JP2000321218A - Sludge densitometer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance measuring sensitivity and measuring accuracy while facilitating maintenance and inspection. SOLUTION: One end of a probe main body 11 comprising a coaxial- waveguide converter is closed and the other end thereof is opened. A first conductor part 12 having a through-hole is attached to the opened end and a high frequency window part 13 comprising a ceramic member is inserted in and fixed to the through-hole of the first conductor part 12 so as to be protruded in the axial direction of the probe main body 11. The high frequency window part 13 is provided in a second conductor part 15 provided with a member 14 forming a groove 16 at a leading end part in a close contact state. The member 14 consists of two members and has the sewage passing groove 16 formed thereon. The first conductor part 12 is attached to the flange 17 provided on a sewage transport pipe. An antenna 18 is provided in the probe main body 11 to be connected to a microwave transmitter/receiver through a coaxial cable.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a sludge used in a process for measuring the concentration of solids and suspended solids in sludge in the treatment process of a sewage treatment plant, a wastewater treatment plant, a water purification plant, and a sludge treatment plant thereof. It relates to a densitometer.

[0002]

2. Description of the Related Art Sewage treatment plants, wastewater treatment plants,
In a water treatment plant and those sludge treatment plants, it is very important for plant operation management to constantly monitor and grasp the amount of solid matter generated from each process or transported from one process to another process. It is. The amount of sludge solids can be calculated from two values, sludge flow rate and sludge concentration.

[0003] For measuring the sludge flow rate, an electromagnetic flow meter, an ultrasonic Doppler type flow meter or the like is used. These flowmeters have achieved relatively reliable measurements. On the other hand, the measurement of the sludge concentration is based on the principle of attenuation of ultrasonic waves and the principle of detection based on the amount of transmitted light or reflected light. At present, these sludge densitometers are inferior in reliability and the like as compared with electromagnetic flowmeters due to factors disturbing measurement and complicated maintenance work.

In recent years, microwave-type sludge densitometers utilizing transmission phase difference detection utilizing microwaves have been developed and used to solve the disadvantages of the conventional sludge densitometers. This microwave-based sludge densitometer using microwave
It is configured as shown in FIG. In FIG. 5, 51
Is a sludge transport pipe, which forms a window facing a predetermined portion of the sludge transport pipe 51. A densitometer detection probe 52 on the microwave transmission side and a densitometer detection probe 53 on the microwave reception side are provided in this window. Reference numeral 54 denotes a microwave transmitter / receiver connected to both probes 52 and 53, and reference numeral 55 denotes a sludge concentration meter converter for obtaining a sludge concentration from a phase difference between the transmission and reception of microwaves.

[0005] The microwave type sludge densitometer shown in FIG.
The phase lag of the microwave transmitted wave in Shimizu (concentration 0%)
The concentration is measured by utilizing the fact that the difference (phase difference) from the phase delay of the microwave transmitted wave in the sludge is linear with the sludge concentration as shown in FIG. Note that the concentration is obtained from a constant × Δθ.

FIG. 7 is a schematic configuration diagram showing a reflection-intensity detection type microwave-type sludge densitometer having a different detecting means from the above-mentioned microwave-type sludge densitometer. In FIG. 7, reference numeral 71 denotes a sludge transport pipe. A window is formed in a predetermined portion of the sludge transport pipe 71, and a microwave reflection intensity detection type probe 72 is provided in the window. The probe 72 transmits microwaves from a set of probes, receives the microwaves reflected on the interface between the probe and the sludge mixture (total sludge including solids) with the same probe, and receives the microwaves with respect to the transmission intensity. Detect the intensity ratio. Reference numeral 73 denotes a microwave generator / receiver, which detects the ratio of the transmission and reception intensity detected and detected by the microwave generator / receiver 73, and inputs the detection signal to a sludge concentration converter 74, where the sludge concentration is detected. Measure the solids concentration. The probe 72
, Devices such as coaxial cables and waveguides are used.

