ES2849475B2 - PHOTOCATALYTIC PURIFICATION SYSTEM - Google Patents

Description

DESCRIPTION

PHOTOCATALYTIC PURIFICATION SYSTEM

technique field

The present invention is directed to a photocatalytic purification system. A photocatalytic purification system is a system intended to produce a purification, in this case of a fluid, preferably a gas such as ambient air, through a photocatalytic process.

A photocatalytic process is a photochemical reaction between a photocatalytic material and incident light that produces photocatalytic activity. When said photocatalytic material comes into contact with the fluid to be purified and simultaneously receives incident light, the generated photocatalytic activity modifies the chemical composition of said fluid, reducing or eliminating unwanted chemical compounds from said fluid, producing its purification.

State of the art

Document EP0993859A1 describes a photocatalytic purification system comprising a duct with a transparent wall that defines an illuminated interior area, a fluid inlet and a fluid outlet, and a plurality of porous slats contained within said duct blocking the flow channel of fluid defined between the fluid inlet and fluid outlet, urging fluid flow to pass through the porous slats. Said porous slats are made of a photocatalytic material and receive incident light from an external light source towards the transparent walls of the duct, producing a photocatalytic activity that purifies the fluid.

But in this document, the porous slats do not implement any improvement to increase the surface of the photocatalytic material that receives incident light or to increase the contact surface between said photocatalytic material that receives incident light and the fluid to be purified.

Document JP2000303756A describes a duct comprised between two parallel windows where a shutter is contained, said shutter including numerous non-porous slats coated with a photocatalytic material. A fluid impeller moves ambient air through the duct, surrounding the non-porous louvers. According to this solution, the air flow passes through the slats and windows, and only occasionally comes into contact with the photocatalytic material coating of the slats, due to the turbulence generated in the flow causing the air to be introduced into the intermediate spaces between the parallel slats , leading to very poor debugging efficiency.

These and other problems are addressed by the proposed invention described below.

Brief description of the invention

The present invention is directed, according to a first aspect, to a photocatalytic purification system for the purification of a fluid, preferably a gas such as ambient air.

The proposed photocatalytic purification system comprises, in a manner already known in the state of the art, the following components:

• to a conduit comprising a perimeter wall including at least one transparent or translucent part, which is transparent or translucent to incident light and which defines an illuminated interior area of the conduit, a fluid inlet and a fluid outlet separated from each other determining a fluid flow channel therebetween;

• a plurality of separate porous slats made of, or coated with, a photocatalytic material contained in said interior illuminated area of the duct, each porous slat being transverse to the fluid flow channel covering a complete cross-section of the duct such that a flow of the fluid flowing through the fluid flow channel is forced to pass through said porous slats, each porous slat having a first side including first openings, having a first cross-sectional area, directly exposed to incident light from the illuminated interior area and a second side, including the second openings, opposite the first side defining a shadowed side, each second opening having a second cross-sectional area.

Accordingly, the fluid flow channel is defined within the conduit, between a fluid inlet and a fluid outlet defined in said conduit, typically at ends opposites of it. It will be understood that the fluid flow channel is the path followed by the fluid passing through the conduit.

The perimeter wall of the conduit, which surrounds said fluid flow channel, includes at least one transparent or translucent part so that a light incident on said perimeter wall from outside the conduit passes through said transparent or translucent parts of the wall that enter the duct and the illuminating areas inside the duct, determining an illuminated interior area, which is the area inside the duct reached by the incident light passing through said transparent or translucent part of the wall. Typically, said interior illuminated area is comprised of at least a portion of the conduit whose wall comprises said transparent or translucent part.

A plurality of separate porous slats are contained within said illuminated interior area, within the duct, such that each porous slat has a first side exposed to the incident light of the illuminated interior area and a second side opposite the first side and therefore a shaded side that receives no light when incident light enters from a single light source, such as sunlight.

The porous slats are porous to fluid flowing within the fluid flow channel, and each porous slat covers the entire cross-section of the conduit, blocking the fluid flow channel and forcing fluid through the pores of the ducts. porous slats. Preferably, each porous slat is in contact with the perimeter wall through an elastic sealing strip comprised between the porous slats and the perimeter wall.

The present invention also proposes, in a manner not known in the state of the art, that:

• the second cross-sectional area is smaller than the first cross-sectional area; and that

• the first openings communicate with the second openings through branched passage channels of decreasing section, determining a deep penetration of incident light in the porous slat from the first side to the second side.

