JP2001147204A - Sludge densitometer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance concentration measuring accuracy by removing the conductivity of sewage when the concentration of sludge is calculated from measured data. SOLUTION: A sewage passing groove 20 is formed to the member 14 provided to the leading end part of a high frequency window part 13 and a part of the high frequency window part 13 is exposed to the sewage passing groove 20 and microwaves are emitted to the interior of a sludge transport pipe from the exposed part and the microwaves reflected from the boundary surface of a sludge mixed liquid are received by an antenna from the exposed part through the high frequency window part 13. Thereafter, the microwaves are converted to the concentration of sludge through a microwave transmitter-receiver and a sludge densistomer converter and the concentration of sludge is displayed on a sludge densitometer. The sewage passing groove 20 is arranged in the sewage flowing direction so as to facilitate the passage of the sewage flowing through the sludge transport pipe.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a sludge concentration for a process for measuring the concentration of solids and suspended solids in sludge in a treatment process of a sewage treatment plant, a wastewater treatment plant, a water treatment plant, and those sludge treatment plants. The present invention relates to a sludge concentration meter in which the influence of the conductivity of sewage is removed from measurement data measured using microwaves.

[0002]

2. Description of the Related Art In a sewage treatment plant, a wastewater treatment plant, a sludge treatment plant, or the like, it is necessary to constantly monitor and grasp the amount of solid matter of sludge generated from each process or transported from one process to another process. Is very important in the operation management of The amount of sludge solids can be calculated from two values, sludge flow rate and sludge concentration. For measuring the sludge flow rate, an electromagnetic flow meter, an ultrasonic Doppler flow meter, and the like are commercially available, and relatively reliable measurement is realized.

[0003] On the other hand, as for the measurement of the sludge concentration, those based on the principle of attenuation of ultrasonic waves and those based on the detection principle of the amount of transmitted light and the amount of reflected light are commercially available. However,
At present, these sludge densitometers are inferior in reliability and the like as compared with the flowmeter due to factors disturbing the measurement and complicated maintenance work. In recent years, microwave-type sludge densitometers have been developed using microwaves to solve the disadvantages of conventional sludge densitometers, and are commercially available.

[0004]

In the microwave type sludge densitometer described above, the measured data is simultaneously affected by the solid matter concentration, the temperature, and the electric conductivity. Unless the solid concentration is calculated and obtained, an error may occur in the concentration measurement.

First, the dielectric constant of water is about 80, which is very large as compared with other substances. On the other hand, in sewage, other substances are suspended as fine particles or colloids. For this reason,
The dielectric constant of the colloidal material is about 1-3, and the dielectric constant of water is small. Thus, the dielectric constant of water will decrease with the concentration of the suspended material.

Next, a function established between the dielectric constant and the concentration of sewage will be described. In general, the concentration of solids in sewage is usually as low as 0 to 6%, and the change in dielectric constant is also as small as about 0 to 6%. Therefore, whatever the shape of the function, approximation by Taylor expansion is effective. This is expressed by the following equation.

F (1−x) = f (1) −x × f (1) + 0.5 × x ² × f (1) + (3rd or higher) (1) In the above equation (1), the function f is Shows the dielectric constant of water. x means solids concentration. In the above equation (1), f (1) indicates the dielectric constant of 100% water (ie, fresh water). Specifically, x is 0.
Assuming 06, the square of x is 0.00036, and the squared term is
You can almost ignore it.

At the same time, the same problem occurs when the measured data reflects a power of the dielectric constant. Here, assuming that x is the solid concentration and n is a power of a constant, when n in Expression (2) below is small, it can be approximated by Taylor expansion. In this case, if n is a constant, the solid concentration x can be determined.

F ((1-x) ⁿ = f (1-nx) = f (1) −nx × f (1) (2) Next, the dielectric constant of water is determined not only by the solid matter concentration, It also depends on the conductivity of water and the temperature of water, which also has the same problems as in the above equations (1) and (2), for example, the difference between the standard temperature T0 and the standard temperature is ΔT , The conductivity is σ,
When the measured data corresponding to the dielectric constant is represented by f (1-x, T0 + ΔT, σ), the reference data of fresh water is 0% concentration and 0 mS / cm in conductivity.
Therefore, when x = 0, ΔT = 0, and σ = 0 are substituted for the measurement data, the measurement data becomes f (1, T0, 0). Then, the following expression (3) is established by Taylor expansion. Note that A,
B and C are constants.

