EP1700515B1 - Electrode for generating a dielectric barrier discharge plasma - Google Patents

Abstract

The electrode has a portion of an electrical conductor wire covered by a dielectric sheath material. A support includes an opening, where the portion of the conductor wire extends through the opening. Segments of the conductor wire are spaced regularly with respect each other. A tension system (17) exerts tractive force to two ends (10a, 10b) of the portion of the conductor wire. An independent claim is also included for a gas stream processing device including a plasma generator.

Description

The present invention relates to an electrode for the generation of dielectric barrier discharge plasma.

It also relates to a dielectric barrier discharge plasma generator using the electrodes according to the invention, as well as a device for treating a gas flow using such a plasma generator.

In general, the present invention relates to the treatment of a gas stream by means of a dielectric barrier discharge (DBD or Dielectric Barrier Discharge) plasma.

In such a plasma generator system, the electrodes are generally made of metal plates arranged in parallel and between which a dielectric barrier discharge plasma is generated.

A non-conductive material is interposed between the electrodes to form the dielectric barrier.

In some applications, it is interesting that the gas flow to pass through the plasma, can also pass through the electrodes. The electrodes are then arranged transversely to the gas flow.

Perforated plates forming electrodes are thus known, arranged facing one another so that the plasma is generated between these electrodes and that the gaseous flow can pass through these same electrodes thanks to the perforations.

A perforated dielectric material is also added transversely to the gas flow to obtain the dielectric barrier discharge plasma.

In this type of embodiment, there are privileged paths between the two electrodes, through the openings of the dielectric material. These zones promote the generation of arcs from one electrode to another, thus destroying these electrodes.

Electrodes of this type are disclosed for example in the document US-2002/015 3241 A1 .

The present invention aims to solve the aforementioned drawbacks and to propose a new type of electrode for complete isolation of the electrode and thus eliminating any risk of generating arcing.

For this purpose, the present invention relates in a first aspect to an electrode for generating a dielectric barrier discharge plasma comprising a portion of electrically conductive wire coated with a sheath of dielectric material fixed on a support.

The holder has an opening, the portion of sheathed conductive wire extending through the opening.

By thus using an electrical wire coated with an insulating sheath, the electrode is entirely coated with a dielectric material. No preferential path can thus exist between the electrodes whatever the geometry used.

Thus, when two electrodes in accordance with the invention are used and the portions of electrically conductive wire are placed in parallel, two metal parts facing one another are obtained separated by two layers of dielectric material formed. by sheaths encapsulating the electrical conductor wire.

In addition, easily manipulable electrodes are available which can be fixed in a plasma generating device, the supports of the electrodes being arranged opposite one another in order to form plasma generation zones therebetween.

Such an electrode can, thanks to its opening, be traversed by a gaseous flow to be treated by plasma, the portion of sheathed conducting wire extending through the opening making it possible to generate a plasma zone at the right of this opening.

According to another preferred feature of the invention, the electrode comprises a support extending substantially in a plane, this support having an opening and the portion of sheathed conductive wire extending in the plane of the support through the opening .

This type of embodiment is particularly simple to implement. The electrode is thus in the form of a substantially flat part.

In order to obtain a homogeneous plasma generation at the opening of the electrode, the sheathed conductive wire portion forms several segments of sheathed conductive wire extending through the opening.

The homogeneity of the plasma is also ensured since the segments of sheathed conducting wire passing through the opening are spaced regularly from each other.

So that the spacing remains constant, the electrode preferably comprises tensioning means adapted to exert a tensile force at two ends of the portion of sheathed conductive wire.

According to a second aspect of the invention, it relates to a dielectric barrier discharge plasma generator, comprising at least two electrodes according to the invention, arranged facing one another.

A dielectric barrier discharge plasma generator is thus obtained in which the electrode is entirely coated with a dielectric material, thus avoiding any risk of arcing from one electrode to the other.

Preferably, these electrodes respectively comprise openings arranged facing each other.

A dielectric barrier discharge plasma generator is thus obtained in which a gas stream to be treated by the plasma can pass through the electrodes.

