JP5458258B2 - Suspended matter analysis method and suspended matter analysis system - Google Patents

Description

The present invention relates to a suspended matter analysis method and a suspended matter analysis system for analyzing suspended matter in a liquid.

  In dams, rivers, and other water systems, suspended matter concentrations are measured for water quality management and other purposes. Such concentration measurement needs to be accurately performed even when the suspended matter becomes a high concentration, and in order to realize such measurement, measurement using ultrasonic waves is being used. As an apparatus used for ultrasonic measurement, for example, there is an apparatus that irradiates a sample liquid with ultrasonic waves and calculates the concentration of suspended solids from an electrical signal corresponding to a pulse that has passed. This measurement apparatus can improve measurement efficiency by providing a reflector that reflects a pulse to the receiving unit side while sharing a pulse transmitting unit and a receiving unit (see, for example, Patent Document 1).

  However, the above-described measuring apparatus can accurately measure the concentration of suspended matter having a constant particle size, but it is difficult to correctly estimate the concentration when the particle size of suspended matter changes. This is because the characteristics such as the type, shape, and particle size of the suspended matter differ depending on the water system, and the concentration changes if the suspended particle size distribution varies even though the same ultrasonic attenuation rate is exhibited. Among the water systems, especially in dams, suspended solids settle and accumulate. Therefore, in order to effectively implement measures against sediment accumulation in the dam, the amount of suspended solids flowing into and out of the dam must be accurately determined. And it is necessary to grasp quickly.

  Accordingly, there is a need to provide a method for analyzing suspended solids that can measure the concentration of a sample liquid that reflects the particle size of suspended solids. For example, an ultrasonic attenuation rate and a scattered light method that has been optically measured in advance. Based on the relationship between turbidity, the product of the relative particle amount of suspended solids and scattered light turbidity is the objective variable, and the multiple regression model is obtained with the ultrasonic attenuation rate corresponding to each frequency as the explanatory variable. Based on the measured concentration value, a suspended matter analysis method for measuring the turbidity (concentration) of water in consideration of the particle size of the suspended matter and the inherent attenuation rate based on the particle size has been proposed (for example, see Patent Document 2). .

JP 2004-271348 A JP 2009-025027 A

In view of the above-described background art, the present invention is based on the measured ultrasonic attenuation rate value without using the optically measured turbidity, and the concentration by particle size in the liquid as the sample, and by particle size. Proposed a suspended solids analysis method that can calculate the total concentration (concentration), in addition, enables calculation of the relative particle amount using the calculated total concentration (concentration) by particle size and ultrasonic attenuation rate. By dividing the total concentration (concentration) by particle size by the density of soil particles and displaying the volume as a volume, for example, even when the density of soil particles varies from river system to river system, suspended matter in the river It proposes a suspended matter analysis method and a suspended matter analysis system that make it possible to measure the volume concentration.

Among the suspended matter analysis methods of the present invention, the method according to claim 1 is characterized by comprising the following steps.
(1) Systematically changing the frequency of ultrasonic waves applied to the sample liquid, measuring the attenuation rate α (f) of each frequency, and measuring the attenuation derived from the sample liquid as a medium and the attenuation derived from the particles The value is expressed as Equation 1 below.
(Where α medium (f) is the ultrasonic attenuation factor derived from the medium when the frequency is f, and α mono (f, D) is the ultrasonic attenuation derived from monodisperse particles having the frequency f and the particle size D. The rate, g (D), is the mass percentage of particles whose particle size is between D and D + dD (hereinafter referred to as relative particle amount).
(2) The water temperature is measured, and the measured value of the reference spectrum of each frequency band that varies depending on the water temperature is obtained as a function of the water temperature by the following formula 2.
(Here, M0 (fj) is a measured value of the reference spectrum of the frequency fj at the water temperature t, t is the water temperature [° C.] at the time of measurement, and aj, bj, cj, dj are constants for calculating the reference spectrum of the frequency fj. However, the reference spectrum means the frequency spectrum of the sample liquid when the medium is only water.
Here, α (fj) is the ultrasonic attenuation rate (dB / MHz) of the frequency fj, fj is the frequency (MHz), M0 (fj) is the measurement value of the reference spectrum of the frequency fj, and M (fj) is the frequency fj. It is a measured value of the frequency spectrum of the suspension. )
(3) (a) Water temperature at the time of measurement obtained in the step ( 2 ) , (b) Measurement value of frequency spectrum , and (c) Measurement value of reference spectrum at water temperature t and reference spectrum at reference water temperature t0 Using the water temperature correction coefficient τ (fj) of the frequency fj, which is a ratio to the measured value of, the correction based on the water temperature is performed by Equations 4 and 5, and the ultrasonic attenuation rate under the reference water temperature is obtained.
(Where α (fj) is the ultrasonic attenuation rate [dB / MHz] of the frequency fj, fj is the frequency [MHz], and M0 (fj) t = t0 is the frequency fj at the reference water temperature t0 calculated by Equation 2. Measured value of reference spectrum, M0 (fj) t = t: Measured value of reference spectrum of frequency fj at water temperature t calculated by Equation 2, M (fj) t = t is suspension of frequency fj at water temperature t The measured value of the frequency spectrum of τ, τ (fj) is the water temperature correction coefficient of frequency fj, t0 is the reference water temperature [° C.], and t is the water temperature [° C.] at the time of measurement.
(4) The concentration conversion rate represented by the following formula 6 in each frequency band is verified (concentration conversion rate λ (fj) is a rate for converting the ultrasonic attenuation rate in formula 6 into a concentration, that is, a unit concentration Ultrasonic attenuation rate, called unit concentration attenuation rate)
(Where α (fj) is the ultrasonic attenuation rate [dB / MHz] at the frequency fj, C is the concentration [mg / liter], and λ (fj) is the concentration conversion rate (unit concentration attenuation rate) at the frequency fj. .)
(5) As a conversion procedure applying a multiple regression model using the relative particle amount g (Di) of each particle size floor as an objective variable and the unit concentration decay rate λ (fj) calculated by the equation 6 as an explanatory variable,
(Where g (Di) is the relative particle amount (%) of the particle size class Di, fj is the frequency [MHz], βij is the partial regression coefficient, λ (fj) is the unit concentration decay rate of the frequency fj, and m is the particle size. The number of divisions of the radial floor, n is the number of frequencies fj, and ε is the residual)
(6) Substituting the formula 6 and the formula 7 into the formula 8 respectively to arrange the concentration C, the following formula 9 is obtained,
The concentration C of the sample liquid is obtained by multiple regression analysis as a function of the ultrasonic attenuation rate α (fj). Note that in the expression in the second row of Equation 9, the residual + ε shown in Equation 7 should originally appear in {} on the left side, but this residual ε is ignored as it is small and is omitted. .

