SELF-SUPPORTING INDUSTRIAL AIR FILTER

Abstract

A self-supporting filter media as well filter element and filtration system including the same is provided. A method of manufacturing the self-supporting filter media is also provided. The self-supporting filter media is formed such that it has a rigidity which permits the omission of filter support cage or other internal media support structure.

Claims

1. A method for manufacturing a self-supporting filter media, the method comprising: providing a forming device; placing a deactivated filter media on the forming device; activating the deactivated filter media to form an activated filter media; removing the forming device from the activated filter media.

2. The method of claim 1, wherein the forming device is a mandrel which has a circular cross section.

3. The method of claim 1, wherein the forming device is a mandrel which has a non-circular cross section.

4. The method of claim 1, wherein the deactivated filter media comprises a fibrous material and a binder.

5. The method of claim 4, wherein the fibrous material comprises at least one of glass fibers, thermoplastic fibers, and metal fibers, polymer fibers.

6. The method of claim 4, wherein the binder comprises one of a phenolic, polyester, polyurethane, vinyl ester, epoxy, silicone, melamine, diallyl phthalate, polypropylene, polyethylene, nylon, polyphenylene sulfide, polyvinylidene fluoride, or polytetrafluoroethylene polymer.

7. The method of claim 1, wherein activating includes curing in a curing oven.

8. The method of claim 1, wherein activating includes chemical curing.

9. The method of claim 4, wherein the fibrous material has a fiber diameter of 0.2 micron to 30 micron.

10. The method of claim 1, wherein the filter media has a mean flow pore size of 0.1 micron to 100 micron.

11. The method of claim 1, wherein the filter media comprises multiple layers of filter media, wherein the multiple layers of filter media have differing compositions from one another.

12. The method of claim 1, further comprising applying a coating to at least one of an interior or exterior surface of the filter media prior to curing.

13. The method of claim 1, further comprising applying a coating to at least one of an interior or exterior surface of the cured filter media after curing.

14. The method of claim 1, wherein the filter media comprises at least one of a high efficiency filtration layer and a surface filtration layer.

15. A self-supporting filter media, comprising at least one layer of filter media, the at least one layer of filter media including a binder and a fibrous material.

16. The self-supporting filter media of claim 15, wherein the fibrous material comprises at least one of glass fibers, thermoplastic fibers, metal fibers, and polymer fibers.

17. The self-supporting filter media of claim 15, wherein the fibrous material has a fiber diameter of 0.2 micron to 20 micron.

18. The self-supporting filter media of claim 15, wherein binder comprises one of a phenolic, polyester, polyurethane, vinyl ester, epoxy, silicone, melamine, diallyl phthalate, polypropylene, polyethylene, nylon, polyphenylene sulfide, polyvinylidene fluoride, or polytetrafluoroethylene polymer.

19. The self-supporting filter media of claim 15, wherein the at least one layer of the filter media has a mean flow pore size of 0.1 micron to 100 micron.

20. The self-supporting filter media of claim 15, wherein the at least one layer of filter media includes a plurality of filter media layers, wherein the plurality of filter media layers have differing compositions from one another.

21. The self-supporting filter media of claim 15, further comprising a coating on at least one of an interior and exterior surface of the at least one layer of filter media.

22. The self-supporting filter media of claim 15, wherein the at least one layer of filter media comprises at least one of a high efficiency filtration layer and a surface filtration layer.

23. A filter element, comprising: at least one layer of filter media, the at least one layer of filter media including a binder and a fibrous material; a first end cap, the first end cap configured to form a seal with a tube sheet of a filtration housing; and wherein the filter element is free of an internal support structure such that only the at least one layer of filter media is situated between the end caps.

24. The filter element of claim 23, further comprising a second end cap, the first and second end caps respectively positioned at first and second ends of the at least one layer of filter media.

25. The filter element of claim 23, wherein the fibrous material comprises at least one of glass fibers, thermoplastic fibers, metal fibers, and polymer fibers.

