PASSIVE DEVICE FOR CAPTURING MICROPARTICLES SUSPENDED IN THE AIRBORNE

Abstract

PASSIVE DEVICE FOR CAPTURING MICROPARTICLES SUSPENDED IN THE AIRBORNE The present application relates to a device for capturing microparticles suspended in the air which is devoid of active ventilation means and electrical power supply means, the device comprises a structured support crossed by a large number of openings with a minimum dimension of between 1 millimeter and 15 mm, said structured support having a void rate greater than 80%, the structured support being coated with a medium for capturing microparticles suspended in an air flow chosen from: vegetable oils, mineral oils, silicone oils, animal fats, the structured support coated with said capture medium being configured to be crossed by an air flow with a linear speed of between 0.1 and 5 m / s without causing a pressure drop greater than 250 Pa.The present application also relates to a method for capturing microparticles suspended in the air and the use of the device, particularly in an underground network dedicated to passenger rail transport. Figure for abstract: figure 7.

Description

Title of the invention: PASSIVE DEVICE FOR CAPTURING MICROPARTICLES SUSPENDED IN THE AIRBORNE TECHNICAL FIELD OF THE INVENTION

[0001] The present invention relates to the field of air purification devices and methods. More particularly, it relates to devices and methods for capturing a significant portion of the microparticles contained in the ambient air. The invention finds a particularly advantageous application in the purification of the ambient air of underground traffic and transport networks. The present invention relates to a device provided with a structured support for capturing microparticles suspended in the air, devoid of active mechanical ventilation means and electrical power supply means. The present invention also relates to a method for capturing microparticles by a device which is the subject of the invention. PRIOR ART

[0002] Particulate air pollution in urban and peri-urban environments from various sources causes significant public health problems and is the cause of respiratory illnesses for exposed populations and additional costs for health organizations.

[0003] In its 2018 report, the European Environment Agency indicated that excessive concentrations of suspended particles (or "PM", abbreviated from "Particulate Matter") were responsible for approximately 422,000 premature deaths annually in 41 European countries, including approximately 391,000 in the 28 states of the European Union. Thus, providing air with a lower concentration of suspended particles is a public health issue.

[0004] To reduce the concentration of particles suspended in the air in an enclosed space where this concentration is particularly high, an effective ventilation system can be implemented. This solution, mainly implemented in underground networks, consists of renewing the air in the underground network with air less loaded with particles coming from outside, the underground air being discharged outside without any treatment. This solution has the disadvantage of not eliminating the pollutants, but only moving them from the inside to the outside, which increases the pollution of the outside air. In addition, this solution is not suitable for implementation outside an enclosed space, for example in the open air.

[0005] Other systems currently in use aim to capture and retain microparticles suspended in the air. Among the most common technologies we can cite the use of filter media with pores of an appropriate size to retain particles, the electrostatic precipitation of microparticles by application of an electric field or the absorption of microparticles in a flow of liquid circulated through the system.

[0006] These technologies require a power supply for their proper functioning, which prevents the installation of such systems in places without connection to the electrical network or in places where changing a battery would be impractical.

[0007] Furthermore, for their proper functioning, these technologies require an oriented air flow that circulates from an air inlet where an air flow to be purified enters to an air outlet from which an air flow discharged of some of its suspended particles escapes. The oriented nature of an air purification system means that the air purification system ceases to function correctly in the absence of an air flow directed according to the intended orientation. This oriented nature may also involve a risk of release, that is to say a risk that the particles captured by the air purification system are released in the event of a reversal of the air flow. In order to guarantee a constant and oriented air flow, the air flow is usually generated by a fan or other equivalent mechanical means, which has the disadvantage of complicating the installation by the addition of moving parts.In particular, systems using a filter medium, i.e. one with pore sizes that retain suspended particles, require a sufficiently powerful air flow to compensate for the significant pressure drop caused by the filter. OBJECTS OF THE INVENTION

[0008] It is recalled that a microparticle is a particle whose size is between 0.1 pm and 100 pm. In the context of the invention, the terms “suspended particles” designate microparticles suspended in the air and in particular microparticles with a diameter of less than or equal to 10 pm, also called PM 10, as well as microparticles with a size of less than 2.5 pm, also called PM2.5 and of a size of less than 1 pm, also called PMI.

[0009] The applicant set itself the objective of reducing the concentration of microparticles suspended in the air of collective urban spaces, in particular near road or rail transport infrastructures and especially for application in an underground transport network, which may in particular be road or rail. For these applications, the applicant sought a device which combines good ease of maintenance, a certain robustness, a capacity to operate without electrical power supply and a very low pressure drop. Since none of the solutions of the prior art meet all of these criteria, the applicant developed the device and the method which are the subject of the present invention. The present invention aims to remedy all or part of the drawbacks of the solutions of the prior art.

[0010] To this end, according to a first object, the present invention aims at a device for capturing microparticles suspended in the air which has the following characteristics: - the device is devoid of active means of ventilation and devoid of means of supplying electrical energy, - the device comprises a structured support crossed by a large number of openings of minimum dimension between 1 millimeter and 15 millimeters, said structured support having a void rate greater than 80%, preferably greater than 85%, preferably greater than 90%, very preferably of the order of 95%, - the structured support being coated with a medium for capturing microparticles suspended in an air flow chosen from: vegetable oils, mineral oils, silicone oils, paraffin oils or animal fats and - the structured support coated with said capture medium being configured to be crossed by an air flow with a linear speed of between 0.1 and 5 m / s without causing a pressure drop greater than 250 Pa.

[0011] For the purposes of the invention, the minimum dimension of an opening passing through the structured support corresponds to the diameter of the opening measured at its narrowest point. In other words, a minimum dimension of an opening of 1 millimeter means that a spherical particle of 1 millimeter in diameter can pass through said opening without being blocked.

[0012] Preferably, the average dimension of the openings is of the order of 5 millimeters. For example, the average dimension of the openings is between 3 and 10 millimeters.