According to claim 2, in the suspended matter analysis method of claim 1,
In the above formula 9 showing the concentration by particle size
Is expressed as Equation 11 below.
(Where c _i is the concentration [mg / liter] of particle size floor D _i , α (f _j ) is the ultrasonic attenuation rate [dB / MHz] at frequency f _j , β _ij is the partial regression coefficient, and n is the frequency f is the number of _j .)
Thus, the concentration of the suspended substance in the sample liquid is determined for each particle size.

According to claim 3, in the suspended matter analysis method of claim 2,
Substituting the equation 11 into the equation 9 to obtain the following equation 12,
(Where C is the concentration [mg / liter], c _i is the concentration [mg / liter] of the particle size floor D _i , and m is the number of particle size floor divisions.)
It is possible to measure the relative particle amount considering the attenuation rate,
It is characterized in that the concentration of the sample liquid is obtained as the sum of the concentrations by particle size.

According to a fourth aspect of the present invention, in the suspended matter analysis method according to the third aspect, the unit concentration attenuation rate λ (f _j ) is calculated from the concentration C of the sample liquid and the ultrasonic attenuation rate α (f _j ) using the formula 6. The relative particle amount g (D _i ) is calculated by using the partial regression coefficient of the multiple regression model and the unit concentration decay rate λ (f _j ) of Equation 7
(Where g (D _i ) is the relative particle amount (%) of the particle size stage D _i , f _j is the frequency [MHz], β _ij is the partial regression coefficient, and λ (f _j ) is the unit concentration of the frequency f _j Attenuation rate, m is the number of particle size divisions, and n is the number of frequencies f _j .)
The relative particle amount is obtained by the following.

The suspended sand concentration analysis method according to claim 5 is the suspended sand concentration analysis method for obtaining the suspended sand concentration in the river bed fluctuation calculation using the suspended matter analysis method according to any one of claims 1 to 3,
(1) The concentration of the floating sand is displayed in the volume display as in the following formula 14,
(Here, the flow rate is Q [m3 / s], and the amount of floating sand in the flow rate is Qs [m3 / s].)
(2) Assuming that the density of the soil particles is ρ [mg / cm 3], the relationship between the concentration Cw in weight display and the concentration Cvol in volume display is expressed by the following formula 15.
When calculating the unit concentration attenuation rate λ (fj) shown in Equation 6 above, the concentration C calculated by Equation 12 is analyzed as a dimensionless amount by analyzing the concentration as a volume display concentration Cvol using Equation 15 above. It is characterized by the density Cvol of volume display.
(Here, C is the concentration [mg / liter], ci is the concentration [mg / liter] of the particle size floor Di, and m is the number of particle size floor divisions.)

  A suspended matter analysis system according to a sixth aspect is characterized in that the suspended matter in a liquid is analyzed using the suspended matter analysis method according to any one of the first to fourth aspects.

  The suspended sand concentration analysis system according to claim 7 is characterized in that the suspended sand concentration analysis method according to claim 5 is used to obtain the suspended sand concentration in the river bed fluctuation calculation.

  According to the present invention, even in a liquid in which particulate matter is mixed at a high concentration and the transparency is extremely inferior, the particle size of the suspended solids, the sum of the concentration (concentration) by particle size in consideration of the inherent attenuation rate based on the particle size, The quantity and the volume (volume) concentration can be measured.

Block diagram of an analysis system used for carrying out the suspended matter analysis method according to the present invention The figure which shows an ultrasonic concentration measuring device (detection part) Diagram showing an example of a plano-concave ultrasonic transducer Diagram showing particle size distribution of test sample Water frequency spectrum (reference spectrum) Diagram showing the effect of water temperature on the reference spectrum Figure showing frequency spectrum measurement results Diagram showing attenuation spectrum calculation results The figure which shows the relationship between SS density | concentration after correction | amendment, and attenuation factor (alpha). Figure showing unit concentration decay spectrum (concentration conversion rate) Flow chart of measurement procedure Diagram showing concentration measurement results by particle size Figure showing concentration measurement results Diagram showing measurement results of relative particle amount Figure showing the measurement result of particle size distribution (relative particle amount)

  The measurement method of the present invention measures the concentration and particle size distribution (relative particle amount) in a suspension that is a sample liquid, and radiates from an ultrasonic transducer, for example, in a number of frequency bands of about 1 to 10 MHz. From the ultrasonic attenuation rate, the concentration, concentration, and particle size distribution (relative particle amount) by particle size are measured simultaneously.

