CN101811751B - traveling wave ultrasonic reactor - Google Patents

Abstract

The invention provides a traveling wave type ultrasound reaction vessel, which relates to a device for processing liquid by using the ultrasound cavitation effect. The traveling wave type ultrasound reaction vessel comprises a box body (4), at least one pair of ultrasound energy exchangers and an ultrasound energy exchanger driving circuit, wherein the box body (4) is used for containing liquid to be processed, each pair of ultrasound energy exchangers consists of a first energy exchanger (2) and a second energy exchanger (6) which are respectively arranged on the box wall in opposite directions, and ultrasound traveling waves are formed in the box body of the reaction vessel by the overlapping of ultrasound standing waves with the 90 degrees of phase difference on space and 90 degrees of phase difference on time. The sound reaction vessel uses a traveling wave ultrasound field for working. Although each field point has different time phases, each field point has the same sound pressure amplitude value in theory. Because the intensity of the sound cavitation effect in the liquid only depends on the sound pressure amplitude value, and is irrelevant with the phases of the sound pressure, the sound cavitation effect in the traveling wave ultrasound field is more uniform than that in the standing wave ultrasound field.

Description

traveling wave ultrasonic reactor

technical field

The traveling wave ultrasonic reactor of the invention relates to a device for treating liquid by using ultrasonic cavitation effect.

Background technique

The ultrasonic reactor uses the local high temperature and high pressure generated by the ultrasonic cavitation effect to treat liquids such as water. Structurally, the ultrasonic reactor system includes a tank, the liquid to be processed in the tank, an ultrasonic transducer for applying ultrasonic waves to the liquid to be processed, and a drive circuit for the ultrasonic transducer. It is used in disinfection and sterilization of drinking water, decomposition of carcinogens in drinking water, disinfection and sterilization of wastewater, decomposition of organic matter in wastewater, physical catalysis of chemical synthesis and crystallization process, acceleration of fermentation process, production of biomass gas and liquid fuel, etc. It has great application prospect. The working principle of the existing ultrasonic reactor, as described in references (T.J.Mason, J.P.Lorimer, Applied Sonochemistry, Wiley-VCH, Weinheim, 2002), mainly uses the standing wave ultrasonic field in the box to cause acoustic cavitation effect. In this way, the sound pressure amplitude of the ultrasonic field is not uniform in space, and there are sound pressure nodes and anti-nodes. The sound pressure amplitude is zero at the sound pressure node, and the sound pressure amplitude is maximum at the sound pressure antinode. For this reason, there occurs a phenomenon that the liquid near the acoustic pressure antinode is excessively sonicated, and the liquid near the acoustic pressure node is not sufficiently processed. This leads to problems of uneven sound treatment and low utilization of sound energy.

Contents of the invention

In order to overcome the problems of uneven sonication and low utilization of sound energy in existing ultrasonic reactors, the patent of the present invention provides a new ultrasonic reactor, which uses a uniform ultrasonic field to sonicate the liquid in it to achieve Uniform sonication of the acoustic reactor and improvement of the utilization rate of acoustic energy in the acoustic reactor.

A traveling wave ultrasonic reactor, characterized in that: it includes a tank containing the liquid to be processed, at least one pair of ultrasonic transducers, and an ultrasonic transducer drive circuit; each pair of ultrasonic transducers is provided separately The first transducer and the second transducer are formed on two opposite walls of the box, and the first and second ultrasonic transducers meet the following conditions: the sound radiation surfaces of the first and second transducers are mutually positive in space Yes, with the same structure and size, the applied AC drive voltage has the same frequency f, amplitude and 90° time phase difference, and the distance d between the first and second transducer sound radiation surfaces satisfies d= (2m+1)c/(4f), where c is the sound velocity of the liquid to be processed, f is the frequency of the AC driving voltage, and m is a natural number greater than or equal to 0. In order to ensure the uniformity of the sound energy density of the ultrasonic field, the traveling wave ultrasonic field generated by each pair of ultrasonic transducers is in a parallel state without intersecting parts.

