JP2965712B2 - Densitometer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a densitometer for measuring the concentration of suspended matter, for example, the concentration of sludge, pulp, or the concentration of a substance dissolved in a liquid.

[0002]

2. Description of the Related Art FIG. 7 is a block diagram of a conventional ultrasonic densitometer. An ultrasonic transmitter 02 and an ultrasonic receiver 03 are arranged opposite to each other on the pipe 01. The ultrasonic transmitter 02 and the ultrasonic receiver 03 are provided on the pipe wall of the pipe 01 so as to be in contact with the fluid flowing through the pipe 01. With such a configuration, the ultrasonic oscillator 02
When an ultrasonic signal is input from the, the ultrasonic transmitter 02 emits an ultrasonic wave. This ultrasonic wave propagates through the fluid and is received by the ultrasonic receiver 03. At this time, the intensity of the ultrasonic wave attenuates according to the concentration of the suspended substance in the fluid. The ultrasonic receiver 03 outputs an electric signal corresponding to the received ultrasonic intensity, and the electric signal is sent to the ultrasonic attenuation rate measuring circuit 05. In the ultrasonic attenuation rate measuring circuit 05, a calibration curve indicating the relationship between the concentration of the suspended substance and the attenuation rate of the ultrasonic wave corresponding to the concentration is set in advance, and the attenuation rate is obtained from the input electric signal to obtain the concentration. Get.

However, the above densitometer has the following problems.

(1) Since the ultrasonic transmitters / receivers 02 and 03 are in contact with the liquid, suspended substances adhere to the contact surfaces, causing measurement errors, and require periodic cleaning. In particular, it easily adheres to suspended substances such as sewage sludge.

(2) On the other hand, an ultrasonic transceiver 02,
03 may be attached to the outside of the pipe 01. In this case, the thickness of the attached portion of the pipe 01 must be reduced. In addition, it is easily affected by the vibration of the pipe 01 and causes an error.

(3) Ultrasonic waves have an extremely large attenuation rate in a gas as compared with a liquid. For this reason, when air bubbles are mixed in the fluid, the attenuation of the ultrasonic wave is much larger than that of the suspended substance. Therefore, it becomes impossible to measure, or it is measured as an apparently very high concentration. Therefore, a defoaming type densitometer is used. This densitometer samples the fluid and puts it in the pressurized defoaming chamber and pressurizes it.
In this way, the bubbles are dissolved and the concentration is measured. However, since the concentration meter samples the fluid, continuous measurement cannot be performed. In addition, a mechanical movable mechanism is required to perform sampling and pressurization, and the long-term reliability is low.

(4) Since the method utilizes the fact that ultrasonic waves are dispersed and attenuated by a suspended substance, the method cannot be applied to a case where the suspended substance is a substance that dissolves in a liquid.

[0008]

As described above, substances which are affected by the adhesion of suspended substances or bubbles in liquid, and in which suspended substances are dissolved in liquid, cannot be applied to measurement, and have a long-term reliability. Poor.

Accordingly, the present invention provides a long-term reliable concentration that can measure a concentration without being affected by the adhesion of a suspended substance or bubbles in a liquid and can measure a substance in which a suspended substance is dissolved in a liquid. The purpose is to provide a total.

[0010]

According to the present invention, there is provided a microwave transmitter / receiver which is disposed opposite to a pipe through which a fluid to be measured containing a substance to be measured flows or a container containing the fluid, and which is radiated from the transmitter / receiver. The phase difference Δθ between the phase delay θ2 of the microwave passing through the fluid to be measured and received by the receiver and the phase delay θ1 previously measured using a fluid not containing the substance to be measured, that is, Δθ = θ2 − By measuring θ1, the concentration of the fluid to be measured is measured.

There is provided a phase difference correction means for measuring the conductivity of the fluid to be measured and correcting the phase difference based on the difference from the conductivity of the fluid which does not contain the substance to be measured, which has been measured in advance. .

[0012]

[0013]

By providing such means, the phase delay θ2 of the microwave emitted from the transmitter, passing through the fluid to be measured and received by the receiver, and the fluid containing no substance to be measured in advance can be used. Phase difference Δ from measured phase delay θ1
That is, the concentration of the fluid to be measured is measured by obtaining θ, that is, Δθ = θ2−θ1.

In this case, the conductivity of the fluid to be measured is measured,
The phase difference is corrected based on the difference from the previously measured conductivity of the fluid not containing the substance to be measured.

[0015]

[0016]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a configuration diagram of a densitometer of the present invention. Between the pipes 1 and 2, a detecting section pipe 3 and an auxiliary pipe 4 are connected to each other. Gate valves 5 and 6 are provided at connection portions between the pipes 1 and 2 and the detection section pipe 3 and the attached pipe 4, respectively. In addition, water pipe 7
And a drain pipe 8, and a water supply valve 9 and a drain valve 10 are provided in these pipes 7, 8, respectively.