First, the measurement principle of the suspended solids analysis method according to the present invention, that is, the measurement principle of the particle size distribution will be described.
When the fine particles are put to practical use, there are many dispersion systems in which the particle concentration is high and light is not transmitted. Therefore, it cannot be measured by a technique using light such as a laser. Therefore, it is necessary to perform complicated operations before measurement, such as diluting the sample carefully. Further, it has been pointed out that dilution may cause a change in the state of the dispersion, and the particle size distribution in the lean system does not necessarily indicate the particle size distribution in the rich state. Ultrasonic attenuation spectroscopy and electro-acoustic effect method are based on measurement principles that are completely different from conventional particle size distribution measurement methods. In this method, ultrasonic waves are used instead of light. Or an alternating electric field. Therefore, particle size analysis is possible even for a suspension with a very high particle concentration that cannot transmit light.

When ultrasonic waves are applied to the suspension, the particles cause relative movement with respect to the solvent. The attenuation rate of the acoustic energy resulting from the movement is measured with respect to the transmitted acoustic energy, and this is applied to various attenuation mechanisms. And is converted into a particle size distribution function. In actual measurement, the frequency of the ultrasonic wave to be irradiated is systematically changed, and the attenuation rate α (f) of each frequency is measured (in this specification, a curve indicating the attenuation rate change for a certain frequency is called an attenuation spectrum). ). The measured value is composed of the attenuation derived from the medium and the attenuation derived from the particles, and is expressed as the following Expression 16.
Here, α _medium (f) is an ultrasonic attenuation factor derived from the medium when the frequency is f, α _mono (f,
D) is an ultrasonic attenuation rate derived from monodisperse particles having a frequency of f and a particle size D, and g (D) is a mass percentage of particles having a particle size between D and D + dD (hereinafter referred to as relative particle amount). It is. g (D) basically assumes a lognormal distribution. The conversion procedure to the particle size distribution function varies the particle size distribution function g (D) in various ways, calculates the second term on the right side of Equation 16, and best matches the ultrasonic attenuation rate measured over the entire frequency range. The distribution function is used as the particle size distribution function of the measured system. A method for measuring the particle size distribution using the dependency of the ultrasonic attenuation spectrum on the particle size distribution is called ultrasonic attenuation spectroscopy.

  Next, in ultrasonic concentration measurement, when ultrasonic waves pass through the suspension, acoustic energy is lost due to the particles and media present in the suspension, so the ultrasonic attenuation rate of the frequency spectrum for each concentration is low. Measurement is performed based on the measurement principle that solid fine particles increase in relation to concentration. As for the attenuation rate, the attenuation rate at each concentration is represented by 0 when the medium is only water.

  Embodiments of the suspended matter analysis method according to the present invention will be described below with reference to the drawings.

First, a measuring apparatus that can be used in this embodiment will be described.
As shown in FIG. 1, the analysis system 10 used for carrying out the suspended matter analysis method includes an ultrasonic attenuation rate measuring device 11, a particle size measuring device 12, a control unit 13, and a particle size analyzing device 14 configured using, for example, a personal computer. It can comprise from the analysis apparatus 30 which consists of. The personal computer can use the CPU (Central Processing Unit) as the control unit 13, an internal memory such as a rewritable RAM, or a hard disk or other external storage device as the storage unit 15. In the case of using a personal computer, it is preferable to provide an input means (for example, a keyboard and a mouse) and an output means (for example, a monitor and a printer). For example, an instruction signal for controlling the operation of each device is input by the input means. It is preferable that measurement conditions and measurement results can be output to the output means. Further, temperature measuring means (not shown) such as a thermometer is used for measuring the water temperature of the sample liquid. If the analysis device 30 and the temperature measuring unit cannot communicate the measurement data by wire or wireless, the input by the input unit described above can be substituted.

  In the ultrasonic attenuation rate measuring apparatus 11, a plano-concave type ultrasonic transducer 20 (hereinafter sometimes simply referred to as the transducer 20) as shown in FIG. 2 is used as a detection unit for measuring the ultrasonic attenuation rate. Using the reflection plate 21, an ultrasonic pulse wave is applied to the sample liquid containing floating substances, and a reflected pulse signal obtained from the reflected ultrasonic pulse wave after passing through the sample liquid is obtained.

  In order to form a plano-concave surface (plano concave), the plano-concave type ultrasonic transducer 20 is formed, for example, on one surface of a commercially available circular lead titanate transducer having a diameter of 20 mm as shown in FIG. As shown in (B), a concave surface is processed with a radius of curvature r = 30 mm, and electrodes are attached to the processed surface and the back surface. A reflector 21 is placed at the focal point of the plano-concave transducer 20, and the echo wave of the radiated broadband ultrasonic pulse wave is received by the same transducer 20 to measure the ultrasonic attenuation rate. As shown in FIG. 3B, since the thickness of the vibrator 20 continuously changes, it is possible to radiate ultrasonic waves in a wide frequency band of, for example, 1 to 10 MHz, and further, an ultrasonic radiation surface. Because of the concave surface, it is possible to emit focused ultrasonic waves. Therefore, when an impulse voltage is applied to the vibrator, it is possible to radiate a broadband focused ultrasonic wave with little ringing. In order to use such an ultrasonic attenuation rate measuring apparatus 11 for the sample liquid, for example, the plano-concave ultrasonic transducer 20 can be arranged on one side inside the container for containing the sample liquid, and on the other side inside the container. The size and the like are configured so that the reflector 21 can be arranged.

