EP3909684A1 - Electrostatic precipitator/manifold with collection electrode(s) coated with one or more film(s) comprising an electrically conductive layer and an absorbent layer of particles and gas, associated set of peelable film(s) - Google Patents

Abstract

The invention relates to an electrostatic precipitator / collector (3) for an air purifier (1) or aerosol cleaner, comprising: - at least one collection electrode (30); - a set (5) of film (s) applied to the collection electrode and comprising at least one film (50) comprising at least one particle and gas absorption layer (52) and an electrically conductive layer (51) electrically connected to the collection electrode and of which a main face is covered with the absorption layer.

Description

Technical area

The present invention relates to the field of air purification and aerosol purification, which may contain particles in suspension.

The present invention aims to improve existing air purifiers and aerosol cleaners, in particular in order to reduce their manufacturing and operating costs while guaranteeing constant efficiency over time.

Although described with reference to an air purification application, the invention applies to any aerosol purification.

Prior art

Many air filtration techniques intended to respond to the growing problem of atmospheric pollution have been developed, in particular for the industrial sector. The general principle of filters consists of recycling the air by sucking, filtering and then rejecting the air thus purified of its pollutants.

In order to trap particles or dust, mention may in particular be made of mechanical filters, hydraulic filters, filters with filter layers, electric filters: [1]. Generally, there are several filters arranged one after the other in the flow of air to be filtered. A single filter grouping together different functional layers can also be implemented.

Electric filters, also known as electrostatic precipitators names, electrostatic filters and electrostatic precipitators (ESP, English acronym for "Electrostatic Precipitator") are filtration methods used since the early ^20th century to purify fumes including facilities industrial (iron and steel industry, waste incineration, cement factories, energy production units, etc.).

Precipitation or electrostatic collection is a method of choice which allows the collection of aerosol particles for a wide particle size range.

1. i/ application d'un champ électrique, en particulier d'un champ électrique intense pour créer un effet de décharge couronne (en anglais « corona discharge ») qui participe à la charge des particules en suspension dans les gaz à traiter ;
2. ii/ collecte des particules chargées selon l'étape i/;
3. iii/ récupération des particules collectées.

The functioning of electrofiltration or electrostatic precipitation or electrostatic collection is based on the implementation of three essential steps:

1. i / application of an electric field, in particular an intense electric field to create a corona discharge effect which participates in the charge of the particles in suspension in the gases to be treated;
2. ii / collecting the charged particles according to step i /;
3. iii / recovery of the collected particles.

When an intense electric field is generated in a volume where aerosol particles are present, the latter can become electrically charged according to two distinct charging mechanisms and this can occur concomitantly.

The publication [2], in particular figure 15. 4 of page 330 of this work, shows that the mechanism of electric charge by diffusion of unipolar ions, associated with the mechanism of electric charge by field, is applicable to a wide range of particle sizes, at least for particles of dimensions included between 0.01 to 10 µm. It also emerges that the mechanism of electric charge by diffusion of unipolar ions is especially preponderant for the finest particles, typically those of dimensions less than 300 nm. Conversely, the field charge mechanism is more efficient for large particles, that is to say particles of micron and submicron size (≥300 nm). By way of example, if we consider the electric mobility of a particle, denoted Z, of the order of 1 cm ² /st.Vs in electrostatic unit CGS, i.e. 3.3x10 ^-7 m ² / Vs in SI unit, then this particle placed between two plane and parallel plates which generate an electric field E of 105 V / m, acquires a speed W equal to the product Z ^∗ E, that is to say W of the order of 0.033 m / s. It is clearly demonstrated that the electrostatic force generates speeds much higher than the other fields of forces undergone by a particle, which are the fields of gravity, inertial, thermal and radiative. This advantage is taken advantage of in the operation of commercial electrostatic scrubbers, where the diffusion charge and field charge processes can act together.

Electrically charging aerosol particles requires the presence of unipolar ions in high concentration. By far the most efficient method of creating these ions in atmospheric air is corona discharge.

To produce a corona discharge, an electrostatic field must be established in a geometry which makes it possible to make it non-uniform. More exactly, this high electric field (several thousand to tens of thousands of volts per centimeter in the vicinity of the discharge electrode) is induced by two electrodes arranged close to one another: one first polarized electrode or discharge electrode, generally in the form of a wire or tip, being disposed opposite a second electrode, the latter being in the form of a counter-electrode, generally of planar or cylindrical geometry. The electric field existing between the two electrodes ionizes the volume of gas located in the inter-electrode space, and in particular a sheath or ring of ionized gas located around the discharge electrode. The charges created, by migrating towards the counter-electrode, charge the particles to be separated contained in the gas. The charged particles thus created then migrate towards the counter-electrode, on which they can be collected. This counter electrode is usually called a collection electrode. Due to the level of electric field required, it is necessary to use a discharge electrode which has a (very) small radius of curvature. The discharge electrodes encountered are therefore generally either fine points or wires of small diameter. Thus, by a process which originates from the electrons and ions created by natural irradiation, the electrons are accelerated in the intense electric field created in the vicinity of the electrode with (very) small radius of curvature. By the high voltage imposed, if this field exceeds a critical value, an avalanche effect causes ionization of the air in this space. This phenomenon is called corona discharge.

By way of example, we have shown in figures 1A to 1E some of the most suitable electrode configurations for obtaining a corona discharge, namely a point-to-plane arrangement ( figure 1A ), plate-plane ( figure 1B ), wire-plane ( figure 1C ), wire-wire ( figure 1D ), wire-cylinder ( figure 1E ).

For example in a point-to-plane configuration, if the point is positive with respect to the plane, the electrons move rapidly towards the point while the positive ions move towards the plane, then creating a positive unipolar space. In addition, an ion wind, also called an ionic wind, is established, characterized by an air flow directed from the tip to the plane, originating from the impacts of the positive ions with the surrounding neutral molecules.

Conversely, if the tip is negative with respect to the plane, the positive ions move towards the tip, and the electrons move towards the plane, attaching themselves to the air molecules to form negative ions. In all cases, even if the process of creating positive or negative ions is not exactly symmetrical, the unipolar ions migrate from the tip to the plane with a large concentration of the order of 10 ⁶ to 10 ⁹ / cm ³ and, whatever the polarity, there appears an electric wind directed from the point towards the plane.

Thus, the introduction of aerosol particles into the tip-plane space allows them to be charged with the same polarity as the tip, according to a charge process per field. In addition, the field used to create the corona effect and the electric wind also participate in the field charging process.

For the other configurations shown in figures 1B to 1E , the processes of ion production and particle field charge are in all respects similar.

Electrostatic precipitators / collectors which use a wire-cylinder configuration have been known for a very long time. This type of precipitator / collectors largely relates to the purification of industrial gaseous effluents but little to the field of indoor air purifiers.

They seem particularly interesting, because of their very simple operating principle and their high efficiency.

This principle consists in putting under high tension, a wire stretched in the axis of a cylinder connected to the mass. By corona effect on the wire, the ions created charge the particles which are precipitated on the internal wall of the cylinder.

That is, in the simplest electrostatic precipitators, with a wire-cylinder geometry, a very high electric potential is applied to the wire, called the emitter electrode, placed in the axis of the cylinder, called the collector electrode, which is connected to earth. The particles carried by the gas pass through the inter-electrode space and become electrically charged.

