JP2007209936A - Ultrasonic decomposition apparatus and ultrasonic decomposition method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultrasonic decomposition apparatus for efficiently decomposing an organic compound contained in the liquid to be treated. <P>SOLUTION: The ultrasonic decomposition apparatus 5 is provided with: a decomposition tank 51 in which VOC-containing washing water W1 is put; a first ultrasonic vibrator 52 arranged on the outside of the bottom surface of the decomposition tank 51; and a second ultrasonic vibrator 53 arranged on the outside of the side face of the decomposition tank 51. An ultrasonic wave 10 of 400-500 kHz is transmitted from the first ultrasonic vibrator 52 toward the washing water W1 in the decomposition tank 51 from the bottom surface of the decomposition tank 51. The ultrasonic wave 10 of 400-500 kHz is transmitted from the second ultrasonic vibrator 53 toward the washing water W1 from the side face of the decomposition tank so that the ultrasonic wave from the second ultrasonic vibrator and the ultrasonic wave 10 from the bottom surface of the decomposition tank perpendicularly cross each other. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an ultrasonic decomposition apparatus and an ultrasonic decomposition method for decomposing an organic compound by irradiating ultrasonic waves into a liquid to be treated containing the organic compound.

  Contaminated soil, industrial wastewater, and the like contain organic compounds such as organic chlorine compounds and volatile organic compounds (VOC) as harmful substances. In order to detoxify these organic compounds, it is difficult to decompose the organic compounds only by microbial treatment, and therefore, oxidation treatment using ozone, hydrogen peroxide, ultraviolet rays, a photocatalyst, ultrasonic waves, or the like is performed. In particular, decomposition treatment using ultrasonic waves has advantages such as easy operation, high reaction temperature, difficulty in producing harmful by-products such as dioxin, and decomposition even at low concentrations. Therefore, development of a decomposition device using ultrasonic waves is underway.

For example, Patent Document 1 proposes an apparatus that renders VOC contained in an aqueous solution harmless by irradiating ultrasonic waves. In this apparatus, a catalytic substance made of a basic metal salt is added to an aqueous solution containing VOC, and ultrasonic waves with a relatively low frequency (for example, 20 kHz to 100 kHz) are irradiated. When ultrasonic waves are irradiated in an aqueous solution, bubbles called cavitation are generated, and a reaction field of several thousand degrees and several thousand atmospheres called a hot spot is locally formed through compression and collapse processes. And it is thought that VOC is thermally decomposed in this extreme reaction field.
JP 2005-169389 A

  By the way, in order to perform the decomposition treatment of the organic compound at a low cost, it is preferable to omit the addition of the catalyst substance. Further, in order to render VOC harmless without using such a catalyst substance, it is necessary to irradiate ultrasonic waves having a frequency higher than the current level (specifically, 200 kHz or more). However, ultrasonic vibrators that irradiate high-frequency ultrasonic waves have problems in durability compared to low-frequency ultrasonic vibrators, so strong ultrasonic waves necessary to form a suitable reaction field are required. It becomes difficult to irradiate. For example, when purifying the aqueous solution of VOC extracted from the contaminated soil, the aqueous solution contains soil particles. Therefore, when the frequency of the ultrasonic wave is increased, it is expected that the soil particles in the aqueous solution become an obstacle to the propagation of the ultrasonic wave and the organic compound cannot be decomposed efficiently.

  The present invention has been made in view of the above problems, and an object thereof is to provide an ultrasonic decomposition apparatus and an ultrasonic decomposition method capable of efficiently decomposing an organic compound contained in a liquid to be treated. It is in.

  In order to solve the above-mentioned problem, in the invention described in claim 1, a decomposition tank containing a liquid to be processed containing an organic compound decomposed by ultrasonic irradiation, and a super tank from a first direction toward the liquid to be processed A first ultrasonic transducer for irradiating a sound wave and an ultrasonic wave toward the liquid to be treated from a second direction different from the first direction so as to overlap the ultrasonic wave from the first direction The gist of the ultrasonic decomposing apparatus comprising the second ultrasonic transducer.

  According to the first aspect of the present invention, a synergistic effect by superimposing ultrasonic waves can be obtained by irradiating ultrasonic waves from a plurality of different directions toward the liquid to be treated in the decomposition tank. That is, when ultrasonic waves are irradiated from a plurality of different directions, bubble nuclei that did not generate cavitation by single ultrasonic irradiation are used as the root of cavitation by ultrasonic irradiation from other directions. Therefore, more cavitation can be generated in the liquid to be treated, and the cavitation broadens the region of the high-temperature and high-pressure reaction field, so that the organic compound contained in the liquid to be treated can be efficiently decomposed in a short time. Can do.

  In addition, as an organic compound in this invention, volatile organic compounds (VOC), such as organic chlorine compounds, such as PCB, DDT, dioxins, trichloroethylene, tetrachloroethylene, benzene, toluene, xylene, acetone, etc. can be mentioned.

