EP2131875A2

EP2131875A2 - Air purification method and air purification device for implementing same

Info

Publication number: EP2131875A2
Application number: EP08719424A
Authority: EP
Inventors: Marie-Charlotte Bernard
Original assignee: Individual
Current assignee: Individual
Priority date: 2007-04-05
Filing date: 2008-04-07
Publication date: 2009-12-16
Also published as: US20100047117A1; FR2914559A1; WO2008122871A2; FR2914559B1; WO2008122871A3

Abstract

The invention relates to the purification of indoor air using a method that essentially comprises forcing the air to be processed to flow through an active medium exposed to a germicidal radiation in the presence of a photocatalytic material contained therein, with a destructive action on the microorganisms optionally present in the air and retained in the active medium such as reduced and/or weakened due to the impact on wall members provided therefor in the active medium. A first active medium includes a mass made in the form of a three-dimensional network of walls with photocatalytic surfaces and located in the immediate vicinity of a germicidal radiation source. A second active medium includes a liquid mass in which particles with a photocatalytic surface are dispersed and submitted to a germicidal radiation. The liquid mass is agitated by feeding air therein in order to generate a vortex.

Description

AIR PURIFICATION METHOD AND AIR PURIFYING APPARATUS FOR ITS IMPLEMENTATION

The present invention relates to a method for purifying the indoor air of a building and an air cleaning apparatus designed for the implementation of this method.

It is applicable in all sectors in which there is a need for sanitary control of the quality of ambient air, be it private premises or collective premises. It applies particularly, but not exclusively, to the purification of indoor air in the hospital sector and other areas of health or hygiene, as well as the purification of ambient air in all areas. places of life, especially those where people with respiratory problems live, as well as air purification in all enclosed or semi-enclosed premises, for sanitary reasons as well for comfort issues. In all environments of this type, it has the advantage of allowing the effective destruction of pollutants that may be contained in the air, knowing that the most harmful pollutants that one wishes to eliminate in these circumstances are mainly organic pollutants, in the form of bacteria or other microorganisms.

In order to ensure control of the quality of the air inside the buildings, in particular in closed rooms, the invention provides for subjecting the air to be treated to a treatment carried out in a continuous loop by operating on sampled air. in the ambient atmosphere which is returned to the same atmosphere after treatment. This procedure is favorable to the prevention of respiratory diseases and other conditions related to airborne infectious agents. It represents in particular an interesting alternative to the renewal of the air by ventilation in the rooms of the health establishments. It is also particularly useful in domestic applications for combating the presence of biocontaminants such as microorganisms such as viruses, bacteria, spores, lower fungi or allergens such as pet dander, pollens, dust mites, bacterial fragments, especially since the presence of these biocontaminants is favored by a confinement that is sought to more and more frequently as a measure of energy saving.

Among the ways of combating indoor pollution, in addition to improving ventilation and / or limiting the emission of pollutants, there are known air purifying apparatus implementing the photo-catalytic effect, with the aim of to truly destroy the organic compounds carried by the air rather than keeping them trapped on a filter. The catalyst of the destructive electronic process is generally titanium dioxide which, exposed to ultraviolet radiation, emits electrons acting by oxidation of the organic compounds to be removed.

Some of the preferred embodiments of the present invention are similar to this known technique, insofar as a photo-catalytic effect is also used under UV irradiation. However, the invention provides for operating under conditions which lead to very significantly improved results, thanks in particular to a better control of the contact between the air to be treated and the catalytic surface, also thanks to a mechanical action that attacks the particles within the same effect treatment medium destructive for organic material.

More specifically, the invention exploits the combination of a photo-catalytic treatment destructive organic pollutants with particle trapping favored by their reduction and / or their embrittlement caused by impaction on solid wall elements present within the active medium for photo-catalytic treatment.

