RU2725584C1 - Device for ultrasonic coagulation of foreign particles in gas flows - Google Patents

Abstract

FIELD: chemistry; physics.SUBSTANCE: device for ultrasonic coagulation of foreign particles in gas streams relates to chemical engineering, specifically to devices for accelerating the process of cleaning dust and fog, hazardous to the environment, as well as for separation of gas streams of useful substances formed in form of particles of different size, including submicron. Device for ultrasonic coagulation of foreign particles in gas streams comprises cleaned gas feed branch pipes and purified gas flow outlet, coagulation chamber, flow distributor, particle collecting hopper and two ultrasonic emitters, mechanically and acoustically connected to piezoelectric transducers. Ultrasonic emitters are made in the form of parallel plates, the distances between the plates are selected as multiple to the wavelength of ultrasonic vibrations in the gas medium of the cleaned flow, increased by the value of the thickness of the plate, each of the plates is mechanically and acoustically connected to the piezoelectric transducer, wherein the plates of one of the emitters are symmetrically located between the plates of the other radiator.EFFECT: higher efficiency of coagulation process of particles of submicron range.1 cl, 1 dwg

Description

The invention relates to the field of technology of active influence on gas-dispersed systems containing solid or liquid particles of various sizes, released during production in various industries (mining, chemical, thermal energy, food) industries, and in particular, to devices for accelerating the cleaning process of environmentally hazardous dusts and mists, as well as for separating from gas streams useful substances formed in the form of particles of various sizes, including submicron.

Today, the problem of protecting the public and the environment from exposure to particles of 2.5 microns or less is particularly acute. It is considered proven that there is a connection between the level of air pollution with fine aerosols of non-biological origin and mortality. Toxicological and epidemiological studies performed in recent years have revealed a correlation between the number of fine particles less than 2.5 microns in air and an increase in cardiovascular and respiratory diseases.

The negative effect of fine particles is caused by the properties of the respiratory system of humans and animals to inject fine aerosols directly into the bloodstream and accumulate toxic material in human organs.

Therefore, of particular importance is the task of protecting residential and working premises and the people in them from fine aerosols.

Such cleaning is carried out by passing gas contaminated with particles through cleaning devices, the action of which is based on the use of various physical principles of exposure to particles and which are manufactured according to various design schemes.

However, the existing cleaning devices, due to the lack of effective principles of exposure, do not allow efficient capture of particles smaller than 2.5 microns, and have a number of concomitant disadvantages associated, for example, with low dust absorption (HEPA filters), the formation of nitrogen oxides and ozone, which are no less than harmful to the environment and human health (electrostatic precipitators), etc.

The most effective devices are the electrophysical effect on aerosols, which ensures the combination of particulate matter or moisture droplets suspended in a gas under the action of high-intensity acoustic (including ultrasonic) vibrations. The use of high-intensity ultrasonic (US) effects on small particles accelerates the agglomeration processes, combining small particles, which are then easier to capture using conventional capture devices (various types of separators).

Since high-intensity acoustic vibrations are dangerous for humans, ultrasonic vibrations (with a frequency of more than 20 kHz) are used in practice, which, even at high intensity (more than 130 ... 150 dB), are harmless to humans and the environment. Therefore, the process of combining small particles in gas flows is called ultrasonic coagulation, and the devices that implement it are called ultrasonic coagulation devices.

In practice, the most widely used devices are ultrasonic coagulation, made according to traditional schemes [1, 2, 3], but supplemented by ultrasonic devices for influencing the gas flow.

Among the known devices for ultrasonic coagulation of particles in gas streams, the device closest in technical essence to the proposed technical solution and one of the most effective devices using ultrasonic emitters is the device according to [4, prototype].

The ultrasonic coagulation device for foreign particles in gas streams, adopted as a prototype, contains nozzles for introducing the gas to be purified and the outlet for the stream of purified gas, a flow distributor, a coagulation purification chamber, a hopper for collecting particles and two ultrasonic emitters, mechanically and acoustically connected with piezoelectric transducers.

In the device adopted for the prototype, the effect of ultrasonic vibrations on the gas flow is carried out using ultrasonic disk emitters, made, for example, according to [5]. Under ultrasonic treatment, foreign particles acquire an additional oscillatory motion, more often collide with each other, combine into large agglomerates, which fall into the hopper to collect particles. Ultrasonic disk emitters act on particles by elastic vibrations propagated within the process volume through which the gas stream moves.

