NL2007755C2

NL2007755C2 - Apparatus with conductive strip for dust removal.

Info

Publication number: NL2007755C2
Application number: NL2007755A
Authority: NL
Inventors: Willibrordus Nicolaas Johannes Ursem; Elizabeth Johanna Jacoba Vorle-Houben; Johannes Anthonius Wilhelmus Haar
Original assignee: Univ Delft Tech
Priority date: 2011-11-09
Filing date: 2011-11-09
Publication date: 2013-05-13

Description

Apparatus with conductive strip for dust removal Field of the invention

The invention relates to a gas purification system, to an accommodation equipped 5 with such gas purification system, to the use of the purification system, and to a method for purifying gas, especially air, from an accommodation with the use of such gas purification system.

Background of the invention 10 Smut particles, fine dust and exhaust gas particles, of for instance traffic, are a source of pollution with undesired consequences on public health. In order to prevent the exhaust of such particles or in order to remove the exhausted particles, a number of methods are known in the art. For instance, smut filters and catalysts can be used in exhaust systems to reduce the exhaust of such particles. Nevertheless, there may still be 15 some emission of those particles.

Other solutions are for instance described in US6511258. US6511258 describes a method for controlling the amount of ionized gases and/or particles suspended in the air above roads, streets, open spaces or the like. This is done by establishing an electrical field between the top layer of a road, street, open space or the like, and the ionized 20 gases and/or particles. By controlling the electrical field the amount of ionized gases and/or particles can be controlled, which are attracted or repelled. The electrical field is established by making at least the top layer of the surface concerned electrically conductive and connecting it to earth or to one pole of an electrical voltage generator. In order to make the surface electrically charged, a network of conductive metal or a 25 piezoelectric material is employed under the top layer which is placed in contact with earth or a negative voltage generator. The electrically charged top layer may also be composed of a coating which is laid on top of the entire or parts of the surface, for example in the form of road marking or the like. This solution provided by US6511258 is a rather complicated solution that has the disadvantage that only positively charged 30 particles are caught at the surface.

US6106592 describes a gas cleaning process and apparatus for removing solid and liquid aerosols entrained in a gas stream. The gas to be treated is passed through a wetted, electrostatic ally charged filter media. The polarity of the electrostatic charge 2 on the filter media is selected to enhance the removal of captured solid particles from the filter media. The apparatus is readily adaptable to a modular gas cleaning system configuration wherein varying numbers of the apparatus may be operated in parallel to provide a gas cleaning system of any desired gas flow capacity. Fields of 80-800 kV/m 5 are applied.

EP0808660 describes a dust collector which can collect dust, especially fine dust (submicron particles). The dust collector, which removes dust and/or mist contained in a gas, comprises a charging means for charging dust and/or mist contained in a gas, a spraying means for spraying the charged dust or charged mist or spraying a dielectric 10 material to the charged dust or mist, an electric field forming means for forming an electric field for subjecting the dielectric material to dielectric polarization, and a collecting means for collecting the dielectric material which have arrested at least either of the charged dust and charged mist. A field of 500 kV/m is applied.

W02007100254 describes a method for the removal of smut, fine dust and 15 exhaust gas particles from polluted air comprising providing a particle catch arrangement with a charged surface, the particle catch arrangement being arranged to generate a static electric field, wherein the electric field is at least 0.2 kV/m. The invention further provides a particle catch arrangement comprising a surface that can be charged, further comprising a generator arranged to generate charge to the surface that 20 can be charged and to generate a static electric field of at least 0.2 kV/m, wherein the particle catch arrangement is part of, or integrated with, an object comprising street furniture.

Summary of the invention 25 There is a need for good and efficient systems that may remove for instance fine dust and/or germs from gas, especially from air. Prior art systems, such as described above, may not perform sufficiently and/or may further be optimized and/or may be simplified. Therefore, it is an aspect of the invention to provide an alternative gas purification system and method for purifying air, especially for agricultural 30 applications, which preferably further at least partly obviate one or more of above-described drawbacks.

Hence, in a first aspect the invention provides a gas purification system (herein also indicated as “system”) comprising a corona discharge system, the corona discharge 3 system comprising (a) a conductive strip (“first electrode”) with a longitudinal edge comprising tooth structures, wherein the tooth structures have tooth tops with shortest distances (between the tooth tops) selected from the range of 0.5-1000 mm, especially selected from the range of 2-200 mm, and (b) a counter electrode (“second electrode”).

5 The gas purification system may further comprise (c) a voltage generator configured to apply a DC voltage of at least 5 kV, especially at least 10 kV, to the conductive strip.

The conductive strip is used as electrode (herein also indicated as “first electrode”), to which a potential is applied, preferably at least a voltage of 10 kV (i.e. during use, this electrode is positively charged with a voltage of e.g. at least 10 kV). It 10 appears that with such configuration, gas comprising particles between the conductive strip and counter electrode may be purified from particles. It further surprisingly appears that substantially better purification results are obtained than when using wires as electrodes and/or lower power consumption may be achieved. It also surprisingly appears that with the present invention, dimensional freedom is larger than with pure 15 needles, which dimensional freedom may for instance be of relevance when applying the corona discharge system within a channel. Not only are the purification results better, also the energy consumption is lower.

The invention uses the principle that the electrode(s) create a kind of an “electric wind” and an electric charging of the particles in the air, which will be directed by the 20 “electric wind” due to the electric field between the conductive strip (first electrode) and the counter electrode (second electrode). The charged particles may be guided in the direction of the second electrode and deposit (on the second electrode or counter electrode). In this way, gas, such as air, can be purified.

The term “corona discharge” is known in the art. A corona is a process by which 25 a current, perhaps sustained, develops from an electrode with a high potential in a neutral fluid, usually air, by ionizing that fluid so as to create a plasma around the electrode. The ions generated eventually pass charge to nearby areas of lower potential, or recombine to form neutral gas molecules. When the potential gradient is large enough at a point in the fluid, the fluid at that point ionizes and it becomes conductive. 30 If a charged object has a sharp point, the air around that point will be at a much higher gradient than elsewhere. Air (or another gas) near the electrode can become ionized (partially conductive), while regions more distant do not. When the air near the point becomes conductive, it has the effect of increasing the apparent size of the conductor.

4

Since the new conductive region is less sharp (or curved), the ionization may not extend past this local region. Outside of this region of ionization and conductivity, the charged particles slowly find their way to an oppositely charged object and are neutralized. If the geometry and gradient are such that the ionized region continues to 5 grow instead of stopping at a certain radius, a completely conductive path may be formed, resulting in a momentary spark, or a continuous arc.

Electric charges on conductors reside entirely on their external surface (see Faraday cage), and tend to concentrate more around sharp points and edges than on flat surfaces. This means that the electric field generated by charges on a curved conductive 10 point is much stronger than the field generated by the same charge residing on a large smooth spherical conductive shell. When this electric field strength exceeds what is known as the corona discharge inception voltage (CIV) gradient, it ionizes the air about the tip, and a small faint purple jet of plasma can be seen in the dark on the conductive tip. Ionization of the nearby air molecules result in generation of ionized air molecules 15 having the same polarity as that of the charged tip. Subsequently, the tip repels the like-charged ion cloud, and the ion cloud immediately expands due to the repulsion between the ions themselves. This repulsion of ions creates an “electric wind" that emanates from the tip.