The positively charged particles then undergo a force due to the electric field which leads them towards the electrode connected to the ground.

If the particles are insulating, they retain their charge in contact with this electrode and thus adhere to the wall until they are removed by washing, scraping or knocking. If the particles are conductive, they lose their charge on contact with the wall and charge in the opposite polarity.

The efficiency of an electrostatic precipitator depends among other things on the following parameters: resistivity, particle size and nature of the particles, particle concentration, speed, temperature and composition of the gaseous effluent, voltage applied to the electrodes.

We can distinguish three categories of electrostatic precipitators.

The first category consists of single-stage electrostatic precipitators in which ionization and particle collection are carried out simultaneously along the length of the stage. Among these, we can cite, in addition to the wire-cylinder already mentioned, the configurations of the wire-plate type. where a plurality of parallel wires constitute the emissive electrodes and a plate constitutes a collecting electrode. Reference may be made to publication [3] to view different concrete embodiments according to these configurations.

The second category consists of “double-stage” electrostatic filtration devices, that is to say those comprising a first stage forming an ionizer extended by a precipitation stage or collection strictly speaking. The two stages are generally supplied with voltage separately.

We have represented in figure 2 an example of a double-stage geometry air purifier 1, ie an ionizer 2 and an electrostatic precipitator 3 in the continuity of the ionizer 2.

Purifier 1 comprises grounded plates 4, which are common to ionizer 2 and precipitator 3.

The ionizer 2 comprises wires 20 stretched between the plates 4 to ground.

The precipitator 3 comprises electrically conductive plates 30, 31 parallel to each other and to the ground plates 4 between which they are arranged.

The operation of such a purifier 1 is as follows: the particles present in the air flow Q to be purified are first of all electrically charged by the corona effect by passing in the vicinity of the wires 20 brought to high voltage Uf, then they are collected on the plates 30 between which an electric field is established under the action of a high bias voltage Up. This geometry is practically always that in flows of rectangular section, the charging and then collecting operations being carried out between the flat and parallel plates.

Finally, the third category consists of so-called wet electrostatic precipitators, whose operating principle is identical to that of single or double-stage dry electrostatic precipitators but which, unlike the latter, use a wet film by trickling onto the collecting electrode. . The wet electrodes have a collection efficiency less sensitive to the electrical characteristics of the particles and allow the purification of effluents loaded with particles, which is difficult to achieve with dry electrostatic precipitators. The use of a liquid can also advantageously allow the absorption of certain gases such as SO ₂ , H2S, HCl: [3], [4].

On the other hand, wet electrostatic precipitators suffer from major drawbacks, namely the cost of added energy investment for the washing process, the operating temperature limited to 90 ° C., and the need to treat the liquid effluent.

To return more specifically to single or double-stage dry electrostatic precipitators, their effectiveness depends, among other things, on the concentration, the migration speed and the charge of the particles, the turbulent nature or not of the flow, or even the reentraining phenomenon.

Re-entrainment occurs when the particles deposited on the collecting electrode discharge rapidly and therefore can no longer be subjected to electrostatic force. They therefore detach from the collecting electrode and are carried away by the flow. This re-flight phenomenon can also be caused by a poor distribution of the flow and in particular by the effects of turbulence [5]. The re-entrainment can also be observed by the effect of scouring the dust accumulated on the collection electrode by the gaseous effluent, for example following poor gas flow conditions or by the discharge of the particles recovered on the gas. 'collection electrode, less subject to electrostatic adhesion forces. Large and granular particles are more vulnerable to this phenomenon than fine particles.

In practice, dry electrostatic precipitators are cleaned in different ways depending on the application considered.

For example, for industrial electrostatic precipitators dealing with large quantities of dust, the cleaning operation can be carried out by dropping the dust collected by vibrations (fog horns, ultrasound) or by percussion, scraping and repeated striking of the water. collector electrode. This action involves the collection and handling of more or less powdery dust depending on the nature and size of the particles captured. Moreover, this cleaning operation does not guarantee to find truly clean electrodes.

Many air purifiers already on the market use dry electrostatic precipitators with instructions for use which mention the cleaning of electrodes to be carried out.

Mention may be made, for example, of that marketed under the name “HexaOne” from the company Nectar, whose maintenance instructions recommend, once dismantled, to clean the collecting electrodes by rubbing them with a cloth and degreaser and / or by immersion, then rinse and dry them before reassembling.

• en ce qui concerne la complexité à nettoyer efficacement l'appareil : le démontage, la manipulation et le remontage des pièces impliquent certaines connaissances techniques qui peuvent être complexes pour certains utilisateurs ;
• sur le nettoyage à l'eau : le transfert de la pollution particulaire collectée par l'appareil dans les eaux usées va nécessiter des étapes ultérieures de filtration dans sa phase de traitement. Le principe de nettoyer à l'eau est par conséquent discutable et non satisfaisant ;
• sur le séchage : l'assemblage des plaques collectrices génère de nombreuses zones de rétention d'eau et d'interstices (tôle pliée, fentes, visserie...). Par conséquent, l'obtention d'un délai court pour un séchage complet garanti est illusoire ou alors complexe à mettre en œuvre.

When reading this HexaOne purifier maintenance manual, several comments can be made:

• with regard to the complexity of effectively cleaning the device: the disassembly, handling and reassembly of the parts involve certain technical knowledge which may be complex for some users;
• on cleaning with water: the transfer of the particulate pollution collected by the device into the wastewater will require subsequent filtration steps in its treatment phase. The principle of cleaning with water is therefore questionable and unsatisfactory;
• on drying: the assembly of the collector plates generates numerous areas of water retention and interstices (folded sheet, slots, screws, etc.). Consequently, obtaining a short time for guaranteed complete drying is illusory or else complex to implement.

Another type of dry electrostatic precipitator has been proposed in the publication [6]: it is designed to be compact and to capture both particles and gaseous pollutants.

As illustrated in figure 1 of the publication, the electrostatic precipitator comprises, in the direction of circulation of the aerosol, an upstream section and a downstream section.

In the upstream section, a high voltage is applied between a brush of carbon fibers and a metal part connected to the ground. The air circulates in the space between the brush and the metal part, and when particles circulate in said space, they are charged and for the larger ones, collected in part or in whole.

The downstream section comprises a cylinder and an activated carbon fabric, arranged around the cylinder. High tension is also applied between the cylinder and the fabric. The functions of this downstream section are on the one hand to filter the fine particles by collecting them on the cylinder, and on the other hand to adsorb gaseous pollutants by the activated carbon when the air passes through the fabric.

The major drawbacks of this electrostatic precipitator are, as for the other dry electrostatic precipitators mentioned, reliability and maintenance. Regarding reliability, it is possible that there is reentraining of particles. Furthermore, when subjected to vibrations, the activated carbon fabric can itself emit particles in the gas flow. Regarding maintenance, it involves disconnecting the high voltage, physically disassembling the collecting electrodes on which the particle agglomerates are located and likely to be resuspended in the gas volume. The operator in charge of dismantling can then expose his respiratory tract and his skin, which is, of course, not desired.