A microwave transmitting antenna 20 and a receiving antenna 21 are closely attached to the detecting section piping 3, and the transmitting antenna 20 and the receiving antenna 21 are arranged at positions facing each other via the detecting section piping 3. ing. The transmitting antenna 20 and the receiving antenna 2
The part of the detection part pipe 3 to which 1 is attached is formed of an insulator, for example, fiber resin plastic (FRP).

A power splitter 23 is connected to the oscillator 22. The transmitting antenna 20 and the phase difference measuring circuit 24 are connected to the power splitter 23, and branch the microwave signal output from the oscillator 22 to output to the transmitting antenna 20 and the phase difference measuring circuit 24. The transmitting antenna 20 emits a microwave into the detection unit pipe 3 based on the microwave signal received from the power splitter 23. The microwave passes through the fluid in the detector pipe 3 and is received by the receiving antenna 21. The receiving antenna 21 outputs the microwave to the phase difference measuring circuit 24 as a received signal.

The phase difference measurement circuit 24 calculates the phase delay θ 2 between the reception signal output from the reception antenna 21 and the microwave signal transmitted from the power splitter 23 and the phase delay previously obtained from a fluid containing no substance to be measured, for example, tap water. The phase difference Δθ from the delay θ 1, that is, Δθ = θ 2 −θ 1 (1) is obtained. Here, the phase differences θ2 and θ1 in the equation (1) are respectively expressed by the following equations.

[0021]

(Equation 1)

Accordingly, from the above equations (1), (2) and (3), the phase difference Δθ is

[0023]

(Equation 2)

Is represented by

In this equation, C0 is the propagation speed of a radio wave in a vacuum, d is the thickness (distance) of the liquid layer to be measured, ω is the angular frequency of the microwave, εs is the relative permittivity of the liquid to be measured, ε0 Is the relative dielectric constant of a vacuum, εw is the relative dielectric constant of a fluid having a concentration of the substance to be measured of 0%, σ is the conductivity of the liquid to be measured, and σw is the conductivity of the fluid having a concentration of 0% of the substance to be measured.

Further, a conductivity detector 25 and a temperature detector 26 are provided in the attached pipe 4. The conductivity detector 25 and the temperature detector 26 are mounted so as to be in contact with the fluid flowing in the attached pipe 4. The conductivity detector 25 and the temperature detector 26 are connected to a correction operation circuit 29 via signal conversion circuits 27 and 28, respectively.

The correction operation circuit 29 has a function of correcting the influence of the fluid conductivity and temperature. this is,
This solves the fact that the phase difference Δθ is affected by the conductivity σ and the temperature in the above equation. For example, first, the conductivity will be described. In the case of sewage sludge concentration measurement, the reference concentration measurement method is a dry weight measurement method. Therefore, the influence of the conductivity σ due to components (ionic components and the like) dissolved in the liquid is excluded.

The actual correction relation of the arithmetic circuit 29 and a conductivity sigma, as shown in FIG. 2, for example the phase difference correction value [Delta] [theta] _sigma is stored.

The relationship shown in FIG. 2 is a result obtained by dissolving sodium chloride or the like in water and changing the conductivity σ. Accordingly, the correction operation circuit 29 has a function as a conductivity correction unit that subtracts the phase difference correction value Δθ _σ from the phase difference Δθ measured by the phase difference measurement circuit 24 to obtain a phase difference Δθ ′.

Next, the temperature will be described. The relative dielectric constant εs of the fluid changes depending on the temperature, which affects the phase difference Δθ. Therefore, the relationship between the temperature difference Δt and the phase difference correction value Δθε shown in FIG. 3 is stored in the correction calculation circuit 29 in advance. This relationship is a measurement result of the temperature difference Δt and the phase difference correction value Δθε. Accordingly, the correction operation circuit 29 has a function as a temperature correction means for subtracting the phase difference correction value Δθε from the phase difference Δθ measured by the phase difference measurement circuit 24 to obtain a phase difference Δθ ′.

Further, the correction operation circuit 29 has a function of simultaneously performing each correction for the conductivity and the temperature, and can obtain the corrected phase difference by the following equation: Δθ ′ = Δθ−Δθσ−Δθε.

The signal conversion circuit 30 has a phase difference Δ shown in FIG.
The relationship between θ ′ and the density is set in advance, and the correction operation circuit 29
Has a function of obtaining a density from the phase difference Δθ ′ corrected by the above and outputting a current signal corresponding to the density.

Next, the operation of the above-configured device will be described.