The conductive strip comprises an electrically conductive material, such as iron, 20 aluminium, copper, titanium or steel. Also a noble metal, such as ruthenium, rhodium, palladium, silver, osmium, iridium, platinum, or gold, may be applied. Further, also an alloy of two or more of the afore-mentioned metals might be applied. Especially stainless steel may be applied.

The strip has (sharp) features on a longitudinal edge. Such features may for 25 instance be obtained by laser cutting, flow (water jet) cutting, whetting, polishing, punching, die-cutting, etc. The strip will in general have two transversal ends, two longitudinal edges and two longitudinal faces. The distance between the transversal ends define the length of the strip; the distance between the two longitudinal edges the height of the strip, and the distance between the two longitudinal faces the width of the 30 strip. In general, the length is larger than the width and the height, such as least 10 times. Further, in general the height is larger than the width. In an embodiment, the conductive strip has a thickness in the range of 0.1-10 mm, especially in the range of 0.1-5 mm, such as 0.2-2 mm.

5

Especially, the height/length ratio is especially <1 and the width/length ratio is especially <1. Further, preferably the height/width ratio <1. In a specific embodiment, the ratios are height/length ratio <0.1, the width/length ratio <0.1, and the height/width ratio <0.5, such as ranges of 0.001-0.1 and 0.001-0.5, respectively. Especially, the 5 height of the conductive strip is in the range of 1 - 500 mm, especially 2-50 mm (i.e. without tooth structures).

The term conductive strip may in an embodiment also refer to a plurality of conductive strips. In an embodiment, the conductive strips may be arranged parallel. The mutual smallest distance between two parallel arranged conductive strips is 10 preferably at least 200 mm, even more preferably at least 300 mm, yet even more preferably at least 400 mm, like at least 500 mm.

The tooth structures are a kind of needles or other “sharp” structures which are present on one, or optionally both of the longitudinal edges. In the description below, for the sake of argument it is assumed that on one of the longitudinal edges the tooth 15 structures are present. The tooth structure may have the shape of a needle, a tetrahedron, a square pyramid, a pentagonal pyramid, a pyramid having more faces then pentagonal, a star pyramid, a wedge like shape (like a triangular prism), a cone. The wedge like shape may have its ridge parallel to the longitudinal direction, or perpendicular, or under any angle with a longitudinal. The tooth structures can 20 therefore be seen as protrusions or extension on the longitudinal edge. The tooth structures are used to generate corona discharges. In an embodiment, the strip comprises a plurality of different types of tooth structures. The tooth structures can also be seen as extended parts or spikes on the conductive strip. Note that the conductive strip and tooth structures especially are a single unit or entity, i.e. form an integral part 25 (of the same material).

In an embodiment, the tooth structures have tooth structure heights, defined by the difference in height between the tooth tops and valleys between adjacent tooth structures, selected from the range of 0.5-500 mm, preferably in the range of 0.5-200 mm, such as 1-200 mm, like for instance 0.5-50 mm.

30 In an embodiment, the tooth structures have a ratio between the shortest distances and tooth structure height selected from the range of 0.5-1000, especially 1-500, such as 2-200 mm, even more especially 1.5-20, such as 2-5 (i.e. the height of the tooth structures is in general smaller than the spacing between adjacent tooth tops).

6

Alternative to the term “shortest distance”, one might use spacing or interval. The shortest distance between adjacent tooth structures, i.e. between adjacent tooth tops is especially in the range of 0.5-1000, such as 1-500 mm, even more especially 2-200 mm, such as 5-100 mm. Hence, nearest neighbouring tooth structures have (shortest) 5 distances of the tooth tops in the range of 0.5-1000 mm, such as 1-500 mm, etc.

Especially, the tooth structures are sharp structures. In an embodiment, each tooth structure has cross-sectional areas within an intra top distance in the range of larger than 0 mm and equal to 0.5 mm from the tooth top in the range of 10 mm2 or smaller, especially in the range of 2 mm2 and smaller, like 0.5 mm2 and smaller. This implies 10 that starting from the tooth top in a direction of the strip, over a distance of at least 0.5 y mm, the cross-sectional area is at each cross-section 0.5 mm or smaller. In an embodiment, this relative narrow cross-sectional area may even be found beyond the intra-top distance of 0.5 mm, for instance at least 0.5 mm and up to 50-100 % of the tooth structure height (measured from the top). For instance, when the tooth structure 15 has a height of 10 mm, over 0-7.5 mm from the top (i.e. 75 % of the tooth height, measured from the top), has such narrow cross section. In an embodiment, the cross-sectional area is lower than 0.1 mm (especially over 50 % of the tooth height, measured from the top), and the tooth height is 0.5-5 mm. Hence, in an embodiment within said intra top distance, measured from the tooth top, the tooth structure(s) may have the 20 indicated (preferred) cross sectional area(s).

As indicated above, the tooth structures are preferably sharp. The tooth structures especially have a tangent angle (0) between tangents to the to the tooth top within an intra top distance (d6) in the range of larger than 0 mm and equal to 0.5 mm from the tooth top in the range of larger than 0° and equal to or smaller than 135° (in fact this 25 may also be considered blunt), especially in the range of larger than 0° and equal to or smaller than 90°, even more especially the range of larger than 0° and equal to or smaller than 35°. Hence, in an embodiment within said intra top distance, measured from the tooth top, the tooth structure(s) may have the indicated (preferred) tangent angle(s).

30 In general, the sharper the structure, the easier the corona discharge may be generated. In a specific embodiment, the above indicated tangent angle(s) may even be found beyond the intra-top distance of 0.5 mm, for instance at least 0.5 mm and up to 50-100 % of the tooth structure height (measured from the top). For instance, when the 7 tooth structure has a height of 10 mm, over 0-7.5 mm from the top (i.e. 75 % of the tooth height, measured from the top), has such tangent angle(s). In an embodiment, the tangent angle(s) are equal to or smaller than 45° (especially over 50 % of the tooth height, measured from the top), especially equal to or smaller than 35 0 (especially over 5 50 % of the tooth height, measured from the top), and the tooth height is 0.5-5 mm.

The counter electrode is of an electrically conductive material. The same materials as mentioned above, may be applied. The counter electrode may comprise a conductive plate. In another embodiment, the counter electrode comprises a conductive wire mesh, such as a 2D wish mesh, or a 3D wire mesh. In yet another embodiment, 10 which may be combined with the former embodiments, the counter electrode comprises one or more curvatures. Hence, in a specific embodiment, the counter electrode comprises a concave part, such as a concave plate. For instance, the counter electrode may comprise a (concave) conductive plate, having substantially the same length as the first electrode or strip.

