FIELD OF THE INVENTION

The present invention relates to a photocatalytic oxidation apparatus.

BACKGROUND OF THE INVENTION

Photocatalytic oxidation (PCO) systems are known in the art for decomposing harmful pollutants to produce less harmful chemicals. Such photocatalytic oxidation systems generally comprise a light source and a photocatalytic material. The light source is arranged to shine light onto the catalytic material to cause a reaction to occur that produces radicals. The radicals degrade pollutants, for example, volatile organic compounds (VOCs), to produce less harmful chemicals such as water (H ₂ 0) and carbon dioxide (C0 ₂ ). However, it can prove difficult to orientate the light source relative to the photocatalytic material such that 'shadowing' is avoided, wherein part of the light emitted by the light source is blocked from reaching the photocatalytic material thus reducing the efficiency of the PCO system.

An air cleaner is disclosed in US201/50075384A1. The air cleaner has a filter material which includes an optical fibre layer. The filter material is coated with a

photocatalyst. The photocatalyst is irradiated by a light source to activate the photocatalyst to kill harmful microorganisms.

CN102626614 discloses a method of preparing a photocatalytic material. The method comprises coating an optical fibre with titanium dioxide.

It can prove difficult to arrange the photocatalytic material of the prior art such that it is correctly configured to enable decomposition of pollutants.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a photocatalytic oxidation apparatus which substantially alleviates or overcomes one or more of the problems mentioned above.

The invention is defined by the independent claims. The dependent claims define advantageous embodiments.

According to the present invention, there is provided a photocatalytic oxidation apparatus comprising: a light source with a light emitting surface and the light source comprising a lamp operable to generate a light output; and, a photocatalytic layer adjacent the light emitting surface comprising photocatalytic material and a plurality of light transmittal regions configured to allow light emitted from the light emitting surface to irradiate photocatalytic material adjacent the light transmittal regions.

At least one of the light transmittal regions comprises a space or gap in the photocatalytic layer.

The photocatalytic oxidation apparatus is in particular in the form of an air purifier or filter, a water purifier or filter, an air conditioner or an HVAC system.

The light transmittal regions of the photocatalytic layer allow for light emitted from the light emitting surface to irradiate a portion of the photocatalytic material that is spaced from the light emitting surface. The light transmittal regions therefore allow for hydroxyl radicals to be formed that can react with the pollutants in fluid flowing over the surface of the photocatalytic material, regardless of the thickness of the photocatalytic material.

The gap or space in the photocatalytic layer may include a gap or space in the photocatalytic material comprised by the layer.

In one embodiment, each light transmittal region comprises a gap in the photocatalytic layer.

In one embodiment, the photocatalytic material partially covers the light emitting surface.

The light transmittal regions may be arranged in a regular array. In one embodiment, the light transmittal regions are each configured to allow light emitted from the light emitting surface to irradiate a portion of the photocatalytic material spaced from the light emitting surface.

The light emitting surface may comprise a planar surface and may comprise a plate-shaped light guide. In another embodiment, the light source comprises a cylindrical light guide.

In one embodiment, the light source comprises an optical fibre. The light emitting surface may comprise a plurality of light outcoupling structures. The light outcoupling structures may each comprise a roughened surface area of the light source. In one embodiment, each light transmittal region overlies a light outcoupling structure.

The photocatalytic material may comprise titanium dioxide. The light source may comprise a light generator. Preferably, the light generator comprises an ultraviolet light generator.

According to the present invention, there is also provided a fluid treatment apparatus comprising a photocatalytic oxidation apparatus according to the invention.

In one embodiment, the fluid treatment device comprises first and second photocatalytic oxidation apparatus, wherein at least a portion of the light emitting surface of the first photocatalytic oxidation apparatus faces the light emitting surface of the second photocatalytic oxidation apparatus.

According to the present invention, there is also provided a filter comprising a plurality of filter fibres, wherein each filter fibre comprises a photocatalytic oxidation apparatus according to the invention, wherein the light source of each photocatalytic oxidation apparatus comprises an optical fibre. Preferably, the filter is a HEPA filter.