In the remainder of this discussion, two main ways of carrying out the invention will be distinguished according to whether the treatment takes place in the dry phase or in the wet phase. It will be seen that in all cases, the invention preferably provides that the wall elements that are present in the active medium to receive the shocks particles in suspension in the air are also the carrier of the activating catalyst for the radiation to which this medium is exposed. The beneficial consequence in the effectiveness of the treatment for the destruction of the organic constituents present in the air is twofold: first, it allows a higher density of the active material in the treatment medium, since the active material is the same for photo catalysis and for impaction; on the other hand, the impact of organic molecules on the photocatalyst walls leads to trapping them as close as possible to the site of the germicidal photo-catalytic effect and even where they have just undergone the mechanical destructive effect of impaction. .

For impaction as well as for the photo-catalytic effect or still for the trapping of the polluting compounds, it is furthermore that the solid elements of the active medium are in divided form, hence the form advantageously of particles dispersed, and they are in constant renewal in the path of the air to be treated, hence the utility of a stirring that can be imposed either on the air circulating through the mass of active medium, or in the treatment medium as a whole, again to the active material read itself when it comes to particles dispersed in the treatment medium.

According to another characteristic of the invention which is common to the dry or wet implementation variants, the conditions of the photocatalytic treatment are advantageously determined in order to exploit a germicidal effect specific to the radiation used, in addition to the photo-catalytic effect. The choice of titanium dioxide as catalyst is then particularly suitable in that it is advantageously used under irradiation with ultraviolet radiation in the UVC range. In the range of 10 to 280 nanometers wavelength, about 260 nanometers which is the preferred wavelength for the direct germicidal effect.

In the following we will begin by focusing on an embodiment of an air purification apparatus according to the invention designed for operation in the dry phase. The photo- Catalyst is then distributed in a porous mass disposed along a radiation source which advantageously elongates for a flow of air in the longitudinal direction of the porous mass.

In a preferred process according to the invention, the active medium through which a forced circulation of the air to be treated is organized consists of a stationary active mass produced in the form of a three-dimensional mesh network exposed to germicidal, destructive radiation. organic pollutants possibly present in the air and trapped in the voids of said mass by impact on the internal walls constituting its specific surface (which constitute the photo-catalytic effect wall elements of which we spoke above).

For a dry phase operation, the invention thus proposes, in particular, an air purification apparatus which has the characteristic of comprising an active mass produced in the form of a three-dimensional mesh network exposed to a long-term source of germicidal radiation, as well as a ventilation system forcing the air to be treated to flow through said mass mainly in the longitudinal direction of the long-range germicidal radiation source.

For an optimal use of the radiation source and a homogeneous distribution of the effects of the active mass, it is particularly advantageous to adopt a cylindrical configuration, where the active mass offered to the circulation of the air to be treated forms an envelope surrounding the longiform source. This gives the best advantage of the germicidal radiation for a light source emitting in the ultraviolet range, but it can also be provided, in combination or alternatively, in particular in the combination of a germicidal effect to a photocatalytic effect promoting the light source. destructive effect of pollutants within the active mass. The active mass is preferably itself produced, at least in part, if not in its entirety, so that in its specific surface it is constituted by a photocatalytic action material in the presence of the radiation to which it is exposed. on the path of the air that the crosses. In this way, the germicidal and photo-catalytic effects combine in the sense of an effective destruction of the organic pollutants contained in the indoor air, the former acting rather by opening the double bonds of the DNA molecules and the latter acting rather by promoting the oxidation of organic matter.

The active mass may be based on different materials in themselves known for other applications. In particular, we are thinking of metal cloths, and more particularly those made of a mesh of knitted wire. All mesh networks and made of wire or metal fibers have the advantage of being easy to process to obtain photocatalyst surface properties. This is done in particular by depositing a coating of photocatalyst compound by dipping in a solution of this compound webs, fibers, or son, which are then shaped or assembled into a three-dimensional mutilayer mass. Moreover, the knitted fabrics have, better than the woven or non-woven fabrics, the ability to lend themselves to deformations making it possible, for example, to elastically tighten the meshed network on a central tube which is the source of the cooperating radiation; or folding the product on itself to obtain a multilayer assembly, or to compress it more or less on itself to vary the density of material offered impaction or photocatalysis or to vary the dimensions of mesh from one point to another of the global active mass.