15 The counter electrode may in an embodiment be integrated in for instance street furniture, see also below.

Especially, the counter electrode is grounded. Alternatively, the counter electrode has opposite sign of the first electrode. It appears that an electric field is created that may lead the particles to the counter electrode, especially when the conductive strip 20 (first electrode) is configured as positive electrode. Hence, the voltage generator may especially be arranged to generate a positive charge at the conductive strip. In yet a further embodiment, the counter electrode is earthed (grounded). Especially, the conductive strip is configured as positive electrode, the voltage generator may especially be arranged to generate a positive charge at the conductive strip, and the 25 counter electrode is earthed. Optionally, the counter electrode is negatively charged. In an alternative embodiment, the conductive strip is negatively charged and the counter electrode is earthed or positively charged. Preferably, the conductive strip is positively charged, and the counter electrode is earthed or is negatively charged (during use). Preferably, a static electric field is applied (see also below). Hence, in an embodiment, 30 the counter electrode is configured to be grounded during use, and in another embodiment, the counter electrode is configured to be negatively charged during use.

The voltage generator may be any voltage generator suitable for generating a DC voltage. Optionally an AC signal may be superimposed on the DC voltage, as long as 8 (during use of the apparatus) the sign of the signal does not change. The voltage generator may especially be configured to apply (during use of the apparatus) a DC voltage of at least 10 kV to the conductive strip, more preferably a DC voltage of at least 20 kV. Hence, the method of the invention includes applying a DC voltage of at 5 least 10 kV, preferably at least 20 kV to the conductive strip. The voltage applied may not be larger than 50 kV, such as not larger than 40 kV, especially not larger than 30 kV (i.e. especially between the conductive strip and the counter electrode, with the conductive strip having the indicated voltage relative to the counter electrode). Optionally, a negative voltage is applied to the conductive strip. In those instances, the 10 indicated voltages are the same, but with opposite sign. In such instances, the counter electrode may also be grounded. Optionally, the counter electrode is positively charged, see also below. Hence, in such embodiments, the voltage generator may in fact be configured to apply a DC voltage of at least -5 kV (i.e. -5 kV and more negative potentials), especially at least -10 kV (i.e. -10 kV and more negative potentials), to the 15 conductive strip. Hence, in an embodiment, during use, a voltage difference of preferably at least 10 kV is applied between the conductive strip and the counter electrode, with in an embodiment the conductive strip having a higher voltage than the counter electrode. For instance, to the conductive strip a voltage of 10 kV may be applied, while the counter electrode being earthed (grounded).

20 As indicated above, the counter electrode is preferably earthed, although in an embodiment, during use this counter electrode may also be negatively charged. Hence, in an embodiment, the voltage generator may be configured to apply a positive charge to the conductive strip and optionally a negative charge to counter electrode or the counter electrode is earthed. Hence, in an embodiment the conductive strip may be 25 configured as positive electrode and the counter electrode may be earthed.

The voltage generator may further be configured to apply an electric current of at least 5 pA, such as at least 8 pA, more especially at least 10 pA, per meter conductive strip. With lower currents, the discharge may not be created or may not be effective enough. Hence, the method of the invention may further comprise applying an electric 30 current of at least 5 pA, such as at least 8 pA, more especially at least 10 pA, per meter conductive strip 310.

Further, the gas purification system, more precisely the corona discharge system, may be configured to generate a current of at least 0.1 pA, even more especially at least 9 0.2 (iA between the conductive strip and counter electrode, per tooth structure. Hence, assuming a strip with 10 tooth structures, the current generated between the conductive strip and counter electrode may for instance be 1 pA.

Preferably, the corona discharge system may be configured to generate a current 5 of not more than 1A, especially not more than 50 mA, such as not more than 10 mA, especially not more than 5 mA, such as at maximum 500 pA per conductive strip. In yet a further embodiment, the corona discharge system may be configured to generate a current of especially not more than 100 pA between the conductive strip and counter electrode, per tooth structure, such as not more than 40 pA between the conductive 10 strip and counter electrode, per tooth structure.

Due to the application of a positive (or negative) voltage to the conductive strip (during use of the system), an electric field is created between the conductive strip and the conductive counter electrode. Hence, the corona discharge system is especially arranged to create an electric field between the conductive strip (first electrode) and the 15 counter electrode. The electric field is especially in the range of about 0.1-100 kV/m. In a specific embodiment, the electric field is in the range of about 0.5-100 kV/m, even more especially in the range of about 2-100 kV/m, yet even more especially in the range of about 4-100 kV/m. Especially, the electric field may be smaller than about 50 kV/m, more especially smaller than 20 kV/m. The electric field is applied between a 20 first electrode, especially being a positive electrode arranged to generate a corona discharge, and a second electrode, especially being an earthed electrode.

In an embodiment, the tooth structures point in a direction of the counter electrode, i.e. the conductive strip and counter electrode are configured in such a way that the tooth structures point in a direction of the counter electrode. However, in yet 25 another embodiment, the tooth structures may point in another direction. Depending upon the dimensions of the gas purification system and upon gas flow conditions, it may be desirable to select such configuration.

Even when pointing in a different direction, an electrical field may be generated between the conductive strip and the counter electrode. Hence, in another embodiment, 30 the tooth structures point in a direction away from the counter electrode, i.e. the conductive strip and counter electrode are configured in such a way that the tooth structures point in a direction away from the counter electrode.

10

Assuming an earthed counter electrode, preferably, the counter electrode is from any other earthed surface or conductive surface preferably the closest to the conductive ship. Assuming a negatively charged earthed counter electrode and a positively charged conductive strip, the counter electrode is from any other earthed surface or 5 conductive surface preferably the closest to the conductive strip. Assuming a positively charged earthed counter electrode and a negatively charged conductive strip, the counter electrode is from any other earthed surface or conductive surface preferably the closest to the conductive strip. As indicated above, the counter electrode is electrically conductive (as also the conductive strip is).

10 In an embodiment, the conductive strip is attached to bushings, wherein each bushing has a creeping length, wherein the creeping length is configured to be at least 5 mm creeping length per kV DC voltage, especially at least 10 mm creeping length per kV DC voltage.

In a specific embodiment, the gas purification system comprises an elongated gas 15 channel, the elongated gas channel comprising (especially enclosing) the counter electrode and the conductive strip, the gas purification system further comprising a gas transport unit, configured to transport gas through the elongated gas channel. An advantage of such system may for instance also be the relative ease with which gas flow and optionally gas circulation, may controlled.

20 In a specific embodiment, the elongated gas channel, has a first face, a second face opposite of the first face, edges, wherein the elongated gas channel further has a rectangular cross-section, a channel height (hi), and a longitudinal axis; wherein the counter electrode within the elongated gas channel has a counter electrode distance (d3) to the first face, with in an embodiment y2hl<d3<hl; wherein the conductive strip 25 within the elongated gas channel has a first distance (dl) to the first face and a second distance (d2), measured from the tooth tops to the counter electrode, with in an embodiment V^hl<dl<hl and with in an embodiment dl/d2>l, wherein the conductive strip is preferably configured parallel to the edges. The fact that the conductive strip may be arranged parallel to the edges may especially indicate that the plane of the 30 conductive strips is parallel to the edges. In an embodiment, the cross section is square. In yet another embodiment, the cross-section is rectangular, but non-square.

In a specific embodiment, the distances from the conductive strip to each of the first face and the edges are larger than the second distance (d2) from the conductive 11 strip to the counter electrode. Especially such asymmetric configuration may provide the advantages of the invention, although a symmetric arrangement may in an embodiment also be applied.

