JP2007017454A - Microwave type concentration measuring method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a concentration measuring method dispensing with correction of a concentration measured value based on the temperature or the conductivity of suspended matter mixed liquid, and having heightened measurement accuracy. <P>SOLUTION: The concentration is measured by using a frequency in a domain wherein a reflection intensity or a reflection phase difference is not changed relative to a change of the temperature or the conductivity of the mixed liquid containing suspended matters. The temperature of the mixed liquid containing suspended matters is known, and the mixed liquid containing suspended matters is irradiated with a microwave having a frequency wherein the reflection intensity is not influenced by the concentration change of the suspended matter, and the conductivity is determined from the reflection intensity at that time. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for measuring the concentration of suspended solids in a suspension mixed solution in a treatment process of a sewage treatment plant, a wastewater treatment plant, a water purification treatment plant, or a sludge treatment plant using a microwave.

  There are mainly the following methods for measuring the concentration of the suspended substance in the suspended substance mixture.

  (1) Scattered light measurement method: The amount of light received in accordance with the concentration is obtained in the light receiver by scattering the light irradiated toward the suspension substance mixed solution from the suspension substance.

  (2) Ultrasonic measurement method: The amount of reception corresponding to the concentration is obtained in the ultrasonic receiver by reflecting or attenuating the ultrasonic wave radiated toward the suspension substance mixed solution by the suspension substance.

  (3) Microwave measurement method: Microwave is applied to the suspension substance mixture, and the phase difference between the irradiation wave and the transmitted wave, or the transmission intensity or reflection intensity is obtained in accordance with the concentration (for example, patent document) 1).

  Since the above scattered light measurement method is easily affected by the color of the suspended substance, the measurement concentration range becomes small when the color of the measurement object is dark. In addition, contamination of the detection window for light irradiation and light reception on the suspension substance mixture tends to affect the measurement accuracy.

  The ultrasonic measurement method is easily affected by bubbles in the suspension material mixture. In order to remove the bubbles, there is a method in which a mechanical bubble removing device such as a pressure defoaming device is provided. However, this method has a large measuring device and has a problem of maintenance.

  The configuration of the transmission method of the microwave measurement method is shown in FIG. In the figure, a window made of glass or ceramic is provided to face a predetermined portion of the suspended solid mixture transport pipe 1. A densitometer detection probe 2 on the microwave transmission side and a densitometer detection probe 3 on the microwave reception side are provided in this window. 4 is a microwave transmitter / receiver connected to both probes 2 and 3, and 5 is a densitometer converter that obtains the concentration of suspended substances from the phase difference or transmission intensity of microwave transmission and reception waves.

  The microwave densitometer using the phase difference is the difference between the phase lag of the microwave transmission in fresh water (concentration 0%) and the phase lag of the microwave transmission in the suspension in the suspension mixture. The concentration is measured by utilizing the fact that (phase difference) is proportional to the concentration of suspended solids as shown in FIG. Further, the concentration can be measured by detecting the ratio of the transmission intensity to the microwave irradiation intensity.

  As another microwave measurement method, there is a method shown in FIG. In the figure, a microwave is irradiated from one probe 6 to the suspended substance mixture in the transport pipe 1 and a reflected wave from the suspended substance is detected, and the intensity of the irradiated wave and the reflected wave is measured. The concentration is measured from the ratio.

  FIG. 22 shows the structure of the above-described probes 2 and 6, for example, a measurement method using a reflection method. A window 8 made of glass or ceramic is provided in the suspension material mixture transport pipe 1 by a flange 7, a microwave antenna 10 is projected into a waveguide 9 provided outside this, and a coaxial cable 11 is connected from the microwave transceiver 4. The transmitted microwave is radiated from the antenna 10 or received. Reference numeral 12 denotes a stub that determines the microwave frequency characteristics of the waveguide 9.

