RU2733395C1 - Electrophysical device for cleaning gases from environmentally harmful impurities, air disinfection and sterilization - Google Patents

Abstract

FIELD: high-voltage engineering.

SUBSTANCE: invention relates to high-voltage engineering and can be used for cleaning gases from environmentally harmful impurities, air disinfection and sterilization by means of low-temperature plasma generated by pulsed streamer corona discharges. To this end, an electrophysical device is provided, comprising at least one grounded electrode and at least one high-voltage electrode comprising initiators of pulse streamer corona discharges on at least one of its sides, with formation between adjacent earthed and high-voltage electrodes of reactor chamber, in which initiators of pulse streamer corona discharges are located, as well as pulse voltage generator, to which high-voltage electrode is connected. At that, initiators of pulse streamer corona discharges located on high-voltage electrode are made in the form of half-ellipsoids of rotation.

EFFECT: invention provides higher efficiency of the device.

7 cl, 7 dwg

Description

The invention relates to high voltage technology, in particular - to an electrophysical device for cleaning gases from environmentally harmful impurities (gaseous impurities, as well as dust and fine aerosol particles), for air disinfection (reducing air contamination by pathogenic microorganisms and viruses to a safe level), sterilization both air and dielectric and metal objects using low-temperature plasma created by pulsed streamer corona discharges.

Known devices [Masuda S., Nakao H. Removal of NOx in the exhaust gas from a diesel engine using pulsed plasma. // IEEE-IAS Annual Conference. 1986. Denver. P. 1173.3., A. Z. Ponizovsky, S. G. Gosteev, O.S. Kuzhel, A. S. Smirnov. Industrial installations for air purification using low-temperature nonequilibrium gas discharge plasma. Chemical safety 2018 Volume 2 No. 2, p: 212-228.], In which the air is purified from environmentally harmful gaseous impurities, dust and fine aerosol particles using a pulsed streamer corona discharge. These devices consist of reactor chambers through which the flow of air passes, bounded by coaxial or planar high voltage and grounded electrodes. The high voltage electrodes are connected to a high voltage pulse generator that generates nanosecond voltage pulses. Under the action of pulses, a streamer corona discharge arises in the space between the high-voltage and grounded electrodes, which creates a low-temperature plasma. Low-temperature plasma is characterized by significant densities and energies of electrons capable of creating in the discharge gap high concentrations of active intermediate particles (atomic oxygen, ions, and radicals), which enter into radiation-chemical reactions with pollutant molecules. As a result of the reactions, the conversion of gaseous impurities into environmentally friendly gases or aerosols occurs [Ponizovsky A.Z. Cleaning vent emissions using pulsed and permanent corona discharges. Environmental systems and devices. 2007 No. 11 p.9-14]. Fine aerosol, dust and products formed under the action of a corona discharge, due to a constant corona discharge, which takes place in the pause between pulses, settle on the grounded electrode, from where they are washed off with water. In addition, in the low-temperature plasma generated by a pulsed streamer corona discharge due to the high energy density of electrons, radicals, atomic oxygen, ozone and ultraviolet radiation, air is disinfected from microorganisms and viruses [T.Xia1, A.Kleinhekse, E.M. Lee, Z. Qiao, K. R. Wigginton H. L. Clack. Inactivation of airborne viruses using a packed bed non-thermal plasma reactor. J. Phys. D: Appl. Phys. 52 (2019) 255201 (12pp)]. Similarly, sterilization of objects takes place in the area of action of low-temperature plasma [J Ehlbeck, U Schnabe, M Polak, J Winter, Th von Woedtke, R Brandenburg, T von dem Hagen, K-D Weltmann Low temperature atmospheric pressure plasma sources for microbial decontamination. J. Phys. D: Appl. Phys. 44 (2011) 013002 (18pp)].

Closest to the proposed invention is the device described in US patent No. 6224653, containing a reactor chamber formed between a cylindrical grounded electrode and concentrically mounted inside it cylindrical high-voltage electrode containing a large number of tips. The tips on this electrode are designed for a point amplification of the field, which makes it possible to create conditions for the occurrence of a streamer corona discharge. The high voltage electrode is connected to a Fitch multistage generator, which generates a high pulse voltage. As a result, multipoint streamer corona discharges arise between the tips and the grounded electrode.

