CA2240848A1 - Air filtration apparatus - Google Patents
Air filtration apparatus Download PDFInfo
- Publication number
- CA2240848A1 CA2240848A1 CA 2240848 CA2240848A CA2240848A1 CA 2240848 A1 CA2240848 A1 CA 2240848A1 CA 2240848 CA2240848 CA 2240848 CA 2240848 A CA2240848 A CA 2240848A CA 2240848 A1 CA2240848 A1 CA 2240848A1
- Authority
- CA
- Canada
- Prior art keywords
- filter
- high voltage
- corona discharge
- electret
- filter member
- 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.)
- Abandoned
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
- B03C3/34—Constructional details or accessories or operation thereof
- B03C3/66—Applications of electricity supply techniques
- B03C3/68—Control systems therefor
-
- 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
- B03C3/14—Plant or installations having external electricity supply dry type characterised by the additional use of mechanical effects, e.g. gravity
- B03C3/155—Filtration
-
- 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
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- Engineering & Computer Science (AREA)
- Automation & Control Theory (AREA)
- Electrostatic Separation (AREA)
Abstract
Air filtration apparatus comprises a casing (12) with an inlet (14) and an outlet (16). A fan (18) draws air through the apparatus into a corona discharge cell (20) to charge pollutant particles which are subsequently collected on an electret filter member (22).
Description
~ CA 02240848 1998-06-17 -- ' t TITLE: Air ~lltration apparatus.
DESCRIPTION
This invention concerns air filtration appalalus.
There are two main methods of cleaning air of respirable pollutant particles at high efflciency. The first method is to use a mechanical filter of fine fibres, typically glass fibres. By this method filtration efficiencies of up to 99.97% may be achieved but with the drawback of very high pressure drop across the filter.
The second main filtration method uses a filter composed of electret fibres which have electrical charges embedded therein. These electrical charges exert an attractive force on airborne particles, causing them to be trapped in the filter more efflciently than an equivalent non-electret filter. These filters have a lower pressure drop but can only practically achieve filtration efflciencies of up to about 95%.
US-A-S456741 discloses an air filtration appa,dlus comprising discharge electrodes which generate a corona emission for electrically charging pollutant particles passing through the appalalus and a filter member for collecting charged pollutant particles.
US-A-5268009 discloses an air filter system having a removable air filter which is grounded and an ionizer for supplying negative ions to air exiting the system. The filter inchl~es electrost~t~11y charged fibrous material in a removable cartridge.
An object of this invention is to provide an imploved air filtration AMEI~ D S~F~.1 .
apparatus.
According to the present invention there is provided air filtration apparatus comprising corona discharge means connected to a high voltage source for electrically charging pollutant particles passing through the appalalus and an filter member for collecting charged pollutant particles, characterized in that the filter member is an electret filter member and in that the corona discharge means comprises a tube having a corona discharge electrode on its central lon~ibl-lin~l axis, the inner surface of the tube being of or coated with electrically conductive material.
The appa,dLus of the invention preferably further comprises means for drawing air through the apparatus to pass through the filter. Typically an electrically operated fan will be provided for that purpose. The fan may be upstream or downstream of the filter member.
The arrangement of the tube having a corona dischalge electrode within it with a high voltage between the tube and the electrode is hereinafter referred to as a "celln. The tube is preferably circular in section. The contl~lcting surface is preferably held at a ~;lirrere-,L voltage from the discharge electrode by ~ 3,000 volts to + 20,000 volts. The inner surface of the tube is preferably connecte~l to the low voltage side of the high voltage source.
The appa,d~us of the invention may comprise a plurality of cells each having its own associated electret filter or common electret filter. The cells may be in a parallel or in series. In the latter case an electret filter member is prere,ably provided after each cell.
A single point source of charge in each cell of the appcudlus of the AMEh.'~E~ SHEET
invention surrounded by a discharging electrode has the advantage of producing a flow of charging air ions em~n~tin~ from the point and flowing orthogonally across the path of the pollutant particles through the apparatus.
The flow of such ions is substantially even, radially of the point to provide symmetry of arr ion flux with respect to the particle fl_ ~ ~ u~
AM~NDED SHEFT
W O 97/23294 PCT/GB~ 3074 is very litt~e chance of a poll~lt~nt particle passing through the a~)araluS
willulul. receiv;ng a charge and hence not being collto,ct~ by the electret filter.