Other materials to be recommended in alternative embodiments of the invention are represented by the porous materials in the mass. It is known, for example, that properties similar to those which are sought according to the invention in metal mesh or mesh can be obtained from other types of porous masses.

From the point of view of the role of the active mass in the process according to the invention, it will be noted that it is known that particles which are projected at high speed on a target tend to be retained on the surface thereof. This is called the impaction phenomenon. It is used in a known manner for the collection of living microorganisms, whereas according to the invention it is instead used to contribute to their destruction.

However, this is not the only effect which the invention takes advantage of because of the impact of the airborne particles on the inner walls of the active mass. The energy loss that tends to adhere these particles to the active surface is certainly already favorable to the efficiency of the process, especially in the case of a photo-catalytically treated surface, but it adds that on the one hand the slowed particles remain a trapped time in the voids of the active mass, so that overall they are more restrained than the air in their path exposed to germicidal radiation, and it is added on the other hand that the particles are weakened by these shocks on the inner walls of the active mass. These shocks tend in particular to cause a bursting of relatively large particles and to break the envelopes of particularly resistant microorganisms such as spores, allowing the germicidal radiation to reach more easily to the heart to alter growth and cell division and stop their reproduction.

As already indicated, the photocatalyst incorporated in the active mass is preferably composed of titanium dioxide. In combination with such a photocatalyst, a source of germicidal radiation emitting around 250 to 270 nanometers is advantageously provided. The UV radiation C is very energetic and it is able to penetrate the voids of the active mass by traversing it radially in all its thickness around an emitter tube constituting the elongated source, especially when at the same time, it extends over a sufficient length so that the time of travel of the air in the longitudinal direction parallel to the source ensures complete destruction of the polluting organic particles. On the other hand, it is easy to prevent ultraviolet radiation from producing ozone even when the wavelength conditions enabling the activation of a titanium dioxide-based catalyst are observed. On the other hand, the desired germicidal activity is optimal in this range of wavelengths for the usual viruses and bacteria and it is also vis-à-vis the spores insofar as the resistance of their walls has been previously reduced by the mechanical effect of the shocks suffered at within the active mass.

In order to achieve a further object of the invention, which is to obtain that the exposure of the active mass to the radiation which illuminates it is complete and homogeneous, so as to ensure the complete destruction of the particles which are temporarily trapped in within it, the invention advantageously provides that the mesh network, or mesh, occupies the entire section of a cylindrical shell delimiting the functional space of the device around the light source. This source is disposed in the device in the axis of an annular volume occupied by the mesh, which allows it to illuminate homogeneously the entirety of it.

From this point of view, a particularly advantageous arrangement of the invention consists in supplementing the apparatus by means reflecting the radiation tending to return it to the active mass. It is thus possible, on the one hand, firstly to improve the operating efficiency of the radiation emitted for the purposes of the process, in particular with regard to the germicidal effect, and secondly to improve its efficiency in each cell or mesh of the active mass, favoring that it is returned in all directions to hit the different walls with photo-catalytic properties.

We will now focus more particularly on situations where it is preferred to operate in the wet phase rather than in the dry phase as before. While preserving a design of the equipment and operating conditions that essentially provide the same combined effects of germicidal irradiation, photo-catalysis and impaction, it is a question of replacing the trapping of organic pollutants by course of destruction that took place in the voids of the stationary active mass by a similar trapping taking place this time in a liquid mass which is stirred by the air to be treated and exposed to the germicidal radiation, while it contains and the solid wall elements for impaction and the photocatalyst (advantageously on the same walls) in the form of particles maintained dispersed in the liquid mass.