  According to a second aspect of the present invention, in the first aspect, the first ultrasonic transducer is provided outside the bottom surface of the decomposition tank, and the second ultrasonic transducer is provided outside the side surface of the decomposition tank. The gist of this is

  According to the invention described in claim 2, since both the first ultrasonic transducer and the second ultrasonic transducer are provided not on the inner surface side of the decomposition vessel but on the outer surface side, the unevenness on the inner surface side of the decomposition vessel is not increased. As a result, the ultrasonic wave can be uniformly propagated in the liquid to be treated in the decomposition tank. Further, in this case, since the ultrasonic waves can be irradiated so as to be orthogonal from the lower side and the side of the decomposition tank, a synergistic effect due to superposition of the ultrasonic waves can be reliably obtained. Furthermore, with such an arrangement mode, the risk that the ultrasonic waves generated by the first ultrasonic transducer and the ultrasonic waves generated by the second ultrasonic transducer cancel each other is reduced.

  A third aspect of the present invention provides the first inclined surface according to the first aspect, wherein the decomposition tank has first and second inclined surfaces opposed to each other at the bottom thereof, and the first ultrasonic transducer is the first inclined surface. The gist is that the second ultrasonic transducer is provided outside and provided outside the second inclined surface.

  According to the invention described in claim 3, since both the first ultrasonic transducer and the second ultrasonic transducer are provided not on the inner surface side of the decomposition tank but on the outer surface side, there are irregularities on the inner surface side of the decomposition tank. As a result, the ultrasonic wave can be uniformly propagated in the liquid to be treated in the decomposition tank. Further, it is possible to irradiate ultrasonic waves in different directions from each inclined surface, and it is possible to reliably obtain a synergistic effect by superimposing ultrasonic waves. Furthermore, with such an arrangement mode, the risk that the ultrasonic waves generated by the first ultrasonic transducer and the ultrasonic waves generated by the second ultrasonic transducer cancel each other is reduced.

  The gist of a fourth aspect of the present invention is that the apparatus according to any one of the first to third aspects further comprises a liquid flow generating means for generating a flow of the liquid to be processed in the decomposition tank.

  According to the fourth aspect of the present invention, the flow of the liquid to be processed is generated by the liquid flow generating means, so that the organic compound contained in the liquid to be processed is made uniform and the reaction frequency between the organic compound and cavitation is high. In addition, the effective cavitation due to the reaction of organic compounds increases. Therefore, the organic compound can be efficiently decomposed in a short time. Specific examples of the liquid flow generating means include a stirrer for stirring the liquid to be processed and a pump for circulating the liquid to be processed.

  In the invention according to claim 5, the ultrasonic wave is irradiated from the first direction toward the liquid to be treated containing the organic compound decomposed by the ultrasonic irradiation so as to overlap the ultrasonic wave from the first direction. The gist of the ultrasonic decomposition method is to irradiate ultrasonic waves toward the liquid to be treated from a second direction different from the first direction.

  According to the fifth aspect of the present invention, the ultrasonic wave is applied to the liquid to be treated in the decomposition tank from a plurality of different directions, and as in the first aspect, the superposition of the ultrasonic waves is performed. A synergistic effect can be obtained. That is, more cavitation can be generated in the liquid to be processed, and the formation region of the high-temperature and high-pressure reaction field is widened by the cavitation, so that the organic compound contained in the liquid to be processed can be efficiently decomposed. .

  The ultrasonic wave applied to the liquid to be processed from the first and second directions may have a frequency of 100 kHz to 1000 kHz, more preferably 200 kHz to 600 kHz, and particularly preferably 400 kHz to 500 kHz. ). When the liquid to be treated is irradiated with ultrasonic waves of 400 kHz to 500 kHz, a lot of cavitation occurs, so that the decomposition efficiency of the organic compound can be further increased. Furthermore, by irradiating ultrasonic waves in the same frequency range from a plurality of different directions, the existence area of the standing wave is widened, so that the synergistic effect by superposition of ultrasonic waves can be increased. Moreover, when irradiating the ultrasonic wave of the same frequency range, the ultrasonic oscillation circuit can be made common and the manufacturing cost of the ultrasonic decomposition apparatus can be reduced.

  As described in detail above, according to the first to sixth aspects of the invention, the organic compound contained in the liquid to be treated can be efficiently decomposed.

  Hereinafter, an embodiment in which the present invention is embodied in a contaminated soil purification system equipped with an ultrasonic decomposition apparatus will be described in detail with reference to the drawings. FIG. 1 is a schematic configuration showing a contaminated soil purification system. In FIG. 1, an arrow indicated by a broken line indicates an electrical connection between the devices, and an arrow indicated by a solid line indicates a flow-like connection between the devices.

  As shown in FIG. 1, the contaminated soil purification system 1 includes a hopper 2, an ultrasonic cleaning device 3, a solid-liquid separation device 4, an ultrasonic decomposition device 5, a drain tank 6, and a control device 7. This contaminated soil purification system 1 purifies contaminated soil containing a volatile organic compound (VOC) such as trichlorethylene (TCE) at a contaminated site such as a factory site, and decomposes VOC extracted from the contaminated soil to be harmless. It is a system to make it. The contaminated soil purification system 1 is a portable system having a size that can be mounted on a vehicle such as a truck. Of course, the contaminated soil purification system 1 may be a fixed system not specifically intended for transportation.

  Specifically, the contaminated soil E1 excavated by an unillustrated excavator is put into the hopper 2, mixed with the hopper 2, and then supplied to the ultrasonic cleaning device 3.

