FR2841800A1 - Method of collecting soot particles in an electrostatic filter designed for filtration of a gas flow containing electrically charged soot particles - Google Patents

Abstract

The gas flow (3) is braked in a collection zone (4) for the soot particles (1) separate from a flow zone (5) where the gas flow flows normally. An electrostatic field is applied to the collection zone and in the flow zone so the electrified soot particles, passing from the normal flow zone to the collection zone, deposit themselves in the collection zone as they come to a stop. The gas flow containing the soot particles flows across an elongated tube (7) with a central part (8) and a peripheral part (9). The process brakes the flow in the particle collection zone by placing an obstacle (10) in its way, in particular made of glass fibre or a metal mesh in the central part. The collection zone has a reduced diameter. To apply an electrical field in the collection zone, a difference in potential is created between a central electrode (12) in the central part and a peripheral electrode (13) in the peripheral part. These electrodes form the walls of the collection zone with almost stationary flow, and the normal flow zone. Depending on the version used, the soot is deposited around the periphery of the electrostatic filter near the peripheral electrode, or in the central part of the filter near the central electrode. The potential difference between the two electrodes is between 5 and 100 kV. An intermediate electrode can also be used between the peripheral and central electrodes, placed near the obstacle. The potential difference between the intermediate electrode and the central electrode and between the intermediate electrode and the peripheral electrode is between 5 and 100 kV. The potential of the intermediate electrode is near that of the mass, to reduce the risk of electrical accidents. The collected soot particles are eliminated by thermal degradation using an electrical resistance, by mechanical means such as a vacuum, or the collection zone is in the form of a removable cartridge, which is extracted and replaced by a new one. An independent claim is also included for an electrostatic filter for carrying out the above process.

Description

METHOD AND DEVICE FOR COLLECTING SOOT PARTICLES IN

  A ZONE ALLOWING THEIR DISPOSAL

Preamble to the description

  Field concerned, problem posed The present invention relates to a method and an electrostatic filter for collecting, in an area allowing their elimination, the soot particles contained in a flow

  gas, especially at the outlet of an internal combustion engine.

  Solution Method The invention relates to a method for collecting soot particles in an electrostatic filter intended for the

  filtration of a gas stream containing the soot particles.

  Prior to the implementation of the process or during the implementation of the process, the electrical state of the soot particles has been modified, in a manner known per se, in particular according to the process described in French patent application No. 96 0198 or in French application No. 99 11474. The method comprises the step of slowing down the flow of the gas flow in a zone for collecting soot particles. The collection zone is distinct from a flow zone where the gas flow flows nominally. It results from the combination of technical features which can be distinguished in the two-stage electrostatic filter, on the one hand a stage where the gas flow flows nominally, on the other hand a stage o the gas flow containing the soot particles is practically stationary. The method further comprises the step of applying an appropriately oriented electric field in the collection zone where the flow of the gas flow is slowed down and in the flow zone where the gas flow flows in a slow manner. nominal. Under the action of the applied electric field, the soot particles, whose electrical state has been modified, pass from the zone of nominal flow to the collection zone with stationary flow. Electrified soot particles are deposited in the collection area where it is

possible to eliminate them.

  Preferably, according to the invention, the gas stream containing the soot particles flows through an elongated tube. The elongated tubing has a central portion and a peripheral portion. To slow the flow of the gas flow in the area for collecting soot particles, at least one obstacle is placed along its path. Preferably, according to a first alternative embodiment of the invention, to slow the flow of the gas flow in the area for collecting soot particles, at least one obstacle is placed in the central part. This obstacle can, for example, be made of fiberglass or take the form of a metallic knit of the type described in French application No. 99 11474. It results from the combination of technical features that the particle collection zone of soot, located in the center of the electrostatic filter, is of reduced size. Preferably, according to the invention another alternative embodiment, to slow the flow of the gas flow in the area for collecting soot particles, at least one obstacle is placed, in particular made of fiberglass or of the knitted type.

  metallic, in the peripheral part.