There is a need to further improve precipitators / electrostatic collectors / electrostatic precipitators, in particular in order to increase their efficiency, reliability and safety and also to allow, in addition to collecting particles, the filtration of gases. The general aim of the invention is then to respond at least in part to this need.

Disclosure of the invention

• au moins une électrode de collecte ;
• un ensemble de film(s) appliqué sur l'électrode de collecte et comprenant au moins un film comprenant au moins une couche d'absorption des particules et des gaz et une couche électriquement conductrice reliée électriquement à l'électrode de collecte et dont une face principale est recouverte de la couche d'absorption.

To do this, the invention firstly relates to an electrostatic precipitator / collector for an air purifier or aerosol purifier, comprising:

• at least one collection electrode;
• a set of film (s) applied to the collection electrode and comprising at least one film comprising at least one particle and gas absorption layer and an electrically conductive layer electrically connected to the collection electrode and one side of which main is covered with the absorption layer.

According to an advantageous embodiment, the assembly comprises a stack of at least two films fixed peelable one on the other, the electrically conductive layers of the films being electrically connected to each other, only the electrically conductive layer of one of the films. films comprising an adhesive applied directly to the collection electrode, while before successive peeling of each of the other films, each absorption layer is covered with the electrically conductive layer of one of the other films, with the exception of the absorption layer of one of the other films furthest from the collection electrode which is in contact with air or an aerosol.

The stack can comprise a number between 3 and 200 fixed films peelable one on the other. It is understood that in the context of the invention, the layer directly applied in contact with the electrode is peelable in order to expose the electrode and be able to coat the latter again, with a set of renewed film (s).

Also in the context of the invention, all the films of the same set may not be identical. Thus, each film can include a specific absorbent layer (composition, thickness, topology, etc.) and / or even a specific conductive layer (nature, thickness, structure, etc.) which is (are) distinct from that ( s) another of the films in the set.

The collection electrode (s) can each be formed by a metal strip or a metal plate.

• un précipitateur/collecteur électrostatique tel que décrit précédemment;
• un ioniseur agencé en amont du collecteur électrostatique.

The invention also relates to an air purifier or aerosol purifier comprising:

• an electrostatic precipitator / collector as described above;
• an ionizer arranged upstream of the electrostatic collector.

• deux couches de protection pelables,
• au moins un film comprenant :
  • une couche d'absorption des particules et des gaz, destinée à être au contact avec l'air ou un aérosol, et dont une face principale est revêtue d'une des deux couches de protection pelables,
  • une couche électriquement conductrice, destinée à être reliée électriquement à l'électrode de collecte, dont une face principale est recouverte de la au moins une couche d'absorption, et l'autre face principale est revêtue d'un adhésif à appliquer directement sur l'électrode de collecte, l'adhésif étant lui-même revêtu de l'autre des deux couches de protection pelables. Selon un mode de réalisation avantageux, l'ensemble comprend un empilement d'au moins deux films fixés pelables l'un sur l'autre, seule la couche électriquement conductrice d'un des films étant revêtue de l'adhésif et l'autres des deux couches de protection pelables, les couches électriquement conductrices des films étant reliées électriquement entre elles, chaque couche d'absorption étant recouverte de la couche électriquement conductrice d'un des autres films à l'exception de la couche d'absorption la plus éloignée de l'électrode de collecte recouverte de l'une des deux couches de protection pelables.

The invention also relates to a set of peelable film (s), intended to be applied by peeling onto a collecting electrode of a precipitator / electrostatic collector, comprising:

• two peelable protective layers,
• at least one film comprising:
  • a particle and gas absorption layer, intended to be in contact with air or an aerosol, and one main face of which is coated with one of the two peelable protective layers,
  • an electrically conductive layer, intended to be electrically connected to the collection electrode, one main face of which is covered with the at least one absorption layer, and the other main face is coated with an adhesive to be applied directly to the 'collection electrode, the adhesive itself being coated with the other of the two peelable protective layers. According to an advantageous embodiment, the assembly comprises a stack of at least two attached films peelable one on the other, only the electrically conductive layer of one of the films being coated with the adhesive and the other with two peelable protective layers, the electrically conductive layers of the films being electrically connected to each other, each absorption layer being covered with the electrically conductive layer of one of the other films except for the absorption layer furthest from the collection electrode covered with one of the two peelable protective layers.

Advantageously, each peelable protective layer is made of a polymer chosen from polyethylene (PE), polycarbonate (PC), polyethylene terephthalate (PET), ethylene polynaphthalate (PEN), poly (methyl methacrylate (PMMA), or a mixture of these Further advantageously, each peelable protective layer has a thickness of between 10 and 1000 μm.

Advantageously, each electrically conductive layer is made of metal or of a polymer material charged with metal, in particular in the form of a conductive ink. The metal can be chosen from aluminum, gold, copper, stainless steel.

Again advantageously, each electrically conductive layer is in the form of a thin layer, a grid, a mesh, a textile, possibly non-woven, consisting of fibers, threads or metal strands, woven or knitted, or coated fibers continuous or discontinuous conductor. In the context of the invention, a grid is periodic and inscribed in a two-dimensional plane, while a mesh can be irregular and not necessarily in a plane (curve, three-dimensional).

According to an advantageous characteristic, each electrically conductive layer can have reliefs and / or hollows, in particular in the form of a sinusoidal surface undulation. A sinusoidal surface ripple can have a period of a few mm, and an amplitude of a few hundred microns.

Again advantageously, each electrically conductive layer having a thickness of between 1 and 200 μm.

Advantageously, each absorption layer is made of one or more pure viscoelastic materials or loaded with particles, functionalized or not. It can be an elastomer such as polydimethylsiloxane (PDMS).

Again advantageously, each absorption layer is in the form of a thin layer, a grid, a textile, possibly non-woven, consisting of fibers, threads or strands, coated with an absorbent coating. viscoelastic.

Again advantageously, each absorption layer can have reliefs and / or hollows, in particular in the form of a sinusoidal surface undulation. A sinusoidal surface ripple can have a period of a few mm, and an amplitude of a few hundred microns.

Again advantageously, each absorption layer has a thickness of between 1 and 1000 μm.

1. a/ fourniture d'un ensemble de film(s) pelable(s) tel que décrit précédemment;
2. b/ retrait par pelage d'une des couches de protection de sorte à rendre apparent l'adhésif ;
3. c/ report de l'ensemble sur l'électrode de collecte par application de l'adhésif sur cette dernière ;
4. d/ retrait par pelage de l'autre des couches de protection de sorte à mettre en contact la couche d'absorption la plus éloignée de l'électrode de collecte avec l'air ou un aérosol. Selon un mode de réalisation avantageux, le procédé comprend, après un cycle initial de fonctionnement du précipitateur/collecteur électrostatique, les étapes ultérieures suivantes :
5. e/ mise hors tension du précipitateur/collecteur électrostatique ;
6. f/ retrait par pelage du film le plus éloigné de l'électrode de collecte de sorte à mettre en contact la couche d'absorption du film sous-jacent en contact avec l'air ou l'aérosol.