[0013] These openings are present in the structured support of a device according to the invention "in large number", and a minimum number can be set, more or less arbitrarily, at approximately one thousand. For example, the structured support comprises on average at least one opening per square centimeter, or at least 4 openings per square centimeter, or at least 16 openings per square centimeter.

[0014] For the purposes of the invention, the void rate corresponds to the ratio between the volume of the structured support which is empty and the volume of the space delimited by the structured support which is occupied by solid matter.

[0015] The structured support may for example be a cross-shaped metal support having large openings or a polyester mesh forming large hexagonal openings. Any structured support according to the invention comprises large and numerous openings of substantially identical sizes, that is to say in the same order of magnitude in size. The structured support does not have a filtration role but rather a role of support for the capture medium. Indeed, the diameter of the openings of the structured support according to the invention, of the order of a millimeter, is much greater than the diameter of the microparticles captured by means of the device, of the order of a micrometer or a few tens of micrometers. These arrangements contribute to the very low pressure drop of the structured support.

[0016] The capture medium coated on the structured support ensures the capture of the microparticles either by a mechanism of sticking the microparticles to the medium, or by a mechanism of partial penetration of the microparticles into the medium, or by a combination of these mechanisms. Thanks to these arrangements, a portion of the microparticles present in an air flow passing through the device are captured by the capture medium. It is understood that the device does not require for its proper operation that the air flow circulates across the device in a predetermined direction, as long as contact between the air flow and the capture medium takes place. In this, the device is not oriented, which is particularly advantageous for positioning the device in a location where the direction of the air flows is likely to vary.The direction of an air flow is particularly likely to vary when the device is positioned outdoors, depending on the direction of the wind or when it is positioned near a road or rail transport route, depending on the direction of passage of vehicles.

[0017] Furthermore, since the microparticles do not accumulate only on one face of the structured support and since said microparticles are stuck and / or penetrate at least partially into the medium, the device is unlikely to release previously captured microparticles into the air in the event of a change in direction of the air flow passing through the device.

[0018] It is also clearly understood that the device which is the subject of the invention does not require, for its proper operation, active ventilation means, such as fan blades, nor an electrical power supply, no component of the device requiring such a power supply. This greatly facilitates its installation in a desired location, which may be a location that is difficult to access, for example in a railway tunnel, where carrying out specific electrical installation work would represent an unacceptable cost, and where the use of photovoltaic panels is not possible due to lack of light.

[0019] Over time, the accumulation of microparticles in the medium will be likely to lower the capture efficiency of the device which is the subject of the invention. Thus, at regular time intervals, it will be useful to replace the saturated capture medium with a fresh capture medium (new or recycled). Preferably, the capture medium is stripped of the structured support so that the structured support can be coated again and used at new.

[0020] In embodiments, the structured support is formed from a non-porous material.

[0021] In the context of the invention, a distinction is made between “pores” and “openings”. Pores are small cavities, typically less than 10 microns, and which are not necessarily through-holes. In contrast, openings are through-holes and their size is between 1 mm and 15 mm. Thus, the porosity of a non-porous material according to the invention, expressed as a percentage of voids left by the pores as defined above, relative to the remainder of the volume occupied by the structured support, is preferably less than 1%, very preferably less than 0.1%.

[0022] Thanks to these provisions, the capture medium is not absorbed by the material constituting the structured support. These provisions make it possible to prevent a reduction in the efficiency of capture of the particles by the structured support coated with capture medium which would be less if a significant part of the capture medium penetrated into the pores of the material constituting the structured support.

[0023] In embodiments, the structured support is arranged substantially vertically and the capture medium is a material that is liquid at ambient operating temperatures, held by surface tension on the structured support.

[0024] For example, the structured support is inclined at an angle less than or equal to 25°, preferably less than 15° relative to the vertical; such a slight inclination is understood here as a “substantially vertical” arrangement.

[0025] In embodiments, the capture medium is a vegetable oil. Preferably, the vegetable oil is chosen from compositions containing few unsaturated and polyunsaturated fatty acids or containing a high antioxidant content (for example vitamin E or polyphenols) which gives them good stability over time. For example, olive, apricot kernel, jojoba, sweet almond, castor, coconut, shea, hazelnut, plum, sea buckthorn, argan, avocado, hemp, macadamia, high oleic sunflower or palm oils are preferred. Other vegetable oils can also be used in poorly lit environments or when the ambient temperature is sufficiently low (for example winter).

[0026] In embodiments, the stability of the vegetable oil is extended by the addition of antioxidants.

[0027] In embodiments, the capture medium is a mineral oil, such as a paraffin oil, or a silicone oil.

[0028] In embodiments, the capture medium is a silicone oil, for example chosen from polydimethylsiloxanes, pure or modified by polyethers. Silicone-polyether copolymers have the advantage of being water-soluble.

[0029] In embodiments, the structured support comprises a woven textile. According to a particular embodiment, the textile is woven from polyester fibers.

[0030] In embodiments, the structured support is a cellular foam whose cells are open and whose size is between 2 mm and 10 mm. These cellular structures can be flexible, typically made of polyurethane, or rigid, for example made of metal or ceramic based on alumina or a mixture of metal oxides.

[0031] In embodiments, the structured support comprises a plurality of plates assembled together. Said plates are substantially planar parts, crossed by holes of minimum diameter between approximately 1 mm and 15 mm and coated with capture medium. Said plates can for example be superimposed or joined by one of their ends and inclined between them in a “V” or “W” arrangement. It is emphasized that the structured support coated with capture medium must as a whole, even when it is an assembly, have a low pressure drop according to the limits set by the invention. For example, the structured support as a whole is configured to be crossed by an air flow with a linear speed of 5 m / s without causing a pressure drop greater than 250 Pa.

[0032] In embodiments, the structured support comprises a metal structure. More particularly, the structured support may be a metal structure made of expanded metal, a metal plate obtained by stamping, or an expanded and stamped metal plate.

[0033] In embodiments, the structured support is an assembly of several metal plates. In embodiments, the structured support comprises a metal plate made of expanded metal and corrugated by stamping, sandwiched between two metal plates made of expanded metal.

[0034] It is recalled that an expanded metal plate is a metal plate that is cut and then stretched. In other words, expanded metal is produced by shearing a metal plate or coil in a press, equipped with knives creating a generally diamond-shaped metal mesh leaving voids surrounded by interconnected metal bars. Preferably, the metal constituting the metal plate is steel or aluminum. Aluminum is preferred because it is lighter. Furthermore, it is not a known catalyst for the oxidation of vegetable oils, unlike iron.

[0035] In embodiments, the metal support is anodized.

[0036] Thanks to these provisions, the metal has increased roughness and more easily retains the coated medium on the structured support.

[0037] In embodiments, the structured support comprises a honeycomb metal structure forming a pattern of polygonal cells, in particular hexagonal or rectangular. The metal constituting the walls of the cells is preferably aluminum.

[0038] In embodiments, the device which is the subject of the invention comprises a box housing the structured support coated with capture medium. Preferably, the box has a thickness of less than 40 cm, preferably less than 30 cm and very preferably less than 25 cm. This low thickness allows installation in constrained spaces, in particular under the nose of a platform in a railway station.

[0039] According to a second aspect, the invention aims at the use of a device for capturing microparticles suspended in the air according to the invention, implemented in an underground system, in particular in a complex dedicated to public rail transport, particularly in passenger pedestrian circulation areas, at the nose of a platform, at the mouth of a railway tunnel, in a railway tunnel in a braking zone, or even in a railway tunnel in an acceleration zone.

[0040] The use of a device which is the subject of the invention in a network of railway tunnels intended for the transport of passengers is particularly useful because this closed environment sees a large number of passengers passing through who are exposed to a high concentration of microparticles generated by rail transport.

[0041] In embodiments, the microparticle capture device which is the subject of the invention, placed in a railway tunnel, comprises a substantially planar structured support and said structured support is substantially parallel to the main axis of a rail sheltered by the railway tunnel.

[0042] In embodiments, the device according to the invention is positioned in a railway tunnel in a braking zone or in an acceleration zone, preferably in a braking zone.

[0043] A braking zone or an acceleration zone is defined as the area located less than 5 meters from a section of rail along which the train brakes before arriving at the station or accelerates when leaving the station. Preferred zones are those less than 100 meters from the entrance of the station, and even more preferably less than 50 meters from the entrance of the station.

[0044] The device according to the invention is preferably placed at the braking zones which are the main zones of microparticle emissions in an underground rail transport network. For example, the device according to the invention is placed near the mouth of the station, on the side where the train enters the station, either on the tunnel wall or on the vertical wall of the platform at the height of the train bogies.

[0045] In embodiments, the device according to the invention is positioned in the last meters of the tunnel before arrival at the station, as close as possible to the outer rail and ideally opposite the braking system of a train when the train enters the station, and positioned at a height corresponding to the height of the braking system of the train. or just above.

[0046] According to a third aspect, the present invention relates to a method for capturing microparticles suspended in the air, which comprises: - the provision of a structured support crossed by a large number of minimum dimensions between 1 millimeter and 15 millimeters, said structured support having a void rate greater than 80%, preferably greater than 85%, preferably greater than 90%, very preferably of the order of 95%, - coating the structured support with a capture medium configured to capture, by contact, microparticles suspended in an air flow and chosen from: a vegetable oil, a mineral oil, a silicone oil and an animal fat, - the structured support coated with medium being configured to be crossed by an air flow with a linear speed of between 0.1 m / s and 5 m / s without causing a pressure drop greater than 250 Pa and - bringing the structured support into contact with a flow of air loaded with microparticles without active means of ventilation allowing forced circulation of the flow of air loaded with microparticles.

[0047] In embodiments, the method comprises: - a step of stripping at least part of the medium coated on the structured support and - a step of replacing the stripped capture medium by coating the structured support with a fresh capture medium.

[0048] In embodiments, the stripping step comprises washing the medium-coated structured support with soapy water.

[0049] In embodiments, the stripping step comprises stripping the structured support coated with medium by a pressurized air flow.

[0050] In embodiments, the stripping step comprises stripping the structured support coated with medium by a flow of pressurized water vapor.

[0051] In embodiments, the stripping step comprises cryogenic cleaning.

[0052] The aims, advantages and particular characteristics of the method which is the subject of the present invention being similar to those of the device which is the subject of the present invention, they are not recalled here. BRIEF DESCRIPTION OF THE FIGURES

[0053] Other advantages, aims and particular characteristics of the invention will emerge from the following non-limiting description of at least one particular embodiment of the device and method which are the subject of the present invention, with reference to the appended drawings, in which:

[0054] [Fig. 1] schematically represents a first particular embodiment of the device which is the subject of the present invention,

[0055] [Fig.2] represents a photograph of a structured support implemented in the first particular embodiment of the device which is the subject of the present invention,

[0056] [Fig.3] represents a photograph of a structured support implemented in the first particular embodiment of the device which is the subject of the present invention,

[0057] [Fig.4] represents a structured support implemented in a second particular embodiment of the device which is the subject of the present invention,

[0058] [Fig.5] represents a photograph of a structured support implemented in a third particular embodiment of the device which is the subject of the present invention,

[0059] [Fig.6] represents, schematically and in perspective, a particular embodiment of the device which is the subject of the present invention which comprises a protective box,

[0060] [Fig.7] represents a photograph of a particular embodiment of the device which is the subject of the present invention, installed under a platform in a railway station and

[0061] [Fig.8] represents, schematically and in the form of a flowchart, a succession of particular steps of the method which is the subject of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0062] The present description is given without limitation, each characteristic of an embodiment being able to be combined with any other characteristic of any other embodiment in an advantageous manner.

[0063] It should be noted, from now on, that the schematic figures are not to scale. The figures representing a photograph are to scale, but the scales may vary between them.

[0064] [Fig. 1] shows a schematic view of an embodiment of the device 100 which is the subject of the present invention. According to this particular embodiment, the device 100 for capturing microparticles comprises a structured support 105 formed from a network composed of hexagonal meshes connected to each other. Such a mesh network can be produced by weaving fibers. These fibers can be polyester fibers.

[0065] The structured support 105 is crossed by a large number of openings 115 with a minimum dimension greater than 1 millimeter and average dimensions of the order of 5 millimeters. It is preferred not to exceed a maximum dimension of 15 mm, and preferably not to exceed a maximum dimension of 10 millimeters. The structured support 105 has a void rate greater than 80%, preferably greater than 85%, preferably greater than 90%, very preferably of the order of 95%.

[0066] The structured support 105 is configured to have a very low pressure drop. In addition to the large size of the openings which allows little hindrance to the circulation of an air flow through the structured support 105, care will be taken not to add other elements to the device 100, for example which would be likely to increase the overall pressure drop of the device beyond 250 Pa or preferably beyond 160 Pa. Thus, the structured support 105 coated with said capture medium is configured to be crossed by an air flow with a linear speed of between 0.1 and 5 m / s without causing a pressure drop greater than 250 Pa. Preferably, the structured support 105 coated with said capture medium is configured to be crossed by an air flow with a linear speed equal to 3 m / s, very preferably equal to 5 m / s without causing a pressure drop greater than 250 Pa.In embodiments, the structured support 105 coated with said capture medium is configured to be crossed by an air flow with a linear speed equal to 3 m / s, very preferably equal to 5 m / s without causing a pressure drop greater than 160 Pa.

[0067] In a particular embodiment, the structured support 105 coated with said capture medium is configured to be crossed by an air flow with a linear speed equal to 2 m / s without causing a pressure drop greater than 25 Pa, or configured to be crossed by an air flow with a linear speed of 5 m / s without causing a pressure drop greater than 156 Pa, or configured to be crossed by an air flow with a linear speed of 0.1 m / s without causing a pressure drop greater than 0.06 Pa.

[0068] In embodiments, the structured support may be composed of several layers of materials superimposed on each other. For example, the structured support illustrated in Figures 2 and 3 is a woven support with a surface area of ​​0.045 m2 and a thickness of 6 mm formed by three-dimensional weaving of polyester fibers. The weaving makes it possible to obtain two parallel layers comprising meshes with an average opening of 5 mm representing approximately 63% of the surface. The density of the woven support is 380 g / m2. It has a void rate of around 95%. The Aerosleep® product marketed by the company QLEVR may, for example, be used as a structured support.

[0069] Note that the scale visible in the photograph in [Fig.2] is expressed in centimeters.

[0070] According to an essential characteristic of the invention, the structured support 105 is coated with a capture medium 110. This capture medium is advantageously chosen from: vegetable oils, silicone oils, mineral oils and fats of animal origin. Preferably, the capture medium 110 is a liquid held in place on the structured support by surface tension.

[0071] In embodiments, the vegetable oil is selected from olive oil, apricot oil, jojoba oil, sweet almond oil, castor oil, coconut oil, shea oil, hazelnut oil, plum oil, sea buckthorn oil, argan oil, avocado oil, macadamia hemp oil, sunflower oil oleic or palm oil. In other embodiments, the mineral oil is a paraffin oil. In still other embodiments, the animal fat is pork fat.

[0072] In a particular embodiment, the structured support 105 illustrated in Figures 2 and 3 is immersed in a bath of capture medium so that its entire surface is covered with this capture medium. The coated support is removed from the bath, then suspended vertically for 5 hours so that the excess capture medium drains naturally. The support coated with capture medium thus obtained has a density of 590 g / m2. Its void rate is close to 91%. The coated structured support thus obtained is ready for use, optionally after having been mounted in a suitable protective box, and in particular of the type illustrated in Figures 6 and 7. Such structured supports coated with capture medium have been tested by the applicant under different operating conditions. These tests and their results in terms of microparticle capture efficiency are presented at the end of this description.

[0073] [Fig. 4] shows a schematic view of another embodiment of a structured support 205 that can be implemented in a microparticle capture device according to the invention. The structured support 205 is made of metallic material, for example steel or aluminum. Preferably, the metallic material is anodized.

[0074] The structured metal support may comprise a single layer of expanded metal or several layers superimposed on each other. In one embodiment (not shown) the structured support comprises a metal plate made of expanded metal corrugated by stamping interposed between two metal plates made of expanded metal.

[0075] As an example, to form this support, a first expanded aluminum sheet of 4 mm thickness is provided, having open meshes of 16 mm large width and 8 mm small width. These openings represent a volumetric void rate of 88%. A second expanded sheet is then obtained by stamping a sheet similar to the first expanded sheet, so as to create a corrugated plate whose final apparent thickness amounts to 8 millimeters. The second sheet has a volumetric void rate of 95%. Finally, the structured support is prepared by inserting the second sheet between two expanded sheets similar to the first sheet. This structured support, composed of the assembly of three sheets, has a total thickness of 16 mm and a void rate of 92%.

[0076] Preferably, if the openings formed in the deployed sheets are not perfectly symmetrical, care will be taken to turn the interposed sheet by an angle of 90° relative to the orientation of the other two sheets. In other words, the orientation of the meshes of the sheet arranged in the center is turned by 90° relative to the orientation of the meshes of the sheets arranged on the outside. For example, if the meshes of the two sheets external have their greatest width horizontally, then the interposed sheet is oriented so that its meshes are positioned with their greatest width in the vertical direction.

[0077] In [Fig.5], we observe a photograph of a structured support 305 which can be implemented in a particular embodiment of the invention. The structured support 305 is a cellular foam whose cells are open and whose size is between 2 and 10 mm. These cellular structures are flexible and formed from polyurethane.

[0078] Note that the scale visible in the photograph in [Fig.5] is expressed in centimeters.

[0079] In other embodiments, the structured support may comprise a rigid cellular foam, for example made of metal or ceramic based on alumina or a mixture of metal oxides.

[0080] In embodiments (not shown), the structured support comprises a honeycomb structure formed by polygonal cells, in particular rectangular or hexagonal. The diameter of the hexagonal cells may for example be between 1 and 25 millimeters. Preferably, the cells are made of metallic material and in particular aluminum; aluminum is advantageous because it is inert, light and has good fire resistance. The thickness of the walls of the cells is for example less than 3 millimeters, preferably less than 1 millimeter.

[0081] In embodiments, the structured support comprises a honeycomb structure of the type described above but pierced with numerous holes passing through the side walls forming the cells.

[0082] For example, a honeycomb structured support can be obtained by welding together previously drilled and then corrugated sheets.

[0083] [Fig.6] shows a particular embodiment of a device 300 for capturing microparticles according to the invention. The device 300 comprises a box 351, for example formed from steel or thermoformed plastic, housing a structured support according to the invention (not visible in [Fig.6]). The box 351 is of rectangular and flattened section. The box 351 is intended to be fixed to a surface, for example on a wall. For example, [Fig.7] illustrates an installation of the device 300 on the vertical surface of a train platform, opposite the rails, in an underground station. In embodiments, the housing 351 includes a removable front panel 352, for example secured by screws at each corner of the panel, or by a hinge connection between the front panel 352 and the body of the housing 351, or by fitting one edge of the front panel 352 onto the housing 351 and mechanically locking it to the opposite edge of the panel.In another embodiment, the supports are introduced into the box through the side openings. In any event, . device 300 preferably comprises a means of access to the structured support housed in the box, so as to be able to carry out maintenance operations on the structured support; these maintenance operations will be described in greater detail below.

[0084] Preferably, the structured support is formed of one or more flat plates, that is to say that they have a thickness significantly smaller than their width and height dimensions. Each plate is arranged in the box so that their plane forms an angle of 5 to 90° with the plane of the box, preferably between 10 and 45°. A box can house a structured support formed of several flat plates, arranged for example in a V or W shape depending on the thickness available inside the box.

[0085] The microparticle capture device 300 comprises ventilation openings allowing outside air to circulate inside the box 351. For example, holes are drilled on the surface of the front plate 352, or lateral ventilations 353 are provided. Any other configuration allowing easier circulation of ambient air flows towards the inside of the box may be implemented without deviating from the invention.

[0086] Preferably, the box 351 has a thickness of less than 40 cm, preferably less than 30 cm and very preferably less than 25 cm. This low thickness allows installation in restricted spaces, in particular under the nose of a quay.

[0087] In addition to the implementation illustrated in [Fig.7], other implementations of the device that is the subject of the invention are advantageous. Other uses in a tunnel, in particular in an underground complex dedicated to public rail transport, include installation in areas intended for pedestrian passenger traffic, at the nose of a platform, at the mouth of a railway tunnel, in a railway tunnel in the braking zone, or in a railway tunnel in the acceleration zone. According to a particularly advantageous implementation mode, the microparticle capture devices will be positioned in the braking zone of a train, that is to say along the platform in the station or less than 100 meters, preferably less than 50 meters, from the mouth of the station, on the side from which a train comes during its normal circulation.

[0088] In other embodiments, a device according to the invention is installed in a road tunnel, for example on the wall at a height of between approximately 20 cm and approximately 200 cm from the ground, knowing that this height corresponds to the heights of highest particle concentration due to the combination between their point of generation by the emission of exhaust gases, by the abrasion of the wheels and brakes, and by the circulation of dust deposited on the road, and their dilution by air currents. present in the environment.

[0089] In yet other embodiments, a device according to the invention is installed outdoors, for example in a public space with frequent pedestrian traffic and positioned not far from a road.

[0090] We now describe methods for capturing airborne microparticles in relation to [Fig.8] which shows a succession of steps of a particular embodiment of a method 1000 of using a device for capturing airborne microparticles.

[0091] The method 1000 comprises a step 1005 of providing a structured support according to the invention. Such a structured support may be of the type described above, with reference to FIGS. 1 to 5.

[0092] During a step 1010, the structured support is coated with a capture medium configured to capture microparticles suspended in an air flow by contact.

[0093] The coating methods may vary depending on the properties of the capture medium used. It is recalled that this capture medium is chosen from: a vegetable oil, a mineral oil, a silicone oil and an animal fat.

[0094] For example, the coating step 1010 may be carried out by immersing a structured support in a bath of capture medium. The capture medium may be heated to lower its viscosity prior to the immersion operation. Alternatively, the coating step 1010 may be carried out by spraying the capture medium onto the structured support. Any other means for applying a layer of capture medium to the structured support may be implemented without deviating from the invention.

[0095] Preferably, the capture medium is a liquid material at room temperature. For example, the capture medium is liquid at a temperature between 15°C and 25°C, preferably liquid at a temperature between 10°C and 30°C. In this case, a step of draining the structured support after immersion or spraying may be provided to remove the excess capture medium.

[0096] In the case where the support is a metal support made of anodizable metal (such as aluminum), it will preferably be anodized prior to the coating step 1010.

[0097] During a step 1015, the structured support is brought into contact with a flow of air loaded with microparticles. It is recalled that the oil-coated structured support is configured to be crossed by a flow of air with a linear speed of between 0.1 and 5 m / s without causing a pressure drop greater than 250 Pa. It is also recalled that the device which is the subject of the invention does not require, for its proper operation, active ventilation means allowing the forced circulation of the flow of air loaded with microparticles. Thus, ambient air flows are used so that the air flows loaded with microparticles to be captured come into contact with the capture medium coated on the structured support. During this step, the capture medium gradually becomes loaded with microparticles which adhere to the capture medium and / or partially penetrate the medium.

[0098] It should be noted that the expression "active ventilation means" as used here is limited to the device according to the invention, but does not include any mechanical machines or devices generating an air current, such as a train or a vehicle, or any fans which provide an air current in a tunnel: such an air current, even generated by a machine or device external to the device according to the invention, is included here in the expression "ambient air flow".

[0099] At the end of step 1015, preferably when the saturation of the capture medium reaches a level which excessively lowers the capture performance of the medium, said medium is replaced. In a particular embodiment, the structured support as a whole is removed from the capture device which is the subject of the invention and discarded. Preferably, the capture medium is stripped from the capture support and the support is used again.

[0100] In the latter case, during a stripping step 1020, at least a portion of the medium coated on the structured support is removed. The modalities of the stripping step 1020 are selected according to the nature of the capture medium, so as to maximize the proportion of capture medium stripped from the structured support and to minimize the degradation of the support.

[0101] In embodiments, the stripping step 1020 comprises washing the structured support coated with medium with water loaded with a detergent, for example with soapy water. This cleaning method will be particularly suitable for capture media soluble in soapy water. A jet of water is projected onto the structured support to detach and cause the capture medium to flow. The water jet may be under high pressure and the water may be heated, depending on the needs.

[0102] In embodiments, the stripping step 1020 comprises stripping the structured support coated with medium by a pressurized air flow.

[0103] In embodiments, the stripping step 1020 comprises stripping the structured support coated with medium by a pressurized steam flow. For example, the steam flow has a pressure of 4 bars and a temperature between 150°C and 180°C.

[0104] In embodiments, the stripping step 1020 comprises cryogenic cleaning. Cryogenic cleaning is a process similar to sandblasting but in which the media used is solid CO2 or dry ice. The dry ice is projected onto the surfaces to be cleaned in a stream of compressed air.

[0105] It is specified that several methods mentioned above for the counting step 1020 may be combined without deviating from the invention.

[0106] Once the structured support has been stripped during step 1020, a replacement step 1025 of the stripped capture medium is implemented. During the replacement step 1025, the structured support is coated again with a fresh capture medium, i.e. one with a low microparticle content. The coating during step 1025 is preferably identical to that already described for the initial coating step 1010 of the structured support.

[0107] In embodiments, at the end of the stripping step 1020, the used capture medium loaded with microparticles is treated in order to reduce its microparticle content. For example, a filtration method is implemented or a centrifugation method, so as to obtain a fraction of recycled capture medium whose microparticle content is lower than that of the used capture medium. Thus, the “fresh” capture medium mentioned in the present application can relate to both a new capture medium and a recycled capture medium.

[0108] It is specified at this stage that the steps 1020 of stripping the saturated capture medium and 1025 of replacing the medium by coating the structured support with a fresh medium may be carried out on site, at the location where the device which is the subject of the invention is installed, or in a workshop, or in a factory. In the first case, a mobile workshop will for example be installed on a train wagon or on a mobile service vehicle (for example a van) so as to be able to carry out these steps on site. In the case where steps 1020 and 1025 are carried out in a workshop or factory, workers will collect the “used” structured supports and install new (or recycled) ones. The structured supports will then be brought back to the workshop or factory for recycling by implementing steps 1020 and 1025.

[0109] Microparticle capture performance tests carried out by the applicant on particular embodiments of the microparticle capture device according to the invention are now described. Several particular embodiments of a device according to the invention are prepared, they are numbered 1 to 7 below.

[0110] Device for capturing microparticles No. 1 (Olive oil / Aerosleep ®): a woven support with a surface area of ​​0.045 m2 and a thickness of 6 mm is provided, formed by 3D weaving of polyester fibers such as the Aerosleep product marketed by the company QLEVR. The weaving consists of two parallel faces comprising meshes with an opening of 5 mm (average dimension) representing approximately 63% of the surface. The density of the woven support is 380 g / m2. It has a void rate of around 95%. The support is immersed in an olive oil bath preheated to 60°C so that its entire surface is covered with oil. The coated support is removed from the bath, then suspended vertically for 5 hours to allow excess oil to drain naturally. The resulting structured support coated with capture medium has a density of 590 g / m2. Its void ratio is close to 91%.

[0111] Device No. 2 (Sunflower oil / Aerosleep ®): device No. 1 is reproduced by replacing the olive oil with sunflower oil.

[0112] Device No. 3 (Peanut oil / Aerosleep ®): device No. 1 is reproduced by replacing the olive oil with peanut oil.

[0113] Device No. 4 (Lard / Aerosleep ®): Device No. 1 is reproduced by replacing the olive oil with lard previously heated to 80°C. The lard thus deposited represents approximately 60% of the final mass of the structured support coated with capture medium.

[0114] Device No. 5 (Castor oil / Aerosleep ®): device No. 1 is reproduced by replacing the olive oil with castor oil.

[0115] Device No. 6 (Olive oil / 8ppi PU foam): Device No. 1 is reproduced by replacing the woven support with an 8 ppi, 3cm thick open-cell polyurethane foam (reference RegiCell 8 FM2 marketed by the company Foampartner). This support has a density of 27 kg / m3. The diameter of the open cells is approximately 4.5mm. The void rate calculated from the intrinsic density of the polyurethane (typically 1200kg / m3) is approximately 98%. It increases to 97% after coating with oil.

[0116] Device No. 7 (Peanut oil / PU foam 8ppi): Device No. 6 is reproduced by replacing the olive oil with peanut oil.

[0117] For each of devices No. 1 to 7, the structured support coated with a capture medium, described above, is housed in a box.

[0118] During a first test (test 1), the applicant carried out an evaluation of the performance of capturing microparticles by devices according to the invention in an underground passenger rail transport network, in a tunnel.

[0119] Test 1: Devices 1 to 7 detailed above are exposed to the air of a tunnel in an underground passenger rail transport network, approximately 15 meters from the entrance of an underground station. The average content of fine PM 10 particles in the station was previously measured at 93 pg / m3, and the speed of passage of the polluted air through the boxes was measured at 0.14 m / s as a daily average. The box housing the structured support coated with capture medium is fixed on the tunnel wall, approximately 1.5 meters from the nearest rail. The bottom of the box is 20 cm from the ground. The structure of the box is similar to that illustrated in [Fig.6]. It has two open opposite faces, positioned perpendicular to the tunnel wall so that the air flow generated by the passage of trains can pass through it. Inside the box several structured supports coated with capture medium form a 15 degree angle with the tunnel wall.

[0120] After exposure, the structured supports coated with capture medium are removed and then washed by keeping them for 15 minutes in agitated soapy water heated to 80°C so as to detach the fine particles that have been trapped. The washing water is then filtered through a cellulose membrane with openings of 0.45 μm. The filtered particles and the membrane are rinsed with ethanol to remove oil residues. The quantity of PM collected is determined by weighing the membrane, after drying at 60°C for 2 hours.

[0121] The results obtained are grouped in Table 1 for different structured supports coated with capture medium and for different exposure durations. They are expressed in grams (g) of solid particles (PM) collected on the structured support coated with capture medium per day and per square meter of structured support coated with capture medium (gPM / m2 / d), on average over the exposure period. Reference Device tested Exposure time (in days) Particles captured (gPM / m2 / d) Testl -a Device 1 14 0.35 Testl -b Device 1 17 0.61 Testl -c Device 1 17 1.01 Testl -d Device 1 25 0.38 Testl -e Device 1 42 0.47 Testl -f Device 1 56 0.57 Testl -g Device 2 11 0.18 Testl -h Device 2 17 0.37 Testl -i Device 3 14 0.92 Testl -j Device 3 14 0.51 Testl -k Device 3 17 0.75 Testl -1 Device 3 28 0.25 Testl -m Device 3 28 0.44 Testl -n Device 3 42 0.10 Testl -o Device 4 17 0.86 Testl -p Device 5 11 0.28 Testl -q Device 5 11 0.24 Testl -r Device 5 14 0.25 Testl -s Device 6 14 0.52 Testl -t Device 7 14 0.41

[0123] The devices tested show good performance in capturing ambient air in an underground partitioned environment. A quantity of particles is observed captured between 0.18 gPM / m2 / day and 1.01 gPM / m2 / day depending on the tests, with an average of around 0.47 gPM / m2 / day. It is noted that a longer duration of exposure, up to 56 days, does not appear to significantly reduce the average quantity of particles captured.

[0124] The granulometric analysis of the suspended particles carried out on the wash waters of the tests referenced Testl-b and Testl-c in Table 1 (reproduction tests) indicate, in both cases, a volume fraction of PM 10, PM2.5 and PMI of 48%, 19% and 4% respectively.

[0125] During a second test (test 2), the applicant carried out an evaluation of the microparticle capture performance of devices having undergone stripping of a used capture medium and then re-coating with a new medium. These reused devices are tested in an underground passenger rail transport network.

[0126] Test 2: The structured supports coated with capture medium from the tests referenced Testl-b and Testl-k in the table above are recycled by re-coating with oil, respectively under the same conditions as those described for devices No. 1 and No. 3 above. The devices obtained after re-coating are exposed again under the same conditions as for test 1. Table No. 2 compares the results obtained for the structured supports coated with new capture medium (referenced Testl-b and Testl-k above) and for the structured supports coated with capture medium recycled once and twice. Reference Device tested Exposure time (in days) Particles captured (gPM / m2 / day) Testl - b Device 1 17 0.61 Test2 - a Device 1 recycled 1 time 14 0.38 Test2 - b Device 1 recycled 2 times 14 0.73 Testl - k Device 3 17 0.75 Test2 - c Device 3 recycled 1 time 14 0.41 Test2 - d Device 3 recycled 2 times 14 0.81

[0128] It is observed that the recycled and re-coated structured supports (Test2-a, b, c and d) capture a comparable quantity, i.e. of the same order of magnitude, of particles as the new supports coated with new capture medium (Test1-b and k).

[0129] During a third test (test 3), the applicant carried out an evaluation of the performance of capturing microparticles by devices according to the invention in an underground passenger rail transport network, at the level of a platform in a station.

[0130] Test 3: The conditions of test 1 are reproduced but the box containing the structured supports coated with capture medium are placed in a station, under a platform nose. The bottom of the box is at the level of the ballast, in the middle of the station and its distance from the nearest rail is 0.8 meters. On average daily, the air speed through the box was measured at 0.31 m / s. The results at this location are given in table 3 for different structured supports coated with capture medium and exposure times. Reference Device tested Exposure time (in days) Particles captured (gPM / m2 / d) Test3 -a Device 1 14 0.32 Test3 -b Device 1 14 0.35 Test3 -c Device 1 28 0.41 Test3 -d Device 1 47 0.23 Test3 -e Device 1 14 0.21 Test3 -f Device 6 14 0.38 Test3 -g Device 6 14 0.52

[0132] It is noted that the supports placed under a platform nose (Test3- a to g) capture a comparable quantity, i.e. of the same order of magnitude, of particles as the supports placed in a tunnel (Test1- a to f and s).

[0133] During a fourth test (test 4), the applicant carried out an evaluation of the performance of capturing microparticles by devices according to the invention in an underground passenger rail transport network, at the level of a corridor allowing pedestrian circulation of passengers.

[0134] Test 4: the conditions of the first test are reproduced but by placing the box containing the structured supports coated with capture medium on the wall of a passenger corridor opening onto the station platform at a height of approximately 1.5 meters from the ground. On average daily, the air speed through the box was measured at 0.43 m / s. The results at this location are given in Table 4 for different devices and exposure times. Reference Device tested Exposure time (in days) Particles captured (gPM / m2 / d) Test4 -a Device 1 17 0.12 Test4 -b Device 1 25 0.17 Test4 -c Device 1 42 0.28 Test4 -d Device 1 56 0.10 Test4 -e Device 1 14 0.29 Test4 -f Device 3 14 0.22 Test4 -g Device 3 28 0.21

[0136] It is observed that the supports placed in a passenger corridor (Test4) capture a comparable quantity, i.e. of the same order of magnitude, of particles as the supports placed in a tunnel (Test1) or under the nose of the platform (Test3). However, the quantity of particles captured by the supports placed in a passenger corridor (Test4) is significantly lower.