  The particle size measurement device 12 includes, for example, a pulse generation unit, an echo pulse recording / FFT (Fast Fourier transform) processing unit, and a data transmission / reception unit. The pulse generation unit is connected to the vibrator 20 under the control of the control unit 13. The excitation pulse signal is sent, and the echo pulse recording / FFT processing unit takes in the reflected pulse signal corresponding to the reflected pulse wave (ultrasonic echo) reflected by the reflecting plate 21 and received by the transducer 20 to obtain predetermined data. Convert to Further, the echo pulse recording / FFT processing unit measures the suspended matter concentration and the ultrasonic attenuation rate based on the converted predetermined data. The processing result in the echo pulse recording / FFT processing unit is output to the control unit 13 via the data transmission / reception unit and stored in the storage unit 15. Therefore, the concentration of suspended solids can be measured in real time from the attenuation characteristics of the frequency spectrum of the broadband ultrasonic wave radiated from the transducer 20. The analysis system 10 may include a digital oscilloscope that digitizes and displays the reflected pulse signal.

  The particle size analyzer 14 analyzes the particle size of suspended solids contained in the sample liquid based on the measurement results stored in the storage unit 15, and includes a memory unit (not shown) in which an analysis program is stored. And a calculation unit (not shown) for executing the analysis program. As the memory unit and the calculation unit, for example, a storage device and a CPU of a personal computer can be used, so that the storage unit 15 and the control unit 13 may be used in common. That is, the particle size analysis can be performed by providing the control unit 13 with the function of the arithmetic unit of the particle size analyzer 14 and the memory unit 15 with the function of the memory unit of the particle size analyzer 14.

The particle size analysis will be described.
In the apparatus of the present embodiment, broadband ultrasonic waves radiated into a sample liquid containing fine particles from a detection unit (sensor) using the plano-concave ultrasonic transducer 20 as described above and being in a suspension. The concentration of fine particles is measured from the ultrasonic attenuation rate of the echo wave. A rectangular impulse voltage as a broadband excitation pulse wave is applied to the vibrator 20 from the pulse generator of the particle size measuring device 12. The rectangular impulse voltage is, for example, a pulse width of 80 ns at which the maximum value of the measured value of the reference spectrum at the reference water temperature (20 ° C.) at the basic thickness resonance frequency (1 to 10 MHz) of the vibrator is 1.0 mV, 5 V _{p−. Let p} .

  The ultrasonic pulse wave radiated from the transducer 20 propagates in the sample liquid, and the echo pulse waveform reflected by the reflecting plate 21 is captured and A / D converted. Then, the frequency spectrum of the waveform is obtained. The analyzed value becomes the measured value.

  Next, a measurement procedure actually performed by the inventors will be described. However, the following substances, numerical values, and the like are examples of tests, and the present invention is not limited with respect to these substances and numerical values.

  First, about 120 g of a wet sample was placed in a measurement container containing 6 liters of distilled water, and the ultrasonic attenuation rate as described above was measured while stirring the sample liquid as a suspension with a pump. In addition, water temperature and scattered light turbidity were measured. 2 liters of water was collected from the 6-liter suspension after measurement, and SS concentration measurement and particle size analysis were performed. SS concentration measurement is based on JIS-K0102. The SS concentration was measured twice for each sample, and the average value was calculated. The particle size distribution was measured using a laser diffraction particle size analyzer (for example, SALD-3000J manufactured by Shimadzu Corporation). Each measurement was performed twice, and the average value was adopted. Next, 2 liters of distilled water was added to the sample liquid to obtain a 6-liter suspension, and the concentration was diluted to 2/3, and the same measurement was performed. The sample liquid was diluted 10 times in total, and the same measurement test was performed on all samples.

The purification of the test fine particles used in the above test will be described.
The fine particles for the test were those obtained by classifying the sediments collected in the Taki adjustment pond (Tadami-machi, Minamiaizu-gun, Fukushima Prefecture) with water and purifying them in a wet state. There are five types of sieves used for classification: 106 μm, 75 μm, 53 μm, 38 μm, and 25 μm. The particle size distribution of the test fine particles is shown in FIG. “−25-01” shown in FIG. 4 represents the first test result of the fine particles having passed through a sieve having a particle diameter of 25 μm. Similarly, “38-25-01” represents the first measurement result of fine particles that passed through the 38 μm sieve and remained on the 25 μm sieve. This is the same with respect to all the drawings in FIGS.

Next, the reference spectrum will be described.
First, the ultrasonic attenuation rate will be described. The ultrasonic attenuation rate α (f _j ) is obtained by calculating the attenuation rate at each concentration from the following equation 17 with 0 when the medium is only water at each frequency. Here, the frequency spectrum when the medium is only water is hereinafter referred to as “reference spectrum”.
here,
α (f _j ): ultrasonic attenuation rate of frequency f _j [dB / MHz]
f _j : Frequency [MHz]
M ₀ (f _j ): a measured value of the reference spectrum at the frequency f _j M (f _j ): a measured value of the frequency spectrum of the suspension at the frequency f _j .

  The above-described reference spectrum has a characteristic that changes depending on the water temperature. The result of having measured the reference | standard spectrum by changing the water temperature by putting the detection part of the ultrasonic attenuation rate measuring apparatus 11 mentioned above in the thermostat water tank which put 10 liters of distilled water is shown in FIG. In this figure, the horizontal axis indicates the frequency, and the vertical axis indicates the measured value of the reference spectrum. Since the measured value of the reference spectrum increases as the water temperature rises, the reference water temperature is set, and the measured value is adjusted so that the maximum value of the measured value of the reference spectrum at the reference water temperature is 1.0 mV.

Next, the measurement results of the reference spectrum for each frequency are arranged as shown in FIG. In FIG. 6, the horizontal axis represents the water temperature, and the vertical axis represents the measured value of the reference spectrum corresponding to each frequency. The measured value of the reference spectrum in each frequency band can be expressed by the following Equation 18 as a function of the water temperature.
here,
M ₀ (f _j ): measured value of reference spectrum of frequency f _{j at} water temperature t: water temperature during measurement [° C.]
a _j , b _j , c _j , d _j : constants for calculating the reference spectrum of the frequency f _j .

