JPS62278439A - Water content monitoring apparatus - Google Patents

Abstract

PURPOSE:To enable the monitoring of water content in a nondestructive manner being distinguished from hydrogen in an organic material by determining the area or a value of a peak with the half-value width less than 10Hz in a nuclear magnetic resonance absorption spectrum. CONSTITUTION:A magnetic field is applied to powdery material 3 to be measured being fluidized through a piping 2 from a magnet 1. When a radio wave within a nuclear magnetic resonance frequency of hydrogen nuclus is made incident on the powdery material 3 in a magnetic field from a transmitting coil 4, a resonance absorption takes place by the hydrogen nuclus to cause a change in the direction of the magnetization, which is detected with a receiving coil 5 and amplified with a receiver 7 to be sent to a data processor 8. Generally, the half-value width is less than 10Hz in the nuclear magnetic resonance absorption spectrum of the hydrogen nuclus of water and hence, water can be distinguished clearly from an organic solid, which is more than several tens of Hz. Therefore, the area or value of a peak with the half-value width less than 10Hz is determined with a processor 8 in a nuclear magnetic resonance absorption spectrum of the powdery material 3 as function of the frequency obtained from the output of the receiver 7 and multiplied by a fixed coefficient to calculate the water content of the powdery material 3.

Description

[Detailed Description of the Invention] 3. Detailed Description of the Invention [Industrial Field of Application] The present invention relates to a moisture content monitoring device, and particularly to a device for non-destructively monitoring the moisture content of a measurement target including organic matter. The present invention relates to a device suitable for.

[Conventional technology]

Conventionally, a neutron moisture meter (Special Publication No. 53-8630) was used to non-destructively monitor the moisture contained in powders, etc.
0, etc.) have been used. However, because neutron moisture meters actually detect the amount of hydrogen, not water, they cannot be used for measurements that contain organic substances that contain hydrogen as one of their main constituent elements. However, in fields such as radioactive waste treatment, it has become necessary to monitor the moisture content of objects containing organic solids such as ion exchange resins.

[Problem that the invention seeks to solve]

As mentioned above, since a neutron moisture meter detects the presence of hydrogen, it cannot distinguish between hydrogen, which is a constituent element of water, and hydrogen, which is a constituent element of organic matter. The purpose of the present invention is to non-destructively monitor the moisture content of a substance such as a solid powder containing an organic substance whose constituent element is water. The goal is to provide equipment.

[Means for solving problems]

The present invention applies a magnetic field to the measurement target, obtains a nuclear magnetic resonance absorption spectrum of radio waves of hydrogen nuclei in the magnetic field as a function of frequency, and in the spectrum, the half-width of the peak is 1
Find the area or peak value of the peak smaller than 0Hz,
The water content is calculated by multiplying this by a certain coefficient.

[Effect]

Among the nuclear magnetic resonance absorption spectra, the spectrum of hydrogen contained in organic matter is significantly larger than the spectrum of hydrogen constituting water (which is smaller than 10 Hz). Utilizing this fact, in addition to determining the area or peak value of the former peak, it is also possible to measure the water content as distinguished from the latter.

〔Example〕

An embodiment of the present invention will be explained below with reference to FIG. This example shows a case where the present invention is applied to monitoring the water content of powder flowing through a pipe.
A magnetic field is applied. When a nucleus with spin exists in a magnetic field, the nucleus precesses at a frequency expressed by the following equation 〇γ υo = −Ho ・Old... (1) 2 in υO; Precession Frequency γ: Magnetic rotation ratio HO: Magnetic field strength When an electromagnetic wave of the same frequency as the above frequency is incident on a precessing nucleus, the nucleus resonates with it and absorbs energy. This is called nuclear magnetic resonance. The magnetic field that can usually be used is about 1 to 10 T (Tesla),
The frequencies for it are in the megahertz radio frequency range.

By the way, hydrogen nuclei (1H) are atomic nuclei that cause very strong resonance absorption, and when a radio wave with a frequency determined by equation 11 is incident from the radio wave transmission coil 4, resonance absorption by the hydrogen nuclei occurs, and the direction of magnetization changes. changes, so it is detected and amplified by the reception filter 5.The total resonance absorption amount is proportional to the number of hydrogen nuclei.

However, the resonance frequency differs slightly depending on the chemical state due to differences in the electron jamming effect depending on the electronic state around the hydrogen nucleus.

FIG. 2(a) shows the frequency spectrum of nuclear magnetic resonance of hydrogen nuclei in water, and FIG. 2(b) shows the frequency spectrum of nuclear magnetic resonance of hydrogen nuclei in organic resin. As can be seen from this figure, the Is@ of the spectra differs greatly between water and resin. The line width depends on conditions such as the strength or uniformity of the magnetic field, but in general, the half-width in water is as small as 10 Hz, while in organic solids it is several tens of Hz or more, and more than 1 lid.
--It's different. Therefore, even if both are mixed, Figure 2 (c
), it is easy to identify the base. Therefore, if we calculate the resonance absorption amount of only the hydrogen nuclei of water, which has a narrow linewidth on the frequency spectrum, rather than the total resonance absorption amount of hydrogen nuclei, it is possible to create a calibration curve for a sample whose water content is known in advance. Therefore, the water content can be easily determined.