  Preferably, according to an alternative embodiment of the invention, to create and apply an electric field in the collection zone where the flow of the gas flow is slowed down and in the flow zone where the gas flow flows so nominal, a potential difference is created between: - a central electrode located in the central part, and - a peripheral electrode located in the peripheral part. The central electrode and the peripheral electrode

  form the walls of the quasistationary flow collection zone and the nominal flow flow zone.

  The obstacle, in particular in fiberglass or in the form of a metallic knit, slowing down the flow of the gas flow is disposed

  between the central electrode and the peripheral electrode.

  According to the embodiment considered, the soot particles are deposited in the collection zone: either at the periphery of the electrostatic filter, in the vicinity of the peripheral electrode,

  - either in the central part of the electrostatic filter, in the vicinity of the central electrode.

  Preferably, according to the invention, the potential difference between the peripheral electrode and the central electrode is between 5 kV and 100 kV. The potential difference will be chosen in particular according to the geometry of the filter.

  as well as the shape or polarity of the signal.

  Preferably, according to an alternative embodiment of the invention, to create and apply an electric field in the collection zone where the flow of the gas flow is slowed down and in the flow zone where the gas flow flows so nominal, we create: - on the one hand, a first potential difference between a central electrode located in the central part and an intermediate electrode located at the level of the obstacle preventing the flow of the gas flow, in particular by constituting a conductive armature supporting glass fibers, - on the other hand, a second potential difference between a peripheral electrode located in the part

  peripheral and the intermediate electrode.

  The central electrode and the peripheral electrode

  form the walls of the quasistationary flow collection zone and the nominal flow flow zone.

  According to the variant embodiment, the collection zone is either in the center of the filter or on the periphery of the filter. It results from the combination of technical features that, according to the variant embodiment, the soot particles are deposited: either at the periphery of the electrostatic filter, in the vicinity of the peripheral electrode,

  - either in the central part of the electrostatic filter, in the vicinity of the central electrode.

  Preferably, according to the invention, the potential difference between the central electrode and the electrode

  intermediate is between 5 kV and 100 kV.

  Preferably, according to the invention, the potential difference between the intermediate electrode and the electrode

  device is between 5 kV and 100 kV.

  Preferably, according to the invention, the peripheral electrode is brought to a potential close to that of the ground. As a result, the risk of electrical accidents

are thus reduced.

  Preferably, according to the invention, the method further comprises the step of removing the collected soot particles.

in the collection area.

  Preferably, according to the invention, the method is such that to remove the soot particles, in particular when the collection zone is located in the center of the electrostatic filter, they are thermally degraded with an energy supply. In the case where the collection zone is located in the center of the electrostatic filter, the particles are collected in a more restricted volume and degraded with lower heat losses than in the case where the collection zone is situated at the periphery of the filter; in this case it is possible to thermally degrade the soot particles with a reduced energy supply, in particular by means of an electrical resistance. Preferably, according to another alternative embodiment of the invention, to remove the soot particles, in particular when the collection zone is located in the center of the electrostatic filter, the collection zone produced under the

  form of a removable cartridge and it is replaced by a new one.

  Preferably, according to the invention, the method is such that to remove the soot particles, in particular when the collection zone located at the periphery of the electrostatic filter is easily accessible, the soot particles are mechanically extracted, in particular by creating a vacuum . Filter The invention also relates to an electrostatic filter for filtering and collecting soot particles from a gas flow containing the soot particles. The electrical state of the soot particles was modified prior to the use of the electrostatic filter or during the use of the electrostatic filter. The electrostatic filter comprises: - a flow zone where the gas flow flows in a nominal manner, - a zone for collecting soot particles, distinct from the flow zone, - elements, in particular obstacles, braking the flow of gas flow in the collection area of

soot particles.

  It results from the combination of technical features which can be distinguished in the two-stage electrostatic filter, on the one hand a stage where the gas flow flows nominally, on the other hand a stage o the gas flow containing the soot particles is practically stationary. The electrostatic filter further comprises electrodes for applying an electric field in the collection zone where the flow of the gas flow is slowed down and in the flow zone where the gas flow flows nominally. Under the action of the electric field, the electrified soot particles pass from the nominal flow zone to the stationary flow collection zone and settle in the collection zone where it is

possible to eliminate them.