  Accordingly, by analyzing the relationship between the water temperature and the measured value of the reference spectrum in each frequency band, the constant represented by Expression 18 is determined, and the water temperature is measured together with the measurement of the frequency spectrum, whereby Expression 17 is used. Thus, the measured value of the reference spectrum in each frequency band can be obtained from the water temperature.

Next, an example of a measurement test result will be described.
The measurement result of the frequency spectrum by the ultrasonic attenuation rate measuring device 11 is shown in FIG. In FIG. 7, the horizontal axis indicates the frequency, and the vertical axis indicates the measured value of the frequency spectrum. Measurement data of a frequency spectrum corresponding to 1024 frequencies in the frequency band of 0 to 12.5 MHz can be obtained from one measurement data of the used measuring apparatus (SSH100). The maximum value of the frequency spectrum is around 5.5 MHz in frequency. The measurement test performed this time employs the dilution method, and as the number of measurements increases, the concentration decreases, so the attenuation decreases and the measured value of the frequency spectrum increases.

The water temperature correction of the ultrasonic attenuation rate will be described. As described above, the measured value of the reference spectrum varies depending on the water temperature. Therefore, the ultrasonic attenuation rate of Equation 17 needs to be corrected for water temperature. The water temperature correction is performed by the following Equations 19 and 20 using the water temperature correction coefficient τ (f _j ), which is the ratio of the measured value of the water temperature and frequency spectrum at the time of measurement and the measured value of the reference spectrum at the reference water temperature t _0. .
here,
α (f _j ): ultrasonic attenuation factor of frequency f _j [dB / MHz]
f _j : Frequency [MHz]
M ₀ (f _j ) t = t ₀ : Measured value of the reference spectrum of the frequency f _j at the reference water temperature t ₀ calculated by Equation 18 M ₀ (f _j ) t = t: at the water temperature t calculated by Equation 18 frequency _f measured value of the reference spectrum _{j M (f j) t =} t: measured value of the frequency spectrum of a suspension of a frequency _{f j} of the water temperature t tau _(f j): the water temperature correction coefficient for the frequency _{f j t 0} : Reference water temperature [℃]
t: Water temperature during measurement [° C]
It is.

  FIG. 8 shows the ultrasonic attenuation rate calculated from the frequency spectrum measurement values shown in FIG. The horizontal axis indicates the frequency, and the vertical axis indicates the ultrasonic attenuation rate expressed by Equation 19. This curve is called an attenuation spectrum. As seen in FIG. 8, the measured value of the ultrasonic attenuation spectrum depends not only on the concentration but also on the particle size distribution. For example, the attenuation rate in the frequency band of 8.0 MHz tends to increase as the particle size increases. On the other hand, the attenuation rate in the frequency band of 3.0 MHz shows a tendency to decrease as the particle size increases.

FIG. 9 shows the relationship between the SS concentration (average value) and the ultrasonic attenuation rate α (f = 8.0 MHz). The horizontal axis represents the ultrasonic attenuation rate α (f _j ), and the vertical axis represents the SS concentration. The SS concentration measurement value is obtained from the concentration measurement value and the attenuation rate at the frequency f = 8.0 MHz by obtaining an average concentration conversion rate by the least square method, and the ultrasonic attenuation rate α (f _j ) is calculated as the average concentration conversion rate. The density was corrected by multiplication. FIG. 9 shows the relationship between the corrected SS concentration and the attenuation rate α.

Next, the concentration conversion rate of each frequency band is verified. The density conversion rate λ (f _j ) is expressed by the following formula 21. The concentration conversion rate in the equation was defined as a rate for converting the ultrasonic attenuation rate into a concentration. In other words, the concentration conversion rate is the ultrasonic attenuation rate of the unit concentration, and is hereinafter redefined as the unit concentration attenuation rate.
here,
α (f _j ): ultrasonic attenuation rate of frequency f _j [dB / MHz]
C: Concentration [mg / liter]
λ (f _j ): concentration conversion rate (unit concentration decay rate) at frequency f _j

The unit concentration decay rate λ (f _j ) is shown in FIG. The horizontal axis indicates the frequency, and the vertical axis indicates the unit concentration attenuation rate λ (f _j ) expressed by Equation 21. The SS concentration C used in Equation 21 was the previously corrected concentration. When the particle size distribution is constant, the ultrasonic attenuation rate is proportional to the concentration as a measurement principle, and therefore the unit concentration attenuation rate λ (f _j ) at each frequency is a constant value. However, as shown in FIG. 10, there is a variation in the unit concentration attenuation rate in some samples. This variation causes a decrease in measurement accuracy of concentration and particle size distribution (relative particle amount).

Next, concentration measurement by ultrasonic attenuation spectroscopy will be described.
The principle of particle size distribution measurement by ultrasonic attenuation spectroscopy is as described above. That is, the relationship between the ultrasonic attenuation rate and the relative particle amount is expressed by Equation 16. In order to simplify the procedure for converting the unit concentration attenuation spectrum (concentration conversion rate) to the particle size distribution function, one method for measuring the particle size distribution using the particle size distribution dependency of the ultrasonic attenuation spectrum is as follows. A conversion procedure is performed using a multiple regression model (Equation 22) in which the relative particle amount g (D _i ) is an objective variable and the unit concentration decay rate λ (f _j ) calculated by Equation 21 is an explanatory variable.
here,
g (D _i ): Relative particle amount [%] of the particle size floor D _i
f _j : Frequency [MHz]
β _ij : Partial regression coefficient λ (f _j ): Unit concentration decay rate m of frequency f _j m: Number of particle size divisions n: Number of frequencies f _j ε: Residual.

Next, by substituting Equation 21 and Equation 22 into Equation 23 and rearranging the concentration C, the following Equation 24 is obtained.