The above-mentioned traveling wave ultrasonic reactor can be an immersed flat panel ultrasonic transducer, or an inserted Langevin ultrasonic transducer with a flat radiating surface.

When the above-mentioned working conditions are satisfied, the ultrasonic standing waves generated by the first and second ultrasonic transducers in the liquid between them have a phase difference of 90° in both time and space, and they will produce a running in Ultrasonic traveling waves between the first and second ultrasonic transducers.

The acoustic reactor works by using the traveling wave ultrasonic field, although each field point has different time phase, but theoretically has the same sound pressure amplitude. Since the intensity of the acoustic cavitation effect in the liquid only depends on the amplitude of the sound pressure and has nothing to do with the phase of the sound pressure, the acoustic cavitation effect in the traveling wave ultrasonic field is more uniform than that in the standing wave ultrasonic field.

The sound energy density in the ultrasonic reactor box is made more uniform by using the ultrasonic traveling wave in the ultrasonic reactor box, so that the acoustic treatment of the ultrasonic reactor is more uniform, and the energy utilization rate of the sound field is higher. The performance of the ultrasonic reactor in terms of sonication uniformity and sound energy utilization can be expressed by the non-uniformity index NU1 of the sound field:

${\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="NU"\; filenames="HSA00000088484000011.png"\; state="\{\{state\}\}">NU</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; am</span>}}}\sqrt{\frac{{<span\; class="notranslate">\; \&Integral;</span><span\; class="notranslate">\; \&Integral;</span><span\; class="notranslate">\; \&Integral;</span>}_{{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; Pa</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; am</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; dV</span>}}{{\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

Where p _a is the sound pressure amplitude at the field point, p _am is the spatial average of p _a , and V ₀ is the volume of the sound field. The smaller the non-uniformity index NU ₁ of the sound field, the better the performance of the ultrasonic reactor in terms of sound treatment uniformity and sound energy utilization. The NU ₁ of the traditional standing wave ultrasonic reactor is 0.447. Theoretical calculation shows that the patent of the invention can reduce the NU ₁ index to 0.07.

Description of drawings

Fig. 1: the structural diagram of the ultrasonic reactor casing of embodiment 1 and transducer; Wherein Fig. 1 (a) is the sectional view of ultrasonic reactor, and Fig. 1 (b) is the top view of ultrasonic reactor.

Fig. 2: the structural diagram of the ultrasonic reactor casing and transducer of embodiment 2; Wherein Fig. 2 (a) is the sectional view of ultrasonic reactor, Fig. 2 (b) is the top view of ultrasonic reactor.

Label names in the figure: 1. The liquid being sonicated, 2. The first transducer, 3. The first wall, 4. The box, 5. The traveling wave sound field in the liquid, 6. The second transducer, 7 , the second wall surface, 8, the radiation surface of the first transducer, and 9, the radiation surface of the second transducer.

Detailed ways

The ultrasonic reactor of Embodiment 1 is shown in FIG. 1 .

The water to be treated is contained in a rectangular metal tank of an ultrasonic reactor with a pair of submerged flat-panel ultrasonic transducers. The first immersion-type flat-panel ultrasonic transducer and the second immersion-type flat-panel ultrasonic transducer are respectively fixed on the first wall 3 and the second wall 7 of the box body 4 . The first transducer 2 and the second transducer 6 are planar ultrasonic transducers, and the radiation surface 8 of the first transducer and the radiation surface 9 of the second transducer face each other. The first and second ultrasonic transducers have the same structure, size and material. The AC drive voltages applied to the first and second transducers have the same frequency f, amplitude and time phase difference of 90°. The distance d between the sound radiating surfaces of the first and second transducers satisfies d=(2m+1)c/(4f), where m=8 and c is the sound velocity of water (=1500m/s). Under the above conditions, an ultrasonic traveling wave is formed between the first and second transducers.

The internal dimensions of the rectangular metal box are 33.88cm (length) x 13cm (width) x 36cm (height). The height of the water in the box is 31cm. The dimensions of the first and second immersion-type flat-panel ultrasonic transducers 2 and 6 are 30cm (height) × 12cm (width) × 1cm (thickness), the operating frequency f is 20kHz, and the operating voltage is 65Vrms.