The invention advantageously results in this case in the form of an air purification process consisting in causing the air to be treated to circulate in contact with a liquid mass in which particles are dispersed on which the organic pollutants contained in this air are projected, said liquid mass being further exposed to irradiation with a germicidal radiation activated by a photocatalyst dispersed in the liquid mass. The photocatalyst is preferably carried by the particles dispersed in the liquid mass and on which the phenomenon of impaction of the pollutants occurs.

In order to increase the contact area between pollutants and dispersed particles, to increase the irradiation surface by the source of germicidal radiation, and to improve the mixing of both pollutants and particles dispersed in the liquid mass, the air circulation is preferably carried out so as to cause the rotating liquid mass on itself to create a vortex within the latter. This results in improved efficiency of the photo-catalytic treatment, both by increasing the air travel time in contact with the liquid mass, resulting from the vortex, and by increasing the residence time of the pollutants under irradiation. resulting from the trapping of said pollutants within the liquid mass.

The invention also relates to an air purification apparatus which comprises, on the one hand, a container containing a liquid mass in which particles are dispersed, on the other hand a source of illumination of this liquid mass by a germicidal radiation, preferably ultraviolet radiation of the "C" range, and, moreover, a ventilation system requiring the air to be treated to circulate in contact with the liquid mass to create in it a vortex. The pollutants contained in the air introduced into such a purifying apparatus are caused by this vortex to be projected onto the particles dispersed in the liquid mass and they are trapped in the latter where they undergo a reaction. photocatalytic treatment initiated by the source of germicidal radiation and activated by a photocatalyst dispersed in this liquid mass.

In order to promote the creation and maintenance of this vortex, the invention provides that the container containing the liquid mass is preferably of conical shape, with a portion of larger diameter located on the side through which the air to be treated is introduced into the container. In addition, the invention provides that the air to be treated is preferably introduced into this container tangentially to the walls thereof so as to initiate the vortex effect as soon as the air is introduced into the purification apparatus according to the invention. the invention.

In this case, for optimal irradiation of the liquid in all its volume, the source of germicidal radiation is preferably placed along the axis of revolution of the cone formed by the container containing the liquid mass.

On the other hand, it is useful to promote a long residence time of the air to be treated in contact with the particles dispersed in the liquid mass, both for the effectiveness of the impaction phenomenon and for that of the effect. photocatalytic. To this end, the invention provides in particular that the air to be treated is injected into this container through a conduit opening into the larger diameter portion thereof, and that it is removed from said container also in the vicinity of the part larger diameter of the latter. Thus, under the effect of the vortex initiated by its tangential injection into the container containing the liquid mass, the air to be treated is forced, by the geometry of the receiving container, to circulate in a first step to the smaller part diameter of the container (that is to say towards the top of the cone that forms this container), then in a second time, to circulate again towards the part of large diameter of this container. The residence time in contact with the particles dispersed in the liquid mass is thus increased, which promotes greater efficiency of the treatment.

The ventilation system is, for its part, dimensioned in such a way that the speed that it communicates to the air to be treated is sufficient so that the latter, by its tangential injection into the container containing the liquid mass, can generate the desired vortex.

The particles dispersed in the liquid mass are preferably made of titanium dioxide, at least on the surface. This may include polyethylene particles

(Inert material) coated with titanium dioxide, although it will often be preferable to choose particles incorporating titanium dioxide in the mass, in order to maintain the catalyst effect regardless of the wear of the particles over time.

In the practical implementation of the invention, the dry scrubber as defined above will generally have the advantage of efficiently removing highly polluted ambient air from almost all of its organic pollutants, whereas the wet phase process will rather be reserved for finishing treatments.

As a result, a particularly elaborate air purification method according to the invention will comprise two cascade purifiers, one of each type, with preferably the stationary three-dimensional network purifier arranged upstream of the dispersed particle purifier. liquid medium on an air circuit to treat them browsing in series.

The invention thus makes it possible, by combining the two main treatment routes that have been described, to ensure optimum efficiency of the elimination of microorganisms in the polluted air. It extends to an air purification unit combining the two scavengers trapping respectively dry phase and liquid phase. From this complete apparatus, a particularly advantageous embodiment will be described below, where the two scrubbers are mounted side by side in a configuration which has the advantage of being compact and compact for optimal conditions of air circulation. in full respect of the specificities of each of the two treatment environments.