26. The filter element of claim 23, wherein the fibrous material has a fiber diameter of 0.2 micron to 20 micron.

27. The filter element of claim 23, wherein binder comprises one of a phenolic, polyester, polyurethane, vinyl ester, epoxy, silicone, melamine, diallyl phthalate, polypropylene, polyethylene, nylon, polyphenylene sulfide, polyvinylidene fluoride, or polytetrafluoroethylene polymer.

28. The filter element of claim 23, wherein the at least one layer of filter media has a maximum mean flow pore size of 0.1 micron to 100 micron.

29. The filter element of claim 23, wherein the at least one layer of deactivated cured filter media includes a plurality of deactivated cured filter media layers, wherein the plurality of deactivated cured filter media layers have differing compositions from one another.

30. The filter element of claim 23, further comprising a coating on at least one of an interior and exterior surface of the at least one layer of deactivated cured filter media.

31. The filter element of claim 23, further comprising a high efficiency filtration layer.

32. The filter element of claim 31 wherein the high efficiency filtration layer comprises at least one of electro-spun, nano, fine, spunbonded, or meltblown fibers, or ePTFE membrane.

33. A filtration system, comprising: a housing having an inlet and an outlet, the inlet separated from the outlet by a tube sheet; at least one filter element mounted to the tube sheet, the filter element comprising at least one layer of filter media, the at least one layer of filter media including a binder and a fibrous material.

34. The filtration system of claim 34, wherein the at least one filter element comprises a plurality of filter elements arranged in an array relative to the tube sheet.

35. The self-supporting filter media of claim 15, wherein less than 70 pulses are required during 2 hour performance testing using Pural NF dust per ASTM D6830-02.

36. The self-supporting filter media of claim 15, wherein less than 200 pulses are required during 6 hour performance testing using Pural NF dust per ASTM D6830-02.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The accompanying drawings incorporated in and forming a part of the specification illustrate several aspects of the present invention and, together with the description, serve to explain the principles of the invention. In the drawings:

[0040] FIG. 1 is a front view of a filtration system incorporating a filter element which utilizes self-supporting filter media according to the teachings herein;

[0041] FIG. 2 is a cross section of the filter element of FIG. 1;

[0042] FIG. 3 is a partial view of the cross section of FIG. 2; and

[0043] FIG. 4 is a perspective schematic illustration of a stage of manufacturing the self-supporting filter media; and

[0044] FIG. 5 is a flow chart depicting one embodiment of a method according to the teachings herein.

[0045] While the invention will be described in connection with certain preferred embodiments, there is no intent to limit it to those embodiments. On the contrary, the intent is to cover all alternatives, modifications and equivalents as included within the spirit and scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION OF THE INVENTION

[0046] Turning now to the drawings, a self-supporting filter media as well as a filter element incorporating the same are shown and described. Also shown is an exemplary embodiment of a filtration system employing the aforementioned filter element. As will be understood from the following, the self-supporting media described herein advantageously allows for the provision of a filter element which does not require any support structure to support the filter media. The filter media itself is self-supporting and strong enough to maintain its shape under typical pressure differentials seen in a variety of filtration applications. Such a configuration leads to a filter element which lasts longer, and is less costly to produce. As a result, the invention achieves a substantial cost and labor reduction in the maintenance and operation of a baghouse filtration system.

[0047] With particular reference now to FIG. 1, a filtration system 20 is illustrated. This filtration system 20 includes a schematically illustrated housing 22 which carries a filter element 24 that employs a self-supporting filter media according to the teachings herein. Housing 22 includes an inlet 26 and an outlet 28. Filter element 24 is situated within housing 22 such that it is sealingly mounted within an opening 30 of a tube sheet 32. Tube sheet 32 divides the interior of filter housing 22 into a dirty side which opens to inlet 26, and a clean side which opens to outlet 28. Air entering inlet 26 passes through the aforementioned self-supporting filter media of filter element 24 and then exits housing 22 via outlet 28. It will be recognized by those of skill in the art that FIG. 1 represents a generally schematic exemplary configuration of a typical baghouse filtration system. However, the self-supporting media described herein may be incorporated into filter elements which are utilized in applications not associated with a baghouse. Further, although a single filter element 24 is illustrated, it will be recognized that in a typical configuration multiple filter elements 24 are mounted to tube sheet 32 within the interior of housing 22.

