EP2794117B1 - Device for generating an aerosol with a controlled particle size - Google Patents

Description

GENERAL TECHNICAL FIELD

The invention relates to a device and a method for generating an aerosol from a powder.

STATE OF THE ART

An aerosol is a set of solid or liquid particles of a chemical substance suspended in a gaseous medium.

• Baron P., Maynard A. Foley M. : « Evaluation of aerosol release during the handling of unrefined single walled carbon nanotube material, » NIOSH DART-02-191 rev 1.1 April 2003 ;
• Ku B.K., Maynard A.D., Baron P.A., Deye G.J.: « Observation and measurement of anomalous responses in a differential mobility analyzer caused by ultrafine fibrous carbon aerosols, » Journal of Electrostatics, 65, 542-548 ;
• Maynard A., Baron P., Foley M., Shvedova A., Kisin E., Castranova V.: « Exposure to carbon nanotube material: aerosol release during the handling of unrefined single-walled carbon nanotube material, » J. Toxicol. Env. Health part A, 67, 87-107 .

Various techniques are known for generating an aerosol from a powder and the techniques described in the following documents are known in particular:

• Baron P., Maynard A. Foley M .: "Evaluation of aerosol release during the handling of a single walled carbon nanotube material," NIOSH DART-02-191 rev 1.1 April 2003 ;
• Ku BK, Maynard AD, Baron PA, Deye GJ: "Observation and measurement of anomalous responses in a differential mobility analyzer caused by ultrafine fibrous carbon aerosols," Journal of Electrostatics, 65, 542-548 ;
• Maynard A., Baron P., Foley M., Shvedova A., Kisin E., Castranova V .: "Exposure to carbon nanotube material: aerosol release during the handling of a single-walled carbon nanotube material," J. Toxicol. Approx. Health part A, 67, 87-107 .

In these documents, to generate an aerosol, a powder is mixed with bronze balls in a test tube. The suspension of the particles for the generation of the aerosol is carried out by shaking the tube (either by rotating or by vibration) while injecting a flow of air from the top of the test tube, the aerosol being extracted from the top of the tube as well.

We know more about the document US 3,472,430 A which shows a device according to the preamble of claim 1.

A problem with these techniques is that the reproducibility over time of the generated aerosol is not guaranteed. In particular, the particle size of the aerosol particles is very variable, in particular because of the presence of aggregates.

PRESENTATION OF THE INVENTION

The invention proposes a device for generating an aerosol whose particle size is controlled, in particular the maximum size of the particles extracted.

• un système de dispersion des particules comprenant :
  • o un récipient inférieur dit zone de production adapté pour recevoir une poudre ;
  • o un récipient supérieur dit zone de sélection comprenant une base supérieure ; un orifice d'entrée ; une base inférieure en liaison aéraulique avec le récipient inférieur ; une partie intermédiaire entre la base supérieure et la base inférieure ; un orifice de sortie disposé en partie supérieure de la base supérieure ;
• un canal plongeant de l'orifice d'entrée jusque dans le récipient inférieur pour acheminer de l'air directement dans ledit récipient inférieur, la section interne du canal étant dimensionnée pour obtenir un jet d'air turbulent dans le récipient inférieur.
• le dispositif étant caractérisé en ce qu'il comprend en outre: un agitateur comprenant un logement adapté pour loger le récipient inférieur et mettre en rotation le système de dispersion ;

For this purpose, the invention proposes a device for generating a controlled particle size aerosol from a powder, the device comprising:

• a particle dispersion system comprising:
  • o a lower container said production area adapted to receive a powder;
  • o an upper container said selection area comprising an upper base; an inlet port; a lower base in aeraulic connection with the lower container; an intermediate portion between the upper base and the lower base; an outlet disposed in the upper portion of the upper base;
• a channel plunging from the inlet port into the lower vessel for conveying air directly into said lower vessel, the inner section of the channel being sized to provide a turbulent air jet into the lower vessel.
• the device being characterized in that it further comprises: an agitator comprising a housing adapted to house the lower container and rotating the dispersion system;

• le récipient supérieur présente un axe de symétrie longitudinal le long duquel s'étend le canal ;
• le récipient supérieur est dimensionné en fonction de la granulométrie souhaitée pour l'aérosol ;
• l'orifice d'entrée est sur la base supérieure et dans lequel l'orifice de sortie est sur la partie intermédiaire ;
• la partie intermédiaire est convergente entre la base supérieure et la base inférieure ;
• le récipient inférieur présente une section hémisphérique ;
• le récipient inférieur est amovible par rapport au récipient supérieur ;
• il comprend en outre un élément d'étanchéité entourant le canal pour assurer l'étanchéité entre le canal et le contour de l'orifice d'entrée.