Finally, a subject of the invention is a method for producing an electrostatic precipitator / collector, comprising at least one collection electrode, comprising the following steps:

1. a / supply of a set of peelable film (s) as described above;
2. b / removal by peeling off one of the protective layers so as to make the adhesive visible;
3. c / transfer of the assembly onto the collection electrode by applying the adhesive to the latter;
4. d / removal by peeling of the other of the protective layers so as to bring the absorption layer furthest from the collection electrode into contact with air or an aerosol. According to an advantageous embodiment, the method comprises, after an initial operating cycle of the precipitator / electrostatic collector, the following subsequent steps:
5. e / switching off the precipitator / electrostatic collector;
6. f / removal by peeling of the film furthest from the collection electrode so as to bring the absorption layer of the underlying film into contact with the air or the aerosol.

According to an even more advantageous embodiment, the method comprises, after each operating cycle of the precipitator / electrostatic collector, following the initial cycle, the repetition of steps e / and f / until the last absorption layer is brought into contact. remaining, in contact with air or aerosol.

Thus, the invention essentially consists in applying to a “conventional” collection electrode of an electrostatic precipitator an assembly of a stack of fixed films peelable one on the other, each comprising an electrically conductive layer coated with a layer. absorption of particles and gas molecules of a flow to be treated.

Each electrically conductive layer which is connected to the collection electrode has the function of serving as an electrode to establish the inter-electrode electric field necessary for the collection of the particles.

• une adhérence de surface supérieure à celle d'une surface métallique comme celle d'une électrode de collecte selon l'état de l'art ;
• une absorption des polluants, mécanisme permettant de renouveler la surface ;
• la possibilité de suivre l'état de saturation de chaque couche absorbante pelée après un cycle, par mesure physique (optique, électrique, capacitive...)

Each absorbent layer in contact with the flow to be treated has the function of trapping the particles or gaseous molecules deposited on the surface. Each absorbent layer increases the efficiency of the electrostatic precipitator, thanks to:

• a surface adhesion greater than that of a metal surface such as that of a collection electrode according to the state of the art;
• absorption of pollutants, a mechanism for renewing the surface;
• the possibility of monitoring the saturation state of each peeled absorbent layer after a cycle, by physical measurement (optical, electrical, capacitive, etc.)

• une simplification de la maintenance d'un électrofiltre comparativement à ceux de l'état de l'art: pas d'outillage ni de liquide et/ou détergent à utiliser, pas de transfert de pollution à gérer ;
• une efficacité accrue de l'épuration : pas de risque de ré-envol des polluants dans le volume gazeux, pas de réentrainement, les surfaces absorbantes étant véritablement renouvelées après chaque cycle de maintenance. Autrement dit, à chaque remise en service, la surface absorbante au contact de l'air pollué est neuve et vierge ;
• une sécurité pour l'opérateur lors de la maintenance : pas de liquide de rinçage à utiliser, pas de pulvérulence, une action simple de pelage à réaliser ;
• un traitement/recyclage aisé des déchets: chaque film pelable confine la pollution et peut entrer dans une filière courante de recyclage comme l'incinération ou spécifique, par exemple pour récupérer et donner une seconde vie aux particules collectées ;
• la possibilité d'instrumenter un électrofiltre selon l'invention afin de connaitre le nombre de films pelables restant sur l'électrode de collecte et de connaitre l'état d'encrassement de l'ensemble de films ;
• la possibilité d'utiliser chacun des films pelables pour une analyse à posteriori des polluants collectés (contamination des locaux, incidents process...). D'ailleurs, chaque film pelable peut être positionné aisément sur des surfaces sous tension ou non, autres que les électrodes de collecte.

The advantages of the invention are numerous, among which may be mentioned:

• simplification of the maintenance of an electrostatic precipitator compared to those of the state of the art: no tools or liquid and / or detergent to use, no pollution transfer to manage;
• increased purification efficiency: no risk of pollutants re-airing into the gas volume, no re-entrainment, the absorbent surfaces being truly renewed after each maintenance cycle. In other words, each time it is put back into service, the absorbent surface in contact with the polluted air is new and virgin;
• safety for the operator during maintenance: no rinsing liquid to use, no pulverization, a simple peeling action to perform;
• easy treatment / recycling of waste: each peelable film confines pollution and can enter a common recycling channel such as incineration or specific, for example to recover and give a second life to the particles collected;
• the possibility of instrumenting an electrostatic precipitator according to the invention in order to know the number of peelable films remaining on the collection electrode and to know the fouling state of the set of films;
• the possibility of using each of the peelable films for a posteriori analysis of the pollutants collected (contamination of premises, process incidents, etc.). Moreover, each peelable film can be easily positioned on surfaces under tension or not, other than the collection electrodes.

• de réduire voire supprimer leur perte d'efficacité lié au phénomène de réentrainement des particules ;
• de réduire voire supprimer leur perte d'efficacité et leur manque de fiabilité lié à la difficulté de garantir qu'à l'issue de l'étape de nettoyage des plaques collectrices selon l'état de l'art, la surface des électrodes soit véritablement décontaminée et exempte de pollution ;
• de garantir la sécurité de l'opérateur lors de l'opération de maintenance liée à la pulvérulence des particules : en effet, les particules collectées sur les plaques de collecte selon l'état de l'art sont liées entre elles et à la surface même des électrodes par des forces électrostatiques pouvant être considérées comme faibles. Par conséquent, lors de la maintenance une remise en suspension dans le volume gazeux est possible, ce que les couches absorbantes selon l'invention évitent ;
• de garantir la sécurité à la remise en service de l'appareil après maintenance : Toutes les surfaces internes d'un électrofiltre ou purificateur d'air selon l'état de l'art n'étant pas accessibles, la pollution peut s'accumuler, certaines zones piéger l'eau ou rester humides.
• de réaliser une filtration à la fois des gaz et des particules.

In other words, the invention makes it possible to overcome the drawbacks of electrostatic precipitators according to the state of the art, and in particular:

• to reduce or even eliminate their loss of efficiency linked to the phenomenon of particle re-entrainment;
• to reduce or even eliminate their loss of efficiency and their lack of reliability linked to the difficulty of guaranteeing that at the end of the step of cleaning the collector plates according to the state of the art, the surface of the electrodes is truly decontaminated and free from pollution;
• guarantee the operator's safety during the maintenance operation linked to the dustiness of the particles: in fact, the particles collected on the collection plates according to the state of the art are linked to each other and to the surface itself electrodes by electrostatic forces that can be considered weak. Consequently, during maintenance a resuspension in the gas volume is possible, which the absorbent layers according to the invention avoid;
• to guarantee safety when the appliance is put back into service after maintenance: As all the internal surfaces of an electrostatic precipitator or air purifier according to the state of the art are not accessible, pollution can accumulate, some areas trap water or stay moist.
• to achieve filtration of both gases and particles.

Other advantages and characteristics will emerge better on reading the detailed description, given by way of illustration and not by way of limitation, with reference to the following figures.

