JPS649574B2 - - Google Patents

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 measurement method that has extremely high measurement accuracy by calculating the moisture content according to the weight factor of the powder and granules. It is related to.

Conventionally, methods using microwaves have been used to measure the moisture content of powder and granular materials, for example,
It is described in Publication No. 56-39448, 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, when the present inventors measured various wood chips using the apparatus described in the above-mentioned Japanese Patent Application Laid-open No. 56-39448, the results obtained by measuring the same samples using the absolute dry method (JIS P-8002) were A considerable difference in the moisture content was observed in comparison with the results obtained. That is, the conventional water 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 found that this phenomenon also occurs due to the dielectric dispersion of the granules themselves, and found that when calculating the moisture content of granules, taking into account the influence of their weight significantly improves the measurement accuracy. 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 is Vi, the input of the microwave received by the receiving antenna is Vs, the amount of attenuation of the microwave is ΔV (unit: electric potential), and the amount of granular material is Air dry weight Wt
(Kg), the moisture content of the granular material is WH ₂ O (Kg), and the moisture content of the granular material is φ (%), the moisture content φ is derived by the following empirical formula.

ΔV≡Vi−Vs ΔV=A+BWH ₂ O+CWt φ=WH ₂ O/Wt×100=(Vi−Vs)−A−CWt/BWt×100 (1) Here, A, B, and C are the frequency, output, and conductivity. These are constants related to the shape of the wave tube, etc., and the numerical values of A, B, and C are determined using powder and granular material whose moisture content is known through bone-dry measurement or the like before starting the measurement. The results measured by the method based on such an empirical formula have a very good correlation with the values determined by the bone-dry method, and extremely accurate measurement values can be obtained.

In the present invention, a measuring waveguide including a transmitting waveguide and a receiving waveguide is filled with powder, and the output Vi of the microwave transmitted from the transmitting waveguide is
Equation in which Vs of the microwave input received by the receiving antenna and Wt of the air-dried weight of the powder and granular material are variables φ=(Vi-Vs)-A-CWt/BWt×100 (Here, A, B, C is a constant related to the frequency, output, shape of the waveguide, etc.) is input into the calculation section in advance, and the transmitted voltage value from the oscillator, the received voltage value from the detector, and the weight value from the weight measurement mechanism are input in advance to the calculation unit. This is a method for measuring the moisture content of a powder or granular material, characterized in that the moisture content of the powder or granule is calculated by inputting the following into the setting formula.

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 indicates the measurement waveguide, and by combining the slide-opening type upper lid 2 and the swing-opening type lower lid 3, it is possible to create a sealed structure inside the measurement waveguide 1 during measurement. It is becoming. It is desirable that such a measuring waveguide has an internal volume that can be filled with at least 1 kg of granular material in order to ensure measurement accuracy. Regarding the upper lid 2 and lower lid 3, measurement errors will occur if microwaves are reflected by the inner walls during measurement, so it is desirable to attach a suitable microwave absorbing material to the inner walls, for example. In FIG. 1, a transmitting waveguide 5 equipped with a transmitting antenna section 4 and a receiving waveguide 7 equipped with a receiving antenna section 6 are suitably disposed on the left side of the measurement waveguide 1. They are placed at a distance apart.

At the boundary between these two waveguides and the measurement waveguide 1, an intrusion prevention plate 8 is provided with a slit portion of an appropriate shape in order to prevent powder particles from entering the inside of these two waveguides. 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 1.
Antenna section 4 for transmitting microwaves oscillated at 0
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 then passes through the receiving waveguide 7.
After passing through, the signal is received by the receiving antenna section 6, and then converted into an electrical signal. After the electrical signal is demodulated by the detector 11, it is sent to the arithmetic unit 12.
is input. On the other hand, the weight of the filled powder is measured by a weight measuring mechanism such as a load cell 13, and the electrical signal is sent to the calculation unit 12.
is input.

The calculation unit 12 performs calculations based on the oscillation resonance voltage signal from the oscillator 10, the reception resonance voltage signal from the detector 11, and the weight signal from the weight measurement mechanism 13, and displays the results on the display unit 14.

When implementing the automation of the above process, for example, a control unit, a carry-in conveyor for collecting powder and granules from the main conveyor in batches, a carry-out conveyor for returning the powder and granules that have been measured to the main conveyor, and an upper lid. Equipped with automatic opening/closing mechanism, automatic lower lid opening/closing mechanism, etc.
Each part may be controlled based on a program input into the control part in advance.

Note that as the frequency of the microwave increases, the proportion of the weight of the powder material that influences its attenuation decreases, but as the frequency increases, the dimensions of the waveguide become uniquely determined by the wavelength used. becomes small, resulting in an error. Therefore,
In order to obtain sufficient measurement accuracy in the method of the present invention, the microwave frequency must be between 300MHz and 300G.
Those in the Hz range are preferable, and those in the range of 600 MHz to 7 GHz are particularly preferably used. Also,
As the powder or granular material to be measured, for example, wood chips, grains, coal, etc. can be measured, but wood chips can be measured particularly efficiently.

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 turned into chips using a chipper, the moisture content of hardwood chips from which dust was removed using a chip screen was measured. The measurement waveguide 1 of the device used in this example has an inlet length and width of 25 cm x 20 cm.
It has a rectangular parallelepiped shape with a length of 100 cm and a structure that allows the use of 1 GHz microwaves. Before starting the measurement of the sample, the constants A, B, and C of the above-mentioned experimental formula (1) for determining the water content were determined to be 8.512, 0.084, and 0.036, respectively. The sample was measured using 1 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 very high accuracy.

[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 lid, 3: Lower lid, 4:
Transmission antenna section, 5: Transmission waveguide, 6: Receiving antenna section, 7: Receiving waveguide, 8: Intrusion prevention plate, 9: Hopper, 10: Oscillator, 11: Detector, 12: Calculation Section 13: Load cell (weight measurement mechanism), 14: Display section.

Claims (1)

[Claims] 1. A measurement waveguide including a transmission waveguide and a reception waveguide is filled with powder, and Vi of the microwave output transmitted from the transmission waveguide, Equation in which Vs of the microwave input received by the receiving antenna and Wt of the air-dried weight of the powder and granular material are variables φ=(Vi-Vs)-A-CWt/BWt×100 (Here, A, B, C is a constant related to the frequency, output, shape of the waveguide, etc.) is input into the calculation section in advance, and the transmitted voltage value from the oscillator, the received voltage value from the detector, and the weight value from the weight measurement mechanism are input in advance to the calculation unit. A method for measuring moisture content in a powder or granular material, characterized in that the moisture content of the powder or granule is calculated by inputting the following into the setting formula.