These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Fig. 1 is a schematic cross-sectional side view of a photocatalytic oxidation apparatus, shown for information purposes only;

Fig. 2 is a schematic side view of a photocatalytic oxidation apparatus according to an embodiment of the invention

Fig. 3 is a schematic cross-sectional side view of a portion of the photocatalytic oxidation apparatus of Fig. 2;

Fig. 4 is a schematic side view of a photocatalytic oxidation apparatus according to another embodiment of the invention; and,

Fig. 5 is a schematic cross-sectional front view of the photocatalytic oxidation apparatus of Fig. 4, viewed along line X-X shown in Fig. 4. DETAILED DESCRIPTION OF THE EMBODIMENTS

Referring now to Fig. 1, a photocatalytic oxidation apparatus 1 is shown for information purposes. The photocatalytic oxidation apparatus 1 comprises a light source 2 and a layer of photocatalytic material 3. The photocatalytic oxidation apparatus 1 forms part of a fluid treatment device (not shown), for example, an air or water purification device. The light source 2 comprises a light generator 4 and a light guide 5. The light guide 5 comprises a plate of transparent material, such as glass, polycarbonate or acrylic resin.

The light generator 4 is configured to radiate ultraviolet (UV) rays and may comprise a UV lamp or UV light emitting diode. The light generator 4 is arranged to shine light into a first end 5A of the light guide 5 such that the light propagates through the light guide 5 and is radiated out of a light emitting surface 6 of the light guide 5. The light emitting surface 6 is a major planar surface of the light guide 5.

The layer of photocatalytic material 3 comprises titanium dioxide (Ti0 ₂ ). The layer of photocatalytic material 3 is provided on the light emitting surface 6 of the light guide 5 and covers the entire light emitting surface 6. The layer of photocatalytic material 3 comprises an inner surface 3A that is adjacent to the light emitting surface 6 and an outer surface 3B that is remote to the light emitting surface 6. The outer surface 3B of the layer of photocatalytic material 3 faces away from the light emitting surface 6.

The fluid treatment device (not shown) is configured to draw a fluid to be treated, for example, air or water, into the fluid treatment device via an inlet (not shown). The fluid flows over the outer surface 3B of the layer of photocatalytic material 3 (in the direction of arrow 'A' in Fig. 1) and is subsequently expelled from an outlet (not shown) of the fluid treatment device.

In use, the light generator 4 is powered to shine UV rays into the first end 5A of the light guide 5. The UV rays propagate through the light guide 5 and are radiated from the light emitting surface 6 such that the inner surface 3A of the layer of photocatalytic material 3 is irradiated by the UV rays (Fig. 1 shows a schematic illustration of a photon P irradiating the inner surface 3A). This causes electrons in the titanium dioxide of the layer of photocatalytic material 3 to be promoted from the valence band to the conduction band and thus electron-hole pairs are created that generate free radicals, including hydroxyl radicals (OH*).

The layer of photocatalytic material 3 has a sufficiently small thickness T that the hydroxyl radicals are generated at the outer surface 3B of the photocatalytic layer 3 despite the fact that the UV rays irradiate the inner surface 3A of the layer of photocatalytic material 3. Therefore, the hydroxyl radicals react with pollutants in the fluid flow A passing over the outer surface 3B of the layer of photocatalytic material 3 to decompose the pollutants. For example, the hydroxyl radicals will oxidise volatile organic compounds (VOCs) present in the fluid flow A such that the volatile organic compounds are decomposed into less harmful chemicals, such as, carbon dioxide and water. The purified fluid flow is then expelled from the outlet (not shown) of the fluid treatment device.