  Preferably, according to the invention, the gas flow containing the soot particles flows through an elongated tube comprising a central part and a peripheral part. The electrostatic filter is such that the area for collecting soot particles comprises at least one obstacle, in particular made of fiberglass or in the form of a knitted fabric.

  metallic, slowing the flow of the gas flow.

  Preferably, according to an alternative embodiment of the invention, the area for collecting soot particles is

  located in the central part and has at least one obstacle.

  Thus, the soot particle collection zone, located in the center of the electrostatic filter, can be reduced in size. Preferably, according to another alternative embodiment of the invention, the area for collecting soot particles is located in the peripheral part and comprises at least one

obstacle.

  Preferably, according to the invention, to create an electric field in the collection zone where the flow of the gas flow is slowed down and in the flow zone where the gas flow flows in nominal fashion, a difference of potential between: - a central electrode located in the central part, and - a peripheral electrode located in the peripheral part. The central electrode and the peripheral electrode

  form the walls of the quasistationary flow collection zone and the nominal flow flow zone.

  The obstacle, in particular made of fiberglass or in the form of a metallic knitted fabric, is disposed between the central electrode and the peripheral electrode. According to the variant embodiment, the soot particles are deposited in the collection zone: either at the periphery of the electrostatic filter, in the vicinity of the peripheral electrode,

  - either in the central part of the static electro15 filter, in the vicinity of the central electrode.

  Preferably, according to the invention, the electrostatic filter is such that the potential difference between the peripheral electrode and the central electrode is included

between 5 kV and 100 kV.

  Preferably, according to another alternative embodiment of the invention, for applying and creating an electric field in the collection zone where the flow of the gas flow is slowed down and in the flow zone where the gas flow flows from nominal manner, there is applied: - on the one hand, a first potential difference between a central electrode located in the central part and an intermediate electrode located at the level of the obstacle slowing down the flow of the gas flow, - on the other hand , a second potential difference between a peripheral electrode located in the part

  peripheral and the intermediate electrode.

  The central electrode and the peripheral electrode

  form the walls of the quasistationary flow collection zone and the nominal flow flow zone.

  According to the variant embodiment, the soot particles are deposited: either on the periphery of the electrostatic filter, in the vicinity of the peripheral electrode, - or in the central part of the filter

  electrostatic, in the vicinity of the central electrode.

  Preferably, according to the invention, the electrostatic filter is such that the potential difference between the central electrode and the intermediate electrode is included

between 5 kV and 100 kV.

  Preferably, according to the invention, the electrostatic filter is such that the potential difference between the intermediate electrode and the peripheral electrode is

between 5 kV and 100 kV.

  Preferably, according to the invention, the electrostatic filter is such that the peripheral electrode is brought to a potential close to that of the ground. So the risks

  electrical accidents are reduced.

  Preferably, according to the invention, the collection zone further comprises a source of thermal energy, in particular an electrical resistance, intended to degrade the particles of

  soot located in the collection area.

  Preferably, according to an alternative embodiment of the invention, the collection zone is located in the center of the electrostatic filter; the particles are collected in a smaller volume and degraded with lower heat losses than in the case where the collection zone is located on the periphery of the filter, in this case, it is possible to thermally degrade the soot particles with a reduced energy supply, in particular by means of an electrical resistance. Preferably, according to an alternative embodiment of the invention, the collection zone is produced in the form of a removable cartridge capable of being replaced by a new one. Thus, it is possible to ergonomically remove soot particles, especially when the collection area

  is located in the center of the electrostatic filter.

  Preferably, according to an alternative embodiment of the invention, the electrostatic filter further comprises or is capable of being associated with mechanical means for removing soot particles from the collection zone, in particular with suction means. of these through an opening

in the electrostatic filter.