  The ultrasonic cleaning apparatus 3 includes a cleaning tank 31 into which a mixture of the contaminated soil E1 and the cleaning water W1, a stirrer 32 that stirs the contaminated soil E1 and the cleaning water W1 in the cleaning tank 31, and the cleaning tank 31. The ultrasonic transducer 33 for irradiating the cleaning water W1 with ultrasonic waves and an oscillation circuit 34 for driving the ultrasonic transducer 33 are provided. The washing tank 31 of the present embodiment has a capacity of 110 liters, and, for example, 10 kg of contaminated soil E1 and 100 liters of washing water W1 are placed in one washing process. And by stirring with the stirrer 32, soil particles are disperse | distributed in the washing water W1. In addition, as the cleaning water W1 supplied to the cleaning tank 31 of the ultrasonic cleaning apparatus 3, inexpensive water such as tap water is used. Of course, water other than tap water (for example, rainwater, seawater, etc.) or liquid other than water is allowed.

  The ultrasonic transducer 33 is made of a plate-shaped piezoelectric ceramic, and outputs an ultrasonic wave having a low frequency (specifically, 20 kHz) in its thickness direction based on the oscillation signal of the oscillation circuit 34. In the ultrasonic cleaning apparatus 3 of the present embodiment, a plurality of ultrasonic transducers 33 are provided at the bottom of the cleaning tank 31, and ultrasonic waves are irradiated upward from each ultrasonic transducer 33. At this time, the ultrasonic waves act on the soil particles in the cleaning water W1, and the contaminated soil E1 is ultrasonically cleaned by the vibration energy of the ultrasonic waves. At that time, VOC is extracted from the contaminated soil E1 side to the wash water W1 side.

  The solid-liquid separation device 4 is provided in the middle of a supply passage for supplying the cleaning water W1 from the ultrasonic cleaning device 3 to the ultrasonic decomposition device 5. The solid-liquid separator 4 separates the soil particles contained in the washing water W1 from the washing water W1, and supplies the washing water W1 from which the soil particles have been removed to the ultrasonic decomposition apparatus 5. The soil E2 separated in the solid-liquid separation device 4 is drained outside the device after moisture is removed by a dryer (not shown), and reused as purified soil containing no VOC.

  As shown in FIG. 2, the ultrasonic decomposition apparatus 5 irradiates the ultrasonic wave 10 to the decomposition tank 51 into which the cleaning water W <b> 1 separated by the solid-liquid separation apparatus 4 is put, and the cleaning water W <b> 1 in the decomposition tank 51. A first ultrasonic transducer 52 and a second ultrasonic transducer 53, and an oscillation circuit 54 for driving the ultrasonic transducers 52 and 53 are provided.

  The decomposition tank 51 is formed in a box shape that forms a rectangular parallelepiped, and has a capacity of 100 liters, for example. A plurality of first ultrasonic transducers 52 are provided outside the bottom surface of the decomposition tank 51, and a plurality of second ultrasonic transducers 53 are provided outside the side surface of the decomposition tank 51. Each of the ultrasonic vibrators 52 and 53 is made of a plate-shaped piezoelectric ceramic, and outputs the ultrasonic wave 10 having a high frequency (specifically, 500 kHz) in the thickness direction thereof based on the oscillation signal of the oscillation circuit 54. . Therefore, the ultrasonic wave 10 is irradiated from below (first direction) toward the cleaning water W <b> 1 in the decomposition tank 51 by the first ultrasonic vibrator 52. Further, the ultrasonic wave 10 is irradiated from the side (second direction) toward the cleaning water W <b> 1 by the second ultrasonic vibrator 53 so as to be orthogonal to the ultrasonic wave 10.

  The decomposition tank 51 in the present embodiment is provided with a partition plate 56 that partitions the inside of the tank and divides it vertically. Here, a plate material (for example, an acrylic resin plate) having a thickness of ½ of the wavelength of the ultrasonic wave 10 is used as the partition plate 56. Specifically, since the wavelength of the ultrasonic wave 10 having a frequency of 500 kHz is about 3 mm, an acrylic resin plate having a thickness of about 1.5 mm is used here. The acrylic resin plate having such a thickness also has desired rigidity and strength required for the partition plate 56. Therefore, even if water pressure is applied during use, deformation and destruction are unlikely to occur. Further, by using the partition plate 56 having a thickness of ½ of the wavelength, the ultrasonic wave 10 is transmitted through the partition plate 56 and efficiently propagated to the upper region.

  In the decomposition tank 51 partitioned by the partition plate 56, the upper half area is a primary treatment chamber 57 in which the treatment of the cleaning water W <b> 1 by the ultrasonic wave 10 is first performed, and the lower half area is the ultrasonic wave 10. Is a secondary treatment chamber 58 in which the treatment of the cleaning water W1 is performed next. Further, when the first ultrasonic transducer 52 provided on the bottom surface of the decomposition tank 51 is used as a reference, the secondary processing chamber 58 is closer to the first ultrasonic transducer 52 and the primary processing chamber 57 is the first. 1 Located far from the ultrasonic transducer 52. Further, on the side surface of the decomposition tank 51, the second ultrasonic transducer 53 is provided at a position corresponding to the primary processing chamber 57 and the secondary processing chamber 58.