Hence, in an embodiment, the invention also provides a gas purification system 5 comprising: (a) an elongated gas channel, having a first face, a second face opposite of the first face, edges, wherein the elongated gas channel further has a, preferably rectangular, cross-section, a channel height (hi), and a longitudinal axis; (b) optionally a gas transport unit, configured to transport gas through the elongated gas channel; (c) a corona discharge system comprising: (c.i) a counter electrode within the elongated gas 10 channel, having a counter electrode distance (d3) to the first face (with preferably 1/2hl<d3<hl); (c.ii) a conductive strip within the elongated gas channel, having a first distance (dl) to the first face and a second distance (d2) to the counter electrode (with preferably Vihl<d 1 <h 1 and preferably dl/d2>l), wherein the conductive strip is preferably configured parallel to the edges; wherein d2<dl and d2<ll, with 11 being the 15 distance between the corona discharge electrode and the (nearest) edge; and (c.iii) optionally a voltage generator configured to apply a DC voltage of preferably at least 10 kV to the conductive strip, and especially configured to apply preferably a positive charge to the conductive strip (during use of the system).

Especially however, when seen from the first face in a direction of the second 20 face, the counter electrode and the conductive strip are preferably beyond the first half of the gas, i.e. in general these will be situated in the lower half of the elongated gas channel. Hence, the counter electrode distance d3 to the first face is preferably V2hl<d3<hl, with hi being the height of the elongated gas channel (i.e. the distance between the first face and the second face). Likewise, the first distance dl of the 25 conductive strip to the first face is preferably l/2hl<dl<hl. An asymmetric arrangement of the conductive strip (and the counter electrode) may add to the effect of the purification method, although a symmetric arrangement may in an embodiment also be applied.

Of course the conductive strip and the counter electrode are not in (direct) 30 contact. Their distance to each other is preferably defined as dl/d2>l, with d2 being the second distance of the conductive strip to the counter electrode. The conductive strip is configured parallel to the first face (and the second face and the edge faces, i.e. parallel to the longitudinal axis). However, in an embodiment, dl/d2 is in the range of 0.8-1.2.

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Herein, the term “parallel” and similar terms may especially indicate that an angle with one or more of those faces (or longitudinal axis) is equal to or less than 2°, and especially substantially 0° with one or more of those faces (or longitudinal axis).

The above preferred relations indicate an asymmetric arrangement of the 5 conductive strip, with distances to the counter electrode being shorter than distances to any other conductive or earthed surface. However, in another embodiment, the conductive strip may also be arranged alternatively. For instance, as already indicated above, in an embodiment dl/d2 may be in the range of 0.8-1.2

Herein the term elongated gas channel may especially refer to embodiments 10 wherein the length (longitudinal length) is larger than the width and height of the elongated gas channel. Therefore, the longitudinal axis will be longer than the centre lines (defining width and height) perpendicular to the longitudinal axis.

In general, to make use of gravity, the gas purification system is arranged -during use - such that the second face is the lower face, and the first face is above the 15 second face. Hence, “opposite of the first face” may also indicate below the first face. In general, the first and the second face will be arranged horizontally. Hence, the first face may be the upper face or top face, and the second face may be the lower face or the bottom face. As indicated above, preferably, the cross-section is rectangular. In an embodiment this may include square. The term “cross-section” herein especially refers 20 to the cross-section of the elongated gas channel perpendicular to the longitudinal axis.

As the gas channel preferably has a rectangular cross-section, the first and the second faces are parallel to each other; the edges (or (their) edge faces) are parallel to each other and perpendicular to the first and the second faces. All of those faces are preferably configured parallel to the longitudinal axis.

25 However, the gas channel may also have other types of cross-sections, such as round, triangular, hexagonal, etc.

The gas transport unit is preferably present, although the gas purification system may also be part of a channel through which by natural pull gas flows in a direction from an inlet (or entrance) of the gas channel to an outlet (or exhaust) of the gas 30 channel. However, in general the gas transport unit will be present. The term “gas transport unit” may also relate to a plurality of such units. The gas transport unit may comprise a pump, a ventilator, a blower, etc., or in principle any other means known in 13 the art to generate a gas flow in a channel. Different types of gas transport unit may be applied to lead (flow) the gas (to be purified) through the elongated gas channel.

The conductive strip(s) may be isolated from the elongated gas discharge channel, especially the first face, below which the conductive strip(s) may be 5 positioned. To this end, insulators may be applied. The conductive strip may therefore be arranged between insulators, such as bushings (see also above). Especially, the bushing may essentially consist of Teflon (PTFE).

Especially good results may also be obtained when the counter electrode is removable. In this way, the counter electrode may be cleaned from deposits. In a 10 specific embodiment, the counter electrode is part of a belt of a conveyor belt, wherein the conveyor belt is configured to run the belt through the elongated gas channel. Outside the gas channel, the conveyor belt may be cleaned from deposit(s), and return to the internal of the gas channel, for receipt of new deposition. The belt may for instance comprise stainless steel parts. In an embodiment, the belt is from stainless 15 steel. As will be clear to the person skilled in the art, the counter electrode comprises an electrically conductive material

To further improve the result of the method, at least part of the purified gas may be returned to the gas purification system to be subjected again to the method for purifying air. Hence, the gas purification system may further comprise a gas return 20 system, configured to recirculate at least part of the gas through the elongated gas channel.

In yet a further aspect, the invention provides a method for purifying a gas, especially air, from an accommodation, wherein the accommodation may for instance be selected from the group consisting of a shed, a stable, a sty, a fold and a poultry 25 farm, wherein the method comprises leading gas of the accommodation through the gas purification system as defined herein, while applying a DC voltage of at least 10 kV to the conductive strip, with the conductive strip preferably being the positive electrode, and the counter electrode preferably being earthed.

Especially, the method may comprise applying a DC voltage of at least 20 kV to 30 the conductive strip. As indicated above, the conductive strip may be configured as positive electrode and the counter electrode may be earthed. The method may further comprise applying an electric current of at least 0.2 pA per tooth structure. In yet a further embodiment, the method may further comprise applying a stationary electric 14 field between the conductive strip and the counter electrode in the range of 2-100 kV/m.

The system and method may be applied in existing accommodations such as a shed, a stable, a sty, a fold, or a poultry farm. Hence, the gas purification system and 5 the method for purifying of the invention may especially be applied in agricultural applications. The term “accommodation” may relate to any cage, stable, shed, sty, fold, and also farm, for hosting one or more animals, especially a plurality of animals, such as pigs, cows, horses, goats, pigeons, birdhouse birds, tropical birds, gooses, mink animals or fir animals. The method may be applied within such building, or a unit 10 (comprising the gas purification system, see below), may be provided to which the air of the building is guided for treatment according to the invention. The phrase “method for the removal” and/or the term “purification” include a partial removal and does not necessarily indicate a total removal or total purification.

However, the gas purification system may for instance also be used to remove 15 undesired particles (and optionally gasses) from for instance (gas, especially air, from) a laboratory, a plant, a hospitality area, a clean room, an operation chamber, etc.