  Preferably, according to an alternative embodiment of the invention, the collection zone is located at the periphery of the electrostatic filter. Thus, it is possible to eliminate

  ergonomically soot particles.

detailed description

  Other characteristics and advantages of the invention

  will appear on reading the description of variants of

  embodiment of the invention, given by way of non-limiting example, and of the figures: - FIG. 1 which represents a perspective view cut away from a first alternative embodiment of an electrostatic filter, - FIG. 2 which represents a longitudinal section view of the alternative embodiment shown in FIG. 1, FIG. 3 which represents a longitudinal section view of a second alternative embodiment of an electrostatic filter. We will now describe a first alternative embodiment of a filter according to the invention with reference to Figures 1 and 2 which respectively show a perspective view cut away and a view in longitudinal section of this

first variant.

  The electrostatic filter 2 is intended to filter and collect the soot particles 1 present in a gas flow 3, in particular in the gas flow leaving the engine of a motor vehicle. The electrical state of the soot particles 1 has been modified at the input 21 of the filter in a manner known per se, in particular by using an effect device such as that described in French patent application No. 96 0198 or in the French application No. 99 11474. For example, this device can consist of tapered conductive tips 22 brought to a potential of several thousand volts. The tapered conductive tips 22 are the seat of corona effect. This corona effect device can be placed inside the electrostatic filter 2 as shown in FIG. 1, in which case the electrical state of the soot particles is modified during the implementation of the electrostatic filter 2. It can also be placed upstream of the electrostatic filter 2, in which case the electrical state of the soot particles is modified prior to the use of the electrostatic filter 2. In this case, the particles present in the gas flow are optionally at a stage d agglomeration (as described in EP 203 928) before the

  use of the electrostatic filter 2.

  The gas flow 3 enters the electrostatic filter 2 through an inlet pipe 30, it exits therefrom through an outlet pipe 31. The electrostatic filter 2 comprises: - a flow zone 5 o the gas stream 3 flows from nominal manner - a collection area 4 for soot particles 1, distinct from the flow area 5, - obstacles 10, in particular in the form of fiberglass elements or in the form of a metallic knitted fabric, slowing the flow of gas flow 3 in the area

  collecting 4 soot particles 1.

  We can thus distinguish in the electrostatic filter 2 two stages, on the one hand a stage where the gas flow 3 flows nominally, on the other hand a stage where the gas flow 3 containing the soot particles 1 is practically stationary . The electrostatic filter 2 further comprises electrodes 12, 13 for applying an electric field 6 in the collection zone 4 where the flow of the gas flow 3 is slowed down and in the flow zone 5 where the gas flow 3 flows nominally. Under the action of the electric field 6, the intensity and orientation of which are appropriately chosen, the electrified soot particles 1 pass from the nominal flow zone towards the collection zone 4 to

  stationary flow where they settle.

  Cylindrical geometry of the electrostatic filter 2 In the case of the variant embodiment shown in FIG. 1, the geometry of the electrostatic filter 2 is cylindrical. The gas flow 3 containing the soot particles 1 flows through an elongated tube 7 comprising a central part 8 and a peripheral part 9 coaxial with the central part. A cylindrical shape is well suited to the filtration of gas flows at the outlet of the exhaust pipe of an internal combustion engine. However, the shape of the filter

  electrostatic 2 may not be cylindrical.

  The collection zone 4 is central In the variant embodiment shown in FIG. 1, the collection zone 4 for soot particles 1 is located in the central part 8. This central arrangement of the collection zone 4 makes it possible to produce a filter electrostatic 2 of reduced size. However, the collection zone 4 could be located at the periphery 9 of the electrostatic filter 2. In this case, the flow zone 5 o the gas flow 3 flows nominally is located in the center of the electrostatic filter 2 The filter electrostatic 2 has two electrodes 12 and 13 In the case of an alternative embodiment shown in FIG. 1, to apply an electric field 6 in the collection zone 4 where the flow of the gas flow 3 is slowed down and in the flow zone 5 o the gas flow 3 flows nominally, a potential difference 11 is created between: - a central electrode 12 located in the central part 8, and - a peripheral electrode 13 located in the part

device 9.