Formula 24 is a formula for calculating the concentration C. That is, if the partial regression coefficient β _ij shown in Equation 22 is known, the concentration C can be obtained as a function of the ultrasonic attenuation rate α (f _j ) using Equation 24. The ultrasonic attenuation rate α (f _j ) is calculated from the measured value of the water temperature and frequency spectrum at the time of measurement using Equation 19. Further, β _ij (partial regression coefficient) of Equation 22 is _subjected to a measurement test using fine particles having different particle size distributions, and is subjected to multiple regression from the measurement data of the ultrasonic attenuation rate α (f _j ) and the relative particle amount g (D _i ). It can be obtained by analysis.

The inventors of the present application measure the particle size distribution (relative particle amount) using the measured value of the scattered light turbidimeter because the concentration is unknown, and the concentration conversion rate λ (f _j ) from the relative particle amount. (Patent Document 2) proposed a method for estimating the concentration C as a function of the ultrasonic attenuation rate α (f _j ) using Equation 24 by adopting Equation 22 in the multiple regression model. It was clarified to measure.

In addition, Formula 25 in parentheses of Formula 24
Indicates the concentration for each particle size, and this concentration for each particle size can be expressed as Equation 26 below.
here,
c _i : Concentration of particle size floor D _i [mg / liter]
α (f _j ): ultrasonic attenuation rate of frequency f _j [dB / MHz]
β _ij : Partial regression coefficient n: Number of frequencies f _j .

Substituting Equation 26 into Equation 24 yields Equation 27 below. The concentration of the sample liquid (suspension) can be obtained by Equation 27 as the sum of the concentrations by particle size.
here,
C: Concentration [mg / liter]
c _i : Concentration of particle size floor D _i [mg / liter]
m: Number of particle size floor divisions.

Next, the unit concentration attenuation rate λ (f _j ) is calculated from the concentration C and the ultrasonic attenuation rate α (f _j ) using Equation 21, and the relative particle amount g (D _i ) is calculated from the multiple regression model of Equation 22. Using the partial regression coefficient and the unit concentration decay rate λ (f _j ), it can be obtained by Equation 28.
here,
g (D _i ): Relative particle amount (%) of the particle size floor D _i
f _j : Frequency [MHz]
β _ij : Partial regression coefficient λ (f _j ): Unit concentration decay rate m of frequency f _j m: Number of particle size floor divisions n: Number of frequencies f _j

Next, determination of the multiple regression model will be described.
The partial regression coefficient β _ij of the multiple regression model (Formula 22) is calculated by multiple regression analysis using the measurement data of all 15 times for each fine particle shown in FIG. In addition, the ultrasonic attenuation rate α (f _j ) is stable in the frequency band of 2.0 to 9.0 MHz, and the explanatory variable of the multiple regression model is 0.5 MHz in the frequency band of 3.0 to 9.0 MHz. An ultrasonic attenuation rate α (f _j ) corresponding to 13 frequencies at intervals is used.

Next, the measurement procedure for concentration and particle size analysis in this embodiment will be described with reference to FIG.
First, with the start of measurement, a process as shown in FIG. 11 (hereinafter referred to as a step) is performed on the sample liquid. That is, first, the ultrasonic echo measurement step as described above is performed (step 1). Next, the water temperature is corrected as described above (step 2), frequency analysis is performed (step 3), the concentration by particle size is measured (step 4), the sum of the concentration by particle size is calculated (step 5), and the unit The concentration reduction rate is calculated (step 6), the relative particle amount is calculated (step 7), and the concentration of the volume display is calculated (step 8).

Specifically, the measurement procedure is:
(1) First, the ultrasonic attenuation rate α (f _j ) is calculated by Equation 19 and Equation 20 from water temperature and frequency spectrum measurement data (1024 sets of frequency and spectrum measurement values).
(2) Calculate the concentration c _i for each particle size from the partial regression coefficient β _ij and the ultrasonic attenuation rate α (f _j ) determined by the procedure in the previous section by Equation 26,
(3) The concentration C is calculated from the concentration c _{i by} particle size according to Equation 27,
(4) A unit concentration attenuation rate λ (f _j ) is calculated by Equation 21 from the concentration C and the ultrasonic attenuation rate α (f _j ).
(5) The relative particle amount is calculated from the partial regression coefficient β _ij and the unit concentration decay rate λ (f _j ) by Equation 28.
It becomes that.

Here, the concentration measurement by particle diameter will be described.
A measurement of particle径別concentration c _i that calculated based on the measurement procedures (1) and (2) shown in FIG. 12. The horizontal axis represents the product of the concentration corrected using the average concentration conversion factor and the attenuation factor of the frequency f = 8.0 MHz and the relative particle amount measured by the laser particle size analyzer. The vertical axis represents the concentration by particle size calculated from Equation 26. In this measurement test, as apparent from FIG. 12, the concentration by particle size of less than 1,000 mg / liter is extremely poor in measurement accuracy, but the measured value is in the range of 1,000 to 10,000 mg / liter. It almost coincides with the measured value of the laser diffraction type particle size distribution measuring apparatus.

  Next, the measurement value of the density based on the measurement procedure (3) is shown in FIG. The horizontal axis shows the density corrected using the average density conversion rate and the attenuation rate at the frequency f = 8.0 MHz. The vertical axis indicates the measured value of concentration by this measuring apparatus. By the way, the dilution method adopted this time has the advantage of being able to measure the SS concentration and particle size distribution after measurement, but it is very difficult to keep the suspension concentration uniform during the measurement process, and as a result, the exact concentration is measured. There is a drawback that it is difficult to do. In this measurement test, the measured concentration of SS was not adopted, but the measured concentration was corrected using the average concentration conversion rate. The error between the corrected concentration and the measured value is estimated to be about ± 5% at maximum (see FIG. 13).