There are several methods for separating only the resonance absorption component of water from the spectrum, but if the frequency range of the frequency spectrum is narrowed, the contribution from organic solids can be easily removed by approximating it with a straight line as a packing ground. Further, after performing a peak search, only peaks whose half width is smaller than 10 Hz may be integrated.

In addition, since the apex of a peak with a narrow linewidth is expected to exhibit the highest value in the spectrum ±, integration may be performed only for the peak containing the largest value.

It is accurate to use the peak area to determine the amount of resonance absorption, but if a calibration curve has been prepared in advance, the peak height may be used as a substitute, and the method of using the highest value on the spectrum is easier on the equipment. is the simplest. All such data processing can be easily accomplished using a microcomputer or minicomputer.

A possible method for obtaining the frequency spectrum is to continuously change the frequency generated by the frequency source 6 applied to the transmitting coil 4, and to receive the signal from the transmitting coil 5 using the receiving device 7. However, in this case, it takes time to sweep the frequency, and the detection lower limit becomes high. Another method is to generate radio frequency pulses with a frequency source 6,
This is a method of obtaining a frequency spectrum by recording the time change of free induction attenuation of magnetization after the incidence of a radio wave pulse in a receiving device 7, and then performing Fourier transformation in a data processing device 8. This method requires a data processing device with a relatively large capacity, but since the spectrum is obtained in pulses, one measurement can be performed in about 0.5 seconds, and continuous measurements are possible. Furthermore, by integrating the results of multiple measurements, it is possible to improve the S/N ratio and lower the lower limit of detection.

The free damping vibration spectrum measured by the pulse incident diameter is the third
As shown in Figure (IL), it contains data at various frequencies and can be Fourier transformed from K to Φ
) is converted into a normal frequency spectrum as shown by K.

When the peak area of the resonance absorption component of water is determined from the spectrum obtained in this way, there is a proportional relationship between the water content and the water content as shown in Figure 4. The content can be determined by the data processing device 8, and by inputting this value into the recorder 9, the water content of the powder in the pipe can be monitored. However, in this case, the piping material must be made of a material that allows radio waves to pass through, and it is necessary to choose a material such as ceramics rather than metal material. According to this embodiment, the moisture content in powder containing organic matter can be monitored non-contactly and non-destructively.

Next, as a specific example of the present invention, a case where the present invention is applied to monitoring the water content during powdering and drying of radioactive waste will be described using FIG. 5. A radioactive waste liquid 11 containing an ion exchange resin is stored in a waste liquid storage tank 12 . This waste liquid is fed by a pump 13 to a drying and powdering device l14, where it is powdered and dried.

The generated powder is formed into pellets 24 by a granulator 15 and stored in a drum 16.

At the time of granulation, unless the moisture content of the powder is within a certain range, granulation cannot be achieved successfully. Therefore, in this example, we use a dry powder system! ! A moisture content monitoring device is provided in the powder transfer pipe 17 connecting the i14 and the granulator 15 to control the moisture content. For this purpose, a magnet 18 is arranged to surround the powder transfer tube 17, a radio wave transmitting coil 19 is placed inside the magnet 18, and radio wave pulses generated by a pulse frequency source 20 are irradiated. A receiving coil 21 is attached around the powder transfer tube 17, and a receiving coil 21 is installed around the powder transfer tube 17.
The free damping vibration spectrum from 00 μsec later is received by the receiver 22 and recorded based on the pulse generation signal sent from the pulse frequency source 20. The obtained data is converted into a digital signal in the data processing device 23 and then subjected to Fourier transformation to obtain a frequency spectrum. The peak showing the highest value in this frequency spectrum is detected, and the peak area is calculated by subtracting the puncture ground. The obtained value is multiplied by a calibration coefficient created in advance based on the standard sample to obtain the water content value. The pulse interval is 1 second, and the data processing device 23 integrates the values of 10 times, and then performs Fourier transform to improve the S/N ratio of the frequency spectrum. If necessary, the number of integrations can be automatically adjusted depending on the moisture content to obtain a stable S/N ratio.

When the obtained moisture content value is within the pre-input granulation possible range, the powder is molded in the granulator 15 and stored as waste pellets 24. When it is outside this range, there is no powder in the temporary storage tank 25! Transfer and store.

If operated for a long time, powder will adhere to the inner wall of the powder transfer tube 17, making it difficult to monitor the moisture content correctly.
Pure water 27 is fed from the pure water storage tank 26 once a day for cleaning. At this time, the waste liquid 11 is fed, the powder drying device 14
shall be stopped. The cleaning liquid is sent to the temporary storage tank 25 and returned to the waste liquid storage tank 12 as radioactive waste liquid. After the cleaning operation is completed,
Heated drying air is sent from the prower 28 to the powder transfer tube 17 for drying. During this time, monitoring of the moisture content continues, and once it is confirmed that the monitored moisture content has fallen below a certain value due to drying, the feeding of waste liquid and the operation of the powder drying device 14 are started again. .