The electret filter llle.-lbef is pl~;feldl~ly ccmposed of electret fibres, which are typically of plastics m~t~ l, such as poly~lo~ylene. The electret filter I~ bel may co~ lise a woven or non-woven web of electret fibres. Electret fibr~s have electrical charges embedded therein or thereon.
In a simple yrt;rc;lled embodiment of the invention an air filter appdlaluS CO~ ;Ce~5 a casing having an inlet and an outlet for air to pass ugll the a~aLus and in sequence a fan, a corona discl~ge cell and an electret filter member.
It is plt;fe.led, however, in order to ill~,love filtration effirienries further to have, along with means for drawing air through the a~p~
such as a fan, two or more filter members plGfelably colll~sed of electret fibres each preceded by a corona dischd~,e cell for electrically cha.ging air poll~t~nt particles.
In such an ~l~ gelllent it is pl-t;fel~ed that a first filter 111~,.1113C~ be ~,laLively thick compared to the or each subse~luent filter l,l~,..lber although filter me,.l,be.s of similar ~hi~ n~c~ may be used. The thicker filter Ill~lllbe.
is aimed to give practical filter life, whereas the second and s~ sequent thinner filters improve efficiency without undue h~ ase in pre~ G drop across the filter ap~*~s. With arrange...ell~ of this type it is elvisdged that filter efflciencies between 99.98 and 100% may be achievable.
With regard to the ~l~fell~d corona discharge system col~ isi~g â
cylindrical tube with a central electrode, the inner surface of the tube being con~nrtive, that has the ~I~ lage that virtually all light air ion flux is coll~ct~d by the con~lucting surface, typically CO~...f,ele~ to the low voltage side of the high voltage source, so that virtually no flux escapes from the App-.dt~c that would o~elwise cause dirt deposition on the ,ull.~ flil~g~. In ~lditi-)n, due to this ~-~l.s~ lly coll"~lele capture of air ions in the cl a~ g cell, the only charge escaping the ch~;ing cell and ~ul~se~ y h~illging on the filter is the charge carried by the pollutant pal~iclcs. These are 11y totally ca~,Luled by the filter, so that the charge colllo,Cted can be ,casuled.
A path for return of charge collected on the filter to the high voltage gc~d~r is preferably provided, ~ re~y the ~mr~nnt of pollutant ~ iclcs cnll~rte{l by the apl)~La~us may be measured. It is, Ihe.efole, p-er~ l~d that the filter app~àlus of the invention include means for e~usillg current ç~lullm~g from the filter to the high voltage geneldlor.
The current measured in that way may be used as a signal to aid operation of the filter a~l~alalus. For eY~mple, the return current in(licates the ~ of polllltio~ present and so the signal may be used to control fan speed to inclease or reduce air throughput accol~lingly. Alternatively, operation of the filter a~l)~aLus may be cycled to target a preset level of pollution.
The signal may be used to provide an in~ eous rate of colle,cti~n of polllltiQn particles in order to asct;llain whether or not the a~us is working.
Thirdly, the signal may be used to provide an aggregate of charge collected so as to indicate exhaustion of the filter for timely replacement.
This invention will now be further described, by way of example only, with reference to the accol,lpallyihlg drawings, in which:-Figure 1 shows schematically an air filter according to theinvention;
Figure 2 shows schem~tic~lly a corona discharge system;
Figure 3 shows schematically another air filter according to the invention; and Figure 4 is another ~chem~tic drawing of air filter apparatus of t_e invention.
Referring to Figure 1 of the accompanying drawings, an air filter 10 has a casing 12 with an inlet 14 and an outlet 16. In sequence from the inlet 14 are a fan 18, a charging zone or cell 20 and a filter element 22.
The fan 18 is simply an electrically driven fan to draw air t_rough the air filter inlet 14 and out through the outlet 16.
The charging zone 20 is provided to impart a charge to pollutant part;cles in the air passing through the air filter.
The particle charging system 20 (see Figure 2)-col.lplises a corona discharge electrode 24 in a tube 26, the inner surface of which is of con~lucting material. The inner surface of the tube i=~
~ , .'~
A~ )ED S~Fr-.
W O 97~3294 PCT/GB96/03074 voltage to the corona discharge electrode by + 3,000 to ~ 2û,000 volts and is ~ypically conntocted to earth. The tube 26 is cylinrtric~l and the electrode 24 is on its lon~ ti.)Al central a~cis.