The invention is advantageously completed by the following characteristics, taken alone or in any combination thereof - technically possible:

• the upper container has a longitudinal axis of symmetry along which the channel extends;
• the upper container is sized according to the desired particle size for the aerosol;
• the inlet port is on the upper base and in which the outlet port is on the intermediate portion;
• the intermediate portion is convergent between the upper base and the lower base;
• the lower container has a hemispherical section;
• the lower container is removable relative to the upper container;
• it further comprises a sealing member surrounding the channel for sealing between the channel and the contour of the inlet port.

• disposer une poudre dans le récipient inférieur ;
• amener de l'air au moyen du canal dans le récipient inférieur pour mettre en suspension des particules issues de la poudre pour générer un aérosol ;
• mettre en agitation/rotation le système de génération au moyen de l'agitateur ;
• récupérer l'aérosol ainsi généré par l'orifice de sortie.

The invention also proposes a method for generating an aerosol by means of a generation device according to the invention, comprising the following steps:

• dispose a powder in the lower container;
• supplying air through the channel into the lower vessel to suspend particles from the powder to generate an aerosol;
• stirring / rotating the generating system by means of the stirrer;
• recover the aerosol thus generated by the outlet orifice.

The advantages of the invention are manifold.

The presence of the production and selection zones results in the presence of two aeraulic zones in the same system respectively allowing the suspension and the size selection of the aerosol.

The arrangement of the pipe makes it possible to inject air directly into the production zone, at the point where the particles are suspended.

The rising airflow in the selection zone allows sorting of the particle sizes by vertical elutriation.

The upper container is conical in shape which provides a stable upward flow without turbulence at the connection with the dispersion zone.

The lower container is removable, allowing easy cleaning and powder filling without disassembling the entire dispersion system.

With the invention it is possible to use very low air flows, for example less than 1 L / min, which makes it easy to create a confinement of the powder by cascade of pressure.

The invention makes it possible to control the rate of suspension of the particles, independently of the flow rate of air injected.

Finally, with the invention, a very good stability and a very good reproducibility of the concentration over several hours of operation are obtained thanks to the combination of two aeraulic zones.

PRESENTATION OF THE FIGURE

Other characteristics, aims and advantages of the invention will emerge from the description which follows, which is purely illustrative and nonlimiting, and which must be read in relation to the figure 1 attached which illustrates a device for generating an aerosol according to an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

A device for generating a controlled particle size aerosol, from a powder P, according to one embodiment of the invention is composed of a dispersion system 1, 2 of the particles comprising a lower container 1 said zone in which a powder P to suspend is deposited and an upper container 2 said selection area.

It is specified that the production zone means the zone in which the particles are suspended and, by zone of selection, the zone in which particles originating from the powder P having a certain particle size are selected to generate a certain type of aerosol.

The upper container 2 comprises an upper base 2a having an inlet port 2e and a lower base 2b in aeraulic connection with the lower vessel 1 and an intermediate portion 2d between the upper base 2a and the lower base 2b.

The intermediate portion 2d includes an aerosol outlet port 2c disposed in the upper portion of the upper base 2a. The outlet 2c is in particular arranged on one side of the upper part of the upper container 2.

It is specified that the upper part is understood to mean an area that extends from the top of the upper container 2 to the half of the upper container 2, preferably to one third of the upper container 2.

Alternatively the inlet port 2e may be disposed on the intermediate portion 2d and the outlet port 2c may be disposed on the upper base 2a.

In order to bring the air directly into the lower container 1, the generating device comprises a channel 3 directly dipping into the lower container 1. The channel 3 is for example made of metal and is in particular vertical to extend along an axis of longitudinal symmetry of the upper container 2 in the case of the figure 1 otherwise the channel 3 may be arranged in another way, especially if the inlet orifice 2e is disposed on the intermediate portion 2d and the outlet orifice 2c on the upper base 2a.

The channel 3 has an internal section which is dimensioned to obtain a turbulent air jet in the lower container 1.

The inner section of the channel 3 may be square, ellipsoidal or preferably circular.

The channel 3 is connected to an air supply (not shown) and the injected air is in particular clean air obtained from a conventional compressed air source, the air coming from the source of air. compressed air having been previously dried and filtered. Thus, the internal section of channel 3 is dimensioned according to the air flow, so as to produce a turbulent air jet directly in the lower part 1.

In addition, to control the flow of injected air, a flow meter (not shown) between the 2nd inlet of the channel 3 and the air supply is used.

The generation device also comprises an agitator 4 which is for example of the Vortex Genius 3® type. The stirrer 4 comprises a housing for maintaining the dispersion system via the lower container 1.

The agitator 4 makes it possible to rotate the dispersion system.

Advantageously, the channel 3 is arranged relative to the upper container 2 so that the dispersion system can have a rotational movement without being hindered by it.

Thus, as understood, the arrival of the air flow is by means of the channel 3 which is vertical and which directly plunges into the lower container 1 and which makes it possible to transport the suspended particles, thanks to the agitation powder P caused by the stirrer 4 in the lower container 1, to the outlet 2c.

