WO1997045189A1 - Air filtration device - Google Patents
Air filtration device Download PDFInfo
- Publication number
- WO1997045189A1 WO1997045189A1 PCT/IB1997/000562 IB9700562W WO9745189A1 WO 1997045189 A1 WO1997045189 A1 WO 1997045189A1 IB 9700562 W IB9700562 W IB 9700562W WO 9745189 A1 WO9745189 A1 WO 9745189A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- filter unit
- impregnated
- air
- filter
- aqueous solution
- Prior art date
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/02—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by adsorption, e.g. preparative gas chromatography
- B01D53/025—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by adsorption, e.g. preparative gas chromatography with wetted adsorbents; Chromatography
Definitions
- the invention relates to an air filtration device comprising: a housing having an air inlet and an air outlet; air displacement means for displacing air from the inlet to the outlet in a direction D through a filter element.
- the invention also relates to a filter element for use in such a device.
- air filtration device is intended to refer to any device which can be used to filter certain gaseous substances out of a volume of air.
- air conditioners air humidifiers, air de-humidifiers, evaporative coolers, ventilators, vacuum cleaners, oxygen supply apparatus, breathing masks, etc.
- gaseous as here employed is intended to refer both to gases and vapours.
- a device as specified in the opening paragraph is known from United
- the filter element consists, for example, of a corrugated sheet of fibrous sorption paper which is impregnated with a finely particulate active substance, such as activated carbon or activated silica gel.
- active substance such as activated carbon or activated silica gel.
- a disadvantage of such a filter element is that it is relatively ineffective in filtering out gaseous pollutants having a molecular weight below about 50-60 (and thus possessing a high volatility). This is inter alia due to the fact that absorption of such volatile substances by activated carbon, alumina or silica gel occurs via a rather weak physical interaction, together with the fact that the activity of such substances is rather “general” in nature, in that they cannot be efficiently targeted at specific gaseous pollutants. In addition, the absorption of many gaseous pollutants by activated carbon, alumina or silica gel deteriorates at high relative humidities (RH ⁇ about 60%). As a result, many gaseous substances will only be partially filtered out by the known filter, whereas other gaseous substances (such as NH 3 and formaldehyde vapour, for example) will not be removed at all.
- RH ⁇ relative humidities
- the filter element comprises at least one filter unit comprising an absorbent, fibrous material which is impregnated with an aqueous solution of an acid or a base.
- An immediate advantage of the air filtration device is that the operation of its filter element employs wet-chemical reactions, as opposed to the intrinsically less effective dry physical reactions relied upon in the prior art filter, such wet-chemical reactions being highly effective even at high relative humidities.
- a given filter unit is highly dedicated, being specifically designed to filter out either acidic gaseous pollutants (such as carboxylates, mercaptans, S0 2 , HN0 2 and HNO 3 ) or basic gaseous pollutants (such as amines and ammonia).
- a given filter unit can, if so desired, be impregnated with additional aqueous substances, so as to allow the additional removal of more specific pollutants from the air (such as formaldehyde vapour).
- the filter element in the inventive device can afford to be much smaller (thinner) than a comparable prior art filter.
- a further advantage is that an air stream traversing the inventive filter element will undergo a smaller pressure-drop than in the prior art filter, which results in quieter operation.
- acids and bases are suitable for application in impregnating the fibrous material in the filter element.
- suitable acids include citric acid and phosphoric acid
- suitable bases include XOH, XYHPO 4 , XYZPO 4 , XHCO 3 and XYCO 3 , wherein X, Y and Z represent alkali metals (not necessarily mutually distinct).
- These substances are non-odorous, which is essential to applications in human or animal habitations.
- they are non-volatile at room temperature, which prolongs the useful life of the filter unit.
- they are relatively hygroscopic, so that they tend to attract moisture to the filter unit, thereby promoting continued high efficiency of the wet-chemical reactions on which the operation of a filter unit is based.
- the filter element comprises two filter units in series arrangement, one of which is impregnated with an aqueous solution of an acid and the other of which is impregnated with an aqueous solution of a base.
- a filter unit is impregnated with an acidic or a basic solution or both will depend inter alia on the intended application environment of the air filtration device.