[0007]

(1) 2 shown in FIG.
The two microwave-type sludge densitometers are based on the principle of measuring the sludge concentration by detecting the phase difference of the microwave transmission component in the sludge.
The following problems occur when the above is installed.

[0008] This is because, if the diameter of the transport pipe is large, the attenuation of the microwave reaching the receiving side becomes large, and the phase difference cannot be detected. Therefore, (a) reducing the diameter or (b)
Some pipes are branched (bypassed) with small-diameter pipes,
(C) It is necessary to take measures such as increasing the output power of microwaves.

(A) is possible to some extent, but there is a limit and the condition is that the allowable pressure loss in the plant design should not be exceeded.

As for (b), a large installation space is required, and if there is not enough space, installation may not be possible.

Regarding (c), if the frequency exceeds a certain limit, it is a violation of the Radio Law, and in addition to the price increase accompanying the increase in transmission power, a cost for complying with the Radio Law is required, and the total price becomes high. .

(2) The microwave type sludge densitometer shown in FIG. 5 is based on the principle of measuring the sludge concentration by detecting the phase difference of the microwave transmission component in the sludge. Are arranged to face each other with the sludge transport pipe interposed therebetween.

For this reason, it is necessary to provide a bypass pipe so that the transmitter and the receiver can be removed together with the sludge transport pipe in consideration of a response when a failure occurs in the concentration meter. Therefore, a large installation space is required, and if there is not enough space, installation may not be possible.
Further, in addition to the main body of the concentration meter, construction costs for the bypass pipe are required, so that the total price rises.

(3) In the microwave type sludge densitometer shown in FIG. 5, the transmitter and the receiver cannot be easily removed because the transmitter and the receiver are arranged opposite to each other in the sludge transport pipe. Therefore, comparison and calibration between the chemical analysis value of the sludge concentration and the output of the concentration meter must be performed in the sludge pipe. For example, for zero-point calibration in Shimizu, sludge flows to the bypass side,
By closing the valves at both ends of the densitometer and replacing the sludge in the densitometer with water for measurement, relatively accurate calibration can be performed.

However, when calibrating the span measurement at a certain sludge concentration, the same method as for the zero point causes the sludge to settle, so that accurate calibration cannot be performed. Therefore, for calibration on the span side, sludge flows through the densitometer as in normal measurement,
At a certain point, the sludge collected at a certain point must be chemically analyzed, and a method of comparing and calibrating the sludge output at that time must be adopted. However, since the sludge concentration in the normal sludge transport pipe changes every moment, the sludge collected and the output of the densitometer are
It is difficult to match them as they are. Therefore, the output calibration of the densitometer cannot be accurately performed in many cases, and there is a problem that the measurement accuracy is greatly affected.

The present invention has been made in view of the above circumstances, and since the grooves are formed along the flow of sewage, measurement sensitivity and measurement accuracy are improved, and removal and attachment of the probe main body is simple. Therefore, an object of the present invention is to provide a sludge concentration meter that can easily perform maintenance and inspection.

[0017]

According to the present invention, in order to achieve the above-mentioned object, a first invention is to provide a reflection intensity detecting type microwave detecting probe main body in a sludge transport pipe, 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 detects the solids concentration and suspended solids in the sludge mixture liquid. In a sludge concentration meter that measures the concentration,
The probe main body is configured by a waveguide having one end closed and another end opened, and a first conductor having a member through which microwaves can be transmitted is provided in an opening at the other end of the waveguide. A second conductor 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 member being protruded into the sludge transport pipe, and the member being housed therein. The present invention is characterized in that a unit is provided.

According to a second aspect of the present invention, the member capable of transmitting microwaves has a thickness, a horizontal width and a vertical width of the shape of the member having values obtained from the following equations (a), (b) and (c). , And a value within 10% of the value obtained from these equations.