The filter el.çm~-nt 22 is plefc.ably co~"~osed of so-called electret fibres. These fibres have embedded therem icol~t~l positive and negàLi~re charges. Typically the fibres are made of polyl,lol)ylene.
Air is drawn into the filter by the fan 18 and is charged in the ch~ lg zone inf h~ftin~ dirt particles therein. The corona electrode produces light aero-ions with a high mobility in the electric field. These aero-ions pass across the ch~g.ng zone colliding with pollutant particles to impart elf~ric-~t charge thereto. S~ lly all of the aero-ions are lt;~i.lcd within the chdr~"llg zone by virtue of their high mobility and the i~ ,e~-re on them of the electric field within the charging zone. The charged pollut~nt particles by virtue of their gTeater mass will have a lower mobility in the electric field and will pass completely out of the charging zone and be aU~ ;led to the electret fibres of the filter 22, where they experience greater s~ction than if ul~h~ged, whereby filtration is çnh~nreA The l,lessuç~
drop across the filter may also be relatively low.
The charge on the trapped particles can be caused to flow back to the high voltage generator via the filter 22 and an electrical mea~uli.lg circuit and in-lir~tor to give an in~lic~tion of the degree of air rle~ning and the po~ tion level in the air. Such an arrangement is shown in Figure 4 of the accc,...l.~..yhlg drawings ~iccl-cced below.
In the embodiment illustrated in Figure 3 of the accolllpal.yillg W O 97/23294 PCT/~L,.'~3074 drawings instead of a single corona discl~lge zone/filter co..,l);.--~inn, two such co-l.l)indLions 40, 42 and 44, 46 are provided along with a fan 44. The first filter 42 is thicker than the second filter 46 to provide a practical filter, lifetime and the second relatively thin filter 46 does not unduly increase the l,r~ule drop acr~ss the air filter itself whilst e nh~u ;.~g filtration by removing the n,la~,fly low co.-rf-~l.alion of pollutant ~aLIicles which have ~e..elL~led the first filter. The corona dischalge zones 40 and 44 and the filters 42 and 46 are of the types desc,ribed in relation to the embodiment of Figure 1. Filt~tion effir,iP-ncies l)elw~n 99.98 and 100% may be achieved with this z.. ~.-g.,.. l Finally, Figure 4 of the ;lccol~pA~y~llg d1~LWiU~S has been i~rludp~i to ~le-...oilJ.dt~ return of charge from a filter çll--"l .l wl~ y the return current can be use~ully measured. Figure 4 shows filter appA dluç 50 having a corona cell 52 and an electret f~ter rl~ ---t'--l 54, whel~y pollutant particles 56 e~t~h~g the app~US and travelling in the direction of arrow A, drawn or propelled ~y a fan (not shown), are charged by colli~ion with air ions produce,d by corona di~cha~-ge needle 58 in the cell 52. The corona discl~arge is ge~n~ l~ by high voltage ge~ or 60 connF~ted to the needle 58. The cell 52 has a co~h~live lining co...--F~-led to the low voltage side of the ~enFr~tor~ wl~_.el)y air ions are drawn thereto and discll~ged, so that fhey do not escape from ~e cell.
The resnlt~nt charged particles 62 are collected on the electret filter ele,menf 54, Iy~ ;,( lly of the type described for the other illustrated embo.~ t~ and their charge given up (64)~ The filter cJc~ F ~l is connF,cted W O 97~3294 PCT/GB96/03074 to the high voltage genc~al~r 60 so that tne charge on the filter can return as a ul~ulable current to the ~,en~al~,r.
The current .ne~suled can be used for a llu~uber of ~ull~oscs. The amount of charge collP,ctP~ on the filter elempnt in~lic~t~$ the level of pollnt~nt particles present. The~c~ore, the current "leasured can be used to control the fan speed in ~/alia.lce with the level of pollution.
Current n;e~.l.cl,.cnt may be used to in~ te i~ ous rate of capture of pn~ t~nt particles, thus cign~lling whGLller the appal~Lus is w(~ g~ The current could be used, for e~mrle7 to power a visual display, such as an L.E.D., to show that the àp~alaLuSiS working.