According to this, the first openings, located on the first side of the porous slats exposed to incident light, are larger than the second openings, because its cross-sectional area is greater than the cross-sectional area of the second openings.

It will be understood that the cross-sectional area is the hollow area of the opening measured in a plane transverse to the opening in a region coincident with, or adjacent to, the first or second face of the porous slat where said opening is defined, said plane having a selected slope to define the smallest cross-sectional area of the opening at that point.

The branched tapered passage channels are channels connecting the first openings with the second openings. The channel connected to each first opening branches into several channels, each connected to a different second opening, so that multiple second openings are connected to each first opening. Said channels not only branch, but also narrow from the first openings to the second openings, producing conical channels whose cross-sectional area gradually reduces.

The purification carried out on the fluid by the photocatalytic material depends on the contact surface between the fluid and the photocatalytic material and on the amount of light incident on said photocatalytic material. A larger contact surface and a greater amount of incident light lead to better debugging.

To purify a given flow or fluid, if said flow or fluid is divided and conducted through multiple openings and channels, the smaller the openings and channels, the larger the contact surface. But the inner surfaces of these channels only generate photocatalytic activity and fluid purification if they are exposed to incident light, and the narrow channels prevent light from penetrating them.

The proposed solution provides a porous slat that simultaneously offers maximum illuminated contact surfaces between the fluid and the photocatalytic material. The solution consists of second openings of an optimized size to maximize the contact surface of the fluid with the porous slat. Said second openings are connected with branched passage channels of decreasing section whose interior surfaces are illuminated and, therefore, produce photocatalytic activity. Said branched passage channels of decreasing section are illuminated by the incident light that penetrates from the first openings whose size is optimized to maximize the penetration of light in said branched passage channels of decreasing section. Because the tapering branching passage channels become narrower, incident light that has penetrated into them through the first openings can penetrate deeper compared to an alternative solution where the tapering branching passage channels have a constant or non-decreasing sectional area, producing a better illumination of the internal surfaces of said narrow branched passage channels and a better purification.

As a result, the fluid is purified not only when it is in contact with the external surfaces of the porous slats, but also when said fluid passes through the branched passage channels of decreasing section of the porous slat, which receives incident light thanks to the proposed solution, greatly increasing the surface of the porous slat that produces photocatalytic activity.

According to a preferred embodiment of the present invention, each porous slat has a lower density on the first side than on the second side. Having a lower density on the first side means that the accumulated void area on the first side, resulting from the sum of the first cross-sectional areas of all first openings, is greater than the accumulated void area on the second side, as result of the sum of the cross-sectional area of the entire second opening and thus leads to a better penetration of the incident light from the first side to the second side.

Preferably, the first cross-sectional area is at least twenty times larger than the second cross-sectional area. It is considered that with this dimensional relationship the penetration of light is sufficient.

In a preferred embodiment, the second cross-sectional area is equal to or less than 1mm2. This size produces a large contact surface between the fluid and the branched passage channels of tapered section connected to the second opening having said second cross-sectional area.

Additionally, or alternatively, the first cross-sectional area is equal to or greater than 20mm2, allowing deep penetration of incident light.

The thickness of the porous board can be limited to a size equal to or less than 50mm. A porous board that has a thickness within this range will have light penetration optimal inside the branched passage channels of decreasing section, especially when the first openings are equal to or greater than 20mm2.

The tapered branch passageways may additionally comprise dead-end branch cavities. These dead-end cavities can collect water, for example, condensation water or added water. The evaporation of this water can produce a cooling effect on the fluid that passes through the porous slat.

Each porous slat can be a three-dimensional openwork mesh with interconnected passage channels or, preferably, each porous slat is made up of multiple superimposed layers of openwork mesh, each layer including openings that coincide at least partially with openings in adjacent layers that define said passage channels. branched step of diminishing section. The cross-sectional area of the openings of the successive superimposed layers gradually increases from the second cross-sectional area to the first cross-sectional area.

Preferably the porous slats are made of a ceramic material made of hardened paste or powder, which can be obtained by a 3D printing process, for example by printing overlapping layers with different geometry.

The internal surface of the branching tapered passage channels has a surface roughness value equal to or greater than the surface roughness value of a three-dimensional printed surface that has been printed with a resolution equal to or greater than 0.3mm. Said resolution of the three-dimensional printed surface is the minimum thickness of each superimposed layer of material deposited during the printing process, which generates a surface roughness on the surface of the 3D printed object, typically small parallel grooves with a separation equal to the resolution of the 3D printer.