Brief description of the drawings

• [ Fig 1A ] the figure 1A is a schematic view of a first electrode configuration for obtaining a corona effect by electric discharge.
• [ Fig 1B ] the figure 1B is a schematic view of a second electrode configuration for obtaining a corona effect by electric discharge.
• [ Fig 1C ] the figure 1C is a schematic view of a third electrode configuration for obtaining a corona effect by electric discharge.
• [ Fig 1D ] the figure 1D is a schematic view of a fourth electrode configuration for obtaining a corona effect by electric discharge.
• [ Fig 1E ] the figure 1E is a schematic view of a fifth electrode configuration for obtaining a corona effect by electric discharge.
• [ Fig 2 ] the figure 2 is a schematic view in longitudinal section of a double-stage electrostatic precipitator, ie with a stage forming an ionizer and a stage forming a particle collector, in the continuity of the ionizer.
• [ Fig 3 ] the figure 3 is a schematic view of an example of an electrostatic precipitator with a collection electrode coated with a set of peelable films according to the invention.
• [ Fig 4 ] the figure 4 is a schematic illustration of the peeling of films of an assembly according to the invention.
• [ Fig 5 ] the figure 5 is a schematic view of a single film according to the invention.
• [ Fig 6 ] the figure 6 schematically illustrates a stacking assembly of peelable films according to the invention coated on both sides with a peelable protective layer before placement in an electrostatic precipitator / collector.
• [ Fig 7A ] the figure 7A schematically illustrates a first step of a process for producing an electrostatic precipitator / collector according to the invention.
• [ Fig 7B ] the figure 7B schematically illustrates a second step of a method for producing an electrostatic precipitator / collector according to the invention.
• [ Fig 7C ] the figure 7C schematically illustrates a third step of a method for producing an electrostatic precipitator / collector according to the invention.
• [ Fig 7D ] the figure 7D schematically illustrates a fourth step of a process for producing an electrostatic precipitator / collector according to the invention.
• [ Fig 7E ] the figure 7E schematically illustrates a step of a method for producing an electrostatic precipitator / collector according to the invention, after a first cycle of use.
• [ Fig 7F ] the figure 7F schematically illustrates an operating step of an electrostatic precipitator / collector according to the invention after the step according to figure 7E .
• [ Fig 8 ] the figure 8 is a schematic representation of an experimental device for testing the efficiency of an electrostatic precipitator / collector in accordance with the invention.
• [ Fig 9 ] the figure 9 illustrates in the form of curves the results of the tests carried out with the device of the figure 8 .
• [ Fig 10 ] the figure 10 illustrates the distribution of the particle size distribution of TiO ₂ particles generated by atomization and intended to be collected by a prototype of a film in accordance with the invention.
• [ Fig 11 ] the figure 11 illustrates another experimental device intended for resuspension tests of TiO ₂ particles which have previously been collected by a film in accordance with the invention on a collection electrode or on a bare collection electrode.
• [ Fig 12 ] the figure 12 illustrates the measurement of the concentration of particles collected during blowing by the device of the figure 11 according to different collection electrode configurations.

detailed description

Throughout the present application, the terms “inlet”, “outlet”, “upstream” and “downstream” are to be understood by reference with respect to the direction of the suction flow through an electrostatic precipitator according to the invention. Thus, the inlet orifice designates the orifice of the device through which the air to be purified is drawn in, while that of the outlet designates that through which the air flow leaves.

The figures 1A to 2 have already been commented on in the preamble. They are not detailed below.

For the sake of clarity, the same element according to the prior art and the invention is designated by the same numerical reference.

We specify that in the set of figures 3 to 6 , the plane xOy is in the plane of the collection electrode 30.

We have represented in figure 3 an example of an electrostatic precipitator 3 according to the invention. The precipitator 3 comprises at least one electrically conductive plate forming a collection electrode 30 connected to the ground, not shown.

A set 5 of peelable film (s) is applied to the collection electrode 30.

In the example illustrated, the assembly comprises a stack of three films 50.1, 50.2, 50.3 fixed peelably one on the other as shown partially in figure 4 , being as represented in figure 4 .

As shown in figure 5 , each film 50 comprises at least one electrically conductive layer 51 intended to be electrically connected to the collection electrode 30 and a layer 52 for absorbing particles and gases. One of the main faces of the electrically conductive layer 51 is covered with the absorption layer 52.

The function of the conductive layer 51 is to serve as an electrode connected to the collection electrode 30 equipping the precipitator as a base, in order to establish an inter-electrode electric field necessary for the collection of the particles. This layer 51 can be made of a single material or an assembly of conductive materials, for example chosen from Al, Au, stainless steel, Cu, etc. By way of example, its thickness can be 50 μm.

The absorbent layer 52, in contact with the gas flow to be treated, has the function of trapping the ionized particles and the gas molecules deposited on the surface. This layer exhibits high surface adhesion. This layer 51 can be in a single material or a mixture of pure viscoelastic materials or mixtures, for example polydimethylsiloxane (PDMS). By way of example, its thickness may be 15 μm.

In the stack of the assembly, the electrically conductive layers 51.1, 51.2, 51.3 of the three films are electrically connected to one another, for example by depositing an electrically conductive material 53 on the edge of the films 50.1, 50.2, 50.3.

In the initial operating configuration of the precipitator 3 and before successive peeling of the films 50.2, 50.3, each absorption layer 52.1, 52.2, 52.3 is covered with the electrically conductive layer of one of the other films, with the exception of the layer absorption 52.3 furthest from the collection electrode 30 which is in contact with air or an aerosol. In this initial configuration shown in figure 3 , an electric field is established under the action of a high bias voltage. The operations of collecting gaseous pollutants and ionized particles are carried out on the collection plate 30 and therefore by the guaranteed electrical continuity between the latter and the electrically conductive layers 51.1 to 51.3, directly in the most distant absorption layer 52.3 of plate 30.

To ensure the application of the assembly 5 on the collection electrode 30, the electrically conductive layer 51.1 of one of the films 51 comprises an adhesive 54 to be applied directly to the collection electrode 30.

Before applying the set 5 of films to a collection electrode 30, the set 5 is provided with two peelable protective layers 54, 55 respectively on either side of its stack ( figure 6 ). Thus, the electrically conductive layer 51.1 of the film 50.1 and the absorbent layer 52.3 of the film 50.3 are each covered with a peelable protective coating 54, 55, in order to guarantee the integrity of the surface properties until implementation. of the set 5.

Each of the layers 54, 55 can be polyethylene (PE). By way of example, its thickness can be 100 μm.