The disadvantage of the described device is its low efficiency due to the fact that the design of the high-voltage electrode does not take into account the specifics of its operation when generating a nanosecond pulsed streamer corona discharge.

The objective of the claimed invention is to create an electrophysical device for cleaning gases from environmentally harmful impurities, air disinfection and sterilization using low-temperature plasma created by pulsed streamer corona discharges, the design of which would ensure the achievement of a technical result, which consists in increasing the efficiency of the device.

The problem is solved by the fact that an electrophysical device has been developed for cleaning gases from environmentally harmful impurities, disinfecting air and sterilizing using low-temperature plasma created by pulsed streamer corona discharges, containing at least one grounded electrode and at least one high-voltage electrode containing pulsed initiators streamer corona discharges from at least one of its sides, with the formation of a reactor chamber between adjacent grounded and high-voltage electrodes, in which initiators of pulsed streamer corona discharges are located, as well as a pulse voltage generator to which a high-voltage electrode is connected, while initiators of pulsed streamer corona discharges discharges are made in the form of semi-ellipsoids of rotation.

In the context of this description, adjacent high-voltage and grounded electrodes mean high-voltage and grounded electrodes, between which there are no other electrodes, while the reactor chamber can only be formed by the pair of adjacent grounded and high-voltage electrodes in which the high-voltage electrode contains initiators of a pulsed streamer corona discharge from the side its corresponding grounded electrode (facing the corresponding grounded electrode).

Semi-ellipsoids of revolution in the context of this description should be understood to mean a part of the surface of an ellipsoid of revolution cut off by a plane passing through the semi-minor axes (of the same length) of said ellipsoid of revolution. In this case, the axis of the specified semi-ellipsoid of revolution passes through the semi-major axis of the ellipsoid of revolution, by which it is formed. The specified axis of the semi-ellipsoid of revolution is perpendicular to the surface of the high-voltage electrode.

It is known that the efficiency of operation of electrophysical devices for cleaning gases from environmentally harmful impurities, disinfecting air and sterilizing is determined by the energy introduced into the gas, which, in turn, is directly proportional to the charge introduced into the interelectrode gap by streamers starting from the initiators of a pulsed streamer corona discharge (tips ) [AND. Z. Ponizovsky, S. G. Gosteev, O.S. Kuzhel, A. S. Smirnov. Industrial installations for air purification using low-temperature nonequilibrium gas discharge plasma. Chemical safety 2018 Volume 2 No. 2, pp: 212-228.]. It is also shown there that in existing installations for air purification by a nanosecond pulsed streamer corona discharge, due to the excessive sharpness of corona points on the initiators of a pulsed streamer corona discharge, streamers start long before the amplitude value of the pulse. Based on experimental data on streamer corona discharge [Bazelyan EM, Raizer Yu.P. Spark discharge M. MIPT 1997, 320 p., B. Peck Modeling of avalanche-streamer transition in the Comsol package 17.p. https://tehnick.github.io/seminar/streamers3/streamer_in_Air.pdf Ponizovsky A.Z., Gosteev S.G. Probe measurements of the parameters of streamers of a frequency nanosecond corona discharge. Nuclear Physics and Engineering. 2016 7 (5): 462-470, D.V. Razevig, M.V. Sokolova Calculation of the initial and discharge voltages of gas gaps M.-Energiya, 1970 200 pp.] And the calculated characteristics of electric fields, the authors of this invention found that increasing the value of the initial voltage of the streamer and, thus, increasing the efficiency of the device, it is possible by reducing the sharpness corona points, in particular - due to the implementation of the initiators of the pulsed streamer corona discharge in the form of ellipsoids.

It is obvious that the distribution of corona points of initiators of pulsed streamer corona discharges, made in the form of ellipsoids of revolution, over the surface of the high-voltage electrode, and, accordingly, the sizes of these initiators in each specific version of the device must be different and can be calculated.

Thus, to generate a nanosecond pulsed streamer corona discharge with the maximum possible energy introduced into the gas, the following conditions must be met.

First, the pulsed electric field strength E _max at a distance of at least 0.5 mm from the high-voltage electrode should be more than 30 kV / cm (E _max > 30 kV / cm).