In this embodiment, the theoretical value of the ultrasonic field non-uniformity index NU ₁ obtained according to the finite element calculation (COMSOL MULTIPHYSICS) is 0.07, which is much smaller than the NU ₁ (=0.447) of the traditional standing wave ultrasonic reactor. In the finite element calculation, the harmonic analysis function (Harmonics Analyzes, Acoustics Module) in the acoustics module of the software is used; the absorption coefficient of the sound field is 1.0×10 ^-5 1/m; the ultrasonic field is assumed to be a linear field. This shows that using a single traveling wave ultrasonic field in the ultrasonic reactor can greatly improve the uniformity of ultrasonic treatment and the utilization of acoustic energy.

The ultrasonic reactor of Example 2 is shown in FIG. 2 .

The rectangular metal box of the ultrasonic reactor with two pairs of submerged flat-panel ultrasonic transducers contains the water to be treated. The two first immersion-type flat-panel ultrasonic transducers and the two second immersion-type flat-panel ultrasonic transducers are respectively fixed on the first wall 3 and the second wall 7 of the box body 4 . Radiation surfaces of the first transducer and the second transducer of each pair of transducers face each other. The first and second ultrasonic transducers have the same structure and dimensions. The AC drive voltages applied to the first and second transducers have the same frequency f, amplitude and time phase difference of 90°. The distance d between the sound radiating surfaces of the first and second transducers satisfies d=(2m+1)c/(4f), where m=8 and c is the sound velocity of water (=1500m/s). Under the above conditions, the ultrasonic traveling waves formed by each pair of transducers are parallel to each other.

The internal dimensions of the rectangular metal box are 33.88cm (length) x 26cm (width) x 36cm (height). The height of the water in the box is 31cm. The dimensions of the first and second immersion flat panel ultrasonic transducers are 30cm (high) x 12cm (width) x 1cm (thick), the working frequency f is 20kHz, and the working voltage is 65Vrms.

In this embodiment, the theoretical value of the ultrasonic field non-uniformity index NU ₁ obtained according to the finite element calculation (COMSOL MULTIPHYSICS) is 0.12, which is much smaller than the NU ₁ (=0.447) of the traditional standing wave ultrasonic reactor. In the finite element calculation, the harmonic analysis function (Harmonics Analyzes, Acoustics Module) in the acoustics module of the software is used; the absorption coefficient of the sound field is 1.0×10 ^-5 1/m; the ultrasonic field is assumed to be a linear field. This shows that the use of multiple traveling wave ultrasonic fields in the ultrasonic reactor can also greatly improve the uniformity of ultrasonic treatment and the utilization of acoustic energy.

Claims (3)

1. a traveling wave type ultrasound reaction vessel is characterized in that: comprise holding casing (4), at least one pair of ultrasonic transducer and the ultrasonic transducer driving circuit that is processed liquid; Above-mentioned every pair of ultrasonic transducer is formed by first transducer (2) and second transducer (6) that are separately positioned on the two relative tank walls; And first and second ultrasonic transducers meet the following conditions: the first and second transducer acoustic radiation faces spatially each other over against; Have identical structure and size; The ac drive voltage that is applied has the time phase difference of identical frequency f, amplitude and 90 °, satisfies d=(2m+1) c/ (4f) apart from d between the first and second transducer acoustic radiation faces, and wherein c is the velocity of sound that is processed liquid; F is the ac drive voltage frequency, and m is the natural number more than or equal to 0; In order to guarantee the uniformity of ultrasonic field acoustic density, the traveling-wave ultrasonic field that every pair of ultrasonic transducer produced is in parastate and does not have cross section.

2. traveling wave type ultrasound reaction vessel according to claim 1 is characterized in that: said ultrasonic transducer is the dull and stereotyped ultrasonic transducer of immersion.

3. traveling wave type ultrasound reaction vessel according to claim 1 is characterized in that: said ultrasonic transducer is the bright civilian ultrasonic transducer of plug-in type with dull and stereotyped radiating surface.

Images