The microwave concentration measurement method employed as described above is not easily affected by the color of the suspended matter, and the concentration measurement range is wide. Furthermore, since the antenna or the like that becomes the microwave electrode can be made non-contact with the suspended substance and is less affected by dirt on the window, the maintainability can be improved. Furthermore, microwaves have less influence of bubbles in the suspension material mixture than other methods.
JP 05-322801 A

(First issue)
In the conventional measurement method, the microwave frequency is a fixed frequency that matches the frequency band determined by the waveguide structure. Therefore, the transmission and reflection of microwaves in the waveguide are caused by subtle changes in the transmission characteristics of the waveguide. The characteristic may change and the measurement error may increase.

(Second problem)
In the microwave measurement method, changes in temperature and conductivity of the suspended solid mixture affect the concentration measurement accuracy.

  Therefore, in order to reduce measurement errors due to these factors, it is considered to measure the temperature and conductivity of the suspended solid mixture using a thermometer or conductivity meter and correct the concentration measurement value based on this measurement value. However, since the transmission and reflection characteristics of the microwave with respect to changes in temperature and conductivity are unstable, it is difficult to obtain an appropriate correction characteristic and correct it with high accuracy.

(Third issue)
The method of correcting the concentration measurement value based on the temperature and conductivity of the suspended solid mixture requires measuring devices for these temperatures and conductivity, and measurement errors are likely to occur in the measuring device itself.

  For example, in a conductivity meter, the measured value greatly fluctuates due to contamination and corrosion caused by the suspended solid mixture, so that it is difficult to accurately correct the concentration measured value based on the measured value, and maintenance and calibration are also difficult.

  In addition, it is difficult for the thermometer to detect the temperature change of the suspended solid mixture with high responsiveness, and when the flow of the suspended solid mixture is fast, the detection delay causes a measurement error.

  An object of the present invention is to provide a concentration measurement method that improves the measurement accuracy by eliminating the need to correct the concentration measurement value based on the temperature and conductivity of the suspended solid mixture.

  Another object of the present invention is to provide a concentration measurement method that facilitates concentration correction by measuring conductivity.

(First invention)
In the microwave concentration measurement method, the present invention measures the concentration using the frequency of the region where the reflection intensity or the reflection phase difference does not change with respect to the temperature or conductivity change of the suspended solid mixture. It eliminates the need for correction of concentration measurement values due to changes in the temperature and conductivity of the suspension material mixture, and is characterized by the following method.

In the microwave concentration measurement method for measuring the concentration of suspended substances by detecting the reflection intensity or reflection phase difference of the microwaves irradiated toward the suspension substance mixture,
Irradiate microwaves with a frequency at which the reflection intensity or reflection phase difference becomes almost constant with respect to the change in conductivity of the suspension mixture, or the reflection phase difference with respect to the change in the temperature of the suspension mixture. It is characterized in that the concentration of suspended solids is measured by irradiating microwaves with a constant frequency.

(Second invention)
The present invention relates to a microwave concentration measurement method, in which a suspension material mixture liquid is a microwave whose frequency is such that the reflection intensity is not affected by the concentration change of the suspension material. The measurement is simplified by eliminating the need for a conductivity meter by obtaining the conductivity from the reflection intensity at that time, and is characterized by the following method.

In the microwave concentration measurement method for measuring the concentration of suspended substances by detecting the reflection intensity or transmission intensity or reflection phase difference of the microwaves irradiated toward the suspension substance mixture,
Irradiate the suspension material mixture with microwaves at a frequency at which the reflection intensity becomes almost constant with respect to the concentration change of the suspension material.
From the proportional relationship between the reflection intensity and the conductivity in the microwave irradiation at a constant temperature of the suspension material mixture, the conductivity of the suspension material mixture is obtained,
The concentration measurement value of the suspended solid mixture is corrected from the conductivity.

  As described above, according to the present invention, since the concentration is measured using the frequency in the region where the reflection intensity does not change with respect to the change in temperature or conductivity of the suspension substance mixture, the suspension substance mixture It is not necessary to correct the concentration measurement value due to changes in temperature and conductivity.