Finally, the present invention also relates to a device for treating a gas stream comprising a dielectric barrier discharge plasma generator according to the invention, a catalytic support comprising means for passing a gas stream being disposed between said electrodes.

Other features and advantages of the invention will become apparent in the description below, the invention being defined by the appended claims.

• la figure 1A illustre en vue de dessus une électrode conforme à un premier mode de réalisation de l'invention ;
• la figure 1B est une vue en coupe transversale d'un fil conducteur gainé ;
• la figure 2 illustre en vue de dessus une électrode conforme à un second mode de réalisation de l'invention ;
• la figure 3 illustre en perspective un générateur de plasma de décharge à barrière diélectrique conforme à un mode de réalisation de l'invention ; et
• la figure 4 illustre en perspective écorchée un dispositif de traitement de gaz conforme à un mode de réalisation de l'invention.

In the accompanying drawings, given as non-limiting examples:

• the Figure 1A illustrates in plan view an electrode according to a first embodiment of the invention;
• the Figure 1B is a cross-sectional view of a sheathed conductive wire;
• the figure 2 illustrates in plan view an electrode according to a second embodiment of the invention;
• the figure 3 illustrates in perspective a dielectric barrier discharge plasma generator according to an embodiment of the invention; and
• the figure 4 illustrates in perspective cut away a gas treatment device according to an embodiment of the invention.

We will first describe with reference to the figure 1 an electrode for generating a dielectric barrier discharge plasma according to a first embodiment.

In principle, this electrode comprises a portion 10 of electrically conductive wire coated with a sheath of dielectric material.

Indeed, when two portions 10 of such a conductor wire are arranged parallel to one another, two metal parts facing one another are obtained separated by two layers of a corresponding dielectric material. to each sheath covering the electrical conductor wire.

In cross-section, such a sheathed conductive wire has been illustrated.

This sheathed conductor wire comprises a core constituting an electrical conductor wire 11 surrounded by a sheath 12 of dielectric material.

Preferably, the electrical conductor wire 11 is a single-core core. Indeed, the use of a multi-strand core, made from a twist of the strands, would have the effect of creating variations in distance between two electrodes placed next to each other. These variations in distance would affect the homogeneity of the plasma areas.

The sheath 12 of dielectric material may be made of any type of dielectric material adapted to be brought into contact with the elements present in the generated plasma.

In particular, for the generation of a dielectric barrier discharge plasma adapted to the treatment of a gas flow, the constituent elements of this plasma are ultraviolet and ozone. Suitable dielectric materials for this type of plasma may be fluorocarbon coatings such as polytetrafluoroethylene (PTFE) sold under the trade mark Teflon or else silicone, or possibly a Teflon coating itself covered with a silicone layer.

In the example shown in Figure 1A the electrode comprises a support 13, the portion 10 of sheathed conducting wire being fixed on this support.

This support 13 may be made of resin filled with glass to ensure its mechanical rigidity.

This electrode being intended to be placed transversely to a gaseous flow to be treated, the support 13 has an opening 14 and the portion 10 of sheathed conductive wire extends through this opening 14.

In this embodiment, the support has a substantially square shape and has a circular opening 14 of diameter slightly smaller than the dimensions of the square support.

The portion 10 of sheathed conductive wire thus extends in the plane of the support, through the opening 14.

In order to present a substantially homogeneous electrode surface in the plane of the support 13, the sheathed conductor wire travels on the support by crossing the opening 14 multiple times in order to grind as much as possible the disc-shaped surface here, of this opening 14.

Thus, this portion 10 of sheathed conductive wire forms several segments of sheathed conductor wire which extend through the opening 14.

In this embodiment, the sheathed conductor wire snakes, following a path back and forth between an edge 13a and an opposite edge 13b of the support 13.

The segments of sheathed conductor wire extending through the opening 14 are thus parallel, spaced regularly from each other.

Finally, it is important that the portion 10 of sheathed conductive wire has its two ends 10a, 10b attached to the support 13 substantially adjacent.

