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WO2006048509A1 - Filtre a particules a haut rendement de retention - Google Patents

Filtre a particules a haut rendement de retention Download PDF

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Publication number
WO2006048509A1
WO2006048509A1 PCT/FI2005/050387 FI2005050387W WO2006048509A1 WO 2006048509 A1 WO2006048509 A1 WO 2006048509A1 FI 2005050387 W FI2005050387 W FI 2005050387W WO 2006048509 A1 WO2006048509 A1 WO 2006048509A1
Authority
WO
WIPO (PCT)
Prior art keywords
filter
gas flow
particles
filter structure
charged
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/FI2005/050387
Other languages
English (en)
Inventor
Ilpo Kulmala
Kimmo Heinonen
Aimo Taipale
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
VTT Technical Research Centre of Finland Ltd
Original Assignee
VTT Technical Research Centre of Finland Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by VTT Technical Research Centre of Finland Ltd filed Critical VTT Technical Research Centre of Finland Ltd
Publication of WO2006048509A1 publication Critical patent/WO2006048509A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
    • B03C—MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
    • B03C3/00—Separating dispersed particles from gases or vapour, e.g. air, by electrostatic effect
    • B03C3/28—Plant or installations without electricity supply, e.g. using electrets
    • B03C3/30—Plant or installations without electricity supply, e.g. using electrets in which electrostatic charge is generated by passage of the gases, i.e. tribo-electricity
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
    • B03C—MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
    • B03C3/00—Separating dispersed particles from gases or vapour, e.g. air, by electrostatic effect
    • B03C3/02—Plant or installations having external electricity supply
    • B03C3/04—Plant or installations having external electricity supply dry type
    • B03C3/12—Plant or installations having external electricity supply dry type characterised by separation of ionising and collecting stations
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
    • B03C—MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
    • B03C3/00—Separating dispersed particles from gases or vapour, e.g. air, by electrostatic effect
    • B03C3/34—Constructional details or accessories or operation thereof
    • B03C3/38—Particle charging or ionising stations, e.g. using electric discharge, radioactive radiation or flames