  In addition, the temperature of the suspension material mixture is known, and the suspension material mixture is irradiated with microwaves having a frequency at which the reflection intensity is not affected by the concentration change of the suspension material. Since the rate is obtained, a conductivity meter is not required and the measurement is simplified.

(First embodiment)
FIG. 1 is a data processing flow of a microwave concentration measurement method showing an embodiment of the present invention. Note that the detection of microwaves is not limited to either the transmission method or the reflection method.

  (S1) In the concentration measurement, for microwave irradiation, the microwave frequency generated by the microwave transmitter / receiver 4 is scanned within the frequency band of the waveguide.

  (S2) The microwave reflection intensity or transmission intensity at each frequency by the frequency scanning described above is detected by the microwave transmitter / receiver 4, and based on the detected value, the reflection characteristic or transmission by the suspended substance concentration meter converter 5 or the like. Find characteristics.

  (S3) The sum of the reflection intensity or transmission intensity characteristics at each frequency is obtained from the above reflection or transmission characteristics. In the calculation of the sum of the characteristics, an integrated value or an average value of the reflection intensity or the transmission intensity is obtained.

  (S4) The relative value of the reflection intensity or the transmission intensity with respect to the irradiation intensity of the microwave is obtained by comparing the integrated value or the average value with the calibration curve (microwave irradiation intensity) at that time.

  (S5) The measured concentration of the suspended solid mixture is determined from the above relative values.

  In the above processing, the microwave scanning in the processing S1 will be described. As shown in FIG. 2, an example of the frequency band and inner and outer diameter dimensions of the rectangular waveguide, the frequency band is determined by the shape of the waveguide, and electromagnetic waves having a frequency equal to or higher than the cutoff frequency can pass therethrough. However, since higher-order modes are generated at higher frequencies, a frequency having a wavelength λ having a margin within the main mode band and having the following range is generally used. Note that “a” in the following formula is the width dimension (mm) of the waveguide.

[Equation 1]
(A / 0.95) <λ <(2a / 1.3)
Therefore, the transceiver 4 scans the microwave at a frequency including the range of the frequencies f _{1 to} f ₂ determined by this equation.

  Next, the reflection or transmission characteristics and the integral value or average value calculation in the processes S2 and S3 will be described.

FIG. 3 shows a characteristic A of reflection intensity or transmission intensity by scanning at a microwave frequency. For this characteristic A, the integration of the reflection or transmission intensity is obtained by the integral calculation of the reflection or transmission intensity in the range of the frequencies f _{1 to} f ₂ (the whole main mode band) determined by the above formula. This integration corresponds to the area of the hatched portion in FIG.

In this integration calculation, a method of continuously integrating the reflection / transmission intensity at frequencies f _{1 to} f ₂ using an analog integration circuit, or a discrete reflection / transmission intensity at each scanning frequency is integrated by digital calculation. It can be realized by the method. In addition, when obtaining an average value, it is obtained by dividing an integral value by an integration time in an analog operation, and is obtained by dividing by an number of samples in a digital operation.

  FIG. 4 shows a case where the reflection / transmission intensity characteristic A is obtained by integral calculation of reflection or transmission intensity in the frequency range fa to fb having a half-value width of the peak. If the matching from the waveguide to the suspended solid mixture is electrically matched, the frequency-reflection / transmission intensity characteristic A has a steep or gentle peak of reflection or transmission intensity near a certain frequency (matching frequency). appear. Assuming that the frequency at which the half value of the reflection or transmission intensity S at the peak is S / 2 is fa and fb, the reflection or transmission intensity is integrated in the range of the frequencies fa to fb. This integration corresponds to the area of the hatched portion in FIG.

  The integration calculation and the average value calculation can be realized by analog or digital calculation and division of the reflection / transmission intensity as in the case described above.