The current ll.~ul.,.~el~l can also be C~ J~ 1Y âg~e~d1~ in order to in~ t~ the total amount of pollnt~nt particles collected and hence when the filter rle-..f.~ is likely to be rxl. .~PA Again this llle~ .lle,ll may be used to power a visual display, such as an L.E.D. to show when the filter elemPnt needs repl~ring.
The a~a.dLus of the invention has a llu~ubef of advantages that deserve mPntinn By charging pollutant particles from a single corona dischd.ge point in a cell, virtually no particles can pass through the cell without being charged. Hence the a~)~u~Lu~ of the invention can operate at very high efficiPn~y levels even up to 99.999% efflc~i~n~y.
~Secon-lly, by collectin~ air ions and disch~ g same via the cell 1 wall ~w~-lul~ding the corona electrode, virtually no electric field impinges on the electret filter to hinder its operation.
Thirdly, as virtually all the charge particles are collP,rt~d as well as W O 97/23294 PCT/~5GJ03074 the air ions, vir~a11y no charge escapes from the dp~alaluS to cause charge build up and hence dirt coll~ ion on ~u~r~ces around the appa aLus.
DESCRIPTION
This invention concerns air filtration appalalus.
There are two main methods of cleaning air of respirable pollutant particles at high efflciency. The first method is to use a mechanical filter of fine fibres, typically glass fibres. By this method filtration efficiencies of up to 99.97% may be achieved but with the drawback of very high pressure drop across the filter.
The second main filtration method uses a filter composed of electret fibres which have electrical charges embedded therein. These electrical charges exert an attractive force on airborne particles, causing them to be trapped in the filter more efflciently than an equivalent non-electret filter. These filters have a lower pressure drop but can only practically achieve filtration efflciencies of up to about 95%.
US-A-S456741 discloses an air filtration appa,dlus comprising discharge electrodes which generate a corona emission for electrically charging pollutant particles passing through the appalalus and a filter member for collecting charged pollutant particles.
US-A-5268009 discloses an air filter system having a removable air filter which is grounded and an ionizer for supplying negative ions to air exiting the system. The filter inchl~es electrost~t~11y charged fibrous material in a removable cartridge.
An object of this invention is to provide an imploved air filtration AMEI~ D S~F~.1 .
apparatus.
According to the present invention there is provided air filtration apparatus comprising corona discharge means connected to a high voltage source for electrically charging pollutant particles passing through the appalalus and an filter member for collecting charged pollutant particles, characterized in that the filter member is an electret filter member and in that the corona discharge means comprises a tube having a corona discharge electrode on its central lon~ibl-lin~l axis, the inner surface of the tube being of or coated with electrically conductive material.
The appa,dLus of the invention preferably further comprises means for drawing air through the apparatus to pass through the filter. Typically an electrically operated fan will be provided for that purpose. The fan may be upstream or downstream of the filter member.
The arrangement of the tube having a corona dischalge electrode within it with a high voltage between the tube and the electrode is hereinafter referred to as a "celln. The tube is preferably circular in section. The contl~lcting surface is preferably held at a ~;lirrere-,L voltage from the discharge electrode by ~ 3,000 volts to + 20,000 volts. The inner surface of the tube is preferably connecte~l to the low voltage side of the high voltage source.
The appa,d~us of the invention may comprise a plurality of cells each having its own associated electret filter or common electret filter. The cells may be in a parallel or in series. In the latter case an electret filter member is prere,ably provided after each cell.
A single point source of charge in each cell of the appcudlus of the AMEh.'~E~ SHEET
invention surrounded by a discharging electrode has the advantage of producing a flow of charging air ions em~n~tin~ from the point and flowing orthogonally across the path of the pollutant particles through the apparatus.
The flow of such ions is substantially even, radially of the point to provide symmetry of arr ion flux with respect to the particle fl_ ~ ~ u~
AM~NDED SHEFT
W O 97/23294 PCT/GB~ 3074 is very litt~e chance of a poll~lt~nt particle passing through the a~)araluS
willulul. receiv;ng a charge and hence not being collto,ct~ by the electret filter.
The electret filter llle.-lbef is pl~;feldl~ly ccmposed of electret fibres, which are typically of plastics m~t~ l, such as poly~lo~ylene. The electret filter I~ bel may co~ lise a woven or non-woven web of electret fibres. Electret fibr~s have electrical charges embedded therein or thereon.