• Etape a/ : on fournit un ensemble de film(s) pelable(s) 5 à trois films 50.1, 50.2, 50.3 protégé par les deux couches de protection 54, 55 de part et d'autre de l'empilement (figure 7A).
• Etape b/ : on retire par pelage la couche de protection 54 de sorte à rendre apparent l'adhésif 56 qui va permettre le report de l'ensemble 5 sur l'électrode de collecte 30 (figure 7B, traction T sur la couche 54).
• Etape c/: on reporte alors l'ensemble 5 sur l'électrode de collecte 30 par application de l'adhésif 56 sur cette dernière (figure 7C).
• Etape d/ : on retire par pelage la couche de protection 55 de sorte à mettre en contact la couche d'absorption 52.3 la plus éloignée de l'électrode de collecte avec l'air ou un aérosol (figure 7C).
  On peut alors faire fonctionner le précipitateur électrostatique 3 dont l'électrode de collecte 30 sert de support à l'ensemble pelable équipé de l'ensemble 5 (figure 7D).
  Une haute tension est appliquée, la couche conductrice 51.1 en continuité électrique avec l'électrode de collecte est à la masse. De par la continuité électrique, toutes les couches conductrices 51.1, 51.2, 51.3 sont au même potentiel que l'électrode de collecte. Soumises au déplacement du flux gazeux et à la force de Coulomb, les particules se dirigent vers la surface de l'électrode de collecte 30. Les particules venant au contact de la couche absorbante 52.3 y adhèrent et sont progressivement absorbées. Certains gaz peuvent également venir s'adsorber en surface et être aussi à terme absorbés par la couche 52.3.
• Etapes e/ : Après une durée de fonctionnement correspondant à un cycle initial, une opération de maintenance consiste à couper la haute tension, c'est-à-dire à mettre hors tension le précipitateur électrostatique.
• Etape f/: on procède alors au pelage du film 50.3 le plus éloigné de l'électrode de collecte 30 et donc on le sépare du reste de l'ensemble 5 (figure 7E, figure 7F). Cette opération de pelage peut être manuelle ou mécanique.

We now describe with reference to figures 7A to 7F , the different steps of a process for producing a precipitator / collector 3 provided with a set 5 of films according to the invention, before and after a complete operating cycle.

• Step a / : a set of peelable film (s) 5 with three films 50.1, 50.2, 50.3 protected by the two protective layers 54, 55 on either side of the stack ( figure 7A ).
• Step b / : the protective layer 54 is peeled off so as to make the adhesive 56 visible, which will allow the assembly 5 to be transferred onto the collection electrode 30 ( figure 7B , traction T on layer 54).
• Step c /: the assembly 5 is then transferred to the collection electrode 30 by applying the adhesive 56 to the latter ( figure 7C ).
• Step d /: the protective layer 55 is peeled off so as to bring the absorption layer 52.3 furthest from the collection electrode into contact with air or an aerosol ( figure 7C ).
  The electrostatic precipitator 3 can then be operated, the collection electrode 30 of which serves as a support for the peelable assembly equipped with the assembly 5 ( figure 7D ).
  A high voltage is applied, the conductive layer 51.1 in electrical continuity with the collection electrode is grounded. Due to the electrical continuity, all the conductive layers 51.1, 51.2, 51.3 are at the same potential as the collection electrode. Subjected to the displacement of the gas flow and to the Coulomb force, the particles move towards the surface of the collection electrode 30. The particles coming into contact with the absorbent layer 52.3 adhere to it and are gradually absorbed. Certain gases can also come to be adsorbed on the surface and also be absorbed in the long term by the layer 52.3.
• Steps e /: After an operating period corresponding to an initial cycle, a maintenance operation consists in cutting off the high voltage, that is to say in de-energizing the electrostatic precipitator.
• Step f /: the film 50.3 furthest from the collection electrode 30 is then peeled and therefore separated from the rest of the assembly 5 ( figure 7E, figure 7F ). This peeling operation can be manual or mechanical.

The absorbent layer 52.2 of the intermediate film 50.2 is then in contact with the gas stream to be treated.

On restarting (energizing the precipitator 3), the electric field is then established on the conductive layer 51.2 of the intermediate film 50.2 ( figure 7F ).

The electrostatic precipitator 3 is thus put back into service with a new absorbent layer, and therefore under better conditions of use.

After a new operating cycle of the precipitator / electrostatic collector, following the initial cycle, steps e / and f / can be repeated until the last remaining absorption layer 52.1 comes into contact with air or l 'aerosol.

• une adhérence de surface supérieure à celle d'une surface métallique comme celle d'une électrode de collecte selon l'état de l'art ;
• une absorption des polluants, mécanisme permettant de renouveler la surface ;
• la possibilité de suivre l'état de saturation de chaque couche absorbante pelée après un cycle, par mesure physique (optique, électrique, capacitive...)

Each absorbent layer 52.1, 52.2, 52.3 increases the efficiency of the electrostatic precipitator 3 thanks to:

• a surface adhesion greater than that of a metal surface such as that of a collection electrode according to the state of the art;
• absorption of pollutants, a mechanism for renewing the surface;
• the possibility of monitoring the saturation state of each peeled absorbent layer after a cycle, by physical measurement (optical, electrical, capacitive, etc.)

The inventors carried out three types of experimental laboratory tests in order to prove the feasibility of a peelable film 50 in accordance with the invention, and to demonstrate the efficiency of filtration and retention of particles of particles and gases for an electrostatic precipitator 3 equipped with a peelable film 50.

Tests N ° 1:

These tests consist in producing a peelable film 50.

Choice of material

The absorbent layer 52 can be formed by a viscoelastic polymer such as, for example, polydimethylsiloxane (PDMS), the crude formula of which is (C ₂ H ₆ OSi) _n where n is the number of repetitions.

• son domaine de température d'utilisation est large, typiquement entre -50°C et 200°C ;
• en fonction de la taille de la chaine de monomères, le PDMS a une viscosité ajustable : avec un n faible, l'état est liquide, tandis qu'avec un n élevé, l'état est solide. Il peut donc aussi bien agir comme un liquide visqueux ou comme un élastique rigide, semblable au caoutchouc ;
• le module d'élasticité (module d'Young) E du PDMS, de valeur typique autour de 3 MPa, est ajustable et change en fonction de son état de réticulation ;
• le PDMS est un élastomère hydrophobe à cause des groupes méthyls présents en surface. Les solvants polaires comme l'eau ont du mal à mouiller (angle de contact à 110°C) alors que les contaminants hydrophobes peuvent facilement s'adsorber à la surface ;
• le PDMS est perméable au gaz, les molécules peuvent donc diffuser en son sein;
• en présence d'une pollution de surface, le PDMS se réorganise pour retrouver un équilibre chimique en surface, ceci se traduit par l'encapsulation des agents polluants. La cinétique de ce phénomène dépend du degré de réticulation et donc de la viscosité. La chimie de surface tend à rester hydrophobe spontanément, ceci est possible grâce aux bas poids moléculaires (-CH3 non réticulés) qui remontent à la surface et du réarrangement des chaines pour minimiser l'énergie (réorientation des groupes polaires de la surface vers le volume ou des groupes non polaires du volume vers la surface) ;
• le PDMS est inerte chimiquement ;
• le PDMS est peu coûteux ;
• le PDMS est non toxique ;
• le PDMS présente une bonne déformabilité en traction et en compression ;
• le PDMS peut incorporer aisément des charges ;
• le PDMS peut être optiquement transparent.