Thickness = {light speed × (1 + 2n)} / (square root of ε _s of member × resonant frequency × 4) (a) Width = light speed / (square root of ε _s of member × cutoff frequency × 2) (B) vertical width = width / 2 (c) where ε _s is a relative permittivity, and n is an integer of 0 or more (n = 0.1.2.
…).

According to a third aspect of the present invention, the shape of the groove for guiding the sample to be measured is such that the vertical width and the horizontal width are determined by the following equations (d) and (e). It is characterized in that it includes a value within the division.

The vertical width of the groove> the vertical width of the member through which microwaves can pass .... (d) The horizontal width of the groove = light speed / (square root of sewage ε × resonance frequency of member × 2) (e) where ε Is the dielectric constant.

A fourth invention is characterized in that the depth of the groove for guiding the sample to be measured has a value satisfying the following expression (f).

Depth of groove> = width of groove / 4/4 (f)

[0024]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an enlarged cross-sectional view of a main part of a probe part of a reflection type microwave type sludge densitometer according to a first embodiment of the present invention. In FIG. 1, reference numeral 11 denotes a probe comprising a coaxial-waveguide converter. In the main body, one end of the probe main body 11 is closed and the other end is open. An open end of the probe body 11 has a plate-shaped first conductor portion 1 having a square through hole at the center.
2 is attached. A high-frequency window 13 made of a square rod-shaped ceramic member is inserted and fixed into the square through-hole of the first conductor 12, and the high-frequency window 13 is connected to the probe body 1.
1 and protrudes in the axial direction (inside the sludge transport pipe not shown).

As shown in FIGS. 2 and 3, the high-frequency window portion 13 is provided in close contact with a cylindrical second conductor portion 15 provided with a member 14 for forming a groove, which will be described later, at the distal end. The member 14 is composed of two members, and the two members are arranged as shown in the figure. As shown in FIGS. 2 and 3, the sewage passage 16 through which the sewage can pass is formed in the direction in which the sewage flows in the sludge transport pipe. It is formed. Reference numeral 17 denotes a flange provided on a sludge transport pipe (not shown), and the first conductor portion 12 is attached to the flange 17.

The probe 1 has an antenna 1
The antenna 18 is connected to the microwave generator / receiver 73 shown in FIG. 7 via a coaxial cable. Reference numeral 19 denotes a coaxial cable connector. 20
Is a hollow portion of the probe main body 11. Next, the operation of the above embodiment will be described. A transmission signal from the microwave generator / receiver 73 shown in FIG. 7 is supplied to the antenna 18 via a coaxial cable (not shown). The microwave transmitted from the antenna 18 is transmitted to the high frequency window 1 made of a ceramic member.
When the radiation is radiated from 3 into a sludge transport pipe (not shown), it is reflected at the boundary surface of the sludge mixed liquid, and is received again by the antenna 18 of the probe body 11 through the window 13. After the received signal is received by the microwave generator / receiver 73, it is converted into the sludge concentration by the sludge concentration meter converter 74 and displayed on the sludge concentration meter.

In the above embodiment, the diameter of the second conductor 15 is set to about 50 mm and the length thereof is set to about 300 mm. The probe body can be attached and detached even with a sludge transport pipe whose water pressure is as high as 10 kg / cm ² .

Here, the detection probe of the reflection-intensity measurement type microwave-type sludge densitometer will be described. Of the performances required for this detection probe, the following two are required.

Necessary condition 1: Sufficient matching with load sludge is required. Necessary condition 2: Microwave reflection characteristics change in accordance with change in properties of load sludge.