Definitions

  • the invention relates to a method according to the preamble of the appended claim 1.
  • the invention relates to a filter apparatus according to the preamble of the appended claim 5.
  • Particle filters with a high collecting efficiency such as, for example, HEPA (high efficiency particulate air) filters and ULPA (ultra low penetration air) filters are generally used in different targets where impurities are desired to be prevented from passing with air flow either to the object or from the object.
  • the collecting efficiency of such particle filters is above 80 % for particles of the size 0.3 ⁇ m.
  • the efficiency of the filter depends on the diameter of the filter fibres and the packing density.
  • the packing density increases and the diameter of the fibres decreases, the filtering of small particles becomes more efficient.
  • the pressure loss created by the filter also increases when the density of the filter material increases.
  • the filtering efficiency of filters has been aimed to be increased in different manners.
  • the patent publication US 4,781 ,736 discloses a HEPA filter structure, wherein the particles are first charged electrically and after that a gas flow is directed to the HEPA filter, which comprises electrical intermediate structures.
  • the charged particles can be directed to the filter by means of the charges of the electrical intermediate structures.
  • the solution in question is relatively complex and requires complex special structures for the filter, which is why fitting it to existing apparatuses may be difficult.
  • the method according to the invention is primarily characterized in what will be presented in the characterizing part of the independent claim 1.
  • the filtering apparatus according to the invention is primarily characterized in what will be presented in the characterizing part of the independent claim 5.
  • the other, dependent claims will present some preferred embodiments of the invention.
  • a basic idea of the invention is to charge the particles of the gas flow being filtered electrically before the gas flow is directed to the filter.
  • the charging in the particles can be achieved in several different manners, such as, for example by exposing to radiation or by means of a corona charger.
  • the filter in turn, is advantageously formed of thin, electricity poorly conducting fibres.
  • the filter is in an advantageous embodiment as poorly conductive as possible as a whole.
  • the charging of the fibres is opposite to the charging of the particles (a so-called mirror charging). Under the influence of mutual charges the particles collect in an intensified manner on the surfaces of the fibres.
  • the charge causes the spreading of particles substantially evenly over the entire fibre surface.
  • the collecting efficiency of the fibre increases.
  • the filter is manufactures of fibreglass with a thickness of approximately 0.5 to 4 ⁇ m. In tests it has been detected that the charge has a better effect in a thin fibre (2 ⁇ m) than in a thicker fibre (5 ⁇ m). There is still no absolute certainty of the specifics of the formation of the charge. Some possibilities include mirror charging and/or charge created by the friction between the filter material and the gas flow containing particles, in which case dipole charges are formed in the fibre.
  • the structure according to the invention has several advantages.
  • a significant advantage is that by means of the invention it is possible to intensify the small particle separating capacity of a conventional particle filter with high collecting efficiency, such as, for example, a HEPA filter, without increasing pressure loss.
  • the solution according to the invention offers a simple solution.
  • some kind of an electrode structure has been required in connection with the filter or in its immediate vicinity.
  • the electrode structure in question has typically been required to direct the charged particles to the filter.
  • Known electrode structures require an electric connection, such as, for example earthing or power feed, in which case the structure becomes more complex than the solution according to the invention, wherein the filter part does not require electric connections or earthing.
  • the solution according to the invention is very advantageous when the filter apparatus comprises several filters.
  • the solution according to the invention is advantageous, because no conductive structures are needed in the filters that are visible to the space.
  • the invention is also well applicable for improving filtering efficiency in existing plants.
  • the solution according to the invention typically requires only adding a charger to the system, which in many systems can be added relatively easy.
  • the charger can be an independent unit or it can be integral with another part of the apparatus, such as, for example, a blower, a channel part or some pre-filter.
  • a solution according to an embodiment of the invention extends the change period of the filters. The reason for this is that the charged particles collect evenly around the charged fibre, in which case the area of the fibres in the filter is utilized efficiently and no blockages are formed in the filter either. Thus, the pressure loss created by a fouled filter increases more slowly than in known solutions.
  • Fig. 1 shows an embodiment according to the invention
  • Fig. 2 shows the particle penetration of an embodiment according to the invention in relation to time when the particle size is 0.18 ⁇ m
  • Fig. 3 shows the particle penetration of an embodiment according to the invention in relation to time when the particle size is 0.30 ⁇ m
  • Fig. 4 shows a pressure difference of an embodiment according to the invention in relation to time.
  • Fig. 1 shows in principle a filter arrangement, which is arranged in connection with channel 1.
  • the filter arrangement comprises a charger 2 and a filter 3.
  • the type of the filter 2 is selected according to the target of use.
  • a usable charger 2 is a corona charger, which can also be implemented in several different manners. Corona discharge can be produced, for example, through discharge wires or discharge tips. Charging can in some embodiments be based on ionizing radiation or some other solution.
  • the detailed structure of the charger 2 is not shown in the figure.
  • the gas flows in different points of the filter arrangement are marked in the figure by their own identifiers.
  • the gas flow to be filtered that is directed to the filter arrangement is marked with F1.
  • the gas flow charged electrically with the charger 2 is in turn marked with F2.
  • the gas flow filtered by the filter 3 is marked with F3.
  • the particles of the gas flow F2 charged with the charger are charged positively.
  • the invention does not depend on the sign of the charge of the particles in the gas flow F2. With some charging techniques it is, however, more advantageous to produce either a positive or a negative charge in the gas flow F2, because of which the mark of the charging can often be selected to be advantageous in view of the charging technique being used.
  • the numbers of chargers 2 and filters 3 correspond to each other. It is also possible to implement different entities, wherein the numbers of chargers 2 and filters 3 differ from each other. For example, in some solutions it may be advantageous to produce a charged gas flow F2 in a centralized manner with one charger 2 with a high capacity, which charged gas flow F2 is directed along channels 1 to several different filters 3, which may be located, for example, close to the targets of use. It is also possible in some embodiments to charge the gas flow F2 with several chargers 2 and then direct the charged gas flow F2 to one or a few filters 3. Thus, the chargers can be smallish units, for example, in connection with the inlet valves of the gas flow F1.
  • the charger is integral with the blower, which blower is used to create the flow of the gas flows F1 , F2, F3.
  • the charger 2 is in turn integral with a pre-filter (for example coarse-grain filter), by means of which the larger particles and impurities possibly in the gas flow are filtered before filtering with a higher collecting efficiency.
  • the filter 3 with a higher collecting efficiency used in a solution according to the invention is advantageously formed of thin fibres, which conduct electricity poorly or not at all.
  • the filter 3 is manufactured of fibreglass with a thickness of approximately 0.5 to 4 ⁇ m. In tests it has been detected that the charge has a better effect in a thin fibre (2 ⁇ m) than in a thicker fibre (5 ⁇ m).
  • the filter 3 can be electrically isolated from other structures and no earthing electrodes or other electrodes are needed in connection with it or in its vicinity. In general, in the solution according to the invention, no conductive structures are needed in connection with the filter 3 or in its immediate vicinity.
  • an electrical charge is created in the fibres.
  • Some possibilities in view of forming the charge in the fibres can be mirror charging and/or charge created by the friction between the filter material and the gas flow containing particles, in which case dipole charges are formed in the fibre.
  • the charging of the fibres is opposite to the charging of the particles (a so-called mirror charging). Under the influence of mutual charges the particles collect in an intensified manner on the surfaces of the fibres of the filter 3. In addition, the charge causes the spreading of particles substantially evenly over the entire fibre surface.
  • the filter solution according to the invention intensifies filtering efficiency significantly and increases the operation time of the filter in relation to known solutions.
  • Figs. 2 and 3 show the penetration of the filter as a function of time for different sized particles (in Fig. 2 the particle size is 0.18 ⁇ m and in Fig. 3 the particle size is 0.30 ⁇ m).
  • the measurements have been performed both with the filter arrangement according to the invention, i.e. a charger and a filter, and with a conventional filter arrangement, i.e. only a filter.
  • the filtering efficiency of the filtering solution according to the invention is significantly better than the filtering efficiency of a conventional filter solution regardless of the size of small particles.
  • Fig. 4 in turn shows the change of pressure difference as a function of time both with the filter arrangement according to the invention, i.e. a charger and a filter, and with a conventional filter arrangement, i.e. only a filter.
  • the filter used is a HEPA H10-class filter.
  • the collected particles begin to block the conventional filter 200 after a usage period of an hour.
  • the increase in the pressure difference is detected only after over 400 hours.
  • the operation time reached with the solution according to the invention is 590 hours and with the comparison solution it is 400 hours.
  • the average particle (0.30 ⁇ m) penetration during the operation time is 0.11 % with the solution according to the invention and 0.61% with the comparison solution, i.e. the penetration of the particles of the solution according to the invention is only 1/6 of the transmission of particles of the comparison solution.
  • the average pressure loss at operation time is 57 Pa for the solution according to the invention and 69 Pa for the comparison solution, i.e. the average pressure loss caused by the solution according to the invention is approximately 20 % smaller than that of the comparison solution.