  Connected to the primary processing chamber 57 of the decomposition tank 51 is a supply pipe 60 for supplying the cleaning water W <b> 1 from the solid-liquid separator 4 into the primary processing chamber 57. On the other hand, a discharge pipe 61 for discharging the cleaning water W <b> 1 from the inside of the secondary processing chamber 58 is connected to the secondary processing chamber 58 of the decomposition tank 51. A transfer pipe 62 is provided outside the decomposition tank 51 as a passage for communicating between the primary processing chamber 57 and the secondary processing chamber 58. One end of the transfer pipe 62 is connected to the upper part of the side surface of the primary processing chamber 57, and the other end is connected to the upper part of the side surface of the secondary processing chamber 58. 2 illustrates the transfer pipe 62 curved in a semicircular shape, the shape thereof is not particularly limited and may be changed.

  An opening / closing valve 63 is provided in the middle of the supply pipe 60. When the opening / closing valve 63 is opened, the cleaning water W <b> 1 is first supplied into the primary treatment chamber 57 of the decomposition tank 51 through the supply pipe 60. In the primary processing chamber 57, the VOC in the cleaning water W1 is decomposed by irradiating the ultrasonic wave 10 so as to be orthogonal from below and from the side. Next, the cleaning water W1 in the primary processing chamber 57 is supplied into the secondary processing chamber 58 via the transfer pipe 62, and the ultrasonic waves 10 are also irradiated there from the lower side and the side. The VOC in the cleaning water W1 is decomposed. Thereafter, the cleaning water W <b> 1 in the secondary treatment chamber 58 is discharged from the decomposition tank 51 through the discharge pipe 61.

Furthermore, in the present embodiment, an agitator 65 for agitating the cleaning water W <b> 1 of the primary treatment chamber 57 is provided in the upper part of the decomposition tank 51. The stirrer 65 includes a motor 66 fixed to the upper surface of the decomposition tank 51 and a stirring member (propeller) 67 connected to the rotation shaft of the motor 66. Rotates and stirs the washing water W1. Since the stirring member 67 is disposed in the vicinity of the surface of the decomposition tank 51 that faces the surface on which the second ultrasonic transducer 53 is provided, the stirring member 67 is located away from the second ultrasonic transducer 53. Therefore, unlike the case where the stirring member 67 is in a position close to the second ultrasonic transducer 53, the stirring member 67 does not interfere with the propagation of the ultrasonic wave, and therefore, in the cleaning water W1 in the primary treatment chamber 57. Ultrasonic waves can be propagated uniformly.
An air layer A1 exists above the decomposition tank 51, that is, above the cleaning water W1 in the primary treatment chamber 57.

  The cleaning water W1 discharged from the ultrasonic decomposition apparatus 5 is temporarily stored in the drainage tank 6, and then returned to the cleaning tank 31 of the ultrasonic cleaning apparatus 3 by a pumping means (not shown) such as a pump and reused. Or drained into the sewer as sewage (see FIG. 1).

  The control device 7 includes a well-known microcomputer including a CPU 71, a ROM 72, a RAM 73, an input / output port (not shown), and the like. The ultrasonic cleaning device 3 (the stirrer 32 and the oscillation circuit 34) and the ultrasonic decomposition device 5 ( The oscillation circuit 54, the open / close valve 63, and the stirrer 65) are electrically connected. The ROM 32 constituting the control device 30 stores a control program, and the CPU 31 uses the RAM 33 to execute the control program. As a result, the control device 30 outputs various control signals to the ultrasonic cleaning device 3, the ultrasonic decomposition device 5 and the like to control the entire system in an integrated manner.

  Here, the operation of the ultrasonic decomposition apparatus 5 in the present embodiment will be described in detail.

  First, the control device 7 outputs a control signal to the opening / closing valve 63 to open the opening / closing valve 63. Thereby, the washing water W1 separated by the solid-liquid separator 4 is supplied to the decomposition tank 51 (primary treatment chamber 57). At this time, the control device 7 outputs a control signal to the stirrer 65 and rotates the stirrer 67 of the stirrer 65 to stir the cleaning water W <b> 1 in the primary treatment chamber 57.

  Then, the control device 7 outputs a control signal to the oscillation circuit 54 and causes the oscillation circuit 54 to output an oscillation signal. Based on this oscillation signal, the first and second ultrasonic transducers 52 and 53 vibrate, so that the ultrasonic wave 10 of 500 kHz is simultaneously irradiated.

  Here, the ultrasonic wave 10 generated by the first ultrasonic transducer 52 is first transmitted to the cleaning water W1 in the secondary treatment chamber 58 located at a position close to the first ultrasonic transducer 52, and in the cleaning water W1. Proceed upward. At that time, the sound field is adjusted to some extent. The ultrasonic wave 10 that has passed through the cleaning water W <b> 1 in the secondary processing chamber 58 propagates to the cleaning water W <b> 1 in the primary processing chamber 57 that is further away from the first ultrasonic transducer 52 after passing through the partition plate 56. To do. That is, the cleaning water W1 in the secondary processing chamber 58 acts as a medium for propagating the ultrasonic waves 10 generated by the first ultrasonic transducer 52 to the cleaning water W1 in the primary processing chamber 57. The ultrasonic wave 10 that has propagated into the primary processing chamber 57 travels further upward in the cleaning water W1, and is finally reflected by the surface of the cleaning water W1 (the interface between the cleaning water W1 and the air layer A1). The For this reason, a standing wave is generated near the liquid surface.