The advantages of PDMS with regard to the desired function of layer of a peelable film 50 according to the invention are numerous:

• its temperature range of use is wide, typically between -50 ° C and 200 ° C;
• depending on the size of the monomer chain, PDMS has an adjustable viscosity: with a low n, the state is liquid, while with a high n, the state is solid. It can therefore act as a viscous liquid or as a rigid elastic, similar to rubber;
• the modulus of elasticity (Young's modulus) E of PDMS, with a typical value around 3 MPa, is adjustable and changes as a function of its crosslinking state;
• PDMS is a hydrophobic elastomer because of the methyl groups present on the surface. Polar solvents such as water have difficulty wetting (contact angle at 110 ° C) while hydrophobic contaminants can easily adsorb to the surface;
• PDMS is permeable to gas, molecules can therefore diffuse within it;
• in the presence of surface pollution, the PDMS reorganizes itself to regain a chemical equilibrium at the surface, this results in the encapsulation of pollutants. The kinetics of this phenomenon depends on the degree of crosslinking and therefore on the viscosity. Surface chemistry tends to remain hydrophobic spontaneously, this is possible thanks to the low molecular weights (uncrosslinked -CH3) which rise to the surface and the rearrangement of chains to minimize energy (reorientation of polar groups from the surface to the volume or non-polar groups from the volume to the surface);
• PDMS is chemically inert;
• PDMS is inexpensive;
• PDMS is non-toxic;
• PDMS has good deformability in traction and in compression;
• the PDMS can easily incorporate loads;
• the PDMS can be optically transparent.

Synthesis protocol

PDMS is an elastomer which polymerizes by polyaddition of a crosslinking agent, typically in a base / crosslinking agent ratio equal to 10/1 by weight.

The initial product chosen is the product marketed under the name Sylgard 184 ™ from the company Dow Corning.

• mélange de la base et de l'agent réticulant dans un rapport de 10/1 en masse ;
• dégazage des bulles formées par mise sous vide à température ambiante ;
• dispense du mélange sur le substrat ;
• réalisation d'un échantillon sous la forme d'une couche mince et uniforme par technique d'enduction par centrifugation (en anglais « spin coating ») à un régime de 3000 tr/min pendant 60s ;
• réticulation de la couche obtenue à une température de 100°C pendant une durée de 20 min à pression atmosphérique : l'épaisseur de la couche obtenue est de 15µm ;
• refroidissement de la couche mince d'échantillon à température ambiante ;
• stockage de l'échantillon dans un sachet pour protéger la surface jusqu'à utilisation.

The different successive steps applied to this product are as follows:

• mixture of the base and the crosslinking agent in a ratio of 10/1 by weight;
• degassing of the bubbles formed by placing under vacuum at room temperature;
• dispenses mixture on the substrate;
• production of a sample in the form of a thin and uniform layer by a centrifugal coating technique (in English "spin coating") at a speed of 3000 rev / min for 60s;
• crosslinking of the layer obtained at a temperature of 100 ° C. for a period of 20 min at atmospheric pressure: the thickness of the layer obtained is 15 μm;
• cooling the thin sample layer to room temperature;
• store the sample in a bag to protect the surface until use.

In the end, the weakly crosslinked PDMS absorbent layer obtained exhibits good surface adhesion and allows adhesive rupture (RA), in order to constitute part of an assembly peelable film 5 according to the invention.

Tests N ° 2:

The purpose of these tests is to prove the filtration efficiency of an electrostatic precipitator 3, a collection electrode 30 of which is coated with a peelable film 50 according to the invention.

In other words, it is a matter of showing that the presence of the absorbent layer of PDMS, obtained according to tests No. 1, on the collection electrode does not alter the filtration efficiency of the electrostatic precipitator.

The experiment consists in carrying out comparative efficiency measurements using a laboratory electrostatic precipitator comprising a collecting electrode with a surface area equal to 50x50mm ² .

The first filtration test, as a comparative test, uses a collecting electrode in the form of a single thin aluminum film, with a thickness equal to 100 μm, and with a surface area of 50x50mm ² .

The second test is carried out with the same aluminum film covered with the absorbent layer in PDMS, carried out according to tests No. 1.

To carry out the measurements, the inventors implemented the experimental device 10, illustrated in figure 8 . A solution 11 of potassium chloride (KCl) is atomized by an atomizer 12, in order to create a monodisperse aerosol of KCl particles, 80 nm in diameter sucked by a pump 13, in order to be electrically charged by an electrostatic precipitator 3 with or without of the absorbent layer in PDMS.

More precisely, once generated the aerosol passes through a desiccant 14, then a bipolar neutralizer 16 inside which there is a radioactive source of Kr 85. The bipolar neutralizer 16 has the function of forcing the. aerosol to be at Boltzmann equilibrium, in order to be free from any other charging effect which would distort the measurement. A high efficiency air filter 15 (HEPA) passes filtered air from the room to constitute an additional gas supply at the inlet of the neutralizer 16.

During the tests, the aerosol flow rate is set at 2 L / min as measured by the air mass flowmeter 17 (DMA) upstream of the electrostatic precipitator 3. The voltage applied to the electrostatic precipitator 3 varies from 0 to 10kV.

The particulate concentration is measured upstream and downstream of the electrostatic precipitator 3 by a Condensation Core Meter 18 and 19, respectively.

The efficiency obtained for each of the electrostatic precipitators tested 3 is the ratio between the particle concentration upstream and that downstream.

The result of the measurements is shown in the form of curves in figure 9 .

On reading these curves, it emerges that the filtration performance can be considered as equivalent between a configuration with a collection electrode 3 with bare aluminum film and a configuration with an absorbent layer in PDMS deposited on the aluminum film. In other words, it can be concluded that an absorbent layer made of PDMS does not in any way interfere with the electrostatic collection of particles.

Tests N ° 2:

These tests consist in showing that there is no resuspension in the aerosol of particles previously trapped by an absorbent layer.

In other words, it is a matter of demonstrating by measuring that an absorbent layer in accordance with the invention effectively traps the particles.

The test consists of polluting (contaminating) in a controlled manner with TiO ₂ nanoparticles two collection electrodes, one consisting of a thin film of bare aluminum with a thickness equal to 100 μm and a surface area of 50x50mm ² , the other a thin aluminum film with a thickness equal to 100 μm and a surface area of 50x50mm ² covered with an absorbent layer of PDMS, produced according to tests No. 1.

To do this, TiO ₂ nanoparticles are generated by atomization of a 2000 ppm Ti solution in a vertical tunnel provided for this purpose for 5 hours, in order to contaminate the surface of the aforementioned collection electrodes.

The figure 10 shows the particle size of the TiO ₂ nanoparticles generated.

A blow-molding resuspension test is then carried out.

Blowing with a jet of compressed air on the collection electrodes makes it possible to observe or not the re-flight of the particles previously deposited, and therefore to demonstrate the adhesion of the particles to the surface of the collection electrodes.

The collection electrodes contaminated with the TiO ₂ nanoparticles according to the previous step are used for these tests.

This blowing step is carried out by means of a device illustrated in figure 11 : each collection electrode E is positioned in a glove box, then it is blown using a compressed air blower 5, typically at a pressure of 2 bars. A sampling cone 6 is positioned near the surface of the collection electrode E to take the nanoparticles which therefore undergo re-flight. The cone 6 is connected downstream to a particle counter, not shown, sold under the name TSI 3775.

The measurements made by the particle counter are therefore those of the particulate emission linked to the re-flight of the TiO ₂ nanoparticles.

It should be noted that the measurements were also carried out on a collection electrode in the form of a thin aluminum film, 100 μm thick and with a surface area of 50 × 50 mm ² , which was not previously contaminated, in order to serve as a reference.

The figure 12 illustrates in the form of a curve, the particle concentration measurements obtained during blowing in the three collection electrode configurations mentioned above.