Analysis of the capabilities of the device adopted for the prototype revealed the following significant disadvantages:

1. The low intensity of ultrasonic exposure due to the significant distance between the emitters and the high attenuation of ultrasonic vibrations in a gas stream with foreign particles.

2. Significant diffraction discrepancy of the emitted oscillations, leading to a decrease in the average intensity (less than 130 dB) of ultrasonic vibrations in the coagulation chamber.

3. The unevenness of ultrasonic exposure in different zones of the coagulation chamber due to interference superposition of oscillations in the volume of the coagulation chamber and the appearance of zones, in addition to the zones of effective coagulation (near the emitter), in which there is no coagulation.

4. Low efficiency (less than 50%) of dust collection of particles less than 2.5 microns in size due to the small ultrasonic effect acting on the particles at the input flow rates necessary for practical application, providing an acceptable hydraulic resistance of the apparatus.

All of these disadvantages cause low efficiency of the prototype when capturing solid particles, especially small particles (less than 2.5 microns).

In the proposed technical solution, the task is to create a device in which the above disadvantages are eliminated and which is characterized by increased efficiency of the implementation of the coagulation process.

In the proposed device for ultrasonic coagulation of foreign particles in gas streams, comprising nozzles for introducing a cleaned gas and outputting a stream of purified gas, a coagulation chamber for cleaning the dust and gas stream, a flow distributor, a hopper for collecting particles and two ultrasonic emitters, mechanically and acoustically connected with piezoelectric transducers, ultrasonic emitters made in the form of parallel plates, the distances between the plates are chosen equal to the wavelength of ultrasonic vibrations in the gaseous medium of the stream being cleaned, increased by the thickness of the plate, each of the plates is mechanically and acoustically connected with piezoelectric transducers, and the plates of one of the emitters are symmetrically located between the plates of the other emitter.

In the proposed device for ultrasonic coagulation of foreign particles in gas flows of ultrasound, the task of increasing the efficiency of coagulation is solved by constructively improving the device to increase its efficiency by creating special ultrasonic emitters and their mutual placement, providing a significant increase in the intensity of ultrasound exposure to the gas stream with particles and ensuring uniformity in all exposure zones to significantly increase the effectiveness of ultrasound coagulation ..

The essence of the technical solution is illustrated in FIG. 1, which schematically shows a device for ultrasonic coagulation of foreign particles in gas streams.

A device for ultrasonic coagulation of foreign particles in gas streams comprises an inlet port 1 of the cleaned gas stream, an outlet port 2 of the cleaned gas stream, a coagulation chamber 3 for cleaning the gas stream, a stream distributor 4, a hopper 5 for collecting particles removed from the gas stream, and two ultrasonic emitters 6 and 7 mechanically and acoustically connected with piezoelectric transducers, ultrasonic emitters 8 and 9 are made in the form of parallel plates. The plates of one of the emitters 8 are symmetrically located between the plates of the other emitter 9. The distances between all the plates of each of the emitters are selected in multiples of the wavelength of ultrasonic vibrations λ in the gaseous medium of the cleaned stream, increased by the value of the plate thickness h, each of the plates is mechanically and acoustically connected to its piezoelectric transducer .

In general, the device operates as follows. In the inlet pipe 1 receives a stream of gas containing fine particles. Further, in the direction of gas flow, a flow distributor 4 is installed, which ensures uniform distribution of the gas-dispersed flow between the plates of two emitters 8 and 9 in the volume of the coagulation chamber 3. Distributed highly dispersed particles enter the region of high-intensity resonant ultrasonic exposure, the gap between the plates of ultrasonic emitters. When particles move along oscillating plates, a high-intensity ultrasonic effect on the particles occurs and they, in a very short time (of the order of 0.1 s), coagulate with each other and settle in the hopper when the purified stream is removed.

The implementation of the emitter in the form of parallel plates provides the formation of bending ultrasonic vibrations of high intensity. The ultrasonic effect of each of the emitters provides uniform high-intensity radiation and increase the efficiency of particle coagulation. Placing the plates of one emitter between the plates of another emitter, provided that the distance between the oscillating plates of the two emitters is a multiple of half the ultrasonic wavelength in the gas stream, provides resonant amplification of the oscillations, which provides an additional increase in the coagulation rate.

For the operation of each emitter, piezoelectric transducers are used, powered by synchronously operating ultrasonic electronic generators.