In a simple yrt;rc;lled embodiment of the invention an air filter appdlaluS CO~ ;Ce~5 a casing having an inlet and an outlet for air to pass ugll the a~aLus and in sequence a fan, a corona discl~ge cell and an electret filter member.
It is plt;fe.led, however, in order to ill~,love filtration effirienries further to have, along with means for drawing air through the a~p~
such as a fan, two or more filter members plGfelably colll~sed of electret fibres each preceded by a corona dischd~,e cell for electrically cha.ging air poll~t~nt particles.
In such an ~l~ gelllent it is pl-t;fel~ed that a first filter 111~,.1113C~ be ~,laLively thick compared to the or each subse~luent filter l,l~,..lber although filter me,.l,be.s of similar ~hi~ n~c~ may be used. The thicker filter Ill~lllbe.
is aimed to give practical filter life, whereas the second and s~ sequent thinner filters improve efficiency without undue h~ ase in pre~ G drop across the filter ap~*~s. With arrange...ell~ of this type it is elvisdged that filter efflciencies between 99.98 and 100% may be achievable.
With regard to the ~l~fell~d corona discharge system col~ isi~g â
cylindrical tube with a central electrode, the inner surface of the tube being con~nrtive, that has the ~I~ lage that virtually all light air ion flux is coll~ct~d by the con~lucting surface, typically CO~...f,ele~ to the low voltage side of the high voltage source, so that virtually no flux escapes from the App-.dt~c that would o~elwise cause dirt deposition on the ,ull.~ flil~g~. In ~lditi-)n, due to this ~-~l.s~ lly coll"~lele capture of air ions in the cl a~ g cell, the only charge escaping the ch~;ing cell and ~ul~se~ y h~illging on the filter is the charge carried by the pollutant pal~iclcs. These are 11y totally ca~,Luled by the filter, so that the charge colllo,Cted can be ,casuled.
A path for return of charge collected on the filter to the high voltage gc~d~r is preferably provided, ~ re~y the ~mr~nnt of pollutant ~ iclcs cnll~rte{l by the apl)~La~us may be measured. It is, Ihe.efole, p-er~ l~d that the filter app~àlus of the invention include means for e~usillg current ç~lullm~g from the filter to the high voltage geneldlor.
The current measured in that way may be used as a signal to aid operation of the filter a~l~alalus. For eY~mple, the return current in(licates the ~ of polllltio~ present and so the signal may be used to control fan speed to inclease or reduce air throughput accol~lingly. Alternatively, operation of the filter a~l)~aLus may be cycled to target a preset level of pollution.
The signal may be used to provide an in~ eous rate of colle,cti~n of polllltiQn particles in order to asct;llain whether or not the a~us is working.
Thirdly, the signal may be used to provide an aggregate of charge collected so as to indicate exhaustion of the filter for timely replacement.
This invention will now be further described, by way of example only, with reference to the accol,lpallyihlg drawings, in which:-Figure 1 shows schematically an air filter according to theinvention;
Figure 2 shows schem~tic~lly a corona discharge system;
Figure 3 shows schematically another air filter according to the invention; and Figure 4 is another ~chem~tic drawing of air filter apparatus of t_e invention.
Referring to Figure 1 of the accompanying drawings, an air filter 10 has a casing 12 with an inlet 14 and an outlet 16. In sequence from the inlet 14 are a fan 18, a charging zone or cell 20 and a filter element 22.
The fan 18 is simply an electrically driven fan to draw air t_rough the air filter inlet 14 and out through the outlet 16.
The charging zone 20 is provided to impart a charge to pollutant part;cles in the air passing through the air filter.
The particle charging system 20 (see Figure 2)-col.lplises a corona discharge electrode 24 in a tube 26, the inner surface of which is of con~lucting material. The inner surface of the tube i=~
~ , .'~
A~ )ED S~Fr-.
W O 97~3294 PCT/GB96/03074 voltage to the corona discharge electrode by + 3,000 to ~ 2û,000 volts and is ~ypically conntocted to earth. The tube 26 is cylinrtric~l and the electrode 24 is on its lon~ ti.)Al central a~cis.
The filter el.çm~-nt 22 is plefc.ably co~"~osed of so-called electret fibres. These fibres have embedded therem icol~t~l positive and negàLi~re charges. Typically the fibres are made of polyl,lol)ylene.