First, the reception wave delay θ 1 of a liquid having a concentration of 0%, in this case, tap water is measured. For this purpose, the gate valves 5 and 6 of the pipes 1 and 2 through which the sludge flows are closed to stop the sludge. If the flow of sludge cannot be stopped, a bypass pipe is provided, and the flow of sludge is switched to the bypass pipe. Next, the drain valve 10 is opened to discharge the sludge in the detector pipe 3 and the auxiliary pipe 4, and then the water supply valve 9 is opened to supply tap water into the detector pipe 3 and the auxiliary pipe 4. Then, after cleaning the inside of the detection unit pipe 3 and the attachment pipe 4, the inside of the detection unit pipe 3 and the attachment pipe 4 is filled with tap water.

In this state, a microwave signal is output from the microwave oscillator 22. This microwave signal is split in two directions by the power splitter 23, one of which is sent to the microwave antenna 20 and the other is sent to the phase difference measuring circuit 24. The microwave antenna 20 emits microwaves, and the microwaves pass through the detector pipe 3 as shown in FIG. 5, propagate through tap water, and reach the reception antenna 21. The receiving antenna 21 outputs a signal corresponding to the received microwave. At this time, the phase difference measuring circuit 24 calculates and stores the phase delay θ1 between the output signal of the receiving antenna 21 and the microwave signal from the power splitter 23.

In addition, the zero concentration liquid measured by the conductivity detector 25, here, the conductivity of water and the zero concentration liquid measured by the temperature detector 26, here, the temperature of water are stored.

Next, the drain valve 10 is opened, and the detection section piping 3
And drain the tap water in the attached pipe 4, then each gate valve 5,
6 is opened to flow sludge into the detector pipe 3 and the auxiliary pipe 4.

In this state, a microwave signal is output from the microwave oscillator 22. This microwave signal is sent to the microwave antenna 20 and the phase difference measurement circuit 24 in the same manner as described above. The microwave antenna 20 emits microwaves, and the microwaves propagate through the sludge and reach the receiving antenna 21 as shown in FIG. The receiving antenna 21 outputs a signal corresponding to the received microwave. At this time, the phase difference measuring circuit 24 obtains and stores the phase delay θ2 between the output signal of the receiving antenna 21 and the microwave signal from the power splitter 23.

Next, the phase difference measuring circuit 24 obtains the difference between the phase delays θ1 and θ2 for tap water and sludge, that is, the phase difference Δθ Δθ = θ2−θ1. This phase difference Δθ is sent to the correction operation circuit 29.

On the other hand, the conductivity of the sludge detected by the conductivity detector 25 is converted into a conductivity signal corresponding to the conductivity by a signal conversion circuit 27 and sent to a correction operation circuit 29, and the temperature detector 26 Is converted into a temperature signal corresponding to the temperature by the signal conversion circuit 27 and sent to the correction operation circuit 29.

The correction operation circuit 29 sends the phase difference Δθ to the signal conversion circuit 30 unless the conductivity and temperature are corrected.

When the signal conversion circuit 30 receives the phase difference Δθ, it obtains the sludge concentration from the relationship between the phase difference Δθ and the concentration shown in FIG. 4, and outputs a current signal corresponding to this concentration. This current signal is, for example, 4 to 20 m if the concentration is 0 to 10%.
Corresponds to A.

When the conductivity is corrected, the correction operation circuit 29 receives the conductivity signal and calculates a difference between the conductivity of the zero-concentration liquid measured and stored in advance as shown in FIG. obtains a phase difference correction value [Delta] [theta] _sigma from the relationship between the phase difference correction value [Delta] [theta] _sigma, finding the difference Δθ'Δθ' = _Δθ-Δθ σ the phase difference [Delta] [theta] and the phase difference correction value [Delta] [theta] _sigma. The phase difference Δθ ′ is sent to the signal conversion circuit 30. The signal conversion circuit 30 determines the sludge concentration from the relationship between the phase difference Δθ ′ and the concentration shown in FIG. 4, and outputs a current signal corresponding to the concentration. .

When the temperature is corrected, the correction arithmetic circuit 29 receives the temperature signal and measures the temperature difference between the temperature of the zero-concentration liquid and the phase difference correction value, which is measured and stored in advance as shown in FIG. The phase difference correction value Δθε is determined from the relationship with Δθt, and the difference Δθ ′ Δθ ′ = Δθ−Δθε between the phase difference Δθ and the phase difference correction value Δθε is determined. The phase difference Δθ ′ is sent to the signal conversion circuit 30. The signal conversion circuit 30 determines the sludge concentration from the relationship between the phase difference Δθ ′ and the concentration shown in FIG. 4, and outputs a current signal corresponding to the concentration. .

