Liquid purification or separation – Filter – Material
Reexamination Certificate
1997-10-24
2002-06-04
Savage, Matthew O. (Department: 1723)
Liquid purification or separation
Filter
Material
C095S211000, C096S010000, C096S154000, C210S506000, C210S508000, C261S104000, C261S107000, C264S177130, C264S177140, C428S368000, C428S372000
Reexamination Certificate
active
06398039
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an air cleaning system and more particularly to an effective odor removal system using chemisorptive reagents impregnated within shaped wicking fibers to remove acidic gases.
2. Description of Prior Art
It is known in the prior art to use activated charcoal or a zeolite material as an adsorptive odor removing element or media to purify an air stream. U.S. Pat. No. 4,130,487 shows a filter for liquid or gases which includes activated carbon for removing odors during air filtration. The activated carbon is in an additional layer which is added to the filter material.
In the prior art fibers have had surface coatings ranging from finely divided powder particles to coarse granular particles. The particles have been applied by either an adhesive coating which mechanically retains the particles on the fiber or the powder particles have been embedded on the fiber surface during the tacky stage in the polymer processing.
It is known to use carbon fibers for filter applications. The carbon fibers are formed from organic polymer fibers which are heated and carbonized. The carbon fiber can also be formed by heating polymer fibers and attaching carbon particles when the polymer is sticky or by using an adhesive to hold the carbon particles to a fiber. The ability to coat various powdered particulate material on a surface of a fiber has generally required an adhesive layer to be used to immobilize and hold the powder particles on the fiber surface. The very act of using an adhesive layer to hold the particles results in a portion of the surface of the powder particles being contaminated by the adhesive and therefore becoming ineffective for applications such as filtration. A balance has to be met between the strength of the immobilization versus the maintaining of effectiveness of the powder layer.
In order to minimize this contamination typically larger particles are often used so that the point of contact between the surface adhesive and powder particles is small. In typical gaseous applications using activated carbon the particles used are most frequently 100 microns and larger; and, finely powdered activated carbon is basically only used in liquid decolorization applications despite the fact that fine powder activated carbon holds the potential of much more rapid kinetics.
It is desirable to provide a compact, economical air filter for the continuous removal of H2S and SO2 which avoids the problems of reduced flow rates and reduced removal efficiency over time.
SUMMARY OF THE INVENTION
The present invention provides a filter wherein either alkali-generating chemical reagents, or in conjunction with solid particles, such as an activated carbon powder, are impregnated in the internal cavities of the shaped fibers in a fiber filter mat without the use of an adhesive. Undesirable H2S and SO2 gas molecules are removed from the air stream by reacting with the chemical reagents composed of alkaline compounds of Group 1 metals such as KOH, K2CO3, KHCO3 or K3PO4. and divalent compounds of Group 2 (i.e. Mg
2+
) and Group 6-12 ( i.e. Zn
2+
and Cu
2+
) elements.
This invention demonstrates that the chemical reagent packages described as above has a high affinity for the removal of acidic gases such as H2S, SO2 when impregnated into the internal channels of the shaped wicking fiber even without the presence of any additional solid powders in the systems. This invention also demonstrates that the presence of solid particles in the systems greatly increases the gas removing activity by creating better reagent retaining spaces and larger reaction surface areas for better reaction kinetics.
The fibers have longitudinal extending internal cavities which have openings extending to the outer surface of the fibers. The fiber, the opening size and the particles to be included are selected so that when the particles are forced into the longitudinal cavities they are permanently retained. The fibers selected provide a way to mechanically immobilize powdered activated carbon adsorbent particles without the use of an adhesive. The small solid particles becomes mechanically trapped within the longitudinal cavities of the fibers and is basically irreversible bound. This approach can be extended to any powder which one would like to include within a fiber medium, including such agents as zeolites, baking soda, cyclodextrins or any number of other solid particle of interest.
This invention provides flexible fibers, each having a cross section with internal cavities having openings leading to the surface of the fiber, which are impregnated with solid particles. The internal cavities extend longitudinal along the lengthwise direction of the fiber and they are filled with a solid particulate material which is permanently retained in the cavities and will not spill out through the openings due, we believe, to mechanical restrictions. The fibers are dusted with the solid particles and then rolled, forcing the particles into the fiber cavities. The excess particles are physically removed by agitation and a strong air flow. The particles entrapped in the cavities are surprisingly stable and resistant to physical action. The present invention should have a significant cost savings over carbon fibers and should outperform fibers coated with granular activated carbon.
The longitudinal extending opens inside the solid-particle-impregnated wicking fibers permits the chemical reagents retained in the cavities to interact with the gas molecules within the air stream effectively so as to absorb the unwanted gas molecules. In the disclosed device the open space between the wicking fibers remain so that, in the air stream to be cleaned, the pressure differential problem is minimized and air flow restrictions are not increased by continuous use.
REFERENCES:
patent: 4255487 (1981-03-01), Sanders
patent: 5069970 (1991-12-01), Largman et al.
patent: 5344626 (1994-09-01), Abler
patent: 5704966 (1998-01-01), Rohrbach et al.
patent: 5713971 (1998-02-01), Rohrbach et al.
patent: 5744236 (1998-04-01), Rohrbach et al.
patent: 5891221 (1999-04-01), Rohrbach et al.
patent: 5902384 (1999-05-01), Rohrbach et al.
Bause Daniel
Dondero Russell
Jones Gordon
Rohrbach Ronald
Unger Peter
Allied-Signal Inc.
Fleming Michael A.
Savage Matthew O.
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