Hence, the gas purification system of the invention may in an embodiment be used for cleaning gas, especially air, from an accommodation, such as for instance selected from the group consisting of a shed, a stable, a sty, a fold and a poultry farm, 20 etc., or for instance selected from a laboratory, a plant, a hospitality area, a clean room, and an operation chamber, etc. Especially, the gas purification system of the invention may be used for the removal of fine dust from a gas, especially air, and/or for the removal of germs like bacteria, viruses, spores, fungi (from a gas, especially air) and also for the removal of parasites (from a gas, especially air). More especially, the gas 25 purification system of the invention may be used for the removal of fine dust from a gas and/or for the removal bacteria, viruses and fungi, from a gas, especially air. The gas purification system may be arranged within the accommodation or may be arranged outside the accommodation (in gaseous contact with at least part of the atmosphere within the accommodation).

30 In a specific embodiment, especially when the air is humid or humidified, for instance humidified with a water haze, the gas purification system of the invention may also be used for the removal of ammonia (NH3) and/or undesired odours, and/or other compounds, from a gas. In a specific embodiment, the apparatus further comprises a 15 liquid atomizer or nebulizer, configured to provide a liquid haze, such as a water haze between the conductive strip and the counter electrode. The haze may be generated within the gas elongated channel, but may also be generated upstream from the inlet of the elongated gas channel. Hence, the invention also provides in a further aspect an 5 accommodation, such as selected from the group consisting of a shed, a stable, a sty, a fold and a poultry farm, comprising the gas purification system, as described herein, for purifying the air of the accommodation.

The invention further provides a particle catch arrangement comprising the gas purification system as defined herein, wherein at least part of the gas purification 10 system is part of, or integrated with, an object comprising street furniture, for instance a sound barrier, a crash barrier, a tunnel wall, a road sign, a traffic information system, a street lamp or a traffic light.

For instance, the counter electrode may be part of such street furniture. This may also enclose embodiment wherein a part of street furniture is integrated in the gas 15 purification system. For instance, part of a tunnel wall might be used as counter electrode. In a specific embodiment, the counter electrode is attached to or integrated in one or more of a sound barrier, a crash barrier, and a tunnel. In a specific embodiment, the gas purification system comprises the conductive strip and a plate-like counter electrode, wherein both are arranged parallel to the (local) earth’s surface, wherein in 20 an embodiment the counter electrode comprises a curved element, which may be attached to ore integrated in for instance a tunnel wall. The term “substantially” herein, such as in “substantially parallel” or in “substantially consists”, will be understood by the person skilled in the art. The term “substantially” may also include embodiments with “entirely”, “completely”, “all”, etc. Hence, in embodiments the adjective 25 substantially may also be removed. Where applicable, the term “substantially” may also relate to 90% or higher, such as 95% or higher, especially 99% or higher, even more especially 99.5% or higher, including 100%. The term “comprise” includes also embodiments wherein the term “comprises” means “consists of’.

Furthermore, the terms first, second, third and the like in the description and in 30 the claims, are used for distinguishing between similar elements and not necessarily for describing a sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of 16 the invention described herein are capable of operation in other sequences than described or illustrated herein.

The apparatus herein are amongst others described during operation. As will be clear to the person skilled in the art, the invention is not limited to methods of operation 5 or devices in operation.

It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as 10 limiting the claim. Use of the verb "to comprise" and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. The article "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The invention may be implemented by means of hardware comprising several distinct elements, and by means of a suitably programmed computer. In the 15 device or apparatus claims enumerating several means, several of these means may be embodied by one and the same item of hardware. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

The invention further applies to an apparatus comprising one or more of the 20 characterising features described in the description and/or shown in the attached drawings. The invention further pertains to a method or process comprising one or more of the characterising features described in the description and/or shown in the attached drawings.

The various aspects discussed in this patent can be combined in order to provide 25 additional advantages. Furthermore, some of the features can form the basis for one or more divisional applications.

Brief description of the drawings

Embodiments of the invention will now be described, by way of example only, 30 with reference to the accompanying schematic drawings in which corresponding reference symbols indicate corresponding parts, and in which:

Figs, la-li schematically depict some aspect of possible variants of the conductive strip; 17

Figs. 2a-2b schematically depict some embodiments of the gas purification system;

Fig. 3 schematically depicts some embodiments of possible bushings;

Figs. 4a-4e schematically depicts some embodiment and variants thereon of the 5 gas purification system of the invention;

Figs. 5a-5c schematically depicts some applications of the gas purification system of the invention;

Figs. 6a-6b schematically depict some further applications of the gas purification system; and 10 7a-7d schematically depict some further variants.

The drawings are not necessarily on scale

Description of preferred embodiments

Figs, la-li schematically depict a non-limiting number of embodiments of 15 the conductive strip, indicated with reference 310. Other variants may be possible as well.

The conductive strip 310 has a longitudinal edge 313 comprising tooth stmctures 150. The tooth structures 150 have tooth tops 151 with shortest distances dt, such as selected from the range of 0.5-1000 mm, especially selected from the range of 2-200 20 mm. Hence, the tooth tops 151 have shortest distances dt (between adjacent or nearest tooth tops 151) selected for instance from the range of 5-100 mm.

The conductive strip 310 has (first) longitudinal edge 313 and oppositely arranged thereof second longitudinal edge 314. These define height H of the conductive strip 310. Further, conductive strip 310 comprises transversal edges 312, arranged 25 opposite of each other, which may be arranged parallel to each other, and which define length L of the conductive strip 310. Further, conductive strip 310 comprises third longitudinal edges 315 (herein also indicated as longitudinal faces), with may be arranged parallel, and which define width W of the conductive strip 310.

Especially, the ratios are H/L<1 and W/L<1. Further, preferably the ratio H/W<1. 30 In a specific embodiment, the ratios are H/L<0.1, W/L<0.1, and H/W<0.5, such as ranges of 0.001-0.1 and 0.001-0.5, respectively.

Especially, the transverse edge 312, the second longitudinal edge 314, and the third longitudinal edges 315 are perpendicular to each other.

18

The tooth structures 150 have tooth structure heights hi, defined by the difference in height between the tooth tops 151 and valleys 152 between adjacent tooth structures 150, selected from the range of 0.5-500 mm, preferably in the range of 1-200 mm. The length between the tooth valleys 152 of first longitudinal edge 313 and the 5 second longitudinal edge 314 is the height H of the conductive strip 310 (see also above). Reference 158 indicates a tooth structure longitudinal axis.

In an embodiment, the longitudinal axes 158 point in the same direction. In yet another embodiment, the longitudinal axes 158 point in different directions (not depicted). Especially, the conductive strips 310 comprises a plurality of subsets of tooth 10 structures 150, wherein the longitudinal axes 158 within one subset point in one direction, but wherein the longitudinal axes 158 of tooth structures 150 of different subsets point in different directions.

Fig. lb schematically depicts a possible cross section of the conductive strip 310, wherein the tooth structures 150 may be wedge shaped, with a ridge 159 of the wedge 15 parallel to (first) longitudinal edge 313 and second longitudinal edge 314. Longitudinal axis 158 may be perpendicular to the ridge 159. Assuming the transverse edges 312 being parallel, and the third longitudinal edges 315 being parallel, the longitudinal axis 158 is parallel to the transverse edges 312 and third longitudinal edges 315.