For this, in this embodiment as illustrated in FIG. Figure 1A , the portion 10 of sheathed conductor wire runs in duplicate on the support 13.

As illustrated on the figure 3 the support 13 comprises routing grooves 15 of the sheathed conducting wire.

These routing grooves 15 are made on the surface of the solid part of the support 13. These routing grooves 15 open out towards each other in the opening 14 so that the portion 10 of conducting wire sheathed is housed in these grooves 15 on either side of the opening 14 through which it passes.

In order to keep the sheathed conducting wire in position, and in particular to keep it taut, these routing grooves 15 may comprise lugs 16 of various shapes intended in particular to hold the wire in the curved portions of the routing grooves 15.

In order to obtain a homogeneous plasma between the wires of two electrodes placed vis-à-vis, it is necessary that these son are correctly tensioned so that the spacing between these son remains constant. It is therefore advantageous to provide a tensioning system 17 as illustrated in FIG. figure 3 which is adapted to exert a tensile force at both ends 10a, 10b of the portion 10 of sheathed conductive wire.

This tension system 17 can be made from jaws whose adjustment of the tensile force exerted on the wire can for example be achieved by means of a screw. It may further comprise a compensation system, such as a spring, providing sufficient traction force even in case of possible elongation of the wire.

If this voltage system 17 comprises metal parts, the latter will preferably be connected to the core of the electrical conductor wire 11 they maintain in tension.

Thus, one of the jaws of the tensioning system 17 perforates the sheath 12 to put the metal assembly of the tensioning system 17 to the potential of the electric conductor wire 11.

The path of the portion 10 of sheathed conductive wire makes it possible to bring back its two ends 10a, 10b at the level of the tensioning system 17, avoiding any peak effect on the end of the wire which is no longer insulated.

Of course, the dual coil embodiment as illustrated in FIG. Figure 1A is only one embodiment among others.

We illustrated at the figure 2 another embodiment of an electrode according to the invention.

In this example, the support 13 comprises two opening portions 14a, 14b separated by a cross member 18 on which segments of sheathed conductive wire may be attached.

So that the two ends 10a, 10b of the portion 10 of sheathed conductive wire are fixed next to each other on the support 13, at the cross member 18, the sheathed lead wire is in this example fixed by forming two sinusoidal curves on either side of the crosspiece 18, joined on the side of an edge 13c of the support 13, opposite the edge 13d carrying the two ends 10a, 10b of the sheathed conductor wire.

As previously, routing grooves can be made in the solid portions of the support 13 and a tensioning system can be fixed at the ends 10a, 10b of the sheathed conductive wire in order to exert traction and to keep the sheathed conductive wire taut. .

We will now describe with reference to the figure 3 an example of a dielectric barrier discharge plasma generator according to an embodiment of the invention.

In this example, the generator of a dielectric barrier discharge plasma uses two electrodes as described above with reference to Figures 1A and 1B .

These electrodes 1, 1 'are fixed against each other so that the faces of each support 13, 13', opposite to the faces carrying the portion 10 of sheathed conductive wire, are in contact one against the other. other.

A plasma zone can thus be generated at the openings 14 placed facing each other, between the portions 10, 10 'of sheathed conductive wire mounted facing each other.

In order to avoid having too close electrode outputs, the ends 10a, 10b and 10'a, 10'b of the portions 10, 10 'of sheathed conductor wire of each electrode 1, 1' are arranged at the opposite of each other in the assembly of the generator.

These electrodes 1, 1 'are identical and fit one against the other, the supports 13, 13' being arranged at 180 ° relative to each other.

This type of generator is particularly well suited to the treatment of a gas flow passing through a plasma generated by the electrodes placed transversely to this flow.

The use of a sheathed conductor wire has the advantage of limiting the pressure drops during the transfer of the gas flow through these electrodes. Indeed, the useful section of the openings 14 for the passage of the gas stream is kept at the thickness of the conductor wire sheathed.

In addition, no preferential path exists between these electrodes covered with a dielectric material 12 so that the formation of electric arcs capable of destroying the electrodes is thus carefully avoided.