The surface roughness of the internal surface of the branched passage channels of decreasing section increases the contact surface between the fluid to be purified and the photocatalytic material, and also generates cracks where the particles suspended in the fluid to be purified tend to settle and accumulate, producing not only a chemical purification of the fluid due to the photocatalytic activity, but also a mechanical purification produced by said deposition of the suspended particles.

Preferably, the internal surface of the passage channels has a roughness value greater than 5 pm, preferably greater than 10 pm, and preferably between 10 pm and 50 pm. This roughness is selected to maximize the retention of particles equal to or greater than 2.5 pm.

The transparent or translucent portion of the perimeter wall of the incident light translucent or transparent conduit described above may include one flat surface or two opposing flat surfaces facing each other.

Where the duct includes a flat transparent or translucent surface, the flat surface should face the external light source, eg sunlight, to allow illumination of the illuminated interior area of the duct.

Where the duct includes two flat transparent or translucent surfaces facing each other, one of the flat surfaces shall face the external light source, for example sunlight, to allow illumination of the illuminated inner surface of the duct, and the light of the illuminated interior area can exit the duct through the opposite flat surface, allowing the illumination of a space or a housing located behind said duct.

For example, the duct can be defined between two parallel windows on the facade of a building, allowing natural light to enter the building through it. In this example, the fluid inlet can be at the bottom of the duct, directed towards the outside of the building to absorb ambient air outside the building, and the fluid outlet can be at the top of the duct, directed towards the inside. of the building to introduce purified ambient air into the building. Optionally, said outlet can be connected to a building air conduction system to conduct said purified air to different areas of the building or to carry out additional treatments on said purified air before releasing it inside the building.

At least a transparent or translucent portion of the perimeter wall of the duct is pivotally attached to the rest of the duct, defining a hatch that is movable between a closed position and an open position and that includes a locking device to retain the surface in the closed position . Said hatch can be opened to allow cleaning of the interior of the duct.

The porous slats can be releasably attached to the duct and can also be removable through the hatch, for replacement or deep cleaning operations.

When the duct is vertical, with its entrance at the lower end and its exit at the upper end, the incident light generates a greenhouse effect inside the duct, heating the fluid contained in it and generating a natural rise of said fluid from the lower end. to the upper end of the conduit, generating a fluid flow along the fluid flow channel. Notwithstanding the foregoing, to control or accelerate this fluid movement, or when the conduit is in a different position, the fluid flow channel may include a fluid impeller connected thereto. Such a fluid driver, for example a fan or a pump, will force fluid movement in the desired direction and with the desired flow through the conduit.

Fluid flows from the fluid inlet to the fluid outlet of the duct passing through each porous slat from the second side to the first side.

It will also be understood that any given range of values may not be optimal at extreme values and may require adaptations of the invention to these applicable extreme values, such adaptations being within the purview of a skilled person.

Other features of the invention appear from the following detailed description of an embodiment.

Brief description of the figures

The above and other advantages and characteristics will be more fully understood from the following detailed description of an embodiment with reference to the accompanying drawings, which are taken by way of illustration and not limitation, in which:

Fig. 1 shows a vertical section of the photocatalytic purification system according to an embodiment in which the duct includes two opposing flat surfaces facing each other, transparent or translucent to incident light, where the incident light is shown as thick arrows where ambient air flow through the fluid flow channel is shown as a thin arrow;

Fig. 2A shows a cross section of a porous slat made through a section line indicated in Fig. 2B, according to a first embodiment;

Fig. 2B shows a plan view of the first side of the porous slat shown in Fig. 2A;

Fig. 3A shows a cross section of a porous slat made through a section line indicated in Fig. 3B, according to a second embodiment;

Fig. 3B shows a plan view of the first side of the porous slat shown in Fig. 3A;

Fig. 4A shows a cross section of a porous slat made through a section line indicated in Fig. 4B, according to a third embodiment;

Fig. 4B shows a plan view of the first side of the porous slat shown in Fig. 4A;

Fig. 5A shows a cross section of a porous slat made through a section line indicated in Fig. 5B, according to a fourth embodiment;

Fig. 5B shows a plan view of the first side of the porous slat shown in Fig. 5A.

Detailed description of an embodiment

The above and other advantages and features will be more fully understood from the following detailed description of an embodiment with reference to the accompanying drawings, which is to be taken by way of illustration and not limitation.