  In the present embodiment, the ultrasonic wave 10 is irradiated from the second ultrasonic vibrator 53 provided on the side surface of the decomposition tank 51 toward the cleaning water W <b> 1 in the primary treatment chamber 57. Accordingly, the cleaning water W1 in the primary treatment chamber 57 is irradiated with the ultrasonic wave 10 so as to be orthogonal from below and from the side, and the standing wave increases by multiplexing the sound field. As a result, more cavitation at the nano level to micron level is generated, and a high temperature / high pressure reaction field is formed in a wide range in the cleaning water W1. Since VOC is hydrophobic and volatile, it spontaneously gathers around the cavitation (interface between the cleaning water W1 and the bubbles), and further volatilizes and enters the cavitation. As a result, the VOC is thermally decomposed and rendered harmless by the action of the high-temperature and high-pressure reaction field. As a specific example, for example, when VOC is trichloroethylene or tetrachloroethylene, chlorine ions and harmless hydrocarbons are generated. Further, the cleaning water W1 in the primary treatment chamber 57 is degassed by the occurrence of cavitation.

  The cleaning water W <b> 1 in the primary processing chamber 57 subsequently passes through the transfer pipe 62 and is supplied into the secondary processing chamber 58. Since the secondary processing chamber 58 is located below the primary processing chamber 57, the cleaning water W1 naturally flows down through the transfer pipe 62 due to the action of gravity without using a pumping means such as a pump. . Therefore, according to this configuration, the cleaning water W1 can be smoothly supplied into the secondary processing chamber 58. Further, since the degassed cleaning water W1 is supplied to the secondary processing chamber 58, the ultrasonic wave 10 generated by the first ultrasonic transducer 52 is efficiently propagated to the cleaning water W1 in the primary processing chamber 57. be able to.

  Also in the secondary treatment chamber 58, the ultrasonic wave 10 acts on the cleaning water W1. Specifically, the ultrasonic wave 10 generated by the first ultrasonic transducer 52 and the ultrasonic wave 10 generated by the second ultrasonic transducer 53 are irradiated so as to be orthogonal to each other in the secondary processing chamber 58. A sound field is multiplexed in the washing water W1. In this secondary processing chamber 58, standing waves are not generated as much as in the primary processing chamber 57, so that it is considered that there are few areas where the VOC decomposition reaction occurs. However, by passing the cleaning water W1 into the secondary treatment chamber 58, the VOC remaining in the cleaning water W1 is reliably decomposed and rendered harmless.

  As in the present embodiment, the sound field is multiplexed by irradiating the ultrasonic wave 10 so as to be orthogonal to the lower side and the side of the decomposition tank 51, so that the VOC contained in the cleaning water W1 can be efficiently and in a short time. Disassembled.

  The inventor of the present application conducted experiments by changing the superposition conditions of ultrasonic waves, and confirmed the effect of multiplexing the sound field. As shown in FIG. 3, this experimental apparatus uses a small processing tank 81 (specifically, a container having a size of 175 × 175 × 195 mm in length, width, and height) that is not divided vertically. The first ultrasonic transducer 52 is arranged at the center outside the bottom surface of the processing tank 81, and the second ultrasonic transducer 53 is arranged at the center outside the side surface. Further, a terephthalic acid aqueous solution W2 (concentration 200 μmol / L, volume 5 L) was used as the liquid to be processed supplied into the processing tank 81.

  When the ultrasonic wave 10 is irradiated to the aqueous terephthalic acid solution, water molecules in the aqueous solution W2 are decomposed into hydrogen radicals and OH radicals (hydroxy radicals). Since the OH radical reacts with terephthalic acid to emit light (luminol light emission), the chemical reaction performance can be evaluated by measuring the fluorescence intensity. In addition, as conditions for ultrasonic irradiation, the applied power of the first and second ultrasonic transducers 52 and 53 is set to 60 W, the frequency is changed in the range of 200 to 600 kHz, and the ultrasonic wave 10 of each frequency is applied for 15 minutes. Irradiated.

  In FIG. 4, the measurement result of the fluorescence intensity I corresponding to each frequency (200 kHz, 500 kHz, 600 kHz) is shown. As shown in FIG. 4, it was confirmed that the reaction performance was improved when the frequencies f1, f2 of the first and second ultrasonic transducers 52, 53 were both set to 500 kHz. Although not shown in the figure, it was confirmed that when only ultrasonic waves were irradiated from only the first ultrasonic transducer 53, the reaction performance was highest when the frequency f1 was set to 400 kHz to 500 kHz.

  Further, when the ultrasonic wave 10 is simultaneously irradiated from the first and second ultrasonic vibrators 52 and 53, the reaction performance may be higher than when the ultrasonic wave 10 is individually irradiated from the respective ultrasonic vibrators 52 and 53. confirmed. FIG. 5 shows the result. Here, the fluorescence intensity when the ultrasonic wave 10 is singly irradiated from the first ultrasonic vibrator 52 is I1, the fluorescent intensity when the ultrasonic wave 10 is singly irradiated from the second ultrasonic vibrator 53 is I2, The fluorescence intensity when simultaneously radiated from the sound wave vibrators 52 and 53 is represented by I. And the intensity ratio (I / (I1 + I2)) between the sum of the fluorescence intensities I1 and I2 at the time of single irradiation and the fluorescence intensity I at the time of simultaneous irradiation is shown.