  The central electrode 12 defines, with the obstacle 10 slowing down the flow of the gas flow 3, the collection zone 4 with quasi-stationary flow. The peripheral electrode 13 delimits with the obstacle 10 slowing down the flow of the gas flow 3 the flow zone 5 with nominal flow. The electrode

  central 12 and the peripheral electrode 13 are cylindrical.

  They form the walls of the collection zone 4 with quasistationary flow and of the flow zone 5 with nominal flow. The obstacle 10, in particular made of fiberglass or in the form of a metallic knitted fabric, is disposed between the electrode

  central 12 and the peripheral electrode 13.

  In the case of the alternative embodiment shown in FIG. 1, the soot particles 1 are deposited in the vicinity of the central electrode 12, in the collection zone 4

  located in the central part 8 of the electrostatic filter 2.

  In the case, not shown, where the collection zone 4 is located at the periphery of the electrostatic filter 2, the soot particles 1 are deposited in the vicinity of the electrode

device 13.

  In the case of the alternative embodiment shown in FIG. 1, the potential difference 11 between the peripheral electrode 13 and the central electrode 12 is between kV and 100 kV. The electrostatic filter 2 comprises three electrodes 12, 13 and 15 We will now describe, with reference to FIG. 3, a second alternative embodiment in the case where the electrostatic filter 2 comprises three electrodes 12, 13 and 15. We recognize on Figure 3 most of the elements described with reference to Figures 1 and 2. They have the same references

digital.

  In the case of this second variant, to apply an electric field 6 in the collection zone 4 o the flow of the gas flow 3 is slowed down and in the flow zone 5 o the gas flow 3 flows nominal, we apply: - on the one hand, a first potential difference 14 between a central electrode 12 located in the central part 8 and an intermediate electrode 15 located at the level of the obstacle preventing the flow of the gas flow 3, in particular by constituting a conductive metal frame carrying a glass fiber mat, - on the other hand, a second potential difference 16 between a peripheral electrode 13 located in the part

  peripheral 9 and the intermediate electrode 15.

  The central electrode 12 defines, with the obstacle 10 slowing down the flow of the gas flow 3, the collection zone 4 with quasi-stationary flow. The peripheral electrode 13 delimits with the obstacle 10 slowing down the flow of the gas flow 3 the flow zone 5 with nominal flow. The electrode

  central 12 and the peripheral electrode 13 are cylindrical.

  They form the walls of the collection zone 4 with quasistationary flow and of the flow zone 5 with nominal flow. The obstacle 10 and the intermediate electrode 15 are arranged between the central electrode 12 and the electrode

device 13.

  The central electrode 12 and the peripheral electrode 13

  form the walls of the collection zone 4 with quasistationary flow and of the flow zone 5 with nominal flow.

  In the case of the alternative embodiment shown in FIG. 3, the soot particles 1 are deposited in the vicinity of the central electrode 12, in the collection zone 4

  located in the central part 8 of the electrostatic filter 2.

  In the case, not shown, where the collection zone 4 is located at the periphery of the electrostatic filter 2, the soot particles 1 are deposited in the vicinity of the electrode

device 13.

  The potential difference 14 between the central electrode 12 and the intermediate electrode 15 is between 5 kV and 100 kV. The potential difference 16 between the intermediate electrode 15 and the peripheral electrode 13 is included

between 5 kV and 100 kV.

  In the case of the variant embodiments described with reference to FIGS. 1 to 3, the peripheral electrode 13 is brought to a potential close to that of the ground. So the

  risks of electrical accidents are reduced.

  For the implementation of the device of the invention, it is envisaged to use direct current or alternating current or else a current composed of the superposition of a

  direct current and alternating current.

  Process for eliminating soot particles In the case of the alternative embodiment shown in FIG. 1, the collection zone 4 further comprises a source of thermal energy 19 constituted by an electrical resistance. This thermal energy source is intended to degrade the soot particles 1 located in the collection zone 4. In the case where the collection zone 4, located in the center of the electrostatic filter 2, is of small size, it is possible to thermally degrade soot particles 1

with reduced energy intake.