It has been found that it is difficult to manufacture the layer of photocatalytic material 3 to the requisite small thickness T necessary to enable the hydroxyl radicals to be generated at the outer surface 3B of the layer of photocatalytic material 3. If the thickness T of the layer of photocatalytic material 3 is too large then hydroxyl radicals will not be generated at the outer surface 3B of the layer of photocatalytic material 3 and thus the photocatalytic oxidation apparatus will not be effective at decomposing pollutants in the fluid flow A proximate to the outer surface 3B. Therefore, the layer of photocatalytic material 3 must be manufactured to a high tolerance to ensure that it is the correct thickness T, which can make manufacture of the photocatalytic oxidation apparatus 1 difficult and/or expensive.

Referring to Figs. 2 and 3, a photocatalytic oxidation apparatus 10 according to an embodiment of the invention is shown. The photocatalytic oxidation apparatus 10 comprises a light source 11 and a photocatalytic layer 12. The photocatalytic oxidation apparatus 10 forms part of a fluid treatment device (not shown), for example, an air or water purification device.

The light source 11 comprises a light generator 13 and a light guide 14. The light guide 14 comprises a plate of transparent material, such as glass, polycarbonate or acrylic resin.

A major planar surface of the light guide 14 comprises a light emitting surface

15. The light emitting surface 15 comprises a plurality of outcoupling structures 16. Each outcoupling structure 16 comprises a roughened area of the light emitting surface 15.

The light generator 13 may comprise, for example, a UV lamp or a UV light emitting diode. The light generator 13 is configured to radiate UV rays into a first end 14A of the light guide 14 such that the light propagates through the light guide 14 and is radiated out of the light emitting surface 15 of the light guide 14. More specifically, the light propagates through the light guide 14 and irradiates one of the outcoupling structures 16. The roughened area of the outcoupling structure 16 scatters the light such that it is emitted from the light emitting surface 15 (as shown in Fig. 3).

The photocatalytic layer 12 comprises a photocatalytic material 17 and a plurality of light transmittal regions 18. The photocatalytic material 17 comprises titanium dioxide (Ti0 ₂ ).

The photocatalytic material 17 is provided on the light emitting surface 15 such that an inner surface 17 A of the photocatalytic material 17 contacts the light emitting surface 15. The light transmittal regions 18 each comprise a gap in the photocatalytic material 17 wherein the photocatalytic material 17 does not cover the light emitting surface 15. Therefore, the photocatalytic material 17 partially covers the light emitting surface 15.

The photocatalytic layer 12 is arranged on the light emitting surface 15 such that each light transmittal region 18 overlies a corresponding outcoupling structure 16.

The fluid treatment device (not shown) is configured to draw a fluid to be treated, for example, air or water, into the fluid treatment device via an inlet (not shown). The fluid flows over the photocatalytic layer 12 (for example, in the direction of arrow 'A' in Fig. 3) and is subsequently expelled from an outlet (not shown) of the fluid treatment device.

In use, the light generator 13 is powered to shine UV rays into the first end

14A of the light guide 14. The UV rays propagate through the light guide 14 and are radiated from the outcoupling structures 16 of the light emitting surface 15 such that the UV rays enter the light transmittal regions 18 and then irradiate on photocatalytic material 17 that is adjacent to the light transmittal regions 18 (Fig. 3 schematically illustrates a UV ray L propagating through the light guide 14). As described above, this causes free radicals to be generated, including hydroxyl radicals (OH*). The hydroxyl radicals decompose pollutants in the fluid flow A into less harmful chemicals and the purified fluid flow is subsequently expelled from the outlet (not shown) of the fluid treatment device.

The light transmittal regions 18 therefore allow for hydroxyl radicals to be formed that can react with the pollutants in the fluid flow A, regardless of the thickness of the photocatalytic material 17. This is because the light transmittal regions 18 allow for light emitted from the light emitting surface 15 to irradiate a portion of the photocatalytic material 17 that is spaced from the light emitting surface 15 and therefore is in contact with the fluid flow A. Thus, it is not necessary that the photocatalytic material 17 is applied in a thin layer to the light emitting surface 15 and so manufacture of the photocatalytic oxidation apparatus 10 of Figs. 2 and 3 may be easier than the photocatalytic oxidation apparatus 1 of Fig. 1. On the other hand, if the photocatalytic oxidation apparatus 10 did not comprise light transmittal regions 18 then the UV rays would only irradiate the inside surface 17 A of the photocatalytic material 17, which is generally opaque, and so would not irradiate a portion of the

photocatalytic material 17 that is in contact with the fluid flow A.