Fig. lc schematically depicts a possible cross section of the conductive strip 310, 20 wherein the tooth structures 150 may be needle shaped. Reference 157 indicates the tooth surface. Note that this surface is curved.

Referring to figs, la-lc, the conductive strip 310 may thus have a rectangular cross-section (when not including the tooth structures 150).

Fig. Id further indicates the sharpness/narrowness of the tooth structures 150. 25 Within a distance d6 from the tooth top 151, the area of the cross section, indicated with refer 154 is small, i.e. the cross-sectional area is small, such as 10 mm2 or less, especially 2 mm2 or less, within a distance d6 of at least 0.5 mm from the tooth top 151. Beyond this distance d6, the cross-sectional area may increase, but the first 0.5 mm the tooth top 151 is narrow. This narrow part may also be indicated as top part 153. Hence, 30 any cross-section (perpendicular to longitudinal axis 158) within the range d6 from the tooth top may have this small cross-sectional area. This may show the sharpness of the tooth structures 150.

Fig. le schematically depicts a tooth structure having a pyramidal shape.

19

Fig. If schematically depicts that within distance d6 from the tooth top 151, see also above, tangents 155 to the tooth surface 157 have a tangent angle 0. Within d6, the tangent angle 0 between tangents 155 are especially smaller than 135°. This may especially apply to tooth structures having a circular cross-section (at least within 5 distance d6 from the tooth top 151). Hence, especially the tooth structures 150 have a conical shape (optionally a curved conical shape, as shown in fig. lc, Id and If).

Figs, lg-li schematically depict some variants, with short shortest distances dt (fig. lg) and with relatively larger shortest distances dt (figs, lh-li). In figs lg-lh, the longitudinal edge 313 is substantially planer, except for the tooth structures 150; in fig. 10 li, the longitudinal edge 313 has curvatures, with sharp tooth structures 150.

Note that in a variant, also second longitudinal edge 314 may comprise tooth structures.

Figs. 2a-2b schematically depict embodiments wherein the tooth structures 150 point in a direction of the counter electrode 340. This is a preferred embodiment, 15 though other options are also possible. As can be seen in those figures, the longitudinal axes 158 of the tooth structures, when extended, “touch” the counter electrode 340. In fig. 2b, the counter electrode 340 comprises a concave part 341. Reference 330 refers to a voltage generator.

Fig. 3 schematically depicts possible bushings 320. The bushings have creeping 20 distances cd.

Figs. 4a-4e schematically depicts an embodiment of the gas purification system of the invention. The gas purification system is indicated with reference 10 and comprises an elongated gas channel 100, a gas transport unit 200, and a corona discharge system 300.

25 The schematic drawing 4a is a cross-sectional view in the length direction of the elongated gas channel 100 (“side view”); fig. 4b is a cross-sectional view in the plane of the elongated gas channel 100 (“top view”); fig. 4c is a front view of the elongated gas channel 100.

The elongated gas channel 100 has a first face 101 (which may also be indicated 30 as top face), a second face 102 (which may also be indicated as bottom face) opposite of the first face 101, and edges (or edge faces) 110. The elongated gas channel 100 further has a rectangular cross-section 105. The two opposite edges 110 are further indicated with references 110a and 110b, respectively. The elongated gas channel 100 20 has a channel height hi (“height” hi) and a longitudinal axis 1. The height hi of the channel may for instance be in the range of 0.1-2 m, such as 0.2-1 m. The elongated gas channel 100 has a channel inlet 103, for introduction of gas 20, and a channel outlet 104, for exhaust of purified gas 21. The length, indicated with reference 11, of the 5 elongated gas channel 100 between the channel inlet 103 and channel outlet 104 may for instance be in the range of 0.2-100 m, like 0.5-20 m, even more especially at least 1 m.

The walls are indicates as first wall 201, which has the first surface 101, second wall 202, which has the second surface 102, and edge walls 210, with the edges or edge 10 surfaces 110. The first surface, the edge surfaces 110 and the second surface 102 enclose the channel internal or channel volume 106.

First wall 201, the second wall 202, and the edge walls 210 are preferably of a low or non-conductive material. Relative to the counter electrode, their conductivity is preferably at least 1000 times lower, or even at least 100.000 lower. Of course, in 15 embodiments where the second face 102 includes the counter electrode 340, the conductivity of at least part of the second wall is high, as it should be electrical conductive.

As indicated above, the gas purification system 10 further comprises gas transport unit 200. The gas transport unit 200 is configured to transport gas 20 through the 20 elongated gas channel 100. The gas transport unit may be a fan, a rotator, a ventilator, a pump, etc.

As indicated above, the gas purification system 10 further comprises corona discharge system 300. This corona discharge system comprises a counter electrode 340 within the elongated gas channel 100, i.e. at least partly, but in general entirely, 25 configured within the internal 106 of the elongated gas channel. The counter electrode 340 is configured at a distance from the first face 101. The counter electrode 340 has a counter electrode distance d3 to the first face 101, with in this schematically depicted embodiment 1Ahl<d3<hl. Hence, when seen from the first face 101, the counter electrode is beyond the middle of the elongated gas channel 100 (“behind the 30 longitudinal axis”). The counter electrode is thus, in an embodiment, closer to the second surface 102 than the first surface 101.

21

In an embodiment, not depicted, the second surface 102 may comprise the counter electrode 340. In another embodiment, not depicted, the counter electrode 340 may form the second surface 102. Therefore, d3 may also be equal to hi.

The distance between the counter electrode 340 and the first surface 102 is 5 indicated with reference d4. This distance may be a few millimetres, although, as indicted in the previous paragraph, d4 may also be zero when the second surface 102 comprises the counter electrode 340 or the counter electrode 340 form the second surface 102.

The gas purification system 10, or more precisely the corona discharge system 10 300, further comprises conductive strip 310 within the elongated gas channel 100. The conductive strip 310 has a first distance dl to the first face 101 and a second distance d2, measured from the tooth top 150, to the counter electrode 304.

Like the counter electrode 340, the conductive strip 310 is preferably arranged beyond the longitudinal axis, when seen from the first surface 101. Hence, for the 15 conductive strip applies in this schematically depicted embodiment Vyi^dlchl. Of course, dl^hl, because otherwise the conductive strip 310 would be in physical contact with the second surface 102. Further, for the conductive strip 310 applies dl/d2>l. Hence, the conductive strip 310 is closer to the counter electrode 340 than to the first surface 101. Therefore, in a specific embodiment the distances from the conductive 20 strip (310) to each of the first face (101) and the edges (or edge faces) are larger than the second distance to the counter electrode (304). Especially such configuration appears to provide good purification results.

Preferably, the conductive strip 310 is configured parallel to the first face 101, the second face 102, and the edges 105. In other words, the conductive strip 310 is 25 configured parallel to the longitudinal axis 1.

The gas purification system 10, or more precisely the corona discharge system 300, further comprises a voltage generator 330, especially configured to apply a DC voltage of at least 10 kV to the conductive strip 310. Good results were obtained with a thickness (w) of the conductive strip 310 of about 0.3 mm and a voltage applied in the 30 range of 20-35 kV.

