JP2002365263A - Concentration detector for powdery particulate material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stable and highly sensitive concentration detector at the time of detection of the concentration of a powdery particulate material in a duct. SOLUTION: The concentration detector for the powdery particulate material has a detection probe 10 having a main electrode 11 of which the induction charge is changed by the approach of the charged powdery particulate material and an earth electrode 3 for surrounding the root part of the main electrode 11, a signal detector 20 for detecting the induction charge which is detected by the main electrode 11 of the detection probe 10 as an AC current signal, and a control unit 22 having an operation part 24 for operating the concentration of the powdery particulate material from the output signal of the signal detector 20. The insulator 12 of the detection probe 10 has a monolithically molded structure not only to surround the main electrode 11 and the earth electrode 13 but also to protect the earth electrode 13 from humidity in the duct. The stable detection of concentration over a long period of time is possible.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for detecting the concentration of a granular material, and more particularly, to a charged granular material (powder, granular material, or powder) flowing in a fluid flowing in a duct. The present invention relates to an apparatus for detecting the concentration of a granular material, which is suitably used for detecting the concentration of a mixture of a body and a granular material.

[0002]

2. Description of the Related Art As a detection device for detecting the concentration of a granular material flowing in a duct, a light transmission type detection device and a charge amount type detection device are conventionally known. The charge amount type detection device has the condition that the powder is charged, but has a simple structure, easy installation, and easy maintenance of the detector body compared to the light transmission type. It has various advantages such as One of the joint applicants of the present application is:
In Japanese Patent Application No. 2000-204589, a new type of charge type detection device has already been filed.

FIG. 5 is a schematic structural view showing the principle of a detection device according to an embodiment of the above-mentioned prior application. The detection device includes a detector main body (detection probe) 10 disposed in a target duct 30 and an induced charge q induced to a main electrode 11 of the detector main body 10 by a powdery material 31 charged to a positive polarity.
It has a detection unit 20 for detecting a change in (t) as a current signal i (t), and a control unit 22 for calculating the concentration of the granular material in the air flow based on the detection result of the detection unit 20. The detector main body 10 includes a main electrode 11 entirely covered with an insulator 12 and a ground electrode 13 that covers a root portion of the main electrode 11 adjacent to a mounting portion of the detector main body 10 with the duct 30 and electrostatically shields the base electrode 11. And One end of the main electrode 11 is connected to an inversion terminal of an operation amplifier 21 constituting the detection unit 20, and a non-inversion terminal of the operation amplifier 21 is grounded. The output terminal of the operation amplifier 21 is connected to its inverting terminal via a resistor R.

[0004] The control unit 22 includes a signal processing section 23 having a band-pass filter and a signal processing section 2.
3 is configured by an operation unit 24 that performs an operation based on the output of No. 3. From the voltage signal V (t) output from the detection unit 20, only an AC component having a predetermined frequency component is extracted in the signal processing unit 23, and the density of the granular material is calculated from the amplitude value of the extracted signal component. I do. The present concentration detector is superior in maintainability, sensitivity and reliability as compared with the light transmission type detector.

[0005]

The concentration of carbon in the carbon waste gas discharged from the carbon black producing apparatus was actually detected by using the above-mentioned apparatus for detecting the concentration of granular material. Since the carbon waste gas flowing in the duct 30 is a gas having a considerably high temperature and high humidity, it is cooled in the vicinity of the detector main body 10 and becomes a drain to wet the surface of the detector main body 10. Therefore, shortly after the start of use, the surface of the insulator 12 of the detector main body 10 became conductive due to moisture attached thereto, and the moisture came into electrical contact with the ground electrode 13. Due to this contact, almost the entire length of the detector main body 10 in the longitudinal direction is in a state equivalent to being shielded by the ground electrode 13, and the shielding lowers the sensitivity of the detector. In addition, since the conductive powder or the like adheres to the surface of the detector main body 10 and makes electrical contact with the ground electrode 13, the portion is in a state equivalent to being shielded by the ground electrode 13. The sensitivity sometimes decreased.

SUMMARY OF THE INVENTION In view of the above, the present invention provides a charge amount type concentration detecting device which has stable detection sensitivity even in an environment of high humidity and is capable of detecting the concentration of a granular material with high accuracy. With the goal.

[0007]

In order to achieve the above object, the present invention provides a concentration detecting device for detecting the concentration of charged powder flowing in a duct. A main electrode, a ground electrode surrounding a portion excluding a tip of the main electrode, and insulating between the main electrode and the ground electrode, and A detector main body having an insulator covering the ground electrode, a detecting unit for detecting a change in induced charge induced in the main electrode by the charged granular material, and a granular material based on a detection result of the detecting unit. A calculation unit for calculating the concentration,
The insulator is characterized in that at least a portion protruding into the duct is integrally formed.

