JP2005221322A - Ultrasonic sludge interface level meter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultrasonic sludge interface level meter capable of always keeping high measuring accuracy by cleaning effectively an ultrasonic sensor dipped in liquid. <P>SOLUTION: In this ultrasonic sludge interface level meter, the ultrasonic sensor 11 is fixed in the dipped state in top clear layer water in a tank to be measured, and a time until an ultrasonic wave transmitted from the ultrasonic sensor 11 is reflected by an interface between the top clear layer water and the sludge and returned is measured, and the level of the interface is detected based on the time. The level meter has a constitution wherein two or more gas jet nozzles 17 (18) are provided on a lower part of the ultrasonic sensor 11, and the gas (air) is jetted out of the gas jet nozzles 17 (18) toward the ultrasonic sensor 11, to thereby form the gas-liquid mixed state on the under surface of the ultrasonic sensor 11, and thereby a cleaning mechanism for cleaning the ultrasonic sensor 11 is provided. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an ultrasonic sludge interface level meter that measures an interface level between supernatant water and sludge in a tank to be measured using an ultrasonic sensor, and particularly relates to cleaning of an ultrasonic sensor.

  In a sedimentation tank used for wastewater treatment or sewage treatment, sludge settles at the bottom. Ultrasonic sludge that measures the level of the interface between the supernatant water and sludge in the sedimentation tank using an ultrasonic sensor. Interface level meters are conventionally known. That is, this ultrasonic sludge interface level meter is fixed with the ultrasonic sensor immersed in the supernatant water in the tank to be measured, and the ultrasonic wave transmitted from the ultrasonic sensor is the interface between the supernatant water and the sludge. The time until the light is reflected and returned is measured, and the level of the interface is detected based on the time.

  By the way, in such an ultrasonic sludge interface level meter, suspended matter, sludge, bubbles, etc. are likely to adhere to the transmission / reception surface of the ultrasonic sensor immersed in the supernatant water. Decreases. Accordingly, it is necessary to always or periodically clean the transmission / reception surface of the ultrasonic sensor, and various cleaning mechanisms have been proposed so far (see, for example, Patent Documents 1 and 2).

JP-A-9-318420 JP 2003-302279 A

  However, in the conventional cleaning mechanism, since a method of jetting a liquid such as water from the nozzle toward the transmission / reception surface of the ultrasonic sensor is exclusively used, a good cleaning effect cannot be obtained. That is, the method of jetting liquid in the liquid replaces the liquid in the vicinity of the sensor and pushes the coexisting solid matter, but the jetting speed of the liquid for washing is reduced in the supernatant water. For this reason, it is difficult to remove impurities attached to the sensor. On the other hand, when the liquid jet speed is increased, the effect of removing impurities increases, but there is a problem that the spray diffusion region becomes narrow and an effective cleaning effect cannot be obtained.

  Therefore, in order to adopt a method of injecting a high-pressure liquid, a number of injection pipes are provided so that the jet flows on the entire lower surface of the sensor, and a mechanism for injecting in order so that the mutual jets do not interfere with each other is provided. In addition, it is necessary to add a complicated mechanism such as a variable nozzle mechanism that can arbitrarily change the angle of the nozzle.

  As described above, in the method of ejecting the liquid, it is difficult to obtain a sufficient cleaning effect with a simple mechanism.

  Also, there is an example in which gas is used for cleaning the ultrasonic sensor even in the conventional technology, but as in the case of injecting liquid, this is a technology that uses an extrusion force by a jet flow, and has a low effect of removing impurities. In many cases, a method of injecting a gas from a single gas injection nozzle is employed. In this case, small bubbles remain on the lower surface of the ultrasonic sensor after cleaning, and the ultrasonic waves transmitted from the ultrasonic sensor are refracted by the bubbles. However, there is a problem that the detection accuracy of the ultrasonic sensor is lowered.

  The present invention has been made in view of the above problems, and its objective is to provide an ultrasonic sludge interface that can effectively clean an ultrasonic sensor immersed in a liquid and always maintain high measurement accuracy. To provide a level meter.

  In order to achieve the above-mentioned object, the invention according to claim 1 fixes the ultrasonic sensor in a state where it is immersed in the supernatant water in the tank to be measured, and the ultrasonic wave transmitted from the ultrasonic sensor is the supernatant water and sludge. In an ultrasonic sludge interface level meter that detects the level of the interface based on the measured time until the light is reflected at the interface with the two or more gases at the bottom of the ultrasonic sensor Providing an injection nozzle, injecting gas from the gas injection nozzle toward the ultrasonic sensor, forming a gas-liquid mixed state on the lower surface of the ultrasonic sensor, forming a gas-liquid mixed state on the lower surface of the ultrasonic sensor; A cleaning mechanism for cleaning the ultrasonic sensor using the diffusion force and the stirring force is provided.