- air filtration devices which are specifically tailored to:
- smoky environments e.g. restaurants and bars
- odorous environments e.g. lavatories and locker rooms
- humectants include urea, inorganic lithium salts, X'Y'HPO 4 , X'Y'Z'PO 4 , and various organic alkali-metal compounds, such as X' lactate, X' formate, X' acetate, X' methylsulphate, X' ethylsulphate, X' propylsulphate, X'Y'Z' citrate, X'Y' camphorate, X'Y' glycerophosphate, X' glycolate, X'Y' succinate, X'Y' tartrate, X'Y' malonate, X' formaldehyde sulphoxylate, and their mixtures, wherein X', Y' and Z' represent alkali metals (not necessarily mutually distinct, and not necessarily distinct from the alkali metals X and Y referred to above). If so desired, more than one humectant may be employed in a given filter
- a further embodiment of the device according to the invention is characterized in that at least one filter unit is additionally impregnated with at least one organic amine compound selected from the group formed by urea and the alkanol amines.
- the purpose of such impregnation is the absorption of formaldehyde vapour from the air.
- Formaldehyde (HCHO) occurs in tobacco smoke and vehicle exhaust fumes, and is also emitted from urea-formaldehyde foam insulation and pressed- wood products, for example. Even in concentrations as low as 0.1 ppm, it can cause considerable irritation of the eyes, skin and airways, particularly in people suffering from asthma or emphysema.
- An example of a particularly suitable alkanol amine in the current context is tris- hydroxymethylaminomethane.
- a surprising aspect of the invention is that, whereas XHCO 3 on its own or urea on its own will not absorb formaldehyde vapour, the combination of XHCC ⁇ and urea is very effective at doing so.
- a particular embodiment of an air filtration device according to the invention is characterized in that at least one filter unit is impregnated with an aqueous solution comprising: base: 5-30 wt. % humectant: 0.5-5 wt. % organic amine compound: 2-15 wt. %
- wt. % percentages by weight
- a further embodiment of the inventive air filtration device is characterized in that at least one filter unit is impregnated with an aqueous solution comprising: acid: 5-50 wt. % organic amine compound: 5-30 wt. %
- these concentrations ensure satisfactory use of the filter unit at air humidities in the approximate range 20-95%.
- At least one filter unit is provided with means for visually indicating that the filter unit has been exhausted beyond a certain level.
- the consumer can readily see when a filter unit has been exhausted to a point where its efficiency is no longer satisfactory, and can thus replace the filter unit on time.
- a pH indicator substance is incorporated in the filter unit, which substance changes its color once a certain amount of gas has been absorbed in the filter unit. Examples of suitable pH indicator substances include:
- bromophenol blue, bromochlorophenol blue, bromocresol green, congo red, methyl red and their alkali-metal salts Such substances undergo a color change in dilute aqueous solution when the pH of that solution increases from 3.0 to 5.0, for example;
- - For use in a base-impregnated filter unit: neutral red, phenol red, bromothymol blue, alizarin, bromoxylenol blue and their alkali-metal salts.
- Such substances undergo a color change in dilute aqueous solution when the pH of that solution decreases from 8.0 to 6.0, for example.
- the pH indicator substance can be conveniently incorporated in a given filter unit together with other chemical impregnants if all such chemicals are first mixed together and then dissolved so as to form an aqueous impregnant solution.
- the amount of pH indicator substance should be sufficiently high to ensure clearly visible discoloration of the filter unit when it becomes exhausted; to this end, in a preferential embodiment of the inventive filter unit, the amount of pH indicator substance in the impregnant solution should lie in the range 0.01 - 0.5 wt% .
- the absorbent, fibrous material of the filter unit(s) may, for example, be selected from the group formed by glass fiber papers, crepe papers, Kraft papers, wool, silk, cellulosic fiber fabrics (such as cotton, linen, viscose or rayon) and synthetic fiber fabrics (such as nylon, polyester, polyethene, polypropene, polyvinylalcohol, acrylics, polyamide and carbon fiber). It should be explicitly noted that the fibrous material employed in different filter units need not be the same. In a preferential embodiment of the device according to the invention, the fibrous material is selected from the group formed by hydrophilic glass fiber paper and ozone-bleached crepe paper (such as ozone-bleached coffee filter paper).
- Such papers are particularly odorless when impregnated with the aqueous solutions referred to above.
- Specific example of such papers include Whatman GF/ ⁇ (Whatman, United Kingdom), Sibille Dalle filtre ⁇ caf ⁇ blanc RH 57 gsm and Sibille Dalle sup/super hydrocel blanc 49 gsm (PSG PILLO-PAK, Eerbeek, The Netherlands).
- a further preferential embodiment of the inventive device is characterized in that the fibrous material is interspersed with a plurality of relatively straight, open-ended channels which extend substantially parallel to the direction D.
- the inventors have found that such an embodiment ensures optimal interaction of an air stream in the direction D with the chemicals in a filter unit, allowing the filter unit to have a minimal depth a ⁇ , in the direction D for a given average air speed vchel.