Air is drawn into the filter by the fan 18 and is charged in the ch~ lg zone inf h~ftin~ dirt particles therein. The corona electrode produces light aero-ions with a high mobility in the electric field. These aero-ions pass across the ch~g.ng zone colliding with pollutant particles to impart elf~ric-~t charge thereto. S~ lly all of the aero-ions are lt;~i.lcd within the chdr~"llg zone by virtue of their high mobility and the i~ ,e~-re on them of the electric field within the charging zone. The charged pollut~nt particles by virtue of their gTeater mass will have a lower mobility in the electric field and will pass completely out of the charging zone and be aU~ ;led to the electret fibres of the filter 22, where they experience greater s~ction than if ul~h~ged, whereby filtration is çnh~nreA The l,lessuç~
drop across the filter may also be relatively low.
The charge on the trapped particles can be caused to flow back to the high voltage generator via the filter 22 and an electrical mea~uli.lg circuit and in-lir~tor to give an in~lic~tion of the degree of air rle~ning and the po~ tion level in the air. Such an arrangement is shown in Figure 4 of the accc,...l.~..yhlg drawings ~iccl-cced below.
In the embodiment illustrated in Figure 3 of the accolllpal.yillg W O 97/23294 PCT/~L,.'~3074 drawings instead of a single corona discl~lge zone/filter co..,l);.--~inn, two such co-l.l)indLions 40, 42 and 44, 46 are provided along with a fan 44. The first filter 42 is thicker than the second filter 46 to provide a practical filter, lifetime and the second relatively thin filter 46 does not unduly increase the l,r~ule drop acr~ss the air filter itself whilst e nh~u ;.~g filtration by removing the n,la~,fly low co.-rf-~l.alion of pollutant ~aLIicles which have ~e..elL~led the first filter. The corona dischalge zones 40 and 44 and the filters 42 and 46 are of the types desc,ribed in relation to the embodiment of Figure 1. Filt~tion effir,iP-ncies l)elw~n 99.98 and 100% may be achieved with this z.. ~.-g.,.. l Finally, Figure 4 of the ;lccol~pA~y~llg d1~LWiU~S has been i~rludp~i to ~le-...oilJ.dt~ return of charge from a filter çll--"l .l wl~ y the return current can be use~ully measured. Figure 4 shows filter appA dluç 50 having a corona cell 52 and an electret f~ter rl~ ---t'--l 54, whel~y pollutant particles 56 e~t~h~g the app~US and travelling in the direction of arrow A, drawn or propelled ~y a fan (not shown), are charged by colli~ion with air ions produce,d by corona di~cha~-ge needle 58 in the cell 52. The corona discl~arge is ge~n~ l~ by high voltage ge~ or 60 connF~ted to the needle 58. The cell 52 has a co~h~live lining co...--F~-led to the low voltage side of the ~enFr~tor~ wl~_.el)y air ions are drawn thereto and discll~ged, so that fhey do not escape from ~e cell.
The resnlt~nt charged particles 62 are collected on the electret filter ele,menf 54, Iy~ ;,( lly of the type described for the other illustrated embo.~ t~ and their charge given up (64)~ The filter cJc~ F ~l is connF,cted W O 97~3294 PCT/GB96/03074 to the high voltage genc~al~r 60 so that tne charge on the filter can return as a ul~ulable current to the ~,en~al~,r.
The current .ne~suled can be used for a llu~uber of ~ull~oscs. The amount of charge collP,ctP~ on the filter elempnt in~lic~t~$ the level of pollnt~nt particles present. The~c~ore, the current "leasured can be used to control the fan speed in ~/alia.lce with the level of pollution.
Current n;e~.l.cl,.cnt may be used to in~ te i~ ous rate of capture of pn~ t~nt particles, thus cign~lling whGLller the appal~Lus is w(~ g~ The current could be used, for e~mrle7 to power a visual display, such as an L.E.D., to show that the àp~alaLuSiS working.
The current ll.~ul.,.~el~l can also be C~ J~ 1Y âg~e~d1~ in order to in~ t~ the total amount of pollnt~nt particles collected and hence when the filter rle-..f.~ is likely to be rxl. .~PA Again this llle~ .lle,ll may be used to power a visual display, such as an L.E.D. to show when the filter elemPnt needs repl~ring.
The a~a.dLus of the invention has a llu~ubef of advantages that deserve mPntinn By charging pollutant particles from a single corona dischd.ge point in a cell, virtually no particles can pass through the cell without being charged. Hence the a~)~u~Lu~ of the invention can operate at very high efficiPn~y levels even up to 99.999% efflc~i~n~y.
