TECHNICAL FIELD OF THE INVENTION

The present invention relates to the field of air and liquid purifying. More precisely, the present invention relates to an apparatus for purifying air or liquids by means of emission of charged particles, and a method of purifying air or liquids.

BACKGROUND

Airborne particles of sub-micro class constitute a health issue in virtually any indoor environment. Especially in larger cities, where pollutants from traffic severely reduces the quality of the air, there is a great need for air purification to protect people from inhaling smog or other forms of aerial pollutions. Particularly, to protect people from the increasing amounts of PM1 particles (particles of less than 1 μιτι in size), which are known to contribute to a large amount of deadly diseases like heart attacks, lung cancer, dementia, emphysema, etc.

Today the most common way to get rid of these ultra-fine particles is by air filters, where the air in an indoor environment is circulated, by means of a fan, and processed through a filter designed to filter out particles in the air. This solution is in some systems combined with an ionizer that electrically charges particles in the air before the air is led via a filter adapted to extract the ionized particles from the air flowing through the filter. Drawbacks with any solution using filter and fan is that the fan produces noise, which is inconvenient because the system is often placed in rooms such as bedrooms and living rooms, and that the filter becomes less efficient over time as particles are gathered in it. Moreover, it is known that purifiers relying on filter technology are prone to some general drawbacks in terms of dynamic range (i.e. one must select an appropriate filter for a specific particle size) and also in terms of removing PM1 particles.

GB 2304576 describes a type or air ionizer, which is a device for generating electrons and emitting these electrons into a micro-environment. The device disclosed therein utilizes carbon filament threads in order to ionize the air of the micro-environment, i.e. as emitter components, and making the consequently negatively charged particles settle on positively charged surfaces of the micro-environment. However, such solutions are associated with manufacturing complexity and robustness issues since they are prone to malfunction due to the emitter solution, with carbon filament threads, being sensitive and generally associated with manufacturing complications. Thus, there is a need for a new solution which is robust, simple to manufacture and still efficient.

Even though different types of air purifying devices are available on the market today there is accordingly still a need for a device for purifying air that enables purification of particles of various sizes and in the whole volume of a micro-environment in an efficient and reliable manner. SUMMARY OF THE INVENTION

It is an object of the present invention to provide a particle purifier that provides a good distribution of charged particles in a micro-environment in order to purify air or liquids, and which alleviates all or at least some of the above-discussed drawbacks of the presently known solutions.

This object is achieved by means of an apparatus for purifying air or liquids and a method as defined in the appended independent claims.

According to an aspect of the present invention, there is provided an apparatus comprising: a power unit and an emitter piece electrically connected to the power unit, wherein the emitter piece is a composite piece comprising a matrix material that is reinforced with electrically conductive fibres, and where the composite piece is adapted to produce charged particles in a surrounding environment when electrified.

Hereby, an energy efficient and versatile particle purifier is presented, capable of reducing contaminants and pollutants in air or liquids. Moreover, the inventive particle purifier is even capable of removing more than 90% of the ultrafine particles, down to 20 nanometres, in a surrounding environment, without generating any hazardous amounts of ozone in the process. The emitter piece is preferably connected to the power unit by means of a suitable electrical conductor, such as e.g. a copper, silver, or gold wire. Preferably, the electrical conductor is arranged to have an electrical resistance in the range of 0.1 to 30 Ohm. This may be achieved by suitably controlling the cross-sectional area (i.e. the thickness or diameter of the wire).

Further, the term power unit is to be interpreted as a device for supplying electrical operating power to the emitter piece. For example, the power unit may a battery, super capacitor, an electrical adapter configured to convert a voltage or current from an external source (e.g. power outlet) to an operating voltage or current, or similar.

The term composite piece is to be understood as the matrix material is combined with the electrically conductive fibres, so to form a composite material, i.e. a material having a matrix/binder material (e.g. a polymer or ceramic) reinforced with fibres of an electrically conductive material (e.g. carbon fibres, graphene fibres, carbon nanotubes, aluminium fibres).