  The invention according to claim 2 is characterized in that, in the invention according to claim 1, the angle formed with respect to the lower surface of the ultrasonic sensor of the gas injection nozzle at a water depth of 0 to 50 cm is set to 4 ° to 45 °. To do.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, the phase of the plurality of gas injection nozzles is shifted to provide a phase difference, and the lower surface of the ultrasonic sensor is detected by the gas injected from each gas injection nozzle. It is characterized by generating a swirl flow.

  According to a fourth aspect of the present invention, in the third aspect of the present invention, the positions of the plurality of gas injection nozzles are shifted in the radial direction within the same horizontal plane.

  According to a fifth aspect of the present invention, in the third aspect of the present invention, the positions of the plurality of gas injection nozzles are shifted in the depth direction.

  A sixth aspect of the invention is characterized in that, in the invention of any one of the first to fifth aspects, gases having different pressures or flow velocities are jetted from the plurality of gas jet nozzles.

  According to the first aspect of the present invention, the gas injected from the plurality of gas injection nozzles toward the lower surface, which is the transmitting / receiving surface of the ultrasonic sensor, interferes with each other and is disturbed together with the surrounding water. A mixed state is formed to effectively clean the lower surface of the ultrasonic sensor. The gas-liquid mixed state has a stirring force due to the complicated disturbance, and generates a force for separating impurities. In addition, the process in which the bubbles become larger creates a diffusive force, and has the effect of extruding the separated impurities. For this reason, suspended matter and sludge adhering to the lower surface of the ultrasonic sensor are reliably removed, and the lower surface, which is the transmission / reception surface of the ultrasonic sensor, is kept clean, and its detection accuracy is not reduced. The sonic sludge interface level meter can always maintain high measurement accuracy. In the present invention, gas is used for cleaning the ultrasonic sensor, but gas is injected from two or more gas injection nozzles, and large bubbles formed by the injected gas are caused to interfere with each other. Since the disturbance is generated, small bubbles do not remain on the lower surface of the ultrasonic sensor after cleaning, and therefore, ultrasonic waves emitted from the ultrasonic sensor which has been a problem in the prior art are refracted by the bubbles. As a result, the ultrasonic sensor always has high detection accuracy.

  By the way, the gas released into water tends to rise immediately. Further, since the gas is released in the water, the gas released into the water under pressure is immediately expanded. Therefore, in order to effectively form a gas-liquid mixed state while using these forces, the gas discharge angle is important.

  According to the second aspect of the present invention, the angle formed with respect to the lower surface of the ultrasonic sensor of the gas jet nozzle at a water depth of 0 to 50 cm where the ultrasonic sensor is installed is normally set to 4 ° to 45 °. The gas ejected from the gas diffuses while forming a gas-liquid mixed state, collides over almost the entire lower surface of the ultrasonic sensor as the object to be cleaned, and is used for cleaning the lower surface.

  According to the third, fourth, or fifth aspect of the invention, since the swirling flow is generated on the lower surface of the ultrasonic sensor by the gas ejected from each gas jet nozzle, the swirling flow further reduces the lower surface of the ultrasonic sensor. Washed effectively.

  According to the sixth aspect of the present invention, since the gas having different pressures or flow velocities are ejected from the plurality of gas ejection nozzles, the swirl flow can be generated on the lower surface of the ultrasonic sensor. As a result, the lower surface of the ultrasonic sensor is more effectively cleaned.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

  1 is a side sectional view of the precipitation tank, FIG. 2 is a plan view of the precipitation tank, FIG. 3 is an enlarged sectional view taken along line AA in FIG. 2, and FIG. 4 is a front view of the ultrasonic sensor (view B in FIG. 3). 5 to 7 are bottom views of the ultrasonic sensor showing a state of cleaning (a view in the direction of arrow C in FIG. 4).

  1 and 2, reference numeral 1 denotes a bottomed cylindrical sedimentation tank having an open upper surface, in which treated water such as sewage containing sludge is accommodated. And in this sedimentation tank 1, the sludge 2 contained in to-be-processed water accumulates in the bottom part as shown in figure by sedimentation, and the supernatant water 3 occupies the upper part.

  By the way, a drive motor 4 is installed at the center of the upper portion of the sedimentation tank 1, and the scum skimmer 5 is rotationally driven by the drive motor 4 in the direction of the arrow in FIG. The scum (not shown) floating on the top 3 is scraped and discharged to the channel-shaped trough 6.