Other characteristics and advantages of the invention will emerge on reading the following description of various modes of realization thereof, description illustrated by:

FIG. 1 which is a schematic view of an air purification apparatus according to the invention in its preferred embodiment in which a liquid phase trapping purifier is combined with a dry phase trapping purifier,

FIGS. 2A ₁ 2B, 2C which are respectively a diagrammatic perspective view and a schematic view in longitudinal section of a dry phase trapping air purification apparatus; FIG. 3 which is a schematic perspective view of FIG. a liquid phase trapping air purification apparatus,

FIG. 4 is a schematic representation in section of an embodiment of an air purification apparatus according to the invention in which a common source of germicidal radiation is used for the two air purifiers that it comprises,

and FIGS. 5 and 6 are diagrammatic representations of the apparatus of FIG. 4 in cross-section according to a-a or b-b of FIG. 4 respectively.

For the sake of clarity, the same elements are designated by the same references in the following.

With reference to FIG. 1, an air purification apparatus according to the invention in its preferred embodiment comprises a dry phase trapping air purifier A and a liquid phase trapping air purifier B.

It can be seen that the purification apparatus according to the invention is made mobile and placed on a lower box 6 mounted on rollers 7, which makes it easy to move it from one room to another or from one place to another in the same room. The lower box 6 contains the ventilation system at the inlet in the purifier A, while the purified air is removed from the purifier B.

The description now made with reference to FIGS. 2A, 2B, 2C relates to a dry phase trapping air purifier which can certainly be adapted to constitute the purifier A of Figure 1, but is rather built for use in standalone purifier.

Its construction as a whole respects a geometry with circular symmetry of revolution around a central longitudinal axis occupied by a source of radiation 5. The purifier is delimited by a tubular shell 1, here cylindrical in shape with a circular section, which is arranged , vertically relative to the ground, fixed on the casing 6. This shell, rigid and mechanically resistant, is typically made of plastic or stainless steel. It is lined with a sheath 3, made for example of aluminum foil, the purpose of which is to reflect the ultraviolet rays in the wavelength range of the source used.

The shell 1 encloses a mesh 2 which constitutes the destructive active mass of organic pollutants. It is a three-dimensional mesh network, based on wire, which fills the internal volume to the shell 1. More specifically, provision has been made preferably to use a metal fabric of knitted yarn, which is folded in several layers on itself, for example by winding on itself in the manner of a household metal sponge. In addition, the metal wire used was previously coated with a compound based on titanium dioxide. In this way, the active mass has a specific surface with photo-catalytic action causing an oxidative decomposition of pollutant molecules usually present in the air. In the operating conditions of the apparatus, the mesh sizes are chosen loose enough to allow free diffusion of the ultraviolet radiation within the whole of the active mass.

In the center of the purifier, in the axis of the shell 1, the source of germicidal radiation 5 represents the other essential element of the dry phase trapping air purifier. It is constituted, more particularly, by a longiform lamp emitting ultraviolet radiation which is surrounded by a protective tube 16 which is made of quartz to be transparent to UV rays. The lamp 5 is held in the vertical axis of the tube 16 by any means known per se, the tube 16 being itself maintained by star-shaped support struts whose branches 17 are welded to the shell 1. The assembly is chosen to be emitter in the UVC wavelength range, as we know to obtain it for example by a mercury lamp.

The active mass mesh 2 extends all around the tube 16 enveloping the UV lamp, and radially thereof to the reflective sheath 3 which internally double the shell 1. From place to place its strands of material are welded to vertical rods 18, possibly also on the sheath 3. This prevents the mesh collapses and it also avoids the creation of blades of air flowing through the scrubber from bottom to top. In the longitudinal direction, the active mass is divided into three beds, which together cover the treatment height from the inlet of the air flow through the lower end of the shell until its exit at the upper end, the distance between inlet and outlet being sufficient to ensure the degree of purification desired and avoid that immediately released into the atmosphere clean air mix dirty air not yet treated.

