Angled adsorbent filter media design in tangential flow applications

Abstract

A media design for modular use in an air cleaning or HVAC systems to removes gas phase contaminants. The design allows for a control of gas contaminant removal using variable media length, path length, and contact time to ensure a contained MTZ length and low pressure drop. In one embodiment, the design includes a filter module at an angle to an airflow and an air filter mounted within the filter frame. The filter module may include channels therethrough that are oriented at the optimum angle in relation to the airflow to provide the required dwell time and pressure drop for a given application.

Claims

1. A filter media module for use in an air filter to filter contaminants comprising: a filter frame; and a filter media removably mounted within the filter frame and defining a thickness of the filter media, wherein the filter media comprises channels therethrough, wherein the channels are defined by spacers, wherein the channels and the spacers are shaped in predetermined arrangements, wherein the channels define a channel path length that is longer than the thickness of the filter media, wherein the channels extend through the thickness of the filter media, wherein the filter media comprises more than two layers of filter media, wherein the more than two layers of filter media are separated by the spacers, and wherein the more than two layers of filter media are parallel to each other.

2. The filter media module for use in the air filter of claim 1, wherein the spacers have a circular shape.

3. The filter media module for use in the air filter of claim 1, wherein the spacers have an elongated shape.

4. The filter media module for use in the air filter of claim 1, wherein the spacers are an adhesive.

5. The filter media module for use in the air filter of claim 4, wherein the adhesive connects the more than two layers of filter media.

6. The filter media module for use in the air filter of claim 4, wherein the adhesive does not emanate VOCs.

7. The filter media module for use in the air filter of claim 1, wherein the spacers between the more than two layers of the filter media form the channels.

8. The filter media module for use in the air filter of claim 1, wherein the filter media comprises an activated carbon material.

9. The filter media module for use in the air filter of claim 8, wherein the activated carbon material comprises carbon granules or powder that is located between nonwoven media.

10. The filter media module for use in the air filter of claim 1, wherein the more than two filter media layers are stacked horizontally.

11. The filter media module for use in the air filter of claim 1, wherein the more than two filter media layers are stacked vertically.

12. The filter media module for use in the air filter of claim 1, wherein the filter media is angled to a direction of airflow at an angle of 18-21 degrees.

13. The filter media module for use in the air filter of claim 1, wherein the filter media comprises a pleated filter material.

14. The filter media module for use in the air filter of claim 1, wherein the channels are entirely oriented parallel to airflow.

15. The filter media module for use in the air filter of claim 1, wherein the channels are oriented such that they terminate before a trailing end of the filter media module.

16. The filter media module for use in the air filter of claim 1, wherein the channels are partially oriented at an angle to airflow.

17. The filter media module for use in the air filter of claim 1, wherein the spacers define the bottom and tops of the channels and also space apart the more than two layers of filter media.

18. The filter media module for use in the air filter of claim 1, wherein the spacers are circular beads formed in parallel rows.

19. The filter media module for use in the air filter of claim 1, wherein the channels are shaped in parallel arrangements.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1A shows a mass transfer zone application example.

(2) FIG. 1B shows a filter arrangement of the prior art.

(3) FIG. 2A shows a side isometric view of a filter module.

(4) FIGS. 2B, 2C. 2D, and 2E show side cross sections through the lines 2B-2B, 2C-2C, 2D-2D, and 2E-2E respectively in FIG. 2A.

(5) FIGS. 3A and 3B show front and side views of a filter assembly of the filter modules in use.

(6) FIG. 4A shows an alternate front view of a filter module.

(7) FIGS. 4B and 4C show side cross sections through the lines 4B-4B and 4C-4C respectively in FIG. 4A.

(8) FIG. 4D shows a side view through the lines 4D-4D in FIG. 4A.

(9) FIGS. 5A and 5B show an alternate side view of the view of FIG. 4D.

(10) FIGS. 6A, 6B, 6C, and 6D show an alternative filter media.

(11) FIG. 6E shows yet an alternate filter media arrangement.

(12) FIGS. 7A, 7B, 7C, 7D, and 7E show another alternative filter module.

(13) FIGS. 8A and 8B show a filter housing.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(14) Filter Media Module

(15) As shown in FIGS. 2A-2E, 3A and 3B, 4A-4D, 5A, 5B, an air filter module 200, 400, may be removably placed within in an air filter system 300 (generally called “air filter” herein) that itself may be removably placed within an air duct or passage 90 to filter air passing therethrough. In order to maximize the filter media 214, 414 exposure to the air flow to be filtered, and to minimize pressure drop, a filter module 200, 400 may be angled to the air flow, with it being appreciated that the shortest path for air flow from a front of the filter module (facing the air flow) to the back of the filter module is defined as the thickness 213 through the cross sectional line 2B, 2C, 2D, 2E-2B, 2C, 2D, 2E, which contrasts with the longer channel air flow path lengths through the channels as described throughout this application.