  The particle size analysis will be described. The measurement result of the relative particle amount measured based on the measurement procedures (4) and (5) described above is shown in FIG. The horizontal axis represents the relative particle amount measured by the laser diffraction particle size analyzer, and the vertical axis represents the measured value of the relative particle amount obtained from Equation 28. The particle size distribution (relative particle amount) measured by the measuring device used this time is within 5% of the measured value of the laser diffraction particle size analyzer. Moreover, the measurement result of the relative particle amount of each fine particle is shown in FIG. It can be seen that the measured value of the relative particle amount of a specific particle size has a slightly large error from the measured value of the laser diffraction particle size analyzer, but matches very well as a whole. In addition, the measured value shown in FIG. 15 shows the measured value of the relative particle amount of the suspension with the highest concentration of each sample. Particle size analysis can be performed without diluting a high concentration suspension.

The measurement performance of this example will be described.
The measurement device used utilizes the principle of concentration measurement by ultrasonic waves and the measurement principle of particle size analysis, and adopts a plano-concave ultrasonic transducer capable of emitting broadband ultrasonic waves in the detection unit of the measurement device. Concentration and relative particle amount are simultaneously measured from a plurality of ultrasonic attenuation factors in a frequency band of 10 MHz. As a result of the measurement test, the ultrasonic concentration measuring apparatus was able to verify that the concentration of fine particles and the relative particle amount could be measured simultaneously. It was also found that this measuring device is very suitable for measuring high concentration suspensions. When the particle size of the fine particles is on the order of 1 to 100 μm, it is considered that the measurement range of the concentration can be sufficiently measured up to a maximum of 10,000 mg / liter according to the specification of the present measuring device as seen in FIGS.

  An embodiment will be described in which “volume display concentration” (so-called volume concentration) can be obtained as a value that takes into consideration the characteristics of soil particles such as calcareous and clay that differ for each water system.

First, the volume display density will be described.
The number (volume or weight) of sand contained in a unit volume of water is called “concentration” and is represented by C. The SS concentration is a concentration expressed in units of [mg / liter], and the SS concentration measurement method is defined in JIS-K0102. The SS concentration is used in the environmental standard items for rivers and lakes and in the effluent standard for sewage and drainage.

SS measured by the measurement method defined in JIS-K0102 is weight concentration, but when examining sediment movement in rivers, it is necessary to evaluate sediment volume (volume). The displayed density is used. That is, in the river bed fluctuation calculation, the concentration of floating sand is displayed as the following Expression 29 in volume display.
(Here, the flow rate is Q [m ³ / s], and the amount of floating sand in the flow rate is Qs [m ³ / s].)

Further, when the density of the soil particles is ρ [mg / cm ³ ], the relationship between the concentration _Cw in weight display and the concentration _Cvol in volume display is expressed by the following Equation 30. The density test for soil particles is defined in JIS-A1202.
When calculating the unit concentration decay rate λ (f _j ) shown in the above equation 21, the concentration is analyzed as the volume display concentration C _vol using the above equation 29, and as a result, the equation 11 is calculated. The density is a volume display density (dimensionless amount). This is because, in principle, the ultrasonic concentration measuring device is considered to be a device that measures the concentration of the volume display instead of the concentration of the weight display. The concentration can be measured regardless of the difference in particle density.

  Although the present invention has been described above with reference to the embodiments, the present invention is not limited to the above-described embodiments, and can be improved or modified within the scope of the purpose of the improvement or the idea of the present invention. . In particular, the measurement and measurement objects are not limited to those described above, and the present invention can be applied to various liquids.

  The present invention can measure the turbidity of a river based on an ultrasonic transducer, and can analyze and measure the proposed relational expression based on the data value considering the granularity of suspended matter (SS) in the river. It is possible to grasp the true pollution level of rivers considering the granularity of (SS). There is no need to refer to the optically measured turbidity value. Water with a high concentration of particulate matter, “total concentration by particle size (concentration)”, “relative particle amount”, and “volume ( Volume ”concentration” can be measured very easily. Therefore, sand erosion on sandy beaches and rivers, which is currently an environmental and social issue, dam life reduction (sediment sedimentation in dam lakes), and sabo dams In order to eliminate various problems such as energy loss due to removal and transport of sediment, it is necessary to carry out the analysis according to the present invention for multiple points of the river from the upstream to the estuary, and to move the sediment from upstream to downstream according to the purpose. It is possible to flow efficiently. It is also useful for controlling rivers (opening and closing of sluice gates) so that earth and sand will flow from the estuary into the sea due to typhoons and upstream construction, etc. Can be.

11: Ultrasonic attenuation rate measuring device 12: Particle size measuring device 13: Control unit 14: Particle size analyzing device 15: Storage unit 20: Plano-concave ultrasonic transducer 21: Reflecting plate 30: Analysis system

Claims (7)

A suspended matter analysis method consisting of the following steps.
(1) Systematically changing the frequency of ultrasonic waves applied to the sample liquid, measuring the attenuation rate α (f) of each frequency, and measuring the attenuation derived from the sample liquid as a medium and the attenuation derived from the particles The value is expressed as Equation 1 below.
(Where α medium (f) is the ultrasonic attenuation factor derived from the medium when the frequency is f, and α mono (f, D) is the ultrasonic attenuation derived from monodisperse particles having the frequency f and the particle size D. The rate, g (D), is the mass percentage of particles whose particle size is between D and D + dD (hereinafter referred to as relative particle amount).
(2) The water temperature is measured, and the measured value of the reference spectrum of each frequency band that varies depending on the water temperature is obtained as a function of the water temperature by the following formula 2.
(Here, M0 (fj) is a measured value of the reference spectrum of the frequency fj at the water temperature t, t is the water temperature [° C.] at the time of measurement, and aj, bj, cj, dj are constants for calculating the reference spectrum of the frequency fj. However, the reference spectrum means the frequency spectrum of the sample liquid when the medium is only water.


