Selective aerosol particle collecting method and device, according to particle size

Patent metadata

Field	Value
Publication number	US-2018200727-A1
Application number	US-201615744332-A
Country	US
Kind code	A1
Filing date	Jul 28, 2016
Priority date	Jul 28, 2015
Publication date	Jul 19, 2018
Grant date	—

Abstract

The invention relates to a method and device for collecting particles which may be present in an aerosol. The invention consists in electrostatically collecting all the particles in an aerosol, but uncoupling mechanisms of particle charging by unipolar ion diffusion, for charging then collecting the finest particles, from particle charging by a corona effect electrical field, for charging then collecting the biggest particles in a different collection zone from the collection zone for the finest particles. The invention also relates to the use of such a device as ionisation chamber or for evaluating the exposure of workers or consumers to nanoparticles.

First claim

1 . A method for collecting particles likely to be present in an aerosol, comprising the following steps:
sucking the aerosol through a conduit from its inlet orifice to its outlet orifice; charging the finest particles, downstream of the inlet orifice, by unipolar ion diffusion in a space between an electrode in the form of a gate surrounding an electrode in the form of a wire generating a corona effect, and a first conductive portion of the internal wall of the conduit; generating an electric field without a corona effect in the space between an electrode and a second conductive portion of the internal wall of the conduit, in order to collect the finest particles charged by the diffusion charger by deposition onto a first collection zone (Zn); generating an electric field with a corona effect in the space between the wire or the point of an electrode and a third conductive portion of the internal wall of the conduit, in order to collect the biggest particles not charged by the diffusion charger by deposition onto a second collection zone (Zm) distinct from the first collection zone.

2 . The method for collecting radioactive particles as claimed in claim 1 , further comprising the following steps:
a/ collecting radioactive particles on the first and/or the second collection zone during a time period t 1 ; b/ counting pulses generated by the ionization current of the air in the spaces during a time period t 2 .

3 . The method for collecting radioactive particles as claimed in claim 2 , comprising a step of emitting an alarm in the event that a predetermined threshold value of pulses counted in step b/ is exceeded.

4 . A device for collecting particles likely to be present in an aerosol, comprising:
a conduit comprising an inlet orifice and an outlet orifice, between which the aerosol may circulate; suction means for circulating the aerosol from the inlet orifice to the outlet orifice; a unipolar ion diffusion charger, downstream of the inlet orifice, comprising an electrode in the form of a wire surrounded by an electrode in the form of a gate, the charger being adapted to charge the finest particles in the space separating the gate from a first conductive portion of the internal wall of the conduit by diffusing unipolar ions through the gate; an electrode, downstream of the diffusion charger, adapted to generate an electric field without a corona effect in the space separating the electrode from a second conductive portion of the internal wall of the conduit and to thus collect the finest particles, previously charged by the diffusion charger, by deposition onto a first collection zone (Zn); an electric field charger, downstream of the ion diffusion charger and of the nanoparticle collection zone, comprising an electrode in the form of a wire or a point adapted to generate an electric field with a corona effect in the space separating the wire or the point from a third conductive portion of the internal wall of the conduit and to thus charge, then collect, the biggest particles by deposition onto a second collection zone (Zm) distinct from the first collection zone.

5 . The collection device as claimed in claim 4 , wherein:
the conduit is a hollow cylinder of revolution about a longitudinal axis (X); the suction means are formed by a pump; the first, second and third conductive portions of the wall are cylinder portions forming part of the conduit; the field charger comprises an electrode in the form of a wire in a wire-cylinder configuration with the corresponding cylinder portion; the ion diffusion charger wire, the electrode for generating an electric field without a corona effect and the wire of the field charger are distinct parts and are successively arranged one behind the other along the axis (X).

6 . The collection device as claimed in claim 4 , wherein:
the conduit comprises a hollow element of revolution about a longitudinal axis (X) and a flat substrate arranged at one end of the hollow element orthogonal to the axis (X), the distance separating the hollow element from the flat substrate and its possible support defining the dimensions of the outlet orifice, the flat substrate forming a collection substrate defining both the first (Zn) and the second (Zm) collection zone; the suction means are formed by the outlet orifice; the first conductive portion of the wall is a portion of revolution forming the conduit; the second and third conductive portions are grouped on the same collection substrate; the field charger comprises an electrode in the form of a point in a point-plane configuration with the collection substrate, the point being adapted to generate a corona effect participating in the field charging of the particles but also for creating an electric field promoting the collection of species previously charged by the ion diffusion charger; the wire of the ion diffusion charger, the electrode and the point of the field charger are portions of the same part exhibiting electrical continuity that extends along the axis (X).

7 . The collection device as claimed in claim 6 , comprising plasma actuators arranged in the vicinity of the outlet.

8 . The collection device as claimed in claim 4 , wherein the wire of the ion diffusion charger, the collection electrode rod and the wire or the point of the field charger are connected to a high-voltage power supply.

9 . The collection device as claimed in claim 4 , wherein the gate is connected to a low-voltage power supply.

10 . The collection device as claimed in claim 4 , the first, second and third conductive portions being connected at zero potential.

11 . The collection device as claimed in claim 4 , forming an air ionization chamber.

12 . The collection device as claimed in claim 4 , forming a radioactive particle detector.

13 . The use of a device as claimed in claim 4 , for collecting particles while separating nanoparticles into the first collection zone (Zn) and micron-sized particles into the second collection zone (Zm).

14 . The use of a device as claimed in claim 4 as an ionization chamber.

15 . The use of a device as claimed in claim 4 for evaluating the individual exposure of workers or of consumers to the nanoparticles.

Assignees

• Commissariat Energie Atomique

Inventors

• Clavaguera Simon
• Guiot Arnaud
• Pourprix Michel
• Daniel Nicolas

Classifications

• B03C3/06

  characterised by presence of stationary tube electrodes · CPC title

• B03C3/12

  characterised by separation of ionising and collecting stations · CPC title

• B03C3/38

  Particle charging or ionising stations, e.g. using electric discharge, radioactive radiation or flames · CPC title

• B03C3/025 Primary

  Combinations of electrostatic separators, e.g. in parallel or in series, stacked separators or dry-wet separator combinations · CPC title

• B03C3/368

  by other than static mechanical means, e.g. internal ventilator or recycler · CPC title