(16) For example, channels 212, 212a, 412, 412a through the filter module 200, 400 may be oriented parallel to the air flow to minimize pressure drop through the filter module 200, 400 and increase path length of air flow (and media 214 exposure to the air flow). In the parallel channel arrangement, the possible path length is defined within the area within the channel 212 exposed to filter media 214 and is roughly rectangular in FIG. 2C and additionally exists between the beads 217 in FIG. 2B, which allow for a more meandering path length therethrough. In the embodiment shown in FIGS. 2D, 2E, 5A, and 5B, however, the path length is shaped differently, and creation of turbulence in the air flow using meandering channels may create even more airflow to filter media exposure due to length of the channels and duration within the filter module 200.

(17) The channels are defined between parallel layers of filter media 214, 414, of material types defined below. Within the filter module 200 in FIGS. 2A-2C, which has vertically oriented filter media 214, spacers 216 define the bottom and tops of channels 212, 212a, and also space apart parallel layers of the filter media 214. The spacers 216 may be of any effective size and height that meets design requirements of the air filter 300, and given the ease of assembly, designing a filter with more or less space between layers of filter media 214 would a straightforward matter of changing the height/thickness of the spacer application. Further, layers of filter media 214, 414, of material may be of varying thicknesses and widths.

(18) As FIG. 2B shows, the spacers 216 may be generally circular beads 217, formed in parallel rows that direct air flow across the filter media 214 in order to filter compounds both within the channels 212 and between beads 217 within the same row. The beads 217 may have a semispherical shape or a more flattened cylindrical shape, and they may be formed from adhesive or other polymer that is cured prior to application to prevent joining with adjacent filter media layers 214 (though such joinder may be desired in some context), or in such a way as to engage both sides of a filter media layer.

(19) FIG. 2C shows an embodiment where instead of the spacers 216 being individual beads 217, they are formed as lines 217a having an elongated shape. These elongated lines 217a better define the channels 212a and may promote less turbulent air flow through the filter module 200. The lines 217a may be shaped with a semispherical cross section or flattened similar to the beads 217.

(20) The beads 217 and lines 217a, 217d, 217e may be combined in a filter module 200 and may be shaped as tear drops or with similar aerodynamic structures—or squared off—in any shape that promotes effective filtration through the filter module 200. Different paths 212 may be formed between layers of filter media 214, or even between the same two parallel sheets of filter media 214.

(21) The beads 217 or lines 217a may be silicone, acrylic, epoxy, hot melt, or urethane based where the viscosity of the adhesive allows for the formed bead to retain the desired height of the channel. The adhesive may be dispensed using a hand gun, stationary nozzles over a moving web or a programed glue machine.

(22) The chosen adhesive may be a hot-melt adhesive, which would cure quickly, would not add to the VOCs in the air after it has cured and withstand typical HVAC conditions. Examples of such adhesives may include Henkel Loctite adhesive (which may be of different kinds, listed as low or zero VOCs), Technomelt 232 hot melt adhesive (ethylene vinyl acetate, EVA), a 3M 100% solids hot melt (EVA), or Dow Corning brand silicone hot-melt adhesives with reduced VOCs.

(23) The adhesive may also be minimized to reduce the amount of adsorbent media that is blocked/blinded. Also, the formed channels may not have to be continuous or parallel; the adhesive may act as the method to keep the adsorbent sheets separated and prevent the media from sagging.

(24) The spacers 216 may also include additives to improve filtration or add properties not included in the filter media to further improve the filtration process, and thus not only serve a structural purpose but a filtration one.

(25) FIGS. 2D and 2E show another embodiment of the filter module 200 where the channels 212d and 212e are not directing the airflow through the shortest path through the filter, but instead direct airflow in a meandering path with portions parallel to airflow 232, and portions not parallel to the airflow 252. The paths y and y′ provide added exposure to the filter media 214 over straight paths therethrough because y>x and y′>x as shown—and thus create additional path length. In FIG. 2E, the path y′ terminates within the filter module, and may provide for a turbulent zone 252 within the filter module 200 before the airflow exists the filter module 200. The meandering channels y and y′ may increase the exposure of the airflow to the filter media, i.e., increase the path length for air flow. The meandering channels y and y′ may also allow for specific increased path length and media exposure to meet filtration requirements, while retaining existing infrastructure that only provides for filter width of x (x is commonly 2 inches).

