EP2611522A1

EP2611522A1 - Device and method for generating a barrier discharge in a gas flow

Info

Publication number: EP2611522A1
Application number: EP11760414.0A
Authority: EP
Inventors: Andreas Albrecht; Eckart Theophile
Original assignee: Reinhausen Plasma GmbH
Current assignee: Relyon Plasma GmbH
Priority date: 2010-09-02
Filing date: 2011-08-03
Publication date: 2013-07-10
Also published as: DE102010044252B4; US8696996B2; WO2012028408A1; CN103153435A; US20130177473A1; DE102010044252A1

Abstract

The invention relates to a device and method for generating a barrier discharge in a gas flow, comprising a reactor chamber permeable by the gas from an inflow side to an outflow side, a first electrode, a dielectric that shields the reactor chamber against the first electrode, and a second electrode, wherein the second and the first electrode can be switched to connect to a voltage source. In order to briefly expose a greater portion of the gas flow led through the reactor chamber, preferably the entire gas flow, to a plasma, according to the invention at least two discharge elements associated with the first electrode and made of electrically conductive material protrude at least partially into the reactor chamber, the discharge elements are electrically insulated from each other and from the first and second electrodes, and the second electrode is disposed relative to the discharge elements such that discharges occur between the discharge elements and the second electrode in the reactor chamber.

Description

Apparatus and method for generating a

Barrier discharge in a gas stream

The invention relates to a device and a method for generating a barrier discharge in a gas stream comprising a reactor space which from an inflow side to a

Outflow of the gas can be flowed through, a first

Electrode, a dielectric which shields the reactor space at least against the first electrode and a second

Electrode, wherein the second and the first electrode are switchable to a voltage source.

Modern oxidative air purification processes are increasingly using non-thermal plasmas to destroy and reduce pollutants, such as odors, allergens and germs. These plasmas produce highly reactive radicals that contribute to a wide range of gasborne pollutants

Environmental conditions can implement.

For more than 100 years, the plasma treatment of air according to the principle of dielectrically impeded discharge, also known as barrier discharge known. Large volume non-thermal plasmas can be easily generated by the dielectrically impeded discharge. Between the electrodes connected to a high alternating voltage is the dielectric, usually made of glass. The dielectric impedes the movement of the electrodes and eventually interrupts them. The electrodes are not only stopped in their movement to the anode by the dielectric, but dammed up, creating an opposing field to the

Electrode current driving external field, the

in turn grows until the outer field and the opposing field just compensate and the electrode current comes to a standstill. The properties of the dielectric

Barrier material, as well as their shape, in addition to the arrangement of the inner and outer electrode determine the Appearance of the discharge, which is characterized by the emergence of single discharges, the so-called filaments. These filaments occur for a short time in large numbers. They are normally distributed over the entire area of the plasma generating electrode.

As a plasma generator for the oxidative treatment of air in particular the so-called "Siemens tube" is used. The Siemens tube consists of a tubular dielectric, preferably of quartz glass or boro-O-silicate. The inner wall of the tubular dielectric is lined with an inner electrode. The existing of conductive material

Inner electrode is tight and possible without air gap on the inner glass surface. On the lateral surface of the

Dielektrikums an outer electrode is arranged, which is formed by a close-meshed, for example, steel mesh. Will now be a high alternating voltage of

For example, 3 - 6 KV applied to the inner and outer electrodes, it comes to the dielectrically impeded discharge. It generates ions and ozone (O3 and Oi).

In the plasma treatment of a gas stream with a "Siemens tube" an air flow is passed through the tubular dielectric. For this purpose, a at the inner electrode

Plasma ignited. The plasma at the inner electrode arises only in the outer layers of the air flow, the

get in direct contact with the inner electrode. By far the greater part of the air flow reacts only with the ozone and the oxygen ions that are generated during the discharge.