According to a preferred embodiment of the present invention shown in Fig. 1, the photocatalytic purification system includes a rectangular duct 10 defined by four flat surfaces constituting a perimeter wall 13. Said perimeter wall 13 includes a transparent or translucent part 14 , transparent or translucent to the incident light 1 that penetrates inside the duct 10 through said transparent or translucent part 14. The internal volume of the duct 10 that receives the incident light 1 through said transparent or translucent part 14 of the perimeter wall 13 is called the illuminated interior area. Typically, incident light 1 is sunlight.

Two of said flat surfaces have a larger surface area than the other two surfaces. At least one of said flat surfaces with greater surface area, and preferably both are made of a material that is transparent or translucent to visible light. In the preferred embodiment, said transparent or translucent portions 14 of the conduit 10 are defined by a glass window that is optionally pivotally attached to the rest of the perimeter wall 13 and preferably includes a locking device to retain said glass window in place. the closed position.

According to this embodiment, the duct 10 is defined in the intermediate space between two parallel glass windows, for example, vertical glass windows of a building facade.

Conduit 10 includes a fluid inlet 11 and a fluid outlet 12 at its opposite ends, defining a fluid flow channel 2 therebetween along conduit 10.

In the case shown in Fig. 1, the fluid inlet 11 is at the lower end of the duct 10 and the fluid outlet is placed at the higher end of the duct 10. The fluid inlet 11 takes ambient air from one side of the duct 10, in this case from the same side of the duct 10 exposed to the incident light 1, and the fluid outlet 12 expels the ambient air, once it has been treated in the photocatalytic purification system, to the side of the duct 10 not exposed to incident light 1. When said duct 10 is integrated into the façade of a building, the fluid inlet 11 takes air from outside the building and the fluid outlet 12 introduces said air once it has been purified in the building .

Optionally, the fluid inlet 11, the fluid outlet 12 or both can be connected to a fluid line and/or a fluid impeller 3 to control the flow of the fluid through the photocatalytic purification system.

The duct 10 includes, within the illuminated interior area, a plurality of parallel porous slats 20 separated from each other, each porous slat being transversal to the duct 10 and occupying the entire sectional area of said duct 10, the entire perimeter of each porous slat 20 being in contact with the perimeter wall 13 of the duct 10, each porous slat 20 completely interrupts the fluid flow channel 2, so that the fluid flow can only circulate along the duct 10 passing through the porous slats twenty.

Each porous slat 20 is made of or coated with a photocatalytic material that produces photocatalytic activity when it receives incident light 1. Each porous slat 20 has two opposite sides, a first side 20a exposed to the incident light 1 of the illuminated interior area, and a second side 20b opposite the first side 20a.

The first side 20a includes first openings 21, each of a first cross-sectional area, and the second side includes second openings 22, each of a second cross-sectional area smaller than the first cross-sectional area.

The porous slat 20 also includes branched passage channels of decreasing section 23 that communicate the first openings 21 with the second openings 22 with conical decreasing channels, allowing the passage of a fluid through said branched passage channels of decreasing section 23 through of the porous slat 20.

Preferably, each tapered branched passage channel 23 communicates a first opening 21 with multiple second openings 2, and preferably the second openings 22 are more numerous, for example more than 10 times more numerous, than the first openings 21.

Because the first openings 21 have a larger cross-sectional area than the second openings 22, the internal tapered surfaces of the tapered branch passageways 23 have improved exposure to incident light 1 striking the first surface 20a. and enters the branched passage channels of decreasing section 23 through said first openings 21.

Because said tapering branched passage channels 23 are narrowing, their cross section reduces as it approaches the second side 20b of the porous slat 20, producing funnel-shaped internal surfaces of the branched passage channels of tapered section 23 that can easily intercept incident light 1 penetrating into the branched passage channels with tapered section 23.

Due to the fact that said branched passage channels of decreasing section 23 branch, each first opening 21 is connected to multiple second openings 22 of smaller size, so that the fluid that passes through a first opening 21 is the same amount of fluid which passes not through just one, but through multiple second openings 22. This characteristic allows the internal surface of the branched passage channels of decreasing section 23 to be increased, increasing the surface exposed to incident light and increasing the contact surface between the fluid and the photocatalytic material, but does not produce a significant reduction in the aggregate cross-sectional area through which the fluid passes, because the flow of fluid passing through a first opening 21 is the same as the flow of fluid passing through multiple second openings 22.

This combination of narrowing and at the same time branching channels allows an improved penetration of the incident light 1 therein and increases the contact surface between the fluid and the photocatalytic material.