In order to satisfy the above requirements, the present invention is configured as shown in the embodiments shown in FIGS. The embodiment configured in this way is an electronic circuit,
For example, the high-frequency window portion 13 functions as a resonance frequency transmission circuit, a sewage passage groove 16, and the sludge existing in the groove 16 functions as a filter circuit for the resonance frequency. Therefore, according to the concentration and the conductivity of the sludge, the characteristics of the diaphragm as a filter change, and the matching state fluctuates. By measuring this variation from the amount of reflected microwaves, it becomes possible to obtain information on the concentration and conductivity of the wastewater.

Next, the specific shapes of the high frequency window 13 and the sewage passage 16 will be described. First, the shape of the high frequency window 13 will be described.

The high-frequency window portion 13 is generally formed by using an integer n of 0 or more, such as 1/4, 3/4, and 5/4 wavelengths (thickness of a member through which microwaves can pass). Resonates at) / 4 wavelength. For the resonance frequency at that time, the thickness of the high-frequency window 13 with respect to the resonance frequency to be used can be calculated using the following equation (1).

Thickness = light speed × (1 + 2n) / (ε _{s of} high frequency window part)
(Square root of resonance × resonance frequency × 4) (1) where ε _s is a relative permittivity.

Here, as specific values, the high frequency window 1
When alumina having a relative dielectric constant of “9” is used for 3, the resonance frequency is 2.2 GHz, the thickness is 11.4 mm when n = 0, 34.2 mm when n = 1,
57 mm when n = 2.

Next, with regard to the width, it is desirable that the characteristics of the microwaves match those of the coaxial-waveguide converter to be connected. This is possible by matching the cutoff frequencies. The width of the high frequency window is calculated using the following equation (2).

Width = light speed / (square root of ε _s of high-frequency window part × cut-off frequency × 2) (2) where ε _s is a relative permittivity.

Here, as a temporary value, alumina having a relative dielectric constant of “9” is used for the high frequency window, and the cutoff frequency is 1.37 GHz.
When the coaxial-waveguide converter is used, the width becomes about 36.5 mm. Note that it is customary to set the vertical width to a value that is half of the horizontal width, so the vertical width can be obtained from equation (3).

Vertical width = width / 2 (3) However, if the value obtained by the formulas (1), (2) and (3) is within about 10% of the value, it greatly affects the characteristics. Do not give.

Next, the shape of the sewage passage groove 16 will be described. The vertical width (length of the groove) of the sewage passage groove 16 is as follows.
There is no problem if it is longer than the vertical width of the high-frequency window 13. However, when the length is short, unnecessary capacitance affects the operation, which is not preferable. Therefore, the relationship between the vertical width of the groove and the vertical width of the high-frequency window portion satisfies the following expression (4).

The vertical width of the groove> the vertical width of the high frequency window section (4) Next, the horizontal width of the sewage passage groove 16 will be described. The width of the groove 16 is formed so that the cutoff frequency of the groove and the resonance frequency of the high-frequency window 13 match. This groove resonates, and the way of resonance is an open end on both the outlet side and the inlet side. The width of the groove 16 is given by the following equation.

Width of groove = light speed / (square root of ε of sewage × resonance frequency of high frequency window × 2) (5) where ε is a dielectric constant.

As a tentative value, when the resonance frequency is 2.2 GHz and the dielectric constant of water is 76 in the equation (5), the groove width is 7.8 mm.
become.

If the depth of the groove is too shallow, the microwave will always pass through, and it will not be a filter. Logically, dividing the width of the groove by 3.14 is a measure to push back the microwave. However, sludge is highly viscous,
Since the groove may be clogged, the depth of the groove is preferably as small as possible. Therefore, the lower limit of the design is set to 1/4 of the width.

Groove Depth> = Groove Width / 4/4 (6) However, if the value obtained by the expression (5) is within about 10% of the value, the characteristics are not significantly affected.

FIG. 4 is a specific front view and sectional view of the first conductor portion and the like formed based on the shapes of the high-frequency window portion and the sewage passage groove described above.