[0048] Turning now to FIG. 2, the same illustrates a cross-section of filter element 24. Filter element 24 includes a ring of self-supporting filter media 40. Filter element 24 also includes an open end cap as a first end cap 34 at one end of filter element 24. A closed end cap in the form of a second end cap 36 is positioned opposite first end cap 34. First end cap 34 may incorporate a variety of contemporary tube sheet sealing configurations including gaskets, radial or annular seals, etc. Further, a cap of self-supporting filter media may be utilized in place of second end cap 36 to increase overall filtration area.

[0049] As will be understood in from the following, filter media 40 may be a deactivated filter media which may be activated to transition the same from a deactivated filter media to an activated filter media. Such activation includes, but is not limited to, activing a binder interspersed with the fibers of the filter media and/or curing a resin interspersed with the fibers of the filter media.

[0050] Turning now to FIG. 3, the same illustrates a schematic cross-section of the self-supporting filter media according to the teachings herein. As can be seen in this view, filter media 40 includes at least one layer 48 of filter media. This layer 48 includes a fibrous material represented by fibers 52 and a binder, resin, or other substance (collectively referred to as binder 50) interspersed throughout fibers 52. This binder 50 has been activated such that it has hardened to provide the needed strength and rigidity to filter media 40. As a result, and with momentary reference back to FIG. 2, an interior support structure such as a support cage or other rigid structure is not within the interior 42 of filter element 24 to support the same. Filter media 40 is thus self-supporting. Put differently, because the media itself is responsible for providing support, additional filtration depth is provided by this embodiment which would otherwise not be available. The increased filtration depth increases the filter dust holding capacity and helps to manage differential pressure over the life of the filter. Indeed, the support cage or structure in prior designs takes up a substantial portion of the filter element with which it is incorporated in, yet provides no filtration capabilities.

[0051] Still referring to FIG. 3, filter media 40 may also include additional layers 54, 56 on the interior and exterior surfaces of filter element 24. These additional layers 54, 56 may be other fibrous layers similar to or the same as layer 48, or alternatively, may have different properties. For example, either or both of additional layers 54, 56 may be a high efficiency filtration layer. As non-limiting examples, this high efficiency filtration layer may comprise at least one of electro-spun, nano, fine, spun-bonded, meltblown, melt-spun, or force-spun fibers, or ePTFE membrane. Such a high efficiency layer may present a mean flow pore size of 0.2 to 40 microns. Alternatively or in addition, layers 54, 56 may also be coatings such as fire, moisture, or acid-resistant coatings.

[0052] Further, the outer layer 54 may be designed as a surface filtration layer, having a mean flow pore size of 0.5 to 40 microns. This will allow a dust cake to form on the inlet side of filter media 40 and enhance the filtration efficiency of filter element 24. As non-limiting examples, this surface filtration layer may comprise at least one of electro-spun, nano, fine, spun-bonded, meltblown, melt-spun, or force-spun fibers, or ePTFE membrane. Although only a single layer 54, 56 is shown on the clean and dirty side, respectively, multiple layers may be presented on the inlet side of layer 48, and multiple layers may be presented on the outlet side of layer 48. Use of such a surface filtration layer as described above also allows filter element 24 to be back-pulsed for cleaning purposes. Advantageously, filter media 40 is of a strong enough construction to permit such back pulsing without the need of the support structure of prior designs.

[0053] Layer 48 may present a generally uniform mean flow pore size of 0.1 micron to 100 micron. Alternatively, layer 48 may be constructed by utilizing fibers of different diameter or different spacing to achieve a variable pore size as air moves through filter media 40 to achieve a desired filtration gradient. One example of such a configuration may be to use a very small pore size near the inlet side of filter media 40 to provide for fine filtration at the surface thereof as mentioned above. Alternatively, filter media 40 may utilize a variable pore size which begins large near the inlet side of filter media 40 and progressively becomes smaller towards the outlet side of filter media 40. Still further, layer 48 may in its entirety, or in at least a portion, be provided as a high-efficiency filtration layer as provided above. Accordingly, it is contemplated herein that the filter media 40 includes at least one layer of filter media, which may include those layers 48, 54, 56, described above, as well as fewer or additional layers, as also described above.