Accordingly, combined may be understood as that the polymer is mixed with the fibres and/or which are moulded or integrated into a single piece of fibre reinforced matrix material. Stated differently, the electrically conductive fibres and the matrix material (binder material) may be considered as constituent materials which together make up the composite piece. In more detail, the matrix material surrounds and supports the reinforcement fibres by

maintaining their relative positions in the composite piece.

The present invention is at least partly based on the realization that in order to increase the efficiency of the particle purifier, one must carefully consider the electrical and material properties of the emitter piece (may also be referred to as transmitter piece) used for emitting electrons to the surrounding molecules whereby negative ions are produced. Thus, the present inventors realized that an emitter piece in the form of a composite piece (such as e.g. a carbon fibre reinforced polymer, CFRP) can make for a highly efficient particle purifying apparatus. In more detail, the composite piece proved to be an excellent ionizing component (ionizing emitter) whereby many unexpected and advantageous effects in terms of reliability, efficiency and costs could be achieved. The present inventors further came to the insight that the composite piece has an unprecedented high concentration of fibre thread ends per volume unit, as compared to prior known particle purifying solutions, which makes the composite piece particularly suitable as an emitter piece in an apparatus for purifying air or liquids. More specifically, the high concentration of fibre thread ends, makes it possible to produce charged particles at a very high rate at relatively low power levels (voltage levels) and with relatively small emitter pieces, leading to overall reduced size of the apparatus and increased cost effectiveness.

Furthermore, the inventive apparatus is capable of purifying air at an high purity level, removing more than 90% of particulate contaminants down to 20 nanometres in size, without generating any hazardous amount of ozone.

In accordance with an embodiment of the present invention, the composite piece has an electrical resistance in the range of 5-30 MOhm in at least one direction. The electrical resistance in a direction is to be understood as the electrical resistance from a first end to an opposite end along a substantially straight line through the composite piece body. Moreover, the electrical resistance of the composite piece is preferably in the range of 10 - 30 MOhm in at least one direction, or more preferably in the range of 19 - 26 MOhm, and most preferably in the range of 20 - 25 MOhm. In an

embodiment, the electrical resistance in at least two directions is in the range of 5 - 30 MOhm. It was realized by the present inventors, that the electrical properties of the emitter piece were an important aspect of the apparatus, and that the above mentioned resistance ranges resulted in a surprising effect in terms of ratio of particulate contaminants removed from a surrounding environment, without exceeding recommended thresholds for ozone formation.

Thus, in accordance with another embodiment of the invention, the matrix material is an electrically insulating material. Further, the matrix material of the composite piece may be a polymer, preferably a thermoset polymer, such as e.g. epoxy resin. Moreover, in an embodiment of the invention the proportion of electrically conductive fibre in relation to the matrix material in the composite 25% to 80%, by volume. Stated differently, the ratio, by volume, of electrically conductive fibre to matrix material in the composite piece is 25-80%, such as for example 40-60%, 50-70%, or 35-65%. By having a fibre to matrix material ratio within these ranges, surprising and

advantageous effects in terms of reduction of particulate contaminants can be achieved.

Further, in accordance with an embodiment of the present invention, the emitter piece is cuboidal. In the embodiments where the emitter piece is cuboidal, the electrical resistance in the emitter piece, in all three orthogonal directions may be within the range of 15 - 30 MOhm, or preferably within the range of 19 - 26 MOhm. In some embodiments the piece may be a three- dimensional polygon or of a spherical shape. Furthermore, a first side of the emitter piece may be 1 -50 mm, a second side of the emitter piece may be 1 - 50 mm and a third side of the emitter piece may be 1 -50 mm. A cuboidal shape of the composite piece provides edges to the piece where sought properties relating to emission of charged particles are achieved. A cuboidal shape has proven to achieve reduction of particles in the surrounding environment of sizes all the way below 0.1 μιτι. Alternatively, the composite piece may be a 3D polygon of any other shape to achieve similar properties.

Yet further, the composite piece may comprise at least one treated surface, the treated surface having a roughened surface structure. This may for example be as a result from cutting a larger disc into smaller piece by e.g. water jet cutting. A roughened surface structure provides more sharp edges which enhances the properties related to emission/generation of charged particles. This is another advantage of the composite piece, as the surfaces may be roughened by relatively simple and cost effective production means in order to further increase the efficiency of the apparatus. The surface roughness of the at least one treated surface may for example have a roughness value of Ra > 6.0 μιτι.