  Thus, the settling tank 1 is provided with an ultrasonic sludge interface level meter 10 for measuring the level of the interface between the supernatant water 3 and the sludge 2 (depth of the sludge 2) with ultrasonic waves. As shown in FIG. 3, the ultrasonic sludge interface level meter 10 is transmitted from an ultrasonic sensor 11 installed in a state of being immersed in the supernatant water 3 in the sedimentation tank 1 and the ultrasonic sensor 11. It comprises a measuring means (not shown) for measuring the propagation time of the ultrasonic wave, a calculating means (not shown) for calculating the sludge interface level based on the propagation time measured by the measuring means, and the like.

  2 and 3, the ultrasonic sensor 11 is suspended and supported at the tip of an arm 7 that extends horizontally from the trough 6 in the direction perpendicular to the axis, and is immersed in the supernatant 3. Here, the arm 7 has a base end portion detachably engaged with and fixed to the upper end portion of the trough 6 via a hook 8, and is attached to a U-shaped support member 9 attached to the tip end portion. The ultrasonic sensor 11 is suspended and supported by a wire 12.

  As shown in detail in FIG. 4, the ultrasonic sensor 11 is sandwiched between two upper and lower support plates 13 and 14, and a plurality of (in the present embodiment, a plurality of (in this embodiment) the support plates 13 and 14. Four) bolts 15 are inserted, and nuts 16 are screwed into the respective bolts 15. In the present embodiment, a commercial product of HL2000 manufactured by Honda Electronics Co., Ltd. is used as the ultrasonic sensor 11, and the outer diameter of the lower surface, which is the transmission / reception surface, is φ65 mm.

  Thus, in the present embodiment, a cleaning mechanism is provided for cleaning the lower surface, which is the transmission / reception surface of the ultrasonic sensor 11, with air, but this cleaning mechanism is provided below the ultrasonic sensor 11. The two gas injection nozzles 17 and 18 (only one is shown in FIG. 4) and a compressor 19 (see FIG. 2) for supplying compressed air to the gas injection nozzles 17 and 18 are constituted. The compressor 19 and the gas injection nozzles 17 and 18 are connected via an air hose 20 (see FIG. 2). In the present embodiment, pipes with an inner diameter of 4 mm are used as the gas injection nozzles 17 and 18.

  Here, as shown in FIG. 4, a support member 22 inserted through one bolt 15 and fastened by a nut 21 is fixed to the lower support plate 14, and each gas injection nozzle 17, 18 is fixed to the support plate 14 by a support member 22.

  By the way, the gas injection nozzles 17 and 18 are installed at a position where the water depth is 0 to 50 cm together with the ultrasonic sensor 11, but the tip of the gas injection nozzles 17 and 18 is covered by the ultrasonic sensor 11 as shown in FIG. It is bent at an acute angle toward the lower surface, which is the cleaning surface, and its inclination angle (the angle formed by the center line of each tip of the gas injection nozzles 17 and 18 with respect to the lower surface of the ultrasonic sensor 11, that is, the air injection angle) ) Θ is set to 10 ° ± 5 °.

  Further, as shown in FIG. 5, the two gas injection nozzles 17 and 18 are arranged in a state where the phase is shifted by an angle α in the circumferential direction in a plan view, and the radial position of each injection port in the same horizontal plane. The (position from the center of the ultrasonic sensor 11) is the same, and each ejection port opens toward the center of the ultrasonic sensor 11 at a distance r from the center of the ultrasonic sensor 11. Therefore, both the gas injection nozzles 17 and 18 are arranged so that the center line of the tip portion intersects at the angle α shown in the plan view.

  Next, the operation of the ultrasonic sludge interface level meter 10 according to the present invention will be described.

When an ultrasonic wave is transmitted from the ultrasonic sensor 11 immersed in the supernatant water 3 in the settling tank 1 at regular time intervals, the ultrasonic wave is reflected at the interface between the supernatant water 3 and the sludge 2 (sludge interface). Then, the ultrasonic sensor 11 receives the time (ultrasonic propagation time) t measured by a measurement unit (not shown), and the sludge interface from the ultrasonic sensor 11 based on the measured time t. The depth L _{1 up to} (see FIG. 1) is calculated by the following equation by a calculation means (not shown).

L ₁ = a × t / 2 (1)
(A: speed of sound)
Here, since the distance L ₀ from the ultrasonic sensor 11 shown in FIG. 1 to the lower end of the sedimentation layer 1 is known, the level (depth) L ₂ of the sludge 2 is obtained by the following equation.