  FIG. 5 shows a case where the sum of reflection or transmission intensities at a plurality of frequencies (frequency selected near the matching frequency) is taken. In the figure, the reflection or transmission intensities Sa, Sb, and Sc at the three frequencies fa, fb, and fc are integrated with respect to the characteristic A. These integration results are obtained by simplifying the integration calculation described above, but are different from the conventional method of fixing to one frequency. The average value is calculated by dividing each intensity by the added number.

  As described above, in the present embodiment, the reflection intensity or transmission intensity of microwaves in a certain frequency range or a plurality of fixed frequencies is detected, respectively, and a concentration measurement value is obtained from an integral value or an average value of these detection values. As a result, when measuring the concentration of suspended solids, the reflection or transmission intensity characteristics change due to subtle changes in the transmission characteristics of the waveguide. And the occurrence of density measurement errors can be reduced.

FIG. 6 shows the density measured only from the reflection intensity and the density measured from the integrated value of the reflection intensity, and shows the drooping characteristic and the correlation. In the measurement only from the reflection intensity, the correlation R ^{2 is} 0.7677. On the other hand, the measurement from the integral value showed a high correlation degree of correlation R ² = 0.9518. Therefore, the measurement from the integral value has a better correlation with the concentration than the measurement from the reflection intensity, and the measurement accuracy can be improved as compared with the measurement from the reflection or transmission intensity by the conventional fixed frequency.

(Second Embodiment)
FIG. 7 is a data processing flow of the microwave type concentration measuring method showing the embodiment of the present invention. In FIG. 7, a portion different from FIG. 1 is added with correction processing of the concentration measurement value due to changes in temperature and conductivity. In the point.

  In the temperature / conductivity correction process S6, the concentration measurement value is corrected by measuring the temperature and the conductivity of the suspended solid mixture. Then, the integrated value or average value of the reflection intensity or transmission intensity of the microwave in a certain frequency range or a plurality of fixed frequencies is obtained, and a correction characteristic for a change in temperature or conductivity is obtained from these, and the correction characteristic and the temperature or conductivity are obtained. The concentration measurement value is corrected from the rate measurement value.

  That is, in order to obtain a correction characteristic of temperature or conductivity, a change in the reflection or transmission intensity with respect to a temperature change is not measured by measuring a change in reflection or transmission intensity with respect to a temperature change. Is obtained as a correction characteristic. The calculation of the integral value and the average value can be performed in the same manner as the calculation in the concentration measurement method in the first embodiment.

FIG. 8 shows a case where a change in the reflection intensity with respect to a temperature change and a change in the reflection intensity integrated value are measured, and the drooping characteristics (or correction characteristics) and the degree of correlation are also shown. As shown in the figure, the reflection intensity is correlated R ² = 0.4582 with respect to the temperature change of the suspended solid mixture, whereas the reflection intensity integrated value is high as correlation R ² = 0.9822. The correction accuracy can be improved by obtaining the correction characteristic from the integral value.

FIG. 9 shows a case where the change in the reflection intensity with respect to the change in conductivity and the change in the reflection intensity integrated value are measured, and also shows the drooping characteristics (or correction characteristics) and the correlation. As shown in the figure, the reflection intensity is correlated R ² = 0.7829 with respect to the change in conductivity of the suspended solid mixture, whereas the integrated reflection intensity is as high as R ² = 0.9524. The correction accuracy can be improved by obtaining the correction characteristic from the integral value of.

  These correlations with respect to temperature or conductivity are not limited to reflection intensity, but can also be high with respect to transmission intensity, and high correlation can also be obtained by taking average values instead of integral values. Can do.

  As described above, in the present embodiment, a correction characteristic is obtained from an integrated value or an average value of microwave reflection intensity or transmission intensity with respect to a change in temperature or conductivity, and a concentration measurement value is obtained using this correction characteristic. By correcting this, it is possible to correct the correction of the density measurement value.