• l'électrode de collecte de référence, i.e. celle en aluminium non préalablement contaminé, est notée « plaque vierge » ;
• l'électrode de collecte avec uniquement un film d'aluminium et contaminée aux particules de TiO₂ est notée « plaque chargée » ;
• l'électrode de collecte avec un film d'aluminium revêtu d'une couche absorbante en PDMS contaminée aux particules de TiO₂ est notée « plaque chargée avec film».

We specify that on this graph:

• the reference collection electrode, ie the one made of uncontaminated aluminum, is denoted "blank plate";
• the collection electrode with only an aluminum film and contaminated with TiO ₂ particles is denoted “charged plate”;
• the collection electrode with an aluminum film coated with an absorbent layer of PDMS contaminated with TiO ₂ particles is denoted "plate loaded with film".

It emerges from the graph of this figure 12 , that there are no re-emitted particles in the case of the uncontaminated collection electrode, of reference and in the case of the electrode with the absorbent layer. On the other hand, there is a reemission of particles with the only aluminum electrode previously contaminated on the surface by the TiO ₂ particles. The efficiency of particle retention by an absorbent layer in PDMS is therefore proven. The invention is not limited to the examples which have just been described; characteristics of the examples illustrated can in particular be combined with one another within variants not illustrated.

List of cited documents

• [1]: R. Gouri, “Electrical and geometric optimization of a dielectric barrier electrostatic precipitator in square wire-tube configuration. Application to submicronic particles ”, thesis of the University of Poitiers, 2012 .
• [2]: W. Hinds, “Aerosol Technology”, 2nd Edition, 1999 .
• [3]: S. Souakri, “Optimization of the performance of an industrial electrofiltration process powered by high pulsed power”, thesis of the University of Pau and the Adour countries, 2016 .
• [4]: D. Blanchard, “Collection of fine particles and characterization of dust layers in an electrostatic precipitator”, thesis of the University Joseph Fourier Grenoble 1, HAL Id: tel-01691130, 2001 .
• [5]: B Benamar, “The feasibility of electrofiltration of an atmosphere loaded with wood dust: experimental and numerical study”, thesis of the University Henri Poincaré, Nancy 1, November 13, 2008 .
• [6]: Hak-Joon Kim et al., “Air cleaning performance of a novel electrostatic air purifier using activated carbon fiber filter for passenger cars”, Proc. 2016 Electrostatics Joint Conference .

Claims (15)

Electrostatic precipitator / collector (3) for air purifier (1) or aerosol cleaner, comprising: - at least one collection electrode (30); - an assembly (5) of film (s) applied to the collection electrode and comprising at least one film (50) comprising at least one layer (52) for absorbing particles and gases and one layer (51) electrically conductor electrically connected to the collection electrode and one main face of which is covered with the absorption layer. Precipitator / electrostatic collector according to claim 1, the assembly comprising a stack of at least two films (50.1, 50.2, 50.3) attached peelably to one another, the electrically conductive layers (51.1, 51.2, 51.3) of the films being electrically connected to each other (53), only the electrically conductive layer (51.1) of one of the films comprising an adhesive (56) applied directly to the collection electrode, while before successive peeling of each of the other films, each absorption layer (52.1, 52.2, 52.3) is covered with the electrically conductive layer of one of the other films, with the exception of the absorption layer (52.3) of one of the other films furthest from the 'collection electrode which is in contact with air or an aerosol. An electrostatic precipitator / collector according to claim 2, the stack comprising a number between 3 and 200 attached films peelably attached to one another. Electrostatic precipitator / collector according to one of the preceding claims, the collection electrode (s) each being formed by a metal strip or a metal plate. Air purifier (1) or aerosol purifier comprising: - an electrostatic precipitator / collector (3) according to one of claims 1 to 4; - an ionizer (2) arranged upstream of the electrostatic collector (3). Set (5) of peelable film (s), intended to be applied by peeling on a collecting electrode of a precipitator / electrostatic collector, comprising: - two peelable protective layers (54, 55), - at least one film (50.1, 50.2) comprising: a particle and gas absorption layer, intended to be in contact with air or an aerosol, and one main face of which is coated with one of the two peelable protective layers, an electrically conductive layer, intended to be electrically connected to the collection electrode, one main face of which is covered with the at least one absorption layer, and the other main face is coated with an adhesive to be applied directly to the 'collection electrode, the adhesive itself being coated with the other of the two peelable protective layers, the assembly preferably comprising a stack of at least two attached films peelable one on the other, alone the electrically conductive layer of one of the films being coated with the adhesive and the other with the two peelable protective layers, the electrically conductive layers of the films being electrically connected to each other, each absorption layer being covered with the electrically conductive layer one of the other films with the exception of the absorption layer furthest from the collection electrode covered with one of the two peelable protective layers, each peelable protective layer being t preferably in a polymer chosen from polyethylene (PE), polycarbonate (PC), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), poly (methyl methacrylate (PMMA), or a mixture of those -this. A peelable film assembly (s) according to claim 6, each peelable protective layer having a thickness between 10 and 1000 µm. Set of peelable film (s) according to one of claims 6 or 7, each electrically conductive layer being made of metal or of a polymer material charged with metal, in particular in the form of a conductive ink, and preferably in the shape of a thin layer, of a grid, of a mesh, of a textile, possibly non-woven, consisting of fibers, threads or metal strands, woven or knitted, or of fibers coated with a conductive coating continuous or discontinuous. Set of peelable film (s) according to one of claims 6 to 8, each electrically conductive layer possibly having reliefs and / or hollows, in particular in the form of a sinusoidal surface undulation. Set of peelable film (s) according to one of claims 6 to 9, each electrically conductive layer having a thickness between 1 and 200 µm. Set of peelable film (s) according to one of claims 6 to 10, each absorption layer being in one or more pure viscoelastic materials or loaded with particles, functionalized or not. Set of peelable film (s) according to one of claims 6 to 11, each absorption layer being in the form of a thin layer, a grid, a textile, optionally nonwoven, consisting of fibers, threads or strands, coated with a viscoelastic absorbent coating. Set of peelable film (s) according to one of claims 6 to 12, each absorption layer possibly having reliefs and / or hollows, in particular in the form of a sinusoidal surface undulation. Set of peelable film (s) according to one of claims 6 to 13, each absorption layer having a thickness between 1 and 1000 µm. Method for producing an electrostatic precipitator / collector (3), comprising at least one collection electrode, comprising the following steps: a / supply of a set of peelable film (s) according to one of claims 6 to 14; b / removal by peeling off one of the protective layers so as to make the adhesive visible; c / transfer of the assembly onto the collection electrode by applying the adhesive to the latter; d / removal by peeling of the other of the protective layers so as to bring the absorption layer furthest from the collection electrode into contact with air or an aerosol.
the method comprising, preferably, after an initial cycle of operation of the precipitator / electrostatic collector, the following subsequent steps: e / switching off the precipitator / electrostatic collector; f / removal by peeling of the film furthest from the collection electrode, so as to bring the absorption layer of the underlying film into contact with the air or the aerosol and the method preferably comprising, after each operating cycle of the precipitator / electrostatic collector, following the initial cycle, the repetition of steps e / and f / until the last remaining absorption layer comes into contact with the air or the aerosol.

Images