Preferably, the aggregate cross-sectional area of all the first openings 21 of a porous slat 20 is less than three times the aggregate cross-sectional area of all the second openings of the same porous slat 20.

Figs. 2A to 5B show different possible embodiments of the porous slat 20.

According to the first embodiment of the porous slats 20, shown in Figs. 2A and 2B, each porous slat 20 comprises multiple superimposed layers, each layer having a different number of openings. The top layer includes the first openings 21 arranged in a regular array. The lower layer includes second openings 22, smaller than the first opening 21 and includes multiple second openings 22 in the footprint of each first opening 21. One or multiple intermediate layers may be sandwiched between said upper and lower layers, each intermediate layer including , in the footprint of each first opening 21, more openings than the layer immediately above, but of a smaller size, each of said openings contains in its footprint multiple openings of the layer immediately below. Said interconnected openings determine the branched passage channels of decreasing section 23.

In this example, the first openings, the second openings and the intermediate openings are square openings arranged in rows and columns.

The intermediate layer placed immediately below the upper layer comprises four intermediate openings in the footprint of each first opening 21, which divides said first opening 21 into four by two crossing walls. The lower layer comprises four second openings 22 in the footprint of each intermediate opening, and thus sixteen second openings 22 in the footprint of each first opening 21.

Other embodiments including multiple intermediate layers, eg, first, second, third ... intermediate layers, each with an increasing number of first, second, third ... intermediate openings with respect to the preceding layer, are also contemplated.

According to a second embodiment of the porous slat 20, shown in Figs. 3A and 3B, comprises a lower layer that includes a plurality of second discrete openings 22 and an upper layer that includes a continuous zigzag wall of material that defines the open intermediate spaces that constitute the first openings 21, and that coincide with the second openings. 22, each first opening 21 containing multiple second openings 22. Between said lower and upper layers, one or multiple intermediate layers may be included, each intermediate layer including multiple openings in the tread of the upper layer and containing multiple second openings in the tread of each intermediate layer. Said interconnected openings determine the branched passage channels of decreasing section 23.

According to a third embodiment, shown in Figs. 4A and 4B, the porous slat 20 is made up of layers of parallel strips superimposed in orthogonal directions, the strips having an increasing spacing and/or a decreasing thickness from the lower layer to the upper layer, so that the intermediate spaces between said strips constitute said branched passage channels of decreasing section 23.

In this third embodiment, each first opening 21 is defined by the hollow space defined between four adjacent orthogonal strips of the two upper layers of the porous slat 20. Two strips of the upper layer and two strips of the layer immediately below the upper layer which are perpendicular to the two strips mentioned above. Similarly, each second opening 22 is defined by the hollow space defined between four adjacent orthogonal strips of the bottom two layers of porous slat 20.

According to a fourth embodiment, shown in Figs. 5A and 5B, each first opening 21 is surrounded by a perimeter wall of a certain height. Each first opening 21 contains one or multiple concentric walls of decreasing height that are concentric with the perimeter wall. The concentric walls are connected to the perimeter wall through ribs. The intermediate spaces defined between the perimeter wall, the concentric walls and the ribs define the branched passage channels of decreasing section 23 that connect each first opening 23 with multiple second openings 22.

In this example, the perimeter wall and the concentric walls are square tubes, but other shapes, such as triangular tubes or hexagonal tubes, are also contemplated.

The perimeter wall of this fourth embodiment further comprises dead-end branch cavities 24 where water or condensed water can be stored and evaporated during catalytic activity to reduce fluid temperature. This feature can be added to any of the other described embodiments of the porous slat 20.

The porous slats 20 shown in the first, second, third and fourth embodiments are preferably produced by a 3D printing method, for example, by layer or strip deposition or strip or layer hardening. Preferably, the 3D printing is produced by a printer that has a resolution equal to or greater than 0.3mm, preferably between 0.3mm and 1mm, to produce an optimized surface roughness to retain particles suspended in the fluid to be purified.

In a preferred embodiment, the branched passage channels of decreasing section 23 are not aligned with the fluid flow channel 2 but with a direction that intersects with the transparent or translucent part 14 of the perimeter wall 13 of the duct 10, so that an incident light 1 passing through said transparent or translucent part 14 is more likely to penetrate deeply into the branching passage channels of decreasing section 23.

The direction of each tapering branched passage channel 23 is determined by the average direction of the imaginary lines connecting the center of a first opening 21 with the center of all second openings 22 connected mainly to it through the same passage channel. branched tapering section 23.