[0054] As used above, the terms inlet side and outlet side of the filter media are made relative to the direction of air flow through the filter media. The inlet side is that side of the filter media 40 which air encounters first. The outlet side is that side of filter media 40 which air encounters after encountering the inlet side.

[0055] Various fiber types and fiber sizes may be utilized in layer 48. As non-limiting examples, the fibrous material 52 which makes up layer 48 may be made of one or more of glass fibers, thermoplastic fibers, metal fibers, and/or polymer fibers. Further, such fibers may have an exemplary fiber diameter of 0.2 micron to 30 micron. It will be recognized, however, that other fiber diameter may be utilized and are contemplated herein.

[0056] The binder 50 employed may take on a variety of forms depending upon application. As non-limiting examples, the binder may be one of a phenolic, polyester, polyurethane, vinyl ester, epoxy, silicone, melamine, diallyl phthalate, polypropylene, polyethylene, nylon, polyphenylene sulfide, polyvinylidene fluoride, or polytetrafluoroethylene polymer.

[0057] Such a binder may be a resin which may be activated, i.e. cured via heat, chemically, or via any other known cure methodology based on the resin utilized. Other processing may also be employed. For example, additional chemical and heat treatments may be employed before or after curing. Further, electrostatic charging may also be employed. These processing steps will largely depend upon the application of filter media 40. It will be understood, however, where the binder is not a resin, other activations steps will be utilized outside of curing used with a resin system. For example, the binder may be chemically activated, heat activated, pressure activated, etc. Accordingly, terms such as activating and activate and their derivatives are used herein to mean any operation which transitions a binder into a state which provides the required strength and rigidity to filter media 40 so as to not require an additional support structure.

[0058] Turning now to FIG. 4, the same illustrates a generally schematic view of the formation of filter media 40 into a desired shape. As can be seen in this figure, filter media 40 is in its deactivated state and is wrapped around a mandrel 60. In the illustrated embodiment, filter media 40 is generally very flexible prior to activation allowing it to be shaped around mandrel 60. Once wrapped about mandrel 60, the mandrel is then placed into an activating device. In the illustrated embodiment, this activating device is a curing oven 62 used to cure a resin which constitutes binder 50 in the illustrated example. However, this activating device will vary depending upon the activating method utilized. This curing step is necessary to cure the resin contained within filter media 40 to transform the same from its deactivated state to its activated state. By doing so, filter media 40 becomes rigid and assumes the overall shape of the mandrel 60 upon which it was wrapped.

[0059] Although a cylindrical mandrel 60 is utilized, other shapes are contemplated. For example, mandrel 60 may have a non-circular cross-section. An example of such a configuration may be a triangular or star-shaped cross-section. A star shape is particularly useful as it could be utilized to form pleats to increase the overall surface area of filter media 40. Further, mandrel 60 may be shaped such that filter media 40 follows a twist, i.e. helical axis, along its length. It will be recognized that relatively complex geometries may be achieved based on the shape of mandrel 60.

[0060] Although not shown in FIG. 4, it will be recognized that a conveyor or feeding device may also be used for moving mandrel 60 into curing device 62. Such a system may include a conveyor, rollers, or any combination thereof. The particular system used will depend largely upon the curing device selected. It will be recognized that where multiple layers 48 of filter media are employed, each will be wrapped around mandrel 60 as illustrated in FIG. 4. Further, a pre-cure coating or treatment may be applied to media 40 prior to or after it has been wrapped around mandrel 60. Likewise after curing a post-cure coating may also be applied.

[0061] Broadly, forming a self-supporting filter media for incorporation into a filter element according to the teachings herein includes first providing a forming device. Thereafter, a deactivated layer or layers of filter media is/are applied to the forming device. Thereafter, the layer or layers is/are activated in an activating device. This cases the layer or layers of media to become structurally rigid. The forming device is then removed, and subsequent operations such as end cap installation, etc., may ensue. The forming device may be a mandrel, form, or mold, or any structure which functions to hold a general shape of the deactivated media while transitioning the same form a deactivated state to an activated state. The activating device may be any device used to transition the media from its deactivated to its activated state by interacting with the binder provided within the media.