L ₂ = L ₀ −L ₁ (2)
By the way, as described above, suspended matter and sludge are likely to adhere to the lower surface, which is the transmission / reception surface of the ultrasonic sensor 11 immersed in the supernatant water 3, and if these adhere, the detection accuracy of the ultrasonic sensor 11 decreases. For this reason, in this embodiment, the lower surface of the ultrasonic sensor 11 is cleaned with air by a cleaning mechanism periodically (for example, every 1 hour or every 3 hours).

  That is, at the time of cleaning, the compressor 19 is driven and compressed air is pumped to the two gas injection nozzles 17 and 18 through the air hose 20. Then, as shown in FIG. 5, compressed air having a pressure of about 0.1 to 0.5 MPa is injected from the injection ports of the gas injection nozzles 17 and 18 toward the center of the lower surface of the ultrasonic sensor 11. The jetted compressed air diffuses as shown in the figure, interferes with each other in the area shown by hatching in FIG. 5 and is disturbed to form a gas-liquid mixed state around the area, thereby forming the ultrasonic sensor 11. Effectively clean the lower surface. As a result, the suspended matter and sludge adhering to the lower surface of the ultrasonic sensor 11 are reliably removed, and the lower surface, which is the transmission / reception surface of the ultrasonic sensor 11, is kept clean, and its detection accuracy does not decrease, The ultrasonic sludge interface level meter 10 can always maintain high measurement accuracy.

  In this embodiment, air, which is a gas, is used for cleaning the ultrasonic sensor 11, but air is injected from the two gas injection nozzles 17 and 18, and formed by the injected air. Since the large bubbles interfere with each other to cause disturbance, small bubbles do not remain on the lower surface of the ultrasonic sensor 11 after cleaning. For this reason, the ultrasonic wave transmitted from the ultrasonic sensor 11 is not refracted by the bubbles, and the ultrasonic sensor 11 always has high detection accuracy.

  By the way, in the above embodiment, as shown in FIG. 5, the two gas injection nozzles 17 and 18 are arranged so that the center lines of their tip portions intersect each other. However, as shown in FIG. The injection nozzles 17 and 18 may be arranged such that their tip portions are parallel to each other. In this case, the compressed air injected from the gas injection nozzles 17 and 18 diffuses as shown in FIG. In the region indicated by diagonal lines, they interfere with each other and are disturbed, and a gas-liquid mixed state is formed around the region to effectively clean the lower surface of the ultrasonic sensor 11.

  Further, as shown in FIG. 7, the two gas injection nozzles 17 and 18 are arranged so that the center lines of the tip portions thereof intersect each other, and the positions of the injection ports are shifted in the radial direction within the same horizontal plane ( A deviation amount Δr) may be provided. In this case, the bubble formed by the air injected from one gas injection nozzle 18 collides with the base end of the bubble formed by the air injected from the other gas injection nozzle 17, and the lower surface of the ultrasonic sensor 11. In order to generate a swirling flow of bubbles, the lower surface of the ultrasonic sensor 11 is more effectively cleaned by the swirling flow.

Furthermore, as shown in FIG. 8, the swirl flow of bubbles on the lower surface of the ultrasonic sensor 11 can also be obtained by shifting the positions of the two gas injection nozzles 17 and 18 in the depth direction and providing a phase difference between them. And the lower surface of the ultrasonic sensor 11 can be effectively cleaned. In this case, as shown in the drawing, the inclinations θ ₁ and θ ₂ of the gas injection nozzles 17 and 18 may be set to different values (θ ₁ <θ ₂ ).

  Although not shown, a swirl flow can be generated on the lower surface of the ultrasonic sensor even when gases having different pressures or flow velocities are ejected from a plurality of gas spray nozzles. The lower surface of the sensor can be cleaned more effectively.

  In the above embodiment, two gas injection nozzles are used as the cleaning mechanism, but the same effect can be obtained by using three or more gas injection nozzles. In this embodiment, the inclination angle θ of the gas injection nozzle is 10 ° ± 5 °, but the inclination angle θ of the gas injection nozzle at a water depth of 0 to 50 cm should be set in the range of 4 ° to 45 °. It is. Incidentally, if the inclination angle θ is 4 ° or less, the air injected from the gas injection nozzle flows substantially parallel to the lower surface of the ultrasonic sensor without forming a gas-liquid mixed state, and does not contribute to cleaning. If the inclination angle θ is 45 ° or more, the air injected from the gas injection nozzle becomes a large bubble and does not form a gas-liquid mixed state, or does not reach the entire area of the lower surface of the ultrasonic sensor. It cannot sufficiently contribute to the cleaning of the lower surface of the acoustic wave sensor.