~Secon-lly, by collectin~ air ions and disch~ g same via the cell 1 wall ~w~-lul~ding the corona electrode, virtually no electric field impinges on the electret filter to hinder its operation.
Thirdly, as virtually all the charge particles are collP,rt~d as well as W O 97/23294 PCT/~5GJ03074 the air ions, vir~a11y no charge escapes from the dp~alaluS to cause charge build up and hence dirt coll~ ion on ~u~r~ces around the appa aLus.
Claims (18)
1. Air filtration apparatus comprising corona discharge means connected to a high voltage source for electrically charging pollutant particles passing through the apparatus and a filter member for collecting charged pollutant particles, characterized in that the filter member is an electret filter member and in that the corona discharge means comprises a tube having a corona discharge electrode on its central longitudinal axis, the inner surface of the tube being of or coated with electrically conductive material.
2. Apparatus as claimed is claim 1, further comprising means for drawing air containing pollutant particles through the apparatus to pass through the filter.
3. Apparatus as claimed in claim 1 or 2 comprising a casing having an inlet and an outlet for air to pass through the apparatus and, in sequence, a fan, a corona discharge zone and an electret filter member.
4. Apparatus as claimed in claim 1, 2 or 3 comprising two or more filter members, each preceded by a corona discharge means.
5. Apparatus as claimed in claim 4, wherein a first filter member is relatively thick compared to one or each subsequent filter member.
6. Apparatus as claimed in any one of claims 2 to 5, wherein said drawing means is an electrically operated fan.
7. Apparatus as claimed in any one of claims 1 to 6, wherein the corona discharge means comprises a tube having a corona discharge electrode within it, with a high voltage between the tube and the electrode.
a high voltage between the tube and the electrode.
a high voltage between the tube and the electrode.
8. Apparatus as claimed in any one of claims 1 to 7, wherein said high voltage between the conducting surface and the discharge electrode is in the range of ~ 3000 to ~ 20,000 volts.
9. Apparatus as claimed in claim 8, wherein the conducting surface is connected to the low voltage side of the high voltage source.
10. Apparatus as claimed in claim 9, wherein the conducting surface is connected to earth.
11. Apparatus as claimed in any one of claims 1 to 10, wherein the electret filter is composed of electret fibres.
12. Apparatus as claimed in claim 11, wherein the electret fibres are of plastics material.
13. Apparatus as claimed in claim 12, wherein the electret fibres are of polypropylene.
14. Apparatus as claimed in any one of claims 1 to 13, further comprising a path for return of charge collected on the filter to the high voltage source.
15. Apparatus as claimed in claim 14, further comprising means for measuring current returning along said path to the high voltage source.
16. Apparatus as claimed in claim 15, further comprising means for controlling fan speed in response to return current measured.
17. Apparatus as claimed in claim 15 or 16, further comprising means for indicating operation of the apparatus in response to return current measurement.
18. Apparatus as claimed in claim 15, 16 or 17, further comprising means for indicating filter member exhaustion in response to return current measured over a period of time.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB9526489.1 | 1995-12-22 | ||
| GBGB9526489.1A GB9526489D0 (en) | 1995-12-22 | 1995-12-22 | Air filtration apparatus |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2240848A1 true CA2240848A1 (en) | 1997-07-03 |
Family
ID=10786045
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2240848 Abandoned CA2240848A1 (en) | 1995-12-22 | 1996-12-13 | Air filtration apparatus |
Country Status (6)
| Country | Link |
|---|---|
| EP (1) | EP0868214A1 (en) |