F (1-x, T0 + ΔT, σ) = f (1, T0 + ΔT, σ) −A × x + B × ΔT + C × σ (3) Actually, conductivity, concentration, and temperature Are not independent of each other,
The problem is that the synergistic effect is working. In particular, there is a problem that the change in the conductivity of the sewage greatly affects the concentration measurement accuracy.

The present invention has been made in view of the above circumstances, and provides a sludge concentration meter which removes the conductivity of wastewater when obtaining sludge concentration from measurement data to improve the concentration measurement accuracy. That is the task.

[0012]

According to the present invention, in order to achieve the above-mentioned object, a first invention is to provide a sludge transport pipe with a reflection intensity detection type microwave detection probe main body, and to transmit microwaves from the probe main body. Dispatch to the sludge transport pipe,
The same probe body receives the microwave reflected on the boundary surface of the sludge mixture liquid to be measured in the sludge transport pipe, detects the ratio of the reception intensity to the transmission intensity, and measures the solids concentration in the sludge mixture. In the sludge densitometer, the probe main body is formed of a waveguide having one end closed and the other end opened, and a first member having a microwave-permeable member at an opening at the other end of the waveguide. In addition to providing a conductor,
The member is disposed facing the inside of the sludge transport pipe, and the member is housed therein. One end is fixed to the first conductor portion, and the other end is formed with a groove for guiding a sample to be measured. Providing a conductor portion, the width and depth of the groove, when calculating the sludge concentration of the sample to be measured, using the measurement data with the integrated value of the reflection intensity at a selected frequency in a certain band, the When the measurement data reflects the dielectric constant of the sample to be measured or a power of the dielectric constant, it changes according to the temperature at which the integrated value does not change even if the conductivity of the sewage of the sample to be measured changes. Is what you do.

A second invention is characterized in that the width of the groove is calculated by the following equation. Groove width = wavelength of microwave / 2 / square root of dielectric constant of water at used temperature (water temperature) A third invention is characterized in that the depth of the groove is calculated by the following equation. .

Groove depth = groove width / 4

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the following, embodiments of the present invention will be described with reference to the drawings, in which a schematic configuration of a microwave type sludge concentration meter and details of a detection probe of the sludge concentration meter will be described. FIG. 1 is a schematic configuration explanatory view of a microwave type sludge concentration meter, and FIG. 2 is an enlarged sectional view of a main part of a detection probe portion of the microwave type sludge concentration meter.

First, a schematic configuration of the microwave type sludge densitometer of FIG. 1 (hereinafter, this sludge densitometer is referred to as a diaphragm type microwave reflection detection type densitometer) will be described. In FIG.
Reference numeral 1 denotes a sludge transport pipe, a window is formed at a predetermined portion of the sludge transport pipe 1, and a microwave reflection intensity detection probe 2 is provided on the window.

A microwave is transmitted from the probe 2 into the sludge transport pipe 1, and the same probe receives the microwave reflected on the interface between the probe and the sludge mixture (total sludge including solid matter). , The ratio of the reception intensity to the transmission intensity is detected.

Reference numeral 3 denotes a microwave generator / receiver, which detects the ratio between the transmission and reception intensities of the microwave generator / receiver 3 and inputs the detection signal to a sludge concentration converter 4, where the sludge concentration is detected. The solids concentration of is measured. Note that a device such as a coaxial cable or a waveguide is used for the probe 2.

Next, the details of the probe 2 described in FIG. 1 will be described with reference to FIG. In FIG. 2, reference numeral 11 denotes a probe main body composed of a coaxial-waveguide converter. One end of the probe main body 11 is closed, and the other end is open.
A disc-shaped first conductor portion 12 having a through hole in the center is attached to an end of the probe body 11 which is open.

A high-frequency window 13 made of a ceramic member is inserted and fixed in the through hole of the first conductor portion 12, and this high-frequency window 13 is provided in the axial direction of the probe body 11 (in the sludge transport pipe shown in FIG. 1). It is protruding. In addition, high-frequency window 1
3 is provided in close contact with a cylindrical second conductor portion 15 having a disk-shaped member 14 provided at the tip. Reference numeral 16 denotes a flange provided on the sludge transport pipe. The first conductor 12 is attached to the flange 16.

An antenna 1 is provided in the probe body 11.
The antenna 17 is connected to the microwave transmitter / receiver 3 shown in FIG. 1 via a coaxial cable.
18 is a coaxial cable connector, 19 is the probe body 1
1 is a hollow portion.