  As shown in FIG. 5, when the first and second ultrasonic transducers 52 and 53 are irradiated simultaneously, the intensity ratio becomes larger than 1, and thus a synergistic effect due to superposition of the ultrasonic waves 10 was confirmed. It was also confirmed that when the ultrasonic wave 10 having the same frequency was irradiated from the first and second ultrasonic vibrators 52 and 53, the intensity ratio was increased and the reaction performance was improved.

Furthermore, the inventor of the present application confirmed the effect of the liquid flow on the decomposition reaction by ultrasonic irradiation through experiments. In this experiment, as the liquid to be treated which is put into the decomposition tank, an aqueous solution of tetraphenylporphyrin tetrasulfonic acid (TPPS) (concentration: 3.3 × 10 ⁻³ mol / m ³ ) decomposed by a primary reaction by ultrasonic irradiation is used. The pH was adjusted to 10.6 with a carbonate standard solution and an aqueous sodium hydroxide solution. And while stirring TPPS aqueous solution in a decomposition tank with a stirrer, the ultrasonic wave (frequency 22.8kHz, electric power 520W) was irradiated for 30 minutes from the bottom face of the decomposition tank, and the decomposition rate X after ultrasonic irradiation was measured. . Here, the ratio of the decrease amount of the TPPS concentration after the ultrasonic irradiation to the TPPS concentration before the ultrasonic irradiation is defined as the decomposition rate X. The TPPS concentration was measured with a UV spectrometer.

  As shown in FIG. 6, when the rotation speed n of the stirrer is increased to increase the amount of the liquid flow of the TPPS aqueous solution, the reaction of TPPS is promoted and the value of the decomposition rate X increases. That is, by causing a liquid flow in the TPPS aqueous solution, the TPPS concentration becomes uniform and cavitation generated by ultrasonic irradiation is uniformly dispersed. More specifically, the promotion of the liquid flow is considered to reduce the number of relatively large cavitations (stable cavitations) that do not collapse, while dispersing the aggregated cavitations.

  Therefore, as in the ultrasonic decomposition apparatus 5 (see FIG. 2) of the above embodiment, the cleaning water W1 in the primary treatment chamber 57 of the decomposition tank 51 is agitated by the stirrer 65, thereby being included in the cleaning water W1. It becomes possible to increase the decomposition efficiency of VOC.

  Further, in the primary treatment chamber 57 of the decomposition tank 51, as a means for generating the flow of the cleaning water W1, a circulation pump 91 may be provided as shown in FIG. FIG. 7 shows a cross-sectional view of the primary processing chamber 57 as viewed from above the decomposition tank 51. In FIG. 7, the circulation pump 91 is provided in the middle of the circulation pipe 92, one end of the circulation pipe 92 is connected to the right end portion of the primary processing chamber 57, and the other end of the circulation pipe 92 is connected to the primary processing chamber 57. Connected to the left end. An opening / closing valve 93 is provided in the middle of the transfer pipe 62 connecting the primary processing chamber 57 and the secondary processing chamber 58. The circulation pump 91 and the opening / closing valve 93 are electrically connected to the control device 7 and operate according to a control signal output from the control device 7.

  Specifically, when the ultrasonic wave 10 is simultaneously irradiated from the first and second ultrasonic vibrators 52 and 53 and the VOC of the cleaning water W1 is decomposed, the control device 7 closes the open / close valve 93. At the same time, the circulation pump 91 is driven. Accordingly, the cleaning water W1 flows through the circulation pipe 92, and the cleaning water W1 is circulated between the circulation pipe 92 and the primary treatment chamber 57. As a result, as in the case of stirring the cleaning water W1 with the stirrer 65, the cavitation is uniformly dispersed, so that the decomposition efficiency of VOC contained in the cleaning water W1 is improved. In addition, when the decomposition treatment in the primary processing chamber 57 is completed by irradiating ultrasonic waves for a predetermined time (for example, 5 hours), the open / close valve 93 is opened, so that the cleaning water W1 of the primary processing chamber 57 is opened. Is supplied to the secondary processing chamber 58 through the transfer pipe 62.

  Therefore, according to the present embodiment, the following effects can be obtained.

  (1) In the ultrasonic decomposition apparatus 5 of the present embodiment, the first ultrasonic transducer 52 is provided outside the bottom surface of the box-shaped decomposition tank 51, and the second ultrasonic transducer 53 is provided outside the side surface. . In this case, it is possible to irradiate the ultrasonic waves 10 so as to be orthogonal to the cleaning water W1 in the decomposition tank 51 from below and from the side, and a synergistic effect due to the superposition of the ultrasonic waves 10 can be reliably obtained. Specifically, bubble nuclei in which cavitation was not generated by the single irradiation of the ultrasonic wave 10 are used as the root of cavitation by ultrasonic irradiation from other directions. Therefore, more cavitation can be generated in the washing water W1, and the region of the high-temperature and high-pressure reaction field is widened by the cavitation, so that the VOC contained in the washing water W1 can be efficiently decomposed in a short time. it can.