Here, the waveguide and the waveguide resonator constituting the probe body 11 will be described. A waveguide is a hollow tube made of an electric conductor, and is used for transmitting microwaves of a high frequency of several thousand MHz or more.
Microwaves are transmitted inside the tube. The size inside the tube is designed according to the frequency of the microwave used. A rectangular cross section is called a rectangular waveguide, and a circular cross section is called a circular waveguide. In addition, a type in which a dielectric is packed inside the tube instead of air is called a dielectric waveguide. When the same frequency is used, the size of the dielectric waveguide decreases in inverse proportion to the square root of the dielectric constant of the dielectric.

A waveguide resonator is a microwave circuit device in which both ends or one end of a waveguide are closed so that a standing wave can be generated inside the tube. To reduce the size, a dielectric is often used instead of air.

[0048]

As described above, according to the present invention,
Since the grooves are formed along the flow of the sewage, there are advantages in that the measurement sensitivity and the measurement accuracy are improved, and since the detachment and attachment of the probe main body are simple, maintenance and inspection can be easily performed.

[Brief description of the drawings]

FIG. 1 is an enlarged sectional view of a main part of a probe part according to an embodiment of the present invention.

FIG. 2 is a front view of a second conductor.

FIG. 3 is a plan view of a second conductor.

FIG. 4 is a view showing a configuration of a second conductor portion, wherein n is 1 in the expression (a) of claim 2, a is a front view, and b and c are cross-sectional views.

FIG. 5 is a schematic configuration explanatory view of a transmission type phase difference detection type microwave type sludge concentration meter of a conventional example.

FIG. 6 is a phase difference-concentration characteristic diagram of a conventional transmission type phase difference detection type microwave type sludge densitometer.

FIG. 7 is a schematic diagram illustrating the configuration of a conventional reflection intensity detection type microwave-type sludge densitometer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 ... Probe main body 12 ... 1st conductor part 13 ... High frequency window part 14 ... Member 15 ... 2nd conductor part 16 ... Sewage passage groove 17 ... Flange 18 ... Antenna 19 ... Connector 20 ... Hollow part

Claims (4)

[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 concentration meter which receives the microwave reflected on the boundary surface with the same probe main body, detects the ratio of the reception intensity to the transmission intensity, and measures the solid concentration or suspended solid concentration in the sludge mixture, the probe main body is A first conductor portion having a microwave-permeable member is provided at an opening at the other end of the waveguide, the first conductor portion being constituted by a waveguide having one end closed and the other end opened. A second conductor having one end fixed to the first conductor and the other end formed with a groove for guiding a sample to be measured was provided, protruding into the sludge transport pipe, accommodating the member therein, and having the other end formed with a groove for guiding a sample to be measured. Specially Sludge concentration meter to be. 2. The member through which the microwave can be transmitted has the following thickness (a), width, and length of the member.
2. The sludge concentration meter according to claim 1, wherein the sludge concentration meter comprises values obtained from the expressions (b) and (c) and includes values within 10% of the values obtained from these expressions. Thickness = {light speed × (1 + 2n)} / (square root of ε _s of member × resonant frequency × 4) (a) Width = light speed / (square root of ε _s of member × cutoff frequency × 2) (b) Vertical width = width / 2 (c) where ε _s is a relative permittivity, and n is an integer of 0 or more (n = 0.1.2.
…). 3. The shape of the groove for guiding the sample to be measured is such that the vertical width and the horizontal width are values obtained from the following equations (d) and (e), and are within 10% of the values obtained from these equations. 2. The sludge densitometer according to claim 1, comprising a value. The vertical width of the groove> the vertical width of the member through which microwaves can pass .... (d) The horizontal width of the groove = light speed / (square root of ε of wastewater × resonance frequency of member × 2) (e) where ε is the dielectric constant It is. 4. The sludge densitometer according to claim 1, wherein the depth of the groove for guiding the sample to be measured has a value satisfying the following expression (f). Groove depth> = groove width / 4/4 (f)