The operation of the sludge densitometer configured as described above will be described. A transmission signal from the microwave transmitter / receiver 3 shown in FIG. 1 is supplied to an antenna 17 via a coaxial cable (not shown). When the microwave transmitted from the antenna 17 is radiated into the sludge transport pipe 1 from the high-frequency window 13 made of a ceramic member, the microwave is reflected on the boundary surface of the sludge mixed liquid, and again passes through the high-frequency window 13 to the probe body 11. Is received by the antenna 17. After the received signal is received by the microwave generator / receiver 3, it is converted into the sludge concentration by the sludge concentration meter converter 4, and displayed on the sludge concentration meter.

Next, a first embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG. 3 and 4, the high-frequency window 1
The member 14 provided at the distal end portion 3 has a sewage passage groove 20 as shown in both figures. A part of the high-frequency window 13 is exposed in the sewage passage 20, and the microwaves are radiated from the exposed portion into the sludge transport pipe 1 and are reflected on the boundary surface of the sludge mixture. The microwave is transmitted from the exposed portion through the high-frequency window 13 to the antenna 1.
7 is received. Then, as described above,
The sludge concentration is converted into sludge concentration via the receiver 3 and the sludge concentration meter converter 4, and the sludge concentration is displayed on a sludge concentration meter (not shown).

The sewage passage 20 is disposed in the direction in which the sewage flows so that the sewage flowing in the sludge transport pipe is easily passed. In addition, the sewage passage groove 20 has a groove width “exposed width of the high-frequency window portion 13” (hereinafter referred to as “width of the diaphragm”) and a groove depth (hereinafter referred to as “thickness of the diaphragm”) which will be described below. And the third mode.

In the above-described first embodiment, the density is measured using the aperture-type microwave reflection detection type densitometer configured as described above, and the reflection intensity at a selected frequency in a certain band is added. The obtained value (hereinafter, referred to as an integral value) is used as measurement data.

FIG. 5 is a characteristic diagram of a resonance curve showing a state of reflection characteristics when the above-mentioned aperture-type microwave reflection detection type densitometer is used. In this characteristic diagram, in particular, 2.1GH the f ₁
z, and f ₂ and 2.2GHz, when the summed taking 101 points the frequency to 1MHz intervals, a value proportional to the area of the large part of the variation in the resonance curve is obtained. Here, the above-described integral value is a value reflecting the area of the hatched portion shown in FIG.

Next, the integral value is used for the data measured using the aperture-type microwave reflection detection type densitometer, and the following formulas (4) to (7), which are more precise than the above formula (3), are used. Find the concentration.

Concentration = (measured integrated value−integrated value predicted at 0% concentration) / density coefficient (4) Integral value predicted at 0% concentration = fixed point temperature integral value + temperature coefficient × (actually measured value) (Temperature-fixed point temperature) ... (5)

[0029]

(Equation 1)

Concentration coefficient = constant D × integral value predicted at a concentration of 0% (7) Here, the concept of the fixed point temperature shown in Expression (5) will be described. This fixed point temperature, when the concentration is 0%,
The temperature at which the integrated value does not change even if the conductivity of the sewage changes. This temperature depends on the shape of the detecting part (the above-mentioned sewage passage groove 2).
0), when the width of the diaphragm is 8mm and the thickness is 2mm,
It was experimentally confirmed that there was a fixed point temperature at 22 ° C. The fixed point temperature integrated value is an integrated value at the fixed point temperature when the concentration is 0%.

The above situation will be described with reference to the graph of FIG. In FIG. 6, it is clear that there is no significant change in the integral value even when the conductivity (mS / cm) changes between the fixed point temperature and the range of about ± 10 ° C. Therefore, when the above probe is used, the concentration can be measured in the temperature range of 22 ° C. ± 10 ° C. without causing a great error even if the conductivity value of the sewage is ignored.

The width of the diaphragm in the first embodiment is 8 m.
m, the thickness was 2 mm, and the fixed point temperature was 22 ° C. Usually, of the sewage, a kind called digested sludge is in a state of hot water at 35 to 55 ° C. For this reason, a probe with a fixed point temperature of 45 ° C is more intense than a probe with a fixed point temperature of 20 ° C.
It is preferable for measurement. Therefore, the second and third embodiments described below increase the fixed point temperature by changing the width and thickness of the diaphragm.

In the second embodiment of the present invention, the width of the diaphragm is changed. The width of the diaphragm of 8 mm is obtained from the following equation (8) based on the dielectric constant of water at 20 ° C. of 77.8. is there.

The width of the diaphragm = wavelength of microwave / 2 / square root of permittivity of water (8) When calculated backward, the microwave frequency is 2.13 GHz and the wavelength is 141.
mm. At this time, the peak frequency in FIG. 5 was 2.15 GHz. Considering the processing accuracy of the width of the aperture, the above equation (8) has high accuracy. here,
The dielectric constant of water at 45 ° C is 70.7.
By substituting m into the above equation (8), the width of the aperture is calculated as 8.3
8 mm. FIG. 7 shows the results of an experiment conducted using a diaphragm having a width of 8.4 mm and a thickness of 2 mm.