The outer layers of the air flow which come into direct contact with the plasma become more effective

Pollutants, especially freed from odors and germs, because in plasma the highest energy in the form of free

Electrons, radicals and ions are present. Furthermore The plasma generates an intense UV radiation in the wavelength range <300 nm, which can effectively break up the molecular bonds of air pollutants. A problem in the plasma treatment of a gas stream according to the prior art is that the inner electrode by pollutants contained in the gas stream quickly

dirty and thus loses its effectiveness. An exchange of contaminated inner electrode is possible only with great effort and an interruption of the plasma treatment.

From DE 197 17 160 Al a generic device for the plasma-chemical conversion of exhaust gases is known in which a barrier discharge is generated in the flowing gas. The device comprises a reactor space, which is flowed through in the longitudinal direction from an inflow side to an outflow side of the exhaust gas to be treated. At the first electrode, a dielectric is attached, which shields the reactor space from the first electrode. A second electrode is disposed on the dielectric in the reactor space and as

open-cut sheet formed, wherein the second electrode is switchable to the first electrode. For this purpose, the two electrodes with a

AC voltage source connected. When creating the

AC voltage occurs in the gap between the

Structures of the broken second electrode and the

Dielectric for the formation of the gas discharge. The

Gas discharge is thus generated primarily near the surface of the dielectric. The exhaust gas flowing past is swirled by the perforated sheet and thereby briefly enters the excitation range of the plasma. The second boundary of the reactor space is formed by a wall. No gas discharge is formed between the dielectric and the wall closing off the reactor space. As a result, depending on the distance of the wall more or less large parts of the gas flow does not come directly to the Plasma in contact and therefore flow untreated through the reactor space.

In all devices belonging to the state of the art, the gas flow passed through the reactor space only partially comes into direct contact with the plasma, while the remaining gas stream is enriched only with the ozone produced in the plasma and is thereby purified.

Starting from this prior art, the invention is therefore based on the object to provide a device for generating a barrier discharge in a gas stream, in which a larger part of the guided through the reactor space gas stream, preferably the entire gas stream is briefly exposed to a plasma. In addition, a method for generating a barrier discharge in such

Device are proposed.

This object is achieved in a device of the type mentioned in that at least two of the first electrode associated discharge elements of electrically conductive material at least partially protrude into the reactor space, the discharge elements are electrically isolated from each other and against the first and second electrodes and the second electrode is arranged to the discharge elements such that discharges between the

Discharge elements and the second electrode in the

Reactor space arise.

A method for achieving the object results from the features of independent claim 12.

The discharge elements projecting at least partially into the reactor space are electrically separated from the upstream first electrode by the dielectric. The second electrode, also referred to as counterelectrode, is preferably located in or on the inner wall of the reactor space opposite to the one in the reactor space

extending Dischargeernernenten.

The capacitive coupling of the discharge elements causes a uniform distribution of the filaments between the

Discharge elements and the counter electrode connected to the second electrode. The complete galvanic decoupling of the discharge elements causes them to be capacitively raised to a level. This has the advantage that the gas discharge at one of the discharge elements does not affect the electrical potential of the adjacent discharge element

changed. As a result, a gas discharge can take place at several gas discharge elements at the same time.

The second electrode is arranged to the discharge elements such that discharges occur between the discharge elements and the second electrode in the reactor space. Simultaneous ignition makes it possible to create a discharge curtain over the cross-section of the flow path through which the entire gas flow is passed while being exposed directly to the plasma. An advantage of the arrangement is the local arrangement of the filaments. While with a planar dielectric barrier, the filaments from the entire surface (local electrodes are characterized by high contact resistance of

Neighbor element separated) are ignited, the discharge sites can be focused by the discharge elements.