The number of plates of each of the emitters and their sizes are determined by the size of the coagulation chamber and, accordingly, the performance of the apparatus. In addition, the dimensions of the emitter plates can be selected from the conditions for ensuring the resonant frequency of the emitters, which can be selected in accordance with the requirements of the problem being solved. For example, the use of ultrasonic vibrations of a high frequency (more than 30 ... 50 kHz) is most effective for coagulating highly dispersed particles (less than 1 μm in size), and the use of reduced ultrasonic vibrations is most effective for coagulating particles with a size of more than 2.5 microns (but not perceived by man) frequencies (18 kHz).

Practical designs of the proposed ultrasound coagulation device can be implemented on the basis of existing ultrasonic devices of the Nightingale series of various capacities [6].

Practical implementation of the proposed device in laboratory conditions made it possible to establish that with the proposed placement of emitter plates in the gap between them, ultrasonic vibrations with an intensity of up to 160 ... 170 dB are formed. With such ultrasonic treatment, conditions are created for the appearance of intense acoustic microflows and vortices, which contribute to the coagulation of dispersed particles and the deposition of their aggregates.

Preliminary studies of the proposed device revealed the following advantages:

- increased not less than 100 times the productivity of the coagulation process;

- short ultrasonic exposure time (less than 0.1 sec), necessary and sufficient for coagulation of particles provided by large coagulation plants at exposure times of at least 1 sec;

- high efficiency (more than 90%) for coagulation of particles of micron and submicron ranges;

- lack of need for additional equipment for separating the aggregates of particles formed as a result of coagulation from the gas stream;

- the possibility of creating, according to the proposed design scheme, ultrasound coagulation devices of different sizes of particles with the required performance.

The practical implementation of the proposed technical solution is planned for implementation by AltSTU Center for Ultrasonic Technologies LLC in 2019.

This work was supported by the Russian Science Foundation in the framework of the scientific project No. 19-19-00121.

List of literature used in the preparation of the application

1. Ultrasonic coagulation chamber [Text]: patent PM 102197 of the Russian Federation: IPC B01D 51/08 (2006.1) / Khmelev V.N., Shalunov A.V., Shalunova K.V .; copyright holder - Altai State Technical University named after II Polzunov Altai State Technical University (RU).

2. Device for electrophysical effects on aerosols [Text]: patent for IZ 2430509 RF: IPC A01G 15/00 (2006.01) / Khmelev V.N., Shalunov A.V., Khmelev M.V., Lebedev A.N., Shalunova K.V., Galakhov A.N .; copyright holder - AltSTU Center for Ultrasonic Technologies Limited Liability Company.

3. Catcher of dispersed particles from a gas stream [Text]: Patent PM 133432 RF: IPC B01D 51/08 (2006.1) / B01D 45/12 (2006.1) / Khmelev V.N., Nesterov V.A., Shalunov A.V. ., Galakhov A.N., Golikh R.N .; copyright holder - AltSTU Center for Ultrasonic Technologies Limited Liability Company.

4. Apparatus for capturing dispersed particles from a gas stream [Text]: patent PM 131307 RF: IPC B01D 51/08 (2006.1) / Khmelev V.N., Nesterov V.A., Shalunov A.V., Galakhov A.N. , Naked R.N .; copyright holder - AltSTU Center for Ultrasonic Technologies Limited Liability Company.

5. Ultrasonic oscillatory system for gaseous media: patent PM 132000 RF IPC V06V 1/00 (2006.01) / Khmelev V.N., Galakhov A.N., Shalunov A.V., Nesterov V.A., Golikh R.N .; copyright holder: AltSTU Center for Ultrasonic Technologies Limited Liability Company.

6. Catalog of ultrasonic devices for gaseous media [Electronic resource]. - Access mode: http://u-sonic.com/catalog/apparaty_dlya_uskoreniya_protsessov_v_gazovykh_sredakh/, free - (09.10.2019).

Claims (1)

A device for ultrasonic coagulation of foreign particles in gas streams, comprising nozzles for introducing a purified gas and outputting a stream of purified gas, a coagulation chamber for cleaning a dust and gas stream, a flow distributor, a hopper for collecting particles and two ultrasonic emitters, mechanically and acoustically connected with piezoelectric transducers, characterized in that ultrasonic emitters are made in the form of parallel plates, the distance between the plates is a multiple of the wavelength of ultrasonic vibrations in the gaseous medium of the cleaned stream, increased by the thickness of the plate, each of the plates is mechanically and acoustically connected with piezoelectric transducers, and the plates of one of the emitters are symmetrically located between the plates of the other emitter.

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