(26) The filter module 400 of FIGS. 4A-4D is similar to that of FIGS. 2A-2C except that the filter media layers 414 are oriented horizontally between spacers 416 define the sides of channels 412, 412a, and also space apart parallel layers of the filter media 414. As FIG. 4B shows, the spacers 416 may be generally circular beads 417, formed in parallel rows that direct air flow across the filter media 414 in order to filter compounds both within the channels 412 and between beads 417 within the same row.

(27) FIG. 4C shows an embodiment where instead of the spacers 416 being individual beads 417, they are formed as lines 417a having an elongated shape. These elongated lines 417a better define the channels 412a and may promote less turbulent air flow through the filter module 400.

(28) The filter modules 200, 400 may be combined side by side or end to end in order to extend their lengths, or they may include interim supports therein to prevent sagging of the filter media 214, 414, since such media may be prone to deformation.

(29) FIGS. 5A and 5B show examples that may be necessary in retrofit or limited spaces. FIG. 5A shows an angled filter module 500 with channels 512 defined by beads or lines therethrough that could be used with a mounting 80. Such a design could use filter media layers 514 oriented vertically or horizontally (as shown). This may provide more pressure drop and introduce areas of less air flow 572 through the filter module 500, but it may also prove beneficial in some filtering environments.

(30) FIG. 5B shows an angled filter media that may be usable in some of the more common frame racks including sleeves 80 that are not offset from one another and shaped to accept a rectangular filter module. In such an arrangement, the channels 512a may be angled between spacers 514b. The media could be oriented vertically or horizontally but in any event, the angle of the channels 512a may create an increased path length, while also creating areas of more turbulent flow 572b, where the channels 512a are not a uniform height.

(31) In order to achieve more surface area exposure of the filter media 214, 414 to the airflow, the filter module may be at an angle to the airflow of alpha, which may be 12, 18-21, 30 or other degrees as best seen in FIGS. 3A and 3B in which stacked filter modules 200 comprise an air filter 300 within an air passage 90. In such an air filter 300, the areas of less flow 372 near seams 330 are minimized when compared to similar areas 70, 72 in traditional filters. The seams 330 may be welded, glued, or sealed to prevent air flow therethrough, and each filter media may have one edge towards the air flow, and another away from the air flow. The seams 330 may also be covered by triangular or other appropriately shaped channels 818 of a filter frame 810 (FIGS. 8A and 8B), which channels 818 may be at any filter seam 330, but more likely at the “points” where the filters meet. It should be appreciated that although the filter media 214 shown in FIGS. 3A and 3B is shown in the vertical configuration, it could also be in the horizontal configuration of FIGS. 4A-4D.

(32) Although what is shown thus is a flat filter media with spacers forming channels, the filter media 600 could be pleated as shown in FIGS. 6A-6C. In such a filter media 600, alternating pleat peaks 620 form channels 610 for air passage therethrough, and the filter media 600 may be oriented horizontally or vertically, to create channels 610 therethrough.

(33) The pleated filter media 600 may be formed as shown, namely with evenly cut facing 630 and trailing 640 edges.

(34) An alternative forming of such a pleated filter 600 may involve folding a roughly rectangular-shaped filter media 650 and folding it in alternating directions along folds 660 to result in an angled media 650 as shown in FIG. 6C. The pleated filter media 600 may also be formed from parallelogram flat stock to form different desired channel configurations.

(35) FIG. 6D shows stacking of the pleater filter 600 in a way that it could form an air filter, where layers of the pleated filter media are separated by spacers 640, to create channels therethrough.

(36) FIG. 6E shows an alternate way of forming channels 612f within a filter media 614f using folds 617f that act as spacers between the filter media. As shown, the folds 617f separate layers of media 614f—and add a spacer 617f that has filtration properties itself.

(37) Another configuration could be to corrugate activated carbon paper and then stacking/gluing the corrugated carbon media on an angle to achieve a similar resulting channeled structure through the corrugated channels. Yet another configuration to create channels through a filter media could be to use a honeycomb structure.

(38) To minimize movement and protect the media, a mesh or screen may be used to keep the filter media in place.

(39) To maintain spacing between layers of filter media, a toothed spacer (similar to a toothed comb) or preformed mesh with channels may be used to separate the layers and maintain spacing therebetween, as well as add strength.