The capacitive coupling of the discharge elements to the first electrode preferably takes place in that the

Discharge elements are arranged on the dielectric, which shields the reactor space against the first electrode. To the Gas discharge between the discharge elements and the second electrode to favor, are the discharge elements

preferably aligned in the direction of the second electrode. The discharge between the discharge elements and the second electrode can be further improved by the fact that at least the projecting into the reactor space part of the

Discharge elements is formed pin-shaped, wherein the pins in the reactor chamber preferably terminate in a tip. As a result, a concentration or

Focusing the charge causes at the free end of the pins or their tips. At the same time the power consumption of the device and the ozone emission are reduced. The pin-shaped discharge elements allow a uniform distribution of the gas discharges in the direction of the second electrode. Furthermore, the distance between the free ends or tips of the pin-shaped discharge elements to the second electrode via the

Pin length determine and thereby the homogeneity of the

Improve discharge. If the discharge elements as

Biegeformteile or bending punched parts are configured, the distance to the second electrode and the homogeneity of the discharge by their shape and arrangement can be improved.

When the discharge elements are partially embedded in the dielectric, the reactor space against the first

Shielding electrode, the gas discharge elements can be connected during casting of the dielectric with this in one operation. In particular, the dielectric

be performed completely as a plastic injection molded part, for example, PEEK, PA, PTFE, PE or similar materials, wherein the discharge elements and / or the first and second electrodes are molded as an insert. The discharge elements and the electrodes are made of conductive material, in particular copper, stainless steel or other electrically highly conductive materials. The

Discharge elements can be prefabricated as stampings or bent moldings.

Depending on the manufacturing process, ceramic, glass, plastic or a composite material may be considered as a dielectric.

The second electrode becomes structurally advantageous,

arranged in particular in the form of a ring electrode on the inner surface of the reactor space. In order to protect the second electrode from negative influences of the gas flow in the reactor space, in particular from oxidation and contamination, it is provided in an embodiment of the device according to the invention that a dielectric also shields the reactor space from the second electrode. It can be the same thing

act integrally formed dielectric that the first electrode shields against the reactor space. This one-piece dielectric can form part of a part of the

Forming flow channels and at the same time record the plasma-generating components.

Particularly effective and targeted is exposed to the reactor space flowing through the gas stream of the barrier discharge when between the inflow and outflow of the

Reactor space gas guide means are arranged, which the

Divide gas stream into several streams and each sub-stream is assigned at least one discharge element. Preferred gas guidance means comprise a plurality of flow channels, in particular concentrically arranged with respect to the longitudinal axis of a tubular reactor space. The discharge elements are either

arranged immediately adjacent to the outputs of the flow channels or in the flow channels themselves. The

Flow channels preferably all have one

matching length and geometry. The arrangement of Discharge elements with respect to the outputs of the flow channels or within the flow channels also preferably coincides in all flow channels.

If the discharge elements are arranged adjacent to the outputs, the second electrode is preferably arranged as an annular electrode, which is arranged in the flow direction immediately behind the outputs concentric with these. If the discharge elements are arranged within the flow channels, the second electrode is preferably designed in several parts, and in each case a part of the second electrode is arranged in each flow channel. Each part of the second electrode must be connected to the voltage source.

In order to expose each partial flow as effectively as possible to the plasma, each of them has a plan view of the flow cross-section

Flow channel the second electrode and each

Arranged discharge element opposite. It is harmless if the discharge elements and the second electrode are arranged slightly offset from each other in the direction of the flow channel. Particularly in the case of a round flow cross-section of the flow channels, the arrangement of the electrode and the arrangement opposite one another with respect to the flow cross-section in plan view

Discharge elements achieved a particularly uniform formation of the plasma.

A particularly effective management of the gas flow in the

Reactor space is achieved in that a tubular reactor space has a molded part, in particular a

Plastic injection molded part. In the molding are the

Flow channels arranged for the gas flowing through the reactor space, so that this be in the flow channels be the flow of the reactor space from the inlet to Outflow side into one of the number of flow channels

corresponding number of sub-streams is divided

Preferably, all outlets are the

Flow channels on a concentric circle around di

Longitudinal axis of the tubular reactor space.

Also concentric with the longitudinal axis of the tubular

Reactor space is arranged adjacent to each outlet at least one discharge element. The discharge elements are preferably on a concentric circle with

smaller diameter than the concentric circle on which the outlets of the flow channels are located.