[0008] According to the apparatus for detecting the concentration of a granular material of the present invention,
By adopting a structure in which the main electrode and the ground electrode are insulated and the insulator covering the ground electrode is integrally molded, even in an environment where the humidity is high and the conductive powder fluid easily adheres The main electrode and the ground electrode are not affected by moisture, adhesion of conductive powder fluid, and the like. For this reason, the present concentration detection device has stable detection sensitivity and can perform concentration detection with high accuracy.

The detector body of the concentration detecting device of the present invention is not limited to a specific environment, but can be used in any environment as long as the insulator and the electrode function.
The term “duct” used in the present invention may be of any shape and material as long as it forms a flow path for flowing a fluid containing a granular material. Or a circular one also called a pipe. The granular material includes a granular material, a powder, and a mixture of the granular material and the powder. The main electrode and the ground electrode may be made of any material having conductivity, such as a metal material such as stainless steel, copper, or aluminum. As the insulator, an insulator having an appropriate material is selected depending on its use environment. Under high temperature environment,
Preferably, a ceramic material is used, and in a corrosive environment, a material that is resistant to corrosion is selected. The polarity of the charge of the powder may be either positive polarity or negative polarity.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail with reference to the drawings based on embodiments of the present invention. In addition,
In each figure, similar elements are given the same numbers. FIG.
FIG. 1 is a schematic cross-sectional view showing a configuration of a granular material concentration detection device according to an embodiment of the present invention. The concentration detector is
A detector main body (detection probe) 10 disposed in the target duct 30 and a detection probe 10
A signal detector 20 for detecting a time change of the induced charge q (t) induced in the main electrode 11 as a current signal i (t),
A control unit 22 for calculating the concentration of the granular material based on the detection result of the signal detection unit 20. The detection probe 10 has a main electrode 11 entirely covered by an insulator 12 and a ground electrode 13 that covers the base of the main electrode 11 adjacent to the duct mounting portion 32 of the detector probe 10 and electrostatically shields it. . One end of the main electrode 11 is
0, which is electrically connected to the inverting terminal of the operational amplifier 21, the non-inverting terminal of the operational amplifier 21 is electrically grounded, and the output terminal of the operational amplifier 21 is connected to its inverting terminal via a resistor R. ing.

FIG. 2 shows the charge amount q (t) charged on the main electrode 11 of the detection probe 10 and the input signal i (t) and the output signal V of the detection section in the concentration detection device according to the above embodiment. It is a signal timing chart which shows (t). When dust particles (carbon particles) 31 having a positive charge and flowing in the duct 30 approach the detection probe 10, as shown in FIG. Electric charge q (t) is generated. The induced charge q (t) gradually increases from zero as the charged particles 31 approach the detection probe 10, and the detection probe 1
It reaches a maximum when approaching zero most, and thereafter decreases and becomes zero as the charged particles 31 move away.

As shown in FIG. 1, the induced charge q (t) flows from the detection probe 10 to the output terminal side of the operation amplifier 21 via the feedback resistor R of the operation amplifier 21 of the signal detector 20. i (t). As shown in FIG. 2B, the current i (t) is a pulse-shaped current whose polarity is inverted when the negatively induced charge q (t) is maximized. The signal detection unit 20
The potential generated at the inverting terminal by the outflow current i (t) is compared with the ground potential to generate an output voltage V (t) (FIG. 2 (c)). The output voltage V (t) has a polarity opposite to that of the current i (t), and has a pulse-like waveform whose polarity is inverted when the induced charge q (t) is maximized. The amplitude of the output voltage V (t) depends on the concentration of the charged particles.

The control unit 22 includes a signal processing unit 23 having a band-pass filter and a signal processing unit 2.
3 is configured by an operation unit 24 that performs an operation based on the output of No. 3. From the output voltage V (t) of the signal detection unit 20, only an AC component having a predetermined frequency component is extracted in the signal processing unit 23, and the calculation unit 24 determines the amplitude of the extracted signal component from the amplitude value of the extracted signal component. Calculate the density.

FIG. 3 is a sectional view showing details of the detection probe 10 in a state where the detection probe 10 is attached to the duct 30. Main electrode 11
Is a stainless steel round bar having a diameter of about 12 mm, on which a Teflon (registered trademark) cylinder 12 having a thickness of about 4 to 6 mm covers. Detection probe 1
0 is a mounting boss 32 mounted on the wall of the duct 30
From the duct 30. The root portion of the detection probe 10 is in the mounting boss 32 and is not directly in contact with the uniform air flow passing through the duct 30 but is affected by the suspended suspended particles. For this reason, this root portion is surrounded by a ground electrode 13 made of a stainless steel plate having a thickness of about 1 mm. Thus, the induced charge q (t) generated in the main electrode 11 accurately reflects the charge of the charged particles 31 flowing uniformly in the duct 30. The ground electrode 13 is integrally embedded in a Teflon tube 12, and the detection probe 10 is manufactured by inserting the main electrode 11 into the Teflon tube 12.