Fig. 4b schematically depicts the same embodiment, but now in cross-sectional top view. Note that in fact two conductive strips 310 are applied, both parallel with the longitudinal axis 1, which are connected with connecting wires 311. Those connecting 22 wires 311 are optional. Instead of connecting wires 311, also conductive strips may be applied, see also fig. 4c-4e. Fig. 4b schematically depicts also a variant, with dashed lines, wherein the conductive strip 310 is an endless strip, surrounding two or more (in this schematically depicted embodiment 4) bushings 320. This endless conductive strip 5 with tooth structures is indicated with reference 310’,311’. Hence, in an embodiment, the conductive strip with tooth structures is an endless strip, preferably surrounding the two or more bushings. The creeping distance(s) is(are) of course calculated from the conductive strip.

As will be clear to the person skilled in the art, alternatively only one conductive 10 strip 310 may be applied, or more than 2 conductive strips 310 may be applied. Especially, the distance d5 between the conductive strips is at least 20 cm (as indicated above, the mutual smallest distance between two parallel arranged conductive strips is preferably at least 200 mm), more especially at least 30 cm, even more especially at least 40 cm. The edge walls 210 have edge faces, which are respectively indicated with 15 first edge face 110a and second edge face 110b. The distance between the edge faces (i.e. 110a and 110b) is indicated with width w. Hence, per 20 cm width or more, a conductive strip 310 may be applied. Further, more than one conductive strip 310 may be arranged behind one another, for instance when the elongated gas channel 100 is long. The length 11 of the channel may for instance be in the range of 1-50 m. For 20 instance, in such channel 20 conductive strips 310 may be arranged between one another, with longitudinal distance between one another of for instance at least 20 cm, such as at least 40 cm (especially also equal to d5).

In fig. 4b, reference 2 indicates the centre line of the elongated gas channel 100. Reference 12 indicates the distance from the conductive strip 310 to the edge surface of 25 the (nearest) edge 110. Preferably, 12>d2, although other configurations may be possible as well.

Fig. 4b schematically depicts an embodiment wherein the conductive strips 310 are connected via connecting wires 311 (which are also electrically conductive). When the method of the invention further comprise applying an electric current of at least 5 30 pA, such as at least 8 pA, more especially at least 10 pA, per meter conductive strip 310, and conductive strips are connected with connecting wire, the length in meters of the entire conductive circuit should be used as length. Hence, the invention in this embodiment might also include Hence, applying an electric current of at least 5 pA, 23 such as at least 8 pA, more especially at least 10 pA, per meter conductive strip 310 (in this embodiment the length in meters of first conductive strip 310a, and second conductive strip 310b). Fig. 4b, and also figs. 4e, embodiments wherein the conductive 310 strip(s) is (are) configured parallel to the edge faces (i.e. 110a and 110b).

5 Fig. 4c schematically depicts another cross-sectional view. From this drawing can be seen that the elongated gas channel 100 has a rectangular cross-section. Here, the cross-section perpendicular to the longitudinal axis 1 is meant. This figures shows that the distance from the conductive strip 310 to the closest edge face 110, indicated with 12, is longer than d2. Also the distance dl of the conductive strip 310 to the first face 10 101 is longer than d2. This is also shown by depicting radius rl. Especially, when the radius rl=d2, preferably no other items of the gas transport unit (other than the optional connection wire and an insulator 320), are present within that radius, but are more remote than rl (=d2).

Fig. 4c also schematically depicts a specific variant, wherein an endless conveyor 15 belt 400 is applied. The conveyor belt 400 comprises a belt 401. The conveyor belt 400 is configured to run the belt 401, or at least part of it, through the elongated gas channel 100. Further, the belt 401 is configured as counter electrode 340 or comprises the counter electrode 340. A conveyor belt (or belt conveyor) in general consists of two or more pulleys, with a continuous loop of material (the “belt”) that rotates about them. 20 The term “endless” is used in order to indicate that the belt is in a continuous loop or rotation (around two or more pulleys). For instance, the belt 401 may comprise stainless steel parts.

Fig. 4d schematically depicts a 3D view of an embodiment of the elongated gas channel 100, again with conveyor belt 400. The conveyor belt 400 is configured to 25 have the upper part of the belt 401 run within the elongated gas channel 100 and the lower part of the belt 401 run outside the elongated gas channel. Find dust and/or other particles, like germs, that deposit on the counter electrode, comprises by the belt 401, thus also leaves the elongated gas channel 100 and can be removed from the belt 401 outside the elongated gas channel 100. In a specific embodiment, the conveyor belt 400 30 may be configured to run its belt 401 within the elongated gas channel counter current with the gas flow. This may add to turbulence. Turbulence is desired, in order to maximize deposition of particles, such as fine dust and/or germs.

24

Fig. 4e schematically depicts arts of the gas purification system 10. Reference 250 refers to a wire grid that may be applied at the outlet 104, for instance for protection. Reference 260 refers to a receiver part, that may receive deposited particles that are scraped of the belt 401, and reference 270 refers to a front plate.

5 Other type of elongated gas channels 100 may however also be applied, like round (cross-sectional) or oval (cross-sectional gas channels). Preferably, the distance between the conductive strip and the counter electrode is shorter than the distance between the conductive strip and any other electrically conductive or earthed element.

Figs. 5a-5c schematically depict embodiments wherein an accommodation 50 is 10 equipped with the gas purification system 10 of the invention. For instance, gas, such as air, from the accommodation may be exhausted from the accommodation 50 via the gas purification system. Purified gas 21 may then be exhausted (fig. 5a). However, the gas purification system 10 may also be applied to purify the gas 20 from the accommodation, and return purified gas 21 back into the accommodation 50. Fig. 5e 15 schematically depicts an embodiment of accommodation 50 including the gas purification system 10 for for instance cleaning air.

Fig. 5c schematically depict an application of the gas purification system 10, including a gas return 15. In this way, the purification may even be increased. The return 15 can be used to circulate at least part of the purified gas back into the gas 20 purification system 10.

Figs 6a-6b schematically depict a particle catch arrangement 1010, comprising the gas purification system 10, wherein part of the gas purification system may be integrated in street furniture 1000. In those drawings, a tunnel 1060 with tunnel wall 1064 is shown, as well as a road 1025 through the tunnel 1060. For instance, the gas 25 purification system 10, especially the counter electrode, may be attached to the tunnel wall 1064, see fig. 6a. Fig. 6b schematically depicts an embodiment, wherein the unit as depicted in figs. 4a-4e or 7a are applied.

Fig. 7a schematically depicts an embodiment wherein instead of conductive strips 310, conductive wires 310b are applied, with bushings 320 as defined in one of the 30 preferred embodiments. All embodiments described above may apply, but now wires are applied. Figs 7b-7c schematically depict similar variants, in fig. 7b without the channel, analogous to fig 6a, and in fig. 7c, with channel, analogous to fig. 6b, with again instead of conductive strips 310, conductive wires 310b are applied, with 25 bushings 320 as defined in one of the preferred embodiments. The wire may consist of a material as indicated above, or may comprise tungsten.