- Specific embodiments of this concept include filter elements in which:
- At least one filter unit comprises a plurality of mutually parallel sheets of the fibrous material, each sheet extending substantially parallel to the direction D;
- At least one filter unit comprises a plurality of corrugated sheets of the fibrous material, the corrugations extending substantially parallel to the direction D.
- a further embodiment of the device according to the invention is characterized in that the smallest dimension d c of the channels measured perpendicular to the direction D lies in the range 0.25-4 mm. For air speeds v, of the order of 0.5-1.5 m/s, values of d c in the quoted range generally ensure a laminar flow of air through the filter unit.
- the filter element may comprise additional components (in series arrangement) which are intended to fulfil general or specific purposes.
- a special (dry) filter for absorbing paniculate matter such as dust or soot
- an extra wet- chemical filter which is intended to remove a specific substance such as mercury vapour.
- an activated carbon filter into the device, for the removal of less-volatile hydrocarbon gases, radon, ozone and NO 2 .
- Figure 1 renders a cross-sectional view of a particular embodiment of an air filtration device according to the invention
- Figure 2 is a perspective view of a particular embodiment of a filter unit suitable for use in the subject of Figure 1 ;
- Figure 3 is a perspective view of an alternative embodiment of the subject of Figure 2.
- Figure 1 renders a cross-sectional view of a particular embodiment of an air filtration device 1 according to the invention.
- the device 1 comprises a housing 3 having an air inlet 5 and an air outlet 7. Also present are means 9 for causing a flow of air from the inlet 5 to the outlet 7 in a direction D through a filter element 11.
- the means 9 are here embodied as an electric fan which sucks air through the element 11 in the direction D.
- the filter element 11 comprises a first filter unit 13 and a second filter unit 15 in series arrangement.
- Each of the units 13, 15 comprises an absorbent, fibrous material which is impregnated with an aqueous solution.
- the fibrous material is a hydrophilic glass-fiber paper (Whatman GF/A), and the units 13, 15 are impregnated as follows:
- filter unit 13 may also comprise 5 wt. % t ⁇ s- hydroxymethylaminomethane.
- filter unit 15 may also comprise 24 wt. % H 3 PO 4 and 5 wt. % urea. If so desired, filter unit 13 may additionally comprise 0.07 wt. % phenol red, and filter unit 15 may additionally comprise 0.07 wt. % bromophenol blue.
- the fibrous material is an ozone-bleached crepe paper, and the units 13 and 15 are impregnated as follows:
- rra-HAM is used as shorthand notation for tris- hydroxymethylaminomethane.
- FIG. 2 renders a perspective view of a particular filter unit 13 suitable for use in an air filtration device 1 according to the invention.
- the fibrous material of the unit 13 is interspersed with a plurality of relatively straight, open-ended channels 25 which extend substantially parallel to the direction D.
- this is achieved by embodying the fibrous material as a series of mutually parallel planar sheets 21 which are glued to supports 23 at two opposite extremities, the gaps 25 between neighbouring sheets 21 acting as the channels hereabove referred to. This arrangement corresponds to case (a) above.
- the sheets 21 have a thickness of 0.35 mm and a depth d u of 42 mm in the direction D.
- the smallest dimension c ⁇ of the channels 25 (in this case, the mutual separation of the sheets 21) is 1 mm.
- the filter unit 13 has a square cross-section perpendicular to the direction D, measuring 28 x 28 cm 2 . Assuming an average air speed v, of 1.4 m/s in the direction D, the filter unit 13 can filter 300 m 3 of air per hour, with a pressure-drop of 13 Pa in the direction D.
- Embodiment 4 Figure 3 shows a perspective view of a filter unit 13 which represents a modification of the subject of Figure 2.
- corrugated sheets of fibrous material separate adjacent sheets 21.
- the corrugations 27 define air channels 25' which extend parallel to the direction D.
- the period of the corrugations 27 is greater than their height, so that the smallest dimension d c of the channels 25' is the mutual separation of the sheets 21.
- the filter unit 13 has a square cross-section measuring 28 x 28 cm 2 perpendicular to the direction D, the thickness of the sheets 21 is 0.2 mm, the value of d c is 1 mm, and the depth ⁇ , is 27 mm. Assuming an average air speed v, of 1.7 m/s parallel to the direction D, the filter unit 13 can filter 300 m 3 of air per hour, with a pressure-drop of 27 Pa in the direction D.
- a long corrugated sheet of fibrous material can be rolled up into a spiral roll, and arranged so that its cylindrical axis is parallel to the direction D.
