JPS6018745A - Method for measuring moisture content of particulate material - Google Patents

Abstract

PURPOSE:To enable measurement with extremely high accuracy, by a method wherein a measuring wave guide is filled with a particulate material and the attenuation amount of a microwave from a transmission wave guide is measured by a receiving wave guide to operate the moisture content of the particulate material corresponding to the wt. factor thereof. CONSTITUTION:A measuring wave guide 1 is filled with a particulate material and the wt. of said particulate material is measured by a wt. measuring mechanism 13. The microwave from a transmission wave guide 5 is attenuated by the particulate material and an attenuation amount DELTAV is measured through a receiving wave guide 7. Herein, when the attenuation amount of the microwave is set to DELTAV, the air-dried wt. of the particulate material to Wt, moisture content to phi and A, B, C are set as the constants of frequency, output and the wave guide, moisture content phi is calculated from an experimental formula phi=(DELTAV- A-CWt)/BWtX100. This operation is performed by an operation part 12 to make it possible to calculate the moisture content of the particulate material with extremely high accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for measuring the moisture content of powder and granules, and in particular, a measuring method with extremely improved measurement accuracy by calculating the moisture content according to the weight factor of the powder and granules. It is related to.

Conventionally, as a method for measuring the moisture content of powder and granular materials, a method using microwaves has been proposed, for example, in Japanese Patent Application Laid-Open No. 56-3944.
It is described in Publication No.-8, etc. Although the method using microwaves has the advantage of being able to perform measurements in a short time using relatively simple equipment, there is still room for improvement. Incidentally, (1) the present inventors used various wood chips in the above-mentioned Japanese Patent Application Laid-Open No. 56-39
When measured using the apparatus described in Publication No. 448, there was a considerable difference in the moisture content when compared with the results obtained by measuring the same sample using the absolute dry method (JIS'P-8002). It was done.

That is, the conventional moisture content measuring apparatus may not always be able to perform sufficient practical measurements depending on the type of target substance to be measured.

In view of the current situation, the inventors of the present invention have conducted extensive research into developing a practical measurement method that avoids the above-mentioned defects, and have found that microwave attenuation occurs not only due to dielectric dispersion of water, but also due to powder dispersion. They discovered that this phenomenon also occurs due to the dielectric dispersion of the granules themselves, and found that when calculating the water content of granules, the measurement accuracy can be significantly improved if the influence of their weight is taken into account. Then, a method for measuring the water content based on the following empirical formula was completed.

That is, the output of the microwave transmitted from the transmitting antenna section is Vi, the input of the microwave received by the receiving antenna section is Vs, and the amount of attenuation of the microwave is Δ■(
The unit is electric potential), the air-dry weight of the powder is Wt <kg),
Assuming that the moisture content of the granular material is WIlzO (kg) and the moisture content of the granular material is φ (%), the moisture content φ is derived from the following empirical formula.

ΔVmiVi −Vs ΔV−A+BWII20 +CWt Wt Here, A, B, and C are constants related to the frequency, output, shape of the waveguide, etc., and the water content is determined in advance by bone-dry measurement before starting the measurement. Using powder and granular material for which A is known,
, B, and C are determined.

The results measured by the method based on such an empirical formula have a very good correlation with the values obtained by the bone-dry method, and extremely accurate measurement values can be obtained.

According to the present invention, a transmitting waveguide and a receiving waveguide are provided (3). This is a method for measuring the moisture content of powder and granules, which is characterized by measuring with a receiving waveguide and calculating the moisture content according to the weight factor of the powder and granules.

The method of the present invention will be explained in more detail based on the drawings. FIG. 1 schematically shows an embodiment of an apparatus used in the method for measuring moisture content of powder or granular material according to the present invention. In the figure, (1) shows the measurement waveguide, and the combination of the slide opening/closing type upper lid (2) and the swing opening/closing type lower lid (3) allows the inside of the measuring waveguide (1) to be closed during measurement. It is possible to have a closed structure.

It is desirable that such a measuring waveguide has an internal volume that can be filled with at least I kg of powder or granular material in order to ensure measurement accuracy. Regarding the upper lid (2) and lower lid (3) above, measurement errors will occur if microwaves are reflected by the inner walls during measurement, so for example, an appropriate microwave absorbing material may be pasted on the inner walls. It is preferable to wear them. In Fig. 1, a transmitting waveguide (5) equipped with a transmitting antenna section (4) and a receiving antenna section (6) are installed on the left side of the measuring waveguides (1) and (4). A reception waveguide (7) is provided at an appropriate distance.