  (2) In the ultrasonic decomposition apparatus 5 of the present embodiment, since the cleaning water W1 in the primary treatment chamber 57 of the decomposition tank 51 is stirred using the stirrer 65, cavitation generated by ultrasonic irradiation is uniform. The VOC dispersed and contained in the cleaning water W1 can be efficiently decomposed. Further, as shown in FIG. 7, even when the circulation pump 91 for circulating the cleaning water W1 in the primary treatment chamber 57 in the decomposition tank 51 is provided, the cavitation is uniformly dispersed, and the VOC contained in the cleaning water W1 is efficiently obtained. Can be disassembled.

  (3) The ultrasonic decomposition apparatus 5 of the present embodiment is configured to simultaneously irradiate 500 kHz ultrasonic waves from below and from the side toward the cleaning water W1 in the decomposition tank 51. The synergistic effect is increased and the decomposition efficiency of VOC can be increased. Further, the oscillation circuit 54 of the first ultrasonic transducer 52 and the second ultrasonic transducer 53 can be shared, and the device cost can be suppressed.

  (4) In the ultrasonic decomposition apparatus 5 of the present embodiment, the partition plate 56 that partitions the decomposition tank 51 and divides it vertically is used, and the lower region is used as the secondary processing chamber 58, and the upper region is provided. Is used as the primary processing chamber 57. And while promoting the decomposition | disassembly reaction of VOC by ultrasonic irradiation mainly in the primary processing chamber 57, and also irradiating the ultrasonic wave 10 to the washing water W1 also in the secondary processing chamber 58, the remaining VOC is reduced. It can decompose | disassemble and can improve processing efficiency.

  (5) In the ultrasonic decomposition apparatus 5 of the present embodiment, since the cleaning water W1 is degassed by ultrasonic treatment in the primary processing chamber 57 and then supplied into the secondary processing chamber 58, the decomposition tank 51 The ultrasonic wave 10 irradiated from below can be efficiently propagated to the cleaning water W <b> 1 in the primary processing chamber 57.

  (6) In the ultrasonic decomposition apparatus 5 of the present embodiment, a transfer pipe 62 that communicates with the primary processing chamber 57 and the secondary processing chamber 58 is provided outside the decomposition tank 51. In this case, as compared with the case where the transfer pipe 62 is provided inside the decomposition tank 51, the pipe 62 does not become an obstacle to the propagation of the ultrasonic wave 10, so that a suitable sound field with high reaction efficiency can be easily formed.

  (7) Unlike the apparatus disclosed in Patent Document 1, the ultrasonic decomposition apparatus 5 according to the present embodiment can decompose VOCs without adding a catalyst substance. Moreover, since the wash water W1 as the liquid to be treated is inexpensive tap water, the running cost of the ultrasonic decomposition apparatus 5 can be suppressed. Furthermore, since the cleaning water W1 that has been detoxified by decomposing VOC by the ultrasonic decomposition apparatus 5 can be reused by the ultrasonic cleaning apparatus 3, the running cost of the contaminated soil purification system 1 can be reduced.

  In addition, you may change embodiment of this invention as follows.

  -In the ultrasonic decomposition apparatus 5 of the said embodiment, although the decomposition tank 51 was formed in the box shape which makes a rectangular parallelepiped, the shape is not specifically limited, For example, a cylindrical shape may be sufficient.

  In the ultrasonic decomposition apparatus 5 of the above embodiment, the first and second ultrasonic vibrators 52 and 53 are provided on the bottom and side surfaces of the decomposition tank 51, and the ultrasonic waves are irradiated so as to be orthogonal from below and from the side. However, it is not limited to this configuration. Specifically, it may be configured like an ultrasonic decomposition apparatus 95 shown in FIG. That is, the bottom portion of the decomposition tank 96 of the ultrasonic decomposition apparatus 95 has first and second inclined surfaces (tapered surfaces) 97 and 98 that are opposed to each other, and is formed so that the width of the bottom portion is gradually narrowed. . A first ultrasonic transducer 52 is provided outside the first inclined surface 97, and a second ultrasonic transducer 53 is provided outside the second inclined surface 98. In the decomposition tank 96, similarly to the above embodiment, a supply pipe 60 for supplying the cleaning water W1 and a discharge pipe 61 for discharging the cleaning water W1 are connected. ing. Further, an opening / closing valve 63 is provided in the middle of the supply pipe 60, and a stirrer 65 is provided above the decomposition tank 96.

  Even if comprised in this way, the ultrasonic wave 10 can be irradiated toward the washing water W1 in the decomposition tank 96 from a plurality of directions, and a synergistic effect by superimposing the ultrasonic waves 10 can be obtained.

  8 is not provided with a partition plate that is divided into upper and lower parts. However, as shown in FIG. 9, a partition plate 100 is provided in the decomposition tank 96 so that the primary treatment chamber 101 and the secondary treatment are performed. You may comprise so that it may divide into the chamber 102. FIG. In this decomposition tank 96, in addition to the supply pipe 60 and the discharge pipe 61, a transfer pipe 62 that communicates the primary processing chamber 101 and the secondary processing chamber 102 is provided.

  In the above embodiment, the decomposition tank 51 is partitioned into the primary processing chamber 57 and the secondary processing chamber 58 by the partition plate 56, and the VOC of the cleaning water W1 is decomposed in the primary processing chamber 57 and the secondary processing chamber 58. However, the present invention is not limited to this. For example, you may utilize only the area | region above a partition plate 56 as a process chamber which decomposes | disassembles VOC. In this case, the area below the partition plate 56 is filled with degassed water in order to increase the propagation efficiency of the ultrasonic wave 10. Of course. It is not necessary to divide into two processing chambers 57 and 58 by the partition plate 56, and the decomposition tank 51 without the partition plate 56 may be used.