  The collection zone 4 can be produced in the form of a removable cartridge 17 capable of being replaced by a new one. In particular, this solution is convenient to implement when the collection zone 4 is located in the center of the electrostatic filter 2. Thus, it is possible

  ergonomically remove soot particles 1.

  In the case of another alternative embodiment, the electrostatic filter 2 further comprises or is capable of being associated with mechanical means for removing the soot particles 1 deposited in the collection zone 4. These mechanical means can be constituted in particular by means of suction of the soot particles through a

  opening in the electrostatic filter 2.

  This technical solution can in particular be implemented advantageously in the case where the collection zone 4 is located at the periphery of the electrostatic filter 2. Thus, it is possible to eliminate ergonomically the

soot particles 1.

Claims (29)

  1. Method for collecting soot particles (1) in an electrostatic filter (2) intended for the filtration of a gas flow (3) containing said soot particles (1); the electrical state of said soot particles (1) having been modified prior to the implementation of the method or during the implementation of the method; said method comprising the following steps - the step of slowing the flow of said gas flow (3) in a collection zone (4) of said soot particles (1); said collection zone (4) being distinct from a flow zone (5) o said gas flow (3) flows in a nominal manner; so that one can distinguish in said electrostatic filter (2) two stages, on the one hand a stage o the gas flow (3) flows nominally, on the other hand a stage o the gas flow (3 ) containing said soot particles (1) is practically stationary; said method further comprising the following steps: - the step of applying an electric field (6) in said collection zone (4) where the flow of said gas flow (3) is slowed down and in the flow zone ( 5) o said gas flow (3) flows nominally; so that, under the action of the electric field (6), the electrified soot particles (1) pass from the nominal flow zone to the flow collection zone (4)   stationary and settle in the collection area (4).   2. Method according to claim 1; said gas stream (3) containing the soot particles (1) flowing through an elongated tube (7) comprising a central part (8) and a peripheral part (9); said method being such as to slow the flow of said gas flow (3) in said collection zone (4) of said soot particles (1)   at least one obstacle (10) is placed on its course.   3. Method according to claim 2; said method being such that, to slow the flow of said gas flow (3) in said collection zone (4) of said soot particles (1), at least one obstacle (10) is placed, in particular made of fiberglass or under the shape of a metallic knit in said central part (8); so that the collection area (4) for soot particles (1), located in the center of the electrostatic filter (2), is reduced size.   4. Method according to claim 2; said method being such that, to slow the flow of said gas flow (3) in said collection zone (4) of said soot particles (1), at least one obstacle (10) is placed, in particular made of fiberglass or under the shape of a metallic knit, in said peripheral part (9).   5. Method according to any one of claims 2   to 4; said method being such that to apply an electric field (6) in the collection zone (4) where the flow of said gas flow (3) is slowed down and in the flow zone (5) o the gas flow (3) nominal flow, a potential difference (11) is created between: - a central electrode (12) located in said central part (8), and - a peripheral electrode (13) located in said peripheral part (9) ; said central electrode (12) and said peripheral electrode (13) forming the walls of the collection zone (4) with quasistationary flow and of the flow zone (5) with nominal flow; said obstacle (10), in particular made of fiberglass or in the form of a metallic knitted fabric, being arranged between said central electrode (12) and said peripheral electrode (13); so that, according to the variant embodiment, said soot particles (1) are deposited in the collection zone (4): - either at the periphery of the electrostatic filter (2), in the vicinity of the peripheral electrode (13) , - either in the central part (8) of the filter   electrostatic (2), in the vicinity of the central electrode (12).   