| JP (1) | JP2000502597A (en) |
| AU (1) | AU1106097A (en) |
| CA (1) | CA2240848A1 (en) |
| GB (2) | GB9526489D0 (en) |
| WO (1) | WO1997023294A1 (en) |
Families Citing this family (19)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6524488B1 (en) | 1998-06-18 | 2003-02-25 | 3M Innovative Properties Company | Method of filtering certain particles from a fluid using a depth loading filtration media |
| US6280824B1 (en) | 1999-01-29 | 2001-08-28 | 3M Innovative Properties Company | Contoured layer channel flow filtration media |
| GB9908099D0 (en) * | 1999-04-12 | 1999-06-02 | Gay Geoffrey N W | Air cleaning collection device |
| US6454839B1 (en) | 1999-10-19 | 2002-09-24 | 3M Innovative Properties Company | Electrofiltration apparatus |
| CN1310358C (en) | 2000-06-22 | 2007-04-11 | 松下电器产业株式会社 | Polymer electrolyte fuel cell, and method for manufacturing electrode thereof, and manufacturing apparatus |
| FI20045420A (en) * | 2004-11-04 | 2006-05-05 | Valtion Teknillinen | High resolution particle filter |
| FR2889463B1 (en) | 2005-08-03 | 2008-04-04 | Valeo Systemes Thermiques | DEVICE FOR IONIZING PARTICLES VEHICLED IN AN AIR FLOW, FOR A VENTILATION, HEATING AND / OR AIR CONDITIONING INSTALLATION IN PARTICULAR. |
| US7815720B2 (en) | 2006-12-27 | 2010-10-19 | Strionair, Inc. | Dual-filter electrically enhanced air-filtration apparatus and method |
| BE1018620A5 (en) * | 2008-12-23 | 2011-05-03 | Genano Benelux N V | AIR PURIFICATION METHOD AND APPARATUS. |
| CN101887003B (en) | 2010-06-29 | 2016-06-08 | 上海杰远环保科技有限公司 | A kind of microparticle measuring device and measuring method thereof |
| US9797864B2 (en) * | 2011-05-24 | 2017-10-24 | Carrier Corporation | Current monitoring in electrically enhanced air filtration system |
| US9579663B2 (en) | 2011-05-24 | 2017-02-28 | Carrier Corporation | Detection of electrostatic filter for air filtration system |
| JP5820071B2 (en) | 2011-08-23 | 2015-11-24 | エンパイア テクノロジー ディベロップメント エルエルシー | Self-cleaning electret filter |
| EP2954954B1 (en) | 2014-06-09 | 2019-08-07 | Elfi Elektrofilter Aktiebolag | Air filter arrangement |
| GB2533466A (en) | 2015-10-22 | 2016-06-22 | Darwin Tech Int Ltd | Air cleaning device |
| CN105805032B (en) * | 2016-03-06 | 2019-05-03 | 淄博环能海臣环保技术服务有限公司 | A kind of biparting head air cleaning electric fan |
| WO2017222457A1 (en) * | 2016-06-22 | 2017-12-28 | Blueair Ab | Air treatment device |
| CN109028430A (en) * | 2018-09-06 | 2018-12-18 | 庞凯戈 | A kind of automatic ventilation system of intelligent recognition air pollution degree |
| KR102670722B1 (en) * | 2023-12-14 | 2024-05-30 | 케이씨코트렐 주식회사 | Electric Dust Collection System for Installing Ventilation Equipment in Subway Tunnels with a Discharge Part and a Dust Collection Part Installed Separately |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5035728A (en) * | 1990-07-16 | 1991-07-30 | Tatung Company Of America, Inc. | Air cleaner assembly |
| TW332802B (en) * | 1992-06-04 | 1998-06-01 | Nippon Denso Co | The air purifier |
| US5268009A (en) * | 1992-12-22 | 1993-12-07 | Teledyne Industries, Inc. | Portable air filter system |
-
1995
- 1995-12-22 GB GBGB9526489.1A patent/GB9526489D0/en active Pending
-
1996
- 1996-12-13 JP JP9523381A patent/JP2000502597A/en active Pending
- 1996-12-13 EP EP96941786A patent/EP0868214A1/en not_active Ceased
- 1996-12-13 AU AU11060/97A patent/AU1106097A/en not_active Abandoned
- 1996-12-13 CA CA 2240848 patent/CA2240848A1/en not_active Abandoned
- 1996-12-13 GB GB9626010A patent/GB2308320A/en not_active Withdrawn
- 1996-12-13 WO PCT/GB1996/003074 patent/WO1997023294A1/en not_active Application Discontinuation
Also Published As
| Publication number | Publication date |
|---|---|
| GB2308320A (en) | 1997-06-25 |
| JP2000502597A (en) | 2000-03-07 |
| WO1997023294A1 (en) | 1997-07-03 |
| EP0868214A1 (en) | 1998-10-07 |
| AU1106097A (en) | 1997-07-17 |
| GB9626010D0 (en) | 1997-01-29 |
| GB9526489D0 (en) | 1996-02-21 |
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