  In the above embodiment, the inside of the decomposition tank 51 is vertically divided by the partition plate 56 provided horizontally, but the inside of the decomposition tank 51 may be partitioned left and right by the partition plate 56 provided vertically. .

  In the above embodiment, the first and second ultrasonic transducers 52 and 53 are configured to irradiate the ultrasonic wave 10 of 500 kHz. However, the present invention is not limited to this frequency. Specifically, for example, in the frequency range of 400 kHz to 500 kHz, sufficient decomposition efficiency can be obtained even when the ultrasonic waves 10 having different frequencies are irradiated from the first and second ultrasonic transducers 52 and 53. it can. Further, even when the frequency of 200 kHz or 600 kHz is irradiated, the decomposition efficiency is somewhat inferior to that of 400 kHz to 500 kHz, but a synergistic effect can be obtained as compared with the case of single irradiation. Therefore, you may comprise so that the ultrasonic wave 10 of the frequency range of 200 kHz-600 kHz may be irradiated from the 1st and 2nd ultrasonic transducer | vibrator 52,53.

  -Although the ultrasonic decomposition apparatus 5 of the said embodiment decomposes | disassembles VOC contained in the washing water W1, it is not limited to this, The decomposition apparatus for decomposing | disassembling a non-volatile organic compound It may be embodied in. Of course, the liquid to be treated may be a factory waste liquid containing an organic compound or groundwater of contaminated soil, in addition to the washing water W1.

  Next, in addition to the technical ideas described in the claims, the technical ideas grasped by the embodiment described above are listed below.

  (1) In any one of claims 1 to 4, the inside of the decomposition tank is divided into a primary processing chamber far from the first ultrasonic transducer and a secondary processing chamber close to the first ultrasonic transducer. A partition member and a passage communicating the primary processing chamber and the secondary processing chamber, wherein the liquid to be processed to be decomposed by ultrasonic irradiation can be first supplied to the primary processing chamber, and the secondary processing The ultrasonic decomposition apparatus, wherein the liquid to be processed that has passed through the primary processing chamber can be supplied into the chamber through the passage.

  (2) In the technical idea (1), an ultrasonic wave characterized in that a second ultrasonic transducer for irradiating ultrasonic waves to the liquid to be processed in the primary processing chamber and the secondary processing chamber is provided. Disassembly equipment.

  (3) The ultrasonic decomposition apparatus according to (1) or (2), wherein a passage communicating the primary processing chamber and the secondary processing chamber is provided outside the decomposition tank.

The schematic block diagram which shows the contaminated soil purification system of one Embodiment which actualized this invention. Sectional drawing which shows the ultrasonic decomposition apparatus of one embodiment. Sectional drawing which shows an experimental apparatus. The graph which shows the relationship between the frequency of an ultrasonic wave, and fluorescence intensity. The graph which shows the relationship between the frequency and intensity ratio of an ultrasonic wave. The graph which shows the relationship between the rotation speed of a stirrer, and a decomposition rate. Sectional drawing which shows the ultrasonic decomposition apparatus of another embodiment. Sectional drawing which shows the ultrasonic decomposition apparatus of another embodiment. Sectional drawing which shows the ultrasonic decomposition apparatus of another embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 5,95 ... Ultrasonic decomposition apparatus 10 ... Ultrasonic 51,96 ... Decomposition tank 52 ... 1st ultrasonic vibrator 53 ... 2nd ultrasonic vibrator 65 ... Stirrer as liquid flow generation means 91 ... Liquid flow generation means Circulating pump 97, 98 ... inclined surface W1 ... wash water as liquid to be treated

Claims (6)

A decomposition tank containing a liquid to be treated containing an organic compound decomposed by ultrasonic irradiation;
A first ultrasonic transducer for irradiating ultrasonic waves from a first direction toward the liquid to be treated;
A second ultrasonic transducer for irradiating the liquid to be treated from a second direction different from the first direction so as to overlap the ultrasonic wave from the first direction; A featured ultrasonic decomposition apparatus.   The first ultrasonic transducer is provided outside a bottom surface of the decomposition tank, and the second ultrasonic transducer is provided outside a side surface of the decomposition tank. Ultrasonic decomposition equipment. The bottom of the decomposition tank has first and second inclined surfaces facing each other,
The first ultrasonic transducer is provided outside the first inclined surface, and the second ultrasonic transducer is provided outside the second inclined surface. The ultrasonic decomposition apparatus as described.   The ultrasonic decomposition apparatus according to any one of claims 1 to 3, further comprising a liquid flow generating means for generating a flow of the liquid to be processed in the decomposition tank.   The first direction is different from the first direction so as to irradiate the ultrasonic wave from the first direction toward the liquid to be treated containing the organic compound decomposed by the ultrasonic irradiation and to overlap the ultrasonic wave from the first direction. 2. An ultrasonic decomposition method comprising irradiating ultrasonic waves from the direction of 2 toward the liquid to be treated.   The ultrasonic decomposition method according to claim 5, wherein ultrasonic waves of 400 kHz to 500 kHz are simultaneously irradiated from the first and second directions.

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