Landscapes

  • Electrostatic Separation (AREA)
  • Filtering Materials (AREA)

Abstract

L'invention concerne un procédé de filtrage d'un flux gazeux, procédé dans lequel les particules se trouvant dans le flux gazeux (F1) sont chargées, le flux gazeux (F2) est dirigé à travers une structure de filtre (3), laquelle structure de filtre contient des fibres minces sensiblement non conductrices. Dans le procédé, le flux gazeux (F2) qui contient des particules chargées électriquement est amené dans la structure de filtre (3) dont les fibres sont chargées électriquement par l'effet du flux gazeux contenant les particules chargées, la structure de filtre élimine au moins une partie des particules se trouvant dans le flux gazeux au moyen d'une attraction électrique. De plus, l'invention concerne un appareil filtrant mettant en oeuvre le procédé.
PCT/FI2005/050387 2004-11-04 2005-11-02 Filtre a particules a haut rendement de retention Ceased WO2006048509A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FI20045420A FI20045420L (fi) 2004-11-04 2004-11-04 Korkean erotusasteen hiukkassuodatin
FI20045420 2004-11-04

Publications (1)

Publication Number Publication Date
WO2006048509A1 true WO2006048509A1 (fr) 2006-05-11

Family

ID=33515303

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/FI2005/050387 Ceased WO2006048509A1 (fr) 2004-11-04 2005-11-02 Filtre a particules a haut rendement de retention

Country Status (2)

Country Link
FI (1) FI20045420L (fr)
WO (1) WO2006048509A1 (fr)

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0646416A1 (fr) * 1993-10-04 1995-04-05 Trion Inc. Filtre chargé bipolairement et méthode pour son utilisation
US5518531A (en) * 1994-05-05 1996-05-21 Joannu; Constantinos J. Ion injector for air handling systems
GB2308320A (en) * 1995-12-22 1997-06-25 Pifco Ltd Electrostatic air filtration apparatus
US6364935B1 (en) * 1997-05-06 2002-04-02 Bleuair Ab Method and device for cleaning of a gaseous fluid

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0646416A1 (fr) * 1993-10-04 1995-04-05 Trion Inc. Filtre chargé bipolairement et méthode pour son utilisation
US5518531A (en) * 1994-05-05 1996-05-21 Joannu; Constantinos J. Ion injector for air handling systems
GB2308320A (en) * 1995-12-22 1997-06-25 Pifco Ltd Electrostatic air filtration apparatus
US6364935B1 (en) * 1997-05-06 2002-04-02 Bleuair Ab Method and device for cleaning of a gaseous fluid

Also Published As

Publication number Publication date
FI20045420A0 (fi) 2004-11-04
FI20045420A7 (fi) 2006-05-05
FI20045420L (fi) 2006-05-05

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