the change in the concentration of the dust in the gas is detected by detecting the triboelectricity generated by the dust contained in the gas colliding with the surface of the probe. In the dust monitor, ceramic is used as the probe.

According to an eighth aspect of the present invention, in the dust monitor according to the seventh aspect, a conductive ceramic is used as the probe. According to a ninth aspect of the present invention, in the dust monitor according to the seventh aspect, an insulating ceramic is used as the probe and the surface is coated with a conductive metal.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. FIG. 1 shows an example of an embodiment according to claims 1 to 3 of the present invention, wherein a probe 1 of a dust monitor is inserted into a flow path (not shown), and a gas containing dust from the front to the rear of the figure. Is flowing. In that case, the dust monitor measures the amount of dust contained in the gas according to the specification. At the same time, a Karman vortex corresponding to the gas flow velocity is generated behind the probe, and the probe 1 is alternately subjected to a force in a direction indicated by an arrow A generated by the Karman vortex.

A strain detecting element 3, such as a strain gauge or a piezoelectric ceramic, is attached near the base of the probe 1, and converts forces alternately generated by Karman vortices into electric signals and outputs them as frequencies.

It is known that the following relationship is established between the frequency F and the flow velocity V. F = St.V / d St: Strouhal number (proportional constant) d: Electrode diameter This frequency signal is processed by a known processing method and used as a correction signal of the dust monitor output. Note that the strain detecting element 3 is provided so as to face the vicinity of the root having the largest deflection.

FIG. 2 shows an example of an embodiment according to claims 4 to 6 of the present invention. Here, for example, a known pressure-sensitive element or a diaphragm type pressure sensor 4 is provided in the middle of the probe shown in FIG. , 4a. Also in this example, the gas flows from the front to the rear, and a Karman vortex is generated behind the probe. Probe 1 receives force alternately in the direction shown by arrow A by Karman vortex,
Here, the pressure generated around the two sensors 4, 4a
, And differentially detected.

A signal corresponding to the pressure obtained by the two sensors 4 and 4a is converted into a frequency signal, processed by a known processing method as described above, and used as a correction signal of the dust monitor output.

FIG. 3 shows an example of an embodiment according to claim 7 of the present invention. In this example, the probe is made of a conductive ceramic 1a such as silicon carbide (SiC).
It is formed by.

FIGS. 4 and 5 show an example of an embodiment according to claim 8 of the present invention. In the embodiment shown in FIG. 4, a probe is formed of an insulating ceramic 1b, and the probe is formed on its surface by vapor deposition or the like. The method shown in FIG. 5 in which the conductive metal 1c is adhered by the above method is a probe formed of an insulating ceramic 1b, and a conductive metal pipe 1d is put thereon.

As shown in FIGS. 3 to 5, the probe itself is made of conductive ceramic, or the main body of the probe is made of insulating ceramic, and the probe is covered with metal to provide a probe resistant to high temperatures. As a result, it is possible to realize a probe that is less likely to be deformed by its own weight even when a probe mounted horizontally in a vertical flow path is exposed to high temperatures.

The foregoing description of the present invention has been presented by way of illustration and example only of certain preferred embodiments. Accordingly, the present invention is subject to many modifications, without departing from its essence,
It will be apparent to those skilled in the art that variations can be made. The scope of the present invention defined by the description in the claims section is intended to cover alterations and modifications within the scope.

[0021]

As described above, according to the present invention, a probe is inserted into a gas flowing through a flow path, and triboelectricity generated by collision of dust contained in the gas with the surface of the probe is detected. In a dust monitor that detects a change in the concentration of dust in gas, a means for measuring the gas flow velocity is added to the probe, so that it is possible to reduce the cost of purchasing and installing a current meter, Since the material is made of conductive ceramic or the probe is made of insulating ceramic and covered with conductive metal, it is possible to prevent the deformation of the probe that occurs when it is installed horizontally in a flue, etc. It is possible to realize a small dust monitor.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an example of an embodiment of a dust monitor according to the present invention.

FIG. 2 is an explanatory view showing another embodiment according to the present invention.

FIG. 3 is an explanatory view showing another embodiment according to the present invention.

FIG. 4 is an explanatory diagram showing another embodiment according to the present invention.

FIG. 5 is an explanatory view showing another embodiment according to the present invention.

FIG. 6 is a configuration explanatory view showing a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Probe 2 Transducer 3 Pressure sensitive element 4 Pressure sensor 10 Dust monitor 11 Flow path 12 Current meter

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Mitsuhiko Sasaki 2-9-132 Nakamachi, Musashino City, Tokyo Inside Yokogawa Electric Corporation

Claims (9)

[Claims] A probe is inserted into a gas flowing through a flow path,
In a dust monitor that detects a change in the concentration of dust in a gas by detecting triboelectricity caused by dust contained in the gas colliding with the surface of the probe, a flow velocity measuring means for measuring the flow velocity of the gas is added to the probe. Dust monitor characterized by: 2. The dust monitor according to claim 1, wherein the flow velocity measurement is performed by detecting a deflection of the probe caused by the Karman vortex. 3. The dust monitor according to claim 2, wherein the deflection is detected by a strain detecting element provided near a root of the probe. 4. The dust monitor according to claim 1, wherein the flow rate measurement is performed by detecting a pressure change around the probe caused by the Karman vortex. 5. The dust monitor according to claim 4, wherein the pressure change is detected by a pressure-sensitive element or a pressure sensor provided in the middle of the probe. 6. The dust monitor according to claim 5, wherein the pressure-sensitive elements are provided on two opposing surfaces to detect a differential pressure. 7. A probe is inserted into a gas flowing through a flow path,
A dust monitor in which a ceramic is used as the probe in a dust monitor for detecting a change in the concentration of dust in a gas by detecting triboelectricity generated by dust contained in a gas colliding with the surface of the probe. . 8. The dust monitor according to claim 7, wherein a conductive ceramic is used as said probe. 9. The dust monitor according to claim 7, wherein an insulating ceramic is used as said probe and the surface is covered with a conductive metal.