It has been schematically shown in FIGS. 2B and 2C that the constituent mesh of the active mass is not uniform. It has a gradient of mesh size variation, which decreases along the path of the air. In practical implementation, it is observed that in the three-bed distribution, the mesh is very loose in the lower bed 21, tighter in the intermediate bed 22, and very tight in the upper bed 23. Such a gradient in the longitudinal direction of the circulation of air is advantageous in that large particles present in the air at the entrance of the lower bed can cross the mesh of the latter and reach the upper bed only after having broken up into small particles which can be treated without causing clogging.

In certain embodiments of the invention, it is also possible to provide a transverse gradient, by radially compressing the mesh towards the UV lamp, in a compromise between the speed of passage of the air, the density of filling in walls. accessible to impaction and vacuum density accessible to UV penetration

In the successive stages of the active mass 2, an empty space is provided between the two successive meshing beds, over a much greater layer height than was illustrated at 25 for the example of FIG. 2B. . The space formed by the empty mesh layer provides the circulating air with a turbulent flow zone. While generally conserving a direction of flow in the longitudinal direction of the treatment unit, it is thus caused, at each empty mesh layer, a mixture of air circulation veins, so as to promote that of the air that has been treated closer along the lamp then passes farther, near the outer shell, and vice versa. In addition, the same layer of air between the mesh beds is let live through the UV rays, those emanating from the lamp itself, but also those that come back after reflection on the sheath 3. In addition to the reflections within the mesh, it is created in total a multi-directional diffusion of UV radiation to the adjacent areas of the two neighboring mesh beds.

In the lower part of the shell 1, at the discharge of the fan 8, a deflector screen 14 is interposed in the path of the air so as to prevent it from entering the immediate vicinity of the UV lamp, without first crossing a zone filled with active mass mesh. This deflector is conical in shape, with a point directed downwards. It covers the entire width of the central tube 16. It thus serves to deflect the flow of air out of the zone occupied by the central light source by directing it towards the entrance of the active mass. From the point of view of the mechanical assembly, the deflector 14 is carried fixed by a support 3 with three star stems, which is welded directly to the outer shell and distinct from the star spacer 4 supporting the mesh of the lower bed of active mass 21.

At the upper end of the shell 1, a filter is provided

15 which retains the mineral particles, thus usefully complementing the effect of the active mass under irradiation, since only particles of organic nature have been destroyed during the crossing of the active mass. It should be noted that this type of filter is only useful in the case where the purifier is intended for autonomous operation. Indeed if the treatment in dry phase is followed by a treatment. in the wet phase, the mineral particles will be retained in the liquid medium used in the downstream scrubber, which will thus act as a final filter.

During the path of the air in the mesh beds constituting the active mass, the particles which it entrains undergo a purification process pertaining to the synergistic combination of

W three phenomena that combine their potentiating effects in order to ensure the destruction of pollutants of an organic nature. The germicidal effect of radiation is mainly reflected in the particles of microorganisms, whereas these particles, such as polluting particles, undergo the effect of the impaction process.

On the internal walls of the mesh, their structural and functional characteristics are altered, and at the same time the photo-catalytic effect attacks by oxidation all the molecules that are sensitive to it, all the more so since they remain trapped temporarily in the empty cells of the mesh.

Reference will now be made to FIG. 3, illustrating the constitution of a wet scrubber according to the invention, considering that it is intended to be coupled to a dry scrubber preceding it in the course of the invention. air to treat.