At the boundary between these double-groove wave tubes and the measurement waveguide (1), in order to prevent powder from entering the inside of these double-groove wave tubes,
An intrusion prevention plate (8) having a slit portion of an appropriate shape is provided. In this embodiment, the powder and granular material is filled by hand, using a hopper (9), or by a transport method such as a conveyor device. When filling, it is desirable to fill the inner wall of the top lid (2) to the fullest so that when the top lid (2) is closed after filling, there will be no gaps that may cause errors. In order to prevent the occurrence of such errors, it is a preferred embodiment to always maintain the level of the powder or granular material at a constant level using, for example, a level sensor.

When filling is completed, close the top lid (2) and turn on the oscillator (10
) The microwave oscillated by the transmitting antenna section (4)
The signal is transmitted from the transmitting waveguide (5) into the transmitting waveguide (5). The microwave passes through the granular material through the slit part of the intrusion prevention plate (8), is attenuated by the granular material, and is received by the receiving antenna part (6) after passing through the receiving waveguide (7). , which is then converted into an electrical signal. The electrical signal is demodulated by the detector (11) and then sent to the arithmetic unit (12).
) is entered. On the other hand, the weight of the filled granular material is measured by a weight measuring mechanism such as a load cell (13), and the electrical signal is input to the calculation section (12).

The calculation unit (12) performs calculations based on the transmitted resonant voltage signal from the oscillator (10), the received resonant voltage signal from the detector (11), and the weight signal from the weight measurement mechanism (13),
The results are displayed on the display section (14).

When automating the above process, for example, the control unit,
The control unit is equipped with an inlet conveyor for collecting powder and granules from the main conveyor in batches, an unloading conveyor for returning the powder and granules that have been measured to the main conveyor, an automatic upper lid opening/closing mechanism, an automatic lower lid opening/closing mechanism, etc. Each part may be controlled based on a program input in advance.

(6) Note that as the frequency of microwaves increases, the rate at which the weight of the powder or granular material influences its attenuation decreases; The dimensions of the tube become smaller, resulting in errors. Therefore, in order to obtain sufficient measurement accuracy in the method of the present invention, the frequency of the microwave should be 300 M
Those in the range from Hz to 300 G I-1z are preferred, especially from 600 M T-1z to 70 Ifz
Those are more preferably used. Further, as the powder or granular material to be measured, for example, wood chips, grains, coal, etc. can be measured, but a holochip can be particularly efficiently measured.

The present invention will be explained in more detail below based on one example, but it is of course not limited to this example.

〔Example〕

After being made into chips using a chipper, dust was removed using a chip screen, and the moisture content of the hardwood chips was measured. The measuring waveguide (1) of the device (7) used in this example had an inlet length and width of 25 mm.
It has a rectangular parallelepiped shape with dimensions of cm×20 cm and length of 100 cm, and has a structure that allows use of I GHz microwaves. Before starting the measurement of the sample, the constants A, B, and C of the above-mentioned empirical formula (1) for determining the moisture content were determined, and they were 8.512.0.084.0.036, respectively.
Met. The sample was measured using an I GHz microwave and the moisture content was 34.2%.

For comparison, when the same sample was measured using the bone-dry method, a value of 34.5% was obtained, confirming that the accuracy was very high.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an embodiment of a water content measuring device used in the present invention. (1): Measurement waveguide (2): Upper cover (3): Lower cover (4) Two-emission antenna section (5): Emission waveguide (6): Reception antenna section (7): Reception Waveguide (8): Intrusion prevention plate (8) (9): Bosovar (10): Oscillator (11): Detector (12): Computing section (13): Load cell (weight measurement mechanism) (14): Display section patent applicant Kanzaki Paper Co., Ltd. (9) Figure 1 ←-1〉 ＼ 011

Claims (1)

[Claims] A measuring waveguide with a transmitting waveguide and a receiving waveguide is filled with powder, and the amount of attenuation of the microwaves emitted from the transmitting waveguide is measured using the receiving waveguide. A method for measuring the moisture content of a powder or granule, characterized in that the moisture content of the powder or granule is calculated according to a weight factor of the powder or granule.