Such a generator of a dielectric barrier discharge plasma is particularly well suited to be mounted in a device for treating a gas flow as illustrated in FIG. figure 4 .

This device for treating a gas flow makes it possible in particular to treat cooking fumes in a domestic filter hood. Such a device is in particular described in the patent application French N ° 0216778 whose contents are incorporated by reference in the present description.

Thus, a catalytic support 20, comprising means for passing a gas stream is disposed between two electrodes 1, 1 'according to the invention.

The catalytic support 20 may comprise channels (not shown) extending in the flow direction F of the gas flow.

In particular, this device for treating a gas flow can be adapted to equip a conduit 21 for circulating gases of traditionally cylindrical shape. In this case, the opening 14, 14 'of each electrode 1, 1' has a passage surface corresponding to the transverse surface of the pipe 21.

During this assembly of the device for treating a gas flow, the surface of each opening 14, 14 'is traversed by a network of segments of sheathed conducting wire extending regularly in the plane of each electrode and also arranged remotely. regular electrode 1 to the other electrode 1 '. The plasma is generated between the electrodes 1, 1 '; directly in the catalytic support 20.

Thus, a device for treating a gas stream by catalysis and plasma combined, relatively compact and simple to fix on a pipe 21 for circulation of a gas stream.

In particular, several devices for treating a gas flow as illustrated in FIG. figure 4 can be successively mounted one behind the other in a cylindrical pipe for treating a gas flow.

Of course, the present invention is not limited to the description examples described above and many modifications can be made to these examples without departing from the scope of the invention.

Thus, an electrode made from a portion 10 of sheathed conductive wire could also be used on a solid support, having no opening for the passage of gas.

In particular, electrodes may be made with a sheathed conductor wire snaking on two opposite walls of a ceramic tube through which the plasma will be generated, the gases to be treated circulating inside the tube.

In this case, the electrodes are arranged in planes that are not transverse to the gas flow but instead parallel to this flow.

When the gaseous flow circulates in a cylindrical pipe, it is also possible to produce an internal electrode by means of a sheathed conducting wire extending substantially in the axis of the cylindrical pipe and an external electrode made from a sheathed conducting wire. spirally wound around the cylindrical pipe.

Claims (10)

1. Electrode for generating a dielectric barrier discharge plasma, comprising a portion (10) of electrically conductive wire (11) covered with a sheath of dielectric material (12) fixed to a support (13), characterised in that the support (13) comprises an opening (14), the portion (10) of sheathed conductive wire extending through the opening (14).
2. Electrode according to claim 1, characterised in that it comprises a support (13) lying substantially in one plane, the said support (13) comprising an opening (14) and the said portion (10) of sheathed conductive wire extending in the plane of the said support (13) through the opening (14).
3. Electrode according to one of claims 1 or 2, characterised in that the said portion (10) of sheathed conductive wire forms several segments of sheathed conductive wire extending through the opening (14).
4. Electrode according to claim 3, characterised in that the said segments of sheathed conductive wire passing through the opening (14) are evenly spaced apart from one another.
5. Electrode according to one of claims 1 to 4, characterised in that the said portion (10) of sheathed conductive wire has two substantially adjacent ends (10a, 10b) fixed to the said support (13).
6. Electrode according to one of claims 1 to 5, characterised in that the support (13) comprises grooves (15) for routing the sheathed conductive wire.
7. Electrode according to one of claims 1 to 6, characterised in that it comprises tension means (17) adapted to exert a traction force at two ends (10a, 10b) of the portion (10) of sheathed conductive wire.
8. Dielectric barrier discharge plasma generator, characterised in that it comprises at least two electrodes (1, 1') according to one of claims 1 to 7, disposed opposite each other.
9. Generator according to claim 8, characterised in that the electrodes (1, 1') comprise respectively openings (14, 14') disposed opposite each other.
10. Device for treating a gaseous flow, characterised in that it comprises a plasma generator according to one of claims 8 or 9, a catalytic support (20), comprising means for a gaseous flow to pass being disposed between the said electrodes (1, 1').

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