(Third embodiment)
FIG. 10 shows the frequency-reflection intensity characteristics when the concentration of the suspended solid mixture having the temperature T and the conductivity C is changed. With this characteristic, the reflection intensity is minimal at two frequencies. These two frequencies are called matching frequencies, and the reflection intensity changes greatly as the density changes in the vicinity of the frequencies α ₁ and α ₂ . FIG. 11 shows the density-reflection intensity characteristics at the matching frequency α ₁ , and the density is substantially proportional to the reflection intensity.

  Therefore, if the temperature and conductivity of the suspended solid mixture are constant, the concentration can be determined by measuring the reflection intensity. However, since the temperature and electrical conductivity of an actual suspension mixed liquid change, the reflection intensity also changes thereby reducing the measurement accuracy. As countermeasures against this, correction is conventionally performed by changes in temperature and conductivity. However, if a measurement error occurs in the measurement of temperature or conductivity itself, the measurement accuracy of the concentration is lowered as a result.

  In the present embodiment, the temperature and conductivity of the suspension substance mixture are measured by measuring the concentration using the microwave frequency in the region where the reflection intensity does not change with respect to the change in the temperature or conductivity of the suspension substance mixture. This is a measurement method that eliminates the need for correcting the concentration measurement value based on the rate. Hereinafter, each measuring method will be described.

(A) Measurement method that eliminates the need for conductivity correction FIG. 12 shows the frequency-reflection intensity characteristics when the temperature T of the suspension mixture is constant and the conductivity C is changed from C _{1 to} C _4. At the frequency β, the characteristic curves intersect at one point. That is, at this frequency β, the reflection intensity does not change even if the conductivity of the suspended solid mixture changes.

  FIG. 13 shows the density-reflection intensity characteristics at the temperature T at the frequency β. The density and the reflection intensity are in a substantially proportional relationship, and the correlation is high.

  Therefore, the concentration measurement at the temperature T of the suspended solid mixture is performed by measuring the reflection intensity with the microwave frequency fixed at β, thereby improving the accuracy while eliminating the need for correcting the conductivity C. it can.

(B) Measurement method that eliminates the need for conductivity correction FIG. 14 shows the frequency-reflection phase difference characteristics when the temperature T of the suspended solid mixture is constant and the conductivity C is changed from C _{1 to} C _N. As shown, the characteristic curves are substantially equal at the frequency γ. That is, at this frequency γ, the reflection phase difference does not change even when the conductivity of the suspended solid mixture changes.

  FIG. 15 shows the density-reflection phase difference characteristics at the temperature T at the frequency γ, and the density and the reflection phase difference are approximately proportional to each other, and the correlation is high.

  Therefore, the concentration measurement at the temperature T of the suspension mixture is performed by fixing the microwave frequency to γ and measuring the reflection phase difference, thereby eliminating the correction of the conductivity C and improving the accuracy. Can do.

(C) Temperature compensation measurement method Figure 16 to eliminate the need for is a conductivity of the suspended solids mixture C is constant, the frequency when changing the temperature T to T ₁ through T _K - indicates a reflection phase difference characteristic At the frequency δ, the characteristic curves are almost equal. That is, at this frequency δ, the reflection phase difference does not change even if the temperature of the suspended solid mixture changes.

  Further, FIG. 17 shows the density-reflection phase difference characteristic at the conductivity C at the frequency δ, and the density and the reflection phase difference are substantially proportional to each other, and the correlation is high.

  Therefore, for measuring the concentration of the conductivity C of the suspended solid mixture, the concentration of the microwave is fixed at δ and the reflection phase difference is measured, thereby improving the accuracy while eliminating the need to correct the temperature T. Can do.

(Fourth embodiment)
As shown in FIG. 10, the reflection intensity hardly changes at the frequency α even if the concentration of the suspension mixed liquid changes. Therefore, the change in the reflection intensity measured using the microwave with the frequency α is constant because the temperature T of the suspension substance mixture is constant, due to the change in conductivity.