- a crepe-paper filter unit 15 identical to that described in Embodiment 4 was immersed in a bath comprising approximately 1 kg of an aqueous solution of 24 wt. % H 3 PO 4 and 5 wt. % urea. After being allowed to soak for 10 minutes, the unit 15 was removed from the bath and allowed to dry at ambient humidity (60%). It was found that the unit 15 had absorbed all of the aqueous solution from the bath.
Abstract
Description
Claims
Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP9541923A JPH11509780A (en) | 1996-05-31 | 1997-05-16 | Air purification filter device |
EP97918311A EP0848637A1 (en) | 1996-05-31 | 1997-05-16 | Air filtration device |
Applications Claiming Priority (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP96201523.6 | 1996-05-31 | ||
EP96201523 | 1996-05-31 | ||
EP97200092 | 1997-01-14 | ||
EP97200092.1 | 1997-01-14 |
Publications (1)
Publication Number | Publication Date |
---|---|
WO1997045189A1 true WO1997045189A1 (en) | 1997-12-04 |
Family
ID=26142850
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/IB1997/000562 WO1997045189A1 (en) | 1996-05-31 | 1997-05-16 | Air filtration device |
Country Status (4)
Country | Link |
---|---|
US (1) | US6071479A (en) |
EP (1) | EP0848637A1 (en) |
JP (1) | JPH11509780A (en) |
WO (1) | WO1997045189A1 (en) |
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GB2398006A (en) * | 2003-01-08 | 2004-08-11 | Stephen Atkinson | Method and apparatus for antimicrobial treatment of an airflow |
JP2007069198A (en) * | 2005-08-10 | 2007-03-22 | Japan Vilene Co Ltd | Filter medium for gas removal, composite filter and filter element |
WO2007047557A2 (en) * | 2005-10-14 | 2007-04-26 | Purafil, Inc. | Adsorbent composition with reactive indicator |
ITRM20090224A1 (en) * | 2009-05-07 | 2010-11-08 | Aero Sekur S P A | AGGRESSIVE NBC FILTRATION DEVICE FOR THE TREATMENT OF LARGE AIR MASSES. |
US8007545B2 (en) | 2005-11-18 | 2011-08-30 | Kao Corporation | Deodorant compositions |
EP3046648A1 (en) * | 2013-09-16 | 2016-07-27 | Enverid Systems Inc. | Method and system for filtering formaldehyde from indoor air |
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Cited By (19)
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GB2398006A (en) * | 2003-01-08 | 2004-08-11 | Stephen Atkinson | Method and apparatus for antimicrobial treatment of an airflow |
GB2398006B (en) * | 2003-01-08 | 2006-03-29 | Stephen Atkinson | Method and apparatus for antimicrobial treatment of an airflow |
JP2007069198A (en) * | 2005-08-10 | 2007-03-22 | Japan Vilene Co Ltd | Filter medium for gas removal, composite filter and filter element |
WO2007047557A2 (en) * | 2005-10-14 | 2007-04-26 | Purafil, Inc. | Adsorbent composition with reactive indicator |
WO2007047557A3 (en) * | 2005-10-14 | 2007-08-09 | Purafil Inc | Adsorbent composition with reactive indicator |
US8007545B2 (en) | 2005-11-18 | 2011-08-30 | Kao Corporation | Deodorant compositions |
ITRM20090224A1 (en) * | 2009-05-07 | 2010-11-08 | Aero Sekur S P A | AGGRESSIVE NBC FILTRATION DEVICE FOR THE TREATMENT OF LARGE AIR MASSES. |
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EP3046648A1 (en) * | 2013-09-16 | 2016-07-27 | Enverid Systems Inc. | Method and system for filtering formaldehyde from indoor air |
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WO2018115531A1 (en) | 2016-12-23 | 2018-06-28 | Koninklijke Philips N.V. | A system and method for measuring a concentration of a pollutant within a gas |
US11280705B2 (en) | 2016-12-23 | 2022-03-22 | Koninklijke Philips N.V. | System and method for measuring a concentration of a pollutant within a gas |
WO2019020814A1 (en) | 2017-07-28 | 2019-01-31 | Koninklijke Philips N.V. | System and method for estimating a remaining lifetime of an aldehyde filter |
EP3470824A1 (en) | 2017-10-10 | 2019-04-17 | Koninklijke Philips N.V. | System and method for detection of a gaseous aldehyde |
Also Published As
Publication number | Publication date |
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US6071479A (en) | 2000-06-06 |
EP0848637A1 (en) | 1998-06-24 |
JPH11509780A (en) | 1999-08-31 |
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