6. Method according to claim 5; said method being such that the potential difference (11) between the peripheral electrode (13) and the central electrode (12) is included between 5 kV and 100 kV.   7. Method according to any one of claims 2   to 4; said method being such that, for applying an electric field (6) in the collection zone (4) where the flow of said gas flow (3) is slowed down and in the flow zone (5) o the gas flow (3 ) flows nominally, creating: - on the one hand, a first potential difference (14) between a central electrode (12) located in said central part (8) and an intermediate electrode (15) located at said obstacle (10) slowing down the flow of the gas flow (3), in particular by constituting a reinforcement for glass fibers or a metallic knitted fabric, - on the other hand, a second potential difference (16) between a peripheral electrode ( 13) located in said peripheral part (9) and said intermediate electrode (15), said central electrode (12) and said peripheral electrode (13) forming the walls of the collection zone (4) with quasi-stationary flow and of the flow area (5) at nominal flow; so that, according to the variant embodiment, said soot particles (1) are deposited: - either on the periphery of the electrostatic filter (2), in the vicinity of the peripheral electrode (13), - or in the central part ( 8) of the filter   electrostatic (2), in the vicinity of the central electrode (12).   8. The method of claim 7; said method being such that the potential difference (14) between the central electrode (12) and the intermediate electrode (15) is included between 5 kV and 100 kV.   9. The method of claim 8; said method being such that the potential difference (16) between the intermediate electrode (15) and the peripheral electrode (13) is included between 5 kV and 100 kV.   10. Method according to any one of claims 5   at 9; said method being such that the peripheral electrode (13) is brought to a potential close to that of ground; so the risks of electrical accidents are thus reduced.   11. Method according to any one of claims 1   to 10; said method further comprising: - the step of eliminating soot particles (1)   collected in the collection area (4).   12. Method according to claim 11; said method being such that to remove the soot particles (1), in particular when the collection zone (4) is located in the center of the electrostatic filter (2), they are thermally degraded with a supply of energy; so that, in the case where the collection zone (4) is located in the center of the electrostatic filter (2), it is possible to thermally degrade the soot particles (1) with a reduced energy supply, in particular by means a electrical resistance.   13. Method according to claim 11; said process being such that to remove the soot particles (1), in particular when the collection zone (4) is located in the center of the electrostatic filter (2), the collection zone (4) produced in the form of a removable cartridge (17) and replaces it with a new one.   14. The method of claim il; said process being such that to remove the soot particles (1), in particular when the collection zone (4) situated on the periphery of the electrostatic filter (2) is easily accessible, the soot particles (1) are mechanically extracted, in particular in creating depression.   15. Electrostatic filter (2) for filtering and collecting soot particles (1) from a gas flow (3) containing said soot particles (1); the electrical state of said soot particles (1) having been modified prior to the implementation of the electrostatic filter (2) or during the implementation of the electrostatic filter (2); said electrostatic filter (2) comprising - a flow zone (5) in which said gas flow (3) flows in nominal fashion, - a collection zone (4) for said soot particles (1), distinct from said zone flow (5), - elements, in particular obstacles (10), slowing the flow of said gas flow (3) in said collection zone (4) of said soot particles (1); so that one can distinguish in said electrostatic filter (2) two stages, on the one hand a stage o the gas flow (3) flows nominally, on the other hand a stage o the gas flow (3 ) containing said soot particles (1) is practically stationary; said electrostatic filter (2) further comprising - electrodes (18) for applying an electric field (6) in said collection zone (4) where the flow of said gas flow (3) is slowed down and in the flow zone (5) o said gas flow (3) flows nominally; so that, under the action of the electric field (6), the electrified soot particles (1) pass from the nominal flow zone to the flow collection zone (4)   stationary and settle in the collection area (4).   16. Electrostatic filter (2) according to claim; said gas stream (3) containing the soot particles (1) flowing through an elongated tube (7) comprising a central part (8) and a peripheral part (9); said electrostatic filter (2) being such that said collection zone (4) of said soot particles (1) comprises at least one obstacle (10), in particular made of fiberglass or in the form of a metallic knit, slowing down the flow of said flow gas (3).   17. Electrostatic filter (2) according to claim 16; said electrostatic filter (2) being such that said collecting zone (4) of said soot particles (1), comprising at least one obstacle (10), is located in the central part (8); so that the collection area (4) for soot particles (1), located in the center of the electrostatic filter (2), is reduced size.   18. The electrostatic filter (2) according to claim 16; said electrostatic filter (2) being such that said collecting zone (4) of said soot particles (1), comprising at least one obstacle (10), is located in said part peripheral (9).   