According to this embodiment, after drying the radioactive waste liquid containing the ion exchange resin into powder, the water content can be monitored to enable stable granulation.

Another specific embodiment of the present invention will be described using FIG. 6.

This example is for checking the water content in radioactive waste formed into granulated pellets or rubble. When radioactive waste is granulated, temporarily stored, and then subjected to final solidification treatment, depending on the storage environment, the radioactive waste may absorb water and may not be suitable for final solidification treatment. This example is used to check the moisture content to prevent this, and is a non-destructive,
The moisture content of waste containing ion exchange resins and filter aids can also be checked without contact. In FIG. 6, granulated radioactive waste 32 is being transported through a pipe 33 by a transporter 31. A magnet 34 is installed in this pipe 33. A receiving coil 35 and a transmitting coil 36 are installed inside the piping in this part, and the transmitting coil 36 irradiates radio wave pulses generated by a pulse frequency source 37.
The subsequent free induction attenuation is received by the receiving coil 35 and converted into a digital signal by the receiving device 38, and then the data processing device 3
9 to obtain a frequency spectrum, and obtain a partial value for a peak with a predetermined line width of 10 Hz or less, and multiply it by a calibration coefficient to obtain a water content value. At this time, since the object of measurement was in the form of rubble, the moisture content record was greatly wavy as shown by the solid line in FIG. In order to prevent this, the water content is integrated at intervals of a fixed period of time, as shown in the lower part of FIG.

According to this embodiment, the water content of the granulated waste can be monitored and checked.

In addition, in the present invention, if the radio waves irradiated to the measurement target are given strong directivity and focused, it is possible to detect and monitor the local moisture content of minute parts instead of the overall average moisture content. .

〔Effect of the invention〕

According to the present invention, also for measurement targets including organic solids,
This method has the effect of allowing easy, non-destructive monitoring of the water content, which is distinguished from hydrogen in organic matter.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an example in which the present invention is used for monitoring the moisture content of powder, and FIG. 2 (a). (b), ((This is a diagram showing a typical example of nuclear magnetic resonance spectrum of hydrogen nucleus, Figure 3 (a), (b) is the free induction decay spectrum and the frequency spectrum obtained by Fourier transform of it. Figure 4 is a diagram showing an example of the relationship between water content and peak area, Figure 5 is a schematic diagram of an example in which the present invention is applied to radioactive waste treatment, and Figure 6 is a diagram showing the relationship between water content and peak area. A schematic diagram of an example in which the present invention is applied to checking granulated radioactive waste, and FIG. 7 is a diagram showing the output data of moisture content and the effect of integration. 1... Magnet 2...・Piping 3... Powder 4... Transmitting coil 5... Receiving coil 6... Frequency a source 7... Receiving device
8...Data processing device 11...Radioactive waste liquid 1
2... Waste liquid storage tank 13... Pump 14...
・Dry powderization device 15... Granulator 16...
- Drum 17... Powder transfer tube 18... Magnet 19... Receiving coil 20... Pulse frequency source 21... Receiving coil 22... Receiving device 23.
...Data processing device 24...Pelletization waste 25...
Temporary storage tank 26...Pure water storage tank 27...Pure water
28... Blower 31... Conveyor
32... Granulated radioactive waste 33... Piping
34... Magnet 35... Receiving coil 36.
... Transmission coil 37 ... Pulse frequency source 38 ...
Receiving device 39...data processing device. Tani Kotabe" Figure 3 Figure 4 Peak Mensu Figure 6 Practice 'I Kasuko

Claims (1)

[Claims] 1. A magnetic field generating means that applies a magnetic field to an object to be measured, a transmitter that irradiates the object to be measured with radio waves in the nuclear magnetic resonance frequency region of hydrogen nuclei in the magnetic field, and measurement by nuclear magnetic resonance absorption. A receiver for detecting changes in the magnetization of an object, and the area or peak value of a peak whose half width is smaller than 10 Hz in the nuclear magnetic resonance absorption spectrum of the object to be measured as a function of frequency obtained from the output of the receiver. What is claimed is: 1. A moisture content monitoring device comprising data processing means for determining the moisture content of a measurement target by calculating the moisture content of the object to be measured by calculating the moisture content of the object to be measured. 2. The moisture content monitoring device according to claim 1, wherein the nuclear magnetic resonance absorption spectrum is obtained from the output of the receiver by continuously changing the frequency of radio waves emitted from the transmitter. 3. The radio waves emitted from the transmitter are pulsed;
Moisture content according to claim 1, in which the temporal change in free induction attenuation of the magnetization of the measurement object detected by the receiver is recorded, and this is Fourier transformed to obtain the nuclear magnetic resonance absorption spectrum. Monitoring equipment.