The end of the Teflon tube 12 and the tube portion are integrally formed so that moisture in the duct 30 does not enter the inside of the detection probe 10 exposed in the duct 30. Thereby, good insulation is obtained for both the main electrode 11 and the ground electrode 13, and good detection sensitivity is maintained for a long time.

FIG. 4 shows a modification of the detection probe 10 described above. In the tenth modification, after the main electrode 11 and the ground electrode 13 are fixed in a predetermined arrangement, the insulating portion 12 is integrally formed by an extrusion method. The root portion of the detection probe 10 has a larger diameter than the tip portion.
For example, the detection probe 10 of this modified example includes a main electrode 11
Is 12 mm, the outer diameter of the ground electrode 13 is 20 mm, and the diameter of the insulator 12 is 20 mm at the tip and 28 mm at the root.

The concentration detecting device according to the present invention is a so-called A
It is called a C tribo-type concentration detector. In the AC tribo-type concentration detection device, the detection unit detects the movement of induced charge generated in the main electrode due to electrostatic induction of charged particles. According to this method, compared to the so-called DC tribo-type concentration detection device that detects the electrostatic charge generated by the collision of the charged particles with the main electrode, the measurement range is wider, the resolution is higher, and the flow velocity in a wider range is supported. It has the advantages that it can be performed, is excellent in maintainability, and does not require periodic air purging.

The concentration detecting device according to the above embodiment is used for detecting the concentration of the particulate matter in the waste gas of the carbon black producing device, and the concentration detecting device according to the prior application and the light transmitting type concentration detecting device are used. The results were compared with the detection results. In the comparison, a correlation table was used between the concentration detection unit mg / Nm ³ employed by the tribo-type concentration detector of the present application and the prior application and the Ringerman concentration employed by the light transmission type concentration detector. The correlation table shows the diameter of the duct (in this case, diameter 9
50 mm).

The AC tribo-type concentration detecting device of the present invention and the prior application have a light transmitting type concentration detecting device whose measurement range is at most 2.5 to 1000 mg / Nm ³ ,
It had a wide measurement range and 0.02~1000mg / Nm ^3. In addition, the measurement sensitivity of the optical transmission type concentration detector is 0.02 mg / Nm ³ compared to 0.2 mg / Nm ^3.
Met. Further, the concentration detection device of the prior application, due to moisture attached to the surface of the insulator, the detection sensitivity was reduced several days after the start of measurement, but the concentration detection device of the above embodiment, several months after the start of measurement Also have good sensitivity.

In the above embodiment, an example of detecting the concentration of carbon particles in the waste gas of carbon black has been described. However, the apparatus for detecting the concentration of particulate matter according to the present invention is not limited to any gas or fluid flowing through the duct. Or, for powders,
The density of the charged powder can be detected. In particular, it is suitable for detecting the concentration of moisture-containing powdery granules.

As described above, the present invention has been described based on a preferred embodiment thereof.
It is not limited only to the configuration of the above embodiment,
Various modifications and changes from the configuration of the above embodiment are also included in the scope of the present invention.

[0022]

As described above, according to the apparatus for detecting the concentration of a granular material according to the present invention, the concentration of the granular material flowing through the duct can be maintained without lowering the detection sensitivity even in a humid atmosphere. The density detection with stable and good sensitivity is possible.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing the configuration of a concentration detecting device for granular material according to an embodiment of the present invention.

FIG. 2 is a timing chart showing signal waveforms in the concentration detection device of FIG.

FIG. 3 is a cross-sectional view showing a structure of a detector main body of the concentration detecting device of FIG. 1 in a state where it is attached to a duct.

FIG. 4 is a sectional view showing a modified example of the detector main body of FIG. 3;

FIG. 5 is a schematic cross-sectional view of a concentration detecting apparatus for granular material according to the prior application of the present application.

[Explanation of symbols]

 10: Detector body (detection probe) 11: Main electrode 12: Insulator 13: Ground electrode 20: Signal detection unit 21: Operation amplifier 22: Control unit 23: Signal processing unit 24: Operation unit 30: Duct 31: Charged Powder 32: Detector mounting part

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Fujio Kayahara 2-14 Usaginocho, Kita-ku, Osaka-shi, Osaka Kansai Automation Co., Ltd.

Claims (1)

[Claims] 1. A concentration detecting device for detecting the concentration of charged particles flowing in a duct, comprising: a main body; and a main electrode; A ground electrode surrounding the part to be removed, and a detector main body having an insulator that insulates the main electrode from the ground electrode and covers the ground electrode; A detection unit for detecting a change in induced charge to be performed, and a calculation unit for calculating the concentration of the granular material based on the detection result of the detection unit, wherein at least a portion of the insulator protruding into the duct is integrated. An apparatus for detecting the concentration of a granular material, which is formed in a uniform manner.