  Therefore, microwaves with a frequency α that is constant in temperature T of the suspended solid mixture and unaffected by the change in concentration are irradiated, and the relationship between the reflection intensity and the conductivity at that time is obtained. The conductivity can be determined by measuring the reflection intensity.

  FIG. 18 shows the reflection intensity-conductivity characteristics at the frequency α. The reflection intensity and the conductivity are in a substantially proportional relationship, and the correlation is high.

  Therefore, in order to measure the conductivity of the suspension material mixture, if the proportional relationship between the reflection intensity and the conductivity when the suspension material mixture at temperature T is irradiated with microwaves of frequency α, In measuring the conductivity at the time of measurement, the conductivity at the temperature T can be obtained by measuring the reflection intensity with respect to the irradiation with the frequency α. In the concentration measurement based on this method of determining the conductivity, a conventional conductivity meter is not required, and maintenance thereof is not required.

The data processing flow of the microwave type measuring method which shows the 1st Embodiment of this invention. Example of dimensions of rectangular waveguide. 5 is a reflection / transmission intensity characteristic and integration range in the first embodiment. 5 is a reflection / transmission intensity characteristic and integration range in the first embodiment. Reflected / transmitted intensity characteristics and integrated positions in the first embodiment. Comparison of correlation between reflection intensity and integrated value density in the first embodiment. The data processing flow of the microwave type measuring method which shows the 2nd Embodiment of this invention. Comparison of correlation between reflection intensity and temperature of integrated value in the second embodiment. Comparison of the correlation between the reflection intensity and the integrated conductivity in the second embodiment. Frequency-reflection intensity characteristics when the density is changed in the third embodiment. The density-reflection intensity characteristic at the frequency α1 in FIG. Frequency-reflection intensity characteristics when the conductivity C in the third embodiment is changed. Density-reflection intensity characteristics at frequency β in FIG. Frequency-reflection phase difference characteristics when the conductivity C in the third embodiment is changed. 14 is a density-reflection phase difference characteristic at the frequency γ in FIG. Frequency-reflection phase difference characteristics when the temperature T is changed in the third embodiment. FIG. 16 is a density-reflection phase difference characteristic at the frequency δ in FIG. Relation between reflection intensity and conductivity in the fourth embodiment. Measurement principle of transmission method in microwave concentration measurement method. Microwave phase difference-concentration characteristics diagram. Reflection method measurement principle in microwave concentration measurement method. The structural example of the probe in a microwave type | mold density | concentration measuring method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Suspended substance mixed liquid transport tube 2, 3, 6 ... Probe 4 ... Microwave transmitter / receiver 5 ... Densitometer converter 9 ... Waveguide

Claims (2)

In the microwave concentration measurement method for measuring the concentration of suspended substances by detecting the reflection intensity or reflection phase difference of the microwaves irradiated toward the suspension substance mixture,
Irradiate microwaves with a frequency at which the reflection intensity or reflection phase difference becomes almost constant with respect to the change in conductivity of the suspension mixture, or the reflection phase difference with respect to the change in the temperature of the suspension mixture. A microwave concentration measurement method, wherein the concentration of a suspended substance is measured by irradiating a microwave having a constant frequency. In the microwave concentration measurement method for measuring the concentration of suspended substances by detecting the reflection intensity or transmission intensity or reflection phase difference of the microwaves irradiated toward the suspension substance mixture,
Irradiate the suspension material mixture with microwaves at a frequency at which the reflection intensity becomes almost constant with respect to the concentration change of the suspension material mixture,
From the proportional relationship between the reflection intensity and the conductivity in the microwave irradiation at a constant temperature of the suspension material mixture, the conductivity of the suspension material mixture is obtained,
A microwave concentration measuring method, comprising correcting a concentration measurement value of a suspended solid mixture from the conductivity.

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