Secondly, the average value of the pulsed electric field E _cf , which is calculated by the formula

E _cf = U _p / d, (1)

where U _p is the amplitude of the pulse voltage,

d - interelectrode distance,

should be in the range between 5kV / cm and 10kV / cm (5kV / cm <E _cf <10 kV / cm) (the lower limit of E _cf corresponds to the minimum value for the development of a streamer, the upper limit of E _cf corresponds to the electrical breakdown of the discharge gap).

Thirdly, at the moment of start of streamers, the potential of the high-voltage electrode U _st should be close to U _p (U _st ≈ U _p ), since the charge introduced by the streamer into the interelectrode space is calculated by the formula

Q = 4πε ₀ r _h U _st (2),

where r _h is the radius of the streamer head.

Fourthly, the space charge introduced from each corona initiator of a pulsed streamer corona discharge (tip) should not drastically reduce the electric field at the adjacent corona tip, thereby preventing the formation of a streamer.

These conditions can be met if the initiators of a pulsed streamer corona discharge, located on a high-voltage electrode of such a radius at which, for the given parameters of the voltage pulse on its surface, E _max <25 kV / cm, have the form of semi-ellipsoids of revolution.

Based on the above conditions, the most preferable geometric parameters of the initiators of the streamer corona discharge were calculated, in particular, when the radius of curvature of the high-voltage electrode is more than 3 cm, the initiators of pulsed streamer corona discharges are located at a distance of more than 3 mm between their tops, the length of the semi-major axis of the ellipsoid of revolution forming a semi-ellipsoid of revolution , in the form of which the initiator of the pulsed streamer corona discharge is made, is greater than 1 cm, and the ratio of the minor and major semiaxes of the ellipsoid of revolution forming a semi-ellipsoid of revolution, in the form of which the initiator of the pulsed streamer corona discharge is made, is from 0.2 to 0.6. The calculation of the specified optimal geometric parameters of the initiators of the streamer corona discharge is given below with reference to the attached figures.

The inventive device can be characterized by various specific implementation options, which differ in the number of grounded and high-voltage electrodes, their shape and location.

In one embodiment of the claimed invention, the grounded and high-voltage electrodes are made in the form of flat plates.

In another embodiment of the claimed invention, the grounded and high-voltage electrodes are made in the form of curved plates, in particular, formed by a part of the lateral surface of the cylinder.

In another preferred embodiment of the claimed invention, the grounded and high voltage electrodes are cylindrical and mounted coaxially.

In addition to the embodiment of the device with two electrodes (one grounded and one high-voltage), the device can contain n grounded electrodes and n high-voltage electrodes installed alternately, containing initiators of pulsed streamer corona discharges on one side, where n≥2. It is obvious that the initiators of pulsed streamer corona discharges on each of the high-voltage electrodes are located on the side of the corresponding grounded electrode. This design implies the presence of two or more reactor chambers in the device, each of which is limited by a separate pair of electrodes, including a grounded and high-voltage electrode.

Grounded and high-voltage electrodes can be installed alternately, but in any case in pairs (for example, grounded-high-voltage-high-voltage-grounded), while the initiators of pulsed streamer corona discharges on high-voltage electrodes are located on the side of the corresponding grounded electrodes.

In another preferred embodiment, the device comprises n grounded electrodes and n-1 high-voltage electrodes installed alternately (starting from the grounded electrode), containing initiators of pulsed streamer corona discharges on both sides, where n≥2. This design of the device also implies the presence in the device of two or more reactor chambers, however, in this embodiment, each of the chambers is limited by a separate grounded electrode and one high-voltage electrode common to two adjacent chambers.

Alternatively, the device may comprise n high-voltage electrodes and n-1 grounded electrodes installed alternately (starting from the high-voltage electrode), where n≥2. In such an embodiment, grounded electrodes are installed between pairs of high-voltage electrodes, while the extreme high-voltage electrodes contain initiators of pulsed streamer corona discharges on one side, in particular, from the side of the corresponding grounded electrodes, and internal high-voltage electrodes (if any, i.e. if n> 2) contain initiators of pulsed streamer corona discharges on both sides.