Such a purifier comprises a container 100 containing a

200 liquid mass (actually water) in which are dispersed solid particles in suspension. The container 100 has a conical shape whose apex is directed downwards. The air is admitted into the purifier by a conduit 400 which opens into the enclosure containing the liquid mass, above the water level. It is

30 extracted at the same level by a conduit 500 opening into the surrounding atmosphere. A purge valve 700 is provided at the bottom of the container. It is used to evacuate the water to renew it, partially or totally, when it becomes congested with mineral particles not destroyed by the process or when the

55 catalyst particles are consumed and overused. The air is injected into the container 100 through the inlet duct 400 so as to follow a lamellar path winding in a helix by licking the walls of the container, as illustrated by the arrows F in FIG. 3. The mass liquid is set in motion by this flow of air. This generates a vortex, which ensures a continuous and regular mixing of the liquid mass, bringing with it the particles it contains. To promote the production of the vortex, the supply conduit 400 opens substantially tangentially to the inner wall of the container 100 in its upper part of larger diameter.

The interest of mixing particles under the effect of this vortex is multiple. It is asserted that the air describes a long path through the liquid mass, first following a downward spiral, then following another upward spiral. As for the particles they are constantly brought back from one place to another of the treatment tank, presenting all their faces in turn to the impact of the pollutants being destroyed, by approaching periodically closer to the the radiation source for their photo-catalytic effect. Both the residence time of the air in the active medium and the multiplicity of particles that it encounters are favorable to the phenomenon of impaction, and it adds that the vortex communicates to the pollutants being destroyed that it causes additional energy that also promotes this impaction phenomenon.

The organic pollutants reduced and / or weakened due to the impaction phenomenon are subjected to a photo-catalyzed germicidal treatment during the time they remain trapped within the liquid mass. For this purpose, the purifier comprises a source of germicidal radiation consisting of a tube 600 emitting in the range "C" of the ultraviolet spectrum which is arranged vertically in the tank 100. Where appropriate, it is intended to form the walls of the vessel in a transparent material, so that the user of the purifier can observe the operation of the vortex and see the state of the liquid medium.

The particles dispersed in the liquid active mass are advantageously made of a chemically inert polymer material, preferably based on polyethylene, the surface of which is coated with a compound based on titanium dioxide. Light because of their low density, they can easily remain dispersed within the liquid mass. Inert in their mass, they have very little risk of reaction with pollutants trapped within the liquid mass in the case where their photocatalytic coating would be damaged over time. However, it will often be preferable, alternatively, to form the particles of a material containing titanium dioxide in the mass. This is favorable particularly in view of the possibilities of superficial wear of the particles.

In a purification apparatus according to the invention combining a dry phase trapping air purifier A and a liquid phase trapping air purifier B as shown in FIG. 1, the box 6 is advantageously equipped of swivel casters 7, which allows to easily bring all in all desired points of the room whose indoor air must be purified. The box houses a fan 8 which draws air from inside the room, through the air inlet openings 9 formed on a side face of the box. At the top of the scrubber in the dry phase, the air retains a speed sufficient to be admitted into the wet scrubber and create the vortex effect.

Another configuration of an apparatus according to the invention combining the two types of scrubber is applied in the embodiment illustrated by FIGS. 4, 5 and 6. In this case, the two scrubbers are no longer truly placed side by side. but rather one below the other, and they operate with a single source of radiation, which is common to them.

In the particular case described, the cone of the wet-phase scrubber is arranged lower than the scrubber in the dry phase. Both are centered around a vertical axis, but they are not on the same axis. This allows a compact arrangement, where above the tank 100, the purified air outlet duct 500 passes next to the dry-phase scrubber next to it. The UV radiation source is constituted by a tube 60, of which we see in FIG. 4 that it traverses the hull 1 containing the three-dimensional active mass in the purifier A throughout the entire length of time, and that in the lower part of the apparatus, it enters the tank 100 containing the liquid mass dispersed particles of the purifier B. Given this arrangement, the flow of air in the three-dimensional mass is no longer from the bottom up but from top to bottom.