Moreover, in yet another embodiment of the present invention, the at least one treated surface of the emitter piece may further be treated such that a plurality of threads of the composite piece are exposed. This may for example be as a result from cutting a larger disc into smaller piece by e.g. water jet cutting, from subsequent treatment in the form of abrasive blasting or chemical abrasion/etching. Treating the surface of the emitter piece such that the surface structure is roughened and loosened threads, or at least thread portions, are exposed further enhances the properties relating to emission of charged particles. In other words, a large number of individual thread ends are protruding from a surface of the composite piece, creating a very large number of "sharp edges" which enhances the properties related to emission/generation of charged particles. The length of the thread portions that are exposed may for example be a few microns (e.g. 1 -5 μιτι) up to 1 mm (e.g. up to 500-1000 μηη).

According to yet another embodiment of the invention, the emitter piece is connected to the power unit by means of a first electrode having a first polarity, and wherein the apparatus further comprises a housing for containing at least a portion of the first electrode and the power unit; and wherein a point, situated outside of the housing is connected to a second electrode having a second polarity opposite that of the first polarity in order to polarize an area around the point such that aggregated charged particles attach to the area. The point may for example be a point on a collection plate. Hereby, a compact and easy-to-handle solution is provided, where all of the particulate contaminants are gathered in a general area for facilitating cleaning and maintenance.

The electrically conductive fibres may be a carbon fibre arranged in a random structure in the composite piece. Alternatively, the electrically conductive fibre may be a carbon fibre arranged in a woven structure in the composite piece. Thus, the emitter piece may comprise a carbon fibre reinforced polymer. The electrically conductive fibres may also be (other) carbonaceous fibres such as graphene fibres or a carbon nanotube fibres or a combination of any of the mentioned fibres. However, other non- carbonaceous fibres are feasible, such as e.g. aluminium fibres or non-/poorly conducting substrate fibres coated/embedded with metallic or carbon elements.

According to a second aspect of the invention, there is provided a method for purifying air or liquids, comprising: providing an apparatus according to any one of the embodiments discussed with respect to the previous aspect of the invention, and electrifying the emitter piece via the power unit such that the emitter piece is electrically charged in order to produce charged particles in a surrounding environment.

With this aspect of the invention, similar advantages and preferred features are present as in the previously discussed aspects of the invention, and vice versa.

These and other features and advantages of the present invention will in the following be further clarified with reference to the embodiments described hereinafter. BRIEF DESCRIPTION OF THE DRAWINGS

For exemplifying purposes, the invention will be described in closer detail in the following with reference to embodiments thereof illustrated in the attached drawings, wherein:

Fig. 1 is a perspective view schematic illustration of an apparatus according to an embodiment of the invention;

Fig. 2 is a perspective view schematic illustration of an emitter piece according to an embodiment of the invention;

Fig. 3 is a schematic flow chart representation of a method according to an embodiment of the invention.

The skilled reader readily realizes that the sizes of layers, elements and/or regions may be exaggerated for illustrative purposes and, thus, may be provided to illustrate the general structures of embodiments of the present invention. DETAILED DESCRIPTION

In the following detailed description, an embodiment of the present invention will be described. However, it is to be understood that features or specific elements and details of the apparatus may be readily exchangeable by equivalent means unless specifically indicated. Even though in the following description, numerous specific details are set forth to provide a more thorough understanding of the present invention, it will be apparent to one skilled in the art that the present invention may be practiced without these specific details. In other instances, well known constructions or functions are not described in detail, so as not to obscure the present invention. Like reference numerals refer to like elements throughout.

Fig. 1 schematically illustrates a partial cut-through sectional view of apparatus according to an embodiment of the invention. The apparatus typically includes a power source 1 which is connected to an emitter piece 3 and arranged to supply the emitter piece 3 with power via an electrode 4. The apparatus 10 according to this embodiment has two electrodes in the form of a cathode 4 and an anode 6, with the cathode 4 here being connected to an emitter piece 3. The apparatus here has one single emitter piece 3

(composite piece), here in the form of a carbon fibre reinforced epoxy resin, however the apparatus may include a plurality of emitter pieces (not shown) in other embodiments to the invention.