[0062] Turning now to FIG. 5, the same illustrates one exemplary schematic process of forming the self-supporting media as described herein. At step 70, a forming device in the form of a mandrel is provided. At step 72, the mandrel is wrapped with one or more layers of filter media 40. These layers may have identical or different properties including but not limited to the types of fibers used, or the binders contained therein. This wrapping continues at steps 72, 74 until wrapping is complete.

[0063] Once wrapping is complete, a pre-cure coating may be applied at steps 76 and 78. Whether utilizing a pre-cure coating or not, process then moves to step 80 where the wrapped mandrel is placed in the curing device and the filter media 40 is cured. After curing at step 80, a post-cure coating may be applied at steps 82 and 86. The mandrel 84 is then removed and the self-supporting filter media is formed.

[0064] As discussed above, post-processing steps may also include other treatment such as chemical or heat treating steps. Further electrostatic charges may be applied to enhance the filtration capabilities of the self-supporting media. Also as described above, a high efficiency filtration layer may also be applied to the exterior surface of the cured filter media 40. This high efficiency layer may be formed concurrently during curing step 80 by wrapping mandrel 60 with an outermost wrap of very fine fibers suitable for high efficiency filtration which become rigid after curing. Alternatively, this high efficiency filtration layer may be applied after curing via another process as described above, e.g. electrospinning.

[0065] After being formed and after any additional post-processing, cured filter media 40 may be utilized in the manufacture of a filter element such as that shown in FIGS. 1 and 2. Indeed, first and second end caps 34, 36 may be attached. As discussed above, however, second end cap 36 may be omitted where the same is formed via cured filter media. Additionally, although a basic cylindrical filter element 24 is shown herein, it is contemplated that the self-supporting media described may be utilized to multiple filter elements which nest into one another to form a concentric primary/secondary filtration configuration. It will be recognized that while filter media 40 is cured it can be utilized to form a variety of filter elements not limited to the exemplary configuration shown herein. Indeed, the self-supporting media may be utilized in a variety of applications and advantageously allow for the omission of an internal support structure which is otherwise typically required.

[0066] Other formation methodologies are also contemplated by the teachings herein. For example, the fibers 52 of filter media 40 may be coated with a binder and air-laid in a web, or the fibers 52 may be treated with a binder after the web is formed. As another example, the fibers may be chopped, mixed with a binder, and then sprayed into a sheet or onto a form such as a mandrel or mold for subsequent activation. Still further, the fibers may be wet laid into a sheet, or onto a form such as a mandrel or mold. Still further, sheets, molds and mandrels treated with fiber and binder may have subsequent forming operations performed on them to achieve the targeted size, shape and density of fibers appropriate for filtration. These operations may include compressing in molds, expanding in molds, compressing using consumable components, thermal forming, hydroforming, rotational molding, or blow molding.

[0067] Media 40 according to the invention as described above performs exceedingly well in surface filtration applications. For example, testing of the media 40 per ASTM D6830-02 revealed very good results. According to this test, a dust concentration 8+?1.6 gr/dscf, filtration velocity 6.6+?0.5 ft/min, pulse pressure 75 psi, pulse duration 50 ms, air temperature 78+?4 F and relative humidity 50+?10%, were used. Per this test, a conditioning phase 10,000 pulses at 3-5 second intervals was employed, then a recovery phase at 30 pulses was employed after the pressure differential across a test sample of media 40 reaches 4 w.c. Thereafter performance test phase was conducted During this phase, the number of pulses required during the performance test phase of ASTM were measured at two and six hour time intervals were measured. The results were less than 70 pulses during 2 hour performance test using Pural NF dust per ASTM D6830-02 for the two hour test, and less than 200 pulses during 6 hour performance test using Pural NF dust per ASTM D6830-02 for the six hour test.

[0068] All references, including publications, patent applications, and patents cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein.

[0069] The use of the terms a and an and the and similar referents in the context of describing the invention (especially in the context of the following claims) is to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms comprising, having, including, and containing are to be construed as open-ended terms (i.e., meaning including, but not limited to,) unless otherwise noted. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., such as) provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.

[0070] Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.