The air to be treated is sucked into a box 10 located at the bottom of the device. It is discharged by a fan 20 in a chamber 70 which constitutes a closed envelope, here of square section, all around the two purifiers and the conduit 500. Its upward speed is sufficient so that, without disturbing the entry into the vortex is led to the top of the column of the purifier A, at 30 in Figure 4. From the purifier A, it passes directly into the trapping liquid phase trap B, located below. It emerges from the duct 500, which passes through the enclosure 70 in a sealed manner to re-radiate it into the atmosphere from a collector 40, possibly equipped with an extractor.

Figure 4 shows in 50 the presence of a water reserve. Water is taken automatically to compensate for losses in operation and maintain the liquid mass at a constant, as is desirable for vortex stability. Finally, it is observed from FIG. 6 that the UV tube is in an off-center position with respect to the tank 100 where. it penetrates there to constitute the source of radiation of the purifier B and that it is protected from a too direct arrival of the flow of air by a deflector 80.

Claims

1. A method of purifying air essentially consisting in forcing the air to be treated to circulate through an active medium exposed to a germicidal radiation in the presence of a photo-catalytic material that it contains, with a destructive effect for the microorganisms possibly present in the air and retained in the active medium as reduced and / or weakened by impact on wall elements present for this purpose in the active medium.

2. The method of claim 1 wherein said active medium is constituted by an active mass produced in the form of a three-dimensional network of photocatalytic surface walls exposed to said germicidal radiation, organic pollutants possibly present in the circulating air. through said active mass being trapped in the voids of the latter by impact on the internal walls constituting its specific surface.

3. A method according to claim 2 wherein said active mass (2) consists of a multilayer metal mesh with photocatalytic coating, in particular based on titanium dioxide, which is arranged around a source of germicidal radiation longiform, in particular consisting of an ultraviolet ray emitting tube, preferably in the range of UV C, and in that the air flow is provided in a longitudinal direction parallel to the axis of the elongate source.

4. The method of claim 1 wherein said active medium is a liquid mass in which are dispersed photocatalytically active particles and is exposed to germicidal radiation which, in the presence of said particles with photo-catalytic activity, has a destructive effect for organic pollutants possibly present in the circulating air through said liquid mass which are trapped in said mass by impact on solid wall particles that it contains in suspension.

5. The process of claim 1 wherein the air to be treated is admitted to the liquid mass so as to generate a vortex therein.

6. Air purifying apparatus comprising at least one purifier comprising means for circulating the air to be treated through an active mass containing a photo-catalytic material and solid wall elements is exposed to a source of UV radiation germicidal, destructive effect of organic pollutants possibly present in the circulating air which are reduced and / or weakened by impact on said elements π solid wall and trapped in their vicinity in said active mass.

7. Apparatus according to claim 6 comprising at least one dry phase scrubber comprising means for forcing the air to be treated to flow through said active mass and wherein said active mass is made in the form of a network.

Three-dimensional photo-catalytic surface walls disposed around said source of germicidal radiation and the air flow being provided parallel to the axis of said source.

8. Apparatus according to claim 7, wherein said active mass is surrounded by a sheath (3) reflective for the

Radiation emitted by said source.

9. air purifying apparatus according to claim 7 or 8, wherein said mass is distributed longitudinally in several mesh beds photocatalytic walls separated by empty mesh layers providing air circulating

30 turbulent flow zones and / or wherein said mass active has a mesh size gradient from a looser mesh to a tighter mesh in the direction of airflow.

An air purifying apparatus according to claim 6, comprising at least one wet scrubber in which said active mass is made in liquid form in a vessel containing photocatalytically active particles dispersed in said mass which also constitute said particles. wall elements for the impaction of organic pollutants, and wherein there is provided air intake means which cause the formation of a vortex in said liquid mass.

11. An air purification apparatus according to claim 6 comprising means for forcing the air to be treated to circulate firstly through a dry phase scrubber made according to one of claims 7 to 9 and then through a scrubber. wet phase made according to claim 10, the wet-phase scrubber being preferably arranged vertically below the dry-phase scrubber and the scrubber containing a vertical radiation source which enters the wet-phase evaporator to form therein its source of radiation.