In the above described embodiment, the light guide 14 is pate shaped and has a planar surface which comprises the light emitting surface 15. However, in alternative embodiments (not shown), the light guide has a different shape. For example, the light guide may instead be cylindrical such that the light emitting surface is curved. In the above described embodiment, the photocatalytic layer 12 is provided on a single light emitting surface 15 of the photocatalytic oxidation apparatus 10. However, in an alternative embodiment (not shown), the light guide comprises a plurality of light emitting surfaces and a photocatalytic layer is provided on each light emitting surface. In one such embodiment, the light guide comprises first and second light emitting surfaces on opposite sides of the light guide and a photocatalytic layer is provided on each of the first and second light emitting surfaces.

Referring to Figs. 4 and 5, a photocatalytic oxidation apparatus 20 according to another embodiment of the invention is shown. The photocatalytic oxidation apparatus 20 comprises a light source 21 and a photocatalytic layer 22. The photocatalytic oxidation apparatus 20 forms part of a fluid treatment device (not shown).

The light source 21 comprises a light generator 23 and an optical fibre 24. The optical fibre 24 may be manufactured from a transparent material, for example, silica or fluoride glass.

The peripheral surface of the optical fibre 24 comprises a light emitting surface 25. The light emitting surface 25 comprises a plurality of outcoupling structures (not shown). Each outcoupling structure comprises a roughened area of the light emitting surface 25.

The light generator 23 is configured to radiate UV rays into a first end 24A of the optical fibre 24 such that the light propagates through the optical fibre 24 and is radiated out of the light emitting surface 25 of the optical fibre 24. More specifically, the light propagates through the optical fibre 24 and irradiates one of the outcoupling structures, wherein the light is scattered such that it is emitted from the light emitting surface 25.

The photocatalytic layer 22 comprises a photocatalytic material 27 and a plurality of light transmittal regions 28. The photocatalytic material 27 comprises titanium dioxide and is provided on the light emitting surface 25 such that an inner surface 27A of the photocatalytic material 27 contacts the light emitting surface 25. The light transmittal regions 28 each comprise a gap in the photocatalytic material 27 wherein the photocatalytic material 27 does not cover the light emitting surface 25. Therefore, the photocatalytic material 27 partially covers the light emitting surface 25.

In the present embodiment, the photocatalytic material 27 is arranged as a plurality of discrete bands 27 that subtend entirely about the central axis of the optical fibre 24. A gap 28 is provided between adjacent bands 27. Each gap 28 forms a light emitting region 28. In another embodiment (not shown), each band of photocatalytic material only subtends partially about the central axis of the optical fibre. In yet another embodiment, the bands are joined together by photocatalytic material such that the bands are not discrete.

The optical fibre 24 may form a core and the photocatalytic material 27 may form an outer shell of the photocatalytic oxidation apparatus 10.

The photocatalytic layer 22 is arranged on the light emitting surface 25 such that each light transmittal region 28 overlies a corresponding outcoupling structure.

The fluid treatment device (not shown) is configured to draw a fluid to be treated, for example, air or water, into the fluid treatment device via an inlet (not shown). The fluid flows over the photocatalytic layer 22 and is subsequently expelled from an outlet (not shown) of the fluid treatment device.

In use, the light generator 23 is powered to shine UV rays into the first end 24A of the optical fibre 24. The UV rays propagate through the optical fibre 24 and are radiated from the outcoupling structures of the light emitting surface 25 such that the UV rays enter the light transmittal regions 28 and then irradiate on photocatalytic material 27 that is adjacent to the light transmittal regions 28. As described above, this causes free radicals to be generated, including hydroxyl radicals (OH*). The hydroxyl radicals decompose pollutants in the fluid flow into less harmful chemicals and the purified fluid flow is subsequently expelled from the outlet (not shown) of the fluid treatment device.

