EP3870342A1

EP3870342A1 - Novel device for purifying air by means of plasma

Info

Publication number: EP3870342A1
Application number: EP19794994.4A
Authority: EP
Inventors: Pierre DE LINAGE; Stephen LUNEL
Original assignee: Airinspace SE
Current assignee: Airinspace SE
Priority date: 2018-10-25
Filing date: 2019-10-25
Publication date: 2021-09-01
Also published as: FR3087677B1; CN112912161B; CN112912161A; JP7295945B2; FR3087677A1; JP2022505628A; WO2020084138A1

Abstract

A device for purifying air by means of plasma comprising: i) a least one electrical power source; ii) at least one ionizer (10) connected to the power source; iii) at least one filter (40) downstream of the ionizer; iv) at least one catalyzer (50) downstream of the ionizer (10) and of the at least one filter (40) downstream of the ionizer (10), which catalyzer (50) decomposes ozone; and v) at least one means for pressurizing air (1) so as to ensure that air flows from the ionizer (10) to the catalyzer (50); wherein the ionizer (10) takes the form of at least one corona-discharge plasma cell (11) comprising a) a substantially needle-shaped biased electrode (12) and b) a ground electrode (13), arranged facing the biased electrode (12), which comprises a cylinder (14) that is substantially centered on the biased electrode (12) and a substantially planar porous film (15) perpendicular to the biased electrode (12), wherein the cylinder (14) exhibits a low profile, and wherein the biased electrode (12) does not penetrate into the cylinder (14), the value of the diameter of the cylinder (14) corresponding to at least twice the value of its height.

Description

NEW PLASMA AIR CLEANING DEVICE

This international application claims priority from French patent application FR 18/71306 filed on October 25, 2018, which is hereby incorporated by reference.

Field of the invention

The present invention relates to the field of plasma emission by corona discharge and more particularly that of air purification devices by plasma.

Prior Art

It is known to use a plasma device with corona effect to produce, by corona discharge, a plasma and an ion flux. Such a device advantageously makes it possible to produce a plasma making it possible to ionize a fluid passing through the ionizer. Such ionization finds multiple and complementary functionalities, for example, in the sector of treatment of a fluid, such as air.

According to a first functionality, an ionization makes it possible, by depositing ions, to charge a particle contained in the fluid. This particle thus charged can advantageously be retained by an electrostatic filter, which can be arranged downstream of the ionizer. According to another functionality, an ionization has a neutralizing action on pathogenic organisms, such as viruses, which can be transported in the fluid. According to yet another functionality, an ionization advantageously produces oxidizing chemical species useful for the decontamination of a mechanical filter, such as an activated carbon filter, which can be disposed downstream of the device.

It is known to produce a plasma device with a corona effect, to employ an ionizer with a polarized electrode and a ground electrode, placed opposite the polarized electrode, and to apply between these two electrodes a significant potential difference, of the order of several thousand volts. This creates a plasma as well as corona discharges producing ionic discharges. The ionization effect of the fluid is obtained by creating a circulation of the fluid forcing the fluid to pass through the plasma. To obtain such a plasma, according to the corona effect, two configurations are known: according to a first configuration, called tip-plane, a polarized electrode having a small radius of curvature is arranged perpendicularly to a ground electrode substantially planar; in another configuration called wire-cylinder, a polarized wire electrode is disposed axially in a cylindrical earth electrode.

Patent FR 2818451 proposes to combine these two configurations by using a needle-shaped polarized electrode and an earth electrode comprising a substantially planar metallic trellis, arranged perpendicular to the polarized electrode and a cylinder surrounding the polarized electrode over its whole length. This ionizer is crossed by the fluid in a direction parallel to the coincident axis of the polarized electrode and the cylinder.

There is always a search for an improvement in a plasma device with a corona effect, in terms of efficiency of ionization, reduction of the volume occupied, efficiency of air purification or even of the electrical energy consumed.

Detailed description of the invention

The subject of the invention is a plasma air purification device comprising: i) at least one source of electrical power;

ii) At least one ionizer connected to the power source;

iii) At least one filter downstream of the ionizer;

iv) At least one catalyst downstream of G ionizer and at least one filter downstream of G ionizer, which catalyst allows the decomposition of ozone; and

v) At least one means of pressurizing the air to ensure the flow of air from the ionizer to the catalyst;

Characterized in that G ionizer takes the form of at least one plasma cell with corona effect comprising:

a) a substantially needle-shaped polarized electrode, and

b) a ground electrode, placed opposite the polarized electrode, comprising:

• a cylinder substantially centered on the polarized electrode and

• a substantially planar porous film perpendicular to the polarized electrode,

in which the cylinder has a low profile, and the polarized electrode does not penetrate not in the cylinder, the value of the diameter of the cylinder corresponding to at least twice, preferably at least 3 or even 5 times, and in particular at least 10 times the value of the height of the cylinder, and

wherein the porous film (15,25) is disposed, relative to the polarized electrode (12,22), on the side opposite the cylinder (14,24).

US patent 5,474,600 as well as patent application EP 2 343 090 each describe an air purification and filtration device comprising an ionizer. Now, in neither of these two documents does the structure of the envisaged ionizer include a pair of electrodes in which the polarized electrode takes the form of a needle and the earth electrode takes the form of a porous film and of a low profile cylinder with the polarized electrode which does not enter the cylinder of the earth electrode.

In the device according to the invention, the source of electrical power of the device according to the invention is chosen so as to be able to deliver a sufficient voltage to the ionizer to generate a plasma.

As for G ionizer, its porous film is placed, relative to the polarized electrode, on the side opposite the cylinder. We prefer a porous film made of a metallic material with pores having a size ranging from 0.1 mm to 500 mm, preferably from 5 mm to 50 mm, and a thickness between 0.5 and 50 mm, preferably between 1 and 5 mm. Now, this porous film takes the form of a metallic mesh, the meshes of which can have different shapes (square, rhombus, etc.). Ideally, the metal mesh in question is a sheet of expanded metal.

According to a preferred embodiment, the ionizer comprises at least one dual plasma element with corona effect, which dual plasma element with corona effect comprises:

• A first polarized electrode and a first earth electrode,

• A second polarized electrode and a second earth electrode,

Where the first polarized electrode and the second polarized electrode are arranged on either side of the same support, and where the first earth electrode and the second earth electrode are arranged on either side of this same support and near the first polarized electrode and the second polarized electrode respectively. Advantageously, the first polarized electrode and the second polarized electrode are connected to the same first potential and the first earth electrode and the second earth electrode are connected to the same second potential, different from the first potential. Preferably, the first potential is negative and the second potential is ground. Note that in the case where the polarized electrode (s) are connected to a negative potential, we then speak of discharge electrodes.

Still advantageously, the first polarized electrode and the second polarized electrode are substantially needle-shaped and are supported by a conductive support connected to the first polarized electrode, to the second polarized electrode and to the first potential, which conductive support, which is of preferably substantially planar, is connected to the first polarized electrode, to the second polarized electrode and to the first potential.

Ideally, the first polarized electrode and the second polarized electrode are axially aligned and, preferably, they form a single piece.

Advantageously, the conductive support comprises a printed circuit comprising at least one conductive track connected to the first polarized electrode, to the second polarized electrode and to the first potential. Preferably, each of the two polarized electrodes is arranged in a metallized via pierced in said at least one conductive track. This printed circuit includes days, preferably entirely except for a narrow strip formed around said at least one conductive track.

The genesis of ozone, which constitutes a powerful oxidant, by non-thermal plasma air treatment systems is of great interest in that it considerably improves the elimination of residual pollutants after plasma treatment. Now, the presence of this ozone in the atmosphere at the outlet of these treatment systems generates significant stress on the respiratory tract and is therefore problematic. Consequently, it is imperative to carry out a post-treatment making it possible to eliminate these toxic by-products and more particularly the ozone whose concentration at the outlet can exceed 100 ppm (v) (or 0.2 g / m). To do this, we integrate a catalyst which is chosen from activated carbon, zeolite or manganese oxide (MnO2) and which allows a very rapid decomposition of ozone and nitrogen oxides at room temperature. In this case, it is preferable to use a catalyst taking the form of a honeycomb substrate, for example aluminum, which is covered with manganese oxide. Typically such a honeycomb substrate should have a thickness of at least 10 mm to have sufficient effectiveness in neutralizing ozone.

As for the at least one filter located downstream of the ionizer (but upstream of the catalyst), it must be made of a material allowing it to withstand the strongly oxidizing atmosphere resulting from the presence of ozone in quantity at the outlet of the ionizer.

Preferably, the filter will be made of mineral material such as glass or ceramic and, particularly preferably, the filter will be based on fiberglass. To be effective, said at least one filter must have at least a thickness of at least 10 mm, in particular of glass fibers.

Now, in addition to its filtration function, the filter advantageously also makes it possible to define an oxidation space between the ionizer and the catalyst. In this space, the particles leaving the ionizer are trapped until their almost complete degradation due to their reaction with ozone.

To do this, said at least one filter has a height less than or equal to 100 mm, preferably less than or equal to 200 mm and, in a particularly preferred manner less than or equal to 300 mm.

Typically, the filter may comprise the superposition of at least two layers, preferably at least three or four layers, and in a particularly preferred manner, at least five or six successive layers of mineral material, typically glass fibers .

Each of these layers will have a thickness of at least 10 mm, preferably at least 20 mm and, in a particularly preferred manner, at least 30 mm. Now each of these layers will be less than 50mm thick.

The layers in question may have a linear or V-shaped profile so as to increase the filtration / retention surface.

Regarding the means of pressurizing the air to ensure the flow of air through the ionizer, then through the filter to the catalyst, it can take the form of a fan, a turbine. Preferably, this means of pressurizing the air is a turbine.

Other characteristics, details and advantages of the invention will emerge more clearly from the detailed description given below by way of indication in relation to the drawings in which:

FIG. 1 illustrates, in diagrammatic view, a preferred embodiment of an air cleaning device according to the invention,

FIG. 2 illustrates in sectional view, an ionizer comprising a dual element with two cells,

FIG. 3 illustrates, in perspective view, a plasma reactor,

- Figure 4 illustrates, in top view, a printed circuit carrier of polarized electrodes for such an ionizer.

According to a first aspect, illustrated in FIG. 1, the invention relates to an air cleaning device comprising an ionizer (10) as shown in FIG. 1. Such a device comprises a means for boosting the pressure air (1) in the device which takes the form of a fan (1) which ensures the flow of air in the device, first in G ionizer (10), then in the filter (40) comprising successive layers of glass fibers (41,42,43), and finally in the catalyst (50) to allow the ozone to be removed from the outlet effluents. The ionizer comprises two cells joined and inverted with a polarized electrode (12,22), a ground electrode (13,23). The first polarized electrode 12 and the second polarized electrode 22 are connected to the same first potential 8 and the first earth electrode 13 and the second earth electrode 23 are connected to the same second potential 9, different from the first potential 8; which potentials are obtained at the terminals of an electrical power source.

The signs of the first and second potentials 8.9 can be any. However, it is known that G ionization obtained by corona effect is more effective when the polarized electrode is connected to a negative potential (this is known as a discharge electrode). Also, preferably the first potential 8 is negative and the second potential 9 is the mass. The preferred structure of this ionizer 10 is given in more detail in FIGS. 2 and 3. In this preferred structure, the ionizer has two cells 11, 21 which are assembled symmetrically (in an inverted configuration). Also, G ionizer 10 has a first plasma cell 11 with corona effect and a second plasma cell 21 with corona effect. The first cell 11 comprises a first polarized electrode 12 and a first earth electrode 13, arranged opposite the first polarized electrode 12. The second cell 21 comprises a second polarized electrode 22 and a second earth electrode 23, arranged opposite of the second polarized electrode 22.

Each polarized electrode 12,22 is substantially needle-shaped and has a ground electrode 13,23, placed opposite its polarized electrode 12,22. Each earth electrode 13,23 comprises a cylinder 14,24 substantially centered on its polarized electrode 12,222 and a porous film 15,25 substantially plane perpendicular to its respective polarized electrode 12,22. Each polarized electrode

12.21 is typically fixed on a support 16, 26 advantageously perforated to allow the passage of a flow of fluid. The distance between each polarized electrode

12.22 and each earth electrode 13,23 is held by at least one spacer 17,27.

A cell 11, 21 is improved in that the cylinder 14, 24 is shaped so as to have a low profile. This means that the height of the cylinder 14,24 is negligible compared to its diameter. Typically, the diameter of the cylinder is between 20 and 100 mm, preferably between 25 and 75 mm, for example between 30 and 60 mm and, particularly preferably between 35 and 55 mm. As for the thickness of the cylinder, it is less than 10 mm, preferably between 1 and 5 mm. In addition, each polarized electrode 12,22 is shaped sufficiently short, so as not to enter its cylinder 14,24.

The flow of fluid to be ionized by means of G ionizer 10 is substantially vertical relative to FIGS. 2 and 3.

It has been found that such an ionizer structure has many advantages which are not obvious. Thus, doubling the cells 11,21 makes it possible to greatly improve the efficiency obtained as well as its lifespan. Indeed, an effect detrimental to a corona cell is that its polarized electrode 12,22 precipitates dielectric crystals which, gradually isolating said polarized electrode 12,22, reduce the efficiency of the cell 11,21. The fact of using two cells instead of one has considerably improved the life expectancy of the reactor ionizer 10. The first cell 11, having an orientation opposite to that of the second cell 21, their ionizing effects are combine and complement each other, thereby increasing the overall ionizing effect. The opposite orientation still advantageously makes it possible to apply the same polarization to the two cells 11,21. These two orientation and polarization characteristics combined, advantageously make it possible to fix the first polarized electrode 12 on a first support 16 and the second polarized electrode 22 on a second support 26. Advantageously, these two supports 16, 26 can be a single support. 36 common, the polarized electrodes 12,22 being supported respectively each by one face of the support 36. This advantageously allows, the polarity of the first polarized electrode 12 and of the second polarized electrode 22 being the same (preferably negative), to use a common connector, as well as a common potential source, for polarizing these two polarized electrodes 12,22. This structure is therefore particularly economical and advantageous. Thus, according to an advantageous embodiment, the common support 36 can be conductive and be connected to the first polarized electrode 12, to the second polarized electrode 22 and to the first potential 8.

According to another advantageous embodiment, the common support 36 comprises a printed circuit 36 comprising at least one conductive track 31 connected to the first polarized electrode 12, to the second polarized electrode 22 and to the first potential 8.

The polarization of a corona plasma device requires a large potential difference between the polarized electrode and the earth electrode, which potential difference is of the order of several thousand volts. Also the first potential 8 is very high and could prove to be annoying for an operator. The configuration according to the invention advantageously ensures confinement of this first potential 8 in the middle of the ionizer 10. The first high potential 8 is thus out of the reach of an operator.

The support 16, 26 being a printed circuit 36, the first potential 8 being distributed within the support by means of a conductive track 31, advantageously disposed in said printed circuit 36, according to another characteristic, a polarized electrode 12,22, substantially in the shape of a needle, is advantageously assembled on the support 16,26 to by means of a via 33 drilled in the printed circuit 36. This advantageously allows the polarized electrode 12,22 to be fixed by means of a weld. Advantageously, the via 33 is metallized and drilled in a conductive track 31. The drilling is such that it ensures the electrical connection. Thus the attachment of the polarized electrode 12,22 in via 33 in a connected manner ensures the connection between the polarized electrode 12,22 and the first potential 8. This allows a simple embodiment of the attachment and the connection of the polarized electrode 12.22.

The printed circuit 36 being arranged across the flow of fluid is advantageously perforated in order to allow the passage of this flow of fluid. According to one embodiment, at least one day 38 is carried out for this purpose. In order to maximize the passage of fluid through it, said at least one day 38 can cover the entire surface of the printed circuit 36 with the exception of at least one narrow strip formed around said at least one conductive track 31.

An embodiment of a printed circuit 36 intended for an ionizer usable in a device according to the invention is illustrated in FIG. 4 which presents a printed circuit 36 suitable for an arrangement in square grid. This printed circuit 36 includes a network, for example rectangular of conductive tracks 31. These tracks are advantageously embedded in the insulating thickness of the printed circuit 36. They are electrically connected to the first potential 8. According to an arrangement substantially in square grid, are drilled vias 33, in which the polarized electrodes 12,22,32 are installed. The printed circuit 36 is cut by days 38 occupying a maximum surface in order to maximize the fluid passage section. This maximum surface is just limited by the saving of a narrow strip around the tracks 31. Holes 39 are provided, advantageously without electrical connection, spatially distributed, to allow fixing of the spacers 17, 27, 37, advantageously made made of insulating material.

Claims

1 A plasma air cleaning device comprising:

i) at least one source of electrical power;

ii) at least one ionizer (10) connected to the power source;

iii) at least one filter (40) downstream of the ionizer (10);

iv) at least one catalyst (50) downstream of the ionizer (10) and at least one filter (40) downstream of G ionizer, which catalyst allows the decomposition of ozone; and

v) at least one means for boosting the air (1) to ensure the flow of air from the ionizer (10) to the catalyst (50);

Characterized in that G ionizer (10) takes the form of at least one cell

(11,21) corona plasma comprising: a) a substantially needle-shaped polarized electrode (12,22), and b) a ground electrode (13,23), arranged opposite the polarized electrode

(12.22), including:

- a cylinder (14,24) substantially centered on the polarized electrode

(12.22), and

- a substantially planar porous film (15,25) perpendicular to the polarized electrode (12,22),

wherein the cylinder (14,24) has a low profile, and the polarized electrode

(12.22) does not enter the cylinder (14,24), the value of the diameter of the cylinder (14) corresponding to at least twice the value of its height; and in which porous film (15,25) is arranged, relative to the polarized electrode

(12.22), on the side opposite the cylinder (14,24).

2 The plasma air cleaning device according to claim 1, characterized in that G ionizer (10) comprises at least one dual element (11,21) plasma with corona effect with: A first polarized electrode (12) and a first earth electrode (13), a second polarized electrode (22) and a second earth electrode (23), where the first polarized electrode (12) and the second polarized electrode (22) are arranged on either side of the same support (16,26), and where the first earth electrode (13) and the second earth electrode (23) are arranged by and from other of this same support (16,26) and near the first polarized electrode (12) and the second polarized electrode (13) respectively)

3. The plasma air cleaning device according to claim 2, characterized in that the first polarized electrode (12) and the second polarized electrode (22) are connected to the same first potential (8) and the first electrode earth (13) and the second earth electrode (23) are connected to the same second potential (9), different from the first potential (8).

4. The plasma air cleaning device according to claim 3, characterized in that the first polarized electrode (12) and the second polarized electrode (22) are substantially needle-shaped and are supported by a conductive support connected to the first polarized electrode (12), the second polarized electrode (22) and the first potential (8).

5. The plasma air cleaning device according to claim 4, characterized in that the first polarized electrode (12) and the second polarized electrode (22) are axially aligned and form a single piece.

6. The plasma air cleaning device according to claim 5, characterized in that the conductive support comprises a printed circuit (36) comprising at least one conductive track (31) connected to the first emitting electrode (12), to the second emitting electrode (22) and to the first potential (8).

7. The plasma air cleaning device according to claim 6, characterized in that each of the two polarized electrodes (12,22) is arranged in a metallized via (33) pierced in said at least one conductive track (31 ).

8. plasma air cleaning device according to any one of claims 7 or 8, characterized in that the printed circuit (36) includes days (38), preferably entirely except for a strip narrow formed around said at least one conductive track (31).

9. The plasma air cleaning device according to any one of claims 1 to 8, characterized in that said at least one catalyst (50) is chosen from activated carbon, zeolite and manganese oxide (Mn02).

10. The plasma air cleaning device according to any one of claims 1 to 9, characterized in that said at least one filter (40) located downstream of the ionizer is made of a material allowing it to resist the strongly oxidizing atmosphere resulting from the presence of ozone in quantity at the outlet of the ionizer (10), preferably in mineral material such as glass or ceramic.