The power source 1 is here a converter that is plugged in to the power grid, via a power cable 9, to get a 230/120 V, 50/60 Hz AC input and convert said input to a 12 V DC output that is provided to the emitter piece 3.

However, the power source 1 can be designed to provide power of various voltages and using various different solutions, for instance from battery power. The power is then converted to a voltage across the emitter piece 3, that is sufficiently high to achieve proper generation of negatively charged particles into the micro-environment, however also sufficiently low for the process to essentially not give rise to hazardous levels of ozone in the surrounding air. The voltage range used in this embodiment is between 5-10 kV, preferably 7 kV, as voltages above 12 kV are known to give rise to a considerable amount of ozone in the surrounding air.

The power source 1 is here arranged in a housing 5, with the cathode

4 connected to the emitter piece 3 via an electrically conductive column through a hole in the housing 5, and the anode 6 is connected through a separate hole in the housing 5 to a point 7 outside of the housing 5. This enables for the point 7 outside of the housing to be in contact to a surface, such as a wall or the ceiling, of the micro-environment where it is placed. By positively charging a surface of the micro-environment the impurity particles that become negatively charged from combining with the generated negative particles (which already haven't become large enough to be affected by gravity) will be collected at this surface, thus not only purifying the impurity particles but also ridding the air in the micro-environment from the purified particles.

Fig. 2 shows a schematic perspective view illustration of an emitter piece 3 of the apparatus according to an embodiment of the invention. The emitter piece 3 is, as mentioned, a composite piece, here in the form of a carbon fibre reinforced epoxy resin having a rectangular cuboidal shape with sides of length 15 mm, 30 mm and 4 mm. However, virtually a composite piece comprising an electrically conductive fibre reinforced matrix material of any size is feasible. For instance, the shape of the composite piece 3 may be 3D polygonal with any number of sides, spherical or rhombic. The sides of the cuboid or 3D polygon may be individual pieces of carbon fibre reinforced epoxy resin that are attached to each other using an adhesive to form the emitter piece 3, or the emitter piece 3 may alternatively be made in one single piece of carbon fibre reinforced epoxy resin. The fibre material (e.g. carbon fibre) is typically placed in a mould where the polymer (e.g. epoxy) is added. After the polymer has set the composite piece is taken out of the mould, and if needed, cut according to the desired dimensions. However, as the skilled person readily realizes, there are various other applicable manufacturing techniques and several moulding techniques that are applicable to produce the composite piece 3.

The surface of the emitter piece 3 is preferably treated to achieve a rough surface structure (e.g. with a surface roughness value, Ra, larger than 6.0 μιτι), which may be done by blasting but alternatively using various other techniques as well. The act of roughening up the surface of the emitter piece 3 loosens the structure of the electrically conductive fibre filaments and thus creates more loose threads and ends which enhances the effect widely known as "corona discharging" and thus enhances the distribution of emitted negatively charged particles into the micro-environment. This furthermore provides for the possibility for making small emitter pieces 3, e.g. having a volume of less than 1 cm ³ , with proper ionizing capability.

Fig. 3 is a schematic flow chart representation of a method for purifying air or liquids in accordance with an embodiment of the present invention. The method comprises providing S301 an apparatus 10 according to any one of the previously discussed embodiments of the invention, e.g. the apparatus 10 discussed in reference to Fig. 1 . Further, in use, the emitter piece 3 is electrified via the power unit so that the emitter piece 3 is electrically charged and thereby enabled to produce charged particles in a surrounding

environment.

The person skilled in the art realizes that the present invention by no means is limited to the embodiments described above. On the contrary, many modifications and variations are possible within the scope of the appended claims. For example, the apparatus can comprise any number of electrodes and emitter pieces in combination to scale up the system. Additionally, variations to the disclosed embodiments can be understood and affected by the skilled person in practicing the claimed invention, from a study of the drawings, the disclosure and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality.