Use of a sintered porous ceramic part for air treatment

Abstract

Air treatment device comprising: - a sintered ceramic part (2) having a total porosity greater than 40%, - an air circulator (3) configured to generate an airflow to be treated through the ceramic part.

Description

Title of the invention: Use of a sintered porous ceramic part for air treatment technical field

[0001] The present invention relates to the use of a sintered porous ceramic part, in particular a sintered ceramic foam, to treat, and in particular decontaminate, air, in particular air in enclosed habitable spaces (dwellings, offices, vehicle interiors, ...). Previous technique

[0002] Air quality is an important topic in the field of public health.

[0003] Air can notably contain human pathogenic microbes transmissible by respiratory tract, or "pathogens". These pathogens can cause disease in a human being, particularly in the respiratory tract.

[0004] Viruses, bacteria, and fungi are known to be transmitted through the air. Examples include influenza viruses and coronaviruses, notably SARS and SARS-CoV-2. These pathogens can be attached to suspended particles which, depending on their size, can penetrate the gas exchange regions of the lungs, or even pass through the lungs to affect other organs.

[0005] Filtration with a fiber filter is widely used to retain suspended particles because such a filter generally offers a good compromise between filtration efficiency and energy consumption. Collective or individual protective systems or industrial dust collectors are composed of non-woven fibrous media, that is, a web or sheet of fibers oriented directly or randomly and bonded by friction, cohesion, or adhesion. These systems must be regularly renewed.

[0006] Furthermore, personal protective equipment typically uses paper or fabric filters. However, these filters are single-use. They therefore generate large quantities of waste. They also require an uninterrupted manufacturing and distribution process to avoid shortages.

[0007] Air can also contain pollutants.

[0008] In particular, human activities, such as the combustion of fossil fuels in vehicles and various industrial processes, generate significant quantities of harmful particles. Typical air pollutants in homes and workplaces may include, for example, particulate matter, nitrogen oxides (NOx) or sulfur oxides (SOx), and organic compounds, including formaldehyde. and similar volatile organic compounds (VOCs).

[0009] Activated carbon is widely used for treating molecules by adsorption. Its mechanical resistance is limited. Furthermore, it needs to be replaced regularly.

[0010] Fiber filter filtration is also widely used to separate polluting particles suspended in the air.

[0011] US10188975 finally describes the use of cordierite filters of the "honeycomb" type to remove particulate pollutants, optionally coated with a sorbent and / or a catalyst to remove VOCs. Tests have shown that "honeycomb" type filters result in a high pressure drop.

[0012] Due to their very good chemical and mechanical resistance and their ability to work at high temperature, ceramic membranes can also be used as filters to clean hot polluted gases.

[0013] There is therefore a need for new solutions for decontaminating and / or depolluting air, and in particular air intended to be inhaled.

[0014] One object of the invention is to meet, at least partially, this need. Description of the invention

[0015] The invention relates to an air treatment device, in particular for air at room temperature (20°C), the treatment device comprising a sintered ceramic part having a total porosity greater than 40%, preferably greater than 50%, preferably greater than 55%, or even greater than 60%, or even greater than 70% and preferably less than 90%, or even less than 80%, preferably between 55% and 80%.

[0016] Preferably, at least part of the surface defined by the porous network is coated with a coating for inactivating one or more pathogens, and / or a catalytic coating adapted to a reaction of at least one atmospheric pollutant.

[0017] The ceramic part also has the advantage of being able to be cleaned and / or purified for reuse. It therefore generates little waste.

[0018] Preferably, the treatment device includes a pressure drop detector and an electronic unit programmed to trigger or indicate the need for a cleaning and / or purification operation based on information received from the pressure drop detector. Even more preferably, it includes a cleaning and / or purification tool, preferably controlled by the electronic unit based on information received from the pressure drop detector. Maintenance is thus considerably simplified.

[0019] In one embodiment, the processing device includes a computer memory in which information relating to the ceramic part is recorded, preferably an identifier of the ceramic part and / or at least one photo representing, at least partially, the ceramic part at a specific moment, preferably before the first use of the ceramic part.

[0020] Preferably, the ceramic part also has one or more of the following characteristics:

[0021] - the median pore size is between 1 and 400 pm; as will be seen in more detail later in the description, such total porosity offers a microstructure perfectly suited to the treatment of pathogens and pollutants; - the ceramic part comprises more than 80% by mass of recrystallized silicon carbide, the intergranular porosity being preferably greater than or equal to 5% and less than 25%, preferably greater than or equal to 10% and less than 20%; - the median pore size (D50 in volume, measured by mercury porosity) is greater than 1 pm, or even greater than 5 pm, greater than 7 pm, or even greater than 10 pm, or even greater than 20 pm, or even greater than 30 pm, or even greater than 40 pm and / or less than 400 pm, or even less than 300 pm, or even less than 200 pm, or even less than 160 pm, or even less than 150 pm; - pores larger than 300 pm represent less than 10% by volume, or even less than 5% by volume, of the total porosity; - tortuosity is greater than 1, or even greater than 1.1, or even greater than 1.2, or even greater than 1.3, or even greater than 1.4 and less than 2, or even less than 1.9, or even less than 1.8, or even less than 1.7; - the ceramic piece has a surface layer having a total porosity less than 0.95 times the porosity at the center of the ceramic piece, the pores of the surface layer preferably having a median size greater than 1 pm and less than 20 pm, the total porosity of the surface layer preferably being greater than 30% and less than 70%, the thickness of the surface layer preferably being between 5 and 500 pm.

[0022] The treatment device may be an actively air-filtering device, for example an air conditioner or a heater blowing air, in particular an electric device. It then includes an air circulator configured to generate a flow of air to be treated through the ceramic part.

[0023] The treatment device can in particular be used for air filtration in enclosed habitable spaces such as homes, offices or vehicle interiors.

[0024] The treatment device can also be passive, and in particular be personal protective equipment such as a mask or a cartridge suitable for use in personal protective equipment such as a mask.

[0025] In a first principal embodiment, more than 95%, more than 97%, more than 98%, more than 99% of the total porosity of the ceramic piece is open.

[0026] Preferably, the ceramic part is a ceramic foam having a plurality of interlocking cells, delimited by ceramic walls and connected to each other by interconnecting windows.

[0027] A cell on the surface of the ceramic foam also generally has one or more openings to the outside. The pores are therefore generally accessible to the air outside the ceramic foam. The microstructure is thus well adapted to retain airborne particles, and in particular particles carrying pathogens and pollutants.

[0028] Preferably, the cell walls are formed by agglomeration of grains, this agglomeration leaving interstices or "intergranular pores" between the grains. An example of ceramic foam is described in EP 1 778 601.

[0029] Preferably, the pore size distribution is bimodal. More specifically, the porosity distribution, measured with a mercury porosimeter, has a first main peak centered on a first pore size and a second main peak centered on a second pore size.

[0030] The first pore size is considered to be the median size of the intergranular pores, and is representative of so-called "intergranular" porosity. It is preferably less than 25 pm, or even less than 20 pm, and greater than 4 pm, or even greater than 7 pm.

[0031] Preferably, the intergranular porosity is at least 5%, preferably at least 8%, preferably even at least 10% and / or less than 25%, or even less than 20%.

[0032] The second pore size is considered the median size of the cellular pores and is representative of so-called "interconnection" porosity, constituting substantially the complement to 100% of the intergranular porosity. It is preferably less than 400 pm, or even less than 300 pm, or even less than 200 pm, or even less than 180 pm, or even less than 160 pm and greater than 40 pm, or even greater than 50 pm, or even greater than 80 pm.

[0033] Preferably, the total porosity is greater than 55%, or even greater than 60%, or even greater than 70%.

[0034] A ceramic foam advantageously filters particles up to 30 times smaller than the median pore size, thereby limiting pressure drop. A ceramic foam advantageously offers an excellent compromise between pressure drop and filtration capacity.

[0035] In a second main embodiment, at least part of the piece ceramic is coated with a coating that inactivates one or more pathogens.

[0036] This coating can cover the outer surface of the porous ceramic part, or even the entire available surface area within the porosity network. The microstructure of the ceramic foams described above then provides a large contact surface that promotes the chemical inactivation of pathogens.

[0037] In a third main embodiment, at least a part of the ceramic piece is coated with a catalytic coating catalyzing a reaction of at least one air pollutant, preferably chosen from nitrogen oxides (NOx), sulfur oxides (SOx) and similar volatile organic compounds (VOCs).

[0038] This coating can cover the outer surface of the porous ceramic part, or even the entire available surface area within the porosity network. The microstructure of the ceramic foams described above then provides a large contact surface that promotes the removal of atmospheric pollutants.

[0039] Of course, the characteristics of the different main embodiments can be combined.

[0040] The invention also relates to an air treatment method, and in particular an air decontamination method, using an air treatment device according to the invention, the method comprising bringing the air into contact with the ceramic part of the air treatment device.

[0041] Preferably, the process includes, after said contact, a cleaning and / or purification operation on the ceramic part. This operation may in particular be mechanical, for example by washing, chemical or thermal.

[0042] Preferably, the process comprises the following steps: a) treatment of a first quantity of air using the air treatment device according to the invention; b) cleaning and / or purification of the ceramic part of said air treatment device, then repeating step a) to treat a second quantity of air.

[0043] The treated air is preferably extracted from a dwelling, an office or a vehicle compartment, for example from a car, a train, an aircraft, a truck or a boat. Definitions

[0044] By "decontaminate" is meant to deactivate, preferably eliminate, one or more human pathogens transmissible by respiratory route and contained in the air.

[0045] Any non-metallic and non-organic material is called a “ceramic”.

[0046] A coating comprising or consisting of a catalyst material capable of catalyzing a chemical reaction is called a “catalytic coating”.

[0047] Consolidation by heat treatment at over 1100°C, of ​​a preform, with possibly a partial or total melting of some of its constituents (but not all of its constituents, so that the preform is not transformed into a liquid mass).

[0048] The term "recrystallized silicon carbide" refers to silicon carbide recrystallized by high-temperature treatment of the ceramic part, and in particular of the ceramic foam. Recrystallization is a well-known phenomenon corresponding to the consolidation by evaporation of the smallest silicon carbide grains followed by condensation to form a bond with the larger grains.

[0049] Unless otherwise specified, the term "pores" refers to all the pores.

[0050] The pore size is determined using a mercury porosimeter.

[0051] A bimodal pore size distribution has two main peaks, i.e., peaks that have the highest peaks.

[0052] The median size of a pore population is the size which divides, in volume, said population into two groups: one group representing 50% of the pore volume and whose pores have a size less than the median size and another group representing 50% of the pore volume and whose pores have a size greater than or equal to said median size.

[0053] In a ceramic foam manufactured according to EP 1 778 601, analysis using a mercury porosimeter reveals a bimodal pore size distribution, i.e., exhibiting distinct first and second principal peaks. These peaks are representative of the two pore families, namely intergranular pores and interconnecting pores, and the median pore size of each family is considered to be given by the pore size corresponding to the apex of each peak.

[0054] The total porosity, as a percentage, is classically equal to 100 x (1 - the ratio of the geometric density divided by the absolute density).

[0055] The geometric density is measured according to ISO 5016:1997 or EN 1094-4 and expressed in g / cm3. It is classically equal to the ratio of the mass of the sample divided by the apparent volume.

[0056] The absolute density value, expressed in g / cm3, is classically measured by dividing the mass of a sample by the volume of that sample ground in such a way as to substantially eliminate porosity.

[0057] The term "open porosity" refers to the porosity attributable to all accessible pores. Open porosity can be measured according to ISO 15901-1.

[0058] Tortuosity is measured by nanotomography. The images have a resolution suitable for binarization. The use of software such as iMorph© allows for obtaining a three-dimensional geometric characterization and calculating the tortuosity. Tortuosity is defined as the ratio between the length of the shortest path allowing to traverse the sample in the direction of its thickness, within its porosity, and the length of the straight line segment joining the starting point and the ending point corresponding to this path, that is to say the distance between these points.

[0059] "Understand", "include" and "present" should be interpreted broadly and without limitation unless otherwise indicated. Brief description of the figures

[0060] Other features and advantages of the invention will become apparent upon examination of the drawing, provided by way of illustration and not limitation, in which:

[0061] • [Fig.1] [Fig.1] shows, at first magnification, an image obtained with a Scanning Electron Microscope on samples taken 10 to 20 mm from the surface of a ceramic foam of a treatment device according to the invention; • [Fig.2] [Fig.2] shows, at a second magnification, an image obtained at Scanning Electron Microscope on samples taken 10 to 20 mm from the surface of a ceramic foam of a processing device according to the invention; • [Fig.3] [Fig.3] shows, at a third magnification, an image obtained with a Scanning Electron Microscope on samples taken 10 to 20 mm from the surface of a ceramic foam from a processing device according to the invention; • [Fig.4] [Fig.4] schematically shows a ceramic piece with porosity variable; • [Fig.5] [Fig.5] schematically shows an example of an air treatment device according to the invention.

[0062] In the various figures, identical references are used to designate identical or analogous objects. Detailed description

[0063] An air treatment device according to the invention can be used for decontaminating ambient air intended to be inhaled by a person. The air is typically at a temperature between 0° and 30°C, generally between 15°C and 25°C. Its pressure is atmospheric pressure.

[0064] The processing apparatus comprises a ceramic part whose shape is adapted to the intended application. Tape casting or foaming processes are particularly well suited to the production of preforms with complex shapes, thus avoiding or limiting machining steps.

[0065] In particular, in an embodiment corresponding to personal protective equipment, the ceramic part may have the shape of a flat piece, for example of a lozenge, preferably having, when viewed from the front, a surface area greater than 5 cm2 and / or less than 100 cm2, preferably less than 50 cm2.

[0066] Preferably, the ceramic part according to the invention has, in particular in this embodiment: - a thickness between 1 and 20 mm, preferably greater than 2 mm, or even greater than 3 mm and / or less than 15 mm, 10 mm, or 8 mm, and / or - a length and / or width greater than 1 cm or 3 cm and / or less than 10 cm, 8 cm, or 5 cm.

[0067] In another embodiment, the ceramic piece may in particular have the shape of a flat or tubular piece.

[0068] Preferably, the ceramic part according to the invention has, in particular in this embodiment: - a thickness between 2 mm and 100 mm, preferably greater than 5 mm, or even greater than 10 mm and / or less than 90 mm, 80 mm, 70 mm, and / or - a length and / or width greater than 1 cm, 5 cm, 10 cm and / or less than 100 cm, 80 cm, 50 cm, 30 cm.

[0069] The ceramic part is preferably removable from the treatment device, in particular for the purpose of cleaning and / or purifying it.

[0070] The ceramic part is made of a sintered material.

[0071] All processes for manufacturing a sintered part are conceivable, provided that the porosity is adapted. This adaptation may in particular consist of adding a porogenic agent to the initial feedstock.

[0072] The ceramic part may in particular be made of silicon carbide or cordierite or aluminium titanate or zirconia or alumina or mullite or silica or mixtures thereof.

[0073] According to one variant, the ceramic part comprises more than 80% by mass of silicon carbide (SiC), or even more than 90% of silicon carbide, or even more than 95% of silicon carbide, or is essentially made of silicon carbide.

[0074] According to a preferred embodiment, silicon carbide is recrystallized silicon carbide, in particular in alpha form.

[0075] According to another variant, the ceramic piece is made up, in mass percentage on the basis of the crystallized phases, of 25 to 55% mullite (3Al2O3-2SiO2), 20 to 65% corundum (Al2O3 in alpha crystalline form), 10 to 40% zirconia (ZrO2), the mullite, corundum and zirconia together representing more than 80%, preferably more than 90%, preferably more than 95%, preferably more than 98% of the mass of the crystallized phases.

[0076] The following description refers to an application to an electrical appliance such as an air conditioner. This application is not, however, limiting. In particular, The device can be personal protective equipment such as a mask.

[0077] First principal embodiment: filtration

[0078] Preferably, as shown in [Fig.5], the treatment device 1 comprises a ceramic piece 2 and a circulator 3 for circulating contaminated and / or polluted air A, preferably at a temperature below 30°C, at 25°C and / or above 10°C, preferably above 15°C, through the ceramic piece 2.

[0079] The device may also optionally include a heat exchanger, not shown, to modify the air temperature, and / or a humidifier, not shown, to modify the air humidity.

[0080] Typically, the circulator may consist of, for example, a pump and a set of pipes. It is optional. For example, for a respiratory mask, no circulator is necessary, as circulation results from inhalation by the mask wearer.

[0081] The ceramic part has a high total porosity to allow passage through the filter with reduced pressure drop. However, the porosity must be sufficiently fine to ensure filtration suitable for the targeted particles. But the ceramic part must not clog too quickly.

[0082] Preferably, more than 95%, more than 97%, more than 99% of the total porosity of the product is open.

[0083] Porous ceramic foams, which have a low density (5 to 50% of the theoretical density), have proven to be remarkably well suited.

[0084] They can be made from the vast majority of ceramic powders, in particular alumina or silicon carbide.

[0085] Recrystallized silicon carbide-based ceramic foams described in EP 1 778 601 have particularly high available surface areas or, for an equivalent available surface area, a lower density. They are preferred above all.

[0086] Recrystallized silicon carbide is particularly interesting because it allows for the production of parts with a specific microstructure. Figures 1 to 3 illustrate the specific microstructure of a recrystallized silicon carbide foam.

[0087] The walls of recrystallized silicon carbide delimiting the cells 10 are formed by agglomeration of grains 18, this agglomeration leaving interstices 20, or "intergranular pores" between the grains 18.

[0088] The walls thus exhibit a so-called "intergranular" porosity. Intergranular porosity is therefore constituted by the interstitial spaces that are necessarily created between grains by the agglomeration of these grains.

[0089] The cells 10 are interconnected by interconnection windows 12. Surface cells open outwards through openings 16. The porosity Interconnection is created by the "cellular pores", namely the interconnection windows 12 between cells 10 and the openings 16 to the outside of the surface cells.

[0090] In the particular case of recrystallized silicon carbide foams, intergranular porosity thus coexists with interconnection porosity.

[0091] In the example shown in figures 1 to 3, the presence of cellular pores and smaller intergranular pores can be observed.

[0092] The intergranular porosity is a function of the grain size of the ceramic powder, in particular silicon carbide, used.

[0093] The interconnection porosity is a function of the foaming agent used, in particular depending on its quantity in the starting charge which is shaped to constitute the preform.

[0094] The presence of intergranular porosity provides both a very large available surface area and a low density.

[0095] Foams with intergranular porosity are therefore effective for filtration and / or as a support for a coating for inactivating one or more pathogens, and / or as a catalyst support, while being lightweight.

[0096] Preferably:

[0097] - the median size of intergranular pores is 10 to 100 times smaller than that of cellular pores; and / or - the intergranular porosity is at least 5%, preferably at least 8%, preferably even more preferably at least 10% and / or less than 25%, or even less than 20%; and / or - the median size of the cellular pores is less than 400 pm, or even less than 300 pm, or even less than 200 pm, or even less than 180 pm, or even less than 160 pm and greater than 40 pm, or even greater than 50 pm, or even greater than 80 pm; and / or - the median size of the intergranular pores is less than 25 pm, or even less than 20 pm and greater than 4 pm, or even greater than 7 pm; and / or - the pore size distribution is bimodal; and / or

[0098] - the total porosity is greater than 55%, or even greater than 60%, or even greater than 70%.

[0099] Such foams can in particular be manufactured according to the following successive steps:

[0100] a. preparation of a mixture M containing a suspended ceramic powder, at least one gelling agent and at least one foaming agent, at a mixing temperature higher than the gelling temperature of said gelling agent, b. shearing of said mixture M at a foaming temperature higher than said gelling temperature, until a foam is obtained, c. gelling of said foam by cooling said mixture M to a temperature lower than the gelling temperature of said gelling agent, d. drying of said gelled foam so as to obtain a preform, e. cooking by high-temperature treatment of said preform so as to to obtain a porous ceramic foam.

[0101] EP 1 778 601 provides further details on these foams.

[0102] According to a particular embodiment, the ceramic part, and in particular the ceramic foam, has a lower total porosity on the side of the air to be decontaminated.

[0103] In particular, as shown in [Fig.4], it may comprise a porous body 25 and one or more superimposed surface layers 26-27 from the surface of the porous body, the total porosity and / or the median pore size of the superficial layers being different, preferably less than the total porosity at the center C of the porous body.

[0104] In a particularly advantageous embodiment, the total porosity of the surface layer is less than 0.95, 0.90 or 0.8 times the total porosity at the center of the porous body.

[0105] Preferably the total porosity of the surface layer is greater than 30%, or even greater than 35% and preferably less than 70%, or even less than 60%, or even less than 50%.

[0106] Preferably, the pores of the surface layer have a median size greater than 1 pm, or even greater than 2 pm, or even greater than 3 pm and less than 20 pm, or even less than 10 pm, or even less than 5 pm.

[0107] The thickness of the surface layer is preferably between 5 and 500 pm, preferably greater than 10 pm and / or less than 400 pm, or even less than 200 pm, or even less than 100 pm.

[0108] In one embodiment, the ceramic part comprises several superimposed surface layers from the surface of the porous body, the superimposed surface ceramic layers having different respective total porosities and / or median pore sizes.

[0109] According to one variant, the surface layer(s) may be spaced away from the porous body.

[0110] In one embodiment, the total porosity and / or the median size of the pores is lower the further the surface layer is from the porous body 25. There is thus a gradient of total porosity, the total porosity and the median size of the layer defining the inlet face 30 of the air to be filtered being lower than those of the other layer(s).

[0111] Preferably, the total porosity of a surface layer, preferably of each surface layer, is greater than 30%, or even greater than 35%, and preferably less than 70%, or even less than 60%, or even less than 50%.

[0112] Preferably, the pores of a surface layer, preferably of each surface layer, have a median size greater than 1 pm, or even greater than 2 pm, or even greater than 3 pm and less than 20 pm, or even less than 10 pm, or even less than 5 pm.

[0113] The thickness of a surface layer, preferably of all the surface layers, is preferably between 5 and 500 pm, preferably greater than 10 pm and / or less than 400 pm, or even less than 200 pm, or even less than 100 pm.

[0114] The different layers can result from the juxtaposition of different unit ceramic pieces or from the projection of an adherent coating onto the surface of the porous body or from the impregnation of a part of the porous body in order to locally modify its porosity.

[0115] In particular, when the ceramic part is a recrystallized silicon carbide ceramic foam, a surface layer can be obtained by impregnating a portion of the preform's thickness with a silicon carbide-based slip. The slip may optionally contain pore-forming agents such as a foaming agent. The slip then at least partially fills the pores. After sintering, this results in a surface layer.

[0116] Preferably, the impregnated part extends from the inlet face 30 of the air to be filtered.

[0117] A porosity that varies with depth advantageously allows for the mechanical trapping of particles of different sizes, and thus broadens the spectrum of possible applications.

[0118] According to an advantageous embodiment, regardless of the type of ceramic part, the ceramic part is uncoated. It then acts as a pure filter.

[0119] Second principal embodiment: decontamination

[0120] In one embodiment, at least a part of the outer surface and / or the surface defined by the porous network of the ceramic part is coated with a coating for inactivating one or more pathogens.

[0121] The inactivation coating is adapted to the pathogens to be inactivated.

[0122] In particular, the inactivation coating may be a coating that eliminates one or more pathogens, for example, bactericidal and / or virucidal. The inactivation coating may, in particular, consist of nanoparticles, especially those based on silver and / or copper.

[0123] The inactivation coating can be deposited by impregnation directly into the porous structure. In particular, when dealing with a ceramic foam, the re Inactivation garment can be deposited by impregnation directly onto the walls of the porous network of the foam.

[0124] An inactivation coating is particularly useful if the microstructure of the ceramic part is insufficient to prevent pathogens from passing through it. Simple tests can be performed to verify whether this situation occurs.

[0125] The highly porous microstructure, and in particular the microstructure of a ceramic foam, advantageously offers a very large exchange surface with the inactivation coating.

[0126] Third principal embodiment: pollution control

[0127] In one embodiment, at least part of the surface defined by the porous network is coated with a catalytic coating suitable for removing at least one air pollutant selected from nitrogen oxides (NOx), sulfur oxides (SOx), similar volatile organic compounds (VOCs).

[0128] All coatings used in gas pollution control applications can be used for the ceramic part. In particular, the ceramic part can be provided with a catalytic coating that eliminates nitrogen oxides and / or sulfur oxides. The coating can, in particular, be platinum-based.

[0129] The coating can be deposited on one of the external faces of the ceramic part, preferably the face of the air inlet to be filtered.

[0130] The highly porous microstructure, and in particular the microstructure of a ceramic foam, advantageously offers a very large exchange surface with the catalytic coating. Cleaning, purification

[0131] Regardless of the embodiment, the ceramic part offers excellent mechanical strength under compression and allows for a wide variety of shapes.

[0132] Advantageously, the ceramic part can be cleaned and / or purified for reuse. Cleaning consists of removing unwanted material accumulated in the pores. Purification consists of inactivating pathogens accumulated in the pores.

[0133] The refractoriness, chemical stability and mechanical strength of ceramic materials, in particular silicon carbide, make it possible in particular to subject the ceramic part, or even the air treatment device according to the invention, to a continuous or spot heat treatment (in particular when it is a personal protective equipment such as a mask), in order to eliminate pathogens, and in particular viruses and bacteria, sensitive to heat.

[0134] The duration of the heat treatment is adapted to the pathogens and the temperature applied.

[0135] Heat treatments at higher temperatures can also be implemented to burn the filtered particles and thus clean the filter.

[0136] Cleaning and / or purification can also result from a chemical action, for example bactericidal or virucidal. For example, the ceramic part can be immersed in a bactericidal or virucidal bath.

[0137] Cleaning or purification can also result from a mechanical action, for example by washing the ceramic part, for example by putting it in the dishwasher.

[0138] The processing device may optionally include a pressure loss detector 32 and an electronic control unit 34 for the pressure loss detector 32.

[0139] The pressure drop detector 32 can be, for example, a Pitot tube, with a capillary integrated into the glass or metal capsule.

[0140] The pressure loss detector 32 and the electronic unit make it possible to evaluate the level of fouling continuously or on a spot basis and to inform an operator accordingly, for example by means of a screen.

[0141] Preferably, the treatment apparatus also includes a cleaning and / or purification tool 36. In a preferred embodiment, the ceramic part is disassembled and subjected to this tool.

[0142] Preferably, this tool, for example a heating element, is integrated into the processing unit, for example fixed in contact with the ceramic part. Preferably, it is controlled by the electronic unit 34, preferably based on information received from the pressure drop detector. The electronic unit 34 can thus trigger a cleaning or purification operation of the ceramic part at regular time intervals and / or based on information provided by the pressure drop detector 32.

[0143] The processing device may optionally include a computer memory 38 in which information relating to the ceramic part is recorded, for example an identifier or a photo showing its state at a given moment.

[0144] Such memory, for example of the RFID chip type, advantageously facilitates traceability. Functioning

[0145] The operation follows directly from the preceding description.

[0146] Initially, a photo of the microstructure of the ceramic part is taken and recorded in computer memory 38.

[0147] The circulator 3, powered for example by the electrical network, draws in polluted and / or contaminated air A and circulates it through the ceramic part 2. The contaminated particles and polluting particles are retained by the porous sintered microstructure.

[0148] The variation of porosity per layer, and in particular the presence of the layers Perforations 26 and 27 advantageously allow filtration of a wide range of particles.

[0149] Particles, as well as polluting gases contained in the air, also come into contact with the inactivation coating and the catalytic coating. Contact with the inactivation coating causes the inactivation, and preferably the destruction, of pathogens. Contact with the catalytic coating causes a chemical reaction that destroys certain polluting gases. Filtration helps to ensure prolonged contact of the air with the coatings. The action of destroying pathogens and / or pathogens is therefore very effective.

[0150] The treated air T exits the treatment device, under the effect of the pressure exerted by the circulator.

[0151] After a certain period of use, or on the instruction of an operator, or following the detection of a clogging by the pressure loss detector 32, the electronic unit 34 controls the heating resistance 36 in order to destroy the pathogens and / or eliminate the accumulated material.

[0152] The destruction of pathogens can thus result from contact with the inactivation coating and / or from heating. In some applications, the inactivation coating is therefore optional.

[0153] After cleaning and / or purification, the ceramic part 2 can be reused.

[0154] At any time, the microstructure of the ceramic part can be compared to the photograph stored in computer memory 38.

[0155] As is now clear, the invention makes it possible to optimize air treatment, in particular the air of enclosed habitable spaces such as homes, offices and vehicle cabins.

[0156] In particular, a treatment device according to the invention allows for both the filtration of particles, the inactivation of pathogens, and the elimination of polluting organic substances. The ceramic component used is advantageously reusable, even imperishable, and recyclable.

[0157] Of course, the invention is not limited to the embodiments described, which are provided for illustrative purposes only.

[0158] In particular, any treatment device, whether or not it includes a circulator, is considered. A passive treatment device, i.e., one not powered by an energy source, for example, an individual respiratory mask filtering the air inhaled by a person, is considered a treatment device.

Claims

Demands

1. An air treatment apparatus, at room temperature, for an enclosed habitable space, said apparatus comprising: - a sintered ceramic piece (2) having a total porosity greater than 40%, the pores of size greater than 300 pm representing less than 10% by volume of said porosity, - an air circulator (3) configured to generate a flow of air to be treated through the ceramic piece, the ceramic piece being a ceramic foam having a plurality of interlocking cells, delimited by ceramic walls and connected to each other by interconnecting windows, the walls delimiting the cells being formed by agglomeration of grains, this agglomeration leaving interstices between the grains.

2. Apparatus according to the preceding claim, wherein the sintered ceramic part (2) has a total porosity greater than 55%.

3. Apparatus according to the preceding claim, wherein the sintered ceramic part (2) has a total porosity of less than 90%.

4. Apparatus according to any one of the preceding claims, wherein the ceramic part is made of silicon carbide or cordierite or aluminium titanate or zirconia or alumina or mullite or silica or mixtures thereof.

5. Apparatus according to any one of the preceding claims, wherein the ceramic part has a median pore size greater than 1 pm.

6. Apparatus according to the immediately preceding claim, wherein the median pore size is greater than 10 pm and less than 200 pm.

7. Apparatus according to any one of the preceding claims, wherein the ceramic foam has: - more than 80% by mass of recrystallized silicon carbide.

8. Apparatus according to any one of the preceding claims, wherein the ceramic foam has a pore size distribution, measured with a mercury porosimeter, which is bimodal and has first and second principal peaks centered on first and second pore sizes between 4 and 25 pm and between 40 and 400 pm, respectively, the intergranular porosity, represented by the first peak, being greater than or equal to 5% and less than 25%.

9. Apparatus according to the immediately preceding claim, in which: - said second pore size is greater than 50 pm and less than 200 pm, and / or - said first pore size is greater than 7 pm and less than 20 pm.

10. Apparatus according to any one of the preceding claims, wherein the ceramic part is a ceramic foam having a tortuosity greater than 1 and less than 2.

11. Apparatus according to any one of the preceding claims, wherein, in said ceramic foam: - the open porosity represents more than 98% of the total porosity, and / or - the intergranular porosity is greater than or equal to 10% and less than 20%.

12. Apparatus according to any one of the preceding claims, wherein the ceramic part comprises a surface layer having a median pore size greater than 1 pm and less than 20 pm, the total porosity of the surface layer being greater than 30% and less than 70%, the thickness of the surface layer being between 5 and 500 pm.

13. Apparatus according to the immediately preceding claim, wherein the ceramic part comprises several said surface layers having different respective total porosities.

14. Apparatus according to any one of the preceding claims, wherein - at least a part of the outer surface of the ceramic part and / or the surface of the porous network of the ceramic part is coated with a coating for inactivating one or more pathogens, and / or - at least a part of the outer surface of the ceramic part and / or the surface of the porous network of the ceramic part, is coated with a catalytic coating suitable for a reaction of at least one atmospheric pollutant.

15. Device according to any one of the preceding claims, comprising a pressure drop detector (32) and an electronic unit (34) programmed to trigger or report on the need for a cleaning and / or purification operation based on information received from the pressure drop detector.

16. Apparatus according to the preceding claim, comprising a cleaning and / or purification tool (36) controlled by the electronic unit based on information received from the pressure loss detector.

17. Apparatus according to any one of the preceding claims, comprising a computer memory (38) in which information relating to the ceramic part is recorded.

18. An air treatment method comprising the following steps: a) treating a first quantity of air using an air treatment apparatus according to any one of the preceding claims; b) cleaning and / or purifying the ceramic part of said air treatment apparatus, and then repeating step a) to treat a second quantity of air.

19. A method according to the preceding claim, wherein air is extracted from a dwelling, an office or a passenger compartment of a vehicle selected from a car, a train, an aircraft, a truck and a boat.

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