The last two above-described embodiments of the claimed device are less metal-consuming when compared with the metal-consuming devices with one reactor chamber, which are necessary to ensure the same productivity, and, therefore, are more economical.

In embodiments where the claimed device contains two or more reactor chambers, the latter can be connected in series with each other, or, conversely, air or other gas flows through them in parallel. The first embodiment is expedient, for example, when the device operates with a flow of air or other gas subject to the maximum degree of processing (cleaning, disinfection), when the flow of air or other gas is processed further in the chamber downstream of the flow. The second embodiment is expedient, for example, when it is necessary to increase the productivity of the device, i.e. processing a larger volume of air or other gas per unit of time, or when the claimed device performs the function of sterilizing objects, when their passage through several reactor chambers is excluded.

Typically, the pulse voltage generator contains a charging voltage regulator. In this case, the high-voltage electrode is connected to the pulse voltage generator by means of a bushing through the grounded part of the device, which insulates the conductive elements from the device body through which they pass.

If the outermost electrodes are grounded electrodes, they can also function as a device housing. This version is the most optimal from the point of view of metal consumption, and, consequently, efficiency.

It should also be noted that if the electrodes are cylindrical, regardless of their type (grounded or high-voltage), the outermost inner electrode can be made as hollow (i.e. tubular or, in other words, in the form of a hollow cylinder, like all other electrodes) , and solid, i.e. without center hole.

The sediment that can form on the corresponding wall of the grounded electrode can be removed, for example, by equipping the inventive device with a device for supplying water to the upper part of the working surface of the grounded electrode for washing off the sediment, as well as a drain hole made in the grounded part of the housing, or any other in a suitable manner known from the prior art.

Thus, there are various versions of the claimed device, which differ in the number of reactor chambers, the number of electrodes that form them, the location of these electrodes, as well as their design. Moreover, embodiments of the device are also possible, for example, in the case when the electrodes are cylindrical, where the inventive device will be a battery containing several non-coaxial reactor chambers or several groups of coaxial reactor chambers, the reactor chambers of each of which are non-coaxial reactor chambers of another group or groups. All reactor chambers, if necessary, can be combined in one housing, and all high-voltage electrodes of the battery can be connected to one pulse voltage generator. However, in any of the above-described embodiment or any other embodiment falling under the independent claim of the claimed invention, the initiators of streamer corona discharges on the high-voltage electrode will have the form of semi-ellipsoids of revolution, and their geometric parameters, in turn, will depend on the specific design of the device.

The claimed invention will be disclosed in more detail with reference to the following graphic materials:

fig. 1 is a schematic sectional view of one of the preferred embodiments of the claimed invention;

fig. 2 is a schematic, enlarged cross-sectional view of one pulsed streamer corona initiator located between the high voltage and grounded electrodes;

fig. 3 - dependence of the field strength at the point of calculation of the field with an average electric field strength of 9 kV / cm in the interelectrode gap, depending on the ratio of the semiaxes of the ellipsoid of revolution forming a semi-ellipsoid of revolution, in the form of which the initiator of the pulsed streamer corona discharge is made;

Fig. 4 shows the dependence of the field strength at the point of calculation of the field at an average electric field strength of 7 kV / cm in the interelectrode gap depending on the ratio of the semiaxes of an ellipsoid of revolution forming a semi-ellipsoid of revolution, in the form of which the initiator of a pulsed streamer corona discharge is made;

Fig. 5 - dependence of the field strength at the point of calculation of the field with an average electric field strength of 6 kV / cm in the interelectrode gap, depending on the ratio of the semiaxes of the ellipsoid of revolution forming a semi-ellipsoid of revolution, in the form of which the initiator of the pulsed streamer corona discharge is made;

fig. 6 - dependence of the field strength at the point of calculation of the field with an average electric field strength of 5 kV / cm in the interelectrode gap depending on the ratio of the semiaxes of the ellipsoid of revolution forming a semi-ellipsoid of revolution, in the form of which the initiator of the pulsed streamer corona discharge is made;

Fig. 7 shows the dependence of the electric field strength of the streamer head charge on the distance to it.