From FIG. 7, the fixed point temperature is 45 ° C. as calculated according to the width of the diaphragm. Therefore, when measuring sewage at a temperature around 45 ° C., the influence of the conductivity can be reduced from the measurement data, and the sludge concentration can be measured with high accuracy.

In the third embodiment of the present invention, the thickness of the diaphragm is changed. The thickness of the diaphragm is determined based on the following equation (9) so as to allow microwaves to pass through moderately and to push back moderately. It is a thing.

Thickness of the diaphragm = width of the diaphragm / 4/4 (9) Generally, when the thickness of the diaphragm is small, microwaves can easily pass therethrough. Therefore, the thickness of the diaphragm was designed from the following equation (10).

Thickness of the diaphragm = width of the diaphragm / 5.33 (10) From the above equation (10), when the width of the diaphragm is 8 mm, if the thickness of the diaphragm is 1.5 mm, the microwave easily passes. Has the same effect as expanding the range. FIG. 8 shows the experimental results. From the results shown in FIG. 8, the fixed point temperature can be increased by reducing the thickness of the diaphragm, and the effect of the change in the conductivity is small and the sludge concentration can be measured with high accuracy.

[0039]

As described above, according to the present invention,
Value obtained by adding the reflection intensity at a selected frequency in a certain band in density measurement using microwaves (integral value)
The measurement data, when the measurement data reflects the dielectric constant of the wastewater to be measured or its power or its roots, the temperature at which the integral does not change even if the conductivity of the wastewater changes By changing the width and thickness of the diaphragm, the fixed point temperature suitable for the operating temperature can be obtained, so the effect of the change in the conductivity is small, and the advantage that the sludge concentration can be measured with high accuracy is obtained. is there.

[Brief description of the drawings]

FIG. 1 is a schematic structural explanatory view of a microwave type sludge concentration meter.

FIG. 2 is an enlarged sectional view of a main part of a detection probe part of a microwave type sludge concentration meter.

FIG. 3 is a front view of a tip portion of a detection probe portion showing the first to third embodiments of the present invention.

FIG. 4 is a plan view of a tip portion of a detection probe site.

FIG. 5 is a characteristic diagram of a resonance curve showing a state of reflection characteristics when a microwave reflection detection type densitometer is used.

FIG. 6 is an explanatory graph of a fixed point temperature.

FIG. 7 is a diagram showing a temperature characteristic of a change in conductivity when the width of the diaphragm is changed.

FIG. 8 is a diagram showing a temperature characteristic of conductivity change when the thickness of the diaphragm is changed.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Sludge transport pipe 2 Detection probe 3 ... Microwave generator / receiver 4 ... Sludge concentration meter converter 11 ... Lobe body 12 ... 1st conductor part 13 ... High frequency window part 14 ... Member 15 ... 2nd conductor part 16 ... Flange 17 Antenna 18 Connector 19 Hollow 20 Sewage channel

Claims (3)

[Claims] 1. A sludge transport pipe is provided with a reflection intensity detection type microwave detection probe main body, and a microwave is transmitted from the probe main body into the sludge transport pipe, and a sludge mixture liquid as a sample to be measured in the sludge transport pipe is provided. In the sludge densitometer for receiving the microwave reflected on the boundary surface with the same probe body and detecting the ratio of the reception intensity to the transmission intensity to measure the solid matter concentration in the sludge mixture, the probe body has one end closed. A first conductor having a microwave permeable member is provided in an opening at the other end of the waveguide, and the member is placed inside the sludge transport pipe. A second conductor portion having one end fixed to the first conductor portion and the other end formed with a groove for guiding a sample to be measured, the groove being provided toward the first conductor portion; The width and depth of When calculating the sludge concentration of the sample to be measured, use the measurement data with the integrated value of the reflection intensity at a selected frequency in a certain band as the integral value, and use the measurement data as the dielectric constant or the power of the dielectric constant of the sample to be measured. A sludge concentration meter that changes according to a temperature at which the integral value does not change even when the conductivity of the sewage of the sample to be measured changes when the measurement is reflected. 2. The sludge concentration meter according to claim 1, wherein the width of the groove is calculated by the following equation. Groove width = wavelength of microwave / 2 / square root of dielectric constant of water at used temperature (water temperature) 3. The sludge concentration meter according to claim 1, wherein the depth of the groove is calculated by the following equation. Groove depth = Groove width / 4