19. Electrostatic filter (2) according to any one   claims 16 to 18; said electrostatic filter (2)   being such that to apply an electric field (6) in the collection zone (4) where the flow of said gas flow (3) is slowed down and in the flow zone (5) where the gas flow (3) s' flows nominally, a potential difference (11) is created between: - a central electrode (12) located in said central part (8), and - a peripheral electrode (13) located in said peripheral part (9); said central electrode (12) and said peripheral electrode (13) forming the walls of the collection zone (4) with quasi-stationary flow and of the flow zone (5) with nominal flow; said obstacle (10), in particular made of fiberglass or in the form of a metallic knitted fabric, being disposed between said central electrode (12) and said peripheral electrode (13); so that, according to the variant embodiment, said soot particles (1) are deposited in the collection zone (4): - either at the periphery of the electrostatic filter (2), in the vicinity of the peripheral electrode (13) , - either in the central part (8) of the filter   electrostatic (2), in the vicinity of the central electrode (12).   20. Electrostatic filter (2) according to claim 19; said electrostatic filter (2) being such that the potential difference (11) between the peripheral electrode (13)   and the central electrode (12) is between 5 kV and 100 kV.   21. Electrostatic filter (2) according to any one   claims 16 to 18; said electrostatic filter (2)   being such that, to apply an electric field (6) in the collection zone (4) where the flow of said gas flow (3) is slowed down and in the flow zone (5) where said gas flow (3) is '' flows nominally, creating: - on the one hand, a first potential difference (14) between a central electrode (12) located in said central part (8) and an intermediate electrode (15) located at said obstacle (10) slowing down the flow of the gas flow (3), in particular by constituting a reinforcement for glass fibers or metallic knitting, - on the other hand, a second potential difference (16) between a peripheral electrode (13) located in said peripheral part (9) and said intermediate electrode (15), said central electrode (12) and said peripheral electrode (13) forming the walls of the collection zone (4) with quasi-stationary flow and of the zone d 'flow (5) at nominal flow; so that, according to the variant embodiment, said soot particles (1) are deposited: - either on the periphery of the electrostatic filter (2), in the vicinity of the peripheral electrode (13), - or in the central part ( 8) of the filter   electrostatic (2), in the vicinity of the central electrode (12).   22. Electrostatic filter (2) according to claim 21; said electrostatic filter (2) being such that the potential difference (14) between the central electrode (12) and the intermediate electrode (15) is between 5 kV and kV. 23. Electrostatic filter (2) according to claim 22; said electrostatic filter (2) being such that the potential difference (16) between the intermediate electrode (15) and the peripheral electrode (13) is between 5 kV and kV. 24. Electrostatic filter (2) according to any one   claims 19 to 23; said electrostatic filter (2)   being such that the peripheral electrode (13) is brought to a potential close to that of the ground; so the risks of electrical accidents are thus reduced.   25. Electrostatic filter (2) according to any one   claims 15 to 24; said collection area (4),   further comprising a source of thermal energy (19), in particular an electrical resistance, intended to degrade the   soot particles (1) located in the collection area (4).   26. The electrostatic filter (2) according to claim 25; said collection zone (4) being located in the center of said electrostatic filter (2); so that, in the case where the collection zone (4) is located in the center of the electrostatic filter (2), it is possible to thermally degrade the soot particles (1) with a reduced energy supply, in particular by means a electrical resistance.   27. Electrostatic filter (2) according to any one   claims 15 to 24; said collection area (4) is   produced in the form of a removable cartridge (17) capable of being replaced by a new one; so that it is thus possible to ergonomically remove the soot particles (1), in particular when the collection zone (4) is located in the center of the filter electrostatic (2).   28. Electrostatic filter (2) according to any one   claims 15 to 24; said electrostatic filter (2)   further comprising or being capable of being associated with mechanical means for removing (20) the soot particles (1) from the collection zone (4), in particular with means for sucking them through a opening in said filter electrostatic (2).   29. Electrostatic filter (2) according to claim 28; said collection area (4) being located on the periphery of the electrostatic filter (2).   so that it is thus possible to eliminate from   ergonomically soot particles (1).