FIG. 1 shows a schematic view of an electrophysical device for cleaning gases from environmentally harmful impurities, air disinfection and sterilization using low-temperature plasma created by pulsed streamer corona discharges. The specified device contains installed coaxially one cylindrical grounded electrode 1 and one cylindrical high-voltage electrode 2 containing initiators 3 of pulsed streamer corona discharges on one side facing the grounded electrode 1. Said initiators 3 are made in the form of semi-ellipsoids of revolution. FIG. 1, it can be seen that these electrodes 1 and 2 are installed coaxially, with a reactor chamber 4 being formed between them. The high-voltage electrode 2 is connected to a pulse voltage generator 5 through a bushing 6. FIG. 1 it can be seen that the grounded electrode 1 is the body of the device. References 7 and 8 designate the gas / air inlet and outlet to and from the reactor chamber 4, respectively. Alternatively or in conjunction with the specified inlet and outlet, the device can be equipped with an opening for placing an object in the reactor chamber 4 for sterilization. Grounded 1 and high-voltage 2 electrodes are located at a distance d from each other. The arrows in FIG. 1 shows the direction of movement of the gas / air supplied to the device. The initiators of the 3 streamer corona discharge are located at a distance S between their tops.

FIG. 2 is a schematic enlarged sectional view of one pulsed streamer corona initiator 3 disposed between high voltage 2 and grounded 1 electrodes. As c denotes one of the foci of the ellipsoid of revolution, in the form of which, in turn, the initiator 3 of the pulsed streamer corona discharge is made; said focus c is on said initiator 3. In FIG. 2 in order to further calculate the optimal geometric parameters of initiators 3, the length 2q of the minor axis of the ellipsoid of revolution, forming a semi-ellipsoid of revolution, in the form of which the initiator 3 of the pulsed streamer corona discharge is made, as well as the length q, respectively, of the minor semiaxis and the length t of the major semiaxis of the specified ellipsoid of revolution are indicated. As Δx denotes the distance from the vertex 9 of the semi-ellipsoid of revolution to the point 10 of the field calculation.

Below is an example of calculating the optimal geometric parameters of structural elements of the proposed device (in particular, initiators 3 in the form of semi-ellipsoids of revolution), which, according to one of the preferred embodiments, contains a cylindrical grounded 1 and high-voltage 2 electrodes of large radii of curvature (i.e. such radii, when which at the given parameters of the voltage pulse on the surface of the high-voltage electrode E _max <25 kV / cm). An extreme case is considered when the electric field between flat high-voltage 2 and grounded 1 electrodes, which are shown in Fig. 2 as straight lines, uniform.

Since the length t of the initiator 3 of the pulsed streamer corona discharge is much less than the distance d between the grounded 1 and high-voltage 2 electrodes, to calculate the optimal parameters of the initiator 3, one can use the formula for the distribution of the electric field in the half-ellipsoid gap of rotation between two planes, as shown in Fig. 2. In FIG. 2 initiator 3 in the form of a semi-ellipsoid of revolution with a semi-major axis t, a semi-minor axis q and a focus c of an ellipsoid of revolution forming the specified semi-ellipsoid of revolution is located between flat grounded 1 and high-voltage 2 electrodes spaced apart by a distance d.

Expression (1) allows calculating the electric field strength E (t) at a point located at a distance Δх for a given geometry, depending on the values of t, q, U _p , d:

, (3)E (t) =

, (3)

Where

c =

A (t) =

b (t) =

c (t) =

a (t) = t + Δx

ln

B (t) = 0.5

ln

η = t / c.

Since for the occurrence of a pulsed streamer corona discharge, a zone with a field E _max > 30 kV / cm and a length of Δx ≥ 1 mm is required, then in Fig. Figures 3-6 show the calculation of the field according to (3) at Δx = 0.1 cm for semi-ellipsoids of various heights with the ratio of the semiaxes for the values of E _av 5, 6, 7, 9 kV / cm. The calculation results show that the first condition E _max > 30 kV / cm for Δх = 0.1 cm and 5 kV / cm ≤ E _cf <10 kV / cm are satisfied for t> 1 cm and 0.2 <q / t.

From FIG. 2 it follows that the third condition U _st ≈ U _p will be fulfilled for t> 1 cm and 0.6 <q / t.