  Furthermore, in the present embodiment, air is injected from the gas injection nozzle, but a gas other than air, such as carbon dioxide, may be injected.

  Next, an experiment conducted for confirming the effect of the present invention will be described.

  In the experiment, as shown in FIG. 9, an impurity was simulated at the center of the transmitting / receiving surface having a diameter of 65 mm of the ultrasonic sensor (Honda Electronics HL2000) 11 installed at a water depth of 20 cm, and the length was 3 cm. Three toothpastes (“Clear Clean Plus a” 23) manufactured by Kao Corporation were attached side by side, and compressed air having a pressure of 0.5 MPa was ejected from a gas injection nozzle (not shown) having an inner diameter of 4 mm.

  As experimental conditions, the number of gas injection nozzles was changed to 1, 2, and 3, and the inclination angle θ of each gas injection nozzle was 0 ° (horizontal), 5 °, 10 °, 45 °, and 60 °. In each case, the adhesion state of the toothpaste on the transmission / reception surface of the ultrasonic sensor was visually confirmed. The results are shown in Table 1.

尚、表１において、○は歯磨粉の付着が全く認められない状態、△は歯磨粉の付着が若干認められる状態、×は歯磨粉が可成り付着したままの状態をそれぞれ示す。

In Table 1, ◯ indicates a state in which no adhesion of toothpaste is observed, Δ indicates a state in which the adhesion of toothpaste is slightly recognized, and X indicates a state in which the toothpaste remains fairly adhered.

  As apparent from Table 1, when the number of gas injection nozzles is set to 2 or more and the inclination angle θ of each gas injection nozzle is set to around 10 °, a high cleaning effect can be obtained.

  The present invention is not limited to an ultrasonic sensor used in an ultrasonic sludge interface level meter, but also a transmission / reception surface of an ultrasonic sensor used in a state of being immersed in a liquid, various water quality sensors, and an underwater camera. High availability for cleaning windows.

It is a sectional side view of a sedimentation tank. It is a top view of a sedimentation tank. It is an AA line expanded sectional view of FIG. FIG. 4 is a front view of the ultrasonic sensor (an enlarged detailed view in the direction of arrow B in FIG. 3). It is a bottom view (figure of the arrow C direction of FIG. 4) of the ultrasonic sensor which shows the mode of washing | cleaning. It is a bottom view (figure of the arrow C direction of FIG. 4) of the ultrasonic sensor which shows the mode of washing | cleaning. It is a bottom view (figure of the arrow C direction of FIG. 4) of the ultrasonic sensor which shows the mode of washing | cleaning. It is a side view of the gas washing nozzle part which shows another form of this invention. It is a bottom view of the ultrasonic sensor which shows experimental conditions.

Explanation of symbols

1 Sedimentation tank (measurement tank)
2 Sludge 3 Supernatant Water 10 Ultrasonic Sludge Interface Level Meter 11 Ultrasonic Sensor 17, 18 Gas Injection Nozzle 19 Compressor 20 Air Hose

Claims (6)

Fix the ultrasonic sensor immersed in the supernatant water in the tank to be measured, and measure the time until the ultrasonic wave transmitted from the ultrasonic sensor is reflected at the interface between the supernatant water and sludge and returns. In an ultrasonic sludge interface level meter that detects the interface level based on the time,
Two or more gas injection nozzles are provided below the ultrasonic sensor, gas is injected from the gas injection nozzle toward the ultrasonic sensor, and a gas-liquid mixed state is formed on the lower surface of the ultrasonic sensor to generate ultrasonic waves. An ultrasonic sludge interface level meter provided with a cleaning mechanism for cleaning the sensor.   2. The ultrasonic sludge interface level meter according to claim 1, wherein an angle formed with respect to a lower surface of the ultrasonic sensor of the gas injection nozzle at a water depth of 0 to 50 cm is set to 4 ° to 45 °.   The phase of the plurality of gas injection nozzles is shifted to provide a phase difference, and a swirling flow is generated on the lower surface of the ultrasonic sensor by the gas injected from each gas injection nozzle. Ultrasonic sludge interface level meter.   The ultrasonic sludge interface level meter according to claim 3, wherein the positions of the injection ports of the plurality of gas injection nozzles are shifted in the radial direction within the same horizontal plane.   The ultrasonic sludge interface level meter according to claim 3, wherein the positions of the plurality of gas injection nozzles are shifted in the depth direction. The ultrasonic sludge interface level meter according to any one of claims 1 to 5, wherein gases having different pressures or flow velocities are ejected from the plurality of gas ejection nozzles.

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