(40) Filter Module/Media Calculations and Testing

(41) If the width of the module frame 220 is 2 inches and the angle α=20 degrees (approximately angle of current configuration of three modules in a 24×24 duct), then the horizontal path length of the air is H or 5.85 inches (see equations 1-4). This is almost three times the path length (2 inches) in the current media exposure.

(42) $\begin{array}{cc}\sin \alpha =\frac{O}{H}& \mathrm{Equation}1\\ \sin 20=\frac{2.0}{H}& \mathrm{Equation}2\\ H=\frac{2.0}{0.3420}& \mathrm{Equation}3\\ H=5.85\mathrm{inches}& \mathrm{Equation}4\end{array}$

(43) Testing shows reducing face velocity through the media increases the efficiency and has a far larger impact on the length of the MTZ than comparable reductions in the contaminant concentration. For example, MTZ length at 1 ppm H.sub.2S at 500 ft/min is 4.8 inches compared to 2.8 inches at 100 ft/min. In contrast, the MTZ length is only reduced to 4.6 inches at 0.1 ppm H.sub.2S and 500 ft/min—a ten-fold decrease in concentration. When examining efficiency, certain honeycomb media with 1 ppm H.sub.2S after 120 days, the efficiency was measured at 45% at 500 ft/min, 90% at 250 ft/min, and 100% at 100 ft/min.

(44) Additional testing demonstrated the pressure drop going through an air filter with channels oriented perpendicular to the face of the filter and mounted on a 45-degree angle is approximately double that of the same filter mounted vertically given the same volume of air. When the same media was assembled into an angled filter with parallel channels to the air flow the pressure drop returned to the original vertical pressure drop.

(45) Filter Media Material

(46) The filter media 214, 414 may be any effective media, including that described herein. The filter media 214, 414 may be an activated carbon paper media that can be made with 50 wt % coconut or wood activated carbon (honeycombs are 30 to 60 wt % carbon for IAQ applications). Coconut carbon may be used for the adsorption of VOCs due to the larger micropore volume compared to the wood-based carbon that may be used in honeycombs. The method to make the activated carbon paper allows flexibility for additives to target specific challenge gases or for the addition of alternative sorbents such as zeolites, molecular sieves, or MOFs. In contrast, honeycombs are difficult to make using many sorbents and constrained to additives compatible with the binder system.

(47) The carbon paper media provides easy formability and manipulation—something that is less available in honeycomb and corrugated materials. Channel dimensions can easily be adjusted to decrease the MTZ length or pressure drop by changing the separation of layers and angle of the path length or angle of channels. In contrast, honeycombs require expensive dies for each configuration (wall thickness and channel dimensions). Further, papers with different sorbents or properties could be combined in the same module.

(48) Another option for activated carbon media such as that shown in U.S. Pat. Nos. 6,355,330, 5,147,722, and 5,792,513, incorporated by reference as if fully set forth herein, that use a polymer such as polypropylene (PP) or polyethylene (PE) that binds activated carbon granules or powder and is then sandwiched between a thin nonwoven media. In such a media, the center media may be over 80 wt % activated carbon and the polymer binder does not blind any of the activated carbon pores.

(49) Filter Material with Supporting Framework

(50) FIGS. 7A and 7B show a filter module 700 with filter media 710 supported on a structure that may include a support beam 720. The filter media 710 comprises individual sheet members 710 mounted on the beam (s) 720. Spacers 730 ensure consistent spacing between the media 710 and help form consistent cross-sectioned air channels 740.

(51) FIGS. 7C and 7D show alternate embodiments of the support structure. FIG. 7C shows the beam 720 and spacer 730 mounted through a center of the members 710. FIG. 7D shows the beam 720a and spacer 730a mounted at opposite edges of the members 710a.

(52) The configuration in FIGS. 7A-7D could mount the media 710 in a horizontal (as shown) or vertical direction as shown in in FIG. 7E, that shows the filter media 710e, beams 720e, spacers 730e.

(53) FIGS. 8A and 8B show a filter frame 800 for use with the filter modules 200, 400 described herein. The filter frame 800 includes a removable particle filter 820 and the air filter 300 already described. The particle filter 820 may filter particles so that carbon adsorbent filters 200, 400 do not become clogged with particles. The channels 818 may be attached to upright frame members 816 mounted perpendicular to the airflow in order to direct airflow from the seams 330 as well as hold individual modules 200 together to form the entire air filter 300 gas phase removal section.

(54) Further, banks of filter modules 200, 400 could be combined in series in the airstream and/or combined with other systems or technologies to deliver the required air quality.

(55) While the invention has been described with reference to the embodiments above, a person of ordinary skill in the art would understand that various changes or modifications may be made thereto without departing from the scope of the claims.