Thus, the optimal parameters of the ellipsoid of revolution are t> 1 cm and 0.2 <q / t <0.6.

If the devices are designed for certain values of U _p and d in the range of 5 kV / cm ≤ E _cf <10 kV / cm, then the calculation results allow us to determine the optimal values of the parameters of the semi-ellipsoid of revolution t = 150 / (U _p / d) ^2.5 , q = 3dt / U _p / d for electrodes with a radius of curvature R> 3 cm.

To satisfy condition 4, it is necessary that the introduced space charge Q from one corona point does not screen the adjacent corona point. Based on the available experimental data, streamers with a total charge ∑Q ≈
10 ^-8 Cl. Calculation of the electric field (Fig. 7) from such a charge shows that there is practically no screening at a distance of 3 mm from this charge to the top of the neighboring semi-ellipsoid. Thus, initiators of 3 pulsed streamer corona discharges can be located in the form of semi-ellipsoids of revolution at a distance S> 3 mm between their vertices.

Analysis of the experimental data shows that due to the implementation of initiators 3 in the form of semi-ellipsoids of revolution and the correct choice of the values of t, q, and S, the efficiency of the existing devices of a pulsed streamer corona discharge can be increased by more than 20%.

The operation of the proposed device is described below on the example of its implementation of the function of cleaning gases from environmentally harmful gaseous impurities or air disinfection.

The contaminated gas is fed into the reactor chamber 4 of the device, after which nanosecond voltage pulses are generated using a pulse voltage generator 5. With the help of these pulses, in the space between the grounded electrode 1 and the initiators 3 of the pulsed streamer corona discharge located on the high-voltage electrode 2, a pulsed streamer corona discharge is created, which, in turn, creates a low-temperature plasma, as a result of which the conversion of gaseous impurities into environmentally friendly gases occurs or aerosols or disinfection of air in the presence of biological objects in it.

Thus, an electrophysical device has been developed for cleaning gases from environmentally harmful impurities, air disinfection and sterilization using low-temperature plasma created by pulsed streamer corona discharges, the design of which ensures the achievement of a technical result, which consists in increasing the efficiency of the device.

It should be understood that the claimed electrophysical device as defined in the appended claims is not necessarily limited to the specific features and embodiments described above. On the contrary, the specific features and embodiments described above are disclosed as examples embodying the claims, and other equivalent features may be encompassed by the claims of the present invention.

Claims (7)

1. An electrophysical device for cleaning gases from environmentally harmful impurities, air disinfection and sterilization using low-temperature plasma created by pulsed streamer corona discharges, containing at least one grounded electrode and at least one high-voltage electrode containing initiators of pulsed streamer corona discharges at least at least from one of its sides, with the formation of a reactor chamber between adjacent grounded and high-voltage electrodes, in which the initiators of pulsed streamer corona discharges are located, as well as a pulse voltage generator to which a high-voltage electrode is connected, characterized in that the initiators of pulsed streamer corona discharges, located on a high-voltage electrode, made in the form of semi-ellipsoids of revolution. 2. The device according to claim 1, characterized in that when the radius of curvature of the high-voltage electrode is more than 3 cm, the initiators of pulsed streamer corona discharges are located at a distance of more than 3 mm between their tops, the length of the semi-major axis of the ellipsoid of revolution forming a semi-ellipsoid of revolution is more than 1 cm, and The ratio of the semi-minor and semi-major axes of an ellipsoid of revolution forming a semi-ellipsoid of revolution is from 0.2 to 0.6. 3. The device according to claim 1, characterized in that the grounded and high-voltage electrodes are made in the form of flat plates. 4. The device according to claim 1, characterized in that the grounded and high-voltage electrodes are made in the form of plates formed by a part of the lateral surface of the cylinder. 5. The device according to claim 1, characterized in that the grounded and high-voltage electrodes are cylindrical and installed coaxially. 6. The device according to claim. 1, characterized in that it contains installed alternately n grounded electrodes and n high-voltage electrodes containing initiators of pulsed streamer corona discharges on one side, where n≥2. 7. The device according to claim 1, characterized in that it contains installed alternately n grounded electrodes and n-1 high-voltage electrodes containing initiators of pulsed streamer corona discharges on both sides, where n≥2.

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