The light transmittal regions 28 therefore allow for hydroxyl radicals to be formed that can react with the pollutants in the fluid flow, without requiring that the thickness of the photocatalytic material 27 is made very small. This is because the light transmittal regions 28 allow for light emitted from the light emitting surface 25 to irradiate a portion of the photocatalytic material 27 that is adjacent the light transmittal regions 28 and is thus in contact with the fluid flow. Therefore, manufacture of the photocatalytic oxidation apparatus 20 of Figs. 4 and 5 may be easier than the photocatalytic oxidation apparatus 1 of Fig. 1. On the other hand, if the photocatalytic oxidation apparatus 20 did not comprise light transmittal regions 28 then the UV rays would only irradiate the inside surface 27A of the photocatalytic material 27, which is generally opaque, and so would not irradiate a portion of the

photocatalytic material 27 that is in contact with the fluid flow.

In one embodiment, the fluid treatment device (not shown) comprises a filter

(not shown). The filter comprises a plurality of filter fibres each comprising an optical fibre provided with a photocatalytic layer. Therefore, any light emitted by the light emitting surface of each optical fibre that does not irradiate the photocatalytic material thereon may irradiate photocatalytic material of another filter fibre of the filter to react with the photocatalytic material of said another filter fibre. Thus, the efficiency of the fluid treatment device is increased. The filter fibres may be woven into a felt. In one embodiment, the filter is a high-efficiency particulate arrestance (HEPA) filter.

In the above described embodiments, each light transmittal region 18, 28 comprises a gap or space or aperture in the photocatalytic material 17, 27 such that substantially no photocatalytic material 17, 27 is provided on the light emitting surface 15, 25 at each of the light transmittal regions 18, 28. However, in alternative embodiments (not shown) layer of photocatalytic material is provided on the light emitting surface at one or more of the light transmittal regions that is sufficiently thin, or sufficiently transparent, to allow for light to pass through the photocatalytic material at each of the light transmittal regions to irradiate photocatalytic material adjacent the light transmittal regions.

In the above described embodiments, the light transmittal regions 18, 28 are arranged in a repeating pattern or regular array in the photocatalytic layer 12, 22. However, in alternative embodiments (not shown), the light transmittal regions are arranged in an irregular or random arrangement in the photocatalytic layer.

In the above described embodiments, the photocatalytic material 17, 27 comprises titanium dioxide. However, it should be recognised that photocatalytic oxidation apparatus comprising other photocatalytic materials are intended to fall within the scope of the invention. For example, the photocatalytic material may instead comprise a different metal oxide, such as, zinc oxide (ZnO), tin dioxide (Sn0 ₂ ) or cerium oxide (Ce0 ₂ ).

In the above described embodiments, the light generator 13, 23 is configured to generate UV rays. However, in alternative embodiments (not shown) the light generator is instead configured to generate light having a different frequency, for example, visible light. The frequency of the light should be such to promote electrons in the photocatalytic material from the valence band to the conduction band.

The fluid treatment device may be in the form of, for example, an air purifier, a water purifier or filter, an air conditioner or a HVAC system.

Embodiments of the photocatalytic oxidation apparatus and the fluid treatment device are hence suitable in particular for domestic fluid treatment applications. A domestic photocatalytic oxidation apparatus may be provided for purifying, filtering or otherwise treating air or water within a home or domestic setting or environment. Particular examples of a domestic photocatalytic oxidation apparatus may include a home or domestic air purifier (e.g. a standalone air purifier for purifying air in a room or space), or a home or domestic water purifier such as for use in home water supply system to provide purified drinking water for instance.

The above embodiments as described are only illustrative, and not intended to limit the technique approaches of the present invention. Although the present invention is described in details referring to the preferable embodiments, those skilled in the art will understand that the technique approaches of the present invention can be modified or equally displaced without departing from the spirit and scope of the technique approaches of the present invention, which will also fall into the protective scope of the claims of the present invention. 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. Any reference signs in the claims should not be construed as limiting the scope.