Fig. 7d schematically depicts an alternative conductive strip (310) with a longitudinal edge (313) comprising a longitudinal tooth structure (150), wherein the 5 tooth structure (150) has a tooth top (151). The tooth structure may have a ridge 159 over a substantial part of the length L of the conductive strip, such as over 80-100 % of the length L.

The gas purification system may further comprise a control unit (not depicted), configured to control the corona discharge system, especially the voltage generator, and 10 the gas transport unit.

Experimental

Comparative measurements were performed on a wire and strips according to the invention. Fine dust PM 10 was measured in a channel with rectangular shape, with a 15 flow speed of 4.7 m/s. The length of the conductive strips or wire was 4.45 m. The counter electrode, aluminium, had a surface of 2.9 m2; the voltage was over 32 kV.

The following results were obtained:

Type dt (mm) type Reduction (%) Remarks

Wire - - <60 Relative high power consumption

Tooth structures 15 lg 60 Relative low power consumption

Tooth structures 50 lh 60 Relative low power consumption

Tooth structures 50 li 61 Relative low power consumption

Tooth structure - 7d <50 Relative low power consumption 20 Hence, with lower power consumption, the reduction can be as high or even higher.

Claims

A gas cleaning system (10) comprising a corona discharge system (300), the corona discharge system (300) comprising: a. A conductive strip (310) with a longitudinal edge (313) comprising tooth structures (150), the tooth structures (150) have tooth tips (151) with shortest distances (dt) selected in the range of 2-200 mm; b. a counter electrode (340); and 10 c. a voltage generator (330) arranged to apply a DC voltage of at least 10 kV to the conductive strip (310).

The gas cleaning system (10) of claim 1, wherein the tooth structures (150) have tooth structure heights (h1) defined by the difference in height between the tooth tips (151) and valleys (152) between adjacent tooth structures (150) selected in the Range of 0.5-500 mm, preferably in the range of 1-200 mm.

The gas cleaning system (10) according to claim 2, which has a ratio between shortest distances (dt) and tooth structure heights (h1) selected in the range of 0.5-1000, in particular 1-500, more in particular 1.5-20.

The gas cleaning system (10) according to any of the preceding claims, wherein the tooth tips (151) have shortest distances (dt) selected in the range of 5-100 mm.

The gas cleaning system (10) according to any of the preceding claims, wherein each tooth structure (150) has cross-sectional areas (154) in the range of 10 mm 2 or less within an intra-top distance (d 6) of the tant cup (151) in the range greater than 0 mm and equal to 0.5 mm.

The gas cleaning system (10) according to any of the preceding claims, wherein a tangent angle (0) between tangents (156) on the tooth tip (151) within an intra-tip distance (d6) in the range of greater than 0 mm and equal to 0.5 mm of the tooth tip (151) is in the range of greater than 0 ° and equal to or less than 135 °, in particular in the range of greater than 0 ° and equal to or less than 35 °.

The gas cleaning system (10) of any one of the preceding, wherein the conductive strip (310) has a thickness (W) in the range of 0.1-10 mm, in particular in the range of 0.1-5 mm.

The gas cleaning system (10) according to any of the preceding claims, wherein the tooth structures (150) point in a direction of the counter electrode (340).

The gas cleaning system (10) of any one of the preceding claims, wherein the counter electrode (340) comprises a concave portion (341).

The gas cleaning system (10) according to any of the preceding claims 1-9, wherein the counter electrode (340) is grounded.

The gas cleaning system (10) according to any of the preceding claims 1-9, wherein the counter electrode (340) is negatively charged.

The gas cleaning system (10) of any preceding claim, wherein the conductive strip (310) is attached to insulators (34), wherein each insulator (34) has a creep distance (cd), the creep distance (cd) being selected to provide at least 5 mm creep distance (cd) per kV DC voltage, in particular at least 10 mm creep distance (cd) per kV DC voltage.

13. The gas cleaning system (10) according to any one of the preceding claims, comprising an elongated gas channel (100), wherein the elongated gas channel (100) comprises the counter-electrode (340) and the conductive strip (310), wherein the gas cleaning system (10) furthermore comprises a gas transport unit (200) arranged to transport gas (20) through the elongated gas channel (100).

The gas cleaning system (10) according to claim 13, wherein the elongated gas channel (100) has a first face (101), a second face (102) opposite the first face (101), and walls (110), the elongated gas channel (100) further has a rectangular cross-section (105), a channel height (h1), and a longitudinal axis (1); wherein the counter electrode (340) within the elongated gas channel (100) has a counter electrode distance (d3) from the first surface (101), with '/ 2h 1 <d3 <h 1; wherein the conductive strip (310) has a first distance (d1) from the first plane (101) within the elongated gas channel (100) and a second distance (d2) measured from the tooth tips (151) to the counter electrode (304) with '/ ih 1 <d 1 <h 1 and d 1 / d 2> 1, the conductive strip being arranged parallel to the walls (110);

The gas cleaning system (10) according to any of claims 13-14, wherein the counter electrode (340) is part of a belt (401) of a conveyor belt (400), the conveyor belt (400) being arranged around the belt (401) by transporting the elongated gas channel (100).

The gas cleaning system (10) according to any of the preceding claims 14-15, wherein the distances from the conductive strip (310) to each of the first surface (101) and the walls (110) are greater than the second distance (d2) to the counter electrode (304).

The gas cleaning system (10) according to any of the preceding claims 13-16, further comprising a gas return system (15) arranged to recycle at least a portion of the gas through the elongated gas channel (100).

An accommodation (50) selected from the group consisting of a shed, a stable, a (pig) pen, and a poultry farm, further comprising the gas purification system according to any of claims 1-17 for purifying the air from the accommodation.

A particle collection system (1010) comprising the gas cleaning system (10) according to any one of the preceding claims 1-17, wherein at least a part of the gas cleaning system (10) is part of, or integrated with, an object comprising street furniture (1000), for example, a sound barrier, a guard rail, a tunnel wall, a traffic sign, a traffic information system, a street lamp, or a traffic light.

20. Use of the gas purification system according to any of claims 1-17, for purifying air from an accommodation (50) selected from the group consisting of a barn, a stable, a (pig) pen, and a poultry farm.

Use of the gas cleaning system according to any of claims 1-17, for removing particulate matter from a gas.

22. Use of the gas cleaning system according to any of claims 1-17, for removing bacteria, viruses, spores, fungi and parasites, in particular bacteria, viruses and fungi, from a gas.

A method of purifying air from an accommodation (50) selected from the group consisting of a shed, a stable, a (pig) pen, and a poultry farm, comprising passing gas from the accommodation through the gas purification system according to one of claims 1-17, using a DC voltage of at least 10 kV on the conductive strip (310).

The method of claim 23, comprising applying a DC voltage of at least 20 kV to the conductive strip (310).

The method of any one of claims 23-24, wherein the conductive strip (310) is arranged as a positive electrode and wherein the counter electrode (340) is grounded.

The method of any of claims 23-25, further comprising applying an electric current of at least 0.2 pA per tooth structure.

The method of any one of claims 23-26, comprising applying a stationary electric field between the conductive strip (310) and the counter electrode (340) in the range of 2-100 kV / m.