Here, α (fj) is the ultrasonic attenuation rate [dB / MHz] of the frequency fj, fj is the frequency [MHz], M0 (fj) is the measurement value of the reference spectrum of the frequency fj, and M (fj) is the frequency fj. It is a measured value of the frequency spectrum of the suspension. )
(3) (a) Water temperature at the time of measurement obtained in the step ( 2 ) , (b) Measurement value of frequency spectrum , and (c) Measurement value of reference spectrum at water temperature t and reference spectrum at reference water temperature t0 Using the water temperature correction coefficient τ (fj) of the frequency fj, which is a ratio to the measured value of, the correction based on the water temperature is performed by Equations 4 and 5, and the ultrasonic attenuation rate under the reference water temperature is obtained.
(Where α (fj) is the ultrasonic attenuation rate [dB / MHz] of the frequency fj, fj is the frequency [MHz], and M0 (fj) t = t0 is the frequency fj at the reference water temperature t0 calculated by Equation 2. Measured value of reference spectrum, M0 (fj) t = t: Measured value of reference spectrum of frequency fj at water temperature t calculated by Equation 2, M (fj) t = t is suspension of frequency fj at water temperature t The measured value of the frequency spectrum of τ, τ (fj) is the water temperature correction coefficient of frequency fj, t0 is the reference water temperature [° C.], and t is the water temperature [° C.] at the time of measurement.
(4) The concentration conversion rate represented by the following formula 6 in each frequency band is verified (concentration conversion rate λ (fj) is a rate for converting the ultrasonic attenuation rate in formula 6 into a concentration, that is, a unit concentration Ultrasonic attenuation rate, called unit concentration attenuation rate)
(Where α (fj) is the ultrasonic attenuation rate [dB / MHz] at the frequency fj, C is the concentration [mg / liter], and λ (fj) is the concentration conversion rate (unit concentration attenuation rate) at the frequency fj. .)
(5) As a conversion procedure applying a multiple regression model using the relative particle amount g (Di) of each particle size floor as an objective variable and the unit concentration decay rate λ (fj) calculated by the equation 6 as an explanatory variable,
(Where g (Di) is the relative particle amount [%] of the particle size stage Di, fj is the frequency [MHz], βij is the partial regression coefficient, λ (fj) is the unit concentration decay rate of the frequency fj, and m is the particle size. The number of divisions of the radial floor, n is the number of frequencies fj, and ε is the residual)
(6) Substituting the formula 6 and the formula 7 into the formula 8 respectively to arrange the concentration C, the following formula 9 is obtained,
The concentration C of the sample liquid is obtained by multiple regression analysis as a function of the ultrasonic attenuation rate α (fj). In the suspended matter analysis method according to claim 1,
In the above formula 9 showing the concentration by particle size
Is expressed as the following formula 11,
(Where ci is the concentration [mg / liter] of the particle size floor Di, α (fj) is the ultrasonic attenuation rate [dB / MHz] at the frequency fj, βij is the partial regression coefficient, and n is the number of the frequency fj. .)
Thus, the suspended matter analysis method is characterized in that the concentration of suspended matter in the sample liquid is determined for each particle size. In the suspended matter analysis method according to claim 2,
Substituting the equation 11 into the equation 9 to obtain the following equation 12,
(Here, C is the concentration [mg / liter], ci is the concentration [mg / liter] of the particle size floor Di, and m is the number of particle size floor divisions.)
It is possible to measure the relative particle amount considering the attenuation rate,
A method for analyzing suspended solids, wherein the concentration of a sample liquid is obtained as a sum of concentrations by particle size. In the suspended matter analysis method according to claim 3,
The unit concentration attenuation rate λ (fj) is calculated from the concentration C of the sample liquid and the ultrasonic attenuation rate α (fj) using the above equation 6.
The relative particle amount g (Di) is obtained by using the partial regression coefficient of the multiple regression model of Equation 7 and the unit concentration attenuation rate λ (fj).
(Where g (Di) is the relative particle amount [%] of the particle size stage Di, fj is the frequency [MHz], βij is the partial regression coefficient, λ (fj) is the unit concentration decay rate of the frequency fj, and m is the particle size. (The number of divisions of the radial floor, n is the number of the frequency fj.)
A method for analyzing suspended solids, characterized in that a relative particle amount is obtained by the above method. A method for analyzing suspended sediment concentration using the suspended matter analysis method according to any one of claims 1 to 4 to obtain suspended sediment concentration in river bed fluctuation calculation,
(1) The concentration of the floating sand is displayed in the volume display as in the following formula 14,
(Here, the flow rate is Q [m3 / s], and the amount of floating sand in the flow rate is Qs [m3 / s].)
(2) Assuming that the density of the soil particles is ρ [mg / cm 3], the relationship between the concentration Cw in weight display and the concentration Cvol in volume display is expressed by the following formula 15.
When calculating the unit concentration attenuation rate λ (fj) shown in the above equation 6, the concentration C calculated by the equation 12 is dimensionless by analyzing the concentration C as a volume display concentration Cvol using the above equation 15. A method for analyzing suspended sand concentration, characterized in that the concentration is expressed by volume Cvol.
(Here, C is the concentration [mg / liter], ci is the concentration [mg / liter] of the particle size floor Di, and m is the number of particle size floor divisions.)
5. A suspended matter analysis system, wherein the suspended matter analysis method according to claim 1 is used to analyze suspended matter in a liquid. A floating sand concentration analysis system, wherein the floating sand concentration is calculated in a river bed variation calculation using the suspended sand concentration analysis method according to claim 5.