To seal at the inlet port 2e, the generating device comprises a sealing member 5 for sealing between the channel 3 and the contour of the orifice 2e.

The channel 3 is in particular integral with the upper container 2.

Advantageously, the outlet orifice 2c is disposed sufficiently far from the end of the channel 3 immersed in the lower container.

In addition, the outlet orifice 2c must be located in the part where the section of the upper container is the largest because it is this section which is used to calculate the speeds in the system and which determines the size of the selected particles ( see below).

In order to be able to select a certain particle size, the upper container 2 is further dimensioned in a certain way. In Indeed, depending on the size and shape of the latter can be selected particles having a certain particle size.

The conical shape of the upper container 2 makes it possible to obtain a stable flow during the passage of the aerosol through the upper base 2b in connection with the lower container 1.

The diameter of the upper base 2a makes it possible to impose a specific upward flow velocity limiting the extraction of particles having an aerodynamic diameter greater than a critical value defined by the size of the upper base 2a and the air flow injected into the system through channel 3.

Preferably, the upper container 2 is such that the intermediate portion 2d is convergent between the upper base 2a and the lower base. In this case, the upper container 2 is conical. It is in particular the internal section of the upper container 2 which will make it possible to control the maximum particle size of the aerosol generated.

Thus, by having an intermediate portion 2d converging between the upper base 2a and the lower base 2b the inner section widens from the lower base 2b to the upper base 2b of the upper container 2.

To promote the suspension of the particles in the lower container 1, the latter has a bottom having a hemispherical section

Such a hemispherical section has the further advantage of being easily cleaned (no sharp angle).

Furthermore, this hemispherical section is suitable for adapting the lower container 1 to the stirrer 4.

In addition, still to promote the suspension of the particles, between the lower base of the upper container 2 and the lower container 1 there is a change of section to promote the suspension in the lower container 1. In particular, the lower container has a section wider than the lower base of the upper container 2.

In this way, such a lower container 1 combined with an inner section of the upper container 2 converging from the upper base 2a to the lower base 2b and the channel 3 which directly brings the air into the lower container 1 allows to confine the suspension of particles in the lower container 1.

In addition, to facilitate the deposition of powder P in the lower container 1, the lower container 1 is removable relative to the upper container 2.

Finally it is possible to mix the powder with bronze or copper balls to contribute to the dispersion of the particles.

With the aerosol generating device described above it is possible to generate an aerosol having controlled properties.

For example, to generate an alumina aerosol from an alumina powder whose median grain diameter is 0.65 μm, the generation device has the following parameters: feed air flow rate between 0 , 1 L / min and 0.5 L / min; concentration variability less than 5% over one hour of production.

Claims (9)

1. A device for generating an aerosol with a controlled grain size distribution, from a powder, the device comprising:

   - a system for dispersing (1, 2) particles comprising:

   ∘ a lower container (1) referred to as a production area adapted to receive a powder (P);

   ∘ an upper container (2) referred to as a selection area comprising an upper base (2a); an inlet port (2e); a lower base (2b) in aeraulic connection with the lower container (1); an intermediate part (2d) between the upper base (2a) and the lower base (2b); an outlet port (2c) disposed at the upper part of the upper base (2a);
   the device being characterised in that it further comprises:

   - a channel (3) plunging from the inlet port (2e) down into the lower container (1) to directly convey air in said lower container (1), the inner section of the channel (3) being sized to obtain a turbulent air jet in the lower container (1);

   - a stirrer (4) comprising a housing adapted to accommodate the lower container (1) and rotate the dispersion system (1, 2).
2. The device according to claim 1, wherein the upper container (2) has a longitudinal symmetry axis along which the channel (3) extends.
3. The device according to one of the preceding claims, wherein the upper container (2) is sized as a function of the desired grain size distribution for the aerosol.
4. The device according to one of the preceding claims, wherein the inlet port (2e) is on the upper base (2a) and wherein the outlet port (2c) is on the intermediate part (2d).
5. The device according to one of the preceding claims, wherein the intermediate part (2d) is converging between the upper base (2a) and the lower base (2b).
6. The device according to one of the preceding claims, wherein the lower container (1) has a hemispheric section.
7. The device according to one of the preceding claims, wherein the lower container (1) is removable with respect to the upper container (2).
8. The device according to one of the preceding claims, further comprising a sealing element (5) surrounding the channel (3) to provide sealing between the channel and the contour of the inlet port (2e).
9. A method for generating an aerosol by means of a device according to one of the preceding claims comprising the following steps:

   - disposing a powder (P) in the lower container (1);

   - bringing air by means of a channel (3) in the lower container (1) to suspense particles coming from the powder (P) to generate an aerosol;

   - stirring/rotating the generation system by means of a stirrer (4);

   - recovering the aerosol thus generated through the outlet port (2c).

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