Preferably, said direction of the branching passage channels of decreasing section 23 intersects with the transparent or translucent part 14 of the perimeter wall 13 of the duct 10 forming an angle greater than 30°, preferably between 60° and 30°.

It will be understood that various parts of one embodiment of the invention may be freely combined with parts described in other embodiments, even if such combination is not explicitly described, provided that there is no detriment to such combination.

Claims (15)

1. A photocatalytic purification system comprising: • a conduit (10) comprising a perimeter wall (13) including at least one transparent or translucent part (14), which is transparent or translucent to incident light (1) and which defines an illuminated interior area of the conduit (10 ), a fluid inlet (11) and a fluid outlet (12) separated from each other to determine a fluid flow channel (2) between them; • a plurality of separate porous slats (20) made of, or coated with, a photocatalytic material contained in said inner illuminated area of the conduit (10), each porous slat (20) being transverse to the fluid flow channel (2) and covers a complete cross section of the duct (10) so that the flow of a fluid circulating through the fluid flow channel (2) is forced to pass through said porous slats (20), in which each porous slat (20) has a first side (20a), which includes first openings (21) with a first cross-sectional area, directly exposed to the incident light (1) of the illuminated interior area, and a second side (20b), including second openings (22), opposite the first side and defining a shaded side, each second opening (22) having a second cross-sectional area; characterized because • the second cross-sectional area is smaller than the first cross-sectional area; and • the first openings (21) communicate with the second openings (22) through branched passage channels of decreasing section (23), determining a deep penetration of light incident on the porous slat (20) from the first side (20a ) to the second side (20b).2 2. Photocatalytic purification system according to any of the preceding claims, in which each porous slat (20) has a lower density on the first side (20a) than on the second side (20b). 3. Photocatalytic purification system according to claim 1 or 2, in which • the first cross-sectional area is at least twenty times larger than the second cross-sectional area; or • The second cross-sectional area is equal to or less than 1mm2 and/or the first cross-sectional area is equal to or greater than 20mm2 and/or the thickness of the porous slat (20) is equal to or less than 50mm. 4. Photocatalytic purification system according to any of the preceding claims, in which the branched passage channels of decreasing section (23) also comprise branching cavities without outlet (24). 5. Photocatalytic purification system according to claim 1, in which each porous slat (20) is an openwork three-dimensional mesh with interconnected passage channels. 6. Photocatalytic purification system according to claim 1, in which each porous slat (20) is made up of multiple superimposed layers of openwork mesh, each layer including openings at least partially coincident with openings of adjacent layers that define said branched passage channels. tapering (23), and wherein the cross-sectional area of the openings in the successive overlays gradually increases from the second cross-sectional area to the first cross-sectional area. 7. Photocatalytic purification system according to any of the preceding claims, in which the porous slats (20) are made of ceramic material made of a hardened paste or powder.8 8. Photocatalytic purification system according to any of the preceding claims, in which an internal surface of the branched passage channels of decreasing section (23) has a surface roughness value equal to or greater than the surface roughness value of a printed surface by three-dimensional printing techniques printed with a resolution equal to or greater than 0.3mm. 9. Photocatalytic purification system according to any of the preceding claims, in which an internal surface of the branched passage channels of decreasing section (23) has a roughness value greater than 10 pm. 10. Photocatalytic purification system according to any of the preceding claims, in which said transparent or translucent part (14) of the perimeter wall of the conduit (10) includes a flat surface or two opposite flat surfaces facing each other. 11. Photocatalytic purification system according to any of the preceding claims, wherein said at least one transparent or translucent part (14) of the perimeter wall (13) of the duct (10) is pivotally attached to the rest of the duct (10). ), defining a hatch movable between a closed position and an open position and including a locking device to retain it in the closed position. 12. Photocatalytic purification system according to claim 11, in which the porous slats (20) are detachably attached to the duct (10) and removable through the hatch. 13. Photocatalytic purification system according to any of the preceding claims, in which the fluid flow channel (2) comprises a fluid impeller (3) connected thereto. 14. Photocatalytic purification system according to any of the preceding claims, in which the fluid circulates from the fluid inlet (11) to the fluid outlet (12) of the conduit (10) passing through each porous slat (20) from the second side (20b) to the first side (20a). 15. Photocatalytic purification system according to any of the preceding claims, in which the branched passage channels of decreasing section (23) are aligned with a direction that intersects with the transparent or translucent part (14) of the perimeter wall (13). ) of the duct (10).