When the conductivity and the temperature are corrected together, the correction operation circuit 29 receives the conductive signal and the temperature signal, calculates the phase difference correction values Δθ _σ and Δθε in the same manner as described above, and calculates the phase difference Δθ and the phase difference correction values. Difference Δθ from values Δθ _σ and Δθε
Seek _{'Δθ' = Δθ-Δθ σ -Δθε} . The phase difference Δθ ′ is sent to the signal conversion circuit 30. The signal conversion circuit 30 determines the sludge concentration from the relationship between the phase difference Δθ ′ and the concentration shown in FIG. 4, and outputs a current signal corresponding to the concentration. .

As described above, in the above embodiment, the phase difference Δ between the output signal of the receiving antenna 21 and the microwave signal is obtained.
Since θ is determined and the concentration of the substance to be measured contained in the sludge is obtained from the phase difference Δθ, the concentration can be measured without being affected by the adhesion of the suspended solid contained in the sludge and the bubbles in the sludge, and The concentration can be measured even for a substance in which a suspended substance dissolves in a liquid. In addition, since there is no mechanical mechanism, long-term reliability can be improved.

Further, since the phase difference Δθ is corrected by measuring the conductivity of the sludge, it is possible to eliminate the influence of the conductivity caused by the ionic components dissolved in the sludge.

Further, since the phase difference Δθ is corrected by measuring the temperature of the sludge, even if the relative permittivity changes due to the temperature, the effect can be eliminated and the concentration can be accurately measured.

Further, since the phase difference Δθ is corrected by measuring the electric conductivity and temperature of the sludge, the influence of the electric conductivity caused by the ionic component dissolved in the sludge and the effect of the change of the relative dielectric constant due to the temperature are eliminated. Both can be eliminated.

It should be noted that the present invention is not limited to the above-described embodiment, and may be modified without changing the gist of the present invention. For example, in the above embodiment, the sludge is measured in a flowing state, but the concentration may be measured in a stationary state.
Further, the present invention can be applied not only to sludge but also to concentration measurement of other fluids.
Further, in the embodiment, the description has been made based on the liquid having a concentration of 0%. However, a liquid which can be regarded as zero concentration in consideration of the measurement range without being strictly zero may be used as a reference, or a liquid having a certain known concentration may be measured. A substance containing a substance may be used as a reference.

[0051]

As described above in detail, according to the present invention, the concentration can be measured without being affected by the adhesion of suspended substances or bubbles in the liquid, and the measurement can be performed even on substances in which the suspended substance is dissolved in the liquid. A long-term reliable concentration meter that can be provided.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing one embodiment of a densitometer according to the present invention.

FIG. 2 is a diagram showing a relationship between conductivity and a phase difference in the densitometer.

FIG. 3 is a diagram showing a relationship between a temperature and a phase difference in the densitometer.

FIG. 4 is a view showing a relationship between a density and a phase difference in the densitometer.

FIG. 5 is a diagram showing microwave propagation in the densitometer.

FIG. 6 is a diagram showing microwave propagation in the densitometer.

FIG. 7 is a configuration diagram of a conventional technique.

[Explanation of symbols]

1, 2, ... pipe, 3 ... detector section pipe, 4 ... attached pipe, 5, 6
... gate valve, 9 ... water supply valve, 10 ... drain valve, 20 ...
Transmission antenna, 21 ... Reception antenna, 22 ... Microwave oscillator, 23 ... Power splitter, 24 ... Phase difference measurement circuit, 25 ... Conductivity detector, 26 ... Temperature detector, 29 ... Correction operation circuit, 30 ... Signal conversion circuit .

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Ikuo Arai 1-48-31, Funabashi, Setagaya-ku, Tokyo (72) Inventor Hitoshi Nagao 1-1-1, Shibaura, Minato-ku, Tokyo Inside the Toshiba head office (72) Inventor Seiji Yamaguchi 1 Toshiba-cho, Fuchu-shi, Tokyo Inside the Toshiba Fuchu Plant Co., Ltd. (56) References JP-A-2-298843 (JP, A) JP-A-3-221185 (JP, A) JP-A-60-25446 (JP, A) JP-A-56-43540 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G01N 22/00-22/04

Claims (1)

(57) [Claims] 1. A microwave transmitter / receiver opposed to a pipe through which a fluid to be measured containing a substance to be measured flows or a container containing the fluid, and a microwave radiated from the transmitter and passed through the fluid to be measured. The phase difference Δθ between the phase delay θ2 of the microwave received by the receiver and the phase delay θ1 previously measured using the fluid not containing the substance to be measured.
That is, the concentration of the fluid to be measured is measured by obtaining Δθ = θ2−θ1, and the conductivity of the fluid to be measured is measured, and the fluid of the fluid not containing the material to be measured which has been measured in advance is measured. A densitometer comprising a conductivity phase difference correcting means for correcting the phase difference based on a difference from the conductivity.