[0137] During a fifth test (test 5), the applicant carried out an evaluation of the performance of capturing microparticles by devices according to the invention near a road traffic axis.

[0138] Test 5: The structured supports coated with capture medium are hung on a mesh protected from the rain and exposed directly to the outside air near a busy intersection. The quantities of microparticles collected over the exposure period are determined by washing as in test no. 1. The results are given in table no. 5. Reference Device tested Exposure time (in days) Particles captured (gPM / m2 / d) Test5-a Device 1 7 0.83 Test5-b Device 1 14 1.14 Test5-c Device 1 21 0.98 Test5-d Device 1 28 0.71 Test5-e Device 2 3 0.74 Test5-f Device 2 6 0.75 Test5-g Device 2 7 0.86 Test5-h Device 2 14 1.44 Test5-i Device 2 18 0.48 Test5-j Device 2 77 0.43

[0140] The devices tested show good capture performance in ambient air in an open air environment. A quantity of captured particles of between 0.43 gPM / m2 / day and 1.44 gPM / m2 / day is observed depending on the tests, with an average of around 0.84 gPM / m2 / day.

[0141] The granulometric analysis of the particles suspended in the wash water of example no. 12a indicates that the PM10, PM2.5 and PMI particles represent respective volume fractions of 62%, 23% and 9%.

Claims

Claims

1. Device for capturing microparticles suspended in the air, characterized in that: - the device is devoid of active ventilation means and devoid of electrical power supply means, - the device comprises a structured support crossed by a large number of openings of minimum dimension between 1 millimeter and 15 mm, said structured support having a void rate greater than 80%, preferably greater than 85%, preferably greater than 90%, very preferably of the order of 95%, - the structured support being coated with a medium for capturing microparticles suspended in the air flow chosen from: vegetable oils, mineral oils, silicone oils, or animal fats and - the structured support coated with said capture medium being configured to be crossed by an air flow of linear speed between 0.1 and 5 m / s without causing a pressure drop greater than 250 Pa.

2. The device of claim 1, wherein the structured support is formed from a non-porous material.

3. Device according to one of the preceding claims, in which the structured support is arranged substantially vertically and in which the capture medium is a liquid material at room temperature maintained by surface tension on the structured support.

4. Device according to one of the preceding claims, in which the capture medium is a vegetable oil chosen from olive, apricot, jojoba, sweet almond, castor, coconut, shea, hazelnut, plum, sea buckthorn, argan, avocado, hemp, macadamia, oleic sunflower or palm oil or in which the capture medium is chosen from silicone and paraffin oils.

5. Device according to one of the preceding claims, in which the structured support comprises a woven textile, preferably woven from polyester fibers.

6. Device according to one of the preceding claims, in which the structured support comprises a cellular foam whose cells are open and whose size is between 2 and 10 mm, preferably chosen from a polyurethane foam and a metal or ceramic foam based on alumina or a mixture of metal oxides. metals.

7. Device according to one of the preceding claims, in which the structured support comprises a plurality of plates assembled together.

8. Device according to one of the preceding claims, in which the structured support comprises a metallic structure.

9. Device according to any one of the two preceding claims, in which the structured support is an assembly of several metal plates, preferably comprising a metal plate made of expanded metal and corrugated by stamping, inserted between two metal plates made of expanded metal.

10. Device according to any one of the preceding claims, which comprises a box (351) housing the structured support coated with capture medium and in which the box has a thickness of less than 40 cm, preferably less than 30 cm and very preferably less than 25 cm.

11. Use of a device according to one of the preceding claims, in an underground passage, in particular in a complex dedicated to public rail transport, particularly in passenger pedestrian circulation areas, at the nose of a platform, at the mouth of a railway tunnel, in a railway tunnel in a braking zone, or in a railway tunnel in an acceleration zone.

12. Use of a device according to claim 11, wherein the device is positioned opposite the braking system of a train when the train enters the station, and positioned at a height corresponding to the height of the braking system of the train or just above.

13. Method for capturing microparticles suspended in the air, characterized in that it comprises: - providing a structured support crossed by a large number of openings of minimum dimension between 1 mm and 15 mm, said structured support having a void rate greater than 80%, preferably greater than 85%, preferably greater than 90%, very preferably of the order of 95%, - coating the structured support with a capture medium configured to capture by contact microparticles suspended in an air flow and chosen from: a vegetable oil, a mineral oil, a silicone oil and an animal fat, - the structured support coated with said capture medium being configured to be crossed by an air flow with a linear speed of between 0.1 and 5 m / s without causing a pressure drop greater than 250 Pa and - bringing the structured support into contact with an air flow loaded with microparticles without active ventilation means allowing forced circulation of the air flow loaded with microparticles.

14. Method for capturing microparticles suspended in the air according to the preceding claim, which comprises: - a step of stripping at least part of the medium coated on the structured support and - a step of replacing the stripped capture medium by coating the structured support with a fresh capture medium.

15. A method of capturing airborne microparticles according to the preceding claim, wherein the stripping step comprises washing the structured support coated with medium with soapy water.

16. A method of capturing airborne microparticles according to any one of claims 14 or 15, wherein the stripping step comprises stripping the structured support coated with medium by a pressurized air flow or by a pressurized steam flow.

17. A method of capturing airborne microparticles according to any one of claims 14 to 16, wherein the stripping step comprises cryogenic cleaning.

18. A method of capturing airborne microparticles according to any one of claims 13 to 17, wherein the coating of the structured support with a capture medium is carried out by dipping the structured support into a capture medium or by spraying the capture medium onto the structured support.

19. A method of capturing airborne microparticles according to any one of claims 13 to 18, wherein the coating of the structured support with a capture medium comprises a step of heating the capture medium used for dipping or spraying.

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