The second electrode surrounds all outlets of the

Flow channels immediately downstream of the outlets, so that the discharges between the

Discharge elements and the second electrode as

Form discharge curtains in front of the outlets of the flow channels.

The invention of embodiments will be explained. Show it:

Figure 1 is a schematic view of an inventive

Device for generating a barrier discharge in a gas stream,

2a shows the structure of a device according to the invention for installation in a gas line in section,

FIG. 2b shows the device according to FIG. 1 in side view,

Figure 3a shows another embodiment of a

Device according to the invention as a substructure variant in side view and Figure 3b as a sectional view along the line AA of Figure 3a.

FIG. 1 shows a device (1) for generating a

Barrier discharge in a gas stream (2) through a reactor space (3) from an inflow side (3a) to a

Outflow side (3b) is guided.

The reactor space is delimited on its underside by a laminar dielectric (5) which shields the reactor space from the plate-shaped first electrode (4a) attached to its underside.

On the upper side, the reactor space (3) is delimited by a further dielectric (6) which also shields the reactor space (3) against the second plate-shaped electrode (4b). The second dielectric (6) serves to protect the second

Electrode (4b) against contamination. In principle, therefore, the device (1) can also be carried out without the second dielectric (6).

Laterally, the reactor space is closed by not shown in the sectional view of Figure 1 side walls.

Uniformly over the surface of the plate-shaped first electrode (4a) are several rows of ten each

arranged pin-shaped discharge elements (7). The

pin-shaped discharge elements (7) are partially embedded in the dielectric (5) and partially protrude into the

Reactor space (3) into it. Here are the pen-shaped

Discharge elements (7) in the direction of the second electrode (4b) aligned.

The first and second electrodes (4a, 4b) are against one

Voltage source (8) connected to an AC voltage or pulsed DC voltage between lkV to 20 kV in one

Frequency range of 50 Hz - 500 kHz generated. The pin-shaped discharge elements (7), however, by the dielectric (5), which consists in particular of plastic, electrically against each other and against the first and second

Electrode (4a, 4b) isolated.

Between the discharge elements (7) and the second electrode (4b) aligned with the second electrode (4b), discharges are produced, through which the gas flow (2)

is passed. Due to the on the

Flow cross-section of the reactor chamber (3) tuned

Arrangement of the discharge elements (7) and the second

Electrode (4b), the gas stream (2) is completely transiently transferred to the plasma. The dielectric barrier in the form of the dielectric (5) causes all the pin-shaped discharge elements (7) to be raised to a charge level. A gas discharge at the top of one of the

Discharge elements (7) does not change the electrical

Potential of adjacent pin-shaped discharge elements (7), so that at the same time gas discharges at several

Discharge elements (7) can take place.

Figure 2 shows an embodiment of a device according to the invention for installation in a pipeline, of the

Gas flow (2) is flowed through. The gas stream (2) flows into the device (1) at the inflow side (3a) and flows out of the outflow side (3b) after the plasma treatment

Device (1) off. The device (1) can be connected, for example, by flanges to the pipeline (not shown) at the inflow and outflow sides (3a, 3b). It can therefore swap quickly and easily, especially for cleaning purposes. The reactor space (3) is of a hollow cylindrical tube (9) with circular cylindrical on the inflow and outflow (3a, 3b)

Limited flow cross section. Between the inflow and outflow side (3a, 3b), a shaped part (11) is arranged transversely to the flow direction of the gas flow (2) into the reactor space (3). Concentric with the longitudinal axis (15) of the device (1) a total of 14 flow channels (12) are arranged in the molded part (11), which defines the gas flow (2) in the by the length of the flow channels (12)

Division of the reactor space (3) into several partial streams (13). In the central region of the molded part (11) surrounded by the flow channels (12), a plate-shaped first electrode (4a) is arranged in the direction of the inflow side (3a) of the reactor chamber (3). The longitudinal axis (15) of the device (1) passes through the center of the first electrode (4a). The first electrode (4a) is in one

cylindrical blind hole (16) in the molded part (11) embedded. Immediately adjacent to the exits (17) each

Flow channel (12) is in each case a pin-shaped

Discharge element (7) arranged in the molded part (11). A portion of each pin-shaped discharge element (7) is embedded in the molded part (11) of dielectric material, while the remaining portion (7a) projects into the reactor space (3). The section (7a) projecting into the reactor space (3) can be seen in FIG. The pin-shaped discharge elements (7) are parallel to the axis and concentric with the longitudinal axis (15) embedded in the molded part (11). The second electrode (4b) is formed as a ring electrode and abuts the inner surface of the tube (9) on the outflow side (3b).

In the plan view of the through the exits (17) each

Flow channel (12) defined flow cross-section of the flow channels (12) are the second electrode (4b) and the respective associated discharge element (7, 7a)

opposite sides of the flow channel (12)

arranged between each in the reactor space (3) projecting portion (7 a) of the discharge element (7) and the annular second electrode (4 b) in the axial direction (15) is a slight offset, however, harmless for the formation of the discharges (18) between each discharge element (7, 7a) and the second electrode (4b).

The existing of dielectric material bottom surface of the blind hole (16) shields the reactor space (3) against the first electrode (4a) in the blind hole (16). Preferably, the dead space opposite the flow direction in the blind hole (16) is also filled with dielectric material. From the side view according to FIG. 2 b, it can be seen that, before each outlet, the discharges (18) are similar to one

Discharge curtain between the discharge elements (7, 7a) and the outputs (17) surrounding the second electrode (4b) form. As a result, the partial streams (13) of the gas stream (2) by acting as a gas guide means

Flow channels (12) passed through the plasma.

As a result, the entire gas flow (2) the plasma

immediately exposed. Figures 3a, 3b show a further embodiment of a device (1) according to the invention, which is designed as an underbody device. The housing comprising the reactor space (3) is from below on a plate, for example one

Tabletop fastened by screws or clips. On the inflow side (3a) of the reactor chamber (3) there is a sufficiently dimensioned free space (20), the one

electrically operated, merely indicated fan (21) receives, the fan wheel rotates about a not shown, vertical axis in the representation. The fan (21) forces the gas flow of the air from the inflow side (3a) in the direction of the outflow side (3b) through the reactor space (3).

From the side wall of the free space (20) extend

a total of three flow channels (12) in the direction of

Outflow side (3b) of the reactor chamber (3), as in the embodiment of Figure 2a, 2b, the gas stream (2) in split several partial streams (13). Above the exits (17) are in the housing (19) of the device (1) three

arranged pin-shaped discharge elements (7) whose

Sections (7a) immediately adjacent above the outputs (17) protrude into the reactor space (3).

The dielectric (5) in the form of the housing (19)

dielectric material shields the embedded first

Electrode (4a) against the reactor space (3) from. Below the outlets (17), downstream of the outlets (17), the second electrode (4b) is located in the direction of flow

plate-shaped electrode is configured.

As can be seen in particular from FIG. 3 a, the plate-shaped second electrode (4b) extends over the entire width of the reactor space (3) on the outflow side (3b). Furthermore, it can be seen from FIG

Flow cross sections of the flow channels (12), the second electrode (4b) and the three discharge elements (7, 7a) are arranged on opposite sides of the flow channels (12). This arrangement of the second electrode to the discharge elements (7, 7a) ensures that the discharges (18) like a curtain between the

Forming discharge elements (7, 7a) and the second electrode (4b) and the entire in part streams (13) divided gas stream (2) is passed through the plasma.

The purified gas stream (2) leaves the device (1) on the outflow side (3b). LIST OF REFERENCE NUMBERS

No. Designation

1 device

2 gas flow

3 reactor space

3 a inflow side

3 b Out of the flow side

4 a first electrode

4b second electrode

5 dielectric

6 dielectric

7 discharge elements

7 a section

Entladungselernent

8 voltage source

9 pipe

10 -

11 molding

12 flow channels

13 partial flow

14 -

15 longitudinal axis

16 blind hole

17 outputs

18 discharges (plasma)

19 housing

20 free space

21 fans

Claims

Claims:

1. Device for generating a barrier discharge in

a gas flow comprising a reactor space which can be traversed from an inflow side to an outflow side of the gas, a first electrode

a dielectric that shields the reactor space at least against the first electrode,

a second electrode, wherein the second and the first electrode are switchable against a voltage source, characterized in that at least two of the first electrode (4a) associated discharge elements (7, 7a) of electrically conductive material at least partially into the reactor chamber (3) protrude .

the discharge elements (7, 7a) electrically

against each other and against the first and second electrodes (4a, 4b) are isolated and

the second electrode (4b) to the

Discharge elements (7, 7a) is arranged such that discharges (18) between the discharge elements (7, 7a) and the second electrode (4 b) in the

Reactor space (3) arise.

2. Apparatus according to claim 1, characterized in that the discharge elements (7, 7a) on the dielectric (5) are arranged, which shields the reactor space (3) against the first electrode (4a).

3. Apparatus according to claim 1 or 2, characterized

in that the discharge elements (7, 7a) are aligned in the direction of the second electrode (4b)

4. Device according to one of claims 1 to 3, characterized in that the discharge elements (7, 7a) are partially embedded in the dielectric (5), which shields the reactor space (3) against the first electrode (4a).

5. Apparatus according to claim 4, characterized in that at least in the reactor space (3) protruding into

Section (7 a) of the discharge elements (7) is pin-shaped.

6. Device according to one of claims 1 to 5, characterized

characterized in that the discharge elements (7, 7a) leak in the reactor space (3) in a tip or edge.

7. Device according to one of claims 1 to 6, characterized

characterized in that the dielectric comprising the

Reactor space (3) against the first and or second electrode (4a, 4b) shields, is designed as a casting.

8. Device according to one of claims 1 to 7, characterized

in that the first electrode (4a) is attached to the dielectric (5) or is arranged directly adjacent thereto.

9. Device according to one of claims 1 to 8, characterized

characterized in that the second electrode (4b) is disposed on an inner surface of the reactor space (3).

10. Device according to one of claims 1 to 9, characterized in that a dielectric (6) the reactor chamber (3) and the second electrode (4b) shields 11. Device according to one of claims 1 to 10, characterized in that between the inflow and Outlet side (3a, b) of the reactor chamber (3) arranged gas guide means the gas stream (2) into a plurality of partial streams (13) and each sub-stream (13) at least one discharge element (7, 7a) is assigned.

Apparatus according to claim 11, characterized in that the gas guide means more, in particular

concentric with the longitudinal axis (15) of a tubular

Reactor space (3) arranged flow channels (12).

Apparatus according to claim 12, characterized in that in a plan view of the flow cross-section of each flow channel (12) the second electrode (4b) and each discharge element (7, 7a) are arranged on opposite sides of the flow channel (12).

A method for generating a barrier discharge in a gas stream passing through a reactor space of a

The inflow side is guided to an outflow side, the reactor space having a first electrode, a dielectric shielding the reactor space from the first electrode and a second electrode, characterized in that at least the first electrode (4a) is capacitively connected to at least two of the first electrode (4a). 4a)

associated discharge elements (7, 7a)

electrically conductive material which at least partially into the reactor space (3) protrude, is coupled,

Discharges (18) are generated between the discharge elements (7, 7a) and the second electrode (4b), in which the second and the first electrode (4a, 4b) against a voltage source (8) connected and the

Discharge elements (7, 7a) electrically against each other and against the first and second electrodes (4a, 4b) are isolated and the gas stream (2) in the reactor space (3) by means of guide means (12) forcibly by the

Discharges (18) are passed between the discharge elements (7, 7a) and the second electrode (4b) in the reactor space (3).